Aims Interspecific and intraspecific variation in flower color in natural populations provides an opportunity for us to understand the evolution and maintenance of diversity of floral traits. Compared to corolla color, little is known about the color polymorphism of sexual organs in flowering plants. To explore evolutionary transitions of androecium color and polymorphism within species, interspecific and intraspecific variation in androecium (anther and pollen) color in the genus Epimedium (Berberidaceae) was investigated.
Methods To explore the geographical patterns of anther/pollen color variation in Epimedium species, data of 45 species were collected and their phylogeny was constructed based on available DNA sequences. To investigate whether intraspecific variation in androecium color relates to habitat preference, three environmental factors were measured in the field population of Epimedium pubescens in northeastern Sichuan, China, which plants had green or yellow androecia. Vegetative and reproductive traits of this species were compared between the two color morphs.
Important findings Androecium (anther and pollen) color polymorphism in field populations of Epimedium pubescens is reported here where nine populations are monomorphic with a green androecium but three populations are dimorphic with individuals having either a green or a yellow androecium. Inflorescence stalk height, stalk diameter, leaf number, flower number and spur length (as well as spur and nectar volume) were not significantly different between two morphs. Compared to the yellow morph, the green morph had relatively larger leaves and anthers, but smaller sepals. The green morph produced more pollen and larger seeds, but the same number of ovules. Seed set was not significantly different between green and yellow morph. Investigations of environmental factors in the color dimorphic populations of E. pubescens indicated that the green morph was more likely to occur in habitats with relatively lower light intensity. The distribution survey of 45 Epimedium species showed that species with a green androecium tended to appear at lower elevations. Comparative phylogenetic analysis showed that transitions from yellow to a green androecium or to androecial color dimorphism occurred at least seven times. This genus, characterized by anther color diversity and containing some species with anther color polymorphism, provides a model system in which to study the evolution and maintenance of colorful sexual organs in flowering plants.

Aims Carbon (C) and nitrogen (N) stoichiometry contributes to understanding elemental compositions and coupled biogeochemical cycles in ecosystems. However, we know little about the temporal patterns of C:N stoichiometry during forest development. The goal of this study is to explore the temporal patterns of intraspecific and ecosystem components' variations in C:N stoichiometry and the scaling relationships between C and N at different successional stages.
Methods Along forest development in a natural temperate forest, northeastern China, four age gradients were categorized into ca. 10-, 30-, 70- and 200-year old, respectively, and three 20 m × 20 m plots were set up for each age class. Leaves, branches, fine roots and fresh litter of seven dominant species as well as mineral soil at depth of 0–10 cm were sampled. A Universal CHN Elemental Analyzer was used to determine the C and N concentrations in all samples.
Important findings Intraspecific leaf C, N and C:N ratios remained stable along forest development regardless of tree species; while C, N concentrations and C:N ratios changed significantly either in branches or in fine roots, and they varied with tree species except Populus davidiana (P < 0.05). For ecosystem components, we discovered that leaf C:N ratios remained stable when stand age was below ca. 70 years and dominant tree species were light-demanding pioneers such as Betula platyphylla and Populus davidiana, while increased significantly at the age of ca. 200 years with Pinus koraiensis as the dominant species. C:N ratios in branches and fresh litter did not changed significantly along forest development stages. C concentrations scaled isometrically with respect to N concentrations in mineral soil but not in other ecosystem components. Our results indicate that, leaf has a higher intraspecific C:N stoichiometric stability compared to branch and fine root, whereas for ecosystem components, shifts in species composition mainly affect C:N ratios in leaves rather than other components. This study also demonstrated that C and N remain coupled in mineral soils but not in plant organs or fresh litter during forest development.

Plant height is a key functional trait related to aboveground biomass, leaf photosynthesis and plant fitness. However, large-scale geographical patterns in community-average plant height (CAPH) of woody species and drivers of these patterns across different life forms remain hotly debated. Moreover, whether CAPH could be used as a predictor of ecosystem primary productivity is unknown.

We compiled mature height and distributions of 11 422 woody species in eastern Eurasia, and estimated geographic patterns in CAPH for different taxonomic groups and life forms. Then we evaluated the effects of environmental (including current climate and historical climate change since the Last Glacial Maximum (LGM)) and evolutionary factors on CAPH. Lastly, we compared the predictive power of CAPH on primary productivity with that of LiDAR-derived canopy-height data from a global survey.

Geographic patterns of CAPH and their drivers differed among taxonomic groups and life forms. The strongest predictor for CAPH of all woody species combined, angiosperms, all dicots and deciduous dicots was actual evapotranspiration, while temperature was the strongest predictor for CAPH of monocots and tree, shrub and evergreen dicots, and water availability for gymnosperms. Historical climate change since the LGM had only weak effects on CAPH. No phylogenetic signal was detected in family-wise average height, which was also unrelated to the tested environmental factors. Finally, we found a strong correlation between CAPH and ecosystem primary productivity. Primary productivity showed a weaker relationship with CAPH of the tallest species within a grid cell and no relationship with LiDAR-derived canopy height reported in the global survey. Our findings suggest that current climate rather than historical climate change and evolutionary history determine the geographical patterns in CAPH. However, the relative effects of climatic factors representing environmental energy and water availability on spatial variations of CAPH vary among plant life forms. Moreover, our results also suggest that CAPH can be used as a good predictor of ecosystem primary productivity.

Aims Seed dormancy and the soil seed bank are crucial to plant regeneration strategy, especially in semiarid ecosystems with unpredictable precipitation. The aim of this study was to investigate how seed dormancy is controlled by environmental factors and how it is correlated with the soil seed bank and regeneration of the perennial legume Oxytropis racemosa, a dominant perennial herb in Mu Us Sandland of semiarid China.
Methods Germination and imbibition experiments on fresh intact and scarified seeds of O. racemosa were used to identify physical dormancy (PY) in seeds of this species. Soil seed bank dynamics, timing of seedling emergence and the fate of buried seeds in the natural habitat were investigated.
Important findings PY was broken by mechanical scarification or wet heat/ice water cycles but not solely by dry heat or wet heat treatment. The soil seed bank exhibited seasonal changes in the number of seeds, which was highest in September and lowest in July. Seeds buried at different sand depths gradually lost dormancy; 20–42% of the seeds remained dormant after 20 months of burial. Dormancy break occurs gradually throughout the year. Our results indicate that O. racemosa exhibits hardcoatedness heterogeneity that spreads germination of a seed cohort between seasons and years in the semiarid environment, where the amount of precipitation during the growing season is highly variable.

Aims The functional advantages of arsenic (As) hyperaccumulation by plants are poorly understood. One proposed benefit, termed elemental allelopathy, occurs when hyperaccumulated As is cycled from the plant back into the top layer of soil, allowing As hyperaccumulators to gain an advantage over intolerant species by increasing soil As concentrations ([ As]) underneath their canopy. To date, there are no studies that detail the presence of increased soil [ As] associated with As hyperaccumulators. In this study, we documented variation in the soil [ As] associated with the Chinese brake fern, Pteris vittata L. and also compared the effects of environmentally relevant soil and solution [ As] on competitor plant growth.
Methods Four populations of P. vittata were identified in central Florida, USA. P. vittata tissue samples and soil samples were collected at the base of and at 3 m away from ferns in each population (n = 36). Five sample locations were randomly selected from each site, and soils from the base and 3 m away from each fern were collected to examine the effects of naturally occurring soil [ As] on the germination and growth of a potential competitor plant (Oxalis stricta). Solutions with increasing [ As] were also used to examine the threshold for negative effects of [ As] on O. stricta growth. [ As] were measured using inductively coupled plasma mass spectrometry (ICP-MS).
Important findings Overall, soil [ As] from the base of ferns was nearly twice that of soil 3 m away indicating that ferns hyperaccumulate As. However, ferns and their associated soil, contained different [ As] depending on their collection site, indicating that these populations accumulate and use [ As] differently. O. stricta growth decreased and germination was delayed as solution and soil [ As] increased. However, the relative distance from the fern that the soil was collected from did not affect growth, which would be expected with elemental allelopathy. Our results show that P. vittata is associated with higher soil [ As] and these concentrations are sufficient to inhibit growth of competitors. However, the absence of a strong inhibitory relationship associated with proximity to the fern across all locations suggests that the possible functional advantages of elemental allelopathy may depend on site specific characteristics.

Aims We conducted a simulated nitrogen (N) and sulfur (S) deposition experiment from 2006 to 2012 to answer the following questions: (i) does chronic N and S deposition decrease cation concentrations in the soil and foliage of understory plant species, and (ii) does chronic N and S deposition decrease plant diversity and alter species composition of the understory plant community in a boreal forest in western Canada where intensifying industrial activities are increasing N and S deposition?
Methods Our field site was a mixedwood boreal forest stand located ~100 km southeast of Fort McMurray, Alberta, Canada. The experiment involved a 2 × 2 factorial design, with two levels each of N (0 and 30 kg N ha^-1 yr^-1; applied as NH₄NO₃) and S addition (0 and 30 kg S ha^-1 yr^-1; applied as Na₂SO₄). Four blocks were established in July 2006, each with four plots of 20 × 20 m randomly assigned to the treatments. Soil and understory vegetation were sampled and cover (%) of individual species of herb (height ≤ 0.5 m) and shrub (height 0.5–1 m) layers was determined in August 2012.
Important findings Seven years after the treatments began, N addition increased dissolved organic carbon and N in the mineral soil (P < 0.05), whereas S addition decreased exchangeable cations (P < 0.05) in the forest floor. In the shrub layer, species evenness, and overall diversity were decreased by N addition (P < 0.05) due to increases in abundance of nitrophilous species and S addition (P < 0.01) due to decreased cation concentrations in soils. Total shrub cover decreased with S addition (P < 0.10). Nitrogen and S addition affected neither species richness nor evenness in the herb layer. However, permutational multivariate analysis of variance and non-metric multidimensional scaling analyses (based on plant cover) indicated that the effect of N and S addition on understory plant species composition in the both shrub and herb layers was species-specific. Addition of N decreased foliar phosphorus and potassium concentrations in some species, suggesting potential risk of N-meditated nutrient imbalance in those species. Our results indicate that long-term elevated levels of N and S deposition can negatively impact plant nutrition and decrease the diversity of the understory plant community in boreal forests in northern Alberta, Canada. However, considering that the current N and S deposition rates in northern Alberta are much lower than the rates used in this study, N and S deposition should not negatively affect plant diversity in the near future.

Nitrogen (N) enrichment caused by human activities threatens biodiversity and alters plant community composition and structure. It has been found that heavy and infrequent N inputs may over-estimate species extinction, but it remains unclear whether plant community structure will equally respond to frequent reactive N enriched conditions.

We independently manipulated the rates and the frequencies of N addition in a temperate steppe, northern China, between 2008 and 2013.

We found that plant community structure changes, measured by ‘Euclidean distance’ involving species richness, composition and productivity, were significantly positively related to increasing N enrichment rates rather than frequencies. Changes in aboveground net primary productivity (ANPP), plant species richness and shifts in dominant species were observed. Community ANPP increased with N enrichment, whereas species richness reduced. The frequency of N enrichment increased species richness but had no impacts on community ANPP and the relative ANPP of the two dominant species, C₃perennial bunchgrass Stipa grandis and C₃ perennial rhizome grass Leymus chinensis. The ANPP and relative ANPP of the two dominant species were significantly negatively correlated with each other. Moreover, changes in the relative ANPP of S. grandis was negatively associated with the changes in community structure. After 5 years’ treatment, direct influence of the frequency of N enrichment on plant community structure was not observed, but the effects of the rate of N enrichment were apparent. Our results suggested that further study in various ecosystems and with long-term and well-controlled comparisons the frequency vs. the rate of N enrichment may still be needed.

Aims Dune building processes are affected by interactions between the growth of ecosystem engineering dune grasses and environmental factors associated with disturbance such as sand burial and sea spray. Research investigating how species interactions influence dune community structure and functional trait responses in high abiotic stress environments is minimal. We investigated how species interactions influence the functional trait responses of three dominant dune grasses to common abiotic stressors.
Methods We performed a multi-factorial greenhouse experiment by planting three common dune grasses (Ammophila breviligulata Fern., Uniola paniculata L. and Spartina patens Muhl.) in different interspecific combinations, using sand burial and sea spray as abiotic stressors. Sand burial was applied once at the beginning of the study. Sea spray was applied three times per week using a calibrated spray bottle. Morphological functional trait measurements (leaf elongation, maximum root length, aboveground biomass and belowground biomass) were collected at the end of the study. The experiment continued from May 2015 to August 2015.
Important findings Species interactions between A. breviligulata and U. paniculata negatively affected dune building function traits of A. breviligulata, indicating that interactions with U. paniculata could alter dune community structure. Furthermore, A. breviligulata had a negative interaction with S. patens, which decreased S. patens functional trait responses to abiotic stress. When all species occurred together, the interactions among species brought about coexistence of all three species. Our data suggest that species interactions can change traditional functional trait responses of dominant species to abiotic stress.

Aims Lignin is generally considered as an important indicator of soil organic carbon (SOC) storage and dynamics. To evaluate the effects of plant communities and soil depth on soil lignin is critical to better understand forest carbon cycling.
Methods We compared lignin content and chemical signature in three soil depths of four major plant communities in a subtropical forest, which located in the north part of Wuling Mountains, China. Lignin was measured using CuO oxidation method.
Important findings Both lignin content and its biochemical signature in plant litter varied among communities. However, these differences were mostly no longer exist in the upper soil layers. Lignin chemistry in soils inherited some of the biochemical signature of lignin in litter, but in a diminished magnitude. These results suggest that different plant communities had similar decomposition process with varying rates, caused diminished differences in lignin content and its biochemical signature. Lignin content decreased with soil depth, but the biochemical signature of lignin was not significantly different among soil layers for all communities, which suggests that vertical movement of lignin within the soil profile is very likely a key process causing this similar biochemical signature. These results emphasized the important roles of lignin inputs and soil eluviation in shaping lignin characteristics and distribution in forest soils, which pinpoint the urgent need to consider hydrological processes in studying forest soil carbon cycling.

Aims As a unique geographical unit of the earth, the Tibetan Plateau is extensively covered by various Stipa communities. However, their vegetation features have not been reported systematically till now, especially in some scantily explored regions. In this study, we endeavor to reveal the community types, quantitative characteristics and climatic distribution patterns of Stipa steppes in these areas based on primary relevés obtained from fieldwork.
Methods We collected a total of 223 plots in 79 study sites in the Changthang Plateau and the Yarlung Zangbo Valley, ranging from 79°E to 91°E. The categories of Stipa formations were identified according to the classification scheme in Vegetation of China and then verified by Nonmetric Multidimensional Scaling. We performed detrended correspondence analysis and detrended canonical correspondence analysis to hunt for the alteration of Stipa communities along the precipitation gradient. Quantitative characteristics including species richness, coverage, biomass as well as importance values (IV) of dominant species were calculated and visualized, respectively.
Important findings Stipa steppes in scantily explored regions of the Tibetan Plateau are classified into 11 formations but major formations are rather limited in number. Formation (form.) Stipa purpurea is the most widespread Stipa assemblages not only in scantily explored regions but also across the whole Tibetan Plateau. The characteristics of Stipa communities, including coverage, species richness, productivity and IV of dominant species, demonstrate the features of typical alpine steppes on the Tibetan Plateau. Precipitation proves to be the prime climatic factor controlling the distribution patterns of Stipa assemblages. Form. Stipa subsessiliflora var. basiplumosa and form. Stipa glareosa normally distribute in arid habitats, but rainfall for the former is of greater variance. Form. Stipa roborowskyi and form. Stipa capillacea favor moderately moist environment. Form. Stipa purpurea and form. Stipa roborowskyi can tolerate a fairly broad range of precipitation.

Carbon (C), nitrogen (N) and phosphorus (P) stoichiometry strongly affect functions and nutrient cycling within ecosystems. However, the related researches in shrubs were very limited. In this study, we aimed to investigate leaf stoichiometry and its driving factors in shrubs, and whether stoichiometry significantly differs among closely related species.

We analyzed leaf C, N and P concentrations and their ratios in 32 species of Ericaceae from 161 sites across southern China. We examined the relationships of leaf stoichiometry with environmental variables using linear regressions, and quantified the interactive and independent effects of climate, soil and species on foliar stoichiometry using general linear models (GLM).

The foliar C, N and P contents of Ericaceae were 484.66, 14.44 and 1.06 mg g?1, respectively. Leaf C, N and P concentrations and their ratios in Ericaceae were significantly related with latitude and altitude, except the N:P insignificantly correlated with latitude. Climate (mean annual temperature and precipitation) and soil properties (soil C, N and P and bulk density) were significantly influenced element stoichiometry. The GLM analysis showed that soil exerted a greater direct effect on leaf stoichiometry than climate did, and climate affected leaf traits mainly via indirect ways. Further, soil properties had stronger influences on leaf P than on leaf C and N. Among all independent factors examined, we found species accounted for the largest proportion of the variation in foliar stoichiometry. These results suggest that species can largely influence foliar stoichiometry, even at a lower taxonomic level.

Aims The impact of global warming on belowground processes, especially on fine root production, is poorly understood in comparison with its aboveground counterpart.
Methods Here, we compiled 227 measurements to assess the influence of temperature and precipitation on fine root biomass of Norway spruce (Picea abies [L.] Karst) forest ecosystems in the Eurasia boreal region.
Important findings We found that fine root biomass decreased significantly with latitudes. There was a biomass increase of 0.63 Mg ha^-1 and 0.32 Mg ha^-1 for fine roots <2 and <1 mm in diameter, respectively, with 1°C increase of mean annual temperature. There was an increase of 0.5 and 0.1 Mg ha^-1 per 100 mm year^-1 precipitation for the two size classes of fine roots. If the adaption of root production can match the pace of global warming and water is not a limiting factor for plant growth, fine root biomass would be expected to increase by 40–140% in response to the predicted increase in temperature (3–10°C) over the next century. Our analyses highlighted the strongly positive influences of temperature and precipitation on belowground function, suggesting that predicted future climate change could substantially enhance belowground biomass in the boreal region where the greatest warming is anticipated. This potential increase of belowground biomass, coupled with aboveground biomass, may provide a better understanding of climate–ecosystem feedbacks.

Aims Riparian forests in the Brazilian Cerrado, also known as gallery forests, are very heterogeneous in structure, species composition and ecological features due to strong and abrupt variations of soil, hydrological and topographic properties. However, what are the variables driving forest carbon stock and productivity, mortality and recruitment in disturbed gallery forests?
Methods We used 36 permanent plots data from a gallery forest in the Brazilian Cerrado. We investigated how tree community dynamics vary in a gallery forest on two contrasting disturbance levels—logged and non-logged—across a topographic gradient intrinsically related to differences in moisture conditions, edge effects, as well as soil fertility and texture.
Important findings Soil variables were reduced into principal components and we used structural equation modelling to disentangle covarying variables. We also included carbon stocks as a determinant variable of dynamics rates. Logged forest had 50% higher productivity than non-logged forest and streamside forest had aboveground carbon stocks 70% higher than the forest edge. Both logging and natural disturbance drove variation in the carbon stocks which contributed to shaping productivity and recruitment rates. Distance from the river also drove mortality and carbon stock rates. Areas with high-carbon stocks favoured higher competition and lessened productivity and recruitment rates. Although soil fertility and texture are considered crucial components shaping forest dynamics, there was no clear influence of those variables on the present forest, probably because the strong effects of soil moisture, forest edge and disturbance disrupted the correlation between soil and forest dynamics.

Aims Effects of climate change, especially changes in temperatures and precipitation patterns, are particularly pronounced in alpine regions. In response, plants may exhibit phenotypic plasticity in key functional traits allowing short-term adjustment to novel conditions. However, little is known about the degree of phenotypic plasticity of high elevation species relative to mid elevation congeners.
Methods We transplanted 14 herbaceous perennial species from high elevation into two common gardens (1050 and 2000 m.a.s.l.) in the Swiss Alps, and we examined plastic responses in key functional traits to changes in temperature and soil water availability. This design was replicated with 14 congeneric species from mid elevation to assess if the degree of phenotypic plasticity differs between mid and high elevation species. Survival was assessed across two growing seasons, while aboveground biomass and specific leaf area (SLA) were measured after the first growing season, and biomass allocation to belowground and reproductive structures after the second. Moreover, a phenotypic plasticity index was calculated for the functional traits to compare the degree of plasticity between mid and high elevation species.
Important findings Aboveground biomass was higher in mid elevation species relative to high elevation congeners in all treatments, yet decreased for both with elevation and drought. Similarly, SLA decreased with elevation and drought. Root mass fraction (RMF) was generally higher in high elevation species, and decreased with drought at the lower site. Drought increased the allocation to reproductive structures, especially when plants were grown at their elevation of origin. Interestingly, no difference was found in the degree of phenotypic plasticity averaged across mid and high elevation species for any of the studied functional traits. These results indicate that phenotypic plasticity in the focal traits did not depend on the elevation of origin of the species. Plasticity was not related to environmental heterogeneity, nor constrained by selective pressures at high elevation. However, both species groups showed a remarkable capacity for short-term acclimation to a prospective climate through rapid adjustments in key functional traits.

Cistus albidus reproductive traits have been studied on typical Mediterranean shrublands along a water availability gradient in Northeastern Iberian Peninsula. Germination of this species is known to be highly favoured by fire. Moreover, Mediterranean species are particularly dependent on water availability. Therefore, we establish the hypothesis that in addition to fire disturbance, seedling recruitment in this Mediterranean seeder will be improved in drought-induced episodes resulting in generalized canopy die-off.

Individuals of several populations of C. albidus were collected and the size, weight and number of fruits and seeds were measured. Germination tests were also carried out on five pre-germination treatments: seeds’ exposure to heat shock, imbibition, two cycles of imbibition/desiccation and the combination of heat shock and imbibition and imbibition/desiccation cycles. Moreover, the number of seedlings after a drought event was surveyed in the field and correlated with canopy die-off.

Our study shows the variability of the C. albidus reproductive traits, such as germination rate or fruit production, along the water availability gradient. This variability resulted in a decrease in fruit production but an increase in successful germination under drier conditions. Cistus albidus seeds increased germination with heat, demonstrating their ability to successfully establish after fire. However, recruitment was not exclusively fire dependent since seedling establishment was higher under C. albidus canopies that had collapsed after the extreme drought. Finally, adult density increased C. albidus die-off and mortality, as well as seedling establishment. These results suggest that this species exhibits a trade-off between different reproductive outcomes (i.e. seed production vs. viability), which in turn is determined by climate. This study also provides evidence of how intra-specific competition, climate, particularly drought events and fire disturbance, can determine the success of key early stages of the life history of a common, representative Mediterranean fire-prone seeder shrub.

Aims Distyly is one of the most widespread floral polymorphisms promoting cross-fertilization. Evolutionary transition from obligate cross-fertilized distyly to predominantly self-fertilized homostyly is frequently documented in various groups. However, empirical studies concerning the ecological factors connected with this transition are still lacking. Primula chungensis, suggested to be evolving from distyly to homostyly, provides an ideal model for the study of the ecological factors concerned with this transition. We study P. chungensis to understand if autonomous self-fertilization would provide reproductive assurance for the self-fertilized homo-styled morph in the field.
Methods The incompatibility features of P. chungensis were tested with hand-pollination experiments. We compared the capacity of autonomous self-fertilization between the distylous and homo-styled morph of P. chungensis in the field by excluding the pollinators with bags. In addition, the degrees of herkogamy of some P. chungensis plants were between the short-styled and homo-styled morphs. These plants were studied to understand whether they were able to obtain greater reproductive assurance when the herkogamy in the flowers was reduced.
Important findings All three morphs of P. chungensis were highly self- and intra-morph compatible. The degree of herkogamy positively correlated with the capacity for autonomous self-fertilization. A negative correlation between the degree of herkogamy and the magnitude of pollen limitation was found, but no significant correlation was found between the degree of herkogamy and the contribution of cross-fertilization to overall fertilization. This study suggests that reducing the degree of herkogamy can significantly increase the reproductive assurance for a self-compatible plant. Our results provided evidence that the homo-styled morph of P. chungensis had the highest capacity for autonomous self-fertilization and the highest seed production in the field, because autonomous self-fertilization provided reproductive assurance for the homo-styled morph. This may cause selection towards the transition from distyly to homostyly.

To explore the pattern of the leaf functional traits of shrub species along a latitudinal gradient in eastern China and determine the driving factors of leaf trait variation at a large scale.

We investigated the leaf thickness (LT), leaf area (LA), specific leaf area (SLA) and leaf dry mass content (LDMC) of 185 shrub species from 13 sites across eastern China. The trends of these four-leaf traits were analyzed with respect to latitude, and the differences between different life forms (e.g., evergreen and deciduous) and habitats (e.g., understory and typical) were compared. We quantified the effects of the plant life forms and environmental factors on the leaf traits via mixed-model analyses.

The LT and LA decreased, whilst and the LDMC increased, as the latitude increased, and significant differences in these traits were observed between the different plant life forms. The LT and LA were smaller, whereas the SLA and LDMC were larger in deciduous shrubs than in evergreen shrubs. Among the different habitats, the LA and SLA were larger, while the LDMC was smaller in understory shrubs than in typical shrub species. These results indicate that typical shrub species are better adapted to drier environments, as indicated by a reduced LT and increased LDMC. Furthermore, general linear models showed that variations in the four-leaf traits with respect to latitude were mainly caused by a shift in plant life forms.

Intraspecific trait variation (ITV) has been increasingly recognized to play an important role in understanding the underlying processes influencing community assembly. However, gaps remain in our understanding of how incorporating ITV will influence the relative importance of deterministic (e.g. habitat filtering, limiting similarity) and stochastic processes in driving community assembly at different successional stages.

We used data for eight functional traits from 55 woody species in early (24 ha) and late (25 ha) successional temperate forest plot in northeast China. We employed an approximate Bayesian computation approach to assess the relative contribution of stochastic processes, habitat filtering and limiting similarity in driving community structure. We then compared the results with and without intraspecific trait variation to investigate how ITV influences the inferred importance of each process.

We found that when analyzing interspecific trait variation only (i.e. without ITV), stochastic processes were observed most frequently in driving community composition, followed by habitat filtering and limiting similarity in both forests. However, ITV analyses showed that the relative importance of both deterministic processes (habitat filtering and limiting similarity) increased in early successional forest, but remained virtually unchanged in late successional forest. Our study reveals the distinctive influence of ITV on the inference of underlying processes in a context of succession and reinforces the need to estimate ITV for making correct inferences about underlying ecological processes.

Aims Plants use a variety of hydraulic strategies to adapt to seasonal drought that differ by species and environmental conditions. The early-diverging Magnoliaceae family includes two closely related genera with contrasting leaf habits, Yulania (deciduous) and Michelia (evergreen), which naturally inhabit temperate and tropical regions, respectively. Here, we evaluate the hydraulic strategy of species from both genera that have been ex situ conserved in a subtropical region to determine how they respond to the novel cool–dry season climatic pattern.
Methods We measured ecophysiological traits in five Michelia and five Yulania species conserved in the South China Botanical Garden in both wet and dry season conditions and monitored the whole-year sap flow for four of these species.
Important findings We found that Magnoliaceae species that have been ex situ conserved in a subtropical climate did not suffer from excessive water stress due to the mild drought conditions of the dry season and the ecophysiological adjustments the species made to avoid this stress, which differed by leaf habit. Specifically, deciduous species completely shed their leaves during the dry season, while evergreen species decreased their turgor loss points, dry mass based photosynthetic rates, stomatal conductance and specific leaf areas (SLAs) compared to wet season measurements. In comparing the two distinct leaf habits during the wet season, the leathery-leaved evergreen species had higher leaf hydraulic conductance and leaf to sapwood area ratios than the papery-leaved deciduous species, while the deciduous species had greater hydraulic conductivity calculated on both a stem and leaf area basis, dry mass based photosynthetic rates, leaf nutrients, SLAs and stomatal sizes than the evergreen species. Interestingly, species from both genera maintained similar sap flow in the wet season. Both photosynthetically active radiation and vapour pressure deficit affected the diurnal patterns of sap flow in the wet season, while only vapour pressure deficit played a dominant role in the dry season. This study reveals contrasting hydraulic strategies in Yulania and Michelia species under subtropical seasonal conditions, and suggests that these ecophysiological adjustments might be affected more by leaf habit than seasonality, thus reflecting the divergent evolution of the two closely related genera. Furthermore, we show that Magnoliaceae species that are ex situ conserved in a subtropical climate are hydraulically sound, a finding that will inform future conservation efforts of this ancient family under the threat of climatic change.

The impacts of future global warming of 1.5°C and 2°C on the productivity and carbon (C) storage of grasslands in China are not clear yet, although grasslands in China support ~45 million agricultural populations and more than 238 million livestock populations, and are sensitive to global warming.

This study used a process-based terrestrial ecosystem model named ORCHIDEE to simulate C cycle of alpine meadows and temperate grasslands in China. This model was driven by high-resolution (0.5° × 0.5°) climate of global specific warming levels (SWL) of 1.5°C and 2°C (warmer than pre-industrial level), which is downscaled by EC-EARTH3-HR v3.1 with sea surface temperature and sea-ice concentration as boundary conditions from IPSL-CM5-LR (low spatial resolution, 2.5° × 1.5°) Earth system model (ESM).

Compared with baseline (1971–2005), the mean annual air temperature over Chinese grasslands increased by 2.5°C and 3.7°C under SWL1.5 and SWL2, respectively. The increase in temperature in the alpine meadow was higher than that in the temperate grassland under both SWL1.5 and SWL2. Precipitation was also shown an increasing trend under SWL2 over most of the Chinese grasslands. Strong increases in gross primary productivity (GPP) were simulated in the Chinese grasslands, and the mean annual GPP (GPP_MA) increased by 19.32% and 43.62% under SWL1.5 and SWL2, respectively. The C storage increased by 0.64 Pg C and 1.37 Pg C under SWL1.5 and SWL2 for 50 years simulations. The GPP_MA was 0.670.880.39 (0.82) (model meanmaxmin0.670.390.88 (0.82) (model meanminmax (this study)), 0.851.240.45 (0.97)0.850.451.24 (0.97) and 0.941.300.61 (1.17)0.940.611.30 (1.17) Pg C year−1 under baseline, SWL1.5 and SWL2 modeled by four CMIP5 ESMs (phase 5 of the Coupled Model Inter-comparison Project Earth System Models). In contrast, the mean annual net biome productivity was −18.554.47−40.37 (−3.61),−18.55−40.374.47 (−3.61),18.6564.03−2.03 (10.29)18.65−2.0364.03 (10.29) and 24.1538.778.38 (24.93)24.158.3838.77 (24.93) Tg C year−1 under baseline, SWL1.5 and SWL2 modeled by the four CMIP5 ESMs. Our results indicated that the Chinese grasslands would have higher productivity than the baseline and can mitigate climate change through increased C sequestration under future global warming of 1.5°C and 2°C with the increase of precipitation and the global increase of atmospheric CO₂ concentration.

Probabilistic models of species co-occurrences predict aggregated intraspecific spatial distributions that might decrease the degree of joint species occurrences and increase community richness. Yet, little is known about the influence of intraspecific aggregation on the co-occurrence of species in natural, species-rich communities. Here, we focus on early plant succession and ask how changes in intraspecific aggregation of colonizing plant species influence the pattern of species co-existence, richness and turnover.

We studied the early vegetation succession in a six ha constructed catchment within the abandoned part of a lignite mine in NE Germany. At two spatial scales (1- and 25-m2 plots), we compared for each pair of species the intraspecific degree of aggregation and the pattern of co-occurrence and compared observed relationships with temporal changes in important species functional traits.

The majority of species occurred in an aggregated manner, particularly in the first 2 years of succession. In pairwise comparisons, we found an excess of segregated species occurrences leading to a positive link between intraspecific aggregation and pairwise species segregation as predicted by the aggregation hypothesis, particularly at the lower spatial resolution. The degree of intraspecific aggregation was negatively correlated with the community-wide level of species spatial turnover and with plot species richness. Our results are the first direct confirmation that increasing intraspecific aggregation and interspecific competitive interactions counteract in shaping plant community structure during succession. The respective effects of aggregation were strongest at intermediate states of early succession.

Aims Fires play a crucial role mediating species interactions in the Mediterranean Basin, with one prominent example being the nursing effect of post-fire resprouting shrubs on tree recruits, which then outcompete their benefactors throughout succession. Yet, the community structuring role of resprouting shrubs as potential facilitators of post-fire recruiting subshrub species, which are commonly outcompeted in late post-fire stages, has been overlooked. The aims of this work were to investigate (i) whether proximity to resprouting shrubs increased the demographic performance of a fire-adapted carnivorous subshrub and (ii) whether mature shrubs negatively affected the performance of established plants through interference with prey capture.
Methods To evaluate the facilitative effects of resprouting shrubs, we sowed seeds of Drosophyllum lusitanicum, a carnivorous, seeder pyrophyte, into two microhabitats in recently burned heathland patches defined by proximity to resprouting shrubs. We monitored key demographic rates of emerged seedlings for 2 years. To test for competitive effects of shrubs on plant performance at a later habitat regeneration stage, we placed greenhouse-reared, potted plants into distinct microhabitats in neighboring burned and unburned heathland patches and monitored prey capture. Both experiments were performed in the Aljibe Mountains at the Northern Strait of Gibraltar and were replicated in 2 years.
Important findings Resprouting shrubs significantly improved survival, juvenile size and flowering probability compared with open microhabitats, and had no significantly negative effects on the growth of recruits. Prey capture was significantly lower in unburned heathland patches compared with burned ones, thus partly explaining the decrease in survival of Drosophyllum individuals in mature heathlands. However, microhabitat did not affect prey capture. Our findings suggest that not only periodic fires, removing biomass in mature stands, but also resprouting neighbors, increasing establishment success after fire, may be important for the viability of early successional pyrophytes.

Aims Lianas are expected to influence composition, structure and functioning of forest systems due to unequal distribution across the potential set of host plants. However, our understanding of mechanisms associated with preferences for specific hosts is still limited, and so is our ability to discern between endogenous and exogenous forces driving forest dynamics in the long run. In this paper, we evaluated whether the dominant liana Hedera helix can indirectly contribute to the eventual dominance of the small multi-stemmed tree Corylus avellana in a remnant temperate forest in central Iberian Peninsula from comparatively reduced liana infestation on C. avellana relative to co-occurring woody species.
Methods Through principal component analysis and co-occurrence analysis, we studied the distribution and spatial association between woody species and the liana H. helix. We analyzed the relationship between the number of species in a plot and the number of species infested by the liana to test the hypothesis that H. helix is a generalist liana. Through generalized linear mixed models, we tested the dynamic-multi-stemmed growth form of C. avellana as a plausible life strategy to withstand, in the long run, the liana infestation. In particular, we tested (i) the relationship between stem size and the probability of H. helix infestation including all the tree species within plots and (ii) the relationship between stem size and mortality as evidence of the stem turn over in the tree C. avellana .
Important findings Our results indicate that H. helix and C. avellana significantly co-occur in mature stands of this remnant temperate forest where pioneer woody species are absent. Hedera helix severely infests all the woody species whenever stem size exceed ≈25 cm perimeter and there is physical contact at the base of the stem. This implies that all the trees in the community are potential hosts for H. helix. Mixed models indicate that both, infestation by H. helix and stem mortality, are positively related to C. avellana stem perimeter. Reduced long-term infestation of the liana by means of a multi-stemmed growth form with high stem turnover in C. avellana might be an advantage with respect to unipodial tree species. Thus, the liana-tree coexistence pattern may be interpreted as an indirect positive interaction that, contrary to previous findings, results here in species dominance instead of species coexistence.

Aims Soil plays an important role in the formation and heterogeneity of habitats and thus can cause changes in vegetation structure and plant diversity. The differentiation between Cerrado/savanna and forest is well known, but the relationship between soil and habitats from savannic or forest formations still needs to be better understood, particularly in tropical ecotonal areas. We studied the association between attributes of plant communities, namely structure and diversity, and physicochemical characteristics of soils in the Caatinga domain at the transition to Cerrado in Brazil.
Methods Chemical and physical analyses of soils were performed in samples of 38 plots from savannic formations and 30 plots from forest formations. Vegetation was characterized floristically and structurally in all plots, five habitats being assessed in each plant formation. Soil features and vegetation parameters were highly distinct among the different habitats.
Important findings In general, forest habitats were more nutrient rich than savannic formation. Furthermore, soil variables showed effects both on vegetation structure and on its species diversity, more pronouncedly in the savannic formations. Habitats were structurally distinct, and diversity differed between savannic and forest communities; however, a higher differentiation occurred when the savannic formation habitats were compared among them. Although plant diversity did not differ among forest formation habitats, soil attributes showed a close relationship with edaphic factors and can contribute for similar vegetation. The soil–vegetation relationship in highly diverse ecotonal landscapes is important from the conservation biology point of view and aid in the execution of proactive plans for the maintenance of biodiversity. Thus, we noticed that diversity and soil behaves distinctly between savannic and forest communities.

The productivity of forest plantations in temperate areas is often limited by nitrogen (N), but may shift towards phosphorus (P) limitation with increasing atmospheric N deposition. Nutrient resorption is a nutrient conservation strategy in plants. Although data on nutrient resorption are available for overstory trees, there are few data for understory vegetation.

We examined leaf N and P concentrations and N and P resorption efficiencies (NRE and PRE, respectively) in eight understory species in 11- and 45-year-old Larix principis-rupprechtii stands subjected to N supplementation over a 3-year period.

Leaf N concentrations and N:P ratios increased and P concentrations decreased, with N input in species within the 45-year-old stand, but not in the 11-year-old stand. NRE and PRE were not altered by N input in any of the species in either stand, but N resorption proficiency decreased and P resorption proficiency increased, in the species in the 45-year-old stand. Thus, the growth of understory species may be more P-limited in the 45- versus 11-year-old stand, and nutrient resorption proficiency was more sensitive to N addition than nutrient resorption efficiency. These results will improve the understanding of nutrient use strategies and their responses to N addition in understory vegetation. The contrasting effects of N addition on nutrient status between stand ages cannot be ignored when modeling ecosystem nutrient cycling under global N deposition conditions.

Remote sensing technology has been proved useful in mapping grassland vegetation properties. Spectral features of vegetation cover can be recorded by optical sensors on board of different platforms. With increasing popularity of applying unmanned aerial vehicle (UAV) to mapping plant cover, the study aims to investigate the possible applications and potential issues related to mapping leaf area index (LAI) through integration of remote sensing imagery collected by multiple sensors.

This paper applied the collected spectral data through field-based (FLD) and UAV-borne spectroradiometer to map LAI in a Sino–German experiment pasture located in the Xilingol grassland, Inner Mongolia, China. Spectroradiometers on FLD and UAV platforms were taken to measure spectral reflectance related to the targeted vegetation properties. Based on eight vegetation indices (VIs) computed from the collected hyperspectral data, regression models were used to inverse LAI. The spectral responses between FLD and UAV platforms were compared, and the regression models relating LAI with VIs from FLD and UAV were established. The modeled LAIs by UAV and FLD platforms were analyzed in order to evaluate the feasibility of potential integration of spectra data for mapping vegetation from the two platforms.

Results indicated that the spectral reflectance between FLD and UAV showed critical gaps in the green and near-infrared regions of the spectrum over densely vegetated areas, while the gaps were small over sparsely vegetated areas. The VI values from FLD spectra were greater than their UAV-based counterparts. Out of all the VIs, broadband generalized soil-adjusted vegetation index (GESAVI) and narrow-band nNDVI2 were found to achieve the best results in terms of the accuracy of the inversed LAIs for both FLD and UAV platforms. We conclude that GESAVI and nNDVI2 are the two promising VIs for both platforms and thus preferred for LAI inversion to carry spectra integration of the two platforms. We suggest that accuracy on the LAI inversion could be improved by applying more advanced functions (e.g. non-linear) considering the observed bias for the difference between the UAV- and FLD-inversed LAIs, especially when LAI was low.

Aims Community assembly persists as a key topic in ecology due to the complex variation in the relative importance of assembly forces and mechanisms across spatio-temporal scales and ecosystems. Here we address a forest–savanna vegetation mosaic in the Brazilian Atlantic forest to examine the role played by soil attributes as determinants of community assembly and organization at a landscape spatial scale.
Methods We examined soil and plant assemblage attributes across 23 plots of forest and savanna in a 1600 km 2 landscape exposed to the same climatic conditions in the Atlantic forest region of northeast Brazil. Assemblage attributes included species richness, taxonomic and functional composition (community weighted mean, CWM) and functional diversity (quadratic diversity; Rao's quadratic entropy index) relative to plant leaf area, specific leaf area, leaf dry matter content, thickness and succulence.
Important findings Our results suggest that forest and savanna patches exposed to the same climatic conditions clearly differ in terms of soil attributes, plant assemblage structure, taxonomic and functional composition. By selecting particular plant strategies relative to resource economy, soil potentially affects community structure, with forest assemblages bearing more acquisitive resource-use strategies, while conservative plant strategies are more frequent in savannas. Accordingly, savanna–forest mosaics in the Atlantic forest region represent spatially organized plant assemblages in terms of taxonomic and functional features, with a signal of trait convergence in both vegetation types. Soil-mediated filtering thus emerges as a potential deterministic assembly force affecting the spatial organization of savanna–forest boundaries and mosaics.

Aims Understanding the role of genetics in biological invasions has become an important aspect for modern plant ecology. Many studies suggest that increased ploidy level benefits the success of an invasive species, but the basis for this phenomenon is not fully understood. In its native, North American range, Solidago gigantea has three geo-cytotypes comprising di-, tetra- and hexaploid populations, while in Europe, where it is highly invasive, S. gigantea stands are composed primarily of tetraploid individuals. Our study investigates whether North American hexaploids can induce a greater risk of invasion, due to their higher performance in a non-native range, as compared to the existing tetraploids of that range.
Methods We performed greenhouse and common garden experiments along with microsatellite analyses to test whether differences in chromosome number and origin of the species mean superior fitness in the introduced range.
Important findings Genetic diversity was significantly higher in the native hexaploid populations (A R = 6.04; H e = 0.7794), rather than the non-native tetraploid populations (A R = 4.83; H e = 0.6869). Furthermore, differentiation between geo-cytotypes was moderate (ρ ST = 0.1838), which was also confirmed by their clear segregation in principal component analysis and structure analyses, proving their different genetic structure. In contrast to genetic diversity, the non-native tetraploid geo-cytotype performed better in the common garden experiment, implying that higher genetic diversity does not always mean better success. Our results suggest that native hexaploids do not present a greater risk, as assessed by their performance in the introduced range, when compared to the non-native tetraploids, as was suggested by previous studies. Nevertheless, their introduction is still undesirable due to their different genetic structure, which, through hybridization, could give a new drive to the invasion of S. gigantea .

There is much evidence that plant competition below ground is size symmetric, i.e. that competing plants share contested resources in proportion to their sizes. Several researchers have hypothesized that a patchy distribution of soil nutrients could result in size-asymmetric root competition. We tested this hypothesis.

In a greenhouse experiment, Triticum aestivum (wheat) individuals of different initial sizes were grown alone or with below-ground competition from one neighbour, in 1 m tall, narrow containers in a nitrogen-poor field soil with (i) no added nitrogen, (ii) nitrogen fertilizer mixed into the upper 50 cm, and (iii) the same amount of fertilizer mixed into a 20–30 cm deep layer. We measured total leaf length throughout the experiment, and above-ground biomass and nitrogen concentration at harvest. We also measured root depth and frequency over time in a subset of containers.

Competing plants were half the size of non-competing plants, meaning that root competition was very strong. Root competition was size-asymmetric to some degree in all soil treatments. Neighbours larger than the target plant showed a greater per-unit-size effect on target growth than neighbours smaller than the target. Size variation increased over time for competing individuals, but decreased for non-competing pairs. Contrary to expectations, the presence of a high-nutrient patch reduced the strength and size asymmetry of competition temporarily. Size asymmetry in poor, deep soils may result from directionality in resource interception as roots compete for limited nutrients by growing deeper into soil layers that have not yet been exploited. Root competition can be size asymmetric, but not to the same degree as competition for light.

The ground level of boreal pine forests consists of a dense layer of ericaceous shrubs, herbs, grasses, mosses and lichens. The primary productivity of this forest floor vegetation is notable but the role the most common ericoid dwarf shrub plant species, Calluna vulgaris, Vaccinium myrtillus and Vaccinium vitis-idaea, play in carbon (C) cycling in these ecosystems is poorly understood. Here, we studied their C dynamics in detail using plants of similar size (age 14–19 months) in a microcosm study.

We determined the full C balances of these dwarf shrubs for the first time and compared them to those of Pinus sylvestris by using long-term biomass accumulation, 13C pulse labelling and CO₂ exchange measurements in a controlled laboratory experiment.

Pinus sylvestris had significantly higher biomass-based C fluxes than dwarf shrubs, both aboveground and belowground, but the dwarf shrubs did not differ in the biomass-based fluxes. We showed that root respiration of the evergreen ericoid dwarf shrubs was sensitive to the aboveground light conditions as belowground respiration was 50–70% higher under light compared with dark conditions. Such light-related differences were not observed for Scots pine. The observed differences in C dynamics are important in estimating the origin of belowground CO₂ fluxes and in evaluating their biological relevance. Our results improve current understanding of CO₂ sources and sinks in boreal ecosystems.

Aims Pigment composition is an important functional trait that can be affected by environmental factors. The objective of this study was to investigate the effect of soil salinity on pigment composition in Suaeda salsa by comparing chlorophyll and betacyanin content in the Liaohe estuary wetland, a typical coastal wetland in northeast China.
Methods We investigated the plant biomass, percentage of red leaves and pigment content (chlorophyll a, chlorophyll b and betacyanins) in S. salsa in intertidal and supratidal zones of the upper, middle and lower reaches of the Liaohe estuary wetlands. The Na + content of both the soil and plant was also measured. Full analysis of variance and multivariate analysis were used to compare differences in pigment content and Na + content between the supratidal and intertidal zones.
Important findings Pigment composition was significantly affected by soil salinity. With increasing soil salinity, the percentage of red leaves was higher in the intertidal zone than in the supratidal zone. In all three reaches, plants had lower chlorophyll a content and higher betacyanin content in the intertidal zone than in the supratidal zone. Compared to chlorophyll a, chlorophyll b was less sensitive to soil salinity. There were no differences in chlorophyll b content between the intertidal and supratidal zones in the upper and lower reaches. Furthermore, pigment composition was associated with both the plant tissue and soil Na + content. Compared to the supratidal zone, the intertidal zone had a higher Na + content in plants. There was a negative relationship between plant chlorophyll content and soil Na + content, but a positive relationship between betacyanin content and soil Na + content. Overall, the results indicated that there might be a trade-off between leaf chlorophyll and betacyanin content in S. salsa to maintain its growth and survival in high salinity environments.

Aims The relative plant type sensitivity and selected community interactions under increased UV-B radiation where examined. Specifically, we investigated: (i) if there are differences among growth forms in regard to their sensitivity to UV-B radiation, (ii) if increased UV-B radiation influences the plant competitive balance in plant communities and (iii) the response mechanisms of the UV-B radiation-sensitive species that might increase their fitness.
Methods To answer our research questions, we used a mechanistic model that, for the first time, integrated the effects of increased UV-B radiation from molecular level processes, whole plant growth and development, and community interactions.
Important findings In the model simulations, species types exhibited different levels of sensitivity to increased UV-B radiation. Summer C₃ and C₄ annuals showed similar growth inhibition rates, while biennials and winter C₃ annuals were the most sensitive. Perennials exhibited inhibitions in growth only if increased UV-B radiation results in increases in metabolic rates. In communities, species sensitive to UV-B radiation may have a competitive disadvantage compared to resistant plant species. But, sensitive species may have a wide array of responses that can increase their fitness and reproductive success in the community, such as, increased secondary metabolites production, changes in timing of emergence and reproduction, and changes in seed size. While individual plants may exhibit significant inhibitions in growth and development, in communities, these inhibitions can be mitigated by small morphological and physiological adaptations. Infrequent or occasional increased UV-B radiation events should not have any lasting effect on the structure of the community, unless other environmental factors are perturbing the dynamic equilibrium.

Aims Studies have showed that arbuscular mycorrhizal fungi (AMF) can greatly promote the growth of host plants, but how AMF affect flowering phenology of host plants is not well known. Here, we conducted a pot experiment to test whether life cycle and flowering phenology traits of host plant Medicago truncatula Gaertn can be altered by AMF under low and high soil phosphorus (P) levels.
Methods The experiment was conducted in a greenhouse at Zhejiang University in China (120°19′E, 30°26′N) and had a completely randomized design with two factors: AMF treatments and soil P levels. Six AMF species (Acaulospora scrobiculata, As; Gigaspora margarita, Gma; Funneliformis geosporum, Fg; Rhizophagus intraradices, Ri; Funneliformis mosseae, Fmo and Glomus tortuosum, Gt.) were used, and two soil P levels (24.0 and 5.7 mg kg^-1 Olsen-soluble P) were designed. The six AMF species were separately inoculated or in a mixture (Mix), and a non-AMF control (NAMF) was included. When plants began to flower, the number of flowers in each pot was recorded daily. During fruit ripening, the number of mature fruits was also recorded daily. After ~4 months, the biomass, biomass P content and AMF colonization of host plant were measured. Correlation between root colonization and first flowering time, or P content and first flowering time was analyzed.
Important findings Under the low P level, first flowering time negatively correlated with root colonization and biomass P. Only host plants with AMF species As, Fg, Ri, or Mix were able to complete their life cycle within 112 days after sowing. And treatment with AMF species Fg, Gt, or As resulted in two periods of rapid flower production while other fungi treatments resulted in only one within 112 days after sowing. The cumulative number of flowers produced and biomass P content were highest with species Fg. Host biomass allocation significantly differed depending on the species of AMF. Under both soil P levels, the host plant tended to allocate more biomass to fruits in the Mix treatment than in the other treatments. These results indicated that the effects of AMF on host flowering phenology and biomass allocation differed depending on AMF species and soil P levels.

A plethora of theories explain species invasion, yet when tested in isolation, support or falsification becomes contingent on study species, system and approach. Our objective was to examine community-level species invasion as a function of multiple competing hypotheses.

We used data from >3500 woodland plant species in 2750 plots in 49 national parks in eastern US deciduous forests to test multiple competing theories of species invasion: competition, empty niche, propagule pressure and latitude matching. We also tested interactions with residence time to account for non-native species naturalization and spread since arrival.

The non-native herbs generally thrived at latitudes similar to those from which they originated, but not necessarily where they were originally introduced to the eastern US. Overall, we found that each hypothesis explained at least some aspect of woodland plant species invasion, but examining them simultaneously allowed assessment of their relative strengths and interactions. Our results suggested that residence time is a strong predictor of non-native woodland plant success, particularly as it interacts with other mechanisms of invasion, such as competition (abundance of native woodland plants), climate matching (similar invaded latitude as home range), propagule pressure (distance to putative seed sources) and empty niche (relatedness to native plants). We found that initial barriers, such as distance from propagule source or suboptimal habitat, were overcome, as was resistance from native relatives. However, the biggest challenge for the non-native woodland plants appeared to be time, as they declined after ~1 to 2 centuries.

Forest biomass carbon (C) stocks are usually estimated by multiplying biomass by a C conversion factor, i.e. C concentration. Thus, tree C concentration is crucial to the assessments of forest C cycles. As stems contribute to the large fraction of tree biomass, the canonical value of 50% or other simplified values of stem C concentration are widely used to represent the values of tree C concentration in the estimations of forest C stocks at different scales. However, C concentration variations between tree organs and within tree size and their impacts on forest C stocks are still unclear.

We conducted a global analysis of organ C concentration in age-specific trees based on 576 records of tree age, size (diameter at breast height and biomass) and C concentration data to evaluate the relationships between organ C concentrations and the changes of stem C concentration with tree age and size.

Tree C concentration varied significantly with organs. Stem C concentration of trees was significantly correlated with that of other tree organs, except for barks and reproductive organs. The stem C concentration increased significantly with tree size and age, which contributed to the increases in C contents of stems and trees. Using the C concentration in stems to represent the C concentrations of other organs and the whole tree could produce considerable errors in the estimations of forest C stocks (−8.6% to 25.6% and −2.5% to 5.9%, respectively). Our findings suggest that tree C accumulation in forests is related to the size- and age-dependent increases in stem C concentration and using specific C concentration values of tree organs can improve the estimations of forest C stocks.

Aims Understanding the drivers of grassland structure and function following livestock removal will inform grassland restoration and management. Here, we investigated the effects of fire and nutrient addition on structure and function in a subtropical semi-native grassland recently released from grazing in south-central Florida. We examined responses of soil nutrients, plant tissue nutrients, biomass of live, standing dead and litter, and plant species composition to experimental annual prescribed fire applied during different seasons (wet season vs. dry season), and nutrient additions (N, P and N + P) over 9 years.
Methods Experimental plots were set up in a randomized block split-plot design, with season of prescribed fire as the main treatment and nutrient addition as the subplot treatment. Species cover data were collected annually from 2002 to 2011 and plant tissue and plant biomass data were collected in 2002–2006 and 2011. Soil nutrients were analyzed in 2004, 2006 and 2011.
Important findings Soil total phosphorus (P) levels increased substantially with P addition but were not influenced by prescribed fire. Addition of P and N led to increased P and N concentrations in live plant tissues, but prescribed fire reduced N in live tissue. Levels of tissue N were higher in all plots at the beginning of the experiment, an effect that was likely due to grazing activity prior to removal of livestock. Plant tissue N steadily declined over time in all plots, with annually burned plots declining faster than unburned plots. Prescribed fire was an important driver of standing dead and litter biomass and was important for maintaining grass biomass and percent cover. Nutrient addition was also important: the addition of both N and P was associated with greater live biomass and woody forbs. Removal of grazing, lack of prescribed fire, and addition of N + P led to a reduction of grass biomass and a large increase in biomass of a woody forb. Annual prescribed fire promoted N loss from the system by reducing standing dead and litter, but maintained desirable biomass of grasses.

Epiphytes and hemiparasites do not have direct access to soil nutrients. Epiphytes acquire nutrients through symbiosis, foliar leachates and throughfall, whilst hemiparasites have specialized structures (haustoria) to acquire nutrients from their host. Irrespective of the green leaf nutrient concentrations of epiphytes, hemiparasites and their hosts, nutrient-resorption efficiency and proficiency are expected to be the greater in epiphytes than in their hosts and in hemiparasites. These hypotheses were tested.

Green and senescing leaves of epiphytes (n = 23), hemiparasites (n = 9) and their hosts were collected, and leaf area, leaf dry weight, nutrient (nitrogen-N, phosphorus-P, potassium-K, calcium-Ca) and sodium (Na) concentrations were measured, and resorption efficiency (%) and proficiency were calculated.

Concentrations of N, P, K, Ca and Na in green leaves of epiphytes and hemiparasites were either similar or greater than those of their hosts, except for lower green leaf N concentration in hemiparasites. Epiphytes resorbed N, P, K and Na, while their hosts resorbed only N, P and K. Hemiparasites and their hosts resorbed P, K and Na while N was not resorbed. Overall, resorption efficiency was greatest in epiphytes > hemiparasites = hosts, while the resorption proficiencies were similar or greater for epiphytes and hemiparasites compared with their hosts, except for N in hemiparasites. Relatively high nutrient concentrations in epiphytes were associated with greater resorption efficiency. Understanding contrasting nutrient concentrations in epiphytes, hemiparasites and their hosts will be important in recognising their contribution to ecosystem nutrient cycling.

Aims Decades of empirical work have demonstrated how dominant plant species and nitrogen fertilization can influence the structure and function of plant communities. More recent studies have examined the interplay between these factors, but few such studies use an explicit trait-based framework. In this study, we use an explicit trait-based approach to identify potential mechanisms for community-level responses and to test ecological niche theory.
Methods We experimentally manipulated plant communities (control, ?dominant species, ?random biomass) and nitrogen (N) inputs (control, +organic N, +inorganic N) in a fully factorial design. We predicted that traits related to plants' ability to take up different forms of soil N would differ between dominant and subordinate species, resulting in interactive effects of dominant species loss and N fertilization on plant community structure and function. The study took place in a montane meadow in the Rocky Mountains, Colorado, USA.
Important findings After four years, the plant community in removal plots converged toward a species composition whose leaf and root functional traits resembled those of the previously removed dominant species. Ecosystem productivity generally increased with N addition: soil carbon efflux was ~50% greater when either form of N was added, while inorganic N addition increased aboveground biomass production by ~60% relative to controls. The increase in production was mediated by increased average height, leaf mass:area ratio and leaf dry matter content in plant communities to which we added inorganic N. Contrary to our predictions, there were no interactive effects of N fertilization and dominant species loss on plant community structure or ecosystem function. The plant community composition in this study exhibited resistance to soil N addition and, given the functional convergence we observed, was resilient to species loss. Together, our results indicate that the ability of species to compensate functionally for species loss confers resilience and maintains diversity in montane meadow communities.

The relative roles of ecological processes in structuring beta diversity are usually quantified by variation partitioning of beta diversity with respect to environmental and spatial variables or gamma diversity. However, if important environmental or spatial factors are omitted, or a scale mismatch occurs in the analysis, unaccounted spatial correlation will appear in the residual errors and lead to residual spatial correlation and problematic inferences.

Multi-scale ordination (MSO) partitions the canonical ordination results by distance into a set of empirical variograms which characterize the spatial structures of explanatory, conditional and residual variance against distance. Then these variance components can be used to diagnose residual spatial correlation by checking assumptions related to geostatistics or regression analysis. In this paper, we first illustrate the performance of MSO using a simulated data set with known properties, thus making statistical issues explicit. We then test for significant residual spatial correlation in beta diversity analyses of the Gutianshan (GTS) 24-ha subtropical forest plot in eastern China.

Even though we used up to 24 topographic and edaphic variables mapped at high resolution and spatial variables representing spatial structures at all scales, we still found significant residual spatial correlation at the 10 m × 10 m quadrat scale. This invalidated the analysis and inferences at this scale. We also show that MSO provides a complementary tool to test for significant residual spatial correlation in beta diversity analyses. Our results provided a strong argument supporting the need to test for significant residual spatial correlation before interpreting the results of beta diversity analyses.

Aims The Cape Peninsula is a small area (471 km 2) situated on the south-westernmost tip of the Core Cape Subregion (CCR) of South Africa. Within the Cape Peninsula, Fabaceae are the third most species-rich plant family (162 species) and they have the second highest number of endemic species after the Ericaceae. However, legumes are not the dominant taxa in the vegetation. They tend to show patchy distributions within the landscape and different species assemblages usually occupy particular niches at any given locality. The present study undertook to establish if edaphic factors influence legume species distribution in the Cape Peninsula and to determine the key indicator species for the different assemblages.
Methods Soils from 27 legume sites, spanning all major geological substrates of the Cape Peninsula, were analysed for 31 chemical and physical properties. Legume species present at each site were recorded and a presence/absence matrix was generated. Cluster analysis and discriminant function analysis (DFA) were run to group the sites based on overall similarity in edaphic characteristics and to identify the soil parameters contributing towards discriminating the groups. Canonical correspondence analysis (CCA) was used to test for a correlation between legume species compositions and edaphic factors. The strength of the association between legume species and site groupings based on edaphic properties was assessed using indicator species analysis.
Important findings Based on similarity in overall soil characteristics, the sites formed three clusters: one comprising sites of sandstone geology, one with dune sand sites and the third cluster comprising sites of both shale and granite geologies (hereafter referred to as soil types). The DFA confirmed the distinctness of these clusters and the CCA showed a significant correlation between legume species composition and edaphic factors. The key edaphic parameters were clay content, iron (Fe), potassium (K), sulphur (S) and zinc (Zn). These findings reveal that the Cape Peninsula is edaphically heterogeneous and edaphically distinct habitats contain discrete legume species assemblages that can be distinguished by unique indicator species. Furthermore, multiple soil parameters, rather than a single parameter, are involved. Therefore, edaphic factors play a significant role in driving the distribution of legume species in the Cape Peninsula and discrete legume species assemblages occupy distinct habitats.