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.

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.

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.

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.

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.

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.

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.

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.

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.

Crop nitrogen (N) and phosphorus (P) stoichiometry can influence food nutritive quality and many ecosystem processes. However, how and why N and P stoichiometry respond to long-term agricultural management practices (e.g. N fertilization and film mulching) are not clearly understood.

We collected maize tissues (leaf, stem, root and seed) and soil samples from a temperate cropland under 30-year continuous N fertilization and plastic film mulching treatments, measured their C, N and P concentrations (the proportion (%) relative to the sample mass), and used structural equation models to uncover the responding mechanisms for crop N and P contents (the total amount (g/m2) in crop biomass).

Long-term N fertilization increased N concentrations in all crop tissues but sharply decreased P concentrations in vegetative tissues (leaf, stem and root), thereby reducing their C/N ratio and increasing C/P and N/P ratios. The drop in P concentration in vegetative tissues was due to the dilution effect by biomass increment and the priority of P supply for seed production. In contrast, film mulching decreased N concentration but increased P concentrations in most crop tissues, thereby increasing C/N ratio and reducing C/P and N/P ratios. Film mulching increased crop P content by increasing soil temperature and moisture; whereas, mulching showed little effect on crop N content, because a positive effects of soil temperature may have canceled out a negative effect by soil moisture. This indicated a decoupling of P and N uptake by crops under film mulching. In conclusion, N fertilization and plastic film mulching showed opposite effects of on crop N and P stoichiometry.

Fire has important consequences on vegetation dynamics. In fire-prone areas, natural selection favors plant species, characterized by a large soil seed bank, and that their germination is stimulated by fire. Although seed germination stimulated by fire heat is common in the eastern Mediterranean Basin, only little is known about germination stimulation by smoke. We examined the interactive effect of aerosol smoke and fire history on the germinable soil seed bank (GSSB) community in eastern Mediterranean woodlands.

We collected soil samples from sites that have been subjected to different fire frequencies during the last four decades and exposed them to aerosol smoke, with or without watering. By documenting the seed germination patterns characterizing these samples, we could test for changes in the abundance and richness of the germinable seeds in the soil.

Total GSSB density was higher in sites that were burned more frequently during the last four decades. Exposure to aerosol smoke increased the GSSB density, and this pattern was more pronounced in samples originating from sites burned more frequently, as well as among annual species. Notably, exposing wet samples to aerosol smoke caused a significant reduction in GSSB density and richness. These results highlight the importance of exploring germination responses using intact soil samples, rather than synthetic seed communities. Moreover, our findings emphasize the important role smoke plays in shaping post-fire succession processes in the Mediterranean Basin, mainly by stimulating the germination of annual species.

Diversity in communities is determined by species’ ability to coexist with each other and to overcome environmental stress that may act as an environmental filter. Niche differentiation (ND) results in stronger intra- than interspecific competition and promotes coexistence. Because stress affects interactions, the strength of ND may change along stress gradients. A greater diversity of plant growth forms has been observed in stressful habitats, such as deserts and alpine regions, suggesting greater ND when stress is strong. We tested the hypothesis that niche differences and environmental filters become stronger with stress.

In a semiarid grassland in southern Mexico, we sowed six annual species in the field along a hydric stress gradient. Plants were grown alone (without interactions), with conspecific neighbors (intraspecific interactions) or with heterospecific neighbors (interspecific interactions). We analyzed how the ratio of intra- to interspecific competition changed along the gradient to assess how water availability determines the strength of ND. We also determined if hydric stress represented an environmental filter.

We observed stronger intra- than interspecific competition, especially where hydric stress was greater. Thus, we found ND in at least some portion of the gradient for all but one species. Some species were hindered by stress, but others were favored by it perhaps because it eliminates soil pathogens. Although strong ND was slightly more frequent with stress, our species sample was small and there were exceptions to the general pattern, so further research is needed to establish if this is a widespread phenomenon in nature.

Invasive species, which recently expanded, may help understand how climatic niche can shift at the time scale of the current global change. Here, we address the climatic niche shift of an invasive shrub (common gorse, Ulex europaeus) at the world and regional scales to assess how it could contribute to increasing invasibility.

Based on a 28 187 occurrences database, we used a combination of 9 species distribution models (SDM) to assess regional climatic niche from both the native range (Western Europe) and the introduced range in different parts of the world (North-West America, South America, North Europe, Australia and New Zealand).

Despite being restricted to annual mean temperature between 4°C and 22°C, as well as annual precipitation higher than 300 mm/year, the range of bioclimatic conditions suitable for gorse was very large. Based on a native versus introduced SDM comparison, we highlighted a niche expansion in North-West America, South America and to a lesser degree in Australia, while a niche displacement was assessed in North Europe. These niche changes induced an increase in potential occupied areas by gorse by 49, 111, 202 and 283% in Australia, North Europe, North-West America and South America, respectively. On the contrary, we found no evidence of niche change in New Zealand, which presents similar climatic condition to the native environment (Western Europe). This study highlights how niche expansion and displacement of gorse might increase invasibility at regional scale. The change in gorse niche toward new climatic conditions may result from adaptive plasticity or genetic evolution and may explain why it has such a high level of invasibility. Taking into account the possibility of a niche shift is crucial to improve invasive plants management and control.

Savannahs depend on fire for their persistence. Fire influences regeneration from seeds in several ways: it converts the environment into a more open space which can benefit the establishment of seedlings, and fire itself can also enhance germination by chemical and physical cues, such as smoke and heat. There is limited information as to how seed of Asian savannah species respond to fire, even though Asia has several dry vegetation types that are associated with fire. Our main question was whether fire enhances or triggers the germination of woody species occurring in southwest Chinese dry valleys, which have savannah vegetation.

We conducted tests with heat (80°C) and smoke solution treatments, and tests with real fire by burning grass on top of sand trays containing seeds. We tested 35 species, including savannah species, and gully and forest species. Depending on seed availability, not all species were tested for all treatments. Twenty-six species had total germination >4% and these were used for analysis.

Heat increased germination of three species (strongest reaction: Dodonaea viscosa), smoke increased germination of five species (strongest reaction: Calotropis gigantea). Both treatments decreased germination for five and seven species, respectively. Real fire was detrimental for most species, except for D. viscosa, which is known to respond positively to heat shock. Even though fire-related cues were not a trigger for germination for most species in our study, fire could still be crucial for regeneration by competition release.

The Tibetan Plateau (TP) holds fundamental ecological and environmental significances to China and Asia. The TP also lies in the core zone of the belt and road initiative. To protect the TP environment, a comprehensive screening on current ecological research status is entailed. The teased out research gap can also be utilized as guidelines for the recently launched major research programs, i.e. the second TP scientific expedition and silk and belt road research plan. The findings showed that the TP has experienced significant temperature increase at a rate of 0.2°C per decade since 1960s. The most robust warming trend was found in the northern plateau. Precipitation also exhibited an increasing trend but with high spatial heterogeneity. Changing climates have caused a series of environmental consequences, including lake area changes, glacier shrinkage, permafrost degradation and exacerbated desertification. The rising temperature is the main reason behind the glaciers shrinkage, snow melting, permafrost degradation and lake area changes on the TP and neighboring regions. The projected loss of glacial area on the plateau is estimated to be around 43% by 2070 and 75% by the end of the century. Vegetation was responsive to the changed environments, varied climates and intensified human activities by changing phenology and productivity. Future global change study should be more oriented toward integrating various research methods and tools, and synthesizing diverse subjects of water, vegetation, atmosphere and soil.

Persian walnut (Juglans regia L.), an interesting forest species for the veneering industry, requires adequate management to produce valuable high-quality logs. Since species associations and management level can improve stand productivity, the novelty of this work was to assess Persian walnut performance in different planting mixtures and in pure plantations conditioned to management intensity.

Growth, straightness and survival measurements were taken annually for 7 years after planting pure and mixed plantations under two contrasting management scenarios. Diseases were recorded at Age 7 in all plantations. Under each management intensity, besides the monoculture, three mixtures were tested: a mixture of only main forest species, main forest species plus one arboreal companion species, Black alder (Alnus glutinosa L.) and main species plus the shrub Russian olive (Elaeagnus angustifolia L.) as nurse species. A test of interaction between plantation type and management scenario was conducted using repeated growth data.

The interaction was significant, indicating the presence of different mechanisms underlying plantation effects under high and low management level. Compared with pure plantations, Persian walnut associated with the nurse shrub exhibited 78% higher height and 53% higher diameter growth in plantations under low management. Health benefits (lower presence of walnut blight than in the monoculture) and better straightness were also found in the association including the shrub when the management intensity was not high. These beneficial effects in the presence of Russian olive were not present under high management intensity (irrigation, fertilization, tutoring and frequent pruning). Site-specific designs for Persian walnut plantations would depend on the foreseen management intensity.

Dead plant material (i.e. litter) is the major source of soil organic matter and thus plays a fundamental role in regulating soil carbon cycling in global forest ecosystems. The storage of litter is jointly determined by its production from plants and decomposition in a given environment. However, only few studies have explored the relative importance of environmental (i.e. abiotic) and plant (i.e. biotic) factors in driving the spatial variation of litter mass. The objective of this study is to quantify the relative contributions of biotic and abiotic factors in affecting the spatial variation of aboveground litter stock in a mature subtropical forest.

The aboveground litter mass was sampled in 187 grids of a 20-hm forest dynamics plot in a subtropical broad-leave forest in eastern China. The contributions of environmental variables, topographical and species variables on litter stocks were quantified by the boosted regression tree analysis.

The mean aboveground litter stock was 367.5 g m^?2 in the Tiantong dynamics forest plot across all the 187 grids. The litter stock ranged from 109.2 to 831.3 g m^?2 and showed a large spatial variation with the coefficient of variance as 40.8%. The boosted regression tree analysis showed that slope elevation and soil moisture were the most influential variables on the spatial variation of litter stock. The relatively influence of abiotic factors (environmental and topographical factors) was 71.4%, which is larger than biotic factors (28.6%). Overall, these findings suggest that abiotic factors play a more important role than plants in driving the spatial variation of aboveground litter stock in the subtropical forest. Given that the global carbon-cycle models have been aiming to refine from the hundred kilometers to sub-kilometer scale, this study highlights the urgency of a better understanding of the spatial variation of litter stock on the fine scale.

Aims

Plant community assembly in wetlands usually changes with elevation gradients, which may be due to the direct effect of flooding and indirect effects such as changes in soil properties and competition. However, the respective importance of each factor remains to be investigated.

We investigated patterns of plant diversity, community biomass and soil properties along an elevation gradient of a lakeshore meadow at Poyang Lake, China.

(i) With increasing elevation, species richness and Simpson diversity index decreased. Both aboveground biomass (AGB) and belowground biomass (BGB) increased with elevation, however, the BGB/AGB ratio also increased, which suggests a significant effect of belowground competition. (ii) Soil N content and soil N:P ratio increased, whereas soil pH decreased with elevation. Other soil properties showed no significant response. (iii) Structural equation modeling showed that variation of plant diversity was mainly explained by BGB. Thus, intensified belowground competition seems to be the primary mechanism causing lower plant diversity at higher elevations. (iv) These findings were further supported by the observed greater response ratio of N and P storage in plant communities than the response ratio of soil N and P content to elevation, suggesting that soil nutrient limitation and belowground nutrient competition increased with elevation. Our study has important implications to wetland management and biodiversity conservation under environmental change (e.g. changes in flooding regimes, eutrophication).

Knowledge of genetic structure of natural populations and its determinants may provide key insights into the ability of species to adapt to novel environments. In many genetic studies, the effects of climate could not be disentangled from the effects of geographic proximity. We aimed to understand the effects of temperature and moisture on genetic diversity of populations and separate these effects from the effects of geographic distance. We also wanted to explore the patterns of distribution of genetic diversity in the system and assess the degree of clonality within the populations. We also checked for possible genome size variation in the system.

We studied genetic variation within and among 12 populations of the dominant grass Festuca rubra distributed across a unique regional-scale climatic grid in western Norway, Europe and explored the importance of temperature, precipitation and geographic distance for the observed patterns. We also explored the distribution of genetic diversity within and among populations, identified population differentiation and estimated degree of clonality. The analyses used microsatellites as the genetic marker. The analyses were supplemented by flow cytometry of all the material.

All the material corresponds to hexaploid cytotype, indicating that ploidy variation does not play any role in the system. The results indicate that temperature and precipitation were better predictors of genetic relatedness of the populations than geographic distance, suggesting that temperature and precipitation may be important determinants of population differentiation. In addition, precipitation, alone and in interaction with temperature, strongly affected population genotypic diversity suggesting increased clonality towards the coldest and especially the coldest wettest climates. At the same time, individuals from the coldest and wettest climates also had the highest individual genetic diversity, suggesting that only the most heterozygous individuals survive under these harsh climates. Most of the genetic variation was distributed within populations, suggesting that most populations have sufficient genetic diversity to adapt to novel climatic conditions. The alpine populations, i.e. populations which are likely the most endangered by climate change, however, lack this potential due to the high levels of clonality as detected in our study.

Invasive plants modify the structure and functioning of natural environments and threat native plant communities. Invasive species are often favored by human interference such as the creation of artificial forest edges. Field removal experiments may clarify if invasive plants are detrimental to native plant regeneration and how this is related to other local factors. We assessed the joint effect of environment and competition with the invasive Tradescantia zebrina on tree species recruitment in an Atlantic Forest fragment.

We carried out the experimental study in the Igua?u National Park, located in southern Brazil, using 30 plots distributed across five invaded sites during 6 months. We counted T. zebrina leaves and recorded the abundance and height of tree recruits over time under contrasting environmental (forest edge vs. forest interior) and removal (all aboveground biomass, only T. zebrina removal, and control) treatments. We analyzed the effects of environment and removal treatment using generalized linear mixed models.

The invasive species performed better at the forest edge than in the interior. The higher competitive pressure of T. zebrina led to higher mortality and lower height of tree recruits. Invader removal favored tree recruitment, especially in the forest interior. Our study shows that T. zebrina hampers woody species regeneration in tropical Atlantic Forests, especially at the forest edge.

Geographic patterns of the intensity of plant herbivory in relation to climate factors have garnered little general support and appear to be species specific. However, plant–herbivore interactions are also driven by resource availability, such as soil nutrient content, and it remains unclear whether broad-scale variation in soil factors is reflected in herbivore consumption rates across species’ ranges. Additionally, we know little of how intraspecific variation in tissue quality associates with edaphic and climatic factors, and how this variation controls herbivore consumption. The resource availability hypothesis (RAH) predicts that plant individuals growing in low-resource environments will have lower leaf nutritional quality and more constitutive defenses, which will result in lower rates of leaf consumption.

We collected leaves from the old-field dominant species, Solidago altissima L., from 20 sites across 10 degrees of latitude in the Eastern USA to determine the percentage leaf area consumed by insect folivores. We obtained soil and climate data for each site, as well as plant functional and defensive traits, including specific leaf area (SLA), leaf carbon:nitrogen (C:N), and trichome density.

Although we found no significant latitudinal trend of leaf consumption rate, there was strong evidence that leaf herbivory decreased with leaf C:N and trichome density, which themselves decreased with soil N, supporting our hypothesis that the RAH applies for intraspecific variation across spatial gradients. Additionally, high precipitation seasonality and soil nitrogen predicted decreased herbivory. The results suggest that spatial variation in herbivory can be driven by factors other than herbivore communities and climatic gradients, and that bottom-up processes, where plant traits and soil fertility control leaf consumption, must be incorporated into spatial predictions of herbivory.

Fire and atmospheric nitrogen (N) deposition have the potential to influence growth and productivity of forest canopy. However, their impacts on photosynthesis and growth traits of understory plants in forests remain largely unexplored. This study was conducted to examine the effects of burning and N addition on foliar N content, net photosynthesis and growth traits of three dominant shrub species (Vitex negundo, Lindera glauca and Symplocos chinensis) in a temperate forest in Central China.

The experiment used a pair-nested design, with four treatments (control, burning, N addition and burning plus N addition) and five replicates. Leaf mass area (LMA), area-based concentrations of foliar N and chlorophyll (Narea and Chlarea), net photosynthesis (An), stomatal conductance (gs), maximum photosynthetic rate (Amax) and maximal carboxylation rate (Vcmax), basal diameter, height and branch length (BL) of the three species were measured.

Across the three species, burning stimulated LMA, Narea, Chlarea, An, gs, Amax and Vcmax, and consequently enhanced basal diameter, height and BL. Nitrogen addition increased An and gs but did not affect LMA, Narea, Chlarea, Amax, Vcmax, basal diameter, height or BL. However, N addition strengthened the positive effects of burning on gs, Vcmax, An and BL. The findings indicate the primary role of light resources in determining plant photosynthesis and growth of understory shrub species after fire and highlight that understory plants should be considered in projection of biomass accumulation and productivity of forests under environmental perturbations.

There are different components of carbon (C) pools in a natural forest ecosystem: biomass, soil, litter and woody debris. We asked how these pools changed with elevation in one of China’s ecologically important forest ecosystem, i.e. beech (Fagus L., Fagaceae) forests, and what were the underlying driving factors of such variation.

The four C pools in nine beech forests were investigated along an elevational gradient (1095–1930 m) on Mt. Fanjingshan in Guizhou Province, Southwest China. Variance partitioning was used to explore the relative effects of stand age, climate and other factors on C storage. In addition, we compared the four C pools to other beech forests in Guizhou Province and worldwide.

The total C pools of beech forest ecosystems ranged from 190.5 to 504.3 Mg C ha–1, mainly attributed to biomass C (accounting for 33.7–73.9%) and soil C (accounting for 23.9–65.5%). No more than 4% of ecosystem C pools were stored in woody debris (0.05–3.1%) and litter (0.2–0.7%). Ecosystem C storage increased significantly with elevation, where both the biomass and woody debris C pools increased with elevation, while those of litter and soil exhibited no such trend. For the Guizhou beech forests, climate and stand age were found to be key drivers of the elevational patterns of ecosystem and biomass C storage, while for beech forests globally, stand age was the most important predictor. Compared to beech forests worldwide, beech forests in Guizhou Province displayed a relatively higher biomass C accumulation rate, which may be explained by a much higher precipitation in this area. The present study provides basic data for understanding the C budgets of Chinese beech forests and their possible roles in regional C cycling and emphasizes the general importance of stand age and climate on C accumulation.

To better understand whether and how nitrogen addition impacts the epiphytic lichens in the Shennongjia Nature Reserve (China).

Five dominant epiphytic lichen species, including Usnea longissima, U. luridorufa, Ramalina calicaris var. japonica, U. dasopoga and U. betulina, were selected as materials, and then field and laboratory nitrogen addition experiments were performed. The phosphomonoesterase (PME) activity and nitrogen (N) and phosphorus (P) content of these lichens were measured, and then the effects of nitrogen addition on thallus nutrient balance and PME activity were discussed.

Our results showed that with an increased N deposition from 0.6 to 50 kg N ha?1 a?1, the thallus N content of the five lichen species increased significantly, suggesting that those lichens had strong ability to take up and accumulate N, and an universality of N intolerance in epiphytic lichens. Meanwhile, the P content of five lichens increased slower than N content among N treatments, indicating the supply of P was deteriorated when the supply of N increased. The N addition also led to the N:P ratios of five lichens increased from about 10 to 20, and reached a maximum at 50 kg N ha?1 a?1, and the PME activity of the five lichen species was upregulated by the N addition, indicated that the balance between N and P was deteriorated in these lichens. We concluded that increases in N deposition will lead to nutrient imbalance in lichens and that nitrogen enrichment will change these five lichen species from being N limited to being P limited. Our research will be of value in the conservation of lichen diversity in the Shennongjia Nature Reserve (China).

With the global atmospheric nitrogen (N) deposition increasing, the effect of N deposition on terrestrial plant diversity has been widely studied. Some studies have reviewed the effects of N deposition on plant species diversity; however, all studies addressed the effects of N deposition on plant community focused on species richness in specific ecosystem. There is a need for a systematic meta-analysis covering multiple dimensions of plant diversity in multiple climate zones and ecosystems types. Our goal was to quantify changes in species richness, evenness and uncertainty in plant communities in response to N addition across different environmental and experimental contexts.

We performed a meta-analysis of 623 experimental records published in English and Chinese journals to evaluate the response of terrestrial plant diversity to the experimental N addition in China. Three metrics were used to quantify the change in plant diversity: species richness (SR), evenness (Pielou index) uncertainty (Shannon index).

Results showed that (i) N addition negatively affected SR in temperate, Plateau zones and subtropical zone, but had no significant effect on Shannon index in subtropical zones; (ii) N addition decreased SR, Shannon index and Pielou index in grassland, and the negative effect of N addition on SR was stronger in forest than in grassland; (iii) N addition negatively affected plant diversity (SR, Shannon index and Pielou index) in the long term, whereas it did not affect plant diversity in the short term. Furthermore, the increase in N addition levels strengthened the negative effect of N deposition on plant diversity with long experiment duration; and (iv) the negative effect of ammonium nitrate (NH₄NO₃) addition on SR was stronger than that of urea (CO(NH₂)₂) addition, but the negative effect of NH₄NO₃ addition on Pielou index was weaker than that of CO(NH₂)₂ addition. Our results indicated that the effects of N addition on plant diversity varied depending on climate zones, ecosystem types, N addition levels, N type and experiment duration. This underlines the importance of integrating multiple dimensions of plant diversity and multiple factors into assessments of plant diversity to global environmental change.

South American Pampa grasslands are habitats of great conservation interest, with a distinct and rich flora, but have been intensely converted to other land uses, including tree plantations. While necessity for restoration grows, no information on restoration potential of grasslands after afforestation exists. Here, we aim at analyzing composition and structure of grassland vegetation with a history of eucalyptus plantations in order to assess recovery potential of these areas. We hypothesized that areas with history of eucalyptus would differ from reference grasslands with no history of land-use change in terms of floristic and functional composition and would present lower species richness.

Our study region comprised four sites in the southeastern part of the Pampa biome, in the coastal plain in the extreme south of Brazil, always with sites with long (50 years) history of eucalyptus plantation and reference grassland. We sampled vegetation at post-eucalyptus sites (with and without resprouting) 10 years after clearclutting and in natural grasslands. We analyzed data by analysis of variance and ordination techniques, considering compositional parameters and life forms, and indicator species analysis.

Species richness and vegetation cover were higher in reference grassland than in resprout areas but did not differ from post-eucalyptus areas. Exotic species cover was significantly higher in areas with afforestation history. In terms of total composition, natural grasslands differed significantly from areas with past plantation use. Indicator species analyses revealed considerable differences between grassland types. In conclusion, vegetation development led to grassland communities that are still quite distinct from reference sites. Likely, the specificity of grassland management has a high importance in defining vegetation trajectories in time and importance for grassland recovery, and restoration needs to be addressed in more studies.

Clonal integration, i.e. resource sharing between interconnected ramets, can help clonal plants tolerate abiotic stress. However, few studies have directly examined the ecological significance of clonal integration in the ability of clonal plants to tolerate biotic stress such as herbivory.

We grew clonal fragments of an invasive clonal plant Alternanthera philoxeroides, each consisting of an apical part (relatively young) and a basal part (relatively old), at two levels (low and high) of soil nitrogen (N). For each fragment, the apical part was subjected to either no herbivory or herbivory for 2 weeks by a specialist insect, Agasicles hygrophila, and was either connected with or disconnected from the basal part not subjected to herbivory.

Herbivory in the apical part severely reduced leaf growth (leaf mass, leaf number or leaf area) and ramet production of both apical and basal parts, and increased root to shoot ratio of the apical part. Irrespective of herbivory and soil N, stem connection between the apical and the basal part decreased root to shoot ratio of the apical part, but did not change its growth measures. Meanwhile, connection increased stem N concentration of the apical part growing under high-N supply and decreased stem carbon (C) concentration of the apical part under low-N supply. By contrast, connection increased root to shoot ratio of the basal part, but reduced its leaf and ramet production. Connection also increased leaf and stem C concentrations of the basal part under low-N supply. Thus, clonal integration can be beneficial for the early development of young A. philoxeroides ramets, but not for their local adaptation to herbivory damage by A. hygrophila.

Natural hybridization between invasive and native species, as a form of adaptive evolution, threatens biodiversity worldwide. However, the potential invasive mechanisms of hybrids remain essentially unexplored, especially insights from soil chemical properties and soil microbial communities.

In a field experiment, soil microbial community, potassium-solubilizing bacteria, phosphorus-solubilizing bacteria, enzyme activities, and light-saturated photosynthetic rate were measured in invasive Sphagneticola trilobata and its hybrid with native Sphagneticola calendulacea in 2 years.

In general, soil dissolved organic carbon and the biomass of phosphorus-solubilizing bacteria were significantly higher under the hybrid treatment than S. trilobata and S. calendulacea. However, there were no significant differences in acid phosphatase, total PLFAs, bacterial PLFAs, fungi PLFAs, cellulase, and urase in these treatments. The hybrids had significantly higher light-saturated photosynthetic rate, photosynthetic nitrogen-, phosphorus-, potassium- use efficiencies than the invasive S. trilobata, but no significant difference with S. calendulacea. The total biomass and root biomass of hybrids were higher than S. calendulacea. Our results indicate that the hybrids species have a higher invasive potential than S. calendulacea, which may aggravate the local extinction of S. calendulaceain the future.

Riparian corridors play vital roles in the maintenance of biodiversity. Nonetheless, plant species diversity and vegetation coverage in riparian corridors are seriously threatened by increasing pressure owing to livestock consumption and anthropogenic disturbance; even the stability of river courses has been threatened. The establishment of enclosures is a widely used strategy to restore degraded grassland ecosystems, but its impact on degraded herbaceous riparian vegetation and soil properties remains unclear. The aim of this study was to evaluate whether species composition, richness, diversity, and soil properties can be recovered by the enclosure.

Twenty long-term monitoring sample plots were set in the Liaohe main stream river, Liaohe main stream river was enclosed for grazing and farmland exclusion in 2012. The height, coverage and individual numbers of plant were recorded for species richness and diversity evaluation from 2012 to 2017; soil nutrients were measured for comparative analysis in 2012 and 2017. We examined the effects of the establishment of enclosures on plant species diversity and soil properties from 2012 to 2017 in the riparian corridors of the Liaohe River system in China.

Plant species richness and diversity significantly increased from 2012 to 2017. The dominance of Asteraceae plants increased, while the abundance of Gramineae plants decreased over time. The difference in abundance increased each year since enclosure was implemented in 2012. The concentrations of phosphorus and potassium in the soil significantly decreased as a result of the combined effects of vegetation restoration and prohibition of farming practices following the establishment of enclosures. There was also a lag time related to the response of soil organic matter to the establishment of enclosures. In conclusion, our study provides new evidence regarding the response of species diversity, species composition and soil properties following riparian vegetation restoration efforts through enclosure development.

Larch is the dominant timber species in Northeast China. However, compared with the adjacent secondary forests, soil available nitrogen (N) significantly declined in ~40-year-old larch plantations. Thus, it is of great importance to determine how N use strategies in larch change in response to declining soil N availability.

We investigated the changes in N concentration and 15N natural abundance (δ15N) from 18 August to 25 October in the leaves, stems, branches and roots of 1-year-old Larix kaempferi seedlings under nutrient-sufficient (NSu) and nutrient-starvation (NSt) conditions with a pot experiment in Northeast China.

Stem and branch N concentrations exhibited upward trends, and leaf N concentration exhibited a downward trend. Root N concentration exhibited an upward trend under NSu conditions, but a downward trend under NSt conditions. These results suggested that stems and branches were served as N storage organs, but roots shifted from storage to resorption organs when switched from NSu to NSt. Leaf nutrient resorption was intensely occurred on 11 October, as indicated by the sharply decreased leaf N concentration and increased stem, root and branch N concentrations. The δ15N of roots, branches and leaves overlapped between NSu and NSt approximately on 11 October, which may be regulated by isotope discrimination during N resorption. Leaf N resorption efficiency under NSt (76.33%) was significantly higher than that of NSu (56.76%), indicating that nutrient stress stimulates leaf N resorption. Taken together, larch seedlings enhance leaf nutrient resorption and shift roots from nutrient storage to nutrient resorption to adapt to NSt conditions. These changes might relieve the adverse effects of declining soil nutrient availability on seedling survival and regeneration.

As extreme climatic events including droughts and heat waves become more common in a changing climate, tree mortality has increased across the globe. In order to determine whether certain species have a competitive advantage over others, we explored the water-relations and leaf-gas exchange of four co-occurring species in a forest in northern Aotearoa-New Zealand. We studied the ecologically and culturally significant foundation species, Agathis australis (a conifer), two additional conifers, Phyllocladus trichomanoides and Podocarpus totara and the angiosperm Knightia excelsa.

We measured sap flow, leaf-gas exchange and xylem water potentials of leaves and terminal branches with concurrent measures of micrometeorological data on days with very few clouds. We derived whole tree hydraulic conductance and instantaneous water-use efficiency (WUE_i) at our remnant forest in west Auckland during February 2015 (southern hemisphere summer).

The four species behaved similarly in their diurnal curves of gas exchange and water potential. Rates of assimilation, stomatal conductance and WUE_i were similar among trees of different species. Whole tree hydraulic conductance was also similar among species. These results indicate functional convergence in water relations, possibly driven by low nutrient soils at the site. Our results suggest that there is no species with a clear adaptive advantage over the others in the context of climate change.

Soil organisms can influence the plant diversity-productivity relationship at species level; however, little is known about their role in the relationship at an intraspecific level. This study aimed to investigate the interaction between the effects of plant intraspecific diversity and a root-knot nematode on primary production and community evenness.

A greenhouse experiment was conducted by using intraspecific diversity of a clover-grass community through sowing 2-, 4-, 8- and 16-cultivar mixtures of Trifolium pratense L. and Lolium perenne L. and by adding the nematode Meloidogyne hapla. We investigated the effects of plant intraspecific diversity and M. hapla on biomass of plant community, biomass of cultivar individuals and community evenness.

We found that L. perenne dominated the communities, yet its biomass was not affected by the treatments. Meloidogyne hapla influenced the effect of plant intraspecific diversity on aboveground biomass of T. pratense at the four-cultivar mixture level of plant intraspecific diversity. Community evenness increased linearly with increasing plant intraspecific diversity, and M. hapla affected community evenness at the four-cultivar mixture level. Both T. pratense and L. perenne cultivars differed in aboveground biomass. Depending on plant intraspecific diversity and cultivar identity, nematode addition positively affected the aboveground biomass of T. pratense individuals. The response of T. pratense cultivars to M. hapla and to various plant intraspecific diversity levels influenced the intraspecific diversity-productivity relationship. This study highlights the influence of M. hapla on the effect of plant intraspecific diversity on aboveground biomass of T. pratense, suggesting that future research on the impact of intraspecific plant diversity on ecosystem functions should consider the effects of soil organisms.

We aim to investigate variations in the resorption efficiencies of 10 mineral nutrients [i.e. nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), zinc (Zn), aluminum (Al), iron (Fe) and copper (Cu)] in leaves of desert shrubs and to explore effects of aridity on resorption efficiency of these nutrients.

Plant samples were collected from 10 sites in northern Xinjiang Uygur Autonomous Region of China. Samples of green and senesced leaves were analysed to determine concentrations of N, P, K, Mg, Ca, Mn, Zn, Al, Fe and Cu and thus the nutrient resorption efficiency.

The mean nutrient concentrations in the desert shrubs varied, with the stoichiometric ratio Ca:N (19.3 mg g^?1):K (10.5 mg g^?1):Mg:P (1.01 mg g^?1):Al:Fe:Mn:Zn:Cu (4.78 mg kg^?1) = 4038:2950:2199:1816:211:37:32:11:2:1 in green leaves; and Ca:N (12.6 mg g^?1):Mg:K (7.6 mg g^?1):P (0.56 mg g^?1):Fe:Al:Mn:Zn:Cu (2.85 mg kg^?1) = 5583:3710:2943:2523:178:133:119:19:3.7:1 in senesced leaves. Resorption generally occurred for six elements (N, P, K, Cu, Mg and Mn, with average resorption efficiency 47.8%, 52.0%, 38.6%, 41.0%, 12.7% and 7.89%, respectively) during leaf senescence, while the other four nutrients tended to accumulate in senesced leaves, showing averagely negative resorption efficiencies [Ca (–3.87%), Al (?57.1%), Zn (?62.6%), Fe (?89.6%)]. Aridity showed strikingly different effects on the resorption process of the 10 nutrients. Of the four elements with totally (N/P/K) or mostly (Cu) positive observations of resorption efficiency, their resorption generally decreased with aridity, suggesting that drought stress had negative effects on the resorption efficiencies of these elements. In contrast, with at least one-third observations of resorption efficiency being negative, the other elements (Mg/Mn/Ca/Zn/Al/Fe) showed generally increasing resorptive tendency with aridity, except for Zn. This research provided a systematic analysis on the large variation and contrasting responses of the resorption of multi-elements to aridity in typical desert shrubs. Our findings foster the understanding of nutrient resorption patterns of desert plants and enable us to better predict the contrastive effects of drought stress on the cycling of diverse nutrients and the consequent stoichiometric decoupling in plants of desert ecosystems.

Morphological variation of leaves is a key indicator of plant response to climatic change. Leaf size and shape are associated with carbon, water and energy exchange of plants with their environment. However, whether and how leaf size and shape responded to climate change over the past decades remains poorly studied. Moreover, many studies have only explored inter- but not intraspecific variation in leaf size and shape across space and time.

We collected >6000 herbarium specimens spanning 98 years (1910–2008) in China for seven representative dicot species and measured their leaf length and width. We explored geographical patterns and temporal trends in leaf size (i.e. leaf length, leaf width and length × width product) and shape (i.e. length/width ratio), and investigated the effects of changes in precipitation and temperature over time and space on the variation in leaf size and shape.

After accounting for the effects of sampling time, leaf size decreased with latitude for all species combined, but the relationship varied among species. Leaf size and shape were positively correlated with temperature and precipitation across space. After accounting for the effects of sampling locations, leaf size of all species combined increased with time. Leaf size changes over time were mostly positively correlated with precipitation, whereas leaf shape changes were mostly correlated with temperature. Overall, our results indicate significant spatial and temporal intraspecific variation in leaf size and shape in response to climate. Our study also demonstrates that herbarium specimens collected over a considerable period of time provide a good resource to study the impacts of climate change on plant morphological traits.

Grasslands are dominant vegetation of China, support outstanding biodiversity and sequester bulk amount of atmospheric CO₂. These grasslands are highly degraded and fragmented due to remarkable anthropogenic and grazing loads. Chinese Government has made great attempt to restore by grazing exclusion. The relations of carbon fluxes with species composition and diversity in the communities sensitive to grazing by large herbivores are needed to be analysed under the global climate change scenario. The objective of present study was to comprehend the effects of grazing and fencing on the ecosystem structure and function of the typical steppe grassland.

To meet the objectives, overgrazed and fenced (since year 2001) systems were selected in typical steppe grassland at the Duolun Restoration Ecology Research Station, Inner Mogolia, China. Within each system, three dominant communities with three replicates were selected. In each replicate community, three 1 × 1 m plots, were randomly located. Each plot was divided into four 50 × 50 cm quadrats. A total of 216, 50 × 50 cm quadrats were sampled. From each quadrat, number of individuals and above-ground herbaceous biomass for each species, soil respiration (SR), ecosystem respiration (ER), net (NEE) as well as gross (GEE) ecosystem CO₂ exchanges were recorded in June 2015. Data were well analysed using statistical software. Canonical correspondence analysis showed differential responses of communities to the structure and function of the typical steppe grassland.

Across the communities, fencing reduced the soil temperature by 12% and at the same time increased the soil moisture by 44.30%, thus, increased the species richness by 28%, evenness by 21%, above-ground biomass by 19% and plant carbon by 20%. Interestingly, fencing increased NEE by 128%, GEE by 77%, SR by 65% and ER by 39%. Under fencing, species composition partially governed the CO₂ exchange processes.

Fencing reduces soil temperature and thereby improves species diversity and more efficient CO₂ sequestration and long-term and in-depth study is desirable for a better understanding of the relationship between species diversity and ecosystem carbon uptake.

The divergent changes of plant species under land use changes are key mechanisms underlying vegetation succession. Stipa grandis steppe and Stipa krylovii steppe are two plant communities widely distributed on the Mongolian Plateau. They have been speculated to be able to succeed into each other under different land use types and intensities based on the observations on their presence and abundance at the sites with different land use history. However, no direct evidence, neither the underlying mechanisms, have been reported for this speculation. Here, we verified this speculation and explored the underlying mechanisms in the typical steppe region of Inner Mongolia.

We investigated the abundance and reproductive behavior of S. krylovii and S. grandis under different land use types and intensities. We used 18 grassland paddocks to run a 6-year experiment with 6 management treatments (T0—unused, T1—grazing monthly in plant growing season, T2, T4, T6—grazing in different months in plant growing season, and T8—mowing) replicated three times. We measured the relative density and cover of S. krylovii and S. grandis using line sampling method and examined their number and biomass of vegetative and reproductive tillers using quadrat method in each paddock after treatments for 4 and 6 years. We also determined these plant attributes in 14 pairs of heavily versus lightly used grassland plots in a wide area (150 km × 200 km) of the typical steppe region.

1. Grazing largely and mowing moderately decreased the density ratio and coverage ratio of S. grandis to S. krylovii in grasslands (P < 0.05), and the differences in these ratios between grazed and unused grasslands increased with time.

2. Grazing, but not mowing, significantly enhanced the relative density (Nrep = reproductive tiller number/total tiller number) of, and biomass allocation (Brep = reproductive tiller biomass/total biomass) to, reproductive tillers of S. krylovii (P < 0.05), but not S. grandis. This grazing enhancement to sexual reproduction of S. krylovii, and additionally inhibition to Nrep of S. grandis (P < 0.05), were found across the 14 pairs of heavily versus lightly used plots.

3. Seasonal pattern of grazing affected sexual reproduction of S. krylovii. The Nrep and Brep was higher under grazing in July and September (T4) than in July and August (T6) or in May and July (T2) (P < 0.05), suggesting a relatively positive effect of grazing on sexual reproduction in July (tasseling phenophase) than in May or August.

Our results provide direct evidence to the reciprocal change of S. grandis and S. krylovii in steppe communities under different management and indicate that gazing or mowing enhancement of sexual reproduction of S. krylovii relative to S. grandis is one of the mechanisms for the change.