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.

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.

In the context of global change, the impacts of forest structure alteration on climbing plants in extra-tropical ecosystems are poorly understood. It also remains little explored, the functional strategies among climbing plant species and its relationship with the local-scale distribution of climbing plant communities. Here, we aimed at three goals: (i) we studied how climbing plant community composition responds to the modification of the original forest structure in a subtropical dry forest; (ii) we characterized climbing plant species according to functional traits related to the acquisition and use of resources; and (iii) we examined whether functional strategies at the community level are also responding to vegetation structure change, a much less addressed topic in the ecology of climbing plants.

The study was carried out in the Chaco forest of Córdoba Mountains, central Argentina. We selected 18 patches of ‘native forests’, ‘shrublands’ and ‘Ligustrum lucidum forests’. We counted and identified climbing plant individuals in each patch, including woody and herbaceous species. For each species, we measured 10 functional traits: leaf area, leaf area ratio, leaf dry matter content, leaf tensile strength, specific leaf area, stem density, wood saturated water content, inter-node length, petiole length and plant cover. We compared climbing plant composition, richness and abundance among the three vegetation types. Then, we assessed trends of functional variation of climbing plant species by performing a principal component analysis. Finally, we investigated whether simple mean, weighted mean and Functional Richness index of principal component analysis (PCA) axes differed among the climbing plant communities of the three vegetation types.

Multivariate analysis revealed that climbing plant composition of native forests significantly differed from that of shrublands and L. lucidum forests. Also, L. lucidum forests had the lowest climbing plant species richness. Functional variation of climbers was explained by three PCA axes: axis 1 represented the resource-use strategy, axis 2 was associated with light-foraging strategy, and axis 3 related to plant size. The most abundant species in native forests presented a more acquisitive functional strategy and larger sizes than those of shrublands and L. lucidum forest. Furthermore, the most abundant species in shrublands had shorter internodes and petioles than the most abundant climbers of the other vegetation types. Finally, the climbing plant community in the native forests had the highest Functional Richness index regarding the resource-use and the size strategies. Here, we demonstrated that there are floristic and functional differences among climbing plant communities in patches of three vegetation types in a subtropical dry forest biome. Particularly, we found climbers spreading along three functional axes which were directly related to climbing plant community distribution among the different patches, highlighting their ecological importance and the need of further research.

Deforestation and biodiversity loss are two alarming, closely related problems, and the main factors triggering changes in land use. Indigenous agricultural practices in the western Amazon Basin are known as chakras, and their structure and dynamics are seemingly optimal for forest management. However, the variability in tree species and the degree of forest recovery after abandonment is poorly documented in this agroforestry system (AFS). The goals of this study were: (i) to investigate whether the different AFSs (chakras) preserve similar levels of forest diversity, (ii) to determine the effect of transformation of mature forests (MF) to chakras, in particular, forest alpha and beta diversity levels, and (iii) to investigate whether native tree species recovery leads to the original forest structure following chakra abandonment.

We assessed the floristic composition in three AFSs (cassava, corn, and cocoa), the secondary forest (SF), and the forest remnants in the buffer zone of the Northern Ecuadorian Amazon (NEA). All tree species with a diameter at breast height (dbh) ≥10 cm were inventoried in 61 plots (0.28 ha average) representing 17.44 ha. Alpha diversity was calculated in all systems to determine the levels of variability using species richness and the Shannon diversity index. Also, beta diversity was examined to evaluate the degree of dissimilarity among all AFSs with the MF in order to analyze changes in floristic composition. The divergence between the SF and the MF was analyzed to ascertain forest recovery after chakra abandonment.

A total of 4,060 trees (dbh ≥ 10 cm) representing 109 species, 96 genera, and 43 plant families were inventoried in 17.44 ha sampled in five systems in the buffer zone of the NEA. The most dominant plant families were Arecaceae, Myristicaceae, Fabaceae, Meliaceae, and Malvaceae, and the most representative genera included Iriartea, Virola, Guarea, Ocotea, Cordia, Chrysophyllum, and Inga. The MF in this zone is composed of 81 tree species circumscribed in 74 genera and 30 plant families. Transforming this MF to different chakras leads to a decrease of alpha diversity between 52% and 75%, particularly in AFS practiced for local food security (corn and cassava). However, all the AFSs preserve ca. 56% of the native flora existing in the MF, in which at least 8% of the species are threatened; however, the status of the remaining 92% of species is still unknown, indicating that the assessment of the rarity of the native trees is virtually unexplored. Additionally, all sites investigated consistently formed three clusters that corresponded to AFS, MF, and SF. Thus, the trend of forests to recover the original structure is facilitated by native trees left intact in the chakras. These results strongly support the potential to execute sustainable forest management and preservation of endangered tree species practicing this AFS.

Clonal integration can increase performance of clonal plants suffering from environmental stress, and clonal plants in many wetlands commonly face stress of flooding accompanied by salinity. However, few studies have tested roles of clonal integration in amphibious plants expanding from terrestrial to aquatic saline habitats.

Basal (older) ramets of clonal fragments of Paspalum paspaloides were grown in soil to simulate terrestrial habitats, whereas their apical (younger) ramets were placed at the surface of saline water containing 0, 50, 150 and 250 mmol l?1 NaCl to mimic different salinity levels in aquatic habitats. Stolons connecting the apical and basal ramets were either intact (connected) to allow clonal integration or severed (disconnected) to prevent integration.

Increasing salinity level significantly decreased the growth of the apical ramets of P. paspaloides, and such effects on the leaf growth were much higher without than with stolon connection after 60-day treatment. Meanwhile, leaf and total mass ratios of the connected to the disconnected apical ramets were higher at high than at low saline treatments. Correspondingly, Fv/Fm and F/Fm′ of the apical ramets were higher with than without stolon connection in highly saline treatments. The results suggest that clonal integration can benefit the spread of apical ramets from terrestrial soil into saline water, and that the positive effects increase with increasing salinity. However, clonal integration did not significantly affect the growth of the whole fragments. Due to clonal integration, Na+ could be translocated from the apical to the basal ramets to alleviate ion toxicity in apical ramets. Our results suggest that clonal integration benefits the expansion of P. paspaloides from terrestrial to aquatic saline habitats via maintained photosynthetic capacities and changed biomass allocation pattern.

Shrub encroachment has taken place in many of China’s northern grasslands. This study attempts to answer the following questions: which plant communities are present in these shrub-encroached grasslands (SEGs)? What are the species richness and composition of these communities? Which environmental factors determine the spatial distribution thereof?

We investigated the community characteristics of 255 SEG plots with a size of 20 m × 20 m at 69 locations across grasslands in northern China. In each plot, paired 1-m² quadrats were established within shrub patches and the neighbouring grassy matrix to record herb species composition. The quantitative characteristics (abundance, coverage and height) of herbs were measured in 0.25-m² subquadrats, and soil samples were collected in the quadrats. Two-way indicator species analysis (TWINSPAN), detrended canonical analysis (DCA) and canonical correspondence analysis (CCA) were used for community clustering and ordination.

The DCA and TWINSPAN results suggested that the SEGs in northern China can be divided into six community types: Potentilla fruticosa + Carex atrofusca, Spiraea hypericifolia + Festuca ovina, Caragana acanthophylla + Stipa sareptana, Caragana microphylla + Leymus chinensis, Caragana microphylla + Stipa klemenzii and Caragana tibetica + Cleistogenes songorica. At a regional scale, climate and soil nutrients controlled the spatial patterns of species richness and community composition of the SEGs in northern China. Temperature exerted a negative impact, whereas precipitation and nutrients had positive effects on species richness. Among the environmental factors used, climate was the major controller of the variations in community structure. These results provide new insights into the community composition of SEGs in China and enrich the global dataset of SEGs.

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.

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.

In arid communities, it has been proposed that individual plants can extend their roots beyond their canopy exploring neighbouring bare ground areas. This becomes relevant in systems where the vegetation is distributed in patches surrounded by bare soil. However, whether roots of different species may be overlapping under bare ground areas is still controversial. The factors controlling root responses when no plants appear to be directly influencing the gap among patches are still unclear. The aim of our study was to detect perennial grasses responses to an N enrichment pulse.

In a semi-arid steppe (Patagonia, Argentina), we buried root traps filled with sieved soil with and without N addition, under bare soil patches. Traps were harvested after 4 and 6 months. Trap neighbourhoods (30 cm in diameter) included at least three of the dominant tussock species. After harvests, we identified species in the traps by root traits and quantified diversity, biomass and specific relative growth rates.

Bare ground areas show simultaneous root growth of different species. Diversity of perennial grass roots was higher with N addition than without it in the first harvest (4 months), but this difference disappeared in the second harvest (6 months). Root biomass was maximal after 6 months in N addition traps. Species preferred by herbivores (Bromus pictus and Poa ligularis) showed rapid growth and responses to N addition. Differences between harvests may be an indicative that N pulses interact with rising temperatures and soil water content as growing season progress.

Canopy height is a key driver of forest biodiversity and carbon cycling. Accurate estimates of canopy height are needed for assessing mechanisms relating to ecological patterns and processes of tree height limitations. At global scales forest canopy height patterns are largely controlled by climate, while local variation at fine scales is due to differences in disturbance history and local patterns in environmental conditions. The relative effect of local environmental drivers on canopy height is poorly understood partly due to gaps in data on canopy height and methods for examining limiting factors. Here, we used airborne laser scanning (ALS) data on vegetation structure of boreal forests to examine the effects of environmental factors on potential maximum forest canopy height.

Relationships between maximum canopy height from ALS measures and environmental variables were examined to assess factors limiting tree height. Specifically, we used quantile regression at the 0.90 quantile to relate maximum canopy height with environmental characteristics of climate (i.e. mean annual temperature [MAT] and mean annual precipitation), terrain (i.e. slope) and depth-to-water (DTW) across a 33000 km2 multiple use boreal forest landscape in northeast Alberta, Canada.

Maximum canopy height was positively associated with MAT, terrain slope and terrain-derived DTW, collectively explaining 33.2% of the variation in heights. The strongest explanatory variable was DTW explaining 26% of canopy height variation with peatland forests having naturally shorter maximum canopy heights, but also more sites currently at their maximum potential height. In contrast, the most productive forests (i.e. mesic to xeric upland forests) had the fewest sites at their potential maximum height, illustrating the effects of long-term forest management, wildfires and general anthropogenic footprints on reducing the extent and abundance of older, taller forest habitat in Alberta’s boreal forest.

Quantifying the relative importance of the mechanisms that drive community assembly in forests is a crucial issue in community ecology. The present study aims to understand the ways in which niche-based and spatially based processes influence community assembly in areas in different climatic conditions and how these processes change during the transition from seedling to adult.

In this study, we investigated how taxonomic and phylogenetic beta diversity in seedling and adult stages of forest trees change across three elevational transects in tropical, subtropical and subalpine forests in Southwest China, and the relationships of these changes to the environment and inter-site distances. We quantified the relative contribution of environmental conditions and spatial distribution to taxonomic and phylogenetic beta diversity of both seedling and adult life stages along each elevational transect. We also quantified the taxonomic and phylogenetic similarity between seedlings and adult trees along elevations.

Taxonomic and phylogenetic beta diversity of both seedlings and adult trees increased with an increase in both environmental distance and spatial distance in all three transects. On both taxonomic and phylogenetic levels, the effects of environmental filtering and spatial disposition varied between life stages and among forest types. Phylogenetic similarity between seedlings and adult trees increased with elevation, although the taxonomic similarity did not show clear elevational patterns. Our results suggest that the relative contribution of niche-based and space-based processes to taxonomic and phylogenetic assemblages varies across major plant life stages and among forest types. Our findings also highlight the importance of ontogenetic stages for fully understanding community assembly of long-lived tree species.

Pollinators are traditionally considered to be the primary agent of selection on floral traits. However, floral traits may also be under selection from abiotic agents (e.g. rain), which makes considering the relative importance of pollinators and abiotic selective agents on floral traits essential. The functional significance of floral orientation is often ascribed to pollinator attraction, but orientation can also protect reproductive structures from rain. Therefore, a study that incorporates both factors will enhance our understanding of the ecological roles of floral orientation in plant fitness. Mertensia brevistyla and M. fusiformis are herbaceous species that differ in their floral orientations. A series of field and laboratory experiments was used to investigate the adaptive function of floral orientation in these species, particularly with respect to pollinators and rain.

We measured and compared floral orientation and visitor assemblages between M. brevistyla and M. fusiformis populations in western Colorado, USA. We manipulated floral stems and conducted a choice experiment with floral visitors, and also compared orientations of pollinator-visited stems with those of unvisited stems in a natural setting. We examined pollinator- and rain-mediated selection on floral orientation by manipulating orientation, conducting supplemental pollinations, applying watering treatments and measuring subsequent seed set. We also experimentally tested the likelihood of rain contact with anthers, and the effect of rainwater on pollen germinability.

Mertensia brevistyla had a significantly more upright floral orientation than M. fusiformis, and seed set was highest in upright M. brevistyla and in horizontal/pendant M. fusiformis stems, supporting an adaptive function (via female fitness) of the interspecific difference in orientation. However, floral visitor assemblages did not differ significantly between the two species; visitors did not exhibit significant preference for either orientation; and pollinator-mediated selection on orientation was undetectable. Similarly, there was little effect of water on seed set in either species, regardless of floral orientation. However, pollen germinability was reduced in both species by immersion in water; and water was more likely to contact anthers in M. fusiformis than in M. brevistyla, due to interspecific differences in floral morphology. We conclude that pollinators are likely not the primary selective agent driving differences in orientation in these Mertensia species. Instead, the negative effect of rain on pollen germinability helps explain the more pendant orientation of M. fusiformis, while short anthers in more upright M. brevistyla provide an alternative adaptation to rain. The selective agent driving effects of orientation on seed set remains unclear. This study illustrates the necessity of considering male fitness and abiotic agents in interpreting the functional significance of inflorescence traits.

Plant stature can be strongly modified via regulation of endogenous levels and signalling of the plant hormone gibberellin (GA). Down-regulation of GA can produce semi-dwarf tree varieties with improved qualities such as reduced susceptibility to wind damage, enhanced root growth and more compact cultivation. However, these modifications may have unintended, non-target consequences for defence against herbivores, via either of two mechanisms: (i) reduced biomass production may cause trade-offs with chemical resistance traits, as predicted by the growth-differentiation balance hypothesis, and (ii) altered biomass allocation to either roots or photosynthetic tissues may affect regrowth potential and thus tolerance to defoliation.

We studied GA down-regulated (GE) and non-transgenic wild-type hybrid poplar (Populus alba × P. tremula) in an outdoor, aboveground common garden and defoliated half of all replicate trees to simulate defoliation. We then quantified the independent and interactive effects of genotype and defoliation on growth and chemical resistance-related traits, including phenolic glycosides (PGs), condensed tannin and nitrogen. We also calculated tolerance to defoliation as the differential in relative growth between undefoliated and defoliated trees.

Our results indicate that two of the four GA down-regulated genotypes had significantly reduced stem height, basal diameter, volume (d²h), total biomass and increased allocation to leaves relative to the wild type. One of those two genotypes also had reduced allocation to roots. One and sometimes both of these same two genotypes also had at least 20% lower levels of condensed tannins and PGs and similar increases in lignin and nitrogen. Tolerance, as calculated by the differential in relative growth between undefoliated and defoliated trees, was similar among all experimental genotypes. However, two GE genotypes flushed fewer leaves in response to defoliation relative to the wild type. Our results indicate that GA down-regulation strongly alters biomass production and allocation in poplar but does not necessarily compromise the ability of these trees to tolerate damage. However, some of the modifications we observed do have the potential to alter non-target resistance traits over time, and warrant further research, especially under plantation conditions.

Most flowering plants engage in mutualisms with animals to move pollen between individuals, and it is expected that pollinators play an essential role in the evolution of selfing, yet few studies have determined how distinct pollinator types affect a plant’s mating system and reproductive success differentially. We investigated the effect of two different pollinators on the reproductive success of Incarvillea sinensis, an annual with showy, insect-pollinated, one-day flowers.

We marked flowers after a single visit from both pollinator species (Bombus patagiatus and Amegilla quadrifasciata) and calculated the number of pollen grains deposited on the stigma and pollen left in the anthers, the fruit and seed set, the outcrossing rate and the correlations of paternity.

There was no significant difference in the number of pollen grains deposited on the stigma, or in the seed and fruit set between the two pollinators in both years. The mean number of pollen grains removed by B. patagiatus was significantly higher than that removed by A. quadrifasciata. The outcrossing rate of flowers pollinated by B. patagiatus was significantly higher than that of flowers pollinated by A. quadrifasciata. The correlation of paternity of flowers pollinated by B. patagiatus was significantly lower than that of flowers pollinated by A. quadrifasciata. For I. sinensis, B. patagiatus may exhibit larger pollen wastage, thus reducing the male reproductive success of the plant, but it causes higher female reproductive success because of its higher outcrossing rate and the lower correlation of paternity. Our findings highlighted that different animal pollinators could indeed cause differential mating systems and reproductive success.

Nothofagus species are constitutive elements of the temperate forests along the Southern Andes Mountains. The deciduous Nothofagus alpina is a fast-growing, but long-lived opportunistic pioneer species (‘pioneer-climax species’) and co-occurs with the evergreen N. dombeyi. We tested whether N. alpina is competitively superior to N. dombeyi in mature stands and whether intra-specific competition in N. alpina is stronger than inter-specific competition with N. dombeyi.

In a pristine old-growth forest in South-Central Chile, we compared the growth of N. alpina trees in pure stands and in mixture with N. dombeyi to the growth of N. dombeyi and calculated competition indices. We related growth variables to climate data and weather extremes.

In N. alpina, juvenile basal area increment was significantly higher in pure than in mixed stands. Contrary to our hypothesis, N. dombeyi exhibited larger radial stem increments than N. alpina in the most recent 40 years. In the most recent two decades, this was caused by high growth rates of large N. dombeyi trees. In both Nothofagus species, stem growth was negatively related to temperature, but N. dombeyi responded more sensitively to weather conditions than N. alpina. In N. alpina, stem increment was negatively related to the intensity of competition, but the size of the competition effects on this species was similar in pure and mixed stands. Thus, compared to N. alpina, the ‘pioneer-climax species’ concept is even more appropriate for N. dombeyi with its relatively high growth rates even in the early stages of its life.

The loss of species that engage in close ecological interactions, such as pollination, has been shown to lead to secondary extinctions, ultimately threatening the overall ecosystem stability and functioning. Pollination studies are currently flourishing at all possible levels of interaction organization (i.e., species, guild, group and network), and different methodological protocols aimed to define the resilience of pollination interactions have been proposed. However, the temporal dimension of the resilience of pollination interactions has been often overlooked. In the light of these considerations, we addressed the following questions: does a temporal approach help to reveal critical moments during the flowering season, when pollination interactions are less resilient to perturbations? Do pollination interactions evaluated at species, guild, group and network level show different patterns when assessed through time?

We monitored contacts between plant and pollinator species in dry grassland communities every 15 days during the overall community flowering season (12 surveys). For each survey, we built a quantitative plant–pollinator interaction matrix and we calculated two sets of metrics characterizing, respectively, the diversity and the distribution of interactions across hierarchical levels. To describe the diversity of interactions, we calculated partner diversity (PD) at the species level, vulnerability/generality (V/G) at the guild level, and interaction diversity and evenness at the network level. The distribution of interactions was characterized by calculating selectiveness at the species and the network level, and modularity at the group level. We assessed the temporal variation of PD, V/G at the level of plants and pollinators, and species selectiveness, by means of Linear Mixed Models (LMMs). To investigate the temporal variation of indexes calculated at group and network level, we applied simple linear and quadratic regressions after checking for temporal autocorrelation in residuals.

When taking into account the temporal dimension of interactions, the diversity of interactions showed different patterns at different levels of organization. At the species level, no relationship was disclosed between PD and time, when assessing the temporal trend of V/G separately for the guild of plants and pollinators we observed an asymmetric structure of interactions. Pollination interactions showed to be asymmetric throughout the flowering season; however, evenness of interactions and network selectiveness showed significant positive relationships with time, revealing a poorer network of interactions during the end of the flowering season. The temporal analysis of pollination interactions revealed a stronger risk of secondary extinctions at the end of the flowering season, due to a lower degree of redundancy and thus of resilience of the overall network of interactions.

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.

Comparisons of climate envelopes among species have shown that niche conservatism tends to break down over time. Here, we use the Asian tree genus Platycarya (Juglandaceae) as a case study to test this tendency at relatively short timescales in a single lineage. This, together with a reanalysis of the extant literature, should help evaluate prospects of using correlations between climate and species occurrence data to infer evolutionary processes.

We rely on species distribution models (SDMs) and multivariate analyses to compare current and past (Last Glacial Maximum ~21ka) climatic envelopes between the two extant Platycarya species (Platycarya strobilacea and Platycarya longipes) and between mainland and Taiwan populations of P. strobilacea, paying particular attention to autocorrelation issues. We also review interpretations provided in similar studies comparing climate envelopes between and within species, including in studies involving native and introduced populations of the same species.

We find intraspecific but not interspecific differentiation in climate envelopes of Platycarya, despite the prediction that niche differentiation should be stronger between older groups. Our review also suggests that differentiation in climate envelopes need not imply rapid evolutionary divergence. Whereas SDMs can be used to raise evolutionary hypotheses to be validated with other data, we conclude that it should not be used to directly infer short-term evolutionary processes.

Gallery forests within grasslands have natural edges with open environments and offer a unique opportunity to examine how species performances vary across environmental gradients. Here, we asked if demographic rates of tree functional groups varied along the edge, if we could explain differences in plant strategies and performance through functional traits and which traits increase growth and survival in natural edges.

We examine mortality and recruitment within the first 10 m of natural edges of eight gallery forests using demographic data from five annual inventories. We defined a priori plant strategies using tree functional groups: light demanding, pioneer and shade tolerant.

The shade-tolerant group had the lowest mortality rates and basal area (BA) loss, while pioneer and light-demanding species had similar behavior for these rates. The survival and growth of functional groups were affected differently by the distance from the edge. The pioneer group survived more near the edge, while light-demanding and shade-tolerant groups toward the forest interior. All groups had higher growth in the grassland. Those differences could be explained by functional traits since most species have an acquisition strategy: higher specific leaf area and growth, lower leaf dry matter content, lighter stem density, deeper crowns and less slender stems. Acquisitive traits enhanced growth. However, mortality selected both strategies, but in distinct edge’s zones. Our study showed that the high diversity found in natural edges can be explained by a niche and functional perspective, where differences in functional traits lead to differential performance along the environmental gradient.

Carbon fluxes and species diversity in grazed and fenced typical steppe grassland of Inner Mongolia, China
R. Sagar, G.Y. Li, J.S. Singh and Shiqiang Wan

J Plant Ecol 2017 XX: XX–XX doi:10.1093/jpe/rtx052

The Publisher would like to apologize for a spelling error in the name of the author Shiqiang Wan in the original version of this
paper. This has now been corrected.