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.

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.

Accurate estimates of bamboo biomass and net primary productivity (NPP) are required to evaluate the carbon sequestration potential of bamboo forests. However, relevant data that are important for climate change mitigation, have rarely been collected in regions outside of East Asia and India. Information on seasonal patterns of NPP and its components will enable the quantification of factors that influence the carbon balance in bamboo forests. In this study, we quantified the aboveground biomass (AGB) and aboveground NPP of five major bamboo species in northern Laos using monthly data collected over a 12-month period.

All live culms in 10, 2 m × 2 m plots (for one monopodial bamboo species: Indosasa sinica) and 30 clumps per species (for four sympodial bamboo species: Bambusa tulda, Cephalostachyum virgatum, Dendrocalamus membranaceus and Gigantochloa sp.) were numbered and measured at breast height. We set 10 or 20 litter traps per species to collect litterfall. Censuses of dead and recruited culms and litterfall collection were performed once per month for 12 months.

The AGB was highest in I. sinica (59.87 Mg ha−1) and lowest in C. virgatum (11.54 Mg ha−1), and was mostly below the plausible global range for bamboos (32–256 Mg ha−1). The sympatric distribution of multiple bamboo species at the study sites may have suppressed the AGB in four of the five studied species. The aboveground NPP estimates were between 3.43 and 14.25 Mg ha−1 yr−1; those for D. membranaceus (8.20 Mg ha−1 yr−1) and I. sinica(14.25 Mg ha−1 yr−1) were comparable to mean global estimates for temperate evergreen forests (8.78 Mg ha−1 yr−1) and tropical moist forests (10.56 Mg ha−1yr−1). High culm recruitment rates (15.20–23.39% yr−1) were major contributors to aboveground NPP estimates. Seasonal patterns of aboveground NPP were largely influenced by the phenology of the new culms. In the four sympodial bamboo species, new culms began to emerge following the onset of persistent rainfall, mainly in July and August. However, the sprouting of new culms in the monopodial species I. sinica followed a trend of increasing temperatures, mainly in March and April. Thus, our results indicate that bamboos have considerable potential for sequestering carbon in northern Laos, but that this potential may be affected by climate change.

Grazing exerts profound effects on grassland ecosystem service and functions by regulating species composition and diversity, and structuring community assembly worldwide. However, adaptions of phylogenetic diversity and phylogenetic community structure to long-term grazing disturbance remain poorly studied, especially for ecosystems distributed in extreme environments.

Here, we conducted an experiment with multigrazing intensities to explore the impacts of grazing disturbance on plant phylogenetic diversity and community structure in an alpine grassland of the Tibetan Plateau.

Grazing disturbance enriched plant species richness (SR), and stimulated species turnover from regional species pool, consequently changing community species composition. Under low intensities, grazing exerted no obvious effects on phylogenetic diversity and community structure, whereas communities changed from overdispersion to clustering under high grazing intensity. High grazing intensity resulted in stronger environmental filtering, which consequently selected those species with high resilience to grazing disturbance. The observed clustering structure was associated with the colonizing species which were closely related to resident species, and locally extinct species, and distantly related to residents. At the plant functional trait level, high grazing intensity increased species colonization largely by altering the effect of root depth on species colonization compared to light grazing. Our results highlight that solely utilization of SR and diversity cannot fully represent grassland communities responses to grazing. The effects of species turnover on community phylogenetic diversity and structure are entailed to be explored in the future grazing studies.

Established invasive plant species have more diverse gene pools than single populations in their home range. This genetic and often phenotypic variation allows for natural selection to act and produce rapid adaptations as an invasive species interacts with other members of the community. For an invasive flowering plant, interactions with pollinators may lead to adaptations to a heterogeneous pollinator community. The variation in the pollinator community in the invaded range is similar to variation in the native range, suggesting that adaptations may mirror patterns seen in the home range. In this study, we investigated variation in flower size in Cytisus scoparius, an invasive leguminous shrub, along an elevation gradient.

This study took place in the Capitol State Forest in Washington State. We measured flower widths and the proportion of visited flowers, using 10 plants per field site. Sites were located along an elevation gradient and were visited three times to measure phenological variation on a per-plant basis.

We saw positive selection for flower size, albeit without a distinct pattern of higher selection at higher elevations. The pattern of natural selection could be seen both in terms of pollinator visitation rates and in seed production. We also found that the largest contributor to changes in seed production was not elevation or flower size but management practices.

Understanding the factors that control biodiversity distributions at different spatial scales has been a key challenge for conservation efforts. That biodiversity, reflected in differences in species compositions among sites (beta diversity), can be derived from species replacement (turnover) and is driven by multiple factors. Here, we sought to tackle this issue through two questions related to threatened Brazilian seasonally dry forests: (i) what is the contribution of species turnover to beta diversity? and (ii) which factors drive variations in species compositions among forest patches?

We sampled tree species and environmental variables (soils and climate) in 17 dry forest patches spaced almost 300 km apart. We used the beta diversity partitioning framework to determine the contribution of turnover. We used redundancy analysis, with properly controlled spatial structure, to assess the contributions of the environmental and spatial factors to the variations of the species composition.

Beta diversity among the patches was mainly represented by the turnover component (98.2%), with Simpson dissimilarity superior to other regions of the country (means of 0.89 and 0.71 in multiple site and pairwise measures, respectively). The environmental factors measured explained more than space, representing 30.3% of the variation of the species composition, of which 28.1% was nonspatially structured. We suggest that 300 km represents a threshold at which edaphic and climatic predictors have similar effects in determining community turnover (14.9% and 12.6%, respectively, without spatial structure). Thus, conservation strategies should be considered across landscapes to effectively protect tropical forest diversity, as even considering the different climatic aspects covered by the scale, landscaped edaphic varieties are important drivers of species turnover.

To explain how plant community copes with a recurring anthropogenic forest fire in Himalayan Chir pine forest, it is important to understand their postfire regeneration strategies. The primary aim of the study was to know: (i) how fire impact soil seed bank composition and (ii) how much soil seed bank composition differs with standing vegetation after the forest fire.

Soil samples were collected from burned and adjoining unburned sites in blocks using three layers down to 9 cm depth immediately after a forest fire and incubated in the net-house for seedling emergence. Same sites were revisited during late monsoon/early autumn season to know the species composition of standing vegetation recovered after a forest fire.

Soil contained viable seeds of >70 species. The average seed bank density was 8417 and 14 217 seeds/m² in the burned and unburned site, respectively. In both sites, it decreased with increasing soil depth. Overall fire had no significant impact on seed density; however, taking individual layers into consideration, fire had a significant impact on seed density only in the uppermost soil layer. The species richness of soil seed bank and standing vegetation was 73 and 100, respectively (with 35 shared species), resulting in a similarity of about 40%. In contrast, >80% species in soil seed bank was found similar between burned and unburned sites. Further, there were no significant differences in species richness of standing vegetation in burned (87 spp.) and unburned (78 spp.) sites. Our results showed that fire had an insignificant impact on soil seed bank composition and restoration potential of a plant species from seeds. The understory herb and shrub plant community’s ability to form a fire-resistant viable soil seed bank and capable to recover in the postfire rainy season, explains how they reduce the risk of recurring fire damage in maintaining their population.

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.

Exotic invasive species are often exposed to strong selection pressures in their new ranges that can often lead to substantial intraspecific variation. Population differentiation in the timing of life history events in response to climate gradients is thought to be an important mechanism facilitating the range expansion of many invasive species. For seed producing plants, the timing of seed germination determines the first environmental conditions experienced by newly emerged germinates, and can have important implications for the successful colonization, establishment and spread of invasive plants—though the role of germination in the success of invasive plants remains poorly understood.

We assessed the variation in seed germination dynamics among 10 populations of the invasive plant Johnsongrass (Sorghum halepense) across its North American distribution, capturing both a temperature and precipitation gradient, and whether that variation is associated with home climate. Seeds were exposed to a wide range of temperatures (11–48°C) and two water availability treatments.

We found that Johnsongrass seeds germinated across a wide range of temperatures, but there was substantial variation among populations in the proportion of seeds that germinated in response to both temperature and water availability. Evidence indicates that as Johnsongrass expanded its range from warmer climates into cooler climates, there was a concurrent shift in the germination temperature niche to cooler temperatures. Our results suggest that the germination of Johnsongrass seeds has adapted to home climate allowing this invader to maximize germination throughout its range, and that this may be an important contributing factor to its invasion into new environments.

In estuarine salt-marshes, nitrate supply and soil salinity, which are known as two main environmental drivers, simultaneously affect the interspecific interactions between plant species. However, to date, their interactive effects on interspecific interactions have not been closely examined for salt-marsh plant species.

Juvenile plants of Suaeda salsa L. (Chenopodiaceae) and Scirpus planiculmis Fr. (Cyperaceae) were grown in rinsed river sand to conduct a greenhouse experiment with three treatment categories: interspecific interaction (mixed culture or monoculture), three salinity levels (1, 50 and 100 mmol L−1) and three nitrate levels (0.5, 5 and 10 mmol L−1). First, height and biomass of all plants were measured. Then, the growth data, relative interaction index and competitive important index of the two species were analyzed.

The interspecific interactions between S. salsa and S. planiculmis were facilitation across the salinity gradients. The promotion of S. salsa growth with high nitrate supply did not enhance the facilitative effect of the species, especially at low salinity. However, high nitrate supply significantly shifted the interspecific interactions of S. planiculmisfrom facilitation to competition at high salinity. Our results suggest that excessive nitrate application changes the prediction of the stress-gradient hypothesis along a salinity gradient, leading to collapse of the two species coexistence in the salt-marshes. These findings make a contribution to the understanding of how S. salsaand S. planiculmis, as well as salt-marsh communities, respond to the human modification of estuarine nutritional levels.

Woody plants are widely distributed in various grassland types along the altitudinal/climatic gradients in Xinjiang, China. Considering previously reported change in carbon (C) storage following woody plant encroachment in grasslands and the mediating effect of climate on this change, we predicted that a positive effect of woody plants on plant C storage in semiarid grasslands may revert to a negative effect in arid grasslands. We first investigated the spatial variation of aboveground C (AGC) and belowground C (BGC) storage among grassland types and then tested our prediction.

We measured the living AGC storage, litter C (LC) and BGC storage of plants in two physiognomic types, wooded grasslands (aboveground biomass of woody plants at least 50%) and pure grasslands without woody plants in six grassland types representing a gradient form semiarid to arid conditions across Xinjiang.

Important Findings Living AGC, LC, BGC and total plant C storage increased from desert to mountain meadows. These increases could also be explained by increasing mean annual precipitation (MAP) or decreasing mean annual temperature (MAT), suggesting that grassland types indeed represented an aridity gradient. Woody plants had an effect on the plant C storage both in size and in distribution relative to pure grasslands. The direction and strength of the effect of woody plants varied with grassland types due to the mediating effect of the climate, with wetter conditions promoting a positive effect of woody plants. Woody plants increased vegetation-level AGC through their high AGC relative to herbaceous plants. However, more negative effects of woody plants on herbaceous plants with increasing aridity led to a weaker increase in the living AGC in arid desert, steppe desert and desert steppe than in the less arid other grassland types. Under greater aridity (lower MAP and higher MAT), woody plants allocated less biomass to roots and had lower BGC and had a more negative impact on herbaceous plant production, thereby reducing vegetation-level BGC in the desert, steppe desert and desert steppe. In sum, this resulted in a negative effect of woody plants on total plant C storage in the most arid grasslands in Xinjiang. As a consequence, we predict that woody plant encroachment may decrease rather than increase C storage in grasslands under future drier conditions.

Species-rich plant communities are more resistant to invasions. In the past decade it was demonstrated that genetic variation also has many ecological effects. In our study we aimed to test whether the patterns of response to the genetic diversity of a resident species differ between colonizing species of different growth forms and whether the response is affected by soil nutrients.

We established experimental stands of a common grass, Festuca rubra, harbouring three levels of genetic diversity (1, 6 or 18 clonal genotypes, referred to as genotypic diversity) under two soil nutrient levels. In the fourth year after the stands were established, we sowed a mixture of four colonizers into the stands: a stoloniferous legume (Trifolium repens), a broad-leaf tussock grass (Anthoxanthum odoratum), a large-rosette forb (Plantago lanceolata) and a small-rosette forb (Campanula rotundifolia). We observed species establishment and growth over 3 years. We tested whether colonization success depended on genotypic diversity, specific Festuca genotypes, soil nutrients and colonizer growth form.

The colonization success and biomass of the colonizers were significantly affected by the genotypic diversity and the genotype identity of the resident clonal grass. The response, however, differed between the colonizers. The strongest response to the genotypic diversity of the resident species was observed in the tussock grass with a growth form and architecture similar to the resident species. The large-rosette species responded in early stages of growth whereas the stoloniferous legume did not respond at all. The intraspecific genotypic diversity and genotype identity of the resident species play an important role in the assembly of plant communities.

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.

Very little is known about the performance of non-agricultural plant species in monocultures, even though nearly all agricultural species have experienced the transition from multi-species environments to dense monospecific stands during the breeding process. In the light of recent work that highlighted the possibility that the weedy species Arabidopsis thaliana can offer novel insight into crop breeding, we aimed to test the effect of sowing density on group and individual performance in different photoperiod environments in A. thaliana.

We studied the performance of A. thaliana Cvi-0 ecotype. The choice of Cvi-0 was based on a preliminary experiment in which plants of Cvi-0 ecotype exhibited high competitive performance. Sowing densities used were 17.6, 8.8, 4.4, 2.2 and 1.1 cm² per plant and photoperiod environments 12 or 16 h of day light.

In this experiment, populations attained constant total seed yield for all densities. Some interaction effect occurred, as at high sowing density and at longer day length plants produced heavier seeds, whereas at shorter day length seed weight was negatively related to plant density. These results shed light on different strategies that annual plants can adopt when they face intense intraspecific competition, and could help to offer new perspectives for breeding crops with enhanced group performance.

Variations in vegetation spring phenology are widely attributed to temperature in temperate and cold regions. However, temperature effect on phenology remains elusive in cold and arid/semiarid ecosystems because soil water condition also plays an important role in mediating phenology.

We used growing degree day (GDD) model and growing season index (GSI) model, coupling minimum temperature (T_min) with soil moisture (SM) to explore the influence of heat requirement and hydroclimatic interaction on the start of carbon uptake period (SCUP) and net ecosystem productivity (NEP) in two alpine meadows with different precipitation regimes on the Qinghai-Tibet Plateau (QTP). One is the water-limited alpine steppe-meadow, and the other is the temperature-limited alpine shrub-meadow.

We observed two clear patterns linking GDD and GSI to SCUP: SCUP was similarly sensitive to variations in preseason GDD and GSI in the humid alpine shrub-meadow, while SCUP was more sensitive to the variability in preseason GSI than GDD in the semiarid alpine steppe-meadow. The divergent patterns indicated a balance of the limiting climatic factors between temperature and water availability. In the humid meadow, higher temperature sensitivity of SCUP could maximize thermal benefit without drought stress, as evidenced by the stronger linear correlation coefficient (R2) and Akaike’s information criterion (AIC) between observed SCUPs and those of simulated by GDD model. However, greater water sensitivity of SCUP could maximize the benefit of water in semiarid steppe-meadow, which is indicated by the stronger R2 and AIC between observed SCUPs and those of simulated by GSI model. Additionally, although SCUPs were determined by GDD in the alpine shrub-meadow ecosystem, NEP was both controlled by accumulative GSI in two alpine meadows. Our study highlights the impacts of hydroclimatic interaction on spring carbon flux phenology and vegetation productivity in the humid and semiarid alpine ecosystems. The results also suggest that water, together with temperature should be included in the models of phenology and carbon budget for alpine ecosystems in semiarid regions. These findings have important implications for improving vegetation phenology models, thus advancing our understanding of the interplay between vegetation phenology, productivity and climate change in future.