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Questions: Interannual precipitation changes, both in amount and frequency, are expected to increase due to climate change, and these changes could dramatically affect the structure and function of ecosystems. However, how plant life‐forms and dominant species regulate the plant community structure after precipitation changes remains unclear. Location: Gaolan Experiment Station for Ecology and Agriculture Research of the Northwest Eco‐Environment and Resources Research Institute of the Chinese Academy of Sciences, located in the desert grassland of the western Loess Plateau, China. Methods: To investigate the effect of precipitation changes on the growth of communities, life‐forms, and species, we used rain shelters and irrigation to create a variety of precipitation gradients (i.e., −40%, −20%, 0% [= CK, i.e., control treatment], +20%, +40% of ambient precipitation) in desert grasslands from 2014 to 2015. Results: The plant community density, coverage, and height were significantly decreased in the −40% treatment compared to CK. In contrast, species richness, Shannon–Wiener index, and Pielous' evenness did not respond significantly to the precipitation treatment. In addition, at the level of life‐forms, the density of perennial herbaceous plants was significantly increased by the +40% treatment in 2015, while the richness and density of annual herb were significantly inhibited by extreme drought. The effect on the shrub growth index of increasing and decreasing precipitation compared to the CK was insignificant. Furthermore, at the level of species, the growth of dominant species was obviously suppressed by the −40% and +40% treatment in 2015. However, the positive effect of the +40% treatment on the growth of rare species reached significant levels in 2015. Also, the change in precipitation did not have a significant effect on the growth of companion species. Dominant species primarily drove the response of community‐level plant growth to precipitation changes over the three‐year study period. Conclusion: The response of plant community composition to changes in precipitation in desert grassland is largely regulated by changes in the composition of the dominant species. This finding could also provide a better prediction of the effects of extreme drought on desert grassland plant communities in the scenarios of future global climate change. [ABSTRACT FROM AUTHOR]

Questions: Drought timing during the growing season can profoundly influence plant diversity and cover, with subsequent impacts on ecosystem functions and services in terrestrial environments. However, the different responses of plant communities to drought in different periods of the growing season remain uncertain. Location: The research was conducted in a semi‐arid grassland at the Duolun Restoration Ecology Research and Demonstration Station, in Inner Mongolia, China. Methods: The responses of plant species richness and cover to early‐ and late‐season drought with a four‐year field experiment were examined in a semi‐arid grassland in northern China. Soil moisture at different depths was measured to explore the underlying mechanisms of the drought effects on plant richness and cover. Results: Over the four years, late‐ rather than early‐season drought suppressed plant richness. Decreased species richness (−1.65 species) under late‐season drought was mainly due to suppressed perennial forb richness (−1.88 species). Late‐season drought also exerted greater negative effects on plant cover than early‐season drought. Effects of late‐season drought on plant cover depended on annual precipitation. Reduced plant cover (−7.5%) under early‐season drought stemmed from declines in shrubs and semi‐shrubs, particularly Artemisia frigida cover (−4.9%), which is sensitive to water deficits because of its shallow root depth (14.01 cm). Declined plant cover (−39.0%) under late‐season drought was mainly caused by suppressed perennial forb (−21.5%) and shrub and semi‐shrubs cover (−17.4%). The combined effects of early‐ and late‐season drought on plant cover were greater than the treatment alone, likely due to aggravating water deficits under growing‐season drought. Conclusions: Our results suggest late‐season drought is more critical for shifting plant communities. than early‐season drought. Our findings highlight the regulatory role of drought timing on plant community composition and development in arid and semi‐arid regions. [ABSTRACT FROM AUTHOR]

Question: The impact of ants on the vegetation and soil seed bank of alpine meadows on the Qinghai‐Tibetan Plateau is largely unknown. We questioned how the mound‐building ant, Camponotus herculeanus, affects the above‐ground vegetation, the soil seed bank and physico‐chemical properties of the soil. Location: An alpine meadow in the northeast margin of the Qinghai‐Tibetan Plateau (37°40′ N, 102°32′ E), China. Methods: We used field and greenhouse studies to determine the above‐ground vegetation parameters and soil physico‐chemical properties, and the soil seed bank composition under the mound (UM), the herbage circle at about 10 cm width around the outside of the mound (mound edge, ME) and the area 1 m from the center of the mound (control). Results: (a) The mound edge had higher vegetation height, greater above‐ground biomass, lower vegetation coverage and lower plant richness than controls; (b) Gramineae had a higher total importance value, which was based on the height, coverage and biomass of each plant species, and composed a higher biomass proportion in the mound edge than in controls (68% vs. 38%), while most of the perennial dicotyledons were restricted to the controls; (c) dicotyledons were the main seed group in the 0–8 cm layer of soilUM (43%), soilME (51%) and soilcontrol (60%), while Gramineae had a significantly higher seed density and percentage of total seeds in the soilUM (16,507 ± 2,882.7 seeds/m3, 28.1%) than in the soilcontrol (4,200 ± 799.5 seeds/m3, 10.2%); and (d) soil in the 0–8 cm layer under the mound had lower water content and lower bulk density than soil on the mound edge and in controls. Conclusions: Mound‐building activity of Camponotus herculeanus increased the proportion of Gramineae and decreased the proportion of dicotyledons at the site of the study indicating, that mound building could enhance the transformation of a grass and sedges community to mainly a grass community in the alpine meadow. [ABSTRACT FROM AUTHOR]

Question: Bivariate relationships among functional traits reflect how plants adjust to environments through the allocation of limiting resources. Bivariate relationships are well studied across species, but whether the nature of these trait relationships changes across organizational levels (individual, species, community), and whether processes driving these relationships vary across these levels, is seldom explored. Location: The tropical cloud forests of the Bawangling Nature Reserve, Jianfengling Nature Reserve and Limushan Nature Reserve on Hainan Island, Southern China. Methods: We measured leaf mass per area (LMA), plant height (H) and wood density (WD) for 4,748 individual trees, 174 species and 48 communities in three tropical cloud forests, and recorded five soil characteristics that are important for plant growth. We evaluated bivariate relationships between these traits across the three organizational levels, and assessed the effects of soil conditions on these trait relationships. Results: LMA versus H, WD versus H, and LMA versus WD were all positively and disproportionately related, suggesting differential carbon investment between leaves and stem, as well as between stem height and stem density. The slopes of these relationships did not differ significantly across the three levels, suggesting a similar allocation strategy operating at different hierarchical levels. Soil phosphorus had a significant effect on the scaling exponents across all three organizational levels, indicating that phosphorus limitation in cloud forests is a principal driver of resource allocation patterns in trees. conclusions: We conclude that tropical cloud forest trees have relatively consistent scaling relationships between three primary functional traits across the individual, species, and community levels. The coordinated resource allocation strategies in plants are most likely driven by the prevailing environmental constraints. [ABSTRACT FROM AUTHOR]

Question: Vegetation recovery and succession patterns after fire are not completely explained by the interactions of climate, disturbance, and species pool. Site‐specific factors can substantially change vegetation succession. We hypothesize that on sites exposed to fire and surface permafrost degradation, successional trajectories will produce different species assemblages than typical post‐fire succession. Location: Da Xing'an Mountains, northern China. Methods: Vegetation and environmental data were collected at eight sites of past natural wildfire events. These sites represented different topographical situations, with four sites on slopes (lacking surface permafrost) and four sites in valleys (with surface permafrost). Three plots were established on each site, representing three different fire presence zones (burned, ecotone and unburned areas), giving a total of 24 plots. We used non‐metric multidimensional scaling (NMS) to describe post‐fire vegetation recovery at different sites and multi‐response permutation procedures (MRPP) to test our hypothesis. Results: The variation in dates of last fire was similar between the slope and valley sites. Slope sites that had been burned prior to 2003 had recovered to a composition similar to unburned sites by the time the study was conducted in 2017. However, none of the burned valley sites had fully recovered, even those exposed to fire in 1986, suggesting that the surface permafrost conditions affected the recovery pattern of vegetation. On burned valley sites, shrub species that are tolerant of saturated soils had become dominant and the number of tree saplings and seedlings became significantly lower than on the slope sites. Conclusion: The interaction of fire and topographic site type (through the influence of surface permafrost degradation) was revealed as a primary factor affecting species composition and tree density of post‐fire communities. On valley sites, melting of the surface permafrost after fire caused a failure of tree recruitment and prompted shrub species tolerant of saturated soils to become dominant. [ABSTRACT FROM AUTHOR]

Questions: All else being equal, populations of dioecious species with a 50:50 sex ratio have only half the effective reproductive population size of bisexual species of equal abundance. Consequently, there is a need to explain how dioecious and bisexual species coexist. Increased mean individual seed mass, fecundity, and population density have all been proposed as attributes of unisexual individuals or populations that may contribute to the persistence or resilience of dioecious species. To date, no studies have compared sympatric dioecious and cosexual species with respect to all three components of fitness. In this study, we sought evidence for these compensatory advantages (higher seed mass, greater seed production per unit basal area, and higher population density) in dioecious species. Location: Five 20–25 ha forest dynamic plots spanning a latitudinal gradient in China, including two temperate, two subtropical, and one tropical forest. Methods: We used a phylogenetically corrected generalized linear modelling approach to assess the phylogenetic dependence and joint evolution of sexual system, seed mass and production, and ecological abundances among 48–333 species and 32,568–136,237 individuals per forest. Results: Across all five forests, we detected no consistent advantage for dioecious relative to sympatric cosexual species with respect to mean individual seed mass, seed production or the density of stems in any size class. Conclusions: Our study suggests that seed traits may provide compensatory mechanisms in some forests, but most often the coexistence of sexual systems cannot be explained by advantages of dioecy related to seed quality and demographic parameters. Future investigations of the factors that promote coexistence may increase our understanding by expanding the search to include attributes such as lifespan and tolerance or resistance to herbivores. [ABSTRACT FROM AUTHOR]

Question Do the three chosen species ( Caltha palustris, Veratrum nigrum and Stellera chamaejasme) in humid alpine meadows take up water from different depths? Do these species differ in their responsiveness to rainfall? Location Mt. Balang, China. Methods Rainwater, soil water and plant water were collected from three plots over a 15-day period during June-July 2006, and water isotopes analysed. The linear mixed models procedure was used to compare δD and δ18O values across soil depths, while three-factor ANOVA was performed to compare δD and δ18O values among the three species. The contributions of different soil depths to plant water sources were analysed using Mix Sir. A classic two-endmember linear mixed model was used to calculate the proportion of rainwater in plant stem water. Results Soil water showed substantial temporal shifts in isotopic profile from day to day, as influenced by rainwater input. The three plant species, C. palustris ( CP), V. nigrum ( VN) and S. chamaejasme ( SC), acquired water from different soil depths, with their reliance on deeper soil water increasing in the order of CP < VN < SC. Moreover, CP, VN and SC absorbed 69.18%, 35.50% and 13.46% of their stem water, respectively, from the 4 July rainwater, suggesting that their responsiveness to rain pulses significantly differed in the order of CP > VN > SC. Conclusions The isotopic profiles of soil water shifted dramatically in response to rainfall, suggesting rapid movement of soil water. There was separation of the plant water uptake depths among the three species, with SC depending less on surface soil and being associated with drier soil habitats compared with CP and VN. Moreover, CP absorbed rainwater before it percolated below the root zone, while VN and SC did not; the differential responsiveness to water pulses may be related to their different water requirements as a result of adaptation to different soil water conditions. Our study demonstrates inter-specific differentiation in plant water uptake in humid alpine meadows. Such information is important for species co-existence and plant community composition. [ABSTRACT FROM AUTHOR]

Question: Are species-specific regeneration strategies and competition the dominant processes facilitating species coexistence in a Quercus liaotungensis dominated temperate deciduous forest? Location: Dongling Mountains, North China. 1300 m a.s.l. Methods: Ripley's K-function was used to characterize the spatial patterns and spatial associations of two dominant tree species. Quercus liaotungensis and Betula dahurica, and a common subcanopy species. Acer mono, at different growth stages (adult, sapling, seedling). Results: Seedlings, saplings and adults of all three species exhibited clumped distributions at most spatial scales, Quercus seedlings and saplings were positively associated with conspecific adult trees and spatially independent of dead trees suggesting that seed dispersal and vegetative regeneration influenced the spatial patterning of Quercus trees, Betula .seedlings and saplings were positively associated with both Live and dead trees of conspecific adults at small scales (<5 m) but negatively associated with live and dead trees of other species indicating sprouting as an important mechanism of reproduction. Saplings of Acer had a strong spatial dependence on the distribution of conspecific adult trees indicating its limited seed dispersal range. Negative associations between adult trees of Betula and Quercus demonstrated interspecific competition at local scales (<5 m). Conclusions: Different regeneration strategies among the three species play an important role in regulating their spatial distribution patterns, while competition between individuals of Betula and Quercus at the adult stage also contributes to spatial patterning of these communities. The recruitment limitations of Betula and Quercus may affect the persistence of these species and the long-term dynamics of the forest. [ABSTRACT FROM AUTHOR]

Studies how water availability influences the composition of plant functional types, soil organic matter, net primary production, trace gas flux and land-use patterns using the Northeast China Transect. Relations of plant species number, soil C and N and aboveground biomass with a precipitation gradient and interactions with land-use practices; Results of the study.

. In order to understand the influence of edaphic factors on the spatial structure of inland halophytic plant communities, a 2.6 km2 study site, located on the lower fringe of the alluvial fan of the Hutubi River, in an arid region of China, was sampled and mapped. 105 patches were found to be homogeneous in species composition. Plant species and their coverage were recorded in each patch. 45 patches were randomly selected for the measurement of edaphic variables. A map with quadrat locations and boundaries of patches was digitized into a GIS and related to the vegetation and edaphic data matrices. CCA was used to evaluate the relative importance of edaphic factors in explaining the variation of the species assemblages and to identify the ecological preferences of species. The spatial structure of the communities and the main edaphic factors were analyzed using correlograms, Mantel correlograms and clustering under constraint of spatial contiguity. Gradient analysis showed that there are two distinct vegetation gradients in the study area, one of which is determined mainly by soil moisture (determined by depth to the water table), and the other by soil salinity (determined by electrical conductivity and hydrolytic alkalinity of the first soil layer). However, spatial analyses showed that at the sampling scale the halophytic communities in the study area are structured along one main spatial gradient determined by the water table level. Similar spatial autocorrelation structures between the factors related to the first soil layer and the communities, given our sampling scale, could not be detected. Our results suggest that the relative importance of the effects of different edaphic factors on the spatial structure of halophytic communities is scale-dependent. The partitioning of species variation indicates that in addition to edaphic factors, other factors, such as biotic interactions, may play an important role in structuring these communities. [ABSTRACT FROM AUTHOR]

. Stand mapping and vertical and oblique tree crown projections were used to study gap characteristics and gap effects on the regeneration and stand development of Larix gmelini. The hypothesis is that waves of advance Larix regeneration are recruited into the canopy layer following the creation of canopy openings. In old-growth Larix forests of the northern Da Xingan Ling Mts., at 52 °N, obliquely projected gaps (OPG) begin at a distance of 60 - 80% of the canopy tree height from the southernmost stems bordering the gap and thus the OPGs may extend beyond the northern boundaries of the vertically projected gaps (VPG). Changes in the environment and resource availability in the OPG result in increased Larix sapling survival. Due to a greater incidence of light, 10 - 30 yr old OPG saplings were more abundant than saplings in either a near-oblique projected gap (NOPG) or in the shadow of obliquely projected crowns (SOPC). The survival of saplings more than 30-yr old was highest when they were found in the OPG of one canopy opening and the VPG of another. This means that, following recruitment into an OPG, saplings then require the space found in a VPG to permit growth into the canopy. Thus, various-sized gaps contribute to the survival of different aged saplings by increasing the complexity of stand structure. Although individuals may regenerate in an OPG, successful recruitment into the canopy requires the available growing space of a VPG. This research suggests that shade intolerant Larix gmelini can maintain its canopy dominance without fire via gap regeneration. [ABSTRACT FROM AUTHOR]