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Vegetation maps are important sources of information for biodiversity conservation, ecological studies, vegetation management and restoration, and national strategic decision making. The current Vegetation Map of China (1:1000000) was generated by a team of more than 250 scientists in an effort that lasted over 20 years starting in the 1980s. However, the vegetation distribution of China has experienced drastic changes during the rapid development of China in the last three decades, and it urgently needs to be updated to better represent the distribution of current vegetation types. Here, we describe the process of updating the Vegetation Map of China (1:1000000) generated in the 1980s using a “crowdsourcing-change detection-classification-expert knowledge” vegetation mapping strategy. A total of 203,024 field samples were collected, and 50 taxonomists were involved in the updating process. The resulting updated map has 12 vegetation type groups, 55 vegetation types/subtypes, and 866 vegetation formation/sub-formation types. The overall accuracy and kappa coefficient of the updated map are 64.8% and 0.52 at the vegetation type group level, 61% and 0.55 at the vegetation type/subtype level and 40% and 0.38 at the vegetation formation/sub-formation level. When compared to the original map, the updated map showed that 3.3 million km2 of vegetated areas of China have changed their vegetation type group during the past three decades due to anthropogenic activities and climatic change. We expect this updated map to benefit the understanding and management of China’s terrestrial ecosystems.

Tree architecture is crucial to maximizing light capture, determined by carbon allocation of individual trees, and consequently characterizes species-specific growth strategies. Its variation and associated life-history strategies have been examined in tropical and temperate forests, but not in subtropical forests. Moreover, a similar architectural pattern was found using a hierarchical Bayesian model in a tropical forest, which differed from most of previous studies. Here, we employed a hierarchical Bayesian model to examine tree architecture differences and associations with adult stature and light requirement among 59 subtropical co-occurring species. Architectural variations among tree species with different seed dispersal and leaf phenology types were analyzed. Most species showed similar architecture in the height of the lowest foliage-tree height relationships (F-H) and the long side of crown- tree height relationships (W1-H), but some species showed interspecific variations in tree height-stem diameter relationships (H-D) among the 59 co-occurring species in the subtropical montane forest. Trees developed deeper and larger crowns at mid-elevation compared to the tropical and temperate forests. Parameters of H-D relationship differed in leaf phenology and dispersal types, and intercepts of F-H relationship and W1-H relationship differed in leaf phenology. Large-statured species had more slender stems, and shallower and narrower crowns at small sizes, but similar crowns at large sizes. Light-demanding species showed weak correlations between architectural variables and light requirement but exhibited wide crowns at the intermediate sizes. In general, size-dependent architectural differentiation was driven mainly by adult stature and light requirement in subtropical forest. Coexistence species showed different life-history strategies in light capture, which may help provide options in forest thinning and harvesting in subtropical forest. Species-specific tree architectural models of 59 co-occurring species represent three-dimensional (3D) structure of this subtropical forest accurately, but also support for future terrestrial laser scanning (TLS) data analysis.

Understanding how plant species respond to extreme climate events is crucial for planning management and conservation actions. As extreme precipitation accelerates, the waterlogging related to it is predicted to be more severe and frequent. To date, however, empirical studies addressing the effects of extreme precipitation-induced waterlogging on the seeds of wild plants are still scarce. In this study, we compared the size, mass and element concentration of seeds produced by non-inundated and inundated individuals of Sinojackia huangmeiensis, a critically endangered tree species with only one extant wild population. Compared to the seeds from non-inundated individuals, the seed length, seed width, and seed mass were all smaller for seeds from inundated individuals. However, the concentrations of four chemical elements in the seed displayed an opposite trend, except those elements (e.g., C, K, Ca, Mg, Al, Fe, Ni, B, Mo, and Cu) with no significant difference. Some toxic elements (e.g., Mn) accumulated in the seeds from inundated individuals, as well as some nucleic acid-protein elements (e.g., N and P) and enzymatic (e.g., Zn) elements. Our study provides rare empirical evidence that wild plants could respond to extreme precipitation-induced waterlogging by changing both seed morphological traits and element concentrations.

Seed traits related to recruitment can directly affect plant fitness and persistence. Phenotypic variability in seed traits among populations could increase species resilience and reduce the risk of extinction under climate change. However, seed trait variations along geographic gradients of relict mountain tree species remain poorly explored despite their vulnerability to environmental changes. Here, we collected seeds of Euptelea pleiospermum from 18 populations across its natural distribution in China, measured seed morphology and seed nutrients, and performed a germination test. We investigated geographic patterns of seed traits and analyzed the relationships between environmental factors and seed traits. We also analyzed the relationships between seed intrinsic attributes and seed germination percentage. In addition, we explored the direct and indirect effects of climatic and edaphic variables on seed germination percentage. We found substantial variation in seed traits of this species among populations. Seed mass decreased from low to high latitude, and seed size (length and width) decreased with longitude from west to east. Seed germination timing increased from low to high altitude. Temperature and soil phosphorus determined the geographic variation of seed traits. Seed mass and seed nitrogen had positive effects on seed germination percentage. Seed intrinsic attributes, rather than maternal environmental factors, were the dominant drivers of the variability in seed germination percentage. However, maternal environmental variables could indirectly affect the seed germination percentage through their effects on seed morphology and nutrients. These results demonstrate that among-population seed trait variations are mainly driven by climatic variables and soil nutrients, and indicate that climate warming is likely to alter seed germination patterns by shifting seed intrinsic attributes. Our study provides insight into how mountain tree species regulate seed traits and germination time to adapt to heterogeneous environments and improves our power to predict how relict plants may respond to climate change.

How well ex situ living collections capture the genetic variation of their wild-source populations, is an efficient indicator for assessing the success of ex situ conservation. Here, we explore the origins and genetic representation of multiple species' ex situ living collections that have been established for 20–35 years. We only sampled the potential wild-source populations, which cover parts of the focal species’ natural distribution ranges. Using microsatellite loci, we compared the genetic diversity between ex situ and wild populations, and verified the wild-source populations of ex situ living collections for five endangered tree species (i.e., Davidia involucrata, Dipteronia sinensis, Tetracentron sinense, Cercidiphyllum japonicum, and Tapiscia sinensis). We found that the genetic diversity of ex situ populations is comparable to their wild-source populations for all five plant species. We detected weak genetic structure among ex situ and wild-source populations for each species. Our results suggested that ex situ living plant collections may have comparable genetic diversity compared with their corresponding wild-source populations. We recommend that additional ex situ collections from different maternal lines across ex situ institutions or the distribution range of the target species would contribute to high level of genetic representation of ex situ populations, and (2) complete collection records and optimal sampling strategies are required for effective ex situ plant conservation.

Ex-situ conservation, the transplanting of individuals outside of their natural range, can dramatically alter biotic interactions among species. Here, we explored the shifts in the herbivory pressure and defense strategies of ex-situ populations of five endangered tree species (Pterostyrax psilophyllus, Davidia involucrata, Dipteronia sinensis, Tapiscia sinensis, and Tetracentron sinense) after 20–35 years since translocation. All species were not native to the ex-situ site and only P. psilophyllus had a closely related native species (Pterostyrax corymbosus). We compared the leaf damage type, herbivory rate, and chemistry (total phenols, tannins, N, and P) of each species, and assessed the relationship between the herbivory rate and leaf chemistry between the ex-situ and wild populations. Excluding P. psilophyllus, all species in the ex-situ populations showed changes in the type of leaf damage and lower overall herbivory rates. Ex-situ populations of P. psilophyllus showed reduced total phenol, N, and P levels, while the other four species showed decreased total phenol and tannin levels, or increased N and P levels. The herbivory rate was positively correlated with the N and P levels in wild populations, and negatively correlated with the total phenol content in ex-situ populations. These differences reflect the reduced herbivory pressure, decreased defense ability, and shift in defense strategy of ex-situ populations. We showed that prolonged exposure to the ex-situ environment led to the maladaptation of these endangered plant species to herbivory pressure in the natural environment, and that these shifts should be considered in ex-situ conservation and reintroduction strategies.

A mechanistic understanding of factors driving forest biomass will help stewards manage carbon storage in forests. We examined the potential biotic and topographic factors in regulating subtropical forest carbon storage. We utilized data from the Badagongshan 25 ha (500 × 500 m) forest dynamics plot to examine the factors regulating the spatial variation of large trees and forest biomass. We mapped forest biomass and large tree biomass distributions and applied variation partitioning analysis to examine a suite of topographic and biotic factors related to the distributions. The average biomass of the 25 ha plot is 252.7 Mg/ha but varied substantially from 39.16 to 1024.53 Mg/ha in the 20 × 20 m quadrats. Overall, large tree (diameter at breast height ⩾25 cm) density accounted for 71% of variation in forest biomass distribution. Variance partitioning showed that biotic, topographic and spatial factors altogether explained 64.8% and 57.5% of the variation in the distribution of forest biomass and large tree density, respectively. Fractions of variance explained by the convexity and topographic wetness index (TWI) were much larger than other topographic variables in both distributions. For biotic variables, stem density and wood specific gravity were important in predicting forest biomass and large tree density distributions. Both biomass and large tree density showed an increasing trend with increasing convexity, stem density and wood specific gravity, but decreased as TWI increased. Convexity and TWI explained more variation among topographic variables, indicating that water deficiency may play an important role in shaping the distribution of forest biomass and large tree density. In conclusion, the crucial relationship between forest biomass and large tree density distribution should attract more attention, and suggests a mechanistic control of forest carbon storage that may help provide options in forest carbon management.

Poleward and upward range shifts are important strategies for range-restricted tree species in the face of climate warming, but empirical studies of both latitudinal and altitudinal shifts are scarce. We investigated regeneration dynamics of an endemic Tertiary-relict tree (Euptelea pleiospermum) along (i) a latitudinal gradient across its range in China and (ii) altitudinal gradients along three mountains at low, middle and high latitudes. Sprouting ratio and relative seedling density present contrasting latitudinal patterns, with more seedlings at the leading edges and more sprouts at the trailing edges. We detected no apparent shift, a downslope shift and an upward shift along mountains located at low, middle and high latitudes, respectively. Sprouting ratio and relative seedling density also show contrasting altitudinal patterns. Our results suggested (i) northward migration along the latitudinal gradient and (ii) disparity in altitudinal shifts of the same tree species along different mountains. Furthermore, we emphasize that sprouting is an important strategy for sprouting tree species to buffer range contraction at the trailing edges in the face of climate warming.

It has been hypothesized that differences in spatial arrangements change the relative frequency of intra- and interspecific encounters between plant species. Manipulating spatial arrangement may play a role in invasive plant suppression when native species are used as competitors against introduced species. In this study, a replacement series experiment was performed to investigate the effects of intraspecifically random and aggregated spatial arrangements on interactions between the native plant Hemarthria compressa and the invasive plant Alternanthera philoxeroides, to test the possibility and effectiveness of H. compressa in suppressing A. philoxeroides. When both species were planted in intraspecifically random spatial patterns, H. compressa had a competitive advantage over A. philoxeroides at relative densities of 2:2 and 3:1. However, aggregation increased the strength, and therefore the cost, of intraspecific competition in H. compressa, resulting in lower biomass production, which reduced its effectiveness as an interspecific competitor. As the relative density of H. compressa in mixtures decreased, plants allocated more biomass to belowground parts, but fewer interspecific encounters lowered its inhibitory effects on A. philoxeroides. The results not only confirm that the frequency of conspecific and heterospecific encounters can influence competitive outcomes, but also suggest that a reduction in the degree of spatial aggregation in H. compressa and an increase in its relative densities may be essential to increase the suppression of A. philoxeroides.

Spatial and temporal variation in species abundances and distributions of the seedling community, which plays a pivotal role in maintaining species diversity, can help predict future changes in forest communities. We monitored the dynamics of 12,830 seedlings within 405 1-m2 seedling plots in the Badagongshan (BDGS) 25-ha forest dynamic plot over a 6-year period (2012–2017). We presented changes in the relative abundance for 15 dominant seedling species during the last six years, assessed temporal changes in species richness, species turnover, seedling density, species reordering (mean rank shift of the relative abundance; MRS) and community similarity within three topographically defined habitats (ridge, slope and valley), and explored the mechanisms underlying dynamics of seedling communities. Furthermore, we explored differences in species’ ecological indicator values (EIVs) and functional groups for species gained and lost during the study period. Across three habitat types, there were enormous reordering of the 15 dominant seedling species; a few mast-seedling events were clearly identified. Both species richness and seedling density continually declined over the entire census year, except for an increase of species richness during 2012–2013. Species turnover fluctuated temporally in three habitat types; overall, species emigration rate was higher than species immigration rate in three habitats. Valleys with lower soil C:N ratio, light availability and VDCN (vertical distance above the channel network), but higher soil pH and TWI (topographic wetness index), had lower species richness and stem density, and higher species turnover and species reordering than slopes and ridges. At the community-wide scale, significant directional changes in species composition occurred on ridges and slopes. Newly colonizing species were typically more shade- tolerant, water- and temperature- demanding shrub species and grown on soil with low pH but high fertility. In the BDGS plot, species richness and seedling density fluctuated in the first two years and then decreased over time, which reflects that both habitat filtering and seed input regulated temporal dynamics of species composition, but the relative importance varied among studied years. In this subtropical forest, species composition showed obvious directional changes. Shrub species increased more than species of other strata in ridge and slope areas. It is worth noting that an increased dominance of species that are more water-demanding could increase the risk of mortality under global climate change (e.g. drought).

Transient dynamics is a growing concern in population biology and is particularly relevant for rare species that colonize ecotones. Euptelea pleiospermum is a threatened species endemic to eastern Asia and a common component in riparian forests. Transient amplification and attenuation envelopes, as well as elasticities of population growth rates and population momentum, were explored based on stage-structured transition matrix models to articulate the population dynamics of this species. The results demonstrated that transient population growth rates and eventual population sizes (i.e. population momentum) differed sufficiently from asymptotic expectations. But transient population fluctuations as measured by amplification and attenuation envelopes were modest in size. The potential of transient amplification and attenuation are perhaps associated with reproduction of early mature individuals and the mortality of juveniles, respectively. Both asymptotic and transient population growth of E. pleiospermum are most sensitive to survival, less sensitive to tree growth, and largely insensitive to fecundity, whereas the importance of vegetative reproduction is pronounced over fecundity. Underrepresented or overrepresented stages in the initial structure relative to stable stage distribution have comparatively larger elasticities of transient population growth and population momentum, suggesting the importance of vital rates of “biased” stages in driving transient dynamics. Our results highlight the use of transient envelopes and elasticities in guiding the adaptive management for the target species.

Euptelea pleiospermum and Cercidiphyllum japonicum are dominant relictual tree species of the riparian plant communities in the subtropical region of Shennongjia Mountains, central China. Community survey and multivariate analysis were carried out to characterize their ecological ranges and regeneration characteristics, and further to explore the factors determining their present distribution boundaries and the barriers restricting their range expansion. We recorded 303 woody species, among which there were 14 relictual, rare and/or endemic woody species. Results obtained from cluster analysis corroborated the results from non-metric multidimensional scaling (NMS) ordination, classifying the 42 plots into three well-defined associations. Correlation analysis revealed that variation in species composition among associations was partly explained by some physical (altitude, slope, soil temperature) and chemical (available K, NH4, pH) properties. Multiple regression analyses with data of adults and seedlings with physical and chemical variables revealed contrasting patterns of the two dominant relictual species. Both taxa have a high resprouting rate that keeps the stands stable irrespective of scarcity of seedlings. However, expansion of the distribution range is difficult in such a situation. E. pleiospermum prefers riparian habitats with poor nutrients in the south-facing slope of the Shennongjia Mountains, which may indicate that this species is light-demanding at some life stages and well adapted to a nutrient-poor habitat where competition from other species is limited. The Cercidiphyllum japonicum population was more scattered and fragmented, and preferred riparian habitats on gentle slopes. Both species are favored by the mild and moist microclimate, but the current conditions in these subtropical mountain riparian habitats probably do not really provide optimal ecological conditions for the two relictual species.

Paspalum distichum, Cynodon dactylon and Hemarthria altissima distribute widely in natural water fluctuation zone of the Three Gorges region. To investigate whether they are suitable for growing in the artificial water fluctuation zone, which has longer submergence time and different submergence rhythm, of the Three Gorges reservoir, three complete submergence depths (0.5, 1 and 2 m) were conducted for about 6 months (from 12 November 2007 to 30 April 2008), and the survival and recovery growth of the three species were recorded after re-emergence for two weeks. The three species could start recovery growth within one week and more than 50% plants could survive. Among the three species, P. distichum had the largest increments in branch number and maximum stem length, and the smallest root shoot ratio. C. dactylon, however, had the smallest maximum stem length increment, and its survival and branch number increment were both larger than those of H. altissima. For C. dactylon and H. altissima, the survival and branch number increment significantly increased, while maximum stem length increment tended to decrease when submergence depth went higher. For P. distichum, the survival and the shoot mass were the lowest after 2 m submergence depth, but the other parameters were not different among different submergence treatments. Compared with control plants, submergence increased root shoot ratio of C. dactylon and H. altissima, but did not affect that of P. distichum. These results demonstrated that the three species are submergence-tolerant and can be applied in vegetation reconstruction in water fluctuation zone of the Three Gorges reservoir. Meanwhile, the results also suggested that the three species developed different survival tactics during the long-term submergence.

Age structure and regeneration dynamics of subalpine fir (Abies fargesii) forest were studied across the altitudinal range in both the north and south aspects of the Qinling Mountains, China. Ages of individual fir trees were determined based on the number of rings counted from cores and the number of years to reach coring height estimated using age–height regression. Fir age structure and regeneration dynamics were similar in both the north and south aspects. A unimodal population age structure was found at the low- and mid-elevations in both aspects, indicating that environmental factors might play an important role in shaping A. fargesii age structure and regeneration at those sites. There was a recruitment pulse during the time period 1830–1890 at each altitudinal site, but no stem recruitment occurred at the low- and mid-elevations in the last century, which might be attributed to the intensive cover of understory bamboo. Fir trees were, however, persistently recruited at the upper limits during the last 150 years, and the fir tree density at the upper limits was significantly higher than that at the lower limits in both aspects. The fir population at the upper limits showed a significant increase in recruitment and stem density relative to the fir population at the low- and mid-elevations in the last century. We propose that the differences in recruitment might promote variations in stand structure and regeneration dynamics of the subalpine fir forests along the altitudinal gradient in the Qinling Mountains, China.

Dendroecological techniques have been employed to investigate the relationship between subalpine fir (Abies fargesii) growth and climatic variability throughout its elevational range on both south and north aspects in the Qinling Mountain of Shaanxi Province, China. Correlation analyses indicate that early spring and summer temperatures are the principal factors limiting its growth in the low- and middle-elevation distributional areas. In the high-elevation areas, it is the summer precipitation that affects A. fargesii radial growth. The previous year August and November temperatures show positive correlation with the radial growth in the low- and middle-elevation distributional areas of the south aspect, and in the high-elevation areas, precipitation in previous November has significantly negative influences on the radial growth. The previous year's temperature and precipitation have no significant effects on the radial growth of the fir trees in the north aspect. Thus, the growth of the subalpine A. fargesii responds differently to climatic conditions along the elevational gradient and in different aspects.