As one of the main food bamboo species of the giant panda (Ailuropoda melanoleuca), Fargesia denudata is widely distributed in the understory of spruce–fir forests in the mountainous area of southwestern China. However, the driving factors of its biomass and distribution in the forests are still unclear. We conducted a systematic investigation of the tree and shrub layers (including bamboos) of 209 subplots (20 m × 20 m) in a Forest Global Earth Observatory plot, the Wanglang Plot (25.2 ha), to explore the effects of abiotic (topographic and soil characteristics) and biotic (tree density, total basal area (TBA), shrub coverage, etc.) factors on the aboveground biomass of F. denudata (bamboo biomass hereafter). Bamboo biomass averaged 1.17 ton/ha, with a large variation from 0 to 4.88 ton/ha (95% confidence interval) among the 209 subplots. Bamboo biomass increased significantly with elevation, slope and mean diameter at breast height of trees, and decreased significantly with tree density, shrub coverage and soil pH. However, bamboo biomass was not significantly correlated with tree TBA, aspect, soil organic matter or total nitrogen content. The random forest model indicated that topographic factors and biotic factors had greater influences on the bamboo biomass than soil characteristics in general. Specifically, topographic factors mainly affected the bamboo biomass by changing tree density and soil characteristics. Our results can provide valuable guidance for the protection of giant pandas and the management of subalpine spruce–fir forests.

We explored if and how seasonal fires interact with microhabitat type (i.e. under Pistacia shrub, under Cistus shrub or a canopy gap) to influence the composition of the germinable soil seed bank (GSSB) community in a typical eastern Mediterranean woodland. We conducted a field experiment, involving prescribed spring and autumn burns, and thereafter quantified the seed germination patterns using soil samples collected from both burned and adjacent unburned control plots. Soil temperature was significantly higher during autumn burns, while being more variable during spring burns. Fire caused overall reductions in GSSB density, richness and diversity. The reductions in GSSB richness and diversity were significantly stronger under Pistacia and Cistus shrubs located within plots subjected to autumn burns, and these patterns were mainly evident among annuals. GSSB density of dwarf shrubs was higher in samples collected from burned plots, and this pattern was more pronounced in samples collected under Pistacia and Cistus shrubs. Together with the appearance of unique species, seasonal fires led to significant changes in the composition of the GSSB community. Our results illustrate that seasonal fires interact with spatial heterogeneity to influence the composition of the GSSB community mostly via differential effects on the germination densities of annuals and dwarf shrubs. These findings imply that the increase in the frequency of seasonal fires, which has occurred in the eastern Mediterranean basin during the last few decades, may translate into a shift in eco-evolutionary selection pressures, operating on plants inhabiting this unique ecosystem.

Temporary ponds play substantial roles in preserving biodiversity in the Sahel. This study investigated the influence of anthropic and eco-hydrological factors on the plant diversity around two grazed ponds and one ungrazed pond in Ferlo, northern Senegal. Two phytoecological transects were established per pond. On each transect, homogenous herbaceous vegetation units were identified and characterized (herbaceous cover, exposure, soil texture, soil moisture and pH, average height and slope). The herbaceous flora comprised 55 species, 41 genera and 22 families across the three ponds. Species of the Poaceae, particularly Eragrostis tremula and Enteropogon prieurii, mostly colonized the grazed ponds, while the ungrazed pond favored other families’ species such as Achyranthes sp., Commelina forsskaolii, Corchorus sp. The Shannon’s diversity index (H′) of Wendu Marodi (ungrazed pond) was slightly higher (4.9 bits) than that of Belel Lougal and Belel Sow (grazed ponds) with 4.8 and 4.5 bits, respectively. The equitability indices were relatively high in the three ponds (0.85, 0.83 and 0.78). Eco-ecological factors distinguished four species’ groupings: a Tribulus terrestris grouping colonizing the constraining and over-grazed zones, a Digitaria horizontalis grouping, and Chloris barbata grouping found in the transition zones, and an Achyranthes aspera grouping in the wetlands, where woody plants were strongly present and the anthropic action low. This study highlighted the importance of maintaining a landscape mosaic of ungrazed or semi-protected ponds and grazed ponds to preserve the herbaceous floristic diversity in the center of Ferlo (Senegal) and the Sahel in general.

Floral traits and the number of visitors are expected to change with different mating systems. We tested this hypothesis by comparing flowers of Prunella vulgaris (Lamiaceae) with inserted and exserted styles across a strongly exserted style biased, an exserted style biased, and a strongly inserted style biased subalpine population. We examined flowering phenology, floral morphology, flower visitation rate, capacity for autonomous self-pollination and visitor contribution to seed production for each style type and in each population. We also examined inbreeding depression (ID) by comparing the relative performance of progeny from self- and cross-pollination. Exserted style plants had larger and more open flowers, increased pollen production, higher amounts of nectar rewards and higher visitation and outcrossing rates than inserted style plants. Similarly on the population level, the visitation rates were higher in the exserted style-biased populations than in the inserted style-biased population. Inserted style plants provided a stronger reproductive assurance (RA) through autonomous selfing than exserted style plants. RA and outcrossing rates did not differ among populations, showing low visitation rates may be sufficient for adequate seed production in P. vulgaris. Although inserted style plants had a lower ID level than exserted style plants, the ID of both was less than 0.5, suggesting that an ID should not counteract the evolution of selfing in this species. Inserted style plants provide RA through autonomous selfing, and exserted style plants ensure outcrossing through pollinator services, supporting a stable mixed mating system in this subalpine plant.

Precipitation (PPT) changes affect both aboveground vegetation dynamics and belowground carbon cycling processes, particularly in arid and semiarid regions. However, it remains unclear how extreme PPT variation can affect soil carbon sequestration potential. A 3-year PPT manipulation experiment with five levels (±40%, ±20% and ambient PPT) was conducted in a desert grassland of western Loess Plateau. Aboveground net primary productivity (ANPP) and soil respiration (Rs) were measured to examine whether the responses of ANPP and Rs to PPT changes displayed a double asymmetry model. The ANPP was more sensitive to extreme drought than extreme wet treatments in wet and dry years, which displayed a negative asymmetric model. The change in ANPP was mainly due to the direct effect of PPT change, and plant density variation also exerted some influence in the dry year. In contrast, Rs displayed a positive asymmetry response to PPT change in dry year. This may be ascribed to enhanced autotrophic respiration due to the enhanced positive responses of plant growth and ANPP to wet treatments as well as stronger birch effect of rainfall events on heterotrophic respiration. The saturating response of Rs to extreme drought (−40% PPT treatment) was also found in the dry year. Nevertheless, the response of Rs to PPT change displayed a negative asymmetry model in wet years. The contrasting models for ANPP and Rs in response to altered PPT regime suggest that extreme wet or dry treatments may increase soil C pools effluxes toward debt in this desert grassland.

Shrub patches often support the colonizers particularly under stressful and/or disturbed environments. The intensities of stresses and disturbances on mountains are often related to an elevation gradient and are decreased by shrub patches (canopy and litter). We aim to clarify these relationships by using shrub patches at different elevations on a volcano. We monitored all shoots in plots established inside and outside of patches of Salix reinii (Salicaceae) and their related environments, such as temperature, light, moisture and chemistry, at three elevations on Mount Koma (1131 m a.s.l.), northern Japan, from early spring in 2005 to summer in 2006. The patch structures were evaluated by area, branch density and litter thickness. The structures of shrub patches did not differ among the elevations. The patches increased the diversity of rare species, by an overall increase in plant species richness. The moisture, nitrogen and phosphate contents in the patches were higher than outside of patches. The effects of shrub patches on the cohabitants were overall positive, although the effects were negative on seedling abundance, shoot survival and flowering. These results suggest that the growth patterns of shrub patches determine the plant community structures and facilitate plant diversity.

Despite a large number of studies examining the effects of abiotic stress factors on plants, the mechanistic explanations of drought-induced tree mortality remain inconclusive and even less is known about how multiple stressors interact. The role of non-structural carbohydrates (NSCs) in preventing or postponing drought mortality is gaining attention. Here, we tested the role of NSCs in mitigating the effects of drought and salinity in New Zealand mangroves, Avicennia marina subsp. australasica. We experimentally manipulated plant NSC levels, prior to subjecting them to combinations of drought and salinity. Plant growth and survival rates were 2- and 3-fold higher in the high-NSC (H-NSC) group than in the low-NSC (L-NSC) group under high salinity and drought conditions, respectively. After 12 weeks under high salinity–high drought conditions, the H-NSC group showed higher stem hydraulic conductivity (281 ± 50 mmol cm⁻¹ s⁻¹ MPa⁻¹) compared with the L-NSC group (134 ± 40 mmol cm⁻¹ s⁻¹ MPa⁻¹). Although starch levels remained relatively constant, we found a 20% increase in soluble sugars in the stems of H-NSC group under high drought and high salinity in week 8 compared with week 12. Our results suggest (i) an important role of NSCs in mitigating the effects of low soil water potential caused by drought and salinity, and (ii) sink-limited growth under conditions of combined salinity and drought.

The mechanisms regulating spring phenology have been extensively studied in angiosperm species. However, given that gymnosperms and angiosperms diverged 300 million years ago, phenology may be triggered by different cues in gymnosperm species. The regulatory mechanisms of phenology in subtropical regions remain largely unknown. In combination, it remains untested whether subtropical gymnosperm species have chilling requirements and are photosensitive. We conducted a climate chamber experiment with three chilling and three photoperiod treatments to investigate budburst during an 8-week forcing period. We tested whether budburst of eight gymnosperms species (Cryptomeria japonica, Cunninghamia lanceolata, Cupressus funebris, Ginkgo biloba, Metasequoia glyptostroboides, Pinus massoniana, Pseudolarix amabilis and Podocarpus macrophyllus) was photoperiod sensitive or has strong chilling requirements and whether photoperiod or chilling was more important for advancing budburst. Chilling advanced budburst and increased the percentage of budburst for gymnosperm species. Gymnosperm species required moderate chilling days to advance budburst. Interestingly, the forcing requirement for gymnosperm species was higher than that for angiosperms in the same forest, suggesting that gymnosperms may need more cumulative forcing to initiate budburst than do angiosperms. Compared with temperate gymnosperm species in Germany (194–600 °C days), the subtropical species studied here had a much higher forcing requirement (814–1150 °C days). The effects of photoperiod were minor, suggesting that chilling outweighs photoperiod in advancing budburst of gymnosperm species in this subtropical region. These results reveal that increased winter temperatures with continued global warming may impact not only angiosperms but also gymnosperms, leading to their delayed spring budburst.

Our objectives are to examine the effects of hummock–depression spatial heterogeneity on plant communities and soil properties, and to understand the process of maintaining and adjusting microtopography-mediated hydrological inputs and their spatial fluctuations that produce obvious microhabitats. We set up 36 plots (1 m × 1 m) and sampled 45 plant and 225 soil samples in flooded (FH) and non-flooded hummocks (NFH) and depressions of the marshy, and the surrounding non-wetland meadows as well as in the Yellow River Source Zone, west China. We evaluated whether the alpine marshy wetland has a fertile island effect by the comparison method. Our results show that hummock presence can increase the spatial heterogeneity of the microhabitat and promote the plant diversity and soil fertility of the Kobresia tibetica community. Plant height, coverage, above-ground biomass, species richness and diversity were significantly higher in the FH and NFH microhabitat than in the areas between hummocks and surrounding non-wetland meadows. Compared with broad alpine meadows, the hummock–depression complex provided a microhabitat favorable to the growth of Cyperaceae. In the 0–50 cm soil layer, the closer the soil layer was to the ground surface, the higher its soil organic carbon and total nitrogen contents. Thus, in deeper layers, the gap between soil nutrients in wetland hummock–depression microhabitat and in the surrounding alpine meadows becomes smaller. Hence, the wetland hummock–depression microhabitat formed a fertile island pattern. Therefore, these results contribute toward improving our understanding of ecosystem restoration in alpine marshy meadows.

Studies of competition in mangroves are mostly limited to seedlings and artificial settings like forestry projects. We conducted the first experimental study of intraspecific competition among adult mangroves in a natural mangrove forest to examine how important competition is in determining tree size compared with abiotic conditions. We conducted a study near Port Aransas, TX, USA, which is near the geographical limit of mangroves and dominated by monospecific stands of ‘scrub’ form black mangroves, Avicennia germinans. We thinned 10 plots to create a gradient of mangrove cover, and quantified the effects of mangrove cover on the growth of tagged mangroves from 2013 to 2019, and the mangrove canopy height in 2019. The relative growth rate of tagged mangroves declined as mangrove cover increased, and plants in the plot with 100% mangrove cover did not grow, indicating that they had attained their maximum size. In plots with reduced mangrove cover, plant height increased sharply, with plants in the plot with 11% mangrove cover growing ~52% taller over 6 years. Canopy height was ~30% taller in the plot fringe than in the interior, and canopy height in both fringe and interior declined as mangrove cover increased. Measures of leaf chlorophyll concentration and light interception suggested that plants were primarily limited by nitrogen. Our results showed that scrub mangroves compete strongly despite being limited by abiotic conditions, and that the importance of competition was greater in magnitude than that of abiotic differences between the fringe and interior.

Afforestation is helpful to improve soil functions and increase soil organic carbon (SOC) sequestration in semiarid deserts. However, the fine-scale (around a single plant) spatial distribution of SOC and its liable organic carbon (LOC) fractions after afforestation in semiarid deserts are poorly understood. Pinus sylvestris and Salix psammophila afforested on shifting sandy land (S_land) were selected to quantify fine-scale (at 20, 80, 150 and 240 cm away from the trees) spatial distribution of SOC and its LOC fractions in the southeast edge of Mu Us Desert, China. The results showed that the afforested S. psammophila and P. sylvestris significantly increased SOC, total nitrogen, dissolved organic carbon, microbial biomass carbon and readily oxidized organic carbon (ROOC). At 20 cm distance, SOC storage of P. sylvestris was 27.21% higher than S. psammophila in 0–100 cm soil layers, and SOC storage of S. psammophila at 80 and 150 cm distances was 5.50% and 5.66% higher than P. sylvestris, respectively. Compared with S_land, SOC storage under S. psammophila and P. sylvestris significantly increased by 94.90%, 39.50%, 27.10% and 18.50% at 20, 80, 150 and 240 cm distance, respectively. ROOC accounted for 14.09% and 18.93% of SOC under S. psammophila and P. sylvestris, respectively. Our results suggest that afforestation can promote SOC accumulation at different distances from the plants, and that P. sylvestris allocates more organic matter to the closer soil compared with S. psammophila (<80 cm from the tree).

The environmental factors that influence tree–grass abundances in tropical savanna and grasslands are not well understood, particularly for woodland–grassland mosaics in humid zones. We studied the effects of abiotic and spatial variables on woody and herbaceous species distributions in a Terai ecosystem of northeastern India. We evaluated the importance of climatic and non-climatic factors that maintain variable tree–grass ratios across the landscape, and also accounted for spatial connectivity and dispersal. We measured species abundances of woody and herbaceous plant species in 134 plots with each 30 m × 30 m in a 519 km² protected Terai habitat, and derived several climatic and non-climatic environmental factors. We constructed variables based on different models of spatial connectivity among sites, to test their influence on species abundances. We then used redundancy analyses and variation partitioning to quantify the importance of environmental variables and spatial structure on variation in tree–grass abundances. We found that environmental variables including rainfall, fire, water stress, topography and soil nutrients had statistically significant effects on species abundance and tree–grass ratios. Spatial structure was significant, and the best spatial model was an inverse distance-weighted model with linkage extending to 23.5 km, indicating weak dispersal limitation. About 21% of the variation in species abundance was explained by the selected environmental and spatial factors. The results indicate that dynamic plant communities in which spatial–temporal variation in environmental factors may drive stochasticity in species distribution and abundance, thus dominantly influencing on the vegetation mosaic.

The ecological consequences of precipitation change and increased atmospheric nitrogen (N) deposition have profound impacts on ecosystem CO₂ exchange in grassland ecosystems. Water and N can largely influence grassland productivity, community composition and ecosystem functions. However, the influences of water and N addition on the ecosystem CO₂ exchange of alpine grassland ecosystems remain unclear. A field manipulative experiment with water and N additions was conducted in an alpine meadow on the Tibetan Plateau over 4 years with contrasting precipitation patterns. There were four treatments: control (Ctrl), N addition (N), water addition (W) and N and water addition (NW), each replicated three times. N addition, but not water addition, increased gross ecosystem productivity (GEP), plant biomass, community cover and community-weighted mean height. The responses of ecosystem CO₂ exchange to water and N addition varied between the wet and dry years. Water addition had a positive effect on net ecosystem carbon exchange (NEE) due to a larger increase in GEP than in ecosystem respiration (ER) only in the dry year. On the contrary, N addition significantly enhanced ecosystem CO₂ exchange only in the wet year. The increased GEP in N addition was attributed to the larger increase in NEE than ER. Moreover, N addition stimulated NEE mainly through increasing the cover of dominant species. Our observations highlight the important roles of precipitation and dominant species in regulating ecosystem CO₂ exchange response to global environmental change in alpine grasslands.

Danjiangkou Reservoir is water source of Middle Route Project of the South-to-North Water Diversion (SNWD) Project, research on the dynamic changes in vegetation cover and its influencing factors is of great significance for understanding the ecological environment of the water diversion area and formulating protection measures. In this study, the normalized difference in vegetation index (NDVI) was used to analyze the dynamic changes and influencing factors of vegetation in the upstream and downstream of Danjiangkou Dam from 1982 to 2018. The results showed that the NDVI exhibited an upward trend of 0.017 year⁻¹ (P < 0.05), and that the significantly increased area was located near the valley upstream of the dam, while the significantly decreased area was mainly distributed in the basin downstream of the dam and around the central city. The comprehensive contributions of climate and human activity factors to NDVI changes were 92.03% and 7.97%, respectively. The human activities in the upstream of the dam were mainly reflected in the ecological measures such as returning farmland to forest; the human activities at the downstream of the dam were mainly reflected in urban expansion, occupation of cultivated land and forest land by construction land.

In this study, we investigated (i) the differences in flower colour composition among growth forms of woody plants in China and (ii) the influences of biogeographic regions, evolutionary age and climatic conditions on geographic variation in the proportions of different flower colours. Using distribution maps and flower colour information (white, red, yellow, yellow-green, green and blue-purple) of 7673 Chinese woody plant species and a dated genus-level phylogenetic tree, we compared flower colour composition among different growth forms (shrubs, trees and lianas). We further estimated the relationships of geographical patterns in the proportions of different flower colours with seven different biogeographic regions, evolutionary age and different contemporary climatic variables. Compared with trees or lianas, shrubs showed a higher proportion of species with anthocyanin-based red and blue-purple flowers. The geographic patterns of flower colour composition of woody plants in China were strongly influenced by regional effects and contemporary climate, especially precipitation and ultraviolet B irradiance. The proportion of species with presumably bee-pollinated yellow and blue-purple flowers and stress tolerant anthocyanin-based red and blue-purple flower colours tended to be high in the northwestern part of China. Green flowers tended to evolve earlier than others, but evolutionary age had quite weak influences on the geographic pattern of flower colours. Our results reflect both evolutionary and environmental constraints on the distribution of flower colours of woody plants in China.

Heterogeneity of soil salinity is a prominent environmental characteristic in the intertidal zone of estuaries, affecting the plant growth and the shift of biotic interactions in the salt marsh. This study aims to examine the interactive effects of a salinity gradient and salinity fluctuations on intraspecific interactions of a euhalophyte. We assessed the impact of daily fluctuating salinity on the outcome of intraspecific interactions by cultivating seeds of Suaeda salsa (Chenopodiaceae) in river sand. The experiment was conducted in a greenhouse with three treatments: daily salinity fluctuations (static and fluctuating salinity), a salinity gradient (200 and 400 mmol L⁻¹) and three planting densities (1, 2 and 4 plants/pot). First, height and biomass of plants were measured at both the start and end of the experiment. Then, the growth indexes and log response ratio of S. salsa were analyzed. The outcome of intraspecific interactions of S. salsa shifted from competition in low salinity to facilitation in high salinity, and high conspecific density strengthened the competition and facilitation intensities. Daily salinity fluctuation did not significantly affect the plant growth and the outcome of intraspecific interactions, but did have a significant influence on belowground biomass. Our results suggest that the stress-gradient hypothesis may apply to predicting the variation of the intraspecific relationship of a salt-tolerant species along a salinity gradient, and the magnitude of this variation is density dependent. These findings help us understand how individuals and populations of a euhalophyte species respond to the natural variation or human modification of salinity conditions.