Phosphorus (P) is a limiting nutrient in tropical forest, where soil microorganisms play a crucial role in nutrient cycling and ecosystem functioning. However, how microbial communities regulate soil multifunctionality under altered P availability remains poorly understood. To address these gaps, we conducted a two year (2022-2024) in-situ P addition experiment in a tropical cloud forest in Bawangling, Hainan Tropical Rainforest National Park. We then examined microbial species diversity, phylogenetic diversity, and network complexity and their roles in driving soil multifunctionality. Results showed that P addition significantly increased soil available phosphorus (AP) and acid phosphatase activity (ACP). Fungal diversity and network complexity decreased with increasing P concentration, whereas bacterial diversity remained nosignificant changes. Variance partitioning revealed that fungal network complexity was the primary driver of soil multifunctionality (31.8 %), with synergistic effects from fungal species and phylogenetic diversity (12.7 % and 11.1 %, respectively). Structural equation modeling indicated that P addition enhanced multifunctionality primarily through an indirect pathway by improving soil conditions. Conversely, P exerted significant direct negative effects on microbial network complexity and species diversity. Despite these negative direct effects, both microbial network complexity and species diversity themselves had strong positive direct effects on multifunctionality. The overall model explained 63.2 % of the variance in soil multifunctionality. These findings suggest that moderate P input can enhance soil nutrient status while preserving fungal network complexity, a key bio-indicator of ecosystem recovery, thus offering a scientific basis for managing P inputs in tropical cloud forests and cautioning against the ecological risks of excessive P enrichment.

Rocky desertification severely constrains ecosystem functioning and vegetation in karst landscapes. Understanding how soil environmental changes influence plant functional coordination is therefore critical for ecological restoration. Here, we investigated soil physicochemical properties and leaf functional traits across a rocky desertification gradient in a karst ecosystem of southwest China. Using leaf trait network (LTNs) to evaluate changes in trait coordination and identify key regulatory traits under different desertification intensities. We found that severely desertified (SRD) habitats were characterized by alkaline soils with lower bulk density, soil organic carbon (SOC), and total phosphorus(TP), but relatively higher total nitrogen(TN), total potassium(TK), and calcium(Ca) than lightly and moderately decertified habitats. Along the rocky desertification gradient, LTNs exhibited progressively lower edge density but higher average path length, diameter, and modularity, indicating reduced overall trait integration together with stronger functional compartmentalization under increasing environmental stress. Hub traits also shifted systematically across desertification stages. In lightly rocky desertified habitats, leaf water content, leaf thickness, and leaf nitrogen concentration acted as central traits, whereas specific leaf P and chlorophyll became dominant in moderately desertified habitats. In SRD habitats, leaf thickness and leaf tissue density emerged as the major hub traits associated with structurally conservative strategies. Redundancy analysis further showed that soil nutrient availability, pH, bulk density, and calcium jointly regulated changes in network topology across desertification stages. Overall, our results demonstrate that rocky desertification drives stage-dependent reorganization of leaf trait coordination, reflecting a transition from resource-acquisitive to structurally conservative adaptive strategies as environmental constraints intensify.

ABSTRACT Animals exhibit different foraging strategies in environments characterized by patchily distributed resources and seasonal variation. Hainan gibbons (Nomascus hainanus) are Critically Endangered primates with a largely frugivorous diet. They inhabit tropical rainforests where food resources are characterized by pronounced spatiotemporal heterogeneity; however, their foraging strategies remain poorly understood. We conducted field monitoring on two groups of Hainan gibbons from March 2023 to August 2025 in the Bawangling region of Hainan Tropical Rainforest National Park, China. Group C inhabited higher‐altitude montane rainforest, whereas Group E inhabited disturbed secondary lowland rainforest. Gibbon behaviors were recorded at 5‐min intervals using instantaneous scan sampling, and the spatial locations of behaviors were documented at 15‐min intervals. The results showed that, at the spatial scale, Group C exhibited higher movement directionality and spent a greater proportion of time in the extensive search phase (pE = 0.22) than Group E (pE = 0.04); this phase was characterized by straighter, long‐distance movements. In contrast, Group E spent a lower proportion of time in extensive search and exhibited longer mean step lengths but weaker directionality. At the temporal scale, gibbons primarily engaged in short‐distance, localized intensive search during the mixed‐diet period (October–March, characterized by lower fruit availability), whereas they spent more time in the extensive search phase during the fruit‐eating phase (April–September, when fruit resources were more abundant). Overall, Hainan gibbons flexibly switched between extensive and intensive search modes to achieve directional inter‐patch movements while maximizing within‐patch exploitation, thereby effectively coping with temporal and spatial variation in fruit resources. These findings indicate that movement behavior in Hainan gibbons is closely associated with habitat characteristics and the spatial and temporal distribution of food resources. Our study also highlights that low‐altitude tropical secondary forests are important for the survival of the Hainan gibbons and thus have high conservation value.

Understanding primate behavioral responses to food supply provides critical insights into their adaptive strategies in dynamic environments. The Critically Endangered Hainan gibbon (Nomascus hainanus), a China-endemic species, has recently exhibited range expansion into low-altitude forests. However, the foraging strategy of this species in lower-elevation habitats remains poorly understood. In this study, we examined two Hainan gibbon groups within the National Park of Hainan Tropical Rainforest, representing old-growth and secondary forest habitats, respectively. We assessed plant diversity in their home ranges through plot sampling at 100 m intervals and collected behavioral data via instantaneous scan sampling at 5-min intervals. Our findings revealed low similarity in both overall forest composition and food plant availability between the two habitats. Although the two groups consumed a comparable number of food items, their dietary composition differed significantly. Notably, both groups exhibited a strong negative correlation between feeding preference and plant importance values, indicating that gibbons preferentially forage on non-dominant tree species. These results demonstrate that Hainan gibbons exhibit dietary flexibility in response to spatial variation in food plant supply. Consequently, habitat restoration initiatives should prioritize key food plant availability to ensure sufficient foraging resources for this threatened species.

ABSTRACT β‐diversity is a central concept to understanding community assembly, yet how its decomposition components and underlying drivers vary with spatial extent remains insufficiently understood. We used a nested metacommunity framework to examine the scale dependence of total β‐diversity and its species replacement and richness difference components, and to identify how environmental and spatial predictors contribute across scales. We analyzed woody plant diversity in 250 plots arranged on a contiguous 1 × 1 km grid in a tropical rainforest on Hainan, China. By aggregating nearest‐neighbor plots into metacommunities, we constructed a continuous gradient of spatial extent and quantified total β‐diversity (BDtotal), species replacement (Repl), and richness difference (RichDif) for each metacommunity realization. β‐diversity increased modestly with spatial extent, but its internal structure was remarkably stable: species replacement consistently dominated total β‐diversity, whereas richness differences contributed less and changed little across scales. Environmental heterogeneity was positively associated with β‐diversity, primarily through replacement rather than richness differences. The variation explained by both environmental predictors and spatial structure increased with extent before approaching a plateau. Spatial structure explained the largest share of variation in BDtotal, Repl, and RichDif, while the relative importance of environmental predictors shifted with scale: soil variables were more influential at finer extents, whereas bioclimatic variables gained importance at broader extents. Environmental predictors were more strongly associated with species replacement than with richness differences, whereas spatial structure explained both components to a similar degree. Overall, increasing spatial extent amplified the magnitude of β‐diversity more than it altered the balance between its components, revealing species replacement as a scale‐robust feature of tropical forest metacommunities. These findings show that tropical forest β‐diversity emerges from the joint effects of environmental heterogeneity and spatial structure, and they highlight the need to conserve spatially dispersed, compositionally complementary habitat mosaics rather than focusing solely on local richness hotspots.

Tropical forests, renowned for their exceptional biodiversity, often thrive despite inherently low soil phosphorus (P) availability. However, a comprehensive synthesis of the mechanisms that facilitate the coexistence of diverse species, and how these mechanisms respond to P addition, remains poorly understood. This review consolidates research findings on how tropical forest biodiversity is sustained under low P conditions, how P addition influences the overall biodiversity system, identifies research gaps, and suggests future directions. The relationship between P and biodiversity is complex: while P-limited forests support high diversity, P addition may lead to species disappearance, raising the question of why some forests that maintain high species diversity under P limitation continue to do so, while others experience a decline in diversity following P addition. Despite P limitation, forests can support high species diversity through adaptive strategies such as resource partitioning and P-use efficiency, which enable diverse communities to flourish. In low-P environments, species conserve P through resorption from older tissues and allocation to leaves, promoting photosynthesis and growth. These species exhibit lower specific leaf area and higher leaf dry matter content. While functional diversity is constrained, species diversity remains high as species adopt similar strategies. Specialized root traits, including finer roots and mycorrhizal symbioses, facilitate P uptake in low-P soils. However, P addition may lead to competitive exclusion, with species adapted to P-rich conditions outcompeting low-P specialists. Some species may dominate early successional stages by rapidly utilizing available P, suppressing other species, and reducing biodiversity over time. Anthropogenic P additions, such as agricultural fertilization and erosion, can intensify this effect, further decreasing species diversity and altering community composition, including fauna and microbial components of the forest. Due to the complexity and variability of tropical environments, critical knowledge gaps remain in understanding how diverse forest components, soil organisms, and environmental conditions interact with P addition, particularly at local and regional scales. Long-term studies, especially in less accessible or underfunded tropical regions, are essential to improve understanding of species interactions, resource partitioning, and biodiversity functioning under P-limitation.

Large trees are keystone structures in tropical forests, providing critical food and lodging resources for threatened wildlife. The Hainan gibbon (Nomascus hainanus), the world's rarest primate, depends mainly on large canopy trees for feeding and lodging. However, poorly understood about the differences in species composition, functional traits, and terrain distribution of trees reported as food and lodging trees in current habitat. We characterized 2215 large trees (DBH ≥30 cm) across five transect blocks in Hainan gibbon's current habitat, analyzing species identity, structural attributes, landform distribution (valley, hillside, ridge), and functional traits (leaf economics, wood density, fruit type). The results showed that large food trees have higher specific leaf area and leaf nitrogen content, and fruits are mainly syconium and drupe. Conversely, large lodging trees have larger wood density, maximum height, and DBH. Species richness, stand density, and basal area of large food and lodging trees are highest in hillside areas, and generally decrease with increasing altitude. Combining functional ecology with terrain features can provide more targeted references for the restoration of degraded habitats. Specifically, low-altitude hillside areas may have higher potential restoration value; restoration efforts should prioritize food species with resource-acquiring leaf traits, as well as lodging species with high wood density and large tree structure. This trait-based, topography-explicit approach can identify potential resource constraints in current habitats and provides verifiable ecological evidence for habitat management of the Hainan gibbon and other arboreal primates.

Soil organic carbon (SOC) from rubber plant roots enhances soil aggregate stability; however, the role of soil internal forces (SIFs), including electrostatic repulsive force (Perf), van der Waals attractive force (Pvdw), and surface hydration repulsive force (Ph), remains unclear. This study investigated the effects of root characteristics, SOC, and root chemical composition on soil aggregate stability, focusing on the role of SIFs, by comparing rubber plantations of four distinct ages: 5-year-old (5Y_RP), 11-year-old (11Y_RP), 20-year-old (20Y_RP), and 27-year-old (27Y_RP). Among the rubber plants, 20Y_RP had the largest root diameter (RD) (0.88 mm) and root length density (RLD) (2.81 cm/cm3), along with a higher proportion of fine and medium roots, resulting in greater SOC (13.55 g/kg) and chemical composition (higher cellulose and lower lignin) than younger rubber plants. Greater SOC concentration of 20Y_RP resulted in a higher specific surface area (SSA) and lower surface charge density (sigma0), surface charge number (Qs), and surface potential (phi0) compared to younger rubber plants, and the control, with significant correlations (r = 0.60 to 0.99) confirming the relationship between root traits, SOC, and soil surface charge properties. Consequently, older rubber plantations exhibited higher Pvdw, lower Perf, and a decrease in the net repulsive force (Pnet) (sum of three SIFs), with the average Pnet in order of 20Y_RP (12.63 MPa) < MF (14.09 MPa) < 27Y_RP (14.22 MPa) < 11Y_RP (14.83 MPa) < 5Y_RP (15.59 MPa) < CK (24.57 MPa) at a 2 nm distance. Furthermore, the release of small particles (<20, <15, and <5 mu m) from aggregates was lower in rubber plantations than in the control, showing that plant roots enhance SOC, chemical composition, and soil aggregate stability by reducing repulsive Pnet. These results highlight the need to select rubber plants with optimal root traits to enhance soil structure and carbon sequestration, providing practical benefits for sustainable land management and long-term agricultural productivity in tropical areas.

Primates rely heavily on habitat trees (foraging and night lodging trees) for growth and reproduction, yet primates' and their habitat trees' spatial ranges often shift with environmental changes. Therefore, endangered primates are severely threatened by habitat degradation and climate change. Hainan gibbon (Nomascus hainanus) is the world's most endangered primate. Using 18 years (2000 to 2018) of gibbon activity observations and data from 186 plant plots within a tropical nature reserve, we assessed the suitable distributions of gibbon and its 95 associated habitat trees using MaxEnt model, incorporating climate, topography, anthropogenic disturbance, and soil (excluded for gibbon) as predictors. Priority conservation areas were delineated by integrating habitat tree hotspots with suitable gibbon ranges. We also used Partial Least Squares Path Modeling to assess the direct and indirect effects of key factors shaping their distributions. Results showed that the gibbon occur in the central and eastern reserve, while habitat trees are mainly in the central region, both occur between 500 and 1400 m elevation. Climate change led to an upward shift and contraction in gibbon and habitat trees, accompanied by fragmentation. Spatial overlap between gibbon distributions and habitat tree hotspots was high (80.12 %-100 %). Priority conservation, primarily shaped by temperature and precipitation, were projected to become increasingly concentrated around two high-elevation hilltops. From current to future, climate remains the dominant driver of gibbon distribution, while the influence of habitat trees increases initially before declining. Our findings highlight the importance of integrating climate and habitat factors into conservation planning for endangered species.

Understanding how spatiotemporal habitat variability shapes endangered species' behavior is crucial for effective conservation. This study examined the impact of fine-scale habitat variation on four behavioral patterns (feeding, resting, social, and traveling) of the critically endangered Hainan gibbon. Year-round behavior data were collected from two groups: GC inhabiting an area with abundant food resources, and GE in a secondary forest with sparse resources. Using 135 monitoring plots, we analyzed variation in 27 habitat variables categorized into food, nutrients, plant diversity, safety and stability, and topography. Linear models revealed crown height, food plant abundance, and crude fat as key variables shaping behaviors. Higher community plant and food plant richness significantly enhanced feeding frequency, while steeper slopes increased traveling. Habitat quality variation shaped distinct behavioral strategies: in GC, feeding and resting were primarily influenced by food, social behavior by safety and stability, and traveling by plant diversity. In GE, resting, social, and traveling behaviors were mainly driven by topography, while feeding was influenced by nutrients. Likewise, food variables dominated during the dry season, whereas safety and stability, and topography variables were more important in the wet season. This study provides the first analysis of Hainan gibbons' behavioral strategies linked to fine-scale habitat variability and seasonal dynamics. The findings highlight the importance of protecting diverse habitats, as different Hainan gibbon groups exhibit distinct behavioral adaptations to their varying resource availability. This underscores the need for habitat-specific primate conservation and management in fragmented landscapes.

To investigate the direct effects of phosphorus (P) fertilisation on key tree photosynthetic traits and productivity, as well as its indirect effects mediated through forest community structure (tree size, species richness, and abundance). Worldwide. 1990–2024. Trees. We conducted a meta-analysis of 906 paired (control vs. treatment) P-fertilisation experiments and employed structural equation modelling to examine the impacts of P on seven whole-plant traits: aboveground biomass productivity (ABP), leaf chlorophyll content (Chl), leaf surface area (LSA), net carbon assimilation rate (NCA), belowground biomass productivity (BBP), specific root length (SRL), and root average diameter (RAD). Our meta-analysis revealed that P-fertilisation increased ABP by 56%, LSA by 11%, Chl by 31%, NCA by 24%, BBP by 17%, and SRL by 26%, while RAD decreased by 8%. These effects were stronger in late successional stages compared to early stages for all traits. The effect of P on productivity decreases with latitude and is stronger in the tropics, while studies on other traits remain very limited towards the poles. P (through duration and P dose rate) influenced most traits indirectly by shaping community structure, particularly tree ontogenetic variations, and interacting with precipitation, temperature, and other experimental factors. Phosphorus fertilisation enhances tree traits related to photosynthesis and productivity, with the stronger effects observed in late successional stages and tropical regions. Its indirect influence is through shaping community structure and interacting with climate and experimental factors, providing global evidence of P-limitation that constrains current and future forest functioning and productivity.

In southern China, the island of Hainan faces land degradation risks due to a combination of soil physical, chemical, and climatic factors: soil physical properties like a high proportion of microaggregates (<0.25 mm), chemical properties such as low soil organic matter (SOM) content, and a climatic factor of frequent uneven rainfall. The cohesive force between soil particles, which is influenced by plant root properties and root-derived SOM, is essential for improving soil aggregate stability and mitigating land degradation. However, the mechanisms by which rubber plant root properties and root-derived SOM affect soil aggregate stability through cohesive forces in tropical regions remain unclear. This study evaluated rubber plants of different ages to assess the effects of root properties and root-derived SOM on soil aggregate stability and cohesive forces. Older rubber plants (>11 years old) showed greater root diameters (RDs) (0.81–0.91 mm), higher root length (RL) densities (1.83–2.70 cm cm−3), and increased proportions of fine (0.2–0.5 mm) and medium (0.5–1 mm) roots, leading to higher SOM due to lower lignin and higher cellulose contents. Older plants exhibited higher soil cohesion, with significant correlations among root characteristics, SOM, and cohesive force, whereas the random forest (RF) model identified aggregates (>0.25 mm), root properties, SOM, and cohesive force as the key factors influencing mean weight diameter (MWD) and geometric mean diameter (GMD). Furthermore, partial least squares path models (PLS-PM) showed that the RL density (RLD) directly influenced SOM (path coefficient 0.70) and root-free cohesive force (RFCF) (path coefficient 0.30), which subsequently affected the MWD, with additional direct RLD effects on the SOM (path coefficient 0.45) and MWD (path coefficient 0.64) in the surface soil. Cohesive force in rubber plants of different ages increased macroaggregates (>0.25 mm) and decreased microaggregates (<0.25 mm), with topsoil average MWD following the order control (CK) (0.98 mm) < 5Y_RF (1.26 mm) < mixed forest (MF; 1.31 mm) < 11Y_RF (1.36 mm) < 27Y_RF (1.48 mm) < 20Y_RF (1.51 mm). Rubber plant root traits enhance soil aggregate stability and mitigate land degradation risk in tropical regions, offering practical soil restoration strategies through targeted root trait selection to strengthen soil cohesion, ensure long-term agricultural productivity, and preserve environmental quality, highlighting the need for further research across diverse ecological zones and forest types.

Litterfall production is fundamental to various functions and processes within forest ecosystems. Yet, it has been primarily investigated within single vegetation types, with its dependence on biotic conditions remaining largely undefined, particularly in the tropics. In this study, litterfall monitoring and community investigations were conducted on five representative vegetation types of the tropical natural forests on Hainan Island, China, including the tropical lowland rainforest, montane rainforest, monsoon rainforest, coniferous forest, and cloud forest. On that basis, the litterfall production characteristics in the various vegetation types were distinguished, and their dependence on different community properties (species composition, species diversity, functional diversity, stand structure, and functional traits) was assessed. The lowland rainforest displayed the highest total, monthly maximum, and variance of litterfall production, followed by the montane rainforest, while the lowest levels were observed in either the cloud forest or the coniferous forest. The temporal variations turned out pronounced in all vegetation types except for the coniferous forest, which was distinguished by a unimodalpattern of litterfall dynamics. Meanwhile, a bimodal pattern was also observed, particularly prominent in the cloud forest, followed by the montane rainforest. Moreover, litterfall production characteristics significantly depended on community properties, with stand structure being the most crucial factor. Overall, these findings emphasize the considerable regional-scale variation in litterfall production across vegetation types and its dependence on community properties. From a forest management perspective, maintaining stand structural complexity contributes to sustaining nutrient return through increased litterfall production.

Soil phosphorus, a crucial limiting nutrient in tropical forests, shapes plant morphology and functional strategies, thereby affecting overall forest productivity. However, most research to date on plant responses to phosphorus fertilization has focused only on aboveground traits, and little is known as to how trade-offs between above- and below-ground functional strategies may be affected. To address this research gap, we conducted a two-year (2022-2023) in-situ phosphorus fertilization experiment, situated in the tropical cloud forest within Bawangling, Hainan Island, South China. We tested how fertilization affected both above- and below-ground functional traits in saplings (1 cm <= DBH < 5 cm) belonging to five dominant tree species. The experiment included 24 fixed 10 x 10 m plots, with treatments including an unfertilized control and five phosphorus application rates (1, 2, 4, 8, and 16 g/m(2) yr(-1)); low (4 g/m(2) yr(-1)), medium (8 g/m(2) yr(-1)), and high (16 g/m(2) yr(-1)) phosphorus treatments were individually compared. When phosphorus was limiting, we found negative correlations between above- and below-ground resource-use traits (e.g., leaf dry mass and root dry mass, leaf surface area and root surface area, leaf thickness and specific root length, and specific leaf area and specific root length), suggesting that phosphorus stress leads to trade-offs between above- and below-ground traits. Increasing phosphorus significantly increased the leaf chlorophyll content and total biomass, highlighting that phosphorus limitation constrains carbon assimilation and biomass production in tropical cloud forests. In contrast, traits such as leaf thickness, root dry mass, root surface area, root volume, and specific root length generally decreased as phosphorus availability increased, suggesting a shift toward greater photosynthetic efficiency and aboveground biomass production. Comparing study years, we found evidence that root traits responded faster to fertilization, with belowground traits responding more strongly in 2022 than 2023, while aboveground traits showed the opposite pattern. Although most community-weighted mean traits showed little variation among phosphorus treatments, species-specific responses were observed, suggesting that fertilization had a greater impact at the species versus community level. Our findings highlight that phosphorus plays a fundamental role in shaping sapling development in the tropical cloud forest, underlining the need for targeted management schemes to enhance carbon storage and ecosystem stability, thereby supporting climate change mitigation efforts.

Natural restoration of tropical forests is an effective strategy for mitigating global climate change and enhancing ecosystem carbon stocks. Although studies have shown soil organic carbon storage following forest restoration efforts, the responses of organic carbon sources and their stabilisation to these restoration practices remain unclear. In this study, we employed amino sugars and lignin phenols as biomarkers to explore the contributions of microbial necromass and plant lignin components to soil organic carbon across a chronosequence of tropical lowland forest restorations (<30, >40, >70 years and old-growth forests). Following forest restoration, the concentration of amino sugars in soil organic carbon substantially decreased, whereas the concentration of lignin phenols showed no notable change. The contribution of microbially derived carbon to soil organic carbon steadily declined from 55 % to 33 % as forest restoration progressed, while the contribution of plant-derived carbon increased from 2.7 % to 3.4 %. Microbial-derived carbon remained the dominant source of soil organic carbon accumulation, although its proportion in the organic carbon pool decreased during the restoration process. The Mantel test and structural equation models showed that soil nutrient availability (available phosphorus, available nitrogen, and inorganic nitrogen) and microbial biomass nitrogen were the primary variables influencing microbially derived carbon, whereas plant-derived carbon was regulated by plant root biomass and microbial biomass nitrogen. These findings highlight the importance of combining plant lignin and microbial necromass in regulate soil organic carbon accumulation during tropical forest restoration. This study supports the development of effective carbon management strategies for tropical forests.

Climate change and plant diversity loss are anticipated to alter plant disease dynamics across the tropics. However, our understanding of how climate variation interacts with host plant and pathogen communities to shape plant diseases in natural tropical forests remains limited. We surveyed foliar disease symptoms on 5016 leaves from 1672 seedlings belonging to 238 species along a 1200 m tropical montane elevational gradient to characterize foliar pathogen-disease relationships and assess how these relationships change in response to variations in temperature and humidity. MiSeq sequencing of ITS1 gene markers was used to identify fungal pathogens sampled from diseased leaves. We found that dry lowland rainforests had a higher community pathogen load than other forest types. Fungal pathogen diversity decreased, and phylogenetic distance increased with increasing elevation. Plant community diversity was negatively correlated with community pathogen load, but was not related to fungal pathogen diversity. Plant communities with greater phylogenetic similarity harbored fungal pathogen communities with smaller phylogenetic distance. Structural equation modeling further indicated that decreased humidity could increase community pathogen load by reducing seedling evenness and overstory tree diversity, and by reducing fungal pathogen phylogenetic distance. These findings imply that humidity shifts and biodiversity loss-induced changes in the plant and pathogen communities may influence plant disease patterns in tropical regions, with potential severe impacts on lowland rainforests.

Understanding how epiphytic vascular plants respond to drought is essential for elucidating the potential mechanisms that may contribute to their resilience in the context of global climate change. Despite numerous studies have estimated tropical epiphytic vascular plants' water source and use efficiency, their response to drought induced water scarcity poorly understood. We conducted an in-situ water reduction control experiment (i.e., controlling rain and fog water, each with three treatments) on epiphytic vascular plant communities in a biodiverse hotspots region of Hainan tropical cloud forest. We then investigated the water sources and water use efficiency (WUE) of epiphytic vascular plants under different drought gradients. We found a significant seasonal variation in water sources: 63 %-67 % in the dry season (November to April of the next year) and 64 %-70 % in the wet season (May to October) came from fog and rain, respectively In the wet season, epiphytic ferns utilized 39 % fog and 61 % rain, while orchids utilized 31 % fog and 69 % rain. Ferns absorbed significantly more fog water than orchids under all drought gradients. In the dry season, 63 % of the water in epiphytic ferns and 64 % in orchids originated from fog, while 37 % and 36 % from rain for ephiphytic ferns and orchids respectively. The WUE of ferns was significantly higher than that of orchids under all drought gradients. These findings reveal that both epiphytic vascular plant communities and epiphytic taxa display selective and complementary water uptake strategies, with distinct differences in water use strategy between epiphytic ferns and orchids.

Understanding the availability of food resources is essential for effectively conserving endangered species. This study quantified the distribution of food plants within the Hainan gibbon habitat and assessed the environmental drivers of these distributions to guide targeted habitat restoration efforts. A total of 122 habitat plots were surveyed across five gibbon groups to collect the environment and food plant diversity data. Groups A to D occupied tropical montane rainforests (800-1200 m), while group E inhabited secondary lowland rainforests (500-700 m). Results revealed: 1) Climate and soil factors differed significantly between high- and low-altitude habitats. 2) Food plant species richness was higher in high-altitude habitats, while dry-season foods and preferred foods were more abundant in A and C groups. 3) Elevation, soil C/N ratio, soil alkaline dissolved nitrogen, and soil fast-acting phosphorus significantly affected food plant distribution. Soil content and climate are key drivers, with varying effects across different altitudes and food plant types. These findings indicate that successional low-altitude secondary forests are potential habitats for Hainan gibbons (e.g., group E) but require further restoration in lower quality areas. Our study highlights the need for habitat-specific restoration: in low-altitude forests, improving soil conditions (i.e., introducing native nitrogen-fixing species such as Albizia spp. to reduce C/N ratios and enhance alkaline dissolved nitrogen) can promote key food plant growth. In high-altitude forests, introducing climate-resilient species (e.g., Ficus spp.) can offset temperature and precipitation limitations. Such targeted actions are critical to ensuring food stability and supporting Hainan gibbon conservation.

The Hainan gibbon (Nomascus hainanus) is one of the most endangered primates globally, threatened by habitat destruction, genetic diversity loss, and ecological competition. In this study, given the critical role of the gut microbiota in host immune regulation and nutrient metabolism, we investigated the composition of and age-related variations in the gut microbiota in Hainan gibbons. Using 16S rRNA sequencing, we systematically investigated the gut microbial diversity of Hainan gibbons. We collected 41 fecal samples from Hainan Tropical Rainforest National Park, covering three age groups: juveniles (4-6 years), subadults (7-10 years), and elderly animals (≥13 years). This study found that microbiota composition changed significantly with age. Juveniles had higher microbial diversity and complexity, while subadults showed an increased abundance of Fibrobacter and Prevotella in their microbial communities, along with a Tax4Fun-predicted enrichment of functional genes related to energy metabolism, cell motility, and nervous system functions. LEfSe analysis identified statistically significant microbial taxa among different age groups, with Bacteroidota and Firmicutes being the dominant phyla across all groups with varying proportions. These results highlight the critical role of the gut microbiota in the health and adaptability of Hainan gibbons, offering insights for conservation strategies. The findings of this study are significant for understanding the changes in gut microbiota and their ecological functions across different life stages of endangered primates.