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.

β‐diversity patterns (the compositional variations across sites) and their drivers are the major concerns of biodiversity research and conservation practices, whereas such information remains scarce for vascular epiphytes, especially in tropical forest communities. This study aimed to reveal the pattern and driving process of the compositional variations of vascular epiphytes in a tropical cloud forest on Hainan island, southern China, and their differences from those of terrestrial woody plants. To this end, we quantified their between‐habitat compositional variations and distinguished the underlying components of β‐diversity (nestedness and turnover). We then examined the relative roles of niche‐based and neutral processes in driving the compositional variations by using a null model approach. Our results showed that the between‐habitat compositional variations were significant for both plant assemblages and stronger in vascular epiphytes than in terrestrial woody plants. The turnover component of β‐diversity was significantly stronger in terrestrial woody plants, accounting for 73.16–80.08% of the variations. By contrast, the nestedness component was significantly stronger in vascular epiphytes and characterized 46.82–67.5% of the variations. Besides, the compositional variations of both plant assemblages, especially terrestrial woody plants, were generally poorly fitted by the simulated niche‐based scenarios but well fitted by the simulated neutral scenarios. Overall, the compositional variations of both plant assemblages were significant and mainly due to dispersal limitation, albeit to varying degrees. Hence, further studies of these plant assemblages at local scales should not be ideologically limited to the niche‐based framework. Moreover, the stronger nestedness observed in vascular epiphytes suggests the greater importance of prioritizing conservation efforts in the species‐rich habitats for these plants.

The composition and diversity of rhizosphere microbial communities may be due to root–soil–microbial interactions. The fine root functional traits and rhizosphere soil environmental factors of 13 representative plants in the Bawangling tropical cloud forest of Hainan Island were measured, to assess the key factors driving plant rhizosphere microbial communities. Illumina MiSeq sequencing technology was used to sequence the v3-V4 region of the 16SrDNA gene of 13 plant rhizosphere soil bacteria and the ITS1 region of the fungal ITSrDNA gene. Results showed that there were 355 families, 638 genera, and 719 species of rhizosphere soil bacteria as well as 29 families, 31 genera, and 31 species of rhizosphere soil fungi in the tropical cloud forests. The fine root traits, such as root phosphorus content, the specific root length and specific root area, were significantly negatively correlated with the Faith-pd indices of the bacterial community but were not correlated with the diversity of fungi communities. The soil pH was significantly and positively correlated with the Chao1 index, OTUs, Faith-pd and Simpson indices of the bacteria and fungi communities. The soil available phosphorus content was significantly and negatively correlated with the bacteria Simpson and the fungus Faith-pd indices. ABT analysis showed that soil pH and soil available phosphorus were the most important environmental conditions contributing to the rhizosphere bacterial and fungi communities, respectively. Our findings demonstrate that the soil environments had more influence on rhizosphere soil microbial diversity than the fine root functional traits.

The present projected rates of global species loss emphasize the need to precisely understand how biodiversity promotes ecosystem function in different types of ecosystems. Some known mechanisms such as niche complementarity and selection effects have been tested to explain the biodiversity-ecosystem function (BEF) relationships in several ecosystems, but less work has been done in high-altitude forests with environmental stresses. Therefore, we measured key diversity attributes including species richness (SR), functional trait diversity (Rao’s quadratic entropy, RaoQ), and mean pairwise distance (MPD) in functional trait space and compare them to an important functional attribute (aboveground biomass, AGB, as a proxy for productivity) and resource stress (soil phosphorus). The results showed that both SR and RaoQ showed positive relationships with AGB, while MPD exhibited a negative relationship with AGB, suggesting that increases in plant species ameliorated by neighboring plants with similar functional and evolutionary roles in a stressful environment will help enhance ecosystem productivity. Together with plant diversity, the proportion of variance in AGB increased from 23.90 to 65.80% when soil phosphorus was added into analyses, suggesting that SR, RaoQ, and MPD all exhibit potentiality in the variation of AGB and that soil nutrients play important roles in the BEF relationships. The BEF relationships in tropical cloud forests are mediated by facilitative interactions due to low soil phosphorus. Our findings suggested that conservation of neighboring plant species with functional similarity and close relatedness be important in these forest managements. Additionally, our results showed a comprehensive consideration of environmental factors in BEF relationship analysis.

附生维管植物是热带森林中重要的特征性组分,研究附生维管植物对宿主树的选择性对热带森林生物多样性及生态系统保护有重要意义。该研究以海南热带雨林国家公园霸王岭片区热带云雾林中的附生维管植物为研究对象,通过设置21个20 m×20 m的固定样地,调查样地内所有胸径＞1 cm的乔、灌木的数量、种类、胸径、植株高、基质类型及其上生长的附生维管植物的数量、种类,用混合线性模型、单因素方差、附生选择性指数分析附生维管植物分布与宿主树种、胸径、高度、基质类型（裸树皮、苔藓、凋落物及土壤）的关系。结果表明:在热带云雾林8 400 m~2样地内,附生维管植物共计51种2 650株,附生兰科植物和附生蕨类植物为优势类群,附着在10.6%的个体木上;附生维管植物多度和丰富度与宿主树胸径显著正相关;多度较大的琼崖石韦（Pyrrosia eberhardtii）、流苏贝母兰（Coelogyne fimbriata）、阴石蕨（Davallia repens）、蔓九节（Psychotria serpens）对宿主树种表现出一定的选择性,显著偏好1–4个树种;附生维管植物对轻基质类型（苔藓植物）也存在显著偏好,70%以上的附生维管植物生存在苔藓基质上。

Functional trait ecology demonstrates the significance of the leaf economics spectrum in understanding plants’ trade-off between acquisitive and conservative resource utilization. However, whether trait variations of different vegetative organs are coordinated and whether the plant economics spectrum is characterized by more than one vegetative organ remain controversial. To gain insights into these questions, within a tropical cloud forest in Hainan Island, a total of 13 functional traits of 84 tree species were analyzed here, including leaf, stem and root traits. By using standardized major axis (SMA) regression and principal components analysis, we examined the trait variations and correlations for deciphering plants’ trade-off pattern. We found decreases of leaf phosphorus content, leaf nitrogen content and specific leaf area and increases of leaf mass per unit area (LMA), wood density and leaf thickness along the first principal component, while there were decreases of specific root length and specific root area and increases of root tissue density along the second principal component. Root phosphorus and nitrogen contents were significantly positively associated with the phosphorus and nitrogen contents of both stem and leaf. Wood density was significantly positively associated with LMA and leaf thickness, but negatively associated with leaf thickness and specific leaf area. Our results indicate that, in the tropical cloud forest, there is a “fast–slow” economic spectrum characterized by leaf and stem. Changes of nutrient trait are coordinated, whereas the relationships of morphological traits varied independently between plant above- and below-ground parts, while root nutrient traits are decoupled from root morphological traits. Our findings can provide an insight into the species coexistence and community assembly in high-altitude tropical forests.

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.

研究热带云雾林植物N、P及可溶性糖分配规律,对了解植物生长及对环境的适应性有重要意义.通过测定海南岛3个林区热带云雾林282种植物的枝条与叶片中N、P和可溶性糖含量,比较枝条、叶片中各个养分的差异,分析养分间的关联性.结果表明,植物叶片N、P和可溶性糖含量均显著高于枝条,其中枝条和叶片可溶性糖含量分别为(15.06±9.4)和(32.14±19.57)g·kg-1,氮含量分别为(3.48±1.02)和(9.51±5.26)g·kg-1,磷含量分别为(0.23±0.15)和(0.56±0.44)g·kg-1.黎母山植物枝条、叶片的N和P含量最高,霸王岭植物最低;霸王岭植物枝条可溶性糖含量显著高于黎母山和尖峰岭,而霸王岭植物叶片可溶性糖含量显著低于黎母山和尖峰岭.在植物枝条、叶片中,N与P含量均呈显著正相关,而可溶性糖与P含量无显著相关性;在枝条与叶片之间,可溶性糖含量无显著相关,而N含量和P含量显著正相关.此外,P元素是海南岛热带云雾林植物生长及种群发育的主要限制性因子.

沉香树为瑞香科沉香属多年生常绿乔木，是我国特有珍贵的药用树种，具有较高的经济价值及园林、绿化等生态价值。本文从资源分布、形态学特征、生态习性、繁育技术、利用价值以及沉香产业等方面进行了论述，同时对目前沉香繁育技术研究与产业化发展当中存在的问题进行了分析和探讨，并提出相应的对策措施，以期为沉香的资源保护及开发利用研究提供一些参考。

生态系统水质净化功能对于削减面源污染、保障流域水质具有举足轻重的作用。但城市化过程中，不透水建设用地的扩张对流域生态系统水质净化功能带来严重损害。明确建设用地扩张对生态系统水质净化功能的影响及其调控策略对于流域水环境管理具有重要意义。

探讨户外瑜伽场地景观营建中应注意的问题，把握户外瑜伽场地的空间设计、户外瑜伽场地植物造景的配置原则，以及其他配套设施的设计。