Increasingly, tropical studies based on aboveground traits have suggested that lianas have a more acquisitive strategy than trees, thereby possibly explaining the increase in lianas relative to trees in many tropical forests under global change. However, few studies have tested whether this pattern can be extended to root traits and temperate forests. In this study, we sampled 61 temperate liana-host tree pairs and quantified 11 commonly studied functional traits representative of plant economics in roots, stems, and leaves; we aimed to determine whether root, stem and leaf traits are coordinated across lifeforms, and whether temperate lianas are also characterized by more fast and acquisitive traits than trees. Our results showed that leaf and stem traits were coordinated across lifeforms but not with root traits, suggesting that aboveground plant economics is not always correlated with belowground economics, and leaf and stem economic spectra cannot be expanded to the root directly. Compared with host trees, lianas had more acquisitive leaf and stem traits, such as higher specific leaf area and lower leaf dry matter content, leaf carbon content, leaf mass per area, and wood density, suggesting that lianas have a more acquisitive strategy than host trees in the temperate forest. The differences between lianas and trees in plant strategy may drive their contrasting responses to the changing temperate forest environment under global change.

To investigate the diversity and distribution of rhizobia associated with Sophora davidii in habitats with different light and soil conditions at the Loess Plateau, we isolated rhizobia from root nodules of this plant grown at 14 sites at forest edge or understory in Shaanxi Province. Based on PCR-RFLP and phylogenies of 16S rRNA gene, housekeeping genes (atpD, dnaK, recA), and symbiosis genes (nodC and nifH), a total of 271 isolates were identified as 16 Mesorhizobium genospecies, belonging to four nodC lineages, and three nifH lineages. The dominance of M. waimense in the forest edge and of M. amorphae/Mesorhizobium sp. X in the understory habitat evidenced the illumination as a possible factor to affect the diversity and biogeographic patterns of rhizobia. However, the results of Canonical Correlation Analysis (CCA) among the environmental factors and distribution of rhizobial genospecies illustrated that soil pH and contents of total phosphorus, total potassium and total organic carbon were the main determinants for the community structure of S. davidii rhizobia, while the illumination conditions and available P presented similar and minor effects. In addition, high similarity of nodC and nifH genes between Mesorhizobium robiniae and some S. davidii rhizobia under the forest of Robinia pseudoacacia might be evidence for symbiotic gene lateral transfer. These findings firstly brought an insight into the diversity and distribution of rhizobia associated with S. davidii, and revealed illumination conditions a possible factor with impacts less than the soil traits to drive the symbiosis association between rhizobia and their host legumes.

Community ecologists often assume that species-level trait differences drive habitat differentiation that promotes species coexistence. Direct empirical studies testing trait-habitat relationships in forest ecosystems are critical for understanding the functional basis of tree coexistence and predicting the effects of forest disturbance on diversity, but such studies have been rarely performed. Considering the importance of the regeneration niche in tree coexistence, here, we tested regeneration niche differentiation and species-level trait-habitat relationships by measuring nine microhabitat variables and seven functional traits of seedlings of three common tree species in a temperate mixed forest in Taibai Mountain in China. Our results showed that most tree seedlings grew in microhabitats with more light and distant neighbor than random points. The three species were separated in the microhabitat space defined by canopy cover and neighbor distance gradients and in the trait space defined by leaf economic traits, seed mass, and wood density. Leaf economic traits were mostly related to light microhabitat variables, whereas seed mass and stem wood density were mostly associated with neighbor distance. These results suggested that the heterogeneity of light availability and neighbor distance were the main ecological gradients in distinguishing different tree species in seedling microhabitats. Differences in seedling functional traits drive the differentiation of species regeneration niches, potentially facilitating the coexistence of tree species. Leaf economic traits, seed mass, and wood density could be used to predict the regeneration microhabitat of tree species.

Elevational gradients strongly affect microbial biodiversity in bulk soil through altering plant and soil properties, but the effects on rhizosphere microbial patterns remain unclear, especially at large spatial scales. We therefore designed an elevational gradient experiment to examine rhizosphere microbial (bacteria, fungi and arbuscular mycorrhizal fungi) diversity and composition using Illumina sequencing of the 16S rRNA and ITS genes for comparison to plant and soil properties. Our results showed that bacterial and fungal alpha diversity was significantly higher at mid-elevation, while AMF alpha diversity decreased monotonically. The beta diversities of the three groups were significantly affected by elevational gradients, but the effect on bacterial beta diversity was larger than on fungal and AMF beta diversity. Proteobacteria, the dominant phyla of bacteria, was significantly higher at the mid-elevation, while Acidobacteria and Actinobacteria significantly decreased as elevation increased. The main fungal taxa, Basidiomycota, significantly decreased with elevation, and Ascomycota significantly increased with elevation. Glomeromycota, the dominant AMF phyla, responded insignificantly to the elevational gradients. The responses of bacterial and fungal alpha diversity were mostly associated with tree diversity and organic carbon, whereas AMF alpha diversity mainly depended on litter N and P. Changes in bacterial community composition along the elevational gradient were explained primarily by litter N and P, and litter P was the main driver of fungal and AMF community composition. Overall, our results suggest that plant litter, particularly litter N and P, were the main source of external carbon input and drove the observed differences in rhizosphere microbial diversity and community composition. Our results highlight the importance of litter nutrition in structuring rhizosphere microbial communities in mountain ecosystems.

物种丰富度的海拔梯度格局一直是生态学研究的热点内容.在森林生态系统中攀援植物是一个重要组成部分,秦岭太白山是一个具有代表性的地区,其攀援植物种类丰富且海拔梯度变化明显,但有关攀援植物丰富度的海拔梯度格局鲜有研究.通过收集《太白山自然保护区生物多样性研究与管理》和《秦岭植物志》记录数据,统计分析太白山攀援植物的物种丰富度,并研究比较不同生活型和攀援方式攀援植物物种丰富度沿海拔梯度的变化模式.结果表明:1)秦岭太白山包含攀援植物26科44属103种.其中,草质攀援植物共计15科23属44种,木质攀援植物共计17科25属49种;2)秦岭太白山攀援植物包括4种攀援方式:缠绕、卷须、蔓生和吸附.草质攀援植物种数,缠绕类>卷须类≥蔓生类;木质攀援植物种数,缠绕类>卷须类>吸附类>蔓生类;3)在科、属、种3个水平上,总攀援植物、草质攀援植物和木质攀援植物都随着海拔的升高呈现出明显的单峰分格局,且最大值都出现在1200～1400 m的海拔梯度.本研究结论对于深入理解秦岭太白山攀援植物多样性的影响因素以及开展该类群植物的保护利用有一定的参考价值.