Contrasting effects of space and environment on functional and phylogenetic dissimilarity in a tropical forest

Aims The evolutionary history and functional traits of species can illumi-nate ecological processes supporting coexistence in diverse forest communities.However,little has been done in decoupling the rela-tive importance of these mechanisms on the turnover of phylogenetic and functional characteristics across life stages and spatial scales.Therefore,this study aims to estimate the contribution of environment and dispersal on the turnover of phylogenetic and functional diversity across life stages and spatial scales,in order to build a coherent pic-ture of the processes responsible for species coexistence.Methods We conducted the study in Xishuangbanna Forest Dynamics Plot in Yunnan Province,southwest China.We used four different spatial point process models to estimate the relative importance of disper-sal limitation and environmental filtering.The functional traits and phylogenetic relationships of all individual trees were incorporated in the analyses to generate measures of dissimilarity in terms of pair-wise and nearest-neighbor phylogenetic and functional characteris-tics across life stages and spatial scales.Important Findings We found non-random patterns of phylogenetic and functional turnover across life stages and spatial scales.Environmental filtering structured pairwise phylogenetic and functional beta diversity across spatial scales,while dispersal limitation alone,and in combination with environment filtering,shaped nearest neighbor phylogenetic and functional beta diversity.The relative importance of dispersal limitation and environmental filtering appeared to change with life stage but not with spatial scale.Our findings suggest that phylogenetic and functional beta diversity help to reveal the ecological processes responsible for evolu-tionary and functional assembly and highlight the importance of using a range of different metrics to gain full insights into these processes.

增温驱动的核心微生物的迁移可指示土壤属性的改变

尽管微生物-气候的相互作用已得到越来越多的研究者和决策者的认可,但微生物的高多样性和对气候环境变化多变量的响应导致预测微生物在未来气候背景下的分布格局非常困难.本研究依托于中国土壤微生物组计划,基于采集自中国东部森林的1600多个样品的16S r RNA基因测序数据,首先证实了微生物群落组成和多样性的纬度分布规律且温度对微生物群落组成有显著的直接作用.其次,利用核心微生物代替整体群落来进行多样性的缩减,并将这些核心微生物根据其对环境的偏好性划分为不同的生态集群,这些生态集群在空间上的热点区域,即高丰度区域相互不重叠.此外,通过Cubist模型预测未来不同气候变化情景下(RCP2.6和RCP8.5)各生态集群的丰度变化并将其投影到中国森林生态系统分布区域,通过与现在的分布格局做对比得到增温驱动的生态集群空间分布格局的变化.这些变化一方面可以指示集群内微生物对未来气候变化的适应性,另一方面考虑到每一类生态集群所代表的环境偏好性,这些变化也可进一步用来指示未来气候变化背景下土壤属性的变化.

The potential for biochar application in rubber plantations in Xishuangbanna,Southwest China:a pot trial

Biochar can enhance crop production and sequester carbon,but there have been few studies with tree crops.Rubber plantations cover more than 8 million hectares in Southeast Asia,so we assessed the feasibility of biochar application in these plantations with a pot trial.Rubber seedlings were planted in soil with four concentrations(0,1.25%,2.5% and 5%,w/w)of biochar combined with two concentrations of compound fertilizer(0 kg/ha and 300 kg/ha).Soil properties and seedling growth were measured,and a leaching experiment was conducted in the rainy season.Our results show that biochar increased pH,water content(27.4-65.1%),total carbon(25.4-53.6%),nitrate nitrogen,and available phosphorus in the soil,and decreased bulk density(3.2-23.9%).Biochar treatment reduced leaching of ammonium nitrogen and ortho-P.Biochar increased seedling nutrient uptake(C,N,P and K),with 2.5% and 5% biochar showing the largest effects,but seedling biomass was the highest with 1.25%,and declined in 2.5% and 5%.Our results suggest that biochar addition is an effective way to improve rubber plantation soils,sequester more carbon and decrease nutrient leaching,but the optimum application rate under field conditions needs further research.