In forest ecosystems,plant communities shape soil fungal communities through the provisioning of carbon.Although the variation in forest composition with latitude is well established,little is known about how soil fungal communities vary with latitude.We collected soil samples from 17 forests,along a latitudinal transect in western China.Forest types covered included boreal,temperate,subtropical and tropical forests.We used 454 pyrosequencing techniques to analyze the soil communities.These data were correlated with abiotic and biotic variables to determine which factors most strongly influenced fungal community composition.Our results indicated that temperature,latitude,and plant diversity most strongly influence soil fungal community composition.Fungal diversity patterns were unimodal,with temperate forests(mid latitude)exhibiting the greatest diversity.Furthermore,these diversity patterns indicate that fungal diversity was highest in the forest systems with the lowest tree diversity(temperate forests).Different forest systems were dominated by different fungal subgroups,ectomycorrhizal fungi dominated in boreal and temperate forests;endomycorrhizal fungi dominated in the tropical rainforests,and non-mycorrhizal fungi were best represented in subtropical forests.Our results suggest that soil fungal communities are strongly dependent on vegetation type,with fungal diversity displaying an inverse relationship to plant diversity.
以2年生三叶漆(T erm inth ia p an icu la ta)幼苗为实验材料,研究了生长于全自然光和遮荫条件(光强相当于自然光强的50%)下幼苗的光合特性和叶绿素荧光参数对不同土壤水分条件的响应,探讨了其对干旱和强光胁迫的生理适应机制.结果表明,叶片相对含水量(RW C)、叶水势(Ψ)、最大光合速率(Pm ax)、表观量子效率(AQY)、暗呼吸速率(Rd)和光合色素含量都随干旱胁迫的加剧而下降.Pm ax、AQY、Rd和比叶重(LM A)随光强的增加而升高,色素含量则随光强升高而降低.Ch la/b、C ar/Ch l随干旱程度和光强的增加有升高的趋势.PSⅡ的最大光能转换效率(Fv/Fm)和光化学量子效率(ФPSⅡ)在日间光较强时明显降低,说明发生了光抑制.电子传递速率(ETR)和非光化学猝灭系数(N PQ)随日间光强的增大而升高,表明三叶漆可能通过增强光呼吸和热耗散抵御光抑制、保护光合机构.二元方差分析表明,水分和光强具有明显的交互作用.全自然光下严重干旱的幼苗仍有较高的Pm ax(9.65μm o l.m-2.-s 1),说明三叶漆对干旱和强光具有极强的适应能力,这也是其成为干热河谷植被优势种的重要原因.
Soil horizon and vegetation cover significantly impact the spatial patterns of soil fungal and bacterial communities.However,such impacts and their interactions are poorly characterized in dry–hot environments.Soil samples were collected from two soil horizons(humus and mineral)along a vegetation gradient(shrubland,grassland,and shrub–grass ecotone)in a dry-hot valley of Southwestern China to assess the effects of vegetation versus soil horizons on shaping soil microbial communities.We used denaturing gradient gel electrophoresis to estimate the microbial spatial pattern change across the vegetation gradients and clone libraries targeting small subunit rRNA genes to characterize the microbial community structures between distinct vegetation types and soil horizons.Bacterial DNA profile patterns were not significantly different across vegetation types but strongly correlated with soil horizons,with significant interaction effects.By contrast,fungi were remarkably different across vegetation types and soil horizons,without significant interactions effect.Distinct vegetation types did not necessarily harbor distinct bacterial or fungal community compositions.Rather,both community compositions were most strongly affected by the soil horizons.Together with these results,the soil vertical heterogeneity rather than vegetation changes is suggested to best predict shifts in soil microbial communities in this dry-hot valley area.
