柳枝稷引种对黄土区典型草本植物生态效应及其机制研究

With the continuous introduction of species, the ecological effects of exotic introduced plants on grassland vegetation has attracted more and more attention. Previous studies have paid little attention to the feedback of soil legacy effects of exotic plants on grassland vegetation, and the inadequate quantification of ecological effects after introduction of exotic plants has seriously restricted the comprehensive evaluation of introduction of exotic plants based on ecological effects. The project will study the exotic plant Panicum virgatum and the typical herbaceous plants in the process of local vegetation restoration in the Loess Hilly Region through combining field plot simulation test with laboratory analysis. The influence of P. virgatum competition and its soil legacy effects on photosynthetic characteristics, biomass, carbon, nitrogen, phosphorus and non-structural carbohydrate concentrations and allocation in native plants will be analyzed. The responses characteristics of soil components carbon, nitrogen and phosphorus concentrations, microbial biomass, enzyme activity, microbial community structure and diversity to the competition of P. virgatum and feedback of native plants will be addressed. The coupling relationship between soil nutrients and microbial communities and plant physiological and biochemical characteristics will be analyzed to reveal the main soil nutrient factors and key microbial groups affecting the growth and recovery of native plants. The ecological effects of P. virgatum on the plant-soil-microbial system of native species will be quantified and evaluated comprehensively. In further, it would be useful to provide scientific basis for the management of exotic introduced plants and the local vegetation restoration in the Loess Hilly region.

随着物种引进的持续发生，外来植物引种对草地植被的生态效应越来越引起人们关注。已有研究较少关注外来植物土壤遗留效应对草地植被的反馈作用，且对外来植物引种后的生态效应量化不足，严重制约了基于生态效应的外来植物引种的综合评价。以黄土丘陵区外来植物柳枝稷和当地植被恢复过程中的典型草本植物为对象，采用野外小区模拟试验与室内分析相结合方法，分析柳枝稷竞争作用及其土壤遗留效应对本地植物光合特性、生物量、碳氮磷和非结构性碳水化合物含量及分配的影响；阐明土壤各组分碳氮磷含量、微生物量、酶活性及微生物群落结构与多样性对柳枝稷竞争作用及本地植物反馈作用的响应特征；剖析土壤养分和微生物群落与植物生理生化特性间的耦合关系，揭示影响本地植物生长与恢复的主要土壤养分因素和关键微生物类群；量化并综合评价柳枝稷对本地物种的植物-土壤-微生物系统的生态效应，为黄土丘陵区外来引种植物管理和本地植被恢复提供科学依据。

针对外来植物引种后的竞争及其土壤遗留效应对本地植物-土壤系统的生态效应缺乏系统研究这一问题。研究以黄土丘陵区外来引种植物柳枝稷和本地植被撂荒演替恢复过程中的典型草本植物为对象，采用野外调查与盆栽试验相结合方法，分析了柳枝稷竞争及其土壤遗留效应对本地植物-土壤-微生物系统的影响，探讨了以上过程中影响植被生长的主要土壤养分因子和关键微生物类群，明确了柳枝稷竞争及其土壤遗留效应对本地植被的生态效应。结果表明：（1）柳枝稷竞争显著降低了本地植物铁杆蒿和白羊草的生物量，但对植物养分含量的影响则因植物种类而异。柳枝稷竞争主要增加了白羊草土壤养分含量，而降低了铁杆蒿土壤养分含量。柳枝稷竞争对白羊草与铁杆蒿土壤微生物群落的多样性及其相对丰度在门与属分类水平上均无明显影响；其在一定程度上增加了白羊草土壤微生物群落网络结构的复杂性，并改变了其共现网络的关键微生物类群，但对铁杆蒿土壤微生物群落网络结构的影响则不明显。柳枝稷与本地植物竞争过程中，影响白羊草、铁杆蒿和柳枝稷生长的主要土壤因子分别为土壤水溶性硝态氮和担子菌门、土壤硝态氮和厚壁菌门、土壤速效磷和变形菌门。柳枝稷竞争对铁杆蒿和白羊草均具有较强的生态效应，从生物量的角度分析均以负效应为主，表明柳枝稷的竞争对本地植物的生长具有较强的抑制作用。（2）柳枝稷土壤遗留效应对本地植被的光合特性、养分含量和生物量的影响并不无一致特征，主要显著降低了狗尾草（演替早期）和铁杆蒿（演替中期）生物量，而显著增加了白羊草（演替后期）生物量；柳枝稷土壤遗留效应影响狗尾草、铁杆蒿和白羊草生长的主要土壤因子分别为土壤铵态氮、pH和土壤速效氮；柳枝稷土壤遗留效应对狗尾草和铁杆蒿主要为负效应，对白羊草主要为正效应。因此，在柳枝稷引种后的管理及其移除后的本地植被恢复过程中可以通过调控土壤养分和引入演替后期物种促进本地植被恢复，研究可为区域植被恢复与管理提供理论依据。