黄土高原半干旱区不同林龄柠条人工林土壤线虫群落特征

Characteristics of soil nematode communities in Caragana korshinskii plantations with different stand ages in semi-arid region of Loess Plateau, Northwest China

为了解柠条人工林对半干旱地区脆弱生态环境的改善作用,在黄土高原柠条种植的重点区域——宁夏南部山区,选取4个林龄(4、14、24和34年生)的柠条人工林作为对象,调查林中土壤线虫群落的组成、结构与多样性特征,并分析它们与土壤理化性质之间的关系,探明黄土高原半干旱区柠条林植被恢复过程中土壤线虫群落的演变特征及其环境影响因素。结果表明:林龄对土壤线虫数量有显著影响,线虫数量随林龄增加呈先上升后降低的变化趋势,在14年生达到峰值;线虫群落组成和营养类群结构在不同林龄柠条林中呈现较大分异,杂食-捕食性线虫比例在14年生达到最高(40.3%),而在24年生植食线虫比例占绝对优势(61.3%),食细菌和食真菌线虫比例分别在4和34年生达到最高;土壤线虫群落生态指数也随着林龄的增加发生改变,其中线虫成熟度指数、瓦斯乐斯卡指数和结构指数均在14年生达到最大,但在24年生,这些生态指数以及线虫多样性指数和均匀度指数均降至最低,表明土壤生物多样性下降,生态系统恢复状况受到影响;在柠条人工林植被恢复过程中,土壤含水量、有机碳、全氮及微生物生物量碳是影响线虫群落特征的主要环境因子,在不同林龄柠条林中它们的变化对线虫数量和群落组成有一定的调控作用,而线虫群落的改变能够有效指示土壤健康与生态系统恢复状况,对综合评价柠条人工林植被的生态环境效应有着重要意义。

To clarify the improvement effect of Caragana korshinskii plantation on fragile eco-environment in semi-arid areas, we selected four C. korshinskii plantations with different ages(4-, 14-, 24-, and 34-year-old) in the mountainous area of southern Ningxia as the research objects, where was one of the key C. korshinskii planting areas on the Loess Plateau. We investigated the composition, structure, and diversity of soil nematode communities, and analyzed their relationships with soil properties, to explore the evolution of soil nematode community and their environmental influencing factors in the restoration process of C. korshinskii plantation in the semi-arid region of the Loess Plateau. The results showed that the stand age of C. korshinskii plantation significantly affected soil nematode abundance, which increased first and then decreased with increasing stand age, and peaked in the 14-year-old plantation. The nematode community composition and trophic group structure differed greatly among different stand ages. The percentages of omnivorous-predatory and plant-parasitic nematodes were highest in the 14-and 24-year-old plantations(40.3% and 61.3%), respectively, while that of bacterial-and fungal-feeding nematodes reached the maximum in the 4-and 34-year-old plantations, respectively. The ecological indices of soil nematode communities changed with stand age. The maturity index, Wasilewska index, and structure index all reached the maximum in the 14-year-old plantation, while those three ecological indices as well as the Shannon diversity index and Pielou evenness index of nematode community decreased to the lowest in the 24-year-old C. korshinskii plantation, indicating decreased soil biodiversity and poor ecosystem restoration. Across the chronosequence of C. korshinskii plantations, soil water content, organic carbon concentration, total nitrogen concentration, and microbial biomass carbon were the main influencing factors driving the changes in the abundance and community composition of soil nematodes. Such changes in soil nematode communities can effectively indicate soil health and ecosystem restoration status, which are of great significance for the comprehensive evaluation of eco-environmental impacts of C. korshinskii plantations.