黄土丘陵区坡面柠条(Caragana korshinskii)林地草本植物分布特征

人工植被恢复会显著影响林下草本的分布及多样性,而人工植被恢复耦合坡面微地形变化对草本群落分布及其多样性响应尚缺乏系统的认识。以位于半干旱黄土丘陵区的甘肃定西龙滩小流域为研究区,系统调查和监测了不同坡向上、中和下坡位人工柠条(Caragana korshinskii)林地草本群落组成、生物量与柠条生长状况、凋落物量及土壤水分含量,分析草本群落的分布特征及其影响因素。结果表明:(1)不同坡向草本群落组成明显不同,阴坡人工柠条林地草本物种丰富度、优势度和多样性指数显著高于半阳坡和阳坡,而均匀度指数各坡向间差异不显著;(2)不同坡向间草本地上生物量为阴坡>半阳坡>阳坡,但差异不显著;阴坡上、中坡位草本生物量显著高于下坡位,半阳坡和阳坡各坡位间草本生物量差异不显著;(3)pRDA分析结果表明,坡向影响了坡面水热条件,对草本分布的影响最大,解释了15.2%的草本群落变异;(4)柠条种植密度和坡向与草本物种丰富度呈显著负相关;阿尔泰狗娃花(Heteropappus altaicus)和长芒草(Stipa bungeana)与坡向呈显著正相关,主要分布在阴坡,茵陈蒿(Artemisia capillaris)和赖草(Leymus secalinus)等与坡向呈显著负相关,主要分布在阳坡。半干旱黄土丘陵区坡向通过影响水热条件从而影响了植被生长,坡面微地形调整可以在一定程度上削弱坡位对草本植物生长的影响,但坡向及人工植被种植密度决定了草本的分布格局。

Distribution and diversity of herbage under Caragana korshinskii plantation at hillslope scale in the semi-arid loess hilly region

Distributions and diversity of herb community were significantly influenced by the introduced shrub restoration. However,the recognition of responding mechanism by which the micro-landform modification and artificial shrub restoration influence the distribution and diversity of herbage at the hill slope scale is limited. In this study,we selected a typical artificial Caragana korshinskii shrub on the hill slope as a research model,and the data of composition of herbaceous community,herbaceous above-ground biomass,C. korshinskii growth,litter moisture content and soil moisture content were collected. The following results were obtained in this study.(1)the composition of herbaceous community was significant difference at different slope aspect. The species richness,dominance and diversity index of herbaceous community in shady slope were significant highly than in semi-sunny and sunny slope. On the contrary,there was no significant difference on the evenness index in different slope aspects.(2)Herbaceous above-ground biomass in different slope aspects was shady slope>semi-sunny slope>sunny slope,but there was not significant difference. Herbaceous above-ground biomass at upper and middle slope positions were significantly higher than at foot slope position in the shady slope aspect,and there was not significant difference between different slope positions in the semi-sunny and sunny slope aspect.(3)Slope aspect affected the hydro thermal conditions on hill slope,and then significantly influenced the diversity of herb community and explained 15.2% variation in herb community.(4)Shrub density of C. korshinski and slope aspect had a significant negative relationship with the species richness of herb community. Heteropappus altaicus and Stipa bungeana had a significant positive relationship with slope aspect,and they were mainly distributed at the shady slope. Artemisia capillaris and Leymus secalinus had a significant negative relationship with slope aspect,and they mainly distributed at the sunny slope. The slope aspect affected the hydro thermal conditions on hill slope,and then reflected the vegetation growth. And the effect of slope position on the growth of herbage can be weakened by the changes of micro topography. And the slope aspect and the shrub density of artificial vegetation determined the distribution pattern of the herbage.