中文摘要：

幼苗是植物生活史中一个不可缺失的阶段,对自然植被恢复起着非常重要的作用。为了探索黄土丘陵沟壑区不同侵蚀环境下幼苗库特征及其与地上植被的关系,选择不同植被带的3个典型小流域,通过野外样方调查,运用单因素方差分析法对幼苗密度、物种多样性以及幼苗与地上植被的物种相似性进行分析。结果表明,1）调查共记录幼苗75种,分属25科,地上植被105种,分属29科,主要由菊科、禾本科和豆科构成,且以旱生和中旱生的多年生草本为主;2）不同侵蚀环境下幼苗密度和物种多样性指数呈现不同差异。不同植被带上,森林草原带和草原带大于森林带。同一植被带上,森林带幼苗密度是峁顶〉阴坡〉阳坡,多样性指数是梁/峁坡〉沟坡;草原带二者在不同侵蚀环境下均无显著差异;而森林草原带表现为阴坡尤其是阴沟坡幼苗密度较大,物种较为丰富;3）侵蚀环境不同对幼苗与地上植被物种相似性无显著影响,3个流域草本植被的相似性系数均值都在0.5以下,表现出较小的相似性。可见,黄土丘陵沟壑区立地环境条件差,幼苗不易存活和建植。

英文摘要：

Seedlings are an indispensable stage in the plant cycle life and are important in natural vegetation res- toration. The objective of this paper was to explore seedling characteristics and their relationship with the standing vegetation under different erosion environments in the hill-gully Loess Plateau region. Three typical watersheds in different vegetation zones were selected, and One-Way ANOVA was used to analyze seedling densities, species diversity and the similarity between seedlings and the ground vegetation using quadrat sur- veys. In the seedling bank,there were 75 species belonging to 25 families, while in the ground vegetation there were 105 species belonging to 29 families. Most species were Compositae, Gramineae and Leguminoseae com- posited, while Xerophytic and Mesoxerphytic were the main water ecotypes, and perennial herbs were the dominant life-form. Seedling densities and diversity were different in different erosion environments. They were greater in the forest-grassland and grassland zones than in the forest zone. In the same vegetation belt, seedling densities in the Dongzigou watershed was in the order mao topshady slopesun slope, while diversi- ty was in the order liang/mao slopegully slope. In the Gaojiagou watershed, there was no significant differ- ence in seedling density or diversity. In the Zhangjiahe watershed, seedling densities were bigger and species were richer on shady slopes, especially on shady gully slopes. Different erosion environments had no significant effect on the similarity between seedlings and the standing vegetation. The Sorensen similarity index of herbs in the 3 watersheds was less than 0.5, showing smaller similarity. Therefore, the site conditions in the hill-gully Loess Plateau region are poor, and the seedlings cannot survive and establish easily.