中文摘要：

幼苗是植被恢复演替的基础,在生态系统中具有非常重要的作用。为了探索黄土丘陵沟壑区坡沟立地环境下幼苗的存活特征,在陕西省安塞县宋家沟和纸坊沟流域设置15个固定样地进行定点动态监测,运用单因素方差分析法和系统聚类分析法对不同立地环境下的幼苗密度和幼苗存活率进行了分析。结果表明：1）不同坡沟立地环境下,幼苗存活特征差异明显,整体表现为阳坡幼苗密度较小而存活率较高,阴坡幼苗密度较大但存活率较低。2）细裂叶莲蒿（Artemisia gmelinii）、菊叶委陵菜（Potentilla tanacetifolia）、阿尔泰狗娃花（Heteropappus altaicus）等物种具有较高的幼苗存活率,在生存竞争中幼苗是以＂质＂取胜;而猪毛蒿（Artemisia scoparia）、中华苦荬菜（Ixeris chinensis）、阴行草（Siphonostegia chinensis）等物种具有较高的幼苗密度,在生存竞争中是以＂量＂取胜。3）同一物种在坡沟立地环境下表现出不同的存活曲线,不同物种在不同立地环境下也可呈现同一存活曲线;细裂叶莲蒿、菊叶委陵菜、长芒草（Stipa bungeana）、阿尔泰狗娃花、兴安胡枝子（Lespedeza davurica）等物种,幼苗不仅在雨季存活能力强且具有较强的越冬能力;猪毛蒿、香青兰（Dracocephalum moldavica）、臭蒿（Artemisia hedinii）等物种在雨季前幼苗存活能力较强,但冬季存活能力弱。4）坡面不同微环境下幼苗存活特征也存在差异,即微环境的改变在一定程度上影响着幼苗的生长、存活和越冬。因此,在黄土丘陵沟壑区应根据物种幼苗存活特性对幼苗进行适当的抚育管理,这将有利于幼苗的建植和植被更新。

英文摘要：

Aims Seedling is the fundament of vegetation restoration succession and plays a very important role in ecosystems. The objective of this paper was to explore the characteristics of seedling survival in habitats of hill and gully slopes in a hill-gully Loess Plateau region. Methods Fifteen permanent plots in Zhifanggou and Songjiagou watershed in Ansai County were established for sentinel dynamic monitoring, and one-way ANOVA and hierarchical cluster analysis were used to analyze seedling density and survival rate in different habitats. Important findings There were significant differences in the characteristics of seedling survival among different habitats, with smaller seedling density and higher survival rates observed on the sunny slopes and larger seedling density but lower survival rate found on the shady slopes. In competition for survival, Artemisia gmelinii, Potentilla tanacetifolia, and Heteropappus altaicus etc. took advantage of quality and were characterized by a higher seedling survival rate, while Artemisia scoparia, Ixeris chinensis, Siphonostegia chinensis etc. adopted a strategy of ＂quantity＂ and characterized by a higher seedling density. The same species in different habitats had different survival curves, and the same survival curves in different habitats applied to different species. The seedlings of Artemisia gmelinii, Potentilla tanacetifolia, Stipa bungeana, Heteropappus altaicus, and Lespedeza davurica etc. had a strong survival capability in the rainy season and were easy to overwinter successfully, whereas the seedling survival capability in Artemisia scoparia, Dracocephalum moldavica, and Artemisia hedinii etc. was strong priorto the rainy season but weak in winter. The characteristics of seedling survival in different micro-environments also differed. A change in micro-environment affected seedling growth, survival, and overwintering to some extent. Thus, a proper tending for seedlings according to the survival characteristics of species is conducive to the seedling establishment