Focused on different rehabilitation ages grassland in Wuqi County in loess hilly region, the present study aimed to explore niche characteristics of populations and their influence factors. The results showed that the dominant species were Artemisia sacrorum, A. leucophylla, A. scoparia, Lespedeza daurica and Poa sphondylodes, and the dominant species varied along with the rehabilitation age. The niche breadth of dominant populations increased with increasing rehabilitation age from 5 to 10 years, indicating enhanced adaptability to the environment. The niche breadth indices of the populations decreased from 10 to 20 years, and then increased from 20 to 25 years. After 25 years, the niche breadth of the grassland narrowed gradually, indicating weakened adaptability. The niche breadth indices of most populations peaked at 10 and 25 years, respectively. There was no li-near relationship between synthetic dominance index and niche breadth in different grass communities. With the increasing rehabilitation age, the niche overlap indices were highest at 15 years with a single hump pattern, indicating that the interspecific competition increased to the highest at 15 years and then decreased. It was shown that attitude, soil water content (SWC) and soil organic matter content (SOM) were the main factors affecting the niche breadth, while soil total nitrogen content (STN), attitude and SWC were the main factors affecting the niche overlap. There was no linear relationship between niche breadth and niche overlap of tested species in different rehabilitation ages due to resource spatial heterogeneity and growth stages of grass species. These findings indicated that with the increasing rehabilitation age, the population adaptability to the environment are generally enhanced and the resource competition among populations increases and then decreases. It was concluded that attitude, SWC and STN were the key environmental factors that affect population adaptability and interspecific relationship in natural grassland of loess hilly region.
以黄土丘陵区不同生长年限撂荒草地群落为对象,研究种群生态位特征及其影响因素.结果表明: 铁杆蒿、茭蒿、猪毛蒿、达乌里胡枝子和硬质早熟禾等为优势物种,且不同生长年限优势种不同.草地生长从5年到10年,种群生态位宽度随年限的增加逐渐拓宽,对环境适应性增强;草地生长从10年到25年,种群生态位宽度随年限的增加先变窄(20年)再拓宽;草地生长超过25年,种群生态位宽度逐渐变窄,对环境适应性减弱.多数种群分别在10、25年生态位宽度达到峰值,对环境适应性最强.种群优势度与生态位宽度受种群动态影响而无线性关系.种群间生态位重叠均值先增大后减小,且在15年时达到最大值,表明种间竞争先增强后减弱,且在15年时种间竞争最为激烈.海拔、土壤含水量、土壤有机质含量为草地群落种群生态位宽度的主要影响因素;土壤全氮含量、海拔、土壤含水量为种群生态位重叠的主要影响因素.种群生态位宽度与生态位重叠主要影响因素不同,受资源空间异质性以及生长阶段影响而无线性关系.随着草地生长年限增加,种群适应性普遍增强,种群间对资源竞争先增强再减弱.海拔、土壤含水量、土壤全氮含量是影响种群适应性、种间关系的主要环境因子.
Keywords: Loess Plateau hilly region; abandoned grassland; environmental interpretation; niche characteristics.