中文摘要：

在全球变化如氮沉降及温度升高等可能导致土壤氮有效性增加的背景下,细根动态如何变化一直是陆地生态学研究中的一个重要内容.本文综述了前人提出的细根动态响应土壤N有效性提高的4个代表性假说：1）细根生产量和周转率都提高;2）细根生产量和周转率都下降;3）细根生产量下降,周转率提高;4）细根生产量提高,周转率下降.根据2000年以来以微根管方法为主测得的根系动态数据,笔者认为假说1）和假说2）得到的支持最为充分.此外,还探讨了树种、细根异质性、菌根真菌、细根采样方法和施肥方法等对上述各假说检验的影响.

英文摘要：

With global changes such as increasing temperature and enhanced N deposition, soil nitrogen （N） availability is predicted to increase substantially, and how fine root dynamics responds to the altered soil N has become one of the key questions in terrestrial ecology. As such, a number of hypotheses have been proposed to explain the relationship between increasing soil N availability and fine root production, mortality, and turnover. This article considered four major hypotheses： with increasing soil N availability, 1 ） both fine root production and turnover rate would increase, 2） both fine root production and turnover rate would decrease, 3 ） fine root production would decrease while fine root turnover rate would increase, and 4） fine root production would increase while fine root turnover rate would decrease. Current evidence suggests that the patterns depicted in hypothesis 1 ） and 2） could both occur in nature and may reflect characteristics of different species. Hypotheses 3 ） and 4） were thought to characterize only a transient stage of the responses of fine root dynamics to increasing N availability. To better understand the response of root dynamics to increasing soil N, future studies should consider： 1 ） the definition of fine roots and heterogeneity in fine root structure and function; 2） methods used in estimating fine root production and turnover rate ; 3 ） changes of soil N availability both in space and time. More attention should also be paid to the influences of mycorrhizal infection on root dynamic responses to soil N availability.