小叶锦鸡儿根系生长对土壤水分和氮肥添加的响应

Responses of fine root growth of Caragana microphylla shrub plantation to irrigation and nitrogen addition in a semi-arid region of northern China

采用微管法结合内生生长袋方法,研究了科尔沁沙地成龄小叶锦鸡儿灌木根系生长动态、根系分布及细根生产对旱季补水和氮肥添加的响应。结果表明:旱季补水,氮肥添加和"水+氮"处理均增加了微管表面的根长密度和细根生产,但只有氮肥添加和"水+氮"对根长密度和细根生产(0～20cm)有显著影响。在旱季,旱季补水、氮肥添加及"水+氮"均没有显著增加根长密度;在雨季,氮肥添加显著增加了根长密度,同时促进了根系在土壤深层的分布。说明在低氮土壤中,当土壤水分适宜时,提高土壤氮肥有效性有助于沙地灌木的根系生长,提高灌木人工林的稳定性。

Root growth, distribution and production of a desert shrub in arid and semiarid areas can be regulated by water and nitrogen. We examined the responses of root growth （root length density and fine root production） to short-term irrigation, nitrogen addition and the interaction of irrigation and nitrogen addition in a 21-year-old artificial Caragana microphylla Lam. plantation in the Horqin Sandy Land in northern China. Root length density （RLD） and fine root production （FRP） in the growth season were estimated using minirhizotrons and ingrowth cores, respectively. Irrigation, nitrogen addition and their interaction significantly increased RLD （0- 140 cm）, and FRP （0-20 cm）. In dry season, irrigation, nitrogen addition and their interaction did not have significant effects on RLD. In wet season, nitrogen addition had a significant effect on RLD by promoting root distribution into deeper soil layer. These results indicate that in the low N soil condition, root development, distribution and production of desert shrubs are strongly stimulated by N availability when soil water content is in the proper status.