模拟氮沉降对华北地区绣线菊灌丛凋落物养分输入量的影响

Impacts of Simulated Nitrogen Deposition on Annual Nutrient Input from Litterfall in a Spiraea sal⁃icifolia shrubland in North China

中国是全球高氮沉降区之一,氮沉降对陆地生态系统造成了严重影响。我国北方灌丛通常为氮限制生态系统,易受环境变化的影响。为了研究氮沉降增加对灌丛生态系统凋落物养分输入量的影响,对北京东灵山绣线菊灌丛进行了模拟氮沉降试验,设置4个氮处理水平,分别为对照(0N0)、低氮(20N_(1))、中氮(50N_(2))、高氮(100N_(3))kgN/hm^(2)·a。结果表明:模拟氮沉降5年后,4个不同氮沉降水平绣线菊灌丛的年凋落量分别为162.93、205.81、190.96和189.65g/m^(2)·a,表明氮沉降对凋落物量具有促进作用;氮沉降提高了凋落叶和凋落花果的N含量,降低了凋落花果的Ca含量,对凋落物各组分其他元素含量均未产生显著影响;不同氮沉降水平在一定程度上增加了绣线菊灌丛凋落物的养分输入量。

China is one of the regions with high N deposition in the world,nitrogen deposition has a serious impact on the structure and function of terrestrial ecosystem.The natural or semi-natural shrublands in north China are most⁃ly distributed in nutrient poor sites,and are usually considered relatively vulnerable to environmental changes.In or⁃der to investigate the effects of increasing N deposition on the nutrient input from litterfall in shrublands,a simulated nitrogen(N)deposition experiment was conducted in a Spiraea salicifolia shrubland in Dongling Mountain,Beijing,and 4 treatments were designed as CK(N0,0 kg N/hm^(2)·a),low N(N1,20 kg N/hm^(2)·a),medium N(N2,50 kg N/hm^(2)·a)and high N(N3,100 kg N/hm^(2)·a).The results from the one-year observation showed that among the four nitrogen treatments,the annual litterfall productions were 162.93,205.81,190.96 and 189.65 g/m^(2)·a for N0,N_(1),N_(2 )and N_(3) treatment,respectively.Nitrogen deposition promoted annual production of total litterfall production.Nitrogen deposi⁃tion increased the N concentration of leave litter and flower and fruit litter,decreased the Ca concentration of flower and fruit litter,and had no significant effects on other elements concentration in litter fractions.Compared with N0,N treatment increased the annual input of N,P,K,Ca and Mg to a certain extent,but did not reach statistical signifi⁃cance among all nitrogen treatments.Different simulated nitrogen deposition promoted the litterfall annual productiv⁃ity and its nutrient input of S.salicifolia shrubland to a certain extent.