落叶松人工林草本植物群落特征和生物量对氮添加的响应

以华北落叶松(Larix principis-rupprechtii)人工林幼龄林为研究对象, 设置3个梯度的氮添加水平(0, 20和50 kg N/(ha·a), 即N0, N20和N50), 研究氮添加对人工林草本植物群落特征及地上生产力的影响, 得到以下结果。1) 氮添加改变了土壤微环境, 降低土壤温度、显著地增加土壤水分。2) 氮添加在一定程度上促进落叶松人工林草本植物群落的生长(P>0.05)。与对照组(N0)相比, 植物群落总盖度在N20和N50样方中分别增加6.83%和15.03% (2014 年), 或9.80%和12.94% (2016年), 但草本植物地上生物量的累积无显著变化; 群落总盖度和地上生物量与土壤含水量显著正相关(P<0.05)。3) 氮添加对落叶松人工林草本植物群落的多样性和均匀度无显著影响, 但是低浓度氮添加(即N20)显著地增加单位面积内物种的丰富度(2014年单位面积内物种丰富度在N20样方中增加23.33%, P<0.05)。4) 氮添加对不同植物功能群的影响不同, 其中氮添加促进蓼科和莎草科植物的生长, 抑制禾本科和菊科植物的生长, 对豆科植物无影响, 说明温带落叶松人工林草本植物群落对氮沉降的响应敏感, 氮添加在一定程度上促进草本植物的生长, 同时氮添加改变了草本植物不同功能群间的竞争力。

Responses of Herbaceous Community Characteristics and Biomassto Nitrogen Addition in a Larix principis- rupprechtii Plantation

The research was conducted in a sapling Larix principis-rupprechtii, plantation set three nitrogenaddition levels (0, 20 and 50 kg N/(ha·a), called N0, N20 and N50), in order to assess the influence of nitrogenaddition on plant communities characteristics and above-ground biomass. The results showed that nitrogen additionaltered soil micro-environment, reduced soil temperature and significantly increased soil moisture. Nitrogenaddition partly promotes the growth of herb community (increased by 6.83% and 6.83% in N20 and N50 in 2014,respectively, compared with the control; while increased by 9.80% and 6.83% in N20 and N50 in 2016,respectively, P>0.05). The community coverage and aboveground biomass were significantly and positivelycorrelated with soil moisture (P<0.05). The diversity and evenness had no significant response to nitrogen addition,but N20 significantly increases the species richness per area (significantly increased by 23.33% in N20 samples in2014, P<0.05). Nitrogen addition exerted different influences on plant functional groups, i.e., nitrogen additionpromoted the growth of polygonaceae and cyperaceae plants, restrained gramineae and compositae plants and hadno influence of leguminous plants. The results suggested that herb communities are sensitive to nitrogen addition intemperate Larix principis-rupprechtii plantations, and nitrogen addition partly promotes the growth of herb plantsand changes competition among different herbaceous plants functional groups.