选取亚热带典型的常绿阔叶甜槠林为研究对象,从2011年4月至2013年6月进行模拟氮(N)沉降试验,以探讨甜槠林凋落物养分归还量对N沉降的响应。氮沉降水平分别为:对照(CK,0 kg N hm-2a-1),低氮(LN,50 kg N hm-2a-1),高氮(HN,100 kg N hm-2a-1),高氮+磷(HN+P,100 kg N hm-2a-1+50 kg P hm-2a-1),每个处理重复3次。在模拟氮沉降2 a后,于2012年7月开始收集各样地的凋落物样品,分析凋落物及其养分归还量。结果表明:不同处理凋落物量没有显著差异,表明氮沉降增加没有显著提高林分凋落物产量;不同处理落叶、落枝中N、P、K、Ca、Mg含量均无显著差异,表明氮沉降亦没有显著增加凋落物各养分含量;模拟氮沉降处理均增加了各养分元素年归还量,但不同元素对N沉降的响应不同。N、K和Mg年归还量与CK存在显著差异,而P和Ca年归还量与CK处理无显著差异。
Aims Road effects from maintenance and traffic have the potential to alter plant communities,but the exact relationships between these effects and changes in plant community composition have not often been studied in diverse environments.To determine the direction and level of community composition changes in saline environment due to road effects,we conducted a study along roads of different ages and in nearby non-road(i.e.natural)areas in the Yellow River Delta,China.Additionally,to potentially elucidate the mechanisms underlying the changes in the richness and composition of plant communities along roads,we evaluated physiochemical changes in soil of roadside and non-road areas.Methods Floristic and environmental data were collected along roadside of different ages and nearby non-road areas.To evaluate plant communities at each site,six 2 m 32 m quadrats were placed at 3-m intervals along roads and six quadrats were arranged randomly in non-road areas.To determine the difference in plant community composition betweenroadside andnon-road areas,wemeasuredspecies richness and the abundance of each species,examined species turnover and floristic dissimilarity between the two areas and positioned plant species and sites in an abstract multivariate space.Plant community(species richness,percentage of halophytes)and soil physicochemical properties(pH,salinity,moisture content,bulk density,nitrate and ammonium nitrogen concentration)were compared between roadside and non-road areas(young roadside vs.corresponding non-road areas,old roadside vs.corresponding non-road areas)by using t-tests.Classification and ordination techniques were used to examine the relationship between vegetation and related environmental variables in both roadside and non-road areas.Important Findings For both the young and old roadside areas,species richness in roadside areas was significantly higher than in non-road areas and high floristic dissimilarity values indicated that roadside and non-road areas differed greatly in community compositio
