围封和放牧对科尔沁沙地群落物种多样性与地上生物量的影响

Effect of Enclosure and Grazed Management on Aboveground Biomass and Species Diversity in Sandy Grasslands of Horqin Sandy Land, Eastern Inner Mongolia, China

以科尔沁沙地自由放牧和围封10年的沙质草地为研究对象,采用野外调查与室内分析的方法,分析了围封和放牧对科尔沁沙地群落物种多样性与地上生物量的影响,旨在为退化沙地恢复与重建提供科学依据。试验选择围封和自由放牧草地的典型地段,分别设置50个面积1m^2的草本样方,调查每个样方的种类组成及其特征值(盖度、高度和密度),采用针刺法测定样方总盖度和每种植物的分盖度;每种植物随机选5株,用直尺测量其伸长高度;对样方中出现的植物进行分类,记录同一种植物出现的个数;采用齐地面刈割法调查其地上生物量。主要结论如下,(1)经过围栏封育后,群落物种数提高了67%。方差分析表明,围封群落的盖度(F=90.536,n=50,P<0.001)、高度(F=63.964,n=50,P<0.001)、密度(F=10.274,n=50,P=0.001 8)以及地上生物量(F=83.64,n=50,P<0.001)显著大于放牧群落,分别提高了178%、100%、67%和201%。围封和放牧群落均以一年生草本占绝对优势,分别为66%和73%,围封使群落多年生草本的优势度增加了52%。(2)围封群落物种丰富度显著高于放牧群落,但多样性指数没有显著性差异,均匀度指数显著低于放牧群落。(3)回归分析表明,放牧群落的物种多样性与地上生物量呈现显著负二次函数关系(P<0.05),而围封围封群落物种多样性和地上生物量的关系不显著。

Species biodiversity and biomass of the community is one of the central topics in ecological research.In the Horqin Sandy Land of Inner Mongolia in China,vegetation restoration occurs under proper management regimes in fragile environmental conditions,e.g.,enclosing and non-grazing.However,few information is available about the effects of grazing and fencing on plant communities in the semi-arid desert environment.Therefore,a field experiment was performed to examine the aboveground biomass and species diversity of grazed and enclosed communities.In 2014,the grazed(near the enclosure)and enclosed(ten years of enclosure)communities were selected as experimental sites.At each site,two parallel 250 m line transects(20 m apart)were established.For each transect,25 sampling points of 1 m×1 m were established at 10 m intervals.At each of the 100 sampling points,species composition,coverage,height,and density were surveyed,and heights of 5 plants which were selected randomly for each plant were measured by the ruler.Meanwhile,aboveground biomass was measured using a level cutting method,and the dry weight of the biomass was measured after drying in an oven at 85℃for 24 h.The frequency of each species was calculated at each of the two sites,based on the frequency of occurrence among the 50 sampling points.(1)The number of plant species increased by 67%in the enclosure management.There was a significant difference among the coverage(F=90.536,n=50,P<0.001),height(F=63.964,n=50,P<0.001),density(F=10.274,n=50,P=0.001 8)and aboveground biomass(F=83.64,n=50,P<0.001)of grazed and enclosed communities,and the coverage,height,density and aboveground biomass increased respectively by 178%,100%,67%and 201%in the enclosure management.Annual herbaceous plants were dominant in each community,the percentages were 66%and 73%respectively.However the perennial increased by 52%from the grazed community to the enclosed community.(2)The species richness was increased significantly under enclosed management,but there was no significant difference of the Simpson and Shannon-Wiener diversity index between two communities.The Pielow evenness index of the enclosed community was significantly lower than that of grazed community.And(3)regression analysis indicated a marked relationship between aboveground biomass and species diversity under the grazed management.The fitting curve was a negative quadratic function(P<0.05),while there was no a significant relationship between species diversity and aboveground biomass of the enclosed community.