Effect of spatial scale and topography on spatial heterogeneity of soil seed banks under grazing disturbance in a sandy grassland of Horqin Sand Land, Northern China
XiaoAn ZUO 1,2, ShaoKun WANG 1,2, XueYong ZHAO 1,2, WenJin LI3, Johannes KNOPS4, Amy KOCHSIEK4
1 Naiman Desertification Research Station, Cold and Arid Regions of Environmental and Engineering Research Institute, Chi-nese Academy of Sciences, Lanzhou 730000, China;
2 Laboratory of Plant Stress Ecophysiology and Biotechnology, CAREERI, Chinese Academy of Sciences, Lanzhou 730000, China;
3 Key Laboratory of Arid and Grassland Ecology of Ministry of Education, Lanzhou University, Lanzhou 730000, China;
4 School of Biological Sciences, University of Nebraska-Lincoln, Lincoln 62588, USA
Effect of spatial scale and topography on spatial heterogeneity of soil seed banks under grazing disturbance in a sandy grassland of Horqin Sand Land, Northern China
XiaoAn ZUO 1,2, ShaoKun WANG 1,2, XueYong ZHAO 1,2, WenJin LI3, Johannes KNOPS4, Amy KOCHSIEK4
1 Naiman Desertification Research Station, Cold and Arid Regions of Environmental and Engineering Research Institute, Chi-nese Academy of Sciences, Lanzhou 730000, China;
2 Laboratory of Plant Stress Ecophysiology and Biotechnology, CAREERI, Chinese Academy of Sciences, Lanzhou 730000, China;
3 Key Laboratory of Arid and Grassland Ecology of Ministry of Education, Lanzhou University, Lanzhou 730000, China;
4 School of Biological Sciences, University of Nebraska-Lincoln, Lincoln 62588, USA
摘要 Soil seed banks play an important role in the distribution and composition of plant communities in semiarid grassland ecosystems. However, information on how spatial scale influences the spatial heterogeneity of soil seed banks in a grassland under grazing disturbance is still lacking. Based on field sampling and greenhouse germination, we measured the species composition and seed density of soil seed banks at different spatial scales (30 m×30 m, 30 m×60 m and 30 m×90 m) along a topographical gradient in a sandy grassland in Horqin Sand Land, Northern China. By applying geostatistical methods, we examined how spatial scale and topography affected the spatial distribution of soil seed banks in the study area. Our results showed that the total number of species in soil seed banks, as well as the number of dominant annuals, increased with the increase of spatial scales. Seed density in soil seed banks decreased with the increase of spatial scales due to an increase in the slopes and relative heights of the sampling points. Geostatistical analysis showed that the relative structural variance (C/(C0+C)) of seed density and species richness were over 65% for all spatial scales, indicating that these variables had an obvious spatial autocorrelation and the spatial structured variance accounted for the largest proportion of the total sample variance. Spatial autocorrelation of seed density in soil seed banks increased with the increase of measured scales, while that of species richness showed a reverse trend. These results suggest that the total number of species in soil seed banks is spatial scale dependent and lower topography may accommodate more seeds. Spatial distribution of seed density in soil seed banks is also scale dependent due to topographic variation. Grassland management, therefore, needs to consider local grazing disturbance regime, spatial scale and topography.
Abstract: Soil seed banks play an important role in the distribution and composition of plant communities in semiarid grassland ecosystems. However, information on how spatial scale influences the spatial heterogeneity of soil seed banks in a grassland under grazing disturbance is still lacking. Based on field sampling and greenhouse germination, we measured the species composition and seed density of soil seed banks at different spatial scales (30 m×30 m, 30 m×60 m and 30 m×90 m) along a topographical gradient in a sandy grassland in Horqin Sand Land, Northern China. By applying geostatistical methods, we examined how spatial scale and topography affected the spatial distribution of soil seed banks in the study area. Our results showed that the total number of species in soil seed banks, as well as the number of dominant annuals, increased with the increase of spatial scales. Seed density in soil seed banks decreased with the increase of spatial scales due to an increase in the slopes and relative heights of the sampling points. Geostatistical analysis showed that the relative structural variance (C/(C0+C)) of seed density and species richness were over 65% for all spatial scales, indicating that these variables had an obvious spatial autocorrelation and the spatial structured variance accounted for the largest proportion of the total sample variance. Spatial autocorrelation of seed density in soil seed banks increased with the increase of measured scales, while that of species richness showed a reverse trend. These results suggest that the total number of species in soil seed banks is spatial scale dependent and lower topography may accommodate more seeds. Spatial distribution of seed density in soil seed banks is also scale dependent due to topographic variation. Grassland management, therefore, needs to consider local grazing disturbance regime, spatial scale and topography.
The National Natural Science Foun-dation of China (41171414), the Knowledge Innovation Pro-gram of Chinese Academy of Sciences (KZCX2-EW-QN313), the National Science and Technology Support Program (2011BAC07B02), the National Basic Research Program of China (2009CB421303) and the West Light Foundation of the Chinese Academy of Sciences (0928711001).
XiaoAn ZUO, ShaoKun WANG, XueYong ZHAO, WenJin LI, Johannes KNOPS, Amy KOCHSIEK. Effect of spatial scale and topography on spatial heterogeneity of soil seed banks under grazing disturbance in a sandy grassland of Horqin Sand Land, Northern China[J]. 干旱区科学, 2012, 4(2): 151-160.
XiaoAn ZUO, ShaoKun WANG, XueYong ZHAO, WenJin LI, Johannes KNOPS, Amy KOCHSIEK. Effect of spatial scale and topography on spatial heterogeneity of soil seed banks under grazing disturbance in a sandy grassland of Horqin Sand Land, Northern China. Journal of Arid Land, 2012, 4(2): 151-160.
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