Analysis of Grassland Vegetation of the Southwest Heilongjiang Steppe (China) Using the Power Law

Abstract

In 1997, we conducted a vegetation survey in three semi-arid natural grasslands (steppes) with different livestock grazing intensities in Southwest Heilongjiang Province, China. The dominant grassland species was the grass Stipa baicalensis Roshev. Grasslands with light, intermediate, and heavy grazing intensities were located 10, 5, and 2 km from a village, respectively. Villagers use the steppe to raise cattle, horses, sheep, and goats. Each of the three grasslands was surveyed by placing 100 quadrats (50 cm×50 cm) along a 50 m line transect. Each quadrat was divided into four equal areas (25 cm×25 cm; S-quadrats) and all plant species occurring in each of these smaller areas were identified and recorded. These data were summarized into frequency distributions and the percentage of S-quadrats containing a given species and the variance of each species were estimated. The power law was applied to these estimates. The power law was used to evaluate the spatial heterogeneity and frequency of occurrence for each species in the grassland community. The lightly grazed grassland exhibited high spatial heterogeneity (caused by large plant size), the highest species diversity, and a high occurrence of S. baicalensis. In contrast, the heavily grazed grassland exhibited high spatial heterogeneity (caused by patchy populations of small plant size), low species diversity, and a low occurrence of S. baicalensis. We judged that the heavily grazed grassland was overgrazed and exclusion of livestock from the degraded areas is necessary for recovery.

Vegetation of the Stipa loess steppe in Ningxia (northern China) in relation to grazing intensity

“…In the area of investigation, vegetation cover and species diversity strongly decreases with increasing grazing intensity. This phenomenon has been found in many studies (Ye 2000;Yasuda et al 2003;Zhang et al 2004;Tsuiki et al 2005). However, a decrease in species richness with increasing grazing intensity is typical for nutrient-poor environments whereas in nutrient-rich habitats species diversity increases with increasing grazing intensity (Proulx and Mazumder 1998).…”

“…Within each belt in areas of high grazing pressure, plant communities are floristically less different than the communities growing at low grazing intensity. Thus, the often discussed hypothesis that strong grazing pressure leads to a loss of vegetational diversity (Ye 2000;Yasuda et al 2003;Zhang et al 2004;Tsuiki et al 2005) is once again verified. However, for the area of investigation another hypothesis has been disproved by our study: Artemisiadominated communities (e.g.…”

Vegetation and its spatial pattern analysis on salinized grasslands in the semiarid Inner Mongolia steppe

“…; Tsuiki et al . ; Chen and Shiyomi ; Xie et al . ) to analyze the frequency of each individual species per L‐quadrat and its spatial pattern.…”

“…0, 1, 2, 3 or 4). We applied the power law Tsuiki et al 2005;Xie et al 2009) to analyze the frequency of each individual species per L-quadrat and its spatial pattern. The estimated mean occurrence of species i per S-quadrat, p i , is defined by:…”

Spatial heterogeneity and diversity of vegetation at the landscape level in Inner Mongolia, China, with special reference to water resources

“…Shiyomi et al ( , 2001 and proposed simple methods to measure spatial heterogeneity that have been successfully applied to the analysis of grassland vegetation Wang et al, 2002;Yasuda et al, 2003;Shiyomi et al, 2004;Chen et al, 2005;Tsuiki et al, 2005;Chen et al, 2006) and landscape-scale analyses using vegetation and land-use maps (Huang et al, 2004;Hori et al, 2005;Song et al, 2005). Here, we used the power law (Madden and Hughes, 1995;Shiyomi et al, 2001) as a statistical model to determine the macro-scale spatial heterogeneity of vegetation within and among landscapes with special reference to water resources.…”