ABSTRACT
We conducted an experiment to test the characteristics and differences of the spatial distribution of constructive species Stipa breviflora at different scales under different stocking rates in the S. breviflora desert steppe in Siziwang Banner, Inner Mongolia. The spatial distribution of S. breviflora under four treatments (control, light grazing, moderate grazing, and heavy grazing) at different scales (small scale as 1 m×1 m and mesoscale as 5 m×10 m) were analyzed. The results showed that the population density of S. breviflora at mesoscale in the control and light grazing was significantly lower than that at the small scale. Grazing significantly increased the population density of S. breviflora in the meso- and small scales. At the small scale, the population distribution of S. breviflora in the control, light grazing, moderate grazing, and heavy grazing treatments conformed to linear, exponential, exponential and exponential models, respectively, and Gaussian, exponential, Gaussian and exponential models at mesoscale fitted by semi-variance function. The spatial distribution pattern at small scales in the control was simple and better but was more complex and poorer under the heavy grazing. At the mesoscale, it was simple and better under the heavy grazing but complex and poor under the moderate grazing. The spatial heterogeneity of S. breviflora population reduced and were more uniform under the moderate and heavy grazing at meso- and small scales. In addition, the trend of population distribution in the enclosure, moderate and heavy grazing were generally the same, while light grazing showed inconsistent trend at different scales.
Subject(s)
Poaceae , ChinaABSTRACT
We examined the effects of mowing height on community structure and stability in August from 2014 to 2018 in a Stipa grandis steppe of Xilingol, Inner Mongolia, China. Three mowing height treatments (2, 5 and 8 cm) were manipulated, with enclosure as the control. Results showed that 27 species from 23 genera of 15 families were recorded in the community. The community was dominated by S. grandis, Anemarrhena asphodeloides, Leymus chinensis and Cleistogenes squarrosa. The cumulative relative importance value of those four species was 76.1%. Of all species, there were 15 perennial forbs, 5 annuals biennials, 3 perennial bunch grasses, 3 shrubs semi-shrubs, and 1 perennial rhizome grasses. S. grandis was in the upper layer of the community, L. chinensis and A. asphodeloides were in the middle layer, C. squarrosa, Chenopodium aristatum and Salsola collina were at the bottom layer. Mowing decreased the relative importance value (RIV) of S. grandis and perennial bunch grasses, but increased that of C. squarrosa, C. aristatum, S. collina and annuals biennials. The RIV of L. chinensis was decreased in the 2 cm treatment but increased in the 5 cm and 8 cm treatments. The RIV of A. asphodeloides was increased in the 5 cm treatment but decreased in both the 2 cm and 8 cm treatments. The RIV of perennial forbs was decreased in the 8 cm treatment but increased in both the 2 cm and 5 cm treatments. Species and functional groups diversity showed significant interannual variation. Generally, species richness and diversity were little affected by mowing, while functional groups diversity was significantly impacted, indicating that compensation between different functional groups would stabilize the community under mowing. Mowing increased community stability. Community stability was higher in the 5 cm and 8 cm treatments, with the variability being larger in the 5 cm than in the 8 cm treatment. Therefore, the 8 cm treatment was beneficial for the stability and sustainable utilization of grassland community.
Subject(s)
Poaceae , Rhizome , ChinaABSTRACT
This study evaluated the changes of spatial distribution of the constructive species Stipa breviflora in the desert steppe under different grazing intensities (control, light, moderate, and heavy grazing) in Siziwang, Inner Mongolia. The small-scale spatial distribution of S. breviflora was measured. Results showed that population density of S. breviflora was following the order: heavy grazing (27.81 individuals·m-2) > moderate grazing (22.17 individuals·m-2) > control (11.31 individuals·m-2) > light grazing (10.76 individuals·m-2). The moderate and heavy grazing significantly increased population density of S. breviflora. According to the model fitting by semi-variance function, the population density of S. breviflora under the control, light, moderate and heavy gra-zing treatments were consistent with the exponential model, spherical model, exponential model and spherical model, respectively. Results from spatial distribution pattern analysis showed that structural ratio of S. breviflora population was control (99.7%) > heavy grazing (94.7%) > light grazing (92.7%) > moderate grazing (87.9%). Such a result indicated that the spatial autocorrelation of the four treatments was high, which were mainly affected by structural factors. In comparison, S. breviflora population structure ratio under moderate grazing treatment was the smallest, and partly affected by random factors. Based on fractal dimension analysis, spatial structure of the four treatments was good with simple spatial distribution. With the increases of grazing intensity, the spatial distribution was simpler and more homogeneous. Combined with 2D and 3D views, both light and heavy grazing changed spatial distribution of S. breviflora population from gradient distribution to patch distribution and resulted in the reduction of spatial heterogeneity.
