The effects of grazing on the spatial pattern of elm (Ulmus pumila L.) in the sparse woodland steppe of Horqin Sandy Land in Northeastern China.

The aim of this study was to explore the effects of grazing on the formation of the spatial pattern of elm growth in a sparse woodland steppe. We used a point pattern method to analyze the elm trees within different diameter classes in both grazed and fenced plots, which were established in Horqin Sandy Land, northeastern, China. The results showed that, in the grazed plot, the distances where transformation between random and aggregated patterns occurred in class 1 (10 cm ≤ DBH ≤ 15 cm) and class 2 (15 cm ≤ DBH ≤ 20 cm) were 2.27 and 2.37 m, respectively. Meanwhile, in the fenced plot, the distances between random and aggregated patterns that occurred in class 1, class 2 and class 3 (DBH > 20 cm) were 3.13, 3.13 and 7.85 m, respectively. In the fenced plot, in distances larger than 67.72 m there were a negative association between class 1 and class 2, which was also the case between class 2 and class 3 and between class 1 and class 3 for distances greater than 104.09 and 128.54 m, respectively. Meanwhile, negative associations occurred only with distances larger than 29.38 m in the grazed plot. These findings suggest that grazing reduced the competition intensity between elm trees; and therefore, grazing management could be an effective strategy used to regulate the elm population in the degraded sandy land of Northern China. [ABSTRACT FROM AUTHOR]