Topography and Pasture Management in the Mountainous Slopeland. : 3. Yearly and spatial changes in pasture vegetation

Abstract

In our previous papers, we suggested that mountainous sloping pasture was characterized by the interactions between inclination of pasture and grazing pressure that means tramping, grazing and excreting. This study was conducted to investigate the relations between those interactions and the yearly and spatial changes in pasture vegetation. The subject pasture was established in 1969 using the unplowed method, and in 1972, 40 examination points were set up in the pasture to observe the shifts in vegetation. With the passage of time, the dominant species in the pasture has changed from orchardgrass (Dactylis glomerata L.) into Kentucky bluegrass (Poa pratensis L.). However, the process of the change on the concave slope site was more complex than the change observed on the convex and linear slopes. The period of shift from one dominant species to another was much longer on the steep sloping site than on the gentle slope, though this did not hold true for the concave slope site. Observations made in 1992 revealed that Kentucky bluegrass covered about 80% area on the pasture. The number of perennial grass species was higher at the steep sloping site than on the gentle slope with the exception of the strong concave slope site. The complexity of plant community composition was increased relative to the increasing the angle of the sloping site. These results suggest that the yearly and spatial changes in the pasture vegetation were caused by the variation of the grazing pressure according to topography.