Pits Conserve Species Diversity in an Overgrazed Grassland

Abstract

Abstract. Decrease in species diversity by overgrazing is one of the crucial indicators for ecosystem deterioration. Sika deer (Cervus nippon Tamminck) has grazed various plants on Nakajima Island, Hokkaido, Japan, for a few decades, due to low food availability. We examined if diverse microtopography supported high species diversity by conserving specific plants on the grassland of the island where overgrazing by deer occurred. Based on TWINSPAN analysis, three plant community types were classified: grasslands represented by short seed plants, ferns, and unpalatable forbs. Grasslands dominated by short and/or unpalatable seed plants established on the flat ground, while fern species except Equisetum arvense did not establish there. Soil hardiness was higher on short-plant grasslands than on unpalatable-forb grasslands, suggesting that palatability on plants was related to plant community differentiation on the flat ground. Of 10 fern species recorded, 9 species established mostly in deep pits. Pit depth was more important than pit area to maintain high fern diversity. Those results indicated that diverse microtopography, i.e., pit development, supports fern diversity, because of the multiplier effects of predator avoidance and preferable sites for fern establishment. Diverse and/or specific microtopography must be a prerequisite to conserve rare species and high diversity in such disturbed areas.

Effect of grazing on the population of Matteuccia struthiopteris at the southern limit of its distribution in Europe

“…Other studies agree with our results, indicating the genus Oxalis as an unpalatable plant (Reimoser et al 1999) and including the genus Cardamine among common species germinating from dung (Gill & Beardall 2001;Pakeman et al 2002). In addition, several studies found both genera more frequent in grazed areas than in fenced areas: for Oxalis see McEvoy et al (2006) and Tsuyuzaki and Takahashi (2007); for Cardamine see Webster et al (2005). So although the plant community results showed that tall species increased in fenced areas, the cover of M. struthiopteris indicated that this fern is very competitive when not subject to grazing.…”

“…In addition, several studies found both genera more frequent in grazed areas than in fenced areas: for Oxalis see McEvoy et al . () and Tsuyuzaki and Takahashi (); for Cardamine see Webster et al . ().…”

Plant species diversity in the ecological species groups in the Kandelat Forest Park, Guilan, North of Iran

“…The analyses done in relation to topographic factors and their relationships with ecological groups can be concluded that the aspect was the important variable among topographic factors in this study. Tsuyuzaki and Takhashi (2007) stated that topography and it's relationship with environmental factors such as light and soil moisture is the most important factor in determining the structure of plant communities and also, is a necessary condition for maintaining high diversity of rare species in degraded areas of Hokkaido in Japan. Also, the topographic factors were introduced as an important factor in distribution of alpine vegetation in the mountains of New Zealand (Mark et al 2000).…”