The method of conserving herbaceous grassland specialists through silvicultural activities under deer browsing pressure

Abstract

Early-successional herbs such as grassland specialists in semi-natural grasslands are decreasing because the intensity of using semi-natural grassland is decreasing for the decrease of human population or the usage of fossil fuel as energy source. Deer browsing also decreases grassland specialists. Silvicultural activities such as clearcutting, mowing of understory vegetation, and deer countermeasures may provide a suitable habitat for such grassland specialists. We aimed to clarify the method of conserving grassland specialists through silvicultural activities. We recorded all plant species that emerged in each quadrat, and measured their maximum heights within 80 quadrats that were established in four types of treatment sites in Yanagidaira, Japan. The four treatment sites were clearcut, fenced, and mowed (hereafter “fence site”); clearcut and mowed with tubed saplings (hereafter “tube site”); clearcut without deer countermeasures and mowing (hereafter “open site”); and not clearcut forest (hereafter “forest”). The total number of species and the number of species that occurred only in one treatment site of the four sites were highest in fence sites among the treatments. Those of tube and open sites were intermediate, whereas those of forest were the lowest. Grassland specialist forbs dominated in fence site, and grassland specialist graminoids and unpalatable grassland specialist forbs dominated in tube and open sites. The presence probabilities and maximum heights of grassland specialist forbs were significantly increased by deer exclusion, but those of grassland specialist graminoids were rarely affected by deer exclusion. Establishment of deer-proof fences in clearcut sites is effective in conserving grassland specialist forbs.