Soil nutrient and moisture environments and shoot growth of Quercus crispula canopy trees in two areas that experienced contrasting effects of deer overabundance over an 11-year period

ABSTRACT

To elucidate the effects of modification of the understory aboveground plant biomass and soil nutrient and moisture environments on canopy tree growth in deer overabundance sites, we compared the canopy shoot growth of oak trees (Quercus crispula), which are not a target for bark stripping or bark feeding by deer, understory aboveground plant biomass, and components of soil nutrient and moisture between inside (protected) and outside (exposed) a large fenced area. We found that canopy shoot growth in the exposed area was reduced compared with that in the protected area. Net nitrogen (N) mineralization rates did not differ between areas, although understory aboveground plant biomass, total carbon (C) and N, and total soil inorganic N content were significantly lower in the exposed area than in the protected area. Indices of canopy shoot growth correlated significantly with soil water content, but due to the limited scope of our study this result does not confirm an effect of soil moisture on canopy shoot growth. Further study is required to clarify the effects of deer overabundance on canopy tree growth.

KEYWORDS:

• Browsing
• canopy shoot
• exclosure
• inorganic nitrogen
• mineralization

Acknowledgments

We thank Takeshi Hirai for his help with the sample collection, and Dr. Masae Ishihara and Dr. Atsushi Takayanagi for preparation of our field survey. We also thank the staff of the Ashiu Forest Research Station for the permission to conduct our field study and their support.

Disclosure statement

No potential conflict of interest was reported by the author(s).