Abstract

Collaboration between Private Sector-led Nature Positive Initiatives and Research in the University of Tokyo Forests

Naoto KAMATA

The University of Tokyo Chiba Forest, The University of Tokyo Forests
Graduate School of Agricultural and Life Sciences, The University of Tokyo
kamatan@uf.a.u-tokyo.ac.jp

The University of Tokyo Forests (UTF) manage approximately 33,000 hectares across seven sites, all of which currently face biodiversity crises—primarily driven by unmaintained plantations and deer overpopulation. To address these challenges, UTF utilizes private funding to conduct empirical research. While efforts at the Hokkaido Forest and the Chichibu Forest (UTCF) focus on converting coniferous plantations into natural forests, this presentation specifically examines the impact of deer-induced vegetation decline on the nitrogen dynamics of stream water in the UTCF. Following the 1997 opening of a highway through the UTCF, stream nitrate (NO3-) concentrations exhibited a marked increase. Although this trend was initially attributed to vehicular NOx emissions, significant understory depletion due to deer herbivory has been observed since the mid-2000s. Our comparative analysis of vegetation inside and outside deer-exclusion fences revealed distinct differences in understory coverage and species composition. To quantify these effects, we determined the nitrate reductase activity (NRA) as a proxy for the nitrate assimilation rate for each plant taxon. The estimated community-level NRA inside the fences was 5.6 times higher than that outside. Furthermore, elevated nitrate levels in streams distant from the highway suggest that deer-induced vegetation loss, rather than traffic-related deposition alone, is a primary driver of nitrogen leaching. Total of 30 deer-exclusion fences—15 in each of the two studied stream catchments—have been utilized to monitor ecosystem recovery from multiple viewpoints since 2013.