Soil erosion decreases soil microbial respiration in Japanese beech forests with understory vegetation lost by deer

ABSTRACT

Increases in the number of wild herbivores resulted in understory degradation because of their overgrazing in forest ecosystems. Deer overgrazing has occurred soil erosion in Japanese beech forests where dwarf bamboo used to be densely covered. Soil erosion can result in a decrease in soil carbon and nutrient contents, causing the soil microbial respiration in such forest ecosystems to be degraded. The objective of this study was to clarify the effects of soil erosion, which sporadically occurs within the forests, on soil properties and microbial activity. Soil erosion indices, such as the maximum height of exposed roots from the soil surface (MAXH), tree and soil properties, microbial basal and substrate-induced respiration, were measured under the canopy of 16 beech trees in each of three deciduous broadleaved forests on southern Kyushu Island, Japan. Soil properties such as the humus mass and the organic matter contents of soil and humus decreased with MAXH. Basal and substrate-induced respiration decreased with increases in MAXH. Soil properties associated with organic matter increased with basal and substrate-induced respiration. These results suggest that soil surface layers that were rich in organic matter ran off because of soil erosion, resulting in the degradation of soil microbial activity. This study suggests that increases in wild herbivore populations degrade soil ecosystem functioning owing to the soil erosion induced by understory disappearance.

KEYWORDS:

• Browsing
• ungulate
• soil loss
• soil respiration
• spatial variation

Acknowledgements

We thank the technical staff of the Shiiba Research Forest of Kyushu University for their help and support in the field. We also appreciate the staff at the Kyushu branch office of the Japanese Ministry of the Environment for giving us permission to access Mt. Shiraga.

Disclosure statement

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

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/13416979.2023.2235499

Additional information

Funding

This work was supported by the JSPS KAKENHI [Grant Number JP22H03793] and the Nippon Life Insurance Foundation [2021-03].