Short-Term Response of Sasa Dwarf Bamboo to a Change of Soil Nitrogen Fertility in a Forest Ecosystem in Northern Hokkaido, Japan.

Tsunehiro Watanabe,Hideaki Shibata,Karibu Fukuzawa

doi:10.3390/plants5020019

Abstract

In forest ecosystems, a change of soil nitrogen (N) cycling after disturbance is regulated by various factors. Sasa dwarf bamboo (hereafter referred to as Sasa) is an understory plant that grows thickly on the forest floor in northern Hokkaido, Japan. However, the ecosystem function of Sasa after disturbances in the soil N cycling is not fully understood. The purpose of this study was to determine the short-term response of Sasa to a change of soil N fertility. Biomass, litterfall, litter decomposition, soil N pool, and N leaching from soil were measured in control, and low- (5 g N m−2 year−1) and high-N (15 g N m−2 year−1) addition plots. Sasa immobilized much N as the soil N fertility increased. However, the leaf N concentration in aboveground biomass did not increase, suggesting that the N in leaves was maintained because of the increase of leaf biomass. As a result, the decomposition and mineralization rates of the produced litter before and after N addition were comparable among plots, even though the soil inorganic N fertility increased greatly. These results suggest that immediate response of Sasa to an increase of soil inorganic N mitigates the excess N leaching from soil.

Highlights

Forests supply a variety of ecosystem services, such as the maintenance of water regulation, primary production, carbon (C) sequestration, and biodiversity, which are based on complex balances that occur in forest ecosystems
N amount effects by N addition were detected for leaf in Sasa aboveground biomass except for current leaf biomass (Table 1)
N amount effects were not found for the N concentration in each organ of the Sasa aboveground biomass (Table S2)

Summary

Introduction

Forests supply a variety of ecosystem services, such as the maintenance of water regulation, primary production, carbon (C) sequestration, and biodiversity, which are based on complex balances that occur in forest ecosystems. Human activities, such as logging, fossil fuel consumption, and fertilizer inputs to farmland, degrade ecosystem services by altering the amount of C dioxide and nitrogen (N) oxide emissions, as well as the material cycling between plants and soil in forest ecosystems [1,2,3,4,5,6]. An increase of the leaf N concentration and decrease of the soil C/N ratio results in a higher risk of N

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