The Impact of Long-Term Nitrogen Addition on Microbial Community Composition in Three Hawaiian Forest Soils

Teri C Balser

doi:10.1100/tsw.2001.450

Abstract

We evaluated the microbial communities in three Hawaiian forest soils along a natural fertility gradient and compared their distinct responses to long-term nitrogen (N) additions. The sites studied have the same elevation, climate, and dominant vegetation, but vary in age of development, and thus in soil nutrient availability and nutrient limitation to plant growth. Fertilized plots at each site have received 100 kg ha year N addition for at least 8 years. Soil parameters, water content, pH, and ammonium and nitrate availability differed by site, but not between control and N-addition treatments within a site at the time of sampling. Microbial biomass also varied by site, but was not affected by N addition. In contrast, microbial community composition (measured by phospholipid analysis) varied among sites and between control and N-addition plots within a site. These data suggest that microbial community composition responds to N addition even when plant net primary productivity is limited by nutrients other than N. This may have implications for the behavior of forests impacted by atmospheric N deposition that are considered to be “nitrogen saturated,” yet still retain N in the soil.

Highlights

During the past several decades, human activity has dramatically increased the quantity of nitrogen (N) added annually to terrestrial ecosystems[1,2]
Most studies of N addition have focused on temperate ecosystems; with expected future increases in industrial development and agricultural intensification in the humid tropics, N dynamics in tropical ecosystems will be increasingly important[3,4]
Net primary productivity in tropical ecosystems is often limited by elements other than N, and as a result controls over net primary productivity, litter quality, and competition for N among plants and microbial populations differ from those in temperate zones[4]

Summary

Introduction

During the past several decades, human activity has dramatically increased the quantity of nitrogen (N) added annually to terrestrial ecosystems[1,2]. Because N is often limiting to plant productivity in terrestrial ecosystems, excess N availability can have a large impact on the biodiversity and function of such systems[2]. Net primary productivity in tropical ecosystems is often limited by elements other than N, and as a result controls over net primary productivity, litter quality, and competition for N among plants and microbial populations differ from those in temperate zones[4]. N added to temperate zone soils tends to be retained in plant and microbial biomass[5]

Methods

Results

Conclusion