Document: GRI-3-58-25

Microbial biomass and soil fauna: Comparisons between tropical and subalpine forests.

GONZALEZ, G.* ¹, R.E.LEY ¹, S.K.SCHMIDT ¹ and X.ZOU ²

University of Colorado, Boulder, CO 80309-0450 USA ¹
Institute of Tropical Ecosystem Studies, University of Puerto Rico, PO Box 363682, San Juan, PR 00936, USA ²

Abstract:
Soil fauna can influence soil processes through interactions with the microbial community. Due to the complexity of the functional roles of fauna and their effects on microbes, little consensus has been reached on the extent to which soil fauna can regulate microbial activities. We quantified soil microbial biomass and maximum growth rates in control and fauna-excluded treatments in dry and wet tropical forests and north- and south facing subalpine forests to test whether soil fauna exhibit different effects on microbes under diverse climatic conditions. Exclusion of fauna was established by physically removing the soil macrofauna and applying naphthalene. The effect of this naphthalene application on the biomass of microbes that mineralize salycilate was quantified using the substrate induced growth response (SIGR) method. We found that: (1) The exclusion of soil fauna resulted in a higher total microbial biomass and lower maximum growth rate in the subalpine forests, (2) soil fauna exclusion did not affect the microbial biomass and growth rate in the tropical forests, and (3) the microbial biomass of salycilate mineralizers was significantly enhanced in the fauna-exclusion treatment in the tropical wet and the south-facing subalpine forests. We conclude that non-target effects of naphthalene on the microbial community alone cannot explain the large differences in total microbial biomass found between control and fauna-excluded treatments in the subalpine forests. Soil fauna have relatively larger effects on the microbial activities in the subalpine forests than in tropical dry and wet forests.

Keywords: soil fauna; wet tropics; dry tropics; subalpine; microbial biomass; maximum growth rate; naphthalene; salycilate; substrate induced growth response.

This abstract is being presented at: 9:45 AM in session:
Oral Session #71: Soil Microbial Biomass and Soil Respiration.