Fungal community structure and microbial biomass in a semi-arid environment: Roles in root decomposition, root growth, and soil nitrogen dynamics
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Although the roles of fiingi in ecosystems are recognized, few studies have examined the enzymatic activities of fungi during plant litter decomposition and the changes in species composition of microbial communities as they influence soil nutrient levels, root growth, and plant litter decomposition in a semi-arid or arid environment. To examine aspects of the potential linkages among plant growth, soil levels, and microbial activities in a semi-arid environment, five 40-m transects were established in a sand shinnery-oak (Ouercus havardii Rydb.) ecosystem in West Texas in 1993. Along these transects, species conqx)sition of fungal communities and community-level enzymatic activities were evaluated during decomposition of fine roots of sand shinnery-oak. Soil microbial biomass and nitrogen transfonnation processes were evaluated along the transects to establish the linkages between plant density, microbially mediated processes, and nutrient availability. Temporal pattems of ectomycorrhizal colonization levels and fine root production also were estimated to integrate microbial enzymatic activities, nutrient fluxes, and root growth. In response to results obtained during the fall of 1993 and spring of 1994, a nitrogen addition experiment was established to examine the effects of nitrogen on amount of soil microbial biomasscarbon, net nitrogen mineralization rates, fine root production and ectomycorrhizal colonization levels. To better understand the strengths of the interrelationships among root growth, nutrient fluxes and microbial enzymatic activities, conceptual models exploring the relationships were developed and evaluated using path analysis.