Variation with slope aspect in effects of temperature on nitrogen mineralization and nitrification in mineral soil of mixed hardwood forests

• Published in: Canadian journal of forest research Vol. 45; no. 7; pp. 958 - 962
• Main Authors: Gilliam, Frank S, Julia E. Galloway, Jacob S. Sarmiento
• Format: Journal Article
• Language: English
• Published: Ottawa NRC Research Press 01.07.2015; Canadian Science Publishing NRC Research Press
• Subjects: bags; Chemical properties; Climate change; Deciduous forests; Environmental aspects; Fagus; forest ecology; Forest ecosystems; Forest soils; Forests; forêts tempérées; Global climate; global warming; hardwood forests; Identification and classification; lakes; latitude; Microbial activity; microbial communities; mineral soils; Mineralization; Minerals; minéralisation de l’azote; Mixed forests; Nitrification; Nitrogen; nitrogen mineralization; overstory; polyethylene; prediction; réchauffement climatique; Soil nitrogen; Soils; Temperate forests; Temperature effects; Thermal properties; écologie forestière; West Virginia; United States > US; USA, West Virginia; USA, West Virginia, Fernow Experimental Forest
• ISSN: 1208-6037; 0045-5067; 1208-6037
• DOI: 10.1139/cjfr-2015-0087

This study examined the effects of temperature on soil nitrogen (N) dynamics and variation with slope aspect (northeast (NE) versus southwest (SW)) at two forested sites in West Virginia — Beech Fork Lake (BFL) and Fernow Experimental Forest (FEF) — with similar soil and overstory characteristics but with different latitudes and elevations. Previous work on mineral soil from both sites had shown sharp differences in microbial communities between SW slopes and NE slopes. Mineral soil was sampled from three and eight plots per aspect at FEF and BFL, respectively. Inorganic N was extracted from samples, which were then divided into polyethylene bags for 7-day incubations at 4 °C, 15 °C, 25 °C, and 35 °C. Following incubation, soils were extracted and analyzed for inorganic N. Net N mineralization varied significantly between aspects and temperatures but did not vary between sites; net nitrification varied significantly between aspects, temperatures, and sites. Net N mineralization increased with incubation temperature at all aspects and sites. Net nitrification rates increased with incubation temperature for BFL soils; however, maximum net nitrification rates occurred at 20–25 °C for FEF soils. Net nitrification was essentially undetectable for SW soils at either site. Results underline the complexities of the N cycle in temperate forest ecosystems, representing challenges in predicting alterations in soil N dynamics under conditions of global climate change.