期刊
BIOGEOCHEMISTRY
卷 125, 期 2, 页码 149-165出版社
SPRINGER
DOI: 10.1007/s10533-015-0120-5
关键词
Iron reduction; Poorly-crystalline minerals; Redox; Root biomass; Soil carbon; Soil oxygen
资金
- DOE Office of Science Graduate Fellowship Program - American Recovery and Reinvestment Act [DE-AC05-06OR23100]
- A.E.S [CA-B-ECO-7673-MS]
- DOE [DE-FOA-0000749]
- NSF [EAR-08199072, DEB 0620910]
- NSF Luquillo Critical Zone Observatory [EAR-0722476]
- USGS Luquillo WEBB program
- Division Of Earth Sciences
- Directorate For Geosciences [1331841] Funding Source: National Science Foundation
- Division Of Environmental Biology
- Direct For Biological Sciences [1239764] Funding Source: National Science Foundation
Humid tropical forests support large stocks of surface soil carbon (C) that exhibit high spatial variability over scales of meters to landscapes (km). Reactive minerals and organo-metal complexes are known to contribute to C accumulation in these ecosystems, although potential interactions with environmental factors such as oxygen (O-2) availability have received much less attention. Reducing conditions can potentially contribute to C accumulation, yet anaerobic metabolic processes such as iron (Fe) reduction can also drive substantial C losses. We tested whether these factors could explain variation in soil C (0-10 and 10-20 cm depths) over multiple spatial scales in the Luquillo Experimental Forest, Puerto Rico, using reduced iron (Fe(II)) concentrations as an index of reducing conditions across sites differing in vegetation, topographic position, and/or climate. Fine root biomass and Fe(II) were the best overall correlates of site (n = 6) mean C concentrations and stocks from 0 to 20 cm depth (r = 0.99 and 0.98, respectively). Litterfall decreased as reducing conditions, total and dead fine root biomass, and soil C increased among sites, suggesting that decomposition rates rather than C inputs regulated soil C content at the landscape scale. Strong relationships between Fe(II) and dead fine root biomass suggest that reducing conditions suppressed particulate organic matter decomposition. The optimal mixed-effects regression model for individual soil samples (n = 149) showed that aluminum (Al) and Fe in citrate/ascorbate and oxalate extractions, Fe(II), fine root biomass, and interactions between Fe(II) and Al explained most of the variation in C concentrations (pseudo R-2 = 0.82). The optimal model of C stocks was similar but did not include fine root biomass (pseudo R-2 = 0.62). In these models, soil C concentrations and stocks increased with citrate/ascorbate-extractable Al and oxalate-extractable Fe. However, soil C decreased with citrate/ascorbate-extractable Fe, an index of Fe susceptible to anaerobic microbial reduction. At the site scale (n = 6), ratios of citrate/ascorbate to oxalate-extractable Fe consistently decreased across a landscape O-2 gradient as C increased. We suggest that the impact of reducing conditions on organic matter decomposition and the presence of organo-metal complexes and C sorption by short-range order Fe and Al contribute to C accumulation, whereas the availability of an Fe pool to sustain anaerobic respiration in soil microsites partially attenuates soil C accumulation in these ecosystems.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据