Recipient Organization
CORNELL UNIVERSITY
(N/A)
ITHACA,NY 14853
Performing Department
Natural Resources
Non Technical Summary
Soil organic matter (SOM) plays a variety of important roles in forest ecosystems, storing carbon, maintaining fertility and promoting favorable structure and porosity of soil. Organic carbon in soils is a major pool in the global C cycle, and potential changes in this pool could serve as either a significant sink or source for atmospheric carbon dioxide. Management options for promoting the C sink strength in soil have been proposed including forest management activities; however, fundamental understanding of the dynamics of forest SOM is incomplete. The principal justification for this proposed research is to improve understanding of the sources of forest SOM so that society has a better basis for judging the effects of forest management activities on this crucial ecosystem component. The proposed work is particularly timely as a result of recent and likely future developments in energy and carbon markets. Among the variety of schemes to reduce the carbon footprint of human activity are two that the proposed research would inform: woody biofuels and forest carbon offset markets. In both cases inadequate understanding of the source and fates of forest SOM constrain our capacity to promote an optimal pathway forward. By improving understanding of the contribution of woody biomass to SOM stabilization, this research will facilitate mechanistic modeling of these processes. The key society issue that the proposed research will address is the interaction between land use and global climate change. Society can help incentivize forest management activities that will reduce our C footprint but only if basic information on soil C dynamics is available to inform policymakers. By quantifying the sources of stabilized SOM in forests the proposed research will contribute to this pressing issue.
Animal Health Component
(N/A)
Research Effort Categories
Basic
(N/A)
Applied
(N/A)
Developmental
(N/A)
Goals / Objectives
The overall goal of the proposed study is to improve understanding of the sources of stabilized soil organic matter (SOM) in temperate deciduous forest ecosystems. Four specific objectives for the project are: 1. To quantitatively trace carbon from decomposing woody detritus into stabilized SOM pools including different aggregate fractions. 2. To examine the differences in stabilization in soil of C from woody detritus between wood inoculated with brown-rot vs. white-rot fungi. 3. To quantitatively trace carbon from decomposing tree root systems into stabilized SOM pools. 4. To quantify the fate of C in ephemeral mycorrhizal fine roots in soil horizons of northern hardwood forest ecosystems. The principal outcome of the proposed research will be estimates of the proportional contribution to stabilized soil C of wood, leaf litter, and fine and coarse roots in northern hardwood forest ecosystems. Based on limited information in the literature we expect that a higher proportion of stabilized SOM will be derived from roots rather than aboveground woody and non-woody detritus. These results will inform improved models of the impacts of forest management activities on long-term soil C sequestration.
Project Methods
The overall approach to be employed in the proposed project is stable isotope tracing using plant tissue highly-enriched in 13C. The labeled material for the study was produced by fumigating sugar maple trees in a northern hardwood forest with 45 percent atom-enriched 13CO2. The procedure was successful in enriching sugar maple leaves, wood and roots to over 200 per mil del 13C, sufficient to successfully trace 13C from decaying leaf litter into the large soil C pool. For the proposed study wood and root tissues will be harvested and utilized to trace detrital 13C into soil pools. For objective 1, we will harvest all the trees from four 13C fumigation chambers, incubate them on the soil surface in a northern hardwood forest and periodically collect subsamples of wood and underlying soil for analysis of 13C. For Objective 2, in conjunction with the main experiment, we will inoculate 13C labeled wood sections with either common brown-rot or white-rot fungi of hardwoods. A third set of wood samples will be uninoculated controls. Samples of decaying wood and the soil underlying the quadrats will be collected after 2, 3 and 5 years of incubation in the field site at Arnot Forest, NY. Treatment (fungal group) effects on wood decay and 13C recovery will be evaluated using ANOVA for repeated measures. For Objective 3, we will quantify delta 13C of soil in the chambers where the maple trees were originally labeled and will be harvested in fall 2012, the latter marking time zero for calculations of stabilization of root system C in SOM. The coring and analysis procedure will be repeated on the same time schedule as for Objectives 1 and 2 (i.e. years 2, 3 and 5, adjusted as necessary). The basis of statistical inference for the root decay study will be the four replicate labeling chambers. For Objective 4, we will quantify the stabilization of C in fine roots collected from the chambers in fall 2011, one year after initial labeling (when delta 13C in fine roots was at a maximum). Root samples will be mixed with mineral soil at a level corresponding to root length density observed in soils at our field site. Random sub-sets of five cores will be collected after 0.5, 1, 1.5 and 2 years. Comparisons of C stabilization between the two classes of fine roots will be conducted using one-way ANOVA.