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FOREST, RANGE & WILDLAND SOILS

Contribution of Root vs. Leaf Litter to Dissolved Organic Carbon Leaching through Soil

^a Ecology, Evolution, and Conservation, Biology Program, and Natural Resources and Environmental Science Dep., MS 186, Univ. of Nevada, Reno, NV 89557
^b Natural Resources and Environmental Science Dep., MS 370, Univ. of Nevada, Reno, NV 89557

^* Corresponding author (uselman{at}unr.nevada.edu).

Very little is known about dissolved organic matter (DOM) originating from fine roots in forest soils in comparison to DOM originating from leaf litter. To compare the fate of root- vs. leaf-derived dissolved organic carbon (DOC), we added ¹⁴C-labeled root litter at depths of 10 cm, a "shallow root treatment," and 40 cm, a "deep root treatment," and leaf litter to 50-cm column soil microcosms. We analyzed the solution leached from the columns during a 47-d simulated snowmelt treatment, trapped respired ¹⁴CO₂, and measured translocation of ¹⁴C within the columns. In general, total C losses, as a percentage of ¹⁴C added, were substantial and highest for the leaf treatment (8.2% leached as DOC, 13.4% translocated, and 14.8% respired), intermediate for the shallow root treatment (2.3, 5.2, and 3.9%, respectively) and lowest for the deep root treatment (2.4, 1.9, and 2.9%, respectively). The C lost to DOC leaching was similar, however, for the deep and shallow root treatments. As a percentage of total losses (i.e., the sum of DOC leaching, respiration, and translocation), ¹⁴C lost as DOC leaching was significantly higher in the deep root treatment than other treatments. These observations suggest that leaf-derived DOC may contribute to the formation of an A horizon and even to accumulation of soil organic carbon (SOC) in the B horizon during soil development, either by adsorption or microbial biomass incorporation. The ¹⁴C data further showed that root-derived DOC, especially from root litter at greater depths, may help explain both the presence of SOC at depth and a portion of the DOC draining from soil profiles.

Abbreviations: DIC, dissolved inorganic carbon • DOC, dissolved organic carbon • DOM, dissolved organic matter • SOC, soil organic carbon • SUVA, specific ultraviolet absorbance