PARENT SESSION
Oral Session #52: Carbon and Nitrogen Cycling: Soil processes and patterns. Presiding: F. Gilliam.
Wednesday, August 8, 2001. 1:00 PM to 5:00 PM. Hall of Ideas E.
From plant to soil organic matter: 14 C Tracing of carbon in arctic tundra soils.
Loya, Wendy1, Johnson, Loretta1, Nadelhoffer, Knute2, 1 2
ABSTRACT- To predict how climate change might affect C storage in arctic ecosystems, we first need to understand the dynamics of C cycling in arctic soils. Through 14C pulse-labeling and incubation experiments, we investigated C dynamics in tussock tundra from Alaska. Our objectives were to determine pathways and rates of C transfer from roots and litter into soils, quantify transformations of C in soil organic matter (SOM), and determine the effects of plants on these processes. Our research revealed that the C cycle in arctic tundra is a dynamic system, with belowground allocation of ~6% of photosynthate C within one day, and immediate uptake by soil microbes. Over the growing season, ~75% of this C accumulates in intermediate and recalcitrant SOM fractions. During incubations of leaf or root litter in cores with growing plants vs. unplanted cores, five times greater C was lost from planted cores, likely due differences in microclimate at the soil surface. Only one-tenth the C from root litter was lost in planted cores vs. unplanted cores, correlating with data from incubations at sub-zero temperatures suggesting that without labile C inputs, microbes mineralize recalcitrant SOM. Movement of C between SOM fractions varied between treatment and litter type. Overall, using 14C tracers has provided critical information on C cycling and storage in arctic ecosystems. These data will be used in models to predict alterations in the C cycle due to climate change.
KEY WORDS: carbon cycling, decomposition, soil organic matter, microbial biomass