Partitioning sources of soil respiration in boreal black spruce forest using radiocarbon
ثبت نشده
چکیده
Separating ecosystem and soil respiration into autotrophic and heterotrophic component sources is necessary for understanding how the net ecosystem exchange of carbon (C) will respond to current and future changes in climate and vegetation. Here, we use an isotope mass balance method based on radiocarbon to partition respiration sources in three mature black spruce forest stands in Alaska. Radiocarbon (DC) signatures of respired C reflect the age of substrate C and can be used to differentiate source pools within ecosystems. Recently-fixed C that fuels plant or microbial metabolism has DC values close to that of current atmospheric CO2, while C respired from litter and soil organic matter decomposition will reflect the longer residence time of C in plant and soil C pools. Contrary to our expectations, the DC of C respired by recently excised black spruce roots averaged 14% greater than expected for recently fixed photosynthetic products, indicating that some portion of the C fueling root metabolism was derived from C storage pools with turnover times of at least several years. The DC values of C respired by heterotrophs in laboratory incubations of soil organic matter averaged 60% higher than the contemporary atmosphere DCO2, indicating that the major contributors to decomposition are derived from a combination of sources consistent with a mean residence time of up to a decade. Comparing autotrophic and heterotrophic DC end members with measurements of the DC of total soil respiration, we calculated that 47–63% of soil CO2 emissions were derived from heterotrophic respiration across all three sites. Our limited temporal sampling also observed no significant differences in the partitioning of soil respiration in the early season compared with the late season. Future work is needed to address the reasons for high DC values in root respiration and issues of whether this method fully captures the contribution of rhizosphere respiration.
منابع مشابه
Changing sources of soil respiration with time since fire in a boreal forest
Radiocarbon signatures (DC) of carbon dioxide (CO2) provide a measure of the age of C being decomposed by microbes or respired by living plants. Over a 2-year period, we measured DC of soil respiration and soil CO2 in boreal forest sites in Canada, which varied primarily in the amount of time since the last stand-replacing fire. Comparing bulk respiration DC with DC of CO2 evolved in incubation...
متن کاملCarbon allocation in boreal black spruce forests across regions varying in soil temperature and precipitation
A common hypothesis for northern ecosystems is that low soil temperatures inhibit plant productivity. To address this hypothesis, we reviewed how separate components of ecosystem carbon (C) cycling varied along a soil temperature gradient for nine welldrained, relatively productive boreal black spruce (Picea marianaMill. [B.S.P.]) forests in Alaska, USA, and Saskatchewan and Manitoba, Canada. A...
متن کاملCarbon allocation in boreal black spruce forests across regions varying in soil temperature and precipitation
A common hypothesis for northern ecosystems is that low soil temperatures inhibit plant productivity. To address this hypothesis, we reviewed how separate components of ecosystem carbon (C) cycling varied along a soil temperature gradient for nine welldrained, relatively productive boreal black spruce (Picea mariana Mill. [B.S.P.]) forests in Alaska, USA, and Saskatchewan and Manitoba, Canada. ...
متن کاملComparison of Boreal Ecosystem Model Sensitivity to Variability in Climate and Forest Site Parameters
Ecosystem models are useful tools for evaluating environmental controls on carbon and water cycles under past or future conditions. In this paper we compare annual carbon and water fluxes from nine boreal spruce forest ecosystem models in a series of sensitivity simulations. For each comparison, a single climate driver or forest site parameter was altered in a separate sensitivity run. Driver a...
متن کاملSoil and root respiration in mature Alaskan black spruce forests that vary in soil organic matter decomposition rates
Climate warming at high latitudes is expected to increase root and microbial respiration and thus cause an increase in soil respiration. We measured the root and microbial components of soil respiration near Fairbanks, Alaska, in 2000 and 2001, in three black spruce (Picea mariana (Mill) B.S.P.) forests. We hypothesized faster decomposition correlates with greater amounts of both root and micro...
متن کامل