Land Use Change Effects On Soil Respiration: From Agriculture to Hybrid Poplar Plantation.

There is increasing interest in exploiting carbon sequestration benefits of short-rotation woody crops (SRWC) established on agricultural sites to mitigate Canada’s emissions of greenhouse gases due to production and consumption of fossil fuels. The fast-growing and high-yielding nature of SRWC allows large amounts of carbon (C) to be sequestered in long-term storage pools, i.e., wood biomass and soil pools. Although the potential of SRWC to sequester C is recognized, the net C benefits of these systems are unclear, particularly as it is expected that they will be C sources during the initial years following establishment. Understanding the variations of C loss via soil-surface respiration is essential to accurately assess the C budget of these plantations, particularly in response to climatic variations and management regimes.

A space-for-time substitution (chronosequence) experiment was set up in north central Alberta, Canada to examine the effect of land use change on soil C loss 2-5 and 9-12 years after converting an agricultural land use to a hybrid poplar plantation (Populus deltoides x Populus x petrowskyana var. Walker). We focused on the measurement and modeling of soil respiration rates taking into account seasonal variations in climate and spatial variability in soil conditions. Annual estimates of C loss via soil respiration, its temporal and spatial variability, and its interaction to temperature and moisture were examined and are reported in this study.