Direct and indirect effects of experimental warming on ecosystem carbon processes in a tallgrass prairie

Abstract

[1] This study was conducted to examine direct and indirect impacts of global warming on carbon processes in a tallgrass prairie in the U.S. Great Plains. Infrared radiators were used to simulate global warming, and clipping was used to mimic hay mowing. Experimental warming caused significant increases in green biomass in spring and autumn and total biomass in summer on most of the measuring dates. Green aboveground biomass showed positive linear correlations with soil temperature in spring and autumn whereas total aboveground biomass in summer was negatively correlated with soil temperature. Experimental warming also affected aboveground biomass indirectly by extending the length of growing season and changing soil nitrogen process. Elevated temperature tended to increase net nitrogen mineralization in the first year but decrease it in the second year, which could be attributable to stimulated plant growth and belowground carbon allocation and consequently enhanced microbial nitrogen immobilization. Warming-induced changes in soil respiration were proportional to those of total aboveground biomass. Clipping significantly reduced aboveground biomass and increased root biomass, but had no effect on net nitrogen mineralization and annual mean soil respiration. The proportional changes in soil respiration to those of aboveground biomass indicate warming-stimulated ecosystem carbon uptake could be weakened by increased carbon release through soil respiration.

Short-term responses of Picea asperata seedlings of different ages grown in two contrasting forest ecosystems to experimental warming

“…The phenological responses noted in this study were in good agreement with many other similar studies (Arft et al, 1999;Wada et al, 2002;Norby et al, 2003;Xu et al, 2009). The phenological differences caused by warming could benefit gross photosynthesis and plant growth (Norby et al, 2003;Wan et al, 2005). Warming-induced phenological changes would lead to a longer favorable period for plant photosynthesis and growth, resulting in increased leaf area index and green biomass during the growing season.…”

Terrestrial carbon-cycle feedback to climate warming: experimental evidence on plant regulation and impacts of biofuel feedstock harvest

“…Third, other studies showed that warming stimulated mineralization (Melillo et al 2002;Rustad et al 2001;), increased plant nutrient uptake and use efficiency (Sardans et al 2008). Similarly, observed increased mineralization and plant nutrient uptake are likely mechanisms leading to stimulated NPP in this study Wan et al 2005). On the other hand, our measurement showed that leaf-level photosynthesis of four dominant species increased significantly in spring, decreased in early fall, and did not change in summer and late fall under warming in comparison with that in control (Zhou et al 2007a).…”

“…Thus, biofuel feedstock production in the US Great Plains may not be C-negative or help offset atmospheric C buildup due to anthropogenic activities. Owensby et al 2006;Wan et al 2005). As a result, net ecosystem production was positive and the amount of soil C loss was less than the amount of C in the removed biomass in the warming and clipping treatment.…”

“…It has been well known that climate warming does not only affect leaf-level photosynthesis but also other processes (Luo 2007), such as biomass growth (Saleska et al 2002;Dukes et al 2005;Wan et al 2005), nutrient availability (Emmett et al 2004), plant nutrient uptake and use efficiency (Melillo et al 2002;An et al 2005), and species composition (Harte & Shaw 1995;Harte et al 2006). Any of those changes that affect plant C uptake will influence C release in intact ecosystems, feeding back to climate change.…”

Modeling Carbon Fluxes Using Multi-Temporal MODIS Imagery and CO2 Eddy Flux Tower Data in Zoige Alpine Wetland, South-West China

“…Warming directly affects plant growth and shifts in plant species across a range of tundra ecosystems (Walker et al 2006;Elmendorf et al 2012). Several studies indicate that plant aboveground net primary production (ANPP) has variable responses to warming in arctic and alpine regions, with reported increases, decreases, or no change (Houborg and Soegaard 2004;Wan et al 2005;Klein et al 2007;Post and Pedersen 2008). Wania et al (2009) modeled strong increases in Arctic annual NPP using a dynamic global vegetation model (DGVM).…”