Effects of increased temperature on C cycling of a wet tropical forest: Initial results from a novel field warming experiment in Puerto Rico
Abstract
Tropical forests are important drivers of the global carbon (C) cycle, yet we are uncertain how rising temperatures will affect tropical forest C balance. Previous research suggests tropical plants are currently operating at or near their thermal optimum temperatures. Tropical plant species have evolved under very narrow temperature ranges, and as a result they may be unable to physiologically acclimate to predicted shifts in temperature regimes. Here, we investigate responses of key C cycling processes to experimental warming within the Luquillo Experimental Forest in Puerto Rico. We conducted 12 months of field-level understory warming using infrared heaters arranged in six 4-m diameter plots (three +4 °C heated and three control) as part of the Tropical Responses to Altered Climate Experiment (TRACE). We investigated effects of warming on soil respiration, root specific respiration, photosynthesis, and foliar respiration of understory shrubs as well as changes in root biomass and production. After 3 months of warming, photosynthesis of the understory species partially acclimated, showing increases in optimum photosynthetic temperatures (Topt) but no change in photosynthetic rates at optimum temperatures (Aopt). After 8 months, however, warmed plants showed increasing signs of stress, where increases in Topt were less pronounced and Aopt declined. Root specific respiration was significantly lower in warmed plots after 6 months of warming, demonstrating rapid acclimation to increased temperatures. At the same time, root biomass was significantly reduced but root production was not affected. Soil respiration rates were significantly higher in warmed plots. Overall, these results suggest that tropical understory plants will take up less carbon dioxide (CO2) in a warmer world, but may also respire less CO2 via roots, likely due to reduced belowground C allocation. While soil respiration rates increased significantly in warmed plots, root biomass was lower, suggesting increases were microbially-driven. Results could indicate a shift towards a net negative C balance in tropical forested ecosystems as global temperatures increase.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.B52A..03W
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCESDE: 0476 Plant ecology;
- BIOGEOSCIENCESDE: 0486 Soils/pedology;
- BIOGEOSCIENCESDE: 1630 Impacts of global change;
- GLOBAL CHANGE