Effects of supplemental warming and precipitation on decomposition of Antarctic vascular plant litter

Background/Question/Methods

Mean annual air temperatures on the Antarctic Peninsula have dramatically increased over the past 50 years.   Regional climate models also predict that precipitation patterns in this area will also change.   We examined how warming and supplemental precipitation altered decomposition of native vascular plant litter in the Antarctic tundra.  Plant litter (Deschampsia antarctica and Colobanthus quitensis) was collected and placed in nylon mesh bags.  Bags were placed in intact cores of Antarctic tundra located under heaters which supplied an additional 28 W m^-2 of infrared radiation or under dummy heaters.  We supplemented half the cores with an additional 25% of ambient precipitation.  The experiment ran for 15 months, with half of the decomposition bags being removed for analysis after 2.5 months. Constituent analysis was performed on the decomposed litter to determine lignin, holocellulose, fat and lipid, and total C and N content. 

Results/Conclusions

Diel canopy air and soil temperatures of cores under heaters averaged 0.8 and 2.2 ^oC higher than those under dummy heaters. Warming accelerated mass loss of D. antarctica and C. quitensis litter by 20.4 and 14.4% above ambient conditions.  After 15 months, warming and supplemental precipitation accelerated mass loss of C. quitensis litter by 5.7 and 1.1%.  The increased mass loss under warming appeared to result primarily from the accelerated decomposition of holocellulose.  Holocellulose concentrations were 9 and 11% lower under warming for D. antarctica and C. quitensis, respectively, than under ambient conditions after 2.5 months of decomposition. Supplemental warming and precipitation also altered C:N ratios in D. antarctica over the course of the experiment.  Our results show how regional warming may influence accumulation of soil organic matter and nutrient cycling in the Antarctic tundra.