Effect of temperature and litter quality on decomposition rate of Pinus patula needle litter

Abstract

Decomposition of plant litter is an important component of the carbon and nitrogen cycles. Litter decomposition is regulated by the physical environment, litter quality and the nature and abundance of microbial communities. Climate has been found to exert strong controls over rates of litter decomposition and climate change may alter both carbon and nitrogen cycles. Global temperatures have increased by 0.74 ºC, and are predicted to increase by 1.1- 6.4 ºC within this century as a result of climate change, increases in temperature coupled with other climatic parameters are expected to affect litter decomposition rate. This study examined the mass loss and CO2 production from Pinus patula (Schlecht et Cham) leaf litter collected from fertilized plots in the Mpumalanga Province. The litter was incubated at various temperature regimes (15 ºC, 18 ºC, 24 ºC and 30 ºC) for 16 weeks. Litter decomposition increased with increasing temperature. Warming between 15 ºC and 18 ºC significantly increased the amount of CO2 emissions from the litter; at 30 ºC there was a marked increase in the amount of CO2 emitted. At the highest temperature there was a marked increase in the amount of CO2 emitted from the litter; when compared to 15 ºC the amount of CO2 evolved from litter incubated at 18 ºC was 58 % higher. Thus, future warming will increase the CO2 emission from the forest floor. Mass loss of the litter was positively correlated with temperature levels with the highest temperature (30 ºC) recorded 41% more mass loss than 15 ºC. Nitrogen fertilizer applications had significant effects on litter decomposition rate but a minor effect on litter nitrogen quality. In addition, the residual effect of fertilizer was reflected in the nitrogen concentration of the litter and the decomposition rate. Nitrogen accumulation of the litter was positively correlated with temperature and nitrogen concentration in the original needle litter. The litter quality was not a strong predictor of litter decomposition rates implying that temperature is the major factor influencing the decomposition rate of Pinus patula needle litter. The results of this study are consistent with the hypothesis that the rate of nutrient cycling in non-limiting environments will increase, due primarily to an increase in litter decomposition as a result of increased temperatures.