Effects of rainfall reduction on litter leaf decomposition of Pinus tabuliformis plantation

  Objective  Litter decomposition plays an important role in carbon and nutrient cycles of forest ecosystems. The effects of rainfall reduction on leaf litter decomposition of Pinus tabuliformis were examined to understand the response of carbon (C) and nitrogen (N) turnover dynamics of P. tabuliformis plantations to future changes in precipitation, and to improve the prediction and assessment of ecosystem functions of plantations under climate change.

  Method  A field rainfall reduction experiment was performed in a plantation at Badaling Forest Farm, about 50 km north of Beijing from May to October, 2018. Losses of mass, C and N dynamics of P. tabuliformis leaf litter were measured and compared among three growing-season rainfall levels, i.e. 100% rainfall reduction, 50% rainfall reduction and control.

  Result  After five months of decomposition, no litter mass loss was detected for the 100% rainfall reduction treatment and slight increase in litter mass was actually observed. The percentages of remaining litter mass, C and N for the 50% rainfall reduction treatment were 75.75%, 49.31% and 71.00%, respectively, while those for the control were 73.18%, 51.92% and 75.50%, respectively. There were no significant differences in remaining litter mass, C and N between the 50% rainfall reduction treatment and control. The annual decomposition coefficients (k) for the 50% rainfall reduction treatment and control were 0.64 and 0.92, respectively. There was a significant positive correlation between the monthly decomposition rate and soil water content. For the 50% rainfall reduction treatment and control, N immobilization was observed in June and N release was observed from July to October.

  Conclusion  In the P. tabuliformis plantation, the effects of rainfall reduction on leaf litter decomposition depend on the magnitude of rainfall reduction. The decomposition dynamics of P. tabuliformis leaf litter may be relatively insensitive to mild and moderate droughts, but severe droughts can strongly restrict the decomposition rate and the turnover of C and N.