Warming and forest management interactively affect the decomposition of subalpine forests on the eastern Tibetan Plateau: A four-year experiment

- Decomposition of two subalpine forest leaf litters on the eastern Tibetan Plateau in relation to climate and soil conditions.
- Regardless of warming regimes and sites, the values of decay constant, k, of red birch were significantly higher than those of dragon spruce.
- Reforestation dramatically altered the litter quality of local forests, and further affected the responses of litter decay to warming.

Increased rates of litter decomposition due to climatic warming have great potential to modify the carbon balance in forest soils, with consequent feedbacks to climate change. Reforestation could affect responses of litter decomposition to warming by altering litter type and soil conditions. However, less is known about the interactive impacts of forest management and climate change on litter decomposition. Here, we conducted a 4-year field experiment to investigate the effects of experimental warming on the decomposition of dragon spruce (Picea asperata Mast.) and red birch (Betula albo-sinensis Burk.) foliar litter in two contrasting sites (a dragon spruce plantation and a natural forest) using litter-bag method on the eastern Tibetan Plateau of China. During the four years of decomposition in the field, a clear pattern of faster mass loss was observed in red birch litter compared to dragon spruce needle. Additionally, regardless of warming regimes and litter types, mass loss rates were higher in the natural forest site than in the plantation site. Warming did not affect mass loss of dragon spruce litter during the early decomposition stage, but increased it over the later decomposition stage. In contrast, warming had enhanced mass loss of red birch litter on most sampling days. Red birch litter was more sensitive to warming compared with dragon spruce needle. Our results clearly indicated that reforestation can alter litter quality and soil conditions, and further affect the litter decomposition of subalpine forest ecosystem to projected climatic warming. This calls for incorporating forest management practice in climate-carbon models to better understand carbon dynamics of forest ecosystems under climate change.