Nitrogen Addition Exacerbates the Negative Effect of Throughfall Reduction on Soil Respiration in a Bamboo Forest

Impacts of drought events and nitrogen (N) deposition on forests are increasingly concerning in the context of global climate change, but their effects, in particular, their interactive effects on soil respiration and its components remain unclear. A two-factor random block field experiment was conducted at a subtropical Moso bamboo forest in Southwest China to explore the response of soil respiration (R-s), autotrophic respiration (R-a), and heterotrophic respiration (R-h) to throughfall re-duction and N addition. Our results showed that throughfall reduction significantly decreased R-s, which is mainly attributed to the decrease in R-a as a result of the decline in fine roots biomass. The N addition led to microbial carbon limitation hence significantly decreased R-h, and thus R-s. We also observed the negative effect of throughfall reduction on R-s was exacerbated by N addition, which is attributed to the significant reduction in R-a under the interaction between throughfall reduction N addition. Our findings suggest that R-a tended to respond more sensitively to potential drought, while R-h responds more sensitively to N deposition, and consequently, increased soil N availability caused by N deposition might aggravate the negative effect of expected drought on soil carbon cycling.

Automated summary

The study found that throughfall reduction led to a decrease in soil respiration, mainly due to a decline in fine roots biomass; N addition caused microbial carbon limitation, leading to a decrease in soil respiration. The negative effect of throughfall reduction on soil respiration was exacerbated by N addition through the interaction between the two factors.