Soil respiration includes two main components: heterotrophic respiration (R_H) and autotrophic respiration (R_A). Forest soil organic carbon decomposition plays an important role in the regional and global carbon cycle. However, no studies on have been conducted in subtropical forests to evaluate warming effect on heterotrophic respiration. It remains unclear how soil warming affects RH in the subtropical evergreen broad-leaved forest in the Ailao Mountains in Yunnan of southwestern China.
Prof. ZHANG Yiping and his team of Xishuangbanna Tropical Botanical Garden (XTBG) conducted ‘trenching alone’ and ‘trenching with warming’ treatments in Ailaoshan subtropical forest. They aimed to test whether heterotrophic respiration acclimated to continuous warming.
To clarify the effect of warming on heterotrophic respiration, the researchers focused on the affecting factor of changes to soil water content. The results showed that soil organic carbon, soil labile organic carbon, and soil microbial carbon did not significantly (p > 0.05) decrease in the trenching treatment and the trenching together with warming treatment comparing to the control treatment during the 4-year measurement period. However, those factors were larger in the trenching together with warming treatment than that in the trenching treatment.
The factors as soil temperature, water content, warming effect on temperature had a significant relationship with warming effects on heterotrophic respiration. Warming effect on temperature seemed to be a controlling factor in the study.  Soil water content affected warming effects on heterotrophic respiration (WE_RH), mediating WERH under the warmer soil temperature conditions. Warming effect on temperature (WET) decreased yearly.
 A positive relationship between WE_RH and WE_T required a specific range of WE_T, and when WE_T exceeded the range, WE_RH became restricted. Therefore, WE_T controlled WE_RH in Ailaoshan subtropical forest.
 The study showed that the warming effect on R_H was controlled by a range of increased soil temperature and regulated by the variation of soil water content. The researchers therefore suggested that global warming would accelerate soil carbon efflux to the atmosphere, regulated by the change in soil water content in subtropical forests.

The study entitled “Heterotrophic respiration does not acclimate to continuous warming in a subtropical forest” has been published in Scientific Reports.

Contact
ZHANG Yiping  Ph.D Principal Investigator
Key laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, 666303, China
E-mail: ypzhang@xtbg.ac.cn
Tel: 86 871 65160904