Tropical forests are vital components of the global carbon cycle and play an important role in mitigating climate change. However, the effects of climate change on the dynamics of these ecosystems are not fully understood.
In a study published in Integrative Conservation, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) explored how different types of tropical forests in Southwest China responded to climate change from 2004 to 2020. They examined the effects of climate change on tropical forest growth, mortality, turnover and stem net primary productivity (NPPstem).
They used forest inventory data collected over 16 years from five tropical forest plots along an successional gradient in Xishuangbanna, Southwest China, including three secondary tropical forests (TSF-1, TSF-2 and TSF-3) and two primary forests (tropical rainforest TRF and tropical karst forest TKF) in Southwest China, each representing different successional stages (i.e., early, late, and mature stages).
By tracking forest growth, mortality, regeneration, and productivity, they found that secondary forests, especially those at early successional (younger) stages, are more vulnerable to extreme climatic events like droughts and heat waves. Early successional secondary forests (TSF-2 and TSF-3) had higher diameter growth rates and relative mortality rates. The extreme drought event in 2009-2010 decreased the growth rate, relative turnover rate and NPPstem for most plots, while increasing the mortality rate for early successional forest plots. In addition, maximum temperature (Tmax) had a significant negative effect on NPPstem and diameter growth rate for all plots, whereas precipitation had a significant positive effect on diameter growth rate for all plots. Tree mortality increased with Tmax, while precipitation significantly enhanced tree turnover.
Consequently, the impacts of climate warming are expected to reduce tree growth and recruitment, thereby diminishing carbon sink capacity, and increasing tree mortality.
"Our study provides valuable insights into the long-term demographic and productivity dynamics of tropical primary and secondary forests at different successional stages in Southwest China,” said FAN Zexin of XTBG.

Contact
FAN Zexin Ph.D Principal Investigator
Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China
E-mail: fanzexin@xtbg.org.cn
Published: 14 July 2024