Growth-climate sensitivity of two pine species varies with site-specific environmental conditions

A better understanding of tree growth-climate sensitivity across regions and species may reduce uncertainties in simulating forest carbon budgets. However, few studies have explored the growth-climate sensitivity of different tree species in Southwest China.

In a study published in Agricultural and Forest Meteorology, researchers from the Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences explored the growth-climate sensitivity of pine species and its spatial heterogeneity across temperature and moisture gradients in Southwest China. They investigated the predominant climatic factors limited tree radial growth and how growth-climate sensitivity of pine species changed along temperature and moisture gradients in Southwest China.

The researchers established tree-ring networks of two pine species (Pinus yunnanensis and Pinus kesiya), which are widely distributed in Southeast Asia and share the same evolutionary origin. They developed tree-ring width chronologies from 22 sites of P. yunnanensis and 20 sites of P. kesiya, totaling 903 trees (1684 cores), covering the region from 21°N to 28°N and from 98°E to 107°E.

They found that the climate sensitivity of P. yunnanensis and P. kesiya revealed species-specific changes along temperature and moisture gradients, which were largely driven by site-specific environmental conditions within the ecological amplitudes of the species.

Tree growth of both P. yunnanensis and P. kesiya in Southwest China were highly sensitive to and primarily driven by early growing season moisture availability, but negatively correlated with moisture availability of late growing season. Moisture sensitivity of P. kesiya species decreased from dry to humid sites.

Meanwhile, P. yunnanensis revealed site-specific temperature sensitivity, i.e., positive temperature sensitivity under wetter site conditions (low temperature limitation), but negative effects of high temperatures in drier sites. Temperature sensitivity of P. yunnanensis decreased from cold to warm sites.

"Our results indicate that the growth-climate sensitivity of both pine species varies with site-specific environmental conditions," said Fan Zexin of XTBG.