Differences in Growth Responses to Climate of Three Conifer Species in Lugu Lake of Northwestern Yunnan, Southwestern China

Responses of tree radial growth to climate are usually species-specific. Northwestern Yunnan has become a hotspot for the study of dendrochronology due to its sensitivity to climate change and the relative integrity of vegetation preservation. In this paper, we take three dominant conifers-<i>Pinus armandii</i>, <i>Pinus yunnanensis</i> and <i>Picea likiangensis</i>-as the research objects and analyze their tree-ring width chronologies in order to reveal the main climate factors affecting tree growth in northwestern Yunnan and to evaluate species-specific variation in climate response. The results showed that the radial growth of the three tree species was co-regulated by temperature and precipitation but that the growth response patterns were varied. Specifically: (1) The radial growth of the three species of conifers was significantly and negatively correlated with the July average maximum temperature (<i>T_max</i>) and the October Palmer Drought Severity Index (PDSI) in the current year. (2) Current May precipitation significantly promoted <i>P. armandii</i> growth and inhibited <i>P. likiangensis</i> growth, and a wet July was beneficial for both <i>P. yunnanensis</i> and <i>P. likiangensis</i> growth, while the radial growth of <i>P. yunnanensis</i> and <i>P. armandii</i> showed a significant and positive correlation with the August <i>T_max</i> in the current year. (3) The sliding analysis supported the results of the response function by showing stable relationships with climate factors which significantly affected tree growth. Results from redundancy analysis (RDA) and response function analysis were basically consistent, demonstrating that these two methods could complement each other in the understanding of relationships between tree radial growth and climatic factors. This study elucidates the climate-growth relationship of the main tree species in the study area and provides theoretical guidance and scientific evidence for regional forest management.