Growth responses of broad-leaf and Korean pine mixed forests at different successional stages to climate change in the Shengshan Nature Reserve of Heilongjiang Province, China
Aims This research examined the different response of tree growth to climate change at the early, middle, late and matured successional stages of Korean pine (Pinus koraiensis) and broadleaf mixed forest. Methods This research used dendroecological methods to analyze radial growth at different successional stages of Korean pine forests in response to climatic change in the Shengshan Nature Reserve of Heilongjiang. Important findings Chronology statistics indicated that the sensitivity of radial growth to inter-annual climate variability decreased from early to later successional stage. Meanwhile, the influence of some climate indices to radial growth also changed during the successional process. Radial growth of matured forest was positively related to mean monthly temperature in June and December of previous year, revealing an obvious "lag effect" of temperature. The ring-width of matured forest had a negative correlation with mean monthly temperature but a positive correlation with monthly precipitation in June of current year, reflecting the limiting role of growing season water availability. However, these limiting effects gradually disappeared towards the earlier stages of forest succession. On the contrary, the growth of early successional forest was negatively correlated to precipitation in June of previous year, and this effect disappeared towards the later successional stages. These differences revealed increased demand of water by dominant species from early to later successional stages. A moving correlation analysis showed that the increased warming and drying climate in the research area had both positive and negative influences on radial growth of each forest type. Earlier successional forests did not show clear long-term growth responses, but Korean pine forests had decreased radial growth in the past decades due to reduced water availability. Climate warming and drying in the future may impose negative impact on the growth, succession and distribution of Korean pine forests.