Climatological response of radial growth for Pinus sylvestris var. mongolica to drought in Hulun Buir Sandland, Inner Mongolia of northern China

ObjectiveHulun Buir Sandland is the southern margin of natural Mongolian pine (Pinus sylvestris var. mongolica) with a warm and dry climatological trend. This study aims at climatological response of Mongolian pine and its resilience to drought.

MethodTwo tree-ring width chronologies of Mongolian pine were established at Nanhui and Yiminhe sites in Hulun Buir Sandland, Inner Mongolia of northern China. Correlations were analyzed using the tree-ring width with climate factors, and tree resilience indexes (including resistance, recovery and resilience) were calculated using the two width chronologies.

ResultResults showed that the tree-ring width had significantly negative correlation with the monthly mean temperature of June, and significantly negative correlation with the maximum temperature from June to July at Nanhui site (P < 0.05); and significantly negative correlation with the monthly mean temperature and the maximum temperature of April, June, July and September at Yiminhe site (P < 0.05). Tree-ring width had positive correlation with the monthly precipitation of June, July and September at both two sites (P < 0.1). In the meanwhile, the tree-ring width had significantly negative correlation with the relative humidity of September at Nanhui site, and significantly positive correlation with the relative humidity of the last October to December and February, March and May in the same year(P < 0.05). The tree-ring width had also significantly positive correlation with the Palmer drought severity index (PDSI) from last October to same September at two sites (P < 0.05), indicating the growth of Mongolian pine was significantly influenced by hydrological factors in Hunlun Buir Sandland. Compared to values in Nanhui site, the drought resistance was lower, but the recovery was larger in Yiminhe site. With drought severity increased, Mongolian pine showed decreased resistance and increased recovery.

ConclusionThe radial growth of natural Mongolian pine was influenced by temperature and precipitation of summer in Hulun Buir Sandland. Difference of two tree-ring chronologies occurred from the year of 1925 to 1935 in two sites may result from younger trees and its lower resistance to drought in Yiminhe site. Stand age, as an important factor influencing tree resilience to drought should be further studied with multi-site data.