UC Berkeley

【Objective】 To develop a sustainable management plan for Larix gmelinii, which is influenced by climate change, it is crucial to understand the dynamic relationship between radial growth and climate in forests with different tree densities.【Method】Based on the stand density index, nine plots with three density levels (low, middle, high) were established in the central and northern Greater Khingan Mountains. Tree cores of L. gmelinii were collected during a field investigation. The Mann-Kendall test method was used to determine the turning point of temperature in the study area. To examine the radial growth trend of L. gmelinii, negative exponential function detrending and a linear function fitting were applied. Then, a Pearson correlation and sliding correlation were used to analyze whether the relationship between the radial growth and climate factors under each stand density remained stable after the temperature turning point.【Result】The radial growth of L. gmelinii displayed trends of both enhancement and decline after the temperature turning point. The proportion of declining trees increased with increasing stand density. The growth of L. gmelinii was strongly inhibited when the stand density was high. Its average growth change rate reached -25% during 1988-1990, indicating a serious growth decline. Instead, the L. gmelinii trees in low density plots maintained a 54% growth enhancement ratio. Stand density may also influence the response of L. gmelinii growth to climate. Under a high stand density, the L. gmelinii growth of the decline group was positively correlated with the standardized precipitation evapotranspiration index in August (P<0. 05) and negatively correlated with summer temperature (P<0. 05), but under a low stand density, the growth of L. gmelinii was positively correlated with temperature. With the warming and drying trend in the study area, the relationship between tree growth and temperature shifted from positive to negative with increasing stand density. 【Conclusion】 The proportion of declining trees increased with increasing stand density after the significant change of temperature. The impact of water limitation on growth was alleviated at a low stand density, while the trees in high density plots were more sensitive to climate factors. Reducing the stand density could mitigate the negative impacts of climate warming on the growth of L. gmelinii. Therefore, adjusting stand density is a necessary management operation to slow the declining trend of L. gmelinii.