Relationship between diameter structure dynamics and climate factors of Larix gmelinii under fire disturbance
： 2020 - 06 - 28
： 2020 - 10 - 21
： 2020 - 11 - 01
150 0 0

Abstract & Keywords
Abstract: Background, aim, and scope Diameter structure plays a decisive role in the future development of a forest. Using tree-ring data and survey data in a climate change background, we explore changes in the relationships between fire disturbance, the growth of Larix gmelinii (larch), and climate change by reconstructing the historical diameter structure. Materials and methods In this study, we investigate L. gmelinii in areas disturbed by fire in 1987, 2003, and 2015 in the Greater Khingan Mountains. Nearby areas not disturbed by fire are selected as control sites. Results (1) Fire disturbance caused the diameter structure of L. gmelinii to be positively deviated and the kurtosis value increased. After 15 years of recovery from moderate fire disturbance, there was a negative bias and the kurtosis value decreased. Fifteen years after recovery from severe fire disturbance, it remained positive and reached the peak of kurtosis but then showed a tendency to negative bias, and the kurtosis value decreased. (2) Fire disturbance changed the response relationship between the diameter growth of L. gmelinii and climate. Under moderate fire disturbance, the growth of L. gmelinii was steadily and significantly negatively correlated with the winter temperature of the previous year (p < 0.05). The positive correlation with the temperature in the growing season changed from positive in the initial stage of fire disturbance to a negative correlation in the mid-term (15 years of recovery) (p < 0.05), while the relationship with precipitation in the growing season of the previous year was positively correlated (p < 0.05). Under severe fire disturbance, the diameter growth of L. gmelinii was significantly negatively correlated with precipitation in the current growing season (May—August), the previous year’s growing season (July—September), and winter of the previous year (November—December) (p < 0.05). The negative correlation with the winter temperature of the previous year changed from the initial period of recovery to a positive correlation (p < 0.05) in the later period (31 years of recovery), and a negative correlation with a change in precipitation in the current growing season (p < 0.05). Discussion Different fire disturbances can change the diameter structure of L. gmelinii by changing the forest’s light intensity, degree of competition, and soil composition. With increased recovery time, the distribution of the diameter of L.gmelinii forest is difficult to restore to the original ecological state. Under global warming, the growth of L. gmelinii in the Greater Khingan Mountains will be more sensitive to climatic factors, with increased temperatures increasing the respiration of L. gmelinii, promoting growth and development. Transpiration led to a change in the water distribution pattern of larch in the Greater Khingan Mountains and a decrease in environmental water content, which hindered growth. Fire disturbance can also change the diameter structure of the forest stand, which in turn can change the response of larch growth in the Greater Khingan Mountains to climate change. Conclusions (1) Increased fire intensity has a suppressive effect on diameter growth. Prolonged fire disturbance recovery time promotes diameter growth, and forest restoration time is shorter under moderate fire disturbance conditions than under severe fire disturbance conditions. (2) Fire disturbance changed the response relationship between the diameter growth of L. gmelinii and the climate in the Greater Khingan Mountains. The diameter growth showed an obvious lag response to temperature and precipitation. Under future climate warming conditions, the diameter distribution of L. gmelinii may move to a small and medium diameter level. Simultaneously, the diameter growth rate after fire disturbance will slow significantly, the recovery process from fire disturbance will be longer, and it will be difficult to restore the larch to its original natural state. Recommendations and perspectives Under the trend of increasing global warming and increasing fire disturbance events, the response relationship between the diameter structure of L. gmelinii in the Greater Khingan Mountains and the climate may change significantly under the influence of fire disturbance. This warrants further research and scrutiny.
Keywords: diameter structure; fire disturbance intensity; climatic factors; Larix gmelinii

1材料与方法
1.1研究区概况及样本采集

 样地代号 Plot code 纬度 Latitude 经度 Longitude 火干扰程度 Degree of fire interference 时段 Timespan 样本量 No.trees/radii 87c 87s 03c 03m 15c 15m 15s 50°54' 50°54' 51°2' 51°5' 50°59' 50°59' 50°58' 121°23' 121°21' 121°42' 121°31' 122°24' 122°25' 122°25' 对照 重度 对照 中度 对照 中度 重度 19732017 19962017 19772017 19732017 19452017 18992017 19772017 15/21 72/95 31/52 38/59 66/79 34/46 12/12
1.2直径结构分析

（1）

（2）

（3）

1.3气候数据来源

2结果
2.1火干扰对直径结构的影响

Fig 1 Different fire interference intensity and diameter distribution under recovery period
a：2003年各火干扰样地及对照样地2018年情况；b：2003年中度火干扰样地-恢复15 a；c：1987年重度火干扰样地-恢复31 a。a: 2003 different fire disturbance plots and control plot in 2018; b: 2003 moderate fire disturbance plot-15 years of recovery; c:1987 severe fire disturbance plots -31 years of recovery.

 样地类型 Plot 偏度 Skewness 峰度 Kurtosis 变异系数 Coefficient of variation 15s 1.14 2.32 0.39 15m 0.64 1.40 0.28 03c -0.32 0.04 0.31 03m 0.95 2.04 0.32 03s 1.62 0.73 0.13

 样地类型 Plot 恢复年限 Recovery period 偏度 Skewness 峰度 Kurtosis 变异系数 Coefficient of variation 03m 0 1 1.78 3 1.01 1.68 0.35 15 0.95 2.04 0.32 87s 3 -0.12 -5.29 0.21 15 3.7 14.23 0.97 31 3.44 13.99 0.55
2.2火干扰下直径生长—气候因子相关关系

Fig.2 Diameter growth-climate factor correlation under different fire disturbance intensities during the same recovery period (P represented the previous year, p＜0.05)
2.3   直径结构预测

$$\mathrm{Y}=0.2674{x}_{1}-0.3073{x}_{2}-0.4183{x}_{T}+0.0352{x}_{P}+3.3381$$

3讨论
3.1火干扰对兴安落叶松直径结构动态的影响

3.2火干扰下兴安落叶松生长对气候变化响应的差异

3.3全球变暖背景下未来大兴安岭地区兴安落叶松直径结构

4结论
（1）火干扰能够改变林分直径分布，中度火干扰下兴安落叶松直径结构向大、中径级（1224cm）移动，峰度值降低，而重度火干扰导致直径分布正偏显著，中度火干扰恢复15，兴安落叶松林分直径分布呈负偏低峰态趋势。
（2）火干扰改变了兴安落叶松直径生长对温度和降水变化的响应，并表现出明显的“滞后响应”。火干扰程度增加，当年生长季温度和上年生长季降水促进生长，冬季温度、当年生长季降水和冬季降水抑制生长作用增强；火干扰后恢复时间延长，当年生长季温度和上年生长季的降水促进生长，冬季温度和冬季降水抑制生长作用更显著。
（3）基于直径生长-气候关系的火干扰下直径结构动态表明在频繁的高强度火干扰影响下，大兴安岭地区兴安落叶松直径结构将向中小径级发生移动，同时火干扰后的恢复速度将会大幅度减缓，兴安落叶松直径结构将呈现正偏，高峰态分布，因此，在研究火干扰对林分直径结构影响时需要考虑对气候因子的差异性响应关系，进而为当地火干扰迹地恢复提供更加科学的经营管理意见。

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CHEN Junyu

LIU Mingqian

YANG Jing

WANG Anbin

MA Shenyuan

GAO Lushuang

National Key Research and Development Program of China（2017YFC0504003-1）

Journal of Earth Environment