热带季节雨林多花白头树年内径向生长动态及其对环境因子的响应

Intra-annual radial growth of Garuga floribunda in tropical seasonal rain forest and its response to environmental factors in Xishuangbanna,Southwest China

为了解热带地区树木的季节性生长动态和规律,在西双版纳热带季节雨林利用高精度生长仪和微树芯法对落叶树种多花白头树的径向生长季节动态进行监测。结合木质部非结构性碳水化合物和环境因子的监测,分析其形成层活动和径向季节动态的生理生态驱动因子。结果表明:在2020年,生长仪的监测显示,多花白头树于5月底(儒略日DOY:149.3±7.2)开始生长,8月底(DOY:241.0±14.7)生长结束,年生长量为3.12 mm,最大生长速率为0.04 mm·d^(-1)。而微树芯法显示,扩大细胞3月9日(DOY:69.2±6.2)开始出现,9月19日(DOY:262.8±2.8)细胞加厚结束,木质部生长量为1.76 mm,最大生长速率为0.009 mm·d^(-1)。多花白头树径向日生长量与生长季的降水、相对湿度、日最低气温、深度为20 cm的土壤含水量和温度呈显著正相关,而与日最高气温、水汽压亏缺、最大风速和水汽压呈显著负相关。多花白头树边材淀粉含量和可溶性糖含量均在生长季开始之前保持较高水平,淀粉含量在3月底达到最低,而可溶性糖含量5月中旬达到最低,随着生长季的结束淀粉和可溶性糖的含量分别在10月中旬和12月底达到最高。

We examined the seasonal growth dynamics of a deciduous tree species Garuga floribunda in the tropical seasonal rain forest in Xishuangbanna and monitored the stem radial growth with both high resolution dendrometer and microcoring methods.Combining with the monitoring of non-structural carbohydrates(NSCs)in stem and environmental factors,we analyzed the eco-physiological drivers underlying the seasonal cambial activity and radial growth dynamics.The results of high reso-lution dendrometer method showed that the growth of G.floribunda began at the end of May(day of year,DOY:149.3±7.2)and ended at the end of August(DOY:241.0±14.7)in 2020,the annual total radial growth was 3.12 mm,and the maximum growth rate was 0.04 mm·d^(-1).Based on the microcoring methods,we found that xylem cell enlarging started from March 9 th(69.2±6.2)and cell wall thickening ended on September 19 th(DOY:262.8±2.8).The cumulative xylem radial growth was 1.76 mm,and the maximum growth rate was 0.009 mm·d^(-1).The daily radial growth rate of G.floribunda was significantly and positively correlated with precipitation,relative humidity,daily minimum air temperature,soil moisture and temperature at the depth of 20 cm,and was negatively correlated with daily maximum air temperature,vapor pressure deficit,maximum wind speed,and water vapor pressure.The starch and soluble sugar contents in the sapwood of G.floribunda were relatively higher before the growing season.The starch content was lowest in the end of March,while the content of soluble sugars was lowest in middle of May.At the end of the growing season,the contents of starch and soluble sugar in G.floribunda peaked in the middle of October and the end of December,respectively.