【目的】明确土壤水碳特征和林木水碳生理过程对抚育间伐的响应机制,为速生树种高效结构调控技术的优化提供理论参考。【方法】以华北平原8年生三倍体毛白杨S86[(Populus tomentosa×P. alba var. pyramidalis)×(P. alba×Populus canadensis)]人工林为研究对象,设置3种间伐强度:不间伐(NT)、隔行间伐(间伐50%,T50)、隔行隔株间伐(间伐75%,T75)。分析间伐后毛白杨叶片水分性状、气体交换参数、非结构性碳水化合物的变化规律及土壤水碳分布特征,从而探究不同间伐强度下土壤水碳特征与林木水碳生理过程的关系。【结果】①土壤含水率和土壤有机碳含量间存在显著的负相关关系(P<0.05)。整体来看,土壤含水率和有机碳含量均受到间伐的调控,随着土层深度的增加,土壤含水率逐层升高,有机碳含量逐层递减。②间伐后短期时间内,毛白杨的蒸腾速率发生改变,随着间伐强度的增加,蒸腾速率先升高后降低,其中T50处理的叶片蒸腾速率相比T75处理高40.94%,但其他气体交换参数并不受间伐的短期效应影响。③间伐后短期时间内叶片的碳、氮含量和非结构性碳水化合物含量变化并无显著差异,其质量分数分别为470.01~511.85、21.30~22.53、102.31~113.65 g/kg。④间伐能调控林木形成更大的树冠并显著促进林木胸径的增长(P<0.05),随着间伐强度的增加,这种促进作用更明显。⑤叶片光合速率和土壤有机碳含量呈极显著正相关关系(P<0.01),土壤有机碳含量正向影响叶片的光合过程从而促进林木生长,而土壤水分负向调控叶片水分生理过程从而抑制林木生长。【结论】抚育间伐对土壤水、碳含量的影响不同,且不同土层深度的土壤水、碳含量存在差异。间伐后短时间内,土壤水、碳含量的改变并未引起毛白杨叶片净光合速率、水分性状、养分含量和非结构性碳水化合物的改变。林木将养分和光合产物转移到林木枝、干等储存器官从而增加了林木胸径和冠幅的生长发育。

【Objective】This research aims to clarify the response mechanism of soil moisture and carbon characteristics and forest water-carbon physiological processes to thinning, and provide a theoretical reference for the optimization of efficient structural control technology of fast-growing tree species.【Method】Taking 8-year-old triploid P. tomentosa S86 ((Populus tomentosa×P. alba var. pyramidalis)×(P. alba×Populus × canadensis)) plantations in the North China Plain as the research object, three thinning intensities were set: no thinning (NT), alternate row thinning (50% thinning, T50), and alternate row and alternate tree thinning (75% thinning, T75). We analyzed the changes in leaf water traits, gas exchange parameters, and non-structural carbohydrates of P. tomentosa after thinning, as well as the distribution characteristics of soil moisture and carbon, to explore the relationship between soil moisture and carbon characteristics and the physiological processes of water and carbon in trees under different thinning intensities.【Result】(1) A significant negative correlation was found between soil moisture content and soil organic carbon content(P<0.05). Overall, both soil moisture content and organic carbon content were regulated by thinning. As the soil depth increased, the soil moisture content increased layer by layer, while the organic carbon content decreased layer by layer. (2) In the short period after thinning, the transpiration rate of P. tomentosa changed. As the thinning intensity increased, the transpiration rate first increased and then decreased. Among them, the leaf transpiration rate of the T50 treatment was significantly increased by 40.94% compared with the T75 treatment, but other gas exchange parameters were not affected by the short-term effects of thinning. (3) There was no significant difference in the carbon, nitrogen content and non-structural carbohydrate content of leaves in the short period after thinning. Their mass fractions were 470.01-511.85, 21.30-22.53, and 102.31-113.65 g/kg, respectively. (4) Thinning could regulate forest trees to form a larger canopy and significantly promoted the growth of tree diameter at breast height (P<0.05). As the thinning intensity increased, this promoting effect became more obvious. (5) There was a significant positive correlation between leaf photosynthetic rate and soil organic carbon (P<0.01). Soil organic carbon content positively affected the photosynthetic process of leaves and thereby promoted forest growth, while soil moisture negatively regulated leaf water physiological processes and inhibited forest growth.【Conclusion】Tending thinning had different effects on soil moisture and carbon content, and there were differences in soil water and carbon content at different soil depths. In the short time after thinning, changes in soil water and carbon content did not affect in the net photosynthetic rate, water status, nutrient content and non-structural carbohydrates of P. tomentosa leaves. Forest trees transferred nutrients and photosynthetic products to storage organs such as tree branches and trunks, thereby increasing the growth and development of tree diameter at breast height and crown width.