长白落叶松再造林的清林效应形成机制

Stand cleaning including pre commercial logging residual removals after pre-commercial thinning, a major forest operation in northeast China, can influence the quantity of coarse woody debris and lead to increased heterogeneity of micro-environment in the forest ecosystems. Logging residual removals influence soil moisture and nutrients, stand structure and dynamics. How logging residue removals affect on long-term site productivity, however, is poorly understood. To fill this gap, the responses of stomatal characteristics to logging residue removals and fertilization will be investigated. This research will use the plots that have been established in two types of larch forests (secondary forest and larch plantation) with different thinning, logging residue treatment and nutrient addition, and measure numerical parameters related to stomatal and soil physical and chemical characteristics, plant secondary compounds, organic carbon components, soil microorganism composition and functional gene biodiversity, carbon and nitrogen mineralization, sap flow density, carbon and nitrogen stable isotope. The variations of stomatal characteristics, its inducement and its relation to gas exchange characteristic will be analyzed. Timing of the thinning and its effect on stand productivity will be examined. The effects of different logging residual treatments after thinning on the productivity of larch plantations will be analyzed at different temporal (daily, monthly, yearly) and spatial scales (needle, tree, stand), in viewpoint of site environmental change, nutrient cycle, morphological response and physiological process. The findings of this study will develop and deliver science-based information to forest managers for plantation management.

清林是当前东北森林主要作业方式，影响林内粗木质残体数量，改变林地微环境。清林后林分长期生产力响应及其生理生态学机制还不清楚，尚无系统科学数据予以支持。本研究以两种造林地类（杨桦次生林和落叶松人工林皆伐迹地）的长白落叶松再造林为对象，依托定量间伐后的长期固定样地（60年），结合抚育清林后剩余物留地／移出林地基础上的养分添加试验，通过调查分析气孔参数、土壤理化特性和次生代谢物含量及有机碳组成、微生物组成和功能基因多样性、碳氮矿化速率、树干液流密度和树轮纤维素碳氧稳定同位素组成，揭示气孔参数的变化规律及影响因素；量化针叶气体交换特征响应；评价适时间伐和延迟间伐对林分长期生产力影响；以气孔功能为重心，围绕立地变化、养分循环过程、形态响应和生理生态过程调整，从不同时间（日-月-年）和空间（针叶-单木-林分）尺度，阐明清林效应（间伐清林后林分生产力变化）形成机制，为人工林经营技术提供科学依据。

清林是当前东北森林主要作业方式，影响林内粗木质残体数量，改变林地微环境。清林后林分长期生产力响应及其生理生态学机制还不清楚，尚无系统科学数据予以支持。本研究以两种造林地类（杨桦次生林和落叶松人工林皆伐迹地）的长白落叶松再造林为对象，依托五种定量清林（低强度、中强度、高强度、超高强度清林和未清林）的长期固定样地（1958年栽植），结合幼龄林首次清林后剩余物留地／移出林地、中龄林首次四种强度（低强度、中强度、高强度和超高强度清林）和四种清林后林地养分的大剂量配施（施氮肥、施氮磷肥、施氮磷钾肥和仅清林）控制试验，评价了落叶松人工林适时清林和延迟清林后的林木形质、大径木株数和蓄积量及比例、林木死亡率和林分生产力的响应特征，探讨了落叶松近熟林和过熟林适时清林和延迟清林后2020-2021年间超高死亡率（高达91.9%）的原因；通过清林后林冠结构、林内微气象、土壤物理和化学特性、表层土壤细菌和真菌群落组成、多样性和功能基因多样性、林木蒸腾耗水量（2019-2021年153株落叶松树干液流密度数据）和林木水分利用效率（1961-2021年的树轮纤维素碳稳定同位素组成）的响应变化，探讨了落叶松人工林清林效应（间伐清林后林分生产力变化）形成机制，旨在为提高东北落叶松人工林林分生产力、筛选改善林木形质的集约化经营技术，尤其是采用适度、适时的清林强度提高落叶松人工林抵抗灾害性因素的能力、降低气候变化背景下人工林中落叶松的死亡风险提供科学依据。

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