Climate control of wood formation measured at high precision in a southern boreal pioneer and a climax tree species (Larix sibirica and Betula platyphylla)

在南方北方先锋树种和顶峰树种（西伯利亚落叶松和白桦）中高精度测量木材形成的气候控制

基本信息

批准号：
328288092
负责人：
Dr. Choimaa Dulamsuren
金额：
--
依托单位：
Professur für Angewandte Vegetationsökologie
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2016
资助国家：
德国
起止时间：
2015-12-31 至 2020-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/328288092?language=en
关键词：
Climate control wood formation measured

项目摘要

Boreal forests suffer increasingly from summer drought as the result of climate warming, whereas originally they were limited by low summer temperatures and low nitrogen availability in most of their distribution range. The mechanisms leading to widespread growth limitations due to summer drought and to reduced annual stem increment with progressive climate warming are insufficiently known.In the proposed project, we want to elucidate the causalities behind the drought limitation of wood formation. We therefore want to study cambial activity (i.e. cell division) and xylem differentiation (including cell enlargement, wall thickening, and lignification) at high temporal resolution. The study will be carried out at the southern edge of the boreal forest in Inner Asia in Mongolia, where forests border on grasslands in the forest-steppe ecotone. In this region, most boreal forests are drought-limited since ever and forest health and productivity has been declining since the late 20th century due to climate warming. We plan to collect microcores of stemwood weekly for the detailed analysis of xylem formation. These investigations are combined with analyses of microclimate, tree water relations (shoot water potential, xylem sap flow) and the levels of stored non-structural carbohydrates (NSC) in the stem. Cambial activity is further related to phenological observations, especially to bud break. The studies will be carried out in pure and mixed stands of Siberian larch (Larix sibirica) and Siberian silver birch (Betula platyphylla). Larch is the dominant climax tree species, whereas birch is the dominant broadleaved pioneer tree species at disturbed sites of the southernmost boreal forests in Mongolia.The key hypotheses tested address the causality behind the observed drought-related long-term trends toward reduced earlywood and latewood formation in the two tree species. We hypothesize that stemwood formation is limited at the start of the growing season by the lack of stored assimilates from the previous growing season. Warmer and drier summers should result in reduced annual carbon gain, leading to reduced NSC storage over winter, which is thought to be a key factor causing reduced earlywood formation in the subsequent growing season. We further hypothesize that cambial activity and xylem differentiation in the late growing season are limited directly by low water availability. The presence of birch trees, which are promoted by natural and anthropogenic disturbances, is hypothesized to increase the drought stress experienced by larch due to asymmetric interspecies competition for water.

由于气候变暖的结果，北方森林受到夏季干旱的越来越多，而最初受到夏季温度低的限制和在其大部分分布范围内的氮供应率低。由于夏季干旱而导致广泛生长限制并随着渐进的气候变暖而减少茎的增量的机制不足以熟悉。在拟议的项目中，我们希望阐明木材形成干旱限制背后的因果关系。因此，我们希望在高时空分辨率下研究牙周活性（即细胞分裂）和木质部分化（包括细胞增大，壁增厚和木质化）。该研究将在蒙古内亚洲北方森林的南部边缘进行，森林在森林steppe Ecotone的草原上接壤。在该地区，大多数北方森林都是自有限制的，因为由于气候变暖，自20世纪后期以来，森林健康和生产力一直在下降。我们计划每周收集茎木每周的微孔，以详细的木质部形成分析。这些研究与微气候，树水关系的分析（芽水势，木质部SAP流动）和茎中储存的非结构性碳水化合物（NSC）的水平结合在一起。坎巴活动进一步与物候观察结果有关，尤其是芽中断。这些研究将在西伯利亚落叶尔奇（Larix Sibirica）和西伯利亚银桦树（Betula plathyphylla）的纯和混合林中进行。落叶松是主要的高潮树种，而桦木是蒙古最南端北方森林的干扰地点的主要阔叶先锋树种。经过的主要假设检测到了观察到的与干旱相关的长期趋势背后的因果关系，这些因果关系是降低了两种树种的早期木材和莱特伍德形成。我们假设，由于上一个生长季节，由于缺乏储存的同化，Stemwood组在生长季节开始时受到限制。温暖和干燥的夏天应导致年度碳增益减少，导致NSC在冬季的储存减少，这被认为是导致随后生长季节早期形成减少的关键因素。我们进一步假设生长季节后期的牙周活性和木质部分化受到低水量的直接限制。假设由自然和人为障碍促进的桦树的存在可以增加由于水的种间间隙竞争而导致落叶松所经历的干旱压力。