Apportionment study of calcium nutrition of boreal tree species

本研究的目的是评估钙（Ca）营养对北方针叶林树木生长的作用。密集的森林采伐可能有利于增加钙从生态系统的输出，以至于钙可能在氮之前限制在树木上。空气污染的加剧，加上雨水酸度的增加和钙的浸出，只会加剧钙的出口。因此，有人认为，如果钙的出口量超过自然或通过施肥添加的量，空气污染和/或商业北方森林的叶面钙缺乏和随后的健康问题/生长下降将会发生。这些森林生长在粗糙的酸性土壤上，土壤矿物风化会缓慢释放钙，因此，树木中的钙是那些因风化而被调动到土壤溶液中的钙的范式正在受到研究的挑战，研究表明，在一些生态系统中，大气来源的钙对树木的贡献非常大，而且树木几乎完全与来自深层土壤来源的钙分离。因此，今后五年的目标将是确定具有不同功能特征的加拿大和斯堪的纳维亚北方树种促进土壤矿物风化的能力，并在可用性低和/或激烈竞争（缺乏）时利用释放的Ca。申请人的计划是利用碱土元素比例和锶同位素作为示踪剂来研究钙的营养。树种将在生长室内和田间沿着土壤肥力、植物竞争和生产力的梯度进行研究。然后，这些结果将用于寻找钙供应和树木生长的最佳指标，并将其应用于以永久场地变量（例如，气候和排水）和氮为驱动变量的景观生产力模型中。从森林管理的角度来看，这些指标很重要，因为它们将使科学家和森林管理者能够更好地预测林分的增长率，从而更好地规划森林利用。从长远来看，这项研究将有助于确定中国的一些林分是否对出口敏感，以及这些森林的完整性是否因采伐而受到损害。

The goal of this research is to assess the role of calcium (Ca) nutrition on tree growth in boreal forests. Intense forest harvesting practices may favor increased exports of Ca from the ecosystem to a point that Ca may become limiting to trees before nitrogen. Increased air pollution with a concomitant increase in rain acidity and leaching of Ca will only exacerbate its export. It has therefore been suggested that foliar Ca deficiencies and subsequent health problems/growth declines will occur in air polluted and/or commercial boreal forests if Ca exports are in excess of those added naturally or by fertilization. These forests grow on coarse-textured acidic soils that slowly release Ca from soil mineral weathering and thus, the paradigm that the Ca in trees are those mobilized into the soil solution from weathering is being challenged by studies showing that contributions of atmospherically derived Ca to the trees in some ecosystems is very large and that the trees are almost fully decoupled from Ca coming from deeper soil sources. The next five years will therefore aim at determining the capacity of Canadian and Scandinavian boreal tree species with different functional traits to promote soil mineral weathering and make use of the released Ca when availability is low and/or being intensely competed for (deficient). The applicant's plan is to investigate Ca nutrition by using alkali earth element ratios and strontium isotopes as tracers. Tree species will be studied in growth chambers and in the field along gradients of soil fertility, plant competition, and productivity. The results will then be used to find the best indicators of Ca supply and tree growth and implement them in landscape productivity models with permanent site variables (e.g., climate and drainage) and nitrogen as driver variables. These indicators are important from a forest management perspective as they will allow scientists and forest managers to better forecast growth rates of forest stands and therefore, make better planning of forest utilization. In the long term, this research will help identify if some stands are sensitive to exports in Ca and whether the integrity of these forests is jeopardized by harvesting.