Community and Ecosystem Dynamics of the Yukon Boreal Forest

育空地区北方森林的群落和生态系统动态

• 批准号: RGPIN-2014-04189
• 负责人: Krebs, Charles
• 金额: $ 2.48万
• 依托单位: University of British Columbia
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2015
• 资助国家: 加拿大
• 起止时间: 2015-01-01 至 2016-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=587658
• 关键词: Community; Ecosystem; Dynamics; Yukon; Boreal

The boreal forest occupies half of Canada’s landmass and is undergoing marked change because of human-induced climate change and natural variation. Our research in the southwestern part of the Yukon will address the underlying causes for these key changes and their long-term ecological impacts. This part of Canada is a global hotspot for rapid climate change. Physical changes in temperature and rainfall are relatively easy to document and measure, but ecological changes are more complex. The boreal forest is a boom-and-bust ecosystem, driven by cycles in plant and animal production. Our research focuses on three levels. Plant primary production is predicted to be most immediately driven by changes in temperature and rainfall. We developed models that use summer rainfall and temperature to predict the annual crop size of berries (crowberry, bearberry, red bearberry, cranberry), white spruce cones, and above-ground mushrooms. We will develop similar models to predict the growth of the two major shrubs (grey willow, dwarf birch) from rainfall and temperature. If we are to understand the impacts of climate change we must develop these kinds of environmental models for the dominant species of plants and then test the models with subsequent field data. Animal populations in the boreal forest are strongly affected by the 9-10 year cycle of snowshoe hares, the dominant herbivore. We have shown that the hare cycle is driven by a suite of predators that fluctuate in synchrony with the hares, and these fluctuations set the ecological pulse of the boreal zone. The peak density of the snowshoe hare cycle has been slowly collapsing since 1971, a general trend found also in many small rodent cycles in Europe. This collapse has ecosystem consequences with hare browse in winter being reduced, allowing increased shrub growth in the forest understory. One explanation for the collapse of cyclic peaks has been increased predation in winter due to a mismatch in coat colour and snow onset and melt. If hares turn white too soon in the autumn, they become highly visible to predators, with the reverse problem in the spring. We will test this hypothesis with radio-collared hares in collaboration with ecologists working in Montana on the same problem. An alternative hypothesis is that predation has intensified as additional predators (marten, weasels) have become more common in the boreal forest and are increasing the mortality rate of hares. Arctic ground squirrels were a major herbivore in the Yukon boreal forest until 2000 when populations collapsed to virtual extinction. We are studying the landscape ecology of this collapse over a region of 15,000 km2, since ground squirrels remain abundant in some but not all alpine areas but not in forested areas. The alternative hypotheses are that they are held down by predators in the forest or that they are being affected by climate change via winter icing of hibernation sites. By reintroducing ground squirrels into previously occupied habitats we will test the predation model directly. Previous research has determined that stress from repeated unsuccessful predator attacks reduces reproductive rates in snowshoe hares over the population cycle. This work will be followed up by replicating the experiments carried out in the previous 10-year cycle and extending the results to measure how stress affects epigenetic changes in DNA and subsequent brain function in hares. Since the hare cycle is into the increase phase in 2013 we are poised over the next 5 years to advance these studies at the molecular and physiological level. Our overall research objective is to increase our ecological understanding to how boreal forest plants, herbivores, and predators are responding to rapid climate change in northwestern Canada.

北方森林占据了加拿大陆地的一半，由于人类引起的气候变化和自然变化，它正在经历显着的变化。我们在育空地区西南部的研究将解决这些关键变化的根本原因及其长期生态影响。加拿大的这一地区是全球气候快速变化的热点。气温和降雨量的物理变化相对容易记录和测量，但生态变化则更复杂。北方森林是一个起伏不定的生态系统，由动植物生产的循环驱动。我们的研究主要集中在三个层面。据预测，植物初级生产力最直接的驱动因素是气温和降雨量的变化。我们开发了利用夏季降雨量和温度来预测浆果(红莓、熊莓、红熊莓、蔓越莓)、白云杉球果和地上蘑菇的年度作物大小的模型。我们将开发类似的模型，根据降雨量和温度来预测两种主要灌木(灰柳、矮桦)的生长。如果我们要了解气候变化的影响，我们必须为主要植物物种开发这些类型的环境模型，然后用随后的田间数据来测试这些模型。 北方森林中的动物种群受到雪鞋野兔9-10年周期的强烈影响，雪鞋野兔是主要的草食动物。我们已经证明，野兔的循环是由一系列与野兔同步波动的捕食者驱动的，这些波动决定了北方地带的生态脉冲。自1971年以来，雪鞋兔周期的峰值密度一直在缓慢下降，这一普遍趋势也出现在欧洲的许多小型啮齿动物周期中。这种崩塌对生态系统产生了影响，冬季的野兔觅食减少，从而增加了森林下层灌木的生长。周期性高峰坍塌的一种解释是，由于毛色不匹配以及雪的开始和融化，冬季捕食增加了。如果野兔在秋天变白得太快，捕食者就会很容易看到它们，而春天的情况正好相反。我们将与蒙大拿州研究同一问题的生态学家合作，用无线电项圈野兔来检验这一假说。另一种假说是，随着更多的捕食者(貂、黄鼠狼)在北方森林中变得更加常见，并正在增加野兔的死亡率，捕食行为已经加剧。 北极地松鼠一直是育空地区北方森林中的主要食草动物，直到2000年种群崩溃，几乎灭绝。我们正在研究这一面积为15,000平方公里的崩塌的景观生态，因为在一些但不是所有的高山地区，地松鼠仍然很多，但在森林地区不是。另一种假设是，它们是被森林里的捕食者按住了，或者是因为冬眠地点的冬季结冰而受到气候变化的影响。通过将地松鼠重新引入以前占领的栖息地，我们将直接测试捕食模型。 先前的研究已经确定，在种群周期中，来自反复失败的捕食者攻击的压力会降低雪鞋野兔的繁殖率。这项工作的后续工作将复制在前10年周期中进行的实验，并扩展结果，以衡量压力如何影响DNA的表观遗传学变化和随后的兔子大脑功能。由于2013年野兔周期进入增长阶段，我们准备在未来5年在分子和生理水平上推进这些研究。 我们的总体研究目标是增加我们对北方森林植物、草食动物和捕食者如何应对加拿大西北部快速气候变化的生态学理解。