Paleoecological studies across northwestern Canada

加拿大西北部在过去50年里经历了加拿大最大的变暖，许多树状气候学研究也表明，20世纪可能是过去3个世纪或更长时间里最温暖的时期。气候模拟实验表明，在本世纪，该地区的气温将继续上升。气温的这种上升可能对北方生态系统产生重大影响，包括改变一些生物群落的组成和位置，改变生物群落对气候的反应，或可能改变干扰事件的频率和强度。本研究将有三个主要目标：1.确定北部林线树木生长的控制措施。为了研究这一点，将使用自动点树度计以非常高的时间分辨率(每15分钟)测量树木的生长。在麦肯齐三角洲东部地区的生长季节。现场气候数据也将使用便携式气象站收集。气候数据将被用来开发树木生长的机械模型，这将极大地提高我们对气候-生长关系的理解。2.研究树木年轮生长记录中替代指标在过去气候研究中的应用。鉴于树木生长和气候之间的差异，需要研究替代数据来源，以准确重建过去的气候，并将最近的气候变化放在长期背景下考虑。我们将在最初工作的基础上，开发来自树木年轮的稳定碳和氧同位素的年度解析记录。我们希望从加拿大西北部开发一个千年长度的同位素记录，这样就可以比较最近的变暖和所谓的中世纪暖期。3.确定森林火灾的自然频率和火灾对加拿大西北部北方类型森林演替和发展的影响。利用高分辨率湖泊沉积物记录、树木建树和火痕记录，我们将重建全新世的火灾频率。这些类型的记录将帮助我们更好地限制加拿大西北部的自然火灾频率。

Northwestern Canada has experienced the greatest warming in Canada during the past 50 years and numerous dendroclimatological studies also suggest that the 20th century may have been the warmest period during the past 3 centuries or more. Climate modeling experiments suggest temperatures will continue to increase in this region during the current century. Such increases in temperature are likely to have dramatic impacts on northern ecosystems, including altering the composition and position of some biomes, altering the response of biotic communities to climate or possibly changing the frequency and intensity of disturbance events. This research will have three main objectives: 1. Determining the controls on tree growth at northern treeline. To investigate this automatic point dendrometers will be used to measure tree growth at very high temporal resolution (every 15 mins.) during the growing season in the eastern Mackenzie Delta region. Onsite climate data will also be collected using a portable weather station. The climate data will be used to develop a mechanistic model of tree growth which will greatly improve our understanding of climate-growth relations. 2. Investigating the utility of alternative proxy indicators from tree ring growth records for studies of past climate. Given divergence between tree growth and climate, alternative data sources need to be investigated to develop accurate reconstructions of past climate and to put recent climate change in a long term context. We will expand on our initial work developing annually resolved records of stable carbon and oxygen isotopes from tree rings. We hope to develop a millennial length isotope record from northwestern Canada so that comparisons can be made between recent warming and the so-called Medieval Warm Period. 3. Determining the natural frequency of forest fires and the impact of fire on succession and development in boreal type forests of northwestern Canada. Using high-resolution lake sediment records and tree establishment and fire scar records we will reconstruct fire frequency during the Holocene. These types of records will help us better constrain the natural fire frequency in the northwest of Canada.