The dynamics and carbon implications of fires in the Andes

火是自然生态系统中生物群落结构形成、生物群落退化、大气污染和碳排放的主要媒介。在这个建议中，我们将把注意力集中在一个潜在的重要的，但几乎没有研究的生态系统：热带山地云雾森林（TMCFs）的安第斯山脉的火动力学。在安第斯山脉，潮湿的TMCF位于高度易燃的高海拔干燥草原（普纳）下方，这些草原数千年来一直遭受人为火灾的反复发生，树木线位于大约3000米处。这条树线是一个生态和气候紧张的区域：一方面，气温上升和云层高度可能有一种将生态交错带向上推的趋势，鼓励森林向普纳扩张。另一方面，普纳地区日益干旱（由于气温上升和蒸散，也可能由于降水减少），加上人为压力加剧，使火灾发生率和对云雾林的渗透率增加。有大量的证据表明，这样的火灾现在广泛存在于安第斯TMCFs，但是，很少有系统的研究这些火灾事件，因为这个研究系统的偏远。我们对卫星数据的分析表明，安第斯山脉的火灾可能正在大量增加，并显示出神秘的五年周期。火灾增加的趋势在海拔2000米以上特别明显，这可能与潜在蒸腾速率随温度上升而上升时水压力增加有关。鉴于火灾的发生率越来越高，我们推测，越来越多的火灾正从普纳地区向周围的TCMF移动，这些TCMF正在退化为草地或灌木群落。TMCF含有大量的碳，并且它们通过火灾的损失是二氧化碳和其他燃烧化合物到大气中的潜在的大来源。无论是碳储存量还是燃烧损失量，都与低地亚马逊雨林非常相似，但在山区，几乎所有的损失都来自土壤有机层。在这项提案中，我们将进行第一次详细评估的空间和时间动态的火灾在安第斯树线，并试图量化其对碳排放的影响。我们将集中在秘鲁南部的一个密集的研究区域安第斯山脉（在和周围的马努国家公园），在那里我们将确定火灾点火和蔓延的环境控制，量化与特定火灾相关的碳排放和恢复时间，并评估遥感数据的潜力，以扩大火灾排放到更广泛的安第斯地区。我们的项目将涉及以下组件：1. 2.制作详细的火灾历史和安第斯森林线地区火灾地图，涵盖1990-2011年期间;对2009-2011年期间我们研究区域的所有火灾进行密集跟踪和评估。3.测量未燃烧和燃烧森林的生物量和碳储存量4.在燃烧前在森林中安装一些碳块，并在燃烧后访问它们。进行干燥和点燃实验，以确定在树线6处的可燃性阈值。使用我们详细的现场数据来评估和校准基于卫星的火灾发生率，范围和强度的估计。利用校准的卫星数据估算热带安第斯山脉火灾的碳排放

Fire in natural ecosystems is a major agent of biome structure formation, biome degradation, atmospheric pollution and carbon emission. In this proposal we will focus attention on fire dynamics on a potentially important but barely studied ecosystem: the tropical montane cloud forests (TMCFs) of the Andes. In the Andes, humid TMCFs sit immediately below highly flammable, high altitude dry grasslands (the puna) that have suffered from recurrent anthropogenic fires for millennia, with the treeline sitting at approximately 3000 m. This treeline is a zone of ecological and climatic tension: on the one hand, rising temperatures and cloud heights may have a tendency to push the ecotone upwards, encouraging forest expansion into the puna. On the other hand, increased aridity in the puna (driven by rising temperates and evapotranspiration, and possibly by reducing precipitation), coupled with intensified human pressure, is increasing fire occurrence and penetration into the cloud forest. There is plentiful evidence that such fires are now widespread in Andean TMCFs However, there have been few systematic studies of these fire events because of the remoteness of this study system. Our analysis of satellite data has shown that Andean fires may be increasing in abundance, and display a mysterious five year cycle. The tendency to increased fires is particularly marked at elevations above 2000m, and may be linked to increasing water stress as potential transpiration rates rise in response to rising temperatures. Given the increasing occurrence of fire, we conjecture than an increasing number of fires are therefore moving down from the puna region towards the surrounding TCMFs, which are being degraded into grasslands or shrub communities. TMCFs contain a large stock of carbon, and their loss through fire is a potential large source of carbon dioxide and other combustion compounds to the atmosphere. Both the carbon stock and the loss on ignition are very comparable to those from a lowland Amazonian rainforest, but in the mountains almost all of this loss comes from soil organic layers. In this proposal we will conduct the first detailed evaluation of spatial and temporal dynamics of fire at the Andean treeline, and attempt to quantify their implications for carbon emissions. We will do this by focussing on an intensive study region in the southern Peruvian Andes (in and around Manu National Park), where we will determine the environmental controls on fire ignition and spread, quantify the carbon emissions and recovery times associated with specific fires, and evaluate the potential of remote sensing data to scale up fire emissions to the wider Andean region. Our project will involve the following componets: 1. Construction of the fire detailed fire history and fire map of a region of the Andean treeline, covering the period 1990-2011; 2. Conducting intensive tracking and evaluation of all fires in our study region in the period 2009-2011. 3. Measuring the biomass and carbon stocks in unburned and burned forests 4. Installing some carbon plots in forests prior to burn, and visiting them afterwards 5. Conducting drying and ignition experiments to determine thresholds of flammability at the treeline 6. Using our detailed field data to evaluate and calibrate satellite-based estimates for fire occurrence, extent and intensity 7. Using calibrated satellite data to estimate carbon emissions from fires across the tropical Andes