NSFDEB-NERC:Tropical deadwood carbon fluxes: Improving carbon models by incorporating termites and microbes

该项目的目标是测量热带枯枝（粗木质残体;CWD）周转率，并确定在当前和未来气候条件下决定CWD碳（C）命运的机制。木本植物是最大的地上陆地生物碳库，CWD生物量可能很大，但估计不足。我们对周转率的了解大多来自温带系统，在那里CWD被认为是缓慢的循环。尽管活树生物量很大，但对热带CWD库和周转率知之甚少。由于气候的差异（温暖的温度，有时更大的降水），木材结构，和损失途径（白蚁的作用越来越大），这是可能的CWD是动态的热带系统。该项目结合了领域，分子和建模方法在热带澳大利亚，白蚁和真菌是木材周转的关键代理商。从热带雨林到热带稀树草原的连续森林带，加上现有的长期数据和基础设施，使其成为一个理想的地点。什么控制CWD C的周转率？周转率将由白蚁和真菌活动决定，这取决于气候和木材结构。温暖和潮湿的条件下，应增加营业额，但白蚁应增加营业额相对更多的干燥条件下，因为他们有水的保护策略。密度高的木材腐烂得慢一些。Q2.是什么控制了CWD中C的命运？C命运（CO2，CH 4，有机残留物）将取决于白蚁和微生物群落的腐烂阶段和功能组成。腐烂的后期阶段，增加产甲烷菌，减少甲烷氧化物和白蚁种类的变化应导致更大的CH 4：CO2。当C通过白蚁损失时，将发生更大的有机残留物形成。Q3.在气候变化下，木材周转机制如何影响生态系统水平的C通量？澳大利亚北方气候变暖将增加周转率并改变木材的碳命运。迄今为止，CWD在地球系统模型中的参数化程度很低（例如，CWD仅通过物理碎裂衰变）。第一季度和第二季度的现场数据将用于驱动气候变化下木材周转和温室气体（GHG）产生的新预测模型。为了测试Q1和确定相对腐生物和白蚁腐烂率对降水变化的响应，将在6个地点放置已知吸引白蚁的新型基质（辐射松）块（降雨梯度实验）。块将被封闭在细网中，有或没有孔，以控制白蚁的进入;块将在4年的雨季和旱季结束时收获。为了确定木结构对腐烂的影响，将10个物种/地点的复制日志类似地封闭放置在热带雨林和萨凡纳稀树草原的网站（共同花园实验）。将在两个雨季和两个旱季结束时收获甘蔗。对于原木/木块，将测量初始和最终质量、密度和化学成分。当地气象站将提供气候数据。为检验Q2，将采集木材子样和木材中的白蚁，以确定白蚁群落、微生物群落和功能基因组成以及有机残留物的形成。CO2和CH 4将被测量收获的原木/块。由于部分白蚁生活在土丘中，因此将建立实验土丘（白蚁中尺度实验），每月测量土丘昼夜CO2和CH 4通量，为期1年。为了测试Q3，现场数据将被纳入woodCLM，这是一个来自社区土地模型的生态系统模型。利用woodCLM模拟未来气候情景下的木材动态和温室气体排放

Objectives of this project are to measure rates of tropical deadwood (coarse woody debris;CWD) turnover and identify mechanisms that determine fates of CWD carbon (C) under currentand future climates. Woody plants are the largest aboveground terrestrial biotic C store,and CWD biomass is likely substantial but poorly estimated. Much of our knowledge of turnovercomes from temperate systems, where CWD is thought to be slow cycling. Less is known abouttropical CWD pools and turnover, despite large living tree biomass. Due to differences inclimate (warmer temperatures and sometimes greater precipitation), wood construction, andloss pathways (increasing role of termites), it is likely that CWD is dynamic in tropicalsystems. This project combines field, molecular, and modeling approaches in tropical Australia,where termites and fungi are key agents of wood turnover. A continuous belt of forest fromrainforest to savanna with existing long-term data and infrastructure makes it an ideal location.Three questions will be addressed: Q1. What controls rates of CWD C turnover? Turnover rateswill be determined by termite and fungal activity, which are dependent on climate and woodconstruction. Warmer and wetter conditions should increase turnover, but termites should increaseturnover relatively more in dry conditions as they have water conservation strategies. Densehighly lignified wood should decay more slowly. Q2. What controls fates of C from CWD? C fates(CO2, CH4, organic residues) will depend on stage of decay and functional composition of termiteand microbial communities. Later stages of decay, increased methanogens, decreased methanotrophsand changes in termite species should result in greater CH4:CO2. Greater organic residue formationwill occur when C loss is via termites. Q3. How do mechanisms of wood turnover scale up toaffect ecosystem-level C fluxes under climate change? Climate warming in Northern Australiawill increase turnover rates and alter C fates of wood. To date, CWD is poorly parameterizedin Earth system models (e.g., CWD decays only via physical fragmentation). Field data fromQ1 and Q2 will be used to drive new predictive models of wood turnover and greenhouse gas(GHG) production under climate change. To test Q1 and determine relative saprobic microbeand termite decay rates in response to precipitation variation, blocks of a novel substrate(Pinus radiata) known to attract termites will be placed at 6 sites (Rainfall gradient experiment).Blocks will be enclosed in fine-mesh with or without holes manipulating termite access; blockswill be harvested at end of wet and dry seasons for 4 years. To determine influence of woodconstruction on decay, replicate logs of 10 species/site similarly enclosed will be placedat rainforest and savannah sites (Common garden experiment). Logs will be harvested at endof 2 wet and 2 dry seasons. For logs/blocks, initial and final mass, density and chemistrywill be measured. Local weather stations will provide climate data. To test Q2, wood subsamplesand termites in wood will be collected to determine termite community, microbial communityand functional gene composition, and organic residue formation. CO2 and CH4 will be measuredfor harvested logs/blocks. As some termites live in mounds, experimental mounds (Termite mesocosmexperiment) will be established and mound diel CO2 and CH4 fluxes will be measured monthlyfor 1 yr. To test Q3, field data will be incorporated into woodCLM, an ecosystem model derivedfrom the Community Land Model. Results from the modified and original models will be compared.Using woodCLM, wood dynamics and GHG emissions will be simulated under future climate scenarios