Incentivising fire management in Pindan (Acacia shrubland): A proposed fuel type for Australia's Savanna burning greenhouse gas emissions abatement methodology

The Australian Government has sanctioned development of greenhouse gas emissions (GHG) abatement methodologies to meet international emissions reduction obligations. Savanna burning emissions abatement methodologies have been available since 2012, and there are currently 72 registered projects covering approximately 32 million ha. Abatement to date has exceeded 4 million tonnes of carbon dioxide equivalent (CO2‐e) principally through the application of low intensity early dry season fire management to reduce the amount of biomass combusted in higher intensity late dry season (LDS) fires. Savanna burning projects can only be conducted on areas with eligible fire‐prone vegetation fuel types where implementing the improved fire management regime is considered ecologically appropriate. This study assesses the suitability of including tall Acacia shrublands (‘Pindan’) as a new eligible fuel type. These shrublands make up 12% (~2 million ha) of the Kimberley region, Western Australia, where, on average, 32% is fire affected annually, mostly in the LDS. A standard assessment protocol was applied to describe vegetation fuel type structural and pyrolysis characteristics. We show that Pindan (i) can be identified and mapped as a unique tall Acacia shrubland vegetation fuel type, (ii) characterised by a significantly greater shrubby fuel load biomass, and (iii) the conservation status of which would benefit from imposition of strategic prescribed burning programme. Savanna burning projects in the Pindan fuel type could potentially abate up to 24.43 t.CO₂‐e/km² per year, generating significant income and employment opportunities for predominantly Indigenous land managers in the region.     

我国林火发生预测模型研究进展

通过文献回顾,总结了国内林火发生预测模型的研究现状,并从林火发生驱动因子、林火发生概率预测模型、林火发生频次预测模型和模型检验方法等方面进行归纳分析。得出以下结论: 1)气象、地形、植被、可燃物、人类活动等因素是影响林火发生及模型预测精度的主要驱动因子;2)林火发生概率模型中,地理加权逻辑斯蒂回归模型考虑了变量之间的空间相关性,Gompit回归模型适宜非对称结构的林火数据,随机森林模型不需要多重共线性检验,在避免过度拟合的同时提高了预测精度,是林火发生概率预测模型的优选方法之一;3)林火发生频次模型中,负二项回归模型更适合对过度离散数据进行模拟,零膨胀模型和栅栏模型可以处理林火数据中包含大量零值的问题;4)ROC检验、AIC检验、似然比检验和Wald检验方法是林火概率和频次模型的常用检验方法。林火发生预测模型研究仍是我国当前林火管理工作的重点,预测模型的选择需要依据不同地区林火数据特点。此外,构建林火预测模型时需要考虑更多的影响因素,以提高模型预测精度;未来,需要进一步探索其他数学模型在林火发生预测中的应用,不断提高林火发生预测模型的准确度。     

森林可燃物及其管理的研究进展与展望

森林可燃物是森林生态系统的基本组成部分, 是影响林火发生及火烧强度的重要因素之一, 因此, 受到国内外学者的广泛关注。该文从以下4个方面综述了国内外可燃物研究的最新进展: 森林可燃物特性, 森林可燃物类型与火行为, 森林可燃物类型、载量的调查与制图, 森林可燃物管理。同时提出了我国森林可燃物今后的研究方向: 开展多尺度可燃物研究; 可燃物类型与火行为的研究; 把以试验观测为基础的静态研究与以空间技术和生态模型为基础的动态预测相结合, 研究可燃物处理效果; 全球气候变化背景下可燃物处理与碳收支。     

Woody overstorey effects on soil carbon and nitrogen pools in South African savanna

Abstract Woody plant encroachment in savannas may alter carbon (C) and nitrogen (N) pools over the long‐term, which could have regional or global biogeochemical implications given the widespread encroachment observed in the vast savanna biome. Soil and litter %C and %N were surveyed across four soil types in two encroached, semi‐arid savanna landscapes in northern South Africa. Litter at sampling points with a woody component had a higher %N and lower C : N ratio than litter at solely herbaceous points. Severely encroached areas had lower C : N ratios throughout the soil profile than less encroached areas. Soil %C and %N were highly influenced by soil texture but were also influenced by the presence of a woody overstorey, which increased surface soil %C on three soil types but decreased it on the most heavily encroached soil type. Soil C sequestration may initially increase with bush encroachment but then decline if bush densities become so high as to inhibit understorey grass growth.     

基于FWI湿度码的塔河林业局地表凋落物含水率预测

加拿大火险天气指标系统(FWI)是目前世界上应用最广的火险天气系统,其可燃物含水率预测方法成为一种重要的研究方法.本文以黑龙江省大兴安岭地区塔河林业局典型林分为研究对象,通过野外地表凋落物含水率的连续观测,分析了凋落物含水率与FWI系统3个湿度码\[细小可燃物湿度码（FFMC）、枯落物下层湿度码（DMC）、干旱码（DC）\]之间的关系.结果表明： 对于研究地区8个样地单独取样的地表凋落物,用FWI系统的湿度码FFMC所建立的线性预测方程的平均绝对误差和平均相对误差分别为14.9%和70.7%,低于气象要素回归模型,说明采用FWI湿度码来预测地表凋落物含水率具有一定优势,可用于预测可燃物含水率,但这种优势是有限的.今后应加强对FWI系统在我国应用的修正工作,特别是雨后可燃物湿度码的修正.     

大兴安岭北部地区原始林火干扰历史的研究

在大兴安岭阿龙山林业局的一个集水区,通过样地法（９６个样地）,调查了大量的火疤木,研究了景观水平上的火状况。结果表明,由１８２５至１９９３年间样区共发生１４次火灾,火烧种类主要是地表火,但也有少量树冠火;火烧强度主要为弱度火;火场面积通常很大;火烧平均间隔期为３７ａ,火烧轮回期的约３０ａ。这些指标对大于大兴安岭北部林区有一定的代表意义。大兴安岭北部林区的火状况主要决定于兴安落叶松的抗火特性和森林群     

Forest biogeochemistry in response to drought

Trees alter their use and allocation of nutrients in response to drought, and changes in soil nutrient cycling and trace gas flux (N₂O and CH₄) are observed when experimental drought is imposed on forests. In extreme droughts, trees are increasingly susceptible to attack by pests and pathogens, which can lead to major changes in nutrient flux to the soil. Extreme droughts often lead to more common and more intense forest fires, causing dramatic changes in the nutrient storage and loss from forest ecosystems. Changes in the future manifestation of drought will affect carbon uptake and storage in forests, leading to feedbacks to the Earth's climate system. We must improve the recognition of drought in nature, our ability to manage our forests in the face of drought, and the parameterization of drought in earth system models for improved predictions of carbon uptake and storage in the world's forests.     

新疆玛纳斯热气泉免培养土壤细菌多样性分析

【目的】了解新疆玛纳斯热气泉土壤免培养细菌群落组成及多样性。【方法】采用免培养法直接从土壤样品中提取总DNA,利用细菌通用引物对土壤总DNA进行16S rDNA扩增,构建细菌16SrDNA文库。使用HaeⅢ限制性内切酶对阳性克隆进行限制性片段长度多态性分析(restriction fragment length polymorphism,RFLP),挑选具有不同酶切图谱的克隆进行测序、比对并构建16SrDNA系统发育树。【结果】从土壤细菌16S rDNA文库中随机挑选了170个阳性克隆,共得到29个不同的分类单元(operational taxonomic unit,OTU)。系统发育分析归为6个门:酸杆菌门(Acidobacteria)、放线菌门(Actinobacteria)、拟杆菌门(Bacteroidetes)、厚壁菌门(Firmicutes)、变形菌门(Proteobacteria)和浮霉菌门(Planctomycetes)。其中厚壁菌门(Firmicutes)为绝对优势类群,占整个细菌文库的71%。29个OTUs中有14条序列与GenBank中相关序列的相似性低于97%(序列长度约1.5kb),占序列总数的48%。【结论】热气泉土壤细菌种群多样性较低,但存在大量潜在细菌新种。