Mondal Nandita, Sukumar Raman
Centre for Ecological Sciences, Indian Institute of Science, Bangalore-560012, Karnataka, India.
Divecha Centre for Climate Change, Indian Institute of Science, Bangalore-560012, Karnataka, India.
PLoS One. 2016 Jul 21;11(7):e0159691. doi: 10.1371/journal.pone.0159691. eCollection 2016.
The "varying constraints hypothesis" of fire in natural ecosystems postulates that the extent of fire in an ecosystem would differ according to the relative contribution of fuel load and fuel moisture available, factors that vary globally along a spatial gradient of climatic conditions. We examined if the globally widespread seasonally dry tropical forests (SDTFs) can be placed as a single entity in this framework by analyzing environmental influences on fire extent in a structurally diverse SDTF landscape in the Western Ghats of southern India, representative of similar forests in monsoonal south and southeast Asia. We used logistic regression to model fire extent with factors that represent fuel load and fuel moisture at two levels-the overall landscape and within four defined moisture regimes (between 700 and1700 mm yr-1)-using a dataset of area burnt and seasonal rainfall from 1990 to 2010. The landscape scale model showed that the extent of fire in a given year within this SDTF is dependent on the combined interaction of seasonal rainfall and extent burnt the previous year. Within individual moisture regimes the relative contribution of these factors to the annual extent burnt varied-early dry season rainfall (i.e., fuel moisture) was the predominant factor in the wettest regime, while wet season rainfall (i.e., fuel load) had a large influence on fire extent in the driest regime. Thus, the diverse structural vegetation types associated with SDTFs across a wide range of rainfall regimes would have to be examined at finer regional or local scales to understand the specific environmental drivers of fire. Our results could be extended to investigating fire-climate relationships in STDFs of monsoonal Asia.
自然生态系统中火灾的“变化限制假说”假定，生态系统中火灾的范围会根据可用燃料负荷和燃料湿度的相对贡献而有所不同，这些因素会沿着气候条件的空间梯度在全球范围内变化。我们通过分析印度南部西高止山脉结构多样的季节性干燥热带森林（SDTFs）景观中火灾范围的环境影响，来研究全球广泛分布的SDTFs能否在这一框架中被视为一个单一实体，该景观代表了季风影响的南亚和东南亚的类似森林。我们使用逻辑回归，利用1990年至2010年的火烧面积和季节性降雨数据集，以代表两个层面（整体景观和四个定义的湿度状况（年降水量在700至1700毫米之间））的燃料负荷和燃料湿度的因素为变量，对火灾范围进行建模。景观尺度模型显示，在这一SDTFs中某一年的火灾范围取决于季节性降雨与上一年火烧面积的综合相互作用。在各个湿度状况下，这些因素对年度火烧面积的相对贡献各不相同——旱季早期降雨（即燃料湿度）在最湿润的状况下是主要因素，而雨季降雨（即燃料负荷）在最干燥的状况下对火灾范围有很大影响。因此，必须在更精细的区域或局部尺度上研究与广泛降雨状况下的SDTFs相关的不同结构植被类型，以了解火灾的具体环境驱动因素。我们的结果可扩展到研究季风亚洲SDTFs中的火灾-气候关系。
