Cornwell William K, Elvira Alba, van Kempen Lute, van Logtestijn Richard S P, Aptroot André, Cornelissen J Hans C
Systems Ecology, Department of Ecological Science, Faculty of Earth and Life Sciences, VU University, De Boelelaan 1085, 1081 HV, Amsterdam, the Netherlands; Ecology and Evolution Research Centre, School of Biological, Earth and Environmental Science, University of New South Wales, Sydney, NSW, 2052, Australia.
New Phytol. 2015 Apr;206(2):672-81. doi: 10.1111/nph.13317. Epub 2015 Feb 12.
Fire is important to climate, element cycles and plant communities, with many fires spreading via surface litter. The influence of species on the spread of surface fire is mediated by their traits which, after senescence and abscission, have 'afterlife' effects on litter flammability. We hypothesized that differences in litter flammability among gymnosperms are determined by litter particle size effects on litterbed packing. We performed a mesocosm fire experiment comparing 39 phylogenetically wide-ranging gymnosperms, followed by litter size and shape manipulations on two chemically contrasting species, to isolate the underlying mechanism. The first-order control on litter flammability was, indeed, litter particle size in both experiments. Most gymnosperms were highly flammable, but a prominent exception was the non-Pinus Pinaceae, in which small leaves abscised singly produced dense, non-flammable litterbeds. There are two important implications: first, ecosystems dominated by gymnosperms that drop small leaves separately will develop dense litter layers, which will be less prone to and inhibit the spread of surface litter fire. Second, some of the needle-leaved species previously considered to be flammable in single-leaf experiments were among the least flammable in litter fuel beds, highlighting the role of the litter traits of species in affecting surface fire regimes.
火对气候、元素循环和植物群落至关重要，许多火灾通过地表凋落物蔓延。物种对地表火蔓延的影响是由其性状介导的，这些性状在衰老和脱落之后，对凋落物可燃性具有“后续”影响。我们假设裸子植物之间凋落物可燃性的差异是由凋落物颗粒大小对凋落物层堆积的影响所决定的。我们进行了一项中型火灾实验，比较了39种系统发育范围广泛的裸子植物，随后对两个化学性质不同的物种进行了凋落物大小和形状的操控，以分离潜在机制。在两个实验中，对凋落物可燃性的一级控制实际上都是凋落物颗粒大小。大多数裸子植物高度易燃，但一个显著的例外是非松科松属植物，其单独脱落的小叶会产生致密、不易燃的凋落物层。有两个重要影响：第一，由单独掉落小叶的裸子植物主导的生态系统将形成致密的凋落物层，这将不易引发并抑制地表凋落物火灾的蔓延。第二，一些在单叶实验中先前被认为易燃的针叶树种在凋落物燃料层中却是最不易燃的，这突出了物种的凋落物性状在影响地表火灾状况方面的作用。
