Landesmann Jennifer B, Gowda Juan H, Garibaldi Lucas A, Kitzberger Thomas
Laboratorio Ecotono, INIBIOMA-CONICET, Universidad Nacional del Comahue, Quintral 1250, CP 8400, Bariloche, Río Negro, Argentina.
Sede Andina, Universidad Nacional de Río Negro (UNRN), CONICET, Mitre 630, CP 8400, Bariloche, Río Negro, Argentina.
Oecologia. 2015 Dec;179(4):1111-22. doi: 10.1007/s00442-015-3431-2. Epub 2015 Sep 3.
Fire severity and extent are expected to increase in many regions worldwide due to climate change. Therefore, it is crucial to assess the relative importance of deterministic vs. stochastic factors producing remnant vegetation to understand their function in the persistence of fire-sensitive plants. Vegetation remnants (areas within the landscape that have not burned for a considerable amount of time) may occur stochastically or in more predictable locations (fire refuges) where physical conditions decrease fire severity. Our aim was to determine if remnant forests of the fire-sensitive conifer Austrocedrus chilensis are associated with biophysical attributes that allow persistence in a fire-prone Patagonian landscape. We conducted a multi-scale approach, determining attributes of forest remnants and their surroundings (matrices) through remote sensing and field-based biophysical and functional characteristics, and quantifying how tree survival probability relates to microsite conditions. Trees within remnants displayed abundant fire scars, were twofold older and had threefold larger growth rates than matrix trees. Remnants were associated with high rocky cover and elevated topographical positions. Tree survival increased in hilltops, eastern aspects, and with sparse vegetation. Trees within remnants experienced severe reductions in growth during droughts. Our results suggest that A. chilensis remnants are mainly the result of refuges, where environmental conditions increase fire survival, but also increase susceptibility to drought. A trade-off between fire survival and drought vulnerability may imply that under increasing drought and fire severity, locations that in the past have served as refuges may reduce their ability to allow the persistence of fire-sensitive taxa.
由于气候变化，预计全球许多地区的火灾严重程度和范围将会增加。因此，评估产生残余植被的确定性因素与随机因素的相对重要性，对于理解它们在对火灾敏感植物的存续中所起的作用至关重要。植被残余区域（景观中相当长一段时间未发生火灾的区域）可能随机出现，也可能出现在更可预测的地点（火灾避难所），这些地方的物理条件会降低火灾严重程度。我们的目标是确定对火灾敏感的针叶树智利南美雪松的残余森林是否与生物物理属性相关，这些属性使其能够在火灾频发的巴塔哥尼亚景观中存续。我们采用了多尺度方法，通过遥感以及实地生物物理和功能特征来确定森林残余区域及其周边（基质）的属性，并量化树木存活概率与微生境条件的关系。残余区域内的树木有大量火灾疤痕，年龄是基质树木的两倍，生长速度是基质树木的三倍。残余区域与高岩石覆盖率和较高地形位置相关。在山顶、朝东方向以及植被稀疏的地方树木存活率增加。残余区域内的树木在干旱期间生长严重减缓。我们的结果表明，智利南美雪松的残余区域主要是避难所的结果，在这些地方环境条件提高了火灾存活率，但也增加了对干旱的敏感性。火灾存活率和干旱脆弱性之间的权衡可能意味着，在干旱和火灾严重程度不断增加的情况下，过去作为避难所的地点可能会降低其让对火灾敏感的分类群存续的能力。
