Flood-deposited wood debris and its contribution to heterogeneity and regeneration in a semi-arid riparian landscape
Flood-deposited wood debris and its contribution to heterogeneity and regeneration in a semi-arid riparian landscape
复制标题
洪水沉积的木材碎片及其对半干旱河岸景观异质性和再生的贡献
作者：
N. Pettit;R. Naiman
我们调查了大型木质残体（LWD）桩是否创建节点的环境资源，有助于恢复河岸植被，也增加了河流系统的异质性和弹性。河流和河岸系统的典型特征是非生物和生物元素之间的高度异质性和复杂的相互作用。洪水等干扰会重新分配LWD等资源，从而增加系统的复杂性。我们研究了这个问题上的半干旱稀树草原河流，在2000年~100年一遇的洪水连根拔起植被，并沉积大量的LWD。我们调查了新建立的LWD桩内的微环境，并将其与不含LWD的相邻参考地点的条件进行了比较。我们发现，土壤养分浓度显着高于随钻桩相比，参考地块（全N +19%，有效P +51%，和全C +36%）。随钻测井桩和参考站点内的环境变量随河流-河岸景观中的景观位置和随钻测井桩特性而变化。观察到的差异一般桩位于陆地和河岸地区相比，桩位于宏观通道地板。3年后，木本物种的数量和覆盖率显着较高时，与LWD桩，无论景观位置或桩类型。我们的结论是，随钻桩形成后，大洪水作为资源节点，积累细沉积物和保持土壤养分和土壤水分。LWD沉积对河岸异质性的后续影响在几个空间尺度上被识别，包括LWD桩内和桩间、跨景观位置和通道类型之间。随钻测井桩显著影响河岸植被的初始发育，因为系统在大的破坏性洪水后再生。
We investigated whether large woody debris (LWD) piles create nodes of environmental resources that contribute to the recovery of riparian vegetation and that also augment the heterogeneity and resilience of the riverine system. River and riparian systems are typified by a large degree of heterogeneity and complex interactions between abiotic and biotic elements. Disturbance such as floods re-distribute the resources, such as LWD, and thereby add greater complexity to the system. We examined this issue on a semi-arid savanna river where a ~100-year return interval flood in 2000 uprooted vegetation and deposited substantial LWD. We investigated the micro-environment within the newly established LWD piles and compared this with conditions at adjacent reference sites containing no LWD. We found soil nutrient concentrations to be significantly higher in LWD piles compared with the reference plots (total N +19%, available P +51%, and total C +36%). Environmental variables within LWD piles and reference sites varied with landscape position in the river–riparian landscape and with LWD pile characteristics. Observed differences were generally between piles located in the terrestrial and riparian areas as compared to piles located on the macro-channel floor. After 3 years the number and cover of woody species were significantly higher when associated with LWD piles, regardless of landscape position or pile type. We conclude that LWD piles formed after large floods act as resource nodes by accumulating fine sediments and by retaining soil nutrients and soil moisture. The subsequent influence of LWD deposition on riparian heterogeneity is discerned at several spatial scales including within and between LWD piles, across landscape positions and between channel types. LWD piles substantially influence the initial developmental of riparian vegetation as the system regenerates following large destructive floods.