Flood-deposited wood debris and its contribution to heterogeneity and regeneration in a semi-arid riparian landscape |
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Authors: | Email author" target="_blank">Neil?E?PettitEmail author Robert?J?Naiman |
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Institution: | (1) School of Aquatic and Fishery Sciences, University of Washington, Box 355020, Seattle, WA 98195, USA;(2) Present address: Murdoch University South St Murdoch, Perth, WA, 6150, Australia |
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Abstract: | 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. |
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Keywords: | Biogeochemistry Flooding disturbance Large woody debris Riparian vegetation Kruger National Park South Africa |
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