Post-flooding distribution and characteristics of large woody debris piles along the semi-arid Sabie River, South Africa

• Published in: River research and applications Vol. 21; no. 1; pp. 27 - 38
• Main Authors: Pettit, N. E., Naiman, R. J., Rogers, K. H., Little, J. E.
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.01.2005; Wiley
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; flooding; Fresh water ecosystems; Freshwater; Fundamental and applied biological sciences. Psychology; geomorphology; Kruger National Park; large woody debris; riparian; semi-arid riparian ecology; South Africa; Synecology; South Africa; Africa; Africa, Sabie R; South Africa, Mpumalanga, Kruger Natl. Park; Geomorphology; Ecology; flooding; Rivers; Climatic zone; Wood waste; Freshwater environment; National park; Flood; Riparian; Semi arid zone; semi-arid riparian ecology; Dead wood; Riverflow control; Water engineering; South Africa; large woody debris; Kruger National Park; Environmental protection
• ISSN: 1535-1459; 1535-1467
• DOI: 10.1002/rra.812

The formation of large woody debris (LWD) piles has a profound impact on channel patterns and riparian succession in temperate rivers. The opportunity to study LWD along the Sabie River, a river in the semi‐arid region of Kruger National Park, South Africa, arose in February 2000 after a significant flood (c. 100‐year return interval) removed a large proportion of the fully mature riparian forest and other plant communities. Much of the uprooted vegetation was deposited as LWD piles (woody vegetation accumulations deposited on the ground > 0.1 m3) throughout the riparian and upland zones. In this article we describe the spatial distribution patterns of LWD as related to geomorphic channel type and flood frequency zone, and assess pile composition characteristics six months after the flood. Within the areas surveyed there were 68 LWD piles per hectare, the median size of LWD piles was 4.6 m3 but pile sizes (by volume) varied widely. Pool/rapid geomorphic channel types had the highest density of LWD piles (79 ha−1) and the largest piles (by volume) were in the bedrock anastomosing channels (mean = 124 m3). Piles were larger in the seasonal and ephemeral flood frequency zones (mean = 54 m3 and 55 m3) than piles in the active zone (c. 2 m3). The patterns of distribution and volume of LWD will affect the subsequent development of vegetation communities as debris piles form a mosaic of patches of surviving organisms and propagules that can strongly influence the initial trajectory of succession. The amount, distribution, and subsequent decomposition of LWD are different from that reported for temperate rivers, suggesting that the role of LWD may be different on non‐floodplain rivers such as the Sabie in semi‐arid South Africa. Copyright © 2004 John Wiley & Sons, Ltd.