Abstract:

In-stream wood is defined as dead wood (>10 cm diameter and >1 m length) in the stream channel. In-stream wood is a common, but important structural component in forest streams, particularly in relatively small creeks. Through review of research from the last 30 years (mainly from North America), we synthesize information on in-stream wood ecological functions (on channel morphology, nutrient cycling, sediment storage, aquatic habitat and biodiversity), dynamics, spatial variation and relationship between in-stream wood (loadings and distribution) and disturbance (natural and human-caused). We also present wood management paradigms and future research directions.

Much research has demonstrated that in-stream wood has important ecological functions for aquatic ecosystems. In-stream wood can significantly change channel morphology through its role in intercepting sediments and water flow as well as stabilizing stream banks. Many aquatic habitat features such as pool, cover and substrate are positively related to in-stream wood characteristics. In-stream wood also affects nutrient cycling through its decomposition and interception of fine organic materials (e.g., tree needles and branches). Because of these ecological functions, in-stream wood supports greater aquatic biodiversity and productivity. However, its ecological significance largely depends on types of forested watersheds and sizes of streams. As stream sizes increase, wood loading and its influence generally decrease. The size of individual wood pieces, however, increases with increasing stream size. In-stream wood also has large temporal variations or dynamics which are mainly driven by large-scale catastrophic forest disturbance (i.e., fire, windthrow, etc). Understanding spatial and temporal variations and differences between natural and human disturbances is important for protecting and maintaining wood ecological functions. We provide suggestions for future in-stream wood ecological research in China.

Key words: In-stream wood, Large Woody Debris (LWD), Ecological functions, Spatial and temporal variability, Disturbance