Control of C,N,P distribution in soils of riparian forests

Abstract

It is now well accepted that riparian forests have an important role in regulating upstream/downstream flow of matter and energy in river ecosystems. Since geomorphic processes determine the structure of channels and floodplains, we have investigated whether different geomorphic features of riparian forests had any effects on the ability of their soils to retain nutrients and organic carbon. Willow riparian forests were chosen within the annual floodplain of the Garonne River, southwest France, to represent two different geomorphic types. Erosional types of riparian forests (E-type) were characterized by sand deposition on their soils because of high current velocity which hampered fine particle deposition. Depositional types of riparian forests (D-type) were characterized by slower overflow velocity; consequently silt and clay were dominant in their soils. Soil samples were taken at the end of the vegetation growth period, coinciding with low water levels prior to annual floods. Erosion and sedimentation processes affected the distribution of total C,N, and P contents in riparian forest soils, since they were significantly correlated with soil grain size. D-type riparian forest soils act as a sink for upstream/downstream nutrients and carbon flows during floods through accumulation of total C,N and P from year to year. In contrast, E-type riparian forests act as potential nutrient sources during high water periods, since they may release from their soils large amounts of easily available C, N and P into the river. These results demonstrate that nutrients and carbon retention ability of riparian forests soils should be analyzed through their geomorphic features rather than by their vegetation composition. Even if they belong to the same vegetation succession, riparian forests should not be considered as a homogeneous buffering system for upstream/downstream flows of nutrients and organic carbon.

Effects of riparian vegetation removal on nutrient retention in a Mediterranean stream

“…Riparian zones play an important role in controlling nutrient fluxes from terrestrial to stream ecosystems (Gregory 1991, Pinay et al 1992. Therefore, removal of riparian trees can also affect the in-stream flux of dissolved nutrients.…”

Phosphorus retention in non-tidal palustrine forssted wetlands of the mid-atlantic region

“…Labile P export was controlled more by water than by sediments, with 62-78% of the labile P in stormflow occurring as soluble P. Frink (1991) found that watershed models that included a sediment transport component tended to overestimate P export from agricultural watersheds and underestimate P export from wooded and urban watersheds and suggested that this was due to an underestimation of soluble P transport as predicted by these models. While the mechanisms associated with sediment removal are primarily geomorphological (Lowrance et al 1984, Pinay et al 1992, the mechanisms associated with dissolved P removal are primarily biogeochemical. For the remainder of this paper, we will limit our discussion of the P retention functions of forested wetlands to the biogeochemical pathways associated with dissoved phosphate removal.…”

Effects of land use on concentrations of metals in surface soils and ecological risk around Guanting Reservoir, China

“…Soil can be polluted by wastewater irrigation. The metals in soils can also reach aquatic ecosystems by erosion and runoff from agricultural land (Pinay et al 1992). Soils contaminated in these ways may have an impact on water quality.…”