Quantifying the contribution of riparian soils to the provision of ecosystem services

Abstract

Riparian areas, the interface between land and freshwater ecosystems, are considered to play a pivotal role in the supply of regulating, provisioning, cultural and supporting services. Most previous studies, however, have tended to focus on intensive agricultural systems and only on a single ecosystem function. Here, we present the first study which attempts to assess a wide range of ecological processes involved in the provision of the ecosystem service of water quality regulation across a diverse range of riparian typologies. Specifically, we focus on 1) evaluating the spatial variation in riparian soils properties with respect to distance with the river and soil depth in contrasting habitat types; 2) gaining further insights into the underlying mechanisms of pollutant removal (i.e. pesticide sorption/degradation, denitrification, etc.) by riparian soils; and 3) quantify and evaluate how riparian vegetation across different habitat types contribute to the provision of watercourse shading. All the habitats were present within a single large catchment and included: (i) improved grassland, (ii) unimproved (semi-natural) grassland, (iii) broadleaf woodland, (iv) coniferous woodland, and (iv) mountain, heath and bog. Taking all the data together, the riparian soils could be statistically separated by habitat type, providing evidence that they deliver ecosystem services to differing extents. Overall, however, our findings seem to contradict the general assumption that soils in riparian area are different from neighbouring (non-riparian) areas and that they possess extra functionality in terms of ecosystem service provision. Watercourse shading was highly habitat specific and was maximal in forests (ca. 52% shade cover) in comparison to the other habitat types (7-17%). Our data suggest that the functioning of riparian areas in less intensive agricultural areas, such as those studied here, may be broadly predicted from the surrounding land use, however, further research is required to critically test this across a wider range of ecosystems.

Relationships between Soil Nutrients and Plant Diversity in Riparian Woodlands Along the Middle and Lower Reaches of the Yellow River, China

“…The lower Yellow River is a perched river with a main-channel width of 0.5 to 3.0 km and a riparian zone with width of 5 to 20 km that was restricted by the left and right levees [36,37]. As such, the riparian zone is larger than that used in the studies conducted by Hazlett et al [47] (5 m and 75 m from the lakeshore), Schilling et al [48] (1, 20, and 40 m from river), Cierjacks et al [49] (518±50 m from main channel), Smith et al [23] (transects 36 m long and separated by 6 m), Lidman et al [12] (4, 12 and 22 m from river), and de Sosa et al [45] (2 and 50 m from river). These differences in distance used, which could be determined by river size and order, topographic feature, and land use and land cover [52], can lead to differences in hydrologic dynamics, geomorphic dynamics, and ecological processes.…”

“…For instance, Burger et al [44] and Smith et al [23] indicated that riparian soils close to the river have higher levels of organic C and N when compared with remnant riparian zones that were far distances from the river. However, several studies observed little or no effect of distance from the river on riparian soil physicochemical properties [45,[46][47][48], even though significant differences were observed among different riparian habitats. The authors attributed their findings to the habitat characteristics that they selected.…”

“…The authors attributed their findings to the habitat characteristics that they selected. These habitats were in a natural state that experienced little to no management intervention [45]. This observation implies that further investigation on heterogeneity of natural factors and intensity of anthropogenic factors (i.e., management intensity) should be conducted [12,13,33,45], as these factors are always expected to be the main driving factors of change in soil nutrients [12,23,44,49,50].…”

“…These habitats were in a natural state that experienced little to no management intervention [45]. This observation implies that further investigation on heterogeneity of natural factors and intensity of anthropogenic factors (i.e., management intensity) should be conducted [12,13,33,45], as these factors are always expected to be the main driving factors of change in soil nutrients [12,23,44,49,50]. For example, studies conducted in agricultural areas subjected to high management intensity showed significant differences between the riparian zone and adjacent riparian fields or upland areas [12,23,44,49,50].…”

“…For example, studies conducted in agricultural areas subjected to high management intensity showed significant differences between the riparian zone and adjacent riparian fields or upland areas [12,23,44,49,50]. In contrast, studies conducted in natural or semi-natural habitat conditions such as grassland, forests, and woodlands, showed no significant changes between riparian zones and adjacent fields or upland forests [45,[46][47][48]. Moreover, some studies have indicated that soil nutrient content increased significantly with distance to the river [49][50][51].…”