Riparian deforestation has a profound impact on stream ecosystems. The reduction of canopy cover induced by deforestation can increase light intensity and excessive nutrient loading in waterways. However, the joint effects of light and nutrients on resource flow and trophic structure in stream ecosystem are not fully understood.

Researchers from Wuhan Botanical Garden of the Chinese Academy of Sciences explored and identified the individual and interactive effects of riparian canopy cover and nutrient pollution on multiple dimensions of the stream food web complexity in three headwater streams in the upper Jinshui River catchment using stable isotope analysis.

The nutrient enrichment with open canopy treatment increased the dietary contribution of periphyton to the diets of macroinvertebrates and comparatively reduced the dietary contribution of allochthonous resources (i.e., leaf litter). The elevated light intensity and nutrient availability caused a rise in trophic diversity and a reduction in trophic redundancy within food webs.

The δ¹⁵N values of periphyton and macroinvertebrates increased with the nutrient enrichment indicating potential δ¹⁵N enrichment of stream benthos by nitrogen pollution.

These results reveal the interactive effects of the nutrient enrichment and increased light intensity caused by riparian deforestation on resource flow and trophic structure in stream benthic food webs. It validates the importance of the protection and restoration of riparian vegetation and the decrease of nutrient inputs to stream ecosystems.

This work was supported by the National Natural Science Foundation of China. Relevant research results have been published in Environmental Research entitled “Open riparian canopy and nutrient pollution interactively decrease trophic redundancy and allochthonous resource in streams”. (Available online 30 May 2023)

Effects of light intensity and nutrient loadings in waterways on stream benthic food webs (Image by WBG)