Topic 12: Impacts of bioenergy crops used as riparian buffer strips on stream ecosystems’ functioning

Introduction/background

Riparian buffer strips (RBS) are vegetated, usually non-cultivated zones between streams and the adjacent agricultural land, which are implemented to protect the aquatic system and its floodplain from excessive sediment and nutrient inputs. Considering the water-energy-food nexus, RBS could be planted with perennial low-input bioenergy crops as part of a sustainable intensification strategy. However, non-natural RBS vegetation may change the streams’ metabolism and functioning by shifting the timing of the detritus supply and changing the detrital food quality.

Main objective/research question/hypothesis

The PhD topic aims at (i) investigating the effects of plant residues of bioenergy crops and other herbaceous plants on the streams’ metabolism and organic matter cycling; (ii) analyzing the effects of bioenergy crop in RBS on nutrient and carbon fluxes into the stream compared to other RBS vegetation; thus (iii) providing information about the potential of using bioenergy crops as RBS in agricultural regions as a strategy of sustainable intensification in the context of the water-energy-food nexus. The following research questions will be addressed: How does detritus of different plants and crops used in RBS affect the metabolism, organic matter decomposition, and organic matter cycling in agricultural streams? How does RBS vegetation influence C, N, and P fluxes into the stream? Close cooperation with PhD topic 11 will extend the stream-RBS link laterally to the agricultural catchment; close cooperation with PhD topic 14 will provide information about the social acceptance of RBS and the use of bioenergy crops.

Approach/methods and time frame

The project focuses on river systems in agricultural regions in Eastern Austria lacking natural riparian zones. A mix of experimental field plots, lab experiments, and modelling will be applied. Field plots will consist of crop fields adjacent to streams, with conventional or sustainable agriculture (e.g. treated with organic amendments) both without and with RBs planted with bioenergy crops and multispecies plants (2x3 matrix). In WP1, the PhD student will investigate the aquatic decomposition of RBS plant residues and analyze the effects of different detritus supply on the rivers’ metabolism and organic matter cycling via lab experiments. In WP2, experimental field plots will be established, and the effects of selected plants on RBS soil conditions, and nutrient and organic matter transport (e.g. infiltration, lateral flow, and surface runoff) to the stream will be modelled. In WP3, experimentally derived data of WP1 will be tested in the field (upscaling) and the potential and limits of the use of bioenergy crops in RBS will be analyzed.