Scale-specific land cover thresholds for conservation of stream invertebrate communities in agricultural landscapes

• Published in: Landscape ecology 2018-12, Vol.33 (12), p.2239-2252
• Main Authors: Grimstead, Jeremy P., Krynak, Edward M., Yates, Adam G.
• Format: Article
• Language: English
• Subjects: Agricultural ecosystems; Agricultural land; Agricultural practices; Agricultural watersheds; Agriculture; Biomedical and Life Sciences; Catchment areas; Communities; Corridors; Ecology; Ecosystem management; Environmental Management; Forest management; Forest protection; Land conservation; Land cover; Landscape Ecology; Landscape preservation; Landscape/Regional and Urban Planning; Life Sciences; Macroinvertebrates; Nature Conservation; Ordination; Research Article; Riparian forests; Strategic management; Streams; Sustainable Development; Thresholds
• ISSN: 0921-2973; 1572-9761
• DOI: 10.1007/s10980-018-0738-5

Context In agricultural landscapes, riparian forests are used as a management tool to protect stream ecosystems from agricultural activities. However, the ability of managers to target stream protection actions is limited by incomplete knowledge of scale-specific effects of agriculture in riparian corridor and catchment areas. Objectives We evaluated scale-specific effects of agricultural cover in riparian corridor and catchment areas on stream benthic macroinvertebrate (BMI) communities to develop cover targets for agricultural landscapes. Methods Sixty-eight streams assigned to three experimental treatments (Forested Riparian, Agricultural Riparian, Agricultural Catchment) were sampled for BMIs. Ordination and segmented regression were used to assess impacts of agriculture on BMI communities and detect thresholds for BMI community metrics. Results BMI communities were not associated with catchment agricultural cover where the riparian corridor was forested, but were associated with variation in catchment agriculture where riparian forests had been converted to agriculture. Trait-based metrics showed threshold responses at greater than 70% agricultural cover in the catchment. Increasing agriculture in the riparian corridor was associated with less diverse and more tolerant BMI communities. Eight metrics exhibited threshold responses ranging from 45 to 75% agriculture in the riparian corridor. Conclusions Riparian forest effectively buffered streams from agricultural activity even where catchment agriculture exceeds 80%. We recommend managers prioritize protection of forested riparian corridors and that restore riparian corridors where agricultural cover is near identified thresholds be a secondary priority. Adoption of catchment management actions should be effective where the riparian corridor has been converted to agriculture.