Individual study: Conflicting demands on wetland ecosystem services: nutrient retention, biodiversity or both?
Hansson L.-A., Brönmark C., Nilsson P.A. & Åbjörnsson K. (2005) Conflicting demands on wetland ecosystem services: nutrient retention, biodiversity or both? Freshwater Biology, 50, 705-714
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Create scrapes and pools
A study of 32 recently (1-7 years) constructed wetlands in an intensive agricultural area in southern Sweden (Hansson et al. 2005) found that a combination of large surface area, high shoreline complexity and shallow depth increased bird, aquatic plant and bottom-dwelling invertebrate diversity. Fish species richness was lower than in natural wetlands. There were 15-54 species of bottom-dwelling invertebrates per wetland, increasing with wetland age up to approximately five years, when numbers levelled off. Wetland bird species richness increased with wetland area up to about 4 ha (12 species). There were 0-2 species of amphibian and 18-51 aquatic plant species per wetland. Wetland plant species richness increased with shoreline complexity, but aquatic plant richness decreased with increasing depth. Fish species richness was lower in constructed wetlands (0-5 species) than natural wetlands (more than 100 years old) in the same region (0-9 species). Sampling was undertaken in 2000 (aquatic plants in 2001). Aquatic plant cover was visually estimated (July and November), vegetation was sampled 0-5 m above shore (September) and submersed vegetation was sampled by throwing an anchor 15 m out into the water (5-15 times). Birds were sampled by walking around each wetland twice during the breeding season (mid-May to early-June) and invertebrates at the bottom of the wetland were surveyed by kick-sampling along four 1 m lengths/wetland. Electro-fishing was undertaken in a 50 m stretch and amphibian larvae sampling in a 100 m length of the shallow, littoral zone.