Tradeoffs and synergies in wetland multifunctionality: A scaling issue

Wetland area in agricultural landscapes has been heavily reduced to gain land for crop production, but in recent years there is increased societal recognition of the negative consequences from wetland loss on nutrient retention, biodiversity and a range of other benefits to humans. The current trend is therefore to re-establish wetlands, often with an aim to achieve the simultaneous delivery of multiple ecosystem services, i.e., multifunctionality. Here we review the literature on key objectives used to motivate wetland re-establishment in temperate agricultural landscapes (provision of flow regulation, nutrient retention, climate mitigation, biodiversity conservation and cultural ecosystem services), and their relationships to environmental properties, in order to identify potential for tradeoffs and synergies concerning the development of multifunctional wetlands. Through this process, we find that there is a need for a change in scale from a focus on single wetlands to wetlandscapes (multiple neighboring wetlands including their catchments and surrounding landscape features) if multiple societal and environmental goals are to be achieved. Finally, we discuss the key factors to be considered when planning for re-establishment of wetlands that can support achievement of a wide range of objectives at the landscape scale

Combined effects of patch size and plant nutritional quality on local densities of insect herbivores

Plant–insect interactions occur in spatially heterogeneous habitats. Understanding how such interactions shape density distributions of herbivores requires knowledge on how variation in plant traits (e.g. nutritional quality) affects herbivore abundance through, for example, affecting movement rates and aggregation behaviour. We studied the effects of plant patch size and herbivore-induced differences in plant nutritional quality on local densities of insect herbivores for two Brassica oleracea cultivars, i.e. white cabbage and Brussels sprouts. Early season herbivory as a treatment resulted in measurable differences in glucosinolate concentrations in both cultivars throughout the season. Herbivore induction and patch size both influenced community composition of herbivores in both cultivars, but the effects differed between species. Flea beetles (Phyllotreta spp.) were more abundant in large than in small patches, and this patch response was more pronounced on white cabbage than on Brussels sprouts. Herbivore-induction increased densities in all patches. Thrips tabaci was also more abundant in large patches and densities of this species were higher on Brussels sprouts than on white cabbage. Thrips densities were lower on induced than on control plants of both cultivars and this negative effect of induction tended to be more pronounced in large than in small patches. Densities of the cabbage moth (Mamestra brassicae) were lower on Brussels sprouts than on white cabbage and lower on herbivore-induced than on uninduced plants, with no effect of patch size. No clear effects of patch size and induction were found for aphids. This study shows that constitutive and herbivore-induced differences in plant traits interact with patch responses of insect herbivores.