Plant functional and taxonomic diversity in European grasslands along climatic gradients

Aim: European grassland communities are highly diverse, but patterns and drivers of their continental-scale diversity remain elusive. This study analyses taxonomic and functional richness in European grasslands along continental-scale temperature and precipitation gradients. Location: Europe. Methods: We quantified functional and taxonomic richness of 55,748 vegetation plots. Six plant traits, related to resource acquisition and conservation, were analysed to describe plant community functional composition. Using a null-model approach we derived functional richness effect sizes that indicate higher or lower diversity than expected given the taxonomic richness. We assessed the variation in absolute functional and taxonomic richness and in functional richness effect sizes along gradients of minimum temperature, temperature range, annual precipitation, and precipitation seasonality using a multiple general additive modelling approach. Results: Functional and taxonomic richness was high at intermediate minimum temperatures and wide temperature ranges. Functional and taxonomic richness was low in correspondence with low minimum temperatures or narrow temperature ranges. Functional richness increased and taxonomic richness decreased at higher minimum temperatures and wide annual temperature ranges. Both functional and taxonomic richness decreased with increasing precipitation seasonality and showed a small increase at intermediate annual precipitation. Overall, effect sizes of functional richness were small. However, effect sizes indicated trait divergence at extremely low minimum temperatures and at low annual precipitation with extreme precipitation seasonality. Conclusions: Functional and taxonomic richness of European grassland communities vary considerably over temperature and precipitation gradients. Overall, they follow similar patterns over the climate gradients, except at high minimum temperatures and wide temperature ranges, where functional richness increases and taxonomic richness decreases. This contrasting pattern may trigger new ideas for studies that target specific hypotheses focused on community assembly processes. And though effect sizes were small, they indicate that it may be important to consider climate seasonality in plant diversity studies

Demographic response and life history of traditional forest resource tree species in a tropical mosaic landscape in Papua New Guinea

Disturbance is well known to play an important structuring role in rainforest succession and in maintaining overall diversity. However, the ecological responses arising from changes in land use such as traditional and modified shifting cultivation practices are less well known. The distribution and dynamics of plant populations may be affected by such changes in land use and often their responses are compounded by a lack of life history data. The life history traits and demographic parameters important to successional species responses to disturbance remain poorly understood beyond broad generalisations, particularly in rainforests outside of the Neotropics. We examined the life history and demography of five rainforest tree species in Papua New Guinea to investigate the effect of shifting cultivation practices on their population dynamics. The demographic parameters most successful for continued population growth were medium to high recruitment, low seedling mortality and high seedling abundance, relatively low growth rates (compared to many pioneer species) and moderate to high abundance in all life stages. Successful life history traits were high seed mass, moderate shade-tolerance and high cultural value. In accordance with their demographies and life histories, Pterocarpus indicus, Vitex cofassus and Artocarpus altilis were classified as early successional species, while Pometia pinnata and Canarium indicum were considered mid-successional. The results suggest that the earlier successional species do not necessarily have an advantage in disturbed environments; persistence is more likely to rely on the response of inherent demographic processes to external influences

Stability of pollination services decreases with isolation from natural areas despite honey bee visits

Sustainable agricultural landscapes by definition provide high magnitude and stability of ecosystem services, biodiversity and crop productivity. However, few studies have considered landscape effects on the stability of ecosystem services. We tested whether isolation from florally diverse natural and semi-natural areas reduces the spatial and temporal stability of flower-visitor richness and pollination services in crop fields. We synthesised data from 29 studies with contrasting biomes, crop species and pollinator communities. Stability of flower-visitor richness, visitation rate (all insects except honey bees) and fruit set all decreased with distance from natural areas. At 1 km from adjacent natural areas, spatial stability decreased by 25, 16 and 9% for richness, visitation and fruit set, respectively, while temporal stability decreased by 39% for richness and 13% for visitation. Mean richness, visitation and fruit set also decreased with isolation, by 34, 27 and 16% at 1 km respectively. In contrast, honey bee visitation did not change with isolation and represented > 25% of crop visits in 21 studies. Therefore, wild pollinators are relevant for crop productivity and stability even when honey bees are abundant. Policies to preserve and restore natural areas in agricultural landscapes should enhance levels and reliability of pollination services