Factors affecting plant species distribution in hedgerows of southern Quebec

Woody linear features of farmlands have received much attention as pools of diversity in European countries, but they have, in comparison, been little considered in eastern North American ecological studies. Here, we evaluate the relative contribution of environmental conditions, history of management practices within hedgerows, and adjacent land-use on herb and shrub species distribution in woody hedgerows of agricultural landscapes of southern Quebec, Canada. We pay particular attention to the distribution of forest herbs and weed species and identify the main factors that explain their presence. We also evaluate the amount of spatial structuring in the species data and explanatory variables.Our results show significant differences in species composition related to the unique influence of all sets of factors considered. Adjacent land-use (from intensive crop to fallow land) remains the best predictor of overall species distribution, followed by environmental conditions and history of management practices. The probability of finding forest herbs in hedgerows increases as intensity of adjacent agricultural practices (from intensive crop to fallow land) decreases. Potential weed species, on the other hand, are more likely to be found within narrow hedgerows adjacent to the more intensively managed fields. We discuss the results in terms of the interactions between the different determinants of plant diversity in hedgerows and demonstrate the necessity to distinguish between multiple structuring factors to devise proper conservation strategies. Such strategies will have to take into account the ecological as well as the agricultural exploitation context in which linear features are found to be effective.     

Flower preferences of woodland butterflies in the UK: nectaring specialists are species of conservation concern

We report on a long-term study of the flower preferences of feeding adult butterflies undertaken in the Wyre Forest, UK. Examination of 5638 observations of nectar-feeding clearly demonstrates several findings: (i) that butterflies differ in their range of flower use, some are generalists and others specialists, respectively, exploiting more or less sources than expected; (ii) certain flower species are preferred over others. We find that (iii) generalism and specialism in flower use corresponds to generalism and specialism, respectively, in larval host range and biotope occupancy; that (iv) generalism in flower use is accounted for by life history and resource variables that increase opportunity for contact with a wider variety of flowering herbs; that (v) specialist flower users are more typically woodland butterflies and generalist flower users species of more open biotopes. A key finding is that (vi) many specialist flower users are butterfly species of conservation concern listed in Biodiversity Action Plans. We suggest that management of woodland sites for butterfly conservation should give as much consideration to nectar sources as to host plant sources.     

Evaluating hedgerow corridors for the conservation of native forest herb diversity

The maintenance of connecting habitats such as hedgerows in production landscapes could become increasingly critical as species migration is expected to accelerate with climate change. Species of particular conservation interest that could benefit from connecting habitats especially in agroecosystems are native forest herbs. It is still unclear, however, which hedgerow habitats have the best potential of supporting diverse forest herb communities, making it hard to target particular structures for conservation. Our objective was to identify the local and landscape characteristics of hedgerows that could help predict their potential at maximizing the richness, abundance, and diversity of native forest herbs of temperate deciduous forests of North-East America. We used multiple regression, Moran’I correlograms, and conditional autoregressive models to assess the effect of landscape and historical variables (hedgerow age, amount of adjacent forest cover, connection to forests and other hedgerows) and of local variables (hedgerow width, canopy cover, cover of other species) on the response variables. The results show an increase in forest herb diversity and abundance in hedgerows with time and with increasing nearby forest cover. Local factors such as greater width and reduced cover of other species also relate to a greater abundance and diversity of forest herbs in linear habitats. The fact that forest herb communities can reassemble in hedgerow corridors with time implies that there could be long-term benefits in maintaining and even creating linear habitats where there is a pool of dispersing forest herbs.