Forest fragments and their tree canopies may act as important reservoirs for biodiversity, but their role in supporting diversity is poorly understood in the context of their spatial arrangement. We examine the influence of landscape configuration and location within forest patches (e.g. canopy, edge or patch interior) on patterns of arthropod biodiversity associated with sugar maple trees across an agricultural landscape in southern Quebec (Canada). We sampled arthropods from sugar maples in 20 sugar maple-beech-dominated forest patches that varied in size and isolation from other forest patches. Within each patch, arthropods were collected in the interior, edge and canopy of patches over two seasons. Size and isolation of forest patches did not affect arthropod family or functional group diversity, but patch canopies supported a higher diversity than understories. Both configuration and within-patch location affected taxonomic and functional composition of arthropods. For example, phytophages and saprophages were found in greatest abundance in canopies and large patches, while entomophages were in highest abundance in interiors. We conclude that even in relatively small (e.g. 5–10 ha) forest patches, canopies are providing critical reservoirs for arthropod diversity, and draw our attention to the conservation value of small patches in fragmented forest landscapes.

Sap flux (F_t) measurements are extensively used to scale-up canopy transpiration and conductance, but time lag between sap flux and canopy transpiration is a problem. As canopy transpiration is nearly synchronous with micrometeorological drivers, better understanding of the lag relationships between F_t and micrometeorological drivers and soil water conditions would benefit the up-scaling of canopy transpiration from sap flux. Time series modeling at different spatial and temporal scales can identify and incorporate time lag effects, as well as multiple variables affecting transpiration and the interactions between them. SARIMAX and GARCH hybrid models were used to capture seasonality and autoregressive conditional heteroscedasticity effects. Two univariate hybrid models were designed to measure vapor pressure deficit (VPD_t) and photosynthetic active radiation (PAR_t), and one multivariate hybrid modelwas used in each season. Sap flow lagged behind canopy transpiration by 0–10 min in the dry season and 10–20 min in the wet season. VPD_t had a stronger influence on transpiration than PAR_t . Only the interaction between VPD_t and PAR_t in the wet season was observed. This study extends the application of time series modeling to the prediction of sap flow dynamics.

Resilience of tundra vegetation to disturbance by herbivores can be low and lead to ecosystem state shifts. Pink-footed geese Anser brachyrhynchus are the most numerous herbivore on Svalbard and disturb vegetation when foraging for below-ground plant biomass (grubbing). We assessed grubbing extent (occurrence of vegetation disturbance) and intensity (proportion of vegetation disturbed) in 2006/07/08 when goose numbers were approximately 56,000 and in 2013 when they increased to approximately 81,000. Despite a 36% increase in population size, in 2013 the grubbing extent at pre-breeding sites was similar to that in 2007/08 but grubbing intensity was lower. Extensive snow cover in 2013 probably dispersed geese over larger areas in search of snow-free patches for feeding, thereby reducing grubbing intensity. At the largest known breeding site, both grubbing extent and intensity increased with more geese. Birds preferentially fed close to nests in previously grubbed wet habitat, probably aiding nest defence and permitting feeding on plants that were easier to remove from the soil. A greater impact on tundra vegetation may occur at nesting areas if the breeding population continues to grow. However, timing of snowmelt appears key in moderating the impact of disturbance on tundra vegetation since it controls spatial distributions of feeding geese.

Using modeled geographic range and importance projections of 133 tree species in the eastern United States we compare regional scale patterns of forest species diversity, similarity, evenness and community composition under present conditions with two future climate change scenarios. Overall, there is an increase in tree species richness on a pixel-by-pixel basis under future conditions, with a general shift to higher diversity in the northern portion of the United States. Percent similarity in species composition between current forest composition and future species composition under the low scenario averages 53.1%, and is lower for the high climate change scenario (45%), with the lowest similarity occurring in northern forests and the northern United States forest-prairie ecotone. In the future, species evenness increases over a large portion of the study area compared with current conditions. Forest community composition is stable in the southeastern United States, lower Great Lakes region and western extent of the eastern forests. Novel species assemblages develop in northern Wisconsin and Michigan, the northeastern United States, the southern forest-prairie ecotone and the southern coastal plain. Our study highlights geographic regions likely to experience substantial shifts in species composition and forest structure that should be monitored for early signs of forest change.