RESUMO
Coastal resilience is threatened as storm-induced disturbances become more frequent and intense with anticipated changes in regional climate. After severe storms, rapid recovery of vegetation, especially that of dune-stabilizing plants, is a fundamental property of coastal resilience. Herbivores may affect resilience by foraging and trampling in disturbed areas. Consequently, assessing the impacts of herbivores on recovering vegetation is important for coastal land management.We combined imagery classification, wildlife monitoring, and trend analysis to investigate effects of white-tailed deer on recovery rates of vegetation four years poststorm in nine overwashed areas. We estimated local deer density with trail cameras, how it relates to an index of primary productivity, and assessed the relationship between deer density and rates of vegetation recovery in overwash fans.Prestorm vegetation cover consisted of shrubs and sporadic patches of beach grass. Poststorm cover was dominated by beach grass. At current rates, vegetation coverage will return to prestorm conditions within the decade, though community transition from grasses to shrubs will take much longer and will vary by site with dune formation.The effect of deer on rates of vegetation recovery was negative, but not statistically significant nor biologically compelling. Although effects of deer trampling on beach grass are evident in classified imagery, deer foraging on beach grass had little effect on its rate of spread throughout overwash fans.While the rate of spread of the primary dune-building grass was not deleteriously affected by deer, locally high deer densities will likely affect the future establishment and development of herbs and shrubs, which are generally more palatable to deer than beach grass.
RESUMO
We documented the impacts of an abundant deer population on dune vegetation recovering from severe storm surge on a barrier island through use of permanent plots and a repeated measures analysis. Three years after landfall of the storm, vegetation cover was dominated by American beachgrass, Ammophila breviligulata, though we observed 12 plant species among plots surveyed. We documented significantly greater vegetation cover in fenced than unfenced plots in overwash fans in two consecutive years. The difference in species richness between fenced and unfenced plots was significant, though richness was consistently low (≤4 species per plot) and we did not detect a statistically significant difference between years. Both deer trampling and foraging effects were captured in this study, though separation between these effects was not possible. Because trampling effects are often exacerbated on sandy soils, trampling and foraging effects should be isolated and investigated in future assessments of deer impacts on coastal vegetation. Managing deer to lower abundance may enhance coastal resilience if vegetation is allowed to recover unimpeded by foraging and trampling, though a better understanding of the precise nature of deer impacts on dune vegetation is necessary.
RESUMO
We present a summary of a long-term field study that examined the effects of forest disturbance on the availability of palatable fruit and its utilization by V. variegata. Forest structure and tree species composition were measured in three adjacent study areas, with different histories of disturbance, in Ranomafana National Park (RNP), Madagascar. V. variegata abundance was monitored by frequent encounters with resident groups and periodic censuses conducted along trails. Finally, the abundance of mature fruit in species used by V. variegata was scored monthly at representative trees at several locations. V. variegata abundance was most consistent in the least anthropogenically disturbed site, while no established lemur groups were observed in the heavily logged site for over a decade post-harvest. Lemur abundance was variable in the selectively logged site. The presence of select food trees, particularly specimens with voluminous crowns capable of producing abundant fruit crops, appears to be key to the establishment and expansion of V. variegata groups. Our analysis of year-long fruit utilization revealed a high degree of preference for several species of trees. Two species exhibited mature fruit in a low percentage of stems but were available for a protracted period of time, while two additional species showed high intraspecific fruiting synchrony and were available for a shorter period of time. These contrasting phenologies, rather than the individual tree species, may be most important to V. variegata due to their coincident timing of fruit maturation with key lemur life-history events. Any disturbance-natural or anthropogenic-that disrupts the phenology cycles of food trees has the potential to impact lemur abundance and dispersion. Intense disturbances, such as heavy logging or severe cyclones, have long-lasting impacts on fruit production, while selective logging or moderate cyclonic windthrow cause more transient impacts. V. variegata is adapted to deal with an intrinsically erratic food supply by virtue of its reproductive biology and social behavior.