Spatial structure in protected forest-grassland mosaics: Exploring futures under climate change.

In mosaic ecosystems, multiple land types coexist as alternative stable states exhibiting distinct spatial patterns. Forest-grassland mosaics are ecologically valuable, due to their high species richness. However, anthropogenic disturbances threaten these ecosystems. Designating protected areas is one approach to preserving natural mosaics. Such work must account for climate change, yet there are few spatially explicit models of mosaics under climate change that can predict its effects. We construct a spatially explicit simulation model for a natural forest-grassland mosaic, parameterized for Southern Brazil. Using this model, we investigate how the spatial structure of these systems is altered under climate change and other disturbance regimes. By including local spatial interactions and fire-mediated forest recruitment, our model reproduces important spatial features of protected real-world mosaics, including the number of forest patches and overall forest cover. Multiple concurrent changes in environmental conditions have greater impacts on tree cover and spatial structure in simulated mosaics than single changes. This sensitivity reflects the narrow range of conditions under which simulated mosaics persist and emphasizes their vulnerability. Our model predicts that, in protected mosaics, climate change impacts on the fire-mediated threshold to recruitment will likely result in substantial increases in forest cover under Representative Concentration Pathway (RCP) 8.5, with potential for mosaic loss over a broad range of initial forest cover levels. Forest cover trajectories are similar until 2150, when cover increases under RCP 8.5 outpace those under RCP 2.6. Mosaics that persist under RCP 8.5 may experience structural alterations at the patch and landscape level. Our simple model predicts several realistic aspects of spatial structure as well as plausible responses to likely regional climate shifts. Hence, further model development could provide a useful tool when building strategies for protecting these ecosystems, by informing site selection for conservation areas that will be favourable to forest-grassland mosaics under future climates.

A local optimization framework for addressing conservation conflicts in mosaic ecosystems.

An effective strategy to resolve conservation conflicts on lands outside of nature reserves is to consider the spatial arrangement of agricultural and native vegetation parcels such that the ecological value of the landscape is improved without reducing the amount of land used for agricultural production. Global optimization methods have been used to identify the best spatial arrangement of land parcels for a given project goal, but these methods are not designed to provide pathways to reach the optimum from the initial landscape. Here we describe how local search algorithms can be used to develop land parcel rearrangement pathways to obtain a landscape that sustains greater species richness than the initial landscape without changing the amount of land used for agricultural production. To demonstrate how the local optimization framework can be applied, an ecological setting based on a forest-grassland mosaic ecosystem in Rio Grande do Sul, Brazil was constructed. Plant samples collected from this region were used to construct species area curves. Multiple locally optimal solutions that improved the modeled species richness of the landscape almost to globally optimal levels were identified. To support the results, the algorithm was also applied to a 306,250 ha forest-grassland region of Rio Grande do Sul. The case study results suggested that conservation polices solely based on landowners satisfying a legal reserve percentage on their property should be revised to consider landscape-level connectivity. Providing multiple possible solutions for landscape configurations using local optimization methods may improve managerial flexibility for decision-makers, compared to global optimization approaches providing a single solution. Furthermore, the algorithm details the parcel exchange pathways that are required to reach the optimal land state. We conclude that local and global optimization approaches can be used in combination to improve land use decision-making for conservation, in mosaic ecosystems as well as other terrestrial ecosystems.

Alternative stable states and the sustainability of forests, grasslands, and agriculture.

Endangered forest-grassland mosaics interspersed with expanding agriculture and silviculture occur across many parts of the world, including the southern Brazilian highlands. This natural mosaic ecosystem is thought to reflect alternative stable states driven by threshold responses of recruitment to fire and moisture regimes. The role of adaptive human behavior in such systems remains understudied, despite its pervasiveness and the fact that such ecosystems can exhibit complex dynamics. We develop a nonlinear mathematical model of coupled human-environment dynamics in mosaic systems and social processes regarding conservation and economic land valuation. Our objective is to better understand how the coupled dynamics respond to changes in ecological and social conditions. The model is parameterized with southern Brazilian data on mosaic ecology, land-use profits, and questionnaire results concerning landowner preferences and conservation values. We find that the mosaic presently resides at a crucial juncture where relatively small changes in social conditions can generate a wide variety of possible outcomes, including complete loss of mosaics; large-amplitude, long-term oscillations between land states that preclude ecosystem stability; and conservation of the mosaic even to the exclusion of agriculture/silviculture. In general, increasing the time horizon used for conservation decision making is more likely to maintain mosaic stability. In contrast, increasing the inherent conservation value of either forests or grasslands is more likely to induce large oscillations-especially for forests-due to feedback from rarity-based conservation decisions. Given the potential for complex dynamics, empirically grounded nonlinear dynamical models should play a larger role in policy formulation for human-environment mosaic ecosystems.

Cytisus scoparius (Fam. Fabaceae) in southern Brazil - first step of an invasion process?

The occurrence of Scotch broom Cytisus scoparius (L.) Link (Fabaceae), is reported for the first time in Brazil. The species has been registered in the species-rich Campos Sulinos grasslands, in the Campos de Cima da Serra, and in the Serra do Sudeste. Naturalizing populations were frequently formed in natural habitats near to human settlements, where prevailing land uses and disturbances facilitate dispersal and establishment. The plant is an invasive species that has globally caused significant damage to biodiversity and economic losses. In Brazil, the species has a strong potential for spreading into a wide range of ecosystems. The Atlantic Forest biome and part of the Pampa biome, together known as the Campos Sulinos, represent optimal areas for the species. Features of the observed populations and recommendations for management are presented.

Landowner perceptions of the value of natural forest and natural grassland in a mosaic ecosystem in southern Brazil.

The forest-grassland mosaics of southern Brazil have been subject to many land use and policy changes over the decades. Like many grasslands around the world, the Campos grasslands are declining with few conservation efforts underway. In contrast, forests receive much attention and many incentives. It is hypothesized that perception of land cover has the potential to shape ecosystems. Here we conduct a questionnaire to further our understanding of decision-making practices that alter landscapes (Campos grassland, Araucaria forest, agriculture and plantation) and direct land policies in the region. Our analysis reveals that plantations are significantly less desirable than the other landscape types. However, plantation land use has increased by 87 % over the past few decades, as a result of industry and government incentives. The proportions of other landscape types have remained consistent over the past two decades. Restoration of native vegetation is not a priority of landowners and restoration would require a financial incentive.

A model-based method for estimating effective dispersal distance in tropical plant populations.

Dispersal is a key mechanism to help populations propagate across space and thus is important in helping to understand spatial patterns. However, it is often difficult to quantify empirically as it requires intensive and detailed field study. Here we describe a method for estimating the effective dispersal distance of tropical plant populations. The method integrates a simple spatially explicit, individual-based dynamic model and spatial statistical analysis. The model is partly parameterized from spatial point pattern data as well as time series data from a 50 ha tropical forest plot in Barro Colorado Island (BCI) in Panama. Correlation between our estimated dispersal distances and those from inverse modeling based on field studies to date on BCI raises some questions about the match between our methods and those previously used. The method we propose can be generalized to any population for which spatial point pattern data are available. Additional field studies would be useful to further validate our method.