Plant diversity patterns in neotropical dry forests and their conservation implications

This is the author accepted manuscript. The final version is available from American Association for the Advancement of Science via the DOI in this record.Seasonally dry tropical forests are distributed across Latin America and the Caribbean and are highly threatened, with less than 10% of their original extent remaining in many countries. Using 835 inventories covering 4660 species of woody plants, we show marked floristic turnover among inventories and regions, which may be higher than in other neotropical biomes, such as savanna. Such high floristic turnover indicates that numerous conservation areas across many countries will be needed to protect the full diversity of tropical dry forests. Our results provide a scientific framework within which national decision-makers can contextualize the floristic significance of their dry forest at a regional and continental scale.This paper is the result of the Latin American and Caribbean Seasonally Dry Tropical Forest Floristic Network (DRYFLOR), which has been supported at the Royal Botanic Garden Edinburgh by a Leverhulme Trust International Network Grant (IN-074). This work was also supported by the U.K. Natural Environment Research Council grant NE/I028122/1; Colciencias Ph.D. scholarship 529; Synthesys Programme GBTAF-2824; the NSF (NSF 1118340 and 1118369); the Instituto Humboldt (IAvH)–Red colombiana de investigación y monitoreo en bosque seco; the Inter-American Institute for Global Change Research (IAI; Tropi-Dry, CRN2-021, funded by NSF GEO 0452325); Universidad Nacional de Rosario (UNR); and Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). The data reported in this paper are available at www.dryflor.info. R.T.P. conceived the study. M.P., A.O.-F., K.B.-R., R.T.P., and J.W. designed the DRYFLOR database system. K.B.-R. and K.G.D. carried out most analyses. K.B.-R. R.T.P., and K.G.D. wrote the manuscript with substantial input from A.D.-S., R.L.-P., A.O.-F., D.P., C.Q., and R.R. All the authors contributed data, discussed further analyses, and commented on various versions of the manuscript. K.B.-R. thanks G. Galeano who introduced her to dry forest research. We thank J. L. Marcelo, I. Huamantupa, C. Reynel, S. Palacios, and A. Daza for help with fieldwork and data entry in Peru

Recovery Times and Sustainability in Logged-Over Natural Forests in the Caribbean

Despite the widespread use and strong promotion of the sustainable forest management approach, there are still uncertainties about the actual contribution of current forest management practices to sustainability. We studied the problem of sustainable timber production in four tropical countries (Belize, Guyana, Suriname, and Trinidad and Tobago). Data assessed on experimental plots covering 10 km2 were used to compare management practices of four forest tenure types that commonly exist in the study countries: large scale concessions (LSC), private forests (PR), periodic block system forests (PBS), and community managed forests (CM). As an indicator of sustainable timber production, we calculated the recovery times expected under the initial condition of the stands and compared them with currently practiced cutting cycles. Three growth scenarios were simulated using diameter growth rates (1.6/2.7/4.5 mm year−1) from empirical data from studies in the region. Initial volumes were determined for all commercial trees as well as for commercial trees with a DBH-threshold ≥45 cm. Highest initial volumes were found in LSC and PBS managed forests. Lowest volumes were found in CM and PR forests. Assuming the lowest growth rate for all commercial trees, none of the stands studied reached the initial pre-harvest volumes within the currently practiced cutting cycles. Assuming the highest growth rate for all trees, LSC, PBS, and PR forests reach the initial pre-harvest volume. Looking at the subset of commercial trees with a DBH ≥45 cm, all stands will reach the initial volume within 30 years only if the highest growth rate is assumed. We show that general harvest codes do not guarantee sustainable forest management in the tropics. Local stand conditions must always be one of the guiding principles of sustainable timber utilization. Applying the rigid rules, which do not take into account the current conditions of the stands, entails long-term risk of forest degradation

Estimation of soil clay content from hygroscopic water content measurements

Soil texture and the soil water characteristic are key properties used to estimate flow and transport parameters. Determination of clay content is therefore critical for understanding of plot-scale soil heterogeneity. With increasing interest in proximal soil sensing, there is the need to relate obtained signals to soil properties of interest. Inference of soil texture, especially clay mineral content, from instrument response from electromagnetic induction and radiometric methods is of substantial interest. However, the cost of soil sampling and analysis required to link proximal measurements and soil properties, for example, clay mineral content, can sometimes outweigh the benefits of using a fast proximal technique. In this paper, we propose that determination of a soil's hygroscopic water content at 50% atmospheric relative humidity (RH50), which is time and cost efficient, and particularly suitable for developing countries, can act as a useful surrogate for clay content in interpreting soil spatial patterns based on proximal signals. We used standard clays such as kaolinite, illite, and montmorillonite to determine the water release characteristic as a function of hygroscopic water content. We also determined clay content of soils from temperate (Arizona, United States) and tropical (Trinidad) regions using the hydrometer method and hygroscopic water content for soils equilibrated at RH50. We found linear dependence of clay percentage and RH50 for a range of soil mineralogies. Hygroscopic water measurements offer an inexpensive and simple way to estimate site-specific clay mineral content that in turn can be used to interpret geophysical signal data in reconnaissance surveys

Status, trends and future dynamics of biodiversity and ecosystems underpinning nature’s contributions to people

Biodiversity is linked to ecosystem functions and is highly relevant to NCP across the ecologically diverse and species-rich Americas. All units of analysis of the Americas considered contribute to human well-being. However, Tropical and subtropical moist forests, Temperate and boreal forests and woodlands, Tropical and subtropical dry forests, Mediterranean forests, woodlands and scrub, and Tundra and high elevation habitats stand out as particularly critical for NCP delivery. For quatic systems, freshwater is considered somewhat more important for NCP than marine. Except in a limited number of cases, this chapter shows that the biodiversity in the Americas´ terrestrial biomes and freshwater and marine habitats continues to undergo serious erosion. The introduction and spread of alien species can be expected to continue causing direct and indirect impacts on human well-being and biodiversity. The subregions currently undergoing most dramatic land use change, considering their spatial extent, are South America and Mesoamerica, where conversion of vegetation to support pastures, agriculture and exotic plantation forestry is widespread. These changes are leading to major losses of habitat with concomitant population and species declines. In the marine and freshwater realms, the number of threatened species is high, and many fish species are over-exploited. Climate change has begun to affect the distribution of biodiversity, but to a greater degree in North America than South America for the moment. Increased fire frequency in several biomes constitutes a growing threat. Despite significant progress in developing protective measures for the land and in the sea, they are often insufficient. The greatest challenges to policymakers and decision makers will be to: arrest or slow habitat loss; encourage more ecologically-friendly management practices to ensure long-term food- and water-security; and promote alternative biodiversity-based economic activities that are less destructive than current activities. These are not new challenges. Progress necessarily implies a conscious, collective societal effort. Many lessons can be learned from indigenous peoples who have succeeded in living in harmony on the land.EEA Santa CruzFil: Cavender-Bares, Jeannine. University of Minnesota; Estados UnidosFil: Arroyo, Mary T. K. Universidad de Chile; Chile.Fil: Abell, Robin. Conservation International; Estados UnidosFil: Ackerly, David. University of California. Berkeley; Estados UnidosFil: Ackerman, Daniel. University of Minnesota; Estados UnidosFil: Arim, Matias. Universidad de la República de Uruguay; Uruguay.Fil: Belnap, Jayne. U.S. Geological Survey; Estados UnidosFil: Castañeda Moya, Francisco. Universidad de San Carlos de Guatemala; Guatemala.Fil: Dee, Laura. University of Minnesota; Estados UnidosFil: Estrada-Carmona, Natalia. CGIAR; FranciaFil: Gobin, Judith. University of West Indies, Trinidad y Tobago.Fil: Isbell, Forest. University of Minnesota; Estados UnidosFil: Köhler, Gunther. Senckenberg Research Institute and Natural History Museum Frankfurt; AlemaniaFil: Koops, Marten. Fisheries and Oceans Canada; Canadá.Fil: Kraft, Nathan. University of California. Los Angeles; Estados UnidosFil: Macfarlane, Nicholas. IUCN; Estados UnidosFil: Martínez-Garza, Cristina. Universidad Autónoma del Estado de Morelos; México.Fil: Metzger, Jean-Paul. Universidade de São Paulo; Brasil.Fil: Mora, Arturo. IUCN-SUR; Ecuador.Fil: Oatham, Michael. University of West Indies; Trinidad y Tobago.Fil: Paglia, Adriano. Universidade Federal de Minas Gerais; Brasil.Fil: Pedrana, Julieta. Instituto Nacional de Tecnología Agropecuaria; Argentina.Fil: Peri, Pablo Luis. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Santa Cruz; Argentina.Fil: Peri, Pablo Luis. Universidad Nacional de la Patagonia Austral; Argentina.Fil: Peri, Pablo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Piñeiro, Gervasio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Randall, Robert. Fisheries and Oceans Canada; Canadá.Fil: Weis, Judith. Rutgers University; Estados UnidosFil: Walker Robbins, Wren. North Star AISES Alliance; Estados UnidosFil: Ziller, Silvia Renate. Horus Institute; Brasil