H. Ricardo Grau

The Ecological Consequences of Socioeconomic and Land-Use Changes in Postagriculture Puerto Rico

Abstract Contrary to the general trend in the tropics, forests have recovered in Puerto Rico from less than 10% of the landscape in the late 1940s to more than 40% in the present. The recent Puerto Rican history of forest recovery provides the opportunity to study the ecological consequences of economic globalization, reflected in a shift from agriculture to manufacturing and in human migration from rural to urban areas. Forest structure rapidly recovers through secondary succession, reaching mature forest levels of local biodiversity and biomass in approximately 40 years. Despite the rapid structural recovery, the legacy of pre-abandonment land use, including widespread abundance of exotic species and broadscale floristic homogenization, is likely to persist for centuries.

RAINFALL-CONTROLLED TREE GROWTH IN HIGH-ELEVATION SUBTROPICAL TREELINES

It is generally assumed that tree growth in the upper limit of a forest is mainly controlled by summer temperature. This general statement is mostly based on studies from extra-tropical mountains and has been rarely evaluated in subtropical latitudes frequently characterized by drier climates. In the subtropical mountains from Northwestern Argentina (∼23° S), annual precipitation decreases with elevation from >1500 mm at 1200– 1500 m, to <200 mm above 4000 m. In consequence, tree growth at high elevations in the region may be seriously limited by water supply. In order to assess the influence of precipitation on tree growth, we evaluated the relationships between climatic variations and radial growth in four species growing at different altitudinal zones: Juglans australis from the montane cloud forest at 1800 m; Alnus acuminata from the montane savanna-like woodland at 2700 m; Prosopis ferox from the subalpine dryland at 3500 m; and Polylepis tarapacana from the high-elevation alpine dryland at 4750 m. D...

Globalization and soybean expansion into semiarid ecosystems of Argentina.

Deforestation is the product of complex interaction among local idiosyncratic properties of natural and social systems and driving forces that commonly operate at large spatial scales (1). Social and economic globalization, particularly reduced communication and transportation barriers, has increased the relative importance of global drivers of environmental change (e.g. deforestation). For example, agriculture expansion is increasingly influenced by technological changes that are rapidly disseminatedworldwide (2) and by changes in consumption patterns of a few countries that have a disproportionate influence on the global markets because of their large population (e.g. China) or high levels of consumption (e.g. USA, European Union). The increased importance of soybean production in the global economy is an example of how local and global factors can interact and have large effects on natural systems. A number of characteristics of soybean havemade it an attractive crop in the globalized context. Soybean has low water content, high nutritive value, and the capacity to yield a variety of products (e.g. human food, animal food, oil, and industrial derivates) (3). These characteristics reduce vulnerability tomarket fluctuations, reduce storage and transportation costs, and have contributed to its rapid expansion. Furthermore, the increasing global demand for soybean products has resulted in large investments in research and development and the widespread use of transgenic cultivars that have increased yields, reduced costs by reducing herbicide use, and increased the range of appropriate planting environments (4). A major factor influencing the growing demand for soybean has been a global increase inmeat consumption (5), much of which is produced with soybean meal. Until 1993, China was a major exporter of soybeans, but the increasing demand for meat, particularly pork and chicken, associated with the socioeconomic changes during the last 10 y has converted China into the number one soybean importer in the world (6). This increasing demand for soybeans is reflected in a doubling in planted area during the last 30 y (7). Globally, approximately 80 million ha are planted in soybean, and .70% is in the United States, Brazil, and Argentina. During the last 10 y, production in the United States has been relatively stable, but South America has experienced a dramatic increase, much of which was established by deforesting extensive areas of tropical dry forest (3, 4, 8). In this communication, we describe how increasing demand, technological advances, and climate change are driving soybean expansion in Argentina and seriously jeopardizing the integrity of extensive semiarid biomes.

Cropland/pastureland dynamics and the slowdown of deforestation in Latin America

Latin America has the planet’s largest land reserves for agriculture and had the most rapid agricultural expansion during the twenty-first century. A large portion of the expansion replaced forests, as shown by many local and regional studies. However, expansion varied regionally and also replaced other land covers. Further, it is important to distinguish between changes in cropland and pastureland as they produce food at different levels of efficiency and intensity. We used thirteen years (2001–2013) of MODerate Resolution Imaging Spectroradiometer satellite imagery to characterize cropland and pastureland expansion at multiple scales across Latin America. From 2001 to 2013, 17% of new cropland and 57% of new pastureland replaced forests throughout Latin America. Cropland expansion from 2001 to 2013 was less (44.27 Mha) than pastureland (96.9 Mha), but 44% of the 2013 cropland total was new cropland, versus 27% of the 2013 pastureland total, revealing higher regional expansion rates of row crop agriculture. The majority of cropland expansion was into pastureland within core agricultural regions of Argentina, Brazil, Bolivia, Paraguay, and Uruguay. On the contrary, pastureland largely expanded at frontiers, such as central Brazil, western Paraguay, and northern Guatemala. As others have suggested, regional agriculture is strongly influenced by globalization. Indeed, we find an overall decrease in agricultural expansion after 2007, coinciding with the global economic slowdown. The results illustrate agricultural cropland and pastureland expansion across Latin America is largely segregated, and emphasize the importance of distinguishing between the two agricultural systems, as they vary in land use intensity and efficiency.

Are Rural–Urban Migration and Sustainable Development Compatible in Mountain Systems?

Abstract Rural–urban migration is having a considerable socioeconomic and environmental effect in mountain regions. In response, most rural development programs discourage outmigration on the grounds that it has negative social consequences and compromises ecological sustainability. However, rural–urban migration generally improves the living standards of migrants and leads to the disintensification of land use in fragile ecosystems with low productivity, thus stimulating ecosystem recovery and improving watershed and biodiversity protection—as shown by experience in the Caribbean and South America. These advantages have emerged even in the absence of any planning and could be maximized if international funding agencies, NGOs, and local governments re-evaluated rural development strategies. At a minimum, rural–urban migration is a reality that should not be ignored. More importantly, rural–urban migration provides an opportunity to improve the living conditions of marginal populations while protecting the environment.

Liana-host tree associations in a subtropical montane forest of north-western Argentina

In a subtropical montane forest of north-western Argentina (27 ◦ S, 1000 m elevation), we analysed the effect of crown illumination, trunk diameter, foliar phenology and tree species identity as determinants of liana-host tree associations, as well as the spatial pattern of liana abundance in a 6-ha permanent plot. We recorded 2346 liana individuals ≥ 2 cm and 2320 trees ≥ 10 cm dbh. Sixty-five per cent of the trees hosted at least one liana stem. Large and well-lit trees were more likely to support lianas and supported more liana abundance than small and shaded trees. Yet, when trees were standardized by their size (liana basal area/tree basal area ratio), lianas were more abundant in smaller and less-exposed trees. Foliar phenology and tree species identity showed no association with the frequency of liana colonization and their abundance. Overall, tree features played a minor or even neutral role in structuring the liana community within this forest. Instead, lianas showed a positive autocorrelation at spatial scales up to 40 m. This suggests that lianas might be mostly structured by light- and dispersal-related factors such as those involving canopy access or canopy disturbances, with a negligible effect of host species identity and foliar phenology.

Land-use and land-cover effects on regional biodiversity distribution in a subtropical dry forest: a hierarchical integrative multi-taxa study

Abstract Latin American subtropical dry ecosystems have experienced significant human impact for more than a century, mainly in the form of extensive livestock grazing, forest products extraction, and agriculture expansion. We assessed the regional-scale effect of land use and land cover (LULC) on patterns of richness distribution of trees, birds, amphibians, and mammals in the Northern Argentine Dry Chaco (NADC) over c. 19 million hectares. Using species distribution models in a hierarchical framework, we modeled the distributions of 138 species. First, we trained the models for the entire Argentinean Chaco with climatic and topographic variables. Second, we modeled the same species for the NADC including the biophysical variables identified as relevant in the first step plus four LULC-related variables: woody biomass, distance to crops, density of livestock-based rural settlements (puestos), and vegetation cover. Third, we constructed species richness maps by adding the models of individual species and considering two situations, with and without LULC variables. Four, richness maps were used for assessing differences when LULC variables are added and for determining the main drivers of current patterns of species richness. We found a marked decrease in species richness of the four groups as a consequence of inclusion of LULC variables in distribution models. The main factors associated with current richness distribution patterns (both negatively) were woody biomass and density of livestock puestos. Species richness in present-day Semiarid Chaco landscapes is strongly affected by LULC patterns, even in areas not transformed to agriculture. Regional-scale biodiversity planning should consider open habitats such as grasslands and savannas in addition to woodlands.

Landscape Context and Local-scale Environment Influence Regeneration of Pioneer Tree Species in Treefall Gaps'

ABSTRACT Composition of pioneer tree species was recorded for 23 to 76 treefalls in the forests of La Selva (LS), Barro Colorado Island (BCI), Cocha Cashu Research Station (CC), and KM41 to evaluate the hypothesis that distance to secondary forests influences the composition of pioneer tree species at scales of thousands of hectares and to assess the relative importance of distance to seed sources compared to two microenvironmental factors: soil and gap size. Discriminant function analysis (DFA) was used to assess the relative importance of the landscape and environmental factors in controlling the presence in gaps of Cecropia species that are typical of secondary forests regenerating after large-scale disturbances. Principal component analysis (PCA) was used as an ordination technique based on pioneer species composition of each gap. The PCA ordination axes were regressed against soil type, gap size, forest type, and distance values of each site to explore the relationship between composition and control factors. At the four sites, the variable best correlated to the discriminant function of gaps with and without Cecropia was the distance to secondary forests, although such discriminant function was statistically significant at only one site. In three of the four sites (with the exception of BCI, where there are no typical young secondary forests), distance to secondary forests was correlated with at least one axis of the PCA (P < 0.06). Other significant correlations included soil variables (CC and KM41), gap size (KM41), and forest type (secondary vs. primary; BCI). Overall, the results provide some support for the hypothesis that at the spatial scale of this study, distance to young secondary forests (both natural and anthropogenic) influences treefall gap composition at a level comparable to endogenous and exogenous microenvironmental factors.

Landscape context and microenvironment influences on liana communities within treefall gaps

Abstract Questions: How do gap aspect, openness, age and gap density in the surroundings affect diversity and composition of lianas within treefall gaps? Are the variation patterns in liana communities within treefall gaps associated with their climbing mechanisms? Location: Subtropical montane forests in northwestern Argentina. Methods: We used ordination analyses (NMDS) and multiple regressions to describe liana communities (species and climbing groups, stems ≥ 1 cm) in 35 gaps located in a 6-ha plot and to assess relationships with aspect, canopy and subcanopy openness, age and density of recent (three to eight years old) and old (> 8 years old) gaps. Results: Treefall gaps segregated in the ordination diagrams based on their liana species and climbing mechanisms composition: gaps surrounded by a higher density of recent gaps showed higher densities of lianas species using tendrils, spines / hooks and voluble stems. Liana density and richness (independent of stem density) were also positively associated with the density of recent gaps in the surroundings, and negatively associated to gap age. The number of liana species corrected per area was negatively associated to gap aspect and subcanopy openness, and absolute number of liana species was positively associated to gap canopy openness. Conclusions: This study integrates the analysis of different factors influencing liana communities within treefall gaps, and shows that spatial context of gap density (a variable largely neglected in previous studies) is particularly important on lianas composition and diversity, probably by increasing propagule input and the availability of small trellises for support. Nomenclature: Zuloaga & Morrone (1999).

Forest conservation: Remember Gran Chaco

TROPICAL AND SUBTROPICAL dry forests around the globe are experiencing rapid clearing and concomitant biodiversity loss ([ 1 ][1]). In their Research Article “Plant diversity patterns in neotropical dry forests and their conservation implications” (23 September 2016, p. [1383][2]), DRYFLOR et al