Ricardo Augusto Gorne Viani

Convergence of soil nitrogen isotopes across global climate gradients

Quantifying global patterns of terrestrial nitrogen (N) cycling is central to predicting future patterns of primary productivity, carbon sequestration, nutrient fluxes to aquatic systems, and climate forcing. With limited direct measures of soil N cycling at the global scale, syntheses of the 15N:14N ratio of soil organic matter across climate gradients provide key insights into understanding global patterns of N cycling. In synthesizing data from over 6000 soil samples, we show strong global relationships among soil N isotopes, mean annual temperature (MAT), mean annual precipitation (MAP), and the concentrations of organic carbon and clay in soil. In both hot ecosystems and dry ecosystems, soil organic matter was more enriched in 15N than in corresponding cold ecosystems or wet ecosystems. Below a MAT of 9.8°C, soil δ15N was invariant with MAT. At the global scale, soil organic C concentrations also declined with increasing MAT and decreasing MAP. After standardizing for variation among mineral soils in soil C and clay concentrations, soil δ15N showed no consistent trends across global climate and latitudinal gradients. Our analyses could place new constraints on interpretations of patterns of ecosystem N cycling and global budgets of gaseous N loss.

How to Organize a Large-Scale Ecological Restoration Program? The Framework Developed by the Atlantic Forest Restoration Pact in Brazil

Large-scale ecological restoration programs across the world have begun to extensively transform degraded lands into young native ecosystems. However, more projects like these will be necessary in the coming years to fulfill the goal of restoring 150 million ha established by United Nations Convention on Biological Diversity. Here, we present and discuss the steps required for and the lessons learned from the organization of a large-scale ecological restoration program in Brazil, the Atlantic Forest Restoration Pact. These lessons are organized around 9 steps: (a) the presentation of the motivations driving the promotion of large-scale restoration, (b) the organization of the main stakeholders, (c) the definition of goals, (d) the organization of a database, (e) the indication of both available and priority areas for restoration, (f) the proposal of science-based and field-validated methods, (g) the establishment of a monitoring protocol, (h) the proposal of a communication program to unite members and interact with society, and (i) the strategies for promoting the establishment of public policies conducive to restoration. This framework may provide a template to help other initiatives to mainstream isolated restoration projects into a large and well-organized movement, which may increase the chances of successful restoration in the future.

Savanna soil fertility limits growth but not survival of tropical forest tree seedlings

Background and AimsCerradão (Brazilian woodland savannas) and seasonally dry forests (SDF) from southeastern Brazil occur under the same climate but are remarkably distinct in species composition. The objective of this study was to evaluate the role of soil origin in the initial growth and distribution of SDF and Cerradão species.MethodsWe conducted a greenhouse experiment growing Cerradão and SDF tree seedlings over their soil and the soil of the contrasting vegetation type. We evaluated soil nutrient availability and seedling survivorship, growth and leaf functional traits.ResultsDespite the higher nutrient availability in SDF soils, soil origin did not affect seedling survivorship. The three SDF species demonstrated home-soil advantage, enhanced growth with increasing soil nutrient availability and had higher growth rates than Cerradão species, even on Cerradão soils. Growth of Cerradão seedlings was not higher on Cerradão soil and, overall, was not positively correlated with soil nutrient availability.ConclusionsSDF species are fast-growing species while Cerradão trees tend to be slow-growing species. Although savanna soil reduces growth of forest species, our findings suggest that soil chemical attributes, alone, does not exclude the occurrence of SDF seedlings in Cerradão and vice-versa.

Environmental gradients and the evolution of successional habitat specialization: a test case with 14 Neotropical forest sites

Successional gradients are ubiquitous in nature, yet few studies have systematically examined the evolutionary origins of taxa that specialize at different successional stages. Here we quantify successional habitat specialization in Neotropical forest trees and evaluate its evolutionary lability along a precipitation gradient. Theoretically, successional habitat specialization should be more evolutionarily conserved in wet forests than in dry forests due to more extreme microenvironmental differentiation between early and late-successional stages in wet forest. We applied a robust multinomial classification model to samples of primary and secondary forest trees from 14 Neotropical lowland forest sites spanning a precipitation gradient from 788 to 4000 mm annual rainfall, identifying species that are old-growth specialists and secondary forest specialists in each site. We constructed phylogenies for the classified taxa at each site and for the entire set of classified taxa and tested whether successional habitat specialization is phylogenetically conserved. We further investigated differences in the functional traits of species specializing in secondary vs. old-growth forest along the precipitation gradient, expecting different trait associations with secondary forest specialists in wet vs. dry forests since water availability is more limiting in dry forests and light availability more limiting in wet forests. Successional habitat specialization is non-randomly distributed in the angiosperm phylogeny, with a tendency towards phylogenetic conservatism overall and a trend towards stronger conservatism in wet forests than in dry forests. However, the specialists come from all the major branches of the angiosperm phylogeny, and very few functional traits showed any consistent relationships with successional habitat specialization in either wet or dry forests. Synthesis. The niche conservatism evident in the habitat specialization of Neotropical trees suggests a role for radiation into different successional habitats in the evolution of species-rich genera, though the diversity of functional traits that lead to success in different successional habitats complicates analyses at the community scale. Examining the distribution of particular lineages with respect to successional gradients may provide more insight into the role of successional habitat specialization in the evolution of species-rich taxa.

Changing precipitation regimes and the water and carbon economies of trees

Climate change is predicted to affect the water balance of several ecosystems mostly through changes in the energy budget and hydrological input (rainfall frequency, intensity, and timing). Changes in rainfall patterns and cloudiness directly affect incoming radiation, atmospheric water vapor saturation deficit and soil water availability, the main variables controlling the rates of water uptake and transport along the soil–plant–atmosphere continuum (SPAC). Developing a predictive framework about vegetation responses to a changing climate is challenging because it involves complex non-linear interactions between these environmental variables and species-specific responses. By examining the hydraulic traits of functional groups within plant communities we can better predict the impacts of changes in rainfall regimes within functional groups and therefore, generate more realistic predictions of ecosystem carbon and water balance changes due to local and regional changes in precipitation regimes. In this review, we discuss several aspects of plant hydraulic functioning and then explore how predicted changes in precipitation regimes may affect tree water and carbon balance. We examine the impacts of changes in rainfall patterns on the SPAC and also explore the multiple ways that plants can absorb and transport water. Finally, we explore the diversity of hydraulic traits and potential mechanisms causing large-scale drought-induced mortality recently observed in several ecosystems.

Sobrevivência em viveiro de mudas de espécies nativas retiradas da regeneração natural de remanescente florestal

Seedling survival was evaluated regarding transplanted saplings obtained from natural regeneration of a Semideciduous Seasonal Forest fragment, located at Bofete, Sao Paulo State, Brazil. Shrub and trees species seedlings up to 30 cm height were collected from samples sited on a forest remnant, transplanted to a nursery under 50% shade tissue, and evaluated periodically during nine months. A total of 2,424 seedlings, belonging to 110 species were transferred to the nursery. Average survival reached 69%, although this survival rate was quite variable according to the species, families and height classes of the evaluated individuals. In spite of the fact that pioneer species presented higher survival rate, several non-pioneer species also obtained high values of survival. Besides, many of the survivor species are usually not available in forest nurseries of the Sao Paulo State. The transference of seedlings from natural regeneration of forest fragments to forest nurseries seems to be a complementary and a viable method in order to produce saplings of native species, increasing diversity within nurseries with forest restoration purposes.

POTENTIAL OF THE SEEDLING COMMUNITY OF A FOREST FRAGMENT FOR TROPICAL FOREST RESTORATION

Forest restoration projects are usually planted with a reduced number of species as compared to standing forests, largely due to the low availability of native species in seedling nurseries. In the present study, the potential of the native seedling community as a source of seedlings for forest restoration is analyzed. To do so, the seedling community from a forest fragment located in the southeast of Brazil was evaluated. Individuals (tree and shrub species) up to 30 cm height were measured and identified in 20 4 × 4 m plots. Altogether, 6,136 individuals (17 individuals m -2 ) belonging to 119 species were sampled. The seedling community showed a spatial heterogeneity with respect to the density of individuals and composition of species, and also a spatial aggregation for the 10 most abundant species. Several species that occurred in high densities in the seedling community are not presently available in regional forest nurseries and are therefore not used in restoration projects. This result and the high number of individuals and species found in the fragment suggest a great potential of this type of forest remnants as a source of highly diverse seedling banks for use in restoration projects.

Impacto da remoção de plântulas sobre a estrutura da comunidade regenerante de Floresta Estacional Semidecidual

Palavras-chave: ecologia florestal, plântulas, recuperacao de areas degradadas, regeneracao natural, restauracao ecologica ABSTRACT - (Impact of seedling removal on regenerating community structure of a seasonal semideciduous forest). Transplanting seedlings and saplings from natural forests has been considered an alternative to producing saplings of native species for forest restoration purposes, but the possible impact of this procedure on plant community regeneration has not been investigated. This work evaluates the impact of different treatments of shrub and tree-seedling (up to 30 cm) removal from a seasonal semideciduous forest fragment located in southeastern Brazil on the natural regeneration process. Eighty 2×2 m plots were installed in two habitats (forest edge and interior) and submitted to four seedling-removal treatments (I, II - 100% removal with or without soil mixing; III - 50% removal without soil mixing; and IV - control treatment without seedling removal). Regeneration density and richness were evaluated before treatment as well as 6, 12 and 18 months later. The results were compared among treatments for each evaluation period and among periods within treatments. There were similarities between edge and interior. The natural regeneration process did not improve with soil mixing. Plots submitted to seedling removal partially recovered plant density; however, these plots had lower species richness when compared to the control and to the initial values before treatment. Seedling removal has a negative impact on the regeneration process of low-density species, thus the use of natural regeneration as a sapling source for forest restoration purposes should focus only on high- density species with well-known regeneration strategies and not on the community as a whole.

Protocol for Monitoring Tropical Forest Restoration: Perspectives From the Atlantic Forest Restoration Pact in Brazil

Monitoring protocols are needed to evaluate the millions of hectares of land that are being proposed for forest restoration in the coming decades. Standardized proposals are critical to evaluate efficacy of restoration strategies, identify triggers for corrective actions, compare results across projects, and generally learn from past projects to inform future restoration efforts. We describe an iterative process, including over 200 stakeholders, to develop a protocol for monitoring Brazilian Atlantic Forest restoration. We give an overview of the ecological, socioeconomic, and management criteria, indicators, and metrics included in the protocol. Strengths of the protocol include the following: (a) testing and use across sites with a range of ages, forest types, past land uses, restoration techniques, and implementing institutions; (b) participation by a broad range of government, nongovernment, private, and academic institutions in the protocol development process; and (c) inclusion of socioeconomic and management criteria. Next steps for facilitating the broad adoption of the protocol in the Atlantic Forest region include providing in person and online training courses, establishing an online repository for storing and comparing monitoring data, and developing smartphone applications to facilitate data collection. Although the protocol was developed for the Atlantic Forest context and further refinements are needed, we think that the Atlantic Forest Pact monitoring protocol may serve as a model to inform the development of similar protocols in other regions, which ultimately could be integrated to produce a pantropical protocol for common use by several restoration forest programs worldwide.

Caracterização florística e estrutural de remanescentes florestais de Quedas do Iguaçu, Sudoeste do Paraná

O sudoeste paranaense localiza-se na transicao entre a Floresta Estacional Semidecidual (FES) e a Floresta Ombrofila Mista (FOM), numa regiao de grande relevância ecologica, por conter duas importantes formacoes florestais do sul-sudeste brasileiro. Entretanto, essa mesma regiao e marcada pela escassez de levantamentos floristicos e de caracterizacao da vegetacao. Nesse trabalho e feita a caracterizacao floristica e estrutural de tres areas de vegetacao nativa, localizadas em Quedas do Iguacu, sudoeste do Parana, na bacia do rio Iguacu. Alem disso, foi feita a caracterizacao fitogeografica das florestas estudadas, com base nos dados coletados e na listagem de especies amostradas em outras 52 areas de FES ou FOM do Brasil. Em cada uma das tres areas estudadas, a vegetacao arbustivo-arborea (diâmetro a altura do peito > 5 cm) foi caracterizada por meio da alocacao de pontos quadrantes. No total foram encontradas 128 especies, com variacao entre 63 a 78 para cada area. Cada area apresentou distincao quanto a estrutura e as especies mais abundantes. Alem disso, as areas se distinguem quanto ao grau de influencia da FES e da FOM em sua composicao floristica. Comparativamente, a area de menor altitude, localizada no vale do Rio Iguacu, apresenta mais elementos de FES em sua composicao floristica, enquanto as outras duas areas, localizadas em trechos mais elevados, tem maior influencia da FOM, contando inclusive com a ocorrencia de Araucaria angustifolia (Bertol.) Kuntze.