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Knowledge on the structure and dynamics of Bulnesia sarmientoi ("palo santo") populations is necessary for forest management aimed at the conservation and high-quality timber production by this species and the preservation of the ecosystem services of its forests. We characterized forest structure and dynamics in stands with palo santo presence in the Nothern Argentinian Dry Chaco. We sampled 21 forest sampling clusters. Each forest sampling cluster includes four sets of concentric circular plots of 1000 m² (diameter >20 cm) and 500 m² (diameter >10 cm), located at the vertices of a square of 100 m side. Forest clusters were measured in 2007 and 2012. We calculated the importance value index (IVI) of each species in each conglomerate. We identified three typical structures with palo santo: a) palosantales in regularly flooded soils, b) palo cruz con palo santo, and c) Chaco mixed forest with the presence of palo santo. Periodic annual increment in diameter was 1.14 mm for all diameter classes. Taking as a reference the structure of a conglomerate with palo santo that was selective logged, we simulated alternative interventions (80% removal of all diameter classes or a diameter restriction of >40 cm) on stand dynamics. Cutting of 80% of the trees was a very severe intervention, suggesting that the removal of the smallest sizes for rural construction could compromise the recovery of the stand. A minimum size restriction could warrant recovery in 50 years. We suggest that the harvest of palo santo trees should be focused on large individuals with the highest added value potential. [ABSTRACT FROM AUTHOR]

Carbon emissions from land-use changes in tropical dry forest systems are poorly understood, although they are likely globally significant. The South American Chaco has recently emerged as a hot spot of agricultural expansion and intensification, as cattle ranching and soybean cultivation expand into forests, and as soybean cultivation replaces grazing lands. Still, our knowledge of the rates and spatial patterns of these land-use changes and how they affected carbon emissions remains partial. We used the Landsat satellite image archive to reconstruct land-use change over the past 30 years and applied a carbon bookkeeping model to quantify how these changes affected carbon budgets. Between 1985 and 2013, more than 142 000 km2 of the Chaco's forests, equaling 20% of all forest, was replaced by croplands (38.9%) or grazing lands (61.1%). Of those grazing lands that existed in 1985, about 40% were subsequently converted to cropland. These land-use changes resulted in substantial carbon emissions, totaling 824 Tg C between 1985 and 2013, and 46.2 Tg C for 2013 alone. The majority of these emissions came from forest-to-grazing-land conversions (68%), but post-deforestation land-use change triggered an additional 52.6 Tg C. Although tropical dry forests are less carbon-dense than moist tropical forests, carbon emissions from land-use change in the Chaco were similar in magnitude to those from other major tropical deforestation frontiers. Our study thus highlights the urgent need for an improved monitoring of the often overlooked tropical dry forests and savannas, and more broadly speaking the value of the Landsat image archive for quantifying carbon fluxes from land change. [ABSTRACT FROM AUTHOR]

Native forests are the natural ecosystems with the greatest social concern in terms of conservation and management. The scope of the definition of native forest has changed over time, which has influenced the adoption of different forest management instruments carried out by different institutions (e.g., the forest cover obtained from forest inventories in jurisdictions of Argentina). This leads to different results and misunderstandings, which often leads to incomparable outputs (e.g., native forest cover). The objective of this work was to analyse the current definition of the native forest implemented by the Argentine Government within the framework of Law 26331/07, which regulates the implementation of institutional policies. We propose a new definition based on the available scientific knowledge, and try to correct the conceptual gaps identified in the aforementioned law. The proposed definition differs from the original one in the inclusion of the minimum patch size, as well in the assessment of the connectivity and composition of the surrounding landscape. Other main aspects for its implementation are discussed, as well as the impacts at different spatial scales. [ABSTRACT FROM AUTHOR]

Permanent forest plots are sampling areas where tree identity, abundance and size are recorded periodically, in order to study how forests change with climate, natural disturbances, uses and management. So far, patterns of change observed with permanent plots in Argentina have been local or regional. To promote scientific collaborations between different research groups within and among regions of Argentina, we created the Network of Permanent Plots of Native Argentinian Forests (RAPP), which includes the regions of Bosques Andino-Patagónicos, Chaco Seco, Chaco Húmedo, Monte de Sierras y Bolsones, Monte de Llanuras y Mesetas, Selva Paranaense and Yungas. Here we synthesize and characterize the information of 317 permanent plots (328.9 ha) included in the RAPP, describing their geographic distribution, objectives, main methodological aspects, and characteristics of the forests where they are established (e.g., disturbance, land tenure, structure, species richness), and after that, discuss the complementarity between the RAPP and the national inventories of native forests. Permanent plots are established over a wide range of latitude (22.02-54.89° S) and elevation (19 a 2304 m a. s. l.), but they are mainly concentrated in Subtropics (Chaco Seco, Chaco Húmedo, Selva Paranaense, and Yungas) and in Bosques Andino-Patagónicos. In all plots, trees are taxonomically identified and different dasometric variables are remeasured, which are the basis for potential collaborations to answer ecological questions at a larger scale. We hope to continue incorporating working groups in the RAPP and encouraging the establishment of plots, mainly in regions with a low number of permanent plots such as Monte, Espinal, and Delta e Islas del Paraná. The goal is that the RAPP advances in the long-term study of all native forests in Argentina, achieving a greater national cover and more interactions among research teams. [ABSTRACT FROM AUTHOR]

Gonopterodendron sarmientoi is a threatened native tree of the Dry Chaco region in South America, adapted to semiarid conditions. However, the relationships among climatic and edaphic conditions and its forest structure have not been defined yet. Up to date, in Argentina, the study of palo santo forest management and conservation is scarce and still depends on basic information. The objectives of this study were 1) to classify forest groups based on forest stand attributes and species composition, 2) to analyze relationships between dasometric parameters of palo santo with climatic and edaphic variables at the regional level and forest types, and 3) to compare total aboveground biomass between forest types as a tool for managing and conserving this species. We compiled forest inventories carried out during the years 2004-2019, containing dasometric data of palo santo for the northern part of the Argentine Dry Chaco region. In the study area, we extracted climatic and edaphic conditions from global data base and national maps. We obtained three forest groups: palosantal, forests with low presence of palo santo and forests with high presence of palo santo. Temperature, precipitation, evapotranspiration and soil textures had significant effects on the forest structure of palo santo at the regional level and on forest types. The total density of individuals of G. sarmientoi has a different effect on the total biomass depending on the type of forest, which allows for different management and conservation practices. Consolidating a national forest plan for palo santo could address more viable proposals to manage and conserve the species in the region. [ABSTRACT FROM AUTHOR]

Anthropogenic activity leading to forest structural and functional changes needs specific ecological indicators and monitoring techniques. Since decades, forest structure, composition, biomass, and functioning have been studied with ground-based forest inventories. Nowadays, satellites survey the earth, producing imagery at different spatial and temporal resolutions. However, measuring the ecological state of large extensions of forest is still challenging. To reconstruct the three-dimensional forest structure, the structure from motion (SfM) algorithm was applied to imagery taken by an unmanned aerial vehicle (UAV). Structural indicators from UAV-SfM products are then compared to forest inventory indicators of 64 circular plots of 1000 m2 in a subtropical dry forest. Our data indicate that the UAV-SfM indicators provide a valuable alternative for ground-based forest inventory' indicators of the upper canopy structure. Based on the correlation between ground-based measures and UAV-SfM derived indicators, we can state that the UAV-SfM technique provides reliable estimates of the mean and maximum height of the upper canopy. The performance of UAV-SfM techniques to characterize the undergrowth forest structure is low, as UAV-SfM indicators derived from the point cloud in the lower forest strata are not suited to provide correct estimates of the vegetation density in the lower strata. Besides structural information, UAV-SfM derived indicators, such as canopy cover, can provide relevant ecological information as the indicators are related to structural, functional, and/or compositional aspects, such as biomass or compositional dominance. Although UAV-SfM techniques cannot replace the wealth of data collected during ground-based forest inventories, its strength lies in the three-dimensional (3D) monitoring of the tree canopy at cm-scale resolution, and the versatility of the technique to provide multi-temporal datasets of the horizontal and vertical forest structure. [ABSTRACT FROM AUTHOR]