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Stem capacitance and water storage are known to play an important role in the water economy of trees by acting as an intermediate water source for transpiring leaves. The bark, in addition to be involved in protection and mechanical support of the trees, can also serve as a water reservoir. We examined the relationship between inner bark and sapwood biophysical properties in tree species occurring in forests at the opposite ends of a moisture gradient in subtropical South America. We also assessed the relationships between wood density, growth rate and the magnitude of the water reservoir. The inner bark thickness varied between 1.89 and 0.50 cm across species and sites and there were not significant differences between forests. Inner bark capacitance of species from the dry forest was higher than sapwood capacitance, and the opposite was found in the moist forest. Sapwood capacitance (262 ± 80.8 Kg m−3 MPa−1) was significantly higher in the moist forest compared to the dry forest (41.9 ± 4.5 Kg m−3 MPa−1), while the opposite was found for inner bark (50.7 ± 8.4 and 83.1 ± 11.4 Kg m−3 MPa−1, respectively). Inner bark capacitance and density were linear and positively correlated across species, while for sapwood the relationship was well-described by a negative exponential function. In species with higher percentage of inner bark, the time lags in the daily contractions of bark and sapwood tissues were lower. Relative growth rate was negatively correlated with inner bark and sapwood density and positively with daily stored water used and percentage of inner bark across species and sites. Our results suggest that sapwood is a relevant water storage tissue in the trees of the moist forest while inner bark is important for tree functioning in the dry forest. High stem capacitance and water storage are needed to cope with short dry spells or seasonal periods of water deficit, and for maintaining growth rates. These stem properties will be more relevant under climatic scenarios with more frequent extreme drought events or seasonal reduction in precipitation in these forest ecosystems.

Humans place strong pressure on land and have modified around 75% of Earth's terrestrial surface. In this context, ecoregions and biomes, merely defined on the basis of their biophysical features, are incomplete characterizations of the territory. Land system science requires classification schemes that incorporate both social and biophysical dimensions. In this study, we generated spatially explicit social-ecological land system (SELS) typologies for South America with a hybrid methodology that combined data-driven spatial analysis with a knowledge-based evaluation by an interdisciplinary group of regional specialists. Our approach embraced a holistic consideration of the social-ecological land systems, gathering a dataset of 26 variables spanning across 7 dimensions: physical, biological, land cover, economic, demographic, political, and cultural. We identified 13 SELS nested in 5 larger social-ecological regions (SER). Each SELS was discussed and described by specific groups of specialists. Although 4 environmental and 1 socioeconomic variable explained most of the distribution of the coarse SER classification, a diversity of 15 other variables were shown to be essential for defining several SELS, highlighting specific features that differentiate them. The SELS spatial classification presented is a systematic and operative characterization of South American social-ecological land systems. We propose its use can contribute as a reference framework for a wide range of applications such as analyzing observations within larger contexts, designing system-specific solutions for sustainable development, and structuring hypothesis testing and comparisons across space. Similar efforts could be done elsewhere in the world. Copyright © 2022 by the author(s).

ispartof: Remote Sensing vol:23 issue:12 pages:4005-4005 status: published

Las plantaciones forestales representan formas de uso de la tierra con posibles impactos sobre el balance de carbono, la fertilidad del suelo y la diversidad biológica. Estos efectos dependen del tipo de manejo que reciben y la situación de partida en la que se establecen. En este proyecto se pretende estudiar la dinámica de los almacenajes de carbono y sus tasas de recambio, en plantaciones de Eucalyptus spp. a escala regional en la cuenca forestal del rio Uruguay. Los objetivos particulares son: estimar la superficie de plantaciones de Eucalyptus spp. y su evolución en los últimos 25 años; evaluar el efecto de diferentes prácticas silvícolas, historia de uso, y destino de producción en el almacenaje de carbono; explorar las relaciones entre las características del productor y el tipo de manejo realizado; desarrollar un modelo que permita explorar el balance de carbono según las prácticas de manejo y el análisis de escenarios de uso. La hipótesis de este trabajo es que las diferencias en la historia de uso y la silvicultura se encuentran asociadas con diferencias en las características de los productores y resultan en diferentes almacenajes y tasas de recambio del carbono en la biomasa y el suelo de las plantaciones forestales. El trabajo se llevará a cabo en la zona sedimentaria de la cuenca media e inferior del río Uruguay a lo largo del área limítrofe entre Argentina y Uruguay, un área de aproximadamente 20000 km2 de superficie. Se generará cartografía de plantaciones forestales utilizando métodos de teledetección y sistemas de información geográfica con imágenes satelitales y se realizaran clasificaciones para realizar análisis de series temporales en un período de 25 años. Se calculará almacenaje de carbono a partir de la biomasa estimada de mediciones de altura, DAP y muestras de raíces y suelo. Se realizarán encuestas a productores forestales con el objetivo de caracterizarlos e indagar a cerca del objetivo de producción para realizar análisis multivariados e identificar agrupamientos de productores. Se estimará la cantidad de carbono almacenada en la región y su proyección. Se probaran modelos más complejos que incorporen prácticas de manejo para explorar impactos ante cambios en esos factores., Universidad Nacional de La Plata

El conocimiento de la estructura y la dinámica de las poblaciones de Bulnesia sarmientoi ("palo santo") es necesario para una gestión forestal capaz de conservar la especie, asegurar la producción maderera de alta calidad y preservar los servicios ecosistémicos que brindan los bosques donde se encuentra. Se caracterizó la estructura y la dinámica forestal en bosques con presencia de palo santo en el norte del Chaco Seco argentino. Se establecieron 21 conglomerados compuestos cada uno por cuatro juegos de parcelas concéntricas de 1000 m² (diámetro >20 cm) y 500 m² (diámetro >10 cm), ubicadas en los vértices de un cuadrado de 100 m de lado. Los conglomerados se midieron en 2007 y 2012. Se realizaron cálculos de parámetros estructurales y del índice de valor de importancia de cada especie en cada conglomerado. Se hallaron tres estructuras típicas: a) palosantales de bañado, b) palo cruz con palo santo, y c) bosque chaqueño con presencia de palo santo. A partir de la remedición de los árboles de palo santo se calculó un incremento periódico anual de 1.14 mm/año. Tomando como referencia la estructura de un conglomerado con palo santo que fue aprovechado entre mediciones se realizaron simulaciones de intervenciones alternativas (remoción de 80% de individuos de todas las clases diamétricas o aplicación de restricción de diámetro >40 cm) sobre la dinámica del rodal. Las proyecciones a 50 años muestran que la corta de 80% es muy severa, lo que indicaría que los aprovechamientos de tamaños menores para postes pueden comprometer la recuperación del rodal. En las cortas centradas en los tamaños mayores se lograría una recuperación en 50 años. En función de nuestros resultados, se sugiere un enfoque de uso de la especie centrado en productos de gran tamaño y con el mayor valor agregado posible. 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.

The Dry Chaco is a semi-arid ecoregion in South America, covering parts of Argentina, Paraguay, and Bolivia. To date, the region hosts one of the largest dry forests in the world, but expansion of dryland agriculture and cattle ranching led to gradual conversion of native vegetation to anthropogenic land cover. The potential impact of these newly established agricultural lands on the surrounding environment is of great concern. Local studies have shown that deforestation leads to changes in the soil-water balance. In the longer term, this can lead to a gradual rise of the groundwater table, mobilizing water-soluble salts to the surface, and affecting plant growth and crop productivity. Therefore, the main objective of this study was to gain insight into spatio-temporal patterns of soil hydrology and salinity of the Dry Chaco using land surface models (LSMs), remote sensing data, and in situ measurements of soil salinity. The central hypotheses were that (i) the impact of deforestation on soil salinity varies with existing climatic and topographic gradients, and (ii) the susceptibility to severe soil salinization following deforestation is spatially-dependent. First, the impact of deforestation on the different water budget components over the entire Dry Chaco was analyzed using three state-of-the-art LSMs, grouped within the Land Information System (LIS) of NASA. Because most LSMs use climatological vegetation data and static land cover parameters, they lack the ability to correctly represent the ongoing land cover changes in the Dry Chaco. Therefore, land cover changes were implemented using time-varying satellite-derived vegetation indices, together with annually updated land cover information. Our results showed that there are large regional and long-term differences in the simulated water budget components between the three LSMs, mainly due to differences in LSM structures and model-specific parameters. The different LSMs also redistribute water differently in response to the updated vegetation and land cover treatment. Second, the link between hydrology and soil salinity was studied based on in situ salinity data and environmental variables. In situ salinity data were collected along topographic and climatic gradients in the dry season of 2019. The LSM output at a regional scale, satellite-derived vegetation indices, and topographic data were related to soil salinity data to produce a first physically-based regional estimate of salinity patterns in the central Argentinean Dry Chaco. In the driest parts of the study area, salts are retained in the soil profile as salt leaching is prevented. Primary soil salinization occurs in topographic depressions where groundwater is present near the surface and high evapotranspiration rates enhance the formation of evaporites. With greater precipitation, salts are increasingly leached to deeper layers resulting in low natural soil salinity values. Also, in regions with high hydraulic gradients, salts are effectively removed by subsurface flow and regional groundwater transport. In the last chapter of this dissertation, we took a closer look at the chemical composition of water-soluble salts in soils of the central Argentinean Dry Chaco, and the link between the chemistry of salt-affected soils and deforestation. Previous studies mainly measured the electrical conductivity or chloride content to quantify soil salinity, and little was known about the chemistry of water-soluble salts that contribute to salt stress. We filled this knowledge gap by analyzing the full spectrum of water-soluble salts based on paired soil samples collected in forested and deforested areas. A geochemical analysis revealed that chlorides contribute only 25% to total salinity and that sulphates, calcium, and sodium are equally important. We further showed that the effects of deforestation on soil salinity are spatially dependent and closely related to the geomorphological setting. (SC - Sciences) -- UCL, 2021