Search

In southern Patagonia, fire and domestic herbivory are the main disturbances affecting native forest dynamics. The effects of disturbances such as fire and livestock on the diversity and structure of plant communities depends on the intensity of these disturbances and the characteristics of the stand type. The overall objective of this study was to evaluate changes in forest diversity and structure under varying intensities of fire and livestock disturbances in Nothofagus antarctica forests in three different stand types. Two types of disturbances, fire and cattle, were evaluated at three different intensities; maximum disturbance, medium disturbance and no disturbance in high, medium and low stand types. Ecological and structural parameters were calculated for each experimental unit and their corresponding interactions. Diversity increased for the three stand types at maximum and medium disturbance intensities. Herbaceous cover increased for the three stand types at maximum and medium disturbance intensities. Shrub cover decreased in the high and medium stands due to the disturbances, but not in the lower stands. Understanding the responses of plant communities to fire and domestic livestock disturbances under different intensities and stand types is fundamental to predict the dynamics of native vegetation recovery and to guide sustainable management practices for each stand type. [ABSTRACT FROM AUTHOR]

High mountain forests are often restricted to ravines and much debate has existed on the explanations of this distribution, with arguments ranging from abiotic site conditions being more favorable in ravines to there being reduced herbivory or reduced fire frequency and damage in ravines. We aim at understanding the contribution of fire damage and provide data to help test the hypothesis that fires are less damaging and that trees recover faster in ravines as compared to ridge sites. We evaluated crown damage, post-fire survival, regeneration by resprouts and seeds, and browsed stems in burned and unburned control Polylepis australis trees situated in a ravine and in a ridge forest in the west slope of the mountains of Central Argentina. The proportion of the tree crown scorched by fire was 28 % higher on the ridge than in the ravine (94.3 ± 1.9 % and 66.1 ± 4.5 %, respectively) and was negatively related to tree height which was lower on the ridge. Survival was not differentially affected, but post-fire re-growth and establishment through seeds was lower in the ridge as compared to the ravine. Browsed stems were about twice as frequent in the ridge as in the ravine, more so in the resprouting burned trees. Our study provides evidence that forests are restricted to ravines in part because the effects of fires are less severe at these sites than in ridges, which adds to other possible causes like reduced livestock use of ravines, enhanced regeneration by seed and faster tree growth within ravines all of which are probably mediated by abiotic factors. [ABSTRACT FROM AUTHOR]

• Livestock use slightly modifies physical and chemical properties of Andisols. • Xeric Andisols are more susceptible to livestock than Udic Andisols. • Large scale impacts (grazing + clear cutting + fire) lead to severe changes in soil. • Livestock exclusion allows quick recuperation of physical fertility in Udic Andisols. • Localized stocking rate covariate is a good indicator in Xerands. Livestock can affect physical and chemical soil properties, depending on both stocking rates, and intrinsic soil properties. This study aimed to analyze changes in physicochemical properties in volcanic soils under silvopastoral systems. Two contrasting study sites were selected in Patagonia, Argentina, where Nothofagus antarctica silvopastoral systems develop on volcanic soils with different moisture regimes: Udands and Xerands. In each site, four treatments were considered according to canopy openness and accessibility for livestock: closed forests (control), open forests, 5-year exclosures in open forests, and finally, degraded areas affected by large-scale disturbances (i.e., grazing + clear cutting + fire). Localized stocking rate was estimated, and soil properties were analyzed at two depths (0–10 and 10–20 cm). Results showed that physicochemical properties were slightly modified by silvopastoral use, with no critical values found, except for penetration resistance. Soil types behaved differently: while Udands were more fertile and resilient, Xerands were more susceptible to livestock impact, and localized stocking rate was a good short-scale soil degradation indicator for these soils. Although grazing negatively affected soil fertility, increments in carbon stock, nitrogen, and phosphorus were found in Xerands. Besides, an evident improvement in physical soil properties in the short term (5 years) was found in Udands when livestock was excluded. Despite the high resilience of udic volcanic soils under silvopastoral use, total organic matter and organic matter associated with macroaggregates severely decreased. Such decrease occurred especially when grazing was overlapped with other impacts, leading to the loss of forest cover, regardless the soil moisture regime. Nothofagus antarctica forests on volcanic soils seem to form a system capable of sustaining silvopastoral use with controlled stocking rate, but they are highly vulnerable to major impacts. [ABSTRACT FROM AUTHOR]

Brea gum is a phloematic exudate from Parkinsonia praecox, an autoctonous tree that grows in the arid areas of Argentina. In this work, we propose its potential as a food additive. However, as no toxicological safety evaluation of brea gum has yet been reported, this preliminary study was conducted to evaluate its long-term toxicity over a 120-day period in BALB/c mice fed with brea gum at various levels in the diet. The results showed that animals on diets containing up to 5% brea gum were healthy, exhibiting growth curves similar to controls for both males ( P = 0.9138) and females ( P = 0.9459), thereby indicating that feed intake and utilization was not affected. A histopathological examination and weight recording of liver, kidneys, and intestine did not reveal any microscopic abnormalities or adverse toxicological effect (weights respect to control: P > 0.1). Moreover, hematological parameters and enzyme activities were within the normal values previously reported for mice. Our findings suggest that feeding brea gum at levels up to 5% to BALB/c mice do not exert any toxicological effects, supporting its potential use as a food additive for human consumption. [ABSTRACT FROM AUTHOR]

In Argentina there is no productive development of the non wood forestry products (NWFP), so it is difficult to include them in the regional economies. As an example, brea gum from Parkinsonia praecox produces an exudate gum as a food additive and safety to use in human consumption. However, it is not known, which is the economical feasibility for the farmers. The aim of this study is to evaluate the socioeconomical aspects of the brea gum production in the Arid Chaco from Córdoba, Argentina. The methodological approach for this study includes socio-economical surveys, gum production and finally, labour costs. Data were analyzed using Benefit/Cost analyses for the different woodland degradation states. The economical feasibility of brea gum production includes Chaco woodland in good state or "monte" and "breal". Additionally, it is possible to include brea gum production within the producer of the social agrarian types with lower incomes, which economies depends mostly on external work. The production of brea gum makes a substantial contribution into farmers' incomes, giving more sustainability to the system. [ABSTRACT FROM AUTHOR]

Wildfires differentially affect specimens of the same woody species, depending, among other factors, on tree size and microenvironment. This has implications for the structuring of forest landscapes, as forest recovery depends, in part, on the severity of fire on woody specimens. We aimed at analyzing how microenvironment and tree size affect fire damage and survival in two woody species common in the Chaco Serrano forest, along an altitudinal gradient in Córdoba Mountains (Argentina). We studied two wildfires that occurred in July and August 2007. We selected 163 espinillos (Vachellia caven) and 48 molles (Lithraea molleoides) located between 800 and 1700 m a. s. l. For each individual, we estimated pre-fire height and volume on the basis of the remaining woody tissues, and microenvironmental characteristics as plant cover, rock proportion under the crown, slope, aspect and insolation by interception. After three months we estimated the fire damage for each individual and three years later we evaluated survival. The espinillos with higher plant cover in their surroundings were more damaged, and this effect was more pronounced at lower altitudes. Additionally, individuals were more damaged in steep southern slopes than in northern slopes, while smaller individuals were more damaged than larger ones. Taller molles experienced less fire damage than shorter molles. The 94% of the espinillos and 92% of the molles survived the wildfire, with higher death probability for smaller individuals in the case of espinillo. We concluded the system becomes less susceptible to fire as succession proceeds, mainly because of the increasing size of woody individuals and the reduction of herbaceous cover. [ABSTRACT FROM AUTHOR]

Soil organic carbon (SOC) content supports several ecosystem services. Quantifying SOC requires: (i) accurate C estimates of forest components, and (ii) soil estimates. However, SOC is difficult to measure, so predictive models are needed. Our objective was to model SOC stocks within 30 cm depth in Patagonian forests based on climatic, topographic and vegetation productivity measures from satellite images, including Dynamic Habitat Indices and Land Surface Temperature derived from Landsat-8. We used data from 1320 stands of different forest types in Patagonia, and random forest regression to map SOC. The model captured SOC variability well (R² = 0.60, RMSE = 22.1%), considering the huge latitudinal extension (36.4° to 55.1° SL) and the great diversity of forest types. Mean SOC was 134.4 ton C ha−1 ± 25.2, totaling 404.2 million ton C across Patagonia. Overall, SOC values were highest in valleys of the Andes mountains and in southern Tierra del Fuego, ranging from 53.5 to 277.8 ton C ha−1 for the whole Patagonia region. Soil organic carbon is a metric relevant to many applications, connecting major issues such as forest management, conservation, and livestock production, and having spatially explicit estimates of SOC enables managers to fulfil the international agreements that Argentina has joined. [ABSTRACT FROM AUTHOR]

In the Patagonia Andean Region, silvopastoral system success depends on forestry management, which seeks to guarantee highest water input into the soil to forage production. The aim of this study was to quantify and compare different components of the water balance in a Pinus radiata forest under two different management practices: silvopastoral and forest treatment (325 and 622 trees/ha, respectively). In order to explain incident precipitation distribution within the forest, different variables were measured: direct precipitation, stemflow, interception, soil moisture content, percolation and evapotranspiration. Additionally, canopy cover, leaf area index (LAI) and forage production was determined. Silvopastoral system, with respect to forest system, presented higher direct precipitation (84±1 vs. 75±2%), lower stemflow (2±0.3 vs. 3±0.27%), lower interception (14±1 vs. 22±2%), higher soil moisture content (24.2±2.5 vs. 20.9±2.1%) and lower canopy cover (70.9±0.05 vs. 74.89±0.34%). In turn, percolation (0.33±0.12 vs. 0.11±0.08%), evapotranspiration (78.2 vs. 73.3%), pasture production (230.76±97.57 vs. 66.60±60.02 kg MS.ha-1.year-1) and LAI (1.28±0.04 vs. 1.31±0.02) were similar in both systems. These results show that management density modified only some components of water balance. However, adding more water the silvopastoral system was not reflected in an increase in pasture production. Density management is key, mainly in silvopastoral system, where different system components must be raised up for a more efficient water usage. [ABSTRACT FROM AUTHOR]