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Land use change is a key process due to its direct effects on the identity and structure of vegetation. In semi- arid Argentinean Chaco, there is scarse information about the consequences of vegetation changes on processes related to nutrient cycling (e.g., decomposition). In this work, we analyse if changes in local climatic conditions due to changes in vegetation structure, related to different land use types, affect decomposition pattern of two common materials. We found that land use change has a clear impact on vegetation cover, but this impact is not reflected into a consistent change in local decomposition environment. Specifically, we found that more intensive land use types were related to a decrease in vegetation cover and height and also to less litter quantity. These changes were associated with lower soil C and N. However, changes in vegetation structure were not related with changes of local climatic conditions, despite the differences of climatic conditions between vegetal configurations. Decomposition of common materials was faster in vegetal configurations with lower vegetation cover and air temperature. These results suggest that land use change has an evident impact on vegetation cover, but this impact is not transferred on changes of local decomposition environment. In future studies is important to evaluate the contribution of abiotic deterioration processes (photodegradation and physical fragmentation) on decomposition and nutrient cycling. [ABSTRACT FROM AUTHOR]

Resilience—the capacity of an ecosystem to recover from disturbance—is a popular concept but quantitative empirical studies are still uncommon. This lack of empirical evidence is especially true for semi‐arid ecosystems in the face of the combined and often confounding impacts of land use and climate changes.We designed a methodology to disentangle vegetation responses to land‐use exclusion and weather variability, and piloted it at the southern extreme of the Gran Chaco forest, the most extensive seasonally dry forest in South America. We established 16 pairs of neighbouring fenced and unfenced plots in four ecosystem types resulting from different long‐term land‐use regimes under the same climate and on highly similar soil parental material. From lower to higher land‐use intensity, related with logging and livestock grazing and trampling, these types were: primary forest (no land use in the last 50 years), secondary forest, closed species‐rich shrubland and open shrubland. In each plot we monitored plant species composition during the first 5 years following land‐use exclusion, and evaluated the resilience as the rate of change of vegetation towards the primary forest, considered as the reference ecosystem.We found that during the first 5 years of exclusion and despite the high rainfall, only grass cover in the secondary forest showed positive resilience (recovery towards the reference ecosystem). The rest of the variables in the other ecosystem types showed either no significant change (null resilience) or even transitioned away from the reference state (negative resilience).Synthesis. The lack of detectable recovery after 5 years of exclusion suggests that (a) long‐term land use, even at lower intensities, has affected the sources of resilience of this ecosystem; (b) rainy periods do not necessarily speed up recovery as suggested in the literature; and (c) study designs should incorporate the variation of the reference ecosystem in order to differentiate the effect of land use from other factors in a context of climate change. Although still confined to the early post‐disturbance stages, our findings suggest that recovery of these systems may be slower and more complicated than predicted in the literature on the basis of space‐for‐time substitutions. [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]

Net emissions of CO 2 from land-use conversion represent a significant driver of global climatic change. This is especially true for subtropical seasonally dry Chaco forests from southern South America, now experiencing one of the highest loss rates globally. However, direct quantifications of the effect of accelerated deforestation on carbon (C) pools of these systems are rare. Considering five dominant ecosystem types within the dry Chaco forest of Argentina, derived by land-use change from the same original vegetation, substrate, and climate, we quantified the magnitude and change of total C pools including trees and shrubs, non-woody plants, coarse and fine debris, and soil organic (SOC) and inorganic (SIC) pools up to 2 m depth. Soil C pools represented the largest C stocks (>74%). Shrubs also represented a large C pool (at least 28% of the aboveground standing biomass), which we quantified in detail for the first time. The conversion of forests to open shrublands and croplands was associated to large losses of organic C both in aboveground biomass and in soils down to 30 cm depth (from 43 to 64%). Although SIC is usually considered as a relatively stable compartment, the forest to crop transition presented here involved carbonate losses of c. 68% at soil depths between 1 and 2 m. Our results indicate that the landscape transformations expected in the region under business-as-usual socioeconomic scenarios will probably lead to a marked reduction of the C stored, with a consequent net C emission and a decline in other C storage-related ecosystem services provided by these ecosystems. [ABSTRACT FROM AUTHOR]