Data from: Functional diversity loss with increasing livestock grazing intensity in drylands: the mechanisms and their consequences depend on the taxa

1. Overgrazing is one of the main drivers of desertification in drylands, and livestock production is expected to increase in the next decades. The analysis of functional diversity can clarify the effects of increasing livestock grazing on ecosystem functioning. 2. We assess the effect of livestock grazing intensity on the relationship between taxonomic (TDH) and functional diversity (FDQ) of plants, ants and small mammals, as well as on within-trait diversity. We compared results using two indices of taxonomic diversity (Shannon and Simpson). We used structural equation modelling (SEM) to assess the causal relationship between grazing intensity, TDH, FDQ and decomposition rate for each taxa. 3. Correlation between TDH vs. FDQ varied across assemblages and seasons, but was consistent between different indices of taxonomic diversity. A similar trajectory of TDH vs. FDQ under land-use intensification was found for all taxa, with a correlated loss of species and functional traits. Also, within-trait diversity was negatively affected by increasing grazing pressure. Vegetation and small mammal SEM models show that increasing grazing intensity had a strong and direct effect on decomposition rate. The ant SEM model was the only one that showed an indirect effect of grazing on decomposition through FDQ. TDH had no effect on decomposition for either taxa. 4. We found higher niche differentiation in animal than in plant assemblages. In vegetation, several species seem to have similar trait diversity (i.e. redundancy), perhaps due to a dominant role of environmental constraints. These results were consistent among diversity indices. But increasing disturbance negatively affected TDH vs. FDQ in all assemblages in a similar way. Livestock grazing affected decomposition rate directly, and indirectly only through the effect of ants FDQ. 5. Synthesis and applications. Under increasing grazing intensity all plant and animal assemblages respond with a mirrored reduction in taxonomic and functional diversity, although vegetation seems to have higher functional redundancy. Our results are robust to diversity indices, showing that several taxa respond similarly to land-use intensification, despite differences in the mechanism behind it. This may facilitate sustainable management. Notably, increasing grazing intensity affects decomposition rate through a stronger direct than indirect effect. The stronger direct effect of livestock on decomposition rate, rather than indirectly through functional diversity, suggests that changes in structure may be more important than changes in community composition

Ecosystem loss assessment following hydroelectric dam flooding: The case of Yacyretá, Argentina

The Yacyretá dam is one of the most important hydroelectric projects in La Plata Basin. As a consequence of the filling of the reservoir to its final height of 83m, approximately 1,076km2 of terrestrial and riparian ecosystems were flooded in Argentina and Paraguay. In order to evaluate the ecosystem loss due to this impounding, we generated two maps of land use/land cover from Landsat satellite images: 1987 (prior to the dam) and 2011 (after the final height was reached). We applied a post classification method and tested the gain, loss, and net change of natural and anthropic ecosystems in the study area with a cross tabulation matrix. Water bodies were the land cover type that showed the greatest degree of change, increasing 14.8% between periods. This was in detriment of, primarily, wetlands by 7.5%, grasslands by 4.0%, and native forests by 2.8%. However, sandbanks presented the highest probability of transition to another land class and, thus, correspond to the most vulnerable land cover in the study area. Also, we detected a differential ecosystem loss, both in type and magnitude, up and downstream of the dam. Our work is the first one to address ecosystem loss in the Yacyretá area and our results should help to improve management policies, such as the design of the current network of compensatory reserves.Fil: Bauni, Valeria. Fundación de Historia Natural Félix de Azara; ArgentinaFil: Schivo, Facundo Mauro. Universidad Nacional de San Martín. Instituto de Investigación en Ingeniería Ambiental; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Capmourteres, Virginia. Fundación de Historia Natural Félix de Azara; ArgentinaFil: Homberg, Marina. Fundación de Historia Natural Félix de Azara; Argentin

Functional diversity loss with increasing livestock grazing intensity in drylands: the mechanisms and their consequences depend on the taxa

Overgrazing is one of the main drivers of desertification in drylands, and livestock production is expected to increase in the next decades. The analysis of functional diversity can clarify the effects of increasing livestock grazing on ecosystem functioning. We assess the effect of livestock grazing intensity on the relationship between taxonomic diversity (TDH) and functional diversity (FDQ) of plants, ants and small mammals, as well as on within-trait diversity. We compared results using two indices of taxonomic diversity (Shannon and Simpson indices). We used structural equation modelling (SEM) to assess the causal relationship between grazing intensity, TDH, FDQ and decomposition rate for each taxa. Correlation between TDH vs. FDQ varied across assemblages and seasons, but was consistent between different indices of taxonomic diversity. A similar trajectory of TDH vs. FDQ under land-use intensification was found for all taxa, with a correlated loss of species and functional traits. Also, within-trait diversity was negatively affected by increasing grazing pressure. Vegetation and small mammal SEM models show that increasing grazing intensity had a strong and direct effect on decomposition rate. The ant SEM model was the only one that showed an indirect effect of grazing on decomposition through FDQ. TDH had no effect on decomposition for either taxa. We found higher niche differentiation in animal than in plant assemblages. In vegetation, several species seem to have similar trait diversity (i.e. redundancy), perhaps due to a dominant role of environmental constraints. These results were consistent among diversity indices. But increasing disturbance negatively affected TDH vs. FDQ in all assemblages in a similar way. Livestock grazing affected decomposition rate directly, and indirectly only through the effect of ant FDQ. Synthesis and applications. Under increasing grazing intensity, all plant and animal assemblages respond with a mirrored reduction in taxonomic diversity and functional diversity, although vegetation seems to have higher functional redundancy. Our results are robust to diversity indices, and show that several taxa respond similarly to land-use intensification, despite differences in the mechanism behind it. This may facilitate sustainable management. Notably, increasing grazing intensity affects decomposition rate through a stronger direct than indirect effect. The stronger direct effect of livestock on decomposition rate, rather than indirectly through functional diversity, suggests that changes in structure may be more important than changes in community composition.Fil: Chillo, María Verónica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; Argentina. University of Guelph; CanadáFil: Ojeda, Ricardo Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; ArgentinaFil: Capmourteres, Virginia. University of Guelph; CanadáFil: Anand, Madhur. University of Guelph; Canad

Chillo et al_Data

Sampling sites locations, Index values for every sampling site, R scripts for SEM analyses and TDvsFD trajectory analyse