Drought responsiveness in two Mexican conifer species forming young stands at high elevations

Aim of study: To determine the response of high-altitudinal forests to seasonal drought.Area of study: Monte Tláloc, Estado de México and Rancho Joyas del Durazno, Municipality of Río Verde, San Luis Potosí, México.Materials and methods: In this study, we evaluate the response to drought and hydroclimate in two young Mexican conifers sampled at high elevation, correlating records of tree-ring growth and the Normalized Difference Vegetation Index (NDVI).Main results: The results show that Pinus teocote and Abies religiosa are vulnerable to the precipitation regime and warm conditions of winter-spring. The physiological response mechanisms seem to be differentiated between the species, according to the effects of drought stress. The NDVI demonstrated the different temporal responses of the species according to their inherent physiological mechanisms in response to hydroclimatic limitations. This differentiation can be attributed to the spatial variation present in the particular physical and geographic conditions of each area. The dry and warm seasonal climates reveal P. teocote and A. religiosa to be species that are vulnerable to drought conditions. However, further evaluation of the resistance and resilience of these species is necessary, as well as disentanglement of the effects of associated mechanisms that can influence the predicted processes of extinction or migration.Research highlights: Pinus teocote and Abies religiosa are vulnerable to the seasonal drought conditions. These results are of particular importance given the climatic scenarios predicted for elevated ecotones. Tree-ring widths and NDVI improved the response of radial growth to the climate, enhancing our understanding of forest growth dynamics. The response to climatic variability depends on the particular species.Keywords: High elevation; tree-ring; ENSO; NDVI; climate-growth relationship. Abbreviations used: Normalized Difference Vegetation Index (NDVI); Tree-Ring Width (TRw); precipitation (PP); maximum temperature (Tmax); minimum temperature (Tmin); El Niño-Southern Oscillation (ENSO); Climatic Research Unit Time-series data version 4.04 data (CRU TS v. 4.04); Standardized Precipitation-Evapotranspiration Index (SPEI); Climatic Research Unit Time-series data version 4.03 data (CRU TS v. 4.03); first-order autocorrelation (AC); mean sensitivity (MS); mean correlation between trees (Rbt); expressed population signal (EPS); Ring Width Index (RWI)

Diversity of Ants (Hymenoptera: Formicidae) in a Sub-Montane and Sub-Tropical Cityscape of Northeastern Mexico

ABSTRACT - The role of urban ecosystems in maintaining biodiversity and ecosystem services is highly variable because of the heterogeneity of habitats in human-use landscapes. We analyzed ant diversity in a sub-montane and sub-tropical urban area of northeastern Mexico to determine the conservation value of this cityscape. Ants were collected in 16 across the cityscape, including spaces at the periphery and urban center, during the rainy season (August to October) of 2015. To capture ants, eight trap traps were installed along a 100-m transect, and hand collections were performed. In total, 7,415 ant workers belonging to 32 species, 23 genera, 11 tribes, and 5 sub-families were collected. The richness and structure of the assemblages varied among the sampling sites. The compositional similarity also varied significantly among sampling sites, and unique species were found in four sites. Each site showed an important and particular ant assemblage that differed from that of the other sites and the surrounding habitats in the cityscape. The results suggest that some sampling sites in the studied cityscape may contribute to the conservation of certain ant groups and invertebrate communities threatened by urban intensification. Ultimately, our findings support the importance of conserved areas and green spaces for the conservation of native species in and near urban areas

Monitoreo de la degradación forestal en México con base en el inventario nacional forestal y de suelos (Infys)

Existen muchas definiciones de degradación forestal. Sin embargo, la mayoría no son operativas dado que no proponen variables para medirla. Su medición es compleja; evaluarla implica comparar el estatus del bosque en un momento dado con un estado previo (condición de referencia o línea base). El reto del seguimiento (monitoreo) de la degradación inicia con su definición y con la identificación de la línea base. En este trabajo se propone un índice general de degradación (IGD) para evaluar la degradación forestal que ocurre en México en el periodo que transcurre entre mediciones del Inventario Nacional Forestal y de Suelos (Infys). El IGD está compuesto de indicadores que toman como insumo la base de datos del Infys. Paralelamente, el estudio pretende construir una línea base que permita dar seguimiento a la degradación forestal en años futuros. Los resultados a escala de entidad federativa indican que los estados de Puebla, Veracruz, Morelos y Colima no muestran evidencia global de procesos de degradación en el periodo evaluado. Contrariamente, Querétaro, Tamaulipas y el D.F. (Ciudad de México) registran cierto proceso de degradación. El valor del IGD ponderado a escala nacional indica que, en general, para los periodos evaluados de cinco años (e.g. 2004-2009, 2005-2010, etc.) los ecosistemas del país no registran procesos considerables de degradación, es decir, el valor obtenido del IGD es igual al valor de referencia. Sin embargo, a escala local es posible identificar áreas severamente degradadas o incluso deforestadas