Pollution pressure drives microbial assemblages that improve the phytoremediation potential of heavy metals by Ricinus communis.

Due to the rapid expansion of industrial activity, soil pollution has intensified. Plants growing in these polluted areas have developed a rhizobiome uniquely and specially adapted to thrive in such environments. However, it remains uncertain whether pollution acts as a sufficiently selective force to shape the rhizobiome, and whether these adaptations endure over time, potentially aiding in long-term phytoremediation. Therefore, in the present study, we aimed to compare whether the microbiome associated with roots from plants germinated in polluted riverbanks will improve the phytoremediation of Cd and Pb under mesocosm experiments compared with plants germinating in a greenhouse. The experimental design was a factorial 2 × 2, i.e., the origin of the plant and the presence or absence of 100 mg/L of Cd and 1000 mg/L of Pb. Our results showed that plants germinated in polluted riverbanks have the capacity to accumulate twice the amount of Pb and Cd during mesocosm experiments. The metagenomic analysis showed that plants from the river exposed to heavy metals at the end of mesocosm experiments were rich in Rhizobium sp. AC44/96 and Enterobacter sp. EA-1, Enterobacter soli, Pantoea rwandensis, Pantoea endophytica. In addition, those plants were uniquely associated with Rhizobium grahamii, which likely contributed to the differences in the levels of phytoremediation achieved. Furthermore, the functional analysis revealed an augmented functional potential related to hormones, metallothioneins, dismutases, and reductases; meanwhile, the plants germinated in the greenhouse showed an unspecific strategy to exceed heavy metal stress. In conclusion, pollution pressure drives stable microbial assemblages, which could be used in future phytostabilization and phytoremediation experiments.

Sustainable Community Forest Management in Mexico: An Integrated Model of Three Socio-ecological Frameworks.

The sustainability of management practices in forest ecosystems should provide ecosystem services and maintain the livelihoods that largely depend on the benefits directly derived from forests; but this goal requires various theoretical and analytical approaches. This research aims to develop a conceptual model for sustainable forest management based on the integration of three conceptual frameworks founded on the society-ecosystem interaction: socio-ecological systems, sustainable forest management, and ecosystem services. The results offer a methodological, analytical, organizational, and operational route to integrate a scientific model at the material, causal, and dynamic levels, considering theoretical and empirical information; it uses grounded theory methodology to select the interactions between variables and socio-ecological dynamics of forest ecosystems under community management. For example, it integrates social components (local knowledge, governance, and social organization) and ecological components (diversity and composition of plant species, carbon pools, and nutrient dynamics) to understand their interactions through management practices and the magnitude of the ecosystem services provided according to the local contexts. We illustrate this process by analyzing the influence of governance, decision-making, resource use, and management practices on forest management and ecosystem services; this exemplifies the factors, interactions, and effects on socio-ecological systems based on experience in forest communities. These integrated frameworks provide steps through which our understanding of specific socio-ecological approaches produces better outcomes for sustainable forest management, preserves ecosystems services and benefits livelihoods in Mexican temperate forests.

Soil organic matter dynamics and microbial metabolism along an altitudinal gradient in Highland tropical forests.

The highland forests of tropical regions are highly vulnerable to climate change because changes in soil organic quality due to the increased soil water deficit conditions through rising temperatures. Several authors have reported that labile molecules dominate soil organic matter at higher elevations, and it is therefore more vulnerable to the rising temperatures associated with climate change. The objective of the present study was to analyze the effect of interaction between the chemical composition of organic matter derived from the dominant plant species and the metabolism of microbial community along an elevational gradient in a highland forest in Central Mexico. The study compared three vegetation-soil systems that represent three different elevational levels: Alnus-system (3100 m.a.s.l.), Abies-system (3500 m.a.s.l.) and Pinus-system (3700 m.a.s.l.). The SOM produced in the lowest site is more recalcitrant (i.e., higher Alkyl:O-Alkyl ratio) as a result of the lower water availability than in the highest site. The results of Threshold Elemental RatioC:N (TERC:N) and TERC:P for the organic layer were lower than their C:N and C:P ratios in the organic layer, supporting that the microbial community of the organic layer in the site of lowest elevation must be limited by the carbon source, rather than by N and P. However, these results were not found in the mineral soil, suggesting that the drivers of organic matter decomposition differ between the organic layer and the mineral soil. As a conclusion, our results suggest that the chemical recalcitrance of organic matter (at the lowest site) and temperature (at the highest site) reduce the microbial metabolic activity in the forest floor. Integrated study of plant-derived organic material and the microbial metabolism of the forest floor is therefore required to achieve a full understanding of the vulnerability of tropical mountain ecosystems to climate change.

Identifying hotspots of land use cover change under socioeconomic and climate change scenarios in Mexico.

This study identifies the hotspots of land use cover change (LUCC) under two socioeconomic and climate change scenarios [business as usual (BAU) and a pessimistic scenario] at the national level for Mexico for three-time periods. Modelling suggests that by 2050 grassland and tropical evergreen forest will be the most endangered ecosystems, having lost 20-33% (BAU) or 43-46% (pessimistic scenario) of their extent in comparison to 1993. Agricultural expansion would be the major driver of LUCC, increasing from 24.4% of the country in 1993 to 30% (BAU) or 34% (pessimistic) in 2050. The most influential variables were distance from roads and human settlements, slope, aridity, and evapotranspiration. The hotspots of LUCC were influenced by environmental constraints and socioeconomic activities more than by climate change. These findings could be used to build proposals to reduce deforestation, including multiple feedbacks among urbanization, industrialization and food consumption.

Metal distribution in coral reef complex Cayo Arcas in the Gulf of Mexico.

This study evaluated the spatial and temporal distribution of metals in the coral reef system Cayos Arcas and Triangulos in the Campeche Bank region, off the Yucatan peninsula in Mexico. No information has been generated before for the incorporation of natural and non-natural occurring metals, some of which are possibly endowed by the oil marine station Cayo Arcas. The multivariate exploratory study of the metals on the coral skeletons, showed the formation of two distinct groups. The metals that have the highest influence on the differentiation of the groups are the metals that are natural constituents of the coral skeletons, in particular Sr can explain much of the differences between the groups, and to a much lesser extent are the metals that could be indicators of pollution. This differentiation suggests that, in our case, the environment around the corals has a higher impact than the non-naturally occurring metals (and possible indicators of pollution). The two groups formed corresponded to: the coral cores influenced by open sea variables and the coral cores in the inner part of the keys which is less exposed to open sea variables. A chronological study was made to two samples that had the longest coral section and were situated in two clearly distinctive zones: an exposed surface subjected to high wave forces and another that was less exposed. Ni and Zn show an accumulation trend in both coral samples, while Ba showed an increase in incorporation around 1980 when the Cayo Arcas oil marine station was constructed.