El karst del estado de Yucatán, México, tiene su origen en los arrecifes coralinos y sedimentos marinos que, al exponerse a la superficie, formaron la roca caliza. Los procesos de solubilización-precipitación de esta roca han promovido la ausencia de corrientes de agua superficiales, un relieve ligeramente ondulado con planicies, depresiones y montículos, afloramientos y presencia de cenotes. Los diferentes grados de porosidad y dureza de la roca han permitido la formación desde pequeñas oquedades y acumulaciones de suelo, hasta complejos sistemas de cuevas secas y húmedas. El manejo de este tipo de áreas debe partir del conocimiento de su origen, morfología y biología para garantizar el uso sustentable de los recursos naturales. Se requiere especial atención en el  manejo de la extracción de roca caliza, las actividades turísticas y productivas relacionadas con el uso de agua del acuífero, así como el volumen y calidad de las descargas de aguas residuales al suelo, cenotes y el mar.

Fodder shrubs are important dry season feed sources for livestock in semi-arid environments. It has been proposed that a mixture of leguminous with non-leguminous shrubs may increase rates of N cycling and improve biomass and fodder quality. The objective of the present study was to assess the biomass productivity and fodder quality of leguminous shrubs growing a mixture with non-leguminous shrubs. Three shrub species—the legume Leucaena leucocephala (Lam.) and the non-legumes Guazuma ulmifolia (Lam.) and Moringa oleifera (Lam.)—were grown as legume/non-legume mixtures and as monocultures. Total fodder production and quality were estimated over five harvests at three-month intervals. The Leucaena–Guazuma mixture had the largest fodder production (9045 kg ha−1 year−1), followed by the Leucaena monocrop (7750 kg ha−1 year−1). Total nitrogen accumulation in the foliage was also high in the Leucaena–Guazuma mixture, reaching 282 kg ha−1 year−1; the Leucaena monocrop accumulated 244 kg N, while the Moringa monocrop took up only 46 kg N ha−1. The concentration of polyphenols was high in Leucaena and Guazuma, while Moringa had the lowest value. The high survival and excellent growth rates, as well as the high foliage production observed in Leucaena and Guazuma, suggest that they have the potential to provide high-quality fodder for livestock.

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Decomposition and N release pattern from the leaves of three shrubs species were studied under field conditions. Leaves of Leucaena leucocephala (Lam.), Guazuma ulmifolia (Lam.) and Moringa oleifera (Lam.) and two mixtures, Leucaena + Moringa and Leucaena + Guazuma, in a complete randomized block design, were studied during the dry and wet seasons. Litterbags were randomly distributed in each experimental block and placed on the soil surface, and residues were recovered after 2, 4, 8, and 16 weeks. Double exponential model decay was better fitted to describe the pattern of the decay of the release of various leaf constituents. Litter dry weight loss and N release were faster from Moringa, followed by the Leucaena + Moringa mixture, while the Guazuma leaf litter decomposed much slower. In the wet period, a rapid N release was observed for Moringa (60%) and Leucaena + Moringa (43%) in the first two weeks. In contrast, Guazuma and the Leucaena + Guazuma mixture released about 46% of N in 16 weeks. In the dry period, leaves released most of their N during the first 8 to 16 weeks. Moringa and Leucaena + Moringa ranked first, having lost 81 and 75% of its initial N, respectively. The ratios of condensed tannin and polyphenols to N were significantly correlated with the N released. It was concluded that the initial mass loss from the leaf litter was high and rapid in the rainy period in comparison to the dry period. The residue disappearance pattern of Moringa, Leucaena and Leucaena + Moringa followed an asymptotic model, with more than 80% of the original residue released during the 16-week study period.

<p><strong>Background.</strong> In recent decades there has been an increase in emissions of carbon dioxide (CO₂) into the atmosphere, this has caused negative impacts on both natural and anthropic systems. Due to the above, the study of the global dynamics of the carbon cycle has become more important, in order to design technologies and propose management strategies and practices that reduce CO₂ emissions into the atmosphere or remove it from it (carbon sequestration). The removal of atmospheric CO₂ can occur by biotic and abiotic processes and can be deposited in different natural reservoirs both in organic and inorganic form. One of the mechanisms for sequestering carbon in an inorganic way is the oxalate-carbonate pathway (OCP), which deposits secondary carbonates to the soil, from calcium oxalate crystals. <strong>Objective.</strong> A review of inorganic carbon sequestration is carried out, emphasizing the deposition of secondary carbonates in soils through the oxalate-carbonate pathway, and we analyzed  its implications in calcareous karst environments.<strong> Main findings. </strong>The OCP has been mainly studied in acid soils, but it could also be important in alkaline soils, since other secondary sources of calcium, such as those carried by the wind, have not yet been considered (i.e. calcium in Sahara desert dust arriving to Yucatan Peninsula annually). <strong>Implications.</strong> The study of the OCP has been intensified in recent years, resulting for us of particular interest in calcareous karst environments, due to its high spatio-temporal dynamics dominated by carbonation-decarbonation reactions. <strong>Conclusion.</strong> Evidence of OCP activity has been found in karst environments; however, this metabolic pathway presents spatial and temporal dynamics, so it is difficult to estimate its contribution to the global dynamics of C, and it may contribute by delaying the return of CO₂ to the atmosphere.</p>