Soils of the municipality of Hocabá, Yucatán, México, were identified according to both Mayan farmers’ knowledge and the World Reference Base for Soil Resources (WRB). To identify Maya soil classes, field descriptions made by farmers and semistructured interviews were utilized. WRB soils were identified by describing soil profiles and analyzing samples in the laboratory. Mayan farmers identified soils based on topographic position and surface properties such as colour and amount of rock fragments and outcrops. Farmers distinguished two main groups of soils: K'ankab or soils of plains and Boxlu’um or soils of mounds. K'ankab is a group of red soils with two variants (K'ankab and Haylu’um), whereas Boxlu’um is a group of dark soils with five variants (Tsek'el, Ch'ich'lu’um, Chaltun, Puslu’um, and Ch'och'ol). Soils on the plains were identified as Leptosoils, Cambisols, and Luvisols. Soils identified in mounds were Leptosols and Calcisols. Many soils identified by farmers could be more than one WRB unit of soil and vice versa; in these cases no direct relationship between both classification systems was possible. Mayan and WRB soil types are complementary; they should be used together to improve regional soil classifications, help transference of agricultural technologies, and make soil management decisions.

<p><strong>Background</strong>. The Milpa is one of the traditional agricultural systems of Yucatan, Mexico; it is implemented by using the agricultural procedure called “Slash &amp; Burn”. Quality and quantity of forest fuel (<em>i.e.</em> biomass) are two of the main factors related to burn severity. Burning affects soil properties related to fertility and crop production. The use of new approaches of remote sensing technologies such as Unattended Aerial Vehicles (UAVs), can allow studying the importance of fire in agriculture to improve productivity in slash &amp; burn agricultural systems. <strong>Objective</strong>. Analyze the land covers and its influence on the severity of the agricultural burning in a "Milpa" agroecosystem with multi-spectral images acquired by UAVs. <strong>Methodology</strong>. The study site was located in the municipality of Tzucacab, Yucatan, Mexico. Two plots were selected [10-15 and 20-25 years of fallow]; land cover was characterized before and after slash &amp; burn. Three multispectral sensors [Red, Green, Blue (RGB); Near Infrared (NIR) and; Thermal Infra-Red (TIR)] were mounted on UAVs, to obtained multispectral imagery and generate orthomosaics for later analyses. <strong>Results</strong>. With the imagery, the Normalized Difference Vegetation Index [NDVI] was calculated and its spectral behavior evaluated. The imagery was used to analyze the fire intensity. On RGB imagery, patterns of areas with greater dry biomass cover associated to high burn severity and, areas with green vegetation or naked soil associated to low burn severity were observed. Land covers with high fuel potential showed low NDVI index values. <strong>Implications.</strong> The analyses of the multispectral imagery taken by drones allow the quick evaluation of the land covers and the intensity of agricultural fires, with the pertinent adjustments, in the near future this could become a standard methodology to accomplish this kind of evaluations. <strong>Conclusions</strong>. This approach allowed to analyze the state of land covers to visually assess the quality of fuel and its influence on the intensity of an agricultural fire. The RGB and NIR imagery obtained by UAVs can be a good tool to predict the intensity of an agricultural fire, TIR imagery could be used to find mathematical relations between land covers and fire intensity.</p>

Abstract. The hydrogen and oxygen isotopic composition of water is a very important tool to estimate water balance, groundwater recharge, and evaporation. Water isotopes have been used to increase our understanding of the distribution and amounts of renewable and non-renewable groundwater. Isotopic data from precipitation and groundwater is available in much of Mexico but there is little information from the Peninsula of Yucatan, an area heavily relying in groundwater in which current estimates of groundwater availability are uncertain. In this paper, we compiled published and unpublished δ2H and δ18O data in meteoric (waters derived from precipitation), ground- and pore-waters, to obtain a regional meteoric water line (RMWL) expressed by the equation δ2H = 8.1846 δ18O + 10.289. The data suggest that precipitation originates in convective systems, low-pressure events, moisture from frontal events, and from re-condensed moisture. The evaporation lines from groundwater suggest mixing of water with different isotopic composition, but also provide clues to recent meteoric water rapid recharge, likely from rain events of great intensity. We present a groundwater isoscape of the Peninsula of Yucatan and finally address the lack of conciliation between hydrogeology and groundwater management.

No abstract

<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>