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Globally, remnant fragments of forests represent the main carbon reservoir of terrestrial ecosystems, but they suffer strong degradation due to uncontrolled wood extraction mainly by tree cut for household fuel use and charcoal production. The present study evaluates the degradation caused by wood extraction on carbon pools and soil nutrient dynamics in temperate forests distributed in remnant fragments located in central Mexico. Four sites with different intensity of wood extraction were chosen for measuring carbon pools and nutrient fluxes during two years. Both, aboveground carbon biomass and soil organic carbon values decreased with the intensity of forest degradation. The degraded forest (DF) showed total carbon content 55 % lower than that shown by the seminatural forest (SF). Additionally, litterfall production was reduced in DF as compared to SF; the decomposition rate of standing litter was higher in the latter site. As a consequence, DF had lower organic matter inputs to the soil than that presented by SF. Soil extractable ammonium and microbial biomass- carbon and -nitrogen were lower in DF than in SF. It was concluded that the uncontrolled wood extraction in these remnants of temperate forest in Mexico significantly reduced the carbon pools, carbon and nutrient fluxes through litterfall and consequently, the soil nutrient dynamics were disrupted., Globalmente, los fragmentos forestales representan un almacén importante de carbono, pero estos fragmentos están bajo una fuerte presión de degradación; principalmente, debido a la extracción ilegal de madera para leña y carbón vegetal. El presente estudio evaluó el efecto de la extracción de leña sobre los almacenes de carbono y la dinámica de nutrientes del suelo en bosques templados de fragmentos remanentes en el centro de México. Se estudiaron cuatro sitios con diferente grado de intensidad de extracción de leña, donde se midieron el carbono almacenado y el flujo de nutrientes durante dos años consecutivos. El carbono en la biomasa aérea y en el suelo se redujo con el aumento de la intensidad de la extracción. El bosque degradado (DF) presentó 55 % menos contenido total de carbono que el bosque seminatural (SF). Así mimo, la producción de hojarasca también se redujo en el DF, pero la descomposición del mantillo fue mayor en el SF. Como consecuencia, el DF presentó menores entradas de carbono orgánico al suelo. El amonio disponible, el carbono y nitrógeno en la biomasa microbiana del suelo también fueron menores en el DF. La conclusión de este trabajo es que la extracción de leña en los fragmentos forestales en México reduce drásticamente las cantidades de carbono almacenado, los flujos de carbono y nutrientes por medio de la hojarasca, y por tanto, la dinámica de los nutrientes del suelo es afectada.

7 páginas.-- Proceedings 1st International Workshop, San Cristobal de la Laguna, Tenerife (Canary Islands), Spain 10-12 April 2013, This Project/work has been funded by the Education, Audiovisual and Culture Executive Agency (EACEA), as an Erasmus Multilateral Project through project number 517629-LLP-1-2011-UK-ER-ASMUS-EMCR.

Three selected soils from three countries with temperate climates have been analyzed. Two of the soils are silty loams (Buenos Aires, Argentina, and Salamanca, Spain) and the third one is a sandy loam (Peccioli, Italy). Soil samples representing three agricultural managements were obtained from the top layer (0-10 cm), i.e. intensively cultivated, cultivated and undisturbed native soils. Soil organic carbon (SOC), total nitrogen (Nt), ATP, urease, protease, phosphatase, b-glucosidase, dehydrogenase (DHA), and arginine ammonification (ARA) were determined and compared. SOC and Nt were significantly higher (P < 0.01) in native than in cultivated and intensively cultivated soils. A good correlation (P < 0.05) was found betweenATP, hydrolase activities, ARA, and SOC and Nt, indicating that all these parameters were related to the biological properties and biochemical activity. Then, these biological parameters can be used as bioindicators of agriculture-induced changesin soils. DHA did not correlate with the SOC and Nt contents, or protease activities, indicating that the soil ecosystems had low concentrations of exogenous substrates to metabolize and that micro-organisms were in a reducedstate of activity, Se compararon las actividades enzimáticas de distintos ecosistemas con diferentes características de uso de suelo para utilizarlas como bioindicadores. Se analizaron suelos de tres países de climas templados. Dos de los suelos presentan textura franco limosa (Buenos Aires, Argentina y Salamanca, España) y el tercero franco arenosa (Peccioli, Italia). Se obtuvieron muestras de 10 cm de profundidad provenientes de tres manejos diferentes en cada uno de ellos: agricultura intensiva, rotación cultivo-pastura y suelo nativo. En todos los sitios se determinaron y compararon el Carbono orgánico(SOC), Nitrógeno total(Nt), contenido de ATP, acividad enzimática de la ureasa, proteasa, fosfatasa, b-glucosidasa, deshidrogenasa (DHA) y arginina(ARA). Se encontró una buena correlación (p < 0,05) entre ATP, DHA, ARA con el SOC y Nt, indicando que estos parámetros del suelo están relacionados con las propiedades biológicas y la actividad bioquímica. No se encontró correlación entre DHA con el SOC, con el Nt , ni con la actividad de la proteasa en suelos de agricultura intensiva, indicando que en ecosistemas de bajos contenidos de sustratos exógenos para metabolizar, los microorganismos están en un nivel bajo de actividad. La similitud de los resultados obtenidos de los suelos de tres diferentes países confirman la utilidad de las variables bioquímicas como indicadores potenciales de la degradación del suelo causadas por las prácticas culturales.

10 páginas, 2 figuras.-- Congreso celebrado en Valencia (Spain) 18-25 September 1995, The distribution of the sodic saline soils of the Duero Basin (Provinces of Salamanca, Avila, Valladolid, Palencia and León) is reviewed. Although they are not very abundant in the area, the sodic saline soils can be mapped south of the River Duero (Province of Valladolid), patches also appearing in the area of surrounding the lakes of Villafáfila (Zamora). La Armuña (Salamanca), the Valle de Amblés (Avila) and in the dried, old lake of La Nava (Palencia). In general, they have been classified as Solonchaks (gleyic or sodic) and Solonetzs (sodic and gleyic); phenomena of solodization (such as in the Valle de Amblés) are rarely observed due to the frequent presence of carbonates. Regardless of the cartographic studies made in the region, overall the analytical data are mostly routine: pH, conductivity (salinity) or typology of clays. Accordingly, for a more complete knowledge of these soils more information concerning the exchange complex and soil solution is required. This should afford the possibility of a better classification and knowledge of the evolution of the soils. Nevertheless, it can be stated that the most important factors involved in the formation of these soils, apart from a semi-arid climate, is the topography (endorrheic zones), a high water level and the presence of soluble salts. The frequent presence of calcium carbonate limits the percentage of sodium ions in the cation exchange complex.

14 páginas, 2 figuras, 8 tablas, (1) Background: Coffee agroforestry systems (CAFS) in Veracruz, Mexico, are being displaced by avocado monocultures due to their high economic value. This change can generate alterations in the type of organic residues produced and soil biological activity (SBA) which is sensitive to climatic variations, changes in floristic composition, and agronomic management. It can be evaluated through soil respiration and macrofauna, both related to soil carbon (C) and nitrogen (N) dynamics. The objective was to: (1) Analyze the variation of SBA as well as the C and N dynamics in modified coffee agroforestry systems; (2) Methods: Three CAFS (renewed, intensive pruning, and with the introduction of avocados) and an avocado plantation were compared. The evaluations were conducted during the period 2017–2019. Soil parameters (respiration, macrofauna, C and N contents) and C content of plant biomass were measured in plots of 25 × 25 m2 from three soil depths in triplicate. Spearman’s test and a principal component analysis were performed to determine the structural dependence on C and N dynamics; (3) Results: The introduction of avocado showed the lowest soil respiration values (with 193 g CO2 ha−1 h−1 at 0–10 cm depth), this system did not display soil macrofauna and increased soil organic carbon content. The soil C/N ratio was sensitive to the introduction of avocado. Correlation between soil respiration and litter-related parameters was positive, but it was negatively correlated with soil organic matter and total soil nitrogen, explaining 67.7% of the variation; (4) Conclusions: Modification of CAFS generated variations in the SBA and soil C and N contents., The authors acknowledgments the Chapingo Autonomus University and National Council of Science and Technology (CONACYT-Mexico) for the PhD’s scholarship awarded tothe first author.