José María Ramos-Prado

Community landscape planning for rural areas: a model for biocultural resource management.

We propose a theoretical model for resource management in the tropics that includes biological and cultural aspects, called the Biocultural Resource Management Model. The model is a strategy for co-responsible landscape planning that could be implemented in rural areas with local populations as the drivers of conservation, restoration, and management of natural resources. It comprises different units of production and management conservation levels and outlines the social and environmental aspects. The model was derived from a 10-year working experience in Mexico through the nongovernmental organization Programa de Acción Forestal Tropical (PROAFT) and the evaluation of 24 management conservation projects, from 20 different organizations and 1421 participants. The model takes into account PROAFTs evaluation regarding the successful participatory research experiences that enhanced diversification of agroecosystems and social organization. We propose and discuss a strategy and the challenges for the model implementation and its further evaluation in rural Mexican communities.

Estructura y composición arbórea de un fragmento de bosque mesófilo de montaña en el estado de Veracruz

Forest decline in Desierto de los Leones National Park in Mexico City affects Abies religiosa, a dominant and hard-to-root species in the region. As a result of this decline, the species requires propagation in the region through rooting of cuttings. In this study, a method of vegetative production was developed to determine whether the effect of origin, age of the material, type of hormone used and the presence of decline symptoms affect the rooting capacity of cuttings of this species. Three experiments were conducted, and only the third one produced rooting of cuttings. In this experiment, a substrate composed of peat moss and perlite was used to test rooting of cuttings of two origins, with and without symptoms, generated in two growing seasons and using two auxins (indolbutyric acid and naphthalene acetic acid), keeping the soil moisture between 75-80 %. The combination of these factors produced 16 treatments, which were replicated 50 times. Data were processed by factorial analysis of variance. Results indicate that early December is the best time to collect plant material for rooting of A. religiosa cuttings, as they are the youngest, and that those that received indol-butyric acid rooted the best. Origin and decline symptoms had no effect on rooting. Recibido:14 de junio de 2011 Aceptado: 06 de marzo de 2013 doi: 10.5154/r.rchscfa.2011.06.038 http://www.chapingo.mx/revistas PALABRAS CLAVE: Propagación vegetativa, procedencia, auxinas, edad de estaca, ácido indol-3butírico, ácido naftalenacético.The below-canopy light environment influences the survival, the tree regeneration growth and the development of the understory plant species. Therefore, there has been much interest in measuring the below-canopy light environment. Several instruments, techniques and methods have been developed to measure directly or to estimate indirectly the below-canopy light environment. To date, many comparisons of direct and indirect methods for the measuring and estimation of below-canopy light environment have been conducted in order to determine the best way to measure the light in the understory. In this review a scientific description of the currently instruments, techniques and methods used to measure or to estimate the below-canopy solar radiation is shown. The nature and properties of the different methods, techniques and instruments are commented. Finally, the choice of equipment to meet the needs of the researcher in this topic is supported. Recibido: 29 de febrero de 2012 Aceptado: 12 de febrero de 2013 doi: 10.5154/r.rchscfa.2012.02.014 http://www.chapingo.mx/revistas PALABRAS CLAVE: Radiación solar, luz, medición directa, estimación indirecta, ambiente bajo el dosel arbóreo.The usefulness of forest species in agricultural production systems is an option that helps to reduce the pressure in natural forests; they can also be used in treeless areas. The aim of this study was to evaluate the nutritional quality, germination, development of seedlings grown in nursery and variety of uses of Leucaena lanceolata S. Watson ssp. lanceolata. Edible material and seeds were collected in Tomatlán, Jalisco. Bromatologic analyses, scarification tests and the evaluation of seedlings grown in nursery using three soils with different pH values were performed. The experimental design was completely randomized, with Tukey (P≤0.05) test for media comparison. A survey study, bibliographical revision and review of specimens in the herbariums were used to know the local and potential diversity of uses of this specie. Results show high content of dry matter (97.40 %) and crude protein (29.05 %), greater germination using heat treatments, better seedling development in slightly acid soil (6.57) and the diversity of uses including firewood, forage and timber among others. L. lanceolata represents a viable option to be used in dry tropical silvopastoral systems due to the high nutritional value and the diversity of uses in rural areas. Recibido: 27 de septiembre de 2011 Aceptado: 01 de febrero de 2013 doi: 10.5154/.r.rchscfa.2011.09.070 http://www.chapingo.mx/revistas PALABRAS CLAVE: escarificación, materia seca, proteína cruda, pH,

The Extraordinary Nature of RNA Interference in Understanding Gene Downregulation Mechanism in Plants

Gene silencing (also known as ribonucleic acid [RNA] interference [RNAi] or interfering RNA) was first recognized in plants and is considered one of the most significant discov‐ eries in molecular biology in the last several years. These short-chain ribonucleic acid molecules regulate eukaryotic gene expression. The phenomenon involves a process that promotes RNA transcripts degradation through complementarity between RNA mole‐ cules and RNAi transcripts, resulting in the reduction of their translation levels. There are two principal classes of regulatory RNA molecules: small interfering RNAs (siRNA) and microRNAs (miRNA). Both are generated from the cleavage of double-stranded self-com‐ plementary RNA hairpins by a DICER enzyme that belongs to the RNase III family. Small RNAs (of about 21–24 nucleotides in size) guide specific effector Argonaute protein to a target nucleotide sequence by complementary base pairing. Thereby, the effector protein complex downregulates the expression of RNA or DNA targets. In plants, cis-regulatory RNAi sequences are involved in defense mechanisms against antagonistic organisms and transposition events, while trans-regulatory sequences participate in growth-related gene expression. siRNA also performs neutral antiviral defense mechanisms and adaptive stress responses. This document is an attempt to scrutinize the RNAi nature in under‐ standing gene downregulation mechanism in plants and some technical applications.