The objective was to determine planting quality and to identify methods to increment efficien- cy in mesquite reforestations performed in Durango, México. Seventeen commercial plots, established as governmental reforestation program during 2009 and 2010 were evaluated in Nombre de Dios (5), Cuencamé (4), Lerdo (2), Pánuco de Coronado (2), Tlahualilo (2), Durango (1) and Mapimí (1). Evaluations were performed during january and february, 2011 using circular and systematic sampling method and only lineal sampling method was used at 10 de Abril, Cuencamé. Data were taken for geographical coordinates, altitude, planting orientation (exposure), reforestation type, planting area, plant survival, plant height, basal stem diameterand ecological traits related to mes- quite survival in each location. In 2011 an experimental plot was established using a Randomized Com- plete Block design in order to determine the effect of four hydrogel doses (0, 20, 30 y 40 g·plant-1) on mesquite plant condition evaluated 63 days after transplant. Commercial plots altituderanged between 1,099 m in San Francisco de Afuera, Tlahualilo, to 2094 m in Lomas de San Juan, Cuencamé, Dgo. Ze- nithal (Z) exposure showed the highest frequency (9), followed by SE (4), S (2), E (1) and NE (1). The real frame (3 m x 3 m, 3 m x 2.5 m) planting method was the most used, although triangular planting method was also observed in two plots. Commercial plots planting area ranged between 4 ha in Sapio- riz, Lerdo, to 100 ha in San Francisco de Afuera, Tlahualilo. High number of plots (7) showing 0 % of mesquite plants survival was observed, while the rest (10 plots) ranged from2.7 % (Lomas de San Juan, Cuencamé) to 58.2 % (San José de Acevedo P2, Nombre de Dios). Plant height ranged from 7.3 cm (San José de Acevedo P1) to 27.8 cm (Ejido Severino Ceniceros). Stem basal diameter showed variations between 1.5 cm (San José de Acevedo P1) to 5.5 cm in Lomas de San Juan and 10 de Abril. There were low rates of survivalin mesquite plantations performed during 2009 and 2010 in Durango, Mexico. One of the most important factors showing strong influence over mesquite plant survival was water stress and then effects of using hydrogel was validated in order to retain water in soil. Treatment including 20 g of hydrogel showed possibilities in order to increment survival in mesquite plantations under field conditions. Forester instruction is needed in order to improve mesquite survival trough better planting techniques which include the use of locally collected seed of adapted species such as Prosopislaevigata, use of plots with deep soils and hydrogel application, as a water retention method in soil.

The mesquite is an important plant resource for the inhabitants of arid and semiarid regions of North-Central Mexico. Despite its usefulness, the conservation of mesquite has been con- troversial, because in some areas of grassland and abandoned land for farming this species is considered an invasive plant. Land use changes, opening up land for agriculture and livestock farming have caused a reduction in the areas occupied by mesquite, causing loss of mesquite areas, plus effects such as soil erosion. The objective was to determine the land-use change that occurred in mesquite areas in the states of Coahuila and Durango, between 1992 and 2002. The total area vegeta- ted by mesquite was 173,455 ha in the study area. Coahuila has 73,868 ha with mesquite and Durango 44,211 ha. In Coahuila, the municipality of Hidalgo had the largest mesquite area (19,904 ha), followed by Guerrero (10,741 ha) and Viesca (7,404 ha). For its part, Hidalgo recorded the largest mesquite area in Durango (10,767 ha), followed by San Juan de Guadalupe (7,391 ha) and Simon Bolívar (6,805 ha).

Climate change seems to aggravate the degradation of natural resources in the upper basin of the Nazas River. This is an important water catchment area where Sardines weather station has recorded anomalous rainfall events in recent years. The aim of this study was to analyze historical and recent rainfall information in the context of climate change. The rainfall recorded from 1970 to 2004 at Sardinas station was obtained from the ERIC III data base and was compared with rainfall of three recent years (2006, 2007 and 2008) then analyzed with the Standardized Precipita- tion Index program. Results show that intensity of humid or drought events tend to increase in recent years probably due to ENSO influence. Analysis of intra-annual periods of rainfall shows that recent years are different from normal historical years and they duration are more fractioned. These changes in the rainfall regime may be associated with climate change whose effects may increase the process of soil erosion.

Many species of native Mexican orchids are scarce in nature or in danger of extinction due to the disappearance of their natural habitat and illegal extraction for commercial exploitation. Considering the available floristic and bibliographic data, including that of the National Herbarium of Mexico (MEXU), in relation to the Orchidaceae of the state of Hidalgo, 73 species are mentioned. Specifically for the Mezquital Valley, reports relating to the orchid flora are scarce and out of date. Amongst the orchid species registered for the region are Laelia speciosa (Kunth) Schltr., an endemic species subject to special protection (SEMAR- NAT, 2010) and highly prized as an ornamental plant. Aiming to obtain basic knowledge of the orchid flora of the region, preliminary research was carried out to identify areas with orchids, and estimate their abundance, using the methodology of random transects in areas selected for their floristic composition. The results indicate the presence of 4 epiphytic species, 1 lithophyte and 15 terrestrial orchids, amongst which a natural hybrid was found which has not yet been registered or taxonomically placed. Despite being an arid zone, the results demonstrate the potential of the Mezquital Valley in terms of orchid germplasm.

This paper aims to present the dasometric characteristics of the mesquite stands presents in the geographical area of the municipality of San Juan de Guadalupe and the tree population density. It aims to present the volume of commercial timber available in the municipality. The identification and delimitation of stands of mesquite in the study are a was conducted with the help of the Charter of Use and Vegetation of INEGI1:250 000 Scale Serie III, identifying the polygons for the vegetation of mesquite and through field trips were located in situstands and locate droads and access gaps. Sampling the population of mesquite was performed by using the vegetation sampling technique quadrant focus on transects located with in stands in each of the sites. The num- ber of sampling points was 12 respecting the accessibility of private property and ejido. We were able tolocate three polygons with areas whose dominant vegetation is mesquite, with a total of 8679.296 ha, corresponding to 17.69% of the total area of the municipality and 3.70% of the area covered by mesquite state wide. The mesquite is associated with shrubs and herbs. The average distance between trees, estimated by the central quadrant point methodis 5.77±1.56 m, resulting in a population density of 402 individual sper ha with an average height of 3.50 m.±0.61. The aerial cover of trees, orarea co- vered by the goblet was on average 20.22±7.97 m2, while the basalarea orwas on average 0.23 m2. The percentage of individuals of commercial interest is 54.17%. We found acommercialtimber volume of 0.33 m3 average, based on population density results in a volume of 106.89 m3 of commercial timber.

There is few information concerning the presence of viral diseases in commercial nurseries and experiment orchards of peach, plum and apricot in Mexico, in consequence the goal of this report was to identify the viruses in stone fruits in the states of Zacatecas and Querétaro, Mexico. During 2010 peach, plum and apricot foliage samples were obtained to be analyzed by means of the technique DAS-ELISA for the Tobacco ring spot virus (TRSV), Peach rosette mosaic vi- rus (PRMV), Prunus necrotic ring spot virus (PNRSV), and Prune dwarf virus (PDV). Presence of these viruses was confirmed in peach, plum, and apricot of both states, however, their incidence was variable; from 75 to 91.1 %, from 62.5 to 100 %, from 31.1 to 100 % for TRSV, PRMV, and PNRSV in commercial nurseries of Zacatecas. The incidence of PDV, PRMV, TRSV, and PNRSV was 100, 100, 88.8, and 11.1 % respectively in an experimental orchard in Queretaro. The incidence of the same viruses was 100, 45.7, 100, and 26.2 % in an experimental orchard in Zacatecas.

According to the international meteorological vocabulary aridity is defined as the characteristic of a climate relating to insufficiency or inadequacy of precipitation to maintain vegetation. In the arid climates precipitation is highly variable and prolonged dry periods are common. In this sense, the term drought is defined as the prolonged absence or marked deficiency of precipitation to cause serious hydrological imbalance. The state of Sonora has very arid, arid and semiarid climates in the 95% of its territory. The plant diversity of Sonora reflects the intermingling of several major biogeographic provinces. There is a mark altitudinal gradient of vegetation types in Sonora extending from the hot, arid coast of the upper Gulf of California to the wet, cold highlandsof the Sierra Madre Occidental.In this work we performed the analyses of the spatial variability of tempe rature and precipitation in Sonora. Thearidityindices of ang and eMartone were studied and their link to observed changes in the distribution of vegetation was evaluated. We used climatic data of So nora between 1920 and 2011. ongterm means of temperature and precipitation were estimated from selected climatic stations according to their location, continuity and length of their records. It was found that e Martonne`s index increases from east to west and from south to north in the Sierra Ma dre Occidental coincident with the spatial distribution of vegetation. For this reason, e Martonne`s index was considered better indicator than ang index for the vegetation types in the state Sonora.