El ensayo contemplo la siembra de un cultivo de maiz (Pioneer 3527, semiprecoz), en un suelo franco - arcilloso de la serie Talca. Los datos diurnos de resistencia estomatica fueron medidos con un analizador infrarrojo de gases (CI - 301 PS, C1D Inc., USA). Para esto se seleccionaron aleatoriamente 3 plantas donde, de cada planta se escogieron 4 hojas con dos orientaciones (norte y sur) y dos alturas (1/3 y 2/3 de planta). Paralelamente, datos meteorologicos en intervalos de una hora, provenientes de una estacion meteorologica automatica (modelo 16.98 Eijkelkamp, Agrisearch Equipment, Holanda), fueron medidos para validar dos modelos de Rcv (modelos A y B). Los modelos A y B utilizan variables climaticas (Temperatura, Humedad Relativa, Radiacion Neta, Calor del Suelo y Velocidad del Viento), para describir el comportamiento de la Rcv, pero el modelo B incorpora el indice de area foliar como factor de cultivo. Los resultados de este estudio indicaron que la resistencia estomatica del maiz no fue afectada significativamente por la orientacion y altura. En este estudio se observo que el valor promedio de resistencia estomatica entre las 12:00 y las 16:00 hrs. fue de 92 s m -1 con una desviacion estandar de 21 s m -1. Por otro lado, grandes variaciones fueron observadas en la tarde despues de las 17:00 hrs. En este analisis se encontro que el modelo B presento una buena asociacion con los valores de Rcv obtenidos del analizador infrarrojo de gases (DEE = 26.26 s m -1 Ea = 10.48%) perfilandose este modelo como una herramienta viable para determinar la Rcv del cultivo y de este modo ser usado en la ecuacion de Penman - Monteith. En el analisis de sensibilidad se encontro que la respuesta de la ecuacion a los cambios de resistencia de la cubierta vegetal para los dias despejados, es mayor en el horario de las 14:00 hrs, es de importancia si se considera que en este horario los flujos de calor latente son maximos, el cambio expresado en la ecuacion para los dias nublados si bien es mayor que para la condicion anterior, no reviste mayor importancia ya que los flujos de vapor de agua son minimos

Monthly time series, from 2001 to 2016, of the Normalized Difference Vegetation Index (NDVI) and the Enhanced Vegetation Index (EVI) from MOD13Q1 products were analyzed with Seasonal Trend Analysis (STA), assessing seasonal and long-term changes in the mangrove canopy of the Teacapan-Agua Brava lagoon system, the largest mangrove ecosystem in the Mexican Pacific coast. Profiles from both vegetation indices described similar phenological trends, but the EVI was more sensitive in detecting intra-annual changes. We identified a seasonal cycle dominated by Laguncularia racemosa and Rhizophora mangle mixed patches, with the more closed canopy occurring in the early autumn, and the maximum opening in the dry season. Mangrove patches dominated by Avicennia germinans displayed seasonal peaks in the winter. Curves fitted for the seasonal vegetation indices were better correlated with accumulated precipitation and solar radiation among the assessed climate variables (Pearson’s correlation coefficients, estimated for most of the variables, were r ≥ 0.58 p < 0.0001), driving seasonality for tidal basins with mangroves dominated by L. racemosa and R. mangle. For tidal basins dominated by A. germinans, the maximum and minimum temperatures and monthly precipitation fit better seasonally with the vegetation indices (r ≥ 0.58, p < 0.0001). Significant mangrove canopy reductions were identified in all the analyzed tidal basins (z values for the Mann-Kendall test ≤ −1.96), but positive change trends were recorded in four of the basins, while most of the mangrove canopy (approximately 87%) displayed only seasonal canopy changes or canopy recovery (z > −1.96). The most resilient mangrove forests were distributed in tidal basins dominated by L. racemosa and R. mangle (Mann-Kendal Tau t ≥ 0.4, p ≤ 0.03), while basins dominated by A. germinans showed the most evidence of disturbance.

Con el fin de estudiar el efecto de la espesura de la cubierta forestal en la disponibilidad de luz y agua para las plantas y su supervivencia, se plantaron brinzales de dos savias de Quercus petraea (Matt.) Liebl. (roble albar) y Quercus pyrenaica Willd. (melojo) en el interior de un pinar de Pinus sylvestris L. (pino albar) situado en el NE de la provincia de Madrid sometido previamente a tres tratamientos: clara del 33% de la densidad original, clara del 50% y ausencia de clara. Se midió la humedad volumétrica del suelo con un TDR y la disponibilidad de luz en el sotobosque por medio de fotografías hemisféricas. La supervivencia se midió al final del primer año y al comienzo del verano de los dos años siguientes. La reducción de la densidad del dosel incrementó la luz disponible en el sotobosque, la humedad de los primeros 10 cm de suelo y la supervivencia de las plantas de melojo, aunque no se apreció un efecto diferente según la intensidad de la clara aplicada. La mortalidad de las plantas de roble albar fue elevada en todos los tratamientos, y superior a la del melojo. Estos resultados apuntan a la necesidad de reducir la espesura del pinar albar en la zona de estudio antes de llevar a cabo plantaciones con melojo en su interior. | Information of tree-nurse shelterwood effects on survival of underplanted seedlings is particularly scant in Mediterranean forest ecosystems. To study light and water resources availability and survival associated to overstory density, two-year-old seedlings of Quercus petraea (Matt.) Liebl. (sessile oak) and Quercus pyrenaica Willd. (pyrenean oak) were planted in the understory of an even-aged Scots pine (Pinus sylvestris L.) plantation located in central Spain, which had been previously assigned to three density treatments: uncut, 33% thinned and 50% thinned of the original density, each replicated four times. Soil moisture was measured with a TDR during the first growing season after planting. Light conditions were estimated by hemispherical photography. Survival was measured at the end of the first growing season in the field and at the beginning of the next two growing seasons. The reduction in density after thinning had a positive effect on light availability and on near-surface soil moisture. Pyrenean oak had higher survival rates than sessile oak, which showed similarly high mortality rates in all three overstory treatments. Thinning had a positive effect on the survival of pyrenean oak, though irrespective of the intensity. Overall, these results point to the necessity to reduce canopy tree density in Mediterranean mountain pinewoods before carrying out enrichment plantations beneath.

‘Blue water’ is the portion of freshwater flowing through rivers and the subsurface (groundwater) that is available for human consumption. ‘Green water’ is the portion stored in the unsaturated soil and vegetation canopy that is available only indirectly. Security of blue and green water resources is assessed over the Dorudzan Dam watershed in southern Iran. Precipitation and temperature data from 22 models of the Coupled Model Intercomparison Project Phase 5 are transiently downscaled at five climatic stations under three Representative Concentration Pathway (RCP) scenarios. The Soil and Water Assessment Tool (SWAT) is used to simulate and quantify blue and green water components over the region at the present time and under climate-change conditions. Climate-change study indicates that precipitation decreases (13–17%) and temperature increases (1.7–3. 3 °C) under the three RCPs, leading to substantial dam-inflow reduction. Evapotranspiration will increase while soil-water content will decrease, further intensifying green-water scarcity and vulnerability. Water use from the Kor River is sustainable at present, but future climate change will raise some ecological hotspots. Groundwater exploitation is currently unsustainable in all aquifers of the study area and climate change will further decrease the available groundwater, leading to intensification of the water crisis. Assessment of inter-annual security under climate change indicates that maximum scarcities of green water and surface blue water occur during spring and summer, and subsurface blue water (groundwater) maxima occur throughout the year. Thus, climate change threatens the future security of water resources in this arid watershed, requiring different management strategies for sustainability.