Carbon fluxes resulting from land-use changes in the Tamaulipan thornscrub of northeastern Mexico

Information on carbon stock and flux resulting from land-use changes in subtropical, semi-arid ecosystems are important to understand global carbon flux, yet little data is available. In the Tamaulipan thornscrub forests of northeastern Mexico, biomass components of standing vegetation were estimated from 56 quadrats (200 m2 each). Regional land-use changes and present forest cover, as well as estimates of soil organic carbon from chronosequences, were used to predict carbon stocks and fluxes in this ecosystem

Estrés hídrico en Pinus engelmannii Carr., producido en vivero

The effect of water stress was evaluated in relation to the water potential and growth of five-month old seedlings of Pinus engelmannii Carr. The essay was conducted from September 21st to October 27th, 2003; in this period of time three water stress cycles were completed. Significant differences between water supply treatments were found (p < 0.01) in regard to the seedlings water potential after the third day of watering. The seedlings under water stress reached final water potentials from –1,96 to –2,29 MPa, while the seedlings without water stress showed values between –0.13 and –0.20 MPa. The morphological response of the seedlings presented two well-defined trends. First, the seedlings irrigated without humidity restriction showed larger growth rates in height (20.7%), collar diameter (69.4%) and total phytomass production (144.1%). On the other hand, the seedlings under water stress showed smaller increments in height (1.3%), collar diameter (9.8%) and total phytomass (73.1%). It is concluded that the seedlings were sensible to the evaluated levels of water stress, therefore allowing management to promote their hardening. Key words: humidity deficit, seedlings quality, growth, preaconditioning phase.Se evaluó el efecto del estrés hídrico en el potencial hídrico y en el crecimiento de plantas de Pinus engelmannii Carr. de cinco meses de edad, sometidas a dos tratamientos de riego (con y sin estrés hídrico). El experimento comprendió del 21 de septiembre al 27 de octubre de 2003, tiempo en el que se aplicaron tres ciclos de estrés hídrico. Se encontraron diferencias significativas entre tratamientos (p < 0,01) en el potencial hídrico a partir del tercer día después del riego. Las plantas sometidas a estrés hídrico alcanzaron valores de –1,96 a –2,29 MPa al final de cada ciclo de estrés hídrico, mientras que los del tratamiento sin estrés variaron entre –0,13 y –0,20 MPa. La respuesta morfológica de las plantas mostró dos vertientes bien definidas; en el tratamiento sin restricción de humedad las tasas de crecimiento fueron mayores en altura (20,7%), diámetro del cuello (69,4%) y producción total de fitomasa (144,1%); mientras que en la condición de estrés los incrementos fueron menores en altura (1,3%), diámetro del cuello (9,8%) y fitomasa total (73,1%). Se concluye que las plantas fueron sensibles a los niveles de estrés hídrico evaluados, lo que permitiría su manejo para favorecer su preacondicionamiento

DISTRIBUCIÓN ESPACIAL DE LA BIOMASA AÉREA EN LOS BOSQUES TROPICALES DE MÉXICO

Artículo de Investigació

Land use change and carbon fluxes in East Africa quantified using earth observation data and field measurements

Carbon-based forest conservation requires the establishment of ‘reference emission levels’ against which to measure a country or region’s progress in reducing their carbon emissions. In East Africa, landscape-scale estimates of carbon fluxes are uncertain and factors such as deforestation poorly resolved due to a lack of data. In this study, trends in vegetation cover and carbon for East Africawere quantified using moderate-resolution imaging spectroradiometer (MODIS) land cover grids from 2002 to 2008 (500-m spatial resolution), in combination with a regional carbon look-up table. The inclusion of data on rainfall and the distribution of protected areas helped to gauge impacts on vegetation burning (assessed using 1-km spatial resolution MODIS active fire data) and biome trends. Between 2002 and 2008, the spatial extents of forests, woodlands and scrublands decreased considerably and East Africa experienced a net carbon loss of 494 megatonnes (Mt). Most countries in the area were sources of carbon emissions, except for Tanzania and Malawi, where the areal increase of savannah and woodlands counterbalanced carbon emissions from deforestation. Both Malawi and Tanzania contain large areas of planted forest. Vegetation burning was correlated with rainfall (forest only) and differed depending on land management. Freely available global earth observation products have provided ways to achieve rapid assessment and monitoring of carbon change hotspots at the landscape scale

Stemflow variation in Mexico’s northeastern forest communities: Its contribution to soil moisture content and aquifer recharge

Artículo de Investigació