Showing papers by "Artemi Cerdà published in 2000"

Aggregate stability against water forces under different climates on agriculture land and scrubland in southern Bolivia

Abstract: Little is known about the combined effect of agriculture and climate on soil aggregate stability. Few places in the world allow the study of the influences of both factors. Climatological gradients in Bolivia, where the agriculture is historically developed at different altitudes, provided opportunity to study the effects of climate and agriculture on soil aggregate stability. Aggregate stability was measured by the modified Emerson water dispersion test (MEWDT), drop impacts (CND and TDI) and ultrasonic disruption (UD) on agriculture ( Zea mays L.) and scrubland ( Acacia caven (Mol.) Mol., Leguminosae) land uses. Different methods and tests were applied in order to validate their ability to characterise aggregate stability. Each test had different range of energy (MEWDT −1 than on 300–400 mm yr −1 . Organic matter was the key factor determining soil aggregate stability on agriculture land ( r 2 =0.80) and scrubland ( r 2 =0.78) use. Agriculture was a driving force leading to the degradation of soil structure. This reflects that land use can exert a great influence on soil structure. Moreover, if climate change reduces mean annual rainfall, then aggregate stability will be reduced drastically.

Limitations to plant establishment on eroded slopes in southeastern Spain

Abstract: The possible causes for the lack of vegetation in five badland sites from southeast Spain were experimentally tested. The main factors affecting seed germination and seedling survival considered were seed availability, regolith water dy- namics in relation to rain events, regolith salinity, seedling predation by herbivores and seedling removal by erosion. Four issues are addressed: 1. Both rainfall and the tempo- ral and spatial dynamics of regolith water during the seedling emergence period were monitored in five different zones at one site (Petrer, Alicante). 2. Effects of salinity and water potential on the rate and speed of germination of local seeds were determined. 3. Seed reserve and seedling emergence and mortality were followed throughout one season. 4. Regolith characteristics of all five sites were compared and the conse- quences for plant colonization discussed. The main factor limiting plant colonization in these sites was the very short duration of available water in the soil, due to the physical and chemical characteristics of the regolith. In addition, high regolith salinity and its effects on seed germina- tion, the aspect of the site and the pattern of rain events, played a very important role reducing germination and survival. Herbivory and erosion were seldom responsible for seedling mortality. However, there were no highly erosive rain events during the study period, although several have been measured during the past few years.

Distribución del banco de semillas en taludes de carretera

Abstract: Se estudia el banco de semillas del suelo en la parte alta, media y baja de dos taludes de carretera de 33° de pendiente, con orientaciones norte y sur en Alberique (Valencia). Se tomaron 18 muestras (50 x 50 x 2 cm) que presentaron una densidad media de 5779 ± 2271 semillas m-2 y una riqueza de 21 ± 4 especies por muestra, siendo el total de especies encontradas de 41. La densidad de semillas del talud orientado al norte fue superior al orientado al sur (5906 ± 2787 y 5658 ± 1767) al igual que la riqueza de especies (24 ± 3 y 18 ± 3), siendo significativa estadisticamente solo las diferencias en la riqueza de especies. Las semillas de menor tamano fueron las mas frecuentes en el banco de semillas y se distribuyeron uniformemente a lo largo de la ladera, mientras que las semillas grandes se acumularon en las partes bajas y presentaron una mayor densidad en el talud orientado al norte.

Distribución del banco de semillas en taludes de carretera: Efecto de la orientación y de la topografía

Abstract: Se estudia el banco de semillas del suelo en la parte alta, media y baja de dos taludes de carretera de 33° de pendiente, con orientaciones norte y sur en Alberique (Valencia). Se tomaron 18 muestras (50 x 50 x 2 cm) que presentaron una densidad media de 5779 ± 2271 semillas m-2 y una riqueza de 21 ± 4 especies por muestra, siendo el total de especies encontradas de 41. La densidad de semillas del talud orientado al norte fue superior al orientado al sur (5906 ± 2787 y 5658 ± 1767) al igual que la riqueza de especies (24 ± 3 y 18 ± 3), siendo significativa estadisticamente solo las diferencias en la riqueza de especies. Las semillas de menor tamano fueron las mas frecuentes en el banco de semillas y se distribuyeron uniformemente a lo largo de la ladera, mientras que las semillas grandes se acumularon en las partes bajas y presentaron una mayor densidad en el talud orientado al norte.