Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Dinámica del contenido de humedad del suelo a lo largo de un gradiente de condición de pastizal en el noroeste de Jalisco

Auteur : Medina Roldán Eduardo

Etablissement de soutenance : Universidad de Guadalajara (UDG)

Grade : Licenciatura en Biología 2003

Résumé
Range condition is a key concept in range management. This concept provides a conceptual framework to evaluate grazing-induced changes on rangeland ecosystems as well as to determine management practices to face these changes. In practice, range condition ís determined from vegetation-based índices such as species composition. The role of vegetation on ecosystem function has been more recognized during the last years. Thus, vegetation changes reflected in range condition míght be correlated with ecosystem function. I examined the relationshíp . between range condition with soil moisture content and soil moisture dynamic in Bouteloua gradlis semíarid grassland at the geographíc subprovince Los Uanos de Ojuelos, Jalisco, Mexico. I was interested in two basic questions : 1) does soil water content vary throughout a range condition gradient ?, and 2) is soil water content variation related to biotic attributes or abiotic attributes which are reflected in the range condition gradient ? A field study was conducted in order to resolve these questions. I examined the soil water content and soil water dynamic along a range condition gradient. Soil water content measurements were made during 14 months at four locatioris which supported contrasting range condition das5es. I found that range condition had a significant effect on soil water content (P < 0.01). Excellent condition dass was less humid than the other range condition dasses (P < 0.01). The soil water content did not vary in the remaining classes (poor, regular and good, P > 0.50). Despite this lack bf statisticai significance, I found a soil water content gradient negatively associated with the range condition gradient. The soil moisture content in the excellent class was 8 percent smaller than the soil moisture content in the poor class (P < 0.01). On the other hand, soil water content dynamic defined as the ra of change in soil water content was similar . among all range condition classes (P > 0.35). Despite this result, I have evidence that the range condition classes _ deferred in their moisture recharge and extraction patterns. Although 1 could not evaluate the separated effects of floristic composition and vegetal cover, the results suggest that the soil moisture content differences among range condition classes are due to Boutr ;loua gracilis functional features. This functional features associated with the

Mots clés : condición de pastizal, contenido de humedad del suelo, dinámica de humedad del suelo, pastizal mediano abierto, ’3outeloua gracilis