干旱区生态环境知识资源中心

Fire plays a fundamental role in the structure of vegetation communities in the Caldenal. However, this effect has decreased considerably since the introduction of domestic cattle, which reduces the amount of fine combustible material. Objectives of this study were (1) to analyze the diversity and composition of a typical vegetation community in the south of the Caldenal after exposure to different fire frequencies, and (2) to show the convenience of using controlled fire for reversing the processes of scrub formation to states with more diverse and productive grassland communities. Forty-five herbaceous and woody species were recorded. Treatment C (control) showed the greatest richness and diversity in December 2006 and 2007. After the last controlled fire, the composition of the vegetation community differed significantly between treatment C and treatments T-1 and T-2 (with burns every 3-4 and 7-8 years, respectively). This change was mainly due to the proliferation of palatable perennial grasses. Vegetation composition was similar for C and T-2 (ANOSIM, R=0.01, p=0.32 and R=0.06, p=0.01, respectively) in 2006 and 2007. However, treatment T, showed significant changes (ANOSIM, R=0.42, p=0.01). Nasella clarazii, which is a characteristic palatable grass in the region, was the perennial forage grass with greatest cover in treatment T2, whereas it was scarce in treatments C and T-1. Unpalatable grasses and bushes grew at sites without fire, e.g. treatment C in this study. Our results show that use of controlled fire of intermediate frequencies would favor the aerial cover of palatable perennial grasses in states that are most useful for sustainable cattle production.