García-Romero Arturo, Oropeza-Orozco Oralia, Galicia-Sarmiento Leopoldo
Departamento de Geografía Física, Instituto de Geografía, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, C.P. 04510, Coyoacán, D. F., México.
Environ Manage. 2004 Dec;34(6):768-85. doi: 10.1007/s00267-004-0178-z.
Land-cover types were analyzed for 1970, 1990 and 2000 as the bases for determining land-use systems and their influence on the resilience of tropical rain forests in the Tehuantepec Isthmus, Mexico. Deforestation (DR) and mean annual transformation rates were calculated from land-cover change data; thus, the classification of land-use change processes was determined according to their impact on resilience: a) Modification, including land-cover conservation and intensification, and b) Conversion, including disturbance and regeneration processes. Regeneration processes, from secondary vegetation under extensive use, cultivated vegetation under intensive use, and cultivated or induced vegetation under extensive use to mature or secondary vegetation, have high resilience capacity. In contrast, cattle-raising is characterized by rapid expansion, long-lasting change, and intense damages; thus, recent disturbance processes, which include the conversion to cattle-raising, provoke the downfall of the traditional agricultural system, and nullify the capacity of resilience of tropical rain forest. The land-use cover change processes reveal a) the existence of four land-use systems (forestry, extensive agriculture, extensive cattle-raising, and intensive uses) and b) a trend towards the replacement of agricultural and forestry systems by extensive cattle-raising, which was consolidated during 1990-2000 (DR of evergreen tropical rain forest = 4.6%). Only the forestry system, which is not subject to deforestation, but is affected by factors such as selective timber, extraction, firewood collection, grazing, or human-induced fire, is considered to have high resilience (2 years), compared to agriculture (2-10 years) or cattle-raising (nonresilient). It is concluded that the analysis of land-use systems is essential for understanding the implications of land-use cover dynamics on forest recovery and land degradation in tropical rain forests.
对1970年、1990年和2000年的土地覆盖类型进行了分析，以此作为确定土地利用系统及其对墨西哥特万特佩克地峡热带雨林恢复力影响的依据。根据土地覆盖变化数据计算了森林砍伐率（DR）和年平均变化率；因此，根据土地利用变化过程对恢复力的影响确定了土地利用变化过程的分类：a）改造，包括土地覆盖保护和集约化，以及b）转变，包括干扰和恢复过程。从粗放利用下的次生植被、集约利用下的栽培植被以及粗放利用下的栽培或诱导植被到成熟或次生植被的恢复过程具有较高的恢复力。相比之下，养牛业的特点是快速扩张、长期变化和严重破坏；因此，包括转变为养牛业在内的近期干扰过程导致了传统农业系统的衰落，并使热带雨林的恢复力丧失。土地利用覆盖变化过程表明：a）存在四种土地利用系统（林业、粗放农业、粗放养牛业和集约利用），以及b）有由粗放养牛业取代农业和林业系统的趋势，这一趋势在1990 - 2000年期间得到巩固（常绿热带雨林的森林砍伐率 = 4.6%）。与农业（2 - 10年）或养牛业（无恢复力）相比，只有不受森林砍伐影响，但受到选择性木材采伐、薪柴采集、放牧或人为火灾等因素影响的林业系统被认为具有较高的恢复力（2年）。得出的结论是，土地利用系统分析对于理解土地利用覆盖动态对热带雨林森林恢复和土地退化的影响至关重要。
