A comparison of productivities and energy values between slash and burn agriculture and secondary succession in the upper Rio Negro region of the Amazon Basin
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引用次数: 43
Abstract
An analysis of the energy inputs and outputs for conuco agriculture (i.e., shifting cultivation) and a comparison of productivity between conuco crops and successional vegetation was undertaken near the town of San Carlos de Rio Negro in southern Venezuela.
The main crop, yuca (Manihot esculenta, Crantz), yielded (m.t. = metric tonnes) 4.31 m.t. ha−1 wet weight in year one; production declined to 2.81 m.t. ha−1 in the second year. The infertile soils of the region are the major cause of these low yields.
Although relatively unproductive, conuco agriculture is much more energy efficient than mechanized agriculture. The ratio of energy output, in the form of processed food, to energy input in the form of human labor, averaged 13.9:1 over two cropping periods. Slightly more energy was devoted to field activities than to processing activities.
The conuco crops were more productive than the adjacent succession site vegetation (532 vs. 109 g m−2 dry weight) during the first year after cutting and burning; but in the second year the successional vegetation was more than twice as productive as the conuco crops (1446 vs. 529 g m−2 dry weight). This difference in second year production was attributable to greater resource allocation to leaves and longer leaf retention time for the successional vegetation.
在委内瑞拉南部的圣卡洛斯德里奥内格罗镇附近,对椰子农业(即轮作耕作)的能源投入和产出进行了分析,并比较了椰子作物和演代植被之间的生产力。主要作物尤卡(Manihot esculenta, Crantz)第一年的湿重为4.31公吨;第二年产量下降到281万吨/公顷。该地区土壤贫瘠是造成这些低产量的主要原因。尽管相对而言生产力较低,但椰子农业比机械化农业更节能。以加工食品的形式输出的能量与以人力劳动的形式输入的能量之比,在两个种植期内平均为13.9:1。用于实地活动的精力略多于用于加工活动的精力。在砍烧后的第一年,椰树作物的产量高于相邻演替地植被(干重532比109 g m−2);但在第二年,演替植被的产量是椰子作物的两倍多(干重1446比529 g m−2)。这种第二年产量差异的原因是演替植被的叶片资源分配较多,叶片滞留时间较长。