Savannization Processes in Tropical Africa - TAGELAQP 88/89

该项目的目标是对热带非洲的自然和人为稀树草原化过程进行比较和年代学研究。从1987年的野外工作中获得的结果可以概括如下。在过去100年里，热带非洲大部分地区的草原化和荒漠化进程都在加速，特别是在1910年代中期和1960年代后期以来的干旱时期。在赞比亚，干燥的万年青森林的消失可以追溯到400-800年前，当铁器时代后期的人们开始轮垦时。现在，干旱的森林只存在于卡拉哈里沙漠中，那里人类的影响最小。相反，由于森林受到反复烧伐的强烈干扰，形成了“miombo”林地，这是南部稀树草原地带的代表性景观，由生长在有机质含量和物理性质都很差的土壤上的矮小稀疏的木本植被组成。在北方喀麦隆，长期的自然稀树草原化和荒漠化在4500年B. P.之后开始，与热带非洲的气候干旱化相对应。虽然过去和最近的气候变化的影响仍然没有答案，萨纳加北部的热带草原景观的主要原因可以归因于最近的农业活动。在过去20年里，在喀麦隆西部的奥库山区，森林被加速烧毁和砍伐，以便为种植粮食作物让路。西喀麦隆高原草原起源的年代构成有待进一步研究。

The object of the project is to make up comparative and chronological studies of natural and anthropogenic savannization processes in tropical Africa. The results obtained from the 1987 season field work can be summarized as follows.1. Over much of tropical Africa, in the last 100 years both savannization and desertification processes have been accelerated, in particular during drought periods of mid-1910s and since late 1960s.2. In Zambia, the disappearance of dry evergreen forest can dates back to 400-800 years ago when the Later Iron age people began shifting cultivation. Now the dry forest exsits only on the Kalahari sands where man's impact has been least. In contrast, intensive interfrence with the forest by repeated burning and cutting has resulted in "miombo" woodlands, a representative landscape in the southern savanna zone, consisting of short and sparse woody vegetation which grows on soils with poor organic content and physical properties.3. In northern Cameroon it is assumed that long-term, natural savannization and desertification began somewhat after 4500 yr B.P. correspondeing to the over all climatic aridification in tropical Africa.4. Although the impact of past and and recent climatic changes remains unanswered, the major cause of the savanna landscape on the north of the Sanaga can be attributed to recent agricultural activities. In the last 20 years, in the Oku Mountains, West Cameroon, forests have been accelerately burned and cleared to make way for cultivation of food crops. The chronological make up of the origin of the Grassfields in the West Cameroon Highlands calls for further research.