Savannization Processes in Tropical Africa - TAGELAQP 88/89

该项目的目的是对热带非洲的自然和人为荒漠过程进行比较和年代学研究。1987赛季野外工作取得的成果可概括如下：1.在热带非洲的大部分地区，在过去100年里，荒漠和荒漠化进程都在加速，特别是在1910年代中期和1960年代末以来的干旱时期。在赞比亚，干燥的常绿森林的消失可以追溯到400-800年前，当时铁器时代的晚期人们开始轮耕。现在，干燥的森林只存在于人类影响最小的卡拉哈里沙漠上。相比之下，反复燃烧和砍伐与森林的密集交错导致了“miombo”林地，这是南部稀树草原地带的一种典型景观，由矮小稀疏的木质植被组成，生长在有机质含量和物理性质较差的土壤上。在喀麦隆北部，人们认为长期的自然荒漠和沙漠化是在4500年B.P.之后开始的，这与非洲热带地区的总体气候干旱化相对应。尽管过去和最近气候变化的影响仍未得到回答，但萨纳加北部稀树草原景观的主要原因可以归因于最近的农业活动。在过去的20年里，在西喀麦隆的奥库山脉，森林被加速焚烧和砍伐，为种植粮食作物让路。西喀麦隆高地草地起源的年代构成需要进一步研究。

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.