INTRODUCTION

This account is based on the dry forest vegetation present today in the valleys of the study region. The distribution of biomes in the very recent past is shown in Figure 3.4 (Chapter 3). What is missing for an assessment of the dry forest resources present before the implementation of a widespread regime of irrigated agriculture some 6,000 years ago is an assessment of the trees and herbaceous vegetation, together with the micro-climates they engendered, within a particular biome. Most botanical descriptions of seasonal forest vegetation have concentrated on the larger trees, neglecting shrubs, forbs, and grasses. A detailed knowledge of all potential plant resources present in the environment is of particular importance for archaeologists studying early hunting and foraging populations and populations making the transition from dependence on game and gathered foods to dependence on cultivated crops.

In the absence of proxy evidence from pollen and phytoliths, the reconstruction of past biomes is dependent on existing plant communities, which are frequently found today in partial form, displaced by cultivation to the margins of the valleys. In contrast, the wetland associations – the back swamps of the littoral, the estuary associations, the riverine biome, and that of the freshwater ponds of the lower valley – may be depauperate but are in approximately the same locations. The arid inter-valley biome, largely populated by Tillandsia and Capparis (zapote), is another biome that has not moved.