Medidas de diversidade de plantas aplicadas na diferenciação de tipos de uso da terra na Amazônia Oriental.

Abstract

Measuring diversity can assist in the assessment of human impacts and in conservation strategies in human-modified landscapes; the problem is that in addition to the costs involved in collecting data, the value of the diversity found often depends on the measure used and the response metrics, which makes it difficult to compare different communities. In this sense, this work aimed to evaluate measures of plant diversity to differentiate the vegetation cover of types of land use in the Eastern Amazon. The study was carried out in the municipalities of Acará, Bujaru, Thailand and Tome-açu, in the region of Vale do Rio Acará. In this region, 20 small family farmers were chosen and in them plots were established where the vegetation cover was inventoried in the main types of land uses: forest, secondary forest, agroforestry systems, annual crops, oil palm plantations and pastures. The vegetation inventory was carried out in three vertical strata: upper, middle and lower. 36 diversity measures were calculated in each stratum, considering four categories of measures: richness, uniformity, heterogeneity and richness estimators. The methods of evaluating measures and comparing the types of uses varied according to the category of the measure. Not all measures are able to differentiate the vegetation cover found in the types of land uses, indicating that some uses have the same diversity; and, the measures that achieve this differentiation vary between strata. There is an increase in the number of measures that differentiate the types of uses from the lower layer (two measures) to the upper layer (26). Some measures are noteworthy for performing greater differentiation in two strata: ACE and Bootstrap (in the lower and upper strata), and Fisher's Alpha and Jacknife 2 (in the middle and upper strata). The strata showed different results, as distinct taxonomic groups. The standardized use of one of these measures must be a methodological principle to be followed, but the importance of choosing the diversity measure for the differentiation and ordering of communities is also very important, as the results vary between the measures and this leads to different results in the evaluation of species losses and, consequently, the conservation potential of a certain type of use.