Abstract
ABSTRACT: Under conditions of high stress, interactions between species can be positive. Islands of perennial vegetation can improve the conditions of the understory and facilitate the establishment of herbaceous plants. The hypothesis of this study is that islands of perennial vegetation in an area of caatinga harbor, a greater richness, diversity and density of herbaceous plants, and that individuals reach a greater height and diameter than in open spaces. The study was conducted in Petrolândia, Pernambuco, Brazil. Twenty-seven plots were installed in the center of the islands, 38 at the edge of the islands (in a total of 38 islands) and 35 in the open spaces. A total of 51 species were recorded in the center and 55 on the edge of the islands and 48 in the open spaces. The mean richness of the open spaces was lower than on the islands. The diversity was greater in the center of the island and became less on the edge of the island and in the open spaces. The mean density was lower in the open spaces than on the islands. The mean density at the edge of the islands was greater than in the center of the islands. There was no difference in mean diameter of herbaceous plants. The mean height of the individuals was higher in the center of the islands. The herbaceous community growing on the islands exhibited higher richness, diversity, density and height than in open spaces. Thus, islands of perennial vegetation facilitate the establishment of herbaceous species.
Highlights
Warm arid and semiarid regions are characterized by high temperatures and low rainfall
In arid and semiarid regions where the community is made up of shrubs and/or trees randomly distributed within a matrix of herbaceous vegetation or bare soil, plant canopies can alter the microclimatic conditions of the understory and play an important role in structuring the community of herbaceous plants (FACELLI; TEMBY, 2002)
The aim of this study was to investigate whether there are differences in the richness, diversity and community structure between the herbaceous community installed in the center and on the edge of the shrub-arboreal islands and in areas of matrix devoid of woody vegetation, in an area of caatinga located in the Brazilian semiarid
Summary
Warm arid and semiarid regions are characterized by high temperatures and low rainfall. The soil below the shrub canopy is richer in nutrients (e.g. N, P and total P) (MORO et al, 1997b; FULLER, 1999; ZHAO et al, 2007) These changes in microclimate and soil fertility contribute to the establishment of herbaceous vegetation below the canopy in the beginning stages of regeneration (MORO et al, 1997a; TRACOL; GUTIÉRREZ; SQUEO, 2011). This process where some species may change the abiotic environment and facilitate the establishment of other species is known as facilitation (BEGON; TOWNSEND; HARPER, 2007). Plants are important facilitators in environments with high abiotic stress because they enhance germination, seedling recruitment and growth of seedlings and juveniles in various types of communities (GUREVITCH; SCHEINER; FOX, 2009)
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