Physiognomy and structure of vegetation along an altitudinal gradient in the semi-arid region of northeastern Brazil
Nogueira Ferraz, Elba Maria; Nogueira Rodal, Maria Jesus; Sampaio, Everardo V.S.B.
A quantitative survey was undertaken in the Pajeú Valley in the State of Pernambuco, Brazil, to characterize the variations in vegetation cover along an altitudinal gradient (1100, 900, 700 and 500 m). Ten 10 × 20 m plots were laid out at the 500 and 1100 m sites; five others were established at each of the two intermediate altitudes. All individual plants with a stem diameter ≥ 3 cm at soil level, and height ≥ 1 m were surveyed. The highest altitudinal site had the greatest density and the largest total basal area. The three lower sites had similar basal areas, although their individual densities varied greatly. Species of Myrtaceae, Simaroubaceae, Lauraceae, and Celastraceae were only encountered in the two highest and most humid sites (1100 and 900 m). The physiognomic and structural differences seen among sites at different altitudes are due to their accentuated climatic differences, in spite of the relatively reduced linear distances which separate them. The highest and lowest sites had 1260 and 679 average annual rainfall and 21.6 and 24.8° C average temperature, respectively.