02820naa a2200253 a 450000100080000000500110000800800410001910000120006024501000007226000090017252021360018165000130231765000130233065000270234365000130237065300110238365300100239465300160240465300230242065300220244370000200246570000210248577300600250614013242022-12-06       1988    bl uuuu     u00u1 u    #d1 aUHL, C.  aAbandoned pastures in eastern Amazonia. I. Patterns of plant succession.h[electronic resource]  c1988  a(1) Vegetation composition, structure, and biomass accumulation were studied on thirteen forest sites that had been cut and burned, used as cattle pasture, and then abandoned in the eastern Amazon near Paragominas, Para, Brazil. (2) The study sites were of two ages (two to four years and seven to eight years) and had received light, medium or heavy use for up to thirteen years. (3) Forest regenerated vigorously on sites of previously light use. Above-ground biomass accumulation averaged 10 t ha-' y-1 or 80 t after eight years (roughly one-quarter of mature forest levels). Tree species richness was also high (about 20 per 100 mi2) and almost all species also occurred in native forest. Moderately grazed pastures also developed forest but biomass accumulation was only 5 t ha'-I y- . Tree species richness was also lower than on light-use sites and there were fewer forest trees. Abandoned pastures subjected to heavy use had the least distinct patterns of succession. The single eight-year-old site was dominated by grasses and forbs with fewer than one tree per 100 m2 and an above-ground biomass accumulation of 0 6 t ha-' y- 1, a value only about 6% of that found on light-use sites. (4) The light-use sites had significantly higher biomass and species richness in both age-classes than either moderate- or heavy-use sites. Site age was a good predictor of above-ground biomass accumulation on light- and moderate-use sites, but not on heavy-use sites. (5) These Amazon cosystems generally can recover after large-scale pasture disturbances. Only where land has been used too intensively for long periods is reforestation uncertain, but probably less than 10% of the pasture land in northern Para has degraded to this level. Nevertheless, the re-growth forest, regardless of pasture-use history, will not necessarily have the same characteristics of physiognomy or species composition as that originally occupying the site. Moreover, as burning becomes more prevalent in eastern Amazonia, abandoned sites may not develop into forest and the irreversible degradation of the entire regional ecosystem must be contemplated.  aAmazonia  aBiomassa  aComposição Botânica  aEcologia  aBrasil  aPará  aParagominas  aPastagem degradada  aSucessão vegetal1 aBUSCHBACHER, R.1 aSERRAO, E. A. S.  tJournal of Ecologygv. 76, n. 3, p. 663-681, Sep. 1988.