02776naa a2200277 a 450000100080000000500110000800800410001902400330006010000160009324501260010926000090023530000080024452019940025265000120224665000270225865000220228565000150230765000130232265000240233565000180235965300170237770000150239470000180240970000190242777300520244614004802022-12-06       1999    bl uuuu     u00u1 u    #d7 a10.1023/A:10061388154532DOI1 aGEHRING, C.  aResponse of secondary vegetation in Eastern Amazonia to relaxed nutrient availability constraints.h[electronic resource]  c1999  cil.  aThis study evaluated the effect of nutrient application on the regrowth dynamics of secondary fallow vegetation in an intensely exploited shifting cultivation area in the eastern Amazon region of Brazil. The importance of N, P, K, Ca, Mg, S and a mixture of micronutrients was tested in a minus-one-trial by comparison with a full complement of nutrients and unfertilized control plots. Fertilizers were applied three times during the experiment and their effects were monitored over 2 1/2 years. Prior to the second fertilization, one third of each experimental plot was cleared of the vegetation cover and planted in maize, prior to the third fertilizer application these subplots were planted in sorghum. Biomass of maize and sorghum were used to indicate nutrient constraints and fertilizing effects due to the different treatments. Both crops were limited by P- and N-availability, with greater responses to P. The initial fertilization did not affect the biomass accumulation of the secondary vegetation during the first 15 months, but two additional applications significantly increased biomass in the complete fertilizer treatment compared to the unfertilized control. Biomass accumulation was primarily P-limited, N-limitation was apparent but not significant. The remaining nutrients did not affect plant growth. Fertilization favored production of nutrient-rich leaves. Application of readily available nutrients gave grasses a competitive edge over slower reacting woody vegetation. Fertilization also caused significant shifts in the contribution of woody species to biomass accumulation, as could be demonstrated for two prominent pioneer tree species. Growth response to fertilization as well as the primary limiting nutrient varied among seven dominant species monitored in the secondary vegetation. We conclude that growth of tropical secondary vegetation can be nutrient limited and it might respond significantly to additional nutrients by increasing biomass production.  abiomass  afertilizer application  asecondary forests  aAdubação  aBiomassa  aFloresta Secundaria  aRegeneração  aRegeneration1 aDENICH, M.1 aKANASHIRO, M.1 aVLEK, P. L. G.  tBiogeochemistrygv. 45, n. 3, p. 223-241, 1999.