Sobrevivência, crescimento e características fotossintéticas de espécies florestais em resposta à fertilização fosfatada

Abstract

The low availability of phosphorus in tropical soils may impair the initial establishment of forest species in reforestation projects in disturbed areas. However, the effects of phosphorus fertilization as a strategy to improve the survival, growth and photosynthesis-related traits of Amazonian tree species in P-limited soils remain elusive. Here, we investigate how contrasting levels of phosphorus fertilization affect the establishment of native forest species belong to different successional status. We measured the survival, growth and leaf traits (SPAD index, chlorophyll a fluorescence parameters, leaf nutrients, N/P ratio and gas exchange) of ten forest species (pioneers and non-pioneers) subjected to contrasting phosphorus supply (-P = 0 kg P2O5 ha-1 and +P = 160 kg P2O5 ha-1) on the field during 24 months. Pioneers species were more sensible to fertilization. Erythrina fusca (pioneers) showed high mortality under -P. However, Apuleia leiocarpa (pioneers) and Dipteryx odorata (non-pioneers), despite high values on leaf N/P ratio, remained growth in P-limited soils. On the other hand, C. fissilis and C. alliodora (pioneers) exhibited the highest increase in growth rates after fertilization. Phosphorus supply improved the phosphorus leaf content in both successional groups, while light absorption (SPAD values) and processing (total performance index, PItotal) and carbon capture (stomatal conductance) were increased only in pioneers species. Conversely, positive effects on carbon assimilation at leaf-level were not observed, then the phosphorus fertilization reduced the phosphorus use-efficiency of non-pioneers species. Thus, phosphorus fertilization affects the initial establishment of Amazonian trees in a species‐specific way. The implications of these results for reforestation efforts in Amazonia are discussed.