Leaf and Soil Nutrients in a Chronosequence of Second-Growth Forest in Central Amazonia: Implications for Restoration of Abandoned Lands

Subsistence agriculture, cattle ranching, and periodical land abandonment are common land-use practices in Amazonia. Because changes in land use affect biogeochemical cycles, secondary forests growing after land abandonment develop at varying speeds and spatial patterns, due in part to varying nutrient dynamics. Leaf and soil nutrient concentrations can provide useful information on nutrient cycling processes and strategies of nutrient use by trees that are suitable for introduction to abandoned areas. To understand nutrient dynamics in secondary forests from different regeneration stages, as well as the importance of pioneer species in the regeneration process, we measured the concentration of macronutrients in leaves of three pioneer tree species (Vismia cayennensis, Cecropia sciadophylla, and Bellucia dichotoma) in central Amazon secondary forests. We also measured macronutrients in the topsoil under the trees. We found that type of prior land use, time since abandonment, and number of fire events were significantly correlated with the concentrations of leaf and soil macronutrients, explaining between 10 and 38% of the variation in macronutrient concentrations. The observed patterns suggest that management practices affect the processes involved in N cycling and availability. Of the three pioneer species, C. sciadophylla showed the highest nutrient resorption efficiency and the highest leaf nutritional quality. We suggest that these two features determine a higher potential of C. sciadophylla for natural regeneration and restoration of abandoned lands.