Title: Dominance of legume trees alters nutrient relations in mixed species forest restoration plantings within seven years
Author: Siddique, Ilyas; Engel, Vera Lex; Parrotta, John A.; Lamb, David; Nardoto, Gabriela B.; Ometto, Jean P.H.B.; Martinelli, Luiz A.; Schmidt, Susanne.
Source: Biogeochemistry. 88:89-101
Description: Failures in reforestation are often attributed to nutrient limitation for tree growth. We compared tree performance and nitrogen and phosphorus relations in adjacent mixed-species plantings of contrasting composition, established for forest restoration on Ultisol soil, originally covered by tropical semi-deciduous Atlantic Forest in Southeast Brazil. Nutrient relations of four tree species occurring in both planting mixtures were compared between a legume-dominated, species poor direct seeding mixture of early-successional species (‘‘legume mixture’’), and a species-diverse, legume-poor mixture of all successional groups (‘‘diverse mixture’’). After 7 years, the legume mixture had 6-fold higher abundance of N2-fixing trees, 177% higher total tree basal area, 22% lower litter C/N, sixfold higher in situ soil resin-nitrate, and 40% lower in situ soil resin-P, compared to the diverse mixture. In the legume mixture, non-N2-fixing legume Schizolobium parahyba (Fabaceae-Caesalpinioideae) had significantly lower proportional N resorption, and both naturally regenerating non-legume trees had significantly higher leaf N concentrations, and higher proportional P resorption, than in the diverse mixture. This demonstrate forms of plastic adjustment in all three non-N2-fixing species to diverged nutrient relations between mixtures. By contrast, leaf nutrient relations in N2-fixing Enterolobium contortisiliquum (Fabaceae-Mimosoideae) did not respond to planting mixtures. Rapid N accumulation in the legume mixture caused excess soil nitrification over nitrate immobilization and tighter P recycling compared with the diverse mixture. The legume mixture succeeded in accelerating tree growth and canopy closure, but may imply periods of N losses and possibly P limitation. Incorporation of species with efficient nitrate uptake and P mobilization from resistant soil pools offers potential to optimize these tradeoffs.
Keywords: Native tree plantations, Nodulating, multi-purpose trees, Nutrient retranslocation, Soil nitrate, Stand nitrogen accrual, Tropical forest restoration
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Siddique, Ilyas; Engel, Vera Lex; Parrotta, John A.; Lamb, David; Nardoto, Gabriela B.; Ometto, Jean P.H.B.; Martinelli, Luiz A.; Schmidt, Susanne. 2008. Dominance of legume trees alters nutrient relations in mixed species forest restoration plantings within seven years. Biogeochemistry. 88:89-101.
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