Dominance of legume trees alters nutrient relations in mixed species forest restoration plantings within seven years

• Published in: Biogeochemistry 2008-03, Vol.88 (1), p.89-101
• Main Authors: Siddique, Ilyas, Engel, Vera Lex, Parrotta, John A, Lamb, David, Nardoto, Gabriela B, Ometto, Jean P. H. B, Martinelli, Luiz A, Schmidt, Susanne
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biogeochemistry; Biogeosciences; Biological and medical sciences; Earth and Environmental Science; Earth Sciences; Earth, ocean, space; Ecosystems; Environmental Chemistry; Environmental restoration; Exact sciences and technology; Forest soils; Fundamental and applied biological sciences. Psychology; Geochemistry; Leaves; Legumes; Life Sciences; Mixed forests; Native tree plantations; Nitrates; Nitrification; Nitrogen fixation; Nodulating multi-purpose trees; Nutrient retranslocation; Nutrients; Original Paper; Plant litter; Plant nutrition; Plant species; Planting; Plants; Reforestation; Resins; Soil and rock geochemistry; Soil microorganisms; Soil nitrate; Soils; Species; Stand nitrogen accrual; Surficial geology; Synecology; Terrestrial ecosystems; Trees; Tropical forest restoration
• ISSN: 0168-2563; 1573-515X
• DOI: 10.1007/s10533-008-9196-5

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, six-fold 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.