Productivity, nutrient cycling, and succession in single- and mixed-species plantations of Casuarina equisetifolia, Eucalyptus robusta, and Leucaena leucocephala in Puerto Rico

• Published in: Forest ecology and management Vol. 124; no. 1; pp. 45 - 77
• Main Author: Parrotta, John A
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 22-11-1999; Elsevier
• Subjects: bark; biogeochemical cycles; Biological and medical sciences; biomass; biomass production; Biomass productivity; calcium; carbon; Casuarina; Casuarina equisetifolia; cation exchange capacity; ecological succession; Eucalyptus; Eucalyptus robusta; Floristic diversity; forest litter; Forest management; Forest management. Stand types and stand dynamics. Silvicultural treatments. Tending of stands. Natural regeneration; forest plantations; Forestry; Fundamental and applied biological sciences. Psychology; Leucaena; Leucaena leucocephala; Litterfall; logging; magnesium; manganese; mixed forests; nitrogen; Nitrogen-fixing trees; nutrient content; phosphorus; Plantations; potassium; soil chemistry; soil fertility; soil organic matter; Soils; tree age; Tropics; understory; vegetation; wood; Puerto Rico; Central America; America; West Indies; Casuarina; Eucalyptus; Floristic diversity; Soils; Plantations; Biomass productivity; Leucaena; Nitrogen-fixing trees; Tropics; Litterfall; Casuarina equisetifolia; Biodiversity; Understory; Dicotyledones; Angiospermae; Myrtaceae; Nitrogen fixation; Hardwood forest tree; Ecological abundance; Symbiosis; Productivity; Litter; Interspecific comparison; Cropping system; Biogeochemical cycle; Vegetation dynamics; Leucaena leucocephala; Multipurpose tree; Vegetation succession; Entisols; Calcareous soils; Mixed cropping; Leguminosae; Artificial forest stand; Casuarinaceae; Spermatophyta
• ISSN: 0378-1127; 1872-7042
• DOI: 10.1016/S0378-1127(99)00049-3

Tree growth, biomass productivity, litterfall mass and nutrient content, changes in soil chemical properties and understory forest succession were evaluated over a 8.5-year period in single- and mixed-species (50
:
50) plantations of two N
2-fixing species,
Casuarina equisetifolia and
Leucaena leucocephala, and a non-fixing species,
Eucalyptus robusta. At the optimal harvest age for maximum biomass production (4 years), total aboveground biomass ranged from 63
Mg
ha
−1 in the
Eucalyptus monoculture to 124
Mg
ha
−1 in the
Casuarina/
Leucaena mixture, and was generally greater in the mixed-species than in single-species treatments due to increased productivity of the N-fixing species in the mixed stands. Total litterfall varied from 5.3 to 10.0
Mg
ha
−1 year
−1 among treatments, or between 5.9% and 13.2% of net primary production. Litterfall production and rates of nutrient return for N, P, K, Ca and Mg were generally highest for
Leucaena, intermediate for
Casuarina and lowest for
Eucalyptus. These rates were usually higher in the mixed-species than in monospecific stands due to differences in biomass productivity, but varied considerably depending on their species composition. Total system carbon and nutrient pools (in biomass plus soils to 40-cm depth) for N, P, K, Ca, Mg, Mn at four years were consistently greater in the plantation treatments than in the unplanted control plots. Relative to the single-species plantations, these system pools were generally larger in the mixed-species plantations for C (−10% to +10%), N (+17% to +50%), P (−1% to +63%), K (−19% to +46%), Ca (−10% to +48%), Mg (+5% to +57%) and Mn (+19% to +86%). Whole-tree harvests at four years would result in substantial system carbon and nutrient losses, although these estimated losses would not exceed the estimated gains realized during the four-year period of tree growth at this site. At 7.5 years, soil organic matter and effective cation exchange capacity were reduced in all plantation treatments relative to the control. Changes in soil nutrient content from 0 to 7.5 years were highly variable and not significantly different among treatments, although stands containing
Leucaena generally showed higher rates of nitrogen and phosphorus accretion in soils than those with
Eucalyptus and/or
Casuarina. Natural regeneration of secondary forest tree and shrub species increased over time in all plantation treatments. A total of 24 native or naturalized forest species were recorded in the plantations at 8.5 years. Woody species abundance at this age was significantly greater beneath
Casuarina than either
Eucalyptus or the
Eucalyptus/
Leucaena mixed stands. Species richness and diversity, however, were greatest beneath stands containing
Eucalyptus and/or
Leucaena than in stands with
Casuarina.