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  • 1
    Electronic Resource
    Electronic Resource
    Nitrogen mineralization patterns of leaf-twig mixtures from tropical leguminous trees (1993)
    Springer
    Agroforestry systems 24 (1993), S. 223-231 
    Details
    ISSN: 1572-9680
    Keywords: alley cropping ; Calliandra calothyrsus ; Gliricidia sepium ; green manure ; incubations ; nitrogen mineralization ; multipurpose tree
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Green manure applications in alley cropping systems often include twigs despite their potential to absorb (immobilize) nitrogen (N). To assess the impact of twigs on net N mineralization or immobilization from hedge row cuttings, we separated cuttings fromCalliandra calothyrsus andGliricidia sepium into leaf-only, twig-only, and mixed (leaf + twig) fractions and incubated them with moist soil in the laboratory. Soil extractable inorganic N did no differ among treatments after two weeks, but after four and eight weeks was greatest in leaf-only, and least in twig-only treatments. After two weeks, extractable N from the leaf-only treatment rose steadily, while that from the twig-only and mixed treatments was variable due to periods of net mineralization and net immobilization. The pattern of variation in mixed treatments paralleled that of twig-only, indicating that net immobilization in the mixture was largely caused by the presence of twigs. Extractable N from the mixture was somewhat lower than that predicted from the sum of leaf-only and twig-only treatments. We conclude that twigs in green manure reduce short-term N availability to associated crops in agroforestry systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00705623
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of chemical composition on nitrogen mineralization from green manures of seven tropical leguminous trees (1992)
    Springer
    Plant and soil 143 (1992), S. 127-132 
    Details
    ISSN: 1573-5036
    Keywords: alley-cropping ; incubations ; lignin ; N-fixing trees ; N mineralization ; polyphenols ; tropical agroecosystems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Green manures from seven tropical leguminous trees were incubated with soil to determine the rates and controls of net nitrogen release. Fresh green manure (leaves and succulent twigs) was mixed with moist soil and incubated in polyethylene bags. Net N mineralization from green manures was estimated by the accumulation of extractable ammonium and nitrate minus the accumulation in soil alone. Patterns of N mineralization were complex, differed among species, and at 12 weeks ranged from 10 to 65 percent of original green-manure N. Cumulative net N mineralization was negatively correlated with initial soluble polyphenol content in the early phases of decomposition (1 through 8 weeks) and with initial lignin content in later phases (4 through 12 weeks). Neither initial percent N nor lignin: N ratio were strongly correlated with N mineralization. The best chemical index of N release was the initial polyphenol: N ratio. This study confirms previous findings that N mineralization from tropical legumes is controlled more by soluble polyphenols than by lignin or N content.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00009137
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Comparisons between generalized and specific tree biomass functions as applied to tropical ash (Fraxinus uhdei) (2000)
    Springer
    New forests 20 (2000), S. 277-286 
    Details
    ISSN: 1573-5095
    Keywords: allometric equations ; Fraxinus uhdei ; Hawaii ; stand biomass estimates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Allometric equations were generatedby harvesting tropical ash (Fraxinus uhdei(Wenzig) Lingelsh) trees growing on organic uplandssoils in the island of Hawaii. One of these equationswas used to estimate aboveground biomass of ten maturestands in the same area. Results indicated that theequation developed in situ, equations for white ash(Fraxinus americana L.), and generalizedfunctions for temperate and tropical forests, providedrelatively similar biomass estimates. Averagedifferences between biomass estimates from the testedequations (excluding the one for moist tropicalforests) and the function generated in situ rangedfrom 10 to 24%. One of the equations for white ashhad the lowest sum of residuals followed by thegeneralized equation for temperate forests. Theresults suggested commonality among biomass estimatesand, therefore, among relationships between treedimensions probably because most of the abovegroundtree biomass is in stem and branches, and thesecompartments are more stable than foliage mass. Equations to estimate commercial biomass and leaf areaof tropical ash are also provided.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006766529550
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Leaf area allometry and evaluation of non-destructive estimates of total leaf area and loss by browsing in a silvopastoral system (1998)
    Springer
    Agroforestry systems 40 (1998), S. 139-147 
    Details
    ISSN: 1572-9680
    Keywords: Acacia koa ; allometric equations ; canopy analysis ; cattle grazing ; LAI-2000
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Tree growth and competition with other vegetation are strongly affected by leaf area, which can be modified by livestock browsing in silvopastoral systems. We studied the relationship of leaf area to stem diameter and sapwood area of koa (Acacia koa), a valuable hardwood tree species native to Hawaii. Because browsing alters allometric relationships, we compared harvest data with two non-destructive optical techniques (LAI-2000 canopy analyzer and photographic estimation of projected crown area). Destructive harvests of 30 trees showed that leaf area was equally well correlated with the diameter at breast height (dbh) or sapwood area of trees ranging from 2 to 16 cm in diameter, 1.3 m above ground level. Both optical techniques correlated with the leaf areas obtained by destructive analysis, but the photographic estimation of projected crown area provided more reliable estimates than the canopy analyzer. The photographic method based on projected crown area provided reliable estimates of leaf area removal within the browse zone (less than 2 m height). this method provides a simple, low-cost means of obtaining non-destructive estimates of changes in leaf area in isolated trees.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006064103080
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    Paper (German National Licenses)
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