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  • 1
    Electronic Resource
    Electronic Resource
    Water supply regulates structure, productivity, and water use efficiency of Acacia koa forest in Hawaii (1999)
    Springer
    Oecologia 121 (1999), S. 458-466 
    Details
    ISSN: 1432-1939
    Keywords: Key words Forest productivity ; Koa ; Hawaii mountain forests ; Water supply ; Carbon isotope discrimination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  We studied changes in stand structure, productivity, canopy development, growth efficiency, and intrinsic water use efficiency (WUE=photosynthesis/stomatal conductance) of the native tree koa (Acacia koa) across a gradient of decreasing rainfall (2600–700 mm) with increasing elevation (700–2000 m) on the island of Hawaii. The stands were located on organic soils on either smooth (pahoehoe) or rough (aa) lava flows. In the greenhouse, we also examined growth and WUE responses to different water regimes of koa seedlings grown from seeds collected in the study area. We tested the hypotheses that (1) stand basal area, aboveground net primary productivity (ANPP), leaf area index (LAI), and growth per unit leaf area decreased with decreasing rainfall, (2) WUE increased with decreasing rainfall or water supply, and (3) WUE responses were caused by stomatal limitation rather than by nutrient limitations to photosynthesis. The carbon isotope composition of phyllode tissues (δ13C) was examined as an integrated measure of WUE. Basal area and LAI of koa stands on both pahoehoe and aa lava flows, and ANPP on aa lava flows decreased with elevation. Basal area, LAI, and ANPP of koa in mixed stands with the exotic tropical ash (Fraxinus udhei) were lower compared to single-species koa stands at similar elevations. Along the gradient, phyllode δ13C (and therefore WUE) increased with elevation from –30.2 to –26.8‰. Koa in mixed stands exhibited higher (less negative) δ13C than in single-species stands suggesting that koa and tropical ash competed for water. In the greenhouse, we observed the same trend observed in the field, as phyllode δ13C increased from –27.7 to –24‰ as water supply decreased. Instantaneous gas exchange measurements in the greenhouse showed an inverse correlation of both maximum (morning) photosynthesis (A) and conductance (g) with δ13C values and, also, a good agreement between instantaneous (A/g) and integrated measures of WUE. Phyllode δ13C was not correlated with foliar concentrations of N or other nutrients in either the field or the greenhouse, indicating that differences in δ13C were caused by stomatal limitation rather than by nutrient-related changes in photosynthetic capacity. This study provided evidence that long-term structural and growth adjustments as well as changes in WUE are important mechanisms of koa response to water limitation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050952
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  • 2
    Electronic Resource
    Electronic Resource
    Indigenous agroforestry of Pohnpei (1991)
    Springer
    Agroforestry systems 16 (1991), S. 159-165 
    Details
    ISSN: 1572-9680
    Keywords: Pacific islands ; Micronesia ; agroforestry ; traditional agriculture ; low-input agriculture ; spatial pattern ; succession
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A vegetation survey of 54 randomly-selected Pohnpeian land holdings quantified agroforest vegetation patterns in terms of horizontal distribution in the landscape and changes over time. Spatial distribution of species, expressed as distance from the main household, varied greatly with successional stages to produce the characteristic pattern of the Pohnpeian agroforest. Food crops, bananas, and Piper methysticum were planted around the house compound first, then gradually planted further away over time. Upland forest and secondary successional trees were removed by girdling, and gradually replaced by annual and perennial crops and breadfruit and other trees. A fallow or reduced management stage was discerned, characterized by low densities of early successional crops and higher densities of weedy secondary successional species; this stage resulted from a reduction in management intensity, mainly due to a variety of socioeconomic factors. Although the indigenous Pohnpeian agroforestry system is permanent and thought to be sustainable, it is dynamic in space and time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00129746
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  • 3
    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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  • 4
    Electronic Resource
    Electronic Resource
    Indigenous agroforestry of Pohnpei (1991)
    Springer
    Agroforestry systems 16 (1991), S. 139-157 
    Details
    ISSN: 1572-9680
    Keywords: Pacific islands ; Micronesia ; agroforestry ; species diversity ; cultivars ; indigenous agriculture ; low-input agriculture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Plant species and cultivars of the indigenous agroforestry system of Pohnpei were surveyed in transects through 54 randomly-selected farms. The agroforestry system was characterized by extensive cultivation of yams (Dioscorea), aroids (Alocasia), and Piper methysticum under a permanent overstory of breadfruit, coconut, and forest remnant trees and a middle canopy of Hibiscus tiliaceus, Musa spp., and Morinda citrifolia. In the 10 ha of survey plots, 161 species were found, of which 102 were trees, shrubs, and crops and 59 were uncultivated herbaceous plants. Numbers of tree, shrub, and crop species per farm ranged from 16 to 37 with an average of 26. Twenty-eight breadfruit and 38 yam cultivars were found in the survey plots, showing that cultivar diversity is an important component of the biological diversity maintained and utilized in Pohnpeian agroforests.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00129745
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  • 5
    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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  • 6
    Electronic Resource
    Electronic Resource
    Alley cropping of maize with nine leguminous trees (1992)
    Springer
    Agroforestry systems 17 (1992), S. 159-168 
    Details
    ISSN: 1572-9680
    Keywords: alley cropping ; maize ; nitrogen fixing trees ; soil degradation ; traditional farming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A maize-leguminous tree alley cropping system was studied on N-deficient soils in Hawaii to determine mulch effects on maize yields. Calliandra calothyrsus, Cajanus cajan, Cassia siamea, Gliciridia sepium, KX1 — Leucaena hybrid (L. pallida X L. diversifolia), L. leucocephala, L. pallida, L. salvadorensis, and Sesbania sesban were evaluated for green manure and yield of intercropped maize. S. sesban, G. sepium, L. pallida, and KX1 produced between 5 and 12 dry t/ha/yr green manure with nitrogen yields between 140 and 275 kg N/ha in 4 prunings. Maize yields responded linearly to nitrogen applied as green manure. Maize yield increased 12 kg for each kg of nitrogen applied. Additions of prunings from hedge rows were able to support maize grain yields at about 1800 kg/ha for two consecutive cropping seasons, while control plot yields averaged less than 600 kg/ha. Maize yields reflected the amount of nitrogen applied as green manure, regardless of tree species from which the nitrogen was derived. In March, maize yields decreased 34% in the row spaced 40 cm from the hedge, relative to the one spaced 110 cm away. In July, increasing the distance away from the hedge to 60 cm and coppicing the hedge earlier in maize growth, significantly improved grain yield. Grain yields decreased only 10% in the row closest to the trees.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00053120
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