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Advisor(s)
Abstract(s)
Neste estudo avaliaram-se aspectos do funcionamento do sistema pastagem-freixo (Fraxinus angustifolia, Vahl) constituĂdo por ĂĄrvores isoladas. O estudo baseou-se na quantificação da produção, decomposição e dinĂąmica da libertação de bioelementos de folhas de freixo, bem como na caracterização fĂsico-quĂmica do solo em ĂĄreas sob e fora da influĂȘncia da ĂĄrvore. Para alĂ©m disto, tambĂ©m foi quantificada a biomassa da vegetação herbĂĄcea por famĂlias (gramĂneas, leguminosas e outras) e avaliado o valor nutritivo da mesma em ĂĄreas sob e fora do coberto arbĂłreo. Os resultados indicaram uma produção de folhas relativamente baixa (0,12 kg m-2) e uma taxa de decomposição anual elevada (k=-1,2). As folhas devolveram ao solo quantidades apreciĂĄveis de nutrientes, principalmente no que respeita ao Ca (24,3 kg/ha) e ao N (12,5 kg/ha). Durante a fase inicial de decomposição das folhas os nutrientes foram libertados em grande extensĂŁo, principalmente o potĂĄssio, seguido do magnĂ©sio e do cĂĄlcio. Na fase subsequente (pĂłs-lixiviação) os nutrientes foram libertados de uma forma mais gradual, ocorrendo mesmo perĂodos de imobilização. O teor de humidade do solo foi mais elevado sob a copa das ĂĄrvores do que fora da influĂȘncia desta, sobretudo no final da Primavera. A massa volĂșmica aparente apresentou valores semelhantes nas duas ĂĄreas. O solo das ĂĄreas sob o coberto do freixo apresentava teor mais elevado de carbono orgĂąnico, N e P extractĂĄvel, Ca, K e Mg de troca do que naquelas nĂŁo influenciadas por aquele coberto. Esta diferenciação apenas se verificou atĂ© 10 cm de profundidade.
Some aspects of interaction soil-isolated tree (Fraxinus angustifolia, Vahl) were studied in N ortheastem Portugal. The study took into account the amount of litterfall, the decomposition and release of nutrients from leaf litter and phisico-chemical properties of the soil occurring beneath and beyond the influence of tree canopy. Additionally, the herbaceous vegetation biomass was quantified and its nutritive value assessed. The annual Ieaf litterfall amounted to O, 12 kg m·2 and returned to the soil significant amounts of Ca (24,3 kg ha·'), N (12,5 kg ha- 1) and Mg (8,6 kg ha-1). Leaf litter showed an high decomposition rate (k=-1 ,2 year1) and releases an high proportion of K, Mg and Ca during the early decomposition stage. The release of P and N occurred especially during the !ater stage. Soil moisture content was significantly higher in areas beneath tree canopy than in others. Bulk density values were not significantly affected by the soil position with respect to tree canopy. Soil beneath tree canopy showed higher content of organic carbon, N Kjeldahl, extractable P and exchangeable Ca, Mg and K, down to 10 cm depth, than that not affected by the presence of trees. The biomass of herbaceous vegetation, especially that of gramineous, was higher in areas influenced by tree canopy than in the others. The former showed higher N content, lower lignin content and a more favourable digestibility index than the latter.
Some aspects of interaction soil-isolated tree (Fraxinus angustifolia, Vahl) were studied in N ortheastem Portugal. The study took into account the amount of litterfall, the decomposition and release of nutrients from leaf litter and phisico-chemical properties of the soil occurring beneath and beyond the influence of tree canopy. Additionally, the herbaceous vegetation biomass was quantified and its nutritive value assessed. The annual Ieaf litterfall amounted to O, 12 kg m·2 and returned to the soil significant amounts of Ca (24,3 kg ha·'), N (12,5 kg ha- 1) and Mg (8,6 kg ha-1). Leaf litter showed an high decomposition rate (k=-1 ,2 year1) and releases an high proportion of K, Mg and Ca during the early decomposition stage. The release of P and N occurred especially during the !ater stage. Soil moisture content was significantly higher in areas beneath tree canopy than in others. Bulk density values were not significantly affected by the soil position with respect to tree canopy. Soil beneath tree canopy showed higher content of organic carbon, N Kjeldahl, extractable P and exchangeable Ca, Mg and K, down to 10 cm depth, than that not affected by the presence of trees. The biomass of herbaceous vegetation, especially that of gramineous, was higher in areas influenced by tree canopy than in the others. The former showed higher N content, lower lignin content and a more favourable digestibility index than the latter.
Description
Keywords
Fraxinus angustigolia Lameiros Solo
Citation
Pereira, Ermelinda; Madeira, Manuel; Martins, Afonso; Monteiro, Maria do Loreto (2002). Aspectos genĂ©ricos da influĂȘncia do freixo nos lameiros do Nordeste Transmontano = General aspects of ash-tree in natural pastures of Northeastern Portugal. Revista de CiĂȘncias AgrĂĄrias. ISSN 0871-018X. 25:1-2, p. 149-160
Publisher
Sociedade de CiĂȘncias AgrĂĄrias de Portugal