Please use this identifier to cite or link to this item: http://hdl.handle.net/10174/11257

Title: Dinâmica de biomassa (carbono) e nutrientes em Cistus Salviifolius L. e Cistus Ladanifer L. influência nas características do solo
Authors: Simões, Maria Paula Duarte
Advisors: Gazarini, Luiz Carlos
Madeira, Manuel A. V.
Keywords: Cistus salviifolius L.
Fenologia
Dinâmicai da biomassa
Folhada
Decomposição
Dinâmica de nutrientes
Issue Date: 2002
Publisher: Universidade de Évora
Abstract: Estudou-se a fenologia e a variação sazonal da biomassa e da queda de folhada de Cistus salviifolius L. (CS) e C. ladanifer L. (CL), numa comunidade arbustiva de montado, durante cerca de 2 anos. Analisou-se a distribuição de N, P, K, Ca e Mg na biomassa e os fluxos dos mesmos, com especial ênfase para os ciclos internos e para o fluxo de devolução ao solo, através da folhada. Determinaram-se as taxas de decomposição e os padrões de libertação de nutrientes da folhada, durante pouco mais de 4 anos, correlacionando-se os padrões observados com a composição química inicial das folhas. Também se quantificou a intercepção da precipitação e a sua alteração por influência do coberto, assim como, as quantidades de nutrientes envolvidas nos fluxos para o solo. Finalmente, avaliou-se o efeito dos arbustos nas características do solo sob a sua influência. O período de crescimento vegetativo foi longo, tendo-se evidenciado uma forte correlação entre as taxas de crescimento e a precipitação. A emergência e expansão foliares iniciaram-se no outono, após as primeiras chuvas, atingiram as taxas máximas no inverno e primavera e prolongaram-se até ao início do verão. A senescência e abscisão foliares antes da secura estival, como mecanismo de adaptação à secura, foram muito acentuadas, principalmente no CS. A biomassa aérea foi de 920-1.075 e 1.605-1.936 g M-2, respectivamente para o CS e o CL. Os caules e ramos (78 e 69% do total) predominaram na base das copas, enquanto as folhas (16 e 26%) se concentraram nos terços médio e superior das mesmas. A razão biomassa subterrânea:biomassa aérea foi de 0,7 e 0,8. A média anual da massa de folhada foi, respectivamente para o CS e o CL, de 335-379 e 434-459 g m-2 (68 e 87% de folhas). A produção primária líquida atingiu no CL (1.414 g m-2) cerca do dobro do CS (713 g M-2). As concentrações de nutrientes foram mais elevadas nas folhas do CS do que nas do CL, à excepção do P. Os valores determinados nas folhas verdes foram, contudo, consideravelmente diferentes dos determinados nas da folhada. Para o N e o P verificaram-se decréscimos para cerca de metade a um terço nas folhas da folhada, enquanto para o Ca estas tinham um teor 1,6 vezes superior ao das jovens. Determinaram-se taxas de translocação de N de 50-73% no CS e de 73-85% no CL, enquanto as de P foram, respectivamente, de 57-75 e 49-72% e as de K de 36-63 e 55-78%. 0 retomo anual médio de N, P, K, Ca e Mg para o solo, através da folhada, foi respectivamente de 2,29, 0,21, 1,54, 4,98 e 0,92 g m-2 , para o CS e de 1,72, 0,41, 1,55, 4,64 e 0,95 g m-2, para o CL. /Abstract -Phenology, standing biomass and litterfall seasonal variation of Cistus saiviifoflus L. (CS) and C. Jadanifer L. (CL) were studied in a shrubland stand, over a 2-year period. N, P, K, Ca and Mg allocation and fluxes were assessed, emphasizing the internal cycles and litterfall fluxes to the soil. Decomposition dynamics of leaf litter and the pattern of nutrient release were studied over a 4-year period. Influence of canopies on interception loss, throughfall chemistry and nutrient fluxes through rainwater were also determined. Finally the effects of shrubs on soil properties were assessed. Vegetative growth period was long and a strong correlation between growth rates and precipitation was determined. Leaf emergence and leaf area increment began in autumn soon after the first rains and stopped in the early summer. Winter and spring were the periods of maximum growth rates. Leaf senescence and abscission in late spring were mainly observed in CS, meaning an important adaptation to summer drought. Mean annual standing biomass was 920-1,075 g M-2 for CS and 1,605-1,936 g M-2 for CL. Stems and branches (making up 78 and 69% of the total) were concentrated at the bottom of the canopy while leaves (16 and 26%) were mainly found in its middle and upper thirds. Root to shoot biomass ratios varied between 0.7 and 0.8. Mean annual amount of litterfall was 335-379 and 434-459 g m-2, for CS and for CL respectively (68 and 87% of leaves). Net primary production of CL (1,414 g M-2) was about twice that of CS (713 g M-2). Nutrient concentrations were greater in CS leaves than in those of CL, excepting for P. The concentrations of N and P were lower in leaf litter (one half to one third) than in live leaves of both species. Conversely, the concentration of Ca in abscised leaves was almost double than that in live foliage. The translocation rates of N, P and K were 50-73%, 57-75% and 36-63%, respectively, in CS and 73-85%, 49-72% and 55-78%, in CL. Mean annual return of N, P, K, Ca and Mg to the soil through litterfall was respectively 2.29, 0.21, 1.54, 4.98 and 0.92 g M-2 in CS and 1.72, 0.41, 1.55, 4.64 and 0.95 g m-2 yC1 in CL. Annual decomposition rates k were -0.78 yr-1 for CS and -0.41 yr1 for CL. There was a pronounced N immobilization, during 1 year in CS and 3 in CL, probably due to the influence of initial litter quality (low N concentrations and high C:N and lignin:N ratios). The remaining proportions at the and of the study period were 8 e 58% of the initial. The remaining proportions of P were 6% for CS and 15% for CL, in spite of the faster initial release in the latter. The release of K through leaching was fast in both species, the retained proportions having been 2 and 12%. At the end of the study, the remaining proportions of Ca were 3 e 25%, and those of Mg were 4 and 38%, respectively
URI: http://hdl.handle.net/10174/11257
Type: doctoralThesis
Appears in Collections:BIB - Formação Avançada - Teses de Doutoramento

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