ABSTRACT: Increasingly, fast-growing forest plantations are able to support the wood supply but may simultaneously reduce water availability. The trade-off between wood production and water supply is more evident in areas with low water availability, high seasonal variation, or high water demand from local communities. The management regime adopted in forest plantations can either increase or reduce this trade-off. Thus, we assess herein the water and wood supply under different fast-growing forest plantation management regimes to understand how forest management practices can balance the provision of these services. The study was conducted at two catchments with a predominance of fast-growing forest plantations, namely, the mosaic management catchment (MMC) and the intensive management catchment (IMC). Rainfall and streamflow were monitored for three water years. Hydrological indexes were calculated to assess the hydrological regime of both catchments, and make inventories of the forest to assess forest growth rates. MMC had streamflow coefficients, baseflow index and baseflow stability higher than those of IMC. Mean annual wood increment was 32.73 m3 ha-1 yr-1 in MMC, with a mean age of 15 years, and 44.40 m3 ha-1 yr-1 in IMC at coppice in the second year. MMC hydrological indexes remained stable over the period studied, while in IMC the hydrological indexes were affected by climatic variations, mainly in drier years. MMC showed potential for supplying both water and wood. However, in IMC there was a trade-off between wood supply at the expense of the water supply. Thus, the intensity of fast-growing management can be adjusted to achieve a balance between water and wood supply on a catchment scale.
The objective of this work was to assess interactions between species on the above and belowground growth, nitrogen uptake and biological nitrogen fixation (BNF) in mixed stands of Eucalyptus grandis and native leguminous N2-fixing trees. A complete randomized block design was installed with seven treatments and three blocks. Within the lines of the E. grandis seedlings, native leguminous N2-fixing trees - Peltophorum dubium, Inga sp., Mimosa scabrella, Acacia polyphylla, Mimosa caesalpiniaefolia - and one exotic leguminous plant, Acacia mangium, were intercropped. E. grandis was also solely planted. Mimosa scabrella and A. mangium were the legume trees that presented the highest growth. Although E. grandis showed a lower growth when combined with M. scabrella, this mixed-species stand exhibited the highest biomass accumulation. Eucalyptus grandis fine root densities (FRD) were 6-20 times higher than the FRD of the leguminous species in the upper soil layer (0-10 cm) 24 months after planting. The FRD of M. scabrella and M. caesalpiniaefolia in the 30-50 cm soil layer was higher than in the 10-30 cm layer. The delta15N values of M. scabrella indicated that 90% of stocked N is derived from BNF.
O objetivo deste trabalho foi avaliar o crescimento inicial da parte aérea e do sistema radicular, a nutrição mineral e a fixação biológica de N2 (FBN) em plantios consorciados de Eucalyptus grandis e leguminosas arbóreas. O delineamento experimental foi o de blocos ao acaso com três repetições e sete tratamentos por bloco. Nas linhas de plantio, entre as plantas de E. grandis, foram plantadas, intercaladamente, leguminosas arbóreas nativas de matas brasileiras - Peltophorum dubium, Inga sp., Mimosa scabrella, Acacia polyphylla, Mimosa caesalpiniaefolia - e uma leguminosa exótica, Acacia mangium. Realizou-se, também, o plantio puro de E. grandis. Mimosa scabrella e A. mangium foram as leguminosas com maior crescimento. Eucalyptus grandis consorciado com M. scabrella cresceu menos, no entanto foi o povoamento com maior acumulação de biomassa. As densidades de raízes finas (DRF) do E. grandis foram 6 a 20 vezes maiores que as DRF das leguminosas na camada superficial do solo (0-10 cm) 24 meses após plantio. A DRF de M. scabrella e de M. caesalpiniaefolia foi maior na camada 30-50 cm e menor na camada 10-30 cm. Os valores de delta15N da M. scabrella indicam que 90% do N acumulado em seus tecidos é oriundo da FBN.