Walter de Paula Lima

Stomatal responses of Eucalyptus species to elevated CO2 concentration and drought stress

Five species of Eucalyptus (E. grandis, E. urophylla, E. camaldulensis, E. torelliana, and E. phaeotrica), among the ten species most commonly used in large scale plantations, were selected for studies on the effects of elevated CO2 concentration [CO2] and drought stress on stomatal responses of 2.5-month old seedlings. The first three species belong to the subgenus Smphyomyrtus, whereas the fourth species belongs to the subgenus Corymbia and E. phaeotrica is from the subgenus Monocalyptus. Seedlings were grown in four pairs of open-top chambers, arranged to have 2 plants of each species in each chamber, with four replications in each of two CO2 concentrations: 350 ± 30 mmol mol-1 and 700 ± 30 mmol mol-1. After 100 days in the chambers, a series of gas exchange measurements were made. Half the plants in each chamber, one plant per species per chamber, were drought-stressed by withholding irrigation, while the remaining plants continued to be watered daily. Drought stress decreased stomatal conductance, photosynthesis and transpiration rates in all the species. The effect of drought stress on stomatal closure was similar in both [CO2]. The positive effects of elevated [CO2] on photosynthesis and water use efficiency were maintained longer during the stress period than under well-watered conditions. The photosynthetic rate of E. phaeotrica was higher even in the fourth day of the drought stress. Drought stress increased photoinhibition of photosynthesis, as measured by chlorophyll fluorescence, which varied among the species, as well as in relation to [CO2]. The results are in agreement with observed differences in stomatal responses between some eucalyptus species of the subgenera Symphyomyrtus and Monocalyptus.

Can land use changes alter carbon, nitrogen and major ion transport in subtropical brazilian streams?

Several studies in tropical watersheds have evaluated the impact of urbanization and agricultural practices on water quality. In Brazil, savannas (known regionally as Cerrados) represent 23% of the countrys surface, representing an important share to the national primary growth product, especially due to intense agriculture. The purpose of this study is to present a comprehensive evaluation, on a yearly basis, of carbon, nitrogen and major ion fluxes in streams crossing areas under different land use (natural vegetation, sugar cane and eucalyptus) in a savanna region of SE Brazil. Eucalyptus and sugar cane alter the transport of the investigated elements in small watersheds. The highest concentration of all parameters (abiotic parameters, ions, dissolved organic carbon DOC - and dissolved inorganic carbon - DIC) were found in Sugar Cane Watersheds (SCW). The observed concentrations of major cations in Eucalyptus Watersheds (EW) (Mg, Ca, K, Na), as well as DIN and DOC, were found frequently to be intermediate values between those of Savanna Watersheds (SW) and SCW, suggesting a moderate impact of eucalyptus plantations on the streamwater. Same trends were found in relation to ion and nutrient fluxes, where the higher values corresponded to SCW. It is suggested that sugar cane plantations might be playing an important role in altering the chemistry of water bodies.

Forest Plantations and Water Consumption: A Strategy for Hydrosolidarity

A case study of a deliberate change in the design of a new Eucalyptus plantation, aimed at alleviating water impacts, was carried out in an experimental catchment located in the center part of the State of Sao Paulo, Brazil. It involved the identification of saturated areas in the catchment, based essentially on topographic analysis, as a tool to help in zoning of the new forest plantation, with the objective of improving the flow of water to downstream users, as well as to avoid water quality changes. The design involved the allocation of part of the identified saturated areas as water conservation areas, as well as a change in the spacing of the planting. Measurements of tree growth at the age of two years of the new plantation reveal that the forest productivity of the new plantation design, in terms of projected annual wood increment at the end of the rotation, will be similar to the old plantation scheme, despite the loss of planted area. Preliminary results of the continuous monitoring of the catchment water balance appear to indicate that the objective of increasing the catchment water yield may possibly also be achieved.

A importância das áreas ripárias para a sustentabilidade hidrológica do uso da terra em microbacias hidrográficas

Zonas riparias sao areas de saturacao hidrica, permanente ou temporaria, cuja principal funcao e a protecao dos recursos hidricos de uma microbacia. Essa pesquisa comparou a adequacao do uso do solo de dois cenarios de planejamento agricola de uma microbacia: o cenario convencional, representando o metodo usualmente empregado, que apenas considera as classes de capacidade de uso da terra, e o cenario hidrologico, que inclui a delimitacao e avaliacao das zonas riparias. Um estudo de caso foi realizado na Microbacia do Ribeirao Sao Joao (3.656 ha), no municipio de Mineiros do Tiete (Sao Paulo, Brasil). Mapas de Classe de Capacidade de Uso da Terra e de Adequacao do Uso do Solo foram elaborados, utilizando o Sistema de Informacao Geografica (SIG), para a construcao dos cenarios convencional e do proposto. Excluindo a Area de Preservacao Permanente (APP), o cenario convencional indicou que 59,0% da area destinada a agricultura esta adequadamente utilizada, 28,2% esta subutilizada e 2,6% esta sobreutilizada. O cenario proposto ou hidrologico, com inclusao da identificacao da zona riparia (24,9% da microbacia) mostrou que muitas areas que, no cenario convencional, possuem pouca restricao para o cultivo intensivo, como as classes II e III, sao zonas riparias, de sensibilidade hidrologica. Existem dentro dos limites da zona riparia 38,9% de classe de capacidade de uso III e 49,5% de classe IV. O planejador, desconsiderando a zona riparia, pode colocar em risco areas vitais que, se degradadas, representam danos para a saude e resiliencia da microbacia.

Soil water dynamics and litter production in eucalypt and native vegetation in southeastern Brazil

High productivity of eucalypt plantations is the result of advances in research that have led to gradual improvements in intensive silvicultural technology. High productivity notwithstanding, eucalypt plantations remain the focus of environmental concerns. Our study aimed to compare the soil water regime, litter fall and nutrients dynamics either in a fragment of native forest or in an adjacent stand of growing eucalypt. We took field measurements during the first three years of eucalypt plantation in a sandy soil in the southeastern region of Brazil. Soil moisture and internal drainage were higher during the early stages of growth of the eucalypt stand, as compared with native vegetation. However, one and a half years after planting, available soil water was similar in both vegetations. Higher water availability under the eucalypt stand during the first year occurs because of silvicultural operations (soil preparation and weed control) and the small size of eucalypt trees; these factors increase water infiltration and decrease transpiration. Total leaf fall, over the study period, was similar for both ecosystems; however, differences were observed in the winter and early spring of 2010. The transfer of nutrients to soil by leaf fall was similar except for N and S, which was higher in native vegetation. Nitrogen concentration in the soil solution was higher in native vegetation, but K was higher under the eucalypt stand, mainly to a depth of up to 0.2 m.