Variabilidade diária da chuva em uma escala local (1000 ha) em Piracicaba, SP, e suas implicações na recarga da água do solo

Daily rainfall variability at a local scale (1,000 ha) was studied at Piracicaba, SP, Brazil, for the period of one year (1993-1994), in order to better understand the process of soil water recharge. Coefficients of variation of daily data for ten observation points varied from 2.2 to 169.3% and the variability was independent of rain type, i.e. whether convective, frontal or of other origin. Data were not related to separation distances between observation points and it is concluded that one observation point does not represent areas as far as 1,000 to 2,500 m apart, for daily, monthly or even quarterly averages. Yearly totals for the ten observation points presented a coefficient of variation as low as 3.06%, indicating that all points can replace each other in annual terms.A variabilidade diária da chuva em uma escala local (1000 ha) foi estudada em Piracicaba, SP, Brasil, pelo período de um ano (1993-1994). Os coeficientes de variação de dados diários para dez pontos de observação variaram de 2,2 a 169,3 % e a variabilidade independeu do tipo de chuva, isto é, se convectiva, frontal ou de outra origem. Os dados não apresentaram correlação com a distância entre os pontos de observação e concluiu-se que uni ponto de observação não representa áreas distantes dele de 1000 a 2500 m, para médias diárias, mensais ou mesmo trimestrais. Os totais anuais dos dez pontos apresentaram um coeficiente de variação de apenas 3,06 %, indicando que cada ponto pode representar qualquer outro em termos anuais

Fitômetros e distribuição da radiação na copa de Hevea brasiliensis cv: RRIM 600

Phytometers were used as standard systems to verify the effect of vertical distribution of leaf area in the canopy profile of Hevea brasiliensis Muell. Arg. cv. RRIM 600 under Rio Claro (SP) conditions and the relation of leaf dispersion to the penetration of light and photosynthesis. These ecological indicators were installed in 30 uniform and randomized trees, with 60 phytometers distributed at 1.50, 1.20 and 3.00 meters above the soil. Variations in growth analysis parameters of the indicator plant (Beta vulgaris L. cv. Asgrow Wonder) were established in three 14 days periods in May, July and September. As from these data, LAR and SLA showed higher values in the upper canopy, while DMV, LAV, RGR, NAR and LWR presented lower values in the lower canopy. Light distribution varied with the hour of the day. The coefficient of absorption of the incoming solar radiation increased in the morning period, presenting a tendency to attain the best landing-place of the asymptot near 11:00 AM and extending throughout the afternoon. The average of the coefficient of absorption at the landing-place of the asymptot was 0.588 for rubber tree.Com o objetivo de realizar o sensoriamento climático, no perfil da copa de Hevea bvasiliensis cv. RRIM 600, utilizaram-se fitômetros com Beta vulgaris cv, Asgrow Wonder em 3 níveis de um seringal com 4 anos de idade, em Rio Claro (SP). Os fitômetros foram alocados na copa das árvores distribuídas ao acaso, nas alturas de 1,50m, 2,20m e 3,00m, do solo; sendo que 30 fitômetros foram colocados em cada nível. A exposição dos fitômetros foi realizada em três épocas: de 04 a 17 de maio, junho e setembro. Os valores médios da RAF e AFE mostraram-se mais altos no nível superior da copa e da VPS, VAF, TCR, TAL e RPF nos níveis inferiores. A radiação líquida revelou-se mais alta: na região inferior da copa pela manhã, na região mediana em torno do meio-dia e na região superior do perfil da copa da seringueira no período da tarde. O coeficiente de absorção aumentou pela manhã, tendendo a atingir um patamar ótimo da assíntota perto das 11:00 horas, estendendo-se pela tarde; sendo que o valor médio do coeficiente de absorção em seu patamar foi da ordem de 0,588

Daily rainfall variability at a local scale (1,000 ha), in Piracicaba, SP, Brazil, and its implications on soil water recharge Variabilidade diária da chuva em uma escala local (1000 ha) em Piracicaba, SP, e suas implicações na recarga da água do solo

Daily rainfall variability at a local scale (1,000 ha) was studied at Piracicaba, SP, Brazil, for the period of one year (1993-1994), in order to better understand the process of soil water recharge. Coefficients of variation of daily data for ten observation points varied from 2.2 to 169.3% and the variability was independent of rain type, i.e. whether convective, frontal or of other origin. Data were not related to separation distances between observation points and it is concluded that one observation point does not represent areas as far as 1,000 to 2,500 m apart, for daily, monthly or even quarterly averages. Yearly totals for the ten observation points presented a coefficient of variation as low as 3.06%, indicating that all points can replace each other in annual terms.<br>A variabilidade diária da chuva em uma escala local (1000 ha) foi estudada em Piracicaba, SP, Brasil, pelo período de um ano (1993-1994). Os coeficientes de variação de dados diários para dez pontos de observação variaram de 2,2 a 169,3 % e a variabilidade independeu do tipo de chuva, isto é, se convectiva, frontal ou de outra origem. Os dados não apresentaram correlação com a distância entre os pontos de observação e concluiu-se que uni ponto de observação não representa áreas distantes dele de 1000 a 2500 m, para médias diárias, mensais ou mesmo trimestrais. Os totais anuais dos dez pontos apresentaram um coeficiente de variação de apenas 3,06 %, indicando que cada ponto pode representar qualquer outro em termos anuais

Influence of orchard and vineyard characteristics on maximal plant transpiration

International audienceIn order to study water use by fruit crops, 9 experimental campaigns were performed in France and Portugal between 1988 and 1997 in commercial orchards (apple, plum, peach) and vineyards. In this paper, some of the data collected were used to assess the use of various fruit crop characteristics for estimating the maximal transpiration (MT) of plants from the reference evapotranspiration (ETo). In the following experiments, transpiration was measured on 5 to 8 representative plants by built-in sap flow gauges. The climatic conditions above the plots were measured: incident and reflected solar radiation, net radiation, air temperature and humidity, wind speed and direction. The reference evapotranspiration ETo was estimated using the Penman equation. The geometry of the rows was represented using simple shapes, and the porosity of the rows was estimated in most experiments. The amount of solar radiation absorbed by rows was measured in some orchards, and was estimated by a simple geometrical model for vineyards. Then the fraction of net radiation absorbed by the rows was evaluated. The leaf area of the plants was also determined in most cases. MT was deduced from mean plant transpiration in well irrigated or in wet soil conditions for vineyards. For fully developed foliage, MT/ETo varied between 0.2 and 1.0. The results were compared to the fractional ground cover, the ground fraction shaded by a row, the amounts of solar and net radiation absorbed by the foliage, and the leaf area index LAI. Except for the vineyard, with tall and narrow rows, MT/ETo can be well estimated by the fraction of ground shaded by a row or the ground cover fraction. By considering the amount of solar radiation or net radiation absorbed by a row, the estimation of MT/ETo is improved for vineyard and the orchard-vineyard ensemble, but not for orchards. The best estimation is obtained from the leaf area index, but this data is very difficult to obtain