Daniela Jerszurki

Water balance output components are distinctly regulated by precipitation and evapotranspiration in Pinus taeda L. plantations in Southern Brazil

The knowledge about the impact of climate variables on estimated water balance hold significant promise for the estimation of critical periods of soil water deficit or surplus. Here we establish the functional relations between water deficit, water surplus and soil water storage with precipitation and evapotranspiration for Pinus, in Southern Brazil. For that purpose a 31-years daily data series of precipitation (P) and reference evapotranspiration (ETo) were used as input components of the modified Thornthwaite and Mather water balance model. Principal component analysis was performed as an exploratory analysis of the water balance components related to P and ETo. The water deficit was mostly affected by the seasonality of evapotranspiration depending on soil water availability. The sole effect of P on water surplus (WS) determined its variability and showed the possible use of P to estimate WS. Soil water storage was not directly influenced by P or ETo.

ATRIBUTOS FÍSICOS E BALANÇO HÍDRICO DO SOLO COM FLORESTA OMBRÓFILA MISTA, EM LATOSSOLO VERMELHO-AMARELO, EM TELÊMACO BORBA - PR

The objective of this study was to characterize the soil physical and hydric attributes and quantify, in one year, the water balance components, carried out for Native Ombrophylous Forest, in an OXISOL, sandy texture, in Telemaco Borba - PR state. The experiment was held at Monte Alegre Farm, which belongs to the company Klabin Florestal, the area was under native forest in an advanced state of regeneration. The following physical and hydric attributes were characterized: bulk density, saturated hydraulic conductivity, soil water retention curve, aeration porosity and total available water ( TAW ). The undisturbed samples were collected in a trench, in five depths. The disturbed samples were collected weekly, in eight different points inside the experiment area, in five depths. The values of soil moisture and internal precipitation were collected and registered throughout the year. The soil water storage was calculated using the trapezoidal rule. The internal drainage and capillary rise were estimated by using the Darcy-Buckingham equation. The values of the bulk density, micro, macro and total porosity of the soil are classified in the range considered adequate for soils with sandy texture. The soil presented a high hydraulic conductivity, which is a characteristic of well drained soils. In average, the storage did not reach the permanent wilting point throughout the year. The average deep drainage was bigger throughout the months with more precipitation, the value being an average of 94.9 mm year –1 . The average value of the real evapotranspiration was 1355.9 mm year - 1 , an average of 3.7 mm day - 1 .

Expanding the geography of evapotranspiration: An improved method to quantify land-to-air water fluxes in tropical and subtropical regions

The development of new reference evapotranspiration (ETo) methods hold significant promise for improving our quantitative understanding of climatic impacts on water loss from the land to the atmosphere. To address the challenge of estimating ETo in tropical and subtropical regions where direct measurements are scarce we tested a new method based on geographical patterns of extraterrestrial radiation (Ra) and atmospheric water potential (Ψair). Our approach consisted of generating daily estimates of ETo across several climate zones in Brazil–as a model system–which we compared with standard EToPM (Penman-Monteith) estimates. In contrast with EToPM, the simplified method (EToMJS) relies solely on Ψair calculated from widely available air temperature (oC) and relative humidity (%) data, which combined with Ra data resulted in reliable estimates of equivalent evaporation (Ee) and ETo. We used regression analyses of Ψair vs EToPM and Ee vs EToPM to calibrate the EToMJS(Ψair) and EToMJS estimates from 2004 to 2014 and between seasons and climatic zone. Finally, we evaluated the performance of the new method based on the coefficient of determination (R2) and correlation (R), index of agreement “d”, mean absolute error (MAE) and mean reason (MR). This evaluation confirmed the suitability of the EToMJS method for application in tropical and subtropical regions, where the climatic information needed for the standard EToPM calculation is absent.

Relações funcionais entre precipitação provável e média em regiões e climas brasileiros

The objective of this work was to determine the statistical parameters of the probability density function (PDF) with the best fit to the values of decennial rainfall observed in several Brazilian localities, and also to determine the relationship between probable rainfall (75% probability, P75%) and average rainfall () in these localities. Five PDFs were evaluated (normal, triangular, gamma, exponential, and uniform), adjusted to data from 43 municipalities, from eight states, in four Brazilian regions. The localities were evaluated singly or grouped into states or climate types. The Kolmogorov‑Smirnov adherence test was used to assess the statistical adjustment of the PDFs to the data series. Gamma and exponential distributions were the ones which more often had the best fit to the series of decennial rainfall (41.2 and 30.8%, respectively). The most promising functional relationships between and P75% were obtained at the climates Cwa (R2 = 0.82), Aw (R2 = 0.70), As (R2 = 0.68), and Cwb (R2 = 0.62), and at the states of Goias (R2 = 0.80), Sao Paulo (R2 = 0.76), and Minas Gerais (R2 = 0.70). The normal (19.3%), triangular (2.2%), and uniform (3.5%) distributions have the lowest participation in the best fits, but are important in the dry season analyzes.