Monthly Soil Water Research Articles

Close-to-nature management effects on tree growth and soil moisture in Mediterranean mixed forests

Given the rising frequency of drought events, close-to-nature principles appear to be a suitable management option for promoting more adapted forests by increasing diversity and vitality (e.g., enhancing tree growth), while preserving soil moisture. In this study, we evaluate individual tree growth from selected trees (including future crop trees) and soil moisture responses to close-to-nature silvicultural treatments in sub-humid Mediterranean mixed forests in Catalonia (Northeastern Spain). We relied on 18 permanent sample plots (i.e., 9 paired-plots: managed / control) representing a competition intensity gradient and different forest types (dominated by either Quercus ilex, Castanea sativa, Quercus pubescens/petraea, Pinus pinea and Pinus sylvestris). From them, 8 plots were subject to intense monitoring in terms of intra-annual tree radial growth, monitored by manual band dendrometers, and hourly soil water content. Basal area increment, and annual and seasonal (May, June, July) radial increment rates were computed as a proxy of tree growth for all plots and for those plots with dendrometers, respectively. We conducted Spearman correlation analyses between tree growth, competition intensity, soil water content and climatic variables to detect significant relations between forest management and variables of interest (e.g., basal area increment, radial increment rates, soil water content). To investigate further into the effect of this silviculture on tree growth, we used mixed-effects models using as predictors variables related to competition intensity and forest management (dummy variable) in combination with monthly soil water content variables. We observed that basal area increment and radial increment rates had a positive (albeit weak) correlation with forest management, while competition intensity had a negative correlation with both variables. The models were not capable of detecting clear species-specific tree growth responses to competition. Compared to control plots, on average, the treatments boosted soil water content by about a 10% in managed plots in Q. ilex, P. sylvestris and P. pinea stands, and this increase was particularly significant during the growing season. Moreover, the best-fitted model predicted seasonal radial increment rates using not only forest management and competition variables, but also monthly soil water content factors. Our results suggest that close-to-nature-forest management may reduce the vulnerability to drought by increasing tree vitality and soil moisture, at least in the short term (<3 years).

Performance analyses of effective rainfall estimation methods for accurate quantification of agricultural water footprint

Water footprint (WF) assessments have become a significant tool for the sustainable management in recent years. Effective rainfall (Peff) is a critical indicator for characterizing soil moisture (green water, WFgreen) and calculating irrigation requirements (blue water, WFblue). However, majority of the water footprint analyses employ empirical or numerical models to predict Peff, and the number of studies for experimental validation of these models are quite insufficient. The main scope of this study is to test the performance of commonly used Peff estimation models in relation to the soil water balance (SWB) of an experimental site. Accordingly, the daily and monthly soil water budget is estimated from a maize field which is characterized as semi-arid land with continental climate (Ankara, Turkey), equipped with moisture sensors. Then, Peff, WFgreen, and WFblue parameters are calculated using FP, US-BR, USDA-SCS, FAO/AGLW, CROPWAT, and SuET methods and compared with SWB method. Employed models were highly variable. CROPWAT and US-BR predictions were the most accurate. In majority of months, the CROPWAT method estimated the Peff with a maximum deviation of 5% from the SWB method. In addition, the CROPWAT method predicted blue WF with an error less than 1%. The widely utilized USDA-SCS approach did not produce expected results. The FAO-AGLW method provided the lowest performance for each parameter. We also find that the errors in estimating Peff in semi-arid conditions cause green and blue WF outputs to be quite less accurate than the dry and humid cases. This study provides one of the most detailed assessments about the impact of effective rainfall on the blue and green WF results with high temporal resolution. The findings of this study are important for the accuracy and performance of the formulae used in Peff estimations and to develop more precise blue and green WF analyses in the future.

Prediction of Rubber Yield Based on Soil Water Content

Fluctuation of monthly rainfall resulted in fluctuation of monthly rubber yield. This study was aimed to determine a model to predict rubber yield based on soil water content. This study was conducted at Indonesian Rubber Research Institute, South Sumatera in May 2022. The plant materials used in this study were rubber clones PB 260 that were planted in 2001 in two blocks of rubber field. The soil texture in these two blocks was clay loam with good drainage conditions. The average of monthly soil water content and rubber yield data for 11 years from the first block was used to determine the model. Whereas the average of monthly soil water content and rubber yield data for 12 years from the second block was used to validate the model. The soil water content was generated by field water balance calculation. The regression and correlation analysis showed that the highest correlation and the most suitable model to predict rubber yield based on soil water content was the power model with formula Y = 0.0668X2.1423 (coefficient of determination (R2) = 0.80). Where, Y = rubber yield (kg/month) and X = soil water content (%). Furthermore, the validation of the model showed that the goodness of match (GOM), Pearson correlation coefficient (R), coefficient of determination (R2), and root mean square error (RMSE) were 0.94, 0.95, 0.90. and 10.3 respectively. These values showed that the model was accurate and strong enough to predict rubber yield based on soil water content.

The Nationwide Water Budget Estimation in the light of the New Permeability Map of Italy

The hydrological budget is one of the fundamental tools for the sustainable management of water resources. In the last decades, the knowledge of the distribution of freshwater resources in space and time is becoming of great concern due to the growing pressure related to increasing population, water pollution, and climate change. Furthermore, in the scope of hydrological balance, the estimation of aquifer assumes particular concern in Italy. In fact, more than 80% of water withdrawal for domestic and drinkable use is derived from groundwater. In this context, the Italian Institute for Environmental Protection and Research (ISPRA) has developed a mathematical model for estimating the hydrological budget components at a national and macro-regional scale called BIGBANG. The aquifer recharge is estimated as a percentage of the monthly soil water surplus by the potential infiltration coefficient defined as a function of the permeability of the hydrogeological complexes beneath the soil layer. In this paper, a comparison highlighting the differences between the estimations of the long-term annual average of two of the main hydrological budget components, aquifer recharge and surface runoff, at national and sub-national levels, is carried out. The estimations are based on the new and more detailed Permeability Map of Italy produced by ISPRA and on the old map of the hydrogeological complexes currently used at national level used so far in the BIGBANG budget model.

Using hybrid modelling to predict basal area and evaluate effects of climate change on growth of Norway spruce and Scots pine stands

ABSTRACT When modelling forest growth, capturing the effects of climate change is needed for reliable long-term predictions and management choices. This remains a challenge because commonly used mensurational forest growth and yield models, relying on inventory data, cannot account for climate change effects. We developed hybrid physiological/mensurational basal area growth and yield models, which combine physiological response to climatic conditions and empirical relations. We included climate and site effects by replacing time with light sums of photosynthetically active radiation and modifying the latter with monthly soil water, vapour pressure deficit, temperature, and frost days. When parameterised with permanent sample plot data for Scots pine and Norway spruce across Sweden, the hybrid models could reproduce observations well, although with no increase in precision compared with time-based mensurational models. When considering different climate scenarios, a significant impact on productivity from climate change emerged. For example, a 2 °C warming enhanced Scots pine production by up to 14% in regions where temperatures were originally cooler and soil water deficit was low (i.e. northwest Sweden), but depressed it, up to 9%, elsewhere. Hence, climate-sensitive models that take local variations into account are necessary for accurate predictions and sustainable forest management.

Analysis of the spatio-temporal variability of soil water dynamics in an arid catchment in South Africa

The accurate quantification of soil water dynamics is critical as it is a key parameter in the soil-plant-atmosphere continuum. This study was conducted to analyse the spatio-temporal variability of soil water dynamics in dry areas. The Soil and Water Assessment Tool (SWAT) was used to estimate the dynamics of soil water balance. The model was calibrated and validated by the regionalization with physical similarity approach. Unlike the revap water (water drawn upwards from shallow groundwater tables), the soil water, percolation and lateral flow increased with precipitation. The Mann Kendall trend test also shows that there was no trend in both the annual and monthly soil water content (SWC) and percolation; however, there was a decreasing trend (1.091 mm per annum) in the revap water. The contribution of the revap water to evapotranspiration (ET) varied from 9% during summer to 32% during spring. The SWC also exhibited a higher spatial variation. Larger part of the catchment recorded a long-term annual mean soil water content varying between 0.1 and 0.2 mm mm−1. The soil water anomaly (SWA) consistently follows the trends of dry and wet seasons in the study area. Although the use of model-derived drought monitoring indices are relevant for farmers and decision makers in arid areas, it requires intensive verification over much larger scales to increase the reliability of model results.

One third of the abiotically-absorbed atmospheric CO2 by the loess soil is conserved in the solid phase

It has frequently been noticed that alkaline soils in arid and semiarid areas can absorb atmospheric CO2 abiotically. However, the fate of the absorbed CO2 is largely unknown, limiting our ability to accurately assess the contribution of abiotic CO2 absorption to carbon sequestration. The hypothesis that some abiotically-absorbed carbon could be fixed in the soil solid phase is yet to be explicitly tested. From April to November 2016, we added 13CO2 to the natural alkaline loess soil at a depth of 0–17 cm and quantified the proportion of 13CO2 conserved in the soil solid phase on the central Loess Plateau of China. The results showed that natural surface soil absorbed 13CO2 at a rate of 475.9 mg m−2 d−1. Of the absorbed 13CO2, 33.2% was conserved in the soil solid phase. The rate of added 13CO2 conserved in the solid phase was positively correlated with mean monthly soil water content but negatively correlated with mean monthly soil temperature. Our results indicated that, loess soil can absorb CO2 from the atmosphere through abiotic processes, and part of the abiotically-absorbed CO2 is stably fixed in the soil solid phase. Soil with a higher water content and lower temperature may promote the abiotic CO2 fixation. The rate of CO2 fixation through abiotic processes at the surface soil accounted for approximately 10%-20% of the reported local annual net ecosystem exchange, implying that the abiotic CO2 uptake by loess soil may play an important role in assessing the capacity of CO2 sequestration in these areas.

Two Applications of Soil Water Balance in Unsaturated Pyroclastic Soils

Evaluation of the monthly soil water balance (SWB) provides a tool for understanding and predicting the effects of seasonal and long-term changes in soil water conditions within many geotechnical problems. In this paper, two applications of the SWB approach in the pyroclastic partially saturated soils are shown. Firstly, rainfall, evapotranspiration, water storage measured or estimated at the experimental site in Monteforte Irpino (in Southern Italy) are shown. Secondly, rainfall, infiltration, actual evapotranspiration and water storage measured by data provided by a physical model are shown. In the both cases, data are reported over two years (2010-2012). The physical model was constituted by a wooden tank filled with reconstituted silty pyroclastic soil taken from experimental site at Monteforte Irpino (AV) and it was exposed to the atmosphere at a site in Napoli. Comparison between soil hydraulic behaviours observed is discussed and the scale effects on the estimation of the SWB are analysed, treating with practical implications. From the results, it is clear that similar trends in SWB and the same value of suction over wet season (10 kPa) can be observed at both the scales in spite of differences in meteorological conditions and hydraulic properties of soils exposed to atmosphere.

Balancing agricultural and hydrologic risk in farming systems of the Chaco plains

Like in other semiarid areas of the world, farming systems in semiarid Chaco tend to use water-conservative crop systems to minimize production risks associated to water stress. While this strategy aims to stabilize crop yields and farmers income, the underutilization of water resources in wet years may result in heavy deep drainage water losses which could potentially lead to the development of dryland salinity. Conversely, more intensive crop systems that consume water exhaustively present lower drainage rates but are more prone to crop failure. We employed a monthly soil water balance approach to analyze the productive and ecohydrologic effects of five different farming systems across the region (winter, spring, summer, late-summer and a winter–summer double crop system) and to assess the possibility of minimizing emerging trade-offs between them through flexible water-informed cropping sequences. Our results indicate that water stress diminishes as crop systems are delayed towards the rainy season (winter > spring > summer > late-summer), but the productively safer late-summer strategy is the one with highest drainage rates. In most of the region, the relatively high production risk and insignificant drainage probability generally determine the convenience of conservative late-summer systems. However, in areas (or years) with higher amount and/or seasonality of rainfall, more intensive double-crop systems are necessary to minimize the likely high drainage fluxes. As rainfall is highly variable from one year to the other, the knowledge of soil water content at the onset of the season is useful to predict part of the available water offer and to asses expected production and ecohydrologic risks. In the most drainage-prone areas the implementation of flexible sequences that alternate conservative and intensive crop systems depending on soil water status, significantly reduced mean annual drainage with an acceptable increase in mean water stress index.

Effects of Throughfall Exclusion on Soil Respiration in a Moso Bamboo Forest Soil in Southeast China

Both soil temperature and soil water condition are important factors that influence soil respiration at different forest. In this study, a throughfall exclusion experiment was carried out to explore effects of increased soil temperature and decreased soil water content on soil respirations in the bamboo forest in North Zhejiang of China. The results showed that 1) monthly variation in soil respiration ranges from 2.00 to 0.63μmol·m-2·s-1 and 2.20 to 0.66μmolm-2s-1in throughfall exclusion and control plots respectively. The soil respiration monthly variation following the monthly variation of soil temperature and in contrast to the monthly soil water content. 2) Soil temperature can explain 65.5%and 73.9% of the variance of soil respiration in throughfall exclusion and control plots respectively. Multivariate linear model based on temperature and soil water content explained 66.9% and 73.4% of the variance of soil respiration in throughfall exclusion and control plots respectively. Soil water content had no significant relationship with soil respiration. Q10 values of throughfall exclusion and control plots were 5.99 and 4.44.

Implications of Parameter Uncertainty on Soil Moisture Drought Analysis in Germany

Abstract Simulated soil moisture is increasingly used to characterize agricultural droughts but its parametric uncertainty, which essentially affects all hydrological fluxes and state variables, is rarely considered for identifying major drought events. In this study, a high-resolution, 200-member ensemble of land surface hydrology simulations obtained with the mesoscale Hydrologic Model is used to investigate the effects of the parametric uncertainty on drought statistics such as duration, extension, and severity. Simulated daily soil moisture fields over Germany at the spatial resolution of 4 × 4 km2 from 1950 to 2010 are used to derive a hydrologically consistent soil moisture index (SMI) representing the monthly soil water quantile at every grid cell. This index allows a quantification of major drought events in Germany. Results of this study indicated that the large parametric uncertainty inherent to the model did not allow discriminating major drought events without a significant classification error. The parametric uncertainty of simulated soil moisture exhibited a strong spatiotemporal variability, which significantly affects all derived drought statistics. Drought statistics of events occurring in summer with at most 6 months duration were found to be more uncertain than those occurring in winter. Based on the ensemble drought statistics, the event from 1971 to 1974 appeared to have a 67% probability of being the longest and most severe drought event since 1950. Results of this study emphasize the importance of accounting for the parametric uncertainty for identifying benchmark drought events as well as the fact that using a single model simulation would very likely lead to inconclusive results.

Demanda hídrica e coeficientes de cultura (Kc) para macieiras em Vacaria, RS

O objetivo do presente trabalho foi determinar a demanda hídrica e os coeficientes de cultura (Kc) para macieiras cultivadas na região de Vacaria, RS. O trabalho foi desenvolvido na Estação Experimental de Fruticultura Temperada (EEFT) da Embrapa Uva e Vinho, localizada em Vacaria, RS, em plantas da cultivar 'Royal Gala' (Malus domestica) sobre porta-enxerto M9. Foram determinados os valores do potencial matricial da água no solo, empregando-se tensiômetros de punção. Com base nesses valores, determinou-se a umidade volumétrica e o balanço hídrico mensal. O consumo hídrico da cultura variou entre 0,3mm dia-1 a 4,5mm dia-1, com média de 1,9mm dia-1. O coeficiente da cultura (Kc) apresentou tendência quadrática, variando entre 0,19 e 0,88, com média igual a 0,58.

The effect of soil data resolution on hydrological processes modelling in a large humid watershed

AbstractHydrological process modelling depends on the data characterizing the heterogeneity of the catchment. In particular, in a large‐scale catchment, could a higher resolution of input data contribute to a more accurate result? In this study, surveyed soil data with two different spatial resolutions were used as input data for a Soil and Water Assessment Tool (SWAT) model simulation in a large humid watershed of Xinjiang River (15 535 km2) in Poyang Lake catchment in China. Simulations of stream flow, soil water storage and evapotranspiration (ET) generated using the two soil datasets were compared, and the impact of soil data resolution was analysed. The results indicate that the different resolutions of soil data have a great impact on the distribution of hydrological response units in the SWAT model, but do not lead to obvious differences in stream flow simulation. The finer resolution data produced a higher monthly soil water storage simulation than the lower‐resolution data across the watershed, while the seasonal variation of soil water content (SW) shows a close relation to the local precipitation and temperature. Results also show that the soil ET calculation method in the SWAT model is not particularly sensitive to the different resolutions of the soil maps. The implications of this study are that improvement of the resolution of soil data does not necessarily contribute to a more accurate prediction of stream flow in large‐scale watersheds. In practical studies, modellers need to select an appropriate resolution of soil data depending on the scale of watershed and the level of accuracy required, and also need to consider the principle of the model and the physical meaning of some key parameters to explain the simulation results. Copyright © 2010 John Wiley &amp; Sons, Ltd.

&lt;b&gt;ANALISIS TREN IKLIM DAN KETERSEDIAAN AIR TANAH DI PALEMBANG, SUMATRA SELATAN&lt;/b&gt;&lt;br&gt;&lt;i&gt;CLIMATE AND SOIL WATER TRENDS ANALYSIS FOR PALEMBANG REGION, SOUTH SUMATRA&lt;i&gt;

Long-term climate trend is being one of greatest research interests amongst climate scientists around the world to see whether climate change occurs or not at local, regional or global scale. However, only a few studies are available that discusses trend of climate extreme in equatorial climate, Indonesia. This paper tries to analyze climate trend and its impact to water availability in Palembang region using daily rainfall and air temperature data for the year of 1984-2009. Trend analysis was performed using Mann-Kendall test at α equal to 5%. We found that daily air temperature indicated that the rise of maximum, average, and minimum temperatures has occurred with statistically significant changes during the observation period. However, daily temperature range did not significantly change. We didn’t find any significant change for rainfall predictors except the number of rainfall event that significantly showed a decrease trend. With a simple water balance, we calculated monthly soil water content indicating that its’ decline was statistically significant (α=5%). With these findings, we have not made a conclusion whether climate change occurred or not yet, until influence of local effect such as urban heat island clearly explained.Long-term climate trend is being one of greatest research interests amongst climate scientists around the world to see whether climate change occurs or not at local, regional or global scale. However, only a few studies are available that discusses trend of climate extreme in equatorial climate, Indonesia. This paper tries to analyze climate trend and its impact to water availability in Palembang region using daily rainfall and air temperature data for the year of 1984-2009. Trend analysis was performed using Mann-Kendall test at α equal to 5%. We found that daily air temperature indicated that the rise of maximum, average, and minimum temperatures has occurred with statistically significant changes during the observation period. However, daily temperature range did not significantly change. We didn't find any significant change for rainfall predictors except the number of rainfall event that significantly showed a decrease trend. With a simple water balance, we calculated monthly soil water content indicating that its' decline was statistically significant (α=5%). With these findings, we have not made a conclusion whether climate change occurred or not yet, until influence of local effect such as urban heat island clearly explained.

Nitrogen Loss from Coffee Agroecosystems in Costa Rica: Leaching and Denitrification in the Presence and Absence of Shade Trees

AbstractCoffee (Coffea arabica L.) management in Costa Rica is changing from traditional agroecosystems, where coffee is grown beneath a tree overstory, to management systems where shade trees are removed and N fertilizer is applied at high rates (ca. 300 kg N ha−1 yr−1). Although fertilization increases coffee bean production, it also increases the potential for substantial loss of N to groundwater and the atmosphere. We investigated NO−3 leaching and the factors controlling denitrification in shaded and unshaded coffee plantations in the Central Valley of Costa Rica; both plantation types were fertilized with 300 kg N ha−1 yr−1. Nitrate leaching was quantified using porous ceramic cup lysimeters placed 60 cm below the soil surface. Losses were estimated by multiplying the soil water NO−3 concentration by the monthly soil water excess, determined as the difference between precipitation and actual evapotranspiration. In addition, a laboratory experiment was conducted to investigate the influence of NO−3, C, and O2 availability on N2O production and total denitrification (N2O‐N + N2‐N). Annual leaching losses of NO−3 were almost three times greater in unshaded plantations (24 kg NO−3‐N ha−1 yr−1) than those in shaded plantations (9 kg ha−1 yr−1). In contrast, mean total denitrification rates in control soil samples from shaded plantations were 60% higher (732 µg N2O‐N kg−1 d−1) than in unshaded plantations (455 µg N2O‐N kg−1 d−1). Carbon additions elicited the largest increase in denitrification, generating nearly a threefold increase (+ C = 8396 µg N2O‐N kg−1 d−1; −C = 2985 µg N2O‐N kg−1 d−1) in both plantation types. Anaerobic conditions also significantly increased denitriflcation (+ O2 = 4331 µg N2O‐N kg−1 d−1; µO2 = 6656 µg N2O‐N kg−1 d−1). In both plantation types, the potential for N loss via NO−3 leaching was small compared with that for gaseous N loss.

WATER BALANCE OF PACIFIC ATOLLS1

ABSTRACT: This study presents an estimate of water balance components for Pacific atolls under average dimatological conditions. Figures show annual potential evapotranspiration, annual recharge for rain‐fed and aquifer‐fed vegetated areas, and the number of months that potential evapotranspiration exceeds actual evapotranspiration (indicating water stress) under average conditions. The method relies on the assumption that small islands have minimal influence on cloudiness and precipitation. The potential evapotranspiration is computed using the equilibrium evaporation concept, and estimates of monthly soil water storage and recharge follow Thornthwaite's bookkeeping method. Gradients in potential evapotranspiration run primarily north‐south, though for the equatorial zone potential evapotranspiration declines from east to west, opposing the trend in rainfall. Recharge estimates range from 250 mm in the central Tuamotu Archipelago and zero in eastern Kiribati to over 2000 mm per year in the southern Caroline Islands (U.S. Trust Territory) and Solomon Islands. The sensitivity of the model to intra‐month rainfall variability and a range of available soil moisture values is discussed.