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Guerra E.,University of Bologna | Ventura F.,University of Bologna | Spano D.,University of Sassari | Spano D.,Centro EuroMediterraneo sui Cambiamenti Climatici CMCC | Snyder R.L.,University of California at Davis
Journal of Irrigation and Drainage Engineering | Year: 2015

It is well known that crop coefficients are not necessarily transferrable from one location to another, for a variety of reasons. For example, the United Nations Food and Agricultural Organization (UN FAO) 24 publication on evapotranspiration listed ranges of midseason crop coefficients for particular crops, depending on wind speed and humidity. In the more recent UN FAO 56 publication, an equation was presented that adjusted crop coefficients for wind speed, humidity, and crop height. Climate correction is important for sharing and adjusting crop coefficient data. However, it was found that the FAO 56 equation gave inaccurate corrections for a crop having the same characteristics as the reference crop surface, and it is likely that it also will be inaccurate for other crop surfaces. Consequently, the aim of this research was to develop and test a new method to correct midseason crop coefficients for climate differences. Climate data were used from the California Irrigation Management Information System and a similar approach was used to develop standardized reference evapotranspiration equations for short and tall canopies, to develop and test the new method. The method estimates the aerodynamic resistance of crops in a base climate as an inverse function of wind speed. This function of wind speed was used in a modified Penman-Monteith equation to account for climate effects on midseason crop coefficients in nonbase climates. The methodology to account for climate data and estimate midseason crop coefficient values in a nonbase climate from base climate crop coefficients is presented in this paper. © 2014 American Society of Civil Engineers. Source

Rianna G.,Centro EuroMediterraneo sui Cambiamenti Climatici CMCC | Pagano L.,University of Naples Federico II | Urciuoli G.,University of Naples Federico II
Engineering Geology | Year: 2014

In the context of landslide-prone pyroclastic soils this paper investigates the physical significance of antecedent rainfalls in relation to the major rainfall event and the influence exerted by evaporation. The work is based on results from tests using a physical model, developed to characterise the hydraulic response of a pyroclastic soil volume subjected to actual meteorological conditions. Rainfall, evaporation, water storage, soil suction and soil volumetric water content were continuously monitored over a meteorological window exceeding two years. Interpretation of the experimental results provides three characteristic values of water storage which are used to explain the physical significance of antecedent and triggering precipitations and shed light on the aspects of major rainfall events triggering landslides. © 2014 Elsevier B.V. Source

Nole A.,University of Basilicata | Collalti A.,Centro EuroMediterraneo sui Cambiamenti Climatici CMCC | Magnani F.,University of Bologna | Duce P.,CNR Institute for Biometeorology | And 6 more authors.
Annals of Forest Science | Year: 2013

Context: Forest ecosystem carbon uptake is heavily affected by increasing drought in the Mediterranean region. Aims: The objectives of this study were to assess the capacity of a modified 3-PG model to capture temporal variation in gross primary productivity (GPP), and ecosystem net carbon uptake (NEE) in two Mediterranean forest types. Methods: The model was upgraded from a monthly (3-PG) to a daily time step (3-PGday), and a soil water balance routine was included to better represent soil water availability. The model was evaluated against seasonal GPP and NEE dynamics from eddy covariance measurements. Results: Simulated and measured soil water content values were congruent throughout the study period for both forest types. 3-PGday effectively described the following: GPP and NEE seasonal patterns; the transition of forest ecosystems from carbon sink to carbon source; however, the model overestimated diurnal ecosystem respiration values and failed to predict ecosystem respiration peaks. Conclusions: The model served as a rather effective tool to represent seasonal variation in gross primary productivity, and ecosystem net carbon uptake under Mediterranean drought-prone conditions. However, its semi-empirical nature and the simplicity inherent in the original model formulation are obstacles preventing the model working well for short-term daily predictions. © 2013 INRA and Springer-Verlag France. Source

Rianna G.,Centro EuroMediterraneo sui Cambiamenti Climatici CMCC | Pagano L.,University of Naples Federico II | Urciuoli G.,University of Naples Federico II
Journal of Hydrology | Year: 2014

This paper investigates the interaction between soil and atmosphere in pyroclastic soils with a view to understanding whether and to what extent the prediction of the hydraulic (and mechanical) behaviour of geotechnical problems (cuts, slope stabilities, embankments, foundation, retaining structures) regulated by rainfall-induced fluctuations of matric suction is influenced by evaporation phenomena. Evaporation fluxes are quantified and compared with other fluxes (precipitation, run-off, deep drainage) affecting soil water content and matric suction. This work is based on the data collected through a physical model over 2years of experimental tests. The model consisted of a 1m3 tank, filled in this case with pyroclastic soil and exposed to natural weather elements. The system was extensively monitored to record atmospheric and soil variables. The results provided by the experiments highlight the importance of the top-soil state in determining the intensities of infiltrating rainfall and actual evaporation. The results also bring to light the significance of evaporation which, during the dry season, largely prevails over infiltration, raising suction to very high values. Also during the wet season, evaporation gives rise to a non-negligible flux with respect to the infiltrated precipitation. The reliability of two pre-existing empirical models to estimate evaporation flux is also investigated and appraised within this paper. © 2014 Elsevier B.V. Source

Chiti T.,University of Tuscia | Chiti T.,Centro EuroMediterraneo sui Cambiamenti Climatici CMCC | Certini G.,University of Florence | Forte C.,CNR Institute of Neuroscience | And 4 more authors.
Ecosystems | Year: 2016

The amount of soil organic carbon (SOC) released into the atmosphere as carbon dioxide (CO2), which is referred to as heterotrophic respiration (Rh), is technically difficult to measure despite its necessity to the understanding of how to protect and increase soil carbon stocks. Within this context, the aim of this study is to determine Rh in two Mediterranean forests dominated by pine and oak using radiocarbon measurements of the bulk SOC from different soil layers. The annual Rh was 3.22 Mg C ha−1 y−1 under pine and 3.13 Mg C ha−1 y−1 under oak, corresponding to 38 and 31% of the annual soil respiration, respectively. The accuracy of the Rh values was evaluated by determining the net primary production (NPP), as the sum of the Rh and the net ecosystem production measured by eddy covariance, then comparing it with the NPP obtained through independent biometric measurements. No significant differences were observed, which suggested the suitability of our methodology to infer Rh. Assuming the C inputs to soil to consist exclusively of the aboveground and belowground litter and the C output exclusively of the Rh, both soils were C sinks, which is consistent with a previous modeling study that was performed in the same stands. In conclusion, radiocarbon analysis of bulk SOC provided a reliable estimate of the average annual amount of soil carbon released to the atmosphere; hence, its application is convenient for calculating Rh because it utilizes only a single soil sampling and no time-consuming monitoring activities. © 2015, Springer Science+Business Media New York. Source

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