Testing three rainfall interception models and different parameterization methods with data from an open Mediterranean pine forest

Various models have been developed to simulate rainfall interception by vegetation but their formulations and applications rely on a number of assumptions and parameter estimation procedures. The aim of this study is to examine the effect of different model assumptions and parameter derivation approaches on the performance of the Rutter, Gash and Liu interception models. The Rutter model, in contrast to the other two daily models, was applied both on an hourly and on a daily basis. Hourly data from a meteorological station, one automatic and 28 manual throughfall gauges from a semi-arid Pinus brutia forest (Cyprus) for the period between 01/Jul/2016 and 31/May/2020 were used for the analysis. We conducted a sensitivity analysis for the assessment of the model parameters and variables: canopy storage capacity (S), canopy cover fraction (c), the ratio of mean wet evaporation rate to mean wet rainfall rate (Ēc/R̄) and potential evaporation (Eo). Three parameter derivation approaches were tested: the widely used regression method and an automatic model parameterization procedure for optimization of S and c and for optimization of S (with c observed). The parameterized models were run with daily meteorological data and compared with long-term weekly throughfall data (2008–2019). The Gash and Liu models showed low sensitivity to Ēc/R̄. Test runs with different combinations of S, c and Ēc/R̄ revealed strong equifinality. The models showed high performance for both calibration and validation periods with Kling–Gupta Efficiency (KGE) above 0.90. Gash and Liu models with the automatic model parameterization procedures resulted in higher KGEs than with the regression method. The interception losses computed from the long-term application of the three models ranged between 18 and 20%. The models were all capable of capturing the inherently variable interception process. However, a representative time series of throughfall measurements is needed to parameterize the models

Current Wildland Fire Patterns and Challenges in Europe : A Synthesis of National Perspectives

Changes in climate, land use, and land management impact the occurrence and severity of wildland fires in many parts of the world. This is particularly evident in Europe, where ongoing changes in land use have strongly modified fire patterns over the last decades. Although satellite data by the European Forest Fire Information System provide large-scale wildland fire statistics across European countries, there is still a crucial need to collect and summarize in-depth local analysis and understanding of the wildland fire condition and associated challenges across Europe. This article aims to provide a general overview of the current wildland fire patterns and challenges as perceived by national representatives, supplemented by national fire statistics (2009-2018) across Europe. For each of the 31 countries included, we present a perspective authored by scientists or practitioners from each respective country, representing a wide range of disciplines and cultural backgrounds. The authors were selected from members of the COST Action "Fire and the Earth System: Science & Society" funded by the European Commission with the aim to share knowledge and improve communication about wildland fire. Where relevant, a brief overview of key studies, particular wildland fire challenges a country is facing, and an overview of notable recent fire events are also presented. Key perceived challenges included (1) the lack of consistent and detailed records for wildland fire events, within and across countries, (2) an increase in wildland fires that pose a risk to properties and human life due to high population densities and sprawl into forested regions, and (3) the view that, irrespective of changes in management, climate change is likely to increase the frequency and impact of wildland fires in the coming decades. Addressing challenge (1) will not only be valuable in advancing national and pan-European wildland fire management strategies, but also in evaluating perceptions (2) and (3) against more robust quantitative evidence.Peer reviewe

Tree Water Dynamics in a Semi-Arid, Pinus brutia Forest

This study aims to examine interactions between tree characteristics, sap flow, and environmental variables in an open Pinus brutia (Ten.) forest with shallow soil. We examined radial and azimuthal variations of sap flux density (Jp), and also investigated the occurrence of hydraulic redistribution mechanisms, quantified nocturnal tree transpiration, and analyzed the total water use of P. brutia trees during a three-year period. Sap flow and soil moisture sensors were installed onto and around eight trees, situated in the foothills of the Troodos Mountains, Cyprus. Radial observations showed a linear decrease of sap flux densities with increasing sapwood depth. Azimuthal differences were found to be statistically insignificant. Reverse sap flow was observed during low vapor pressure deficit (VPD) and negative air temperatures. Nocturnal sap flow was about 18% of the total sap flow. Rainfall was 507 mm in 2015, 359 mm in 2016, and 220 mm in 2017. Transpiration was 53%, 30%, and 75%, respectively, of the rainfall in those years, and was affected by the distribution of the rainfall. The trees showed an immediate response to rainfall events, but also exploited the fractured bedrock. The transpiration and soil moisture levels over the three hydrologically contrasting years showed that P. brutia is well-adapted to semi-arid Mediterranean condition

Quantifying Evapotranspiration and Drainage Losses in a Semi-Arid Nectarine (<i>Prunus persica</i> var. <i>nucipersica</i>) Field with a Dynamic Crop Coefficient (<i>K_c</i>) Derived from Leaf Area Index Measurements

Quantifying evapotranspiration and drainage losses is essential for improving irrigation efficiency. The FAO-56 is the most popular method for computing crop evapotranspiration. There is, however, a need for locally derived crop coefficients (Kc) with a high temporal resolution to reduce errors in the water balance. The aim of this paper is to introduce a dynamic Kc approach, based on Leaf Area Index (LAI) observations, for improving water balance computations. Soil moisture and meteorological data were collected in a terraced nectarine (Prunus persica var. nucipersica) orchard in Cyprus, from 22 March 2019 to 18 November 2021. The Kc was derived as a function of the canopy cover fraction (c), from biweekly in situ LAI measurements. The use of a dynamic Kc resulted in Kc estimates with a bias of 17 mm and a mean absolute error of 0.8 mm. Evapotranspiration (ET) ranged from 41% of the rainfall (P) and irrigation (I) in the wet year (2019) to 57% of P + I in the dry year (2021). Drainage losses from irrigation (DR_I) were 44% of the total irrigation. The irrigation efficiency in the nectarine field could be improved by reducing irrigation amounts and increasing the irrigation frequency. Future studies should focus on improving the dynamic Kc approach by linking LAI field observations with remote sensing observations and by adding ground cover observations

The Impact of a Check Dam on Groundwater Recharge and Sedimentation in an Ephemeral Stream

Despite the widespread presence of groundwater recharge check dams, there are few studies that quantify their functionality. The objectives of this study are (i) to assess groundwater recharge in an ephemeral river with and without a check dam and (ii) to assess sediment build-up in the check-dam reservoir. Field campaigns were carried out to measure water flow, water depth, and check-dam topography to establish water volume, evaporation, outflow, and recharge relations, as well as sediment build-up. To quantify the groundwater recharge, a water-balance approach was applied at two locations: at the check dam reservoir area and at an 11 km long natural stretch of the river upstream. Prediction intervals were computed to assess the uncertainties of the results. During the four years of operation, the check dam (storage capacity of 25,000 m3) recharged the aquifer with an average of 3.1 million m3 of the 10.4 million m3 year−1 of streamflow (30%). The lower and upper uncertainty limits of the check dam recharge were 0.1 and 9.6 million m3 year−1, respectively. Recharge from the upstream stretch was 1.5 million m3 year−1. These results indicate that check dams are valuable structures for increasing groundwater resources in semi-arid regions

A Field Method for Landscape Conservation Surveying: The Landscape Assessment Protocol (LAP)

We introduce a field survey method to assess the conservation condition of landscapes. Using a popular rapid assessment format, this study defines observable &#8220;stressed states&#8222; identified through the use of general metrics to gauge landscape degradation. Fifteen metrics within six thematic categories were selected through a literature review and extensive field trials. Field tests on the Greek island of Samothraki show a strong correlation between a single expert&#8217;s scores and five assessor&#8217;s scores at 35 landscape sites. Only three of the metrics did not maintain a high consistency among assessors; however, this is explained by the difficulty of interpreting certain anthropogenic stressors (such as livestock grazing) in Mediterranean semi-natural landscapes with culturally-modified vegetation patterns. The protocol and proposed index, with five conservation condition classes, identified areas of excellent and good quality, and reliably distinguished the most degraded landscape conditions on the island. Uncertainties and difficulties of the index are investigated, and further research and validation are proposed. The protocol effectively goes beyond a traditional visual aesthetic assessment; it can be used both by experts and non-scientists as a conservation-relevant multi-disciplinary procedure to support a holistic landscape diagnosis. The combination of an on-site experiential survey and its simple integrative format may be useful as a screening-level index, and for promoting local participation, landscape literacy and educational initiatives

Current Wildland Fire Patterns and Challenges in Europe : A Synthesis of National Perspectives

Changes in climate, land use, and land management impact the occurrence and severity of wildland fires in many parts of the world. This is particularly evident in Europe, where ongoing changes in land use have strongly modified fire patterns over the last decades. Although satellite data by the European Forest Fire Information System provide large-scale wildland fire statistics across European countries, there is still a crucial need to collect and summarize in-depth local analysis and understanding of the wildland fire condition and associated challenges across Europe. This article aims to provide a general overview of the current wildland fire patterns and challenges as perceived by national representatives, supplemented by national fire statistics (2009–2018) across Europe. For each of the 31 countries included, we present a perspective authored by scientists or practitioners from each respective country, representing a wide range of disciplines and cultural backgrounds. The authors were selected from members of the COST Action “Fire and the Earth System: Science & Society” funded by the European Commission with the aim to share knowledge and improve communication about wildland fire. Where relevant, a brief overview of key studies, particular wildland fire challenges a country is facing, and an overview of notable recent fire events are also presented. Key perceived challenges included (1) the lack of consistent and detailed records for wildland fire events, within and across countries, (2) an increase in wildland fires that pose a risk to properties and human life due to high population densities and sprawl into forested regions, and (3) the view that, irrespective of changes in management, climate change is likely to increase the frequency and impact of wildland fires in the coming decades. Addressing challenge (1) will not only be valuable in advancing national and pan-European wildland fire management strategies, but also in evaluating perceptions (2) and (3) against more robust quantitative evidence