Canopy wetness patterns in a Mediterranean deciduous stand

Llorens, Pilar; Domingo, Francisco; Garcia-Estringana, Pablo; Mużyło, A.; Gallart, Francesc

doi:10.1016/j.jhydrol.2014.03.007

Cited by 17 publications

(15 citation statements)

References 38 publications

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“…1), one of the Vallcebre research catchments (northeastern Spain; 42 • 12 N, 1 • 49 E) in the eastern Pyrenees. These catchments have been monitored for 30 years for hydrological and ecohydrological purposes (see Latron et al, 2009;Llorens et al, 2018). Nowadays, most of the catchment is covered by Scots pine forests (Pinus sylvestris L.), which arose through afforestation of old agricultural terraces and small original fragmented oak forests (Quercus pubescens Willd.…”

Section: Site Descriptionmentioning

confidence: 99%

Throughfall isotopic composition in relation to drop size at the intra-event scale in a Mediterranean Scots pine stand

Pinos

Latron

Nanko

et al. 2020

Hydrol. Earth Syst. Sci.

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Abstract. The major fraction of water reaching the forest floor is throughfall, which consists of free throughfall, splash throughfall and canopy drip. Research has shown that forest canopies modify the isotopic composition of throughfall by means of evaporation, isotopic exchange, canopy selection and mixing of rainfall waters. However, the effects of these factors in relation to throughfall isotopic composition and the throughfall drop size reaching the soil surface are unclear. Based on research in a mountainous Scots pine stand in northeastern Spain, this study sought to fill this knowledge gap by examining the isotopic composition of throughfall in relation to throughfall drop size. In the experimental stand, throughfall consisted on average of 65 % canopy drip, 19 % free throughfall and 16 % splash throughfall. The dynamics of the isotopic composition of throughfall and rainfall showed complex behaviour throughout events. The isotopic shift showed no direct relationship with meteorological variables, number of drops, drop velocities, throughfall and rainfall amount, or raindrop kinetic energy. However, the experiment did reveal that the isotopic shift was higher at the beginning of an event, decreasing as cumulative rainfall increased, and that it also increased when the median volume drop size of throughfall (D50_TF) approached or was lower than the median volume drop size of rainfall (D50_RF). This finding indicates that the major contribution of splash throughfall at the initial phase of rain events matched the highest vapour pressure deficit (VPD) and, at the same time, corresponded to higher isotopic enrichment, which implies that splash droplet evaporation occurred. Future applications of our approach will improve understanding of how throughfall isotopic composition may vary with drop type and size during rainfall events across a range of forest types.

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Section: Site Descriptionmentioning

confidence: 99%

Throughfall isotopic composition in relation to drop size at the intra-event scale in a Mediterranean Scots pine stand

Pinos

Latron

Nanko

et al. 2020

Hydrol. Earth Syst. Sci.

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“…To ensure the dryness of the canopy between successive rainfall events, the interevent period was set to be at least 6 hr (without any rainfall) during the day and 12 hr during the night (Llorens, Domingo, Garcia-Estringana, Muzylo, & Gallart, 2014). To take into account seasonal changes in canopy cover and possible temporal differences due to air temperature, two time periods were considered: the growing season from May 15 to October 15, which covered the period of higher air temperature; and the dormant FIGURE 3 Relationship between δ 18 O of rainfall and throughfall for the pines (a) and oaks (b), between δD of rainfall and throughfall (c,d), and between d-excess of rainfall and throughfall (e,f) season for the remaining months, which covered the period of lower temperature.…”

Section: Isotopic Samplingmentioning

confidence: 99%

“…To take into account seasonal changes in canopy cover and possible temporal differences due to air temperature, two time periods were considered: the growing season from May 15 to October 15, which covered the period of higher air temperature; and the dormant FIGURE 3 Relationship between δ 18 O of rainfall and throughfall for the pines (a) and oaks (b), between δD of rainfall and throughfall (c,d), and between d-excess of rainfall and throughfall (e,f) season for the remaining months, which covered the period of lower temperature. To ensure the dryness of the canopy between successive rainfall events, the interevent period was set to be at least 6 hr (without any rainfall) during the day and 12 hr during the night (Llorens, Domingo, Garcia-Estringana, Muzylo, & Gallart, 2014). As a result, 22 individual rainfall events that had not been mixed with previous or following events were analysed.…”

Section: Isotopic Samplingmentioning

confidence: 99%

Modification of the isotopic composition of rainfall by throughfall and stemflow: The case of Scots pine and downy oak forests under Mediterranean conditions

et al. 2018

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Most hydrological studies based on stable water isotopes ( 18 O and D) use the isotopic composition of rainfall as input signal. Although stable water isotopes are conservative tracers, previous studies have shown that canopies modify the isotopic composition of rainfall. At present, there is a scientific agreement about the factors involved in isotopic modification, but the effect of each factor and the magnitude of the isotopic shift are still not clear. In this study, we analyse at an interevent and intraevent basis the spatio-temporal differences between the isotopic composition of rainfall, throughfall, and stemflow for two different species (Pinus sylvestris L. and Quercus pubescens Willd). The aim of the study is to analyse the isotopic modification that takes place in throughfall and stemflow and how meteorological variables and structural forest characteristics influence the observed changes. Rainfall and throughfall were sampled by a combination of bulk and sequential collectors, whereas stemflow was collected only by bulk collectors. Results showed that the isotopic modification occurred in both directions, although stemflow was consistently more enriched than throughfall. Despite the contrasting canopy structures, no significant differences between species were found. Moreover, the intraevent analysis suggested that all fractionation factors could occur during one event, but evaporation or isotopic exchange would have a higher impact at the beginning of rainfall, whereas canopy selection processes would be more important at the end of rainfall. Our results emphasize the importance of considering the isotopic composition of throughfall and stemflow in isotope-related studies in forested catchments.

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“…Rainfall events were defined as periods with more than 1 mm of precipitation. To ensure canopy dryness between events, the interevent period was set to be at least 6 hr during the day and 12 hr during the night (Llorens, Domingo, Garcia-Estringana, Muzylo, & Gallart, 2014). Following Latron and Gallart (2007), runoff event duration as well as stormflow depth and coefficient were derived for each rainfall-runoff event selected, using the constant slope method of Hewlett and Hibbert (1967) with a modified slope value of 1.38 l · s −1 · km −2 · day −1 , once a discharge increment in the stream higher than 5.6 l · s −1 · km −2 was identified.…”

Section: Data Analysis and Ihsmentioning

confidence: 99%

Spatio‐temporal variability of the isotopic input signal in a partly forested catchment: Implications for hydrograph separation

Cayuela

Latron

Geris

et al. 2018

Hydrological Processes

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The isotopic composition of precipitation (D and 18O) has been widely used as an input signal in water tracer studies. Whereas much recent effort has been put into developing methodologies to improve our understanding and modelling of hydrological processes (e.g., transit‐time distributions or young water fractions), less attention has been paid to the spatio‐temporal variability of the isotopic composition of precipitation, used as input signal in these studies. Here, we investigated the uncertainty in isotope‐based hydrograph separation due to the spatio‐temporal variability of the isotopic composition of precipitation. The study was carried out in a Mediterranean headwater catchment (0.56 km2). Rainfall and throughfall samples were collected at three locations across this relatively small catchment, and stream water samples were collected at the outlet. Results showed that throughout an event, the spatial variability of the input signal had a higher impact on hydrograph separation results than its temporal variability. However, differences in isotope‐based hydrograph separation determined preevent water due to the spatio‐temporal variability were different between events and ranged between 1 and 14%. Based on catchment‐scale isoscapes, the most representative sampling location could also be identified. This study confirms that even in small headwater catchments, spatio‐temporal variability can be significant. Therefore, it is important to characterize this variability and identify the best sampling strategy to reduce the uncertainty in our understanding of catchment hydrological processes.

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Canopy wetness patterns in a Mediterranean deciduous stand

Cited by 17 publications

References 38 publications

Throughfall isotopic composition in relation to drop size at the intra-event scale in a Mediterranean Scots pine stand

Throughfall isotopic composition in relation to drop size at the intra-event scale in a Mediterranean Scots pine stand

Modification of the isotopic composition of rainfall by throughfall and stemflow: The case of Scots pine and downy oak forests under Mediterranean conditions

Spatio‐temporal variability of the isotopic input signal in a partly forested catchment: Implications for hydrograph separation

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