Rainfall interception by the forest cover causes an important reduction in bulk rainfall in 15 semiarid climates, such as the Mediterranean. Unmanaged, dense pine stands in this 16 area are expected to have an important impact on water resources. This paper studies the 17 effect of forest management on the partitioning of rainfall into throughfall and stemflow 18 in an Aleppo pine plantation in eastern Spain. Three thinning-intensity treatments were 19 compared with unmanaged stands that served as the control. The results revealed a very 20 low throughfall in the control treatments during the study period of 55.9 %, whereas 21 throughfall increased significantly after thinning to 83.8, 67.7 and 61.3 % of the bulk 22 rainfall for high-, moderate-and low-intensity treatments, respectively. Total 23 throughfall was negatively and linearly related to the tree density, forest cover, basal 24 area and leaf area index. In contrast, weekly throughfall was modelled by considering 25 these variables together with bulk rainfall in a multiple exponential expression; the 26 weekly throughfall R 2 values (corrected Pearson coefficient) were above 0.9. These 27 models would facilitate the implementation of hydrology-oriented silviculture via a 28 more accurate prediction of the impacts of thinning on throughfall in this type of forest. 29 30 Keywords: Pinus halepensis Mill., forest management, rainfall partitioning, 31 interception, hydrology 32 33 Introduction 34Interception is one of the major components of the water cycle in forest ecosystems and 35 has been the central topic of several studies and reviews in forest hydrology in recent 36 decades (Bosch and Hewlett, 1982; Brown et al., 2005; Llorens and Domingo, 2007). 37Interception losses may account for, on average, 8 % to 60 % of bulk rainfall depending 38 on the forest type and structure and on climatic conditions (David et al., 2011). In 39 3 Mediterranean climates, a mean interception value of approximately 20 % has been 40 determined in an extensive review of the topic (Llorens and Domingo, 2007), although 41 values of approximately 30 % were reported in the most semiarid conditions. In these 42 drier areas, annual water consumption in forests can be nearly equal to the total annual 43 rainfall (Schiller and Cohen, 1998), with transpiration leading interception in total forest 44 evapotranspiration (David et al., 2011). 45Special attention needs to be paid to the forest-water relationships in the Mediterranean 46 due to the natural scarcity of water, on one hand, and the important values associated 47 with forests in a region where physiographic, climatic, geological and historical land-48 use factors have caused soil erosion and degradation, on the other hand. In this context, 49Aleppo pine (Pinus halepensis Mill.) forests provide landscape quality, soil protection 50 and hydrological cycle stabilisation over approximately 3.5 × 10 5 ha in the 51Mediterranean basin (Fady et al., 2003; Zavala et al., 2000), being one of the tree 52 species best adapted to the mos...

Campo García, ADD.; Gualberto Fernandes, TJ.; Molina Herrera, A. (2014). Hydrologyoriented (adaptive) silviculture in a semiarid pine plantation: How much can be modified the water cycle through forest management?. European Journal of Forest Research. 133(55):879-894. doi:10.1007//s10342-014-0805-7. European Journal of Forest ResearchHydrology-oriented (adaptive) silviculture in a semiarid pine plantation: how much can be modified the water cycle through forest management?--Manuscript Draft-- Order of Authors Secondary Information:Abstract: Hydrology-oriented silviculture might adapt Mediterranean forests to climatic changes, although its implementation demands a better understanding and quantification on the water fluxes. The influence of thinning intensity (high, medium, low and a control) and its effect on the mid-term (thinned plots in 1998 and 2008) on the water cycle (transpiration, soil water and interception) and growth (Basal Area Increment, BAI) were investigated in 55-year-old Aleppo pine trees. Thinning enhanced a lower dependence of growth on climate fluctuations. The high intensity treatment showed significant increases in the mean annual BAI (from 4.1 to 17.3 cm2) that were maintained in the mid-term. Thinning intensity progressively increased the sap flow velocity (vs) in all cases with respect the control. In the mid-term, an increased functionality of the inner sapwood was also observed. Mean daily tree water use ranged from 5 (control) to 18 (high intensity) l tree-1. However, when expressed on an area basis, daily transpiration ranged from 0.18 (medium) to 0.30 mm (control), meaning that, in spite of the higher transpiration rates in the remaining trees, stand transpiration was reduced with thinning. Deep infiltration of water was also enhanced with thinning (about 30% of rainfall) and did no compete with transpiration, as both presented opposite seasonal patterns. The changes in the stand water relationships after ten years were well explained by the forest cover metric. The blue to green water ratio changed from 0.15 in the control to 0.72 in the high intensity treatment, with the remaining treatments in the 0. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 2 velocity (v s ) in all cases with respect the control. In the mid-term, an increased functionality of the inner sapwood was also observed. Mean daily tree water use ranged from 5 (control) to 18 (high intensity) l tree -1 . However, when expressed on an area basis, daily transpiration ranged from 0.18 (medium) to 0.30 mm (control), meaning that, in spite of the higher transpiration rates in the remaining trees, stand transpiration was reduced with thinning. Deep infiltration of water was also enhanced with thinning (about 30% of rainfall) and did no compete with transpiration, as both presented opposite seasonal patterns. The changes ...

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This paper presents the main results obtained from the study of hydrological processes in the Vallcebre Research Catchments since 1988. Distributed hydrometric measurements, environmental tracers and hydrological modelling were used to understand Mediterranean catchment behaviour and to provide new data to help assess the global change effects on these catchments' water resources. Thirty years of hydrological processes observation in the Vallcebre Research Catchments have increased understanding not only of their hydrological response, but also of the main hydrological and erosion processes characteristic of Mediterranean mountain catchments. This paper briefly summarises the main results obtained since 1988 on ecohydrological processes, hydrological response, runoff generation processes, erosion and sediment transport. Some of the main findings from this research are (i) the importance of temporal variability in precipitation to determine the hydrological processes; (ii) the paramount role played by forest cover in reducing soil water content; (iii) the marked influence of antecedent wetness conditions on runoff generation that determine different runoff responses; (v) the dominant contribution of pre-existing water during floods; (vi) the importance of freezing-thawing processes in badland areas on erosion and the role of summer convective storms in controlling sediment transport.

ElsevierGualberto-Fernandes, TJ.; Campo García, ADD.; Herrera Fernandez, R.; Molina Herrera, A. (2016). Simultaneous assessment, through sap flow and stable isotopes, of water use efficiency (WUE) In water-limited regions, adaptive management of forest and water relationships has been put 17 forward, to implement hydrology-oriented silviculture to reduce stand evapotranspiration and, 18 at the tree level, to improve growth and water use efficiency (WUE). The main goal of this 19 study was to evaluate the effect of thinning in the short and medium term on tree growth, 20 climate (drought) sensitivity, WUE performed using growth and sap flow measurements and 21WUEi performed using δ increased growth, but also changed the tree growth-precipitation relationships, with C trees 27 depending more on precipitation than thinned trees did. WUEi after thinning was significantly 28 affected only in the medium term, with C trees being more efficient (94.4 μmolCO2/molH2O) 29 than H98 trees (88.7), especially in dry spells (100.7). WUEi was found to increase when 30 precipitation decreased, regardless of the treatment. However, WUE increased sharply from C 31 was not consistent with our experimental data. Thus, the question of whether stable isotopes 37 can be used as a tool for addressing the ecophysiological impacts of thinning remains open. 38

Water is the key element that modulates the provision of goods and services together with global/climate stressors affecting semiarid forests. In this sense, there is a need to improve the understanding and quantification of forest and water relationships as affected by forest management. This work addresses this issue by comparing net rainfall (Pn) redistribution into different belowground hydrological processes (BHP) in two forest types after a thinning treatment: a holm oak coppice (HU) and a post-fire Aleppo pine regeneration (CAL). The relative contribution (RI) of forest structure, antecedent soil moisture (st), rainfall and meteorological conditions on the BHP was assessed through boosted regression trees models. In both sites, the RI of the forest structure itself was limited (<10%). However, st, which clearly increased significantly with thinning, received an average RI of 29%. Surface and subsurface lateral flows showed values <1% of gross rainfall (Pg) in either site and were not significantly affected by thinning. On the other hand, soil moisture and drainage were affected by the thinning treatment, although with different extent depending on the site: in the drier site (CAL), the increased Pn in the thinning was mainly allocated into increased soil water content, with very limited improvement in drainage (<10 mm/year); in contrast, in the wetter continental site of HU, drainage to deeper soil layers was the most remarkable effect of thinning (50 mm/year higher than in control), given the higher st and hence the lower soil water storage available. Thinning also improved the response of BHP during drought, making these processes more elastic and less vulnerable to climatic extremes. The results presented here complement those previously reported on rainfall partitioning in these sites and all together provide a comprehensive understanding of the short-term effect (3-4 years) of water-oriented silviculture Quercus ilex and Pinus halepensis low-biomass semiarid forests. Questions such as the long-term effects of thinning remain open for these ecosystems. SOC e g Kg-1 28.5±22.1 103.5±32.4 pH (water) 8.3±0.2 7.9±0.2 Carbonates (g g-1 dry soil) 0.34±0.15 0.24±0.10

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Soil water-content (SWC) variability in forest ecosystems is affected by complex interactions between climate, topography, forest structure and soil factors. However, detailed studies taking into account the combined effects of these factors are scarce. This study's main aims were to examine the control that throughfall exerts on local spatial variation of near-surface soil water-content and to combine this information with forest structure and soil characteristics, in order to analyze all their effects together. Two stands located in the Vallcebre Research Catchments (NE Spain) were studied: one dominated by Quercus pubescens and the other by Pinus sylvestris. Throughfall and the related shallow SWC were monitored in each plot in 20 selected locations. The main characteristics of the nearest tree and soil parameters were also measured. The results indicated that mean SWC increment at the rainfall event scale showed a strong linear relationship with mean throughfall amount in both forest plots. The % of locations with SWC increments increased in a similar way to throughfall amount in both forest plots. The analyses considering all the effects together indicated again that throughfall had a significant positive effect in both forest plots, while soil litter depth showed a significant negative effect for the oak plot but lower statistical significance for the pine plot, showing a comparable -although more erratic- influence of the organic forest floor for this plot. These results, together with lower responses of SWC to throughfall than expected in rainfall events characterized by low preceding soil water-condition and high rainfall intensity, suggest that litter layer is playing an important role in controlling the soil water-content dynamics. The biometric characteristics of the nearest trees showed significant but very weak relationships with soil water-content increment, suggesting that stemflow and throughfall may act at lower distances from tree trunk than those presented in our study.