Academic literature on the topic 'Sap flow'

To close the water use budget of irrigated agricultural fields in floodplains with substantial riparian corridors, it is necessary to understand groundwater usage by dominant phreatophytic vegetation, particularly when the primary source of water for irrigation comes from groundwater abstraction. We report here results of estimated evapotranspiration (ET) of a riparian forest, which were based on measurements of sap flow in phreatophytic vegetation within a riparian corridor. The riparian corridor was within a study area 75 to 140 meters wide in the lower portion of the Scotts Creek watershed, which is bounded to the west by the Pacific Ocean in Santa Cruz County, California. Canopy coverage in the study area often approaches 100% during the growing season, with dominant trees being red alder (Alnus rubra Bong.), arroyo willow (Salix lasiolepis Benth.), and pacific willow (Salix lasiandra Benth. var. lasiandra). Other trees include boxelder (Acer negundo L.), bigleaf maple (Acer macrophyllum Pursh.), California bay laurel (Umbellularia californica (Hook. & Arn.) Nutt.), and coastal redwoods (Sequoia sempervirens (D. Don) Endl.). Common understory vegetation includes California blackberry (Rubus ursinus Cham. and Schlecht.), stinging nettle (Urtica dioica subsp. gracilis L.), poison hemlock (Conium maculatum L.), Cape ivy (Delairea odorata Lem.), Italian thistle (Carduus pycnocephalus L. subsp. pycnocephalus), and western poison oak (Toxicodendron diversilobum (Torr. & A. Gray) Greene). We hypothesized that the ET of a riparian forest could be estimated by measuring the sap flow of riparian phreatophytic trees. For the study reported here, only the two most dominant phreatophytic species, namely red alders and arroyo willows, were instrumented with thermal dissipation probes. In addition to diurnal fluctuations, sap flow data collected hitherto also showed expected seasonal variation with summer maxima and winter minima, with transition fall and spring periods. Sap flow measurements from the study area were used to estimate riparian forest ET by projecting them across the canopy areal extent of the riparian forest using sampled tree sapwood areas from six sample plots. The sap flow-based ET results were then compared to ET results reported by two other methods. Additional research, including increased number of trees with thermal dissipation probes, further analysis of sap flow behavior, and continued long-term measurement of sap flow, is needed to further improve the method of using long-term sap flow measurements to estimate the ET of a riparian forest.

The aim of this study was to calibrate and decide on the most appropriate sap flow technique for citrus species in the laboratory by pushing water through cut branches. Various sap flux density techniques, including heat pulse techniques (heat ratio and compensation heat pulse methods) and the heat dissipation technique were calibrated in four citrus species, namely Citrus sinensis (Oranges), Citrus reticulata (Soft citrus), Citrus paradise (Grapefruit) and Citrus limon (Lemons). Sap flux density, determined by these three techniques, was compared to that determined gravimetrically, which was calculated as the rate of change in the mass of water passing through the stem segment divided by the area of conducting wood. Results showed that the sap flux density was consistently underestimated by all techniques and across all citrus species/varieties. However, fairly good correlations (R2>0.7) between sap flux densities determined by a sap flow technique and gravimetric determinations were found for all techniques in some stems. Despite the good correlations found in the study, a single calibration factor for each technique could not be found for citrus using the stem perfusion method. Calibration factors were determined as the inverse of the slope of the linear relationship between sap flux density determined with a sap flow technique and that determined gravimetrically. These correction factors varied between citrus species and even within stems of the same species. Vessel dimensions (lumen diameter) and distance between groups of xylem vessels in citrus species was determined in order to try and explain the underestimation of sap flux density and the large variations in the calibration factors obtained during the calibration of the various sap flow techniques. The results revealed that the variation and underestimation were caused by contact of the probes with inactive xylem and due to differences in the nature of sapwood. The xylem vessels were unevenly distributed throughout the sapwood with large distance between the vessels, meaning that the sapwood of the studied species was considered inhomogeneous and therefore departed from the idealised theory of heat pulse measurements. The theory needs to be adapted to account for such sapwood and because of the large variation in the sapwood properties between different citrus species, calibration of these techniques is probably necessary for each new species and orchard in which measurements are to be made. Our analysis of the performance of sap flow techniques showed that the HR method should perhaps be considered before the CHP and TD methods.<br>Dissertation (MSc (Agric))--University of Pretoria, 2016.<br>Plant Production and Soil Science<br>MSc (Agric)<br>Unrestricted

Water use by mature and sprout (coppice) forms of Emory oak (Quercus emoryi) was estimated by the sap-flow method. Five standards and five coppice trees were sampled in an area that had been harvested for fuelwood and five mature trees were sampled in an uncut area. Differences were recognized between coppice and standards in the cut area and between coppice trees and mature trees from the uncut area. Regression equations were derived relating estimated annual water use to tree diameter, height, and crown measurements for both cut- and uncut-area trees. Seasonal water use by each tree form showed relationship to precipitation, but little relationship to temperature and relative humidity. Woodland density and tree size measurements facilitate extrapolation of water use from the 15 sampled trees to a per area basis. Water use was approximately 1900 cubic meters per hectare per year, based upon drc measurements, for the uncut area and 3168 cubic meters for the cut area. Estimated water use on a per unit area was approximately 1.67 times greater for the cut area than the uncut area.

Doctor of Philosophy<br>Division of Biology<br>Jesse B. Nippert<br>Water availability is a key driver of many plant and ecosystem processes in tallgrass prairies, yet we have a limited understanding of how grassland plants utilize water through space and time. Considering that tallgrass prairies experience tremendous heterogeneity in soil resources, identifying spatiotemporal variation in plant ecohydrology is critical for understanding current drivers of plant responses to water and for predicting ecosystem responses to future changes in climate. Here, I investigated the patterns, drivers, and ecological consequences of plant water use (e.g., water uptake, water redistribution, and water loss) in a native tallgrass prairie located in northeastern Kansas, USA. Using a combination of leaf gas exchange, sap flow, and isotopic techniques, I addressed four main questions: 1) How does fire and grazing by bison impact use of water from different sources and niche overlap for common grasses, forbs, and shrubs? 2) Does hydraulic lift occur in grazed and ungrazed tallgrass prairie, and does this impact facilitation for water within grassland communities? 3) What are the patterns and drivers of nocturnal transpiration in common grassland species? 4) How does diel stem sap flow and canopy transpiration vary among common grassland species? I found that bison grazing increased the depth of water uptake by Andropogon gerardii and Rhus glabra, reducing niche overlap with co-occurring species. Conversely, grazing did not affect hydraulic lift, which was generally uncommon and likely limited by nocturnal transpiration. Further, leaf gas exchange measurements indicated that nocturnal transpiration occurred commonly in tallgrass prairie plants and was greatest among grasses and early in the growing season. Nocturnal transpiration was not driven by vapor pressure deficit or soil moisture, as commonly observed in other systems, but was regulated by nocturnal stomatal conductance in most species. Finally, I found that daytime sap flow rates were variable among species and functional types, with larger flux rates among woody species. Nocturnal sap flow rates were more consistent across species, which caused nighttime sap flow and transpiration to account for a larger proportion of daily flux rates in grasses than in forbs or shrubs. These results show that water uptake, water redistribution, and water loss are all influenced by different biotic and abiotic drivers and have varying ecological impacts across a heterogeneous landscape. Additionally, extensive differences in water flux exist among co-occurring species and plant functional groups, which likely reflect varying strategies to tolerate water limitation. These results suggest that shifts in the abundance of these species with future climate changes, or with ecosystem state changes, will likely impact ecosystem-level water balance.

Thesis (M.S.) -- University of Maryland, College Park, 2005.<br>Thesis research directed by: Dept. of Natural Resource Sciences and Landscape Architecture. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

Mestrado em Viticultura e Enologia - Instituto Superior de Agronomia / Faculdade de Ciências - Universidade do Porto<br>The following thesis is included in the European project Innovine (granted agreement nº FT7-311775), which include the collaboration of several institutions with a long range of scientific areas, with the purpose of presenting results of an essay in an Alentejo sub-region – Reguengos. In this essay several sensors were installed for the use of phytomonitorization as a tool to monitor two types of deficit irrigation, RDI – Regulated Deficit Irrigation; SDI – Sustainable Deficit Irrigation. This phytomonitorization will be important in order to understand some determining physiological parameters of a vineyard in response to water stress, using the variety “Touriga Nacional”. For both types of deficit irrigation a representative grapevine was selected, on which the following phytomonitoring sensors were installed - sap flow, leaf and berry temperature and trunk diameter, canopy humidity). Leaf temperatures ranged from 6,1ºC to 48,7ºC in RDI and from 9,2ºC to 47,3ºC in SDI. For the berry temperatures the temperature ranged from 6,1ºC to 49ºC in both modalities. As possible estimators for physiological parameters, when analyzing a single irrigation period, we obtained high determination coefficients for the leaf temperature (R2=0,90 and R2=0,76) when related with the ψb. As possible estimators of ψfd parameters we obtained high determination coefficients for air temperature (R2=0,0,81 and R2=0,78). For the sap flow the determination coefficients were R2=0,63 and R2=0,60 after irrigation and R2=0,80 and R2=0,76 before irrigation. Also for the leaf temperature vs leaf water potential we obtained R2=0,67 and R2=0,67 after irrigation and R2=0,52 and R2=0,59 before irrigation

Water conservation and pollution concerns from nutrient runoff will very likely dictate precise irrigation regimes for nursery managers in Virginia. Maximum plant growth with minimum input of water and fertilizer is becoming increasingly important. Therefore, water use and growth of red and sugar maple (Acer rubrum L. 'Franksred' and Acer saccharum Marsh.) were studied during two years of pot-in-pot (P+P) production and during three years after transplanting to field soil. Three major experiments were completed. The first experiment studied the effect of frequent irrigation (three-times-a-day) versus standard once-a-day irrigation and found that frequent irrigation increased trunk diameter growth of sugar maples in the second production cycle and for red maples in both production cycles. Height growth of neither species was affected by frequent irrigation. A study of sap flow pattern indicated that late day water stress of red maples was partially alleviated by frequent irrigation. In the second experiment, red and sugar maples were transplanted to field soil after one (1-yr) or two (2-yr) years of P+P production. Irrigation frequency requirement decreased as the trees grew and depended on environmental conditions, size at planting, source of water (rainfall versus irrigation) and species. Height and trunk diameter of 1-yr red maple was equal to that of 2-yr trees after only one year. Height and trunk diameter differences between 1-yr and 2-yr sugar maple trees persisted three years after transplanting. In the third experiment water use of 1-yr and 2-yr red and sugar maple while in P+P production was investigated. Four models of daily water-use were developed. A simple model that is suitable for growers includes species, trunk cross-sectional area (BA) and air temperature (TA) observations. An environmental model was developed using the Penman-van Bavel estimate of evapotranspiration (ET). ET required modifications based on tree characteristics, air temperature, windspeed and relative humidity to be an effective predictor of water-use. A complex model was based on a sine-cosine function of day-of-the-year. This model fits water-use data well for each species and production cycle and includes BA, ET and TA. An alternate simpler model requires only day-of-the-year, TA and BA, offering growers a relatively simple and accurate model of water use.<br>Ph. D.