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Sap flow measurement

What is sap flow?

Sap flow is the movement of water in roots, stems and branches of plants. Typically measured in sapwood xylem, or the water-conducting tissue of the plant, sap flow provides information on water status and water use of plants.

In the field of ecophysiology, sap flow is important in understanding plant transpiration and drought responses. In agriculture, it is important in the measurement of plant water use for irrigation decisions.

How to measure sap flow in plants?

Sap flow is measured by inserting sensors into the xylem tissue of the plant. The sensors are then used to trace known amount of applied heat. In some plants, sensors are attached to either the stem or the trunk. A robust mathematical approach to trace this heat is using heat ratio method.

SFM1C Installed with Dendrometer in Orchard

How the heat ratio method works

The heat ratio method (Burgess, Adams, Turner, Beverly, Ong, Khan and Bleby, 2001) is based on the temperature ratio created between probes positioned symmetrically above and below a line heater. A pulse of heat is provided by a heater needle located in the sapwood area, with a downstream and upstream needle that are accurately spaced to measure the heat difference over time. This measurement, combined with data on the sapwood area allows for the calculation of the sap flow.

In both SFM1 and SFM1x, there are two temperature probes and the central heater probe. A controlled heat pulse is emitted from the central heater probe, which the temperature probes measure as the heat is transported by the sap moving up or down the xylem. The sensors subsequently measure the sap flow velocity, with calculations performed within the SFM1x to derive the plant water use.

2023

Benyahia, F., Bastos Campos, F., Ben Abdelkader, A., Basile, B., Tagliavini, M., Andreotti, C., & Zanotelli, D. (2023). Assessing Grapevine Water Status by Integrating Vine Transpiration, Leaf Gas Exchanges, Chlorophyll Fluorescence and Sap Flow Measurements. Agronomy, 13(2), 464. https://doi.org/10.3390/agronomy13020464
Buyinza, J., Muthuri, C. W., Denton, M. D., & Nuberg, I. K. (2023). Impact of tree pruning on water use in tree-coffee systems on smallholder farms in Eastern Uganda. Agroforestry Systems, 97(5), 953–964. https://doi.org/10.1007/s10457-023-00842-2
Doody, T. M., Gao, S., Vervoort, W., Pritchard, J., Davies, M., Nolan, M., & Nagler, P. L. (2023). A river basin spatial model to quantitively advance understanding of riverine tree response dynamics to water availability and hydrological management. Journal of Environmental Management, 332, 117393. https://doi.org/10.1016/j.jenvman.2023.117393
Perron, N., Baltzer, J. L., & Sonnentag, O. (2023). Spatial and temporal variation in forest transpiration across a forested boreal peat landscape. Hydrological Processes, n/a(n/a), e14815. https://doi.org/10.1002/hyp.14815
Stevenson, J. L., Birkel, C., Comte, J.-C., Tetzlaff, D., Marx, C., Neill, A., Maneta, M., Boll, J., & Soulsby, C. (2023). Quantifying heterogeneity in ecohydrological partitioning in urban green spaces through the integration of empirical and modelling approaches. Environmental Monitoring and Assessment, 195(4), 468. https://doi.org/10.1007/s10661-023-11055-6
Sun, X., Li, J., Cameron, D., Zhou, A., Bayetto, P., & Moore, G. (2023). Assessment of the influence of an Australian native eucalypt, Corymbia maculata, on soil desiccation in a temperate climate. Acta Geotechnica. https://doi.org/10.1007/s11440-023-02075-0
2022
Asiimwe, G., Jaafar, H., Haidar, M., & Mourad, R. (2022). Soil Moisture or ET-Based Smart Irrigation Scheduling: A Comparison for Sweet Corn with Sap Flow Measurements. Journal of Irrigation and Drainage Engineering, 148(6), 04022017.
Campos, F. B., Montagnani, L., Benyahai, F., Callesen, T. O., Gonzales, C. V., Tagliavini, M., & Zanotelli, D. (2022). Disentangling the main sources of evapotranspiration in a vineyard. EGU General Assembly 2022. https://doi.org/https://doi.org/10.5194/egusphere-egu22-8231
Edwards, E. J., Betts, A., Clingeleffer, P. R., & Walker, R. R. (2022). Rootstock-conferred traits affect the water use efficiency of fruit production in Shiraz. Australian Journal of Grape and Wine Research, 28(2), 316–327. https://doi.org/10.1111/ajgw.12553
El Hajj, M. M., Almashharawi, S. K., Johansen, K., Elfarkh, J., & McCabe, M. F. (2022). Exploring the use of synthetic aperture radar data for irrigation management in super high-density olive orchards. International Journal of Applied Earth Observation and Geoinformation, 112, 102878. https://doi.org/10.1016/j.jag.2022.102878
Jardine, K. J., Cobello, L. O., Teixeira, L. M., East, M.-M. S., Levine, S., Gimenez, B. O., Robles, E., Spanner, G., Koven, C., Xu, C., Warren, J. M., Higuchi, N., McDowell, N., Pastorello, G., & Chambers, J. Q. (2022). Stem respiration and growth in a central Amazon rainforest. Trees. https://doi.org/10.1007/s00468-022-02265-5
Lakmali, S., Benyon, R. G., Sheridan, G. J., & Lane, P. N. J. (2022). Change in fire frequency drives a shift in species composition in native Eucalyptus regnans forests: Implications for overstorey forest structure and transpiration. Ecohydrology, 15(3), e2412. https://doi.org/10.1002/eco.2412
Landgraf, J., Tetzlaff, D., Dubbert, M., Dubbert, D., Smith, A., & Soulsby, C. (2022). Xylem water in riparian Willow trees (Salix alba) reveals shallow sources of root water uptake by in situ monitoring of stable water isotopes. Hydrol. Earth Syst. Sci. Discuss., 26, 2073–2092. https://doi.org/https://doi.org/10.5194/hess-2021-456
Luo, Y., & Pacheco-Labrador, J. (2022). Evergreen broadleaf greenness and its relationship with leaf flushing, aging, and water fluxes. Agricultural and Forest Meteorology, 323(109060). https://doi.org/https://doi.org/10.1016/j.agrformet.2022.109060.
Meng, L., Chambers, J., Koven, C., Pastollero, G., Gimenez, B., Jardine, K., Tang, Y., McDowell, N., Negron-Juarez, R., Longo, M., Araujo, A., Tomasella, J., Fontes, C., Mohan, M., & Higuchi, N. (2022). Soil moisture thresholds explain a shift from light-limited to water-limited sap velocity in the Central Amazon during the 2015–16 El Niño drought. Environmental Research Letters, 17.
Montague, M. S., Landhäusser, S. M., McNickle, G. G., & Jacobs, D. F. (2022). Preferential allocation of carbohydrate reserves belowground supports disturbance-based management of American chestnut (Castanea dentata). Forest Ecology and Management, 509, 120078. https://doi.org/10.1016/j.foreco.2022.120078
Peixoto Neto, A. M. L., Cartwright, I., Silva, M. R. F., McHugh, I., Dresel, P. E., Teodosio, B., Jovanovic, D., McCaskill, M. R., Webb, J., & Daly, E. (2022). Linking evapotranspiration seasonal cycles to the water balance of headwater catchments with contrasting land uses. Hydrological Processes, 36(12), e14784. https://doi.org/10.1002/hyp.14784
Schoppach, R., Chun, K. P., & Klaus, J. (2022). Accounting for Dbh and Twi in Prediction of Stand-Scale Sap-Flux Density Reduces the Deviation from Measurement (SSRN Scholarly Paper No. 4129815). https://doi.org/10.2139/ssrn.4129815
Siddiqi, S. A., & Al-Mulla, Y. (2022). Wireless Sensor Network System for Precision Irrigation using Soil and Plant Based Near-Real Time Monitoring Sensors. Procedia Computer Science, 203, 407–412. https://doi.org/10.1016/j.procs.2022.07.053
Smith-Marin, C. M., Muscarella, R., Ankori-Karlinsky, R., Delzon, S., Farrar, S. L., Salva-Sauri, M., Thompson, J., Zimmerman, J. K., & Uriarte, M. (2022). Hydraulic traits are not robust predictors of tree species stem growth during a severe drought in a wet tropical forest. Functional Ecology, n/a(n/a). https://doi.org/10.1111/1365-2435.14235
Sun, X., Li, J., Cameron, D., & Moore, G. (2022). On the Use of Sap Flow Measurements to Assess the Water Requirements of Three Australian Native Tree Species. Agronomy, 12(1), 52. https://doi.org/10.3390/agronomy12010052
Thom, J. K., Fletcher, T. D., Livesley, S. J., Grey, V., & Szota, C. (2022). Supporting Growth and Transpiration of Newly Planted Street Trees With Passive Irrigation Systems. Water Resources Research, 58(1), e2020WR029526. https://doi.org/10.1029/2020WR029526
Yang, J., He, Z., Lin, P., Du, J., Tian, Q., Feng, J., Liu, Y., Guo, L., Wang, G., Yan, J., & Zhao, W. (2022). Variability in Minimal-Damage Sap Flow Observations and Whole-Tree Transpiration Estimates in a Coniferous Forest. Water, 14(16), 2551. https://doi.org/10.3390/w14162551