Water Regime Monitoring of the Royal Walnut (Juglans regia L.) Using Sap Flow and Dendrometric Measurements

Changes in the distribution of annual rainfall totals, together with the increase in temperature over the last 40 years, are causing more frequent periods of drought, and plants are more often exposed to water stress. The aim of this study was to monitor the effect of different water regimes (irrigated and non-irrigated) of individuals of walnut tree (Juglans regia L.) in a private orchard located in the West of Slovakia. Our research was focused on dendrometric and sap flow measurements in the period from 28 March to 2 June 2019. The results showed differences in the sap flow of walnut trees during the budbreak period: when trees were irrigated, sap flow in the diurnal cycle was around 130 g·h−1 (20.48%), higher than in the non-irrigated treatment. Dendrometric differences between the irrigated and non-irrigated treatments were not significant. The sap flow data in the flowering period of the irrigated variant were slightly higher at 150 g·h−1 (35.62%) than non-irrigated. Dendrometric differences were more significant when the difference between the variants was more than 1.5 mm. Continuation of this research and analysis of the data obtained in the coming years will allow us to evaluate the effects of the environment on fruit trees in the long term.

Assessing water requirement of orange trees using sap flow measurements in Narkhed-Pandhurna critical zone observatory (CZO) in central India

We used thermal dissipation method for sap flux measurements in orange trees to assess its water requirement in Narkhed-Pandhurna region. Thermal Dissipation Probe (TDP) sensors were installed in 5-year old (young) and 15-year old (mature) orange trees to measure the diurnal sap flux variations in trees during November 21, 2019, to January 31, 2020 (71 days). The results show that the maximum daily water uptake by the 5-year old tree was 1.1 L observed on 39th day of measurement (December 29, 2019) and in the 15-year old tree it was 5.0 L, and it observed on 38th day (December 28, 2019) of measurement. The cumulative water uptake during the study period by the 5-year old tree was 49.0 L, and the 15-year old tree consumed 257.4 L of water. The results were compared with the recommended irrigational values of Indian Horticulture Board (IHB), Government of India (GoI) and Groundwater Survey and Development Agency (GSDA), Government of Maharashtra (GoMH) for orange orchards. The initial investigation shows that recommended guidelines for irrigation of orange trees are exorbitantly high and needs to be revised. The sap flow methods are more precise that can measure sap flow at a very short interval and can generate a time series of data. It can be used to revise the guidelines with the aim to conserve water and propose precision water irrigation for the study area in particular and different agro-climatic zones of the country in general.

Global transpiration data from sap flow measurements: the SAPFLUXNET database

Plant transpiration links physiological responses of vegetation to water supply and demand with hydrological, energy, and carbon budgets at the land–atmosphere interface. However, despite being the main land evaporative flux at the global scale, transpiration and its response to environmental drivers are currently not well constrained by observations. Here we introduce the first global compilation of whole-plant transpiration data from sap flow measurements (SAPFLUXNET, https://sapfluxnet.creaf.cat/, last access: 8 June 2021). We harmonized and quality-controlled individual datasets supplied by contributors worldwide in a semi-automatic data workflow implemented in the R programming language. Datasets include sub-daily time series of sap flow and hydrometeorological drivers for one or more growing seasons, as well as metadata on the stand characteristics, plant attributes, and technical details of the measurements. SAPFLUXNET contains 202 globally distributed datasets with sap flow time series for 2714 plants, mostly trees, of 174 species. SAPFLUXNET has a broad bioclimatic coverage, with woodland/shrubland and temperate forest biomes especially well represented (80 % of the datasets). The measurements cover a wide variety of stand structural characteristics and plant sizes. The datasets encompass the period between 1995 and 2018, with 50 % of the datasets being at least 3 years long. Accompanying radiation and vapour pressure deficit data are available for most of the datasets, while on-site soil water content is available for 56 % of the datasets. Many datasets contain data for species that make up 90 % or more of the total stand basal area, allowing the estimation of stand transpiration in diverse ecological settings. SAPFLUXNET adds to existing plant trait datasets, ecosystem flux networks, and remote sensing products to help increase our understanding of plant water use, plant responses to drought, and ecohydrological processes. SAPFLUXNET version 0.1.5 is freely available from the Zenodo repository (https://doi.org/10.5281/zenodo.3971689; Poyatos et al., 2020a). The “sapfluxnetr” R package – designed to access, visualize, and process SAPFLUXNET data – is available from CRAN.

CATCHMENT RUNOFF MODELING APPLYING SAP FLOW DATA (CASE OF THE UPPER USSURI RIVER)

Представлены результаты использования данных полевых наблюдений для моделирования речного стока малого водосбора в верховьях р.Уссури. В качестве входного потока данных в гидрологическую модель HBV об эвапотранспирации применены оригинальные данные о стволовом сокодвижении, пересчитанные в объем влаги, транспирируемого древостоем. Показано, что расчетные методы определения эвапотранспирации (Пенмана-Монтейса и Л.Одина) завышают оценки испарения: разница с данными стволового сокодвижения достигает 100 мм слоя за теплый период. Надежной связи между расчетными значениями суточного испарения и измерениями не обнаружено. Выявлено повышение качества расчетов стока при использовании данных стволового сокодвижения в качестве входного потока в гидрологическую модель. The results of applying the field observation data for hydrological modeling in the Upper Ussuri river are presented. The original data of sap flow measurements (recalculated to the evapotranspiration volume of forest stand) was used as input to the HBV model. It is shown that the calculation methods for determining evapotranspiration (Penman-Monteith and L.Oudin) overestimate the daily evaporation volume. In comparison with sap flow data difference reach 100 mm during the warm period. No reliable relationship was found between the calculated values of daily evaporation and measurements. An increase in the quality of runoff calculations is reported while using data from stem sap flow as an input to a hydrological model.

Towards a consistent quantification of ecosystem transpiration and its uncertainty from the SAPFLUXNET database

<p>Transpiration from forests and woodlands is the main component of terrestrial evapotranspiration. Ecosystem-scale transpiration estimates are needed to inform models and remote sensing products so that they can improve their quantification of the magnitudes, spatiotemporal patterns, and environmental sensitivity of transpiration at regional to global scales. Tree-level sap flow measurements can be used to estimate ecosystem transpiration in forests and woodlands and these data are now globally available in the SAPFLUXNET database (Poyatos et al. 2020). However, observational errors, sampling assumptions, and missing data propagate uncertainties in the upscaling process to the ecosystem level. Here we quantify ecosystem transpiration and its uncertainty, from hourly to annual scales, across SAPFLUXNET sites using two different approaches. In a first approach, we estimated hourly sap flow per unit basal area at the species level, which was then aggregated to the stand level using species-specific basal areas available in SAPFLUXNET metadata. In this approach, uncertainty was quantified from the observed variability in tree-level sap flow within a species. In a second approach, we used empirical relationships between tree diameter and sap flow to obtain stand-level transpiration and propagated the uncertainty in this relationship to the stand-level values. For both approaches, sap flow data obtained with uncalibrated heat dissipation probes were also adjusted using a recently published correction based on sap flow calibrations. The different upscaling methods, implemented in R code, will allow reproducible upscaling and uncertainty quantification from SAPFLUXNET datasets, paving the way towards a better understanding of ecosystem transpiration and its controls across the globe.</p><p><span>Poyatos, R., Granda, V., Flo, V., […], Steppe, K., Mencuccini, M., Martínez-Vilalta, J. (2020). </span>Global transpiration data from sap flow measurements: the SAPFLUXNET database, Earth System Science Data Discussions, 1–57, .</p>

Potential Non-Invasive Technique for Accessing Plant Water Contents Using a Radar System

Sap flow measurements of trees are today the most common method to determine evapotranspiration at the tree and the forest/crop canopy level. They provide independent measurements for flux comparisons and model validation. The most common approach to measure the sap flow is based on intrusive solutions with heaters and thermal sensors. This sap flow sensor technology is not very reliable for more than one season crop; it is intrusive and not adequate for low diameter trunk trees. The non-invasive methods comprise mostly Radio-frequency (RF) technologies, typically using satellite or air-born sources. This system can monitor large fields but cannot measure sap levels of a single plant (precision agriculture). This article studies the hypothesis to use of RF signals attenuation principle to detect variations in the quantity of water present in a single plant. This article presents a well-defined experience to measure water content in leaves, by means of high gains RF antennas, spectrometer, and a robotic arm. Moreover, a similar concept is studied with an off-the-shelf radar solution—for the automotive industry—to detect changes in the water presence in a single plant and leaf. The conclusions indicate a novel potential application of this technology to precision agriculture as the experiments data is directly related to the sap flow variations in plant.