Agricultural and Forest Meteorology最新文献

{"title":"Geometry and surface manipulation impact on passive dew and rain collection","authors":"","doi":"10.1016/j.agrformet.2024.110180","DOIUrl":"10.1016/j.agrformet.2024.110180","url":null,"abstract":"<div><p>In water-scarce regions, passive dew collectors may serve as vital supplementary water sources by collecting dew and rainwater, especially in arid or semi-arid African areas. This study examined enhancements to the standard passive dew collectors through a field experiment, which includes modification such as increased surface roughness through sandblasting (25 % coverage), adjusting panel geometry with sharp edges, and adding five cotton wires on the condensing surface. The dew was collected through gravity induced collection method, meaning it was not scraped from the panels.</p><p>The experiment was conducted in a field condition in Helsinki, Finland between Jun 17 and Aug 31, 2022. Panel performance was analysed and compared based on their respective cumulative dew and image analysis of droplets behavioural changes during a dew night event occurring between 10 pm and 4 am.</p><p>Over the 75 days (43 dew events), the partially sandblasted and standard panel each collected 3.4 mm of dew, while the wire panel accumulated 3.0 mm and ridge 2.7 mm. Aside from the partially sandblasted panel, both ridge and wire panels consistently demonstrated lower dew collection rates than the standard panel, with average reduction of 24 % and 16 %, respectively. Theoretical dew amounts were modelled, confirming only dew-related events with a matching trend. However, the model overestimate dew amounts, especially during low-yield events. This discrepancy may be attributed to the experiment's passive gravity-induced collection method, which resulted in incomplete droplet collection. The neglected amount could explain the difference between measured and modelled dew.</p><p>The partially sandblasted panel exhibited better performance under specific meteorological conditions, notably when relative humidity level &gt;75 %. Additionally, over the entire duration of the experiment the wire panel improved rainwater collection by 4.3 mm (8 % increase, total 56.3 mm) compared with the standard panel (52.0 mm).</p></div>","PeriodicalId":50839,"journal":{"name":"Agricultural and Forest Meteorology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0168192324002934/pdfft?md5=872f8883c4b55f35b6c909752263adf7&pid=1-s2.0-S0168192324002934-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141910710","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Solar-induced fluorescence-based phenology of subtropical forests in China and its response to climate factors","authors":"","doi":"10.1016/j.agrformet.2024.110182","DOIUrl":"10.1016/j.agrformet.2024.110182","url":null,"abstract":"<div><p>Vegetation phenology refers to the cyclical changes of plant development in different seasons of the year, and is the result of the interaction between environmental factors and biological internal regulatory mechanisms. Current large-scale phenology studies mainly use vegetation indices for remote sensing retrieval, while the greenness information of subtropical forests is inconspicuous, causing regular vegetation indices to retrieve their phenology ineffectively. SIF (Solar-induced chlorophyll fluorescence) is strongly coupled with GPP (Gross Primary Productivity), and has great potential in vegetation phenology research. In this study, we used m-SG (modified Savitzky-Golay) filter to reconstruct OCO-2 (Orbiting Carbon Observatory 2) GOSIF time-series, and used D-L (Double-Logistic) curve fitting to retrieve subtropical forests phenology in China from 2001 to 2018. Then we used phenology retrieved from GPP products and flux GPP as well as phenology observation data to validate the GOSIF phenology. Finally, we analyzed the spatiotemporal distribution pattern of subtropical forests phenology and the influence of climate factors on it. The results showed that: (1) GOSIF can retrieve subtropical forests phenology, and the R² of SOS (Start of Growth Season), EOS (End of Growth Season) and LOS (Length of Growth Season) based on GOSIF and GPP products reached 0.50, 0.68, 0.59, respectively, while the R² of SOS, EOS, and LOS based on GOSIF and flux GPP as well as phenology observation data were 0.20, 0.43, 0.56, respectively. (2) The spatial distribution of subtropical forests phenology showed that SOS gradually delayed, EOS gradually advanced and LOS gradually shortened from southeast to northwest. Moreover, different types of forests showed different trends of advanced SOS, delayed EOS and prolonged LOS over time. (3) The annual average minimum temperature was the main climate factor affecting the subtropical forests phenology while the impact of annual total precipitation also cannot be ignored. For every 1 °C increase in the annual average minimum temperature, the overall SOS advanced by 2.94 days, EOS delayed by 2.14 days and LOS prolonged by 4.91 days.</p></div>","PeriodicalId":50839,"journal":{"name":"Agricultural and Forest Meteorology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0168192324002958/pdfft?md5=98248c456d22938fc06674faae874376&pid=1-s2.0-S0168192324002958-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141910713","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Trees in cooler regions are more vulnerable to thermal stress: Evidence from temperate poplar plantations in Northern China during the 2022 heatwaves","authors":"","doi":"10.1016/j.agrformet.2024.110181","DOIUrl":"10.1016/j.agrformet.2024.110181","url":null,"abstract":"<div><p>Climate change is resulting in more intense and frequent heatwaves, posing a potential threat to the structure and function of forest biome. However, due to the lack of <em>in-situ</em> data, the responses of forest plantations to heatwaves and the role of growth environments and management practices in mitigating these effects remain poorly understood. To address these knowledge gaps, we took advantage of the 2022 summer heatwave to assess their impacts on 8-year-old poplar plantations in Northern China characterized by differing thermal environments (cooler vs. warmer). Stem daily radial increment and sap flow density were continuously monitored in two regions. Additionally, physiological traits, such as leaf gas exchange and water potential, were measured in the warmer region with two different irrigation treatments. Our results revealed that poplar trees in the cooler region experienced more pronounced negative effects from heatwaves compared to those in the warmer region. Poplar trees exhibited strong physiological plasticity to cope with heatwave stress, with increased sap flow density observed in both regions during heatwaves, facilitating a transpiration-cooling effect for minimizing thermal damage. However, increased transpiration rate also led to stored stem water depletion and higher tree water deficit. The ability of trees to regulate internal water balance, likely dependent on their root water supply capacity, accounted for the different responses of poplar growth to heatwaves in various regions. Unexpectedly, while irrigation assisted the functioning of poplar trees in some aspects, it did not alter their overall growth and physiological performance under heatwave conditions, possibly due to their deep root systems. Overall, growth environment temperatures and physiological plasticity are crucial factors affecting the ability to withstand thermal stress, and these variations will allow trees to persist in fluctuating environments. Our findings offer valuable insights for sustainable forest management under extreme climate conditions.</p></div>","PeriodicalId":50839,"journal":{"name":"Agricultural and Forest Meteorology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141910717","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Attention mechanism-based deep learning approach for wheat yield estimation and uncertainty analysis from remotely sensed variables","authors":"","doi":"10.1016/j.agrformet.2024.110183","DOIUrl":"10.1016/j.agrformet.2024.110183","url":null,"abstract":"<div><p>Rapid and accurate crop yield estimation is an imperative aspect of agricultural planning that is important for crop management, food security and commodity trading. There are many related factors affecting wheat yield and the relationship between them and the yield is complicated, with nonlinear spatial-temporal characteristics that are difficult to describe accurately with mathematical functions. Deep learning models can fit complex nonlinear functions efficiently and transform input data into high-dimensional features automatically. However, the feature learning process does not produce transparent information. There has been considerable evidence that the ability of attention mechanism for modeling interpretation has been demonstrated in many fields. Therefore, an attention mechanism-based multi-level crop network (AMCN) was proposed to estimate the county level wheat yield based on remote sensing data and meteorological data. To explore the difference in spatio-temporal feature extraction ability under parallel and series structures when combining CNN with LSTM, we designed the AMCN models with two forms of structure, one is a parallel module of LSTM and CNN (AMCN1) and the other is a serial connection module between LSTM and CNN (AMCN2). Our results showed that the AMCN1 model provided an improved estimation accuracy as compared to that of the AMCN2 model. We also found remote sensing data contributed significantly to crop yield estimation mainly at the late growth stages, meteorological data provided additional information mainly at the early growth stage. We assessed the estimated uncertainty using Monte Carlo dropout, and the results indicated that the uncertainty level decreased gradually as the growth stages proceeded. In addition, extreme events such as drought and uneven distribution characteristics of the samples were associated with much higher estimated uncertainties. The study highlighted that the proposed model provided more accurate yield estimations by taking advantage of multi-level crop networks while considering the uncertainty involved in model estimations.</p></div>","PeriodicalId":50839,"journal":{"name":"Agricultural and Forest Meteorology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141891981","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Grassland biomass allocation across continents and grazing practices and its response to climate and altitude","authors":"","doi":"10.1016/j.agrformet.2024.110176","DOIUrl":"10.1016/j.agrformet.2024.110176","url":null,"abstract":"<div><p>Biomass allocation in grasslands is key to understanding plant response to environmental changes and grazing management. Yet, global studies on how this split between above-ground and below-ground biomass varies across continents and grazing practices are notably scarce. We employ a comprehensive field-oriented grassland database to examine differences in total net primary productivity (TNPP), above-ground net primary productivity (ANPP), below-ground net primary productivity (BNPP), and the BNPP to ANPP ratio across continents and between grazed and non-grazed grasslands. Oceania showed the greatest ANPP (916 g·m⁻²·a⁻¹), while Asia had the lowest (192 g·m⁻²·a⁻¹). BNPP values were similar among Oceania, Africa, and Asia (∼600 g·m⁻²·a⁻¹), significantly exceeding those in Europe (289 g·m⁻²·a⁻¹) and North America (408 g·m⁻²·a⁻¹). South America, Africa, and Oceania had the highest TNPP (around 1418 g·m⁻²·a⁻¹ to 1466 g·m⁻²·a⁻¹), while Europe had the lowest TNPP (344 g·m⁻²·a⁻¹). The BNPP to ANPP ratio was highest in South America (4.17) and Asia (3.46). Global differences in TNPP and BNPP between grazed and non-grazed grasslands were minimal, but ANPP (169 g·m⁻²·a⁻¹ and 198 g·m⁻²·a⁻¹, respectively) and the BNPP to ANPP ratio (4.87 and 2.40, respectively) differed significantly. Across continents and grazing practices, climate had a greater role in regulating grassland biomass allocation than altitude, and warming may have a more detrimental impact on grazed grasslands than non-grazed grasslands. Distinct biomass allocation trends under various continental and grazing conditions exert effects on the economic and ecological functions of grasslands. Our study underscores the need for balanced grassland utilization strategies at a global scale. This involves optimizing grazing in high ANPP grasslands and protecting those with significant BNPP, thereby contributing to a sustainable and ecologically sound use of grasslands in the future.</p></div>","PeriodicalId":50839,"journal":{"name":"Agricultural and Forest Meteorology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141891999","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Integrated large-eddy simulation for modeling plant-tissue warming induced by wind machines in an orchard canopy","authors":"","doi":"10.1016/j.agrformet.2024.110175","DOIUrl":"10.1016/j.agrformet.2024.110175","url":null,"abstract":"<div><p>Wind machines are increasingly used to mitigate spring frost damage in agricultural sectors. Complementing quasi-3D temperature measurements to quantify the warming effects of wind machines (Dai et al., 2023), this study develops a numerical model to quantify warming effects on air and plant tissues and resolve the dynamic interplay between turbulent rotating plumes and canopy structure. We implement an integrated model in a large-eddy simulation and validate the model against field observations. Simulation results show remarkable agreement with the air mixing and warming effects observed during wind machine operation in Dai et al. (2023). Simulation results reveal significant air and leaf warming near the wind machine due to direct jet-mixing. Beyond 20 m from the machine (<span><math><mrow><mn>3</mn><mtext>–</mtext><mn>4</mn></mrow></math></span> rotor diameters), while wind velocities drop rapidly, the warming is sustained and gradually decreases over distance. This sustained warming, without direct jet mixing, likely results from the advection of jet-entrained warm air. The warming extends 150 m upstream and 550 m downstream, influenced by the background wind. This difference is attributed to the interaction between the machine-induced jet and the background wind, forming convergence patterns when jets oppose the wind and extended warming plumes in wave-like patterns when jets align with the wind. Cross-stream warming symmetrically extends about 250 m. Within these warming regions, leaf temperatures closely follow air temperatures due to strong turbulent heat exchanges. Outside the warming zone, radiative cooling prevails, bringing the leaf–air temperature difference back to approximately 1 degree. These findings collectively give new insights into interactions between the induced warming plumes and air flows within the canopy and provide a useful tool to optimize operational wind machine deployment. This integrated model uniquely provides a full, multi-process representation of outdoor reality with respect to wind machine operation in orchards.</p></div>","PeriodicalId":50839,"journal":{"name":"Agricultural and Forest Meteorology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0168192324002880/pdfft?md5=c87ad27b034fea1d36f4a8eef9a87d66&pid=1-s2.0-S0168192324002880-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141892004","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Agreement of multiple night- and daytime filtering approaches of eddy covariance-derived net ecosystem CO2 exchange over a mountain forest","authors":"","doi":"10.1016/j.agrformet.2024.110173","DOIUrl":"10.1016/j.agrformet.2024.110173","url":null,"abstract":"<div><p>The assessment of net ecosystem CO<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> exchange often relies on eddy covariance measurements. Under stable, low-turbulence conditions, the measured flux may not be representative of the net ecosystem exchange (NEE), as unmeasured fluxes (e.g., advection) can become relevant. Consequently, such periods need to be filtered out for robust flux calculations. Typically, the focus lies on nighttime filtering alone, yet daytime flux measurements can also be unrepresentative. This study evaluates well-established and novel filtering methods applied both at nighttime and daytime at a mountain forest site in Tyrol, Austria (Forest-Atmosphere-Interaction-Research (FAIR) site, AT-Mmg). Established methods, including friction velocity filtering, its counterpart using the standard deviation of vertical velocity fluctuations (<span><math><msub><mrow><mi>σ</mi></mrow><mrow><mi>w</mi></mrow></msub></math></span>) and an after-sunset flux maxima approach (commonly referred to as <em>van Gorsel method</em>), are compared. Additionally, we use a more recent approach with a physically-derived measure of flow decoupling for filtering. Moreover, we introduce a novel K-means clustering approach that groups flow situations into clusters based on vertical profiles of temperature, <span><math><msub><mrow><mi>σ</mi></mrow><mrow><mi>w</mi></mrow></msub></math></span> and wind speed. Clusters in which the measured flux is expected to be a reasonable NEE estimate are retained. Such scenarios are Foehn periods, early-night situations with high turbulence and low stability, or well-mixed afternoon conditions. Despite being based on widely differing assumptions, the various filtering approaches yielded similar carbon budget estimates over 14 months of measurements (-224 to -286 g C m⁻² for nighttime filtering and -440 to -382 g C m⁻² for all-day filtering), in contrast to the unfiltered budget of -534 g C m⁻². Nighttime filtering results in higher respiration rates throughout the night, while daytime filtering suggests increased morning carbon uptake compared to unfiltered data.</p></div>","PeriodicalId":50839,"journal":{"name":"Agricultural and Forest Meteorology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0168192324002867/pdfft?md5=41ffbd20d6a649c4c990d2b0f11c9c23&pid=1-s2.0-S0168192324002867-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141891998","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Eddy covariance fluxes of greenhouse gasses observed in a renewed pasture in the southeast of Brazil","authors":"","doi":"10.1016/j.agrformet.2024.110177","DOIUrl":"10.1016/j.agrformet.2024.110177","url":null,"abstract":"<div><p>The recovery of degraded pastures and the increase in their capacity for storing carbon is a key strategy in Brazil's commitment to meeting its Nationally Determined Contribution (NDC) to the international effort to halt global warming. Here we report the fluxes of CO₂, N₂O and CH₄ gasses and their balances, obtained by the eddy covariance method, from a representative pasture area in southeast Brazil. The measurements covered more than five years, starting with the old degraded pasture, covering the renewal process and then the re-establishment of pasture. The latter only received nitrogen fertilization once after the renewal – the common practice. The net ecosystem carbon balance (NECB), which considered the sum of the net ecosystem exchange (NEE_pasture) of CO₂ and methane (FCH4_pasture) without the cattle respiration and enteric fermentation, as well the export/import of carbon by grazing and as feces (stocking rates of 1.8 to 3.3 AU ha⁻¹), was positive in the old pasture (236 ± 104 g CO₂ <em>m</em>⁻² year⁻¹) representing a source to the atmosphere, but a sink (negative) during the first year of the renewal (-1603 ± 122 g CO₂ <em>m</em>⁻² year⁻¹) when it was fertilized and the recorded rainfall was normal. In the following two years it was neutral (77 ± 93 and 5 ± 100 g CO₂ <em>m</em>⁻² year⁻¹), partially a consequence of the lower rainfall received. In the fourth year it was a sink again (-736 ± 131 g CO₂ <em>m</em>⁻² year⁻¹). On average the cumulative fluxes of CH₄ (42 ± 19 g CO₂ eq. <em>m</em>⁻² year⁻¹) without the animals’ enteric fermentation and N₂O (20 ± 10 g CO₂ eq. <em>m</em>⁻² year⁻¹) were small and positive, being offset by the net carbon gain. The NECB for this site covering the period of measurements was an overall source of 671 ± 254 g CO₂ <em>m</em>⁻².</p></div>","PeriodicalId":50839,"journal":{"name":"Agricultural and Forest Meteorology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141892001","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Drought-induced ecosystem resistance and recovery observed at 118 flux tower stations across the globe","authors":"","doi":"10.1016/j.agrformet.2024.110170","DOIUrl":"10.1016/j.agrformet.2024.110170","url":null,"abstract":"<div><p>Drought resistance and drought recovery are important metrics of ecosystems in responding to extreme climate events. However, it remains unclear how drought resistance and drought recovery vary across different ecosystems and whether an internal relationship exists between them. Here, we used observed evapotranspiration and gross primary productivity from 118 flux tower stations worldwide to investigate drought resilience in nine ecosystems. Our results show that drought resistance is higher for evergreen forests but lower for croplands and shrublands. Overall, the ecosystem recovery times ranged from 4.1 to 6.7 months, with a monthly recovery rate ranging from 8.5% to 24.4%. Drought resistance had a negative relationship (R² = 0.61-0.67, p ≤ 0.01) with the drought recovery rate for the nine selected ecosystems, particularly under mild and moderate drought events. This is beneficial for narrowing the difference in recovery time between ecosystems. Our results provide insights for understanding ecosystem behaviors under climate extremes.</p></div>","PeriodicalId":50839,"journal":{"name":"Agricultural and Forest Meteorology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141892000","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Transpiration and water use sources of poplar (Populus × xiaozhuanica) plantations with 7-years vs. 20-years old in a semiarid sandy region of Northeast China","authors":"","doi":"10.1016/j.agrformet.2024.110171","DOIUrl":"10.1016/j.agrformet.2024.110171","url":null,"abstract":"<div><p>Determination of transpiration and water use sources of trees in arid and semiarid areas is crucial for forest management under climate change scenes. Here, seasonal variations in transpiration and water use sources of the 7– (1167 trees ha⁻¹) and 20 (475 trees ha⁻¹)–year–old poplar (<em>Populus</em> × <em>xiaozhuanica</em>) plantations were determined based on thermal dissipation and stable isotope methods. Results showed that transpiration per unit leaf area averaged 1.6 and 1.7 mm d⁻¹ for the 7– and 20–year–old plantations during the measurement period, respectively, whereas stand transpiration (E_s) was 1.5 and 1.4 mm d⁻¹. Sensitivity of E_s to climatic variables decreased with reduction of soil moisture for both plantations, but larger decrease for 7–year–old plantation indicated higher sensitivity to drought. E_s of both plantations significantly decreased with decline of groundwater levels, but E_s of 7–year–old plantation was more limited by decline of groundwater level under drought conditions. During the measurement period, accumulated E_s occupied 45 % and 44 % of precipitation for 7– and 20–year–old plantations, respectively, indicating that water consumption of plantation did not increase with increasing stand age. Isotope data indicated that both 7– and 20–year–old trees switched water sources from 0 to 100 cm soil layer and groundwater in spring to 0–200 cm soil water and groundwater in summer as soil moisture and groundwater level decreased, but contribution of groundwater decreased from 47 % to 32.3 % and from 39.6 % to 37 % for 7– and 20–year–old plantation, respectively. These findings indicated that transpiration of poplar plantations did not vary with stand age, but a decline of groundwater level reduced contribution of groundwater to transpiration for 7–year–old poplar plantations and thus exacerbated negative effect of soil drought on transpiration compared with 20–year–old poplar plantation.</p></div>","PeriodicalId":50839,"journal":{"name":"Agricultural and Forest Meteorology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141954445","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}