Identifying Canopy Snow in Subalpine Forests: A Comparative Study of Methods

Water Resources Research, Год журнала: 2025, Номер 61(1)

Опубликована: Янв. 1, 2025

Abstract The interception of snow by the canopy is an important process in water and energy balance cold‐region coniferous forests. Direct measurements are difficult at scales larger than individual trees, requiring indirect methods such as eddy covariance, time‐lapse photography, or modeling. At Niwot Ridge Subalpine Forest AmeriFlux site Colorado Front Range, USA, we compared that estimate simulate presence interception. Timelapse photography images were analyzed using thresholding analysis used to train a Convolutional Neural Network (CNN) model presence. Interception was also estimated from covariance above below canopy, well simulations. These applied over January 2019, with binarized results “ground truth” human labeled calculate Balanced Accuracy Score. highest accuracy achieved CNN predictions. Based on Scores, select extended for 2018/2019 winter. All provided insight into subalpine forest but presented challenges, including differing flux footprints above‐ below‐canopy inability red‐green‐blue imagery monitor night, during sunrise, sunset.

Язык: Английский

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Seasonal timing of fluorescence and photosynthetic yields at needle and canopy scales in evergreen needleleaf forests

Ecology, Год журнала: 2024, Номер 105(10)

Опубликована: Авг. 19, 2024

The seasonal timing and magnitude of photosynthesis in evergreen needleleaf forests (ENFs) has major implications for the carbon cycle is increasingly sensitive to changing climate. Earlier spring can increase uptake over growing season or cause early water reserve depletion that leads premature cessation increased loss. Determining start end ENFs challenging due a lack field measurements difficulty interpreting satellite data, which are impacted by snow cloud cover, pervasive "greenness" these systems. We combine continuous needle-scale chlorophyll fluorescence with tower-based remote sensing gross primary productivity (GPP) estimates at three ENF sites across latitudinal gradient (Colorado, Saskatchewan, Alaska) link physiological changes signals during transition seasons. derive theoretical framework observations solar-induced (SIF) solar intensity-normalized SIF (SIF

Язык: Английский

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Predicted Future Changes in the Mean Seasonal Carbon Cycle Due to Climate Change

Forests, Год журнала: 2024, Номер 15(7), С. 1124 - 1124

Опубликована: Июнь 28, 2024

Through photosynthesis, forests absorb annually large amounts of atmospheric CO2. However, they also release CO2 back through respiration. These two, opposite in sign, fluxes determine how much the carbon is stored or released into atmosphere. The mean seasonal cycle (MSC) an interesting metric that associates phenology and (C) partitioning/allocation analysis within forest stands. Here, we applied 3D-CMCC-FEM model analyzed its capability to represent main C-fluxes, by validating against observed data, questioning if sink/source seasonality influenced under two scenarios climate change, five contrasting European sites. We found has, current conditions, robust predictive abilities estimating NEE. Model results predict a consistent reduction forest’s capabilities act as C-sink change stand-aging at all Such predicted despite number annual days evergreen increasing over years, indicating downward trend. Similarly, deciduous forests, maintaining relatively stable throughout year century, show their overall capacity. Overall, both types sites future mitigating potential.

Язык: Английский

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Forest carbon uptake as influenced by snowpack and length of photosynthesis season in seasonally snow-covered forests of North America

Agricultural and Forest Meteorology, Год журнала: 2024, Номер 353, С. 110054 - 110054

Опубликована: Май 17, 2024

Язык: Английский

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Assessing the climate benefits of afforestation in the Canadian Northern Boreal and Southern Arctic

Nature Communications, Год журнала: 2025, Номер 16(1)

Опубликована: Фев. 25, 2025

Abstract Afforestation greatly influences several earth system processes, making it essential to understand these effects accurately assess its potential for climate change mitigation. Although our understanding of forest-climate interactions has improved, significant knowledge gaps remain, preventing definitive assessments afforestation's net benefits. In this review, focusing on the Canadian northern boreal and southern arctic, we identify synthesize existing knowledge. The review highlights regional realities, Earth's climatic history, uncertainties in biogeochemical (BGC) biogeophysical (BGP) changes following afforestation, limitations current assessment methodologies, emphasizing need reconcile before drawing firm conclusions about benefits afforestation. Finally, propose an framework which considers multiple forcing components, temporal analysis, future contexts, implementation details. We hope that research discussed inform afforestation policy Canada other circumpolar nations.

Язык: Английский

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Impact of winter warming on CO₂ fluxes in evergreen needleleaf forests

Biogeosciences, Год журнала: 2025, Номер 22(5), С. 1393 - 1411

Опубликована: Март 12, 2025

Abstract. Compared to drought and heat waves, the impact of winter warming on forest CO2 fluxes has been less studied, despite its significant relevance in colder regions with higher soil carbon content. Our objective was test effect exceptionally warm 2020 budget cold-adapted evergreen needleleaf forests across Europe identify contribution climate factors changes fluxes. hypothesis that leads emissions sites due increased ecosystem respiration. To this hypothesis, we used 98 site-year eddy covariance measurements 14 (ENFs) distributed from north south (from Sweden Italy). We a data-driven approach quantify radiation, air temperature, temperature during 2020. results showed decreased net productivity (NEP) significantly most sites. The variables varied sites: southern warmer mean temperatures, radiation had greater influence NEP. Conversely, at sites, played more critical role affecting During 2020, experienced larger anomalies compared other sites; however did not observe increase warming. varying responses NEP different highlight complex interactions between such as radiation. These findings underscore importance integrating effects accurately predict impacts change dynamics.

Язык: Английский

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Geographic variability of the climate response of Scots pine (Pinus sylvestris L.) radial growth in the Middle Urals

Dendrochronologia, Год журнала: 2025, Номер unknown, С. 126329 - 126329

Опубликована: Март 1, 2025

Язык: Английский

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Modelling decadal trends and the impact of extreme events on carbon fluxes in a temperate deciduous forest using a terrestrial biosphere model

Biogeosciences, Год журнала: 2025, Номер 22(7), С. 1781 - 1807

Опубликована: Апрель 10, 2025

Abstract. Changing climatic conditions pose a challenge to accurately estimating the carbon sequestration potential of terrestrial vegetation, which is often mediated by nitrogen availability. The close coupling between and cycles controls plant productivity shapes structure functional dynamics ecosystems. However, how interactions affect both fluxes traits in dynamic ecotones, are experiencing biotic abiotic changes, remains unclear. In this work, we use situ measurements leaf chlorophyll content (ChlLeaf, 2013–2016) area index (LAI, 1998–2018) parameterize seasonal QUINCY (QUantifying Interactions Nutrient CYcles climate system) biosphere model (TBM) simulate at Borden Forest Research Station flux tower site, Ontario, Canada, over 22 years from 1996 2018. Our goals assess additional value using ChlLeaf parameterization, study well can capture observed trends related cycle investigate processes associated with drought year its legacy effects captured model. was able leaf-level maximum carboxylation capacity (Vc(max),25), manner quite consistent observations. improved parameterization daily gross primary production (GPP) (r2=0.80, root mean square error (RMSE) = 2.2 µmolm-2s-1). Nevertheless, found that although GPP increased significantly during period (22.4 gCm2yr-1yr-1) net ecosystem exchange (NEE) shifted towards stronger sink, these were not Instead, showed significant increasing trend for total respiration (TER) present severe 2007 strongly affected fluxes, lowering TER following as well. some decrease 2007. effect 2008 These results call further work on representing TBMs, have long-lasting impacts functioning.

Язык: Английский

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On the Increasing Occurrence of a Green Christmas: A Perspective from Long-Term Eddy Covariance Observations on Winter Dormancy Interruptions in a Subalpine Forest

ARPHA Conference Abstracts, Год журнала: 2025, Номер 8

Опубликована: Май 28, 2025

Seasonal dormancy in temperate and boreal forests is an adaptive trait that guarantees tree survival during the winter season. This phenomenon mainly affected by temperature photoperiod (Heide 1974). However, increasing evidence suggests not a static state but rather dynamic period influenced intermittent warm spells can temporarily reactivate ecosystem processes. These interruptions, particularly "Green Christmas" events — characterized reduced snow cover anomalous temperatures have potential to alter seasonal carbon fluxes, shift forest phenology, physiological cycles. As climate change intensifies, understanding frequency implications of these interruptions becomes crucial for predicting long-term shifts dynamics energy fluxes. Recent studies reported evergreen initiate photosynthesis well before complete snowmelt (Bowling 2024), while deciduous exhibit delayed response warming trends. Additionally, Körner (2023) challenges conventional meteorological definitions growing seasons, emphasizing photosynthetic activity does always align with temperature-based phenological markers. While there strong influences Eddy Covariance (EC) records reveal mixed trends activity, suggesting additional research needed uncover underlying ecological mechanisms driving shifts. multiple EC flux tower sites established under EUROFLUX project approach three decades continuous observations, they offer valuable opportunity assess effects variability on cycling. extensive datasets allow detailed trend analyses providing insights into their frequency, intensity, impact annual sequestration. For this study, we selected Renon-Selvaverde site (ICOS ID: IT-Ren, eLTER BOL1), subalpine measurement record. To enhance completeness our dataset, incorporated locally processed data, extending NEE record from Warm Winter Dataset (Gharun 2024) up present (1997-2024). ensured continuity observations whole time span analysis. Leveraging investigated how influence dynamics. By integrating environmental drivers, aimed refine responses mid-winter evaluate broader balance context change. were identified based periods when fluxes significantly different zero months. We then examined relationships between NEE, shortwave radiation, soil temperature, air vertical profile interruptions. quantify interactions, conducted correlation analysis strength significance drivers influencing ecosystem-level Our revealed increase beginning 2020. did detect significant pattern duration events. Currently, appear be isolated occurrences, allowing stand return its dormant after each event. observed correspond remain above freezing absent, supporting hypothesis conditions play critical role determining winter. Anyhow, it important distinguish non-freezing (with or without cover) activation driven solar radiation occurring conditions. In latter case, may initiated remains constrained water availability, unclear NEE. At present, do budget ecosystem. hypothesize continued both could lead fundamental even An extended reactivation potentially reduce ability function as sink, affecting contribution neutrality. Future should focus mechanistic modelling approaches predict changes sequestration capacity scenarios increased cover.

Язык: Английский

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Changes in Mean Seasonal Carbon Cycle Due to Climate Change

bioRxiv (Cold Spring Harbor Laboratory), Год журнала: 2024, Номер unknown

Опубликована: Май 21, 2024

Abstract Through photosynthesis, forests absorb annually large amounts of atmospheric CO 2 . However, they also release back through respiration. These two, opposite in sign, fluxes determine, much the carbon that is stored or released to atmosphere. The mean seasonal cycle (MSC) an interesting metric associates phenology and (C) partitioning-allocation analysis within forest stands. Here we applied 3D-CMCC-FEM model analyzed its capability represent main C-fluxes, by validating against observed data, questioning if sink/source seasonality influenced under two scenarios climate change, five contrasting European sites. We found has, current conditions, robust predictive abilities estimating NEE. Model results predict a consistent reduction forest’s capabilities act as C-sink change stand-ageing at all Such predicted despite number annual days evergreen increasing over years, indicating downward trend. Similarly, deciduous forests, maintaining relatively stable throughout year century, show their overall capacity. Overall, both types sites future mitigating potential.

Язык: Английский

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