Numerous efforts to measure land surface fluxes, from leaf to canopy scales, have significantly advanced the field of biogeoscience. However, upscaling these estimates to larger spatial and temporal scales remains a challenge. Recent advancements in remote sensing provide new opportunities to bridge these gaps in upscaling efforts. In this review, I propose that emerging satellite data can support the robust upscaling of land surface fluxes in terms of space through constellations of low Earth orbit satellites, in time through geostationary satellites, and in spectrum via optical, thermal, and microwave satellites. Lastly, I recommend the development of a long-term network integrating tower-based hyperspectral, thermal, and microwave instruments to rigorously evaluate the upscaling process of land surface fluxes.
{"title":"Upscaling Land Surface Fluxes Through Hyper Resolution Remote Sensing in Space, Time, and the Spectrum","authors":"Youngryel Ryu","doi":"10.1029/2023JG007678","DOIUrl":"https://doi.org/10.1029/2023JG007678","url":null,"abstract":"<p>Numerous efforts to measure land surface fluxes, from leaf to canopy scales, have significantly advanced the field of biogeoscience. However, upscaling these estimates to larger spatial and temporal scales remains a challenge. Recent advancements in remote sensing provide new opportunities to bridge these gaps in upscaling efforts. In this review, I propose that emerging satellite data can support the robust upscaling of land surface fluxes in terms of space through constellations of low Earth orbit satellites, in time through geostationary satellites, and in spectrum via optical, thermal, and microwave satellites. Lastly, I recommend the development of a long-term network integrating tower-based hyperspectral, thermal, and microwave instruments to rigorously evaluate the upscaling process of land surface fluxes.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"129 10","pages":""},"PeriodicalIF":3.7,"publicationDate":"2024-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023JG007678","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142525223","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jolanda J. E. Theeuwen, Stefan C. Dekker, Bert V. M. Hamelers, Arie Staal
Mediterranean areas are projected to face increased water scarcity due to global changes. Because a relatively large fraction of the precipitation in Mediterranean areas originates locally, changes at the land surface may further dampen local precipitation. Here, we study the contribution of evaporation to local precipitation for the first time on a scale of approximately 50 km using local evaporation recycling (ELMR) and local precipitation recycling (PLMR), and make a comparison among five Mediterranean climate regions: South West Australia, South West US, central Chile, the Mediterranean Basin, and the Cape region of South Africa. Specifically, this study aims to understand the effects of ecohydrological (dependent on vegetation or the hydrological cycle) and non-ecohydrological variables on ELMR and PLMR. We find that (a) on average, ecohydrological variables correlate more frequently and more strongly to ELMR and PLMR than non-ecohydrological variables; (b) ELMR is large over wet areas and PLMR is large over dry areas; and (c) there are differences in underlying factors of ELMR and PLMR among the regions due to differences in wetness, topography, and land cover. The results suggest that in Mediterranean regions, changes in vegetation cover or the hydrological cycle may strengthen the local water cycle through enhancing ELMR. Finally, ELMR and PLMR help to identify where in Mediterranean regions we might enhance the local water cycle through land cover changes.
{"title":"Ecohydrological Variables Underlie Local Moisture Recycling in Mediterranean-Type Climates","authors":"Jolanda J. E. Theeuwen, Stefan C. Dekker, Bert V. M. Hamelers, Arie Staal","doi":"10.1029/2024JG008286","DOIUrl":"https://doi.org/10.1029/2024JG008286","url":null,"abstract":"<p>Mediterranean areas are projected to face increased water scarcity due to global changes. Because a relatively large fraction of the precipitation in Mediterranean areas originates locally, changes at the land surface may further dampen local precipitation. Here, we study the contribution of evaporation to local precipitation for the first time on a scale of approximately 50 km using local evaporation recycling (ELMR) and local precipitation recycling (PLMR), and make a comparison among five Mediterranean climate regions: South West Australia, South West US, central Chile, the Mediterranean Basin, and the Cape region of South Africa. Specifically, this study aims to understand the effects of ecohydrological (dependent on vegetation or the hydrological cycle) and non-ecohydrological variables on ELMR and PLMR. We find that (a) on average, ecohydrological variables correlate more frequently and more strongly to ELMR and PLMR than non-ecohydrological variables; (b) ELMR is large over wet areas and PLMR is large over dry areas; and (c) there are differences in underlying factors of ELMR and PLMR among the regions due to differences in wetness, topography, and land cover. The results suggest that in Mediterranean regions, changes in vegetation cover or the hydrological cycle may strengthen the local water cycle through enhancing ELMR. Finally, ELMR and PLMR help to identify where in Mediterranean regions we might enhance the local water cycle through land cover changes.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"129 10","pages":""},"PeriodicalIF":3.7,"publicationDate":"2024-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JG008286","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142525222","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yu Zhang, Zhantang Xu, Yuezhong Yang, Huizeng Liu, Wen Zhou, Cong Liu, Zeming Yang, Cai Li
Absorptive substances (AS) embedded in sea ice can alter irradiance transmission, exerting a significant influence on oceanic biogeochemical processes. Their quantification is thus essential, and a regression model based on the normalized difference index of transmittance (T(λ)) has been widely used for retrieving ice algal biomass. However, the potentials of albedo (α(λ)) and the diffuse attenuation coefficient (Kd(λ)) in AS estimation have not been explored. To fill this gap, sea ice optical properties observed in Liaodong Bay in 2009, 2010, 2013, and 2022 were used to investigate the characteristics of α(λ), T(λ), and Kd(λ) in non-destructively estimating As through sensitivity analyses based on the Hydrolight radiative transfer model. The effects derived from AS vertical distribution, scattering coefficient and ice thickness were studied specifically. Ultimately, a significant relationship between α(λ) and the total absorption coefficient of AS was derived (R2 = 0.79) for Liaodong Bay sea ice. Sensitivity analyses revealed that it could only retrieve AS in the upper 15–20 cm, which was influenced by variations in ice thickness and scattering coefficient. In contrast, T(λ) could retrieve AS throughout the ice column and is less affected by scattering variation; but it is significantly affected by the vertical distribution of AS in the upper layer. Kd(λ) has the best potential in AS estimation, but for sea ice thinner than 30 cm, the effect of variation in ice thickness could not be neglected, similar to T(λ). Knowledge of this is helpful for the future development of AS estimation.
嵌入海冰中的吸收物质（AS）会改变辐照度透射，对海洋生物地球化学过程产生重大影响。因此，对其进行量化至关重要，基于透射率归一化差异指数（T(λ)）的回归模型已被广泛用于检索冰藻生物量。然而，反照率（α(λ)）和漫反射衰减系数（Kd(λ)）在 AS 估计中的潜力尚未得到探讨。为填补这一空白，利用2009、2010、2013和2022年在辽东湾观测到的海冰光学特性，通过基于Hydrolight辐射传输模型的灵敏度分析，研究了α(λ)、T(λ)和Kd(λ)在无损估算As中的特性。具体研究了 AS 垂直分布、散射系数和冰厚度的影响。结果表明，辽东湾海冰的α(λ)与AS总吸收系数之间存在显著关系（R2=0.79）。灵敏度分析表明，由于受冰厚和散射系数变化的影响，该方法只能获取上部 15-20 厘米的 AS。相比之下，T(λ)可以获取整个冰柱的AS，受散射变化的影响较小，但受上层AS垂直分布的影响较大。Kd(λ) 在估计 AS 方面最有潜力，但对于厚度小于 30 厘米的海冰，冰厚度变化的影响不可忽视，这一点与 T(λ) 类似。了解这一点有助于 AS 估计的未来发展。
{"title":"The Characteristics of Different Apparent Optical Property Parameters in Non-Destructively Estimating Absorptive Substances Within Sea Ice: A Case Study in Liaodong Bay","authors":"Yu Zhang, Zhantang Xu, Yuezhong Yang, Huizeng Liu, Wen Zhou, Cong Liu, Zeming Yang, Cai Li","doi":"10.1029/2024JG008029","DOIUrl":"https://doi.org/10.1029/2024JG008029","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <p>Absorptive substances (AS) embedded in sea ice can alter irradiance transmission, exerting a significant influence on oceanic biogeochemical processes. Their quantification is thus essential, and a regression model based on the normalized difference index of transmittance (T(λ)) has been widely used for retrieving ice algal biomass. However, the potentials of albedo (<i>α</i>(λ)) and the diffuse attenuation coefficient (<i>K</i><sub>d</sub>(λ)) in AS estimation have not been explored. To fill this gap, sea ice optical properties observed in Liaodong Bay in 2009, 2010, 2013, and 2022 were used to investigate the characteristics of <i>α</i>(λ), T(λ), and <i>K</i><sub>d</sub>(λ) in non-destructively estimating As through sensitivity analyses based on the Hydrolight radiative transfer model. The effects derived from AS vertical distribution, scattering coefficient and ice thickness were studied specifically. Ultimately, a significant relationship between <i>α</i>(λ) and the total absorption coefficient of AS was derived (<i>R</i><sup>2</sup> = 0.79) for Liaodong Bay sea ice. Sensitivity analyses revealed that it could only retrieve AS in the upper 15–20 cm, which was influenced by variations in ice thickness and scattering coefficient. In contrast, T(λ) could retrieve AS throughout the ice column and is less affected by scattering variation; but it is significantly affected by the vertical distribution of AS in the upper layer. <i>K</i><sub>d</sub>(λ) has the best potential in AS estimation, but for sea ice thinner than 30 cm, the effect of variation in ice thickness could not be neglected, similar to T(λ). Knowledge of this is helpful for the future development of AS estimation.</p>\u0000 </section>\u0000 </div>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"129 10","pages":""},"PeriodicalIF":3.7,"publicationDate":"2024-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142525269","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Nitrogen (N) addition can stimulate tree growth; however, the strength of this growth effect usually changes over time and the factors underlying these responses are not fully understood. Based on a decade-long N addition experiment (by adding 0, 20, 50, and 100 kg N ha−1 yr−1) in a boreal forest, we studied responses of tree growth to N addition over time and explored the potential role of temporal precipitation variation and plant stoichiometric changes in mediating this. We found positive growth responses to N addition but this effect changed nonlinearly over time. Annual precipitation was positively related to growth under high-level N addition; hence, a hump-shape temporal pattern in precipitation contributed to the nonlinear tree growth responses. After precipitation effects were accounted for, the positive growth responses to N addition peaked in the seventh year and then declined for all levels of N. Later reductions in growth responses could partly be attributed to increased leaf N:phosphorus (P) ratio over time, especially at higher N addition rates. We also found an increase in soil acid phosphatase, the ratio of labile to occluded soil P fraction, and a decreased ratio in leaf N to P resorption efficiency with increasing N addition rates during the late stage of this experiment, suggesting increased P demand. Collectively, our results imply that changes in plant nutrient stoichiometry with cumulative N input may limit the N stimulation on tree growth over time, while temporal precipitation variation appears unlikely to modulate this effect under the atmospheric N deposition.
{"title":"Temporal Precipitation Variation and Leaf Stoichiometric Changes Mediate the Dynamics of Tree Growth Responses to Nitrogen Addition Over Time","authors":"Aijun Xing, Haihua Shen, Enzai Du, Longchao Xu, Mengying Zhao, Jingyun Fang","doi":"10.1029/2024JG008353","DOIUrl":"https://doi.org/10.1029/2024JG008353","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <p>Nitrogen (N) addition can stimulate tree growth; however, the strength of this growth effect usually changes over time and the factors underlying these responses are not fully understood. Based on a decade-long N addition experiment (by adding 0, 20, 50, and 100 kg N ha<sup>−1</sup> yr<sup>−1</sup>) in a boreal forest, we studied responses of tree growth to N addition over time and explored the potential role of temporal precipitation variation and plant stoichiometric changes in mediating this. We found positive growth responses to N addition but this effect changed nonlinearly over time. Annual precipitation was positively related to growth under high-level N addition; hence, a hump-shape temporal pattern in precipitation contributed to the nonlinear tree growth responses. After precipitation effects were accounted for, the positive growth responses to N addition peaked in the seventh year and then declined for all levels of N. Later reductions in growth responses could partly be attributed to increased leaf N:phosphorus (P) ratio over time, especially at higher N addition rates. We also found an increase in soil acid phosphatase, the ratio of labile to occluded soil P fraction, and a decreased ratio in leaf N to P resorption efficiency with increasing N addition rates during the late stage of this experiment, suggesting increased P demand. Collectively, our results imply that changes in plant nutrient stoichiometry with cumulative N input may limit the N stimulation on tree growth over time, while temporal precipitation variation appears unlikely to modulate this effect under the atmospheric N deposition.</p>\u0000 </section>\u0000 </div>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"129 10","pages":""},"PeriodicalIF":3.7,"publicationDate":"2024-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142524759","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Globally, the emission of biogenic volatile organic compounds (BVOC) by plants represents the dominant source of volatile organic compounds emitted to the atmosphere. Monoterpenes, as the major BVOC group, can contribute to forming secondary organic aerosols and influence cloud properties. In this study, we developed a process-based monoterpene module in the Vegetation Integrative SImulator for Trace gases (VISIT) model by considering the production, storage, and emission of monoterpene as three main processes. We further evaluated the modeled monoterpene emissions against the ecosystem-level observation data at a half-hour scale at a Japanese larch (Larix kaempferi) forest site on Mt. Fuji, Japan. The VISIT model performed with relatively higher accuracy with a Willmott's index of agreement at 0.61, a mean bias error (MBE) at 0.29, and a root mean squared error (RMSE) at 0.43, comparable to that of Model of Emissions of Gases and Aerosols from Nature model with a Willmott's index of agreement at 0.63, a MBE at 0.40, and a RMSE at 0.54. In a long-term simulation under high CO2 emission scenarios, the ratio between monoterpene emission and gross primary production exhibited a stronger correlation with CO2 concentration than temperature. Our study provides a process-based modeling approach for more accurately simulating monoterpene emissions from Japanese larch.
{"title":"Process-Based Modeling of Ecosystem-Level Monoterpene From a Japanese Larch (Larix kaempferi) Forest","authors":"Zhanzhuo Chen, Tomomichi Kato, Akihiko Ito, Tatsuya Miyauchi, Yoshiyuki Takahashi, Jing Tang","doi":"10.1029/2024JG008067","DOIUrl":"https://doi.org/10.1029/2024JG008067","url":null,"abstract":"<p>Globally, the emission of biogenic volatile organic compounds (BVOC) by plants represents the dominant source of volatile organic compounds emitted to the atmosphere. Monoterpenes, as the major BVOC group, can contribute to forming secondary organic aerosols and influence cloud properties. In this study, we developed a process-based monoterpene module in the Vegetation Integrative SImulator for Trace gases (VISIT) model by considering the production, storage, and emission of monoterpene as three main processes. We further evaluated the modeled monoterpene emissions against the ecosystem-level observation data at a half-hour scale at a Japanese larch (<i>Larix kaempferi</i>) forest site on Mt. Fuji, Japan. The VISIT model performed with relatively higher accuracy with a Willmott's index of agreement at 0.61, a mean bias error (MBE) at 0.29, and a root mean squared error (RMSE) at 0.43, comparable to that of Model of Emissions of Gases and Aerosols from Nature model with a Willmott's index of agreement at 0.63, a MBE at 0.40, and a RMSE at 0.54. In a long-term simulation under high CO<sub>2</sub> emission scenarios, the ratio between monoterpene emission and gross primary production exhibited a stronger correlation with CO<sub>2</sub> concentration than temperature. Our study provides a process-based modeling approach for more accurately simulating monoterpene emissions from Japanese larch.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"129 10","pages":""},"PeriodicalIF":3.7,"publicationDate":"2024-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142524713","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Marcelo Henriques, Tim R. McVicar, Kate L. Holland, Edoardo Daly
Land surface phenology (LSP) is useful to understand patterns of terrestrial ecosystems. Detecting LSP in drylands is more challenging when compared to agricultural and mesic environments due to vegetation heterogeneity, the presence of evergreen and seasonal species, and the dominant role of water (which is often received episodically with variable timing) in determining vegetation growth. In this study, LiDAR-derived vegetation classes are defined to guide and improve the interpretation of LSP metrics extracted using temporally decomposed Landsat fPAR time series. This method was applied to waterholes within the Cooper Creek floodplain, in dryland Australia, which are important for ecological conservation. Results showed that phenology is mostly associated with the recurrent vegetation (approximately 80% of all identified phenological events) in all waterholes. However, during high streamflow periods, the number of phenological events associated with the persistent vegetation greatly increased (up to 40% of the identified events). Non-annual phenology was also identified, with more than one phenological event occurring across a water year during high streamflow periods. The duration of the phenological events of the persistent vegetation exceeded one water year during periods of high streamflow. Phenological differences of the LiDAR-derived vegetation classes occupying the riparian zone of the waterholes were also identified. Streamflow movement across the floodplain exerts an important influence on the vegetation phenology, as suggested by a lag in the phenology when comparing southern and northern waterholes. The method developed herein can be applied to other highly spatially heterogeneous ecosystems where vegetation species simultaneously present permanent and seasonal patterns.
{"title":"Extracting Vegetation Phenology in Heterogeneous Drylands Using LiDAR and Landsat Temporal Decomposition: A Latitudinal Assessment of Waterholes Within the Cooper Creek, Australia","authors":"Marcelo Henriques, Tim R. McVicar, Kate L. Holland, Edoardo Daly","doi":"10.1029/2023JG007993","DOIUrl":"https://doi.org/10.1029/2023JG007993","url":null,"abstract":"<p>Land surface phenology (LSP) is useful to understand patterns of terrestrial ecosystems. Detecting LSP in drylands is more challenging when compared to agricultural and mesic environments due to vegetation heterogeneity, the presence of evergreen and seasonal species, and the dominant role of water (which is often received episodically with variable timing) in determining vegetation growth. In this study, LiDAR-derived vegetation classes are defined to guide and improve the interpretation of LSP metrics extracted using temporally decomposed Landsat <i>fPAR</i> time series. This method was applied to waterholes within the Cooper Creek floodplain, in dryland Australia, which are important for ecological conservation. Results showed that phenology is mostly associated with the recurrent vegetation (approximately 80% of all identified phenological events) in all waterholes. However, during high streamflow periods, the number of phenological events associated with the persistent vegetation greatly increased (up to 40% of the identified events). Non-annual phenology was also identified, with more than one phenological event occurring across a water year during high streamflow periods. The duration of the phenological events of the persistent vegetation exceeded one water year during periods of high streamflow. Phenological differences of the LiDAR-derived vegetation classes occupying the riparian zone of the waterholes were also identified. Streamflow movement across the floodplain exerts an important influence on the vegetation phenology, as suggested by a lag in the phenology when comparing southern and northern waterholes. The method developed herein can be applied to other highly spatially heterogeneous ecosystems where vegetation species simultaneously present permanent and seasonal patterns.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"129 10","pages":""},"PeriodicalIF":3.7,"publicationDate":"2024-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023JG007993","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142451767","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xiaolu Li, Carlos M. Carrillo, Toby Ault, Andrew D. Richardson, Mark A. Friedl, Steve Frolking
Accurate simulation of plant phenology is important in Earth system models as phenology modulates land-atmosphere coupling and the carbon cycle. Evaluations based on grid cell average leaf area index (LAI) can be misleading because multiple plant functional types (PFTs) may be present in one model grid cell and PFTs with different phenology schemes have different LAI seasonal cycles. Here we examined PFT-specific LAI magnitudes and seasonal cycles in the Community Land Model versions 5.0 and 4.5 (CLM5.0 and CLM4.5) and their relationship with the onset of growing season triggers in the Northern Hemisphere. LAI seasonal cycle and spring onset in CLM show the best agreement with Moderate Resolution Imaging Spectroradiometer (MODIS) for temperature-dominated deciduous PFTs. Although the agreement in LAI magnitude between CLM5.0 and MODIS is better than CLM4.5, the agreement in seasonal cycles is worse in CLM5.0. Agreements between CLM and MODIS leaf phenology are primarily determined by the PFT and phenology scheme. While productivity depends on the environmental factors to which the plant is exposed during any given growing season, differences in phenology sensitivity to its environment necessitate a decoupling between the seasonality of LAI and GPP, which in turn could lead to biases in the carbon cycle as well as surface energy balance and hence land-atmosphere interactions. Because the discrepancy not only depends on parameterizing phenology but phenology-environment relationship, future improvements to other model components (e.g., soil moisture) could better align the seasonal cycle of LAI and GPP.
在地球系统模型中，准确模拟植物物候非常重要，因为物候会调节陆地-大气耦合和碳循环。基于网格单元平均叶面积指数（LAI）的评估可能会产生误导，因为在一个模型网格单元中可能存在多种植物功能类型（PFTs），而且具有不同物候方案的植物功能类型具有不同的 LAI 季节周期。在此，我们研究了群落土地模型 5.0 和 4.5 版（CLM5.0 和 CLM4.5）中特定植物功能类型的 LAI 幅值和季节周期，以及它们与北半球生长季触发点的关系。对于以温度为主的落叶植物生长季，CLM 中的 LAI 季节周期和春季开始时间与中分辨率成像分光仪（MODIS）显示出最佳的一致性。虽然 CLM5.0 与 MODIS 在 LAI 幅值方面的一致性优于 CLM4.5，但 CLM5.0 在季节周期方面的一致性较差。CLM 和 MODIS 叶片物候的一致性主要取决于 PFT 和物候方案。虽然生产力取决于植物在任何给定生长季节所暴露的环境因素，但物候对环境敏感性的差异必然导致 LAI 和 GPP 的季节性脱钩，这反过来又会导致碳循环和地表能量平衡的偏差，进而导致陆地-大气相互作用的偏差。由于这种差异不仅取决于物候参数化，还取决于物候-环境关系，因此未来对其他模型组件（如土壤湿度）的改进可以更好地调整 LAI 和 GPP 的季节周期。
{"title":"Evaluation of Leaf Phenology of Different Vegetation Types From Local to Hemispheric Scale in CLM","authors":"Xiaolu Li, Carlos M. Carrillo, Toby Ault, Andrew D. Richardson, Mark A. Friedl, Steve Frolking","doi":"10.1029/2024JG008261","DOIUrl":"https://doi.org/10.1029/2024JG008261","url":null,"abstract":"<p>Accurate simulation of plant phenology is important in Earth system models as phenology modulates land-atmosphere coupling and the carbon cycle. Evaluations based on grid cell average leaf area index (LAI) can be misleading because multiple plant functional types (PFTs) may be present in one model grid cell and PFTs with different phenology schemes have different LAI seasonal cycles. Here we examined PFT-specific LAI magnitudes and seasonal cycles in the Community Land Model versions 5.0 and 4.5 (CLM5.0 and CLM4.5) and their relationship with the onset of growing season triggers in the Northern Hemisphere. LAI seasonal cycle and spring onset in CLM show the best agreement with Moderate Resolution Imaging Spectroradiometer (MODIS) for temperature-dominated deciduous PFTs. Although the agreement in LAI magnitude between CLM5.0 and MODIS is better than CLM4.5, the agreement in seasonal cycles is worse in CLM5.0. Agreements between CLM and MODIS leaf phenology are primarily determined by the PFT and phenology scheme. While productivity depends on the environmental factors to which the plant is exposed during any given growing season, differences in phenology sensitivity to its environment necessitate a decoupling between the seasonality of LAI and GPP, which in turn could lead to biases in the carbon cycle as well as surface energy balance and hence land-atmosphere interactions. Because the discrepancy not only depends on parameterizing phenology but phenology-environment relationship, future improvements to other model components (e.g., soil moisture) could better align the seasonal cycle of LAI and GPP.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"129 10","pages":""},"PeriodicalIF":3.7,"publicationDate":"2024-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142451741","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Wen-Bo Lv, Fang-Mei Liu, Kai Cai, Yue Cao, Meng-Ling Deng, Wei Liang, Jian-Wu Yan, Guang-Yu Wang
Vegetation cover is crucial for ecosystem stability, responding sensitively to climate change and human activities, and is prone to irreversible degradation. However, the mechanisms driving vegetation variations due to natural and anthropogenic factors still need to be fully understood. This study focused on the Weihe River Basin to elucidate the response mechanism of vegetation cover change to climate change and human activities from 2001 to 2020. Long time-series multi-source data were combined with a pixel dichotomy model, Theil–Sen median trend analysis, and Mann-Kendall test to examine the trends and delineate five gradients in vegetation cover change. Additionally, Extreme Gradient Boosting, the Shapley value, and a structural equation model were employed to investigate the multidimensional response of vegetation cover in the basin as a whole and different vegetation cover gradients. The results revealed a general upward trend in vegetation coverage in the Weihe River Basin from 2001 to 2020. Topographic conditions and human activities were identified as primary influencers. Notably, accounting for climate change, particularly about changes in maximum climatic variables, was found to be essential, with temperature changes exerting a greater impact on vegetation cover variations compared to precipitation changes. The interaction between human activities, climate change, and topographic conditions can alter the intensity of each factor’s effect. The direction of indicators mentioned above varied across the vegetation cover gradients, emphasizing the need for localized strategies to improve vegetation. These findings offer valuable insights into ecological protection and vegetation restoration in the Weihe River Basin.
{"title":"Distinguishing the Impacts and Gradient Effects of Climate Change and Human Activities on Vegetation Cover in the Weihe River Basin, China","authors":"Wen-Bo Lv, Fang-Mei Liu, Kai Cai, Yue Cao, Meng-Ling Deng, Wei Liang, Jian-Wu Yan, Guang-Yu Wang","doi":"10.1029/2024JG008297","DOIUrl":"https://doi.org/10.1029/2024JG008297","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <p>Vegetation cover is crucial for ecosystem stability, responding sensitively to climate change and human activities, and is prone to irreversible degradation. However, the mechanisms driving vegetation variations due to natural and anthropogenic factors still need to be fully understood. This study focused on the Weihe River Basin to elucidate the response mechanism of vegetation cover change to climate change and human activities from 2001 to 2020. Long time-series multi-source data were combined with a pixel dichotomy model, Theil–Sen median trend analysis, and Mann-Kendall test to examine the trends and delineate five gradients in vegetation cover change. Additionally, Extreme Gradient Boosting, the Shapley value, and a structural equation model were employed to investigate the multidimensional response of vegetation cover in the basin as a whole and different vegetation cover gradients. The results revealed a general upward trend in vegetation coverage in the Weihe River Basin from 2001 to 2020. Topographic conditions and human activities were identified as primary influencers. Notably, accounting for climate change, particularly about changes in maximum climatic variables, was found to be essential, with temperature changes exerting a greater impact on vegetation cover variations compared to precipitation changes. The interaction between human activities, climate change, and topographic conditions can alter the intensity of each factor’s effect. The direction of indicators mentioned above varied across the vegetation cover gradients, emphasizing the need for localized strategies to improve vegetation. These findings offer valuable insights into ecological protection and vegetation restoration in the Weihe River Basin.</p>\u0000 </section>\u0000 </div>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"129 10","pages":""},"PeriodicalIF":3.7,"publicationDate":"2024-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142451740","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
F. M. Iannucci, J. B. Jones Jr., K. L. Olson, M. E. Muscarella, E. R. Hotchkiss
Metabolism in stream ecosystems alters the fate of organic carbon (OC) received from surrounding landscapes, but our understanding of in-stream metabolic processes in boreal ecosystems remains limited. Determining the factors that regulate OC metabolism will help predict how the C balance of boreal streams may respond to future environmental change. In this study, we addressed the question: what controls OC metabolism in boreal headwater streams draining catchments with discontinuous permafrost? We hypothesized that metabolism is collectively regulated by OC reactivity, phosphorus availability, and temperature, with discharge modulating each of these conditions. We tested these hypotheses using a combination of laboratory experiments and whole-stream ecosystem metabolism measurements throughout the Caribou-Poker Creeks Research Watershed (CPCRW) in Interior Alaska, USA. In the laboratory experiments, respiration and dissolved OC (DOC) removal were both co-limited by the supply of reactive C and phosphorus, but temperature and residence time acted as stronger controls of DOC removal. Ecosystem respiration (ER) was largely predicted by discharge and site, with some variance explained by gross primary production (GPP) and temperature. Both ER and GPP varied inversely with watershed permafrost extent, with an inverse relationship between temperature and permafrost extent providing one plausible explanation. Our results provide some of the first evidence of a functional response to permafrost thaw in stream ecosystems and suggest the role of metabolism in landscape C cycling may increase as climate change progresses.
{"title":"Temperature and Flow Control Organic Carbon Metabolism in Boreal Headwater Streams","authors":"F. M. Iannucci, J. B. Jones Jr., K. L. Olson, M. E. Muscarella, E. R. Hotchkiss","doi":"10.1029/2024JG008281","DOIUrl":"https://doi.org/10.1029/2024JG008281","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <p>Metabolism in stream ecosystems alters the fate of organic carbon (OC) received from surrounding landscapes, but our understanding of in-stream metabolic processes in boreal ecosystems remains limited. Determining the factors that regulate OC metabolism will help predict how the C balance of boreal streams may respond to future environmental change. In this study, we addressed the question: what controls OC metabolism in boreal headwater streams draining catchments with discontinuous permafrost? We hypothesized that metabolism is collectively regulated by OC reactivity, phosphorus availability, and temperature, with discharge modulating each of these conditions. We tested these hypotheses using a combination of laboratory experiments and whole-stream ecosystem metabolism measurements throughout the Caribou-Poker Creeks Research Watershed (CPCRW) in Interior Alaska, USA. In the laboratory experiments, respiration and dissolved OC (DOC) removal were both co-limited by the supply of reactive C and phosphorus, but temperature and residence time acted as stronger controls of DOC removal. Ecosystem respiration (ER) was largely predicted by discharge and site, with some variance explained by gross primary production (GPP) and temperature. Both ER and GPP varied inversely with watershed permafrost extent, with an inverse relationship between temperature and permafrost extent providing one plausible explanation. Our results provide some of the first evidence of a functional response to permafrost thaw in stream ecosystems and suggest the role of metabolism in landscape C cycling may increase as climate change progresses.</p>\u0000 </section>\u0000 </div>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"129 10","pages":""},"PeriodicalIF":3.7,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142451187","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Shannon de Roos, Michel Bechtold, Louise Busschaert, Hans Lievens, Gabrielle J. M. De Lannoy
This study assesses the potential of regional microwave backscatter data assimilation (DA) in AquaCrop for the first time, using NASA's Land Information System. The objective is to assess whether the assimilation setup can improve surface soil moisture (SSM) and crop biomass estimates. SSM and crop biomass simulations from AquaCrop were updated using Sentinel-1 synthetic aperture radar observations, over three regions in Europe in two separate DA experiments. The first experiment concerned updating SSM using VV-polarized backscatter and the corrections were propagated via the model to the biomass. In the second experiment, the DA setup was extended by also updating the biomass with VH-polarized backscatter. SSM was evaluated with local in situ data and with downscaled Soil Moisture Active Passive (SMAP) retrievals for all cropland grid cells, whereas crop biomass was compared to SMAP vegetation optical depth and the Copernicus dry matter productivity. The assimilation showed mixed results for root mean square error and Pearson's correlation, with slight overall improvements in the (anomaly) correlations of updated SSM relative to independent in situ and satellite data. By contrast, the biomass estimates obtained with backscatter DA did not agree better with reference data sets. Overall, the SSM evaluation showed that there is potential in using Sentinel-1 backscatter for assimilation in AquaCrop, but the present setup was not able to improve crop biomass estimates. Our study reveals how the complex interaction between SSM, crop biomass and backscatter affect the impact and performance of DA, offering insight into ways to optimize DA for crop growth estimation.
{"title":"Assimilation of Sentinel-1 Backscatter to Update AquaCrop Estimates of Soil Moisture and Crop Biomass","authors":"Shannon de Roos, Michel Bechtold, Louise Busschaert, Hans Lievens, Gabrielle J. M. De Lannoy","doi":"10.1029/2024JG008231","DOIUrl":"https://doi.org/10.1029/2024JG008231","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <p>This study assesses the potential of regional microwave backscatter data assimilation (DA) in AquaCrop for the first time, using NASA's Land Information System. The objective is to assess whether the assimilation setup can improve surface soil moisture (SSM) and crop biomass estimates. SSM and crop biomass simulations from AquaCrop were updated using Sentinel-1 synthetic aperture radar observations, over three regions in Europe in two separate DA experiments. The first experiment concerned updating SSM using VV-polarized backscatter and the corrections were propagated via the model to the biomass. In the second experiment, the DA setup was extended by also updating the biomass with VH-polarized backscatter. SSM was evaluated with local in situ data and with downscaled Soil Moisture Active Passive (SMAP) retrievals for all cropland grid cells, whereas crop biomass was compared to SMAP vegetation optical depth and the Copernicus dry matter productivity. The assimilation showed mixed results for root mean square error and Pearson's correlation, with slight overall improvements in the (anomaly) correlations of updated SSM relative to independent in situ and satellite data. By contrast, the biomass estimates obtained with backscatter DA did not agree better with reference data sets. Overall, the SSM evaluation showed that there is potential in using Sentinel-1 backscatter for assimilation in AquaCrop, but the present setup was not able to improve crop biomass estimates. Our study reveals how the complex interaction between SSM, crop biomass and backscatter affect the impact and performance of DA, offering insight into ways to optimize DA for crop growth estimation.</p>\u0000 </section>\u0000 </div>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"129 10","pages":""},"PeriodicalIF":3.7,"publicationDate":"2024-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JG008231","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142447643","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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