Agricultural and Forest Meteorology最新文献

{"title":"The carbon balance and water use efficiency of an intensively managed forage crop in the Lower Fraser Valley in British Columbia, Canada","authors":"","doi":"10.1016/j.agrformet.2024.110178","DOIUrl":"10.1016/j.agrformet.2024.110178","url":null,"abstract":"<div><p>Intensively managed grasslands have been found to be either carbon (C) sources or sinks depending on management and climate. This study reports the net ecosystem production (NEP) and latent heat fluxes (<em>λE</em>) from a managed forage field at a dairy farm in Agassiz, British Columbia, Canada. The forage crop (ryegrass and tall fescue) was harvested up to 6 times a year. The field received multiple applications of dairy manure slurry and was also fertilized with inorganic nitrogen. Eddy-covariance measurements of NEP were combined with C imports (manure additions) and exports (harvested biomass) to determine the net ecosystem C balance (NECB), and values of gross primary production (GPP) and <em>λE</em> were used to determine water use efficiency (WUE). In terms of environmental controls on NEP, variability of daytime NEP was well described by fitting measured incoming photosynthetically active radiation with a rectangular hyperbolic light-response curve, but variability in nighttime NEP was less effectively described by soil temperature and soil moisture. After accounting for C imports and exports, the NECB of the field was -315 ± 141 and -51 ± 148 g C m^-2 y^-1 (± indicates the uncertainty range) during the 2020 and 2021 study years, respectively, indicating C was lost from the field and was strongly influenced by C imports and exports relative to NEP. Higher than normal soil moisture and precipitation as well as higher than normal air temperature were both found to suppress GPP and ecosystem respiration (<em>R</em>_e), but annual NEP was more impacted by soil moisture in the first year (2020) due to its effect of lowering GPP compared to high air temperature (including the 2021 Pacific Northwest heat dome) and low soil moisture in the second year due to their greater impact on <em>R</em>_e relative to GPP. Crop harvests were found to substantially reduce both GPP and WUE which suggests that the intensity of management in terms of harvest frequency could be modified to improve long-term C sequestration.</p></div>","PeriodicalId":50839,"journal":{"name":"Agricultural and Forest Meteorology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0168192324002910/pdfft?md5=487b7ef6b7b1fd1356026bba1f93e89a&pid=1-s2.0-S0168192324002910-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141994718","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":"Quantifying the effects of diffuse photosynthetically active radiation on water use efficiency in different ecosystems","authors":"","doi":"10.1016/j.agrformet.2024.110191","DOIUrl":"10.1016/j.agrformet.2024.110191","url":null,"abstract":"<div><p>Compared with direct radiation, diffuse radiation could be more efficiently used for photosynthesis because of the diffuse fertilization effect (DFE). Because carbon uptake and water loss are coupled through leaf stomata, DFE probably increases gross primary productivity (GPP) and evapotranspiration (ET) simultaneously. Multi-year eddy covariance flux observation data and simulated diffuse fraction of photosynthetically active radiation (PAR) for nine ecosystems across China (containing forest, grassland, wetland, and cropland) were used to quantify the impact of DFE on water use efficiency (WUE). The results showed that GPP firstly increased and then decreased with increasing diffuse fraction of PAR (<em>k_d-PAR</em> = diffuse PAR/PAR) for each ecosystems. The <em>k_d-PAR</em> values at which maximum GPP occurred varied between 0.34 and 0.76 across nine ecosystems. ET decreased with increasing <em>k_d-PAR</em> in most ecosystems mainly because high <em>k_d-PAR</em> (indicating low PAR) could reduce evaporation in most ecosystems. The relationships between WUE and <em>k_d-PAR</em> were significantly linear with averaged slopes of forest, grassland, wetland, and cropland of 1.64, 0.96, 1.19, and 4.51 g C kg⁻¹ H₂O, respectively. A multiple linear regression method was used to analyze the effect of diffuse PAR (PAR_dif) and direct PAR (PAR_dir) on GPP and ET. The conversion efficiencies for PAR_dif were greater than for PAR_dir, and the relative differences were 178.35% and 23.77% for GPP and ET, respectively. The intensity of DFE for GPP and ET were greater for forest and cropland than for grassland and wetland. The intensity of DFE was 3.05 to 236.96 times higher for GPP than for ET. The mathematical analysis results demonstrated that the promoting effect of PAR_dif was greater for GPP than for ET, thereby inducing an increase in WUE with increasing <em>k_d-PAR</em>. These results will be helpful for improving modeling accuracy of carbon and water cycles under the conditions accompanying global climate change.</p></div>","PeriodicalId":50839,"journal":{"name":"Agricultural and Forest Meteorology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141985356","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":"Soil moisture plays an increasingly important role role in constraining vegetation productivity in China over the past two decades","authors":"","doi":"10.1016/j.agrformet.2024.110193","DOIUrl":"10.1016/j.agrformet.2024.110193","url":null,"abstract":"<div><p>Decreasing soil moisture (SM) and increasing vapor pressure deficit (VPD) are the main drought affecting factors of terrestrial vegetation productivity. Nevertheless, the impact of continued warming on the changing trend of SM and VPD constraints affecting vegetation productivity remains uncertain. Understanding the complex interactive effects of SM and VPD on vegetation is crucial for assessing drought risk and its ecological implications. This study aims to comprehensively quantify the trends in the respective contributions of SM and VPD to vegetation ecosystem productivity in China from 2000 to 2022. The results showed that both low SM and high VPD had significant inhibitory effects on gross primary productivity (GPP) anomaly. Furthermore, the magnitude of water stress on vegetation productivity increases, and is accompanied by a gradual expansion of areas experiencing significant water deficit during the study period. By decoupling the interactions between SM and VPD, we found that SM and VPD were the primary influencing factor of water stress on vegetation productivity, accounting for 60 % and 40 % of the total vegetated area, respectively. Notably, the effects of SM and VPD on GPP exhibited significant variations across different vegetation and climate gradients. The amount of land dominated by the SM constraint expanded, and SM gradually played an increasingly important role in the water stress of GPP over the past two decades. The results of the study are important to accurately assess the interrelationship between vegetation and climate in the context of climate change.</p></div>","PeriodicalId":50839,"journal":{"name":"Agricultural and Forest Meteorology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141985346","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":"The applicability of a SIF-based mechanistic model for estimating GPP at the canopy scale","authors":"","doi":"10.1016/j.agrformet.2024.110192","DOIUrl":"10.1016/j.agrformet.2024.110192","url":null,"abstract":"<div><p>Mechanistically linking gross primary productivity (GPP) and sun-induced chlorophyll fluorescence (SIF) is an essential step to unleash the full potential of SIF for remote sensing-based predictions of GPP across biomes, climates, and spatiotemporal scales. The latest SIF-based mechanistic light response model that includes the fraction of open photosystem II reaction centers as key parameter (qMLR-SIF model), can accurately reproduce leaf-scale photosynthesis under various conditions. However, it remains unclear to what extent the qMLR-SIF model is suitable for estimating GPP at larger scales such as the canopy scale. Therefore, canopy-scale data of tower-based far-red SIF, GPP and key environmental variables from 10 study sites were collected to analyze the SIF-GPP relationship and to compare the qMLR-SIF model with the widely used Farquhar, von Caemmerer, Berry (FvCB) model and with a light use efficiency (LUE) model for different plant functional types (PFTs), photosynthetic pathways (C₃ and C₄), and temporal scales (hourly, daily and 4-day). Results showed that the nonlinear SIF-GPP relationship existed in all PFTs and the degree of linearity increased at larger temporal scales. The qMLR-SIF model exhibited wide applicability to quantify canopy GPP for different PFTs (R² = 0.55–0.80, RMSE = 2.72–11.03 μmol CO₂ m^-2 s^-1), photosynthetic pathways (R² = 0.70–0.78, RMSE = 5.29–9.05 μmol CO₂ m^-2 s^-1) and temporal scales (R² = 0.82–0.97, RMSE = 3.42–8.32 μmol CO₂ m^-2s^-1). Compared with the two other models, the qMLR-SIF model performed best overall, which is mainly due to its simpler model structure and the mechanistic link between SIF and photosynthesis. Particularly, the qMLR-SIF model could more accurately estimate GPP in C₄ species, with higher R² (0.78) and lower RMSE (8.46 μmol CO₂ m^-2s^-1). These findings highlight the advantages of the qMLR-SIF model in GPP estimation at the canopy scale, showing its potential in applications at regional and global scales.</p></div>","PeriodicalId":50839,"journal":{"name":"Agricultural and Forest Meteorology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141985357","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":"A Bayesian inference approach to determine experimental Typha latifolia paludiculture greenhouse gas exchange measured with eddy covariance","authors":"","doi":"10.1016/j.agrformet.2024.110179","DOIUrl":"10.1016/j.agrformet.2024.110179","url":null,"abstract":"<div><p>Measurements of greenhouse gas exchange (GHG) using the eddy covariance method are crucial for identifying strategies to achieve emission reductions and carbon sequestration. There are many sites that have heterogeneous land covers where it would be useful to have balances of particular land areas, such as field trials of emission mitigation strategies, but the flux footprint infrequently covers only the area of interest. Filtering the data based on a footprint area threshold can be done but may result in the loss of a high proportion of observations that contain valuable information. Here, we present a study that uses a single eddy covariance tower on the border of two land uses to compare GHG exchange from a <em>Typha latifolia</em> paludiculture experiment and the surrounding area (SA) which is primarily a dairy meadow. We used a Bayesian inference approach to predict carbon dioxide (CO<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>) and methane (CH<span><math><msub><mrow></mrow><mrow><mn>4</mn></mrow></msub></math></span>) fluxes where the relative contribution of the two source areas, derived from a two-dimensional footprint for each timestep, was used to weight and parameterise equations. Distinct differences in flux behaviour were observed when contributions of the two land areas changed and that resulted in clearly different parameter distributions. The annual totals (posterior mean ± 95% confidence interval) from the simulations showed that <em>Typha</em> was a net sink of CO<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> for both simulation years (−18.5 ± 2.9 and −17.8 ± 2.9<!--> <!-->t<!--> <!-->CO<span><math><mrow><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub><mspace></mspace><msup><mrow><mi>ha</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup><mspace></mspace><msup><mrow><mi>yr</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math></span>) while SA was a net source (16.8 ± 2.9 and 17.4 ± 2.9 <!--> <!-->t<!--> <!-->CO<span><math><mrow><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub><mspace></mspace><msup><mrow><mi>ha</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup><mspace></mspace><msup><mrow><mi>yr</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math></span>). Using the 100-year global warming potential of CH<span><math><msub><mrow></mrow><mrow><mn>4</mn></mrow></msub></math></span>, even though CH<span><math><msub><mrow></mrow><mrow><mn>4</mn></mrow></msub></math></span> emissions were higher for paludiculture in both years (13.6 ± 0.6 and 15.9 ± 1.0<!--> <!-->t<!--> <!-->CO<span><math><mrow><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub><mtext>-eq</mtext><mspace></mspace><msup><mrow><mi>ha</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup><mspace></mspace><msup><mrow><mi>yr</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math></span>) than SA (7.1 ± 0.6 and 6.8 ± 1.2 <!--> <!-->t<!--> <!-->CO<span><math><mrow><msub><mrow></","PeriodicalId":50839,"journal":{"name":"Agricultural and Forest Meteorology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0168192324002922/pdfft?md5=d803f6f52e0e5d265659ba001a84ff8f&pid=1-s2.0-S0168192324002922-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141978766","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":"Forest structural and microclimatic patterns along an elevational gradient in Mount Kenya","authors":"","doi":"10.1016/j.agrformet.2024.110188","DOIUrl":"10.1016/j.agrformet.2024.110188","url":null,"abstract":"<div><p>Tropical mountain forests are important biodiversity hotspots, which host disproportionally high number of endemic species. However, the potential impacts of climate change in these areas are uncertain. A key factor contributing to this knowledge gap is that climatic conditions experienced by organisms inside tropical forests (i.e., microclimate) remain largely understudied. Due to the effects of topography and vegetation, the understory microclimate can differ substantially from free-air conditions (i.e., macroclimate). This study aimed at unveiling vegetation structural characteristics and microclimatic patterns along an elevational gradient in a highly diverse tropical mountain ecosystem (Mount Kenya), by combining hundreds of terrestrial laser scanning measurements with a two-year time-series of microclimate observations. Our results showed that macroclimate temperature and elevation contributed &gt;90 % to the microclimate variability in our study area. The influence of vegetation and soil moisture in regulating temperature differed substantially between day and night, as well as in different periods of the year. The contribution of vegetation to microclimate variation during the day was two times higher than that during the night. Soil moisture had a cooling effect on microclimate temperature during daytime, while the opposite pattern was observed at night. These differences affected lapse rates, which showed a clearly seasonal fluctuation during diurnal periods but a relatively stable pattern in night periods. The diurnal temperature range was regulated by combined effects of vegetation structure, elevation, and soil moisture. Finally, we were able to detect subtle changes in forest structure caused by historical selective logging. These changes resulted in a legacy effect on microclimate, thus demonstrating that human-induced disturbances have long-lasting impacts on tropical mountain ecosystems. These results improve our understanding of the climatic conditions experienced by organisms inside highly diverse African mountain forests, as well as how these conditions are regulated by vegetation structure and environmental factors.</p></div>","PeriodicalId":50839,"journal":{"name":"Agricultural and Forest Meteorology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0168192324003010/pdfft?md5=9d3de5ec5664cfd2441d942eed0a9542&pid=1-s2.0-S0168192324003010-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141979751","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":"Temporal accumulation and lag effects of precipitation on carbon fluxes in terrestrial ecosystems across semi-arid regions in China","authors":"","doi":"10.1016/j.agrformet.2024.110189","DOIUrl":"10.1016/j.agrformet.2024.110189","url":null,"abstract":"<div><p>Precipitation (PRE) plays a vital role in hydrological processes, ecological vegetation, and land-atmosphere interactions in semi-arid regions. Previous research has mainly focused on the impact of PRE on large-scale regional climate change and ecological evolution. However, there have been few studies on the long-term effects of PRE on carbon fluxes in these regions, especially the time-accumulation and -lag effects. Here, we employed observational data from the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL) and integrated multiple data sources, including remote sensing and carbon flux simulation data, to quantitatively assess the lagged response of carbon fluxes to PRE and elucidate the underlying mechanisms from multiple perspectives. Characterization of PRE, soil water content (SWC) and carbon fluxes at SACOL qualitatively reveals the existence of a time-delayed response of carbon fluxes to PRE, both on monthly and finer daily temporal scales. The average lagged response of net ecosystem exchange (NEE) and gross primary productivity (GPP) to accumulated PRE (APRE) is approximately 42 days. When considering time-accumulation and -lag effects, the combined direct and indirect effects of APRE on NEE and GPP increase by 0.37 and 0.58, respectively. Notably, preceding APRE primarily exerts a direct effect on current carbon fluxes, whereas the impact of SWC at a depth of 0.1 m is primarily mediated through the memory effect of preceding APRE, resulting in an indirect effect on carbon fluxes. These findings emphasize the importance of preceding APRE. Significantly, our subsequent study indicates that the delay in NEE and GPP responses to APRE also extends to approximately 40 to 50 days at the regional scale. Our findings emphasize the significant time effects of APRE on carbon fluxes, and considering these effects will contribute to a better understanding of the interplay between PRE and vegetation over semi-arid regions in China.</p></div>","PeriodicalId":50839,"journal":{"name":"Agricultural and Forest Meteorology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141978765","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":"Uncertainty of canopy interception modeling in high-altitude Picea crassifolia forests of Semi-arid regions","authors":"","doi":"10.1016/j.agrformet.2024.110190","DOIUrl":"10.1016/j.agrformet.2024.110190","url":null,"abstract":"<div><p>The study of physically-based rainfall interception is crucial for comprehending the water balance within forest ecosystems and the contribution of vegetation to the hydrological cycle, particularly in arid/semi-arid ecosystems. Despite its importance, there is a lack of comprehensive sensitivity analysis and parameter optimization, resulting in uncertain or suboptimal predictive accuracy. To mitigate these shortcomings, this research involved the establishment and assessment of three quintessential forest canopy interception models namely, the power Návar model, the reformulated Gash model, and the Liu model, within semi-arid forest environments at two different elevations. A global sensitivity analysis conducted on the three physical models indicated that the canopy saturation point and the mean rainfall intensity required for canopy saturation were the parameters to which the reformulated Gash and Liu models were most sensitive when applied to high-altitude settings. Conversely, for the Návar model, the most sensitive parameters were the interception coefficient of the linear equation, and the parameters of the power equation <em>k</em> and <em>c</em>. The quantification indices of model sensitivity exert a certain influence on the ranking of parameter sensitivities. However, for models with a limited number of parameters, the impact of these results is constrained. Conversely, the identification and utilization of characteristics specific to the parameter tuning process can significantly enhance the efficiency of model calibration. The three models employed by the research institute have all demonstrated commendable performance in modeling the canopy interception process of subalpine <em>P. crassifolia</em> in arid, high-altitude regions, achieving a \"good\" rating with Nash-Sutcliffe Efficiency values exceeding 0.7. In practical applications, we recommend giving priority to the use of the Liu model. The findings of this study provide a reference for model selection, sensitivity analysis, parameter calibration, and model evaluation in the context of extensive canopy interception modeling in arid areas with significant altitudinal variation. This constitutes an important theoretical support for the refined modeling of hydrological processes in high-altitude forests within arid zones.</p></div>","PeriodicalId":50839,"journal":{"name":"Agricultural and Forest Meteorology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141978764","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":"Observed surface heat fluxes partitioning during the local growing season over the Tibetan Plateau","authors":"","doi":"10.1016/j.agrformet.2024.110186","DOIUrl":"10.1016/j.agrformet.2024.110186","url":null,"abstract":"<div><p>Turbulent heat fluxes across the surface are an important mechanism of land-atmosphere coupling. But there is still a lack of sufficient observational measurements, particularly over the climate sensitive Tibetan Plateau (TP). This paper examines the partitioning between sensible and latent heat fluxes during growing season using the Bowen ratio as a diagnostic based on eddy covariance measurements from 12 observational sites located on the TP with the altitudes ranging between 3327 m and 4509 m above sea level. The results show an average Bowen ratio of 1.13, indicating that sensible heat flux is only slightly dominant in surface energy balance. For different climate zones, Bowen ratio varies from 0.56 to 1.05 in the semi-arid zone, 0.53 and 0.57 in the subhumid region, and 2.73 to 3.11 in the arid zone. The Bowen ratio shows sensitivity to soil dry and wet condition, with higher values during drier soil conditions. In the arid to semi-arid regions, the Bowen ratio shows a clear positive correlation with the Drought Soil Index (DSI) and a negative correlation with the Normalized Difference Vegetation Index (NDVI), suggesting sensitivity to soil moisture conditions. In the sub-humid climate zone, vapor pressure deficit (VPD) is the dominant factor influencing the Bowen ratio. In the wet and dry transition zone, soil moisture, VPD, NDVI and land-air temperature difference all have a role to play.</p></div>","PeriodicalId":50839,"journal":{"name":"Agricultural and Forest Meteorology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141953797","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":"Annual and seasonal dynamic of carbon sequestration in a Patagonian steppe","authors":"","doi":"10.1016/j.agrformet.2024.110184","DOIUrl":"10.1016/j.agrformet.2024.110184","url":null,"abstract":"<div><p>Arid and semiarid ecosystems comprise approximately 40 % of the global terrestrial surface and play an important role in the carbon-climate system. However, despite their large geographic extension in South America, they are largely under-represented in studies of ecosystem carbon fluxes. Eddy-covariance measurements of net ecosystem carbon exchange (NEE) were carried out in a Patagonian steppe co-dominated by grasses and shrubs in southern Argentina, for four years, including relatively dry and wet years. We evaluated the seasonal and annual variation of NEE, gross primary productivity (GPP) and ecosystem respiration (R_eco), and their environmental controls. This ecosystem exhibits large seasonal fluctuations in global radiation (Rg), air temperature, vapor pressure deficit, soil moisture and leaf area index (LAI). This steppe was a net carbon sink with a mean annual cumulative NEE of -249 g C m⁻² yr⁻¹. The strength as carbon sink was higher (-283.9 g C m⁻² yr⁻¹) in the wet year. NEE was tightly coupled to GPP with a marked peak at the middle of the growing season when LAI achieved its maximum value. R_eco exhibited less fluctuation throughout time than GPP. A random forest machine-learning analysis indicated that Rg, LAI and deep soil moisture are the main drivers contributing to variability in daily and monthly cumulative NEE, GPP and R_eco during the growing season and across the entire study period. Results suggest that deep-rooted shrubs contribute substantially to C fluxes during the growing season (low precipitation and high VPD period) by acceding to deep and more stable water sources which allow extending the period of net carbon capture. This study helps to understand how this ecosystem functions and to predict how this steppe will respond to future climate. In addition, this research highlights the need for conservation of this ecosystem due to its large extension and carbon sequestration capacity.</p></div>","PeriodicalId":50839,"journal":{"name":"Agricultural and Forest Meteorology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141953796","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}