Solar‐induced chlorophyll fluorescence (SIF) has been increasingly used as a proxy for terrestrial gross primary productivity (GPP). Previous work mainly evaluated the relationship between ...satellite‐observed SIF and gridded GPP products both based on coarse spatial resolutions. Finer resolution SIF (1.3 km × 2.25 km) measured from the Orbiting Carbon Observatory‐2 (OCO‐2) provides the first opportunity to examine the SIF–GPP relationship at the ecosystem scale using flux tower GPP data. However, it remains unclear how strong the relationship is for each biome and whether a robust, universal relationship exists across a variety of biomes. Here we conducted the first global analysis of the relationship between OCO‐2 SIF and tower GPP for a total of 64 flux sites across the globe encompassing eight major biomes. OCO‐2 SIF showed strong correlations with tower GPP at both midday and daily timescales, with the strongest relationship observed for daily SIF at the 757 nm (R2 = 0.72, p < 0.0001). Strong linear relationships between SIF and GPP were consistently found for all biomes (R2 = 0.57–0.79, p < 0.0001) except evergreen broadleaf forests (R2 = 0.16, p < 0.05) at the daily timescale. A higher slope was found for C4 grasslands and croplands than for C3 ecosystems. The generally consistent slope of the relationship among biomes suggests a nearly universal rather than biome‐specific SIF–GPP relationship, and this finding is an important distinction and simplification compared to previous results. SIF was mainly driven by absorbed photosynthetically active radiation and was also influenced by environmental stresses (temperature and water stresses) that determine photosynthetic light use efficiency. OCO‐2 SIF generally had a better performance for predicting GPP than satellite‐derived vegetation indices and a light use efficiency model. The universal SIF–GPP relationship can potentially lead to more accurate GPP estimates regionally or globally. Our findings revealed the remarkable ability of finer resolution SIF observations from OCO‐2 and other new or future missions (e.g., TROPOMI, FLEX) for estimating terrestrial photosynthesis across a wide variety of biomes and identified their potential and limitations for ecosystem functioning and carbon cycle studies.
We conducted the first global analysis of the relationship between solar‐induced chlorophyll fluorescence (SIF) and gross primary productivity (GPP) based on OOC‐2 and flux tower observations. Strong linear relationships between SIF and GPP at the ecosystem scale were found for all eight biomes except evergreen broadleaf forests. The nearly universal rather than biome‐specific SIF–GPP relationship can potentially lead to more accurate GPP estimates globally. OCO‐2 SIF can generally better estimate GPP than satellite‐derived vegetation indices and light use efficiency models. Our findings revealed the potential of finer‐resolution SIF observations in ecosystem functioning and carbon cycling studies and model benchmarking efforts.
Understanding how forest ecosystems respond to environmental factors, particularly in the context of global climate change, is essential for devising effective mitigation strategies. This study ...focuses on quantifying the interaction between forest ecosystems and atmospheric gases. To achieve our objectives, we are using the eddy covariance (EC) flux method to measure air turbulence and gas concentrations above the forest canopy at the Station for Measuring Ecosystem-Atmosphere Relations (SMEAR) in southern Estonia. We apply a flux footprint (FFP) model to describe the spatial extent and position of the surface area contributing to the turbulent flux measurements. The FFP analysis provides valuable insights into the long-term changes in SMEAR Estonia, the FFP and its relationship with forest management and land use changes. Our findings reveal that the FFP area varies from year to year due to changes in wind speed and direction, affecting the contribution of different land cover elements to the overall FFP. The average changes in the FFP area at a height of 30 meters were approximately 4.9%, while those at a height of 70 meters were only 1.6%. Moreover, human activities, such as thinning and clear-cutting, influence the growing stock and increment of forest stands.
Water and carbon balances in a hemi-boreal forest Mercuri, Emílio Graciliano Ferreira; Tamm, Toomas; Noe, Steffen Manfred
Metsanduslikud uurimused,
11/2023, Letnik:
78, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The carbon and water fluxes and their inter-relations are key aspects of ecosystem dynamics. In this study, regionalization was used in transferring parameters from the GR4J-Cemaneige model ...calibrated in Reola hydrographic basin to predict daily flows in Kalli basin; both watersheds are located in the southeast of Estonia. Evapotranspiration data was collected from the MODIS sensor of the Terra satellite and from the Station for Measuring Ecosystem-Atmosphere Relations (SMEAR Estonia). Precipitation data was collected from Tartu–Tõravere and SMEAR Estonia stations and river flow from Reola hydrometric station. The year 2011 was used for model warm-up, model calibration was done in 2012–2017 and the 2018–2020 period was used for validation. The GR4J-Cemaneige model was calibrated at Reola Basin, with a Nash-Sutcliffe Efficiency index of 0.73. The 6 constants of Reola subbasin were transferred to Kalli subbasin for river flow simulation. Net ecosystem exchange (NEE) was measured at the 70 m SMEAR tower with the eddy covariance technique. The balances indicate that the ecosystem at Kalli watershed is slowly becoming a source of carbon and less water is available at the catchment reservoir. NEE has increased from -1.23 μmol m
s
in 2015 to -0.62 μmol m
s
in 2020, while the delta water storage decreased from 0.24 mm in 2015 to -0.05 mm in 2020. This behavior may increase soil drying and oxidation, and it will probably release more carbon in the future. This research allows a better understanding of the Järvselja hemi-boreal forest water-carbon dynamics.
The potential of carbonyl sulfide (COS) flux measurements as an additional constraint for estimating the gross primary production depends, among other preconditions, on our understanding of the soil ...COS exchange and its contribution to the overall net ecosystem COS flux. We conducted soil chamber measurements of COS, with transparent chambers, in three different ecosystems across Europe. The in situ measurements were followed by laboratory measurements of soil samples collected at the study sites. The soil samples were exposed to UV radiation to investigate the role of photo‐degradation for COS exchange. In situ and laboratory measurements revealed pronounced intersite and intrasite variability of COS exchange. In situ COS fluxes were primarily governed by radiation in the savannah‐like grassland (SAV), soil temperature and intrasite heterogeneity in the deciduous broadleaf forest, and soil water content and intrasite heterogeneity in the evergreen needleleaf forest. The soil of the ecosystem with the highest light intensity incident on the soil surface, SAV, was a net source for COS, while the soils of the other two ecosystems were COS sinks. UV radiation increased COS emissions and/or reduced COS uptake from all soil samples under laboratory conditions. The impact of UV on the COS flux differed between soil samples, with a tendency toward a stronger response of the COS flux to UV radiation exposure in samples with higher soil organic matter content. Our results emphasize the importance of photo‐degradation for the soil COS flux and stress the substantial spatial variability of soil COS exchange in ecosystems.
Key Points
COS emissions increased after UV exposure of soil samples from three European soils
Primary abiotic driver of COS cycling differs between three European soils
In our recent study in Global Change Biology (Li et al., ), we examined the relationship between solar‐induced chlorophyll fluorescence (SIF) measured from the Orbiting Carbon Observatory‐2 (OCO‐2) ...and gross primary productivity (GPP) derived from eddy covariance flux towers across the globe, and we discovered that there is a nearly universal relationship between SIF and GPP across a wide variety of biomes. This finding reveals the tremendous potential of SIF for accurately mapping terrestrial photosynthesis globally.
Controversial evidence of CO2‐responsiveness of isoprene emission has been reported in the literature with the response ranging from inhibition to enhancement, but the reasons for such differences ...are not understood. We studied isoprene emission characteristics of hybrid aspen (Populus tremula x P. tremuloides) grown under ambient (380 μmol mol−1) and elevated (780 μmol mol−1) CO2 to test the hypothesis that growth CO2 effects on isoprene emission are driven by modifications in substrate pool size, reflecting altered light use efficiency for isoprene synthesis. A novel in vivo method for estimation of the pool size of the immediate isoprene precursor, dimethylallyldiphosphate (DMADP) and the activity of isoprene synthase was used. Growth at elevated CO2 resulted in greater leaf thickness, more advanced development of mesophyll and moderately increased photosynthetic capacity due to morphological “upregulation”, but isoprene emission rate under growth light and temperature was not significantly different among ambient‐ and elevated‐CO2‐grown plants independent of whether measured at 380 μmol mol−1 or 780 μmol mol−1 CO2. However, DMADP pool size was significantly less in elevated‐CO2‐grown plants, but this was compensated by increased isoprene synthase activity. Analysis of CO2 and light response curves of isoprene emission demonstrated that the CO2 for maximum isoprene emission was shifted to lower CO2 in elevated‐CO2‐grown plants. The light‐saturated isoprene emission rate (Imax,Q) was greater, but the quantum efficiency at given Imax,Q was less in elevated‐CO2‐grown plants, especially at higher CO2 measurement concentration, reflecting stronger DMADP limitation at lower light and higher CO2. These results collectively demonstrate important shifts in light and CO2‐responsiveness of isoprene emission in elevated‐CO2‐acclimated plants that need consideration in modeling isoprene emissions in future climates.
Secondary organic aerosols (SOAs) formed from biogenic volatile organic compounds (BVOCs) constitute a significant fraction of atmospheric particulate matter and have been recognized to significantly ...affect the climate and air quality. Atmospheric SOA particulate mass yields and chemical composition result from a complex mixture of oxidation products originating from a diversity of BVOCs. Many laboratory and field experiments have studied SOA particle formation and growth in the recent years. However, a large uncertainty still remains regarding the contribution of BVOCs to SOA. In particular, organic compounds formed from sesquiterpenes have not been thoroughly investigated, and their contribution to SOA remains poorly characterized. In this study, a Filter Inlet for Gases and Aerosols (FIGAERO) combined with a high-resolution time-of-flight chemical ionization mass spectrometer (CIMS), with iodide ionization, was used for the simultaneous measurement of gas-phase and particle-phase oxygenated compounds. The aim of the study was to evaluate the relative contribution of sesquiterpene oxidation products to SOA in a springtime hemiboreal forest environment. Our results revealed that monoterpene and sesquiterpene oxidation products were the main contributors to SOA particles. The chemical composition of SOA particles was compared for times when either monoterpene or sesquiterpene oxidation products were dominant and possible key oxidation products for SOA particle formation were identified for both situations. Surprisingly, sesquiterpene oxidation products were the predominant fraction in the particle phase in some periods, while their gas-phase concentrations remained much lower than those of monoterpene products. This can be explained by favorable and effective partitioning of sesquiterpene products into the particle phase. The SOA particle volatility determined from measured thermograms increased when the concentration of sesquiterpene oxidation products in SOA particles was higher than that of monoterpenes. Overall, this study demonstrates that sesquiterpenes may have an important role in atmospheric SOA formation and oxidation chemistry, in particular during the spring recovery period.
Complex mixtures of substances are in the atmosphere and they can cause diseases in humans and biological communities after acute or chronic exposition. This paper focuses on the physical measurement ...of particulate matter, a proxy for air pollution, and a biological method for mutation assessment due to plants’ exposure to air pollution. The objective of this research was to characterize the air pollution seasonality in municipalities in southern Brazil, and also to understand the relation between air pollution and the biological response of the
sp. clone 4430. The optical sensor SDS011 was used for measurements of particulate matter (PM) and the Trad-SHM bioassay was chosen to quantify the mutagenic alterations that occurred in stamen hairs during the study period, with PM data being measured every 5 seconds and the flowers being harvested approximately every two weeks for laboratory analysis. The Pearson test was applied to verify the correlation between PM and mutations in stamen hair as a result of which it was observed that there is a positive correlation between these data, with the highest value found being r = 0.61. Also, the period with the highest occurrence of pink cells was between autumn and spring, the same period in which an unusual increase in PM concentrations was also observed, a period that corresponds to a less favorable dispersion of pollutants in the atmosphere. The use of
sp. clone 4430 showed sensitivity to the environments in which it was exposed. Biomonitoring is an important tool for understanding the effects of pollutants on the ecosystem.
Effects of elevated atmospheric CO2 on plant isoprene emissions are controversial. Relying on leaf-scale measurements, most models simulating isoprene emissions in future higher CO2 atmospheres ...suggest reduced emission fluxes. However, combined effects of elevated CO2 on leaf area growth, net assimilation and isoprene emission rates have rarely been studied on the canopy scale, but stimulation of leaf area growth may largely compensate for possible CO2 inhibition reported at the leaf scale. This study tests the hypothesis that stimulated leaf area growth leads to increased canopy isoprene emission rates.
We studied the dynamics of canopy growth, and net assimilation and isoprene emission rates in hybrid aspen (Populus tremula × Populus tremuloides) grown under 380 and 780 μmol mol−1 CO2. A theoretical framework based on the Chapman–Richards function to model canopy growth and numerically compare the growth dynamics among ambient and elevated atmospheric CO2-grown plants was developed.
Plants grown under elevated CO2 had higher C:N ratio, and greater total leaf area, and canopy net assimilation and isoprene emission rates. During ontogeny, these key canopy characteristics developed faster and stabilized earlier under elevated CO2. However, on a leaf area basis, foliage physiological traits remained in a transient state over the whole experiment.
These results demonstrate that canopy-scale dynamics importantly complements the leaf-scale processes, and that isoprene emissions may actually increase under higher CO2 as a result of enhanced leaf area production.
Fusarium head blight (FHB) caused by Fusarium pathogens is one of the most devastating fungal diseases of small grain cereals worldwide, substantially reducing yield quality and food safety. Its ...severity is increasing due to the climate change caused by weather fluctuations. Intensive research on FHB control methods has been initiated more than a decade ago. Since then, the environment has been rapidly changing at regional to global scales due to increasing anthropogenic emissions enhanced fertilizer application and substantial changes in land use. It is known that environmental factors affect both the pathogen virulence as well as plant resistance mechanisms. Changes in CO2 concentration, temperature, and water availability can have positive, neutral, or negative effects on pathogen spread depending on the environmental optima of the pathosystem. Hence, there is a need for studies of plant–pathogen interactions in current and future environmental context. Long-term monitoring data are needed in order to understand the complex nature of plants and its microbiome interactions. We suggest an holobiotic approach, integrating plant phyllosphere microbiome research on the ecological background. This will enable the development of efficient strategies based on ecological know-how to fight Fusarium pathogens and maintain sustainable agricultural systems.
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