Historical Survey of Primary Productivity Research

Выполнены измерения чистого экосистемного обмена (NEE) на мочажинном участке грядовомочажинного комплекса олиготрофного болота «Мухрино» с разделением на составляющие компоненты: валовую первичную продукцию (GPP) и дыхание экосистемы (R eco ). Измерения проводились в течение самого тёплого (июль), переходного (сентябрь) и самого холодного (октябрь) месяцев летне-осеннего сезона методом автоматизированных камер с 30-минутным интервалом. Это позволило получить подробную информацию о суточном ходе и сезонной динамике показателей. Для исследованных месяцев по отдельности и полевого сезона в целом осуществлен корреляционный анализ связи между гидрометеорологическими параметрами и величиной потоков. Для дыхания экосистемы (R eco ) наиболее высокий уровень корреляции за сезон выявлен с температурой почвы (0.88), температурой воздуха (0.71) и уровнем болотных вод (-0.73); за июль наиболее сильная корреляция выявлена с температурой воздуха (0.70) и температурой почвы (0.68); за сентябрь -с температурой почвы (0.81) и уровнем болотных вод (-0.78); за октябрь -с фотосинтетически активной радиацией (-0.59). Валовая первичная продукция (GPP) сильнее всего коррелирует с фотосинтетически активной радиацией (PAR) -в июле коэффициент корреляции равен -0.95, в сентябре -0.86, в октябре -0.79, в целом за полевой сезон -0.89. Чистый экосистемный обмен (PAR), аналогично GPP, наиболее тесно связан с PAR. В июле коэффициент корреляции NEE и PAR составляет -0.91, в сентябре -0.74, в октябре -0.71, за весь полевой сезон -0.73. Стоит подчеркнуть, что для каждого рассматриваемого месяца влияние внешних факторов на потоки уменьшается с течением времени от июля к октябрю, достигая минимума корреляции в самом холодном месяце. Ключевые слова: Дыхание экосистемы (R eco ); валовая первичная продукция (GPP); чистый экосистемный обмен (NEE); фотосинтетически активная радиация (PAR); LI-8100A; уровень грунтовых вод (WTL); автоматические камеры; Мухрино; болотные экосистемы Западной Сибири; круговорот углерода. Global climate change is one of the most important and promising phenomena to study in actual time. One of the key causes of global climate change is increasing the greenhouse gas (GHG) concentrations in the atmosphere [IPCC, 2023]. The main greenhouse gases are methane, carbon dioxides and nitric oxide, which contribute to the greenhouse effect and global warming [Lashof, Ahuja, 1990] . Carbon dioxide (CO 2 ) is one of the most significant and widespread gases involved in the planet's global carbon cycle [Lashof, Ahuja. 1990] . At the same time, living organisms play a key role in creation of atmosphere composition. Autotrophic organisms use a carbon dioxide to build their body structures, including complex organic compounds. During ecosystem functioning, the part of the carbon dioxide is released into the atmosphere through organism respiration, while another part is released through the decomposition of dead organic matter. Carbon dioxide may also be produced through natural and anthropogenic processes. Peatland ecosystems play a significant role in the planet's carbon cycle, both locally and globally. Peatlands in their natural undisturbed state are a significant long-term carbon sink 1 . However, the process of carbon deposition is not constantin different years, peatlands may serve either as carbon sink or source 2 . The main factor stimulating the carbon sequestration by peatland ecosystems is climatic conditions [Harenda et al., 2018; Bond-Lamberty et al., 2018] . Peatlands are the second most significant carbon stock on Earth and the largest on land. Despite covering only 2.84% of the Earth's land surface, the amount of soil organic carbon stored in them accounts for about one-third of all soil organic carbon on Earth. Peatlands in the northern hemisphere play a particularly important role in carbon sequestration, with an estimated accumulated carbon quantity of ~473-621 Gt of carbon [Yu et al., 2010] . The largest area of peatlands in Russia is located in Western Siberia, estimated at ~42% of the total Russian area [Vomperskiy et al., 1994; Sheng et al., 2004]. The territory of Western Siberia is featured to a high share of peatlands in original undisturbed state, making them an ideal location to study the impact of global changes on peatland biogeochemical functioning worldwide. The carbon balance of peatlands is mainly determined by two processes: photosynthesis and respiration [Harenda et al., 2018] . The main factors influencing the CO 2 flux from peatlands are photosynthetically active radiation, atmospheric air temperature (T avg ), soil temperature (T soil ), and water table level (WTL) [Miao et al., 2013;

Primary production represents a globally important flux of carbon between the atmosphere and the biosphere. From an ecological perspective, it measures the rate at which solar energy is stored by plants as organic matter, and is therefore a measure of the rate at which solar energy is captured and made available to the rest of the food chain (Odum 1971). From a biogeochemical perspective, primary production provides links between the biosphere and the climate system through the global cycling of C, water and nutrients (Roy et al . 2001). Gross primary production (GPP) is the total amount of C assimilated by plants within a given area over a specified timeframe. (Here GPP refers to the total C fixed by photosynthesis, minus the C lost by photorespiration. We have adopted the convention of specifying productivity in units of C mass per unit ground area per unit time, although we could have alternatively used units of total biomass, or energy: Odum 1971.) Net primary production (NPP) is GPP less the flux of autotrophic respiration of assimilate used for the plant’s own metabolism ( R ), therefore:

Retrieval and assessment of CO2 uptake by mediterranean ecosystems using remote sensing and

Gross primary production (GPP)-the uptake of carbon dioxide (CO2) by leaves, and its conversion to sugars by photosynthesis-is the basis for life on land. Earth System Models (ESMs) incorporating the interactions of land ecosystems and climate are used to predict the future of the terrestrial sink for anthropogenic CO21 . ESMs require accurate representation of GPP. However, current ESMs disagree on how GPP responds to environmental variations 1,2 , suggesting a need for a more robust theoretical framework for modelling 3,4 . Here, we focus on a key quantity for GPP, the ratio of leafinternal to external CO2 (χ). χ is tightly regulated and depends on environmental conditions, but is represented empirically and incompletely in today's models. We show that a simple evolutionary optimality hypothesis 5,6 predicts specific quantitative dependencies of χ on temperature, vapour pressure deficit and elevation; and that these same dependencies emerge from an independent analysis of empirical χ values, derived from a worldwide dataset of >3,500 leaf stable carbon isotope measurements. A single global equation embodying these relationships then unifies the empirical light-use efficiency model 7 with the standard model of C3 photosynthesis 8 , and successfully predicts GPP measured at eddy-covariance flux sites. This success is notable given the equation's simplicity and broad applicability across biomes and plant functional types. It provides a theoretical underpinning for the analysis of plant functional coordination across species and emergent properties of ecosystems, and a potential basis for the reformulation of the controls of GPP in next-generation ESMs.

(1) The above-ground production of an established perennial grass (meadow fescue) ley in central Sweden was analysed by repeated clipping during 1982 and 1983. Standing vegetation was separated into living and dead material and surface litter was collected. Three methods were used to calculate net above-ground primary production (NAPP). Two of them accounted for death and shedding between samplings. (2) Depending on the calculation method, annual NAPP of ash-free dry mass varied between 903-985 and 810-1039 g m-2 in 1982 and 1983, respectively. The two methods which included biomass turnover gave the highest production values. (3) The underestimation in NAPP due to decomposition of litter between samplings was evaluated by applying a decomposition constant, estimated in a separate litter-bag experiment, to the mean amount of litter present during a sampling period. It was found to be <10%. (4) The mean daily growth rates of above-ground crop were 4 7 and 6 0 g m-2 in 1982 and 1983, respectively. The maximum recorded daily crop growth (22 0 g m2) occurred in early June 1983. (5) The study was part of a multi-disciplinary ecosystem project, and estimates of below-ground production and herbivore consumption were available, allowing total net primary production (NPP) to be estimated. Mean annual NPP was 1468 g m-2. (6) NPP was underestimated as rhizodeposition was not measured. Its underestimation from neglecting death and decomposition was less severe above than below ground. The amount of organic matter input to the soil system via litterfall was a minor part of the NPP but a significant part of the total organic matter supplied to the soil organic matter pool during a year. (7) Growth pattern and total NPP were compared with those of a lucerne ley grown in parallel with the meadow fescue ley. A severe drought in 1983 affected the grass ley more than the lucerne ley. Average annual NPP was similar in both crops, but the amount of standing dead was higher in the grass ley than in the lucerne ley. The allocation below ground was similar, about 30%, but root death was higher in the grass ley.

A carbon sink-driven approach to estimate gross primary production from microwave satellite observations

Coastal freshwater wetlands are critical ecosystems for both local and global carbon cycles, sequestering substantial carbon while also emitting methane (CH4) due to anoxic conditions. Estuarine freshwater wetlands face unique challenges from fluctuating water levels, which influence water quality, vegetation, and carbon cycling. However, the response of CH4 fluxes and their drivers to altered hydrology and vegetation remains unclear, hindering mechanistic modeling. To address these knowledge gaps, we studied an estuarine freshwater wetland in the Great Lakes region, where rising water levels led to a vegetation shift from emergent Typha dominance in 2015-2016 to floating-leaved species in 2020-2022. Using eddy covariance flux measurements during the peak growing season (June-September) of both periods, we observed a 60% decrease in CH4 emissions, from 81 ± 4 g C m-2 in 2015-2016 to 31 ± 3 g C m-2 in 2020-2022. This decline was driven by two main factors: (1) higher water levels, which suppressed ebullitive fluxes via increased hydrostatic pressure and extended CH4 residence time, enhancing oxidation potential in the water column; and (2) reduced CH4 conductance through plants. Net carbon dioxide (CO2) uptake decreased by 90%, from -267 ± 26 g C m-2 in 2015-2016 to -27 ± 49 g C m-2 in 2020-2022. Additionally, diel CH4 flux patterns shifted, with a distinct morning peak observed in 2015-2016 but absent in 2020-2022, suggesting changes in plant-mediated transport and a potential decoupling from photosynthesis. The dominant factors influencing CH4 fluxes shifted from water temperature and gross primary productivity in 2015-2016 to atmospheric pressure in 2020-2022, suggesting an increased role of ebullition as a primary transport pathway. Our results demonstrate that changes in water levels and vegetation can substantially alter CH4 and CO2 fluxes in coastal freshwater wetlands, underscoring the critical role of hydrological shifts in driving carbon dynamics in these ecosystems.

Assessing the relationship between microwave vegetation optical depth and gross primary production

Effects of warming and increased precipitation on net ecosystem productivity: A long-term manipulative experiment in a semiarid grassland

Detection and attribution of an anomaly in terrestrial photosynthesis in Europe during the COVID-19 lockdown

“Primary production” refers to energy fixed by plants. The total amount of energy fixed is usually called “gross production.” A certain fraction of gross production is used in respiration by the plants; the remainder appears as new biomass or “net primary production.” Thus for a single plant or a community of green plants: Net Primary Production = Gross Production − Respiration (of Autotrophs) Similar relationships occur in ecosystems except that the organic matter and respiration of heterotrophs must be included. The increase in total organic matter is “net ecosystem production”; respiration is the total respiration of the green plants (autotrophs) and the animal community and decay organisms (heterotrophs). Gross production is of course identical to that of the plant community. Thus for an ecosystem: Net Ecosystem Production = Gross Production − Respiration (of Autotrophs and Heterotrophs) Study of these attributes of terrestrial ecosystems is difficult, both because of the complex interrelations of the processes involved, and because of the problems of working with systems as large as whole forests. Three approaches are in use: (1) Harvest techniques measure weight increase (and caloric equivalent and chemical composition) of net production. A refinement ot this approach based on “dimension analysis” has made possible important recent advances in the study of forests. Other techniques approach gross production and respiration through measurement of exchange of gases, especially CO2. These include: (2) Enclosure studies, involving measurements of CO2 exchange in plastic enclosures of parts of ecosystems and (3) Flux techniques based on measurement of CO2 levels in the environment. All three approaches are being applied to a forest at Brookhaven National Laboratory to determine the production equation of this ecosystem. Results to date have established general ranges of such parameters of ecosystems as total biomass, total surface area of leaves and of stems and branches, rates of decay of organic matter in soils, rates of production of roots, and rates of photosynthesis and respiration under different environmental conditions. In the Brookhaven forest net primary production is 1124 dry g/m2/yr (with an energy equivalent of 492 cal/cm2/yr), and gross production is about 2550 dry g/m2/yr; the producers or green plants thus respire 56% of their gross production. Net ecosystem production is 422 dry g/m2/yr in this young forest. The ratio of total respiration to gross production is a convenient expression of successional status; a value of 0.82 for the Brookhaven forest indicates that this is a late successional community, but not in steady-state or climax condition (1.0). A leaf surface area of 3.8 m2 per m2 of ground surface intercepts sunlight energy, and the ratio of net primary production to incident visible sunlight energy gives a net efficiency of primary production of 0.0088. These and other functional characteristics of ecosystems are currently important topics of research—involving understanding of communities as biological systems, evaluation of the potential of environments to support life and man's harvest; and understanding of the fundamental meaning and consequences of man's alteration, exploitation, and pollution of ecosystems.

Satellite-based models have been widely used to estimate gross primary production (GPP) of terrestrial ecosystems. Although they have many advantages for mapping spatiotemporal variations of regional or global GPP, the performance in agroecosystems is relatively poor. In this study, a light-use-efficiency model for cropland GPP estimation, named EF-LUE, driven by remote sensing data, was developed by integrating evaporative fraction (EF) as limiting factor accounting for soil water availability. Model parameters were optimized first using CO2 flux measurements by eddy covariance system from flux tower sites, and the optimized parameters were further spatially extrapolated according to climate zones for global cropland GPP estimation in 2001–2019. The major forcing datasets include the fraction of absorbed photosynthetically active radiation (FAPAR) data from the Copernicus Global Land Service System (CGLS) GEOV2 dataset, EF from the ETMonitor model, and meteorological forcing variables from ERA5 data. The EF-LUE model was first evaluated at flux tower site-level, and the results suggested that the proposed EF-LUE model and the LUE model without using water availability limiting factor, both driven by flux tower meteorology data, explained 82% and 74% of the temporal variations of GPP across crop sites, respectively. The overall KGE increased from 0.73 to 0.83, NSE increased from 0.73 to 0.81, and RMSE decreased from 2.87 to 2.39 g C m−2 d−1 in the estimated GPP after integrating EF in the LUE model. These improvements may be largely attributed to parameters optimized for different climatic zones and incorporating water availability limiting factor expressed by EF into the light-use-efficiency model. At global scale, the verification by GPP measurements from cropland flux tower sites showed that GPP estimated by the EF-LUE model driven by ERA5 reanalysis meteorological data and EF from ETMonitor had overall the highest R2, KGE, and NSE and the smallest RMSE over the four existing GPP datasets (MOD17 GPP, revised EC-LUE GPP, GOSIF GPP and PML-V2 GPP). The global GPP from the EF-LUE model could capture the significant negative GPP anomalies during drought or heat-wave events, indicating its ability to express the impacts of the water stress on cropland GPP.

Carbon dioxide (CO2) uptake and the mechanical strength of concrete with and without carbon-dioxide-philic (CDP) amine sorbents were assessed in this study. Cement pastes with three amine-based sorbents (5-amino-1 pentanol, piperazine and 3-amino-1-propanesulfonic acid) were hydrated for 28 d. They were then assessed for carbon dioxide uptake and compressive/bending strength. The carbon dioxide in the atmosphere was sequestrated into the concrete as simulated carbonation weathering occurred, and the carbon dioxide uptake was measured using thermogravimetric analysis. Carbon dioxide uptake increased when CDP amine sorbents were mixed into the concrete specimens, with 5-amino-1-pentanol and piperazine showing the best efficiency, with carbon dioxide uptakes of 2·44% and 2·24%, respectively. The compressive and bending strengths also increased with carbonation. The strengths of the concretes with CDP sorbents were higher than that of ordinary concrete due to the microstructural densification, indicating that urban carbon dioxide sequestration can be performed using concrete structures without damaging their structural strength.

A radiogasometric method for the determination of the rates of intracellular decarboxylation of primary and end products of steady-state photosynthesis in the light has been worked out. On the basis of oxygen dependence of the CO2 evolution, two types of decarboxylation, oxygenase (photorespiration) and oxidase (dark respiration), have been distinguished. Oxygenase decarboxylation is linearly dependent on O2 concentration in the range from 0 to 210 mmol mol−1, which is characteristic of the oxygenation of RuBP, the ratelimiting reaction of the glycolate cycle. Oxidase decarboxylation is saturated at relatively low O2 concentration (of about 15 mmol mol−1), similar to the oxidative reactions associated with glycolysis and the Krebs cycle. In the C3 plants (tobacco, wheat, barley) we have studied, primary products were decarb-oxylated predominantly via the oxygenase mechanism; the oxidase component was 3–15% of the total rate of the decarboxylation of primary photosynthates in the light. The oxygenase mechanism was also involved in the decarboxylation of end products of photosynthesis. The rate of this component exceeded by 3 to 5 times the rate of oxidase decarboxylation of end products in the light. It has been suggested that compounds derived from the degradation of end products of photosynthesis are incorporated into the reductive pentose phosphate cycle and, via the cycle, into the glycolate cycle where they are decarboxylated. In this way, four components of plant leaf respiration in the light may be distinguished according to the substrates and mechanisms of decarboxylation. In the dark, only one of them, oxidase decarboxylation of end products, is functioning. The rate of this component has been shown to be partially suppressed by light.

Metabolism Predicts Ecological Response to Warming