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In this study we determined the effect of transformation of a mature sessile oak forest stand into a coppiced forest, and of thinning and throughfall reduction in a coppice stand on soil water content (SWC) and soil CO efflux. The precipitation reduction was induced by installing parallel drainage channels in both unthinned and thinned coppice stands. The driving factor for temporal dynamics of soil CO efflux in all plots was soil temperature. The other factor was soil water content but only up to about 15%. Above this threshold, there was no more effect on CO efflux. We found no clear difference in SWC or soil CO efflux between the mature and coppiced stand eight years after harvesting. On the other hand, thinning of the coppice stand resulted in increase in SWC up to 22% in proportion, which we assume to be a result of increased gap fraction of the canopy. However, no effect on soil CO efflux was observed two years after the thinning. Installation of the drainage channels in two plots covering 30% of the ground area resulted in decrease in SWC up to a proportional 30.5% and thus contributed up to 50.7% reduction in soil CO efflux.222222

Research infrastructures play a key role in launching a new generation of integrated long-Term, geographically distributed observation programmes designed to monitor climate change, better understand its impacts on global ecosystems, and evaluate possible mitigation and adaptation strategies. The pan-European Integrated Carbon Observation System combines carbon and greenhouse gas (GHG; CO 2 , CH 4 , N 2 O, H 2 O) observations within the atmosphere, terrestrial ecosystems and oceans. High-precision measurements are obtained using standardised methodologies, are centrally processed and openly available in a traceable and verifiable fashion in combination with detailed metadata. The Integrated Carbon Observation System ecosystem station network aims to sample climate and land-cover variability across Europe. In addition to GHG flux measurements, a large set of complementary data (including management practices, vegetation and soil characteristics) is collected to support the interpretation, spatial upscaling and modelling of observed ecosystem carbon and GHG dynamics. The applied sampling design was developed and formulated in protocols by the scientific community, representing a trade-off between an ideal dataset and practical feasibility. The use of open-Access, high-quality and multi-level data products by different user communities is crucial for the Integrated Carbon Observation System in order to achieve its scientific potential and societal value.

Recent changes in water availability can be crucial for the development, growth and carbon budget of forests. Therefore, our aim was to determine the effect of reduced throughfall and severe summer drought on stem CO2 efflux as a function of temperature and stem increment. Stem CO2 efflux was measured using the chamber method on oak and hornbeam under four treatments: coppice, thinned coppice, and both coppice and thinned coppice with 30 %-reduced throughfall. The first year of the experiment had favourable soil water availability and the second year was characterized by a dry summer. While reduced throughfall had no effect on stem CO2 efflux, the summer drought decreased efflux by 43–81 % during July and August. The stem CO2 efflux was reduced less severely (by 13–40 %) in September when the drought persisted but the stem increment was already negligible. The stem increment was also strongly affected by the drought, which was reflected in its paired relationship with stem CO2 efflux over the two experimental years. The study showed that summer dry periods significantly and rapidly reduce stem CO2 efflux, whereas a constant 30 % rainfall reduction needs probably a longer time to affect stem properties, and indirectly stem CO2 efflux. [ABSTRACT FROM AUTHOR]

Key message: Forest floor CO2 efflux (Rf; consisted of soil and potential vegetation) increased after forest harvest, but this response was changed by actual weather (especially drought and rains). Context: Soil respiration is a large source of CO2 released to the atmosphere and is sensitive to forest management practices and weather. Aims: To determine effects of harvest, ancient practices and weather in a newly established coppice forest on Rf. Methods: Rf, temperature, and moisture were measured during 1 year before and 2 years after harvest. Results: Pasturing and raking had no effect on Rf. It tended to increase during the first season after harvest. In the second year after harvest, differences in Rf between control and harvested plots became much greater because of intensively developing herbaceous vegetation on harvested plots. No difference between the control and harvested plots was found during severely dry conditions. Following intensive rain pulses, Rf was larger in the control than in the harvested plots. Conclusion: Findings indicate that the Rf response is not uniform in time and depends on microclimate, particularly on soil moisture. This may be crucial for estimation of the harvest impact on soil processes especially under changing climate. [ABSTRACT FROM AUTHOR]

The study focuses on the effect of chemical amelioration of dolomitic limestone (doses of 0, 2, 3, 4, 6, 9 and 26 t ha-1) on soil respiration in a Norway spruce monoculture in mid-altitudinal elevation during one-year period after application. Firstly, the soil respiration was measured in situ as monthly CO2 efflux from the soil surface horizon in the period May to October 2016. Secondly, basal respiration, microbial biomass carbon and metabolic quotient of the organic H and organo-mineral A horizons were assessed under laboratory conditions within one year after the treatment. Soil CO2 efflux increased by 3 to 31% and by 29 to 98% for the ameliorant of 2 and 26 t ha-1, respectively, compared to the unlimed control treatment. The CO2 efflux was significantly driven by external conditions such as soil moisture and temperature, especially in the last seasonal months. Basal respiration of the H horizon increased up to a dose of 9 t ha-1 but decreased at 26 t ha-1. In the A horizon, microbial activity increased in all the limed variants compared to the non-limed variant. A similar trend was observed in microbial carbon and the metabolic quotient of the soil. Our results prove that the ameliorant doses commonly used in the forestry sector (3-4 t ha-1) substantially increase the soil microbial activity during (soil CO2 efflux) and after (laboratory data) the first year after application. This results in the accelerated mineralization of soil organic material and subsequent loss from the forest ecosystem. [ABSTRACT FROM AUTHOR]

One technique for measurement of soil CO2 production and emission is a gradient method using CO2 concentration measurements within soil by polypropylene membrane tubes (Accurel® PP V8/2 HF). In this study, we determined whether these tubes are suitable for monitoring instantaneous CO2 concentration and its rapid changes in the soil. The tested tube was placed within the plastic bag. The CO2 concentration was continuously measured in both the tube and the bag to determine the time lag in CO2 concentration changes in the tube after an evoked rapid increase in CO2 concentration in the bag. We found that higher the CO2 concentration and higher the increase in CO2 concentration around the tube, the faster is the change in CO2 concentration within the tube. These relationships were described by hyperbola models and corresponding equations. Our results confirm that the tested membrane tubes are suitable for monitoring rapid changes in soil CO2 concentration. [ABSTRACT FROM AUTHOR]

Chamber measurements of trace gas fluxes between the land surface and the atmosphere have been conducted for almost a century. Different chamber techniques, including static and dynamic, have been used with varying degrees of success in estimating greenhouse gases (CO2, CH4, N2O) fluxes. However, all of these have certain disadvantages which have either prevented them from providing an adequate estimate of greenhouse gas exchange or restricted them to be used under limited conditions. Generally, chamber methods are relatively low in cost and simple to operate. In combination with the appropriate sample allocations, chamber methods are adaptable for a wide variety of studies from local to global spatial scales, and they are particularly well suited for in situ and laboratory-based studies. Consequently, chamber measurements will play an important role in the portfolio of the Pan-European long-term research infrastructure Integrated Carbon Observation System. The respective working group of the Integrated Carbon Observation System Ecosystem Monitoring Station Assembly has decided to ascertain standards and quality checks for automated and manual chamber systems instead of defining one or several standard systems provided by commercial manufacturers in order to define minimum requirements for chamber measurements. The defined requirements and recommendations related to chamber measurements are described here. [ABSTRACT FROM AUTHOR]

Soil moisture, soil CO2 efflux (RS), and isotopic composition of RS (δR) were studied in three sessile oak forest stands with different management practice: a high forest (HF), a high forest converted from coppice stand (CHF), and a coppice forest (CF). Measurements were taken monthly, with each position described by light parameters. RS was driven by temperature and moisture. RS increased dramatically with moisture in relatively dry soil, while they remained on the same level when moisture exceeded 13%. Differences in mean soil moisture and RS normalized for 10 °C (R10) among the stands usually followed the pattern HF > CF > CHF. The δR was highest in CHF, but during drought the pattern was HF > CHF > CF. To test the effect of stand structure on soil moisture and R10, we analyzed relationship of these variables to light parameters calculated for the angles of 60° and 180°. Subsequently, we analyzed data from all measured positions divided according to gap fraction into six groups. The results showed that forest floor shading by the canopy decreases moisture regardless of stand type, but no significant relationship was found between the light parameters and R10. We may conclude that soil moisture is affected by canopy structure and RS by stand type. [ABSTRACT FROM AUTHOR]

Aims: Ecosystem respiration represents an important component of the carbon cycle. The response of respiration to climate change can have a significant effect on carbon sequestration in terrestrial ecosystems in the future when, according to climate scenarios, spring drought and consequent summer heavy rains are expected. Aims of our study were to determine the effect of repeated spring drought on biomass production and CO2 efflux from a mountain grassland in Beskydy Mountains in the Czech Republic and to evaluate factors driving the differences among the study years. Methods: CO2 efflux was measured on plots with ambient precipitation conditions (AMB) and on plots where drought conditions (DRY) in the first half of the growing seasons and consequent heavy rain were simulated in 2011-14. Important Findings: The spring drought significantly decreased the amount of above-ground biomass sampled just after the simulated drought in all years except for 2014. On the contrary, the spring drought stimulated root production. The drought also resulted in a rapid decrease in CO2 efflux. It was lower by up to 46% for the DRY treatment compared to AMB treatment. After the simulated drought period, differences in CO2 efflux between the treatments gradually decreased. Simulated heavy rains in DRY resulted in fast but temporary increase in CO2 efflux. We can assume that the future spring drought will have a significant effect on carbon balance of grassland ecosystems. The impact will depend on the length of the dry period and the time between the beginning of the growing season and the dry period. [ABSTRACT FROM AUTHOR]

Soil CO2 efflux accounts for about 45-80% of total ecosystem respiration and is therefore an important part of the ecosystem carbon cycle. Soil CO2 efflux has been poorly studied in forests managed in the ancient coppicing manner. In our study, soil CO2 efflux, temperature, and moisture were measured in sessile oak stands with different harvesting intensity (control: 0% intensity; V1: 75%; V2: 80 %; V3: 85%; and V4: 100%) during the fifth and sixth years after harvesting. Soil CO2 efflux was in the range 2-8 µmol CO2 m-2 s-1 and indicated an increasing pattern with increasing harvesting intensity. The slope of that pattern became less steep from the fifth to the sixth year after harvesting, thus indicating gradual recovery of soil carbon dynamics in the coppiced stand toward the equilibrium state existing before harvesting. Temperature sensitivity of soil CO2 efflux ranged between 2.1 and 2.8, with the lowest values measured in the control stand. Soil CO2 efflux in the control stand was more sensitive to changes in soil moisture than was that on harvested plots. By our calculations, 6.2 tC ha-1 was released from the control stand and 6.2-6.8 tC ha-1 from the harvested stands during the sixth year after harvesting. If mean temperature were to rise by 1 °C, the amount of soil carbon released would increase by 7.7% in the control stand and, depending on harvesting intensity, by 9.0-10.8% in the harvested stands. [ABSTRACT FROM AUTHOR]

Although forests store significant amounts of carbon in tree stems, the extent to which stem growth depends on carbon assimilation and environmental factors is poorly understood. In this study, gross primary productivity (GPP) and net ecosystem productivity (NEP) are compared for the first time at daily resolution with stem carbon allocation (SCA) in a spruce forest. We found substantial differences in the seasonal patterns of all variables as a function of environmental conditions, leading to three important findings. First, carbon uptake was only marginally invested in wood growth during the first half of the growing season. This means that there were other priorities for carbon allocation than stem growth at this time of year. Second, our results show that SRI at the beginning of the stem growth period, which mainly involves cell division and expansion, is a process that requires less carbon than the process of xylem lignification and thickening that follows. And third, NEP was generally less sensitive to drought than SCA. This suggests that the carbon uptake balance is less sensitive to dry periods than growth, particularly because the carbon uptake period is much longer than the growth window. These results may change the way we perceive the effects of climate change on forests, as tree carbon dynamics are primarily explained by the seasonal timing of dry periods rather than the intensity of these events. • Novel daily-resolved stem carbon allocation data of spruce trees. • Carbon uptake and allocation are partially decoupled. • Drought limits stem growth of spruce before carbon uptake is affected. • Timing of extreme events determines the impact on the carbon balance of forests. • Spruce trees increasingly suffer under drought stress. [ABSTRACT FROM AUTHOR]

Recent changes in water availability can be crucial for the development, growth and carbon budget of forests. Therefore, our aim was to determine the effect of reduced throughfall and severe summer drought on stem CO 2 efflux as a function of temperature and stem increment. Stem CO 2 efflux was measured using the chamber method on oak and hornbeam under four treatments: coppice, thinned coppice, and both coppice and thinned coppice with 30 %-reduced throughfall. The first year of the experiment had favourable soil water availability and the second year was characterized by a dry summer. While reduced throughfall had no effect on stem CO 2 efflux, the summer drought decreased efflux by 43-81 % during July and August. The stem CO 2 efflux was reduced less severely (by 13-40 %) in September when the drought persisted but the stem increment was already negligible. The stem increment was also strongly affected by the drought, which was reflected in its paired relationship with stem CO 2 efflux over the two experimental years. The study showed that summer dry periods significantly and rapidly reduce stem CO 2 efflux, whereas a constant 30 % rainfall reduction needs probably a longer time to affect stem properties, and indirectly stem CO 2 efflux., Competing Interests: None declared., (© The Author(s) 2024. Published by Oxford University Press on behalf of the Annals of Botany Company.)