scholarly journals Prediction of photosynthesis in Scots pine ecosystems across Europe by needle-level theory

2017 ◽  
Author(s):  
Pertti Hari ◽  
Steffen Noe ◽  
Sigrid Dengel ◽  
Jan Elbers ◽  
Bert Gielen ◽  
...  
Keyword(s):  
Scots Pine ◽  
Boreal Forests ◽  
Co2 Flux ◽  
Field Studies ◽  
Co2 Fluxes ◽  
New Era ◽  
Evergreen Forests ◽  
Eddy Covariance Measurements ◽  
Transition Times

Abstract. Photosynthesis provides carbon for the synthesis of macromolecules to construct cells during growth. This fact generates the key role of photosynthesis in the carbon dynamics of ecosystems (Taiz et al., 2015) and biogenic CO2 consumption. The development of eddy covariance measurements of ecosystem CO2 fluxes started a new era in the field studies of photosynthesis (Baldocchi et al., 2000). However, the interpretation of the very variable CO2 fluxes in evergreen forests has been problematic especially in transition times such as the spring and autumn. We apply two theoretical needle-level equations that connect the variation in the light intensity, stomatal action and the annual metabolic cycle with photosynthesis. We then show that these equations are able to predict quite precisely and accurately the photosynthetic CO2 flux between the atmosphere and different ecosystems in five Scots pine stands located from northern timberline to Central Europe. Our result has strong implications on the interpretation of the effects of the global change on the processes in boreal forests, especially of the changes in the metabolic annual cycle of photosynthesis.

scholarly journals Prediction of photosynthesis in Scots pine ecosystems across Europe by a needle-level theory

2018 ◽  
Vol 18 (18) ◽  
pp. 13321-13328
Author(s):  
Pertti Hari ◽  
Steffen Noe ◽  
Sigrid Dengel ◽  
Jan Elbers ◽  
Bert Gielen ◽  
...  
Keyword(s):  
Scots Pine ◽  
Boreal Forests ◽  
Co2 Flux ◽  
Field Studies ◽  
Co2 Assimilation ◽  
Co2 Fluxes ◽  
New Era ◽  
Evergreen Forests ◽  
Transition Times

Abstract. Photosynthesis provides carbon for the synthesis of macromolecules to construct cells during growth. This is the basis for the key role of photosynthesis in the carbon dynamics of ecosystems and in the biogenic CO2 assimilation. The development of eddy-covariance (EC) measurements for ecosystem CO2 fluxes started a new era in the field studies of photosynthesis. However, the interpretation of the very variable CO2 fluxes in evergreen forests has been problematic especially in transition times such as the spring and autumn. We apply two theoretical needle-level equations that connect the variation in the light intensity, stomatal action and the annual metabolic cycle of photosynthesis. We then use these equations to predict the photosynthetic CO2 flux in five Scots pine stands located from the northern timberline to Central Europe. Our result has strong implications for our conceptual understanding of the effects of the global change on the processes in boreal forests, especially of the changes in the metabolic annual cycle of photosynthesis.

scholarly journals New foliage growth is a significant, unaccounted source for volatiles in boreal evergreen forests

2013 ◽  
Vol 10 (11) ◽  
pp. 18121-18150
Author(s):  
J. Aalto ◽  
P. Kolari ◽  
P. Hari ◽  
V.-M. Kerminen ◽  
P. Schiestl-Aalto ◽  
...  
Keyword(s):  
Scots Pine ◽  
Physiological State ◽  
Field Studies ◽  
Growth Stages ◽  
Emission Rates ◽  
Aerosol Formation ◽  
Emission Pattern ◽  
Evergreen Forests ◽  
Volatile Organic ◽  
Reactive Gases

Abstract. Estimates of volatile organic compound (VOC) emissions from forests are based on the assumption that foliage has a steady emission potential over its lifetime, and that emissions are mainly modified by short term variations in light and temperature. However, in many field studies this has been challenged, and high emissions and atmospheric concentrations have been measured during periods of low biological activity such as in springtime. We conducted measurements during three years, using an online gas-exchange monitoring system to observe volatile organic emissions from a mature (1 yr old) and a growing Scots pine shoot. The emission rates of organic vapours (monoterpenes, methyl butenol (MBO), acetone and methanol) from vegetative buds of Scots pine during the dehardening and rapid shoot growth stages were one to two orders of magnitude higher than those from mature foliage. The normally assumed temperature dependency was not sufficient to explain the variations in emission rates during spring. The diurnal emission pattern of growing shoots differed from the diurnal cycle in temperature as well as from the diurnal emission pattern of mature shoots, which may be related to processes involved in shoot or needle elongation. Our findings imply that global estimations of monoterpene emission rates from forests are in need of revision, and that the physiological state of the plants should be taken into account when emissions of the reactive gases such as monoterpenes are estimated. The significant interannual variation in emission rates, related to changes in plant metabolic activity, has important implications to the aerosol precursor concentrations and chemical reactions in atmosphere, and potentially offers an explanation for the frequent aerosol formation events in spring.

scholarly journals The role of vegetation in the CO<sub>2</sub> flux from a tropical urban neighbourhood

2013 ◽  
Vol 13 (3) ◽  
pp. 7267-7310 ◽  
Author(s):  
E. Velasco ◽  
M. Roth ◽  
S. H. Tan ◽  
M. Quak ◽  
S. D. A. Nabarro ◽  
...  
Keyword(s):  
Anthropogenic Activities ◽  
Co2 Flux ◽  
Accurate Estimation ◽  
Urban Vegetation ◽  
Co2 Uptake ◽  
Co2 Fluxes ◽  
Activity Data ◽  
The Difference ◽  
Residential Neighbourhood

Abstract. Urban surfaces are usually net sources of CO2. Vegetation can potentially have an important role in reducing the CO2 emitted by anthropogenic activities in cities, particularly when vegetation is extensive and/or evergreen. Negative daytime CO2 fluxes, for example have been observed during the growing season at suburban sites characterized by abundant vegetation and low population density. A direct and accurate estimation of carbon uptake by urban vegetation is difficult due to the particular characteristics of the urban ecosystem and high variability in tree distribution and species. Here, we investigate the role of urban vegetation in the CO2 flux from a residential neighbourhood in Singapore using two different approaches. CO2 fluxes measured directly by eddy covariance are compared with emissions estimated from emissions factors and activity data. The latter includes contributions from vehicular traffic, household combustion, soil respiration and human breathing. The difference between estimated emissions and measured fluxes should approximate the biogenic flux. In addition, a tree survey was conducted to estimate the annual CO2 sequestration using allometric equations and an alternative model of the metabolic theory of ecology for tropical forests. Palm trees, banana plants and turfgrass were also included in the survey with their annual CO2 uptake obtained from published growth rates. Both approaches agree within 2% and suggest that vegetation captures 8% of the total emitted CO2 in the residential neighbourhood studied. A net uptake of 1.4 ton km−2 day−1 (510 ton km−2 yr−1 ) was estimated from the difference between the daily CO2 uptake by photosynthesis (3.95 ton km−2 ) and release by respiration (2.55 ton km−2). The study shows the importance of urban vegetation at the local scale for climate change mitigation in the tropics.

scholarly journals Uncertainty analysis of eddy covariance CO<sub>2</sub> flux measurements for different EC tower distances using an extended two-tower approach

2014 ◽  
Vol 11 (8) ◽  
pp. 11943-11983
Author(s):  
H. Post ◽  
H. J. Hendricks Franssen ◽  
A. Graf ◽  
M. Schmidt ◽  
H. Vereecken
Keyword(s):  
Eddy Covariance ◽  
Reference Method ◽  
Co2 Flux ◽  
Weather Conditions ◽  
Co2 Fluxes ◽  
Random Uncertainty ◽  
Extended Approach ◽  
Uncertainty Estimates ◽  
Flux Measurements

Abstract. The use of eddy covariance CO2 flux measurements in data assimilation and other applications requires an estimate of the random uncertainty. In previous studies, the two-tower approach has yielded robust uncertainty estimates, but care must be taken to meet the often competing requirements of statistical independence (non-overlapping footprints) and ecosystem homogeneity when choosing an appropriate tower distance. The role of the tower distance was investigated with help of a roving station separated between 8 m and 34 km from a permanent EC grassland station. Random uncertainty was estimated for five separation distances with an extended two-tower approach which removed systematic differences of CO2 fluxes measured at two EC towers. This analysis was made for a dataset where (i) only similar weather conditions at the two sites were included and (ii) an unfiltered one. The extended approach, applied to weather-filtered data for separation distances of 95 m and 173 m gave uncertainty estimates in best correspondence with the independent reference method The introduced correction for systematic flux differences considerably reduced the overestimation of the two-tower based uncertainty of net CO2 flux measurements, e.g. caused by different environmental conditions at both EC towers. It is concluded that the extension of the two-tower approach can help to receive more reliable uncertainty estimates because systematic differences of measured CO2 fluxes which are not part of random error are filtered out.

The Contemporary Role of Resection and Ablation in Colorectal Cancer Liver Metastases

2020 ◽  
Vol 04 (03) ◽  
pp. 291-302
Author(s):  
Mariam F. Eskander ◽  
Christopher T. Aquina ◽  
Aslam Ejaz ◽  
Timothy M. Pawlik
Keyword(s):  
Colorectal Cancer ◽  
Portal Vein ◽  
Surgical Oncology ◽  
Portal Vein Ligation ◽  
Safe Alternative ◽  
Colorectal Cancer Liver Metastases ◽  
Liver Remnant ◽  
New Era ◽  
Ablation Therapy

AbstractAdvances in the field of surgical oncology have turned metastatic colorectal cancer of the liver from a lethal disease to a chronic disease and have ushered in a new era of multimodal therapy for this challenging illness. A better understanding of tumor behavior and more effective systemic therapy have led to the increased use of neoadjuvant therapy. Surgical resection remains the gold standard for treatment but without the size, distribution, and margin restrictions of the past. Lesions are considered resectable if they can safely be removed with tumor-free margins and a sufficient liver remnant. Minimally invasive liver resections are a safe alternative to open surgery and may offer some advantages. Techniques such as portal vein embolization, association of liver partition with portal vein ligation for staged hepatectomy, and radioembolization can be used to grow the liver remnant and allow for resection. If resection is not possible, nonresectional ablation therapy, including radiofrequency and microwave ablation, can be performed alone or in conjunction with resection. This article presents the most up-to-date literature on resection and ablation, with a discussion of current controversies and future directions.

From Trinidad and Tobago to the World: Determining the role of Calypso in a new Era

2020 ◽  
Vol 5 ◽  
pp. 7-11
Author(s):  
Malek Abdel-Shehid
Keyword(s):  
Trinidad And Tobago ◽  
Regional Integration ◽  
West African ◽  
Major Influence ◽  
New Era ◽  
Transatlantic Slave Trade ◽  
Cultural Sovereignty ◽  
Caribbean Culture ◽  
Musical Cultures

Calypso is a popular Caribbean musical genre that originated in the island nation of Trinidad and Tobago. The genre was developed primarily by enslaved West Africans brought to the region via the transatlantic slave trade during the seventeenth and eighteenth centuries. Although West-African Kaiso music was a major influence, the genre has also been shaped by other African genres, and by Indian, British, French, and Spanish musical cultures. Emerging in the early twentieth century, Calypso became a tool of resistance by Afro-Caribbean working-class Trinbagonians. Calypso flourished in Trinidad due to a combination of factors—namely, the migration of Afro-Caribbean people from across the region in search of upward social mobility. These people sought to expose the injustices perpetrated by a foreign European and a domestic elite against labourers in industries such as petroleum extraction. The genre is heavily anti-colonial, anti-imperial, and anti-elitist, and it advocated for regional integration. Although this did not occur immediately, Calypsonians sought to establish unity across the region regardless of race, nationality, and class through their songwriting and performing. Today, Calypso remains a unifying force and an important part of Caribbean culture. Considering Calypso's history and purpose, as well as its ever-changing creators and audiences, this essay will demonstrate that the goal of regional integration is not possible without cultural sovereignty.

INTERPRETATION OF SINO-RUSSIAN CULTURE AND HUMANITIES COOPERATION IN THE NEW ERA

2020 ◽  
Vol 10 (3) ◽  
pp. 186-193
Author(s):  
REN YANYAN ◽  
Keyword(s):  
Current Status ◽  
Human Relations ◽  
New Era ◽  
Russian Culture ◽  
The People ◽  
Starting Point ◽  
Cooperative Partnership ◽  
Belt And Road ◽  
The Belt And Road

The friendship between nations lies in the mutual affinity of the people, and the people’s affinity lies in the communion of hearts. The cultural and humanities cooperation between China and Russia has a long history. In recent years, under the role of the“Belt and Road” initiative, the SCO, and the Sino-Russian Humanities Cooperation Committee, Sino-Russian culture and humanities cooperation has continued to deepen. Entering a new era, taking the opportunity to promote Sino-Russian relations into a “new era China-Russia comprehensive strategic cooperative partnership”, the development of human relations between the two countries has entered a new historical starting point, while also facing a series of problems and challenges. This article is based on the current status of Sino-Russian human relations in the new era, interprets the characteristics of Sino-Russian human relations in the new era, analyzes the problems and challenges of Sino-Russian human relations in the new era, and tries to propose solutions and solutions with a view to further developing Sino-Russian cultural and humanities relations in the new era. It is a useful reference, and provides a reference for future related research, and ultimately helps the Sino-Russian cultural and humanities relations in the new era to be stable and far-reaching.

Transition Times in Memory

2018 ◽  
Author(s):  
Donatella della Porta ◽  
Massimiliano Andretta ◽  
Tiago Fernandes ◽  
Eduardo Romanos ◽  
Markos Vogiatzoglou
Keyword(s):  
Theoretical Model ◽  
Social Movement ◽  
Transition Period ◽  
Two Dimensions ◽  
Democratic Regime ◽  
Organizational Models ◽  
Different Types ◽  
Transition Times ◽  
Movement Participation

The second chapter covers the main characteristics of transition time in the four countries: Italy, Greece, Spain, and Portugal. After developing the theoretical model on paths of transition, with a focus on social movement participation, the chapter looks at social movements and protest events as turning points during transition, covering in particular the specific movement actors, their organizational models, and their repertoires of action and frames. The chapter focuses on two dimensions: the role of mobilization in the transition period, which implies the analysis of how elites and masses interact, ally, or fight with each other in the process, and the outcome of transitions as continuity versus rupture of the democratic regime vis-à-vis the old one. It concludes by elaborating some hypotheses on how different modes of transition may produce different types and uses of (transition) memories.

scholarly journals CO<sub>2</sub> flux determination by closed-chamber methods can be seriously biased by inappropriate application of linear regression

2007 ◽  
Vol 4 (6) ◽  
pp. 1005-1025 ◽  
Author(s):  
L. Kutzbach ◽  
J. Schneider ◽  
T. Sachs ◽  
M. Giebels ◽  
H. Nykänen ◽  
...  
Keyword(s):  
Linear Regression ◽  
Nonlinear Regression ◽  
Co2 Flux ◽  
Exponential Model ◽  
Co2 Uptake ◽  
Co2 Fluxes ◽  
Closed Chamber ◽  
Exponential Regression ◽  
Closure Time ◽  
Over Time

Abstract. Closed (non-steady state) chambers are widely used for quantifying carbon dioxide (CO2) fluxes between soils or low-stature canopies and the atmosphere. It is well recognised that covering a soil or vegetation by a closed chamber inherently disturbs the natural CO2 fluxes by altering the concentration gradients between the soil, the vegetation and the overlying air. Thus, the driving factors of CO2 fluxes are not constant during the closed chamber experiment, and no linear increase or decrease of CO2 concentration over time within the chamber headspace can be expected. Nevertheless, linear regression has been applied for calculating CO2 fluxes in many recent, partly influential, studies. This approach has been justified by keeping the closure time short and assuming the concentration change over time to be in the linear range. Here, we test if the application of linear regression is really appropriate for estimating CO2 fluxes using closed chambers over short closure times and if the application of nonlinear regression is necessary. We developed a nonlinear exponential regression model from diffusion and photosynthesis theory. This exponential model was tested with four different datasets of CO2 flux measurements (total number: 1764) conducted at three peatlands sites in Finland and a tundra site in Siberia. Thorough analyses of residuals demonstrated that linear regression was frequently not appropriate for the determination of CO2 fluxes by closed-chamber methods, even if closure times were kept short. The developed exponential model was well suited for nonlinear regression of the concentration over time c(t) evolution in the chamber headspace and estimation of the initial CO2 fluxes at closure time for the majority of experiments. However, a rather large percentage of the exponential regression functions showed curvatures not consistent with the theoretical model which is considered to be caused by violations of the underlying model assumptions. Especially the effects of turbulence and pressure disturbances by the chamber deployment are suspected to have caused unexplainable curvatures. CO2 flux estimates by linear regression can be as low as 40% of the flux estimates of exponential regression for closure times of only two minutes. The degree of underestimation increased with increasing CO2 flux strength and was dependent on soil and vegetation conditions which can disturb not only the quantitative but also the qualitative evaluation of CO2 flux dynamics. The underestimation effect by linear regression was observed to be different for CO2 uptake and release situations which can lead to stronger bias in the daily, seasonal and annual CO2 balances than in the individual fluxes. To avoid serious bias of CO2 flux estimates based on closed chamber experiments, we suggest further tests using published datasets and recommend the use of nonlinear regression models for future closed chamber studies.

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