scholarly journals Understanding the uncertainty in global forest carbon turnover

2020 ◽  
Vol 17 (15) ◽  
pp. 3961-3989 ◽  
Author(s):  
Thomas A. M. Pugh ◽  
Tim Rademacher ◽  
Sarah L. Shafer ◽  
Jörg Steinkamp ◽  
Jonathan Barichivich ◽  
...  
Keyword(s):  
Large Scale ◽  
Tree Mortality ◽  
Forest Biomass ◽  
Turnover Time ◽  
Biomass Carbon ◽  
Carbon Turnover ◽  
Turnover Rates ◽  
Wide Range ◽  
The Future ◽  
Total Turnover

Abstract. The length of time that carbon remains in forest biomass is one of the largest uncertainties in the global carbon cycle, with both recent historical baselines and future responses to environmental change poorly constrained by available observations. In the absence of large-scale observations, models used for global assessments tend to fall back on simplified assumptions of the turnover rates of biomass and soil carbon pools. In this study, the biomass carbon turnover times calculated by an ensemble of contemporary terrestrial biosphere models (TBMs) are analysed to assess their current capability to accurately estimate biomass carbon turnover times in forests and how these times are anticipated to change in the future. Modelled baseline 1985–2014 global average forest biomass turnover times vary from 12.2 to 23.5 years between TBMs. TBM differences in phenological processes, which control allocation to, and turnover rate of, leaves and fine roots, are as important as tree mortality with regard to explaining the variation in total turnover among TBMs. The different governing mechanisms exhibited by each TBM result in a wide range of plausible turnover time projections for the end of the century. Based on these simulations, it is not possible to draw robust conclusions regarding likely future changes in turnover time, and thus biomass change, for different regions. Both spatial and temporal uncertainty in turnover time are strongly linked to model assumptions concerning plant functional type distributions and their controls. Thirteen model-based hypotheses of controls on turnover time are identified, along with recommendations for pragmatic steps to test them using existing and novel observations. Efforts to resolve uncertainty in turnover time, and thus its impacts on the future evolution of biomass carbon stocks across the world's forests, will need to address both mortality and establishment components of forest demography, as well as allocation of carbon to woody versus non-woody biomass growth.

scholarly journals Understanding the uncertainty in global forest carbon turnover

2020 ◽  
Author(s):  
Thomas A. M. Pugh ◽  
Tim T. Rademacher ◽  
Sarah L. Shafer ◽  
Jörg Steinkamp ◽  
Jonathan Barichivich ◽  
...  
Keyword(s):  
Large Scale ◽  
Tree Mortality ◽  
Forest Biomass ◽  
Turnover Time ◽  
Biomass Carbon ◽  
Carbon Turnover ◽  
Turnover Rates ◽  
Temporal Uncertainty ◽  
Wide Range ◽  
Total Turnover

Abstract. The length of time that carbon remains in forest biomass is one of the largest uncertainties in the global carbon cycle, with both recent-historical baselines and future responses to environmental change poorly constrained by available observations. In the absence of large-scale observations, models tend to fall back on simplified assumptions of the turnover rates of biomass and soil carbon pools to make global assessments. In this study, the biomass carbon turnover times calculated by an ensemble of contemporary terrestrial biosphere models (TBMs) are analysed to assess their current capability to accurately estimate biomass carbon turnover times in forests and how these times are anticipated to change in the future. Modelled baseline 1985–2014 global forest biomass turnover times vary from 12.2 to 23.5 years between models. TBM differences in phenological processes, which control allocation to and turnover rate of leaves and fine roots, are as important as tree mortality with regard to explaining the variation in total turnover among TBMs. The different governing mechanisms exhibited by each TBM result in a wide range of plausible turnover time projections for the end of the century. Based on these simulations, it is not possible to draw robust conclusions regarding likely future changes in turnover time for different regions. Both spatial and temporal uncertainty in turnover time are strongly linked to model assumptions concerning plant functional type distributions and their controls. Twelve model-based hypotheses are identified, along with recommendations for pragmatic steps to test them using existing and novel observations, which would help to reduce both spatial and temporal uncertainty in turnover time. Efforts to resolve uncertainty in turnover time will need to address both mortality and establishment components of forest demography, as well as key drivers of demography such as allocation of carbon to woody versus non-woody biomass growth.

scholarly journals Visions of Future Warfare in Russian Military Publications

2021 ◽  
Vol 7 (2) ◽  
pp. 27-37
Author(s):  
Piotr Wawrzeniuk ◽  
Markus Balázs Göransson
Keyword(s):  
Large Scale ◽  
The West ◽  
Economic Interests ◽  
Global Power ◽  
Wide Range ◽  
The Future ◽  
Future War ◽  
Russian Military ◽  
Holding Back ◽  
At Home

Abstract The article discusses visions of future warfare articulated in recent Russian military publications. There seems to be agreement among Russian scholars that future war will be triggered by Western attempts to promote Western political and economic interests while holding back Russia's resurgence as a global power. The future war with the West is viewed as inevitable in one form or another, whether it is subversion and local wars or large-scale conventional war. While the danger of conventional war has declined, according to several scholars, the West is understood to have a wide range of non-kinetic means at its disposal that threaten Russia. In order to withstand future dangers, Russia has to be able to meet a large number of kinetic and non-kinetic threats at home and abroad.

scholarly journals Regional and large-scale patterns in Amazon forest structure and function are mediated by variations in soil physical and chemical properties

2009 ◽  
Vol 6 (2) ◽  
pp. 3993-4057 ◽  
Author(s):  
C. A. Quesada ◽  
J. Lloyd ◽  
M. Schwarz ◽  
T. R. Baker ◽  
O. L. Phillips ◽  
...  
Keyword(s):  
Soil Fertility ◽  
Physical Properties ◽  
Forest Structure ◽  
Large Scale ◽  
Amazon Basin ◽  
Forest Biomass ◽  
Turnover Rates ◽  
Structure And Dynamics ◽  
Edaphic Conditions ◽  
Edaphic Properties

Abstract. Forest structure and dynamics have been noted to vary across the Amazon Basin in an east-west gradient in a pattern which coincides with variations in soil fertility and geology. This has resulted in the hypothesis that soil fertility may play an important role in explaining Basin-wide variations in forest biomass, growth and stem turnover rates. To test this hypothesis and assess the importance of edaphic properties in affect forest structure and dynamics, soil and plant samples were collected in a total of 59 different forest plots across the Amazon Basin. Samples were analysed for exchangeable cations, C, N, pH with various P fractions also determined. Physical properties were also examined and an index of soil physical quality developed. Overall, forest structure and dynamics were found to be strongly and quantitatively related to edaphic conditions. Tree turnover rates emerged to be mostly influenced by soil physical properties whereas forest growth rates were mainly related to a measure of available soil phosphorus, although also dependent on rainfall amount and distribution. On the other hand, large scale variations in forest biomass could not be explained by any of the edaphic properties measured, nor by variation in climate. A new hypothesis of self-maintaining forest dynamic feedback mechanisms initiated by edaphic conditions is proposed. It is further suggested that this is a major factor determining forest disturbance levels, species composition and forest productivity on a Basin wide scale.

scholarly journals Pervasive decreases in living vegetation carbon turnover time across forest climate zones

2019 ◽  
Vol 116 (49) ◽  
pp. 24662-24667 ◽  
Author(s):  
Kailiang Yu ◽  
William K. Smith ◽  
Anna T. Trugman ◽  
Richard Condit ◽  
Stephen P. Hubbell ◽  
...  
Keyword(s):  
Tree Mortality ◽  
Temporal Trends ◽  
Turnover Time ◽  
Forest Carbon ◽  
Cold Climate ◽  
Forest Plot ◽  
Carbon Turnover ◽  
Climate Zones ◽  
Vegetation Carbon

Forests play a major role in the global carbon cycle. Previous studies on the capacity of forests to sequester atmospheric CO2 have mostly focused on carbon uptake, but the roles of carbon turnover time and its spatiotemporal changes remain poorly understood. Here, we used long-term inventory data (1955 to 2018) from 695 mature forest plots to quantify temporal trends in living vegetation carbon turnover time across tropical, temperate, and cold climate zones, and compared plot data to 8 Earth system models (ESMs). Long-term plots consistently showed decreases in living vegetation carbon turnover time, likely driven by increased tree mortality across all major climate zones. Changes in living vegetation carbon turnover time were negatively correlated with CO2 enrichment in both forest plot data and ESM simulations. However, plot-based correlations between living vegetation carbon turnover time and climate drivers such as precipitation and temperature diverged from those of ESM simulations. Our analyses suggest that forest carbon sinks are likely to be constrained by a decrease in living vegetation carbon turnover time, and accurate projections of forest carbon sink dynamics will require an improved representation of tree mortality processes and their sensitivity to climate in ESMs.

The wind in confined thermal convection

2001 ◽  
Vol 449 ◽  
pp. 169-178 ◽  
Author(s):  
J. J. NIEMELA ◽  
L. SKRBEK ◽  
K. R. SREENIVASAN ◽  
R. J. DONNELLY
Keyword(s):  
Rayleigh Number ◽  
Large Scale ◽  
Turnover Time ◽  
Turbulent Convection ◽  
Physical Explanation ◽  
Dynamical Parameter ◽  
Large Scale Circulation ◽  
Wide Range ◽  
Circulation Velocity ◽  
Rayleigh Benard

A large-scale circulation velocity, often called the ‘wind’, has been observed in turbulent convection in the Rayleigh–Bénard apparatus, which is a closed box with a heated bottom wall. The wind survives even when the dynamical parameter, namely the Rayleigh number, is very large. Over a wide range of time scales greater than its characteristic turnover time, the wind velocity exhibits occasional and irregular reversals without a change in magnitude. We study this feature experimentally in an apparatus of aspect ratio unity, in which the highest attainable Rayleigh number is about 1016. A possible physical explanation is attempted.

scholarly journals Re-estimating the changes and ranges of forest biomass carbon in China during the past 40 years

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Xiaolu Zhou ◽  
Xiangdong Lei ◽  
Caixia Liu ◽  
Huabing Huang ◽  
Carl Zhou ◽  
...  
Keyword(s):  
Forest Ecosystem ◽  
Forest Biomass ◽  
Biomass Carbon ◽  
National Scale ◽  
Step Process ◽  
Stem Biomass ◽  
Growing Stock ◽  
True Value ◽  
Significant Bias ◽  
The Future

Abstract Background In recent decades the future of global forests has been a matter of increasing concern, particularly in relation to the threat of forest ecosystem responses under potential climate change. To the future predictions of these responses, the current forest biomass carbon storage (FCS) should first be clarified as much as possible, especially at national scales. However, few studies have introduced how to verify an FCS estimate by delimiting the reasonable ranges. This paper addresses an estimation of national FCS and its verification using two-step process to narrow the uncertainty. Our study focuses on a methodology for reducing the uncertainty resulted by converting from growing stock volume to above- and below-ground biomass (AB biomass), so as to eliminate the significant bias in national scale estimations. Methods We recommend splitting the estimation into two parts, one part for stem and the other part for AB biomass to preclude possible significant bias. Our method estimates the stem biomass from volume and wood density (WD), and converts the AB biomass from stem biomass by using allometric relationships. Results Based on the presented two-step process, the estimation of China’s FCS is performed as an example to explicate how to infer the ranges of national FCS. The experimental results demonstrate a national FCS estimation within the reasonable ranges (relative errors: + 4.46% and − 4.44%), e.g., 5.6–6.1 PgC for China’s forest ecosystem at the beginning of the 2010s. These ranges are less than 0.52 PgC for confirming each FCS estimate of different periods during the last 40 years. In addition, our results suggest the upper-limits by specifying a highly impractical value of WD (0.7 t∙m− 3) on the national scale. As a control reference, this value decides what estimate is impossible to achieve for the FCS estimates. Conclusions Presented methodological analysis highlights the possibility to determine a range that the true value could be located in. The two-step process will help to verify national FCS and also to reduce uncertainty in related studies. While the true value of national FCS is immeasurable, our work should motivate future studies that explore new estimations to approach the true value by narrowing the uncertainty in FCS estimations on national and global scales.

Spray dispersion regimes following atomization in a turbulent co-axial gas jet

2021 ◽  
Vol 932 ◽  
Author(s):  
P.D. Huck ◽  
R. Osuna-Orozco ◽  
N. Machicoane ◽  
A. Aliseda
Keyword(s):  
Gas Phase ◽  
Large Scale ◽  
Near Field ◽  
Stokes Number ◽  
Turnover Time ◽  
Droplet Dispersion ◽  
Momentum Ratio ◽  
Dimensional Phase Space ◽  
Wide Range ◽  
Two Fluid

A canonical co-axial round-jet two-fluid atomizer where atomization occurs over a wide range of momentum ratios: $M=1.9 - 376.4$ is studied. The near field of the spray, where the droplet formation process takes place, is characterized and linked to droplet dispersion in the far field of the jet. Counterintuitively, our results indicate that in the low-momentum regime, increasing the momentum in the gas phase leads to less droplet dispersion. A critical momentum ratio of the order of $M_c=50$ , that separates this regime from a high-momentum one with less dispersion, is found in both the near and far fields. A phenomenological model is proposed that determines the susceptibility of droplets to disperse beyond the nominal extent of the gas phase based on a critical Stokes number, $St=\tau _p/T_E=1.9$ , formulated based on the local Eulerian large scale eddy turnover time, $T_E$ , and the droplets’ response time, $\tau _p$ . A two-dimensional phase space summarizes the extent of these different regimes in the context of spray characteristics found in the literature.

scholarly journals Lianas Significantly Reduce Aboveground and Belowground Carbon Storage: A Virtual Removal Experiment

2021 ◽  
Vol 4 ◽  
Author(s):  
Félicien Meunier ◽  
Geertje M. F. van der Heijden ◽  
Stefan A. Schnitzer ◽  
Hannes P. T. De Deurwaerder ◽  
Hans Verbeeck
Keyword(s):  
Carbon Storage ◽  
Large Scale ◽  
Tree Mortality ◽  
Net Primary Productivity ◽  
Removal Experiment ◽  
Root Turnover ◽  
Turnover Rates ◽  
Belowground Carbon ◽  
The Impact

Lianas are structural parasites of trees that cause a reduction in tree growth and an increase in tree mortality. Thereby, lianas negatively impact forest carbon storage as evidenced by liana removal experiments. In this proof-of-concept study, we calibrated the Ecosystem Demography model (ED2) using 3 years of observations of net aboveground biomass (AGB) changes in control and removal plots of a liana removal experiment on Gigante Peninsula, Panama. After calibration, the model could accurately reproduce the observations of net biomass changes, the discrepancies between treatments, as well as the observed components of those changes (mortality, productivity, and growth). Simulations revealed that the long-term total (i.e., above- and belowground) carbon storage was enhanced in liana removal plots (+1.2 kgC m–2 after 3 years, +1.8 kgC m–2 after 10 years, as compared to the control plots). This difference was driven by a sharp increase in biomass of early successional trees and the slow decomposition of liana woody tissues in the removal plots. Moreover, liana removal significantly reduced the simulated heterotrophic respiration (−24%), which resulted in an average increase in net ecosystem productivity (NEP) from 0.009 to 0.075 kgC m–2 yr–1 for 10 years after liana removal. Based on the ED2 model outputs, lianas reduced gross and net primary productivity of trees by 40% and 53%, respectively, mainly through competition for light. Finally, model simulations suggested a profound impact of the liana removal on the soil carbon dynamics: the simulated metabolic litter carbon pool was systematically larger in control plots (+51% on average) as a result of higher mortality rates and faster leaf and root turnover rates. By overcoming the challenge of including lianas and depicting their effect on forest ecosystems, the calibrated version of the liana plant functional type (PFT) as incorporated in ED2 can predict the impact of liana removal at large-scale and its potential effect on long-term ecosystem carbon storage.

Electron microscopy study of reactively sputter-deposited Ti/N films on silicon

1992 ◽  
Vol 50 (2) ◽  
pp. 1362-1363
Author(s):  
V. C. Kannan ◽  
A. K. Singh ◽  
R. B. Irwin ◽  
S. Chittipeddi ◽  
F. D. Nkansah ◽  
...  
Keyword(s):  
Integrated Circuits ◽  
Large Scale ◽  
Hexagonal Phase ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Process Conditions ◽  
Tin Films ◽  
Wide Range ◽  
Fcc Phase ◽  
Circuits Vlsi

Titanium nitride (TiN) films have historically been used as diffusion barrier between silicon and aluminum, as an adhesion layer for tungsten deposition and as an interconnect material etc. Recently, the role of TiN films as contact barriers in very large scale silicon integrated circuits (VLSI) has been extensively studied. TiN films have resistivities on the order of 20μ Ω-cm which is much lower than that of titanium (nearly 66μ Ω-cm). Deposited TiN films show resistivities which vary from 20 to 100μ Ω-cm depending upon the type of deposition and process conditions. TiNx is known to have a NaCl type crystal structure for a wide range of compositions. Change in color from metallic luster to gold reflects the stabilization of the TiNx (FCC) phase over the close packed Ti(N) hexagonal phase. It was found that TiN (1:1) ideal composition with the FCC (NaCl-type) structure gives the best electrical property.

Features of optative modality in Macedonian language (with emphasis on the functionalities of independent da-construction)

2020 ◽  
pp. 301-323
Author(s):  
Natalya I. Kikilo ◽  
Keyword(s):  
Detailed Analysis ◽  
Present Article ◽  
Literary Language ◽  
Natural Context ◽  
Wide Range ◽  
Verb Forms ◽  
Text Types ◽  
The Future ◽  
The Subject ◽  
Ritual Context

In the Macedonian literary language the analytic da-construction used in an independent clause has a wide range of possible modal meanings, the most common of which are imperative and optative. The present article offers a detailed analysis of the semantics and functions of the Macedonian optative da-construction based on fiction and journalistic texts. The first part of the article deals with the specificities of the optative as a category which primarily considers the subject of a wish. In accordance with the semantic characteristics of this category, optative constructions are used in those discourse text types where the speakers are explicitly designated (the most natural context for the optative is the dialogue). The analysis of the Macedonian material includes instances of atypical usage of the optative da-construction, in which the wish of the subject is not apparent and thereby produces new emotional tonalities perceptible to the reader of a fiction/journalistic text. The study describes Macedonian constructions involving two different verb forms: 1) present tense form (da + praes) and 2) imperfective form (da + impf). These constructions formally designate the hypothetical and counterfactual status of the optative situation, respectively. Thus, the examples in the analysis are ordered according to two types of constructions, which reflect the speaker’s view on the probability of the realisation of his/her wish. Unrealistic wishes can be communicated through the present da-construction, while the imperfective construction denotes situations in which the wish can be realised in the future. The second part of the article is devoted to performative optative da-constructions, which express formulas of speech etiquette, wishes and curses. The analysis demonstrates that these constructions lose their magical functions, when used outside of the ritual context, and begin to function as interjections.

Sign in / Sign up

Export Citation Format

Share Document