The NEE-PAR relationship for a young spruce plantation

2021 ◽  
Author(s):  
Holger Lange ◽  
Junbin Zhao ◽  
Raika Bethke
Keyword(s):  
Carbon Sink ◽  
Net Ecosystem Exchange ◽  
Young Age ◽  
Parameter Estimates ◽  
Spruce Stands ◽  
Variable Sensitivity ◽  
Primary Driver ◽  
Footprint Analysis ◽  
Annual Nee ◽  
The Relationship

<p>In a young Norway spruce stand (planted in 2012) at Hoxmark, Southeast Norway, Net Ecosystem Exchange (NEE) was measured using Eddy Covariance. The data were carefully processed with time-dependent stand parameters (i.e. canopy height), a detailed footprint analysis and calculated at 30 min temporal resolution. Photosynthetic Active Radiation (PAR) as the primary driver for carbon uptake was also available at the site.</p><p>Despite its young age, the plantation already acted as a net carbon sink according to the annual NEE budget, e.g. by ca. 300 g C m<sup>-2</sup> in 2019. However, the response of the system depended strongly on hydrometeorological conditions. We demonstrate this by investigating the relationship between NEE and PAR for this system in a temporally local fashion (30 days moving windows), using a Michaelis-Menten approach involving three parameters. Although the regression captured up to ca. 80% of the variance, the parameter estimates differed substantially throughout the season, and were contrasting between the very dry year 2018 and the close to normal year 2019.</p><p>Comparison with other EC-equipped sites in a future study will clarify whether this variable sensitivity is due to the young age or is a pattern pertaining also to mature spruce stands.</p>

scholarly journals Carbon Fluxes Over an Even-Aged Pure Masson pine (Pinus Massoniana) Stand

2020 ◽  
Author(s):  
Zheng-Hong Tan ◽  
Fang-Jun Ding ◽  
Yan-Hui Liu ◽  
Peng Wu ◽  
Wen-Jun Zhao ◽  
...  
Keyword(s):  
Light Intensity ◽  
Dark Respiration ◽  
Carbon Sink ◽  
Seasonal Pattern ◽  
Net Ecosystem Exchange ◽  
Pinus Massoniana ◽  
Transitional Period ◽  
Stomatal Control ◽  
Masson Pine ◽  
Annual Nee

Abstract Masson pine (Pinus massoniana) is a tree species widely planted in central and south China. In the present pioneer study, we reported about our two years of carbon flux observations over an even-aged pure Masson pine stand. Light intensity could explain nearly half (47%) of the variance in daytime net ecosystem exchange (NEE). Daytime dark respiration was lower than nighttime NEE, suggesting a possible effect of light inhibition on respiration. The mean annual NEE was -557 g C m-2 yr-1, which indicated that this stand is a medium to large carbon sink. This NEE estimates were defensive because we checked the data with thorough quality controls and in consistency with previous independent estimates. An unexpected seasonal pattern of NEE was observed with a clear reduction around the transitional period between summer and autumn (around July). This NEE reduction is probably a consequence of water stress induced stomatal control, and not of a decrease in light intensity. The updated optimal stomatal theory did not provide the best description of stomatal control in relation to photosynthesis. Whether this is a new emergent property of the ecosystem scale needs further investigation.

scholarly journals Shifting environmental controls on CH<sub>4</sub> fluxes in a sub-boreal peatland

2013 ◽  
Vol 10 (12) ◽  
pp. 7971-7981 ◽  
Author(s):  
T. G. Pypker ◽  
P. A. Moore ◽  
J. M. Waddington ◽  
J. A. Hribljan ◽  
R. C. Chimner
Keyword(s):  
Soil Temperature ◽  
Net Ecosystem Exchange ◽  
P Value ◽  
Co2 Uptake ◽  
Ch4 Flux ◽  
Environmental Controls ◽  
Poor Fen ◽  
Abiotic And Biotic Factors ◽  
The Relationship ◽  
Northern Michigan

Abstract. We monitored CO2 and CH4 fluxes using eddy covariance from 19 May to 27 September 2011 in a poor fen located in northern Michigan. The objectives of this paper are to: (1) quantify the flux of CH4 from a sub-boreal peatland, and (2) determine which abiotic and biotic factors were the most correlated to the flux of CH4 over the measurement period. Net daily CH4 fluxes increased from 70 mg CH4 m−2 d−1 to 220 mg CH4 m−2 d−1 from mid May to mid July. After July, CH4 losses steadily declined to approximately 50 mg CH4 m−2 d−1 in late September. During the study period, the peatland lost 17.4 g CH4 m−2. Both abiotic and biotic variables were correlated with CH4 fluxes. When the different variables were analyzed together, the preferred model included mean daily soil temperature at 20 cm, daily net ecosystem exchange (NEE) and the interaction between mean daily soil temperature at 20 cm and NEE (R2 = 0.47, p value < 0.001). The interaction was important because the relationship between daily NEE and mean daily soil temperature with CH4 flux changed when NEE was negative (CO2 uptake from the atmosphere) or positive (CO2 losses to the atmosphere). On days when daily NEE was negative, 25% of the CH4 flux could be explained by correlations with NEE, however on days when daily NEE was positive, there was no correlation between daily NEE and the CH4 flux. In contrast, daily mean soil temperature at 20 cm was poorly correlated to changes in CH4 when NEE was negative (17%), but the correlation increased to 34% when NEE was positive. The interaction between daily NEE and mean daily soil temperature at 20 cm indicates shifting environmental controls on the CH4 flux throughout the growing season.

scholarly journals Greenhouse gas flux measurements in a forestry-drained peatland indicate a large carbon sink

2011 ◽  
Vol 8 (11) ◽  
pp. 3203-3218 ◽  
Author(s):  
A. Lohila ◽  
K. Minkkinen ◽  
M. Aurela ◽  
J.-P. Tuovinen ◽  
T. Penttilä ◽  
...  
Keyword(s):  
Carbon Sink ◽  
Accumulation Rate ◽  
Peat Soil ◽  
Net Ecosystem Exchange ◽  
Flux Measurement ◽  
Co2 Exchange ◽  
Co2 Uptake ◽  
Flux Measurements ◽  
Ch4 And N2o ◽  
Carbon Dioxide Co2

Abstract. Drainage for forestry purposes increases the depth of the oxic peat layer and leads to increased growth of shrubs and trees. Concurrently, the production and uptake of the greenhouse gases carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) change: due to the accelerated decomposition of peat in the presence of oxygen, drained peatlands are generally considered to lose peat carbon (C). We measured CO2 exchange with the eddy covariance (EC) method above a drained nutrient-poor peatland forest in southern Finland for 16 months in 2004–2005. The site, classified as a dwarf-shrub pine bog, had been ditched about 35 years earlier. CH4 and N2O fluxes were measured at 2–5-week intervals with the chamber technique. Drainage had resulted in a relatively little change in the water table level, being on average 40 cm below the ground in 2005. The annual net ecosystem exchange was −870 ± 100 g CO2 m−2 yr−1 in the calendar year 2005, indicating net CO2 uptake from the atmosphere. The site was a small sink of CH4 (−0.12 g CH4 m−2 yr−1) and a small source of N2O (0.10 g N2O m−2 yr−1). Photosynthesis was detected throughout the year when the air temperature exceeded −3 °C. As the annual accumulation of C in the above and below ground tree biomass (175 ± 35 g C m−2) was significantly lower than the accumulation observed by the flux measurement (240 ± 30 g C m−2), about 65 g C m−2 yr−1 was likely to have accumulated as organic matter into the peat soil. This is a higher average accumulation rate than previously reported for natural northern peatlands, and the first time C accumulation has been shown by EC measurements to occur in a forestry-drained peatland. Our results suggest that forestry-drainage may significantly increase the CO2 uptake rate of nutrient-poor peatland ecosystems.

Introduction

2020 ◽  
Author(s):  
Tom C. O’Donnell
Keyword(s):  
Foster Parents ◽  
Young Age ◽  
Early Exposure ◽  
Medieval Period ◽  
Foster Families ◽  
Narrative Literature ◽  
The Relationship ◽  
Medieval Ireland

In this Introduction the case is made for using the narrative literature of the medieval period to access the emotional lives of foster families in medieval Ireland. Foster families in this context are those formed when freeborn families send their children – often at a very young age – to another family to be raised and educated until the child entered its late teens. The early exposure and continued association between foster parents and siblings to these children created close and lasting emotional ties. The current study will examine those emotional ties by critically engaging with the language used around fosterage and the assumptions that underpin the relationship, as expressed in narratives, to trace the emotional ties of medieval Irish fosterage.

scholarly journals Net Ecosystem Exchange of CO2 in Deciduous Pine Forest of Lower Western Himalaya, India

Resources ◽  
2019 ◽  
Vol 8 (2) ◽  
pp. 98 ◽  
Author(s):  
Nilendu Singh ◽  
Bikash Ranjan Parida ◽  
Joyeeta Singh Charakborty ◽  
N.R. Patel
Keyword(s):  
Carbon Cycle ◽  
Carbon Balance ◽  
Net Primary Productivity ◽  
Carbon Sink ◽  
Net Ecosystem Exchange ◽  
Western Himalaya ◽  
Pine Forest ◽  
Environmental Controls ◽  
Carbon Release ◽  
The Himalaya

Carbon cycle studies over the climate-sensitive Himalayan regions are relatively understudied and to address this gap, systematic measurements on carbon balance components were performed over a deciduous pine forest with an understory layer. We determined annual net carbon balance, seasonality in components of carbon balance, and their environmental controls. Results indicated a strong seasonality in the behavior of carbon exchange components. Net primary productivity (NPP) of pine forest exceeded soil respiration during the growing phase. Consequently, net ecosystem exchange exhibited a net carbon uptake. In the initial phase of the growing season, daily mean uptake was −3.93 (±0.50) g C m−2 day−1, which maximizes (−8.47 ± 2.3) later during post-monsoon. However, a brief phase of carbon release was observed during peak monsoon (August) owing to an overcast condition. Nevertheless, annually the forest remained as a carbon sink. The understory is extensively distributed and it turned out to be a key component of carbon balance because of sustained NPP during the pine leafless period. Temperature and evaporative fraction exhibited a prime control over the seasonal carbon dynamics. Our observations could lend certain useful insights into the application of coupled climate-carbon cycle models for the Himalaya and ecological functions in the region.

scholarly journals The relationship between total plasma carotenoids and risk factors for chronic disease among middle-aged and older men

2008 ◽  
Vol 100 (4) ◽  
pp. 883-889 ◽  
Author(s):  
Wildon R. Farwell ◽  
J. Michael Gaziano ◽  
Edward P. Norkus ◽  
Howard D. Sesso
Keyword(s):  
Risk Factors ◽  
Logistic Regression ◽  
Chronic Disease ◽  
Chronic Diseases ◽  
Disease Risk ◽  
Alcohol Ingestion ◽  
Health Study ◽  
Parameter Estimates ◽  
Total Plasma ◽  
The Relationship

Individual plasma carotenoids have been associated with various chronic diseases but little is known about the relationship between total plasma carotenoids and risk factors for chronic diseases. In the Physicians' Health Study, we examined 492 men free of CVD and cancer for the relationship between total plasma carotenoids (the sum of α-carotene, β-carotene, lycopene, zeaxanthin, lutein and β-cryptoxanthin) and a wide variety of factors that predict chronic disease. Multivariate linear and logistic regression was performed to calculate parameter estimates (95 % CI) and OR (95 % CI) for total plasma carotenoids. In linear regression models, BMI, hypertension, alcohol intake and plasma levels of each lipid parameter and α-tocopherol significantly predicted levels of total plasma carotenoids. Upon adjustment for multiple chronic disease risk factors, the OR for levels of total plasma carotenoids greater than or equal to the median ( ≥ 1·301 μmol/l) was statistically significant for current smoking (OR 0·21; 95 % CI 0·06, 0·77), weekly alcohol ingestion (OR 2·30; 95 % CI 1·06, 4·99), daily alcohol ingestion (OR 2·46; 95 % CI 1·29, 4·67), each 100 mg/l increase in total cholesterol (OR 0·73; 95 % CI 0·58, 0·91), LDL-cholesterol (OR 1·48; 95 % CI 1·17, 1·89) and HDL-cholesterol (OR 1·58; 95 % CI 1·26, 1·99), each 100 mg/ml increase in intercellular adhesion molecule-1 (OR 0·70; 95 % CI 0·53, 0·93) and each 10 μmol/l increase in α-tocopherol (OR 1·33; 95 % CI 1·12, 1·57), using logistic regression. Few lifestyle and clinical risk factors appear to be related to levels of total plasma carotenoids; however, levels of biomarkers such as plasma lipids and α-tocopherol may be strongly related.

An Approach to Modeling Crustacean Egg-Bearing Fractions as a Function of Size and Season

1991 ◽  
Vol 48 (8) ◽  
pp. 1431-1436 ◽  
Author(s):  
Victor R. Restrepo ◽  
Reg A. Watson
Keyword(s):  
Egg Production ◽  
Logistic Function ◽  
Parameter Estimates ◽  
Seasonal Trends ◽  
Basic Model ◽  
Maximum Likelihood Methods ◽  
Temperature Parameter ◽  
Gravid Females ◽  
The Individual ◽  
The Relationship

We present an approach to the analysis of crustacean egg production ogives with emphasis on detecting seasonal trends. The relationship between the proportion of gravid females (by size) and season is a prerequisite to the estimation of egg production potentials of populations. The basic method consists of relating, for each sample, the proportion of berried females with their size through a three-parameter logistic function where the asymptote may be less than 1. We then provide guidance for detecting seasonal trends in the estimates of the parameters for the individual samples. This is accomplished by restricting the basic model such that some parameters are considered to be either fixed for all samples or as simple functions of time or environmental variables such as temperature. Parameter estimates are obtained via maximum likelihood methods, and comparisons between alternative models are presented graphically and using likelihood ratio tests. We illustrate the approach and its application with data for a tropical shrimp, Penaeus esculentus, from northern Australia.

Time series bias in the estimation of density-dependent mortality in stock-recruitment models

1995 ◽  
Vol 52 (1) ◽  
pp. 223-232 ◽  
Author(s):  
Ransom A. Myers ◽  
N. J. Barrowman
Keyword(s):  
Time Series ◽  
Gadus Morhua ◽  
Large Time ◽  
Atlantic Cod ◽  
Model Misspecification ◽  
Parameter Estimates ◽  
Density Dependent Mortality ◽  
Stock Recruitment ◽  
Iteroparous Species ◽  
The Relationship

Large biases can occur in parameter estimates for stock–recruitment models because the stock sizes are not chosen independently, being correlated with variability in recruitment. We examine the importance of this "time series bias" by a comprehensive analysis of available stock–recruitment data and the use of simulations. For semelparous species, i.e., species that reproduce only once, time series bias is important for all populations for which we had data. For iteroparous species, i.e., species that reproduce more than once, large biases occur if the populations are exploited at close to the maximum that is biologically possible. Notably, when there is autocorrelation in natural mortality, for univoltine species, the direction of bias is reversed due to model misspecification. Given moderate sample sizes and moderate levels of exploitation, time series bias is small for species such as Atlantic cod (Gadus morhua), for which α, the slope of the relationship between recruitment and number of spawners as the number of spawners goes to zero, is large. Time series bias will usually be important in species such as hakes (Merluccius) for which α appears to be relatively small.

Bias in the Estimation of Functional Relationships from Time Series Data

1985 ◽  
Vol 42 (1) ◽  
pp. 147-149 ◽  
Author(s):  
Carl J. Walters
Keyword(s):  
Time Series ◽  
Measurement Errors ◽  
Time Series Data ◽  
Series Data ◽  
Parameter Estimates ◽  
Natural Experiments ◽  
Independent Variables ◽  
Functional Relationships ◽  
Stock Recruitment ◽  
The Relationship

Functional relationships, such as stock–recruitment curves, are generally estimated from time series data where natural "random" factors have generated both deviations from the relationship and also informative variation in the independent variables. Even in the absence of measurement errors, such natural experiments can lead to severely biased parameter estimates. For stock–recruitment models, the bias is misleading for management: the stock will appear too productive when it is low, and too unproductive when it is large. The likely magnitude of such biases can and should be determined for any particular case by Monte Carlo simulations.

The Carbon Sequestration of Pinus tabulaeformis Forests in Shanxi Province, China

2013 ◽  
Vol 807-809 ◽  
pp. 810-813
Author(s):  
Fei Li ◽  
Hua Yong Zhang ◽  
Zhong Yu Wang ◽  
Zong Han Li
Keyword(s):  
Carbon Sequestration ◽  
Field Measurement ◽  
Carbon Sink ◽  
Measurement Data ◽  
Total Carbon ◽  
Pinus Tabulaeformis ◽  
Shanxi Province ◽  
Inventory Data ◽  
Stand Volume ◽  
The Relationship

In order to estimate the carbon sequestration of Pinus tabulaeformis forests in Shanxi Province, field measurement data from 36 Pinus tabulaeformis forest stands and the 8th National Forest Resource Inventory data were collected. Using the field measurement data, the relationship between stand volume and stand biomass was established. By applying the relationship and a specific carbon concentration coefficient to the forest inventory data, the carbon sequestrations of nature and planted Pinus tabulaeformis forests in each age class were estimated respectively. The results show that the total carbon sequestration of Pinus tabulaeformis forests in Shanxi Province is 13.43 Tg (1 Tg=1012 g). The nature forests are acting as the major carbon sink, with the carbon sequestration accounting for 64% of the total amount. Among the forests in different age classes, the mid-aged and premature forests have sequestered around 10.92 Tg C, which accounts for 81% of the total carbon sequestration.

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