F1000ResearchF1000Research2046-1402F1000 Research LimitedLondon, UK10.12688/f1000research.129399.1Data NoteArticlesThe oxygen concentration data in a forest canopy in 2020 in Beijing Gongqing Forestry Farm
[version 1; peer review: 1 approved with reservations]
XingChangShanConceptualizationData CurationFormal AnalysisInvestigationMethodologyWriting – Original Draft Preparationhttps://orcid.org/0000-0002-1109-3922a1
Beijing Gongqing Forestry Farm, Beijing Municipal Forestry and Parks Bureau, Beijing, Chinaxcs5048@163.com
Background: With the outbreak of global climate problems in recent years, more and more countries have proposed carbon neutral plans. The measurement of forest carbon sinks is gradually becoming a research hotspot in the field of carbon sinks.
Methods: Based on observations of the amount of change in oxygen concentration in the forest canopy, we propose a simple and accurate method of forest carbon sinks measurement.
Conclusions: In this data note, we provide the data of oxygen concentration in the canopy of a 160-hectare forest in Beijing, and give a convenient equation for calculating the carbon sequestration and carbon sink according to the changes of 15 days oxygen concentration.
Forest Carbon Sinks; Measurement; Average oxygen concentration; Carbon SequestrationThe author(s) declared that no grants were involved in supporting this work.Introduction
Forest carbon sinks represent the ability of forest ecosystems to absorb and store carbon dioxide by quantifying the mass of carbon dioxide fixed by plants.
1,2 It is an important indicator for assessing the impact of global climate change, management measures, and human disturbance on forest ecological function, growth, and survival.
3,4 Therefore, accurate quantification of carbon sinks is essential for the effective assessment of forest function dynamics. However, the most common way to measure the changes in carbon sequestration right now is the stock-difference method, which calculates the forest gross primary productivity (GPP) rather than net ecosystem productivity.
5 The gain-loss method
6 is based on monitoring the changes of carbon dioxide in the air, which not only have large errors but also cannot be verified by test and measurement. Therefore, an accurate, accessible, low-cost, short-period observation method is useful for observing forest functional dynamics and convenient to promote in the forestry, agriculture, grass industry, and other related industries.
In this data note, we provide the data on oxygen concentration in the canopy of a 160-hectare forest in Beijing, and give a convenient equation for calculating the carbon sequestration and carbon sink according to the changes of 15 days’ oxygen concentration.
MethodsOverview of the research area
The research was conducted in Beijing Gongqing Forestry Farm, which is located in the northeast of Beijing. This area was selected as the ecological environment here is very representative of northern China. The details of the forest are as follows:
The geographical coordinates are 166.40 E and 40.10 N;
The altitude is 25 meters;
The soil type is sandy soil;
The forest type is planted forest;
The main tree species are populus canadensis Moench. The average tree height of the poplars was 21 meters, the average canopy height was 12 meters, and the average tree age was 25 years;
The region has a warm, temperate, semi-humid, continental monsoon climate with four distinct seasons; it is dry and windy in spring, hot and rainy in summer, cool and crisp in autumn and cold and dry in winter;
The annual average temperature is 11.5 °C;
The annual sunshine is about 2750 hours;
The average annual rainfall is about 625 mm; the area is relatively arid.
Experimental setup
The forest carbon sink was observed by a 30 meter high measuring tower which was set in the center of the 160-hectare forest. An oxygen concentration detector (HeNan ChiCheng Electric Co. Ltd, QB2000N) was installed 15 meters above ground on the measuring tower to ensure the detector was located in the middle of the canopy. This setup was designed specifically for this research. The error value of the oxygen concentration detectors had been adjusted to less than ±0.5%.
The oxygen concentration detector measured the oxygen concentration (% Vol.) every 5 minutes per day.
7 Furthermore, we calculated the daily average oxygen concentration of the forest (
Figure 1;
Table 1). Since trees only begin to grow and release oxygen at a temperature higher than their biological zero (and the biological zero of poplar is more than 10 degrees Celsius), and the average temperature of Gongqing Forestry Farm from March 10th to March 24th is 10.17 degrees Celsius, the starting point of data recording in spring was March 10. The endpoint of data recording in autumn should be set at the time point when the oxygen concentration was higher than the starting point in spring, so the endpoint in autumn is October 5th.
Daily average oxygen concentration from March 10th to October 5th.
Forest carbon sinks meter.
Date
Cell
Average oxygen concentration
Difference of average value of oxygen concentration every 15 days
Summation of average difference of oxygen concentration
Unites: oxygen concentration: % vol; Mass: kg; Oxygen Density: kg/m
3; Height: m; Area: m
2
Canopy height
Area
The mass of sequestrated CO
2
The mass of released CO
2
Forest carbon sinks
3.10-3.24
1
20.56
0.43
12
M
CO
2 = 0.43*1.43*12*10000*44/32 = 101458.5 kg
M
CO
2 = -0.36*1.43*12*10000*44/32 = -84942 kg
M = 16516.5 kg
0.08
3.25-4.08
2
20.64
12
0.11
4.09-4.23
3
20.75
12
0.07
4.24-5.08
4
20.82
12
0.01
5.09-5.23
5
20.83
12
0.08
5.24-6.07
6
20.91
12
0.08
6.08-6.22
7
20.99
12
-0.11
-0.36
6.23-7.07
8
20.88
12
10000 m
2
-0.02
7.08-7.22
9
20.86
12
0
7.23-8.06
10
20.86
12
-0.03
8.07-8.21
11
20.83
12
-0.02
8.22-9.05
12
20.81
12
-0.04
9.06-9.20
13
20.77
12
-0.14
9.21-10.05
14
20.63
12
The measurement of forest carbon sinks
During photosynthesis, plants absorb carbon dioxide and release oxygen. Their amount of substance is equal to the mass divided by the molar mass. Therefore, the value of plant carbon sequestration can be calculated by the following formula:
Mco2=∑vρhsmrco2/mro2
M
co
2 is the mass of plant fixed carbon dioxide, and
∑v is the accumulated value of oxygen concentration difference during a specific period (based on experience, 15 days is used as the most appropriate the measurement period), ρ is the oxygen density 1.43kg/m
3, h is the average height of the photosynthetic part of the plant, s is the area of the plant, mr
co
2 is the molecular weight of CO
2 (44), and mr
o
2 is the molecular weight of O
2 (32).
Data availabilityUnderlying data
figshare: The oxygen concentration data in Forest Canopy of 2020 in Beijing Gongqing Forestry Farm,
https://doi.org/10.6084/m9.figshare.22735811.v1.
7
This project contains csv files of oxygen concentration data, labelled with the collection dates.
Data are available under the terms of the
Creative Commons Attribution 4.0 International license (CC-BY 4.0).
Acknowledgments
This article has previously been made available as a preprint (DOI:
https://doi.org/10.21203/rs.3.rs-1141066/v1). Thanks to both authors JIANG LV and YUN SHI for their contributions to this article.
ReferencesUNFCCC:
Kyoto Protocol to the United Nations Framework Convention on Climate Change.1998. Acesso em: 25 out. 2019.
Reference SourcePanYBirdseyRAFangJ:
A Large and Persistent Carbon Sink in the World’s Forests.Science.2011;333:988–993.
2176475410.1126/science.1201609GampeDZscheischlerJReichsteinM:
Increasing impact of warm droughts on northern ecosystem productivity over recent decades.Nat. Clim. Chang.2021;11(9):772–779.
10.1038/s41558-021-01112-8SitchSFriedlingsteinPGruberN:
Recent trends and drivers of regional sources and sinks of carbon dioxide.Biogeosciences.2015;12:653–679.
10.5194/bg-12-653-2015Forestry Carbon Sequestration Editorial Board:
Forestry Carbon Sequestration: practice in Beijing.China Forestry Publishing House;2016. (In Chinese).LiNYLvJ:
Carbon Inventory Methods.China Forestry Publishing House;2009. (In Chinese).Xing:
The oxygen concentration data in Forest Canopy of 2020 in Beijing Gongqing Forestry Farm.[Dataset].
figshare.2023.
10.6084/m9.figshare.22735811.v110.5256/f1000research.142084.r194292Reviewer response for version 1TanZheng-Hong1Referee
Professor of Ecology, Yunnan University, Kunming, Yunnan, China
Competing interests: No competing interests were disclosed.
I can not follow the logic or principle of calculating carbon sequestration by oxygen concentration data as provided by author. As shown in closed chamber method, we will calculate the flux by a linear fitting on concentration data. In this case, there less a confidential control volume below the sensor height where lateral flow might occur. More importantly, it is not reasonable to calculate flux with a too coarse interval (15 days).
By the way, authors did not provide enough information on measurement. i.e. calibrations, maintenance, sampling interval etc.
The major content should match to the title. Since authors want to show some oxygen concentration data, no need jumps into the carbon sequestration issues. If they want to, please provide more methodological information and apply appropriate and theoretically sounding method.
Are sufficient details of methods and materials provided to allow replication by others?
No
Is the rationale for creating the dataset(s) clearly described?
Partly
Are the datasets clearly presented in a useable and accessible format?
Partly
Are the protocols appropriate and is the work technically sound?
No
Reviewer Expertise:
NA
I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above.
XingChangShanBeijing Gongqing Forestry Farm, China
Competing interests: No competing interests were disclosed.
10112023
First of all, thank you very much to the reviewers for their hard work on reviewing this paper.
The reviewer has raised questions about the principle of this method, which have been addressed in the preprint paper available at
https://doi.org/10.21203/rs.3.rs-1141066/v1. In response to the need for validation of the method in a closed space, I will provide the experimental data from experiments conducted in a closed greenhouse later, which fully demonstrates that the regularity of observation results in open and closed spaces is completely consistent. Whether in a closed or open space, the experimental verification of this method has demonstrated its practicality, operability, and accuracy:
The reason for considering a 15-day period as the calculation unit for oxygen concentration is that the rate of photosynthesis is directly related to temperature. By conducting a one-way analysis of variance, we can determine that the temperature differences between 15-day intervals are significant. The following is the additional experimental data provided:
An oxygen concentration detector was installed at the center position of a 11x6 square meter sunlit greenhouse. The detector was placed at a height of 25 centimeters above the ground. The greenhouse contained naturally growing wild plants. Depending on the drought conditions, intermittent irrigation was applied to water the wild plants. The oxygen concentration inside the greenhouse was continuously measured at a frequency of once every 5 minutes. The average daily oxygen concentration value for the wild plants was then calculated. The measurements were taken from February 24, 2020, to November 19, 2020.
The oxygen concentration data for wild plants in an enclosed space：
The carbon sequestration of wild grass in an enclosed space：
The variation of wild grass in an enclosed space over a continuous period of 15 days shows a noticeable increase and decrease at both ends with a relatively stable fluctuation in the middle. From February 24th to March 24th, the oxygen concentration gradually increased. From March 25th to October 5th, it showed a gradual and mild fluctuation. The peak occurred from August 22nd to September 5th during the summer, reaching 21.201 L/mol. Taking the average oxygen concentration from February 24th to March 9th, which is 20.676, as the starting point, we subtract the average oxygen concentration in the later period from the average in the earlier period. Then, using the highest oxygen concentration value as the threshold, we add up all the differences to obtain the total oxygen concentration. Using the formula
,
represents the mass of carbon dioxide fixed by plants,
is the sum of the oxygen concentration,
is the density of oxygen（1.43kg/m³），the average height h of the plant undergoing photosynthesis, and s is the area of the plant，mrCO2 is the molecular weight of CO2, which is 44, and mrO2 is the molecular weight of O2, which is 32.Calculate the total carbon sequestration mass of wild grass in a closed space during the growth period：
MCO=1.429×0.364×0.4×66×(44/32)=18.88kg
MCO=1.429×0.168×0.6×66×(44/32)=13.08kg
MCO=18.88+13.08=31.96kg
During the stage when the oxygen concentration gradually decreases after the inflection point, calculate the mass of oxygen consumed and the mass of carbon dioxide released during the growth process of wild grass.：
MCO=1.429×0.037×0.55×66×(44/32)=2.64kg
MCO=1.429×0.388×0.4×66×(44/32)=20.13kg
MCO=2.64+20.13=22.77kg
The carbon sink is the difference between the absorption of carbon dioxide before the inflection point and the release after the inflection point: MCO=31.96-22.77=9.19kg.
During the growth period, the total carbon sequestration mass of wild grass is 31.96 kilograms. Harvesting 66 square meters of wild grass yields 41 kilograms of dry matter, and after measuring the organic carbon content, the total carbon sequestration mass is determined to be 20.067 kilograms. The measured carbon sequestration mass of the wild grass accounts for 62.8% of the calculated carbon sequestration mass, primarily due to the fact that the carbon sequestration mass of the roots and other plants in the soil was not measured, resulting in a lower measured value than the calculated carbon sequestration mass.
From June 23rd to August 6th, the oxygen released by photosynthesis of the wild grass was less than the oxygen consumed by respiration, mainly due to the high temperature suppressing the photosynthesis of the wild grass.