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Scientia Silvae Sinicae ›› 2023, Vol. 59 ›› Issue (9): 55-65.doi: 10.11707/j.1001-7488.LYKX20220408

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CO2 Concentration and the δ13C Dynamics in Larix gmelinii Ecosystem in Response to Environmental Factors

Zhang Xin1,2, Zhang Qiuliang2,3, Sun Shoujia4, Wang Bing2   

  1. 1. College of Ecology and Environment, Inner Mongolia University Hohhot 010021;
    2. College of Forestry, Inner Mongolia Agricultural University Hohhot 010019;
    3. National Field Scientific Observation and Research Station of Greater Khingan Forest Ecosystem Genhe 022350;
    4. Research Institute of Forestry, Chinese Academy of Forestry Beijing 100091
  • Received:2022-06-14 Revised:2023-03-13 Published:2023-10-28

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Abstract: Objective This study aims to explore the influence mechanism of environmental factors on the CO2 concentration and δ13C dynamics in Larix gmelinii ecosystem, which would help to deeply understand the process and mechanism of carbon exchange in ecosystems, so as to provide reference for simulating and predicting the mutual feedback mechanism between global change and ecosystems, as well as for scientific assessment of carbon sink capacity of cold temperate forest ecosystems.Method The off-axis integral cavity output spectroscopy was used to perform continuous high-frequency observations to the CO2 concentration and δ13C value at different heights in different phenological periods of L. gmelinii ecosystem, and thereby analyze the relationship between environmental factors and CO2 concentration. Result 1) The CO2 concentration at different heights of L. gmelinii ecosystem showed a single peak variation in the growth season and daily scale. The peak value appeared in the leaf spreading period (522.34 μmol·mol-1) and at night (782.81 μmol·mol-1), respectively. The valley value appeared in the leaf falling period (406.07 μmol·mol-1) and at noon (379.72 μmol·mol-1), respectively. The δ13C variation was opposite to CO2 concentration. 2) The CO2 concentration decreased with the increase of vertical height, while δ13C increased with the increase of vertical height. The CO2 concentration and δ13C at different heights had obvious stratification. The increase of atmospheric stability at night (Ri ≥ 0.083) increased the difference inside and outside the canopy. 3) On the 0.5 h scale, air temperature (Ta) was the main factor affecting the variation of CO2 concentration at different heights in day and night (0.714 < PC < 1.288). On a daily scale, soil temperature (Ts5) in 5 cm depth layer was the main factor determining the variation of CO2 concentration at different heights in the growing season (0.473 < PC < 0.718). Conclusion There is a very significant negative correlation between δ13C and CO2 concentration at different heights of L. gmelinii ecosystem. The increase of atmospheric stability at night aggravates their layering phenomenon. The influence level of soil factors on the variation of CO2 concentration at different heights in different phenological periods of L. gmelinii ecosystem is greater than that of meteorological factors. The soil temperature has greater influence on the variation of CO2 concentration than the soil water. The study area is located in a sensitive area to global climate change. Frozen soil is an indispensable environmental factor for forest vegetation in this area. Global warming will have a significant impact on the carbon exchange process of L. gmelinii ecosystem through direct temperature effect and indirect changes in soil physical and chemical properties and biological processes.

Key words: CO2 concentration, carbon isotope, environmental factors, Larix gmelinii

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