Stem Respiration Characteristics And Temperature Sensitivity Of Natural Larix Gmelinii Forest With Different Diameter Classes

Stem respiration is one of the ways of forest life activities and carbon release,so it is important to study stem respiration for forest ecosystem management.Stem respiration rate and temperature of natural Larix gmelinii forest with different diameter classes were measured by Li-Cor6400 Portable Photosynthesis System in natural forest experimental area of the National Field Scientific Observation and Research Station of Daxing’anling Forest Ecosystem from June to September in the growing season of 2021.The variation characteristics of stem temperature,stem respiration rate and the sensitivity of respiration rate to temperature of Larix gmelinii of different diameter classes were analyzed.The results show that:（1）The diurnal variation of the stem respiration rate of Larix gmelinii with different diameter classes showed a unimodal curve regularity.The respiration rate gradually increased from 4:00,and the diurnal variation reached a peak at 14:00-18:00,and then gradually decrease,with a minimum value from 4:00-6:00.In the growing season,the monthly variation reached the peak respiration rate in July and July,and the minimum value in September and September.The variation rule was July>August>June>September.（2）In the growing season（June-September）,the stem respiration of Larix gmelinii of different diameter classes were significantly different,which showed an increasing trend with the increase of diameter classes.;（3）The variation law of of Larix gmelinii stem temperature and air temperature is basically the same,but the variation value has a time lag of 1-2 hours.The diurnal variation characteristics of the stem temperature showed a unimodal curve,the diurnal variation peak appeared at 12:00-16:00,and the minimum value appeared at 0:00-6:00.Stem temperature decreases with increasing diameter.（4）No matter the daily respiration rate or the monthly average respiration rate,the stem respiration rate is affected by the temperature,and the respiration rate increases with the increase of the stem temperature.The stem respiration rate of small-diameter trees is more sensitive to temperature,but when the temperature rises to a certain extent,the stem respiration rate will also be inhibited to a certain extent.The Q₁₀value of stem respiration to stem temperature of Larix gmelinii in different diameter classes from 1.79 to 3.97.