Effects On Twice Mulch To Soil Temperature And CO₂ Emission Rate About Shoot Forest Of Phyllostachys Edulis ’Pachyloen’

Bamboo shoot forest mulching refers to covering the surface with heat-generating substances and thermal insulation materials in winter,which is to increase soil temperature and promote the early emergence and increase the yield and efficiency of bamboo shoots,and it has been widely applied in bamboo forest production.At now,bamboo shoot forest cover tends to adopt the one-time cover method in the production practice,which is to cover the ground surface with the heat-generating substances and heat-insulating materials at one time.Affected by the heat released by the heat-generating substances and the time,the issue of the low soil temperature during the Spring Festival harming the yield and benefit is likely to happen;if the cover time is delayed,the bamboo shoot period would be delayed due to the dormancy of the bamboo forest;if the amount of heat-generating substances and thermal insulation materials is increased,high temperature stress can be generated at the primary stage of cover and affect the growth of the bamboo forest,causing poor or failed covering.As such,some forest farmers have begun to cover bamboo species such as Phyllostachys edulis with high shoot temperature requirements for the twice mulching,and put the covering on ground surface two times,preventing the high temperature threat at the primary stage while improving the soil temperature during the Spring Festival.The previous studies on bamboo shoot forest covering have focused on the one-time covering method,and there are few studies on soil warming and CO₂ emission mechanisms under the twice mulching method of bamboo shoot forest.The way to reasonably allocate the first and second covering amount and the interval time to enhance the covering effect and reduce CO₂emissions is yet to be studied.This study takes the bamboo shoot forest of Ph.edulis’Pachyloen’as the object to conduct the covering experiment.The twice mulching method is adopted.Part of the heat-generating substances and thermal insulation materials are covered on the surface of the forest for the first covering,and the second covering is carried out after some time,putting the remaining heat-generating substance and thermal insulation material on the thermal insulation layer covered for the first time.Two oil cake application rate levels(15 t·hm^-2,18t·hm^-2)and two grain husk layer thickness levels（30 cm,40 cm）are designed,and four kinds of covering treatments are arranged in the way of twice mulching.The dynamic change law of soil temperature and CO₂ emission rate is observed to analyze the influence of the cover factors（oil cake amount and thickness of grain husk layer）and cover mode（combination of different cover factors）on soil temperature and CO₂ emission rate,and the relationship between soil temperature and soil CO₂ emission rate is explored to provide a reference for further research on high-efficiency and low-carbon coverage models with good warming effects and low CO₂ emissions.The following conclusions are arrived at:（1）During the coverage period,the soil temperature indicates a double-peak dynamic curve change law,and there’s a high temperature peak before and after the second coverage,and the second peak is higher;the second coverage measure can obviously improve the soil temperature.There are visible differences in the average soil temperatures and high temperature peaks among the modes,which is showcased as that the more the oil cake application amount,the thicker the grain husk,and the higher the soil temperature.（2）The thickness of the grain husk layer represents the primary factor affecting the soil temperature.The soil temperature of the 40cm grain husk layer is significantly higher than that of the 30cm husk layer layer.There are no evident differences in the soil temperatures under the application amounts of 15 t·hm^-2 and 18 t·hm^-2.（3）The soil CO₂ emission rate during the coverage period is in a single-peak dynamic curve change;the two-time coverage measure significantly increases soil CO₂ emissions,and there’s no prominent differences in the CO₂ average emission speeds and peaks between the soils of different coverage modes.It’s indicated as that the more the oil cake application amount,the thicker the grain husk,and the higher the soil CO₂ emission rate.（4）The thickness of the grain husk layer is the primary factor affecting the soil CO₂ emission rate.The soil CO₂ emission rate of the 40cm grain husk is significantly higher than that of the 30cm grain husk layer.There’s no significant difference in the soil CO₂ emission rates between the soils with the oil cake application amount of 15 t·hm^-2and 18 t·hm^-2.（5）There’s a significant positive correlation between soil temperature and soil CO₂ emission rate as a whole,the response of soil CO₂ emission rate to soil temperature is an exponential function,and the soil Q₁₀ value decreases with the rise of temperature.In conclusion:The twice mulching measure for bamboo shoot forest in winter can obviously improve soil temperature and extend the time when soil temperature exceeds 20℃,but it will also level up soil CO₂ emissions.Taking into consideration the warming effect and carbon emission issues comprehensively,the twice mulching method can be applied for the bamboo species such as Ph.edulis’Pachyloen’and other bamboo species that require a high shoot temperature.The mode of covering 7.5 t·hm^-2 oil cake+20 cm grain husk layer for the first time,and 7.5 t·hm^-2oil cake+20 cm grain husk layer for the second time has a good effect;however,for the bamboo species that require a low shoot temperature,the mode of covering 7.5 t·hm^-2 oil cake+10 cm grain husk layer for the first time and 10.5 t·hm^-2 oil cake+20 cm grain husk layer for the second time can be adopted.