The Effect Of Management Measures On Carbon Balance In Plantations Of Ouercus Acutissima

Quercus acutissima Carr. is one of the most important hard broadleaf species for woodcharcoal in China, and a huge potential exists in exploitation and utilization as forestrybio-energy. Sawtooth oak plantations at Hongyashan Forestry Farm, Chuzhou City, AnhuiProvince，China were studied in this experiment. We used digging method to measure thecarbon densities of different fertilization treatments and used Li-6400soil chamber toinvestigate components of soil respiration in different treatments. Meanwhile the soil chemicaland physical properties, as well as microbial qualities were analyzed. The main results wereconcluded as follows:（1） Fertilization increased the annual net carbon reserves of plantationsThe results of our study indicated that within the level of0.45kg·tree^-1, the wood biomassand forest productivity of different plantations increased with the increase of fertilization. Totalcarbon densities of different fertilization treatments (CK，0.15kg·tree^-1，0.30kg·tree^-1and0.45kg·tree^-1) were73.68t·hm^-2，84.49t·hm^-2，87.20t·hm^-2and91.70t·hm^-2, respectively.There were similar seasonal dynamics for different fertilization treatments. The variationof soil respiration tent to be single peak curves: higher in July, lower in January. With theincrease of the amounts of fertilizer, the soil respiration rate decreased. Besides, themanagement of fertilization decreased both the microbial quantities of plantations and thecontribution of heterotrophic respiration to total soil respiration.The results of statistical analysis showed that within the level of0.45kg·tree^-1, annual netcarbon reserves of different fertilization treatments increased with the increased of fertilizationamount. Compared with the control treatment, the annual net carbon reserves of treatment0.15kg·tree^-1，0.30kg·tree^-1and0.45kg·tree^-1increased26%、41%and55%.（2） Sprouting improved the forest carbon sinks abilityCarbon densities of plantations in different stump heights and sprout numbers existeddifference. The distributions of carbon density in different organs were the same: stem> root> branch> leaf. With the same stump height, the treatments of2sprouting number had highercarbon densities, and the treatments of4sprouting number had lower carbon densities. Withthe same sprouting number, the treatments of5cm stump height had higher carbon densities,and the treatments of100cm stump height had the lower carbon densities. The top threetreatments of total carbon densities were H₅S₂、H₅S₁and H₅₀S₂.There were similar seasonal dynamics for different sprouting plantations. The variation ofsoil respiration tent to be single peak curves: higher in summer, lower in winter. With the samestump height, the control treatments had higher carbon densities, and the treatments of2sprouting number had lower carbon densities. With the same sprouting number, the treatmentsof100cm stump height had the higher carbon densities, and the treatments of5cm stumpheight had the lower carbon densities. The last three treatments of total soil respiration ratewere H₅S₂、H₅₀S₂and H₁₀₀S₂.The results of statistical analysis showed that the management measures of differentstump height and sprouting number could increase the annual net carbon reserves ofplantations. The top three treatments of annual net carbon reserves were H₅S₂(3.42t·hm^-2year^-1)、H₁₀₀S₂(3.10t·hm^-2year^-1)and H₅S₁(2.88t·hm^-2year^-1).（3） Comparison of soil respiration in three forest typeThe three forest types have similar single-peak curve patterns in daily soil respirationprocess. Soil respiration rate varied in the following order: sawtooth oak+sweetgum>sawtooth oak> sawtooth oak+slash pine. Compared with the sawtooth oak plantation, the soilrespiration rate of sawtooth oak and sweetgum increased20.6%, and the soil respiration rate ofsawtooth oak and slash pine decreased16.8%. Significant relationships were found betweensoil respiration rate and soil temperature at5cm soil depth in three plantations, which could bebest described by exponential equations. Soil temperature could explain changes in soilrespiration of84.8%,70.7%and82.4%, in the sawtooth oak, sawtooth oak+sweetgum andsawtooth oak+slash pine plantations, respectively.