林业废弃物生物炭对红壤丘陵区瘠薄土壤碳矿化的影响

The Effects of Forestry-waste Biochar on Carbon Mineralization in An Infertile Soil in Hilly Red Soil Region, China

生物炭施入土壤的固碳潜力已引起了世界范围的关注,研究生物炭对土壤碳矿化的影响机制对深入理解土壤-生物炭的固碳机理有重要科学意义。选取我国红壤丘陵区广泛分布的典型树种马尾松(Pinus massoniana)和杉木(Cunninghamia lanceolata)为原料制备生物炭,在控制培养条件下,生物炭按照1%、2%和5%的质量比加入土壤,研究生物炭对该区典型瘠薄土壤碳矿化的影响。培养过程中定期测定CO_2碳释放量(CO_2-C),培养结束后测定土壤微生物生物量、p H等性质。结果表明,生物炭促进了CO_2-C累积释放量,其中5%的生物炭效果最明显。采用First-order模型拟合相对碳总量(生物炭碳+土壤碳)的CO_2-C累积释放量,结果表明,该值随着生物炭施用量增加而降低,最高值出现在无生物炭的土壤对照处理。当施用量为5%时,生物炭可显著促进土壤碳总量释放;但施用量为2%时,生物炭对土壤碳释放的影响不明显。此外,土壤硝态氮和铵态氮含量均随生物炭施用量增加而降低。两种生物炭均提高了土壤微生物生物量碳含量且最高值均出现在施用5%的处理(分别为53.93±9.87和43.45±3.44 mg·kg^(-1));两种生物炭按5%比例施用时,可显著提高土壤微生物生物量氮,但施用其他比例时土壤微生物生物量氮变化不明显。因此,对采用林业废弃物生物炭改良红壤丘陵区的土壤而言,应采取较低量的施用策略,在达到土壤-生物炭固碳目标的同时亦可避免短期内的土壤碳损失。

Extensive studies have demonstrated the effect of adding biochar on soil carbon （C） sequestration. Typically, investigatingthe effects of biochar on C mineralization possessed significant importance for understanding the mechanism in C sequestrationimprovement with biochar. Trunks from two typical tree species （Pinus massoniana and Cunninghamia lanceolata） were collected inhilly red soil region to produce biochar （labeled as PT and CT） and were furtherly added to soil at weight rates of 1%, 2% and 5%respectively. Treatments of quartz sand ＋ 2% PT, quartz sand ＋ 2% CT, quartz sand ＋ 5% PT and quartz sand ＋ 5% CT were also setas controls. A 42-day incubation experiment was performed and the released CO2 （CO2-C） was measured periodically. Afterincubation, soil properties such as dissolved organic C （DOC）, microbial biomass C （MBC）, pH were determined. Enhancedcumulative CO2-C evolution was observed at 5% biochar addition. However, the total C released in the 2% soil-biochar treatmentshad not different with 2% sand-biochar treatments and CK. The total C in the 5% soil-biochar treatments （4.02 and 4.18 mg） washigher than that in the 5% sand-biochar treatments and CK. The cumulative CO2-C evolution was normalized to total C （addedbiochar C ＋ native soil C） and then fitted with the first-order model. According to fitting results, the cumulative CO2-C evolution perunit C decreased with increasing biochar addition rate and similar results were obtained in the potential size of available C （C0）. SoilMBC was improved by highest biochar additions level at 5%. Soil nitrate and ammonium nitrogen decreased with increasing biocharaddition rate. The results suggest that the mass of the microorganism for stimulating soil C mineralization can be enhanced byhigh-rate （e.g., 5%） biochar addition compare to no large variation in treatments with lower addition rates of biochar. In all, additionof forestry-waste biochar biochar, either at a high or low rate can increase C content in soils. At short period, addition rates as high as5% may result in more stimulate C mineralization in the infertile soils of this region than lower biochar addition rates.