马尾松林采伐迹地火烧黑炭对土壤活性碳氮库的影响

黑炭是火烧过程中不完全燃烧的产物,在火烧迹地的分布具有异质性。为了解黑炭输入量对土壤活性碳氮库的影响,选取中亚热带33年生马尾松人工林采伐迹地为研究对象,对比炼山1年后移除(B0)、单倍(B1)和双倍黑炭输入(B2)处理和未火烧对照土壤可溶性有机碳氮含量(DOC和DON)、矿质氮、土壤微生物量碳氮含量(MBC和MBN)之间的差异。结果表明:炼山对土壤DOC和DON含量的影响因土层而异,在0—10 cm土层,火烧土壤DOC和DON含量与对照土壤没有显著差异,而在10—20 cm土壤要显著低于对照土壤(P0.05)。火烧土壤矿质氮、土壤MBC和MBN含量均低于对照土壤,但差异未达到显著性水平(P0.05)。火烧土壤含水率、pH、全碳和全氮、铵态氮、土壤MBN含量均与黑炭输入量成正比,特别是在10—20 cm土层,B2处理土壤铵态氮含量显著高于B0和B1处理(P0.05)。对于土壤MBN,黑炭输入处理(B1和B2)火烧土壤MBN含量与对照土壤没有显著差异,而去除黑炭处理(B0)火烧土壤MBN含量则显著低于对照土壤(P0.05)。结果说明黑炭输入对火烧土壤的微生物群落恢复和N素保持具有积极意义,因此亚热带人工林管理过程中应重视黑炭的利用。

Effects of black carbon on soil labile carbon and nitrogen pools in a Pinus massoniana plantation subjected to slash burning

Slash and burn is a traditional and efficient way of removing forest harvest residues in south China. This study was conducted to investigate the effects of fire-derived black carbon on soil labile carbon and nitrogen pools in a Pinus massoniana Lamb. plantation in subtropical China. Three levels of black carbonnil (B0), single (B1), and double rates (B2)] were used by transferring black carbon across the plots after slash burning. The unburnt area (UB) adjacent to the burnt site was selected as the reference site. Soil dissolved organic C (DOC) and N (DON), inorganic N, microbial biomass C (MBC), and N (MBN) contents were measured 1 year after the black carbon application. The results showed that the effects of fire on the soil DOC and DON differed among the sampling depths, and no significant differences in soil DOC and DON contents between the burnt and reference soil were observed at the 0-10 cm depth, whereas the DOC and DON contents in 10-20 cm soil layers were significantly lower at the burnt site than they were at the reference site (P < 0.05). The soil inorganic N, MBC, and MBN contents were lower at the burnt site than those at the reference site were, although the differences were not statistically significant (P > 0.05). Soil moisture content, pH, total C, total N, ammonium, and soil MBN content increased with the amount of black carbon input. Especially, the soil ammonium content under the B2 treatment was significantly higher than those under B0 and B1 treatments were at the 10-20 cm depth (P < 0.05). Moreover, the removal of black carbon significantly decreased the soil MBN content compared to that of the reference site. In conclusion, this study suggested that the black carbon input played a key role in the recovery of soil microbial communities and N retention after slash burning, and the underlying mechanisms by which black carbon regulates soil N cycling should be investigated in future studies.