亚热带森林转换对土壤微生物呼吸及其熵值的影响

土壤微生物呼吸及其熵值是表征土壤质量变化的敏感性指标,不仅能衡量土壤微生物碳利用效率,还能揭示土壤有机碳的变化。通过比较亚热带米槠天然林转换为马尾松人工林和杉木人工林后土壤微生物呼吸速率、土壤微生物生物量碳以及微生物熵、代谢熵的差异,研究亚热带森林转换对土壤微生物碳利用效率的影响。研究结果显示:(1)与天然林相比,马尾松人工林0—10 cm土壤微生物呼吸速率上升32%(P0.05),马尾松人工林和杉木人工林10—20 cm土壤微生物呼吸速率分别下降26%和24%(P0.05);但在20—40 cm土层和40—60 cm土层,天然林土壤微生物呼吸速率比马尾松人工林分别高50%和43%;(2)马尾松人工林和杉木人工林0—10 cm土层土壤微生物生物量碳(MBC)比天然林分别下降19%和40%(P0.05),但马尾松人工林10—20 cm土壤MBC上升29%(P0.05);(3)人工林表层土壤微生物熵与天然林没有显著差异,但与天然林相比,杉木人工林和马尾松人工林20—40 cm土层土壤微生物熵分别下降51%和71%(P0.05),40—60 cm分别下降52%、66%(P0.05)。土壤微生物代谢熵的变化主要发生在0—10 cm土层,马尾松人工林和杉木人工林分别比天然林增加38%和29%(P0.05),在深层土壤,3种林分微生物代谢熵没有显著差异。亚热带森林转换导致表层土壤微生物碳利用效率下降,深层土壤易分解碳在总有机碳库中占比下降,有机碳可利用程度降低。

Effects of subtropical forest conversion on soil microbial respiration and its entropy

Soil microbial respiration and its entropy, as a sensitive indicator of soil nutrient variation, are usually used to evaluate the microbial carbon use efficiency and soil carbon concentration variation. In this present study, the effects of forest conversion on microbial carbon use efficiency was studied by comparing differences of soil microbial respiration rate, microbial biomass carbon, microbial entropy, and metabolic entropy between Castanopsis carlessi natural forest (NF) and Pinus massoniana Lamb. plantation (PM) and Cunninghamia lanceolata Lamb. Plantation (CL). The results showed that (1) the soil microbial respiration rate in 0-10 cm of PM was 32% higher than that of NF. The soil microbial respiration rate in 10-20 cm of PM and CL were 26% and 24% lower than those of NF, respectively (P<0.05). The microbial respiration rate in 20-40 cm and 40-60 cm soil layer of NF were 50% and 43% higher than that of PM. (2) Soil microbial biomass carbon (MBC) in 0-10 cm of PM and CL were 19% and 40% lower than those of NF, respectively (P<0.05). The MBC in 10-20 cm of PM was 29% higher than that of NF (P<0.05). (3) Soil microbial entropy in 0-10 cm of CL and PM were not significantly different from that in the natural forest. It decreased 51% and 71% in 20-40 cm, 52% and 66% in 40-60 cm (P<0.05). Effects of forest conversion on metabolic entropy could only be found in 0-10 cm soil layer but not subsurface layer. The metabolic entropy in PM and CL 38% and 29% higher than that of NF, respectively (P<0.05). In conclusion, the forest conversion decreased the soil microbial carbon use efficiency in the surface layer, the ratio of labile to total carbon pool in the surface layer, and availability of organic carbon.