Zhang Jian, Wang Silong, Feng Zongwei, Wang Qingkui
Huitong Experimental Station of Forest Ecology, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China.
J Environ Sci (China). 2009;21(3):352-9. doi: 10.1016/s1001-0742(08)62276-7.
The importance of soil organic carbon (SOC) under forests in the global carbon cycle depends on the stability of the soil carbon and its availability to soil microbial biomass. We investigated the effects of successive rotations of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) plantations on the stability of SOC and its availability to microbes by adopting the two-step hydrolysis with H2SO4 and density fractionation. The results showed that successive rotations of Chinese fir decreased the quantity of total SOC, recalcitrant fraction, and carbohydrates in Labile Pool I (LP I), and microbial properties evidently, especially at 0-10 cm horizon. However, cellulose included in Labile Pool II (LP II) and the cellulose/total carbohydrates ratio increased in successive rotations of Chinese fir. The non-cellulose of carbohydrates included in LP I maybe highly available to soil microbial biomass. Hence the availability of SOC to microbial biomass declined over the successive rotations. Although there was no significant change in recalcitrance of SOC over the successive rotations of Chinese fir, the percentage of heavy fraction to total SOC increased, suggesting that the degree of physical protection for SOC increased and SOC became more stable over the successive rotations. The degradation of SOC quality in successive rotation soils may be attributed to worse environmental conditions resulted from disturbance that related to "slash and burn" site preparation. Being highly correlated with soil microbial properties, the cellulose/total carbohydrates ratio as an effective indicator of changes in availability of SOC to microbial biomass brought by management practices in forest soils.
森林土壤有机碳（SOC）在全球碳循环中的重要性取决于土壤碳的稳定性及其对土壤微生物生物量的可用性。我们采用硫酸两步水解法和密度分级法，研究了杉木（Cunninghamia lanceolata (Lamb.) Hook）人工林连续轮作对SOC稳定性及其对微生物可用性的影响。结果表明，杉木连续轮作显著降低了总SOC、难降解组分以及易变库I（LP I）中碳水化合物的含量，微生物特性也明显下降，尤其是在0-10厘米土层。然而，易变库II（LP II）中的纤维素以及杉木连续轮作中纤维素/总碳水化合物的比例增加。LP I中包含的碳水化合物的非纤维素部分可能对土壤微生物生物量具有高度可用性。因此，随着连续轮作，SOC对微生物生物量的可用性下降。尽管杉木连续轮作过程中SOC的难降解性没有显著变化，但重质组分占总SOC的百分比增加，这表明随着连续轮作，SOC的物理保护程度增加，SOC变得更加稳定。连续轮作土壤中SOC质量的下降可能归因于与“刀耕火种”整地相关的干扰导致的更恶劣的环境条件。纤维素/总碳水化合物的比例与土壤微生物特性高度相关，可作为森林土壤管理措施引起的SOC对微生物生物量可用性变化的有效指标。
