黄土旱塬区冬小麦不同施肥处理的土壤呼吸及土壤碳动态

依据黄土旱塬区黑垆土上中国科学院长武站长期定位试验 (始于1984年),于2008年3月到6月,测定了冬小麦连作系统中返青期、拔节期、抽穗期、灌浆期和收获期土壤呼吸日变化、生育期变化以及土壤可溶性有机碳(Dissolved organic C, DOC)和微生物量碳(Soil microbial biomass C, MBC),研究了施肥措施对土壤呼吸、DOC和MBC的影响以及土壤呼吸与碳组分之间的关系.研究涉及6个处理:休闲地(F)、不施肥(CK)、有机肥(M)、氮肥(N)、氮磷肥(NP)和氮磷有机肥(NPM).结果表明,冬小麦连作系统中土壤呼吸的日变化格局呈单峰曲线,最高值出现在12:00左右(拔节期)和14:30左右(成熟期),最小值出现在0:00～3:00之间或6:00左右;冬小麦土壤呼吸速率拔节期最高,其次是灌浆后期,抽穗期最低;不同施肥条件下,各生育期土壤呼吸速率大小顺序:NPM＞M＞NP＞N＞CK＞F.土壤水分亏缺是导致抽穗期和灌浆期土壤呼吸速率降低的重要原因.各施肥处理DOC含量高低顺序为灌浆期＞抽穗期＞成熟期＞返青期＞拔节期;除M,NPM处理MBC含量拔节期＞灌浆期外,各施肥处理MBC含量高低顺序为成熟期＞抽穗期＞灌浆期＞拔节期＞返青期.同一处理不同生育期土壤呼吸速率与DOC,MBC的相关性较低,但同生育期不同施肥处理土壤呼吸与土壤有机碳组分间存在显著的相关性.以F处理土壤呼吸为基础,估算CK、N和NP处理生育期根系对土壤呼吸的平均贡献率依次为36%、45%和54%.

Soil respiration and carbon fractions in winter wheat cropping system under fertilization practices in arid\|highland of the Loess Plateau

Based on a long\|term location experiment on Caliche soil in Changwu Station of Chinese Academy of Sciences, Changwu, Shaanxi, China, we monitored diurnal changes and seasonal changes of CO2 flux from soils in a continuous winter wheat (Triticum aestivum L.) cropping system by LI-8100 automated soil CO2 flux system, and soil dissolved organic carbon (DOC), soil microbial biomass carbon (MBC) were also measured during returning green, heading, jointing, filling and mature stages during the wheat growing period Six fertilization practices arranged as a block with 3 replicates from the long\|term experiment were selected, which consists of fallow (F), control (CK), farm yard manure (M, 75 t?hm-2), nitrogen (N, 120 kg?hm-2), nitrogen and phosphorus (NP, 120 kg N?hm-2, 39 kg P?hm-2 ), and nitrogen and phosphorus plus farm yard manure (NPM, 120 kg N?hm-2, 39 kg P?hm-2, 75t ?hm-2 ). The soil CO2 flux showed significant diurnal changes and seasonal changes. For the diurnal changes, the soil CO2 flux rate followed a single peak curve with time, and the maximum of soil respiration appeared about at 12:00 or 14:30, and the minimums between 0:00 to 3:00 or about 6:00. Fertilization significantly increased soil CO2 flux rate, and the order of CO2 flux rate under different fertilizations followed as NPM > M > NP > N > CK > F. For the seasonal changes, the soil CO2 flux rate was highest during the jointing stage, followed by late filling stage, and minimum rate appeared during heading stage. Soil water deficit contributed to most of reduction of soil CO2 flux rate during heading and filling stage. Fertilization significantly affect MBC and DOC, there were significant seasonal changes in DOC and MBC. For DOC, the order was filling stage > heading stage > mature stage> turning green stage > jointing stage in all treatments. For MBC, the order followed as mature stage > heading stage > filling stage > jointing stage > returning green stage, and except manure treatments (M, NPM), MBC in jointing stage was more than in filling stage in all treatments. The relationships between DOC, MBC and soil CO2 flux rate under different growth stages was low under the condition of same fertilization, on contrast, the relationships between DOC, MBC and soil respiration rate were significant under different fertilizations. Soil respiration measurement using the root-exclusion technique indicated that fertilization enhance root respiration. Averaged cross the growing stages, the contribution of the root respiration to soil respiration in CK, N and NP treatment, were 36%, 45% and 54%, respectively.