青藏高原多年冻土区典型植被下河流溶解性有机碳的生物可利用性

选取青藏高原多年冻土区12条河流样品进行分析,结合流域内植被类型、流量大小、多年冻土面积与河流溶解性有机碳(DOC)的质量浓度、化学组成、生物可利用性之间的关系及分解动力学进行讨论.结果表明,分别在高寒草甸(AM)、高寒沼泽草甸-高寒草甸(ASM-AM)、高寒草甸-高寒草原(AM-AS)、高寒草甸-高寒草原-裸地(AM-AS-BL)为主的流域内,河流DOC的质量浓度依次为(5.17±0.21)、(5.02±0.50)、(3.55±0.25)和(2.79±0.41)mg·L-1,DOC的生物可降解性程度(BDOC)依次为(23.54±2.62)%、(23.66±3.31)%、(18.17±5.26)%和(11.72±15.56)%;相应地,流域内植被覆盖度越小,河流DOC的芳香性程度越大,DOC的可生物降解性和降解速率随着降低,并且BDOC在培养的过程中的反应遵循一级反应动力学原理;此外,连续多年冻土区河流的BDOC大于非连续多年冻土区的河流BDOC,大河的BDOC小于源头小河的BDOC.研究表明,流域内植被类型是影响多年冻土区河流BDOC的主要影响因素,同时,流量大小和多年冻土对BDOC也有一定的影响.

Bioavailability of Dissolved Organic Carbon in Rivers for Typical Vegetation Types in the Permafrost Regions on the Qinghai-Tibet Plateau

Samples collected from 12 rivers with typical vegetation types in the permafrost regions on the Qinghai-Tibetan Plateau were incubated in the laboratory, and the relationships among the vegetation types, river discharges, the compositions of dissolved organic carbon (DOC), permafrost areas, riverine DOC concentration, biodegradability of dissolved organic carbon (BDOC), and the biodegradation kinetics were examined. The results showed that the DOC concentrations of typical vegetation types in the basin, such as alpine meadow (AM), alpine swamp meadow-alpine meadow (ASM-AM), alpine meadow-alpine steppe (AM-AS), and alpine meadow-alpine steppe-bare soil (AM-AS-BL), were (5.17±0.21), (5.02±0.50), (3.55±0.25), and (2.79±0.41) mg ·L^-1, respectively. The values for the bioavailability of river DOC of different vegetation types were (23.54±2.62)%, (23.66±3.31)%, (18.17±5.26)%, and (11.72±15.56)%, respectively. Correspondingly, the riverine DOC aromaticity increased along with the vegetation cover, while the biodegradation and degradation rates decreased gradually. During the incubation, the reaction of BDOC was in accordance with the first-order kinetics equation. Furthermore, the BDOC in continuous permafrost regions of the rivers was greater than that in the non-continuous permafrost regions. The BDOC in higher discharges were lower than those with lower discharges. Taken together, the results suggested that the vegetation types were the main controlling factors for the BDOC, and BDOC was also related to the discharge and permafrost.