| 1 | Abiotic contribution to total soil CO_2 flux across a broad range of land-cover types in a desert region显示文摘As an important component of ecosystem carbon(C) budgets, soil carbon dioxide(CO_2) flux is determined by a combination of a series of biotic and abiotic processes. Although there is evidence showing that the abiotic component can be important in total soil CO_2 flux(R_(total)), its relative importance has never been systematically assessed. In this study, after comparative measurements of CO_2 fluxes on sterilized and natural soils, the R_(total) was partitioned into biotic flux(R_(biotic)) and abiotic flux(R_(abiotic)) across a broad range of land-cover types(including eight sampling sites: cotton field, hops field, halophyte garden, alkaline land, reservoir edge, native saline desert, dune crest and interdune lowland) in Gurbantunggut Desert, Xinjiang, China. The relative contribution of R_(abiotic) to R_(total), as well as the temperature dependency and predominant factors for R_(total), R_(biotic) and R_(abiotic), were analyzed. Results showed that R_(abiotic) always contributed to R_(total) for all of the eight sampling sites, but the degree or magnitude of contribution varied greatly. Specifically, the ratio of R_(abiotic) to R_(total) was very low in cotton field and hops field and very high in alkaline land and dune crest. Statistically, the ratio of R_(abiotic) to R_(total) logarithmically increased with decreasing R_(biotic), suggesting that R_(abiotic) strongly affected R_(total) when R_(biotic) was low. This pattern confirms that soil CO_2 flux is predominated by biotic processes in most soils, but abiotic processes can also be dominant when biotic processes are weak. On a diurnal basis, R_(abiotic) cannot result in net gain or net loss of CO_2, but its effect on transient CO_2 flux was significant. Temperature dependency of R_(total) varied among the eight sampling sites and was determined by the predominant processes(abiotic or biotic) of CO_2 flux. Specifically, R_(biotic) was driven by soil temperature while R_(abiotic) was regulated by the change in soil temperature(ΔT). Namely, declining temperature(ΔT<0) resulted in negative R_(abiotic)(i.e., CO_2 went into soil) while rising temperature(ΔT>0) resulted in positive R_(abiotic)(i.e., CO_2 released from soil). Without recognition of R_(abiotic), R_(biotic) would be overestimated for the daytime and underestimated for the nighttime. Although R_(abiotic) may not change the sum or the net value of daily soil CO_2 exchange and may not directly constitute a C sink, it can significantly alter the transient apparent soil CO_2 flux, either in magnitude or in temperature dependency. Thus, recognizing the fact that abiotic component in R_(total) exists widely in soils has widespread consequences for the understanding of C cycling. | MA Jie LIU Ran LI Yan | 2017 | Journal of Arid Land2017，9，1： | 4 |
| 2 | 肉苁蓉寄生对梭梭光合特性的影响显示文摘目的探讨肉苁蓉在生长的关键时期(出土期、开花结实期、枯萎期)对其寄主梭梭光合特性的影响。方法选4年生梭梭为研究对象,用LI-6400光合仪分别测定寄生肉苁蓉的梭梭和未寄生肉苁蓉的梭梭的光合作用,测定指标包括净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)、胞间CO_(2)浓度(Ci),并测定光合相关指标-叶绿素。结果3个测定时期内,肉苁蓉的寄生使梭梭的净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)、水分利用率(WUE)、胞间CO_(2)浓度(Ci)日均值和对照组相比均降低;多指标综合评价肉苁蓉的寄生对梭梭光合能力的影响,发现肉苁蓉的寄生使梭梭的光合能力减弱。冗余分析(RDA)表明,3个时期中,寄生了肉苁蓉梭梭的种-环境的相关性都小于未寄生肉苁蓉的梭梭。结论肉苁蓉生长的3个关键时期中,它的寄生使梭梭的光合能力减弱,与净光合速率呈正相关的光合生理及其相关指标也减弱;肉苁蓉的寄生使环境对梭梭的影响作用减弱,寄生肉苁蓉的梭梭植株对环境因子表现出“迟钝型”响应。 | 于霞霞 郭晔红 杜弢 贾存勤 李欠 马兴东 马旭东 | 2021 | 中成药2021，43，9： | 2 |
您所在的机构暂未开通此部分的功能，请联系管理员