施肥是退化草地初期恢复常用的管理措施,被用于改良草地群落结构和提高牧草生产力.本文以藏北轻度和重度退化高寒草甸为研究对象,设置低氮(50 kg N·hm-2·a-1,LN)、高氮(100 kg N·hm-2·a-1,HN)施肥水平,及其与磷配...
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施肥是退化草地初期恢复常用的管理措施,被用于改良草地群落结构和提高牧草生产力.本文以藏北轻度和重度退化高寒草甸为研究对象,设置低氮(50 kg N·hm-2·a-1,LN)、高氮(100 kg N·hm-2·a-1,HN)施肥水平,及其与磷配施组合试验(50 kg N·hm-2·a-1+50 kg P·hm-2·a-1,LN+P;100 kg N·hm-2·a-1+50 kg P·hm-2·a-1,HN+P),研究施肥梯度与施肥类型对两种退化程度高寒草甸群落结构、物种丰富度与多样性、群落生物量及其分配的影响.结果表明:单独施氮对轻度和重度退化高寒草甸群落盖度和生物量均无显著影响,而氮磷配施显著提高群落盖度及地上、地下生物量,其中LN+P处理的促进效果最显著.这表明本研究区地上生产力受到氮和磷的共同限制.施肥处理对重度退化样地总生物量无显著影响,但显著降低了根冠比.HN与HN+P处理均显著降低轻度退化群落的物种丰富度和均匀度,说明HN处理不利于轻度退化草地物种多样性和稳定性的维持.在轻度退化样地,施氮(尤其是HN处理)主要提高了禾草植物的重要值和生物量,而氮磷配施则有利于莎草类植物的生长.施肥对重度退化群落植物的重要值影响较小,主要提高了杂草生物量.说明轻度退化高寒草甸可选择低氮配施磷肥的措施,而对重度退化草地可能需要结合围栏和补播牧草等其他管理措施进行改良.
Atmospheric nitrogen （N） deposition may affect carbon （C） sequestration in terrestrial ecosystem. The main objective of this paper was to test the hypothesis that N addition would increase CO2 emission in the N li...
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Atmospheric nitrogen （N） deposition may affect carbon （C） sequestration in terrestrial ecosystem. The main objective of this paper was to test the hypothesis that N addition would increase CO2 emission in the N limited meadow steppe in Inner Mongolia, China. Response of CO2 fluxes to simulated N deposition was studied in the growing season of 2008 and 2009 by static chamber and gas chromatograph techniques. Parallel to the flux mea- surements, soil temperature, soil moisture, TOC, DOC, soil NH4~ and NO3- were measured at the same time. The results indicated that two-year N additions had no significant effect on NH4＋, but slightly increased NO3- in the later period. The HN treatment tended to increase CO2 fluxes in the two years, and LN treatment tended to decrease CO2 fluxes in 2008, and shifted to increase CO2 fluxes in later growing season of 2009. N addition significantly in- creased the aboveground biomass and root biomass. The correlation between CO2 fluxes and moisture or tempera- ture factors did not significantly change due to N addition, but N addition enhanced the moisture sensitivity of CO2 fluxes as well as the temperature sensitivity of CO2 fluxes. These results suggest that the increasing ammonium N deposition would be likely to stimulate CO2 fluxes in the meadow steppe of Inner Mongolia, China.
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