稻田土壤有机碳矿化及其激发效应对磷添加的响应

采用室内模拟培养和¹³C同位素标记技术相结合的研究方法,探讨了在葡萄糖与无机氮肥共施的条件下,土壤有机碳矿化及其激发效应对外源磷添加的响应,以揭示土壤有机碳矿化的碳磷耦合调控机制.结果表明:外源磷的输入加快了CO_2的释放,但抑制了CH_4的释放;在整个土壤淹水培养期间,磷添加抑制了土壤碳矿化释放CH_4总量的53.1%,其中外源葡萄糖-¹³C矿化成¹³CH_4的总量降低了70.5%;磷添加促使通过微生物转化的葡萄糖-¹³C向易利用态碳库的分配比例增加了3.6%,显著提高土壤有机碳快库矿化速率,缩短土壤碳矿化周期.土壤培养前期,外源有机质的添加表现为短暂的负激发效应;随着葡萄糖不断矿化分解,CO_2累积激发效应(PE_{CO_2})总体上呈现先增加后下降的趋势,而CH_4累积激发效应(PE_{CH_4})稳步增加最终保持基本稳定状态;培养结束时(100 d),在磷添加条件下,PE_{CO_2}增强32.3%,PE_{CH_4}显著降低93.4%.冗余分析和Pearson分析表明,电导率、氧化还原电位和溶解有机碳对稻田土壤碳矿化的影响最为显著;速效磷与¹³CH_4、PE_{CH_4}呈极显著负相关.在外源有机质添加条件下,磷的添加能够抑制CH_4排放及其激发效应,促进土壤有机质的矿化和养分释放,提高土壤原有有机碳的可利用性,促进稻田土壤有机碳循环.

Responses of organic carbon mineralization and priming effect to phosphorus addition in paddy soils.

To understand the coupled controlling of carbon (C) and phosphorus (P) on the minera-lization of soil organic carbon and amended substrates in paddy soil, we investigated the effects of P addition on the decomposition of organic carbon and its induced priming effect by using ¹³C isotope probing technique in microcosm. The results showed that P addition accelerated the release of CO₂ but inhibited the release of CH₄, leading to 53.1% reduction of total accumulated CH₄ and 70.5% reduction of the ¹³CH₄ derived from exotic glucose-¹³C. P addition altered the carbon distribution during the microbial turnover progress, with 3.6% of glucose-¹³C being transferred into the labile carbon pool, therein significantly increased potential of the mineralization rate of exogenous C. A transient negative priming effect was observed in the early stage of incubation. With time prolonging, the priming effect on CO₂ emission (PE_CO2) generally increased and then decreased after a peak. The priming effect on CH₄ emission (PE_CH4) kept increasing and finally fluctuated at a relative stable value until the end of the experiment (100 days). P addition increased PE_CO2 by 32.3% but reduced PE_CH4 by 93.4%. Results from the RDA and Pearson analysis showed that electric conductivity, oxidation-reduction potential and dissolved organic carbon significantly affected soil C mineralization. There were significantly negative correlations between available phosphorus (Olsen-P) and ¹³CH₄, and between Olsen-P and PE_CH4. In conclusion, with the addition of exogenous organic matter, P application could reduce CH₄ emissions and inhibit its priming effect, acce-lerate the mineralization of SOC, probably improve the nutrient supply, and thus enhance the avai-lability of organic C and promote C cycling in paddy soil.