滨海人工林土壤呼吸各组分对台风强降雨的响应

Effects of Great Typhoon Rainfall on Soil Respiration Components in Coastal Plantations

根据预测,随着全球变暖,极端降水将更加频繁和剧烈,可能对土壤呼吸及其组分产生重大影响。然而目前对极端降雨如何影响土壤呼吸各组分的认识仍是缺乏的。因此选取亚热带滨海湿地松和尾巨桉人工林土壤为研究对象,于2015年8月在设置去除根系和对照处理一年后,应用Li-8100土壤CO_2通量测定系统,对2次台风强降雨前后的土壤呼吸速率和环境因子进行原位监测,分析2次台风前后土壤呼吸各组分对强降雨的响应规律。结果表明:(1)2次台风强降雨显著改善了土壤的水分状况,促进了土壤呼吸各组分。2种人工林土壤总呼吸、异养呼吸均呈现出快速上升、后逐渐下降的趋势,而土壤自养呼吸的上升不明显。土壤总呼吸与异养呼吸的峰值与土壤湿度的峰值同步,而自养呼吸峰值要滞后1天。(2)第一次降雨,湿地松和尾巨桉土壤异养呼吸对总呼吸的贡献率分别是自养呼吸的5.15和6.28倍。相比于土壤自养呼吸(R_a),异养呼吸增加的幅度更大且响应更快。(3)第一次降雨湿地松土壤总呼吸、异养呼吸及尾巨桉土壤异养呼吸与土壤湿度的二次曲线关系存在拐点,而第二次降雨促进了2种人工林土壤异养呼吸、总呼吸速率。2次台风强降雨湿地松和尾巨桉人工林的土壤自养呼吸均和土壤湿度无显著相关性(P>0.05)。综上,研究结果强调了极端降水对土壤呼吸及其组分的显著影响,应该将其纳入模型中,以提高对碳-气候反馈的预测。

Extreme precipitation has been predicted to be more frequent and intense accompanying global warming, thus it may have profound impacts on soil respiration(Rs) and its components. However, how natural extreme rainfall events affect soil respiration components are still unclear. Pinus elliottiiand E.ucalyptus urophylla×E.ucalyptus grandis plantation were selected in the subtropical coastal sandy plain forests. In August 2015, a year after root trenching and control treatments were set up, using the Li-8100 soil CO2 flux monitor system to monitor the soil CO2 flux. The Rs rate was monitored for two great rainfall events of the typhoon(before and after) in situ, and the environmental factors were measured simultaneously. The response of Rs components to great rainfall before and after the two typhoons was analyzed. The results were shown as follows:(1) The great rainfall of two typhoons significantly increased soil moisture and Rs components. The Rs and Rh rate of two kinds of plantations showed a rapid increase, and then gradually decreased, but the increase of Ra was not obvious. The peak values of Rs and Rh rates were synchronous with the peak values of soil moisture. Meanwhile the peak values of Ra occurred behind the peak values of soil moisture by one day.(2) During the first rainfall, the rate of Rh was 5.15 and 6.28 times higher than that of Ra in the P.elliottii and E.urophylla×E.grandis plantations, respectively. Rh rate increased more rapidly and responded faster than soil autotrophic respiration.(3) During the first typhoon rainfall, there were inflection points in the quadratic curves between the soil respiration, Rh of P.elliottii and Rh of E.urophylla×E.grandis. The second rainfall improved the heterotrophic respiration and total respiration rates of the two plantations. However, there was no significant relationships(P>0.05) between Ra and soil moisture in two typhoon-heavy rainfalls of P.elliottii and E.urophylla×E.grandis plantations. Overall, our results highlight the significant effects of extreme precipitation on responses of soil respiration and its components, which should be incorporated into models to improve the prediction of carbon-climate feedbacks.