黄土丘陵区不同植被类型间土壤CO2释放与模型模拟及敏感性分析

Soil CO2 release and model simulation among differ⁃ ent vegetation types in the Loess hilly region

摘要:

【目的】探究黄土丘陵区 3 种典型植被(文冠果(Xanthocera ssorbifolium)林地、冰草(Agropy- ron cristatum)荒草地、沙棘(Hippophae rhamnoides)灌丛)覆盖下土壤 CO₂排放规律及影响因素，比较不同植被类型覆盖土壤 CO₂排放的差异，为该地区减少土壤 CO₂排放选择合适的退耕还林还草植被提供依据。【方法】基于 DNDC 模型模拟，结合实际土壤 CO₂排放通量及土壤影响因子，检验该模型对不同植被类型间土壤 CO₂排放模拟的适宜性，并对其进行敏感性分析。【结果】黄土丘陵区 3 种典型植被覆盖土壤 CO₂排放季节变化趋势均呈单峰曲线，与土壤表层(5 cm)温度、含水量变化趋势相似，并且该地区不同植被类型间土壤 CO₂排放通量与土壤表层(5 cm)温度、含水量均呈极显著正相关关系(P＜ 0. 01)，说明土壤温度、含水量是影响 CO₂排放的关键因素；文冠果林地土壤年均 CO₂排放通量最少，分别比冰草荒草地、沙棘灌丛低 40. 785%、40. 835%；DNDC 模型对不同植被类型间土壤 CO₂排放的模拟结果与实测结果较为一致，文冠果林地 R=0. 928(P＜0. 01)，荒草地 R=0. 932(P＜0. 01)，沙棘灌丛 R =0. 983(P＜0. 01)。【结论】 DNDC 模型可以用来模拟该地区 3 种典型植被覆盖土壤 CO₂的排放；土壤表层 SOC 含量是模拟该地区 3 种典型植被覆盖土壤 CO₂排放的敏感因子，其变化程度对模型模拟结果影响最大。文冠果为黄土丘陵区退耕还林还草首选植被。

Abstract:

【Objective】 The study is aimed to explore the law and influencing factors of soil CO₂ emission under three typical vegetation (Xanthocarp woodland， barren grass land and seabuckthorn shrub) cover in Loess hilly re‐ gion， to compare differences of CO₂ emission in soil covered by different vegetation types. It provides the basis for se‐ lecting suitable vegetation for returning farmland to forest and grassland to reduce soil CO₂ emission in this area. 【Method】 Based on the DNDC model， combined with the actual soil CO₂ emission flux measured， the suitability of the model to simulate soil CO₂ emission under different vegetation cover was tested， and its sensitivity was analyzed. 【Result】 The results showed that the seasonal variation trend of forest soil CO₂ emission in Loess hilly region had a single‐peak curve. The peak value appeared between early July and late August， and the minimum value appeared be‐ tween late December and early January of the next year. There was a significant positive correlation between soil CO₂ flux and soil surface temperature (5 cm) and soil water content (P＜0. 01). Soil temperature， moisture content were the key factors affecting CO₂ emissions. The average annual CO₂ emission flux of the soil in the xanthocarp forest was the lowest， which was 40. 785% and 40. 835% lower than those in the grassy land and seabuckthorn shrub， respec‐ tively. The simulation results of soil CO₂ emission among different vegetation types by DNDC model were consistent with the measured results. The R=0. 928(P＜0. 01) in the Xanthocarp fruit forest land， the R=0. 932(P＜0. 01) in the Barren grassland， and R=0. 983(P＜0. 01)in the Seabuckthorn shrub land. The results showed that the model could be used to simulate the CO₂ emission of forest land in this area.【Conclusion】 The model sensitivity analysis showed that soil surface SOC content was the sensitive factor to simulate the CO₂ emission of three typical vegetation-covered soils in this region，and the change degree of SOC content had the greatest influence on the model simulation results.