松嫩平原西部草甸草原5种典型植物群落土壤呼吸的时空动态

Spatio-temporal variations of soil respiration in five typical plant communities in the meadow steppe of the western Songnen Plain, China

土壤呼吸是陆地生态系统碳循环的重要组分,由于受到生物因子与非生物因子的共同作用,土壤碳排放量在时间和空间尺度上都具有一定的变异性。为弄清松嫩平原西部草甸草原植物群落土壤呼吸作用的时空动态变化及其影响因子,以典型植被碱蓬(Suaeda glauca)、虎尾草(Chloris virgata)、碱茅(Puccinellia distans)、芦苇(Phragmites australis)、羊草(Leymus chinensis)群落为研究对象,采用LI-6400土壤呼吸测定系统对该生态系统2011–2012年植物生长季内土壤呼吸作用进行了监测。结果表明:土壤温度可以解释土壤呼吸作用变异的53%–82%,是影响该生态系统土壤碳排放时间变异的主要因素。土壤水分并未对土壤呼吸作用时间变异产生明显的影响。不同植物群落的土壤呼吸的温度敏感性(Q10)有所差异,Q10为2.0–6.7。生长季内,5种植物群落的土壤累积碳排放量的平均值为316.6 g C·m–2。生长季内土壤碳累积排放量与植被地上生物量、土壤有机碳含量、平均土壤温度显著正相关,与平均土壤含水量、pH值、土壤电导率及交换性钠百分比呈负相关关系。土壤的微气候、植被的地上生物量及土壤性质的差异是土壤碳排放空间变异的主要影响因素。

Aims Soil respiration plays a critical role in the process of carbon cycling in terrestrial ecosystems, and it often shows spatio-temporal variations in response to diverse abiotic and biotic factors. Our objective was to examine the seasonal and spatial variations of soil respiration under five typical plant communities in the meadow steppe of western Songnen Plain. Methods Using a LI-6400 soil CO2 flux system, we investigated soil respiration and environmental factors un- der five vegetation types （Suaeda glauca, Chloris virgata, Puccinellia distans, Phragmites australis and Ley- mus chinensis） in the meadow steppe of Songnen Plain during the growing seasons of 2011 and 2012. Important findings Soil temperature was the dominant controlling factor of soil respiration, which explained approximately 64% of the changes in soil CO2 effluxes. Soil water content was not the limiting factor of the sea- sonal variations in soil respiration. The sensitivities of soil respiration to temperature （Q10） ranged from 2.0 to 6.7, showing significant differences among vegetation types. The cumulative CO2 emission averaged 316.6 g C-m-2 during the growing season. The magnitude of soil CO2 emission during the growing season was positively correlated with aboveground plant biomass, soil organic carbon content, and mean soil water content, and negatively linked to mean soil temperature, pH, electrical conductivity, and percentage of exchangeable sodium. The spatial variations of soil CO2 emission were mainly caused by changes in soil microclimate, plant biomass, and soil prop- erties.