沿海不同年限围垦区土壤剖面有机碳同位素与粒度特征——以江苏省东台市为例

Stable Carbon Isotope and Particle Size Characteristics in Coastal Saline Soil with Different Reclamation Age of Dongtai, Jiangsu Province

根据江苏沿海不同年限围垦区土壤剖面有机碳稳定同位素(δ13C)与粒度资料,研究了不同年限围垦区土壤粒度特征变化情况与有机质来源变化特征。结果表明,在气候和母质基本相同的条件下,土壤δ13C和粒度特征主要受围垦年限和人类活动干扰影响。随着围垦年限的增加,土壤平均粒径显著降低,表现为DT7(33.93μm,林地,已围垦近60 a)<DT1(46.10μm,农用地,已围垦16 a)<DT6[48.21μm,盐蒿(Suaeda salsa)滩,已围垦2 a]。其中,DT6、DT7(30 cm以下)、DT1剖面粒度记录均具有自下向上逐渐变细的特点,粗颗粒组分逐渐减少,反映了粉砂淤泥质海岸围垦前原始潮滩沉积物的自然演化特点,DT7剖面30 cm以上逐渐变粗则可能主要由于已围垦近60 a里表层堆积了大量枯枝落叶所致。人类活动干扰在沉积记录中也较明显,DT6盐蒿滩剖面δ13C值总体上表现为海洋自生有机碳,主要反映原始沉积母质特征。DT1农用地剖面0~40 cm耕作层由于受开垦、翻耕、除草、施肥等各种人类活动干扰较大,各粒度组成及粒度参数均开始出现显著变化,这在表层迅速变轻的δ13C值也有所反映。DT7林地剖面尽管受人类干扰相对较小,但由于受到表层堆积的大量枯枝落叶等凋落物的影响,各粒度组成及参数在上部均也表现出明显变化,特别是表层0~10 cmδ13C值已呈明显的陆源性。δ13C值所表现出的陆源和海洋自生有机碳特征与根据经验公式计算的结果也具有较好的一致性。

Based on stable carbon isotope(δ13C) signatures and particle size of coastal saline soil of Dongtai,changes in the particle size characteristics and soil organic matter source with different reclamation age were analyzed. Results showed that under the same climate and parent material conditions, soil organic carbon isotope and particle size were mainly affected by reclamation age and human disturbance. Along with the increasing reclamation age, the mean particle size significantly reduced, with DT7(33.93 μm, forest, with the reclamation age of ~60 a) <DT1(46.10 μm, farmland, 16 a) <DT6(48.21μm, salt artemisia beach, 2 a). Particle size of DT6, DT7(below 30 cm) and DT1 showed an decreasing trend from the bottom to the top, with coarse particle component reduced gradually, reflecting the natural evolution process of tidal flat environment in the silt muddy coast.The gradually coarsening of the top 30 cm layer of DT7 may be mainly due to the large amount of forest litter. The disturbance of human activities was also very apparent in the sedimentary record. δ13C values of core DT6 mainly reflect the characteristics of the original marine sediment. Due to large interference by human activities, all the particle size parameters show an obvious change in the top 0-40 cm soil layer(cultivated layer) of core DT1, a quick lighter shift of δ13C values also support this. Although core DT7 was less interfered by human activities, but due to the large accumulation of forest litter, the particle size parameters in the upper layers showed significant change, the dramatic variation of δ13C value at 0-10 cm layer in core DT7 also suggested the obvious presence of a land-derived component. Relative contribution of terrestrial-derived and marine-derived organic matter showed by δ13C values were in good agreement with the empirical formula calculation results.