潮沟形态对潮滩湿地土壤有机碳空间分布的影响

EFFECTS OF TIDAL CREEK MORPHOLOGY ON SPATIAL DISTRIBUTION OF SOIL ORGANIC CARBON IN SOIL IN TIDAL WETLAND

土壤有机碳是潮滩湿地生态系统的主要碳库。以1条典型天然潮沟为研究对象,通过划分潮沟发育等级并计算潮沟形态特征指数,分析潮沟形态特征空间分布特点;运用地统计学方法探究潮滩湿地土壤有机碳空间分布特点,及潮沟形态特征对土壤有机碳空间分布的影响。结果表明:潮沟形态特征具有明显的空间异质性特点,潮沟在中潮滩比较发育,其密度、曲率与分汊率均大于低潮滩和高潮滩;潮沟长度随着潮沟发育等级的增加而逐渐增加,而潮沟曲率随着潮沟发育等级的增加而逐渐减小。空间插值结果显示:0~10 cm土壤有机碳含量最低值出现在潮沟较发育的中潮滩,10~20 cm土壤有机碳含量呈由海向陆逐渐增加的趋势,并呈条带状的空间分布特点。在低潮滩,三级潮沟土壤有机碳平均值显著大于一级潮沟;在中潮滩,二级潮沟土壤有机碳平均值显著大于三级潮沟和一级潮沟;高潮滩土壤有机碳含量与潮沟发育等级无显著相关性。随着潮沟侧向距离的增加,0~10 cm土壤有机碳含量在低潮滩与中潮滩逐渐增加;而中潮滩10~20 cm土壤有机碳含量随着潮沟侧向距离的增加而逐渐减少;高潮滩土壤有机碳含量与潮沟侧向距离无显著相关性。潮沟形态空间分布异质性是导致潮滩湿地土壤有机碳含量空间分布差异的重要原因。因此,潮滩湿地土壤碳库的精确估算需要关注潮沟形态的影响。

Soil organic carbon is a major carbon pool in tidal wetland ecosystems.By dividing the level of the tidal creek and calculating its morphological characteristic index,the spatial distribution characteristics of the typical tidal creek system were analyzed,taking a typical natural tidal channel as the research object.The spatial distribution characteristics of soil organic carbon were analyzed by geostatistical methods.In addition,the effects of morphological characteristics of the tidal creek on the spatial distribution of soil organic carbon were explored.The results showed that there was obvious spatial heterogeneity in the morphological characteristics of the tidal creek.In the middle tidal flats,the connectivity of the tidal creek network was higher,and the density,curvature and bifurcation ratio were also higher than that in other tidal zones.The tidal creek length gradually increased with the increase of tidal creek development grade,while the tidal creek curvature gradually decreased with the increase of tidal creek development grade.The spatial interpolation results showed that the lowest soil organic carbon in 0 to 10 cm soil layer occurred in the middle tidal flats where tidal creeks were more developed,and within the 10~20 cm soil layer,soil organic carbon showed a gradually increasing trend from sea to land,and showed a strip-shaped spatial distribution choracteristic.In the low tidal flats,the mean value of soil organic carbon in a third-order creek was significantly greater than that in a first-order creek.In the middle tidal flats,the mean value of soil organic carbon in a second-order creek was significantly greater than that in a third-order and a first-order creek.The soil organic carbon of the high tide flats was not significantly correlated with the tide creek development level.Within the 0 to 10 cm soil layer,the soil organic carbon gradually increased with increasing distance to the tidal creek in low and middle tidal flats.Within the 10 to 20 cm soil layer,the soil organic carbon gradually decreased with increasing distance to tidal creek in the middle tidal flats.However,there was no correlation between the soil organic carbon and the distance to the tidal creek in high tidal flats.The spatial heterogeneity in the morphological characteristics of the tidal creek was one of the important factors of spatial differences in soil organic carbon content in the tidal wetland.Therefore,morphology changes in tidal creeks should be considered in order to accurately estimate the soil carbon pools in tidal wetlands.