天山北坡城市群非渗透面下的土壤有机碳特征

Orgnic carbon charasteristics of soils beneath urban impervious surface in northern Tianshan urban cluster

城市非渗透面(Impervious Surface Areas,ISA)的覆盖,强烈地改变了区域土壤理化性状,从而在不同尺度上影响着生态系统碳循环。ISA下土壤样品获得的困难性致使对ISA所封存的土壤有机碳(Soil Organic Carbon beneath ISA,SOCISA)及其分布特征的认识极为缺乏。为揭示ISA下土壤理化特征,本文收集天山北坡城市群在建工程ISA下27个100 cm深土壤样品,同时采集对应ISA点邻近的渗透面(Pervious Surface Areas,PSA)样品作对比分析。利用Landsat 8图像提取了研究区ISA与PSA面积,并结合实测值估算SOC储量。研究发现:1干旱区城市100 cm深土壤剖面平均SOCISA=5.74±0.39 kg C·m-2,显著低于其邻近PSA下的SOC;ISA下土壤容重(Bulk Density,BD)BDISA=1.58±0.02 g·cm-3,显著高于其邻近BDPSA约5%(p【0.01)。2两种地表下SOC和BD均随着深度加深而降低,通过与土层深度的线性拟合,SOCISA和BDISA具有明显降低趋势,PSA下SOC和BD并无显著规律;深层土壤(60~100 cm)SOCPSA显著高于SOCISA(p【0.05),两者间并无稳定的比例关系。3天山北坡城市群SOCISA为总城市土壤碳库的68%,单个城市SOCISA比例50%以上,SOCISA构成干旱区城市土壤碳库的主体。本文不仅加深了对城市ISA下土壤理化性状的了解,而且对评估城市乃至全球生态系统碳循环及碳评估具有重要意义。

Existence of impervious surface areas(ISA) in cities strongly influences the physical and chemical characteristics of regional soil, therefore, has profound impact on ecosystem carbon cycle at multiple scales.However, due to the inaccessibility of soil sample beneath urban ISA, we know little about the biochemical properties and distribution pattern as well as the importance of soil organic carbon under urban ISA(SOCISA). To clarify this issue, 100-cm-depth soil profiles from 27 paired ISA and pervious surface areas(PSA) sites in northern Tianshan urban cluster in a dryland environment of northwestern China were taken. In order to estimate total soil carbon storage, urban land cover was retrieved from cloud-free Landsat8 images. Based on the data of land cover area and SOC, the soil carbon storage of this urban cluster was calculated.(1) averaged 100-cm-depth SOCISAof the northern Tianshan urban cluster is 5.74±0.39 kg C· m-2, which is significantly lower than the paired soil organic carbon of PSA(SOCPSA) of 8.69±0.75 kg C· m-2, about 52% of the latter(p<0.01); averaged soil bulk density(BD) under ISA BDISA=1.58 ± 0.02 g · cm-3, which is significantly higher than its paired BD of PSA of1.51±0.02 g· cm-3, about 5% of the latter(p<0.01).(2) SOC and BD of both ISA and PSA declines with depth.The results of linear fitting between SOC, BD, and depth show that SOCISAand BDISAhave significantly declining trends, however, SOCPSAand BDPSAdoes not show such clear trend. In addition, SOCPSAat the 60~100 cm soil layers is significantly higher than SOCISAbut there is no stable correlation between them.(3) Carbon storage hidden under ISA of northern Tianshan urban cluster is 68% of the total urban carbon storage and for individual cities this percentage is higher than 50%, therefore, SOCISAis the main part of the urban SOC storage. By revealing the SOCISAand its distribution, this study can facilitate the understanding of biochemical characteristics of soils beneath urban ISA, which is significance for estimating carbon cycling in both urban and global ecosystems.