Abstract:

The Henan section of the Yellow River Basin is a region with the most special topographical features in the whole river basin. Hence, estimating and quantifying the vegetation and soil organic carbon storage and spatial differentiation of organic carbon density in this region are important for accurately assessing the carbon balance of and promoting ecological protection and high-quality development in the Yellow River Basin. In this study, the vegetation, soil types, organic carbon storage and its density were analyzed using data from the sixth forest resources survey in Henan Province, the second soil census and digital elevation models. The results showed that (1) the cultivated vegetation area in the study area was 3.28×10⁴ km² with a percentage of 73.04%, mainly distributed in the middle or east of the study area and the valleys of the Yiluo River. In addition, deciduous broad-leaved forest, with an area of 6.80×10³ km², accounts for 15.57%. The dominant species were Quercus variabilis, Quercus acutissima and Quercus aliena, which were mainly distributed in the southwest of the study area and a small amount in the middle and north of the study area. (2) Fluval aquic soil and cinnamon soil were dominant soil types, with an area of 1.55×10⁴ km² and 1.54×10⁴ km², accounting for 35.23% and 35.12%, respectively. Fluval aquic soil was concentrated in the East, and cinnamon soil was distributed in the west. Brown soil was mainly distributed in the southwest, accounting for 11.61%. (3) The value of vegetation organic carbon density in the study area was 53.24 Tg, while 24.88 Tg in deciduous forest and 23.71 Tg in cultivated vegetation with percentages of 46.73% and 44.54%, respectively. For the storage of the soil organic (100 cm depth of soil surface), a total of 294.92 Tg was evaluated and its storage in fluval aquic soil and cinnamon soil was 108.04 Tg and 91.54 Tg with percentages of 36.63% and 31.04%, respectively. (4) The value of vegetation and soil organic carbon density was 5.70-36.37 (average 12.12 Mg∙hm^-2) and 14.9-151.2 Mg∙hm^-2 (average 67.12 Mg∙hm^-2), respectively. The total carbon density of the research area ranged from 15.09 to 187.57 Mg∙hm^-2, showing a higher distribution in southwest and north-central and a lower one in the middle and east. At vertical elevations, from plains to mountains, the mean organic carbon density increased with elevation. Totally, the vegetation, soil type and soil organic carbon density in the Henan section of the Yellow River Basin showed obvious spatial differences in the horizontal direction and at different altitudes. In the central and east of the study area, lower organic carbon density was observed with mainly cultivated crops and fluval aquic soil types. In contrast, the western of the research area, especially the southwest revealed an obvious higher value of organic carbon density with mainly forest vegetation and shrubs and high organic carbon density soil such as cinnamon soil and brown soil. In total, the study highlighted that protecting the vegetation resources in west and improving the cultivation and management of cultivated crops in the central and eastern regions were the key measures to stabilize and increase the carbon storage in the Henan section of the Yellow River Basin.

Key words: organic carbon storage, organic carbon density, Henan section of the Yellow River Basin, vegetation, soil

摘要：

黄河流域河南段是黄河流域地形地貌特征最特殊的地区,估算和量化本区域植被和土壤有机碳储量、有机碳密度及其空间分异特征,对于准确评估黄河流域碳收支平衡、促进黄河流域生态保护和高质量发展均具有重要的意义。利用河南省第六次森林资源调查成果、第二次土壤普查数据、数字高程模型和其他文献资料,对黄河流域河南段（行政区域）的植被和土壤类型、有机碳贮量和有机碳密度及其空间分异特征进行综合分析,并探讨其成因和增碳策略。结果表明,（1）研究区以栽培植被为主,面积为3.28×10⁴ km²,占比74.59%,主要分布于研究区的中部、东部和伊洛河两岸谷地;其次为落叶阔叶林,面积为6.80×10³ km²,占比15.57%,主要分布于研究区域的西南部,优势种包括栓皮栎（Quercus variabilis Bl.）、麻栎（Quercus acutissima Carruth.）和槲栎（Quercus aliena Bl.）等。（2）土壤以潮土和褐土为主,面积分别为1.55×10⁴ km²和1.54×10⁴ km²,占比分别为35.23%和35.12%,潮土集中于东部,褐土分布在西部;其次为棕壤,占比11.61%,主要分布在西南部。（3）研究区植被有机碳贮量为53.24 Tg,其中落叶阔叶林有机碳贮量为24.88 Tg,占比46.73%,栽培植被有机碳贮量23.71 Tg,占比44.54%;土壤有机碳贮量（土层100 cm）为294.92 Tg,其中褐土和潮土有机碳贮量分别为108.04 Tg和91.54 Tg,占比分别为36.63%和31.04%。（4）植被有机碳密度在5.70-36.37 Mg∙hm^-2之间,平均有机碳密度为12.12 Mg∙hm^-2;土壤有机碳密度（土层100 cm）在14.9-151.2 Mg∙hm^-2之间,平均有机碳密度为67.12 Mg∙hm^-2;总有机碳密度（植被和100 cm土层）在15.09-187.57 Mg∙hm^-2之间,呈西南和中北部高而中部和东部低的分布特征;在海拔梯度上,植被、土壤及总有机碳密度表现为平原 (<200 m)<丘陵 (200-500 m)<低山 (500-1000 m)<中山Ⅰ (1000-1500 m)<中山Ⅱ (>1500 m)。综上所述,黄河流域河南段的植被、土壤及其有机碳密度在水平方向和海拔梯度上呈现空间分异特征。中部和东部有机碳密度相对较低,植被主要为栽培作物,土壤以潮土为主;西部（尤其是西南部）有机碳密度高,是森林植被和灌丛的主要分布区,土壤以褐土和棕壤等相对高有机碳密度的土类为主。保护好西部（尤其是西南部）良好的植被资源,改进中部和东部栽培作物的耕作和管理方式,是稳定和增加黄河流域河南段碳贮量的关键举措。

关键词: 有机碳贮量, 有机碳密度, 黄河流域河南段, 植被, 土壤