河北38°N生态样带土壤有机碳特征

为阐明河北38°N生态样带土壤有机碳的空间分布特征,2011年9—10月,根据河北38°N带低山丘陵地区、山前平原地区和滨海低平原地区不同土地利用方式选取代表性样点,分层(0~10 cm、10~20 cm、20~40 cm、40~60 cm和60~100 cm)采集土壤样品,测定土壤有机碳含量。结果表明,河北38°N生态样带,低山丘陵地区土壤有机碳密度显著高于山前平原地区和滨海低平原地区,0~40 cm土层土壤有机碳密度分别为9.03 kg?m?2、4.26 kg?m?2和3.51 kg?m?2。低山丘陵地区与山前平原地区和滨海低平原地区土壤有机碳差异的部分原因是低山丘陵区灌丛土壤有机碳含量较高,明显提升了该地区的土壤有机碳水平。另外,低山丘陵地区林地和农田0~40 cm土层土壤有机碳含量也高于山前平原地区和滨海低平原地区;林地0~40 cm土层土壤有机碳含量在低山丘陵地区、山前平原地区和滨海低平原地区分别为19.45 g?kg?1、7.89 g?kg?1和7.55 g?kg?1,农田土壤有机碳含量在3个地区分别为7.70 g?kg?1、7.09 g?kg?1和6.00 g?kg?1。在整个生态样带上,土壤有机碳含量基本随土壤深度增加而不断减少,但各个地区不同土地利用方式减少的程度不同。低山丘陵地区0~40 cm土层内土壤有机碳含量变幅最大,其次为山前平原地区,滨海低平原地区变幅最小。低山丘陵地区灌丛土壤有机碳含量变化幅度最大,其次为林地,农田最小;山前平原地区土壤有机碳含量变化幅度农田略大于林地;滨海低平原地区土壤有机碳含量变化幅度林地最大,其次是荒地,农田最小。鉴于上述情况,从固碳和经济的双重角度考虑,提出以下建议:低山丘陵区大力发展林业产品和旅游业;山前平原区集中粮食生产,保证国家粮食安全;滨海地平原区加大土壤盐渍化改良,推广棉花种植。

Characteristics of soil organic carbon at 38°N ecological transect of Hebei Province

To understand the characteristics of organic carbon in the 38°N ecological transect of Hebei Province, 35 sampling plots with different land use patterns in 3 regions (low hilly area, piedmont plain of Taihang Mountain and low coastal plain) in the 38°N ecological transect of Hebei Province from west to east were set and soil samples were collected in the 010 cm, 1020 cm, 2040 cm, 4060 cm and 60100 cm layers from September to October in 2011 for soil organic carbon content analysis. The results suggested that the soil organic carbon density was higher in the low hilly area than in the piedmont plain, which was in turn higher than in the low coastal plain. The corresponding soil organic carbon density was respectively 9.03 kgm^-2, 4.26 kgm^-2 and 3.51 kgm^-2. The difference in organic carbon content of the low hilly area from that of other two regions was partly due to the high organic carbon content in scrublands in the low hilly area. Furthermore, organic carbon content in the 040 cm soil in forestland and farmland in the low hilly area was higher than those in the other two regions. The order of soil organic carbon content in forestland and farmland was low hilly area > piedmont plain > low coastal plain. Organic carbon content in 040 cm soil in forestlands was 19.45 gkg^-1 (low hilly area), 7.89 gkg^-1 (piedmont plain) and 7.55 gkg^-1 (low coastal plain). Also soil organic carbon content in farmland was 7.70 gkg^-1 (low hilly area), 7.09 gkg^-1 (piedmont plain) and 6.00 gkg^-1 (low coastal plain). Soil organic carbon content decreased with soil depth and there was some difference among different land use patterns. The sequence of variation in soil organic carbon content with soil depth (from top to bottom) was higher in the low hilly area than in the piedmont plain, which was in turn higher than in the low coastal plain. In the low hilly area, the variation range of soil organic carbon content with soil depth was higher in scrubland than in forest, and it was lowest in farmland. In the piedmont plain, the range of variation in soil organic carbon content with soil depth in farmland was a slight bigger than that in forest land. In the low coastal plain, the range of variation in soil organic carbon content with soil depth was higher in forest land than in abandoned land, it was lowest in farmland. In consideration of carbon sequestration and economic benefits, 3 suggestions were put forward as follows: 1) forest products and tourism should be developed in the low hilly area; 2) the piedmont plain should emphasize the development of grain production; and 3) the low coastal plain should be improved in soil salinization and cotton cultivation.