黄土丘陵区不同植被群落土壤团聚体有机碳及其组分的分布

有机碳是形成土壤团聚体的重要物质,植被群落通过有机残体的输入增加土壤有机碳含量,从而通过影响团聚体的形成而影响土壤结构。为探究不同植被群落对土壤结构改良的意义,对黄土丘陵区森林带和草原带的不同植被群落土壤团聚体中有机碳组分进行了研究。结果表明:(1)研究区域森林带土壤有机碳含量大于草原带,森林带植被群落土壤总有机碳含量大小顺序为:辽东栎群落>人工刺槐群落>狼牙刺群落,草原带植被群落土壤总有机碳含量大小顺序为:人工沙棘群落>达乌里胡枝子+茭蒿群落>铁杆蒿+达乌里胡枝子群落;(2)土壤活性有机碳和腐殖质碳占土壤总有机碳的比例在两种植被带之间基本相同,相同植被群落土壤活性有机碳占土壤总有机碳的比例高于腐殖质碳占总有机碳的比例;(3)森林带土壤>0.25 mm团聚体含量显著高于草原带土壤>0.25 mm团聚体含量,各种形态的有机碳随着土壤团聚体粒级的增大有机碳含量呈先增加后减少或者随着团聚体粒级的增大而增大的趋势,2~0.25 mm和<0.25 mm团聚体中有机碳含量最高;(4)草原带每种植被群落土壤活性有机碳含量空间差异性较大,辽东栎群落各种形态土壤有机碳含量的空间差异性都较大,<0.25 mm团聚体腐殖质碳含量大于其他粒径;(5)草原带人工沙棘群落土壤各种形态有机碳在土壤剖面上的含量差异很小,其他各植被群落0~10 cm土层土壤有机碳含量均大于10~20 cm土层。

Soil organic carbon and its fractions in aggregates under different plant communities in the hill-gully region of the Loess Plateau

Vegetation communities have been noted to affect soil organic carbon content via the addition of outer soil organic matter that in turn contribute to the formation of soil aggregates. The fractions of organic carbon in soil aggregates under different vegetation communities (forest and steppe zones) in the hill-gully region on the Loess Plateau were studied in this paper to explore the effect of different vegetation communities on soil structure. The study showed that: (1) Total soil organic carbon content in the forest zone of the study area was higher than that in the steppe zone. The order of total organic carbon for the plant communities in the forest zone was: Quercus liaotungensis community > Robinia pseudoacacia community > Sophora viciifolia community. Also the order of total organic carbon for the plant communities in the steppe zone was: Hippophae rhamnoides community > Lespedeza davurica + Artemisia giraldii community > Artemisia sacrorum + L. davurica community. (2) The proportions of active to total organic carbon and that of humus to total organic carbon were similar under each vegetation zone. However, the proportion of active to total organic carbon was greater than that of humus to total organic carbon under each vegetation community. (3) The >0.25 mm aggregates under the forest zone was significantly higher than that under the steppe zone. The pattern of the various forms of organic matter in the soil particles suggested initial increase in organic carbon, followed by decrease or flat curve with increasing aggregate size. A large proportion of soil organic carbon existed in 2~0.25 mm and <0.25 mm aggregates. (4) Active organic carbon content was significantly spatially different under the steppe zone. Each form of organic carbon in the Q. liaotungensis community was also significantly spatially different. The <0.25 mm aggregate humus was greater than other aggregates in the Q. liaotungensis community. (5) Unlike the other vegetation communities, there was no significant difference in terms of soil organic carbon between the 0~10 cm and 10~20 cm soil layers in the H. rhamnoides community.