State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710075, China.
Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China.
Sci Total Environ. 2014 Jul 1;485-486:615-623. doi: 10.1016/j.scitotenv.2014.03.105. Epub 2014 Apr 17.
Natural vegetation restoration and tree plantation are the two most important measures for ecosystem restoration on the Loess Plateau of China. However, few studies have compared the effects of the two contrasting measures on soil organic and inorganic carbon (SOC and SIC) sequestration or have further used SOC and SIC isotopes to analyze the inherent sequestration mechanism. This study examined a pair of neighboring small watersheds with similar topographical and geological backgrounds. Since 1954, natural vegetation restoration has been conducted in one of these watersheds, and tree plantation has been conducted in the other. The two watersheds have now formed completely different landscapes (naturally restored grassland and artificial forestland). Differences in soil bulk density, SOC and SIC content and storage, and SOC and SIC δ(13)C values were investigated in the two ecosystems in the upper 1m of the soil. We found that SOC storage was higher in the grassland than in the forestland, with a difference of 14.90 Mg ha(-1). The vertical changes in the δ(13)CSOC value demonstrated that the two ecosystems have different mechanisms of soil surface organic carbon accumulation. The SIC storage in the grassland was lower than that in the forestland, with a difference of 38.99 Mg ha(-1). The δ(13)CSIC values indicated that the grassland generates more secondary carbonate than the forestland and that SIC was most likely transported to the rivers from the grassland as dissolved inorganic carbon (DIC). The biogeochemical characteristics of the grassland were favorable for the formation of bicarbonate. Thus, more DIC derived from the dissolution of root and microbial respired CO2 into soil water could have been transported to the rivers through flood runoff. It is necessary to study further the transportation of DIC from the grassland because this process can produce a large potential carbon sink.
自然植被恢复和人工造林是中国黄土高原生态系统恢复的两个最重要的措施。然而，很少有研究比较这两种截然不同的措施对土壤有机碳和无机碳（SOC 和 SIC）固存的影响，也没有进一步利用 SOC 和 SIC 同位素来分析固存的内在机制。本研究调查了一对具有相似地形和地质背景的相邻小流域。自 1954 年以来，其中一个流域进行了自然植被恢复，另一个流域进行了人工造林。这两个流域现在形成了完全不同的景观（自然恢复的草地和人工林地）。本研究在土壤表层 1m 内调查了这两个生态系统的土壤容重、SOC 和 SIC 含量和储量以及 SOC 和 SIC δ(13)C 值的差异。结果表明，草地的 SOC 储量高于林地，差异为 14.90 Mg ha(-1)。δ(13)CSOC 值的垂直变化表明，这两个生态系统具有不同的土壤表面有机碳积累机制。草地的 SIC 储量低于林地，差异为 38.99 Mg ha(-1)。δ(13)CSIC 值表明，草地比林地产生更多的次生碳酸盐，并且 SIC 很可能作为溶解无机碳（DIC）从草地输送到河流。草地的生物地球化学特征有利于碳酸氢盐的形成。因此，更多源于根溶解和微生物呼吸产生的 CO2 向土壤水中释放的 DIC 可能通过洪水径流输送到河流。有必要进一步研究 DIC 从草地的输送过程，因为这一过程可能产生大量潜在的碳汇。
