Land use change from C3 grassland to C4 Miscanthus : effects on soil carbon content and estimated mitigation benefit after six years
Land use change from C3 grassland to C4 Miscanthus : effects on soil carbon content and estimated mitigation benefit after six years
复制标题
从 C3 草地到 C4 芒草的土地利用变化：对土壤碳含量的影响和六年后的估计缓解效益
DOI：
10.1111/gcbb.12054
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发表时间：
2013
期刊：
影响因子：
5.6
通讯作者：
Zatta A
中科院分区：
文献类型：
--
作者：
Zatta A
到目前为止，大多数农场和商业用地都是在可耕地上种植的。能源作物将需要在不适合种植可耕地的较低等级土地上种植。草原是能源作物的主要土地资源。在土壤有机碳（SOC）水平较高的草原上，人们一直担心，与土地利用变化相关的SOC损失可能会抵消芒草生物能源的碳缓解效益。在英国威尔士的一个地点，我们量化了四种新型芒草杂交种和芒草×巨型芒草在改良草地上的相对短期影响（6年）。6年后，利用稳定碳同位素比值（13C/12C），发现芒草衍生碳（C4）在总有机碳中的含量相当可观（约为12%），且与不同杂交种地下生物量呈正相关。然而，碳储量（0-30 cm）未见显著变化，因为c4芒草碳取代了初始C3草地碳；然而，在地下生物量较高的情况下，初始有机碳的下降幅度更大。我们将这一明显矛盾的结果归因于容易获得的碳源引发的根际激发效应。利用RothC土壤碳周转模型模拟了土壤有机碳分配的变化，并对其进行了20年的预测，结果表明，在芒草的整个预期寿命期间，土壤有机碳没有显著变化。我们认为，从芒草中提取的新的活性碳已经取代了草地中的活性碳，因此，种植芒草对土壤有机碳的影响不显著。因此，总体碳减排效益不会因土壤碳的消耗而降低，而是由于地上生物量替代了化石燃料，在本例中，产量最低和最高的杂交品种在6年后分别为73-108毫克碳公顷- 1。
To date, mostMiscanthustrials and commercial fields have been planted on arable land. Energy crops will need to be grown more on lower grade lands unsuitable for arable crops. Grasslands represent a major land resource for energy crops. In grasslands, where soil organic carbon (SOC) levels can be high, there have been concerns that the carbon mitigation benefits of bioenergy fromMiscanthuscould be offset by losses in SOC associated with land use change. At a site in Wales (UK), we quantified the relatively short‐term impacts (6 years) of four novelMiscanthushybrids andMiscanthus × giganteuson SOC in improved grassland. After 6 years, using stable carbon isotope ratios (13C/12C), the amount ofMiscanthusderived C (C4) in total SOC was considerable (ca. 12%) and positively correlated to belowground biomass of different hybrids. Nevertheless, significant changes in SOC stocks (0–30 cm) were not detected as C4Miscanthuscarbon replaced the initial C3 grassland carbon; however, initial SOC decreased more in the presence of higher belowground biomass. We ascribed this apparently contradictory result to the rhizosphere priming effect triggered by easily available C sources. Observed changes in SOC partitioning were modelled using the RothC soil carbon turnover model and projected for 20 years showing that there is no significant change in SOC throughout the anticipated life of aMiscanthuscrop. We interpret our observations to mean that the new labile C fromMiscanthushas replaced the labile C from the grassland and, therefore, plantingMiscanthuscauses an insignificant change in soil organic carbon. The overall C mitigation benefit is therefore not decreased by depletion of soil C and is due to substitution of fossil fuel by the aboveground biomass, in this instance 73–108 Mg C ha−1for the lowest and highest yielding hybrids, respectively, after 6 years.