Although substantial information had been generated on the effects of land use change on soil organic carbon (SOC) and total nitrogen (TN) storage, studies are absent on multifactorial effects of land use types, land use age, and elevation on SOC and TN storage. SOC and TN were therefore investigated in 30 field sites comprising natural forests, planted forests, shrub, and grasslands. SOC and TN stocks differed and correlated significantly with land use age; the C stocks correlates significantly with land use change compared the TN stocks. However, there was no relation between the C and N stocks with elevation, implying that SOC and TN are solely dependent on land use age. SOC sequestration potentials of the sampled ecosystems were 345.86, 293.19, 266.45, and 251.23 t ha⁻¹ for the natural forests, planted forests, shrub, and grasslands with total mean value of 289.18 t·ha⁻¹ (1,060.42 t·ha⁻¹ CO₂₋eq). A significant SOC stock loss (17.96%, 29.80%, and 37.66%) occurred in converting natural forests to planted forests, shrub, and grasslands, whereas gains (27.36%, 14.31%, and 5.71%) would occur in reconverting grassland to natural forests, planted forests, and shrublands. Therefore, the C that was lost during deforestation and conversion of natural forests into other land use types could not match the carbon gains thereafter. Our results suggest that land use change and land use age have influenced soil C and N stocks. Moreover, natural forests are better in ecological conservation and restoration of degraded lands. This study provides baseline information for C and N management in ecologically restored and degraded lands.

中文翻译：

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土地使用年龄会影响青藏高原的碳循环吗？

尽管已经获得了有关土地利用变化对土壤有机碳（SOC）和总氮（TN）储存的影响的大量信息，但仍没有关于土地利用类型，土地使用年龄以及海拔对SOC和TN储存的多因素影响的研究。 。因此，在包括天然林，人工林，灌木和草原在内的30个田地中调查了SOC和TN。SOC和TN存量与土地使用年龄存在差异，并具有显着相关性。与TN存量相比，C存量与土地利用变化显着相关。但是，C和N存量与海拔之间没有关系，这表明SOC和TN仅取决于土地使用年龄。样本生态系统的SOC隔离潜力为345.86、293.19、266.45和251.23 t ha ^-1天然林，人工林，灌木和草原的平均值为289.18 t·ha ^-1（1,060.42 t·ha ^-1 CO ₂₋eq）。将天然林转变为人工林，灌木和草原后，SOC大量减少（17.96％，29.80％和37.66％），而将草地转变为天然林则会增加（27.36％，14.31％和5.71％）森林，人工林和灌木丛。因此，在森林砍伐和将天然林转换为其他土地利用类型过程中损失的碳无法满足其后的碳增加。我们的结果表明，土地利用变化和土地利用年龄已经影响了土壤碳和氮的存量。此外，天然林在生态保护和退化土地恢复方面更好。这项研究为生态恢复和退化土地中的碳和氮管理提供了基准信息。