Global change includes invasion by exotic (non-native) plant species and altered precipitation patterns, and these factors may affect terrestrial carbon (C) storage. We measured soil C changes in experimental mixtures of all exotic or all native grassland plant species under two levels of summer drought stress (0 and +128 mm). After eight years, soils were sampled in 10 cm increments to 100 cm depth to determine if soil C differed among treatments in deeper soils. Total soil C (organic + inorganic) content was significantly higher under native than exotic plantings, and differences increased with depth. Surprisingly, differences after eight years in C were due to carbonate and not organic C fractions, where carbonate was ~ 250 g C m-2 lower to 1 m soil depth under exotic than native plantings. Our results indicate that soil carbonate is an active pool and can respond to differences in plant species traits over timescales of years. Significant losses of inorganic C might be avoided by conserving native grasslands in sub-humid ecosystems.

中文翻译：

---

外来草原与原生草原相比，较低的土壤碳储量是由碳酸盐流失造成的

全球变化包括外来（非本地）植物物种的入侵和降水模式的改变，这些因素可能会影响陆地碳 (C) 储存。我们测量了在两个夏季干旱胁迫水平（0 和 +128 毫米）下所有外来或所有本地草原植物物种的实验混合物中土壤碳的变化。八年后，以 10 厘米的增量对土壤进行采样，深度为 100 厘米，以确定较深土壤中不同处理的土壤碳含量是否不同。总土壤 C（有机 + 无机）含量在本地种植下显着高于外来种植，并且差异随着深度增加而增加。令人惊讶的是，8 年后碳的差异是由于碳酸盐而不是有机碳部分，其中碳酸盐约 250 g C m-2 在外来种植下比本地种植低至 1 m 土壤深度。我们的结果表明，土壤碳酸盐是一个活跃的池，可以响应多年时间尺度上植物物种特征的差异。通过保护半湿润生态系统中的原生草原，可以避免无机碳的大量损失。