Data from: Diversity effects on root length production and loss in an experimental grassland community

Advances in root ecology have revealed that root standing biomass is higher in species-rich plant communities than in species-poor communities. Currently, we do not know whether this below-ground diversity effect is the result of enhanced root production or reduced root mortality or both, which is essential information to understand ecosystem functioning, as it determines C sequestration and N dynamics in soil. Minirhizotron observations were combined with root coring in five different plant communities (four monocultures and the respective mixture). Molecular markers were used to quantitatively determine species abundance in mixed root biomass samples in order to track shifts in below-ground species composition. In addition, a litterbag experiment was performed to study root decomposition independent of root mortality. Root length production was greater and root length loss was lower in the mixture than expected from monocultures in all years. Simulations suggest that at least two species must have had reduced losses in mixture compared to monoculture. However, the diversity effects on root mortality may partially be explained by selection effects as the species with the longest root life span became dominant in the mixtures. Root length loss from minirhizotrons was very low; the combination of minirhizotron length measurements with root biomass estimates from coring suggested underestimation of root loss in minirhizotrons over time. Root decomposition was not affected by diversity. Diversity enhanced root length production and decreased root loss, resulting in below-ground overyielding. With decomposition unaffected, our results suggest that root mortality is reduced with increasing diversity. Future studies have to reveal the generality of our observations in larger scale biodiversity experiments by using species having a wider variety of root traits.根系生态学领域的研究进展表明，物种丰富的植物群落相较于物种贫乏群落，其根系现存生物量更高。目前学界尚不清楚该地下多样性效应源于根系生产速率提升、根系死亡率降低，还是二者共同作用；而这一信息对于理解生态系统功能至关重要，因其决定了土壤中的碳固存与氮动态。本研究将微根管法（minirhizotron）观测与根系钻取采样相结合，共设置5类植物群落：4个单作群落及对应的混合群落。通过分子标记技术对混合根系生物量样本中的物种丰度进行定量测定，以追踪地下物种组成的变化。此外，本研究还开展了凋落袋实验，以在独立于根系死亡率的条件下探究根系分解过程。所有观测年份中，混合群落的根长生产速率均高于单作群落的预期值，而根长损失则更低。模拟结果表明，相较于单作群落，至少有2个物种在混合群落中的损失得到了降低。不过，多样性对根系死亡率的效应可部分由选择效应解释：根系寿命最长的物种在混合群落中占据了优势地位。微根管法观测到的根长损失量极低；结合微根管法的根长测量结果与根系钻取采样得到的生物量估算值，发现随时间推移，微根管法对根损失的估算存在低估现象。根系分解过程并未受到多样性的影响。多样性提升了根长生产速率并降低了根损失，最终产生了地下超产效应。鉴于根系分解不受多样性影响，本研究结果表明，根系死亡率随多样性升高而降低。未来研究需通过选用根系性状更为多样的物种，在更大尺度的生物多样性实验中验证本研究观测结果的普适性。