Aims

The mechanism by which species diversity drives productivity in different ecosystems is controversial, possibly due to the confounding effects of key environmental variables. Karst ecosystems are fragile and are at great risk of species loss. In these ecosystems, soil depth is a key driver of community diversity and productivity. However, the influence of soil depth on the relationship between species diversity and productivity in karst ecosystems remains unclear.

Methods

We established artificial karst herbaceous communities with different soil depths and species richness levels and determined how two biodiversity effects—complementarity effect (effect of positive interactions among species) and selection effect (effect due to dominance of productive species)—contributed to productivity.

Results

Soil depth, species diversity, and different species combinations were significant predictors of productivity. Species diversity significantly positively affected productivity at all three soil depths, with the effect size of species diversity being the greatest in medium-depth soil. Net diversity effects were greater than 0 in all multi-species communities, indicating that complementarity and selection effects both positively influenced productivity. However, complementarity effect had a greater contribution to productivity than selection effect in all multi-species communities. Furthermore, the contribution of complementarity effect increased with increasing soil depth, while that of selection effect decreased.

Conclusions

Our result indicate that both soil depth and species diversity need be considered simultaneously in maintaining karst herbaceous community productivity. Moreover, complementarity effect is the major mechanism by which diversity increases community productivity, particularly in shallow soil. Thus, the more attention should be paid to promoting species diversity with the decreasing of soil depth for adequately preserve karst key functions such as herbaceous community productivity.

中文翻译：

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土壤深度改变了实验性喀斯特草本群落中物种多样性对生产力的影响

宗旨

物种多样性推动不同生态系统生产力的机制存在争议，可能是由于关键环境变量的混杂影响。喀斯特生态系统很脆弱，物种丧失的风险很大。在这些生态系统中，土壤深度是群落多样性和生产力的关键驱动因素。然而，土壤深度对喀斯特生态系统物种多样性与生产力之间关系的影响尚不清楚。

方法

我们建立了具有不同土壤深度和物种丰富度水平的人工喀斯特草本群落，并确定了两种生物多样性效应——互补效应（物种之间积极相互作用的效应）和选择效应（由于生产物种的优势而产生的效应）——对生产力的贡献。

结果

土壤深度、物种多样性和不同物种组合是生产力的重要预测因素。物种多样性对所有三个土壤深度的生产力都有显着的积极影响，物种多样性的影响在中等深度土壤中最大。所有多物种群落的净多样性效应均大于 0，表明互补性和选择效应都对生产力产生了积极影响。然而，在所有多物种群落中，互补效应对生产力的贡献大于选择效应。此外，互补效应的贡献随着土壤深度的增加而增加，而选择效应的贡献减少。

结论

我们的结果表明，在维持岩溶草本群落生产力时，需要同时考虑土壤深度和物种多样性。此外，互补效应是多样性提高群落生产力的主要机制，尤其是在浅层土壤中。因此，要充分保护岩溶关键功能，如草本群落生产力，应更多地关注随着土壤深度的减少而促进物种多样性。