Background and aims

Although root distributions are assumed to be important for plant growth and coexistence, it remains difficult to quantify how root distributions affect resource uptake and plant landscape abundance.

Methods

In a water- and nitrogen (N)-limited grassland system, Minnesota, USA, we injected water and N tracers to five depths (5–150 cm) during peak growing season. Tracer concentrations in 11 dominant species were measured to describe functional root distributions. Seasonal water and N uptake into these functional root distributions was estimated using depth-specific resource availability. Plant biomass produced from seasonal water and N uptake was estimated using water- and N-use efficiencies. Finally, biomass production was compared to plant landscape abundance.

Results

Differences in functional root distributions resulted in seasonal water uptake between 52 and 67 cm yr⁻¹, and N uptake between 1.0 and 3.1 g m⁻² yr⁻¹ among species. Biomass production caused by water or N uptake was correlated with plant landscape abundance (R² = 0.37, 0.35, for water and N). When combined, biomass production from water and N uptake was better correlated with plant landscape abundance (R² = 0.75).

Conclusion

We show how root systems forage independently for different resources. Consistent with resource availability, water uptake patterns were shallower than N uptake patterns. Root uptake of these two limiting resources affected plant growth and landscape abundance. We provided a quantitative link between functional root distributions, resource uptake, biomass production, and plant landscape abundance. This research represents an important advance from research that describes niche differences among root systems.

中文翻译：

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独立采集的水和氮对于确定草原物种丰度都很重要

 背景和目标

尽管根系分布被认为对植物生长和共存很重要，但仍然很难量化根系分布如何影响资源吸收和植物景观丰度。

 方法

在美国明尼苏达州的水和氮 (N) 有限的草原系统中，我们在生长高峰季节将水和氮示踪剂注入到五个深度（5-150 厘米）。测量了 11 个优势物种的示踪剂浓度来描述功能性根分布。使用特定深度的资源可用性来估计这些功能性根分布的季节性水和氮吸收。使用水和氮利用效率估算由季节性水和氮吸收产生的植物生物量。最后，将生物量生产与植物景观丰度进行比较。

 结果

功能根分布的差异导致物种间季节性吸水量在52至67 cm yr ^-1之间，氮吸收量在1.0至3.1 gm ^-2 yr ^-1之间。由水或氮吸收引起的生物量生产与植物景观丰度相关（对于水和氮，R ² = 0.37、0.35）。综合起来，水和氮吸收产生的生物量与植物景观丰度具有更好的相关性（R ² = 0.75）。

 结论

我们展示了根系统如何独立寻找不同的资源。与资源可用性一致，水的吸收模式比氮的吸收模式浅。根部对这两种限制资源的吸收影响了植物生长和景观丰度。我们提供了功能性根分布、资源吸收、生物量生产和植物景观丰度之间的定量联系。这项研究代表了描述根系统之间生态位差异的研究的重要进展。