Aims

Climate warming in northern ecosystems is triggering widespread permafrost thaw, during which deep soil nutrients, such as nitrogen, could become available for biological uptake. Permafrost thaw shift frozen organic matter to a saturated state, which could impede nutrient uptake. We assessed whether soil nitrogen can be accessed by the deep roots of vascular plants in thermokarst bogs, potentially allowing for increases in primary productivity.

Methods

We conducted an ammonium uptake experiment on Carex aquatilis Wahlenb. roots excavated from thermokarst bogs in interior Alaska. Ammonium uptake capacity was compared between deep and shallow roots. We also quantified differences in root ammonium uptake capacity and plant size characteristics (plant aboveground and belowground biomass, maximum shoot height, and maximum root length) between the actively-thawing margin and the centre of each thermokarst bog as a proxy for time-following-thaw.

Results

Deep roots had greater ammonium uptake capacity than shallow roots, while rooting depth, but not belowground biomass, was positively correlated with aboveground biomass. Although there were no differences in aboveground biomass between the margin and centre, our findings suggest that plants can benefit from investing in the acquisition of resources near the vertical thaw front.

Conclusions

Our results suggest that deep roots of C. aquatilis can contribute to plant nitrogen uptake and are therefore able to tolerate anoxic conditions in saturated thermokarst bogs. This work furthers our understanding of how subarctic and wetland plants respond to warming and how enhanced plant biomass production might help offset ecosystem carbon release with future permafrost thaw.

中文翻译：

---

多年冻土融化后，草炭黑的深根比泥炭地的浅根具有更大的铵吸收能力。

目的

北部生态系统的气候变暖引发了多年冻土的广泛融化，在此期间，深层土壤养分（例如氮）可能会被生物吸收。多年冻土融化会使冷冻的有机物转变为饱和状态，这可能会阻止养分吸收。我们评估了热喀斯特沼泽中维管植物的深根是否可以获取土壤氮，从而可能提高初级生产力。

方法

我们在Carex aquatilis Wahlenb上进行了铵吸收实验。从阿拉斯加内部的喀斯特地貌沼泽挖出的树根。比较了深根和浅根的铵吸收能力。我们还量化了主动解冻边缘和每个喀斯特地貌沼泽的中心之间的根系铵吸收能力和植物大小特征（植物地上和地下生物量，最大苗高和最大根长）之间的差异，作为时间追随的代名词解冻。

结果

深根比浅根具有更高的铵吸收能力，而生根深度而不是地下生物量与地上生物量呈正相关。尽管边缘和中心之间的地上生物量没有差异，但我们的发现表明，植物可以通过投资于垂直解冻前沿附近的资源获取而受益。

结论

我们的结果表明，C。aquatilis的深根可以促进植物吸收氮，因此能够耐受饱和热喀斯特沼泽中的缺氧条件。这项工作使我们进一步了解了北极和湿地植物如何应对变暖，以及提高植物生物量的产量可能如何通过未来的永冻土融化来抵消生态系统的碳释放。