Chen Weile, Tape Ken D, Euskirchen Eugénie S, Liang Shuang, Matos Adriano, Greenberg Jonathan, Fraterrigo Jennifer M
Department of Natural Resources and Environmental Sciences, University of Illinois at Urbana-Champaign, Urbana, IL, United States.
College of Life Sciences, Zhejiang University, Hangzhou, China.
Front Plant Sci. 2020 Dec 11;11:588098. doi: 10.3389/fpls.2020.588098. eCollection 2020.
Deciduous shrubs are expanding across the graminoid-dominated nutrient-poor arctic tundra. Absorptive root traits of shrubs are key determinants of nutrient acquisition strategy from tundra soils, but the variations of shrub root traits within and among common shrub genera across the arctic climatic gradient are not well resolved. Consequently, the impacts of arctic shrub expansion on belowground nutrient cycling remain largely unclear. Here, we collected roots from 170 plots of three commonly distributed shrub genera (, , and ) and a widespread sedge () along a climatic gradient in northern Alaska. Absorptive root traits that are relevant to the strategy of plant nutrient acquisition were determined. The influence of aboveground dominant vegetation cover on the standing root biomass, root productivity, vertical rooting profile, as well as the soil nitrogen (N) pool in the active soil layer was examined. We found consistent root trait variation among arctic plant genera along the sampling transect. and had relatively thicker and less branched, but more frequently ectomycorrhizal colonized absorptive roots than , suggesting complementarity between root efficiency and ectomycorrhizal dependence among the co-existing shrubs. Shrub-dominated plots tended to have more productive absorptive roots than sedge-dominated plots. At the northern sites, deep absorptive roots (>20 cm depth) were more frequent in birch-dominated plots. We also found shrub roots extensively proliferated into the adjacent sedge-dominated plots. The soil N pool in the active layer generally decreased from south to north but did not vary among plots dominated by different shrub or sedge genera. Our results reveal diverse nutrient acquisition strategies and belowground impacts among different arctic shrubs, suggesting that further identifying the specific shrub genera in the tundra landscape will ultimately provide better predictions of belowground dynamics across the changing arctic.
落叶灌木正在跨越以禾本科植物为主的营养贫瘠的北极苔原向外扩张。灌木的吸收根性状是其从苔原土壤获取养分策略的关键决定因素，但在北极气候梯度下，常见灌木属内部和之间的根性状变化尚未得到很好的解析。因此，北极灌木扩张对地下养分循环的影响在很大程度上仍不清楚。在此，我们沿着阿拉斯加北部的气候梯度，从170个样地收集了三种常见分布的灌木属（桦属、柳属和仙女木属）以及一种广泛分布的莎草（苔草属）的根系。测定了与植物养分获取策略相关的吸收根性状。研究了地上优势植被覆盖对现存根生物量、根生产力、垂直根系分布以及活跃土层土壤氮库的影响。我们发现，沿采样样带，北极植物属之间存在一致的根性状变化。桦属和柳属的吸收根相对较粗且分支较少，但外生菌根定殖频率高于仙女木属，这表明共存灌木之间在根效率和外生菌根依赖性方面具有互补性。以灌木为主的样地往往比以莎草为主的样地具有更高的吸收根生产力。在北部地区，桦属为主的样地中，深度吸收根（深度>20厘米）更为常见。我们还发现，灌木根系广泛延伸到相邻的以莎草为主的样地中。活跃土层的土壤氮库一般从南向北减少，但在不同灌木或莎草属为主的样地之间没有差异。我们的研究结果揭示了不同北极灌木之间多样的养分获取策略和地下影响，这表明进一步确定苔原景观中的特定灌木属最终将能更好地预测整个变化中的北极地区的地下动态。
