Evans R D, Ehleringer J R
Stable Isotope Facility for Environmental Research, Department of Biology, University of Utah, 84112, Salt Lake City, UT, USA.
Oecologia. 1993 Jun;94(3):314-317. doi: 10.1007/BF00317104.
We examined the content and isotopic composition of nitrogen within soils of a juniper woodland and found that a cryptobiotic crust composed of cyanobacteria, lichens, and mosses was the predominant source of nitrogen for this ecosystem. Disturbance of the crust has resulted in considerable spatial variability in soil nitrogen content and isotopic composition; intercanopy soils were significantly depleted in nitrogen and had greater abundance of N compared to intra-canopy soils. Variations in the N/N ratio for inter- and intra-canopy locations followed similar Rayleigh distillation curves, indicating that the greater N/N ratios for inter-canopy soils were due to relatively greater net nitrogen loss. Coverage of cryptobiotic crusts has been reduced by anthropogenic activities during the past century, and our results suggest that destruction of the cryptobiotic crust may ultimately result in ecosystem degradation through elimination of the predominant source of nitrogen input.
我们研究了杜松林地土壤中氮的含量和同位素组成，发现由蓝细菌、地衣和苔藓组成的隐生生物结皮是该生态系统氮的主要来源。结皮受到干扰导致土壤氮含量和同位素组成出现显著的空间变异性；林冠间隙土壤的氮显著减少，与林冠下土壤相比，其氮的丰度更高。林冠间隙和林冠下位置的N/N比变化遵循相似的瑞利蒸馏曲线，这表明林冠间隙土壤中较高的N/N比是由于相对更大的净氮损失。在过去的一个世纪里，人为活动导致隐生生物结皮的覆盖面积减少，我们的研究结果表明，隐生生物结皮的破坏最终可能通过消除主要的氮输入源而导致生态系统退化。
