The small semi–fossorial herbivore bioturbation has been verified to affect available soil nitrogen in grasslands, but the effects of small semi–fossorial herbivore bioturbation on soil organic nitrogen (SON) fractions that are main compositions of soil total nitrogen and sources of soil available nitrogen remain poorly known. The plateau pika () bioturbation creates numerous bare patches, which intersperse within vegetated surfaces in grasslands. In this study, plateau pika was considered as an example animal to examine the differences of SON fractions between bare patches and vegetated surfaces under the small semi–fossorial herbivore bioturbation across six sites. This study demonstrated that acidhydrolysable nitrogen (AHN) was 27.58% lower in bare patches than in vegetated surfaces. Amino acid nitrogen (AAN), ammonium nitrogen (AN), amino sugar nitrogen (ASN) and unknown nitrogen (UN) in bare patches were 35.23%, 17.07%, 17.70% and 19.87% lower than those in vegetated surfaces, respectively. The contribution of AAN to AHN was 5.3% lower in bare patches than in vegetated surfaces, but the contributions of AN, ASN and UN to AHN were 2.42%, 1.11%, and 1.77% higher, respectively. The response of AAN to plateau pika bioturbation was more sensitive than AN, ASN and UN. These findings verify the plateau pika bioturbation leads to a lower potential capacity of soil nitrogen supply in bare patches than in vegetated surfaces, and present a possible pattern of SON fractions in relation to small semi–fossorial herbivore bioturbation in grasslands.

中文翻译：

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高原鼠兔生物扰动导致高寒草甸裸地土壤有机氮含量降低


小型半化石食草动物生物扰动已被证实对草地土壤有效氮有影响，但小型半化石食草动物生物扰动对土壤有机氮（SON）组分的影响是土壤全氮的主要组成部分和土壤有效氮的来源仍然鲜为人知。高原鼠兔的生物扰动产生了许多裸露的斑块，这些斑块散布在草原的植被表面内。在这项研究中，高原鼠兔被认为是一个示例动物，以检查六个地点的小型半化石食草动物生物扰动下裸露斑块和植被表面之间 SON 分数的差异。这项研究表明，裸露斑块中的酸水解氮 (AHN) 比植被表面低 27.58%。裸露斑块中氨基酸态氮（AAN）、铵态氮（AN）、氨基糖态氮（ASN）和未知氮（UN）分别比植被地表低35.23%、17.07%、17.70%和19.87%。裸露斑块中 AAN 对 AHN 的贡献比植被表面低 5.3%，但 AN、ASN 和 UN 对 AHN 的贡献分别高出 2.42%、1.11% 和 1.77%。 AAN对高原鼠兔生物扰动的响应比AN、ASN和UN更敏感。这些发现证实高原鼠兔生物扰动导致裸露斑块土壤氮供应的潜在能力低于植被表面，并提出了与草原中小型半化石食草动物生物扰动相关的 SON 分数的可能模式。