1. Dryland communities may mitigate the loss of limited resources by exchanging nutrients through subterranean fungal connections, termed fungal loops. In arid grasslands, fungal loops can influence community composition and primary productivity, yet their ecological significance across dryland systems remains unexplored. We investigated the functional role of fungal loops in nutrient translocation in a North American shrubland ecosystem.
2. We traced the movement of ¹⁵N from moss‐dominated biocrusts to the dominant xeric shrub Larrea tridentata, and the movement of ¹³C from L. tridentata to biocrusts in plots established in situ in the Sonoran Desert. Measurements occurred at three time points spanning 1 week following a simulated 2.5 mm rainfall event, and at distances up to 1 m from tracer application. We also used ITS sequencing to investigate changes in fungal community composition in soils over the 1‐week period.
3. We discovered movement of ¹⁵N from biocrusts into L. tridentata foliage as well as ¹⁵N movement to other spatially isolated moss‐dominated biocrust patches, yet this movement did not occur until 4–6 days post‐rainfall, when significantly higher δ¹⁵N was observed in L. tridentata and biocrusts compared to previous days. We did not observe consistent patterns of ¹³C movement from L. tridentata into neighbouring shrubs or biocrusts, suggesting differential environmental drivers for carbon movement in this system. Fungal communities exhibited a decrease in alpha diversity on the last day of the study, indicative of a delayed community response to rainfall concomitant with nutrient translocation. Fungal endophyte orders Pleosporales and Pezizales dominated all plot soils, and order Pleosporales was significantly more abundant in ¹⁵N enriched plots, suggesting that dark septate endophytic fungi were involved in nitrogen translocation. The delay in nutrient translocation may reflect a rainfall‐triggered rebuilding of mycelial networks between community members following drought.
4. Synthesis. Our results point to fungal‐mediated nutrient exchange pathways in a previously uninvestigated vegetation type, shrublands, where nutrients are translocated between moss‐dominated biocrusts and nearby shrubs. We provide the first evidence that nutrient transfer may be delayed up to 6 days following rainfall, consistent with pulse‐dynamic responses in drylands, and that moss‐dominated biocrusts play a role in fungal loops.

中文翻译：

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灌木丛中真菌环的证据

1. 旱地社区可以通过地下真菌连接（称为真菌环）交换养分来减轻有限资源的损失。在干旱的草原上，真菌环可影响群落组成和初级生产力，但其在整个旱地系统中的生态意义仍待探索。我们调查了北美灌木林生态系统中真菌环在养分转运中的功能。
2. 我们追踪了¹⁵ N从苔藓为主的生物硬壳到占主导地位的干性灌木Larrea tridentata的运动，以及¹³ C从L. tridentata到在Sonoran沙漠中就地建立的生物硬壳的运动。在模拟的2.5 mm降雨事件之后的1个星期中的三个时间点进行测量，并且距示踪剂应用的最大距离为1 m。我们还使用ITS测序研究了1周内土壤中真菌群落组成的变化。
3. 我们发现运动¹⁵从biocrusts成N L.三齿叶子以及¹⁵ ñ移动到其他空间隔离苔为主biocrust补丁，但直到4-6天后降雨，当显著较高δ并没有出现这个运动¹⁵ ñ与前几天相比，在三齿乳杆菌和生物结皮中观察到了这种现象。我们没有观察到来自L. tridentata的¹³ C运动的一致模式进入邻近的灌木或生物结皮，表明该系统中碳迁移的不同环境驱动因素。在研究的最后一天，真菌群落的α多样性降低，这表明群落对降雨的养分响应与养分移位有关。真菌内生菌阶Pleosporales和Pezizales占据了所有样地土壤，而Pleosporales菌在富含¹⁵ N的样地中明显更丰富，这表明深色的隔壁内生真菌参与了氮的转运。养分迁移的延迟可能反映了干旱引发的降雨触发了社区成员之间菌丝网络的重建。
4. 综合。我们的研究结果表明，在以前未经调查的植被类型灌木丛中，真菌介导的养分交换途径在其中，养分在苔藓为主的生物结皮和附近的灌木丛之间转移。我们提供的第一个证据是，降雨后养分的转移可能会延迟最多6天，这与干旱地区的脉冲动力响应一致，并且苔藓为主的生物结壳在真菌环中发挥了作用。