Wildlands of the United States’ Intermountain West contain recurring interspersed plant-community types; namely native sagebrush (Artemisia tridentata spp. wyomingensis Nutt.), non-native invasive cheatgrass (Bromus tectorum L.), and crested wheatgrass [Agropyron desertorum (Fisch. ex Link) Schult.]. Soil nitrogen (N) cycling in these water and N co-limited ecosystems shows very strong spatial and temporal variability, but the mechanism(s) by which these semi-arid plant communities control soil N transformations are not well understood. Over two growing seasons, we conducted field and laboratory incubations of intact soil cores (0–10 cm) with and without water added, and created a mass balance model to predict N mineralization. We found that soils under cheatgrass had the highest net N mineralization, net nitrification and soil moisture compared to soils from under the other two plant communities. Moreover, water additions to field-incubated soil cores under cheatgrass more than doubled net N mineralization (0.18 ± 0.02 vs 0.07 ± 0.01 mg N kg⁻¹ d⁻¹). Temperature had a small effect on net N mineralization and net nitrification, with both rates increasing by < 0.005 mg N kg⁻¹ d⁻¹ per °C. The model’s ability to predict N mineralization was relatively low (R² = 0.33). However, both our model and the data themselves strongly support plant community regulation of soil N cycling through modification of soil moisture.

美国西部山间的荒地包含经常散布的植物群落类型；即原生山艾树 ( Artemisia tridentata spp. wyomingensis Nutt.)、非原生侵入性木耳草 ( Bromus tectorum L.) 和冠麦草 [ Agropyron desertorum(Fisch. ex Link) Schult.]。这些水和 N 共同限制的生态系统中的土壤氮 (N) 循环显示出非常强的空间和时间变异性，但这些半干旱植物群落控制土壤 N 转化的机制尚不清楚。在两个生长季节，我们在加水和不加水的情况下对完整的土芯（0-10 厘米）进行了现场和实验室孵化，并创建了一个质量平衡模型来预测 N 矿化。我们发现，与其他两个植物群落下的土壤相比，金雀花下的土壤具有最高的净氮矿化、净硝化作用和土壤水分。此外，在金雀草下田间培养的土壤芯中添加的水使净 N 矿化增加了一倍以上（0.18 ± 0.02 vs 0.07 ± 0.01 mg N kg ^-1  d ^-1）。温度对净 N 矿化和净硝化作用的影响很小，每摄氏度增加 < 0.005 mg N kg ^-1  d ^{-1 。}该模型预测氮矿化的能力相对较低（R ²  = 0.33）。然而，我们的模型和数据本身都强烈支持植物群落通过改变土壤水分来调节土壤 N 循环。