Plant community effects on soil moisture and nitrogen cycling in a semi-arid ecosystem

• Published in: Biogeochemistry Vol. 159; no. 2; pp. 215 - 232
• Main Authors: Morris, Kendalynn A., Saetre, Peter, Norton, Urszula, Stark, John M.
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01-06-2022; Springer Nature B.V
• Subjects: Aridity; Biogeosciences; Bromus tectorum; Cores; Cycles; Earth and Environmental Science; Earth Sciences; Ecosystems; Environmental Chemistry; Growing season; Life Sciences; Mass balance; Mineralization; Moisture effects; Nitrification; Nitrogen; Nitrogen cycle; Plant communities; Plants; Soil; Soil moisture; Soil water; Temporal variations; Inorganic nitrogen; Gross N mineralization; Nitrification
• ISSN: 0168-2563; 1573-515X
• DOI: 10.1007/s10533-022-00922-y

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 (R
2
 = 0.33). However, both our model and the data themselves strongly support plant community regulation of soil N cycling through modification of soil moisture.