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Abstract Plant‐root uptake underpins the flow of water and nutrients through terrestrial ecosystems. Water and nutrients are heterogeneously distributed in soil and vary among wet and dry years. Shrubs and grasses have different root distributions extending to different soil depths. We asked three questions: (1) What are the depth profiles of root absorption of the dominant shrub and grass species of the northern Chihuahuan drylands? (2) How do their absorption profiles change from wet to dry years? (3) How does the absorption profile of the dominant shrubProsopis glandulosachange with shrub size? Using a tracer, we measured soil‐resource uptake by neighboring shrubs and grasses in the top 120 cm of the soil. Grass absorption profiles were shallower and more flexible than those of shrubs, which showed little change between dry and wet years. Shrub‐rooting depth increased swiftly with size; all shrubs above the 20th percentile of aboveground volume displayed deeper absorption than grasses. We showed that shrub–grass competition for soil resources is minimal and limited to early shrub establishment stages. Our results assist in understanding woody‐plant encroachment and future plant community structure and ecosystem functioning under a hotter, drier, and more variable climate.
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Germination and early establishment of dryland grasses and shrubs on intact and wind-eroded soils under greenhouse conditions
Abstract Aims Grassland-to-shrubland transition is a common form of land degradation in drylands worldwide. It is often attributed to changes in disturbance regimes, particularly overgrazing. A myriad of direct and indirect effects (e.g., accelerated soil erosion) of grazing may favor shrubs over grasses, but their relative importance is unclear. We tested the hypothesis that topsoil “winnowing” by wind erosion would differentially affect grass and shrub seedling establishment to promote shrub recruitment over that of grass. Methods We monitored germination and seedling growth of contrasting perennial grass ( Bouteloua eriopoda , Sporobolus airoides , and Aristida purpurea ) and shrub ( Prosopis glandulosa , Atriplex canescens , and Larrea tridentata ) functional groups on field-collected non-winnowed and winnowed soils under well-watered greenhouse conditions. Results Non-winnowed soils were finer-textured and had higher nutrient contents than winnowed soils, but based on desorption curves, winnowed soils had more plant-available moisture. Contrary to expectations, seed germination and seedling growth on winnowed and non-winnowed soils were comparable within a given species. The N 2 -fixing deciduous shrub P. glandulosa was first to emerge and complete germination, and had the greatest biomass accumulation of all species. Conclusions Germination and early seedling growth of grasses and shrubs on winnowed soils were not adversely nor differentially affected comparing with that observed on non-winnowed soils under well-watered greenhouse conditions. Early germination and rapid growth may give P. glandulosa a competitive advantage over grasses and other shrub species at the establishment stage in grazed grasslands. Field establishment experiments are needed to confirm our findings in these controlled environment trials.
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- PAR ID:
- 10298286
- Date Published:
- Journal Name:
- Plant and Soil
- Volume:
- 465
- Issue:
- 1-2
- ISSN:
- 0032-079X
- Page Range / eLocation ID:
- 245 to 260
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1007/s11104-021-05005-9
