Arid old-field restoration: Native perennial grasses suppress weeds and erosion, but also suppress native shrubs

Porensky, L. M., et al., 2014. Agriculture, Ecosystems and Environment

Original research (primary data)
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Abstract

Rates of cropland abandonment in arid regions are increasing, and abandoned fields in such regions can have low levels of ecosystem function and biodiversity. Long-lived, drought-tolerant shrubs are dominant components of many arid ecosystems, providing multiple ecosystem services such as soil stabilization, herbaceous plant facilitation, carbon storage and wildlife habitat. On abandoned agricultural fields, shrub restoration is hindered by multiple challenges, including erosion, water stress and invasive species. We hypothesized that applying short-term irrigation and seeding native perennial grasses would facilitate native shrub establishment by reducing erosion and weed abundance. Using a blocked split-plot design, we evaluated the separate and combined impacts of short-term irrigation and perennial grass seeding on five-year restoration outcomes (including direct measurements of wind erosion) at two former agricultural fields in North America’s arid Great Basin. After two years, irrigation had increased the density and biomass of seeded grasses by more than ten-fold. The combination of irrigation and seeded grasses was associated with significantly lower wind erosion, weed density and weed biomass. Three years after irrigation ended, seeded grasses remained significantly more abundant in formerly irrigated than non-irrigated plots. Formerly irrigated plots also had significantly less bare ground, annual plant cover and weed biomass than non-irrigated plots. Large plant-canopy gaps were fewer in irrigated and seeded plots. Although seeded grasses reduced erosion and invasion, they failed to facilitate native shrub establishment. Shrub cover and density were highest in plots that had been drill-seeded and irrigated, but lacked perennial grasses. Our results indicate that short-term irrigation has persistent restoration benefits, and that a tradeoff exists between the benefits and costs of seeding perennial grasses into degraded arid shrubland sites.

Case studies

Basic information

  • Case ID: INT-067-1
  • Intervention type: Restoration
  • Intervention description:

    restoration at two sites, one was used for alfalfa production until the start of the experiment, the other denuded pasture formerly used for burro and llama grazing experimental: planted five native grass species: four cool- season perennial bunchgrasses - one species per experimental plot. Experimental plots either had irrigation or no irrigation.

  • Landscape/sea scape ecosystem management: No
  • Climate change impacts Effect of Nbs on CCI Effect measures
    Soil erosion  Unclear results Dust generated/collected at heights of 7, 35, 60 and 100 cm above the soil surface
  • Approach implemented in the field: Yes
  • Specific location:

    Two study sites were located along the lower reaches of the Walker River, 11.5km south of Mason, Nevada USA. The Valley Vista Ranch (VV) site (38◦ 50′ 58′′ N, 119◦ 11′ 04′′ W) and the 5 C’s Cottonwood Ranch (5C) site (38◦ 50′ 45′′ N, 119◦ 11′ 02′′ W)

  • Country: United States of America
  • Habitat/Biome type: Deserts and xeric shrublands |
  • Issue specific term: Not applicable

Evidence

  • Notes on intervention effectivness: although a control was included, results are not reported for the control. Instead, effectiveness is evaluated by comparing erosion mitigation in the restored site to a natural site nearby to act as reference ecosystem outcomes mixed because variable results depending on measures considered
  • Is the assessment original?: Yes
  • Broadtype of intervention considered: Not applicable
  • Compare effectivness?: No
  • Compared to the non-NBS approach: Not applicable
  • Report greenhouse gas mitigation?: No
  • Impacts on GHG: Not applicable
  • Assess outcomes of the intervention on natural ecosystems: Yes
  • Impacts for the ecosystem: Mixed
  • Ecosystem measures: density and biomass of weeds (i.e. non-native plants, which were primarily annual forbs) percent cover perrenial grassed, percent cover annuals percent bare ground average number of gaps more than >2m percent native shrub survival percent native shrub cover average no. shrubs per ha
  • Assess outcomes of the intervention on people: No
  • Impacts for people: Not reported
  • People measures:
  • Considers economic costs: No
  • Economic appraisal conducted: No
  • Economic appraisal described:
  • Economic costs of alternative considered: No
  • Compared to an alternative: Not reported

Evaluation methodology

  • Type of data: Quantitative
  • Is it experimental: Yes
  • Experimental evalution done: In-situ/field
  • Non-experimental evalution done: Not applicable
  • Study is systematic: