Survival and growth analysis of multipurpose trees, shrubs, and grasses used to rehabilitate badlands in the subhumid tropics

Talema, A. P. et al., 2019. Land Degradation & Development

Original research (primary data)
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Abstract

Vegetation plays a vital role for sustainable rehabilitation of degraded lands such as badlands with active gully erosion. However, the establishment of plant species on badlands remains a long-lasting challenge in most regions, including the subhumid tropics. To address this challenge, 18 multipurpose plant species (six trees, three shrubs, and nine grasses), which were preselected from the regional species pool in Southwest Ethiopia, were planted in a badland and monitored from July 2011 to June 2014. The experiment had a split-plot design with farmyard manure (FYM) application as main plot and plant species as subplot factors repeated in three blocks. The study revealed that grasses were the most successful to survive and rehabilitate the gully within the monitoring period compared with trees and shrubs. The survival rate of the four most successful grass species, Chrysopogon zizanioides, Pennisetum macrourum, Pennisetum polystachion, and Pennisetum purpureum ranged from 61% to 90% with FYM application and from 20% to 85% without FYM, while most of the well-known indigenous and exotic trees and shrubs failed to survive. For the grass P. purpureum, shoot height, shoot, and root biomass were enhanced by 300%, 342%, and 578%, respectively, due to FYM application, with a remarkably higher response to FYM compared with all the other studied species. The overall results demonstrate that badlands can be effectively restored by using early successional species such as locally adapted and selected grasses before the plantation of trees and shrubs.

Case studies

Basic information

  • Case ID: INT-263-2
  • Intervention type: Created habitats
  • Intervention description:

    The plant species used in the experiment were selected through an end user driven multicriteria decision analysis procedure among a regional species pool of 129 indigenous and exotic plant species having promis- ing potential for erosion control. … Before plantation, the badland was reshaped with a bull- dozer and then manually and fenced to protect from animal and human interference in sustainable way. The levelling and reshaping were done to provide an appropriate planting bed for the establishment of vegeta- tion and to increase rain infiltration so that sufficient moisture could be stored in the soil to sustain plant growth. Water retention ponds, check dams, and soil bunds were constructed to divert/retain runoff from entering the experimental blocks and plots (Figure 3). … 18 multipurpose plant species, six trees, three shrubs, and nine grasses were planted and monitored under field conditions for 3 years … (each species planted in its own plot) [besides application of farmyard manure (FYM)] There was no other input to the experimental plants (even no extra water supply). à BUT this intervention is just reporting on trees (different tree species tested but not coded separately)

  • Landscape/sea scape ecosystem management: No
  • Climate change impacts Effect of Nbs on CCI Effect measures
    Soil erosion  Unclear results Biomass cover loss: [Positive] Survival rate (number of surviving plants in each plot at each time period) Relative growth rate was selected as a growth indicator to account for size differences. (Calculate for tree height, and dry shoot biomass) Root and shoot biomass (g/plant) Canopy/contact cover – percent coverage of the plot Soil erosion [Unclear] Canopy/contact cover – percent coverage of the plot (indicator of soil erosion- “Canopy cover is well recognized as an important factor to minimize soil erosion”)
    Biomass cover loss  Positive Biomass cover loss: [Positive] Survival rate (number of surviving plants in each plot at each time period) Relative growth rate was selected as a growth indicator to account for size differences. (Calculate for tree height, and dry shoot biomass) Root and shoot biomass (g/plant) Canopy/contact cover – percent coverage of the plot Soil erosion [Unclear] Canopy/contact cover – percent coverage of the plot (indicator of soil erosion- “Canopy cover is well recognized as an important factor to minimize soil erosion”)
  • Approach implemented in the field: Yes
  • Specific location:

    The experiment was conducted in the Gilgel Gibe catchment, at Bulbul (07°43′5′′ N, 37°05′24′′ E, 1,807 m asl.), located at about 30 km to the east of Jimma town, Southwest Ethiopia. The experimental site is a badland area with active gully erosion typical for this region

  • Country: Ethiopia
  • Habitat/Biome type: Created forest |
  • Issue specific term: Not applicable

Evidence

  • Notes on intervention effectivness: "Effectiveness determined by monitoring progress since start of experiment. No control plots were used. (note main aim is to compare different treatments against one another but because they also report effect of each on its own in comparison to start of experiment, not coded as unclear) Soil erosion: effectiveness determined through thresholds - high cover stated to be effective for soil erosion - in this case, low canopy cover was achieved and authors state likely not effective but as per rule of not meeting a threshold, coded as unclear"
  • Is the assessment original?: Yes
  • Broadtype of intervention considered: Another NbS
  • 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: No
  • Impacts for the ecosystem: Not reported
  • Ecosystem measures: N/A
  • Assess outcomes of the intervention on people: No
  • Impacts for people: Not reported
  • People measures: N/A
  • 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: No
  • Experimental evalution done: Not applicable
  • Non-experimental evalution done: Empirical case study
  • Study is systematic: