Assessing the Ecological Success of Restoration by Afforestation on the Chinese Loess Plateau

Jiao, J. Y., et al., 2012. Restoration Ecology

Original research (primary data)
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Abstract

Afforestation has been accepted as a key measure for preventing soil erosion on the Chinese Loess Plateau for 40 years. In this study, we assessed the ecological success of afforestation by comparing afforested with pre-afforested (croplands) and natural recovery sites in a typical watershed on the Loess Plateau. We evaluated the ecosystem response in terms of vegetation structure, plant diversity, and several key ecological processes of soil moisture, soil nutrients, and soil anti-erodibility. Compared with the croplands, we found that the following indexes were significantly enhanced in afforested sites: vegetation structure and species diversity (species richness, Margalef index, Shannon-Wiener index, and Sorensen’s similarity index), soil nutrients (organic carbon, total nitrogen, extractable ammonium nitrogen, available potassium, and available phosphorous), and soil anti-erodibility indexes (water-stable soil aggregates, mean weight diameter, and the ratio of soil structure dispersion). Afforestation offered few additional advantages when compared with natural recovery sites. More importantly, afforestation had significant negative effects on soil desiccation, with negative impacts on the long-term sustainability of these ecosystems. In order to develop self-sustaining and functional ecosystems, our results suggest that natural revegetation offers a more adaptive and appropriate method of ecological restoration on the Loess Plateau.

Case studies

Basic information

  • Case ID: INT-076-3
  • Intervention type: Created habitats
  • Intervention description:

    state-level model watershed of the “Grain for Green” project ... active afforestation with Robinia pseudoacacia (tree species)

  • Landscape/sea scape ecosystem management: Yes
  • Climate change impacts Effect of Nbs on CCI Effect measures
    Soil erosion  Positive indices related to soil anti-erodibility (such as water-stable soil aggregates, mean weight diameter [MWD], ratio of soil structure dispersion, and soil bulk density
    Reduced water availability  Negative soil moisture content.
  • Approach implemented in the field: Yes
  • Specific location:

    Zhifanggou watershed, located in Yan River basin of Ansai County, North Shaanxi Province.

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

Evidence

  • Notes on intervention effectivness: the reference sites (Natural regeneration of vegetation) are compared to the afforested sites and pre-afforested sites (control i.e. agricultural land). These pre-afforested sites can be considered controls, therefore the study is tagged as experimental. study compares natural revegetation to ‘active afforestation’ with Fast growing tree and shrub species the parameters of soil water content and anti-erodibility were compared between active afforestation sites and natural recovery sites. From the above discussion, the changes in soil water, soil nutrients, and soil anti-erodibility among afforested, preafforested, and reference sites suggest that natural vegetation recovery is a better management option than afforestation on the Loess Plateau. Note – conclusion is that with respect to erosion afforestation is not better than natural recovery, but for soil water content natural recovery has positive impacts, whereas afforestation has negative impacts.
  • 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: Yes
  • Impacts for the ecosystem: Positive
  • Ecosystem measures: structure and species diversity (species richness, Margalef index, Shannon–Wiener index, and Sorensen’s similarity index)
  • 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:

Basic information

  • Case ID: INT-076-2
  • Intervention type: Created habitats
  • Intervention description:

    state-level model watershed of the “Grain for Green” project ... active afforestation with Caragana korshinskii (shrub species)

  • Landscape/sea scape ecosystem management: Yes
  • Climate change impacts Effect of Nbs on CCI Effect measures
    Soil erosion  No effect indices related to soil anti-erodibility (such as water-stable soil aggregates, mean weight diameter [MWD], ratio of soil structure dispersion, and soil bulk density
    Reduced water availability  Negative soil moisture content.
  • Approach implemented in the field: Yes
  • Specific location:

    Zhifanggou watershed, located in Yan River basin of Ansai County, North Shaanxi Province.

  • Country: China
  • Habitat/Biome type: Created other |
  • Issue specific term: Not applicable

Evidence

  • Notes on intervention effectivness: the reference sites (Natural regeneration of vegetation) are compared to the afforested sites and pre-afforested sites (control i.e. agricultural land). These pre-afforested sites can be considered controls, therefore the study is tagged as experimental. study compares natural revegetation to ‘active afforestation’ with Fast growing tree and shrub species the parameters of soil water content and anti-erodibility were compared between active afforestation sites and natural recovery sites. From the above discussion, the changes in soil water, soil nutrients, and soil anti-erodibility among afforested, preafforested, and reference sites suggest that natural vegetation recovery is a better management option than afforestation on the Loess Plateau. Note – conclusion is that with respect to erosion afforestation is not better than natural recovery, but for soil water content natural recovery has positive impacts, whereas afforestation has negative impacts.
  • 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: Yes
  • Impacts for the ecosystem: Positive
  • Ecosystem measures: structure and species diversity (species richness, Margalef index, Shannon–Wiener index, and Sorensen’s similarity index)
  • 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:

Basic information

  • Case ID: INT-076-1
  • Intervention type: Restoration
  • Intervention description:

    natural revegetation without intensive human interference 18 plots had been naturally restored for over 20 years

  • Landscape/sea scape ecosystem management: Yes
  • Climate change impacts Effect of Nbs on CCI Effect measures
    Soil erosion  Positive indices related to soil anti-erodibility (such as water-stable soil aggregates, mean weight diameter [MWD], ratio of soil structure dispersion, and soil bulk density
    Reduced water availability  Mixed results soil moisture content.
  • Approach implemented in the field: Yes
  • Specific location:

    Zhifanggou watershed, located in Yan River basin of Ansai County, North Shaanxi Province.

  • Country: China
  • Habitat/Biome type: Montane/Alpine |
  • Issue specific term: Not applicable

Evidence

  • Notes on intervention effectivness: the reference sites (Natural regeneration of vegetation) are compared to the afforested sites (alternative) and pre-afforested sites (control i.e. agricultural land). These pre-afforested sites can be considered controls, therefore the study is tagged as experimental. study compares natural revegetation to ‘active afforestation’ with Fast growing tree and shrub species the parameters of soil water content and anti-erodibility were compared between active afforestation sites and natural recovery sites. From the above discussion, the changes in soil water, soil nutrients, and soil anti-erodibility among afforested, preafforested, and reference sites suggest that natural vegetation recovery is a better management option than afforestation on the Loess Plateau. Note – conclusion is that with respect to erosion afforestation is not better than natural recovery, but for soil water content natural recovery has positive impacts, whereas afforestation has negative impacts. BT - changed coding to mixed effects on water because at the upper-most layer, more water than control (the cropland) but at all other layers have less water --> the paper focuses on making the comparison of water between afforestation and natural regeneration so when saying positive effects on water in fact what they mean is 'less negative' than afforestation. they still can have a negative effect on water but depends on soil depth
  • 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: Yes
  • Impacts for the ecosystem: Positive
  • Ecosystem measures: structure and species diversity (species richness, Margalef index, Shannon–Wiener index, and Sorensen’s similarity index)
  • 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: