Lewa Wildlife Conservancy

Assessment of Rangeland Health using the Land Degradation Surveillance Framework (LDSF)

Tor-G. Vågen and Leigh A. Winowiecki

October 14, 2022

About the LDSF

Global network of sites

• to fill critical data gaps and consistently assess and monitor soil and land health
• each marker on the map represents a 10x10 km LDSF site
• about 240 sites in 43 countries

The Lewa LDSF site

The LDSF indicator framework

Soil health

Multiple functional soil properties are assessed as part of the LDSF

• soil organic carbon (SOC)
• total nitrogen (TN)
• soil pH and base cations (\(\sum(Ca,Mg,K,Na)\))
• soil texture (sand, silt, clay content)
• stable carbon isotopes

Assessing SOC

In the assessment of SOC as part of (range)land health assessments, we focus primarily on SOC concentrations and not SOC stocks, although we also assess SOC stocks as per the cumulative mass method presented in Vågen and Winowiecki (2013)¹.

1. Vågen, T.-G., Winowiecki, L.A., 2013. Mapping of soil organic carbon stocks for spatially explicit assessments of climate change mitigation potential. Environmental Research Letters 8, 015011. https://doi.org/10.1088/1748-9326/8/1/015011

Assessing land degradation status

Key indicators include:

• soil erosion prevalence
• root-depth restrictions
• impact on habitat

Infiltration capacity

Land cover & biodiversity

Key indicators include:

• vegetation structure (adapted from the Land Cover Classification System (LCCS))
• shrub and tree densities
• herbaceous cover ratings
• tree and shrub species abundance and diversity
• vegetation funcional traits

LDSF Rangeland Module

The LDSF is being applied in many contexts:

• Land degradation assessment and monitoring
• Planning and prioritization of land restoration interventions
• Tracking of key soil and land health indicators to assess the effectiveness of land restoration efforts
• Soil and biomass carbon assessment and monitoring (including inputs to VM0042)
• In studies of regenerative agriculture, including natural farming in India
• For national assessments and monitoring of rangeland health (Lesotho, Kenya, Uganda, Eswatini)
• To measure, report and verify progress against key indicators as part of investments to enhance the resilience of agricultural systems to climate change

Results

Vegetation structure

• Summary of vegetation structure types (classes) in the LDSF plots surveyed, including additional clusters.
• Cropland cluster was outside of the LWC boundary.

Unique species

Number of unique species recorded in the LDSF rangeland module on Lewa in October 2021

Note that the survey was conducted in the dry season, after a prolonged dry period. Hence, there are likely to be a number of species, particularly annual grasses, that were not captured.

• Perennial grass species by frequency of occurence
• Perennials and topographic sequence

• Forb species by frequency of occurence
• Forbs and topographic sequence

• Woody species (<1.5m) by frequency of occurence
• Woody species and topographic sequence

Species co-occurence

“Viable populations of species occur in a given place if three conditions are met: the environment at the place is suitable; the species is able to colonize it; co-occurrence is possible despite or because of interactions with other species.” ¹

• Understanding complex interactions between species is important for management
• In other words, a systems approach is needed

1. Araújo, M.B., Rozenfeld, A., Rahbek, C., Marquet, P.A., 2011. Using species co-occurrence networks to assess the impacts of climate change. Ecography 34, 897–908. https://doi.org/10.1111/j.1600-0587.2011.06919.x

Co-occurence with Cenchrus stramineus | Indigofera volkensii | Hibiscus flavifolius

Shrub species abundance

(woody species between 1.5 and 3m height)

• All plots
• Main Lewa only
• Ngare Ndare forest

Tree species abundance

(woody species between above 3m height)

• All plots
• Main Lewa only
• Ngare Ndare forest

Woody vegetation cover

Grassland cover

Soil health assessment and mapping

Soil property	Subsoil N = 148 (44%)1	Topsoil N = 185 (56%)1	p-value2
Soil organic carbon (SOC; g/kg)	16 (13, 19)	21 (17, 24)	<0.001
Soil pH	7.27 (6.73, 8.07)	6.71 (6.44, 7.39)	<0.001
Clay content (%)	71 (66, 74)	67 (62, 71)	<0.001
1 Median (IQR)
2 Wilcoxon rank sum test

Soil organic carbon (SOC) across vegetation structure types

Variations in SOC by soil types

To put SOC from Lewa into context…

Mapping SOC

Key messages

• Dry season sampling means there will be species that were not captured
• While there are some grass species that are dominant, they facilitate a range of other grasses, forbs and woody species
  • Important to consider this when managing these grasslands
  • Important implications for wildlife as well
• The LDSF is designed to provide an unbiased systematic aseessment of multiple indicators across a landscape
• Soil organic carbon (SOC) assessment shows a wide range across Lewa
• Lewa represents an important reference site/area for SOC in grasslands
  • Stocks of SOC will be further investigated

Thank you!

Contacts: t.vagen@cgiar.org

L.A.winowiecki@cgiar.org