Perennials
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Increase vegetation cover
Data collection in progress
Kakheti Steppes
Georgia
Problem: Combined pressures in this landscape such as overgrazing, increasing temperatures and less rainfall leading to erosion and desertification, are contributing to fewer and smaller perennial grassland plant species and lower biomass.
Action: SABUKO is working with farmers and shepherds to implement rotational grazing schemes which mean that grasslands are left ungrazed for longer periods, allowing more regeneration by perennial plant species.
Indicator: The quality of a grassland can be described partly by how vigorously its plant species grow, or how much vegetation cover can be observed. Increasing coverage of perennials will indicate a reversal of the negative trends that are symptomatic of overgrazing.
Methods
Figure 1: Map showing the spatial distribution of permanent monitoring plots (with radius of 200m) throughout the Kakheti Steppes study area.
Each plot has a 200 m radius. Within each plot, three sub-plots of 10 x 10 m were randomly selected for vegetation sampling, which occurred from April to June 2023 (following altitudinal gradients). Within each sub-plot, the presence and percent coverage of each species observed was recorded, using methods to analyse plant communities and the co-occurrence of particular species, as well as how they relate to environmental factors (together termed ‘phytosociology’). The percent cover for the most abundant and common perennial species were used for further analysis.
Drones were also flown over each plot, equipped with a multi-spectral camera, in October 2023. This was timed before the rainy season began, which would stimulate more vegetation growth and introduce noise into the dataset. The photographs captured plots at a resolution of 10cm per pixel, enabling the scaling-up of sub-plot monitoring (where each species is known) to the plot-level, which would be too time-intensive to be done manually, as in the sub-plots. Drone imagery was analysed by computing optimized Soil Adjusted Vegetation Index (SAVI) values, used to estimate vegetation cover.
In addition, in October 2023, the Leaf Area Index (LAI – which quantifies total leaf area relative to the ground surface) was measured using the LAI-2200C Plant Canopy Analyzer across the 52 macro plots in Chachuna, Samukhi, and Vashlovani. Measurements were taken before the rainy season to avoid vegetation growth affecting the results. In each 10 x 10m subplot, random sampling points were established, and scattering corrections were applied during cloudy conditions. These measurements will help quantify the biomass production and grazing pressure by comparing pre- and post-grazing season data.
Results
Baseline data has been collected across all 52 plots, across three sites and differing habitats. The tabs below (Figs 3 and 4) show the percentage cover of all vegetation (Fig. 3) and of perennials only (Fig. 4), revealing differences in coverage between habitat types and sites. Vashlovani has been a protected area for longer, hence why it has more overall vegetation cover, but all the sites have a similar baseline number of perennials.
The SAVI and LAI values tell a similar story as overall vegetation cover (see Fig. 5, showing SAVI values), with greater cover in Vashlovani compared to Chachuna and Samukhi. This indicates that drone surveys may be a useful way of surveying vegetation at larger scales. SABUKO will revisit these plots in future years to see how these values change over time, as farmers continue to employ sustainable grazing practices.
Figure 3: Boxplot showing percentage cover of all vegetation (sampling size for each stratum: n = 4 subplots).
Figure 3: Boxplot showing percentage cover of perennial vegetation (sampling size for each stratum: n = 4 subplots).
Figure 3: Boxplot showing SAVI values from Sentinel 2 imagery (sampling size for each stratum: n = 4 subplots).
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