Results 1: Standard indices
Bare soil
Perennial grasses
Annual grasses
Canopy
Fragmentation
Patch shape
Pattern
| The results of this spatial analysis show that the site closest to the watering hole (KS1) has 48% of its total area covered with bare soil, compared with about 2% in the site that is furthest away from the watering hole (KS5). If bare soil is indicative of heavy grazing and a landscape that is stressed and unable to retain water and nutrients and therefore prone to erosion, then the impacts of grazing regimes close to watering points are quite obvious. |
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Similarly, in the site KS1 about 30% of the area is covered with perennial grasses compared with about 72% perennials in the site KS5. Perennials are more indicative of a healthy, less disturbed rangeland landscape because of their ability to capture and store water and nutrients.
In the site KS1, 19% of the site is covered in annuals compared with only 11% in the site KS5. The higher presence of annuals in KS1 is probably associated with the disturbance that goes with intensive grassing and trampling.
Also site KS5 has about 10% of its area covered in canopy compared with only about 2% in site KS1. This suggests that the site furthest away from the watering point is less disturbed by grazing than the one closest to the watering point, which is what one would expect. This means that the functioning of KS5 is probably more conducive to a healthy landscape which is able to maintain water and nutrients in the system.
The mean nearest neighbour index is a measure of patch isolation and therefore gives some indication of how fragmented the landscape patches are. The nearest neighbour distance of an individual patch is the shortest distance to a similar patch. Therefore, the mean nearest neighbour distance is the average of these distances for individual classes at the class level (Elkie et al., 1999).
The results show that:
- for KS1, average distance between patches of perennial grass are further apart than for site KS5
- patches of annuals are closer in KS1 than in KS5
- patches of bare ground are closer in KS1 than in KS5
This indicates, once more, that the landscape at site KS1 is more disturbed by grazing than site KS5, and that patches of perennials which are important for retaining water and nutrients in the landscape system, as well as providing habitat for native species, are more fragmented in site KS1.
Since the indices in Patch Analyst which measure fractal dimension and patch shape show little difference between the two sites at the class level, we can assume that at this level the actual shapes of patches vary little between the two sites.
At this level of analysis, grazing is affecting the spatial patterning or positioning of patches in this rangeland landscape, but the actual shape of these patches does not seem to be affected by intensity of grassing to the same degree.
At the landscape level, the average weighted mean shape index shows a much higher value (31.74) at site KS5 compared with that for site KS1 (18.08) which suggests that the landscape at site KS5 is more complex.
Shannon's Evenness index shows that the landscape at site KS1 has a pattern that is more evenly distributed (a value of 0.71) than the landscape at site KS5 (0.59). These results suggest that the landscape at site KS5 is more diverse than that at KS1.
Diversity is often related to healthiness, so the landscape furthest away from the watering hole is probably less disturbed, and more natural. Therefore one would expect the processes operating within it to be more stable, and for the landscape to be in a healthier state.
