A group of students investigated the effect of trampling on plant species in a park. They placed quadrats along a transect from a footpath into the surround...

(a) Percentage cover of grass species at 4 m from the footpath [1]

Approximately 50% (accept 48-52%). [1]

This value is read from the graph (Fig. 1.8) by finding 4 m on the x-axis and reading across to the solid line for grass species, then down to the y-axis.

(b) Trend in grass species cover with increasing distance [3]

1. The percentage cover of grass species increases as distance from the footpath increases. [1]
2. Cover rises from approximately 5% at 0 m (on the footpath) to about 90% at 10 m from the footpath. [1]
3. The rate of increase is steepest between 2 m and 6 m, after which the curve begins to level off, suggesting that beyond about 8 m the effect of trampling is negligible. [1]

(c) Comparison of trampling effects on grass species and wildflowers [3]

1. Both grass species and wildflowers show lower percentage cover near the footpath and higher cover further away, indicating that trampling reduces the abundance of both groups. [1]
2. Grass species show a greater overall range of increase (from about 5% to about 90%) compared to wildflowers (from about 2% to about 50%), meaning grasses recover more than wildflowers. [1]
3. Grass species reach a higher maximum percentage cover than wildflowers at all distances, suggesting that grasses are the dominant plant group in undisturbed areas and are better able to recolonise disturbed ground. [1]

(d) Why trampling reduces plant cover near the footpath [4]

1. Trampling compresses and compacts the soil, reducing air spaces between soil particles and making it harder for roots to penetrate and grow. [1]
2. The physical impact of feet on vegetation breaks stems and leaves, killing or stunting plant growth directly. [1]
3. Compacted soil has reduced water infiltration because the smaller pore spaces prevent rainwater from soaking in. Less water is therefore available for plant uptake. [1]
4. Repeated trampling prevents seedlings from germinating and establishing, reducing the ability of plant populations to regenerate and maintain their cover. [1]