Question

many efforts to control the spreading wilding pines have been tried with varying degrees of success. these include the use of poisonous herbicides, cutting individual scattered trees or large areas of the trees. recently, a study was conducted to determine if grazing animals could be used to destroy wilding pine seedlings. sheep, a common farm animal in new zealand, were placed in several enclosures containing newly planted wilding pine seedlings. the numbers of sheep in each enclosure varied from normal herd size (1x), up to eight times (8x) that number of sheep. this was the \stocking rate\ for each enclosure. conditions such as number of seedlings and enclosure size were proportionally adjusted to prevent overcrowding. the results of the study are summarized in the graphs below. effects of sheep - stocking rate on wilding pine seedling height and survival 21. use data from one or both graphs to describe the effect of the stocking rate of sheep on seedlings of these wilding pines. 22. explain how the introduction of the wilding pine trees has had both positive and negative effects in new zealand.

Explanation:

For question 21, from the first graph, as the stocking - rate of sheep increases from 1x to 8x, the relative reduction in height of wilding pine seedlings increases. From the second graph, as the stocking - rate increases from 1x to 8x, the probability of survival of wilding pine seedlings decreases.
For question 22, positive effects could include providing habitat for some species, timber resources in the long - term. Negative effects might be outcompeting native plants for resources, altering the local ecosystem balance.

Answer:

1. As the stocking rate of sheep increases, the relative reduction in wilding pine seedling height increases and the probability of seedling survival decreases.
2. Positive: Habitat provision, potential timber resources. Negative: Outcompeting native plants, disrupting ecosystem balance.