The Height And Diameter At Breast Height Essays

785 Words Aug 24th, 2016 4 Pages
My purpose is to see if there is any relationship between the height and diameter at breast height (DBH) in podocarp trees. My response variable is the DBH and my explanatory variable is height. All of my data comes from a random sample collected from the Waitutu Forest during 2001-2008.

By looking at this graph, I can see that there appears to be a clear linear trend with a positive relationship. Therefore, it would be sensible to use a linear regression model to investigate the relationship. This shows that as the height of the saplings increases, so does the diameter of the saplings at breast height. The rate of increase is not consistent, and the spread of the data increases as the podocarp height does.

An interesting point to note is that according to the Te Papa Museum, deer in lowland areas tend to eat any shrubs, trees and bark they can reach - up to a height of 3 metres. Looking at this model, I can see that there much less spread in the DBH values of podocarps under 3 metres tall. This may be because of deer, but I think that it is unlikely. It is more likely that the greater spread in data as the height increases is due to different rates of growing in different podocarp sapling species (eg rimu, miro, totara)

With the regression line, I can see that for every cm increase in height, there is a tendency for the the DBH to increase by 0.070203cm. This reinforces the linear trend and positive relationship between the height of a podocarp sapling and its DBH in…

Related Documents