Chapter 4 : Temporal Changes in the Vertical and Horizontal Connectivity of an Urban Tree Infrastructure
4.2 Methods
4.3.5 Temporal change in connectivity
The connectivity results of the NBH canopies for the four tree canopy sample plots were compared over three points in time (See Appendix C) for raw results). The temporal change in connectivity for the canopy ≥3m canopy can be viewed in Figure 4-24, the canopy ≥7.2m canopy in Figure 4-25, and the canopy ≥17.1m in Figure 4-26.
For the canopy ≥3m, connectivity reached its peak in 2009 in all tree canopy sample plots (Figure 4-24
)
. In the Lower Kersal and Peel Park sample plots, the canopy ≥3m was leastconnected in 2005. Therefore, connectivity increased from 2005 to 2009 and then decreased again in 2013 but not so much as to be lower in connectivity than 2005. Specifically, in Lower
Kersal, the canopy ≥3m connectivity increased by between 286% (200m gap-crossing capability threshold) and 323% (30m gap-crossing capability threshold) in 2009 and then decreased by
between 6% (2000m) and 9% (30m) in 2013. The canopy ≥3m connectivity results for Peel Park
followed the same pattern, with a less severe increase in connectivity in 2009 (between 70% at 200m and 168% at 30m) but a greater decrease in 2013 (between 8% at 200m and 22% at
30m). The canopy ≥3m canopy in the Higher Broughton and Kersal sample plots were both least connected in 2013 – meaning there was an increase in connectivity from 2005 to 2009 and
then an even greater decrease in 2013. In regards to Higher Broughton, canopy ≥3m canopy connectivity increased from 2005 to 2009 by between 7% (200m) and 20% (30m) and then decreased from 2009 to 2013 by between 19% (220m) and 33% (30m). Kersal’s canopy ≥3m
canopy increased in connectivity from 2005 to 2009 by between 40% (200m) and 62% (30m) and then greatly decreased from 2009 to 2013 by between 60% (200m) and 80% (30m) (Figure 4-24).
The canopy ≥7.2m canopy was most connected in 2009 for all tree canopy sample plots except for Higher Broughton which was at its most connected in 2013 (Figure 4-25). However, there wasn’t much difference between the 2009 and 2013 canopy ≥7.2m canopy IIC values in
Higher Broughton and an inverse relationship was also evident in Peel Park where the 2009
canopy ≥7.2m IIC scores were only very slightly more than the 2013 results. In the Higher
connected in 2005. Therefore, in Higher Broughton connectivity increased from 2005 to 2009 by between 30% (200m) and 40% (30m) and then increased again from 2009 to 2013 by between 0.2% (200m) and 15% (30m). In Lower Kersal, canopy ≥7.2m connectivity increased
from 2005 to 2009 by between 131% (30m) and 142% (200m) and then decreased from 2009 to
2013 by between 34% (200m) and 44% (30m). In Peel Park, canopy ≥7.2m connectivity
increased by between 62% (200m) and 132% (30m) in 2009 and then decreased by between 1% (200m) and 3% (30m) in 2013. Kersal was the only tree canopy sample plot where the canopy
≥7.2m was least connected in 2013. Therefore, connectivity increased from 2005 to 2009 by
between 30% (200m) and 53% (30m) before following a decrease in connectivity from 2009 to 2013 of between 55% (200m) and 73% (30m)(Figure 4-25).
Unlike the other two NBH canopies, the connectivity of the canopy ≥17.1m was at its
highest in 2013 for all tree canopy sample plots except Kersal, which was at its highest in 2005 (Figure 4-26). In the higher Broughton, Lower Kersal, and Peel Park sample plots the
connectivity of the canopy ≥17.1m was at its lowest in 2005. An inverse relationship was observed in Kersal, as the lowest IIC scores for the canopy ≥17.1m were calculated for 2013.
More specifically, in the Higher Broughton sample plot canopy ≥17.1m connectivity increased by between 67% (30m) and 100% (200m) in 2009 and then increased again by between 280% (30m) and 513% (200m) in 2013. In the Lower Kersal sample plot there was no canopy ≥17.1m
in 2005, therefore connectivity only increased from 2009 to 2013 by 650% (however IIC values were still extremely low). In the Peel Park sample plot canopy ≥17.1m connectivity increased
from 2005 to 2009 by between 3% (30m) and 9% (200m) and then increased again in 2013 by between 162% (200m) and 264% (30m). Finally, the canopy ≥17.1m of the Kersal sample plot reached its connectivity peak in 2005 and its trough in 2013. Explicitly, the Kersal sample plots’
canopy ≥17.1m IIC values decreased by between 30% (200m) and 56% (30m) in 2009 and then
decreased again by between 46% (200m) and 53% (30m) in 2013 (the only canopy and survey area to follow such a pattern) (Figure 4-26).
Figure 4-24: Temporal change in the connectivity (IIC) of the tree canopy sample plot’s canopy ≥3m.
The canopy ≥3m for all tree canopy sample plots were most connected in 2009. The canopy ≥3m of the Kersal and Higher Broughton sample plots were least connected in 2013. Conversely, the Peel Park and Lower Kersal sample plots exhibited their least connected canopy ≥3m in 2005.
Figure 4-25: Temporal change in the connectivity (IIC) of the tree canopy sample plot’s canopy ≥7.2m.
The canopy ≥7.2m was most connected in 2013 for the Higher Broughton sample plot (by a few percent). The Lower Kersal, Peel Park, and Kersal sample plots exhibited their most connected canopy ≥7.2m in 2009. The canopy ≥7.2m was least connected in 2005 within the Higher Broughton, Lower Kersal, and Peel
Figure 4-26: Temporal change in the connectivity (IIC) of the tree canopy sample plot’s canopy ≥17.1m.
The canopy ≥17.1m was connected most in 2013 for all the tree canopy sample plots except the Kersal sample plot. For the higher Broughton, Lower Kersal, and Peel Park sample plots the canopy ≥17.1m was least connected in 2005 (non-existent within the Lower Kersal sample plot in 2005). For the Kersal sample plot the canopy ≥17.1m followed a unique pattern of continual reduction in connectivity from 2005 to 2013. 114