Historical Disturbance Trends: Round 2 Results

AKA I forgot to actually store the masked raster for the first round and now everything is different! Also age group statistics!
Author

Madeleine Desrochers

Published

June 8, 2023

What’s Changed Since Last Time?

Unfortunately quite a bit. In the intial round of results I was accidentally (and incorrectly) using an unmasked raster, so instead of looking at just ADK FP land we were looking at trends for the entire ADK park. Oops.

Included in this post:

  • Results for the entire ADK FP (correctly masked)

  • Results for Age Group Divisions

Forest Preserve Wide Man Kendall Test Results for Patch Metrics

Metric Man Kendall Statistic Normalized Test Statistic p Value Trend Sens Slope
area -0.2097 -1.6703 0.0949 no trend -0.0028
cai 0.0121 0.0811 0.9354 no trend 0.0003
circle 0.0121 0.0811 0.9354 no trend 0.0003
contig 0.0121 0.0811 0.9354 no trend 0.0003
core -0.1089 -0.8595 0.3901 no trend -0.0003
enn 0.3710 2.9676 0.0030 increasing 2.0227
frac -0.2621 -2.0919 0.0364 decreasing -0.0004
gyrate -0.2097 -1.6703 0.0949 no trend -0.0939
ncore -0.1331 -1.0541 0.2919 no trend -0.0008
para -0.1452 -1.1514 0.2496 no trend 0.0000
perim -0.2258 -1.8000 0.0719 no trend -2.2405
shape -0.2540 -2.0271 0.0427 decreasing -0.0033
mean_mag 0.3266 2.6108 0.0090 increasing 0.8946
percent_area_dist -0.2621 -2.0919 0.0364 decreasing -0.0074

Metric Plots

All patch metrics derived from the landscape metrics package in r. Descriptions of the patch metrics can be found here.

Average disturbance patch size annually from 1990 - 2021.

Average core area index for disturbance patches from 1990 - 2021

Average size of smallest circumscribing circle for disturbance patches 1990 -2021

Average contiguity index for disturbance patches 1990 - 2021

Average size of patch core area from 1990 - 2021

Average distance to closest neighboring patch annually from 1990 - 2021

Average fractal dimension index from 1990 - 2021

Average radius of gyration for disturbance patches from 1990 - 2021

Average number of core areas in one disturbance patch from 1990 - 2021

Average perimeter to area ratio for disturbance patches 1990 - 2021

Average length of disturbance patch perimeter from 1990 - 2021

Average shape index for disturbance patches 1990 - 2021

Average disturbance magnitude of disturbance 1990 - 2021

Percentage of forest preserve land disturbed annually from 1990 - 2021

Man Kendall Test Results Split by Age Group

Forest preserve properties purchased prior to 1990 were split into 4 groups based on the time since acquistion by the state of New York. Only Forest Preserve parcels with known dates of acquisition were used for this analysis. Additionally, only parcels acquired before 1990 were used so that there were no parcels acquired mid analysis (n = 1364, N = 1950)(462,530 ha of 1,000,000 ha). Age groups were created by assigning roughly equal areas of forest preserve to each bin (~115,000 ha per group).

Group 1: Aquistion prior to 1896

Metric Man Kendall Statistic Normalized Test Statistic p Value Trend Sens Slope
area -102 -1.6379 0.1015 no trend -0.0044
cai -22 -0.3405 0.7334 no trend -0.0021
circle -22 -0.3405 0.7334 no trend -0.0021
contig -22 -0.3405 0.7334 no trend -0.0021
core -80 -1.2811 0.2002 no trend -0.0005
enn 164 2.6433 0.0082 increasing 1.9545
frac -162 -2.6108 0.0090 decreasing -0.0005
gyrate -102 -1.6379 0.1015 no trend -0.1355
ncore -96 -1.5406 0.1234 no trend -0.0015
para -20 -0.3081 0.7580 no trend 0.0000
perim -130 -2.0919 0.0364 decreasing -3.4341
shape -154 -2.4811 0.0131 decreasing -0.0044
mean_mag 166 2.6757 0.0075 increasing 0.9389
percent_area_dist -130 -2.0919 0.0364 decreasing -0.0081

Group 2: Acquisition between 1897 and 1909

Metric Man Kendall Statistic Normalized Test Statistic p Value Trend Sens Slope
area -112 -1.8000 0.0719 no trend -0.0038
cai -14 -0.2108 0.8330 no trend -0.0020
circle -14 -0.2108 0.8330 no trend -0.0020
contig -14 -0.2108 0.8330 no trend -0.0020
core -30 -0.4703 0.6382 no trend -0.0002
enn 168 2.7081 0.0068 increasing 2.2534
frac -144 -2.3190 0.0204 decreasing -0.0004
gyrate -122 -1.9622 0.0497 decreasing -0.1423
ncore -48 -0.7622 0.4460 no trend -0.0007
para 6 0.0811 0.9354 no trend 0.0000
perim -136 -2.1892 0.0286 decreasing -2.9795
shape -138 -2.2217 0.0263 decreasing -0.0040
mean_mag 180 2.9027 0.0037 increasing 0.9451
percent_area_dist -116 -1.8649 0.0622 no trend -0.0054

Group 3: Acquisition between 1910 and 1957

Metric Man Kendall Statistic Normalized Test Statistic p Value Trend Sens Slope
area -92 -1.4757 0.1400 no trend -0.0039
cai -74 -1.1838 0.2365 no trend -0.0117
circle -74 -1.1838 0.2365 no trend -0.0117
contig -74 -1.1838 0.2365 no trend -0.0117
core -72 -1.1514 0.2496 no trend -0.0004
enn 128 2.0595 0.0394 increasing 1.5077
frac -102 -1.6379 0.1015 no trend -0.0002
gyrate -88 -1.4108 0.1583 no trend -0.0928
ncore -90 -1.4433 0.1489 no trend -0.0018
para 56 0.8919 0.3724 no trend 0.0000
perim -96 -1.5406 0.1234 no trend -2.2978
shape -94 -1.5081 0.1315 no trend -0.0024
mean_mag 92 1.4757 0.1400 no trend 0.5244
percent_area_dist -104 -1.6703 0.0949 no trend -0.0052

Group 4: Acquisition between 1958 and 1990

Metric Man Kendall Statistic Normalized Test Statistic p Value Trend Sens Slope
area -72 -1.1514 0.2496 no trend -0.0025
cai 44 0.6973 0.4856 no trend 0.0055
circle 44 0.6973 0.4856 no trend 0.0055
contig 44 0.6973 0.4856 no trend 0.0055
core -42 -0.6649 0.5061 no trend -0.0002
enn 174 2.8054 0.0050 increasing 2.2327
frac -126 -2.0271 0.0427 decreasing -0.0003
gyrate -84 -1.3460 0.1783 no trend -0.0717
ncore -35 -0.5514 0.5813 no trend -0.0004
para -76 -1.2162 0.2239 no trend -0.0001
perim -94 -1.5081 0.1315 no trend -2.1034
shape -130 -2.0919 0.0364 decreasing -0.0030
mean_mag 168 2.7081 0.0068 increasing 1.0427
percent_area_dist -130 -2.0919 0.0364 decreasing -0.0054

Metric Plots

Average Disturbance Area by Acquisition Age Group. No trends in any group.

Average Distance to the Closest Disturbance by Acquisition Age Group. Increasing trends in all groups.

Average Fractal Dimension Index by Acquisition Age Group. Decreasing trends for groups 1, 2 and 4. No trend in group 3.

Average Shape Index by Acquisition Age Group. Decreasing trends for groups 1, 2 and 4. No trend in group 3.

Average Perimieter Length by Aquisition Age Group. Decreasing trends for groups 1 and 2. No trends in groups 3 and 4.

Average Disturbance Magnitude by Acquisition Age Group. Increasing trends for groups 1, 2 and 4. No trend in group 3.

Percentage of Forest Preserve Land Disturbed Annually by Acquisition Age Group. Decreasing trends for groups 1 and 4. No trends in group 2 and 3.