Structural Complexity and Phenology

Usage Rights

This data is Free within projects.

Intellectual rights belong to the authors.The authors will freely share this data with all FunDiv members but would like to be contacted if other researchers would like to use this data or results in a subsequent analysis or publication

Dataset Abstract

The objective of this study was to use side-view digital photography to describe the structure and dynamics of natural forest stands in the context of the FunDiv Europe exploratory network. From April to December 2012, as well as April to December 2013 for some regions, time-series of digital images were recorded at each forest plot using commercially available digital camera units. Three regions of interest (ROI) representing the over-, mid- and under-storey layers of the forest plots were manually delineated for each image time-series. The image processing workflow produced a list of six key variables for each of the three ROIs though additional variables are also provided in this dataset. The six variables we suggest as key foci variables are: 1) Growing season length (days) from Green Cover, 2) Growing season onset from Green Cover (day of the year), 3) Growing season offset (day of the year) from Green Cover, 4) Mean Green Cover (%), 5) Mean ROI texture (Mean information gain; MIG), 6) Mean ROI anisotropy (MIG ratio).

Dataset Design

The sampling design follows that of the exploratory platform. Each plot from each region was sampled though some plots are missing from the dataset due to loss of equipment. "Sampling" means the acquisition of images. Specifically, time-series of digital images were recorded at each forest plot using commercially available digital camera units (PlantCam ™ timelapse camera, Model WSCA04-00106. Wingscapes, Alabaster, AL, USA), which capture repeat side-view digital images at a programmed time interval. Within 5 m from the southern side of each forest plot, one camera was installed on a large (DBH > 10cm) and visually healthy tree. The camera was installed at a height of 2m on the tree side and oriented towards the magnetic North. The camera was fastened to the tree securely and the view angle adjusted parallel to the ground slope. Each camera was programmed to record a single image every 3 hours during daylight (9 am to 5 pm). The sampling period started in early April and images were acquired until late November - December.

Spatial Extent

This dataset covers all exploratory regions with the exception of Romania which is excluded due to loss of equipment and data. Data for one to six plots are missing from each region due to loss of equipment and data. Locations include all plots for the exploratory regions of Finland, Germany, Poland, Spain and Italy.

Published

NA

Temporal Extent

This data is derived from image analysis applied to a time series of images collected during the 2012 and 2013 growing seasosn (approx. April - December depending on region). For the regions of Germany, Poland, Spain and Italy images were acquired during the 2012 growing season, while Finland images were acquired during the 2013 growing season. The German plots were also re-sampled (i.e., images acquired) during the 2013 growing season and, therefor, Germany has two time-series or phenologies (2012 & 2013 seasons). For each plot and each acquisition year, Three images were captured daily for the entire growing season/sampling period. However, the data here represents analysis performed on only images acquired at the 12:00 pm (site local time) acquisition interval. The analysis was performed January - May, 2014.

Measurement Circumstances

These data represent preliminary analysis. To date, no image correction or equalization was done across the image time-series. Images, and thus image metrics, can be influenced by light and weather conditions. These extternal influences particularly apply to the structural image metrics or variables. Image metrics based on greenness indices are less influenced by light conditions. Further analysis will explore image equalization techniques in an attempt to standardize image intensity across an image time-series. As mentioned some cameras were lost in certain plots and thus so too their image data. These plots are not included.

Data Analysis

Three regions of interest (ROI) representing the over-, mid- and under-storey layers of the forest plots were manually delineated for each image time-series. For each ROI in an image time-series, growing season onset (green-up) and offset (green-down) dates were estimated using two image greenness indices that we term "Percent Green" and "Green Cover" (Meyer and Neto, 2008; Sonnentag et al., 2012). The two greenness metrics are somewhat redundant though operate to estimate greenness in slightly different manners. For further details on differentiating the two greenness metrics please see the povided references or contact the data authors. We suggest any users of this data first use the "Green Cover" metric though one can use and compare both. For both greenness metrics, dates of maximum greenness increase (green onset dates) and decrease (green offset dates) were obtained from the 1st and 2nd derivatives of the smoothed greenness time-series (e.g., Noormets, 2009). In addition, the minimum value, maximum value, mean and standard deviation of greenness values for the time-series were also calculated. Furthermore, differences in structural heterogeneity of light interception/reflection patterns for the different forest strata were quantified in the over-, mid- and under-storey image ROIs. Structural heterogeneity metrics of texture and anisotropy were calculated on grey-tone transformed images following the method proposed by Proulx et al. (2014). For each plot, structural heterogeneity metrics were calculated for all images taken during each growing season (i.e., the plot time series; typically May 1 to October 31 though some chronologies extend longer) and subsequently the maximum, minimum, mean and standard deviation values were calculated.Thus, the image processing workflow produced a list of 22 variables for each of the 3 ROIs, for a total of 66 image-derived values per plot. However, for a given ROI we suggest 6 key variables of focus for those wanting to use this dataset: 1) Green Cover Growing season length (days), 2) Green Cover Growing season onset (day of the year), 3) Green Cover Growing season offset (day of the year), 4) Mean Green Cover (%), 5) Mean ROI Texture (Mean information gain; MIG), 6) Mean ROI Anisotropy (MIG ratio). Image-derived values could not be calculated for all forest plots in the FunDiv exploratory network since nearly all cameras were stolen in one bioclimatic region (Romania) and a few other cameras failed in the other regions. Finally, the growing season length, onset and offset dates could not be calculated for time-series that did not present a clear seasonal pattern (i.e., sharp green-up and green-down trends). This situation occurred in ~5% of the forest plots depending on the ROI.

Data columns available in the raw data part of this dataset

PlotID
Unique plot id
Data group: Exploratory plot id
Values
FIN01
FIN04
FIN02
FIN03
FIN05
Year
Year of data acquisition; e.g., 2012; Datagroup description: Year
Data group: Year
Values
2013
2012
OverstoryROISize
Size of the region of interest (ROI) for the overstory portion of the image (pixels)
Unit: pixels
Data group: Structural complexity
Values
1031277
1028718
1049190
1004696
1002132
UnderstoryROISize
Size of the region of interest (ROI) for the understory portion of the image (pixels)
Unit: pixels
Data group: Structural complexity
Values
1013838
1038700
1027169
1045288
1026610
MidstoryROISize
Size of the region of interest (ROI) for the midstory portion of the image (pixels)
Unit: pixels
Data group: Structural complexity
Values
1007954
1031016
1012608
1003168
1014288
OverstoryGreenCoverSeason
Overstory growing season length (days) with Green Cover
Unit: days
Data group: Structural complexity
Keywords: phenology, growing season, overstory
Values
101
105
107
100
102
OverstoryGreenCoverOnset
Overstory green onset date (day of the year) with Green Cover
Unit: day
Data group: Structural complexity
Keywords: phenology, growing season, overstory
Values
102
105
104
101
103
OverstoryGreenCoverOffset
Overstory green offset date (day of the year) with Green Cover
Unit: day
Data group: Structural complexity
Keywords: phenology, growing season, overstory
Values
185
181
168
177
179
OverstoryGreenCoverHigh
Overstory Green Cover maximum value in the time-series (% of green pixels)
Unit: % green pixels
Data group: Structural complexity
Keywords: phenology, overstory, greenness
Values
130
127
132
125
133
OverstoryGreenCoverLow
Overstory Green Cover minimum value in the time-series (% of green pixels)
Unit: % green pixels
Data group: Structural complexity
Keywords: phenology, overstory, greenness
Values
105
122
124
104
103
OverstoryGreenCover_AVG
Overstory mean Green Cover across time-series (% of green pixels)
Unit: % green pixels
Data group: Structural complexity
Keywords: phenology, overstory, greenness
Values
0.015195144
0.028551069
0.028382173
0.025160253
0.030657486
OverstoryGreenCover_STD
Overstory standard deviation in Green Cover across time-series (% of green pixels)
Unit: % green pixels
Data group: Structural complexity
Keywords: phenology, overstory, greenness
Values
0.016420037
0.005100072
0.012876891
0.009558066
0.011578596
OverstoryPrctGreenSeason
Overstory growing season length (days) with Percent Green
Unit: days
Data group: Structural complexity
Keywords: phenology, growing season, overstory
Values
104
100
102
105
106
OverstoryPrctGreenOnset
Overstory green onset date (day of the year) with Percent Green
Unit: day
Data group: Structural complexity
Keywords: phenology, growing season, overstory
Values
105
104
102
101
103
OverstoryPrctGreenOffset
Overstory green offset date (day of the year) with Percent Green
Unit: day
Data group: Structural complexity
Keywords: phenology, growing season, overstory
Values
176
194
185
193
153
OverstoryPrctGreenHigh
Overstory Percent Green maximum value in the time-series (% of green pixels)
Unit: % green pixels
Data group: Structural complexity
Keywords: phenology, overstory, greenness
Values
119
122
121
124
123
OverstoryPrctGreenLow
Overstory Percent Green minimum value in the time-series (% of green pixels)
Unit: % green pixels
Data group: Structural complexity
Keywords: phenology, overstory, greenness
Values
188
103
102
128
104
OverstoryPrctGreen_AVG
Overstory mean Percent Green across time-series (% of green pixels)
Unit: % green pixels
Data group: Structural complexity
Keywords: phenology, overstory, greenness
Values
0.324954431
0.320785138
0.323360988
0.320696197
0.309317117
OverstoryPrctGreen_STD
Overstory standard deviation in Percent Green across time-series (% of green pixels)
Unit: % green pixels
Data group: Structural complexity
Keywords: phenology, overstory, greenness
Values
0.002287532
0.001930718
0.001216288
0.001470808
0.002108462
OverstoryIntTextureHigh
Overstory texture maximum value in the time-series (Mean information gain; MIG)
Unit: MIG
Data group: Structural complexity
Keywords: phenology, overstory, texture
Values
117
116
111
114
118
OverstoryIntTextureLow
Overstory texture minimum value in the time-series (Mean information gain; MIG)
Unit: MIG
Data group: Structural complexity
Keywords: phenology, overstory, texture
Values
122
103
104
125
102
OverstoryIntTexture_AVG
Overstory mean of texture across time-series (Mean information gain of greyscale; MIG)
Unit: MIG
Data group: Structural complexity
Keywords: phenology, overstory, texture
Values
0.180186215
0.190474439
0.145154426
0.18903646
0.191814305
OverstoryIntTexture_STD
Overstory standard deviation of texture across time-series (Mean information gain of greyscale; MIG)
Unit: MIG
Data group: Structural complexity
Keywords: phenology, overstory, texture
Values
0.008975979
0.008508495
0.009225014
0.010539565
0.007800481
OverstoryIntAnisotropyHigh
Overstory anisotropy maximum value in the time-series (MIG ratio; unitless)
Unit: MIG
Data group: Structural complexity
Keywords: phenology, overstory, anisotropy
Values
118
119
117
120
116
OverstoryIntAnisotropyLow
Overstory anisotropy minimum value in the time-series (MIG ratio; unitless)
Unit: MIG
Data group: Structural complexity
Keywords: phenology, overstory, anisotropy
Values
104
125
126
102
103
OverstoryIntAnisotropy_AVG
Overstory mean of anisotropy across time-series (MIG ratio; unitless)
Unit: unitless
Data group: Structural complexity
Keywords: phenology, overstory, anisotropy
Values
0.777094124
0.835743589
0.827470582
0.814279518
0.784903296
OverstoryIntAnisotropy_STD
Overstory standard deviation of anisotropy across time-series (MIG ratio; unitless)
Unit: unitless
Data group: Structural complexity
Keywords: phenology, overstory, anisotropy
Values
0.004948965
0.003884244
0.003796777
0.007231308
0.007049452
UnderstoryGreenCoverSeason
Understory growing season length (days) with Green Cover
Unit: days
Data group: Structural complexity
Keywords: phenology, growing season, Understory
Values
101
102
103
108
104
UnderstoryGreenCoverOnset
Understory green onset date (day of the year) with Green Cover
Unit: day
Data group: Structural complexity
Keywords: phenology, growing season, Understory
Values
101
104
102
103
100
UnderstoryGreenCoverOffset
Understory green offset date (day of the year) with Green Cover
Unit: day
Data group: Structural complexity
Keywords: phenology, growing season, Understory
Values
141
152
145
150
126
UnderstoryGreenCoverHigh
Understory Green Cover maximum value in the time-series (% of green pixels)
Unit: % green pixels
Data group: Structural complexity
Keywords: phenology, Understory, greenness
Values
130
128
127
125
129
UnderstoryGreenCoverLow
Understory Green Cover minimum value in the time-series (% of green pixels)
Unit: % green pixels
Data group: Structural complexity
Keywords: phenology, Understory, greenness
Values
128
127
126
103
125
UnderstoryGreenCover_AVG
Understory mean Green Cover across time-series (% of green pixels)
Unit: % green pixels
Data group: Structural complexity
Keywords: phenology, Understory, greenness
Values
0.008732192
0.005573043
0.004664399
0.010982035
0.009661242
UnderstoryGreenCover_STD
Understory standard deviation in Green Cover across time-series (% of green pixels)
Unit: % green pixels
Data group: Structural complexity
Keywords: phenology, Understory, greenness
Values
0.003215055
0.00547571
0.009317323
0.004432379
0.004007118
UnderstoryPrctGreenSeason
Understory growing season length (days) with Percent Green
Unit: days
Data group: Structural complexity
Keywords: phenology, growing season, Understory
Values
101
103
102
107
105
UnderstoryPrctGreenOnset
Understory green onset date (day of the year) with Percent Green
Unit: day
Data group: Structural complexity
Keywords: phenology, growing season, Understory
Values
105
103
101
102
104
UnderstoryPrctGreenOffset
Understory green offset date (day of the year) with Percent Green
Unit: day
Data group: Structural complexity
Keywords: phenology, growing season, Understory
Values
154
160
159
157
161
UnderstoryPrctGreenHigh
Understory Percent Green maximum value in the time-series (% of green pixels)
Unit: % green pixels
Data group: Structural complexity
Keywords: phenology, Understory, greenness
Values
124
116
127
122
126
UnderstoryPrctGreenLow
Understory Percent Green minimum value in the time-series (% of green pixels)
Unit: % green pixels
Data group: Structural complexity
Keywords: phenology, Understory, greenness
Values
125
116
103
126
127
UnderstoryPrctGreen_AVG
Understory mean Percent Green across time-series (% of green pixels)
Unit: % green pixels
Data group: Structural complexity
Keywords: phenology, Understory, greenness
Values
0.282627154
0.27370148
0.291975091
0.248017399
0.175610912
UnderstoryPrctGreen_STD
Understory standard deviation in Percent Green across time-series (% of green pixels)
Unit: % green pixels
Data group: Structural complexity
Keywords: phenology, Understory, greenness
Values
0.003952958
0.004537297
0.002949336
0.003741938
0.004294015
UnderstoryIntTextureHigh
Understory texture maximum value in the time-series (Mean information gain; MIG)
Unit: MIG
Data group: Structural complexity
Keywords: phenology, Understory, texture
Values
110
104
109
107
111
UnderstoryIntTextureLow
Understory texture minimum value in the time-series (Mean information gain; MIG)
Unit: MIG
Data group: Structural complexity
Keywords: phenology, Understory, texture
Values
130
119
128
129
124
UnderstoryIntTexture_AVG
Understory mean of texture across time-series (Mean information gain of greyscale; MIG)
Unit: MIG
Data group: Structural complexity
Keywords: phenology, Understory, texture
Values
0.141674207
0.166431233
0.170094781
0.172741861
0.175308262
UnderstoryIntTexture_STD
Understory standard deviation of texture across time-series (Mean information gain of greyscale; MIG)
Unit: MIG
Data group: Structural complexity
Keywords: phenology, Understory, texture
Values
0.007016671
0.009225014
0.008189648
0.008424295
0.00915902
UnderstoryIntAnisotropyHigh
Understory anisotropy maximum value in the time-series (MIG ratio; unitless)
Unit: MIG
Data group: Structural complexity
Keywords: phenology, Understory, anisotropy
Values
114
111
115
113
112
UnderstoryIntAnisotropyLow
Understory anisotropy minimum value in the time-series (MIG ratio; unitless)
Unit: MIG
Data group: Structural complexity
Keywords: phenology, Understory, anisotropy
Values
103
112
105
127
102
UnderstoryIntAnisotropy_AVG
Understory mean of anisotropy across time-series (MIG ratio; unitless)
Unit: unitless
Data group: Structural complexity
Keywords: phenology, Understory, anisotropy
Values
0.844797248
0.78597791
0.864253
0.852215028
0.89698049
UnderstoryIntAnisotropy_STD
Understory standard deviation of anisotropy across time-series (MIG ratio; unitless)
Unit: unitless
Data group: Structural complexity
Keywords: phenology, Understory, anisotropy
Values
0.008237707
0.00522892
0.009270104
0.009627778
0.006260784
MidstoryGreenCoverSeason
Midstory growing season length (days) with Green Cover
Unit: days
Data group: Structural complexity
Keywords: phenology, growing season, Midstory
Values
108
102
105
107
101
MidstoryGreenCoverOnset
Midstory green onset date (day of the year) with Green Cover
Unit: day
Data group: Structural complexity
Keywords: phenology, growing season, Midstory
Values
105
103
101
102
104
MidstoryGreenCoverOffset
Midstory green offset date (day of the year) with Green Cover
Unit: day
Data group: Structural complexity
Keywords: phenology, growing season, Midstory
Values
169
174
165
164
126
MidstoryGreenCoverHigh
Midstory Green Cover maximum value in the time-series (% of green pixels)
Unit: % green pixels
Data group: Structural complexity
Keywords: phenology, Midstory, greenness
Values
134
133
132
124
131
MidstoryGreenCoverLow
Midstory Green Cover minimum value in the time-series (% of green pixels)
Unit: % green pixels
Data group: Structural complexity
Keywords: phenology, Midstory, greenness
Values
102
165
128
103
105
MidstoryGreenCover_AVG
Midstory mean Green Cover across time-series (% of green pixels)
Unit: % green pixels
Data group: Structural complexity
Keywords: phenology, Midstory, greenness
Values
0.040389407
0.019263595
0.036772136
0.038008049
0.01397647
MidstoryGreenCover_STD
Midstory standard deviation in Green Cover across time-series (% of green pixels)
Unit: % green pixels
Data group: Structural complexity
Keywords: phenology, Midstory, greenness
Values
0.015801525
0.014898988
0.009278557
0.016355177
0.015296274
MidstoryPrctGreenSeason
Midstory growing season length (days) with Percent Green
Unit: days
Data group: Structural complexity
Keywords: phenology, growing season, Midstory
Values
103
104
101
102
105
MidstoryPrctGreenOnset
Midstory green onset date (day of the year) with Percent Green
Unit: day
Data group: Structural complexity
Keywords: phenology, growing season, Midstory
Values
103
104
101
102
105
MidstoryPrctGreenOffset
Midstory green offset date (day of the year) with Percent Green
Unit: day
Data group: Structural complexity
Keywords: phenology, growing season, Midstory
Values
176
173
172
174
183
MidstoryPrctGreenHigh
Midstory Percent Green maximum value in the time-series (% of green pixels)
Unit: % green pixels
Data group: Structural complexity
Keywords: phenology, Midstory, greenness
Values
119
113
122
121
117
MidstoryPrctGreenLow
Midstory Percent Green minimum value in the time-series (% of green pixels)
Unit: % green pixels
Data group: Structural complexity
Keywords: phenology, Midstory, greenness
Values
104
126
125
127
103
MidstoryPrctGreen_AVG
Midstory mean Percent Green across time-series (% of green pixels)
Unit: % green pixels
Data group: Structural complexity
Keywords: phenology, Midstory, greenness
Values
0.290403055
0.309897193
0.29647768
0.303930257
0.312865746
MidstoryPrctGreen_STD
Midstory standard deviation in Percent Green across time-series (% of green pixels)
Unit: % green pixels
Data group: Structural complexity
Keywords: phenology, Midstory, greenness
Values
0.003871909
0.003065859
0.002736857
0.002815088
0.004078336
MidstoryIntTextureHigh
Midstory texture maximum value in the time-series (Mean information gain; MIG)
Unit: MIG
Data group: Structural complexity
Keywords: phenology, Midstory, texture
Values
115
116
118
117
107
MidstoryIntTextureLow
Midstory texture minimum value in the time-series (Mean information gain; MIG)
Unit: MIG
Data group: Structural complexity
Keywords: phenology, Midstory, texture
Values
103
160
148
102
127
MidstoryIntTexture_AVG
Midstory mean of texture across time-series (Mean information gain of greyscale; MIG)
Unit: MIG
Data group: Structural complexity
Keywords: phenology, Midstory, texture
Values
0.184641806
0.140842051
0.187737493
0.175503337
0.181803669
MidstoryIntTexture_STD
Midstory standard deviation of texture across time-series (Mean information gain of greyscale; MIG)
Unit: MIG
Data group: Structural complexity
Keywords: phenology, Midstory, texture
Values
0.008751465
0.006259217
0.008347062
0.00778399
0.005907508
MidstoryIntAnisotropyHigh
Midstory anisotropy maximum value in the time-series (MIG ratio; unitless)
Unit: MIG
Data group: Structural complexity
Keywords: phenology, Midstory, anisotropy
Values
116
112
115
111
113
MidstoryIntAnisotropyLow
Midstory anisotropy minimum value in the time-series (MIG ratio; unitless)
Unit: MIG
Data group: Structural complexity
Keywords: phenology, Midstory, anisotropy
Values
152
128
153
102
101
MidstoryIntAnisotropy_AVG
Midstory mean of anisotropy across time-series (MIG ratio; unitless)
Unit: unitless
Data group: Structural complexity
Keywords: phenology, Midstory, anisotropy
Values
0.795957338
0.794275452
0.791027495
0.787718874
0.747218691
MidstoryIntAnisotropy_STD
Midstory standard deviation of anisotropy across time-series (MIG ratio; unitless)
Unit: unitless
Data group: Structural complexity
Keywords: phenology, Midstory, anisotropy
Values
0.004880869
0.009750512
0.006022207
0.009674937
0.010316085