# Checking the Consistency of Volunteered Phenological Observations While Analysing Their Synchrony

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## Abstract

**:**

## 1. Introduction

#### 1.1. VGI Attribute Consistency

#### 1.2. Synchrony of Phenological VGI

## 2. Materials and Methods

#### 2.1. VPOs and Temperature Datasets

#### 2.2. Analysing Consistency and Synchrony of VPOs

## 3. Results

## 4. Discussion

## 5. Conclusions

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

## Appendix A

**Figure A1.**Annual graphs for wood anemone flowering onset observations. The graphs were made using a Delaunay triangulation and edges longer than 100 km were pruned.

**Figure A2.**Annual graphs for cow parsley flowering onset observations. The graphs were made using a Delaunay triangulation and edges longer than 100 km were pruned.

**Figure A3.**Annual graphs for pedunculate oak flowering onset observations. The graphs were made using a Delaunay triangulation and edges longer than 100 km were pruned.

**Figure A4.**Linear regression fit between the difference in observed flowering DOY (number of days) and the difference in modelled GDD (number of degree days) for pairs of spatially connected observations of wood anemone flowering onset (see Figure A1). Correlation coefficient and rate of spatial change in DOY per unit of GDDs (i.e., slope of regression line) are given for each observation year.

**Figure A5.**Linear regression fit between the difference in observed flowering DOY (number of days) and the difference in modelled GDD (number of degree days) for pairs of spatially connected observations of cow parsley flowering onset (see Figure A2). Correlation coefficient and rate of spatial change in DOY per unit of GDDs (i.e., slope of regression line) are given for each observation year.

**Figure A6.**Linear regression fit between the difference in observed flowering DOY (number of days) and the difference in modelled GDD (number of degree days) for pairs of spatially connected observations of pedunculate oak leafing onset (see Figure A3). Correlation coefficient and rate of spatial change in DOY per unit of GDDs (i.e., slope of regression line) are given for each observation year.

**Figure A7.**Correlation coefficient (r) between the standard deviation of the reported DOYs for the flowering onset of wood anemone, cow parseley and pedunculate oak and the average GDD for ΔMax values varying from one week to 30 days.

**Figure A8.**Annual percentages of inconsistent observations and of boxplot outliers in volunteered observations of wood anemone, cow parseley and pedunculate oak. Inconsistent observations are unusually early or late DOYs with respect to the regional temperature regime of the observation sites, while the outliers are only very early or late DOY.

**Figure A9.**Wood anemone flowering onset synchrony models for (

**a**) original, (

**b**) outlier-free and (

**c**) consistent observations. Panel (

**d**) shows annual boxplots of the reported DOYs for the original observations.

**Figure A10.**Cow parsley flowering onset synchrony models for (

**a**) original, (

**b**) outlier-free and (

**c**) consistent observations. Panel (

**d**) shows annual boxplots of the reported DOYs for the original observations.

**Figure A11.**Pedunculate oak leafing onset synchrony models for (

**a**) original, (

**b**) outlier-free and (

**c**) consistent observations. Panel (

**d**) shows annual boxplots of the reported DOYs for the original observations.

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**Figure 1.**Flowchart of the proposed workflow that uses the coordinates of the volunteered phenological observations, their observed date and the GDDs accumulated until that date to check their consistency and to model phenological synchrony.

**Figure 2.**Annual graphs for lesser celandine flowering onset observations. The graphs were made using a Delaunay triangulation and edges longer than 100 km were pruned.

**Figure 3.**Linear regression lines fitted between the difference in observed flowering DOY (number of days) and the difference in modelled GDD (number of degree days) for pairs of spatially connected observations of lesser celandine flowering onset (see Figure 1). Correlation coefficient and rate of spatial change in DOY per unit of GDDs (i.e., slope of regression line) are given for each observation year.

**Figure 4.**Correlation coefficient (r) between the standard deviation of the reported DOYs for the flowering onset of lesser celandine and the average GDD for ΔMax values varying from one week to 30 days.

**Figure 5.**Examples of inconsistent observations for the flowering onset of lesser celandine. The highlighted observation is refuted by more than one other observation. Given the difference in GDDs between the highlighted observation and those connected to it, their difference in DOY exceeds the predicted difference by about two weeks. The numbers next to each observation show the reported DOYs.

**Figure 6.**Annual percentages of inconsistent observations and of boxplot outliers in volunteered observations of lesser celandine flowering onset. Inconsistent observations are unusually early or late DOYs with respect to the regional temperature regime of the observation sites, while the outliers are only very early or late DOY.

**Figure 7.**Lesser celandine flowering onset synchrony models for (

**a**) original, (

**b**) outlier-free and (

**c**) consistent observations. Panel (

**d**) shows annual boxplots of the reported DOYs for the original observations.

**Table 1.**The annual number of flowering observations for lesser celandine, wood anemone, and cow parsley and of leafing observations for pedunculate oak.

Year | Lesser Celandine | Wood Anemone | Cow Parsley | Pedunculate Oak |
---|---|---|---|---|

2003 | 160 | 67 | 73 | 23 |

2004 | 202 | 83 | 154 | 43 |

2005 | 279 | 105 | 179 | 58 |

2006 | 309 | 124 | 159 | 41 |

2007 | 303 | 117 | 157 | 59 |

2008 | 330 | 118 | 195 | 57 |

2009 | 259 | 109 | 148 | 50 |

2010 | 239 | 104 | 118 | 53 |

2011 | 262 | 121 | 160 | 39 |

2012 | 197 | 96 | 145 | 32 |

2013 | 190 | 91 | 118 | 45 |

2014 | 163 | 90 | 121 | 47 |

2015 | 149 | 73 | 83 | 40 |

**Table 2.**The coefficient of determination (R-squared) of phenological synchrony models driven from original, outlier-free and consistent observations.

Original | Outlier-Free | Consistent | |
---|---|---|---|

Lesser celandine | 0.54 | 0.00 | 0.61 |

Wood anemone | 0.43 | 0.28 | 0.40 |

Cow parsley | 0.12 | 0.07 | 0.37 |

Pedunculate oak | 0.35 | 0.16 | 0.36 |

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## Share and Cite

**MDPI and ACS Style**

Mehdipoor, H.; Zurita-Milla, R.; Augustijn, E.-W.; Van Vliet, A.J.H. Checking the Consistency of Volunteered Phenological Observations While Analysing Their Synchrony. *ISPRS Int. J. Geo-Inf.* **2018**, *7*, 487.
https://doi.org/10.3390/ijgi7120487

**AMA Style**

Mehdipoor H, Zurita-Milla R, Augustijn E-W, Van Vliet AJH. Checking the Consistency of Volunteered Phenological Observations While Analysing Their Synchrony. *ISPRS International Journal of Geo-Information*. 2018; 7(12):487.
https://doi.org/10.3390/ijgi7120487

**Chicago/Turabian Style**

Mehdipoor, Hamed, Raul Zurita-Milla, Ellen-Wien Augustijn, and Arnold J. H. Van Vliet. 2018. "Checking the Consistency of Volunteered Phenological Observations While Analysing Their Synchrony" *ISPRS International Journal of Geo-Information* 7, no. 12: 487.
https://doi.org/10.3390/ijgi7120487