# CLIMTREE project: Assessment of forest decline in French plots

Laurent Larrieu, Christophe Bouget, Grégory Sajdak, Veronique Cheret, Sylvie Ladet

► To cite this version:

Laurent Larrieu, Christophe Bouget, Grégory Sajdak, Veronique Cheret, Sylvie Ladet. CLIMTREE project: Assessment of forest decline in French plots. 3. Meeting. Bavaria NP, Aug 2019, Spiegelau, Germany. 12 p. hal-02786552

HAL Id: hal-02786552

https://hal.inrae.fr/hal-02786552

Submitted on 5 Jun 2020

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Distributed under a Creative Commons Attribution 4.0 International License
CLIMTREE
Assessment of forest decline

Larrieu L., Bouget C., Sajdak G., Cheret V. & Ladet S.
Assessment of forest decline intensity at several spatial scales

<figure><img src="image_2.png" /></figure>

**Local (i.e. plot) dieback assessment: the ARCHI method** (Drenou et al., 2013)

The ARCHI method analyses tree architecture (whole tree, crown, axes and branches) to establish a diagnosis of tree vitality status

A set of ergonomic keys to perform diagnoses in the field

<figure><img src="image_3.png" /></figure>

<figure><img src="image_4.png" /></figure>
Local (i.e. plot) dieback assessment

Health status of 20 (co)dominant trees the most closer to the plot center

<figure><img src="image_5.png" /></figure>

dominant

co-dominant

<figure><img src="image_6.png" /></figure>

<figure><img src="image_7.png" /></figure>

Focus only on conspicuous tree crowns
(in black)
# Local (i.e. plot) dieback assessment

Defoliation
Crown decline
symptoms

Crown
restoration
process

ARCHI diagnosis
5 tree types

- healthy

- stressed

- resilient

- dying

- crown dieback

<figure><img src="image_8.png" /></figure>

+ Greenness level

<figure><img src="image_9.png" /></figure>

<figure><img src="image_10.png" /></figure>

<figure><img src="image_11.png" /></figure>

Type and vigor of sprouts

<figure><img src="image_12.png" /></figure>
Local (i.e. plot) dieback assessment

<figure><img src="image_13.png" /></figure>

<figure><img src="image_14.png" /></figure>

Ch. Drénou - CNPF
# Post-hoc assessment of the sampling design (plot scale)

## At the plot scale

<figure><img src="image_15.png" /></figure>

<figure><img src="image_16.png" /></figure>

<figure><img src="image_17.png" /></figure>
# Dieback assessment from stand to landscape scales
## The tools

### Remote sensing data
= MODIS Terra NDVI
Time Series (2000-2017)

- Moderate Resolution Imagery Spectroradiometer (MODIS)

- free data

- spatial resolution 250m
  (pixel=6.5 ha)

- Every 8 or 16-days

### Analysis of trends in MODIS NDVI time series

<figure><img src="image_18.png" /></figure>

<figure><img src="image_19.png" /></figure>

SG= phenological indicator linked to **spring vegetation activity**
= sum of NDVI calculated over a fixed period of MODIS images from the onset of SG (end of April) to the maximum NDVI (in end of June) before the dry season (Reed 2006) ⁷
# Dieback assessment from stand to landscape scales
## The tools

Detection and monitoring of gradual or sudden changes in forest health
(Lambert et al., 2013)

Measurement of variations of photosynthesis activity within the period 2000 – 2016
= **index of vitality** trend

<figure><img src="image_20.png" /></figure>

for 1 pixel
= 6ha

Index of vitality trend

$$ \rightarrow Dnor\_SG = \frac{\boxed{\text{2014}} - \boxed{\text{2016}}}{\boxed{\text{max SG}}} + \frac{\boxed{\text{2000}} - \boxed{\text{max SG}}}{\boxed{\text{2002}}} $$

<figure><img src="image_21.png" /></figure>

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<figure><img src="image_23.png" /></figure>
Dieback assessment from stand
to landscape scales

<figure><img src="image_24.png" /></figure>

CLIMTREE

<figure><img src="image_25.png" /></figure>

Legend

ClimTree plots

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54 ha buffer zone

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315 ha buffer zone

<figure><img src="image_28.png" /></figure>

700 ha buffer zone

Vitality trend index

<figure><img src="image_29.png" /></figure>

High : 0,540766

Low : -0,446544
# Dieback assessment from stand to landscape scales

## Calculation procedure

1. Evaluation of fir proportion in the buffer

* Selection of conifer polygons: OSO 2017 map (www.theia-land.fr/raster 10 m, 17 classes)

* Selection of fir stands: BD forest 2014-2018 (IGN, 32 classes)

<figure><img src="image_30.png" /></figure>
# Dieback assessment from stand to landscape scales

## Calculation procedure

2. Evaluation of fir proportion in the buffer

Pixel selection using the
"random spot mask" method

<figure><img src="image_31.png" /></figure>

SG data

<figure><img src="image_32.png" /></figure>

SG difference
High
Low

<figure><img src="image_33.png" /></figure>

<figure><img src="image_34.png" /></figure>

CLIMTREE
# Post-hoc assessment of the sampling design
(stand→ landscape scales)

Dieback level

<figure><img src="image_35.png" /><figcaption>Stand scale</figcaption></figure>

<figure><img src="image_36.png" /><figcaption>Landscape scale</figcaption></figure>

<figure><img src="image_37.png" /></figure>

<figure><img src="image_38.png" /></figure>

<figure><img src="image_39.png" /></figure>

CLIMTREE