Vegetation changes on the island of Saba

(1)

Vegetation changes on the island of Saba

effects of hurricanes, people and non-native species

John Janssen

(2)

(3)

1953

2020

(4)

Content

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What is vegetation (research)?

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Historic research on Saba

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Current research

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Preliminary results for

different zonation belts

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Conclusions

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What has changed in the last decades?

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What is vegetation research?

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Vegetation vs Flora

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Vegetation research:

Inventories

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Plots

(7)

What is vegetation research?

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Vegetation vs Flora

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Inventories

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Plots

Plot 1 Paris Hill 10x10 m²

Steep slope 45°, ENE exposition Tree Layer 30% (3)6(7) m Swietenia mahagoni 2a Coccoloba uvifera 2b Myrcianthes fragrans 2a Schoepfia schreberi + Casearia decandra 2a

Ocotea coriacea +

Shrub layer 30% (8)10(20) dm

Wedelia calycina 2a

Senna bicapsularis 2a Coccoloba uvifera 2a Abrus precatorius + Eugenia axillaris 2a

Eugenia rhombea +

Daphnopsis americana +

(8)

What is vegetation research?

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Vegetation vs Flora

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Inventories

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Plots

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Types (clustering plots)

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Maps (spatial information)

(9)

What is vegetation research?

▪

Vegetation vs Flora

▪

Inventories

●

Plots

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Types (clustering plots)

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Maps (spatial information)

(10)

What is vegetation research?

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Vegetation vs Flora

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Inventories

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overview of biodiversity

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comparison with other islands

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relation with fauna

(11)

What is vegetation research?

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Vegetation vs Flora

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Vegetation research

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Inventories

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Monitoring

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Repeating plots or maps

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Changes => nature management action

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Action needed

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Vegetation vs Flora

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Vegetation research

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Inventories

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Monitoring

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Repeating plots or maps

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Changes => nature management

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Historical vegetation research on Saba

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1956 Stoffers PhD Utrecht University

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Historical vegetation research on Saba

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(15)

Historical vegetation research on Saba

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1999 John de Freitas

with A. Royer, B. Nijhof, D. Debrot Vegetation map of Saba

Published in 2018

(16)

Current research

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Dutch Caribbean Biodiversity Database (www.dcbd.nl)

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Data rescue: recently also terrestrial & nature-inclusive development (KB programm)

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Digitized old plots descriptions

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Overview of all vegetation types

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Repeat plots to understand vegetation dynamics

(17)

Current research

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Dutch Caribbean Biodiversity Database (www.dcbd.nl)

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Data rescue: recently also terrestrial

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Digitized old plots descriptions

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Overview of all vegetation types

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Repeat plots to understand vegetation dynamics

•

Curacao: Erik Houtepen  Christoffelberg NP

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Bonaire: few plots

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Saba: current research

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Current research

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^Problem:

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Exact location unknown, indicated on field maps

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Use field forms:

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exposition, slope

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species composition

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no GPS-coordinates

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no precise descriptions

(19)

Current research

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34 (49) plots repeated (more-or-less same location)

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28 additional plots

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GPS co-ordinates, altitude

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Description of location

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Some results

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For each zonation belt on the map

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1. Elfin forest

730 m Elfin forest

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1. Elfin forest

1999

2020

1991

Better picture?

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1. Elfin forest

1999

2020

Google Earth 2020

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1. Elfin Forest

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2. Elephants ears scrub

Elephant ears, Palm, Treefern

wet “forest”

515 m

730 m Elfin forest

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2. Elephants ears scrub

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2. Elephants ears scrub

Plot numbers 19 24 25 29 30 31 19 24 25 29 30 31

Tree-shrublayer Year 99 99 99 99 99 99 20 20 20 20 20 20

Lobsterclaw (Heliconia bihai ) 3 2 2 2 3 3 2 3 2

Elephants ears (Phil. giganteum ) - epiphyt 3 + 2 1 + 2 2 + Elephants ears (Phil. giganteum ) - terrestrial 3 4 2 2 3 2 3 4

Treefern (Cyathea sp.) 2 + + + 2 + 2 2 2 3 =

Mountain cannage (Prestoea montana ) + + 2 2 2 + + 2 2 2 + =

Bromeliad (Vriesea ringens ) 1 1 + 1 + 2 + 1

(28)

3. Transitional forest

wet “forest”

Balsum, Red wood (Inga), Jack tree 730 m

515 m 450 m

Elephant ears, Palm, Treefern Elfin forest

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3. Transitional forest

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3. Transitional forest

10 plots 1999 2020

% Tree 46 55

Height tree (m) 9 10

% Shrub 50 42

Height shrub (dm) 20 21

% Herb 10 20

Height herb (cm) 28 14

Nr of species Trees/Shrubs 43 27

(31)

3. Transitional forest

10 plots 1999 2020

% Tree 46 55

Height tree (m) 9 10

% Shrub 50 42

Height shrub (dm) 20 21

% Herb 10 20

Height herb (cm) 28 14

Nr of species Trees/Shrubs 43 27

Nr of species Herb layer 13 15 =

(32)

3. Transitional forest

(33)

4. Dry tropical forest

wet “forest”

515 m 450 m

Red wood (Coccoloba), Figs, Soursop, Mahoni dry forest

(34)

4. Dry tropical forest

wet “forest”

515 m 450 m

Red wood (Coccoloba), Figs, Soursop, Mahoni dry forest

(35)

4. Dry tropical forest

The Bottom Expansion houses

2020 1953

(36)

Grassland Shrubland

5 Lowest zonation belt

200 m

5 4 3

2

1 Mule grass

Yellow sage

(37)