Acacia trees survey in the Arava
valley – results and implications
1
Partners
• Editors: Amir Perelberg, Mimi Ron, Uri Ramon (OLI)
• Remote sensing: Oded Nezer & Yohay Carmel (Technion), Sivan
Isaacson & Dan Blumberg (BGU)
• Geohydrology: Yanai Shlomi, Hanan Ginat, Sivan Isaacson, Geva
Ogen (DSASC)
• Botany: Mimi Ron (OLI), Tamer Jum’a (Arava Inst.), Enav
Vidan, Netta Or, Hila Elbaz, Dudi Rivner
• Birds: Yoav Perelman (SPNI)
• Reptiles: Boaz Shacham, Akiva Topper, Eran Banker
• Mammals: Enav Vidan, Benny Shalmon (INPA)
• Invertebrates: Elli Gronner (BGU, Arava Inst., ILTER)
• GIS: Guy Nizry, Dikla Zeidman (OLI), Rahamim Shem-Tov
(DSASC), Micha Silver (Arava D.A.)
Background
• JNF advances a policy document which will
define its reference to Acacia tree habitats at the
Arava & the Negev mountains – from the level
of the single tree, to the area as a whole.
• This document will deal with statutory
protection, management plan, public access,
supervision & interfaces between Acacia
habitats & adjacent areas
Survey goals
1. Background for the JNF policy document
2. Recommendations for statutory protection areas
3. Development of objective criteria for tree felling policy
4. Defining of reference indices to construction plans
5. Recommendations for management & monitoring plan
6. Finding sites for rehabilitation, recovery & public
access
7. Feasibility of conservation & fostering of Acacia trees
in buffer zones between settlements/agriculture &
natural surroundings
Survey borders
Results
142 polygons, 10,000 m2
each, in 32 streams,
representing:
• North-south gradient
• Altitude
• Lithology & soil
• Stream order
Results
• 2,069 trees:
1,305 A. raddiana
757 A. tortilis
7 A. pachyceras
Results
• Distribution range:
A. raddiana: no change
A. pachyceras: expansion north?
A. tortilis: expansion to higher
altitudes? (34 trees in 121-270 m
ASL)
Conclusions
Main factors influencing Acacia trees distribution:
•Geohydrology
Conclusions
Main factors influencing Acacia trees distribution:
•Lithology
‫חצבה‬
‫חצבה‬
‫חצבה‬
Conclusions
Main factors influencing Acacia trees distribution:
•Lithology
Conclusions
Main factors influencing Acacia trees distribution:
•Lithology
Conclusions
Main factors influencing Acacia trees distribution:
•Linear & spatial disturbances
Conclusions
Main factors influencing Acacia trees distribution:
•Linear disturbances (road 90)
Conclusions
Main factors influencing Acacia trees distribution:
•Linear disturbances (road 90)
Conclusions
Main factors influencing Acacia trees distribution:
•Spatial disturbances (edge effect)
Conclusions
Main factors influencing Acacia trees distribution:
•Spatial disturbances (edge effect)
Summary
• Change in distribution range (A. tortilis) – global warming?
• Steeper slope → more trees, higher mortality
• Deeper alluvium → more large trees, less mortality
• Larger stream → less large trees
• More trees on Alluvium, less trees on Limestone/Chalk
• Trees survive best around salinas & on sandstone, die on basalt
• Linear disturbances reduce tree coverage & survival
• Spatial disturbances reduce tree coverage but improve survival
(irrigation?)