The complex adaptive ecosystems of Tannourine cedar reserve in Lebanon

An ancient landscape in the east of the Mediterranean that witnessed many changes over the centuries and gained a variety of landscape characteristics as a result of human practices, and natural history. But now and like any Mediterranean landscape, this reserve is facing the climate change risk which is threatening its ecosystems.

 

Is this landscape resistant to the risks of climate change? Is it endowed with the characteristics and elements that make it resistant to this threat?

Let’s look at the components of this complex ecosystem:

1. Heterogeneity:
Biotic and abiotic components of the forest ecosystem:
The reserve is located at altitudes ranging from 1300 to 1900 meters above sea level, the cedar Forest grows on the north slopes and spreading to the south slopes on calcareous soil type with an annual mean rainfall of between 1060mm to 1650mm.
Flora and fauna :
The forest harbors an approximate number of 500 plant species of trees and shrubs, annuals, and perennials.
• A total of 79 species of birds were confirmed as present in the reserve
• A total of 16 species of mammals belonging to 11 families were confirmed as present in the reserve
• 17 species of reptiles and 4 species of amphibians within the region of Tannourine.

Alectoris chukar (Photo credit: Tannourine cedar reserve management team)

2. Forest structure:

The forest consists of a dominant mature layer of Lebanese cedar with associating trees and shrubs in the understory (Quercus, Prunus, Crataegus…)
This structure is so important for the resilience and the health of the forest as well as the biodiversity as it offers multiple microhabitats to a wide range of organisms depending on the life requirements for each one.
These biotic and abiotic components interact with each other and with the external environment on spatial and temporal scales in different ways to create that complexity which immunes, the ecosystem from the upcoming risks especially the risk of climate change.

Dominant and associated tree species in the reserve (Photo credit: Tannourine cedar reserve management team)

3. Non-linear relationships, positive and negative feedback mechanisms:

The non-linear relationships and their feedback in the forest ecosystem are very important as they represent the key role for the regulation of the plants and animals populations, and in many cases, non-linearity can imply that the dynamics of the forest ecosystems can show the unexpected high or low response of a gradually changes (Anderson, 2013 et al).
To apply this on Tannourine Cedar reserve:
The overpopulation of Vulpes vulpes is affecting the wild hare populations causing the decrement of their numbers dramatically (negative effect). Sciurus anomalus helps with the regeneration of oaks as it stores the nuts under the ground and forgets them so they sprout in the winter which enhances the regeneration for this species (positive effect).
Light promotes the growth of cedar trees until they reach a point where they cease growing vertically and develop the iconic parallel crown shape of the Lebanese cedar (non-linear relationship).

4. Hierarchy:
The reserve is rich in several systems (medium density forest stands, low forest cover, rock outcrops, agriculture lands, open grasslands), each of which has its own elements that are organized hierarchically, and in a certain architecture, those elements interact within the same system as well as from system to system, forming complex food webs within the system as well as with other systems.

5. Openness:
Openness can be expressed at the cross-scale interactions with the surrounding and external components (Puettmann, 2009), and it’s easy to project openness on Tannourine Cedar reserve because it’s Located in two ranges of mountains and a valley that’s opened on the Mediterranean sea from the west, the mountains absorb humidity from the sea and convert it to snow and rain on the peaks (for example), openness also implies social aspects (unsustainable human activities resulted in important shifts in land use and severe exploitation and fragmentation).

6. Memory:
Since the Phoenician times the cedar timber supplied the people with one of the finest timber quality and during the change of civilizations the cedar trees stayed as a resource for many human activities in the area (for example, the Egyptians used cedar oil for mummification, the roman harvested them for building the ships), this intense pressure left the cedar forest with nothing but scattered patches of trees distributed on the mountains, many ancient trees are still standing (many of them with hundreds of years old).
After the deforestation, agriculture began in the area, and we can still see terraces that are in use today, but many of them have been abandoned, and the soil is eroding owing to the lack of vegetation.
The area was badly mined during the Civil War, and the vegetation was eliminated, thus the primer succession is occurring all over again in many spots.

Agricultural terraces (Photo credit: Tannourine cedar reserve management team)

7. Adaptability and Self-organization:
The adaptability is a lot connected to the forest structure and heterogeneity and now it’s becoming critical because of the risk of climate change, species invasion, disturbances…
The management of the Tannourine Cedar Reserve is dealing with numerous challenges caused by disturbances such as insect outbreaks (Cephalcia tannourinensis), wildfires, and wind storms.
The forest has been subjected to numerous disturbances, yet it has survived thanks to the robust structure and great biodiversity provided by the complex adaptive ecology.
Now, climate change is disrupting this flexibility (for example, rising summer temperatures are allowing insect outbreaks to reoccur), as well as changes in forest structure (natural regeneration of cedar trees, moving of trees to higher elevations where temperatures are lower, and so on).

Examining an infected cedar branch with Cephalcia tannourinensis (Photo credit: Tannourine cedar reserve management team)

References:

1. Anderson-Teixeira KJ, Miller AD, Mohan JE, Hudiburg TW, Duval BD, DeLucia EH. Altered dynamics of forest recovery under a changing climate. Glob Chang Biol. 2013;19:2001–21.

2. Management plan of Tannourine cedar reserve in Lebanon.

3. Messier C, Puettmann KJ, Coates KD. Managing forests as complex adaptive systems: building resilience to the challenge of global change. New-York, NY: Routledge; 2013.

4. Puettmann K J, Coates KD, Messier C. A critique of silviculture: managing for complexity. Washington: Island Press; 2009.

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