Post-Fire Recovery of an
East Mediterranean Aleppo Pine Forest Ecosystem
(IFFN No. 15 – September 1996, p. 11-12)
The East-Mediterranean pine forests on Mount Carmel, Israel, have been exposed to human disturbance including frequent fires for as long as 60,000-70,000 years. Fire on Mount Carmel, as in other parts of the Mediterranean basin, is caused mainly by human activity and it has been playing an ecological role, ever since the adoption of fire by mankind. Therefore, it is a main factor affecting communities and shaping landscape in this ecosystem. Fire is a common disturbance of short duration (only few hours). However, the ecological recovery is a very long process which may last several decades. In addition to its great impact on the ecosystem, it affects also human society.
The Mediterranean ecosystem on Mount Carmel has asymmetrical seasonality. The rainy season, which overlaps with the cool season, is relatively short, being only four months long. The dry season spans eight months and for almost half of the year it is accompanied by high ambient daytime temperatures. The mean annual temperature is 20° C with mean temperature differences between winter and summer of 12° C. The mean annual precipitation is 700 mm but over several years, which can be consecutive, it may fall to 500 mm or even less. As in other Mediterranean-type ecosystems, the long, dry and hot season has a significant impact on food quality and its water content. Thus organisms in these ecosystems are exposed to wide seasonal changes in nutrition qualities and may face potential dehydration.
However, these habitats typically are inhabited by species of palaearctic origin. The mixed pine and oak forests in this relatively dry ecosystem may be important for the survival of small mammals and others, as they provide food and thermal protection by reducing direct radiation mainly during the long warm and dry season.
The September 1989 fire destroyed about 300 ha of natural forest of Aleppo pine (Pinus halepensis), which was a part of the Carmel National Park and Nature Reserve, open to the public for leisure purposes. The pine trees formed the upper story of the forest while the oak (Quercus calliprinos) and other evergreen shrubs formed the lower one. The forest was located (33° 44 N; 35° 01′ E), at an altitude of 320 m, and about 7 km from the Mediterranean seashore. The destruction by fire of the forest, which was a favourite recreation site, caused a national trauma resulting in public donations of about three million U.S. Dollars. The Ministry of Environmental Affairs established a scientific professional committee, that was to advise the managing authorities how to restore the burnt forest. Earlier studies on the resilience to fire in this ecosystem in Israel were limited to the recovery of plants but no data were published on the recovery of the fauna. Several teams of scientists from different disciplines joined in an effort to achieve a comprehensive understanding of resilience to fire in this ecosystem. As ecologists we addressed the following question: “What is the appropriate way to treat the post-fire habitat in order to enhance the restoration the original forest community?” However, different designation and public land uses may require different forest structures and therefore other forms of management should be applied.
A group of biologists (Dr. M. Broza, Dr. A. Haim, Dr. I. Izhaki and Dr. G. Ne’eman) representing various disciplines from the Department of Biology, University of Haifa at Oranim, designed an ecological study using the same plots. In order to suggest an appropriate management regime, three treatments were applied to the burned habitat: (1) Burned trees were left untreated; (2) Burned trees were cut down, the trunks were removed but the smaller twigs were left in small piles in the plots; (3) burned trees were cut down, the trunks and the smaller twigs were removed from the plots. In addition to censuses carried out in the post-fire habitat, plots of Aleppo pine forest in the vicinity, which to our knowledge were not burned in the last century, were also sampled as control. The research started in the summer of 1990 (almost one year after the fire) and lasted for three years. The vegetation, micro soil arthropods, passerine birds and small mammals (rodents and shrews) were monitored in the different plots in order to define species composition, density and also percentage of cover of the vegetation. The effect of seedling thinning of Pinus and Cistus was also studied.
The results of the vegetation survey (Ne’eman et al 1995) revealed that cutting or removing the burned trees had less influence on species composition and cover than the natural process of recovery. The thinning of seedlings positively affected their height, biomass and survival. Since pine seeds germinate in the first winter following fire, no classical species succession was recorded. However, the recovery of the vegetation was due to changes in species dominance and life form structure, Pinus halepensis trees replacing Cistus dwarf shrubs. The large burned pine trees affected the spatial pattern of seedling recruitment (Ne’eman et al. 1992).
Thirty three species of passerine birds were recorded during fall, winter and spring (1991-1994). A relative marginal habitat alteration was caused by logging pine trees with control burned forest. The most significant difference in avian community level was found between the unburned forest and the burned one, and between the first (1-2 years) and the successive periods (3-5 years post-fire) (Izhaki and Adar 1996). In unburned pine forest 80% of the soil microarthropodes were of the order Acarina and Collembola, the rest belonged to other 18 orders. In the second post-fire years, only 11 orders were presented. Protura, Pauropoda, which were common in the unburned forest disappeared, while pseudococccid Rhizoecus sp. which were rare in the unburned forest flourished after fire (Broza et al. 1993).
The recovery of the small mammal fauna was by succession. In the first stages, the post-fire habitat was invaded by granivour species which occur in open areas close to the margins of the forest but are not forest dwellers. This group included three different species (two members of the family Gerbillidae Gerbillus dasyurus, and Meriones tristrami and one of the family Muridae Mus macedonicus). During the third year after fire, populations of the two omnivorous wood-mice species (Apodemus flavicollis and A. mystacinus) and of the insectivorous shrew (Crocidura suaveolens) were established in burned plots of various treatments. Therefore, it was concluded that post-fire recovery of small mammal populations was through succession and this was correlated with the changes in vegetation and other primary consumers in the habitat. Species richness and diversity were highest during the third and fourth years after the fire when populations of both invading and forest dwelling small mammals (apart of the black rat Rattus rattus) were present in the plots. It is important to note that recovery in untreated burned plots, at the early stages, seemed to be the fastest. The elapse of time after fire was the most significant factor affecting the recovery of small mammal populations (Haim et al. 1996). The results of the study illuminated the effects of different management regimes on the post-fire recovery of the ecosystem in a short time range. As the elapse of time after fire was found to be the major factor affecting the recovery, our study was extended for another period of three years. Since the expected rate of changes slows with time, plots in similar pine forest, that were burned eleven, twenty, and fifty years ago were selected for monitoring. The same environmental and biotic components as for the 1989 fire are being studied at present. Preliminary results show that biodiversity in all groups decreases with time. It seems as if a period of about half a century is required for a full recovery of this type of ecosystem.
We thank the Carmel Foundation, Ministry for Environmental Affairs, the Ministry of Science and Arts, the State of Israel and The GSF-Forschungszentrum für Umwelt und Gesundheit GmbH, Neuherberg, Germany, for supporting our research on Mount Carmel.
Neeman, G., H.Lahav, and I.Izhaki. 1995. Recovery of vegetation in a natural east Mediterranean pine forest on Mount Carmel, Israel as affected by management strategies. Forest Ecology and Management 75, 17-26.
Ne’eman, G., H.Lahav, and I.Izhaki. 1993. The resilience of vegetation to fire in an East Mediterranean pine forest on Mount Carmel, Israel: the effect of post-fire management. In: L.Trabaud and R.Prodon (eds.), Fire in Mediterranean Ecosystems. Commission of the European Communities, Brussel-Luxembourg, pp. 127-141.
Haim, A., I.Izhaki, and A.Golan. 1996. Rodents species diversity in pine forests recovering from fire. Israel Journal of Zoology (in press).
Broza, M., D.Poliakov, S.Weber, and I.Izhaki. 1993. Soil microarthropods on post-fire pine-forest on Mount Carmel, Israel. Water Science and Technology 7-8, 533-538.
Izhaki, I., and M.Adar. 1996. The effects of post-fire management on bird community succession in an East-Mediterranean natural pine forest on Mount Carmel, Israel. J. Wildland Fire (in press).
From: Abraham Haim and Gidi Ne’eman
Department of Biology
University of Haifa at Oranim
IL – Kiryat Tivon 36006