Silva Balcanica, 15(2)/2014
FOREST FIRES IN STRUMA RIVER WATERSHED REGION – DYNAMICS, REASONS AND IMPACTS Emiliya Velizarova, Ivan Marinov Forest Research Institute – Sofia Bulgarian Academy of Sciences Ivan Nikolov National Institute of Meteorology and Hydrology – Sofia Bulgarian Academy of Sciences Abstract Forest fires is a natural disaster, which destroy forested area, thereby greatly engender flash flood conditions and enable also soil erosion. Additionally, on the territory of our country, a trend of an increasing number, frequency and intensity of forest fires is mentioned. Through current study the dynamics, impacts and reasons for forest fires in Struma river watershed have been examined. DPSIR approach was applied for analysing the impact of forest fires. It was established that for the time period (2000-2010), 1.53% of the afforested area (deciduous and coniferous forests) in Struma river basin have been affected by fires. The deciduous forests have been affected by fires to a higher degree - 3269 ha in comparison with coniferous ones - 2351 ha. For the whole period 704 fires have been registered. The surface fires predominate and have affected 6434 ha, while crown fires have affected almost 10 times less area - 756 ha. The main causes of forest fires are negligence – about 50% and unknown - about 47%. The naturally and intentionally caused fires are only 3%. Key words: forest fire, Struma watershed, Bulgaria, fires frequency, impact Fires are dominant disturbances in the forests, changing the vegetation composition and structure of any given location. Fire frequency affects ecosystems through interrupting or terminating individuals’ life cycles, while fire size determines landscape patchiness and thus post-fire regeneration processes (Flannigan et al., 2002). Taking into account the information for five countries (Spain, Portugal, Italy, France, and Greece) most often affected by forest fires, the maximum for burned area, being overpassed for the last 12 years occurs only by the dramatic 2003, 2005 and 2007 fire seasons (Schmuck et al., 2013). Although the European statistics show that in average policies and measures related to fire prevention and suppression are improving, an extreme climatic conditions, especially in 2003 in Western Europe and in 2007
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in Eastern) result in catastrophic fires (Schmuck et al., 2013). The phenomenon so called ‘summer dryness’ (Manabe et al., 1981) was found to increase in potential forest fire danger for Northern Eurasia (Groisman et al., 2007). In the Mediterranean region, elevation of summer temperature and reduction of precipitation may further increase fire risk (EFI, 2009). Temporal pattern of forest fires occurrence in South Europe shows a peak in summer and also in spring and in autumn. Spring fires are mainly because of the seasonal agricultural practices. Winter fires associates to the foehn effect, which result in dry wind, coming down a mountain and warming up as it descends (Flannigan et al., 2002). During the last 10-15 years, on the territory of our country, a trend of an increasing number, frequency and intensity of forest fires, which is especially pronounced until year 2001 was observed (Jonov et al., 2000; Ovcharov, Tashev, 2000; Velizarova et al., 2006). Detail investigations on forest fire dynamics and post-fire biodiversity changes in Sakar and Rila mountains and have been performed by Alexandrov et al., (2002) and Tsakov et al., (2004). From 1991 to 2008, the burned areas for the country were 198.5 thousand ha or 4.83% of the total forest area (Lyubenov, Konstantinov, 2008). Significantly less forest areas – around 7 thousand ha, have been affected by forest fires for 2010 and 2011 (Pironkov, 2012). Understanding the factors influencing the occurrence of fire and elucidating their dynamic behaviour are of great importance for taking effective fire-prevention measures and post-fire management practices. In this paper we examine the dynamics, impacts and reasons for forest fires in Struma river watershed. MATERIALS AND METHODS The investigation was performed on the territory of Struma river watershed. The geographical location is determined by the coordinates 41°25’ - 42°50’ N and 22°22’- 23°40’ E. Its length on the territory of Bulgaria is 290 km and the average width – 40 km (Martensson, et al., 2001; Marinov, Lubenov, 2007). Bulgarian part of the catchment area is 8545 km2. The dominant tree species on the territory of Struma river watershed are: oak (Quercus sp.) – 22.4%, followed by Scots pine (Pinus silvestris L.) – 21.7%, European beech (Fagus sylvatica L.) – 19.4% and Austrian black pine (Pinis nigra Arn.) – 13.0% (Marinov et al. 2012). The main approach used for analysing the impact of forest fires on the territory of Struma river basin was so called DPSIR approach (Driving forces – Pressure – State – Impact – Response). This approach for analysing environmental problems in terms of sustainability has been introduced by European Commission (OECD, 1993, EEA, 1999). The European Parliament resolution on Natural Disasters (fires, droughts and floods), (2005/2192(INI)), European Forest Fire Information System (EFFIS), White Paper (COM, 2009)147 and Green Paper (COM, 2010 (66), as well as national regulations (Regulation N 8, State Gazette, N 38), dealing with forest
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fires and concerning fire-precaution measures of the forests and lands, have also been taken into account (Lyubenov, Panov, 2000; Lyubenov, Konstantinov, 2008). Based on the DPSIR approach, the analysis of factors, which cause forest fires in this region was performed as well as their influence on the forests has been studied in dynamics. For that purpose, data for the number of forest fires and affected areas, covering an 11- years’ time period for 15 State Forest Enterprises (SFE) and 2 State Hunting Enterprises (SHE) have been analysed. For each year and each Enterprise, data for the type of fires (surface, crown), total areas affected by fire yearly and cumulative data for the entire studied period and for the Enterprises, was assessed according to the main forest tree types (deciduous, coniferous). Map of the fireaffected areas for the last 11 years for Struma river basin were developed. RESULTS AND DISCUSSION Fire impact Overall, for the period from 2000 to 2010, 704 fires were registered, and the average number per year was 64 (Table 1). The spatial distribution of areas affected by fires in the watershed of Struma river for the period 2000-2010 is presented in Fig. 1. The data show that the greatest number of fires was recorded in years 2000 and 2007 - about 170 annually. The maximum number of fires mentioned for Struma river watershed basin repeat the tendency mentioned for whole country (Lyubenov, Konstantinov, 2008). EFFIS EU Fire Database also exhibits a noticeable increase in absolute frequency summarizing data for last 26 years (1980 – 2006) (EFFIS, 2009). For the studied region, lowest number of fires per year have been established in 2002, 2009 and 2010. Enterprises with the biggest number of fires are SHE Osogovo - 105 and the smallest one in SHE Studena – 7. The areas affected by fires (total for deciduous and coniferous) are 1.5% of the afforested territory of Struma watershed, together with mixed forests and grasses this areas increased to approximately 2.0% (Table 2, Fig. 2). The State Forestry Enterprises Rila Monastery and Breznik are with the largest areas affected by fires (in % of total afforested area), respectively 11% and 4% (Table 2). The deciduous forests are affected in both Enterprises. For the SFE Rila Monastery these areas are about 28% of the total afforested with deciduous forests (Table 2). The territories belonging to SFE Katuntsi, Kresna, Sandanski, Blagoevgrad and Studena are affected by fires to less than 0.5% Dynamic of forest fires The dynamics of the number of forest fires for each year of that period is presented in Table 2. Graphical representation of the dynamics of the number of fires (average per year) and affected coniferous and deciduous forests (average per year) shows pronounced peaks in years 2000 and 2007 (Fig. 3). A similar tendency with respect to these indicators was established for the country at whole
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Fig. 1. Spatial distribution of areas affected by fires
by Lyubenov, Konstantinov (2008). They suppose that changes in surface air temperature and drought periods extension over the fire dangerous season, accepted as traditional, could affect both terrestrial ecosystems dynamics and human activity provoking natural and human induced frequency of forest fires. Groisman et al. (2007) also showed that the most significant warming during the past several decades statistically significant increases in indices that characterize the weather conditions conducive to forest fires.
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Table 1 Number of forest fires for SFE or SHE
10 9 2 6 11 3 9
5 7 1 6 4 0 6
3 3 3 0 1 0 0
4 2 1 2 1 0 0
2 3 3 0 0 1 6
2 1 0 0 3 2 5
2 0 0 0 6 2 4
3 7 1 4 22 1 5
6 4 0 3 7 3 9
1 1 0 2 2 2 0
0 1 0 0 0 0 0
Total number for period 38 38 11 23 57 14 44
3
1
0
1
2
3
0
10
4
1
1
26
6
1
1
8
2
3
3
10
2
0
1
37
13
3
1
1
0
2
0
7
3
1
2
33
22 22 21 1 15 8 8 10 169
7 7 3 1 0 1 1 3 54
2 1 1 0 2 1 2 1 21
5 7 0 0 2 9 4 3 47
5 11 1 1 4 2 1 2 44
3 9 0 1 0 2 0 2 36
8 6 3 0 2 6 4 3 46
22 28 17 2 11 7 14 10 171
15 11 10 1 6 1 1 5 86
2 2 4 0 1 0 3 1 22
1 1 0 0 0 0 1 1 8
92 105 60 7 43 37 39 41 704
Years SFE, SHE Petrich Purvomay Katuntsi Sandanski Tsaparevo Kresna Simitli Blagoevgrad Nevestino Rilski manastir Dupnitsa Osogovo Radomir Studena Zemen Trun Breznik Average Total
2000 2001 2002
2003
2004
2005
2006
2007 2008 2009 2010
Temporal patterns of forest fire occurrence in the Mediterranean region exhibit a major peak in summer, and secondary – in spring and/or in autumn. Additional data on the dynamics of fires over a longer time period are necessary in order to confirm the existence of such a relationship for Struma river watershed. Some studies suggest universal increases in fire frequency with climatic warming (Overpeck et al., 2002; Intergovernmental Panel on Climate Change, IPCC 2007). The universality of these results is questionable because an individual fire is a result of the complex set of interactions that include ignition agents, fuel conditions, topography and weather including temperature, relative humidity, wind velocity and the amount and frequency of precipitation. Increasing temperature alone does not necessarily guarantee greater fire disturbance (Flanningan et al., 2000). Type of fires Most areas have been affected by surface fires - 6434 ha, which is an order of magnitude more than crown affected ones - 756 ha (Fig. 4). Fire type - crown
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Table 2 Areas of coniferous and deciduous forests for State Forest Enterprises (SFE), State Hunter Enterprises (SHE) affected by fires
SFE, SHE Kresna Blagoevgrad Katuntsi Petrich Purvomay Sandanski Caparevo Breznik Dupnitsa Zemen Osogovo Nevestino Radomir Rilski manastir Studena Trun Simitli Total
Total afforested area ha 21989 24603 27254 11257 18174 21333 19414 10298 26036 17483 57987 22868 20231 19752 6053 9450 33492 367674
Area of coniferous and deciduous forests, affected by fire Coniferous 16 38 6 5 56 15 93 196 117 64 601 220 194 512 21 21 176 2351
ha Deciduous 7 50 12 52 98 28 88 221 96 163 482 110 66 1646 0 46 104 3269
Total 24 88 18 58 154 43 181 417 213 226 1082 329 260 2159 21 67 281 5620
Fig. 2. Type of forests, affected by fires in Struma river watershed
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% of the afforested area 0.1 0.4 0.1 0.5 0.9 0.2 0.9 4.1 0.8 1.3 1.9 1.4 1.3 10.9 0.4 0.7 0.8 1.5
Fig. 3. Average areas of coniferous (A) and deciduous (B) forests, affected by fires, in Struma River basin for the period 2000 – 2010.
Fig. 4. Distribution of the affected by fire areas in Struma river basin – according to the type of fires – surface and crown
or surface are controlled by fire intensity and depends on the fuel characteristics – stand’s structure, load and moisture. On the other hand the fire severity is other important controlling factor of post-fire ecosystem structure and function through direct impacts on underground plant root and reproductive tissues, soil seed bank, and forest floor microbial populations. Thus surface fires provoke more pronounced influence for forest ecosystems in comparison with the crown fires. It should also be mentioned that pine and oak stands are susceptible to produce fire brands and thus causing spotting far from the fire front (Albini, 1993). Additionally, the surface fires cause significant changes to the soil due to the higher temperature reached dur-
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ing the combustion of organic matter (Velizarova et al., 2006). On steep slopes, the subsequent rainfalls are able to remove a part of the topsoil. Conditions for erosion processes exist (Velizarova et al., 2010). Causing factors for forest fire Data about causing factors of forest fires in Struma watershed are presented in figure 5. The distribution of these factors between represented 4 groups is in accordance with requirements of European Forest Fire Information System (EFFIS). Results show that 47 % of forest fires have been caused by negligence and for another 47% - causes are unknown. At third group – intentional - 3% of forest fires are referred. Thus 97% of forest fires registered in region for the period 2000 - 2010 have been caused by people. The previous studies concerning forest fires causes for country at whole show that 41 % of the forest fires were due to the unknown reasons, while the agricultural burning and pasture lands burning accounts for about 20% and 14% of them (Lyubenov, Konstantinov, 2008). The results exhibit a minor role – about 3% of the natural factors such as thunderstorm lightning. The highest percent - 18% of intentionally caused forest fires have been registered in Tsaparevo SFE. For Kresna and Zemen SFE this percent is 7%. The high (> 50%) is percent of fires caused because of the negligence, especially for SHE – Osogovo and SFE Breznik, Dupnitsa, Zemen, Trun and SHE Studena. Therefore it is important to show the variability of the forest fire statistics at regional and provincial level.
Fig. 5. Causes for the forest fires in the region of Struma river basin for the time period 2000 – 2010
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The pattern of forest fires is not related only to climatic conditions, but also to socio-economic causes, that affect the fire ignition (EFI, 2009). The statistics for the Mediterranean region show that in 90% of causes forest fires are related to human activities (agricultural and forestry operations, garbage dumps, accidents) and behaviour (recreation, unawareness, smoking). Fire escapes can turn into a forest fire. Intentional fires may be set by temporary forest workers who want to preserve their jobs. Other causes are related to poor management practices, such as public works with explosives, badly maintained power lines and vegetation management. CONCLUSIONS For the studied time period (2000-2010), 1.5% of the afforested area (deciduous and coniferous forests) in Struma river basin have been affected by fires. Putting together mixed forests and grasses, this area becomes approximately 2.0% of the territory. The deciduous forests have been affected by fires to a higher degree - 3269 ha in comparison with coniferous ones - 2351 ha. In total, for the whole time period 704 fires have been registered. The biggest number of fires has been registered for the SFE Osogovo (105), while the smallest one (7) – for SHE Studena. The surface fires predominate and have affected 6434 ha of the forest land (forests, grasses, shrubs) of Struma river basin, while crown fires have affected almost 10 times less area - 756 ha. The main causes of forest fires are negligence – about 50% and unknown - about 47%. The naturally and intentionally caused fires are only 3%. REFERENCES Albini, F. A. 1993. Dynamics and modeling of vegetation fires: observations. In: Crutzen, P.J. and Goldammer, J.G. (eds.) Fire in the environment: the ecological, atmospheric, and climatic importance of vegetation fires. Report of the Dahlem Worshop held in Berlin, 15 -20 March 1992, 222-245. Alexandrov, A., H. Tsakov, K. Genov, H. Stoykov, A. Dakov. 2002. Changes in the biodiversity and management of forests destroyed by fires. Journal of Balкan ecology. 2002. No 4. 348-358 Appendices to Regulation N6 (05.02.2004) for structure of forests and forest lands and hunting areas in the Republic of Bulgaria. COM. 2009. 147 Commission of the European Communities. White Paper. Adapting to climate change: Towards a European framework for action, 16. COM (2010) 66, March 2010, Green Paper on Forest Protection and Information in the EU: Preparing forests for climate change, 22. EEA 1999: Environmental indicators: Typology and overview. Technical report No 25. Available at http://reports.eea.eu.int/TEC25/en/tab_content_RLR, 20. EFA Project, EFA – FAO, 2005. Strengthening of the capacity to prevent forest fires, 15. EFF. 2009 European Forest Fire Information System – EFFIS http://effis.jrc.ec.europa.eu /reports/firereports European Parliament resolution on Natural Disasters (fires, droughts and floods) - environmental aspects (2005/2192(INI)), 10. Flannigan M., B. Stocks, M. Weber. 2002. Fire Regimes and Climatic Change in Canadian Forests.
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