Temporal Shifts in Floristic and Avian Diversity in Mediterranean Pine Forest Ecosystems Under Different Fire Pressure: the Island of Zakynthos As a Case Study
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Ann. For. Res. 61(1): 19-36, 2018 ANNALS OF FOREST RESEARCH DOI: 10.15287/afr.2017.917 www.afrjournal.org Temporal shifts in floristic and avian diversity in Mediterranean pine forest ecosystems under different fire pressure: The island of Zakynthos as a case study K. Poirazidis, E. Chaideftou, A. Martinis, V. Bontzorlos, P. Galani, D. Kalivas Poirazidis K., Chaideftou E., Martinis A., Bontzorlos V., Galani P., Kalivas D. 2018. Temporal shifts in floristic and avian diversity in Mediterranean pine forest ecosystems under different fire pressure: The island of Zakynthos as a case study. Ann. For. Res. 61(1): 19-36. Abstract. We evaluated how fire impacts the ecological coherence of Aleppo pine forests and their biodiversity over a 40-year period. The study area forms part of an insular ecosystem of Zakynthos Island (Zante) in western Greece, which forms part of the Ionian Islands. Post-fire effects were stud- ied for both plant and bird diversity at 20 sampling plots, using stratified random sampling, during the summer of 2012. The plots were selected based on the frequency of burning since the 1970s. Sites were categorized as: 1) no burning for >40 years, 2) burnt once in the 1970s, 3) burnt twice, first in the 1970s and again in 2000–2010, 4) burnt three times, first in the 1970s, and twice more in 2000–2010, and 5) burnt four times, first in the1970s, twice more in 2000–2010, and again in 2011. A total of 79 plant species and 26 bird species were recorded at the studied sites. One-way ANOVA analysis showed that fire intensity has a significant impact on alpha floristic diversity. Average plant species richness at sites that burned in 2011 was significantly higher than in those that burned in the 1970s. Detected differ- ences in bird species richness were not significant; however, more species were documented in the forested habitats (unburnt for >40 years, and burnt in the 1970s). The highest Jaccard similarity index was observed between the sites that had not burned for more than 40 years and the sites that burned in the 1970s. The lowest floristic similarity to non-burnt sites was observed between the recently burnt sites in 2011 and the sites that burned in the 1970s. The lowest bird similarity was detected between recently burnt sites in 2011 and sites that had not burned for more than 40 years. DCA ordina- tion showed the presence of a clear fire gradient, from intensively burnt open sites to non-burnt forest sites. We suggest that fire is essential to main- tain biodiversity in Aleppo pine forests, but only at intermediate frequency. Keywords pinewoods, post-fire impacts, biodiversity, ecological coherence, avifauna, flora, Zakynthos Authors. Konstantinos Poirazidis, Evgenia Chaideftou (eugeniachd@gmail. com), Aristotelis Martinis - Department of Environment Technology, Techno- 19 Ann. For. Res. 61(1): 19-36, 2018 Research article logical Educational Institute of Ionian Islands, Panagoula, 29 100 Zante, Greece; Vasileios Bontzorlos - Center for Research and Technology – Hellas (CERTH), Institute for Bio-Economy and Agri-Technology (iBO), Thessaly, Dimarhou Georgiadi Nikolaou 118, Volos, 38333, Greece; Polixeni Galani, NCC- Nature Conservation Consultants Ltd. Chalandri, Athens, Greece; Dionissios Kalivas, Agricultural University of Athens, Laboratory of Agricultural Chemistry and Soil Science, GIS Research Unit, Iera Odos 75, GR11855 Athens, Greece. Manuscript received October 16, 2017; revised December 12, 2017; accepted De- cember 14, 2017; online first December 15, 2017. Introduction incidence of fire is characterized by its high frequency, fire functions both as an eminent Forest fires: natural disturbance of forest life threat and as a natural part of forest ecological cycle processes (Rodrigo et al. 2004), forming a ma- jor key-process of the forest dynamics (Kaza- Forest fires are a form of natural disturbance nis & Arianoutsou 2004, Pausas et al. 2008). in forest ecosystems. Fires affect forest com- With respect to intensity and extension, re- position and structure, as well as vegetation peated fires which occur over the whole exten- processes through variant succession patterns sion of a forest, threaten the resilience of the (Keane et al. 2013). Fires are considered as ecosystem. Fire frequency is the number of the most common natural disturbance in for- fire incidents that occur at a given site over a ests, particularly pine forests (Agee 1998, given period of time (Eugenio et al. 2006a), Vacchiano et al. 2017), leading to biomass can either threaten or strengthen the resilience loss that affects thousands of hectares per year of the ecosystem, and is dependent on struc- (García-Ruiz et al. 2013). Fires also affect the tural and spatial factors (Koutsias et al. 2012). physical, chemical, and biological properties Within the Mediterranean basin, the incidence of soils, through the combustion of litter and of reoccurring fires has increased since the soil organic matter, which increases the avail- 1960s (Moreno et al. 1998), due to a warming ability of certain nutrients and the volatiliza- and drying trend, but also due to rural depop- tion of others. All fires represent a disturbance ulation, land abandonment, and afforestation that reshapes all inter-linked micro- and mac- with flammable species that increase the accu- ro-organisms of all taxa, which form the forest mulation of fuel-material (Moreira et al. 2009, bio-community. The fire impact forces biolog- Shakesby 2011). According to EC (2013), be- ical response on genetic, species and commu- tween 1980 and 2012, the mean fire frequency nity level and triggers optimization processes per square kilometer was 3.2, 3, and 1.2 fires of morphological and biochemical traits and per km2 of land in Italy, Spain, and Greece, strategies of survival and reproduction (e.g., respectively. With global climate change, fire Kadereit et al. 2014). Fire pressure as a fac- frequencies are expected to increase in the tor of ecological selection culminated in the Mediterranean, making forests even more vul- origin of pyrophilous (`fire-loving´) species nerable (Fyllas et al. 2007, Maia et al. 2014). which are known among plants, fungi, animals including numerous pyrophilous insects (Cap- A positive role for forest fires? inera 2008). In parts of eastern and southern Europe, fires Corona et al. (2014) showed that pine forests are considered the most common threats to constitute a major landscape feature of the forests (Krivtsov et al. 2009, Gil-Romera et al. Mediterranean Basin, accounting for 25% of 2010). In the Mediterranean basin, where the the forested Mediterranean surface, with Pi- 20 Poirazidis et al. Temporal shifts in floristic and avian diversity ... nus halepensis Mill. being the most abundant frequency of occurrence that must be placed species. In the western Mediterranean Basin, under detailed study in each different case in pine forests account for 2.5 million ha of land order to assess if fires actually degrade forest (Ganteaume et al. 2009). On average, approx- ecosystems, or promote species diversity (Tin- imately 600,000 ha of forests burn each year gley et al. 2016), and sustain biodiversity in- in the Mediterranean. This land transformation stead of being a major factor for biodiversity also increases the risk of reoccurring forest loss in the forest ecosystems of southern Eu- fires (Krivtsov et al. 2009). More specifically, rope (Doblas-Miranda et al. 2017). the recurrent fires that occur in the Mediterra- nean regions of Spain, southern France, Italy, Post-fire effects on vegetation and avifauna and Greece are considered as major causes for assemblages the decrease of natural forests in this region (López-Bermúdez 2008, García-Ruiz et al. The different degree of post-fire regeneration 2013). Because of the high-severity of fires, of forest species, such as the Aleppo pine, in leading to their being characterized as me- recently burnt forests might create a variety ga-fires (Miller et al. 2008), a strong negative of new landscape features through the pro- impact was recorded on forest resilience in the cess of regeneration (Arianoutsou & Ne’eman region, in combination with climate change 2000, Rodrigo et al. 2004). For most taxa in a factors (Keane et al. 2013, Fernandes et al. healthy forest ecosystem, diversity and patch 2017). connectivity are essential landscape features Consequently, people commonly perceive (Chuvieco et al. 2010). With respect to avifau- fire-shaped forests in the Mediterranean basin na, Fuhlendorf et al. (2012) and Standish et al. as being linked to habitat loss and degradation, (2014) showed that birds prefer habitat hetero- rather than as a beneficial fragmentation pro- geneity, and are unlikely to move through de- cess (Herrando & Brotons 2002). When a fire graded, homogeneous rangelands. is not a destructive mega-fire, it has a positive However, post-fire effects on vegetation role in enriching diversity patterns and rich- and the avifauna assemblages of Mediterra- ness, a fact that is widely recognized (Taylor nean forests are complex, and mainly depend 2000). Thus, fire, apart from threatening eco- on the new conditions created after each fire system resilience, also represents a key dis- in each distinct geographical area, as well as turbance route to reviving forest landscapes, the pre-existing floristic and avifauna assem- and is a fundamental element of ecosystem blages and their ecological niches (Viedma functioning (Sakulich & Taylor 2007, Gillson 2008, Maia et al. 2014). For instance, avifauna 2009). Fires of limited extent create habitat species that are considered to be strictly forest heterogeneity by converting homogeneous dwellers are strongly affected by forest fires, woody landscapes into more complex for- because they lose their main habitat. In com- est-shrub mosaics (Herrando & Brotons 2002), parison, species with a broader habitat spec- because they re-introduce early-successional trum are able to utilize adjacent areas too, by communities within existing mature forests nesting outside recently burned areas, but also (Brotons et al.