Surface wildfire in conifer broad-leaved forests of the Hyrcanian region of Iran:short-term effect on regeneration and damage to trees

Seyed Abdolkhalegh Yadegarnejad?Mehdi Dylam Jafarabad?Najmeh Mohammadi Savadkoohi

Surface wildfire in conifer broad-leaved forests of the Hyrcanian region of Iran:short-term effect on regeneration and damage to trees

Seyed Abdolkhalegh Yadegarnejad1?Mehdi Dylam Jafarabad1?Najmeh Mohammadi Savadkoohi2

Wildfires in recent years have resulted in degradation and damage to the Hyrcanian forest ecosystems in Northern Iran.This study was carried out to investigate fire damage to trees and changes in regeneration in early-season growth after wildfires in the Golestan Province.For this purpose,a random sampling plan was used,with 60 circular plots(each plotis 1000 m2)for each stand and 240 circular(25 m2)plots for regeneration within the burned and unburned areas,respectively.In each plot, habitat factors were recorded,including crown canopy percentage,forest stratum,herb-layer cover percentage, species,diameter at breast height,tree and regeneration quality,and quantity of seedlings and saplings.Our results showed thatbark is an importantfactor for fire resistance in Hyrcanian forests.The Persian ironwood and European yew has the highest and lowest fire resistance;as broad leave species are more resistant than needle leaf species. Density of regeneration in unburned area was higher than burned area,and statistical analysis showed significant differences for all species between two areas.Fire effects on sapling were different among species which indicates sapling has different resistance to fire.Forest floor fuel, season,stand composition and microclimate have more effects on fire severity while environmental factors,regeneration and management practices shaping future composition stands.

Broad leave·European yew·Seedling and sapling·Wildfire

Introduction

Total forest cover in Iran is 12 million hectares(about8% of the total land area),of which 15%is located in the northern part of the country,an area known as the Hyrcanian Forests(Sagheb-Talebi et al.2004).The Hyrcanian Forests cover the northern expositions of the Alborz Mountains,facing the Caspian Sea,which supports a mild and moist climate(600–2000 mm annual rainfall).The forest area has a unique ecotype because it hadn’t been affected by glaciations since the last Ice Age,some 10 million years ago(Marvie Mohajer 2006).Itcontains a rich diversity of mainly deciduous trees—Oriental beech; hornbeam;Caspian alder(Alnus subcordata);Chestnut leaved oak(Quercus castaneifolia)and velvet maple(Acer velotinum)—with an understory of box(Buxus hyrcana) and European yew(Taxus bacata).Fires in northern Iran normally occur in autumn when hot-dry winds and short periods of drought cause forest floor litter to dry.These are mostly surface fires that rarely exceed 10–30 cm in flame height under normal fuel and humidity conditions.Fire burns 300–400 ha of forest annually in these forests(Banj Shafiei et al.2010).

Fire is one ofthe mostwidespread phenomena to resultin highly damaged ecological,economic and social effects (FAO 2001).It has different effects on:the hydrology and geomorphology ofthe area;biogeochemicalproperties of the soil,the vegetation cover,consequently,the characteristics ofsubsequentfires(Whelan 1995);and forestfires have changed the structure and have differenteffects on tree species composition(Banj Shafieietal.2010).

Simulating short-term,first-order fire effects,including plant injury and its mortality,are necessary tools to evaluate long-term ecosystem and fire interactions(Butler and Dickinson 2010).Vegetation responds to burning according to its severity(Phillips and Waldrop 2008)and adaptability of plant species to fire can be accounted for as a variable(Ellis 2000).Forests that differ in their composition can represent distinct fire potentials due to differences in nature,quantity,and arrangement of fuels(Fernandes 2010).Fuels in the hardwood forests consist mainly of compact litter,and branch wood will support surface fires. Crown fires are very rare in hardwood forests due to relatively high foliar moisture content(compared with many conifers),density of the canopy and possibly low content of flammable extractives(Van Wagner 1978).

The Hyrcanian Forests have an uneven topography and very steep slopes like the ones found in European forests. Fires burn ata rate of 300–400 ha annually in these forests, while 6000 ha/year are burned throughout all of Iran’s forests(FAO 2005).These forests are normally thought to be fire resistant because of high atmospheric and soil moisture,and major wildfires have been historically rare (Banj Shafiei et al.2010).However,as a result of recent climatic oscillations and global climate warming,fire occurrence has increased during recent years(Goldhammer 1999).Fires in the north of Iran normally occur in autumn when forest floor litter dries due to hot dry winds.Approaches to the study of post-fire regeneration include analyses of post-fire vegetation dynamics,tree and shrub responses(Crotteau et al.2013),dynamics and reestablishmentof regeneration(Spanos etal.2000;Shatford etal. 2007;Oliveira and Fernandes 2009;Marzano et al.2012). Allthese studies provide important,butnevertheless partial approaches to the understanding of forest response to fire and the ecologicaleffects of fire disturbance,as mostfocus either on the resistance or on the resilience of forest systems(Proenc?a etal.2010).This study was conducted in the first growing season after a single fire event burned a large area in the JafarAbad reservation.In 2010,an extensive wildfire caused high damages to this forest,which is located mainly in Golestan Province in northeast Iran. Sorkhdari JafarAbad forests are located in this region and contain one of the beststands of European yew,which was burnt by wildfire in October and November 2010.These forests have relatively deep floor with conservative stands European yew.Fire risks have proven to be high in such forests(unmanaged or virgin versus managed).This study seeks to answer the following questions:How does the fire affectthe mostcommon tree species(especially yew)?And how does the fire change the forest regeneration?

Materials and methods

Study area

The study area is located in the JafarAbad area,part of the Sorkhdari forests,located 24 km east of Gorgan City in Golestan Province,in northern Iran(36°42′02′to 36°49′39′′N latitude and 54°39′58′′to 54°46′11′′E longitude)(Fig.1).Elevation within the study area ranges from 760 to 1860 m,with slopes between 40 and 75%.Common forest soils are deep brown soil and the climate is mildly humid with a cold winter.The mean of annual precipitation at the nearest meteorologicalstation(Gorgan) is reported to be 580 mm,with a 5-month dry season(July, August,September,October,and November).The mean temperature is 22.7°C during the hottest month and 0.8°C during coldest month.

In Hyrcanian forests,trees(live or dead)are harvested using either a single-selection or group-selection system based on forest management planning.But in the study area,forest managementplanning had notbeen completed. The forest cover is uneven in terms of age,with a mix of needle and broadleaf trees.European yew and hornbeam (Carpinus betulus)are the dominant species.A fire started on 26 November 2010,in all of Golestan Province,covering about1760 ha in 16 days,and in the Sorkhdariforest, the fire covered about 300 ha.Data collection was done 8 months later in July 2011.

Data collection

Our study included both burned(B)and unburned(UB) areas of 60 ha each.The aim was to select areas with similar composition species and topography.UB plots were selected to be welldistant(ca.30 m)from the burned areas in order to avoid the fire effect;in the meantime,a random sampling plan was conducted,including 60 circular plots (each plot is 1000 m2)within the burned and unburned areas,respectively;summing up to 120 circular plots.The position of each sample was registered with GPS.In each plot,habitat factors such as geographical directions,slope percentage,crown canopy percentage,forest stratum,herbal layer cover percentage,and species were recorded. Diameter at breast height(DBH)of those trees was more than 7.5 cm,and effects of fire were documented based on conditions described in Table 1.Mortality was documented (defined as the death of all above-ground tissue)based on an examination of cambial damage at the basal of the tree trunk as well as on the drying and abscission of leaves.

Fig.1 Location of study area(Hillshade map,B and UB areas and site samples)

Table 1 Trees and regeneration quality classes in burned(B)and unburned(UB)areas(Revised method of Lotfi1999;BanjShafieietal.2010)

Four subplots within each larger plot were used to determine the regeneration assessment.Each subplot was 25 m2and was located along one of the four geographical directions within the larger plot.Therefore,each area contained 60 plots and 240 subplots.All seedlings and saplings were tallied as follows:height＜1.3 m, DBH＜2.5 cm,and 2.5 cm＜DBH＜7.5 cm.Classes, depicted in Table 1,show the regeneration quality.All of the resprouts were considered as natural regeneration and were added to other regeneration types,such as seedlings, which have offspring from seeds.In order to compare B and UB,tree regeneration and basal area densities were expressed on a per-hectare basis.

Data analysis

Kolmogorov–Smirnov tests were used to testthe normality of all parameters(excluding mortality),which followed normal distribution.Comparisons of canopy cover percentage,herbal layer percentage,mean DBH,and basal area between B and UB were conducted by means of nonparametric test of Mann-Witheny U test.Simple linear regression was used to analyze the relationship between mortality and DBH.The statistical package was SPSS 15.0.

Results

Forest structure

The number of trees per hectare in B and UB was approximately equal(Table 2).Canopy cover of trees and the herbal layer were higher in UB than B.In B,mean DBH (trees)was higher(Table 2).Regarding density,European yew(Taxus baccata)was dominantin B(40.45%)and UB (43.6%)areas(Fig.3).Both B and UB showed a reverse-J diameter distribution for the tree assemblage as a whole (Fig.2).

Tree quality

All trees were affected by fire(lightly to severely burned). Classification of the fire effect on each species shows that Caucasian Persimmon(Diospyrus lotus)had the greatest percentage of lightly damaged trees(30%),and for European yew it was 13.8%.In the moderately burned class,velvet maples had the highest proportion(86%)and European yew had the lowest proportion with 48.6%. Considering the severely burned tree class,large-leaved lime(Tillia platyphyllos Scop.)(42.9%)was greater than European yew(37.6%)(Fig.2).Altogether,10.5%of all trees in burned area were classified as lightly burned, 60.3%were moderately burned,and 29.3%were severely burned(Fig.4).In the unburned area,94.4%of all trees was safe(live)and healthy;the maximum of unsafe(fallen and standing dead)trees happened to European yew (1.2%),and allof the trees for Persian ironwood(Parrotia persica),wild myrobalan plum(Prunus divaricata Ledeb.), velvet maple(Acer velotinum),and Caucasian Persimmon came to be safe(Fig.4).

Relationship between severely burned class and DBH

Within B,there was a relatively weak negative relationship between the DBH and the percentage of severely burned and dead trees of all species(R2=0.324),with smaller stems having higher mortality(Fig.5).

Fig.2 Diameter distribution for all species in burned and unburned areas 8 month after wildfire

Fig.3 Proportion(%)of damage to species based on Table 1

Effects of stand density and aspect on the proportion of damaged trees

Results showed that the relationship between stand density and proportion of damaged trees was relatively low (R2=0.33)in that the proportion of damaged trees increased with the increase in forest density(Fig.6).The results showed that in the burned area,the damage had no significant difference for the mentioned aspects(Table 3).

Regeneration

In the shorter than 1.3 meter class,species of Acer genus (velvet Maple and coliseum maple)were dominant inburned and unburned areas,but the density of total species per ha in unburned area was higher than burned areas.In the burned area,Scots elm(Ulmus glabra Huds.)could be found,but in unburned area,it was absent.Also,other species in unburned areas had higher N/ha than burned areas.The regeneration densities of unburned area were higher than burned area for this DBH class(approximately four times)and had a significant difference(Table 4). Statistical analysis showed that the density of regeneration between burned and unburned areas for velvet Maple, Caucasian Persimmon,coliseum maple(Acer cappadocicum),hornbeam,elm and large-leaved lime species had significant differences at 95%confidence level(Table 5).

Table 2 Characteristics of the study areas

Fig.4 Density distribution of tree’s quality categories expressed in terms of DBH classes

Fig.5 Relationship between DBH(diameter at breast height)and mortality percent of all species

Fig.6 Relationship between forest density and proportion of damaged trees(lightly burned)

Table 3 Effect of aspect on proportion of damaged trees

Lower than 2.5 cm DBH class

In this class,species of Acer genus(velvet Maple and coliseum maple)were dominant in both areas and yew had the lowest density among all of the species(Table 4).The regeneration densities of unburned areas were higher than the burned areas for this DBH class(approximately twofold).Statistical analysis showed that the density of Caucasian Persimmon,hornbeam,and velvet Maple were significantly different between burned and unburned areas. However,other species showed no significant difference; total density for this class had significant difference at the 95%confidence level(Table 5).

Table 4 Density of regeneration(number/ha)by size class:1-Height＜1.3 m;2-DBH＜2.5 cm;3-DBH between 2.5 and 7.5 cm in burned (B)and unburned(UB)areas

Table 5 Comparison of regeneration densities(N/ha)by size class:1-Height＜1.3 m;2-DBH＜2.5 cm;3-DBH between 2.5 and 7.5 cm in burned and unburned areas

2.5-7.5 cm DBH class

The regeneration densities of UB area were higher than B area.In both areas,velvet Maple had the higher density (Table 4),whereas statistical analysis showed that velvet Maple,Persian ironwood,alder and Diospyrus were significantly differentbetween B and UB areas and the density of other species was not different in the two areas.

The regeneration densities(N/ha)of velvet maple, Caucasian Persimmon,Scots elm,hornbeam,large-leaved lime,Caucasian alder and European yew species were higher in unburned areas,while coliseum maple and wild myrobalan plum were higher in burned areas.Statistical analysis at 95%confidence level showed significant difference in regeneration densities of Persian ironwood, velvet maple species,alder and Diospyrus between burned and unburned areas,while other species showed no significance difference(Table 5).

The total regeneration densities of B area was lower than UB area,total seedling and sapling in UB area was 6854 N/ha,but in B area was 3113 N/ha(Table 4).Statistical analyses showed significant differences in total regeneration densities between the two areas(Table 5).Also, densities of seedling and sapling for all species had significant difference in B and UB area(Table 5).

Regeneration quality

In general,100%of all of lower than 2.5 cm DBH regeneration in burned area was affected by fire.Velvet maple was the highest vulnerable to fire among allspecies, because 86.4%of these species were affected as severelyburned(Table 6),while in moderately burned class 100% of Persian Ironwood trees was affected by fire(Table 6).

Table 6 Proportion of regeneration densities of burned area for lower than 2.5 cm DBH class for all species

Table 7 Proportion of burn intensity of regeneration for 2.5–7.5 cm DBH class for all species

In 2.5–7.5 cm DBH classes of regeneration,there were no records of any sapling as undamaged.The forest fire killed most saplings,particularly European yew and Caucasian Alder(Table 7),other species,except Persian Ironwood were affected by severely burned between 30 and 50%of total each species.

Discussion

This study showed that different aspects of density of trees (number/ha)had no significant effects on the proportion of damaged trees.Forestfires did notchange canopy cover and density of trees(N/ha).Since this study was carried out in early season growth after a fire,the change in density and canopy cover(death of trees)was slow,occurring some two to three years after the fire(Fowler and Sieg 2004;Hood et al.2007)and in some species occurs over much longer periods(Butler and Dickinson 2010).Although mean DBH was greater in B area,Fig.1 shows that diameter distribution after fire has no wide changes,but Fig.4 shows that small tree mortality decreases with tree size.

Tree mortality was strongly size-dependent,with small stems(10–25 cm DBH)suffering higher mortality(Banj Shafiei et al.2010;Haugaasen et al.2003).With regard to severely burned and dead trees,21.4%were in 10–50 cm DBH(11.3%for10–25 cmand 10.1%for30–50 cm DBH), while only 7.9%of high and dead trees were in＞50 cm DBH.Banj Shafieietal.(2010)suggested an increase in tree loss after 7 years,because the injured trees gradually succumbed to infections of fungior other pathogens,and eventually died whether standing or fallen.It was expected that mortality could continue in the following years.

A tree’s resistance to bole damage is highly correlated to bark thickness,which varies by species,age,height above the ground,and the pre-fire health and vigour of the tree (Brown and Smith 2000).Our data showed a wide variety in damages between species:29.3%of all trees areseverely burned and most of these trees died after the next fire.Trees with thick bark tended to protect the cambium from fire injury,and larger trees were more fire-resistant (Agee and Skinner 2005;Thies etal.2005;Sieg etal.2006; Fettig et al.2010).Those species with thick bark(Banj Shafiei etal.2010)reduced cambium injury(Mantgem and Schwartz 2004;Hood et al.2008).

The main factor determining crown mortality on broadleaved species is bark thickness(Catry et al.2010); small differences in bark thickness can have a big impact on fire resistance(Moreira et al.2007).Thick bark species, such as Persian ironwood,hornbeam and velvet maple, were less affected by fire and have the lowest proportion of mortality.Persian ironwood has great capacity for renewability:it can scab its bark annually,which helps the tree in a low-intensity fire(such as a surface fire).Only a scaly portion is burned and damages to the cambial layer are very slaking.There has been no record that Persian ironwood is severely burned,but the cambium can still be damaged by prolonged burnout or smouldering near the base of the tree.

European yew has relatively thick bark,but the proportion of severely burned stems was relatively high;our results showed difference in the capabilities of fire resistance between different tree species.Also,in the same fire intensity,broadleaf species had more resistance than needle-leaved species.Diaz-Delgado etal.(2004)reported less fire incidence from pine to evergreen broadleaved to deciduous broadleaved forests,and Gonzalez et al.(2006) found that hardwoods(Quercus robur,Q.ilex)and shortneedled mountain pines were less fire prone than the more flammable pine species(Pinus pinaster and Pinus pinea) (Fernandes 2010).Systematic differences in stem damage—perhaps mediated by differences in fuels characteristics(Mantgem and Schwartz 2004),bark(Banj Shafiei et al.2010),and stem diameter(Mantgem et al.2003)—provide a partial explanation of the variable mortality responses between these species.This suggests that fire resistance depends on species,size,and fuel loading; moreover fire intensity can be considered as an important variable that determines the degree of injury to trees (Amman and Ryan 1991;Agee 1993).However,bark in some species such as hornbeam and velvet maple is an important cover for protection of trees against surface fire.

Char heightwas effectively employed as a tree mortality predictor,but it does not necessarily quantify fire injury, especially as bark depth increases(Catry et al.2010). When fire occurred,most seedlings and saplings were removed from the burned forest;fire caused a decrease in totaland a change of composition regeneration.Significant differences were observed between density of velvet maple,persimmon and large leave lime in all regeneration classes that include shade-intolerant species(more data showed in Tables 4 and 5).Although the numbers of regeneration species,such as hornbeam and maple,are dominant and other species like scots elm and morbalan palm have lower density in natural conditions of these forests,the range of variation showed thatestablishment of shade-intolerant species after the occurrence of a fire occurs earlier than other species.However,fire also appeared to facilitate maple species establishment in the year of the wildfire.

After the fire,regeneration of some species halts and they are replaced with other species such as maple(Table 4).The lack of Persian ironwood,alder,and yew regeneration in burned forests sites suggests that the initial high-intensity burn was sufficient for their eradication.In sapling class with 2.5–7.5 cm DBH,density in both burned and unburned trees was approximately equal,which suggests that with an increase of age,elimination of regeneration decreases and regeneration is more about survival.Other studies show that older seedlings are more likely to survive in highly density of the canopy conditions(Hermann and Lavender 1990). This indicates that fire burns the majority of small trees (Lotfi1999).Mostof the early tree regeneration afterfire are shade-intolerant(light demanding)species such as velvet maple,coliseum maple,and hornbeam,while yews(known as shade tolerant)have greater regeneration density in UB than B areas.This is consistent with a study of tree regeneration responses to fire in the Sierra Nevada mixed-conifer (1998–2005)forestwhere the many shade-tolerantseedlings and saplings were killed(Zald et al.2008).Another note is that top killing in these forests is rare and most of the damage to regeneration occurred with the burning of tree trunks,leading to cambium damages.Seedling height was negatively correlated with mortality,as revealed in other studies(Trabaud 1988;Thanos et al.1996).

Ourresults showed thatmostofthe damages were to lowdiameter trees,and those trees recovered after few years because seed rain,seed bank,sprout,and birds and animals helped to fosterregeneration.Broadleaved forests had more capacity for recovery and regeneration than other forest types such as pine forests(Dominguez et al.2002;Calvo etal.2003).Fire,due to the decrease and change in densities of all species,may lead to changes in regeneration composition:BanjShafieietal.(2010)and Lotfi(1999)showed that fire changed regeneration composition in the burned area in Hyrcanian forests.All of the saplings and seedlings were damaged by fire and the damage measure was higher for seedling.In both classes,(0–2.5 and 2.5–75 cm),Coliseum maple and Persian ironwood regeneration had more resistance than otherspecies while yew showed lower resistance and other species could be found on the continuum of these species.Ourresultsuggests thatsaplings and seedlings have different resistances to fire,although more studies are required to clarify such mechanisms.

Conclusion

Wildfire occurrence in Hyrcanian forests resulted in wide damages to vegetation in that most of trees were damaged and signs could be found on their bark that could lead to increased mortality at the next fire.Broad and needle leaved species have different degrees of resistance to fire and broadleaved species are more resistant than others. Therefore protection of yew stands against fire is clearly important for forest managers and for biodiversity conservation.The ability to spur growth in the height and diameter of saplings and seedlings willlead to decreases in damages and in the mortality rate.

AcknowledgmentsThe authors are grateful to Nemat Dylam, Alireza Tanburani,Saeed Dylami,and Mostafa Amirnia for their valuable contributions to fieldwork and data preparation.

Agee JK(1993)Fire ecology of Pacific Northwest forests.Island Press,Washington DC,p 493

Agee JK,Skinner CN(2005)Basic principles of forestfuel reduction treatments.For Ecol Manag 211:83–96

Amman GD,Ryan KC(1991)Insectinfestation of fire-injured trees in the Greater Yellowstone Area.Research Note INT-398,USDA Forest Service,Intermountain Forest and Range Experiment Station,Ogden,UT

Banj Shafiei A,Akbarinia M,Jalali G,Hosseini H(2010)Forest fire effects in beech dominated mountain forest of Iran.For Ecol Manag 259:2191–2196

Brown JK,Smith JK(eds)(2000)Wild land fire in ecosystems: effects of fire on flora.General Technical Report RMRS-GTR-42-Vol 2.U.S.Department of Agriculture,Forest Service, Rocky Mountain Research Station,Ogden,UT

Butler BW,Dickinson MB(2010)Tree injury and mortality in fires: developing process-based models.Fire Ecol 6(1):55–79

Calvo L,Santalla S,Marcos E,Valbuena L,Tarrega R,Luis-Calabuig E (2003)Regeneration afterwildfire in communities dominated by Pinus pinaster,an obligate seeder,and in others dominated by Quercus pyrenaica,a typical resprouter.For Ecol Manag 184:209–223

Catry F,Rego F,Moreira F,Fernandes P,Pausas J(2010)Post fire tree mortality in mixed forests of central Portugal.For Ecol Manag 260:1184–1192

Crotteau JS,Varner JM,Ritchie MW(2013)Post-fire regeneration across a fire severity gradientin the southern Cascades.For Ecol Manag 287:103–112

Diaz-Delgado R,Lloret F,Pons X(2004)Spatial patterns of fire occurrence in Catalonia,NE,Spain.Landsc Ecol 19:731–745

Dominguez L,Calvo L,Luis E(2002)Impact of wildfire season on regeneration of Quercus pyrenaica forest and Pinus sp.stands. J Mediter Ecol 3:47–54

Ellis LM(2000)Short-term response of woody plants to fire in a Rio Grande riparian forest,Central New Mexico,USA.Biol Conserv 97:159–170

FAO(2005)Global forest resources assessment,progress towards sustainable forest management.FAO,Rome

FAO—Food and Agriculture Organization of the United Nations (2001)Global Forest Fire Assessment 1990–2000,UN

Fernandes PM(2010)Creating fire-smart forests and landscape. Mediterranean forest week of Antalya,Antalya,pp 417–722

Fettig CJ,McKelvey SR,Cluck DR,Smith SL,Otrosina WJ (2010)Effects of prescribed fire and season of burn on direct and indirect levels of tree mortality in Ponderosa and Jeffrey pine forests in California,USA.For Ecol Manag 260: 207–218

Fowler JF,Sieg CH(2004)Post fire mortality of ponderosa pine and Douglas-fir:a re-view of methods to predict tree death.USDA Forest Service GeneraltechnicalreportRMRS-GTR-132.Rocky Mountain Research Station,Fort Collins,Colorado,USA

Goldhammer JG(1999)Forests on fire.Science 284:1782–1783

Gonzalez JR,Palah M,Trasobares A,Pukkala T(2006)A fire probability model for forest stands in Catalonia(north-east Spain).Ann For Sci 63:169–176

Haugaasen T,Barlow J,Peres CA(2003)Surface wildfires in central Amazonia:short-term impacton foreststructure and carbon loss. For Ecol Manag 179:321–331

Hermann R,Lavender,D(1990)Pseudotsuga menziesii(Mirb.) Franco.In:Burns RM,Honkala BH,(eds)Silvics of North America.US Department of Agriculture Forest Service,Washington,DC,pp 522–540

Hood SM,McHugh CW,Ryan KC,Reinhardt E,Smith SL(2007) Evaluation of a post-fire tree mortality model for western USA conifers.Int J Wild land Fire 16:679–689

Hood SM,Cluck DR,Smith SL,Ryan KC(2008)Using bark char codes to predict post-fire cambium mortality.Fire Ecol 4:57–73

LotfiA(1999)Effectof fire in Khiroudkenar Forest.M.Sc.Seminar. Tehran University,p 44

Mantgem PJ,Schwartz M(2004)An experimental demonstration of stem damage as a predictor of fire-caused mortality for ponderosa pine.Can J For Res 34:1343–1347

Mantgem PJ,Stephenson NL,Mutch LS,Johnson VG,Esperanza AE, Parsons DJ(2003)Growth rate predicts mortality of Abies concolor in both burned and unburned stands.Can J For Res 33:1029–1038

Marvie Mohajer MR(2006)Silviculture.Tehran University Press, Tehran In Persian

Marzano R,Lingua E,Garbarino M(2012)Post-fire effects and shortterm regeneration dynamics following high severity crown fires in a Mediterranean forest.iForest 5:93–100

Moreira F,Duarte I,Catry F,Acacio V(2007)Factors affecting postfire cork oak survival in southern Portugal.For Ecol Manag 253:30–37

Oliveira S,Fernandes PA(2009)Regeneration of Pinus a nd Quercus after fire in Mediterranean-type ecosystems:naturalmechanisms and management practices.Silva Lusit 17(2):181–192

Phillips RJ,Waldrop TA(2008)Change in vegetation structure and composition in response to fuel reduction and composition in response to fuel reduction treatments in the South Carolina Piedmont.For Ecol Manag 225:3107–3116

Proenc?a V,Pereira HM,Vicente L(2010)Resistance to wildfire and early regeneration in natural broadleaved forest and pine plantation.Acta Oecol 36:626–633

Sagheb-Talebi K,Sajedi T,Yazdian F(2004)Forests of Iran. Research Institute of Forests and Rangelands,Tehran

Shatford JPA,Hibbs DE,Puettmann KJ(2007)Conifer regeneration after forestfire in the Klamath-Siskiyous:how much,how soon? J For 105:139–146

Sieg CH,McMillin JD,Fowler JF,Allen KK,Negrfn JF,Wadleigh LL,Anhold JA,Gibson KE(2006)Best predictors for postfire mortality of ponderosa pine trees in the Intermountain West.For Sci 52:718–728

Spanos IA,Daskalakou EN,Thanos CA(2000)Postfire,natural regeneration of Pinus brutia forests in Thasos island,Greece. Acta Oecol 21(1):13–20

Thanos CA,Daskakakou EN,Nikolaidou S(1996)Early postfire regeneration of a Pinus halepensis forest on Mount PaA?rnis, Greece.J Veg Sci 7:273–280

Thies WG,Westlind DJ,Loewen M(2005)Season of prescribed burn in ponderosa pine forests in eastern Oregon:impact on pine mortality.Int J Wildland Fire 14:223–231

Trabaud L(1988)Survie de Jeunes plantules de pin d’Alep apparues apreA′s incendie.Stud Oecol 5:161–170

Van Wagner CE(1978)Age-class distribution and the forest fire cycle.Can J For Res 8:220–227

Whelan RJ(1995)The ecology of fire.Cambridge University Press, Cambridge

Zald HSJ,Gray AN,North N,Kern RA(2008)Initial tree regeneration responses to fire and thinning treatments in a Sierra Nevada mixed-conifer forest,USA.For Ecol Manag 256: 168–179

21 December 2012/Accepted:6 February 2013/Published online:28 April 2015

?Northeast Forestry University and Springer-Verlag Berlin Heidelberg 2015

The online version is available at http://www.springerlink.com

Corresponding editor:Hu Yanbo.

?Seyed Abdolkhalegh Yadegarnejad yadegarnejad@yahoo.com

1Department of Forestry,Gorgan University of Agricultural Sciences and Natural Resources,Gorgan,Iran

2Forest Engineering,Sari Agricultural Sciences and Natural Resources University,Sari,Iran