Folia Forestalia Polonica, series A, 2014, Vol. 56 (2), ORIGINAL ARTICLE

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1 Foli Forestli Polonic, series A, 214, Vol. 56 (2), ORIGINAL ARTICLE DOI: /ffp Vriility of selected trits of Ips typogrphus (L.) (Col.: Scolytine) popultions in Beskid ywiecki (Western Crpthins, Polnd) region ffected y rk eetle outrek Wojciech Grodzki 1, Jerzy R. Strzyk 2, Mieczysłw Kosiowicz 1 1 Forest Reserch Institute, Deprtment of Mountin Forestry, Fredry 39, 3-65 Krków, Polnd, phone: , fx: , e-mil: W.Grodzki@iles.ww.pl 2 University of Agriculture, Chir of Forest Protection, Forest Entomology nd Forest Climtology, Al. 29 Listopd 46, Krków, Polnd Astrct In , investigtions on Ips typogrphus popultions were crried out in Norwy spruce stnds recently ffected y rk eetle outrek in the Beskid Żywiecki Mts. in Polnd. The im of the study ws to test the usefulness of severl trits descriing I. typogrphus popultions for evlution of their ctul outrek tendency. Infesttion density, sex rtio, gllery length, progeny numer nd eetle length were used s the trits. Trit vriility ws nlyzed in reltion to infested tree mortlity in the current yer of oservtion nd outrek tendency defined y the comprison of dt on tree mortlity in the current yer nd tht in the yer efore. The highest infesttion density ws found in the stnds representing the highest tree mortlity in the current yer nd in those chrcterized y decresing outrek tendency. The gllery system with 2 mternl glleries dominted. The sex rtio of ttcking eetles inclined towrds femles (63.8%) nd remined stle during 3 yers of oservtions; the highest percentge of femles ws found in loctions eing in stiliztion/ltency outrek phse. The length of mternl glleries ws somewht negtively ffected y infesttion density nd positively correlted with the numer of progeny in the gllery. The verge eetle length ws 4.8 mm (±.293), rnging etween nd mm nd eing the highest in the uppermost clss of tree mortlity recorded in the current yer of oservtion. The shortest eetles were collected in the stnds with incresing outrek tendency, nd slightly longer in the stnds with outrek stle nd decresing tendencies. None of the trits tested cn e selected s direct indictor for prediction of outrek tendency in I. typogrphus popultions. Possile resons of vriility in the nlyzed trits re discussed. The trits indicte tht I. typogrphus in the study re represent very high reproductive potentil, thus the risk of repeted outrek is very high. Key words rk eetles, glleries, progeny, sex rtio, ody length, popultion dynmics 214 y Forest Reserch Institute 214 y Polish Acdemy of Sciences Received 5 Ferury 214 / Accepted 17 Mrch 214

2 8 Wojciech Grodzki, Jerzy R. Strzyk, Mieczysłw Kosiowicz Introduction In the Western Crpthins, strting from 22, n extended rk eetle Ips typogrphus (L.) outrek developed in Norwy spruce Pice ies (L.) H. Krst. stnds growing in the Beskid Śląski (erlier) s well s the Beskid Żywiecki mountins (lter) nd culminted in The outrek generlly strted in the lower mountin zone, in Norwy spruce stnds lredy ffected y root rott (Armillri spp.), nd then spred towrds higher ltitudes up to mountin crests (Grodzki 21). The outrek course, however, ws not sptilly homogenous, thus t certin point of time it seemed possile to distinguish some su-res representing vrious outrek phses. It is known tht popultion dynmics of rk eetles in Norwy spruce stnds depends on severl environmentl fctors resulting from site nd stnd chrcteristics (Netherer nd Nopp-Myr 25). However, n nlysis of these fctors in the Beskid Żywiecki reveled tht under outrek conditions, the ptterns descriing rk eetle preferences seemed to e not s distinctive s those known from preceding studies (Grodzki et l. 214). On the other hnd, knowledge on I. typogrphus popultion trits with respect to outrek tendencies of this species hs not een yet completed. It is recognized tht popultion sex rtio vries in prticulr outrek stges nd the percentge of femles is higher in progrdtion phse (Loinger 1996). Other prmeters, such s: infesttion density nd gllery length (Anderrnt 199; Anderrnt nd Schlyter 1989), ody size or dry weight of dults (Atkins 1975), elytr weight (Botterweg 1983), length of eetles (Grodzki 24) or severl iometric mesures of dults (Sllé et l. 25) hve een so fr used to chrcterize I. typogrphus popultions in reltion to vrious reeding conditions. Yet, for the most prt knowledge gined requires further tests nd/or verifiction in outrek conditions in Centrl Europen P. ies forests. The im of this study ws to explore vrious trits descriing popultions of the spruce rk eetle I. typogrphus infesting Norwy spruce trees in order to determine trit vriility ptterns connected with pest popultion sttus nd outrek tendency. Informtion otined might e very useful in risk ssessment nd prediction of rk eetle popultions dynmics in the future. Mterils nd methods The investigtions were done in The study re extended in the Beskid Żywiecki (Western Crpthins, Polnd) within rnge of three Forest Districts: Jeleśni, Ujsoły nd Węgiersk Górk (49º º38 54 N; 18º º27 16 E) ffected y I. typogrphus outrek to different degrees. Generlly, sed on historicl dt, the Forest Districts Ujsoły nd Węgiersk Górk could e defined s the re in outrek retrogrdtion phse, nd Jeleśni in stiliztion/ltency phse with reltively lower rk eetle popultion numers (Grodzki et l. 214). Field investigtions were crried out on reserch plots temporrily estlished in Norwy spruce stnds. The plots (32) represented the prts of stnds, where dying or ded trees lredy infested y I. typogrphus were felled nd dissected. Additionlly, rk eetles for ody mesurements were smpled from pheromone trps situted in 35 loclities. In some cses the pheromone trps were instlled within plot loctions, which enled comprisons of eetles collected from the trps nd from under the rk of dissected trees. The plots nd trps were georeferenced using GPS receiver (fig. 1) in order to precisely ssign field results to dt, concerning tree mortlity in corresponding su-comprtments tken from the Stte Forests dtse. Three clsses of rk eetle-relted Norwy spruce mortlity were defined sed on the yerly volume of infested trees per 1 h: I < 5 m 3, II 5 1 m 3, III > 1 m 3 in given su-comprtment nd used in further nlyses. The prmeters descriing selected trits of rk eetle popultions in the prts of infested trees were ssessed using 3 hlf-meter-long sections of the stem, locted in its distinctive zones: I t the stem se, II midwy etween the stem se nd crown se, III under the crown se (Grodzki 27, modified). The sections were selected nd mrked fter tree felling, when the circumference ws mesured with the im to clculte the surfce of nlyzed rk. The following fetures were registered in ech stem section: infesttion density (the numer of gllery systems including those with 1, 2, 3 or 4 mternl glleries), sex structure of rk eetle popultion infesting nlyzed trees, using the numer of nuptil chmers s the numer of mles nd the numer of mternl glleries s the numer of femles, Foli Forestli Polonic, series A, 214, Vol. 56 (2), 79 92

3 81 Vriility of selected trits of Ips typogrphus (L.) (Col.: Scolytine) popultions in Beskid Żywiecki km Plots in forest District: Jeleśni Węgiersk Górk Ujsoły Forest su-comprtments Forest comprtments Izolines Figure 1. Loction of reserch sites in the Beskid Żywiecki (Forest Districts: Jeleśni, Węgiersk Górk nd Ujsoły) the length of mternl glleries 1 glleries were rndomly chosen from the systems with 1 4 femles nd mesured, effective reproduction understood s the numer of eggs nd lrve per one mternl gllery. The mesurements of I. typogrphus ody length were performed y mens of the imge nlysis method using flted scnner nd softwre for ccurte mesurements WinSEEDLE (Regent Instruments Cnd Inc.). The rk eetles were collected in June-July from Theysohn trps ited with Ipsodor (ZD Chemipn, Polnd). The eetles, fter storing in ethnol, were dried efore mesurements nd then undmged individuls with closed elytre were orgnized in 1-specimen smples nd plced on dorsl side on scnner glss nd then utomticlly mesured. The prmeters descriing I. typogrphus popultions in individul study plots were relted to rk eetle-relted tree mortlity in individul su-comprtments in given yer, with outrek tendency defined y the comprison of dt on tree mortlity in the current yer of oservtion nd tht oserved in the yer efore, reflecting outrek phse. Tree mortlity ws ssessed using dt tken from the Stte Forests IT system (SILP) s regrds the volume of trees infested y rk eetles nd felled within given yer in the individul forest su-comprtment. Definite outrek tendency (incresing decresing stle) in given sucomprtment ws determined y the comprison of the volume of infested trees per 1 h, felled in the yer of nlyses nd the yer efore. Sttisticl dt tretment imed to test significnce of differences in the trits nlyzed using: nonprmetric Kruskl-Wllis (K-W) test for infesttion density, chrcteristics of glleries nd sex structure of ttcking eetles, K-W test nd Person correltions for gllery length nd the numer of progeny, nd K-W test long with one-wy ANOVA for ody length of eetles. For dt processing there were used MSExcel with XLSTAT 212 (Addinsoft) nd Sttistic 5. (SttSoft Inc. 29). Foli Forestli Polonic, series A, 214, Vol. 56 (2), 79 92

4 82 Wojciech Grodzki, Jerzy R. Strzyk, Mieczysłw Kosiowicz Results 1.2 of infesttion density ws found in the stnds representing the highest (III) clss of tree mortlity nd it significntly differed from tht oserved for the intermedite (II) clss: (p =.2). In cse of the current yer of infesttion, the highest vlues were oserved in the stnds representing the lowest (I) nd highest (III) clsses of tree mortlity nd they significntly (p <.1) dif Infesttion density nd chrcteristics of glleries In totl, 321 sections from 17 infested trees on 32 loctions were nlyzed. Men (±SD) density of gllery systems (mting chmers per dm 2 ) in 285 infested stem sections during the whole 3-yer period ws.57 (±.425) nd vried in rnge etween.13 nd 1.2 mting chmers per dm 2 on individul plots. A B m.ch./dm 2 m.ch./dm < Infested trees (m 3 /h) > 1 < > 1 Infested trees (m 3 /h) men men Figure 2. Density of I. typogrphus mting chmers in nlyzed Norwy spruce stem sections in with respect to volume of trees infested in the yer efore nlysis (A) nd in the current yer (B) Infesttion density vried significntly in reltion to ttck intensity expressed y the volume of infested trees per 1 h in the previous [K-W H(DF = 2, N = 285) = 7.64, p =.22)] nd the current yer of infesttion [K-W H(DF = 2, N = 222) = 22.48, p <.1]. In cse of the previous yer infesttion, the highest vlue m.ch./dm decresing stle Tendency incresing men Figure 3. Density of I. typogrphus mting chmers in nlyzed Norwy spruce stem sections in with respect to outrek tendency A No. of gllery systems B % No. of mternl glleries No. of mternl glleries: Figure 4. Numer of gllery systems with 1 4 mternl glleries in nlyzed Norwy spruce stem sections (A) nd percentge of systems with 1 4 femles in (B) Foli Forestli Polonic, series A, 214, Vol. 56 (2), 79 92

5 Vriility of selected trits of Ips typogrphus (L.) (Col.: Scolytine) popultions in Beskid Żywiecki 83 A.8.75 min mx 25 75% medin.7 Femles (1% = 1).65.6 B WG2 WG1 WG3 WG4 U1 U2 J_1 J_3 J_4 WG_1_11 WG_2_11 WG_3_11 U_1_11 U_9_11 U_11_11 J_2_11 Plot J_3_11 J_4_11 J_1_22 J_1_21 Uj_17 Uj_15 Uj_13 J1_12 J2_12 WG1_12 WG5_12 U1_12 U2_12 J13_12 J11_12 Femles (1% = 1) Yer 212 Figure 5. Percentge of femles in Norwy spruce stem sections nlyzed on individul reserch plots (A) nd in individul yers (B) in Foli Forestli Polonic, series A, 214, Vol. 56 (2), 79 92

6 84 Wojciech Grodzki, Jerzy R. Strzyk, Mieczysłw Kosiowicz fered from those oserved in the intermedite (II) clss (fig. 2). Infesttion density ws the highest in the stnds representing decresing outrek tendency, nd the lowest in those with incresing tendency, ut only the vlues ttriuted to incresing tendency differed significntly [K-W H(DF = 2, N = 222) = 14.41, p <.1] from others (fig. 3). The gllery systems with 2 mternl glleries dominted in the stem sections nlyzed, nd 1 nd 3 glleries were quite frequently found s well, wheres the systems with 4 mternl glleries were very rrely oserved (fig. 4A). The percentge of the systems with given numer of mternl glleries ws quite stle in susequent yers of the study (fig. 4B). Sexul structure of ttcking eetles Men (±SD) percentge of femles in the popultions infesting nlyzed trees ws 63.8% ± 5.2 (sex rtio 1 : 1.82), vrying strongly etween the study sites nd rnged from 55.9 to 69.2% (fig. 5). No sttisticlly significnt differences were found when compring the dt collected during 3 yers on the plots locted in the res eing in different outrek phses (retrogrdtion, stiliztion). The percentge of femles ws significntly diverse etween the yers of investigtions (K-W H(DF = 2, N = 285) = 25.31, p <.1), reching significntly (p <.1) higher men vlue in 211 (65.1%) thn in 21 nd 212 (62.3 nd 63.6%, respectively; fig. 6A). The percentge of femles relted to the volume of infested trees felled in the yer efore ws the highest (65.%) in the lowest (I) clss of tree mortlity, slightly lower (63.8%) in the highest (III) clss nd the lowest (62.2%) in the clss of intermedite (II) mortlity (fig. 6B), ut the results differed significntly only etween clsses I nd II (p <.1). The percentge of femles decresed with incresing mortlity of infested trees within the current yer (fig. 6B), ut significnt differences (p =.15) were found only etween clsses I nd III. The sexul structure of I. typogrphus popultions, nlyzed in reltion to outrek tendency defined for ech of the reserch plots, ws lso significntly diversified (K-W H(DF = 2, N = 222) = 23.81, p <.1). The highest shre of femles (67.1%) ws found for stiliztion/ltency outrek phse (fig. 7), wheres in cse of oth incresing nd decresing tendencies, femle shre A Femles (1% = 1) B Femles (1% = 1) < Infested trees (m 3 /h) > 1 < > 1 Infested trees (m 3 /h) min mx 25 75% medin min mx 25 75% medin Figure 6. Percentge of femles in stem sections of Norwy spruces nlyzed on reserch plots ccording to tree mortlity in the yer efore nlysis (A) nd in the current yer (B) Femles (1% = 1) decresing stle Tendency incresing Figure 7. Percentge of femles in Norwy spruce stem sections nlyzed on the plots with different outrek tendency evluted for the yer of nlysis min mx 25 75% medin Foli Forestli Polonic, series A, 214, Vol. 56 (2), 79 92

7 Vriility of selected trits of Ips typogrphus (L.) (Col.: Scolytine) popultions in Beskid Żywiecki 85 ws lower (62.7 nd 63.6%, respectively). Only the dt ssigned to stle outrek phse differed significntly ( p <.1) from those representing incresing nd decresing tendencies. Gllery length nd progeny During 3-yer-long reserch, there were mesured in totl 279 mternl glleries in 321 nlyzed stem sections. Men gllery length highly vried [K-W H(DF = 23, N = 24) = 227.2, p <.1] etween individul reserch sites (fig. 8). The verge vlue ws 6.75 cm with rnge etween.6 nd 2.4 cm. The studied prmeter vried upon the numer of femles strting from one mting chmer [K-W H(DF = 3, N = 24) = 26.7, p <.1], nd generlly decresed with incresing numer of femles (fig. 9A), lthough the difference ws sttisticlly significnt (t p <.5) in cse of 2 nd more femles in the gllery system. Tking into ccount high percentge of the systems with 2 3 mternl glleries (fig. 4A), the decrese of gllery length with incresing numer of femles only somehow confirms the existence of intrspecific competition mechnism in I. typogrphus. Length (cm) U1 WG_1_11 U2 WG2 WG1 WG3 WG4 WG_2_11 WG_3_11 U_1_11 U_9_11 U_11_11 J_2_11 J_3_11 Plot medin J_4_11 J_1_22 Uj_17 Uj_15 Uj_13 J1_12 J2_12 WG 1_12 WG1_12 WG5_12 Figure 8. Length of mternl glleries in I. typogrphus gllery systems in Norwy spruce trees nlyzed on ll plots in Competition mechnisms (especilly sptil) ffected the numer of progeny in the gllery systems estlished with vrious numer of femles strting from the sme mting chmer (fig. 9B). The men numer U1_12 of eggs or lrve in one mternl gllery ws 21.4 with rnge from 1 to 91. The numer of eggs decresed with incresing numers of femles in one gllery system [K-W H(DF = 3, N = 1998) = 46.8, p <.1], however sttisticlly significnt differences t p <.5 were reveled only in cse of 2 nd more femles in the gllery systems. A B Gllery length (mm) Numer of progeny Numer of mternl glleries Numer of mternl glleries c c min mx 25 75% medin min mx 25 75% medin Figure 9. Length of mternl glleries (A) nd the numer of progeny (B) in the systems with 1 4 I. typogrphus femles on ll reserch sites in The numer of progeny (eggs nd lrve) in one mternl gllery ws positively correlted with its length (r =.72, p <.1, N = 25) (fig. 1) nd this reltionship, found in ll the study yers, cn e descried y the following eqution of regression: y =.3376x where: y is the numer of progeny nd x is gllery length. Foli Forestli Polonic, series A, 214, Vol. 56 (2), 79 92

8 86 Wojciech Grodzki, Jerzy R. Strzyk, Mieczysłw Kosiowicz 2 R 2 =,52 15 Gllery (cm) 1 5 Active Model Conf. intervl (Men 95%) Conf. intervl (Os. 95%) Numer of progeny Figure 1. Reltion etween the numer of progeny in mternl gllery nd gllery length in nlyzed spruce sections in Density of glleries in the nlyzed sections ws found s fctor slightly limiting oth the length of mternl glleries (r =.14, p <.1) nd the numer of progeny in given gllery (r =.9, p <.1). Body length of eetles During 3 yers of oservtions, in totl 3234 I. typogrphus eetles were collected on 37 loclities. The 1-eetle smples were usully used for mesurements, except for some cses when eetles were collected from the glleries nd then the smple size ws smller. Distriution of the trit nlyzed ws norml. The verge eetle length ws 4.8 (±.293) mm, with rnge etween nd mm. Differentition etween the smples collected from the loclities oserved ws quite high [K-W H(DF = 36, N = 3234) = 23.66, p <.1]. The lowest men ody length vlue ws mm nd the highest 5.75 mm (fig. 11A). The men vlues in smples collected from 16 loclities representing 141 eetles were ove the overll verge vlue, while the men vlues in smples from 21 loclities (1832 eetles) were elow this vlue. No temporl or sptil pttern of ody length vriility ws found. No sttisticl differences (ANOVA F =.9, p =.91) were found for the yers of oservtions (fig. 11B), thus pooled dt were used for further nlyses. When nlyzing reltions etween I. typogrphus ody length nd tree mortlity, there were used dt on the volume of trees infested y rk eetles in given su-comprtment during the current yer nd the yer efore. The verge length of eetles incresed with incresing tree mortlity in the current yer [K-W H(DF = 2, N = 3234) = 14.43, p <.1], ut the differences t p <.5 were shown only for mortlity clss I when compred with clss II (fig. 12A). The eetle length relted to tree mortlity in the yer efore ws less diversified [K-W H(DF = 2, N = 1842) = 5.8, p <.5], nd hd no pttern s defined for the current yer tree mortlity (fig. 12B). The vriility of eetle length in reltion to outrek tendency, defined for the su-comprtments where the eetles were collected, showed tht the shortest eetles were collected in the stnds with incresing outrek tendency, nd slightly longer in cse of those with stle nd decresing tendencies (fig. 13). However, the differences found were not sttisticlly significnt [K-W H(DF = 2, N = 1842) = 2.33, p =.31]. Foli Forestli Polonic, series A, 214, Vol. 56 (2), 79 92

9 Vriility of selected trits of Ips typogrphus (L.) (Col.: Scolytine) popultions in Beskid Żywiecki 87 A 5.4 medin I.t. ody length (mm) B I.t. ody length (mm) Yer J3_21 J5_21 J6_21 J7_21 J8_21 J9_21 J1_21 J11_21 J12_21 J1_211 Jel1_12 Jel4_12 Jel11_12 Jel12_12 U1_zer_2 U2_zer_2 U2_pf_2 Uj14_21 Uj15_ medin Smple ID Uj16_21 U1_211 U2_211 U3_211 U4_211 U5_211 U1_212 U2_212 U3_212 WG1_pf WG1_zer WG2_zer WG3_zer WG4_zer WG5_pf WG6_pf WG2_12 WG3_12 Figure 11. Averge length of I. typogrphus eetles collected from individul loclities during 3-yer reserch (A) nd in the vegettion sesons in the yers (B) In two loclities, it ws possile to collect eetles from the glleries in the infested trees nlyzed s well s from pheromone trps instlled in close proximity. In the first loclity (Ujsoły) the eetles from the glleries were significntly (ANOVA F = 3.939, p <.5) longer, while in the second one (Węgiersk Górk) the pttern ws opposite (longer eetles in pheromone trps) ut this difference ws not significnt (fig. 14). Foli Forestli Polonic, series A, 214, Vol. 56 (2), 79 92

10 88 Wojciech Grodzki, Jerzy R. Strzyk, Mieczysłw Kosiowicz A I.t. ody length (mm) B I.t. ody length (mm) < > 1 Infested trees (m 3 /h) men I.t. ody length (mm) pher. trp gllery Ujsoły Source pher. trp gllery Węgiersk Górk men Figure 14. Averge length of I. typogrphus eetles collected from glleries nd pheromone trps t the sme loclities < Infested trees (m 3 /h) > 1 men Figure 12. Averge length of I. typogrphus eetles relted to mortlity of infested trees per 1 h in the Beskid Żywiecki: in the yer of eetle collection (A) nd in the yer efore smpling (B) I.t. ody length (mm) incresing stle Tendency decresing men Figure 13. Averge length of I. typogrphus eetles relted to outrek tendency determined for su-comprtments where I. typogrphus eetles were collected Discussion The primry intention of the study ws to explore sptil diversity of nlyzed trits y defining su-res different in terms of outrek phse. As the level of rk eetle-relted tree mortlity ws highly vrile within the study re (Grodzki et l. 214), determintion of such continuous su-res ws not possile. Thus, we decided to nlyze diversity of the trits in reltion to some generl fetures, regrdless of sptil distriution of the study sites. Infesttion chrcteristics The highest infesttion density ws found in the stnds in which tree mortlity due to rk eetle infesttion (volume of infested trees) recorded in the yer efore the nlysis ws the highest, i.e. more thn 1 m 3 /h. In these stnds, where I. typogrphus popultion density ws lredy high, the ttck of eetles on trees ws very intense, which resulted in high infesttion density. We cn suppose tht in line with the TSA model (Christinsen et l. 1987), very numerous eetles ttcked reltively helthy trees, s it hppens in outrek eruptive phse or in the epidemic stge of rk eetle popultions. The highest infesttion density found in Foli Forestli Polonic, series A, 214, Vol. 56 (2), 79 92

11 Vriility of selected trits of Ips typogrphus (L.) (Col.: Scolytine) popultions in Beskid Żywiecki 89 the stnds defined s eing in the decresing phse of the outrek cn indicte tht rk eetle popultions proly hd to leve the infested stnd due to very high popultion size, intrspecific competition nd/or shortge in ville reeding mteril (the effect of snitry felling), nd strted to serch for new infesttion sites. Distriution of gllery systems in reltion to the numer of mternl glleries ws quite typicl: the most frequent (38%) were the systems with 2 mternl glleries, lthough the systems with 1 nd 3 glleries occurred frequently s well. Strzyk et l. (2) lso found prevlence (47.1%) of 2-gllery systems nd high frequency of 1-gllery ones. Schlyter nd Zhng (1995) pointed out tht the hrems with more thn 2 femles reduce femle reproductive success due to lrvl competition. The pttern found in the Beskid Żywiecki should e seen s eing relted with species life strtegy, ensuring high reproduction t n epidemic popultion level. The verge gllery length in our study mteril (6.75 cm) ws lower thn those reported from rk eetle outrek re in the Šumv Mts. in the Czech Repulic 7.8 cm (Mtoušek et l. 212) nd the Bieszczdy Mts. in Polnd 7.4 cm (Strzyk et l. 2). These differences my result from higher infesttion density in the Šumv Mts. nd the Bieszczdy Mts..68 nd.63 mting chmer/dm 2, respectively, versus.57 mting chmer/dm 2 in our study re, which cn indicte lower tree resistnce ginst the pressure of rk eetle popultions in outrek eruptive phse. On the other hnd, density of mternl glleries per dm 2 oserved in the present study 1.5, s well s reported y Strzyk et l. (2) nd likely (tking into ccount infesttion densities) in other studies mentioned ove, ws t lest twice s high s.5 the vlue reported s optiml for I. typogrphus reproduction (Schopf nd Köhler 1995). Infesttion density negtively ffected the length of mternl glleries nd oviposition, s it ws erlier demonstrted y Anderrnt (199) nd Weslien (1994). Nevertheless, the diversity pttern of gllery length relted to the hrem size (the numer of femles in one gllery system), similr s this reported y Strzyk et l. (2), confirms strong intrspecific competition mechnisms in I. typogrphus. Bsed on lortory tests, Anderrnt (199) showed the reltionship etween the mternl gllery length nd the numer of eggs lid y the femle, y mens of the following regression eqution: y =.53x 1.5 where: y is the numer of eggs, x is gllery length. If we pplied this eqution using our field dt, the men numer of eggs in one mternl gllery would e 34.25, while the men numer clculted using our regression eqution ws nd the verge vlue of oserved dt The possile reson of these differences might ly in environmentl conditions: controlled in lortory versus totlly nturl in the field, proly less fvorle for oviposition nd gllery construction on stnding, living trees. It should lso e noted, tht our dt concern effective reproduction, i.e. do not contin contrrily to dt reported y Anderrnt (199) lid eggs from which lrve did not emerge or died t erly stges. Our results correspond with those reported y Lukášová et l. (212) from nother mountin re (Šumv, the Czech Repulic), where the verge numer of eggs per femle otined from stnding infested trees ws On the other hnd, similr smpling done on lying trp trees (with wek or no defense mechnism) showed tht the men numer of eggs lid y one femle ws 35 (Mtoušek et l. 212), thus it ws higher thn tht in nturl infesttions of stnding trees, which supports the hypothesis out the resons of differences oserved. The effect of infesttion density (the numer of gllery systems per surfce unit), determined s fctor slightly limiting oth mternl gllery length nd the numer of progeny, reflects the mechnisms of intrspecific competition in I. typogrphus, known from severl erlier studies (e.g. Anderrnt 1985; DeJong nd Grijpm 1986). Sex rtio It ws demonstrted tht the sex rtio in I. typogrphus popultions vried etween outrek phses from 72% of femles in progrdtion to out 5% in retrogrdtion (Loinger 1996). All the sme, quite similr pttern seemed to pper in reltion to rk eetle popultions infesting windthrown trees in two outrek res in Polnd: in the Gorce Mts. (Grodzki et l. 26) nd in the Ttr Mts. (Grodzki et l. 27). When the outrek reched its eruptive phse, the shre of femles incresed thus we supposed tht the ove rules should e vlid lso in reltion to the popultions ttcking stnding trees, nd then useful for the ssessment of outrek tendency (Grodzki et l. 211). Unfor- Foli Forestli Polonic, series A, 214, Vol. 56 (2), 79 92

12 9 Wojciech Grodzki, Jerzy R. Strzyk, Mieczysłw Kosiowicz tuntely, it ws not possile to demonstrte such pttern sed on the results otined in reltively short time spn (3 growing sesons) nd from limited re. One of possile resons could e the fct tht the sex rtio is lso vrile within the growing seson more mles occur during spring swrming when compred with lter prts of the seson (Fccoli nd Buffo 24), nd the nlyses were not performed lwys in the sme prt of the yer. The mteril, represented y recently infested stnding trees, ws not ville lwys nd everywhere, so the choice of nlyzed trees ws to certin level hzrdous. In cse of I. typogrphus trees re ttcked first y mle eetles, then femles re ttrcted to the nuptil chmers. According to the TSA model (Christinsen et l. 1987), successful infesttion depends on the numer of ttcking eetles needed to overcome tree defense rection t given physiologicl nd resistnce sttus. This cn explin higher numer (nd proportion) of mles in the stnds with higher tree mortlity, where the numer of ttcking mles is driving fctor. Fccoli nd Buffo (24), when nlyzing sesonl vriility of the sex rtio in I. typogrphus eetles cught in pheromone trps, demonstrted higher proportion of mles during spring swrming thn in other prts of the vegettion seson. In multivoltine popultions (oserved in this study) the spring flight (nd ttck) is usully much more intense thn in cse of sister nd second roods (Fccoli nd Buffo 24, Grodzki 27). On the other hnd, pulished results on the sex rtio in spruce rk eetle popultions re hrdly comprle with those otined in the present study. The pttern of sex rtio vriility during individul phses of n outrek, descried y Loinger (1996), concerns I. typogrphus progeny in the glleries, while our results the eetles ttcking stnding trees. The erlier findings (Grodzki et l. 26, 27) suggesting the similr pttern during infesttion phse were sed on eetles collected mostly from lying (roken or uprooted) trees, where wek or no defense mechnisms occur. Nevertheless, we hve to conclude tht sed on our results the sex rtio of ttcking eetles, especilly generlly incresing percentge of femles during the 3-yer study period, reflect high potentil of oserved I. typogrphus popultions nd point to their strong outrek tendency in still ongoing epidemic phse in the Beskid Żywiecki. Length of eetles The results of mesurements of ody length of I. typogrphus eetles collected during 3 growing sesons did not sttisticlly differ etween the yers of oservtion, thus it ws decided to use pooled dt for further nlyzes. The longest eetles were collected in the stnds with the highest tree mortlity in the yer of collection. Botterweg (1982) found tht popultion density negtively influenced qulity of individul eetles (expressed y elytr weight), however ccording to the TSA model (Christinsen et l. 1987) high tree mortlity does not result directly from I. typogrphus popultion density, s ttck density on trees cn e similr in oth epidemic nd ltent popultions (Sllé et l. 25). Thus, the vriility in the length of eetles reflects rther qulity of reeding conditions s whole (including undnce of trees with reduced resistnce). Consequently, in specific conditions (i.e. higher tree mortlity) eetles were longer, which fits into the scheme proposed y Grodzki (24). Lrger length of eetles collected in the stnds with decresing tendency of tree mortlity might result from shortges in exploited reeding mteril the eetles from such decresing sites spred to surrounding prts of stnds with currently lower tree mortlity. Such spreding of popultions in tree stnds could explin why the longest eetles were collected in the sites with medium level of tree mortlity in the yer efore smpling. There re some wek points concerning the smpling of eetles for ody length mesurement. The proposed pttern, found in reltion to tree mortlity in the current yer only, suggests tht the eetles collected for mesurement originted from offspring genertion cptured in pheromone trps in lte spring/erly summer. The results otined using overwintered eetles smpled in the spring would proly e different. The sme concerns the question of locl origin of smpled eetles, s the results concerning eetles collected from pheromone trps nd from infested trees t the sme loclities re quite different, without ny pttern. This could suggest tht the eetles smpled from pheromone trps might not originte from locl popultions, s dispersl ilities in I. typogrphus re very high (Botterweg 1982, Gries 1985), consequently dt from pheromone trps re reltively hrd to use for the estimtion of popultion sptil distriution (Grodzki 27). Concluding, it seems tht the size of eetles lone is still not sufficient trit to predict popultion density trends (Sllé et l. 25). Foli Forestli Polonic, series A, 214, Vol. 56 (2), 79 92

13 Vriility of selected trits of Ips typogrphus (L.) (Col.: Scolytine) popultions in Beskid Żywiecki 91 The present results were minly otined during field investigtions (except for ody mesurements), therefore they re difficult to interpret. In field conditions it is not possile to keep the time regime when collecting dt. As it ws lredy mentioned, reserch mterils (infested trees, eetles) re not ville lwys nd everywhere it is I. typogrphus popultion which determines work timing nd dt qulity in the lst prt. In view of this, experiments crried out in controlled (lortory) conditions usully provide more homogenous dt, thus much esier for sttisticl tretment. However, if we wish to study the trits or fetures of rel popultions or to vlidte the results from lortory tests, the only wy is to investigte popultions in nturl conditions, even though the ptterns serched re more difficult to e found nd confirmed. Bsed on dt on the volume of trees infested y rk eetles felled in forest su-comprtments, for the most prt of the study re (Forest Districts Ujsoły nd Węgiersk Górk) outrek phse ws determined s retrogrdtion, nd for the remining re (Forest District Jeleśni) s stiliztion/ltency (Grodzki et l. 214). The trits nlyzed in this study indicted high potentil of rk eetle popultions in terms of outrek tendencies, suggesting tht I. typogrphus ws still in the epidemic stge within the whole investigted re. Tking into ccount the mount of potentil reeding mteril offered y Norwy spruce stnds in this re nd likelihood of wind or snow dmge tht stimulte rk eetle reproduction (Grodzki et l. 26; Grodzki 21), the risk of repeted outrek in the Beskid Żywiecki should e ssessed s extremely high. Conclusions The nlyzed trits of I. typogrphus showed high vriility nd dependence upon the locl mortlity of infested trees tht indirectly reflects rk eetle popultion level, however the defined ptterns of vriility re not cler enough to enle their use s direct predictors of outrek tendency in the future. These trits, however, indicte tht I. typogrphus popultion in the study re represents very high outrek potentil, s the vlues otined re typicl for the popultions t the epidemic stge or in progrdtion outrek phse. This suggest tht, in spite of decresing volume of infested trees removed from Norwy spruce stnds in slvge cuttings during lst yers, rk eetle popultions in the Beskid Żywiecki re still in eruptive phse nd the risk of repeted outrek in fvorle wether/reeding conditions is extremely high. Acknowledgements The investigtions were finnced from the funds for science in s the reserch project sed on the decision no 4278/B/P1/21/38. The uthors thnk the dministrtion of the Forest Districts: Jeleśni, Ujsoły nd Węgiersk Górk for ccess to the Stte Forest IT System (SILP) dt nd digitl mps s well s for support in field investigtions. References Anderrnt O Intrspecific competition ffecting prents nd offspring in the rk eetle Ips typogrphus. Oikos, 45, Anderrnt O Gllery construction nd oviposition of the rk eetle Ips typogrphus (Coleopter: Scolytide) t different reeding densities. Ecologicl Entomology, 15, 1 8. Anderrnt O., Schlyter F Cuses nd effects of individul qulity in rk eetles. Holrctic Ecology, 12 (4), Atkins M.D On fctors ffecting the size, ft content nd ehviour of scolytid. Zeitschrift für ngewndte Entomologie, 78, Botterweg P.F Dispersl nd flight ehviour of the spruce rk eetle Ips typogrphus in reltion to sex, size nd ft content. Zeitschrift für ngewndte Entomologie, 94, Botterweg P.F The effect of ttck density on size, ft content nd emergence of the spruce rk eetle Ips typogrphus L. Zeitschrift für ngewndte Entomologie, 96, Christinsen E., Wring R.H., Berrymn A.A Resistnce of Conifers to Brk Beetle Attck: Serching for Generl Reltionships. Forest Ecology nd Mngement, 22, Foli Forestli Polonic, series A, 214, Vol. 56 (2), 79 92

14 92 Wojciech Grodzki, Jerzy R. Strzyk, Mieczysłw Kosiowicz DeJong M.C.M., Grijpm P Competition etween lrve of Ips typogrphus. Entomologi Experimentlis et Applict, 41, Fccoli M., Buffo E. 24. Sesonl vriility of sexrtio in Ips typogrphus (L.) pheromone trps in multivoltine popultion in the Southern Alps. Journl of Pest Science, 77, Gries G On the question of dispersl of the engrver eetle (Ips typogrphus L.) (in Germn with English sumry). Zeitschrift für ngewndte Entomologie, 99, Grodzki W. 24. Some rections of Ips typogrphus (L.) (Col.: Scolytide) to chnging reeding conditions in forest decline re in Sudeten Mountins, Polnd. Journl of Pest Science, 77, Grodzki W. 27. The use of pheromone trps for the monitoring of Ips typogrphus (L.) popultions in selected ntionl prks in the Crpthins (in Polish with English sumry). Prce Instytutu Bdwczego Leśnictw, Rozprwy i monogrfie, 8, Grodzki W. 21. The decline of Norwy spruce Pice ies (L.) Krst. stnds in Beskid Śląski nd Żywiecki: theoreticl concept nd relity. Beskydy, 3 (1), Grodzki W., Loch J., Armtys P. 26. Occurrence of Ips typogrphus L. in wind-dmged Norwy spruce stnds of Kudłoń mssif in the Gorce Ntionl Prk (in Polish with English summry). Ochron Beskidów Zchodnich, 1, Grodzki W., Strzyk J.R., Kosiowicz M., Michlcewicz J., Mączk T. 27. Effect of windthrowns on the popultions of cmiophgous insects nd thret to Norwy spruce stnds in the Ttr Ntionl Prk. Report from the reserch done in within the project 2 P6L (in Polish). Instytut Bdwczy Leśnictw. Grodzki W., Strzyk J.R., Kosiowicz M Cn the functionl trits in Ips typogrphus (L.) reflects its outrek tendency? Freiurger Forstliche Forschung Berichte, 89, Grodzki W., Strzyk J.R., Kosiowicz M Influence of selected stnd chrcteristics on the intensity of rk eetle Ips typogrphus (L.) occurrence in Beskid Żywiecki (in Polish with English summry). Leśne Prce Bdwcze, 2, Loinger G Vritions in sex rtio during n outrek of Ips typogrphus (Coleopter: Scolytide) in Southern Bvri. Anzeiger für Schädlingskunde, Pflnzenschutz, Umweltschutz, 69, Lukášová K., Holuš J., Grucmnová Š Reproductive performnce nd nturl ntgonists of univoltine popultion of Ips typogrphus (Coleopter, Curculionide, Scolytine) t epidemic level: study from Šumv Mountins, Centrl Europe. Beskydy, 5 (2), Mtoušek P., Modlinger R., Holuš J., Turčáni M Numer of eggs lid y the spruce rk eetle Ips typogrphus (L.) (Coleopter: Curculionide: Scolytine) on trp trees: influence of selected fctors (in Czech with English summry). Zprávy Lesnického Výzkumu, 57 (2), Netherer S., Nopp-Myr U. 25. Predisposition ssessment systems (PAS) s supportive tools in forest mngement rting of site nd stnd-relted hzrds of rk eetle infesttion in the High Ttr Mountins s n exmple for system ppliction nd verifiction. Forest Ecology nd Mngement, 27, Sllé A., Bylc M., Lieutier F., 25. Size nd shpe chnges of Ips typogrphus L. (Coleopter, Scolytine) in reltion to popultion level. Agriculturl nd Forest Entomology, 7, Schlyter F., Zhng Q.-H Testing vin polygyny hypotheses in insects: hrem size distriution nd femle egg gllery spcing in Ips rk eetles. Oikos, 76, Schopf R., Köhler U Investigtions on the popultion dynmics of spruce rk eetle in Byerischer Wld Ntionl Prk. In: Bierlriether, H. et l.: 25 yers towrds nturl forest (in Germn). Pssvi Druckerei GmH, Pssu, Strzyk J.R., Groń K., Hłdś E. 2. Cmio- nd xylophgous insects in spruce (Pice ies (L.) Krst.) stnds of the Upper Sn River Vlley in the Bieszczdy Mountin Ntionl Prk (Estern Crpthins). Scientific Ppers of the Agriculturl University of Crcow, Forestry, 29, SttSoft, Inc. 29. STATISTICA for Windows [Computer progrm mnul]. Tuls, OK: SttSoft, Inc., Weslien J Interctions within nd etween species t different densities of the rk eetle Ips typogrphus nd its predtor Thnsimus formicrius. Entomologi Experimentlis et Applict, 71, Foli Forestli Polonic, series A, 214, Vol. 56 (2), 79 92