DIGITALNA ARHIVA ŠUMARSKOG LISTA
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ŠUMARSKI LIST 3-4/1969 str. 3 <-- 3 --> PDF |
ŠUMARSKI LIST SAVEZ INŽENJERA I TEHNIČARA ŠUMARSTVA I DRVNE INDUSTRIJE HRVATSKE GODIŠTE 93 OŽUJAK—TRAVANJ GODINA 1969 OPADANJE PRIRASTA U NAŠIM VRIJEDNIM HRASTOVIM SUMAMA Prof. dr DUŠAN KLEPAC, Zagreb Kad sam se nakon dvogodišnjeg boravka u Meksiku vratio početkom 1968. godine u domovinu i ponovno pregledao pokusne plohe Katedre za uređivanje šuma u nizinskim posavskim šumama gospodarske jedinice »Josip Kozarac«, bio sam prilično iznenađen. Još prije nego što je slavonska šuma prelistala, učinila mi se na prvi pogled nešto slabija nego prije. Kad sam pojedine parcele detaljnije promatrao, primijetio sam, da je hrastova kora na mnogim stablima nabubrila i dobila mjestimično poseban izgled. To se očitovalo najviše u donjem dijelu hrastova debla, gdje sam mjestimično mogao prstima skidati inače tvrdu hrastovu koru. Ispod kore primijetio sam, da se drvo crni a tu i tamo vidio se micelij. Odmah sam pomislio na gljivu Armilaria melea (Škorić, K i spa ti ć). Mogu reći, da je u srednjedofonim, pa i u najstarijim hrastovim mješovitim sastojinama gotovo svako četvrto hrastovo stablo tako napadnuto. To sam primijetio više puta u proljeće 1968. godine u mješovitim sastojinama hrasta lužnjaka s običnim grabom, u sastojinama koje smo* biološki smatrali otpornima, koje su bile vanredno lijepe, vrijedne i vrlo produktivne. Baš u tim sastojinama izmjerio sam pred više godina velike tečajne priraste od oko 10 kubičnih metara po hektaru na godinu. Ti su podaci više puta provjereni i kao takvi usvojeni. Istina je, da sam već i ranijih godina konstatirao smanjenje tečajnog prirasta bilo zbog napadaja gubara (Lyrnantria dispar), bilo zbog ostalih insekata kao što su hrastova osa listarica (Apethymus abdominalis Lep.), četnjak (Cnethocampa processionea L.), hrastov savijač (Tortrix viridana L.) i drugih*. Ovoga puta činilo mi se vrlo zanimljivim i važnim da ponovno izmjerim prirast tih sastojina, jer sam već na prvi pogled uočio njihovu slabiju vitalnost. Na to me još više ponukala činjenica, da su mnogi kolege na fakultetu i u operativi već poduzeli akciju za sprečavanje sušenja naših hrastovih šuma, pošto su primijetili tu pojavu mnogo prije mene. Imajući to pred očima, ograničit ću se ovdje na mjerenje prirasta i utvrđivanje gubitaka koji su nastali zbog sušenja hrastovih šuma. U tom smjeru odlučio sam izvršiti četvrtu inventuru najstarijih pokusnih ploha. To su prva (odjel 157), treća (odjel 155), četvrta (odjel 155) i šesta (odjel 165) pokusna ploha u gospodarskoj jedinici »Josip Ko^ zarac« u šumariji Lipovljani. Prema tome moje je želja utvrdit i egzakt * D. Klepac: Zuwachsverluste in Eichnmischbeständen, die durch Kalamität des Schwammspinners und anderer blattfressender Schädlinge befallen wurden, Wissenschaftliche Zeitschrift der Technischen Universität Dresden, 15 (1966) Heft 2 Herausgeber: der Rektor. Referat održan na Internacionalnom savjetovanju o prirastu u THARANDTU, listopad 1965. |
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n i m metodama kako danas prirašćuju te iste sastojine koje smo do nedavno ubrajali među najproduktivnijenajljepše hrastove nizinske šume. METODA RADA Metoda rada na terenu sastojala se u ponovnom mjerenju opsega stabala u prsnoj visini pomoću čelične vrpce isto onako kako sam to radio za vrijeme prve i druge inventure sa prof, dr M. Plavšiće m i asistentom ing. R. Križance m za vrijeme treće inventure. U proljeće 1968. obavio sam četvrt u inventuru , koja nosi naziv inventura 1967. Prvu inventuru obavio sam u proljeće 1951. (inventura 1950), drugu u jesen 1955. (inventura 1955) i treću u proljeće 1962. (inventura 1961). S obzirom na to da su na pokusnim plohama stabla numerirana i da smo ing. R. K r i ž a n e c, sveuč. asistent i ja mjerili naizmjence svaku pokusnu plohu dva puta, grube su pogreške eliminirane a sistematske su svedene na minimum. Obračun prirasta izveden je po kontrolnoj metodi onako kako sam to opisao u svojoj knjizi »Rast i prirast šumskih vrsta drveća i sastojina«, Zagreb, 1963, strana 199—-212 s tom napomenom da je u toj knjizi uzeta kao primjer jedna od navedenih pokusnih ploha (četvrta pokusna ploha, odjel 155). No ovoga sam puta pored volumnog prirasta mjerio i računao debljinski prirast po kontrolnoj metodi. Pri obračunu volumnog prirasta pojavilo se pitanje da li je potrebno promijeniti tarife, koje sam upotrebljavao prilikom prethodnih inventura, jer se ovdje radi o jednodofonim sastojinama. Prvi pokusi i računi su pokazali da u ovom slučaju ne bi imalo pravoga smisla mijenjati tarifu za obračun tečajnog prirasta u pojedinim periodama između dvije inventure. Tabela 1 Tečajni godišnji volumni prirast po hektaru u razdoblju godina Current annual volume increment per hectare in different periods of years a " Prosjek-Average o <> -g,o 1950—1955 1955—1961 1961—1967 1950—1967 a « 2 2 2 g i t L * isti & s 3^ Sg &S ä * lie I s 8 * gg f I L c/oNo 1 ffiO « Q S H ffiO oiQ s L ffiO Biß 2 H Ä O 0 Odjel |
ŠUMARSKI LIST 3-4/1969 str. 5 <-- 5 --> PDF |
Zato sam izvršio obračun prirasta na bazi tarifa, izabranih na početku mjerenja. Prema tome tečajni godišnji volumni prirast sam izračunao za ove vremenske intervale: 1. perioda od 1950. do 1955. godine (1951, 1952, 1953, 1954 i 1955 god); 2. perioda od 1955. do 1961. godine (1956, 1957, 1958, 1959, 1960 i 1691 g.); 3. perioda od 1961. do 1967. godine (1962, 1963, 1964, 1965, 1966 i 1967 g.). Prvi vremenski interval ili kontrolna perioda je duga 5 godina, drugitreći svaki po 6 godina, što ukupno iznosi 17 godina otkako sam započeo ova mjerenja i istraživanja. Obračun prirasta izvršen je također i za cijeli vremenski interval od 1950. do 1967. uzimajući u obzir samo prvu i četvrtu inventuru. I taj je obračun izvršen na temelju istih tarifa, iako bi za obračun četvrte inventure možda trebalo upotrebiti nešto višu tarifu. No kako razlike u rezultatima nisu osjetljive, odlučio sam i u ovom slučaju zadržati iste tarife. To obrazlažem slabim »pomakom visinske krivulje« u istraživanim sastojinama. Ipak tom problemu ću obratiti posebnu pažnju u daljnjim istraživanjima. REZULTATI Rezultate o tečajnom godišnjem volumnom prirastu prikazao sam u tabelama 1 i 2. Iz tabele 2 se vidi kako se kretao godišnji volumni prirast hrast a lužnjak a u pojedinim vremenskim intervalima. Tabela 2 Vremenski interval Prva ploha Treća ploha Četvrta ploha Šesta ploha (odjel 157) (odjel 155) (odjel 155) (odjel 165) godine tečajni godišnji volumni prirast: 1950 _ 1955 8.4 m> 8.6 m3 10.9 m3 9.3 m=> 1955 — 1961 6.3 m3 8.5 m3 8.9 m3 6.8 m3 1961 — 1967 4.9 m> 4.2 m3 5.2 m3 5.5 m3 1950 — 1967 6.4 m3 7.0 m3 8.2 m" 7.0 m3 (prosjek) Napominjem da prosjek za vremenski interval od 1950 do 1967 nije obračunan kao aritmetička sredina izmjerenih prirasta u pojedinim periodama nego je dobiven kao razlika između četvrte i prve inventure. DISKUSIJA Dobiveni rezultati jasno govore da je tečajni godišnji volumni prirast u vremenskom intervalu od 1961. — 1967. pao za oko 50% u usporedbi na isti prirast pred desetak godina. Da bi se uvjerio u tačnost toga, izvršio sam po kontrolnoj metodi posebni obračun debljinskog prirasta i došao do istog zaključka: godišnji debljinski prirast u vremenskom intervalu od 1961. — 1967., tj. u posljednjih šest godina pao je također za oko 50% u usporedbi na debljinski prirast u vremenskom intervalu od 1950. — 1967. Sigurnosti radi izveo sam naknadne pokuse i to tako, da sam pomoću prirasnog svrdla uzeo izvrtke iz susjednih odjela iste gospodarske jedinice. Analiza tih izvrtaka pokazala je manje ili više istu tendenciju opadanja prirasta. Čemu pripisati to naglo smanjenje prirasta u našim najljepšim hrastovim šumama? |
ŠUMARSKI LIST 3-4/1969 str. 6 <-- 6 --> PDF |
Na to je pitanje u prvi čas teško odgovoriti bez timskog rada jedne veće grupe stručnjaka, koja danas obrađuje taj problem. No ipak — čini se — da je po srijedi kompleks različitih faktora od kojih spominjem na prvom mjestu gubara i ostale insekte, koji su u toku duljeg vremena sad jače sad slabije napadali ove šume te su s nekim gljivama u određenim okolnostima prouzrokovan sušenje hrastika. Na drugom mjestu naveo bih klimatske, edafske i gospodarske faktore, koji su vrlo vjerojatno stvorili povoljne preduvjete za različite napadaje na hrastove šume i tako utjecali na smanjenje prirasta. Na trećem mjestu istaknuo bih starost istraživanih sastojina. Kako se ovdje radi o 80-godišnjim jednodobnim sastojinama, jasno je, da u toj dobi tečajni prirast sa starošću postepeno opada. Prema tome, u ovom je slučaju starenje sastojina također jedan od uzroka smanjenja prirasta. Na četvrtom mjestu spomenut ću metodu rada, tj. kontrolnu metodu, koja bi u ovom slučaju mogla dati nešto niže rezultate o prirastu zbog upotrebe istih tarifa. Na kraju bih ukazao i na nepoznate uzroke, koji se upravo istražuju u timskom radu novog Zavoda za šumarska istraživanja Zagrebačkog šumarskog fakulteta. Sve u svemu zasad se može izvući ovaj ZAKLJUČAK Na pokusnim plohama Katedre za uređivanje šuma Zagrebačkog šumarskog fakulteta u Lipovljanima različiti faktori — poznati i nepoznati — prouzrokovati su u toku posljednih 6 godina smanjenje volumnog prirasta hrasta lužnjaka za oko 50% u usporedbi na prirast pred 10 godina. Zasad je teško reći koliki udio ima pojedini faktor na to smanjenje prirasta, u toliko više, što treba utvrditi posebnu metodu rada s obzirom na intenzitet zaraze i ostale faktore, što će između ostaloga biti jedan od predmeta istraživanja novog Zavoda za šumarska istraživanja Šumarskog fakulteta u Zagrebu. LITERATURA Androi ć M.: Ekonomske i biocenotske posljedice kasnog tretiranja sastojina protiv gubara, Šumarski list, Zagreb, 1959. K i š p a t i ć J.: Fitopatološki praktikum — Izdanje: Nakladni zavod Hrvatske, Zagreb, 1950, str. 128, si. 80. Klepa c D.: Izračunavanje gubitka na prirastu u sastojinama koje je napao gubar, Šumarski list, Zagreb, 1959. Klepa c D. — Spai ć I.: Utjecaj nekih defolijatora na debljinski prirast hrasta lužnjaka, Šumarski list, Zagreb, 1965. Škori ć V.: Erysiphaceae Croatiae (Prilog fitopatološko-sistematskoj monografiji naših pepelnica). (Contribution to the phytopathologic-systematic monograph of our powdery mildews). Škori ć V.: Uzroci sušenja naših hrastovih šuma (Causes of dying away of our oak-forests). Glasnik za šumske pokuse, br. 1, Zagreb, 1926. Proda n M.: Holzmesslehre, Frankurt am Main, 1965. Vajd a Z.: Naučno istraživačke studije o sušenju hrastika, Šumarski list, Zagreb, 1968. NAPOMENA. Ova istraživanja financirao je Republički fond za naučni rad SR Hrvatske putem Instituta za šumarstvo SR Hrvatske i Zavoda za istraživanje u šumarstvu Šumarskog fakulteta u Zagrebu, koji su mi pri ovim istraživanjima izašli u susret pa im na tome ovdje najljepše zahvaljujem. Također zahvaljujem drugu ing. Radovan u Križancu , asistentu Katedre za uređivanje šuma, kao i upravitelju šumarije Lipovljani ing. Mat i Markanović u koji su mi pomogli u radu. ´ci´,) |
ŠUMARSKI LIST 3-4/1969 str. 7 <-- 7 --> PDF |
DIMINUTION OF INCREMENT IN OUR VALUABLE OAK FORESTS by Prof. Dr Dušan Klepac, Zagreb When after a two-year stay in Mexico I returned home early in 1968 and inspected again the experimental plots of the Chair for Forest Management situated in the lowland forests of the Sava River area, management unit »Josip Kozarac«, I was in for a surprise. Even before the Slavonian forest had flushed, it seemed to me at first sight somewhat less vigorous than before. I at once thought it might suffer from a disease. On inspecting individual plots in more detail, however, I noticed that the bark on numerous Oak trees was swollen up and assuming a specific appearance in places. This was mainly manifest in the lower parts of the stem where I was able to remove with the fingers the normally hard Oak bark. Beneath the bark I noticed that the wood was blackened, and that the mycelia were visible in places. I may say that in middle-aged and even oldest mixed Oak stands nearly every third or fourth Oak tree was attacked in this manner. I had noticed this on several occasions in the spring of 1968 in mixed Oak stands with Hornbeam which were considered biologically resistant, and which were exceptionally well formed, valuable and highly productive. It was exactly in these stands that a few years ago I determined high current volume increments of about lOcu.m. per ha./year. These data were repeatedly verified and accepted as such. True, already in previous years 1 had established reductions of current volume increment owing to attacks by the Gipsy Moth (Lymantria dispar L.) or by other insect pests such as the Oak Leaf Wasp (Apethymus abdominalis Lep.), the Pine Processionary Moth (Thaumetopoea processionea L.), the Oak Leafroller Moth (Tortrix viridana L.), etc.* On the same occasion it seemed to me very interesting and important to measure again the increment of the mentioned stands, for already at first sight I had noted that their vitality was weakened. I was prompted to this even more by the fact that my colleagues at the Faculty had already undertaken steps to control the die-back of our Oak forests, having noticed this phenomenon much earlier than I. Bearing this in mind, I will limit myself here to the measurement and determination of the losses caused by the die-back of Oak forests. In this connecttion I made up my mind to carry out a fourth inventory of the oldest experimental plots. They were: the first (compt. 157), third (compt. 155), fourth (compt. 155) and sixth experimental plots (compt. 165) in the management unit »Josip Kozarac«, forest district of Lipovljani (Croatia). Accordingly, I wanted to determine by exact methods toda´s growth rates of these same stands which — until recently — had ranked among the most productive and well-formed lowland Oak forests. Work method The work method consisted in the remeasurement of breast height girths of trees by means of a steel girthing tape in the same manner as done by myself during the first and second inventories in association with Prof. Dr M. Plavsic, and the third inventory in association with ing. R. Križanec. In fact, last spring I performed a fourth inventory marked as inventory 1967. The first inventory was done in the spring of 1951 (inventory 1950), the second in the autumn of 1955 (inventory 1955), the third in the spring of 1962 (inventory 1961). Considering that stems on the experimental plots are marked numerically, and that ing. R. Križanec and myself had by turns measured each experimental plot twice, rough errors were eliminated and the systematic errors were reduced to a minimum. The calculation of increment was made according to the control method in the manner described in my book »Rast i prirast šumskih vrsta drveća i sastojina« (Growth and Increment of Forest Tree Species and Stands, Zagreb, 1963, pp. 199— 222, with the remark that in this book one of the mentioned experimental plots (the 4th experimental plot, compt. 155) was taken as a model. This time, however, in addition to the volume increment I also measured and computed the diameter increment according to the control method. When calculating the volume increment there arose the question whether it was necessary to change the tariffs which I had * D. Klepac: Zuwachsverluste in Eichenmischbeständen, die durch die Kalamität des Schwammspinners und anderer blattfressender Schädlinge befallen wurden. Wiss. Z. Techn. Universität, Dresden, 15 (1966), Heft 2. (A report held on the International Symposium on Increment at Tharandt, October, 1965). 89 |
ŠUMARSKI LIST 3-4/1969 str. 8 <-- 8 --> PDF |
used during the previous inventories, because here we were concerned with even- aged stands. Experiments and calculations demonstrated that in this case it would be of no use changing the tariff for computation of the current increment in individual periods between two inventories. Hence I computed the increment on the basis of tariffs chosen at the beginning of the measurements. Consequently I calculated the current volume increment for the following time intervals: 1) period 1950—1955 (years: 1951, 1952, 1953, 1954, and 1955); 2) period 1955—1961 (vears: 1956, 1957, 1958, 1959, 1960, and 1961); 3) period 1961—1967 (years: 1962, 1963, 1964, 1965, 1966, and 1967). The first time interval or control period lasted 5 years, the second and third 6 years each, which totals 17 years from the time I had started these measurements and investigations. The calculation of increment was carried out also for the whole time interval 1950—1967 taking into consideration only the first and fourth inventories. This computation too was performed on the basis of the same tariffs, although for the calculation of the fourth inventory it would have been convenient to use a little higher tariff. But as the differences in the results are not significant, I decided to retain also in thisheight curve« in the stands case the same invest tariffs, becauseigated. of weak »displacement of the Results The results concerning the current annual volume increment are classified in Table 1- From Table 2 the fluctuation of the annual volume increment of Pedunculate Oak in the periods investigated may be seen. Table 2 Period lrst plot 3rd plot 4th plot 6th plot investigated (Compt. 157) (Compt. 155) (Compt. 155) (Compt. 165) Years Current annual volume increment, cu.m. per ha 1950—1955 8,4 8,6 10,9 9,3 1955—1961 6,3 8,5 8,9 6,8 1961—1967 4,9 4,2 5,2 5,5 1950—1967 (Average) 6,4 7,0 8,2 7,0 It should be stated that the average value lor the time interval 1950—1967 was not computed as an arithmetical mean of the measured increments in individual periods, but was obtained as the difference between the fourht and first inventories. Discussion The results obtained show clearly that the current annual volume increment of Oak stands in the time interval 1961—1967 had dropped by about 50 V« if compared with the same increment ten years ago. In order to verify this, I made according to the control method a special calculation of the diameter increment and came to the same conclusion: The annual diameter increment in the period 1961—1967, viz. in the last six years, also experienced a drop of about 50"/» in comparison with the diameter increment in the preceding period 1950—1967. For the sake of safety I carried out supplementary tests, so that by means of increment borer I took increment cores from the neighbouring compartments of the same management unit. An analysis of these increment cores showed more or less the same tendency to increment drop. What is this rapid drop of increment in our best Oako forests to be accounted for? Among the various factors which have caused this loss in increment I should point in the first place to the Gipsy Moth and other insect pests which for quite a time have been attacking more or less severily these forests, and in association with certain fungi in definite circumstances have caused the die-back of Oak stands. Second, I should mention the climatic, edaphic and silvicultural factors which most probably produced favourable preconditions for various atacks on Oak forests and thus brought about a serious reduction of the increment. |
ŠUMARSKI LIST 3-4/1969 str. 9 <-- 9 --> PDF |
Third, I should point to the age of investigated stands. As we are dealing here with 80-year even-aged stands, it is clear that at this age the current increment gradually decreases with age. Accordingly, in this case the ageing of stands also is one of the causes of increment regression. Fourth, I shall mention the method of work, viz. the control method which in this case yielded somewhat lower values concerning the increment owing to the use of the same volume tariffs. Finally I should point also to the unknown causes which will still be investigated and likely to be establiched later on. Taken as a whole, for the time being the following may be said: Conclusion On the experimental plots of the Chair for the Forest Management of the Zagreb Faculty of Forestry, situated at Lipovljani, varied known and unknown factors have caused in the course of the last 6 years a sharp reduction of the Oak stand volume increment by about 50a/o if compared with the increment of 10 years ago. For the moment it is difficult to say what share has the individual factor in this increment reduction. This, among other things, will be the subject of investigations by the new Institute for Forest Research of the Zagreb Faculty of Forestry. |