Uticaj proreda na strukture sastojina i prirast stabala budućnosti bele lipe (Tilia tomentosa Moench) na području Nacionalnog parka ,,Fruška gora''

Abstract

U okviru ophodnje jednodobnih sastojina, period nege traje najduže, a naročito njegov deo u kojem se primenjuju prorede. Efekti različitih uzgojnih strategija nege sastojina mogu se sagledati samo na osnovu dugoročnih istraživanja na trajnim i komparativnim oglednim površinama. U zavisnosti od godine osnivanja oglednih površina, u tezi je istraživan 25 ili 26-godišnji uticaj dva tretmana proređivanja izdanačkih sastojina bele lipe različitih starosti na području Fruške gore. Prvi tretman je selektivna proreda, usmerena na stabla budućnosti koja su izdvojena 1993/94. godine na trajnim oglednim površinama (tretman E), a drugi je niska proreda na komparativnim, novopodignutim oglednim površinama 2019. godine (tretman P) u istim sastojinama. Istraživan je uticaj sprovedenih tretmana proreda na strukturu sastojina i izdvojenih uporedivih kolektiva stabala — stabala budućnosti na tretmanu E i uporedivih stabala na tretmanu P, izdvojenih po istim kriterijumima kao i stabla budućnosti na tretmanu E, ali 25–26 godina kasnije. Istraživanja su sprovedena u sastojinama starosti 52, 69 i 86 godina na kraju 2019. godine. Na oglednim površinama izvršen je premer prečnika i visina stabala, ocenjivanje stabala po biološkom položaju, stepenu stešnjenosti krošnje i kvalitetu debla, i izvršeno je njihovo kartiranje. Na nivou stabala budućnosti i uporedivih stabala izvršen je premer elemenata vertikalne i horizontalne izgrađenosti krošnji i uzimani su izvrci Presrelovim svrdlom kako bi se utvrdili elementi debljinskog i temeljničnog prirasta stabala u istom posmatranom periodu primene različitih tretmana proreda. Za posmatrani period, sastojine negovane selektivnom proredom, primarno usmerenom na stabla budućnosti, karakteriše manji broj stabala, manja ukupna temeljnica i zapremina, veća horizontalna i vertikalna strukturna varijabilnost i znatno veće učešće stabala u okviru istog broja uporedivih kolektiva sa prečnikom većim od 35,0 cm bez kore (što je osnovni kriterijum za furnirski trupac) u odnosu na sastojine negovane niskom proredom. Stabla budućnosti karakterišu manje vrednosti stepena vitkosti i pravilnije razvijene krošnje u odnosu na uporedivi kolektiv stabala pod tretmanom niske prorede. U istraživanom periodu u sastojinama različitih starosti, reakcija debljinskog i temeljničnog prirasta je značajno veća kod stabala budućnosti negovanih selektivnom proredom u odnosu na uporedivi kolektiv stabala negovanih niskom proredom. Međutim, kod početka primene selektivne prorede u sastojinama starosti 44 i 61 godinu zabeležen je trend opadanja debljinskog prirasta u odnosu na starost 26 godina. Time je definisana okvirna starosna granica sastojina do koje je izražena prirasna reakcija stabala na primenu selektivne prorede. Iz razloga većih prečnika i većeg učešća zapremine stabala budućnosti u tretmanu E, ciljnog broja 150 stabala po hektaru u oba tretmana, njihove slabije prirasne reakcije posle 44. godine starosti, a uz jaku prirasnu reakciju u 26. godini, potvrđena je mogućnost korišćenja izražene prirasne reakcije stabala lipe, uz primenu selektivne prorede u sastojinama mlađim od 44 godine. Potvrđene su mogućnosti odgajivanja bele lipe sa većim prečnicima u periodu planske ophodnje uz primenu selektivne prorede, za razliku od uobičajene niske prorede, čime potvrđujemo mogućnosti ostvarivanja različitih funkcija šuma u nacionalnom parku kod različito formiranih sastojina lipe pod uticajem proreda.

Within a rotation period, tending takes the longest in even-aged stands, especially the part that involves thinning. The effects of different maintenance strategies can only be discerned on the basis of long-term studies on permanent and comparative plots. In this work, the influence of two thinning treatments over a period of 25–26 years in coppice silver lime stands of different ages in the Fruška Gora area was studied. The first treatment is a selective thinning targeting elite trees selected in 1993 and 1994 on permanent sampling plots (treatment type E). The second treatment is thinning from below on comparable, newly established plots in 2019 (treatment P) in the same stands. The effects of treatments on stand structure and selective tree collectives was investigated on treatment E (elite trees) and comparison trees on treatment P that were selected using the same criteria as the elite trees, but 25–26 years later. Surveys were conducted at ages 52, 69, and 86 years at the end of 2019. An inventory of diameters and heights was conducted at the sample plots, which included an assessment of trees by social class, crown insulation, and stem quality. All trees were mapped. A crown inventory was conducted at the elite and comparison tree levels, which included vertical and horizontal crown development parameters. The two groups of trees were also drilled through with an increment borer (Pressler) to determine the diameter and basal area increment of the trees over the 25–26 year period following the application of various thinning methods. In the 25–26 year period studied, stands where selective thinning was conducted, primarily targeting elite trees, were characterized by a lower number of trees, lower total basal area and volume, and more pronounced vertical and horizontal structure. In addition, a significantly higher number of trees with a mean breast height diameter of 35.0 cm without bark (the main criterion for veneer lumber) was found compared to the comparison trees in the thinning from below. The elite trees are characterized by lower values of the slenderness coefficient and more regularly developed crowns compared to the trees in thinning from below. In the studied period of 25–26 years, in the stands of different ages, the growth response of the trees, expressed in diameter and basal area increment, was significantly higher in the elite trees than in the comparable trees in the thinning from below. However, when selective thinning is initiated in stands at 44 and 61 years of age, there is a trend toward a decrease in growth response compared to initiation at 26 years of age. Therefore, a general age limit for the application of selective thinning was established. Within the target of 150 trees per hectare, the proportion of elite trees with a breast height diameter greater than 35.0 cm without bark was higher in the selective thinning treatment than in the thinning from below treatment. This, together with the decreasing growth response after 44 years and a strong response in the 26-year-old stand, confirms that the growth response of silver lime can be exploited by intensive selective thinning in stands younger than 44 years. It is confirmed that silver lime with higher breast height diameters can be grown in the planned rotation by selective thinning, which is not the case with the commonly used thinning method from below. Therefore, the high quality silver lime stands already established can be used for a number of other forest functions in the National Park.