Regeneration ecology of black locust (Robinia pseudoacacia L.) in managed stands on Rožnik

V diplomski nalogi smo ugotavljali zmožnost širjenja robinije (Robinia pseudoacacia L.) v notranjost gozda iz skupin matičnih dreves, ki rastejo na gozdnem robu. Poleg tega smo ugotavljali tudi poglavitni način širjenja (semena, koreninski poganjki, panjevski poganjki) in ekološke razmere, ki omogočajo ter pospešujejo širjenje robinije. V ta namen smo iz izhodiščnih točk, ki so bile postavljene v bližini matičnih sestojev robinije, potegnili transekt v notranjost gozda. Skupno smo naredili tri transekte, na vsakem transektu pa smo postavili pet ploskev velikosti 5 x 5 m. Rezultati so potrdili uspešnost širjenja robinije v notranjost sestoja, saj ima pomembno vlogo v pomladku in je v vseh višinskih razredih druga najpomembnejša drevesna vrsta. Ugotovili smo, da širjenje robinije poteka predvsem prek koreninskih poganjkov, medtem ko je pomen semenskih poganjkov majhen. Zaradi tega ima velik vpliv na gostoto mladja robinije prav gostota matičnih dreves v bližini rastišča. Rezultati so pokazali, da je pomemben dejavnik pri pomlajevanju robinije tudi svetloba, čeprav je pomen le te manjši od pričakovanega. Na pomlajevanje robinije ima negativen učinek zastrtost rastišča z zeliščno plastjo, ki verjetno vpliva na manjši delež robinije na močno osvetljenih rastiščih. Močnejše širjenje robinije je možno preprečiti že z obstoječimi ali nekoliko prilagojenimi načini gospodarjenja, ki vključujejo malopovršinsko gospodarjenje in pomlajevanje pod zastorom matičnega sestoja, ter izvedbo negovalnih ukrepov, ki zagotavljajo čim večjo stabilnost in odpornost na naravne ujme, medtem ko je smiselnost bolj intenzivnega zatiranja vprašljiva. Vlogo robinije je potrebno ponovno pretehtati in se sprijazniti, da je postala del našega naravnega okolja.This thesis examines the invasion success of black locust (Robinia pseudoacacia L.) in a mature forest stand on Rožnik. We also tried to determine the prevalent type of regeneration (seeds, root sprouts, stump sprouts) and the optimal ecological conditions that enable or encourage the growth and spread of black locust. For that purpose, we located adult black locust trees growing on the edge of the study area and placed transects toward the forest stand interior. All together, we made three such transects and placed five plots measuring 5x5 m on each of them. The results showed that black locust does spread successfully into the inner parts of the forest. It was abundant in all height classes. We found that black locust spread primarily by means of its underground shoots, while seed regeneration was rare. As such, the density of young black locust plants depends on the density of larger black locust trees. The results suggest that light conditions also play a role in the spread of black locust, but the importance of light was less than expected. A potential obstacle for invasion of black locust is the understory herbaceous layer which % especially in well lit areas % may prevent further spread. A more pronounced spread of black locust may be prevented with existing adapted management measures, including small-scale silviculture and adult-tree management. It can also be prevented by tending native tree growth, enabling a higher stability and resistance to natural disturbances. The sensibility of intensive and direct removal is, however, questionable. The role of black locust is yet to be determined but we must face the fact that is has become a part of our environment