A forest management unit (FMU) is a management−planning unit containing stands distinguished in terms of their similar production possibilities (e.g. on account of site type). In Polish forestry, the shelterwood FMU category groups together stands managed using a uniform shelterwood cutting system, group cutting, and a stepwise cutting system (with a regeneration period of up to 40 years). However, the forecasting of stand development in FMUs of this type proves more difficult than in clear−cutting FMUs, due to the presence of stands with young−generation trees (formally assigned to classes ‘in regeneration’ or ‘with regeneration to be improved’). Such stands transition into one of the lower age classes depending on the age of regeneration after the clear−up cuts, but thus far there has been uncertainty as to the probability of the regeneration process completion (when the last cut is completed and regeneration layer covers presumed area), and as to the aspects that might make such completion more or less likely. Hence the work detailed here, which has sought to determine the nature of influences on the probability of the regeneration process being completed, as well as the dependence of that on type of cutting. The data put to this use were collected by Poland’s Forest Management and Geodesy Bureau in line with the Forest Management Instruction, in respect of 64 Forest Districts located within 14 of Poland’s 17 State Forests’ Regional Directorates, and with a view to forest management plans being developed and made available by the Directorate General of the State Forests . More specifically, data from plans elaborated in 2009 and 2010 were used, as were (in essence) repeat−data from plans elaborated for the same Districts 10 years later – in 2019 and 2020. The degree to which regeneration processes could be considered completed was then estimated empirically by overlaying the vector map of stands of Forest Districts with a 100×100 m grid of sample plots. Probabilities were calculated using logistic regression in line with type of cutting applied (uniform, group or stepwise), and the mean age or mean height of trees in the regeneration layer, along with assumed regeneration periods (of up to or more than 10 years). The relationship between the mean heights and mean ages of trees in the regeneration layer was checked, with the calculated probability then used to develop theoretical distributions of stands in age classes of the regeneration layer and height classes of young trees, with these then set against the distributions determined empirically. In the event, no correlation was found between the maximum age/height of trees in the regeneration layer or the age/height of the dominant tree species in the regeneration layer (where dominant means those present in the highest proportion), on the one hand; and the probability of the regen eration process being completed, on the other. Also looked for, though not confirmed, was an influence on completion of the regeneration process exerted by closure and dominant tree species in the upper storey, and degree of cover of the stand area achieved by the regeneration layer. In turn, completion of the regeneration process was shown to be influenced by the average age and height of trees in the regeneration layer.

Banaś, J., 1996a. Prawdopodobieństwo przeżycia I wyrębu drzewostanów w przerębowo-zrębowym sposobie zagospodarowania. (Likelihood of survival and cutting of stands in the selection-clearcutting system of forest management). Sylwan, 140 (9): 85-92.
Banaś, J., 1996b. Prognozowanie rozmiaru użytkowania rębnego w przerębowo-zrębowym sposobie zagospodarowania. (Forecasting the size of the final yield in a shelterwood management system). Sylwan, 140 (12): 41-46.
Banaś, J., Zięba, S., Bujoczek, L., Zygmunt, R., Drozd, M., 2015. Metoda określania średniego wieku gospodarstwa w przerębowo-zrębowym sposobie zagospodarowania lasu. (Method of assessment average age of forest range in shelterwood cutting system). Sylwan, 159 (9): 732-739. DOI: https://doi.org/10.26202/sylwan.2015022.
Borecki, T., Orzechowski, M., Stępień, E., Wójcik, R., 2017. Przewidywane oddziaływanie zmian klimatu na ekosystemy leśne oraz ich konsekwencje w urządzaniu lasu. (Expected impact of climate change on forest ecosystems and its consequences in forest management planning). Sylwan, 161 (7): 531-538. DOI: https://doi.org/10.26202/sylwan.2017008.
Borecki, T., Stępień, E., 2017. Ewolucja roli i aktualnych zadań urządzania lasu. (Evolution of the role and current tasks of forest management planning). Sylwan, 161 (3): 179-188. DOI: https://doi.org/10.26202/sylwan.2016105.
Buongiorno, J., 2001. Quantifying the implications of transformation from even to uneven-aged forest stands. Forest Ecology and Management, 151: 12-132. DOI: https://doi.org/10.1016/S0378-1127(00)00702-7.
Drozdowski, S., 2006. Wykorzystanie modelu macierzowego do prognozowania rozwoju drzewostanów o złożonej postaci. (Application of a matrix model for projecting the development of stands with complex structure). Sylwan, 150 (2): 3-13. DOI: https://doi.org/10.26202/sylwan.2005059.
Forests in Poland, 2022. Report. Warszawa: Centrum Informacyjne Lasów Państwowych.
Gazda, A., Miścicki, S., 2016. Prognoza zmian składu gatunkowego Białowieskiego Parku Narodowego. (Forecast of changes in the tree species composition of forest stands in the Białowieża National Park). Sylwan, 160 (4): 309-319. DOI: https://doi.org/10.26202/sylwan.2015106.
Gołos, P., Kaliszewski, A., 2016. Społeczne i ekonomiczne uwarunkowania realizacji publicznych funkcji lasu w Państwowym Gospodarstwie Leśnym Lasy Państwowe. (Social and economic conditions for providing public forest services in the State Forests National Forest Holding). Sylwan, 160 (2): 91-99. DOI: https://doi.org/10.26202/sylwan.2015084.
IUL, 2003. Instrukcja Urządzania Lasu. Warszawa: Centrum Informacyjne Lasów Państwowych.
IUL, 2012. Instrukcja Urządzania Lasu. Warszawa: Centrum Informacyjne Lasów Państwowych.
Kanabus, R., Miścicki, S., 2022. Forest-stand survival in different age classes. (Przeżywalność drzewostanów w klasach wieku). Sylwan, 166 (7): 415-430. DOI: https://doi.org/10.26202/sylwan.2022044.
McElhinny, C., Gibbons, P., Brack, C., Bauhus, J., 2005. Forest and woodland stand structural complexity: Its definition and measurement. Forest Ecology and Management, 218: 1-24. DOI: https://doi.org/10.1016/j.foreco.2005.08.034.
Miścicki, S., 2016. Changes in the stands of the Białowieża National Park from 2000 to 2015. Forest Research Papers, 77 (4): 371-379. DOI: https://doi.org/10.1515/frp-2016-0038.
Poznański, R., 1999. Nowa metoda programowania rozwoju zasobów leśnych w przerębowo-zrębowym sposobie zagospodarowania z rębnią stopniową. (A new method of programming the development of forest resources in a selection clearcutting methods of forest management with gradual cutting). Sylwan, 143 (5): 13-25.
Poznański, R., Boroń, A., Wróblewska, I., 1999. Długość okresu odnowienia a intensywność cięć rębnych w przerębowo-zrębowym sposobie zagospodarowania. (The length of regeneration time and the cutting intensity in a selection-clearcutting system of forest management). Sylwan, 143 (4): 91-96.
Poznański, R., Jaworski, A., 2000. Nowoczesne metody gospodarowania w lasach górskich. Warszawa: Centrum Informacyjne Lasów Państwowych, 228 pp.
Poznański, R., 2003. Wpływ czynników otoczenia na przeżywanie i ubywanie drzewostanów w klasach wieku. (Influence of environmental factors on survival and mortality of stands in age classes). Kraków: Wydawnictwo Akademii Rolniczej, 156 pp.
Pukkala, T., 2013. Introduction to multi-objective forest planning. In: T. Pukkala, Multi-objective forest planning. Berlin/
Heidelberg: Springer Science & Business Media, pp. 1-19.
Rosenvald, R., Rosenvald, K., Kaart, T., Solmann, E., 2020. Effects of stand parameters on conifer regeneration success in pine shelterwood stands in Estonia. European Journal of Forest Research, 139: 29-40. DOI: https://doi.org/10.1007/s10342-019-01255-6.
StatSoft Inc., 2017. Statistica (data analysis software system). Available from: http://www.statsoft.com.
WISL, 2022 Wielkoobszarowa inwentaryzacja stanu lasów. Wyniki za okres: 2017-2021. Sękocin Stary: Biuro Urządzania Lasu i Gospodarki Leśnej, 124 pp.
Zarządzenie, 2022. Zarządzenie nr 58 Dyrektora Generalnego Lasów Państwowych z dnia 5 lipca 2022 w sprawie wprowadzenia „Wytycznych do zagospodarowania lasów o zwiększonej funkcji społecznej na gruntach w zarządzie Lasów Państwowych”.