Radka Stolariková

Relation between forest stand diversity and anticipated log quality in managed Central European forests

ABSTRACT This study examined the influence of tree species and structural diversity on the production of high-quality logs. The data were from the regional forest inventory of the University Forest Enterprise, Czech Republic, performed from 2009 to 2011 on 1188 sample plots. For every sample plot, we quantified 38 diversity indicators. The plots were divided into four age groups (young, middle-aged, old and uneven-aged stands). The anticipated proportion of high-quality logs was determined using local assortment tables. For each age group, the impact of species and structural diversity indicators on the volumetric proportion of high-quality logs was assessed using backwards multiple regression. The relationship between diversity measures and log quality changed with stand age. In old stands, horizontal structure had a more profound effect on the proportion of high-quality logs. In young stands, species diversity and vertical structure were more influential. In middle-aged stands, the impact of stand diversity on log quality was most complex. In uneven-aged stands, vertical structure was the diversity component most affecting the proportion of high-quality logs. Overall, the proportion of best quality logs increased with the increasing stand diversity in all age classes, suggesting that timber production and stand diversity are not contradictory management goals. EDITED BY Sheila Ward

Functions for the aboveground woody biomass in Small-leaved lime (Tilia cordata Mill.) / Funkce pro hodnocení biomasy nadzemních částí lípy malolisté (Tilia cordata Mill.)

Abstract The Small-leaved lime (Tilia cordata Mill.) is currently not commercially important species, therefore the knowledge of biomass partitioning in a tree is rather incomplete. Moreover, lime biomass is estimated mostly using biomass functions designated for other species, without the knowledge of limits of such a use. For these reasons, we developed functions for the estimation of lime biomass in the aboveground woody parts. The functions were parameterized using 81 tree samples collected in two plots in the Czech Republic. In addition, we compared the biomass estimates produced by our functions with estimates produced by a function for beech, which have been obviously used as a surrogate for missing lime models in the Czech Republic and Slovakia. On average, 78% of lime aboveground biomass was found to account for tree stem, 20% for branches and 2% for stump. Average biomass density was 374 kg m−3 and no significant differences between tree compartments were found. Accuracy of all models in terms of the Root Mean Square Error (RMSE) significantly differed between tree diameter classes; in case of total aboveground biomass, the RMSE was ca. 20% of the average biomass weight in a given class up to a diameter of 45 cm, and then it rose sharply. The RMSE was higher in case of compartments with variable dimensions, such as branches and stump. RMSE was slightly higher in case of estimates produced using a beech-specific function than using that developed in the current study (average RMSE 27.95 and 29.42%, respectively); at the same time, beech-specific function overestimated lime stem biomass by ca 12%. The almost equal RMSE implies the usability of both parameterisations for lime biomass estimation, though the correction of the mentioned overestimation should be applied. Abstrakt Lípa malolistá (Tilia cordata Mill.) v současnosti nepředstavuje hospodářsky významnou dřevinu, což je jeden z důvodů proč jsou poznatky o distribuci její biomasy v rámci stromu značně nekompletní. Kromě toho, biomasa lípy je většinou hodnocená pomocí rovnic navrhnutých pro jiné dřeviny, přičemž možné nedostatky tohoto postupu jsou ve značné míře neznámé. Z těchto důvodů jsme na základě údajů získaných z 81 stromů na dvou plochách v České republice vytvořili parametrizace rovnic pro odhad dřevnatých částí nadzemní biomasy lípy. Následně jsme porovnali odhady objemu biomasy lípy získané pomocí námi navrhnutých modelů s odhadem získaným modelem parametrizovaným pro buk, který je v České republice a na Slovensku pro hodnocení biomasy lípy obvykle používaný. V průměru připadalo 78% nadzemní biomasy na kmen stromu, 20% na korunu a 2% na pařez. Průměrná hustota biomasy činila 374 kg na m−3 a nebyl zjištěn signifikantní rozdíl mezi hustotou jednotlivých kompartmentů. Přesnost všech modelů v intencích procentuální RMSE (Root Mean Square Error) byla vyšší do tloušťkové třídy 45 cm, následně se zhoršila. V případě celkové nadzemní biomasy se pohybovala kolem 20% z průměrných hodnot dané třídy, vysokých hodnot dosahovala při stromových komponentech s variabilními dimenzemi jako koruna a pařez. Rozdíly v hodnotě RMSE při odhadu biomasy kmene lípy pomocí námi navržených funkcí a na základě funkce pro odhad biomasy buku byly minimální (průměrné hodnoty RMSE 27.95 a 29.42%). Biomasa vzorníků lípy určena pomocí rovnice parametrizované pro buk nadhodnotila biomasu o přibližně 12%. Z hodnot RMSE vyplývá vhodnost využití obou typů funkcí, avšak uvedené systematické nadhodnocení by mělo být zohledněno.

Comparison of tree volume equations for small-leaved lime (Tilia cordata Mill.) in the Czech Republic

Although the small-leaved lime (Tilia cordata Mill.) is a native tree in the Czech Republic, there are no volume tables, and its volume has so far been estimated according to beech (Fagus sylvatica L.) tables. In order to increase accuracy of timber volume calculations, the most appropriate volume equations should be selected to develop volume tables specifically for lime. Based on literature sources eight volume equations were selected, and their accuracy was tested by statistical evaluation of assessed parameters and differences between calculated and sampled lime tree volume. Eighty-one sample trees were randomly selected for this study. The most suitable equation was Børsets equation according to the evaluation of equation parameters and comparison of the results obtained from the volume formula and from sample trees (difference of mean value 0.000009 m3). Finally, the calculated lime volumes were compared with the beech tables. The lime volumes are higher than beech volumes according to beech tables and positive differences for the lime, which varied from 0.05 m3 to 0.35 m3, support the need for new lime volume table.