This paper presents the results of an analysis on characteristics of birch crowns (Betula pendula Roth) in relation to measures of the growth space occupied by a single tree at a young age. It also presents the relationships between the seedling height and certain crown characteristics. The study focused on four-year-old common birches growing in four different areas in the Elk Forest District in either fresh mixed coniferous or broadleaved forest. The measurements conducted on the chosen trees were used to calculate their crown characteristics such as crown diameter, length, height to the crown base, relative length and spread. They were also used to determine the growth characteristics of a single tree’s growth space, such as the crown area projected onto the ground, single tree space and the percentage use of unit area. Furthermore, fresh and dry leaf mass was determined. The birches growing in the fresh mixed coniferous forest reached an average height of 1.30 m, whereas in the fresh mixed broadleaved forest, the height of the trees was lower and amounted to 0.67 m. 95% of the trees had crown diameters of 0.57 m to 0.74 m in the fresh mixed coniferous forest, but only 0.19 m to 0.25 m in the fresh mixed broadleaved forest. The average lengths of the crowns in the fresh mixed coniferous and broadleaved forests amounted to 0.97 m and 0.37 m respectively. The author shows that there is a statistically significant correlation between the seedling height and the other examined characteristics. The best correlation was found between the height and the length of the crown (r=0.9858) for birches growing in the fresh mixed coniferous forest and between the height and single tree space (r=0.8468) for birches growing in the fresh mixed broadleaved forest.
The presented study deals with new capabilities of tree height estimation based on the remote sensing techniques. The main goal of this study is to find out the accuracy of tree height estimation based on LiDAR data and stereo−photogrammetric measurements. The area of investigation is located in the Western Sudetes Mountains (southern Poland). There were 75 trees chosen (Picea sp.) and measured using three different methods: traditional field measurements, stereo – photogrammetric observations and Airborne Laser Scanning (ALS). Tree heights estimated using LiDAR data and stereo−photogrammetric measurements were compared to heights acquired in the field. The mean tree height difference between LiDAR and field measurements was 0.60 m (RMSE=1.47 m), whereas the mean tree height difference between stereo−photogrammetric measurements and field equaled to –0.55 m (RMSE=1.04 m). The obtained results allow the conclusion to be drawn that Airborne Laser Scanning and stereo−photogrammetric observations are competitive with traditional methods of forest parameters measurements owing to the automation and accuracy of surveys. This study has confirmed that remote sensing techniques are effective and reliable methods of obtaining data for forest inventory.
The study presents the assessment of the accuracy of two generalized height−diameter models, such as skwB [Bruchwald et al. 2001] and skwO [Orzeł et al. 2014], developed in Poland for black alder (Alnus glutinosa (L.) Gaertn.) stands. Verification of these models was conducted on empirical material that was collected in 127 alder stands located in the western part of Sandomierz Basin (southern Poland). Selected alder stands aged 6−89 years, while average breast height diameter ranged from 4.5 to 43.0 cm and average height from 6.3 to 32.7 m. The stand density varied from 222 to 4360 trees/ha. The accuracy assessment for uniform height−diameter curves was based on the analysis of single tree absolute error distributions. Synthetic indicators of goodness−of−fit, such as: average and standard errors, coefficients of variation and determination were calculated based on absolute errors. The final evaluation of the compared uniform height−diameter models results from the structure of the goodness−of−fit measures that was observed within all analyzed stands and within age classes of 20 years. The efficiency of uniform height−diameter models was also compared with stand height−diameter curve, which was developed based on the Näslund function. General height−diameter models overestimated height in alder stands on average from 0.26 (1.67) to 0.19 m (1.39%), based on skwB and skwO models, respectively. Bias depended on the age of stand and decreases from almost 3% in I age class to nearly 0.5% in IV and V age class. For both analyzed models, a positive systematic error was observed for the standardized breast height diameter. Bias in estimating the height of single stand depended on the accuracy of stand height estimations. In case of estimation based on the measurements of three trees height, bias in single stand can range from –13% to +14%. Due to the range and nature of observed systematic errors, uniform height curves should be applied to groups of stands that have different age and breast height diameter structure, as it allows for partial reduction of the error.
European black alder (Alnus glutinosa (L.) Gaertn.) is a widespread tree species associated with wetlands and riparian ecosystems, thus it plays an important ecological role. Due to its fast growth and favorable wood properties it also has a potential to satisfy a growing demand for wood and fiber. However, its growth potential is not fully realized in Poland. In this study we investigated variation in growth traits, productivity, and stem straightness among 11 populations of European black alder originating from the lowland distribution of the species in Poland. The common−garden experiment located in 1968 in Kórnik (mid−western Poland) has been so far the only provenance experiment with this species in our country. We measured height and diameter of all trees at the site, assessed stem straightness in a 5−step scale (1−crooked; 5−straight), and calculated productivity at age of 50 years, which should be considered close to the rotation age. We found significant variation among populations in all investigated traits. The difference in productivity between the best and the worst provenance reached 75%. Using published and unpublished data from previous measurements at this site we also analyzed a trend in provenance ranking through time. The best and worst provenance could be identified at age 16 years, but many ranking shifts took place afterwards at the intermediate rank positions. We conclude that growth, productivity and stem quality of black alder could be improved through selection of favorable provenances within the species. Selection decisions can be made at the age below the half the rotation age, although decisions at ¾ of rotation age would be more precise.