Effects of Thinning in a Plantation of Poplar Clone I-214 withWide Spacing

U nasadu topole klona I-214, osnovanom pri razmaku sadnje 6 × 6 m u sistemu kvadratne veze na zemljištu srednje povoljnom za uzgoj topola, analizirani su učinci prorjede koja je izvedena 11 godina nakon osnivanja nasada. Prorjeda je imala selektivan karakter, odnosno izdvojena je grupa tzv. perspektivnih stabala u broju koji odgovara prosječnom razmaku od 8,5 × 8,5 m i uklonjeni su njihovi izraziti konkurenti. Uzgojno neperspektivna stabla i stabla zaostala u rastu, što je uglavnom posljedica naknadnih popunjavanja, također su uklonjena. Prorjedom su uklonjena 122 stabla po hektaru (46 %), 6,45 m2/ha (43 %), 66,08 m3/ha (42 %) i 2645 m2/ha (40 %) površine projekcije krošnje, što je jačina zahvata iznad tzv. kritične temeljnice. Sortimentna struktura prorjednog etata pri selektivnoj prorjedi povoljnija je od shematskih prorjeda u mlađim nasadima na povoljnijim staništima i daje 50 % tehničkog drva, 30 % celuloznog drva i 20 % otpatka. Nakon 5 godina na prorijeđenoj je površini srednji promjer po temeljnici veći za 10,6 %, volumen srednjeg stabla veći je za 21,9 %, a površina projekcije krošnje srednjeg stabla veća je za 59,0 % u odnosu na neprorijeđenu površinu. Nasuprot tomu, srednja visina po Loraju na prorijeđenoj je površini za 4,2 % manja u odnosu na neprorijeđenu površinu. Veći tečajni prirast promjera, volumena i površine projekcije krošnje stabala na prorijeđenoj površini ukazuje na mogućnost produžetka ophodnje i povoljniju sortimentnu strukturu u odnosu na kontrolnu površinu.Research was conducted in the experiment plot of euramerican poplar, clone I-214, which was founded with one year seedling type 1/1 with spacing 6 × 6 m in the square system on the alluvial soils of river Sava basin in which browning processes is expressed. Eleven years after the plantation establishment 3 blocks with two experimental plot of 0.2016 ha, which are separated by a so-called. protective order, were singled out. In the experimental plot all the trees were numbered and measured by two cross-dbh, with an accuracy of 1 mm, and height, with an accuracy of 1 dm. The crown projection radius of 8 positions, each rotated to 45o, were measured. On the three experimental plots (one in each block) selective thinning was carried out (PP-E), at which in each plots 50 % of trees were cut down, or the distance between the trees raised on average 8.5 × 8.5 m. Firstly, a collective called. promising trees set aside, in the number that corresponds to an average distance of 8.5 × 8.5 m, and their main competitors were removed. The trees behind in development, which is mainly due to additional filling in plantations two years after planting, are also removed because they were judged as silvicutural non-perspective. The remaining three experimental plots were control (PP-K). In each repetition trees for dendrometric analysis were sampled, the dominant one (dg20%) and a mean tree which has mean quadratic diameter (dg). In the 16thyears of plantation development diameters at breast height (dbh) and height of each tree were re-measured, sa well as crown projection radius. The development of mean and dominant trees showed that the investigated habitat is the medium favorable for the cultivation of the poplar clone I-214. Current increment of diameter, height and volume in the 11thyear was in the intensive phase, where volume increment has not yet culminated (Figure 1–3). As a suitable element of growth to determine the start of thinning operation on a biological point of view, can be ring width along the spindle tree. In the first five years the tree has had a full solitary growth, and from the seventh year there is a competitive relationship between trees in plantation, which is manifested by changing the ring width along the spindle tree (Figure 4 and 5). This means that before the seventh year thinning does not have any biological justification. Models 1 and 2 of volume tables, constructed measuring felled trees from thinning (Table 2), and which are the dependence of the volume of tree from diameter at breast height (model 1) and from the diameter at breast and height (model 2), proved to be equally good at calculating the volume per hectare in the 11thyear and more convenient compared to other tables and models (Table 3). To calculate the volume in the 16thyear two input volume tables can be successfully used (model 2), while the application of model 1 is limited at the 11thyear. In the 11th year at the experimental plot an average of 263–266 trees per hectare are found, which represents a survival rate of about 95 %. Total basal area averaged from 14.70 to 14.97 m2/ha, while volume was an average from 156.67 to 157.62 m3·ha-1. By applying the statistical t-test significant difference in the number of trees, basal area and volume per hectare was not determined within the experimental plots before applying the silvicultural treatments (Table 4). By applying thinning operation,122 trees per hectare (46%), 6.45 m2/ha (43 %) of the total basal area, 66.08 m3/ha (42%) of the total volume and 2645 m2/ha (40 %) of the the crown projection area were removed, which represent a strong procedure and is located above the so-called. critical basal area (Table 4, 13).Size of allowable cut in the thinning of 66.08 m3/ha was in the limits expected on the basis of previous research for the density of 278 trees per hectare and the habitat medium favorable for the development of poplar clone I-214. However, the assortment structureof allowable cut is more favorable compared to thinning in younger plantations in the more favorable habitats and produces 50 % of technical wood, 30% of pulpwood and 20 % of wastewood (Table 4, 9, 15). Between 11 and 16 years on both series of experimental plot the mortality of trees was not determined. Five years after application of thinning treatment a significant difference in the number of trees, basal area, volume and crown projection areas of trees per hectarewere determined between the experimental and control plots (Table 4). The significant difference in the mean diameters, heights and crown projection areas of the mean and the dominant trees (Table 5, 6), as well as between the diameter strucures (Figure 7) were also determined between investigated plots. For a period of 5 years after application of thinning operation at the experimental field current basal area and volume increment per hectare accounted 85 % of basal area increment and 75 % of volume increment of the control plots wich had the number of trees twice higher than experimental plots (Table 14). For five years of positive reactions to increase growing space of remaining trees on the experimental plots the size of the total basal area and volume of trees removed by thinning operation is not compensated: the total basal area and the volume per hectare amounted to 2/3, and the crown projection area amounted 87 % of the size of the control plot. The reaction of trees on experimental plot with thinning treatment for 5 years is great and is reflected in greater mean diameter by 10.6 %, greater mean tree volume by 21.9 % and increased the crown projection area by 59.0 % compared to control plot. In contrast, the mean Lorey’s height at the experimental plot with thinning treatment decreased by 4.2 % compared to control plot. This has contributed to the intensification of the current (average periodic) volume increment compared to the period before applying thinning operation. Greater assimilation apparatus of trees in the experimental plots with thinning tretament and higher current diameter and volume increment indicate the need to extend the production cycle at the best assortment structure compared to the control plot. The research results indicate the validity of efforts that the thinning operation in poplar plantations should be treated as a biological and an economic category. As a biological category the thinning operation contributes to accelerating the growth of the remaining phenotypically better established trees and achieve optimum production. As economic categories with thinning operation realized the previous crop, and it being understood that the assortment of allowable cut in the thinning cover cost cutting and the establishment of plantations with more trees. In this framework it is necessary to direct further research, because the poplar plantations,which are aimed to applying thinning operation, are flexible enough to allow adaptation to changing market conditions

Effects of Thinning in a Plantation of Poplar Clone I-214 withWide Spacing

U nasadu topole klona I-214, osnovanom pri razmaku sadnje 6 × 6 m u sistemu kvadratne veze na zemljištu srednje povoljnom za uzgoj topola, analizirani su učinci prorjede koja je izvedena 11 godina nakon osnivanja nasada. Prorjeda je imala selektivan karakter, odnosno izdvojena je grupa tzv. perspektivnih stabala u broju koji odgovara prosječnom razmaku od 8,5 × 8,5 m i uklonjeni su njihovi izraziti konkurenti. Uzgojno neperspektivna stabla i stabla zaostala u rastu, što je uglavnom posljedica naknadnih popunjavanja, također su uklonjena. Prorjedom su uklonjena 122 stabla po hektaru (46 %), 6,45 m2/ha (43 %), 66,08 m3/ha (42 %) i 2645 m2/ha (40 %) površine projekcije krošnje, što je jačina zahvata iznad tzv. kritične temeljnice. Sortimentna struktura prorjednog etata pri selektivnoj prorjedi povoljnija je od shematskih prorjeda u mlađim nasadima na povoljnijim staništima i daje 50 % tehničkog drva, 30 % celuloznog drva i 20 % otpatka. Nakon 5 godina na prorijeđenoj je površini srednji promjer po temeljnici veći za 10,6 %, volumen srednjeg stabla veći je za 21,9 %, a površina projekcije krošnje srednjeg stabla veća je za 59,0 % u odnosu na neprorijeđenu površinu. Nasuprot tomu, srednja visina po Loraju na prorijeđenoj je površini za 4,2 % manja u odnosu na neprorijeđenu površinu. Veći tečajni prirast promjera, volumena i površine projekcije krošnje stabala na prorijeđenoj površini ukazuje na mogućnost produžetka ophodnje i povoljniju sortimentnu strukturu u odnosu na kontrolnu površinu.Research was conducted in the experiment plot of euramerican poplar, clone I-214, which was founded with one year seedling type 1/1 with spacing 6 × 6 m in the square system on the alluvial soils of river Sava basin in which browning processes is expressed. Eleven years after the plantation establishment 3 blocks with two experimental plot of 0.2016 ha, which are separated by a so-called. protective order, were singled out. In the experimental plot all the trees were numbered and measured by two cross-dbh, with an accuracy of 1 mm, and height, with an accuracy of 1 dm. The crown projection radius of 8 positions, each rotated to 45o, were measured. On the three experimental plots (one in each block) selective thinning was carried out (PP-E), at which in each plots 50 % of trees were cut down, or the distance between the trees raised on average 8.5 × 8.5 m. Firstly, a collective called. promising trees set aside, in the number that corresponds to an average distance of 8.5 × 8.5 m, and their main competitors were removed. The trees behind in development, which is mainly due to additional filling in plantations two years after planting, are also removed because they were judged as silvicutural non-perspective. The remaining three experimental plots were control (PP-K). In each repetition trees for dendrometric analysis were sampled, the dominant one (dg20%) and a mean tree which has mean quadratic diameter (dg). In the 16thyears of plantation development diameters at breast height (dbh) and height of each tree were re-measured, sa well as crown projection radius. The development of mean and dominant trees showed that the investigated habitat is the medium favorable for the cultivation of the poplar clone I-214. Current increment of diameter, height and volume in the 11thyear was in the intensive phase, where volume increment has not yet culminated (Figure 1–3). As a suitable element of growth to determine the start of thinning operation on a biological point of view, can be ring width along the spindle tree. In the first five years the tree has had a full solitary growth, and from the seventh year there is a competitive relationship between trees in plantation, which is manifested by changing the ring width along the spindle tree (Figure 4 and 5). This means that before the seventh year thinning does not have any biological justification. Models 1 and 2 of volume tables, constructed measuring felled trees from thinning (Table 2), and which are the dependence of the volume of tree from diameter at breast height (model 1) and from the diameter at breast and height (model 2), proved to be equally good at calculating the volume per hectare in the 11thyear and more convenient compared to other tables and models (Table 3). To calculate the volume in the 16thyear two input volume tables can be successfully used (model 2), while the application of model 1 is limited at the 11thyear. In the 11th year at the experimental plot an average of 263–266 trees per hectare are found, which represents a survival rate of about 95 %. Total basal area averaged from 14.70 to 14.97 m2/ha, while volume was an average from 156.67 to 157.62 m3·ha-1. By applying the statistical t-test significant difference in the number of trees, basal area and volume per hectare was not determined within the experimental plots before applying the silvicultural treatments (Table 4). By applying thinning operation,122 trees per hectare (46%), 6.45 m2/ha (43 %) of the total basal area, 66.08 m3/ha (42%) of the total volume and 2645 m2/ha (40 %) of the the crown projection area were removed, which represent a strong procedure and is located above the so-called. critical basal area (Table 4, 13).Size of allowable cut in the thinning of 66.08 m3/ha was in the limits expected on the basis of previous research for the density of 278 trees per hectare and the habitat medium favorable for the development of poplar clone I-214. However, the assortment structureof allowable cut is more favorable compared to thinning in younger plantations in the more favorable habitats and produces 50 % of technical wood, 30% of pulpwood and 20 % of wastewood (Table 4, 9, 15). Between 11 and 16 years on both series of experimental plot the mortality of trees was not determined. Five years after application of thinning treatment a significant difference in the number of trees, basal area, volume and crown projection areas of trees per hectarewere determined between the experimental and control plots (Table 4). The significant difference in the mean diameters, heights and crown projection areas of the mean and the dominant trees (Table 5, 6), as well as between the diameter strucures (Figure 7) were also determined between investigated plots. For a period of 5 years after application of thinning operation at the experimental field current basal area and volume increment per hectare accounted 85 % of basal area increment and 75 % of volume increment of the control plots wich had the number of trees twice higher than experimental plots (Table 14). For five years of positive reactions to increase growing space of remaining trees on the experimental plots the size of the total basal area and volume of trees removed by thinning operation is not compensated: the total basal area and the volume per hectare amounted to 2/3, and the crown projection area amounted 87 % of the size of the control plot. The reaction of trees on experimental plot with thinning treatment for 5 years is great and is reflected in greater mean diameter by 10.6 %, greater mean tree volume by 21.9 % and increased the crown projection area by 59.0 % compared to control plot. In contrast, the mean Lorey’s height at the experimental plot with thinning treatment decreased by 4.2 % compared to control plot. This has contributed to the intensification of the current (average periodic) volume increment compared to the period before applying thinning operation. Greater assimilation apparatus of trees in the experimental plots with thinning tretament and higher current diameter and volume increment indicate the need to extend the production cycle at the best assortment structure compared to the control plot. The research results indicate the validity of efforts that the thinning operation in poplar plantations should be treated as a biological and an economic category. As a biological category the thinning operation contributes to accelerating the growth of the remaining phenotypically better established trees and achieve optimum production. As economic categories with thinning operation realized the previous crop, and it being understood that the assortment of allowable cut in the thinning cover cost cutting and the establishment of plantations with more trees. In this framework it is necessary to direct further research, because the poplar plantations,which are aimed to applying thinning operation, are flexible enough to allow adaptation to changing market conditions

Elements of structure and productivity of clone I-214 (Populus×euramericana (Dode) Guinier) plantations on the river Sava alluvium

Two experimental plantations of Euramerican poplar (Populus×euramericana (Dode) Guinier) - clone I-214 were researched on the river Sava alluvium in Srem. Three sample plots were established in each of the plantations, aged 31 years. The soil type was humofluvisol (alluvial semigley), planting space 6×6 m. The plantations were established with 278 rooted cuttings per hectare, and the number of trees at the age of 31 accounted for 46.5-60.6%. The constructed height curves, mean stand height (hg) and upper (hg20%) heights show that the study plantations were established on different site classes, which was significantly reflected on other plantation growth elements and productivity. However, there was no significant effect of site class on the variability (sd and cv) and shape of diameter structure (α3 and α4). The constructed models of diameter structure for each site class (by Weibull function) differ by location parameter (a), and do not differ by parameter of scale (b) and shape (c). The tree and plantation growth elements show a high production potential of the clone I-214 which indicates that, on optimal soils and with the provided technological measures in the stage of nursery production and in the stage of plantation establishment, clone I-214 presents the good base for high production effects