PRODUCTIVITY OF NORWAY SPRUCE STANDS IN STATE AND PRIVATE FORESTS OF LATVIA

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1 FOREST SCIENCES PRODUCTIVITY OF NORWAY SPRUCE STANDS IN STATE AND PRIVATE FORESTS OF LATVIA Latvia University of Agriculture Abstract In Latvia, almost 5% of all are privately owned. Due to hard economic situation in the 199ies, many private have suffered from illegal forestry operations and overexploitation. One of economically most important tree species for private forest owners is Norway spruce. In this study the productivity of state-owned and private spruce was compared, assuming that the stand productivity of private should be lower compared to those owned by the state. Data gathered in the Forest Resource Inventory in 24, 25 and 26 was used for the analysis. Total standing volume of the dominant stand and the current mean annual volume increment (CMAI) of spruce were used as main productivity indicators. The mean values of the main stand characteristics were found to be rather similar in state and private. The only significant differences were discovered in the mean diameter and CMAI of spruce in 6-9 years old stands; in both cases the values were higher in private. Site type and mixture degree were tested as the possible influencing factors. Although there were differences in the site type distribution between state and private, the influence of this factor on the CMAI of spruce proved to be insignificant. It was found out that the CMAI of spruce depended significantly on the mixture degree. The proportion of mixed stands in the state was considerably higher than in the private ; presumably therefore the value of the CMAI in the state was significantly lower. Key words: Norway spruce stands, productivity, current mean annual increment, state, private. Introduction Forestry is very important for the welfare of Latvian people. According to expert evaluation, the contribution of forestry sector to the GDP presently amounts to 5%. Around 5 thousand people are employed in forestry; furthermore, in many regions of the country wood-processing is the leading branch of industry. (Meža nozare Latvijā, 27) In Latvia, as a result of land restitution and privatization begun shortly after the state independence was regained in 199, almost 5% of all are now privately owned. (Meža resursi, 28) During the 199s collapse of many branches of industry forced a large number of people to face serious economic constraints, especially in the rural areas. In a number of cases provided a quick solution and an easy source of income for the private owners; unfortunately it often led to illegal forestry operations and overexploitation of the. In 1998 the total felled volume in private exceeded that of the state, in the following years the difference steadily increased and already in 22 the felling intensity in private was twice as high as that in the state. (Meža nozare Latvijā, 24; Meža nozare Latvijā, 26) During the last years economic activity in the privately owned has decreased; in 26 the share of wood felled in private made up 55% of the total felled wood volume in the country. (Meža nozare Latvijā, 27) Norway spruce (Picea abies (L.) Karst.) is one of the most widespread tree species in Latvia. According to the data of Latvian State Forest Service, dominated by spruce take up 18.2% of the total forest area. (Valdošo koku sugu sastāvs, 28) More than one third of all spruce-dominated stands belong to private owners (Figure 1). 151

2 1% 39% 6% Figure 1. Ownership structure of the spruce-dominated (Me a statistika, 27): - private owners; - state; - local authorities. Economically spruce is very important, especially for the private forest owners. For example, one fourth of the total wood volume felled in 2 in the final cuttings came from private spruce ; whereas from state-owned spruce only 5%. (Meža statistika, 21) Until 24 the timber volume logged in the final fellings from the other spruce several times exceeded the timber volume logged in the final fellings from the stateowned spruce ; at the same time thinnings in the spruce of other owners were carried out much less intensely than in those owned by the state (Figure 2). Timber logged in final fellings from spruce stands, m Year Timber logged in thinnings from spruce stands, m Figure 2. Timber volume logged in final fellings and thinnings in state and other spruce (Meža statistika 21-27): - state ; - other. Year 26 The above-mentioned facts allow concluding that private spruce have been rather intensely exploited during the last decade. At the same time the intensity of thinnings, one of the most important measures to ensure a fine future development of the forest stands, has been low in the private compared to those owned by the state. Therefore it is possible that the further development of the spruce under private possession is different from those which are owned and managed by the state. It is most likely that the productivity of the private spruce is lower than that of the state. In Latvia, the majority of forestry research projects are carried out in the state, partly because the information regarding private is incomplete. It is possible to obtain approximate data from the Forest Register, where information submitted by all forest owners is gathered. Although it is the duty of the forest owner to carry out the inventory in his property once every ten years, there are no sanctions against those who do not, except some restrictions to economic activities. Also Forest Management Plan is not mandatory but only one prerequisite to receive state and EU support for the development of forest management (Meža likums, 2). Therefore it is most likely that there has been no up-to-date inventory in those private where there has been no economic activities during last 15 years. 152

3 In 24, the Latvian Forest Resource Inventory was launched. Like in many other European countries, in this project data is gathered in all irrespective of the owner. Thus the Forest Resource Inventory provides statistically credible and up-todate information regarding the present situation in all Latvian. This paper attempts to reveal possible differences in the growth of state-owned and privately owned spruce stands comparing the most informative indicator of the present forest condition stand productivity. It is a part of the doctoral thesis Productivity and growth potential of pure Norway spruce (Picea abies (L.) Karst.) stands on fertile sites. Material and Methods In this study data from Forest Resource Inventory gathered in 24, 25 and 26 has been used. The full cycle of Forest Resource Inventory is carried out within five years covering the country with a regular grid of hidden sample plots. These sample plots are located with the help of Global Positioning System (GPS) according to previously computed coordinates. All measurements and calculations of the stand parameters are carried out in accordance with a methodology confirmed by the Agriculture ministry of Latvia. At the present stage of the Forest Resource Inventory data about 1 64 sample plots are available, 2544 of these are established in 24, 367 in 25, 385 in 26. According to the aim of the study following criteria were used to select sample plots: 1. The type of the sample plot. Permanent sample plots which will be re-measured every five years were selected. 2. The land category. Sample plots located in the forest were selected. 3. The area of the sample plot. Sample plots with the area of at least 4 m 2 (or 4/5 of the total sample plot area) were selected to avoid accidental exclusion of those sample plots that contain forest infrastructure objects (firebreaks, ditches). 4. The proportion of the dominant species. Sample plots where the proportion of spruce is at least 5% of the total standing volume of the dominant stand were selected. 5. The number of trees. Sample plots with at least 1 trees ha -1 (5 trees sample plot -1 ) were selected. According to the criteria mentioned above 54 sample plots were selected for the further analysis, 366 of them were located in state, and 174 in private. The stand productivity is most explicitly expressed by two parameters - the standing volume of the stand and current annual volume increment. (Антанайтис и Загреев, 1969; Matuzānis un Tauriņš, 1971) In this study the total standing volume of the dominant stand (m 3 ha -1 ) and the current mean annual volume increment (CMAI) of spruce of the dominant stand (m 3 ha -1 year -1, over last ten years) was used. These parameters were analyzed in two age groups: 3-5 years old stands and 6-9 years old stands. The data distribution was tested with one-sample Kolmogorov-Smirnov test; in all cases it proved to be normal. The productivity differences in state and private were analyzed using t-test and oneway ANOVA. Following zero hypothesis was defined. H : productivity indicator (total standing volume of the dominant stand and current mean annual volume increment of spruce of the dominant stand, respectively) does not differ significantly in state and private. Results and Discussion The age distribution of the spruce stands was uneven; especially in the state the amount of 2-4 years old stands strongly exceeded the amount of the stands in other age classes. (Figure 3) 153

4 Number of sample plots Age (years) Figure 3. Age structure of the analyzed state and private spruce stands: - state ; - private. The trend of the age class distribution in the state revealed by this study corresponded well with the data provided by the Joint Stock Company Latvijas valsts meži. (Fakti par mežu, 28) The main reason for having so many young stands is believed to be expansive establishment of the spruce stands during the 196s. Many sites suitable for pine were regenerated with spruce then; partly due to strong browsing pressure of elk mainly causing damages to pine stands and partly due to unjustified assumption that spruce stands require less careful attendance. Very little number of 11-2 years old spruce stands in the private most likely reflects the situation in the 199s when the forest regeneration after the felling was very often inadequate. The regeneration rate of the private spruce seems to have improved during the last decade; one explanation might be now available state and EU forest management and afforestation support programmes. In order to obtain a general idea about the differences in the productivity of state and private some most informative mean stand characteristics were compared. The mean number of trees is greater in the state ; these differences increase with stand age. Other stand parameters are very similar both in state and private. The numbers are presented in Table 1. Table 1 Main stand characteristics of the state and private in the analyzed age groups Stand characteristics 3-5 years old 6-9 years old State Private State Private Mean number of trees ha Mean diameter of the dominant tree species, cm Mean height of the dominant tree species, m Mean basal area, m 2 ha Mean standing volume of the dominant stand, m 3 ha CMAI of spruce, m 3 ha -1 year The striking similarities between the mean values of the main stand characteristics in state and private were somewhat unexpected. An independent samples t-test was performed to test whether the existing differences of state and private were significant (Table 2). According to the results there were no significant differences in the stand characteristics including productivity parameters of state and private in the age group of 3-5 years. In the age group of 6-9 years two parameters differed significantly in state and private mean diameter of the dominant tree species (p=.16) and CMAI of spruce (p=.2). However, contrary to what was expected, the parameter values were in both cases higher in the private. The fact that the trees are thicker and grow better in the private was repeatedly confirmed when the mean volume of 6-9 years old single tree in state and private was calculated. It was greater in a private forest stand.63 m 3 (.429 m 3 in the state, respectively). 154

5 Table 2 The significance of the differences between mean stand characteristics in state and private ; p-values of the independent samples t-test Stand characteristics 3-5 years old 6-9 years old Mean number of trees ha Mean diameter of the dominant tree species, cm Mean height of the dominant tree species, m Mean basal area, m 2 ha Mean standing volume of the dominant stand, m 3 ha CMAI of spruce, m 3 ha -1 year Further analysis was carried out in the age group where significant productivity differences were detected: in 6-9 years old stands. As the tree diameter directly influences the CMAI, only the latter was examined further. Some factors that might have influenced the previously discovered productivity differences in state and private were tested. Firstly, site type distribution of 6-9 years old stateowned and private spruce was compared. The results of this comparison are presented in figure 4. 19% State Private 11% 47% 2% 1% 13% 32% 2%2% Figure 4. Site type distribution in state-owned and private 6-9 years old spruce : - on dry mineral soils; - on wet mineral soils; - on peat soils; - on drained mineral soils; - on drained peat soils. 53% Some differences were rather obvious. For example, the percentage of on dry mineral soils was higher in private but the contrary was true for the on wet mineral soils. The total amount of on drained sites was rather similar both in state and private. To clarify if there is a relation between the site type and CMAI of spruce, oneway ANOVA was performed. No significant influence of the site type on the CMAI was found although in all site types this parameter was higher in the private, only in on peat soils the values referring to state and private were rather similar (Figure 5). CMAI of spruce, m 3 ha -1 year Forests on dry mineral soils Forests on wet mineral soils Forests on peat soils Forests on drained mineral soils Forests on drained peat soils Figure 5. Current mean annual volume increment of spruce in 6-9 years old state and private on different site types: - state ; - private. 155

6 Evidently, private spruce stands retain a better growth rate in all site types except on peat soils. Another very interesting conclusion can be drawn from this graph: spruce stands of the age group including also stands of the felling age and older on average retain a growth rate above 5 m 3 ha -1 year -1, in private drained even above 1 m 3 ha -1 year -1. This aspect seemed worthwhile of a more thorough examination therefore mean values of CMAI in 8-9 years old spruce stands were calculated. The results were 5.5 m 3 ha -1 year -1 in state and 9. m 3 ha -1 year -1 in private. According to the legislation the felling age for spruce is 81 year. Consequently these are often still highly productive spruce stands that are cut down. On the other hand, unexplained loss of productivity in 3-5 years old spruce stands has recently been reported together with a suggestion to give up the rotation age as the only criterion for the final felling of spruce and build this decision rather upon the present productivity of the stand. (Zālītis un Lībiete, 23; Zālītis un Lībiete, 25; Libiete and Zalitis, 27) The results obtained in the present study repeatedly support this point of view. Another factor that could influence the differences of the CMAI of state and private spruce stands was the share of spruce in the dominant stand. All spruce stands were divided in mixed (the share of spruce 5-74% of the total standing volume of the dominant stand) and pure stands (the share of spruce 75-1% of the total standing volume of the dominant stand). The percentage of the mixed spruce stands was considerably larger in state than in private, 64% and 45%, respectively. Next the CMAI in both mixture groups was compared. Both in state and in private its value was higher in pure stands (Figure 6). CMAI of spruce m 3 ha -1 year State Private Figure 6. Comparison of current mean annual volume increment of spruce in state and private depending on the mixture degree: - mixed stands; - pure stands. Independent samples t-test was once again performed to test if the differences of the CMAI in mixed and pure spruce stands were significant. The results were affirmative: the tested productivity parameter depended strongly on the mixture degree both in state (p=.14) and private (p=.18). Accordingly an explanation for higher CMAI in private spruce stands compared to state-owned spruce stands had been found. There is another possible explanation to the fact that private spruce stands grow better. Even though the official statistics of the State Forest Service report much less intense thinnings in the private than in those owned by the state this information is somewhat doubtful. Compared to state, private have certainly been more subject to illegal forestry operations which do not necessarily involve clearfelling. During the last decade some private spruce stands may have been heavily thinned far exceeding the allowed thinning intensity. The remaining few trees in such stand are now able to utilize the available light and nutrient resources most efficiently and thus strongly increase their current annual increment. Norway spruce is known to be a tree species which extremely fast adapts itself to favourable conditions (Zviedris, 196). However, this is presently only an assumption; broader information and more research are needed to confirm it. 156

7 Conclusions 1. The age distribution of the spruce stands proved to be uneven; especially in the state the amount of 2-4 years old stands strongly exceeded that of the other age classes. The age structure also suggested that the regeneration rate of the private spruce has improved during the last decade. 2. The main characteristics of the state and private spruce stands were found to be very similar in both analyzed age groups. The only significant differences were detected in the mean diameter and current mean annual volume increment (CMAI) of spruce in 6-9 years old stands; in both cases values were higher in the private. 3. The site type distribution differed rather much between state and private ; however, no significant influence of the site type on the CMAI was discovered. 4. The percentage of mixed spruce stands was considerably higher in state ; the CMAI References proved to depend significantly on the mixture degree. Accordingly the difference of the CMAI in state and private spruce could be explained by the higher proportion of pure stands in private. 5. It was discovered that both state and private spruce stands often retain a high growth rate after the rotation age is reached. Therefore we may suppose that many still highly productive spruce stands are clearcut according to existing regulations. 6. The productivity indicators (total standing volume of the dominant stand and current mean annual volume increment of the spruce of the dominant stand) did not differ significantly in 3-5 years old but in 6-9 years old only current mean annual volume increment of the spruce of the dominant stand differed significantly. Thus the zero hypothesis of the study could only partly be rejected. 1. Fakti par mežu (Facts about forest), valsts akciju sabiedrība Latvijas valsts meži. Available at: (In Latvian) 2. Libiete Z., Zalitis P. (27) Determining the growth potential for even-aged stands of Norway spruce (Picea abies (L.) Karst.). Baltic Forestry, 13(1), pp Matuzānis J., Tauriņš J. (1971) Audžu pieaugums (Increment of the forest stands). Latvijas republikāniskais zinātniski tehniskās informācijas un propagandas institūts, Rīga, 32 p. (In Latvian) 4. Meža likums (Forest Law). Available at: (In Latvian) 5. Meža nozare Latvijā 24 (Forest sector in Latvia 24). (24) Latvijas Republikas Zemkopības ministrija, Rīga, 33 p. (In Latvian) 6. Meža nozare Latvijā 26 (Forest sector in Latvia 26) (26) Latvijas kokrūpniecības federācija, Rīga, 35 p. (In Latvian) 7. Meža nozare Latvijā 27 (Forest sector in Latvia 27). (27) Meža īpašnieku biedrība, Rīga, 35 p. (In Latvian) 8. Meža resursi (Forest resources). (28) Valsts meža dienests. Available at: (In Latvian) 9. Meža statistika (Forest statistics 21-27) Valsts meža dienests. Available on CD. 1. Valdošo koku sugu sastāvs (Structure of the dominant tree species). (28) Valsts meža dienests. Available at: (In Latvian) 11. Zālītis P., Lībiete Z. (23) Egļu jaunaudžu augšanas gaitas savdabības āreņos un kūdreņos (The peculiarities ofthe growth of young spruce stands on drained mineral soils and drained peatlands). Mežzinātne, 13(46), pp (In Latvian) 12. Zālītis P., Lībiete Z. (25) Egļu jaunaudžu augšanas potenciāls (Growth potential of young spruce stands). LLU Raksti, 14(39), pp (In Latvian) 13. Zviedris A. (196) Egle un egļu mežs Latvijas PSR (Spruce and spruce forest in Latvian SSR), Rīga: Latvijas PSR ZA izdevniecība, 24 p. (In Latvian) 14. Антанайтис В.В., Загреев В.В. (1969) Прирост леса (Forest increment). Лесная промышленность, Mockвa, 24 c. (In Russian) 157