Jürgen Aosaar

Biomass production of grey alder, hybrid alder and silver birch stands on abandoned agricultural land

Halli lepa, hübriidlepa ja arukase biomassi produktsioon endistel põllumaadel The present study is based on four experimental sites, located in Southern-Estonia: hybrid alder and grey alder plantations located in Põlva county, and two sample plots of silver birch, located in Tartu county. The stand characteristics, above-ground biomass and current annual production (CAP) were estimated in order to evaluate production capacity of different tree species growing on abandoned agricultural lands. Due to fast growth and high biomass production capacity the most promising tree species for short-rotation forestry in Estonia is grey alder. The stem mass in the 13-years-old grey alder and hybrid alder stand was 63.4 t ha-1 and 40.0 t ha-1, respectively. However, the different biomass production is mainly affected by stand densities, 6170 trees per ha and 4080 trees per ha, respectively. During ageing, the differences between the alder stands diminish. At the age of 14, mean height and diameter at breast height were practically equal. Also the mean stem mass in the older, 13-year old stand, is almost equal: 10.3 kg in grey alder stand and 9.8 kg in hybrid alder stand. At a younger age, the mean stem mass was higher in grey alder stand, but later, at the age of 13, the mean stem mass has become almost the same (10.3 kg in grey alder stand and 9.8 kg in hybrid alder stand). The rotation period for hybrid alder is longer than for grey alder and bulk maturity will occur later. Silver birch is also a highly productive tree species and has a prospect for short-rotation forestry. The mean stem mass and annual current increment of 8-year-old silver birch stand was in same the magnitude as in the grey alder stand. Although the average stand diameter and height were lower in the silver birch stand than in the grey alder stand, it is compensated by the higher wood density of birch wood. The number of trees has affected silver birch stand production, the above-ground biomass in the very high density birch stand (35 600 trees per ha) was significantly lower than in the sparse stand (11 600 trees per ha), 22.8 t ha-1 and 31.2 t ha-1, respectively. Biomass production of grey alder, hybrid alder and silver birch stands on abandoned agricultural land Due to the high prices and lack of fossil fuels in the world, it is necessary to look for new, alternative fuel sources. In Estonia one of the possibilities for renewable energy would be growing deciduous tree species on abandoned agricultural land. Usually silver birch (Betula pendula) and grey alder (Alnus incana) are the most common tree species to occupy agricultural lands which are left out of use. Also the hybrid alder (Alnus hybrida) may be considered a fast-growing species in our conditions. The main aim was to investigate the above-ground biomass production and the dynamics of young stands of fast-growing deciduous tree species on former agricultural land. This study is based on four experimental sites, located in South-Estonia: grey alder and hybrid alder plantations in Põlvamaa, established in 1995 and 1996 respectively, and two silver birch natural stands in Tartumaa, Haaslava and Kambja, established in 2001 and 2004 respectively. The basal density of experimental sites was very different. In Haaslava it was the highest (36 200 trees per ha) and in hybrid alder stand it was the lowest (6700 trees per ha). In Kambja it was 11 600 and in grey alder stand 15750 trees per hectare. The soil conditions were very similar in all sites. Mean diameter at breast height and mean height of the stands were measured annually. The above-ground biomass of the stands was estimated during 2003-2007, by the method of model trees. It was not done in every stand every year due to its labor-intensity. 8-year old stands were compared, because the above-ground biomass of all four experimental sites was determined at that age. Mean height and diameter growth of grey alder at young age were higher and faster than in hybrid alder stand, but at the age of 14 these parameters were practically equal. When comparing the above-ground biomasses of the alder stands, it can be noted, that at the age of 8 grey alder overcomes the hybrid alder stand (biomasses respectively 26.8 t ha-1 and 9.76 t ha-1), but later, at the age of 13 the difference between the two sites diminishes (76.1 t ha-1 and 51.5 t ha-1). The average dry mass of grey alder stems in 8-year old stand was bigger than that of hybrid alders (2.87 and 2.01 kg). The annual increment of above ground-biomass was almost at the same level in Kambja birch stand and in grey alder stand (11.9 and 14.0 t ha -1 y respectively). Although the dimensions of trees are smaller in Kambja stand, the large number of trees and the wood density makes the biomass accumulation high per hectare. Mean height, diameter, average tree stem mass, and above-ground biomass was bigger in Kambja than in Haaslava stand. In 8-year old stands, the average dry mass of stem of alders is bigger than that of birches, the highest is grey alders (2.87 kg) and the lowest is in very dense Haaslava stand (0.44 kg).

The growth and production of some fast growing deciduous tree species stands on abandoned agricultural land

Mõningate kiirekasvuliste lehtpuupuistute kasv ja produktsioonivõime endisel põllumaal Several studies about stands growing on abandoned agricultural lands are induced by extensive afforestation of agricultural lands and more intensive use of biomass. Overview of above-ground biomass production of grey alder, hybrid alder and silver birch young stands growing on former agricultural areas are presented in current paper. The results of 16- and 6-year period of alders and silver birch stands, respectively, are reported. Above-ground biomass and biomass production of stands were estimated. The growing stock and current annual increment (CAI) of 16-years-old grey alder stand were 250 m3 ha-1 and 35.6 m3 ha-1, respectively. Due to fast growth and high biomass production capacity grey alder is promising tree species for short-rotation forestry in Estonia. Hybrid alder is productive tree although not exceeding the productivity of grey alders. Stem volume and CAI of the 16-years-old hybrid alder stand were 155 m3 ha-1 and 21 m3 ha-1, respectively. Our results supported earlier data reported in literature: rotation period of hybrid alder is longer than for grey alder and CAI of hybrid alder stands culminate later. The productivity of young silver birch stands on abandoned agricultural land is varying in a broad range. One young silver birch stand growing on abandoned agricultural land was involved into study. Growing stock and CAI in 13-years old stand were 118 m3 ha-1 and 15 m3 ha-1, respectively. These values are exceeding respective values of several yield tables of silver birch and biomass production capability of silver birch stands in favourable conditions is high. The growth and production of some fast growing deciduous tree species stands on abandoned agricultural land In the middle of 1990s considerable amount of abandoned agricultural land came into existence in Estonia. Such areas are often characterized by rapid occupation by pioneer tree species (alders, silver birch, willows) which has led to an increase of woodland area. During the last decade several studies about afforestation of former agricultural areas are published. From the point of view of biomass production and afforestation of abandoned agricultural areas fast growing deciduous tree species (alders, birches, aspens, willows) are most prospective. Current paper presents the overview of above-ground biomass production of grey alder, hybrid alder and silver birch stands growing on abandoned agricultural lands. In case of alders and silver birch the results of the periods of 16- and 6-years, respectively, are reported. In all cases the stand above-ground biomass and biomass production were estimated on the bases of model trees. Growing stock of 16-years-old grey alder stand was 250 m3 ha-1 and CAI 35.6 m3 ha-1 which are high values for Estonian conditions and also compared to results reported from Nordic and Baltic countries. Due to fast growth and high biomass production capacity grey alder is promising tree species for short-rotation forestry in Estonia. Young grey alder stands in Estonia have a potential to grow faster than published yield tables are reflecting. Hybrid alder is also proved to be productive tree species, although not exceeding the respective values of grey alders. Stem volume and CAI of the 16-year-old hybrid alder stand was 155 m3 ha-1 and 21 m3 ha-1, respectively. Our studies have supported earlier results in literature. Rotation period for hybrid alder is longer than for grey alder and the peak of CAI will occur later. Data reflecting growth and yield of hybrid alder are very scarce in the literature. According to earlier results and literature data, the productivity of young silver birch stands on abandoned agricultural areas is very variable, depending mainly on soil conditions and stand density. One productive 13-year-old silver birch stand, growing on abandoned agricultural land has been studied. Growing stock in the stand was 118 m3 ha-1 and CAI 15 m3 ha-1, which exceeded respective values of several birch yield tables. Biomass production capability of silver birch stands in favourable conditions can be high. Taking into account silvicultural properties and economical value of timber, probably the most suitable tree species for afforestation abandoned agricultural lands is silver birch.

Long-term dynamics of leaf and root decomposition and nitrogen release in a grey alder (Alnus incana (L.) Moench) and silver birch (Betula pendula Roth.) stands

ABSTRACT The decomposition of the leaf litter, fine roots (d < 2 mm) and coarser roots (2 ≤ d < 5 mm) of grey alder and silver birch, as well as of α-cellulose sheets using the litterbag method was studied in two experimental stands on Podzoluvisol soils in Southern Estonia. For both tree species, the coarser roots decomposed faster than the fine roots, (p < .05), tree species did not affect the decomposition rate of the roots (p > .5). The nitrogen (N) input to soil from aboveground litter was multiple times higher than the N flux from roots. The remaining relative ash-free mass of the leaves of grey alder and silver birch after three and a half years was similar. After 11 years the remaining relative ash-free mass of the fine and coarser roots of grey alder still accounted for around 10% of the initial value. For silver birch the remaining value was around 20% after 9 years. The litterbag method to underestimates in fertile soils the decomposition of organic matter and thus did not reflect the actual dynamics of decomposition.

Väetamise mõju hariliku kuuse (Picea abies (L.) Karst) poogenditele Pauska seemlas / The effect of fertilization on Norway spruce (Picea abies (L.) Karst) grafts: a case study in Pauska seed orchard

Abstract Altogether 197 grafts were studied in Pauska seed orchard in South-Estonia to find out the effect of the fertilization on Norway spruce grafts. The fertilization trials were carried out in May 1988 and 2006. The grafts of 4 different clones with 5 different fertilization treatments (N, P, K, NPK, control) were under study. The effect of three factors (fertilization, clone and year) on different characteristics of spruce grafts was studied. The linear methods with R software were used to find out relationships between variables. In addition to the morphological features and the content of nutrients in needles, the quantities and qualities of the mean cone and the weight of 1000 seeds were measured. Furthermore, the variation of quantities of needles (density, weight, length) and the content of nutrients in needles between years 1988 and 2007 were compared, using the linear methods with R software package. The morphological characteristics and nutrient content of needles, the mass of cones and seeds have depended the most on a calendar year. During the last research period (2003−2007), the needles of grafts under study were longer, lighter and with lower density compared to earlier research period (1988-1993). The effect of a clone was also essential. Needles of younger grafts were longer, heavier and set sparser than needles of older grafts. The needle nutrient content of younger grafts was also higher compared to the older ones. The effect of fertilizers on the grafts was dependent on the period of time. Nitrogen fertilizers increased the N-content in their needles during the first four years and also after repetitive fertilization. Phosphate fertilizers increased the P-content in their needles starting from the third year after their fertilization. The impact of potassium fertilizers on the K-content of their needles appeared 2−4 years after their fertilization. Combined fertilizers increased the N- and P-content in the needles to some extent, whereas it decreased their Ca- and Mg-content.

Biomass production and carbon accumulation in silver birch stands in Oxalis site type

Biomassi produktsioon jänesekapsa kasvukohatüübi arukaasikutes Present study was carried out in three silver birch (Betula pendula Roth.) stands in the Oxalis site type in South-Estonia. The above-ground biomass, above-ground biomass production and foliar characteristics of 14-, 32- and 45-year-old silver birch natural stands were studied. The above-ground biomass and production of the stand was estimated in August 2008 using dimension analysis (model tree method). The above-ground biomasses in the 14-, 32- and 45-year-old silver birch stands growing on forest land were 39.9; 140.3 and 224.3 t ha-1 respectively. All results are given in dry mass (DM). Current annual production (CAP) of stem mass ranged 4.7-7.5 t ha-1. Leaf area index (LAI) ranged 2.5-4.4 m2 m-2 in the studied stands. Based on these results, stands of silver birch growing in Oxalis site type are very productive and may exceed the respective values presented in yield tables used in Estonian forestry. Biomass production and carbon accumulation in silver birch stands in Oxalis site type The main aim of the present study was to investigate above-ground biomass, production and foliar characteristics of three different-aged silver birch (Betula pendula Roth.) stands growing on forestland, in Oxalis site type. This study is based on three experimental sites, located in Tartu and Põlva county, Southern-Estonia. The above-ground biomass was estimated in August 2008 by the method of model trees (dimension analysis). Above-ground biomasses in the 14-, 32- and 45-year-old silver birch stands were 39.9; 140.3 and 224.3 t ha-1 respectively. Current annual increment (CAI) of stem mass varied from 4.7-7.5 t ha-1. The leaf area index (LAI) ranged 2.5-4.4 m2 m-2 in the studied stands. Biomass production capacity and stem masses were high in cases of all studied sites, comparing to previously worked out yield tables (Henno, Tjurin, Vargas de Bedemar). Biomass production in silver birch stands can be considered as an actual issue in relation of carbon sequestration and mitigation of climate changes and needs future investigations.