TY - JOUR
AU - Johansson, Tord
AB - Abstract The objective of the study was to quantify above- and below-stump biomass of silver (Betula pendula Roth) and downy (Betula pubescens Ehrh.) birches planted at four spacing intervals and growing on two soil types on an area of farmland. The 12-year-old birches had been grown at four spacings (1.3, 1.5, 1.8 and 2.6 m) on two sites: one on medium clay soil and the other on fine sand soil. The dry weight of the stem, branches, leaves, stumps and roots was estimated by drying and weighing sub-samples. The projected leaf area (PLA) m−2 of trees, leaf area index of stands and basic density (kg m−3)of stems were also estimated. A significant greater dry weight of stem, branches, stump and roots and species and spacing for pendula birch were found. The root length of silver birch was significantly greater than that for downy birch and for both species the root length was greatest at the widest spacing (2.6 m). There was also a significant difference between leaf weights of birch of the same species growing on the two soil types. Significant differences were also found between PLA and species, and for both species, between PLA spacing. Basic density of stems was significantly different between soil types. Equations for estimating the above-ground biomass and root biomass from diameter at breast height were developed for birches growing on fine sand and on medium clay soils. The total biomass production per hectare on fine sand was higher for silver birch (19.9–65.9 tonnes ha−1), than for downy birch (13.0–48.3 tonnes ha−1). On medium clay soil, total biomass production for silver and downy birches was 30.8–52.8 and 16.8–42.8 tonnes ha−1, respectively. Introduction Large-scale reforestation of abandoned farmland occurred in Sweden in the late-1960s (Johansson, 1999a), when Norway spruce (Picea abies (L.) Karst.) stands were widely planted on farmland. Figures for the biomass production of these spruce stands, which are now 35–40 years old, have been presented by Johansson (1999a). Later, in 1985–1990, the planting on farmland increased again, but the main species planted this time were birches (Betula pendula Roth and Betula pubescens Ehrh.). When planting on farmland, the stem density in the stand is an important factor affecting yield and wood quality. As the soil on farmland is generally more fertile than on forestland, the trees grow rapidly. However, the wood quality, in terms of characters such as branch diameter and basic density, can be quite different for farmland trees than for forestland trees. Estimates of tree biomass fractions are required in order to predict tree and stand growth and for forest management (Kurz et al., 1996). Researchers have reported results of biomass estimates for various tree species (for an overview, see Pardé, 1980; Canell, 1982). Most studies deal with above-ground biomass and some studies on birch have been reported (Ovington and Madgwick, 1959; Marklund, 1988; Johansson, 1999b). Since measuring root biomass is laborious, few data on this variable are available. In India, Puri et al. (1994) studied the distribution of roots in stands of Populus deltoides. According to Keays (1971), ‘measurements of root biomass are the ecologist's nightmare’. However, there are good reasons for attempting to obtain more information on root biomass and its relationship to other more easily measurable traits. For instance, the growth rate of trees planted on farmland depends on their spacing and a relationship between foliage and root biomass could be used as a predictive tool. In addition, studies on the relationship between the root biomass of trees and their stem density are needed to improve predictions of the amount of root biomass.The influence of soil type on growth is another important factor that requires further attention. Older birch trees (>20 years of age) trees have a typical heart-root system (Köstler et al., 1968). This makes it difficult to remove the stumps with the root system intact. However, young birches do not have this type of root system, which makes root excavations easier. Figures for the root biomass of birch are sparse but have been presented in some studies. Mälkönen (1977) reported figures of 16.9 tonnes ha−1 for 40-year-old downy birch growing in Finland, and Ovington and Madgwick (1959) found the same amount (i.e. 16.9 tonnes ha−1) in 24-year-old silver birch stands growing in the UK. However, the fine root biomass of a single birch tree is difficult to determine, but has been estimated to amount to ∼5 per cent of the total tree biomass (Drexhage and Gruber, 1999). Objective The first objective of the study was to quantify above- and below-stump biomass of silver (B. pendula Roth) and downy (B. pubescens Ehrh.) birches planted in four spacings and growing on two soil types in an area of farmland. The second objective of the study was to examine allometric relationships between diameter at breast height (d.b.h.) and above- and below-ground biomass of the two species. Materials and methods The farmland area was located close to Hedemora (Latitude 60° 10′ N, Longitude 16° 00′ E, Altitude 60 m a.s.l.), and had been used for cattle grazing in the 10 years prior to the start of the experiment. When the experiment was 12 years old, the stands had to be felled because the owner of the land wanted to use it for other purposes. Before planting, soil samples were taken randomly across the experimental area (≈1 ha). Based on the soil sample data, the area clearly comprised two distinct parts. The experiment was, therefore, stratified into two blocks: one covered by fine sand soil (I) and the other by medium clay soil (II). After harrowing the farmland, 1-year-old silver and downy birches seedlings of local provenance were planted, at four spacings (1.3, 1.5, 1.8 and 2.6 m) in plots of 80 seedlings (10 plants in eight rows). The experiment was fenced to exclude moose (Alces alces Lin.), roe deer (Capreolus capreolus capreolus Lin.) and hare (Lepus capensis Lin., Lepus timidus Lin.). Height and diameter (d.b.h.) growth was measured every autumn for the first 5 years, then every second year. Estimation of stand and tree characteristics Before felling the trees, leaf area index (LAI) was estimated, for each of the 16 experimental plots (two species, four spacings and two soil types (Table 1)), using a LAI-2000 plant canopy analyser (LI-COR, Inc., NE, USA). The initial measurement was taken outside the stand and then another five measurements were taken along five transects inside the stand, giving a total of 25 measurements. The transects were located between every second row of birch in the stand. The final measurement, to calibrate LAI, was taken outside the stand in the open. Table 1: Main characteristics for birch plots on abandoned farmland areas Spacing, m Soil type Diameter, d.b.h., mm Height, m Basal area, dm2 per tree Living trees, % LAI Basic density, kg m−3 Betula pendula Roth     1.3 × 1.3 Fine sand 56 ± 2 7.21 ± 0.17 0.27 ± 0.01 95 3.08 428 ± 7     1.5 × 1.5 Fine sand 52 ± 2 7.82 ± 0.17 0.21 ± 0.02 99 2.56 426 ± 2     1.8 × 1.8 Fine sand 64 ± 2 8.20 ± 0.12 0.30 ± 0.02 100 1.57 412 ± 11     2.6 × 2.6 Fine sand 66 ± 2 7.10 ± 0.15 0.32 ± 0.02 97 1.65 408 ± 10     1.3 × 1.3 Medium clay 47 ± 2 6.74 ± 0.17 0.21 ± 0.01 95 2.91 442 ± 10     1.5 × 1.5 Medium clay 62 ± 2 8.21 ± 0.14 0.31 ± 0.01 100 3.00 434 ± 7     1.8 × 1.8 Medium clay 62 ± 1 8.00 ± 0.10 0.29 ± 0.01 100 2.94 426 ± 7     2.6 × 2.6 Medium clay 70 ± 3 7.70 ± 0.19 0.37 ± 0.03 97 1.54 440 ± 11 Betula pubescens Ehrh.     1.3 × 1.3 Fine sand 39 ± 1 5.80 ± 0.17 0.12 ± 0.01 96 2.74 422 ± 10     1.5 × 1.5 Fine sand 38 ± 1 5.88 ± 0.12 0.12 ± 0.01 97 3.57 442 ± 4     1.8 × 1.8 Fine sand 43 ± 2 5.79 ± 0.15 0.15 ± 0.01 96 2.85 420 ± 18     2.6 × 2.6 Fine sand 52 ± 2 6.07 ± 0.12 0.23 ± 0.01 81 1.48 430 ± 7     1.3 × 1.3 Medium clay 27 ± 1 4.44 ± 0.09 0.08 ± 0.01 99 2.03 432 ± 8     1.5 × 1.5 Medium clay 51 ± 2 6.89 ± 0.14 0.22 ± 0.01 100 3.78 440 ± 11     1.8 × 1.8 Medium clay 39 ± 2 5.20 ± 0.13 0.12 ± 0.01 99 0.99 420 ± 1     2.6 × 2.6 Medium clay 58 ± 2 6.31 ± 0.16 0.28 ± 0.01 99 2.09 444 ± 10 Spacing, m Soil type Diameter, d.b.h., mm Height, m Basal area, dm2 per tree Living trees, % LAI Basic density, kg m−3 Betula pendula Roth     1.3 × 1.3 Fine sand 56 ± 2 7.21 ± 0.17 0.27 ± 0.01 95 3.08 428 ± 7     1.5 × 1.5 Fine sand 52 ± 2 7.82 ± 0.17 0.21 ± 0.02 99 2.56 426 ± 2     1.8 × 1.8 Fine sand 64 ± 2 8.20 ± 0.12 0.30 ± 0.02 100 1.57 412 ± 11     2.6 × 2.6 Fine sand 66 ± 2 7.10 ± 0.15 0.32 ± 0.02 97 1.65 408 ± 10     1.3 × 1.3 Medium clay 47 ± 2 6.74 ± 0.17 0.21 ± 0.01 95 2.91 442 ± 10     1.5 × 1.5 Medium clay 62 ± 2 8.21 ± 0.14 0.31 ± 0.01 100 3.00 434 ± 7     1.8 × 1.8 Medium clay 62 ± 1 8.00 ± 0.10 0.29 ± 0.01 100 2.94 426 ± 7     2.6 × 2.6 Medium clay 70 ± 3 7.70 ± 0.19 0.37 ± 0.03 97 1.54 440 ± 11 Betula pubescens Ehrh.     1.3 × 1.3 Fine sand 39 ± 1 5.80 ± 0.17 0.12 ± 0.01 96 2.74 422 ± 10     1.5 × 1.5 Fine sand 38 ± 1 5.88 ± 0.12 0.12 ± 0.01 97 3.57 442 ± 4     1.8 × 1.8 Fine sand 43 ± 2 5.79 ± 0.15 0.15 ± 0.01 96 2.85 420 ± 18     2.6 × 2.6 Fine sand 52 ± 2 6.07 ± 0.12 0.23 ± 0.01 81 1.48 430 ± 7     1.3 × 1.3 Medium clay 27 ± 1 4.44 ± 0.09 0.08 ± 0.01 99 2.03 432 ± 8     1.5 × 1.5 Medium clay 51 ± 2 6.89 ± 0.14 0.22 ± 0.01 100 3.78 440 ± 11     1.8 × 1.8 Medium clay 39 ± 2 5.20 ± 0.13 0.12 ± 0.01 99 0.99 420 ± 1     2.6 × 2.6 Medium clay 58 ± 2 6.31 ± 0.16 0.28 ± 0.01 99 2.09 444 ± 10 Open in new tab Table 1: Main characteristics for birch plots on abandoned farmland areas Spacing, m Soil type Diameter, d.b.h., mm Height, m Basal area, dm2 per tree Living trees, % LAI Basic density, kg m−3 Betula pendula Roth     1.3 × 1.3 Fine sand 56 ± 2 7.21 ± 0.17 0.27 ± 0.01 95 3.08 428 ± 7     1.5 × 1.5 Fine sand 52 ± 2 7.82 ± 0.17 0.21 ± 0.02 99 2.56 426 ± 2     1.8 × 1.8 Fine sand 64 ± 2 8.20 ± 0.12 0.30 ± 0.02 100 1.57 412 ± 11     2.6 × 2.6 Fine sand 66 ± 2 7.10 ± 0.15 0.32 ± 0.02 97 1.65 408 ± 10     1.3 × 1.3 Medium clay 47 ± 2 6.74 ± 0.17 0.21 ± 0.01 95 2.91 442 ± 10     1.5 × 1.5 Medium clay 62 ± 2 8.21 ± 0.14 0.31 ± 0.01 100 3.00 434 ± 7     1.8 × 1.8 Medium clay 62 ± 1 8.00 ± 0.10 0.29 ± 0.01 100 2.94 426 ± 7     2.6 × 2.6 Medium clay 70 ± 3 7.70 ± 0.19 0.37 ± 0.03 97 1.54 440 ± 11 Betula pubescens Ehrh.     1.3 × 1.3 Fine sand 39 ± 1 5.80 ± 0.17 0.12 ± 0.01 96 2.74 422 ± 10     1.5 × 1.5 Fine sand 38 ± 1 5.88 ± 0.12 0.12 ± 0.01 97 3.57 442 ± 4     1.8 × 1.8 Fine sand 43 ± 2 5.79 ± 0.15 0.15 ± 0.01 96 2.85 420 ± 18     2.6 × 2.6 Fine sand 52 ± 2 6.07 ± 0.12 0.23 ± 0.01 81 1.48 430 ± 7     1.3 × 1.3 Medium clay 27 ± 1 4.44 ± 0.09 0.08 ± 0.01 99 2.03 432 ± 8     1.5 × 1.5 Medium clay 51 ± 2 6.89 ± 0.14 0.22 ± 0.01 100 3.78 440 ± 11     1.8 × 1.8 Medium clay 39 ± 2 5.20 ± 0.13 0.12 ± 0.01 99 0.99 420 ± 1     2.6 × 2.6 Medium clay 58 ± 2 6.31 ± 0.16 0.28 ± 0.01 99 2.09 444 ± 10 Spacing, m Soil type Diameter, d.b.h., mm Height, m Basal area, dm2 per tree Living trees, % LAI Basic density, kg m−3 Betula pendula Roth     1.3 × 1.3 Fine sand 56 ± 2 7.21 ± 0.17 0.27 ± 0.01 95 3.08 428 ± 7     1.5 × 1.5 Fine sand 52 ± 2 7.82 ± 0.17 0.21 ± 0.02 99 2.56 426 ± 2     1.8 × 1.8 Fine sand 64 ± 2 8.20 ± 0.12 0.30 ± 0.02 100 1.57 412 ± 11     2.6 × 2.6 Fine sand 66 ± 2 7.10 ± 0.15 0.32 ± 0.02 97 1.65 408 ± 10     1.3 × 1.3 Medium clay 47 ± 2 6.74 ± 0.17 0.21 ± 0.01 95 2.91 442 ± 10     1.5 × 1.5 Medium clay 62 ± 2 8.21 ± 0.14 0.31 ± 0.01 100 3.00 434 ± 7     1.8 × 1.8 Medium clay 62 ± 1 8.00 ± 0.10 0.29 ± 0.01 100 2.94 426 ± 7     2.6 × 2.6 Medium clay 70 ± 3 7.70 ± 0.19 0.37 ± 0.03 97 1.54 440 ± 11 Betula pubescens Ehrh.     1.3 × 1.3 Fine sand 39 ± 1 5.80 ± 0.17 0.12 ± 0.01 96 2.74 422 ± 10     1.5 × 1.5 Fine sand 38 ± 1 5.88 ± 0.12 0.12 ± 0.01 97 3.57 442 ± 4     1.8 × 1.8 Fine sand 43 ± 2 5.79 ± 0.15 0.15 ± 0.01 96 2.85 420 ± 18     2.6 × 2.6 Fine sand 52 ± 2 6.07 ± 0.12 0.23 ± 0.01 81 1.48 430 ± 7     1.3 × 1.3 Medium clay 27 ± 1 4.44 ± 0.09 0.08 ± 0.01 99 2.03 432 ± 8     1.5 × 1.5 Medium clay 51 ± 2 6.89 ± 0.14 0.22 ± 0.01 100 3.78 440 ± 11     1.8 × 1.8 Medium clay 39 ± 2 5.20 ± 0.13 0.12 ± 0.01 99 0.99 420 ± 1     2.6 × 2.6 Medium clay 58 ± 2 6.31 ± 0.16 0.28 ± 0.01 99 2.09 444 ± 10 Open in new tab When the trees were 12 years old, they were all felled and their height, crown length and d.b.h. were measured (Table 1). Then, five undamaged trees per plot were sampled for detailed measurements; these trees were representative for the diameter distribution in the plot, for detailed measurements. The trees selected represented mean diameter, smallest diameter, largest diameter and the upper and lower quartiles. For each tree, two measurements were taken, the first at the widest part of the crown and the second at 90° to this. The fresh weights of the stem, branches and leaves were measured in the field by a portable scale with a precision of ±0.1 kg. The projected leaf area (PLA) for all leaves of each tree was estimated by a leaf-area metre (LI-3000, LI-COR, Inc., NE, USA). The leaves were passed through the leaf-area metre on a plastic belt, which transported the leaves over a lens; this recorded the area and the results were summarized on a monitor. The samples of leaves, stem and branches were then dried at 105°C for 48 h to constant weight and weighed. Dry biomass for the stem, branches and leaves of the each birch was then estimated by multiplying the fresh weight by the percentage dry weight of stem, branch and leaf sub-samples. Estimation of basic density A disc was cut from the stem at a height of 3 m in order to estimate its basic density. Basic density was estimated according to the water-immersion method described by Andersson and Tuimala (1980). The barked disc was saturated in water for 24 h. The fresh weight (g) and volume (cm3) were measured. The dry matter content of the sample was determined after drying for 36 h at 105°C, in an air-ventilated oven. Dry weight per unit fresh volume of the barked sample was then calculated as basic density (kg m−3). Stump and root biomass estimation Stumps from the sampled trees were removed carefully using an excavator and spades. The finest roots <1 mm were not sampled, as it is too time consuming and laborious to identify them, and it is difficult to be sure that all the fine roots have been collected. In the field, the roots of each tree were cut and the length of the root was measured from the stump to the point where the root diameter was <1 mm. Then, the length of all roots per stump was summed. The fresh weight of the roots and the stumps was measured in the laboratory. The roots and the stumps were dried at 105°C for 4–5 days and then the dry weight was determined. Statistical analysis Analysis of variance (ANOVA) was used to evaluate the differences between species, spacings and soil types. Allometric relationships, between d.b.h. and above-ground biomass including the stump and d.b.h. and root biomass were tested. A frequently used model for such relationships is the power model (cf. Kittredge, 1944; Payandeh, 1981; Satoo and Madgwick, 1985; Johansson, 1999b): where X is the d.b.h. (mm), β0 is the intercept coefficient and β1 is the slope coefficient. The SAS/STAT software (Anonymous, 1999) was used for the analyses. A significance level of P ≤ 0.05 was deemed to be significant throughout the study. Residuals of all regressions were normally distributed when tested against a normal probability plot. The fit of the non-linear regressions was evaluated on the basis of the coefficient of determination:r2 = 1 – (Sum of squares error/Sum of squares total (corrected)) (Zar, 1999). Results The percentage of living trees was >90 per cent for every permutation of birch species, soil type and spacing, except for pubescent birch growing on fine sand at a spacing of 2.6 m, where only 81 per cent of the trees survived (Table 1). This lower survival was mainly attributed to vole damage. LAI was highest for silver birch at 1.3 m spacing on fine sand and 1.5 m on medium clay (Table 1). For downy birch, LAI was highest at a spacing of 1.5 m on both fine sand and medium clay soils. As shown in Table 2, there were no interactions between species, spacings and soil types and the attributes measured. There were significant differences between the dry weights of the stem, branches, stump and roots and species (Table 2). Stem, branch, stump and root weights were greater for silver birch than for downy birch (Table 3). There were also significant differences between all dry weights (stem, branches, leaves, stump and roots) and spacing (Table 2). The leaf weight was significantly different between the two soil types (Table 2). The dry weight was greater for trees growing on fine sand than on medium clay soil (Table 3). Basic density was significantly different between soil types (Table 2). The basic density was greater (435 ± 3) for stems on medium clay soil than on fine sand soil (423 ± 3) (Table 1). Table 2: Test of differences between species, spacings and soil types and measurements of stem weight, branch weight, leaf weight, stump weight, root weight, root length, PLA and basic density (under bark) of stems (analysis of variance) Source of variation Degree of freedom F P Stem weight     A (species) 1 21.50 0.0001     B (spacings) 3 3.02 0.0361     C (soil type) 1 0.02 0.8842     A × B 3 0.13 0.9389     A × C 1 0.73 0.3961     B × C 3 2.22 0.0949     A × B × C 3 0.97 0.4114     Residual 64 Branch weight     A (species) 1 6.03 0.0168     B (spacings) 3 6.28 0.0008     C (soil type) 1 1.63 0.2060     A × B 3 0.61 0.6127     A × C 1 1.58 0.2129     B × C 3 1.66 0.1839     A × B × C 3 0.61 0.6098     Residual 64 Leaf weight     A (species) 1 3.55 0.0640     B (spacings) 3 5.77 0.0015     C (soil type) 1 23.61 0.0001     A × B 3 0.66 0.5821     A × C 1 0.02 0.8802     B × C 3 2.59 0.0602     A × B × C 3 0.29 0.8317     Residual 64 Stump weight     A (species) 1 16.13 0.0002     B (spacings) 3 3 0.0371     C (soil type) 1 1.26 0.2660     A × B 3 0.07 0.9760     A × C 1 0.78 0.3793     B × C 3 1.25 0.2995     A × B × C 3 0.33 0.8021     Residual 64 Root weight     A (species) 1 9.25 0.0034     B (spacings) 3 4.68 0.0051     C (soil type) 1 2.24 0.1392     A × B 3 0.58 0.6307     A × C 1 1.43 0.2362     B × C 3 0.74 0.5298     A × B × C 3 0.64 0.5925     Residual 64 Root length     A (species) 1 5.03 0.0284     B (spacings) 3 6.26 0.0009     C (soil type) 1 0.02 0.9016     A × B 3 0.58 0.6306     A × C 1 0.72 0.3992     B × C 3 0.32 0.8083     A × B × C 3 0.2 0.8928     Residual 64 PLA     A (species) 1 4.69 0.0322     B (spacings) 3 0.27 0.8466     C (soil type) 1 16.66 0.0001     A × B 3 0.19 0.9043     A × C 1 0.07 0.7925     B × C 3 2.01 0.1214     A × B × C 3 0.5 0.6858     Residual 64 Basic density of stem     A (species) 1 0.74 0.3928     B (spacings) 3 1.89 0.1395     C (soil type) 1 5.19 0.0291     A × B 3 0.97 0.4146     A × C 1 1.35 0.2488     B × C 3 0.77 0.5165     A × B × C 3 0.09 0.9646     Residual 64 Source of variation Degree of freedom F P Stem weight     A (species) 1 21.50 0.0001     B (spacings) 3 3.02 0.0361     C (soil type) 1 0.02 0.8842     A × B 3 0.13 0.9389     A × C 1 0.73 0.3961     B × C 3 2.22 0.0949     A × B × C 3 0.97 0.4114     Residual 64 Branch weight     A (species) 1 6.03 0.0168     B (spacings) 3 6.28 0.0008     C (soil type) 1 1.63 0.2060     A × B 3 0.61 0.6127     A × C 1 1.58 0.2129     B × C 3 1.66 0.1839     A × B × C 3 0.61 0.6098     Residual 64 Leaf weight     A (species) 1 3.55 0.0640     B (spacings) 3 5.77 0.0015     C (soil type) 1 23.61 0.0001     A × B 3 0.66 0.5821     A × C 1 0.02 0.8802     B × C 3 2.59 0.0602     A × B × C 3 0.29 0.8317     Residual 64 Stump weight     A (species) 1 16.13 0.0002     B (spacings) 3 3 0.0371     C (soil type) 1 1.26 0.2660     A × B 3 0.07 0.9760     A × C 1 0.78 0.3793     B × C 3 1.25 0.2995     A × B × C 3 0.33 0.8021     Residual 64 Root weight     A (species) 1 9.25 0.0034     B (spacings) 3 4.68 0.0051     C (soil type) 1 2.24 0.1392     A × B 3 0.58 0.6307     A × C 1 1.43 0.2362     B × C 3 0.74 0.5298     A × B × C 3 0.64 0.5925     Residual 64 Root length     A (species) 1 5.03 0.0284     B (spacings) 3 6.26 0.0009     C (soil type) 1 0.02 0.9016     A × B 3 0.58 0.6306     A × C 1 0.72 0.3992     B × C 3 0.32 0.8083     A × B × C 3 0.2 0.8928     Residual 64 PLA     A (species) 1 4.69 0.0322     B (spacings) 3 0.27 0.8466     C (soil type) 1 16.66 0.0001     A × B 3 0.19 0.9043     A × C 1 0.07 0.7925     B × C 3 2.01 0.1214     A × B × C 3 0.5 0.6858     Residual 64 Basic density of stem     A (species) 1 0.74 0.3928     B (spacings) 3 1.89 0.1395     C (soil type) 1 5.19 0.0291     A × B 3 0.97 0.4146     A × C 1 1.35 0.2488     B × C 3 0.77 0.5165     A × B × C 3 0.09 0.9646     Residual 64 Open in new tab Table 2: Test of differences between species, spacings and soil types and measurements of stem weight, branch weight, leaf weight, stump weight, root weight, root length, PLA and basic density (under bark) of stems (analysis of variance) Source of variation Degree of freedom F P Stem weight     A (species) 1 21.50 0.0001     B (spacings) 3 3.02 0.0361     C (soil type) 1 0.02 0.8842     A × B 3 0.13 0.9389     A × C 1 0.73 0.3961     B × C 3 2.22 0.0949     A × B × C 3 0.97 0.4114     Residual 64 Branch weight     A (species) 1 6.03 0.0168     B (spacings) 3 6.28 0.0008     C (soil type) 1 1.63 0.2060     A × B 3 0.61 0.6127     A × C 1 1.58 0.2129     B × C 3 1.66 0.1839     A × B × C 3 0.61 0.6098     Residual 64 Leaf weight     A (species) 1 3.55 0.0640     B (spacings) 3 5.77 0.0015     C (soil type) 1 23.61 0.0001     A × B 3 0.66 0.5821     A × C 1 0.02 0.8802     B × C 3 2.59 0.0602     A × B × C 3 0.29 0.8317     Residual 64 Stump weight     A (species) 1 16.13 0.0002     B (spacings) 3 3 0.0371     C (soil type) 1 1.26 0.2660     A × B 3 0.07 0.9760     A × C 1 0.78 0.3793     B × C 3 1.25 0.2995     A × B × C 3 0.33 0.8021     Residual 64 Root weight     A (species) 1 9.25 0.0034     B (spacings) 3 4.68 0.0051     C (soil type) 1 2.24 0.1392     A × B 3 0.58 0.6307     A × C 1 1.43 0.2362     B × C 3 0.74 0.5298     A × B × C 3 0.64 0.5925     Residual 64 Root length     A (species) 1 5.03 0.0284     B (spacings) 3 6.26 0.0009     C (soil type) 1 0.02 0.9016     A × B 3 0.58 0.6306     A × C 1 0.72 0.3992     B × C 3 0.32 0.8083     A × B × C 3 0.2 0.8928     Residual 64 PLA     A (species) 1 4.69 0.0322     B (spacings) 3 0.27 0.8466     C (soil type) 1 16.66 0.0001     A × B 3 0.19 0.9043     A × C 1 0.07 0.7925     B × C 3 2.01 0.1214     A × B × C 3 0.5 0.6858     Residual 64 Basic density of stem     A (species) 1 0.74 0.3928     B (spacings) 3 1.89 0.1395     C (soil type) 1 5.19 0.0291     A × B 3 0.97 0.4146     A × C 1 1.35 0.2488     B × C 3 0.77 0.5165     A × B × C 3 0.09 0.9646     Residual 64 Source of variation Degree of freedom F P Stem weight     A (species) 1 21.50 0.0001     B (spacings) 3 3.02 0.0361     C (soil type) 1 0.02 0.8842     A × B 3 0.13 0.9389     A × C 1 0.73 0.3961     B × C 3 2.22 0.0949     A × B × C 3 0.97 0.4114     Residual 64 Branch weight     A (species) 1 6.03 0.0168     B (spacings) 3 6.28 0.0008     C (soil type) 1 1.63 0.2060     A × B 3 0.61 0.6127     A × C 1 1.58 0.2129     B × C 3 1.66 0.1839     A × B × C 3 0.61 0.6098     Residual 64 Leaf weight     A (species) 1 3.55 0.0640     B (spacings) 3 5.77 0.0015     C (soil type) 1 23.61 0.0001     A × B 3 0.66 0.5821     A × C 1 0.02 0.8802     B × C 3 2.59 0.0602     A × B × C 3 0.29 0.8317     Residual 64 Stump weight     A (species) 1 16.13 0.0002     B (spacings) 3 3 0.0371     C (soil type) 1 1.26 0.2660     A × B 3 0.07 0.9760     A × C 1 0.78 0.3793     B × C 3 1.25 0.2995     A × B × C 3 0.33 0.8021     Residual 64 Root weight     A (species) 1 9.25 0.0034     B (spacings) 3 4.68 0.0051     C (soil type) 1 2.24 0.1392     A × B 3 0.58 0.6307     A × C 1 1.43 0.2362     B × C 3 0.74 0.5298     A × B × C 3 0.64 0.5925     Residual 64 Root length     A (species) 1 5.03 0.0284     B (spacings) 3 6.26 0.0009     C (soil type) 1 0.02 0.9016     A × B 3 0.58 0.6306     A × C 1 0.72 0.3992     B × C 3 0.32 0.8083     A × B × C 3 0.2 0.8928     Residual 64 PLA     A (species) 1 4.69 0.0322     B (spacings) 3 0.27 0.8466     C (soil type) 1 16.66 0.0001     A × B 3 0.19 0.9043     A × C 1 0.07 0.7925     B × C 3 2.01 0.1214     A × B × C 3 0.5 0.6858     Residual 64 Basic density of stem     A (species) 1 0.74 0.3928     B (spacings) 3 1.89 0.1395     C (soil type) 1 5.19 0.0291     A × B 3 0.97 0.4146     A × C 1 1.35 0.2488     B × C 3 0.77 0.5165     A × B × C 3 0.09 0.9646     Residual 64 Open in new tab Table 3: Dry weight ± standard error, g per tree, for birch (Betula pendula Roth and Betula pubescens Ehrh.) fractions growing on abandoned farmland area at different spacing Spacing, m Fraction 1.3 × 1.3 1.5 × 1.5 1.8 × 1.8 2.6 × 2.6 Mean B. pendula Roth     Fine sand         Stem 7.11 ± 1.60 8.40 ± 1.74 7.44 ± 2.77 7.51 ± 1.37 7.61 ± 0.90         Branches 1.87 ± 0.54 1.58 ± 0.36 1.54 ± 0.47 2.59 ± 0.45 1.90 ± 0.23         Leaves 0.98 ± 0.25 0.66 ± 0.22 0.80 ± 0.24 1.35 ± 0.26 0.95 ± 0.13         Stump 0.76 ± 0.20 0.74 ± 0.12 0.77 ± 0.32 0.77 ± 0.19 0.75 ± 0.10         Total above ground 10.73 ± 2.51 11.38 ± 2.38 10.55 ± 3.80 12.22 ± 2.20 11.21 ± 1.29         Root 1.00 ± 0.16 0.97 ± 0.11 1.00 ± 0.23 1.66 ± 0.59 1.16 ± 0.20         Total 11.73 ± 2.75 12.36 ± 2.59 11.55 ± 4.25 13.88 ± 2.74 12.29 ± 1.42     Medium clay         Stem 5.73 ± 1.66 7.28 ± 1.48 7.95 ± 1.88 12.63 ± 2.35 8.40 ± 1.04         Branches 1.52 ± 0.42 1.90 ± 0.47 2.58 ± 0.73 4.32 ± 1.14 2.58 ± 0.43         Leaves 0.33 ± 0.15 0.74 ± 0.20 0.39 ± 0.13 0.63 ± 0.13 0.53 ± 0.08         Stump 0.68 ± 0.15 0.87 ± 0.15 0.86 ± 0.15 1.29 ± 0.22 0.93 ± 0.09         Total above ground 8.27 ± 2.46 10.79 ± 0.45 11.78 ± 2.82 18.87 ± 3.81 12.44 ± 1.61         Root 1.12 ± 0.20 1.08 ± 1.39 1.84 ± 0.32 2.59 ± 0.27 1.71 ± 0.28         Total 9.39 ± 2.85 11.87 ± 2.52 13.63 ± 3.30 21.46 ± 4.31 14.10 ± 1.85 B. pubescens Ehrh.     Fine sand         Stem 5.15 ± 1.42 3.69 ± 0.92 4.26 ± 1.09 5.50 ± 0.99 4.65 ± 0.54         Branches 1.48 ± 0.45 1.25 ± 0.36 1.37 ± 0.34 2.18 ± 0.37 1.57 ± 0.19         Leaves 0.62 ± 0.22 0.44 ± 0.14 0.79 ± 0.20 1.32 ± 0.24 0.79 ± 0.12         Stump 0.43 ± 0.10 0.51 ± 0.14 0.41 ± 0.11 0.66 ± 0.08 0.50 ± 0.06         Total above ground 7.68 ± 2.17 5.89 ± 1.55 6.83 ± 1.72 9.65 ± 1.59 7.51 ± 0.87         Root 0.83 ± 0.25 0.61 ± 0.15 0.70 ± 0.25 1.15 ± 0.18 0.82 ± 0.11         Total 8.51 ± 2.43 6.50 ± 1.71 7.53 ± 1.96 10.80 ± 1.74 8.34 ± 0.98     Medium clay         Stem 1.46 ± 0.22 5.67 ± 1.84 2.72 ± 0.77 6.54 ± 1.05 4.10 ± 0.71         Branches 0.58 ± 0.10 2.03 ± 0.71 1.18 ± 0.39 2.51 ± 0.51 1.58 ± 0.28         Leaves 0.21 ± 0.03 0.29 ± 0.64 0.28 ± 0.10 0.60 ± 0.04 0.34 ± 0.05         Stump 0.20 ± 0.03 0.54 ± 0.18 0.53 ± 0.18 0.77 ± 0.10 0.53 ± 0.08         Total above ground 2.45 ± 0.38 8.53 ± 2.79 4.71 ± 1.43 10.41 ± 1.60 6.52 ± 1.46         Root 0.64 ± 0.07 1.08 ± 0.42 0 51 ± 0.22 1.33 ± 0.42 0.89 ± 0.18         Total 3.09 ± 0.67 9.61 ± 2.52 5.22 ± 1.55 11.74 ± 1.68 7.41 ± 0.45 Spacing, m Fraction 1.3 × 1.3 1.5 × 1.5 1.8 × 1.8 2.6 × 2.6 Mean B. pendula Roth     Fine sand         Stem 7.11 ± 1.60 8.40 ± 1.74 7.44 ± 2.77 7.51 ± 1.37 7.61 ± 0.90         Branches 1.87 ± 0.54 1.58 ± 0.36 1.54 ± 0.47 2.59 ± 0.45 1.90 ± 0.23         Leaves 0.98 ± 0.25 0.66 ± 0.22 0.80 ± 0.24 1.35 ± 0.26 0.95 ± 0.13         Stump 0.76 ± 0.20 0.74 ± 0.12 0.77 ± 0.32 0.77 ± 0.19 0.75 ± 0.10         Total above ground 10.73 ± 2.51 11.38 ± 2.38 10.55 ± 3.80 12.22 ± 2.20 11.21 ± 1.29         Root 1.00 ± 0.16 0.97 ± 0.11 1.00 ± 0.23 1.66 ± 0.59 1.16 ± 0.20         Total 11.73 ± 2.75 12.36 ± 2.59 11.55 ± 4.25 13.88 ± 2.74 12.29 ± 1.42     Medium clay         Stem 5.73 ± 1.66 7.28 ± 1.48 7.95 ± 1.88 12.63 ± 2.35 8.40 ± 1.04         Branches 1.52 ± 0.42 1.90 ± 0.47 2.58 ± 0.73 4.32 ± 1.14 2.58 ± 0.43         Leaves 0.33 ± 0.15 0.74 ± 0.20 0.39 ± 0.13 0.63 ± 0.13 0.53 ± 0.08         Stump 0.68 ± 0.15 0.87 ± 0.15 0.86 ± 0.15 1.29 ± 0.22 0.93 ± 0.09         Total above ground 8.27 ± 2.46 10.79 ± 0.45 11.78 ± 2.82 18.87 ± 3.81 12.44 ± 1.61         Root 1.12 ± 0.20 1.08 ± 1.39 1.84 ± 0.32 2.59 ± 0.27 1.71 ± 0.28         Total 9.39 ± 2.85 11.87 ± 2.52 13.63 ± 3.30 21.46 ± 4.31 14.10 ± 1.85 B. pubescens Ehrh.     Fine sand         Stem 5.15 ± 1.42 3.69 ± 0.92 4.26 ± 1.09 5.50 ± 0.99 4.65 ± 0.54         Branches 1.48 ± 0.45 1.25 ± 0.36 1.37 ± 0.34 2.18 ± 0.37 1.57 ± 0.19         Leaves 0.62 ± 0.22 0.44 ± 0.14 0.79 ± 0.20 1.32 ± 0.24 0.79 ± 0.12         Stump 0.43 ± 0.10 0.51 ± 0.14 0.41 ± 0.11 0.66 ± 0.08 0.50 ± 0.06         Total above ground 7.68 ± 2.17 5.89 ± 1.55 6.83 ± 1.72 9.65 ± 1.59 7.51 ± 0.87         Root 0.83 ± 0.25 0.61 ± 0.15 0.70 ± 0.25 1.15 ± 0.18 0.82 ± 0.11         Total 8.51 ± 2.43 6.50 ± 1.71 7.53 ± 1.96 10.80 ± 1.74 8.34 ± 0.98     Medium clay         Stem 1.46 ± 0.22 5.67 ± 1.84 2.72 ± 0.77 6.54 ± 1.05 4.10 ± 0.71         Branches 0.58 ± 0.10 2.03 ± 0.71 1.18 ± 0.39 2.51 ± 0.51 1.58 ± 0.28         Leaves 0.21 ± 0.03 0.29 ± 0.64 0.28 ± 0.10 0.60 ± 0.04 0.34 ± 0.05         Stump 0.20 ± 0.03 0.54 ± 0.18 0.53 ± 0.18 0.77 ± 0.10 0.53 ± 0.08         Total above ground 2.45 ± 0.38 8.53 ± 2.79 4.71 ± 1.43 10.41 ± 1.60 6.52 ± 1.46         Root 0.64 ± 0.07 1.08 ± 0.42 0 51 ± 0.22 1.33 ± 0.42 0.89 ± 0.18         Total 3.09 ± 0.67 9.61 ± 2.52 5.22 ± 1.55 11.74 ± 1.68 7.41 ± 0.45 Open in new tab Table 3: Dry weight ± standard error, g per tree, for birch (Betula pendula Roth and Betula pubescens Ehrh.) fractions growing on abandoned farmland area at different spacing Spacing, m Fraction 1.3 × 1.3 1.5 × 1.5 1.8 × 1.8 2.6 × 2.6 Mean B. pendula Roth     Fine sand         Stem 7.11 ± 1.60 8.40 ± 1.74 7.44 ± 2.77 7.51 ± 1.37 7.61 ± 0.90         Branches 1.87 ± 0.54 1.58 ± 0.36 1.54 ± 0.47 2.59 ± 0.45 1.90 ± 0.23         Leaves 0.98 ± 0.25 0.66 ± 0.22 0.80 ± 0.24 1.35 ± 0.26 0.95 ± 0.13         Stump 0.76 ± 0.20 0.74 ± 0.12 0.77 ± 0.32 0.77 ± 0.19 0.75 ± 0.10         Total above ground 10.73 ± 2.51 11.38 ± 2.38 10.55 ± 3.80 12.22 ± 2.20 11.21 ± 1.29         Root 1.00 ± 0.16 0.97 ± 0.11 1.00 ± 0.23 1.66 ± 0.59 1.16 ± 0.20         Total 11.73 ± 2.75 12.36 ± 2.59 11.55 ± 4.25 13.88 ± 2.74 12.29 ± 1.42     Medium clay         Stem 5.73 ± 1.66 7.28 ± 1.48 7.95 ± 1.88 12.63 ± 2.35 8.40 ± 1.04         Branches 1.52 ± 0.42 1.90 ± 0.47 2.58 ± 0.73 4.32 ± 1.14 2.58 ± 0.43         Leaves 0.33 ± 0.15 0.74 ± 0.20 0.39 ± 0.13 0.63 ± 0.13 0.53 ± 0.08         Stump 0.68 ± 0.15 0.87 ± 0.15 0.86 ± 0.15 1.29 ± 0.22 0.93 ± 0.09         Total above ground 8.27 ± 2.46 10.79 ± 0.45 11.78 ± 2.82 18.87 ± 3.81 12.44 ± 1.61         Root 1.12 ± 0.20 1.08 ± 1.39 1.84 ± 0.32 2.59 ± 0.27 1.71 ± 0.28         Total 9.39 ± 2.85 11.87 ± 2.52 13.63 ± 3.30 21.46 ± 4.31 14.10 ± 1.85 B. pubescens Ehrh.     Fine sand         Stem 5.15 ± 1.42 3.69 ± 0.92 4.26 ± 1.09 5.50 ± 0.99 4.65 ± 0.54         Branches 1.48 ± 0.45 1.25 ± 0.36 1.37 ± 0.34 2.18 ± 0.37 1.57 ± 0.19         Leaves 0.62 ± 0.22 0.44 ± 0.14 0.79 ± 0.20 1.32 ± 0.24 0.79 ± 0.12         Stump 0.43 ± 0.10 0.51 ± 0.14 0.41 ± 0.11 0.66 ± 0.08 0.50 ± 0.06         Total above ground 7.68 ± 2.17 5.89 ± 1.55 6.83 ± 1.72 9.65 ± 1.59 7.51 ± 0.87         Root 0.83 ± 0.25 0.61 ± 0.15 0.70 ± 0.25 1.15 ± 0.18 0.82 ± 0.11         Total 8.51 ± 2.43 6.50 ± 1.71 7.53 ± 1.96 10.80 ± 1.74 8.34 ± 0.98     Medium clay         Stem 1.46 ± 0.22 5.67 ± 1.84 2.72 ± 0.77 6.54 ± 1.05 4.10 ± 0.71         Branches 0.58 ± 0.10 2.03 ± 0.71 1.18 ± 0.39 2.51 ± 0.51 1.58 ± 0.28         Leaves 0.21 ± 0.03 0.29 ± 0.64 0.28 ± 0.10 0.60 ± 0.04 0.34 ± 0.05         Stump 0.20 ± 0.03 0.54 ± 0.18 0.53 ± 0.18 0.77 ± 0.10 0.53 ± 0.08         Total above ground 2.45 ± 0.38 8.53 ± 2.79 4.71 ± 1.43 10.41 ± 1.60 6.52 ± 1.46         Root 0.64 ± 0.07 1.08 ± 0.42 0 51 ± 0.22 1.33 ± 0.42 0.89 ± 0.18         Total 3.09 ± 0.67 9.61 ± 2.52 5.22 ± 1.55 11.74 ± 1.68 7.41 ± 0.45 Spacing, m Fraction 1.3 × 1.3 1.5 × 1.5 1.8 × 1.8 2.6 × 2.6 Mean B. pendula Roth     Fine sand         Stem 7.11 ± 1.60 8.40 ± 1.74 7.44 ± 2.77 7.51 ± 1.37 7.61 ± 0.90         Branches 1.87 ± 0.54 1.58 ± 0.36 1.54 ± 0.47 2.59 ± 0.45 1.90 ± 0.23         Leaves 0.98 ± 0.25 0.66 ± 0.22 0.80 ± 0.24 1.35 ± 0.26 0.95 ± 0.13         Stump 0.76 ± 0.20 0.74 ± 0.12 0.77 ± 0.32 0.77 ± 0.19 0.75 ± 0.10         Total above ground 10.73 ± 2.51 11.38 ± 2.38 10.55 ± 3.80 12.22 ± 2.20 11.21 ± 1.29         Root 1.00 ± 0.16 0.97 ± 0.11 1.00 ± 0.23 1.66 ± 0.59 1.16 ± 0.20         Total 11.73 ± 2.75 12.36 ± 2.59 11.55 ± 4.25 13.88 ± 2.74 12.29 ± 1.42     Medium clay         Stem 5.73 ± 1.66 7.28 ± 1.48 7.95 ± 1.88 12.63 ± 2.35 8.40 ± 1.04         Branches 1.52 ± 0.42 1.90 ± 0.47 2.58 ± 0.73 4.32 ± 1.14 2.58 ± 0.43         Leaves 0.33 ± 0.15 0.74 ± 0.20 0.39 ± 0.13 0.63 ± 0.13 0.53 ± 0.08         Stump 0.68 ± 0.15 0.87 ± 0.15 0.86 ± 0.15 1.29 ± 0.22 0.93 ± 0.09         Total above ground 8.27 ± 2.46 10.79 ± 0.45 11.78 ± 2.82 18.87 ± 3.81 12.44 ± 1.61         Root 1.12 ± 0.20 1.08 ± 1.39 1.84 ± 0.32 2.59 ± 0.27 1.71 ± 0.28         Total 9.39 ± 2.85 11.87 ± 2.52 13.63 ± 3.30 21.46 ± 4.31 14.10 ± 1.85 B. pubescens Ehrh.     Fine sand         Stem 5.15 ± 1.42 3.69 ± 0.92 4.26 ± 1.09 5.50 ± 0.99 4.65 ± 0.54         Branches 1.48 ± 0.45 1.25 ± 0.36 1.37 ± 0.34 2.18 ± 0.37 1.57 ± 0.19         Leaves 0.62 ± 0.22 0.44 ± 0.14 0.79 ± 0.20 1.32 ± 0.24 0.79 ± 0.12         Stump 0.43 ± 0.10 0.51 ± 0.14 0.41 ± 0.11 0.66 ± 0.08 0.50 ± 0.06         Total above ground 7.68 ± 2.17 5.89 ± 1.55 6.83 ± 1.72 9.65 ± 1.59 7.51 ± 0.87         Root 0.83 ± 0.25 0.61 ± 0.15 0.70 ± 0.25 1.15 ± 0.18 0.82 ± 0.11         Total 8.51 ± 2.43 6.50 ± 1.71 7.53 ± 1.96 10.80 ± 1.74 8.34 ± 0.98     Medium clay         Stem 1.46 ± 0.22 5.67 ± 1.84 2.72 ± 0.77 6.54 ± 1.05 4.10 ± 0.71         Branches 0.58 ± 0.10 2.03 ± 0.71 1.18 ± 0.39 2.51 ± 0.51 1.58 ± 0.28         Leaves 0.21 ± 0.03 0.29 ± 0.64 0.28 ± 0.10 0.60 ± 0.04 0.34 ± 0.05         Stump 0.20 ± 0.03 0.54 ± 0.18 0.53 ± 0.18 0.77 ± 0.10 0.53 ± 0.08         Total above ground 2.45 ± 0.38 8.53 ± 2.79 4.71 ± 1.43 10.41 ± 1.60 6.52 ± 1.46         Root 0.64 ± 0.07 1.08 ± 0.42 0 51 ± 0.22 1.33 ± 0.42 0.89 ± 0.18         Total 3.09 ± 0.67 9.61 ± 2.52 5.22 ± 1.55 11.74 ± 1.68 7.41 ± 0.45 Open in new tab Root length differed significantly not only between species but also between spacings (Table 2). The roots were longest for the widest spacing (2.6 × 2.6 m) for both species (Table 4). There were statistically significant differences between PLA and species and soil type (Table 2). PLA was higher for silver birch (5.7 ± 0.1) than for downy birch (5.3 ± 0.2). Trees growing on medium clay soil had higher PLA than those growing on fine sand (Figure 1). The differences in crown width between the two species were small and not significantly different although the width was greatest on fine sand and at the widest spacing (2.6 m) for both soil types (Figure 2). Table 4: Total root length ± standard error, m per tree, for birch (Betula pendula Roth and Betula pubescens Ehrh.) growing on abandoned farmland area at different spacing Spacing, m 1.3 × 1.3 1.5 × 1.5 1.8 × 1.8 2.6 × 2.6 Mean B. pendula Roth     Fine sand         8.19 ± 1.34 9.04 ± 2.05 8.20 ± 2.52 15.06 ± 4.02 10.12 ± 1.39     Medium clay         7.85 ± 2.02 8.45 ± 1.48 10.93 ± 3.06 16.79 ± 3.77 11.01 ± 1.49 B. pubescens Ehrh.     Fine sand         7.10 ± 1.88 8.74 ± 2.74 7.03 ± 2.10 10.80 ± 1.33 8.42 ± 1.02     Medium clay         3.67 ± 0.65 8.30 ± 2.88 5.09 ± 1.59 11.49 ± 2.98 7.23 ± 1.26 Spacing, m 1.3 × 1.3 1.5 × 1.5 1.8 × 1.8 2.6 × 2.6 Mean B. pendula Roth     Fine sand         8.19 ± 1.34 9.04 ± 2.05 8.20 ± 2.52 15.06 ± 4.02 10.12 ± 1.39     Medium clay         7.85 ± 2.02 8.45 ± 1.48 10.93 ± 3.06 16.79 ± 3.77 11.01 ± 1.49 B. pubescens Ehrh.     Fine sand         7.10 ± 1.88 8.74 ± 2.74 7.03 ± 2.10 10.80 ± 1.33 8.42 ± 1.02     Medium clay         3.67 ± 0.65 8.30 ± 2.88 5.09 ± 1.59 11.49 ± 2.98 7.23 ± 1.26 Open in new tab Table 4: Total root length ± standard error, m per tree, for birch (Betula pendula Roth and Betula pubescens Ehrh.) growing on abandoned farmland area at different spacing Spacing, m 1.3 × 1.3 1.5 × 1.5 1.8 × 1.8 2.6 × 2.6 Mean B. pendula Roth     Fine sand         8.19 ± 1.34 9.04 ± 2.05 8.20 ± 2.52 15.06 ± 4.02 10.12 ± 1.39     Medium clay         7.85 ± 2.02 8.45 ± 1.48 10.93 ± 3.06 16.79 ± 3.77 11.01 ± 1.49 B. pubescens Ehrh.     Fine sand         7.10 ± 1.88 8.74 ± 2.74 7.03 ± 2.10 10.80 ± 1.33 8.42 ± 1.02     Medium clay         3.67 ± 0.65 8.30 ± 2.88 5.09 ± 1.59 11.49 ± 2.98 7.23 ± 1.26 Spacing, m 1.3 × 1.3 1.5 × 1.5 1.8 × 1.8 2.6 × 2.6 Mean B. pendula Roth     Fine sand         8.19 ± 1.34 9.04 ± 2.05 8.20 ± 2.52 15.06 ± 4.02 10.12 ± 1.39     Medium clay         7.85 ± 2.02 8.45 ± 1.48 10.93 ± 3.06 16.79 ± 3.77 11.01 ± 1.49 B. pubescens Ehrh.     Fine sand         7.10 ± 1.88 8.74 ± 2.74 7.03 ± 2.10 10.80 ± 1.33 8.42 ± 1.02     Medium clay         3.67 ± 0.65 8.30 ± 2.88 5.09 ± 1.59 11.49 ± 2.98 7.23 ± 1.26 Open in new tab Figure 1. Open in new tabDownload slide PLA m2 per tree for silver birch (Betula pendula Roth), , and downy birch (Betula pubescens Ehrh.), , growing on farmland. The birch was planted at different spacings (1.3–2.6 m). Figure 2. Open in new tabDownload slide Crown width, cm, for silver birch (Betula pendula Roth), , and downy birches (Betula pubescens Ehrh.), , growing at different spacings on fine sand and medium clay soil. For silver birch, the mean proportion of the total biomass accounted for by silver birch by the above-ground component was 91 per cent on the fine sand and 88 per cent on the medium clay soil (Figure 3). For downy birch, the corresponding figures were 90 per cent (89–91 per cent) and 88 per cent (87–89 per cent), respectively. Figure 3. Open in new tabDownload slide Stem, branch, leaf and stump and root fractions, as percentages of total biomass for silver birch (Betula pendula Roth), upper panel, and downy birch (Betula pubescens Ehrh.), lower panel, growing at different spacings and on fine sand soil, left panel, and medium clay soil, right panel. stem, branches, leaves, stump and roots. The model produced a good fit to the actual data, both for the above-ground (including stump weight) to d.b.h. and the root biomass to d.b.h.. The coefficient of determination was 0.91–0.95 for above-ground biomass and 0.65–0.95 for root biomass (Figure 4 and Table 5). The relationship between root biomass and leaf biomass (Figure 5) was also a good fit, and the coefficients of determination were 0.71 and 0.81, respectively, for silver and downy birches growing on fine sand soil. The figures were lower on medium clay soil, 0.39 and 0.41, respectively (Table 5). Table 5: Estimated parameters and their asymptotic standard errors (SEs) of 12 tested models, mean residual (Mres) between observed biomass (Bo) and predicted biomass (Bp), kg per tree, according to tested model, and coefficient of determination (r2) for biomass estimations of pendula (Betula pendula Roth.) and pubescent (Betula pubescens Ehrh.) birches growing on farmland; RMSE, root mean square error No Soil type Y X β0 SE β1 SE RMSE r2 Diameter – above-ground biomass B. pendula Roth     1 Fine sand Biomass d.b.h. 7.4 × 10-4 4.6 × 10-4 2.2851 0.1428 1.3286 0.95     2 Medium clay Biomass d.b.h. 13.8 × 10-4 8.2 × 10-4 2.1393 0.1338 1.6812 0.95 B. pubescens Ehrh.     3 Fine sand Biomass d.b.h. 1.9 × 10-4 1.4 × 10-4 2.0832 0.1762 1.1814 0.91     4 Medium clay Biomass d.b.h. 1.8 × 10-4 0.9 × 10-4 2.0742 0.1190 0.9816 0.96 Diameter – root biomass B. pendula Roth     5 Fine sand Biomass d.b.h. 2.0 × 10-6 5.0 × 10-6 3.1566 0.6526 0.5652 0.63     6 Medium clay Biomass d.b.h. 4.6 × 10-6 5.7 × 10-6 2.4596 0.2771 0.4559 0.85 B. pubescens Ehrh.     7 Fine sand Biomass d.b.h. 14.2 × 10-6 20.4 × 10-6 2.1763 0.3486 0.2528 0.75     8 Medium clay Biomass d.b.h. 2.7 × 10-6 2.0 × 10-6 2.6041 0.1703 0.1709 0.95 Foliage biomass – root biomass B. pendula Roth     9 Fine sand Foliage biomass Root biomass 1.1343 0.1360 1.2672 0.2021 0.4996 0.71 10 Medium clay Foliage biomass Root biomass 2.5666 0.3570 0.5801 0.2036 0.9368 0.39 B. pubescens Ehrh. 11 Fine sand Foliage biomass Root biomass 1.0198 0.0568 0.7861 0.1074 0.2209 0.81 12 Medium clay Foliage biomass Root biomass 2.2735 0.6250 0.8582 0.3260 0.6090 0.41 No Soil type Y X β0 SE β1 SE RMSE r2 Diameter – above-ground biomass B. pendula Roth     1 Fine sand Biomass d.b.h. 7.4 × 10-4 4.6 × 10-4 2.2851 0.1428 1.3286 0.95     2 Medium clay Biomass d.b.h. 13.8 × 10-4 8.2 × 10-4 2.1393 0.1338 1.6812 0.95 B. pubescens Ehrh.     3 Fine sand Biomass d.b.h. 1.9 × 10-4 1.4 × 10-4 2.0832 0.1762 1.1814 0.91     4 Medium clay Biomass d.b.h. 1.8 × 10-4 0.9 × 10-4 2.0742 0.1190 0.9816 0.96 Diameter – root biomass B. pendula Roth     5 Fine sand Biomass d.b.h. 2.0 × 10-6 5.0 × 10-6 3.1566 0.6526 0.5652 0.63     6 Medium clay Biomass d.b.h. 4.6 × 10-6 5.7 × 10-6 2.4596 0.2771 0.4559 0.85 B. pubescens Ehrh.     7 Fine sand Biomass d.b.h. 14.2 × 10-6 20.4 × 10-6 2.1763 0.3486 0.2528 0.75     8 Medium clay Biomass d.b.h. 2.7 × 10-6 2.0 × 10-6 2.6041 0.1703 0.1709 0.95 Foliage biomass – root biomass B. pendula Roth     9 Fine sand Foliage biomass Root biomass 1.1343 0.1360 1.2672 0.2021 0.4996 0.71 10 Medium clay Foliage biomass Root biomass 2.5666 0.3570 0.5801 0.2036 0.9368 0.39 B. pubescens Ehrh. 11 Fine sand Foliage biomass Root biomass 1.0198 0.0568 0.7861 0.1074 0.2209 0.81 12 Medium clay Foliage biomass Root biomass 2.2735 0.6250 0.8582 0.3260 0.6090 0.41 Open in new tab Table 5: Estimated parameters and their asymptotic standard errors (SEs) of 12 tested models, mean residual (Mres) between observed biomass (Bo) and predicted biomass (Bp), kg per tree, according to tested model, and coefficient of determination (r2) for biomass estimations of pendula (Betula pendula Roth.) and pubescent (Betula pubescens Ehrh.) birches growing on farmland; RMSE, root mean square error No Soil type Y X β0 SE β1 SE RMSE r2 Diameter – above-ground biomass B. pendula Roth     1 Fine sand Biomass d.b.h. 7.4 × 10-4 4.6 × 10-4 2.2851 0.1428 1.3286 0.95     2 Medium clay Biomass d.b.h. 13.8 × 10-4 8.2 × 10-4 2.1393 0.1338 1.6812 0.95 B. pubescens Ehrh.     3 Fine sand Biomass d.b.h. 1.9 × 10-4 1.4 × 10-4 2.0832 0.1762 1.1814 0.91     4 Medium clay Biomass d.b.h. 1.8 × 10-4 0.9 × 10-4 2.0742 0.1190 0.9816 0.96 Diameter – root biomass B. pendula Roth     5 Fine sand Biomass d.b.h. 2.0 × 10-6 5.0 × 10-6 3.1566 0.6526 0.5652 0.63     6 Medium clay Biomass d.b.h. 4.6 × 10-6 5.7 × 10-6 2.4596 0.2771 0.4559 0.85 B. pubescens Ehrh.     7 Fine sand Biomass d.b.h. 14.2 × 10-6 20.4 × 10-6 2.1763 0.3486 0.2528 0.75     8 Medium clay Biomass d.b.h. 2.7 × 10-6 2.0 × 10-6 2.6041 0.1703 0.1709 0.95 Foliage biomass – root biomass B. pendula Roth     9 Fine sand Foliage biomass Root biomass 1.1343 0.1360 1.2672 0.2021 0.4996 0.71 10 Medium clay Foliage biomass Root biomass 2.5666 0.3570 0.5801 0.2036 0.9368 0.39 B. pubescens Ehrh. 11 Fine sand Foliage biomass Root biomass 1.0198 0.0568 0.7861 0.1074 0.2209 0.81 12 Medium clay Foliage biomass Root biomass 2.2735 0.6250 0.8582 0.3260 0.6090 0.41 No Soil type Y X β0 SE β1 SE RMSE r2 Diameter – above-ground biomass B. pendula Roth     1 Fine sand Biomass d.b.h. 7.4 × 10-4 4.6 × 10-4 2.2851 0.1428 1.3286 0.95     2 Medium clay Biomass d.b.h. 13.8 × 10-4 8.2 × 10-4 2.1393 0.1338 1.6812 0.95 B. pubescens Ehrh.     3 Fine sand Biomass d.b.h. 1.9 × 10-4 1.4 × 10-4 2.0832 0.1762 1.1814 0.91     4 Medium clay Biomass d.b.h. 1.8 × 10-4 0.9 × 10-4 2.0742 0.1190 0.9816 0.96 Diameter – root biomass B. pendula Roth     5 Fine sand Biomass d.b.h. 2.0 × 10-6 5.0 × 10-6 3.1566 0.6526 0.5652 0.63     6 Medium clay Biomass d.b.h. 4.6 × 10-6 5.7 × 10-6 2.4596 0.2771 0.4559 0.85 B. pubescens Ehrh.     7 Fine sand Biomass d.b.h. 14.2 × 10-6 20.4 × 10-6 2.1763 0.3486 0.2528 0.75     8 Medium clay Biomass d.b.h. 2.7 × 10-6 2.0 × 10-6 2.6041 0.1703 0.1709 0.95 Foliage biomass – root biomass B. pendula Roth     9 Fine sand Foliage biomass Root biomass 1.1343 0.1360 1.2672 0.2021 0.4996 0.71 10 Medium clay Foliage biomass Root biomass 2.5666 0.3570 0.5801 0.2036 0.9368 0.39 B. pubescens Ehrh. 11 Fine sand Foliage biomass Root biomass 1.0198 0.0568 0.7861 0.1074 0.2209 0.81 12 Medium clay Foliage biomass Root biomass 2.2735 0.6250 0.8582 0.3260 0.6090 0.41 Open in new tab Figure 4. Open in new tabDownload slide Above-ground biomass and root biomass, kg d.w. per tree, for — silver (Betula pendula Roth) and --- downy birches (Betula pubescens Ehrh.) growing on fine sand soil, upper panel, and for — silver and --- downy birches growing on medium clay soil, lower panel. Figure 5. Open in new tabDownload slide The relationship between root biomass and leaf biomass, kg d.w. per tree, for — silver (Betula pendula Roth) and --- downy birches (Betula pubescens Ehrh.) growing on fine sand soil, upper panels, and for silver and downy birches growing on medium clay soil, lower panel. For silver birch, the mean total biomass including roots for pendula birch was higher on medium clay soil than on fine sand soil but the opposite was true for downy birch biomass (Figure 6). The total biomass per hectare was higher for silver than for downy birch. The yield was higher on fine sand than on medium clay soil for downy birch, except at spacings of 1.5 and 2.6 m. For silver birch, the yield was higher on fine sand soil than on medium clay soil for spacings of 1.3 and 1.5 m than on medium clay soil (Figure 6). Figure 6. Open in new tabDownload slide Total biomass, tonnes d.w. ha−1, for silver birch (Betula pendula Roth) and downy (Betula pubescens Ehrh.) birch growing at different spacings on fine sand soil and on medium clay soil. stem, branches, leaves, stump and roots. Discussion The reasons for the low biomass of downy birch at a spacing of 1.3 m and when growing on medium clay soil are not apparent from the data or from what is known about conditions in the field. No damage was found and most of the trees survived (99 per cent). At harvest, the 12-year-old silver and downy birches planted on farmland yielded 17.5–60.3 and 11.7–43.6 tonnes d.w. ha−1 biomass above-stump, respectively. Few comparable studies have been published on the productivity of these species. Most of the reported data are based on stands with higher stem numbers than in this study. However, Johansson (1999b) found an above-stump standing biomass of 9.6–101.3 tonnes d.w. ha−1 for 10- to 12-year-old silver birch and 6.5–60.8 tonnes d.w. ha−1 for 11- to 12-year-old downy birch stands growing in central Sweden. In two Finnish studies, 14-year-old silver birches growing on peatland produced 77.0 and 59.0 tonnes d.w. ha−1 above-stump (Canell, 1982; Ferm and Kaunisto, 1983), while Björklund and Ferm (1982) recorded biomass production figures of 40 tonnes d.w. ha−1 for 10-year-old downy birch growing on peatland in Finland (Latitude 64° N). Mälkönen (1977) reported figures of 16.9 tonnes ha−1 for 40-year-old dwwny birch growing in Finland, and Ovington and Madgwick (1959) found the same amount (i.e. 16.9 tonnes ha−1) above stumps in 24-year-old silver birch stands growing in the UK. The above-stump dry weight was higher for silver than downy birch at all spacings on the two soil types. In a previous Swedish study of young birch stands (Latitude 58–66° N) the total dry weight above-stump was found to be 0.9, 5.8 and 2.3 kg per tree in three stands of 10-, 11- and 12-year-old silver birches growing on silt and light clay and 5.9, 2.3 and 3.9 kg per tree in three stands of 11-, 11- and 12-year-old downy birches growing on silt and fine sand (Johansson, 1999b). In the present study, the mean above-stump dry weight of 12-year-old silver birch growing on fine sand was 10.5 kg per tree and on medium clay 11.5 kg per tree. The equivalent figures for downy birch were 7.0 and 6.0 kg per tree, respectively. There have been several reports concerning the biomass of silver and downy birches. Korsmo (1995), in a Norwegian study, reported a total silver birch above-stump biomass (60 mm d.b.h.) of 7.5 kg per tree, while in a Swedish study Marklund (1988) presented functions for birch and Norway spruce biomass. However, the only data presented for birch in the latter were for stems and branches. In Marklund's study (of a mixture of silver and downy birches), the dry weight of a birch stem of 60 mm d.b.h. and associated branches was found to be 6.9 kg, compared with 10.2 kg for silver birch stems (60 mm d.b.h.) and 6.0 kg for downy birch stems (42 mm d.b.h.) found in the present study. Studies on the correlation between d.b.h. and root biomass for birch are scarce (Drexhage and Gruber, 1999; Drexhage and Colin, 2001), and since it is difficult to sample woody roots, it would be useful to create an allometric model for estimating root system biomass directly from tree diameter at breast height. This putative relationship is based on the hypothesis that the growth of roots depends on stem diameter and that the above- and below-stump development of the tree has an allometric balance (Köstler et al., 1968; Santantonio, 1990). The diameter and root biomass figures obtained for silver and downy birches indicate that the latter have a higher root biomass than the former when the two have the same d.b.h. and are growing on the same type of soil, at least for the two soil types considered here. In the present study, the biomass weight was higher for silver birch than for downy birch. However, the mean d.b.h. for downy birch was lower than for silver birch. When growing on medium clay, both species had higher root biomass as a percentage of total weight (12.1 and 12.0 per cent, respectively) than those growing on fine sand (9.4 and 9.8 per cent, respectively). The only statistically significant differences for the other variables measured were between leaf weight and soil type and between PLA and soil type. As mentioned previously, the total tree weight for silver birch was higher on medium clay soil than on fine sand soil. For both species, however, the leaf weight was greater on fine sand soil than on medium clay soil. For PLA, the values were higher on medium clay soil than on fine sand soil. In a study by Ovington and Madgwick (1959), the PLA per tree in a 6-year-old silver birch stand was 9.3 m2 and in a 7-year-old downy birch stand it was 1.1 m2. Johansson (1989) reported a PLA of 2.1 for 3 m tall downy birches growing in a dense stand (50 000 stems ha−1). In another study, Johansson (1999b) reported PLAs of 0.6 and 5.1 for 11- and 12-year old silver birches and 1.4, 3.4 and 2.0 m2 for 8-, 6- and 6-year-old downy birches. However, the range of PLA for birches in the present study was small, 4.87–6.46 for silver birch and 4.36–5.88 for downy birch. LAI varied between 1.54 and 3.08 for silver birch and between 0.99 and 3.08 for downy birch. Tadaki (1966) reviewed LAI figures for different species and concluded that the normal range of LAI for birch species is 2–7. In a study by Johansson (1999b), the LAI in three 1- to 12-year-old silver birch stands was 0.66–3.21 and in four 11- to 14-year-old downy birch stands was 2.00–5.12, although the stem number was much higher (5000–45000 stems ha−1) than in the present study. The significant differences in basic density between soil types are difficult to explain. The means for silver birch growing on fine sand and medium clay soils were 419 ± 5 and 435 ± 4, respectively, and for downy birch 429 ± 5 and 434 ± 5. As shown by the biomass estimates and the assessed tree characteristics, silver birch had a greater yield on medium clay soil than on fine sand. For downy birch, however, the mean biomass was higher on fine sand than on medium clay with some variations between the different spacings. Conclusions Leaf biomass is a good indicator of growth, since it is strongly correlated with a number of important physiological parameters, especially photosynthetic activity. The percentage leaf dry weight as a proportion of total biomass weight on the two soil types was similar for silver and downy birches, although the percentages were higher for both species when growing on fine sand (7.7 and 9.5 per cent, respectively) than on medium clay soil (3.7 and 4.6 per cent, respectively). This was confirmed by the relationships between d.b.h. and leaf biomass. The positive relationship between leaf biomass and root biomass may indicate the importance of a large leaf biomass for producing a high root biomass. A high root biomass is essential not only for the growth of a tree but also for its stability in strong winds and for withstanding snow breakage. The allometric equations developed for root biomass and d.b.h. or leaf biomass fitted the data well. The results of the study confirmed d.b.h. can be used as a simple variable to estimate the root biomass. This facilitates the efforts to determine root biomass without the high cost of excavating the root system. E. Hurtig and P. Björkens measured and cut the stands; they also weighed and dried the tree components. E. Hurtig carried out the tree-ring analyses, the soil analyses and the leaf characteristic measurements in the laboratory. Sees-editing Ltd provided a linguistic revision. Dr Gary Kerr made valuable comments on the manuscript and an anonymous statistician improved the statistical analysis. All of the above persons are gratefully acknowledged. References Andersson E , Tuimala A . 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TI - Biomass production and allometric above- and below-ground relations for young birch stands planted at four spacings on abandoned farmland
JF - Forestry
DO - 10.1093/forestry/cpl049
DA - 2007-01-01
UR - https://www.deepdyve.com/lp/oxford-university-press/biomass-production-and-allometric-above-and-below-ground-relations-for-RtDBXCk72o
SP - 41
EP - 52
VL - 80
IS - 1
DP - DeepDyve
ER -