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POKORNÝ, R., RAJSNEROVÁ, P., KUBÁSEK, J., MARKOVÁ, I., TOMÁŠKOVÁ, I.: Eff ect of early to late wood proportion on Norway spruce biomass. Acta univ. agric. et silvic. Mendel. Brun., 2012, LX, No. 6, pp. 287–292 Aboveground biomass, allometric relationships and early to late wood proportions were investigated in two even-aged monocultures of Norway spruce (Picea abies [L.] Karst) located at mountain and highland localities of the Czech Republic. However similar stand age and tree size, mountain trees comparing to them from highland showed less/tapering stems, lower aboveground biomass and lower stem wood density along the whole stem vertical profi le as a result of diff erent early to late wood proportion. These proportions were 79 % and 54 % for early wood, and 21 % and 46 % for late wood within mean stem annual circle in mountain and highland locality, respectively. These diff erent proportions seem to refl ected site specifi c growing conditions, particularly highly suffi cient water availability during spring time in mountain regionsupport early wood growth, whereas elevated air temperature during summer time in highland region stimulate late wood growth. allometric relationship, climate, tree ring analysis, wood density Enhancing atmospheric CO2 concentration is undeniably connect with upcomming global change conditions perceived increasing weather instability (i.e. increasing air temperature, increasing frequency and power of storm and tempest, wind velocities, redistribution of precipitation during an year, etc.). Therefore, information about landscape CO2 emission balance as well as accurate evaluation of land use changes and carbon sequestration by diff erent ecosystem types is highly needed. Forests are naturally the highest carbon sinks. To quantify this sinks, it is necessary to evaluate plant biomass and soil carbon content changes in temporal scale. There are expansion factors to scale up common forest inventory data including repeatedly measured stem-wood volume into the stand biomass data and/or there are some specifi c allometric relationships between easy measurable stem or crown dendrometric parameters and total tree biomass or biomass of diff erent plant organs. However the same tree species of similar tree age and dendrometric parameters, allometric relationships can diff er due to site specifi c growing conditions including forest structure. Environmental conditions determinate also wood anatomy and structure properties like a wood density. Stem wood density integrates spatial and temporal development of woody tissue properties, briefl y separated into early and late wood. However, there is not a strict border between early and late wood within a stem circle, the diff erences in wood anatomy, mechanical and other tissue properties are high enough. For example, if early to late wood properties are compared, then they diff er in cell size, cell wall thickness, cell wall to lumen area ratio, wood density, etc. (Požgaj et al., 1997). It seems that there are two main limiting factors for wood cells increment, which are varying during the growing season according to cell type-water availability and air temperature. As cambial activity and early wood development highly correlate with a height of snow cower during the winter time and precipitation amount in the spring (Campelo et al., 2007), the water availability is limiting factor for early wood development in spring time. Contrariwise, as late wood density correlates tightly with an air temperature values especially during the second half of a growing period, air temperature is limiting 288 R. Pokorný, P. Rajsnerová, J. Kubásek, I. Marková, I. Tomášková factor for late wood development in a summer time. For example, SO2 air concentration falls among other factor negatively infl uenced the wood density; particularly they lowered late wood proportions (Sander, 1995). In our previous works, we studied the allometric relationships between stem dendrometric parameters and biomass of diff erent aboveground tree organs of young Norway spruce trees in two climatically diff erent localities (Pokorný and Tomášková, 2007; Marková and Pokorný, 2011). There, even similar age and stem size, high diff erences in biomass values occur when comparing of the both studies. Therefore, we hypothesized that it is an eff ect of diff erent wood density and/or diff erent early to late wood proportion, respectively. MATERIAL AND METHODS Locality and stand description All measurements were carried out on evenaged monocultures of Norway spruce (Picea abies [L.] Karst.) located at the Experimental Ecological Research Station of the Bílý Kříž (the MoravianSilesian Beskids Mts., the Czech Republic) and at the Ecosystems Station of Rájec-Němčice (the Drahanská vrchovina Highland, the Czech Republic). Detailed description of the studied sites and studied stands are shown in Tabs. I–III. I: Description of the studied sites of the Bílý Kříž and of the Rájec-Němčice Bílý Kříž1) Rájec-Němčice2) Geographic coordinates 49o 30 ́ N, 18o 30 ́ E, 49o 29 ́ N, 16o 43 ́ E Altitude 860–910 m a.s.l. 610–625 m a.s.l. Geological subsoil fl ysh layer with dominant sandstone acid granodiorite Soil type typical humo-ferric podzol with mor-moder form of surface humus modal oligotrophic cambisol (KAmd ́) ambisols (CM) with moder form of surface humus Marková and Marek, 2010 1); Marková and Pokorný, 2011 2) II: Climatic conditions at the studied sites of the Bílý Kříž and of the Rájec-Němčice (precipitation amount in brackets displays a sum during the growing season) Bílý Kříž Rájec-Němčice Mean annual air temperature (°C) 5.5 6.9 Annual sum of precipitation (mm) 1 200 (650) 717 (430) Growing season duration (days) 120–140 140–160 Mean air temperature in July (°C) 14.5 16.5 Number of days with snow cower (days) 120–140 60–100 III: Characteristics of the studied stands at the studied sites of the Bílý Kříž and of the Rájec-Němčice B íl ý K ří ž Spruce stand was established at clear-cut area which originated a er felling the mature spruce stand of the fi rst generation (a er pasture) by 4-year old seedlings planted in rows spacing in total stand area of 6.15 ha in 1981 (Pokorný and Tomášková, 2007) Stand density (trees.ha−1) 1 400 Mean tree height (m) 14.9 Mean stem diameter at breast height (cm) 16.9 Mean stem breast height form factor (u.l.) 0.557 ± 0.045 Mean stem wood density (kg.m−3) 359 ± 38 R áj ec N ěm či ce Spruce stand was artifi cially established by reforesting a clear-cut area which originated a er felling the mature spruce stand of the fi rst generation (a er mixed forest stand) in 1978 (Marková and Pokorný, 2011) Stand density (trees.ha−1) 2 700 Mean tree height (m) 13.6 Mean stem diameter at breast height (cm) 12.7 Mean stem breast height form factor (u.l.) 0.489 ± 0.028 Mean stem wood density (kg.m−3) 457 ± 37 (Main characteristics of the studied spruce stands are presented for the study site of the Rájec-Němčice from 2008 and for the study of Bílý Kříž from 2010 (for possible comparison of mean tree size of the same age, i.e. 33-year old trees). Stem breast height form factor (k) and stem wood density () are presented as a mean with standard deviation (n = 21 at the RájecNěmčice; n = 33 at the Bílý Kříž). Eff ect of early to late wood proportion on Norway spruce biomass 289 Measurements and Analyses In our previous measurements, set of site specifi c allometric relationship between stem dendrometric parameters and aboveground tree organs biomass were obtained (Pokorný and Tomášková, 2007; Marková and Pokorný, 2011). During these analyses, breast height stem form factor (k) as well as stem wood density () values were also obtained (Tab. III, Fig. 1). The standard geometric shape for the breast height form factor is a cylinder of the same height as the stem and with a sectional volume equal to the sectional volume of the stem at breast height. Then, the form factor is the ratio of the volume of the stem to the volume of the cylinder. Wood density is valid for wood dry biomass to its volume ratio (including bark). Stem wood blocks (n = 17) for early to late wood proportion analysis were take away from basal stem parts in the both investigated localities during 2010–2011. Stem cross-sectional blocks with 3–5 cm thickness were brushed from one side and then scanned with 300 dpi resolution. Annual ring width was obtained using image-analysis so ware (ACC32, Sofo Brno, the Czech Republic), when the operator marked the early and late wood borders within each annual ring in four perpendicularly diff erent directions. Therefore, each annual ring width and distance proportion of early to late wood value was averaged from the four values. Statistical processing of data Data were statistically processed by Statistica 7 version so ware (StatSo Inc., Tulsa, USA). Pearson correlation coeffi cient was used to test correlation signifi cance. ANOVA and Scheff e‘s test were used for statistically signifi cant diff erence detection on the signifi cance level of  = 0.05. RESULTS AND DISCUSSION Stem biomass proportions enhance much more rapidly among all other above-ground tree organs with increasing of tree age (Assmann, 1968). Changing biomass proportions among diff erent tree organs with increasing tree dimensions and/or age are documented by our previous results from harvest analyses. For example, leaf biomass (LB) on average (± SE) partitioned by 36 % (± 3), branch biomass (BB) by 27 % (± 3) and stem biomass (SB) by 37 % (± 3) on total aboveground biomass (TBA) of tree in 6-year-old spruce monoculture with the stand density of 7.000 tree·ha−1; and LB by 28 % (± 4), BB by 24 % (± 3) and SB by 48 % (± 6) on TBA of tree in 16-year-old mountain spruce monoculture with the stand density of 3 100 tree·ha−1. About ten years later, LB partitioned by 19 % (± 4), BB by 23 % (± 5) and SB by 58 % (± 8) on TBA of tree in the same forest stand with decreased density to 1 400 tree·ha−1 due to thinning, respectivel

Effect of early to late wood proportion on Norway spruce biomass