Petteri Vanninen

Effects of age and site quality on the distribution of biomass in Scots pine (Pinus sylvestris L.)

The distribution of the above-ground and below-ground biomass of Scots pine in southern Finland were investigated in trees of different ages (18–212 years) from two types of growth site. Secondly, some structural regularities were tested for their independence of age and growth site. Trees were sampled from dominant trees which could be expected to have a comparable position in stands of all ages. All stands were on sorted sediments. The biomass of the sample trees (18 trees) was divided into needles, branch sapwood and heartwood, stem sapwood and heartwood, stem bark, stump, large roots (diameter >20 cm), coarse roots (five classes) and fine roots. The amount of sapwood and heartwood was also estimated from the below-ground compartments. Trees on both types of growth site followed the same pattern of development of the relative shares of biomass compartments, although the growth rates were faster on the more fertile site. The relative amount of sapwood peaked after canopy closure, coinciding with the start of considerable heartwood accumulation. The relative amount of needles and fine roots decreased with age. The same was true of branches but to a lesser degree. The relative share of the below-ground section was independent of tree age. Foliage biomass and sapwood cross-sectional area were linearly correlated, but there were differences between the growth sites. Needle biomass was linearly correlated with crown surface area. The fine root to foliage biomass ratio showed an increasing trend with tree age.

Vertical structure of Scots pine crowns in different age and size classes

Abstract. The pipe model theory postulates a static relationship between foliage mass/area and the cross-sectional area of active pipes in branches and stems. If a regular relationship exists, the theory can be used for modelling growth allocation within crowns, provided that the turnover of active pipes and foliage is understood. The objective of this study was to assess to what extent the assumptions of the pipe model hold true within the crowns of 24 Scots pine sample trees of different age and social position. The results suggest that Scots pine crowns are very regular, but some important modifications to the pipe model assumptions are required. The relative vertical foliage density distribution peaked at about 50% down the live crown regardless of age or social position. The ratio of foliage mass to branch cross-sectional area in the top half of the crown increased from the top downwards. The ratio of cumulative branch cross-sectional area to stem cross-sectional area in the top half seemed to increase with tree vigour or growth rate. The ratio of foliage mass to branch cross-sectional area decreased fast in the lower half of the crown, and this decrease was faster than could be predicted from heartwood formation in the branches. This result may be taken as (1) evidence against the pipe model, or as (2) an indication that active pipes cannot always be identified with sapwood. The latter proposition should be studied further.

Effect of sample selection on the environmental signal derived from tree-ring series

Possibilities to improve the expressed population signal (EPS) derived from tree-ring chronology were studied on 19 trees sampled from a permanent Scots pine (Pinus sylvestris L.) thinning experiment in southern Finland. Trees of varying relative size from thinned and unthinned control plots, as well as radii in different compass directions and different positions along the stem, were compared. The EPS values increased with increasing number of chronologies sampled. The effect of increasing tree number was more pronounced compared to increasing number of radii per tree. EPS also increased when the social status of a tree improved, but no clear differences were found between unthinned and thinned plots. Furthermore, no clear trend existed between different heights along the stem. The highest EPS values occurred in the directions west, southwest, and south; correspondingly, the lowest value was on the north side of the bole, followed by the northeast and east. It was concluded that some reduction in the noise present in tree-ring chronologies can be achieved by paying more attention to sample selection within and between stems. The sunny side of the bole especially, as well as dominant trees, should be preferred. However, the most important factor in noise reduction is adequate replication.

BAAD: a biomass and allometry database for woody plants

Understanding how plants are constructed—i.e., how key size dimensions and the amount of mass invested in different tissues varies among individuals—is essential for modeling plant growth, carbon stocks, and energy fluxes in the terrestrial biosphere. Allocation patterns can differ through ontogeny, but also among coexisting species and among species adapted to different environments. While a variety of models dealing with biomass allocation exist, we lack a synthetic understanding of the underlying processes. This is partly due to the lack of suitable data sets for validating and parameterizing models. To that end, we present the Biomass And Allometry Database (BAAD) for woody plants. The BAAD contains 259 634 measurements collected in 176 different studies, from 21 084 individuals across 678 species. Most of these data come from existing publications. However, raw data were rarely made public at the time of publication. Thus, the BAAD contains data from different studies, transformed into standard units and variable names. The transformations were achieved using a common workflow for all raw data files. Other features that distinguish the BAAD are: (i) measurements were for individual plants rather than stand averages; (ii) individuals spanning a range of sizes were measured; (iii) plants from 0.01–100 m in height were included; and (iv) biomass was estimated directly, i.e., not indirectly via allometric equations (except in very large trees where biomass was estimated from detailed sub-sampling). We included both wild and artificially grown plants. The data set contains the following size metrics: total leaf area; area of stem cross-section including sapwood, heartwood, and bark; height of plant and crown base, crown area, and surface area; and the dry mass of leaf, stem, branches, sapwood, heartwood, bark, coarse roots, and fine root tissues. We also report other properties of individuals (age, leaf size, leaf mass per area, wood density, nitrogen content of leaves and wood), as well as information about the growing environment (location, light, experimental treatment, vegetation type) where available. It is our hope that making these data available will improve our ability to understand plant growth, ecosystem dynamics, and carbon cycling in the worlds vegetation.

Estimation of fine root mortality and growth from simple measurements: a method based on system dynamics.

Abstract This study is a further development of a dynamic compartment-flow analysis, intended as an analytical tool for the empirical estimation of fine root growth, mortality and decomposition in forest soil. General properties of the dynamic system are utilised to interpret relatively simple measurements of standing biomass, necromass, and decomposition, in order to derive estimates of the process rates. The method is based on the finding that the ratio of fine root necromass to biomass is related to the specific rates of decomposition, mortality, and net growth. If the decomposition rate is measured and the net growth trend is determined from live root measurements, mortality and gross growth can be estimated using these relationships, provided certain regularity requirements are met. These requirements are explicated, such that the estimates can be easily assessed for reliability. To illustrate the use of the method, it was applied to the estimation of specific mortality rates in seven Scots pine stands of different ages and site types. A reanalysis of a previous sequential coring study yielded consistent results. The advantage of this method is that, unlike the standard analysis of sequential cores, it accounts for the possibility of simultaneous growth, mortality and decomposition. It is therefore applicable to situations with no apparent fluctuations or trend in the biomass and necromass levels. No minimum sampling interval is required; hence the method also allows for more extensive or prolonged studies.

Teachers Insights Into Connected Learning Networks: Emerging Activities and Forms of Participation

The aim of this socioculturally informed study is to explore teachers’ insights into connected-learning activities and networks. An instructional approach based on design-oriented pedagogy (DOP) was employed for a teachers’ in-service project in Finland. An open-ended design task for the participating teachers and educators from kindergartens (N = 27) and primary schools (N = 2) involved designing and implementing a forest-related learning project with their own students or kindergarten children. A deductive content analysis of openly published project portfolios revealed that the teachers and educators harnessed learner interest as a basis for connecting with peers, family, external experts, and extended environments through diverse physical and digital information resources, tool-mediated activities, and the externalization of the learners’ evolving object-oriented ideas. Conclusions are drawn about extended learning networks and activities that afforded inquiry activities to emerge.