Wood decaying polypores in boreal forests of Finland and northwestern Russia - Mariko Lindgren

Field instructions for collecting tree-, dead tree-, and biotope data

1. Common principles

2. Diameter

On the study plots the breast height diameters of all target trees are estimated on the accuracy of 1 cm. Along counting lines, dead trees are divided into the following diameter classes: 5-9 cm, 10 - 19 cm, 20 - 29 cm, 30 - 39 cm etc., but the diameters of living aspens (Populus tremula), goat willows (Salix caprea) an old pines (Pinus sylvestris)(see definition below) are estimated on the accuracy of 1 cm, just as on the study plots.

Fallen and sawn branches are measured from their basal part (not on the cut surface), an additional information is given: "branch" or "sawn branch". Sawn tree-crowns are measured from their cut surface and marked with an epithet "sawn crown".

For logs that are well decayed and/or covered by mosses, the original diameter is roughly, but conservatively estimated. The same approach applies for a broken or burned stump, if its original dimension can be detected from its basal part. If there is only a single splinter left, some kind of "ecological" diameter for it is estimated.

For oval, flat or ramified stems an average diameter is estimated. For example, a group or goat willow stems is considered as one tree if the stems are connected from their base, if not, they are counted as separate trees.

3. Decay classes

DC1a	Recently dead, phloem untouched (no holes of bark beetles visible).
DC1b	Bark and almost all branches still attached. Wood hard, but not dried. Usually holes of bark beetles visible.
DC2	Twigs and small branches fallen down. Wood still hard or dried (knife penetreartes up to two centimeters). On coniferous trees, bark is loosened or missing.
DC3	Wood is partly rottened or in a fast decay process (e.g. knife penetreates halfway, trunk is rustling when kicked, top breaks of when lifted). If the trunk is dried, only big branches are still attached and the knife penetreates at least two centimeters, or the otherways hard trunk is well decayed or hollow inside.
DC4	It is possible to push the blade of a knife all the way to the wood, although there is some resistance left. Trunk has maintained its shape or - especially for dry trees - some parts are missformed while others are still in fairly original shape.
DC5a	Wood is well decayed, it is possible to squeeze it by fingers. Usually the trunk is at least partly covered by mosses, but still clearly visible. It is easy to push the blade of a knife all the way to the wood, only the bark of birch trees give clear friction.
DC5b	Very decayed and (almost) unvisible logs. Of birch trees, only bark is left. This deacay class includes trunks that can be detected for example by walking on them, although they would easilly go unnoticed by an untrained eye.

The decay class of a log is determined according to an average part of a log, giving more weight to the basal part. In many cases, for example on DC5 pines, the top is still hard (dry), this is left unnoticed.

Standing dead trees:

DC1a	Recently dead, phloem untouched (no holes of bark beetles visible).
DC1b	Bark and almost all branches still attached. Wood hard, but not dried. Tree is still standing firmly. Dead leaves or needles often still present. Holes of bark beetles usually present.
DC2	On coniferous trees and goat willows the bark is getting loose (because of woodpeckers or otherwise), but some bark is still left. Twigs and smll branches have been fallen down. Wood is hard (maybe drying) and the tree is still standing firmly.
DC3	Only the biggest branches are still attached. Conifers (and sometimes aspens) are dried, pines are decorticated but spruce have often some bark left. Conifers are still standing firmly, but birch is getting unstable, and could be pushed down with strength. Birch has soft parts into which knife penetreates from few centimeters up to halfway.
DC4	Conifers are decaying from their base, they are getting unstable or are not standing straight. Also conifers that have been snapped of (from the height 1,3 - 4 m) because of a decay, are classified into this group, if they are not otherwise well decayed. Birch is already softened to the extent that it is possible to push the blade of a knife all the way to the wood, although there is some resistance left.
DC5	Conifers are not standing independently, but they are leaning on other trees or are easy to push down, or the stem has already been broken, and is hollow or well decayed. Birch is usually standing supported only by its bark.

3. What is not counted as dead trees ?

• Standing snags and stumps shorten than 130 cm. Depending on the data set they are counted as stumps or left unnoticed if there is no polypores present.
• Separate pieces of logs shorter than 100 cm (if they are not part of a longer log, when they are considered as a single tree). They are mentioned only if there is a polypore present, with a notion of their length.
• Dead parts of a living tree, if the dead parts are connected to living ones above ground.
• Fallen spruce trees which have formed new roots and thus have living parts.

4. Living trees to consider

Of living trees aspens (Populus tremula), goat willows (Salix caprea) and hemiborel hardwoods (Acer platanoides, Tilia cordata, Quercus robur, Fraxinus exelsior, Ulmus ssp.) are considered, as well as old pines according to two definitions (see below). In some data sets also alders (Alnus incarnata and A. glutinosa) and rowans (Sorbus aucuparia) are recorded.

Definitions of an old pine "aihki":

Strict definition: An old pine which has either a) a thick bark comprised of large shield-like formations, or b) which has clearly flat top, with ceased growth, or 3) is clearly older than the dominant tree-generation and has fire scars. Basicly the trees which can be called "aihki" with no great disagreement or doubt. In my field-notes and data I refer to these trees as "aihki".

Wide definition: An old pine with some features mentioned above, but not necessarily as clearly. Usually these trees are clearly older than the dominant tree generation, or if not, the dominant generation is itself very old. Basicly the trees of which the classification as "aihki" is somewhat uncertain, but possible for some observers. In my field-notes and data I refer to these trees as "almost aihki" or "maihki".

In the results, the total number of aihki -trees should be given as a range of variation of values given by the two definitions above, with an epiteth "depending on definition". In this way, the numbers should be comparable with those given in other studies or reports.

5. Some special cases

It is quite typical that of a single dead, standing birch tree, pieces fall down at separate moments of time. As a consequence there is several pieces of a birch-log lying on the ground, with different lengths and classes of decay. Ecologically these pieces are separate wood-units. In such cases, different decay classes are counted as different logs (so that if there is several pieces of a same decay class, they are together counted as one log). Separate dacay classes are given lengths (sum of the lengths of all pieces belonging to that class). Classes with total length less than 1 m are left unnoticed. Different "ecological logs" originating from the same real tree are connected in field data and data-base by arrows, numbers etc.

Dead trees leaning to other trees are counted as dead standing trees, if the angle between the tree and ground is over 45 degrees. Otherwise they are counted as downed trees. (There is no clear ecological basis for this rule, only a practical need to make the separation at some point.)

High stumps broken by mechanical stress (not because of a decayer) are classified to decay classes as if they were unbroken dead standing trees.

Broken top attached to a dead, standing tree so that the top is at ground, and it's angle with the ground is less than 45 degrees, is counted as a downed log. If the height of the standing part is over 130 cm and the top is hanging downwards of it with an angle to the ground over 45 degrees, the basal part and the top are together counted as one dead, standing tree.

Branches fallen down from standing trees are treated in the same way as pieces fallen from dead standing birch-trees. If all the branches originating from a single host tree belong to a same decay class, they are counted as one fallen tree with a diameter of the basal part of the biggest fallen branch, and marked with an epithet "branch" or "branches".

Logs which are difficult or impossible to identify by tree species in the field are counted as "unidentified logs".

5. Dead tree volumes

I have roughly estimated following variables to be able to roughly estimate volumes of dead trees:

• length of broken dead, standing trees
• length of separate pieces of downed logs, if counted as separate (ecological) tree-units and if more than 1 m in length
• legth and % volume (of the original volume of a piece of this diameter and length) of burned stumps (> 1,3 m in height) or other misformed trees. Etc. "burned stump, 1,4 m, 33%."

At least a short description of the forest site type, forest structure and vegetation is written about each study quadrate, counting-line unit, or study plot. I have recorded at least following features:

• Forest site type as a nutrition and moisture level according to the finnish forestry site type system (KK = dry heath, KVK = dryish heath, TK = mesic heath, LmKg = herb rich heath), if needed I have used used epithets + or - to indicate that the site is richer or poorer in its nutritious level than this type on average. Rocky or stony sites are noted. Of paludified sites I have recorded mire-vegetation type according to Eurola-Kaakinen system and level of paludification and other characteristics (etc. slightly paludified, with Sphagnum-patches, with Ledum palustre, paludified, KgK/KgR/KgKR = intermediate between heath and spruce mire, pine bog etc., mire or swamp with sparse forest, mire or bog with few trees (not counted as forest-biotope), open mire, streamside etc.). Of open or almost open mires and bogs the strict vegetation type is not so valid for a polypore study, of them I have recorded at least their nutritious levels.

• If I'm unsure about the forest site type or mire vegetation type, I have written down the dominant plant species of field- and groundlayer as well as the precense of indicator species or some other species, with a note of their abundance.

• (Most important!) Stand structure in following classes:
  • (Relatively) even-sized pine stand: Living and dead aihkis as well as other hold-overs are practically missing. Under the dominant tree layer several tree generations can be present. In addition, an undergrowth of birch or spruce is usually present. Note the age or age class, or state of development of the dominant tree layer.

  • Pine-broadleved mixed stand: Usually a mixed forest variation of the type above. Proportion of broad leaved trees in dominant tree layer is 20% or more. Note the age or age class, or state of development of the dominant tree layer as well as the proportion and species of broad-leaved trees.

  • Uneven-sized pine stand: Living or dead aihkis or other hold-overs are present. Previoius forest fire(s) or other disturbance(s) has/have not replaced the stand. As a result the age-and size-structure of trees (especially in upper crown layers) is uneven. Note the tree species, age or state of development of the undergrowth or subdominant tree-cohort and the density and maximum sizes of aihkis or other hold-overs. Note also the number of fire-scars present in aihki-trees or other living or dead old/big pines.

  • Stand with spruce grown over: Spruce has just risen to the dominant tree layer. Dead lying spruce logs of dominant tree-layer-size are only sparsely (if at all) preesent, and they belong to decay classes 1 or 2. Smaller-size dead spruces may be very abundant. Note the tree species and their proportions of the previous dominant tree cohort (usually pine/broad-leaved trees).

  • Spruce-broad-leaved mixed stand: ("Slash-and-burn type on mesic sites"). Pine is not forming a clear, dominant tree cohort. There can be up to 30 % of pines present, but they are not considerably older than the spruce-cohort. Basic idea is that dominant spruce and broad-leaved trees (and pine, if present) all have regenerated basicly at the same time after a disturbance. The proportion of broad-leaved trees is 20 % or more. Note the proportion and species of broad-leaved trees (and pine) as well as the age or state of development of the dominant tree layer.

  • Spruce stand: Spruce forms the dominant tree layer. Dominant tree-layer-size spuce logs occur regularly at decay classes (1)-2-3, and occasionally also at class 4).

  • Spruce-refugium/Gap-dynamics spruce stand: Spruce forms the dominant tree layer (which may be relatively uneven aged- or sized and may have considerable gaps). Dominant tree-layer-size spuce logs occur commonly also at decay stage 5.

  • Pine-refugium: Old-growth stands with no signs of fire, but pine is still a major dominant tree species, or pine and spruce dominate together. Possible reasons: A) Stand has escaped fire, but the site type is too poor/dry/rocky for spruce to take over. B) Stand has escaped fire, but the site is too wet/paludified for spruce to take over (pine bogs or intermediate types between heath-forests and pine bogs). C) Site is so poor, or there is such a thick (Hylocomium) moss-cover on the ground, that spruce regeneration is limited and spruce-layer becomes sparse. There is enough light and space for pine to regenerate on favourable spots. Basic idea: There is both a pine- and spruce-continuum, usually also a a continuum of broad-leaved trees (Betula pubescens, Salix caprea, Populus tremula) regenerating by root or suckers or stump sprouts.

    Note that the classification of a stand to either pine- or spruce-dominated is done according to the dominant tree layer, not according to what the stand "looks like in general". Spruce comes dominant when spruces really reach the dominant-tree-layer-height, only the hold-over-pines (and sometimes aspens) are still taller at this stage. If you are unsure about the forest structure class, describe what you see and what you do not see.

• Sometimes I have recorded the proportion and species of broad leaved trees even if their proportion is less than 20 % of the dominant tree layer.

• Mention the state and density of possible spruce undergrowth (dense, relatively sparse, aggregated, few groups, patchy, sparse, very sparse, sigle saplings etc. ) and the height of tallest of them in relation to the maximum dominant tree layer height (10%, 50%, 60-70%, 80% etc.). If the undgergrowth is very uneven-aged or -sized, note it or, if reasonable, make a description of it's main features.

• Sometimes I have also noted the height and density of the possible Betula pubescens or Sorbus aucuparia -undergrowth.