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Towards a taxonomic classification of humus forms : third approximation Klinka, Karel; Krestov, Pavel; Fons, Jaume; Chourmouzis, Christine 1997

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Horizon designations and definitions Master horizon Subordinate horizon Freely-drained upland horizons L (litter); a surface horizon that consists of relatively fresh plant residues readily identifiable as to their origin. Ln  (new); an L horizon that consists of newly accreted and essentially fresh, non-fragmented plant residues. Lv  (variative); an L horizon that consists of the plant residues showing initial decay and strong discolouration. S (bryophytes); a surface horizon that consists of tissues of living bryophytes (commonly Sphagnum spp.) intermixed to a minor extent with litter. G (graminoid); a thin surface horizon that consists of tissues of living graminoids intermixed to various extents with their residues. F (fermented); an organic horizon in which partly decomposed plant residues predominate; the partial structures of plant residues are macroscopically discernible. Fm (mycogeneous); an F horizon in which more or less disintegrated plant residues are aggregated in a compact-matted, banded fabric interwoven by fungal hyphae (mycelia), with a tenacious consistence. If present, faunal droppings are very infrequent and localized. Fr (root residues); an F horizon in which fine root residues constitute nearly all fabric; fungal mycelia are infrequent and localized. Frm (root residue, mycogeneous); an Fm horizon in which fine root residues constitute nearly all fabric; fungal mycelia are common and frequently abundant. Fs (bryophytes); an F horizon that consists of partly disintegrated tissues of Sphagnum spp.; residues are weakly aggregated, fungal mycelia absent or very infrequent and localized. Fsm (bryophytes, mycogeneous); an Fs horizon with fungal mycelia but rarely as common and frequent as in the Fm horizon. Fz (zoogenous); an F horizon in which residues are weakly aggregated with a loose or friable consistency as result fragmentation and comminution by soil fauna; faunal droppings and dropping residues are numerous, fungal mycelia are infrequent and localized. Fsz (bryophytes, zoogeneous); an Fs horizon with faunal droppings but rarely as common and frequent as in the Fz horizon. Fa (amphi); an F horizon that has the characteristics of both Fm and Fz horizons; plant residues are aggregated into a weak to moderate, non-compact-matted fabric. Fsa (bryophytes, amphi); an Fs horizon with both fungal mycelia and faunal droppings but rarely as common and frequent as in the Fa horizon. Scientia  Silvica Extension Series,  Number  9, 1997 Towards a Taxonomic Classification of  Humus Forms: Third Approximation The importance of humus form or forest floor as a principal component of terrestrial forest ecosystems has led to the development of a taxonomic classification of humus forms for BC (first approximation: Klinka et al. 1981; second approximation: Green et al. 1993). This classification, as all others, is based on the field-observable (morphological) features because we expect that they reflect differences in the nature and development of humus forms. However, there is a continuing need to test (1) whether humus forms that appear different are in fact different in their physical, chemical, and biotic properties, and (2) the portability of the classification outside the area in which it was developed. As a result of recent studies of the biotic component of humus forms and recent testing of the classification outside British Columbia (Scandinavia, southeastern Russia, and northeastern China), we have recognized several new diagnostic horizons, and hence new taxa. In this pamphlet, we present synopsis of the third approximation of the classification for review and testing. For more detailed information on the background, methodology, and classification of humus forms, the readers should consult Green et al. (1993). Each humus form is represented by the sequence of organic and mineral horizons that constitute the humus form profile. Identification of a humus form, i.e., giving it a name, requires description of the humus form profile – the identification of master and subordinate horizons. For this reason we have included a description of the horizon designations as well as a synopsis of the classification and a key to the identification of humus forms. Freely-drained upland horizons continued H (humic); an organic horizon in which well decomposed plant residues (fine substances) predominate; the original plant structures are not macroscopically discernible. Hf (fine); an H horizon that has a very fine granular structure; very small faunal droppings predominate in the fabric. Hg (granular); an H horizon that has a fine (to medium) granular structure; small faunal droppings predominate in the fabric. Hh (humic); an H horizon that has a massive (ancient) or weak, coarse, blocky structure; the colour is typically dark gray (black), the material is greasy and stains fingers when rubbed. Hc (recalcitrant); an H horizon that contains macroscopically recognizable plant residues (roots, bark, and/or wood) imposing yellow, brown, or particularly red colours; fine substances predominate and the material is slightly greasy but does stain fingers when rubbed. Poorly-drained, waterlogged, wetland horizons O (organic); a wetland organic horizon Of (fibric); a surface O horizon that consists of poorly decomposed plant residues readily identifiable as to their origin. Om (mesic); an O horizon that consists of partly decomposed plant residues at a stage of decomposition intermediate between Of and Oh horizons. Oh (humic); an O horizon that consists of well decomposed plant residues which for the most part have been transformed into humic materials. Mineral horizons A the uppermost  mineral horizon that contains < 17% organic C (about 30% organic matter) by weight. Ah (humic); an Ah horizon enriched with organic matter. Other designations w (wood); any organic horizon containing >35% of the volume of solids) of coarse woody debris in various stages of decomposition. Third Approximation: Synopsis of humus form taxa Order Characteristic humus form profiles 1 Variation from the Orthic or true form Group Mor Lignomor L, Fmw or Fsw, Hw Tenuic, Pachic,Hemic, Humic Hemimor L, Fm, (H) Tenuic, Pachic Rhizomor L, Frm, (H) Tenuic, Pachic Sphagnomor S, Fs and/or Fsm, H Tenuic, Pachic Humimor L, Fm, Hh Pachic, Hemic, Perhumic Resimor L, Fm, Hc Pachic, Hemic Modermor L, Fm and/or Frm, Hf and/or Hg Hemic, Humic Lamimor L, Fm and/or Frm, Hf and/or Hg and Hh and/or Hc Hemic, Humic Fibrimor S, (F, H), Of, Om, Oh Hemic, Sapric Mesimor S, (F, H), Of, Om, Oh Fibric, Sapric Moder Lignomoder L, Faw and/or Fzw, Hw Tenuic, Pachic, Hemic, Humic Mormoder L or G, Fa, H Tenuic, Pachic, Hemic, Humic Sphagnomoder S, Fs and/or Fsa and/or Fsz, H Hemic, Humic Lamimoder L, Fm, Frm, Fs and/or Fsm, Fa, Fsa, Fz and/or Fsz, H Hemic, Humic, Sphagno L, Fa, Fsa, Fz, and/or Fsz, Fm, Frm, and/or Fsm, H Leptomoder L or G, Fz, H Tenuic, Pachic, Hemic, Humic Mullmoder L or G, Fa and/or Fz, H, Ah Hemic, Humic Saprimoder S or G, (Of, Om), Oh Fibric, Mesic Mull Vermimull (L, F), Ahz Tenuic, Pachic, Ochric, Pellic,  Micro, Meso, Micro Rhizomull G, (F), Ahg Tenuic, Pachic, Ochric, Pellic Paramull (L, F), Ah Tenuic, Pachic, Ochric, Pellic 1 Diagnostic horizons are printed in bold fonts; less commonly occuring, non-diagnostic horizons are given in parentheses. 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Klinka, Jaume Fons (jfons@filnet.es), and Pavel Krestov (farrex@vtc.ru) Production and design: Christine Chourmouzis (chourmou@interchange.ubc.ca) Financial support: Forest Renewal British Columbia and the Spanish Government (Ministerio de Education y Ciencia) For more information contact: K. Klinka Copies available from: www.forestry.ubc.ca/klinka or  K.Klinka, Forest Sciences Department, UBC, 3036-2424 Main Mall, Vancouver, BC, V6T 1Z4 Green, R.N., R.L. Trowbridge, and K. Klinka. 1993. Towards a taxonomic classification of humus forms. Forest Science Mono- graph. 29: 1-48. Reference , -G46!%G46()*.		"! , -G46!%G46≤)*.		 !  +/ -G46!%()*.		 "! +/ -G46!%≤)*.		 ++  ++ '≥0G46 G46
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