- Fig. 1. Scheme representing development of trees in a forest under different light conditions [21]. Ontogenetic stages: p – seedling; j – juvenile; im1, im2 – immature, first and second subgroups; v – virginile; g – generative. 1 – development at constant irradiance mode at light minimum (dashes – boundaries between ontogenetic stages); 2 – transition from one stage to another with improved light conditions (after treefall gap forms); 3 – transition to quasi-senile (qs) state (“snag”); 4 – death
- Fig. 2. Absolute age (x-axis) and change of biological parameters of undergrowth plants (y-axis) growing in minimum light below the forest canopy. Y-axis: A – the ratio (%) of the mass of photosynthetic (F) and non-photosynthetic (N) parts of j individuals of Acer platanoides; B – net assimilation (mg cm-2 year-1) of j individuals of Carpinus betulus (C.b.) and Ulmus glabra (U.g.); C – annual increments in height (cm) of im1 individuals of Ulmus glabra (U.g.) and Acer campestre (A.c.); D – growth in height (cm) of im1 individuals of Quercus robur (Q.r.) and Fraxinus excelsior (F.e.)
- Fig. 3. The appearance of im1 trees in the undergrowth in minimum light below the forest canopy. U.g. – 11-year-old Ulmus glabra; F.e. – 13-year-old Fraxinus excelsior; P.s. – 8-year-old Pinus sylvestris (picture by N. A. Tatarenkova); P.a. – 12-year-old Picea abies (picture by A. M. Romanovsky); A.p. – 18-year-old Acer platanoides. Crosses – dead shoots
- Fig. 4. Change in the ratio of the mass of photosynthetic (F) and non-photosynthetic (N) plant parts in minimum light below the forest canopy. The x-axis represents ontogenetic stages, while the y-axis represents percentages. Ontogenetic stages: j – juvenile, im1 – first immature subgroup, im2 – second immature subgroup, v1 – first virginile subgroup, v2 – second virginile subgroup
- Fig. 5. The appearance of virginile undergrowth in the first subgroup (v1) which was formed in treefall gaps (A, B) and under the forest canopy at light minimum (C, D). The top row (A, C) is Acer platanoides, the bottom row (B, D) is Quercus robur. Undergrowth height is 5 metres. Legend: 1 – annual increment in height in treefall gap; 2 – annual increment in height in minimum light; 3 – borders of annual increment; 4 – side branches extending at an acute angle; 5 – side branches extending at a right angle (plagiotropic shoots); 6 – dead side branches; 7 – part of the trunk cleared of lower branches; 8 – fracture of the cortex at the base of the stem
- Fig. 6. Quasi-senile plants (qs) of Quercus robur: A, B – uniaxial juvenile “snags” which originated from im1 individuals; C, D – biaxial immature “snags” which originated from im2 individuals. Legend: 1 – xylopodium; 2 – “stump” or basal part of aboveground dead shoot; 3 – dormant bud on xylopodium; 4 – main root; 5 – lateral root; 6 – adventitious root; 7 – xylorhizome; 8 – border of annual growth; 9 – dormant bud on above-ground shoot; 10 – dead shoots; 11 – leaves of semi-mature (immature) type. The encircled number is the absolute age of the above-ground shoot which was formed from dormant buds in the xylopodium. Fig. D was made by A. A. Chistyakova [56]
- Fig. 7. Quasi-senile (qs) Quercus robur plants. A – multiaxial immature “snag” which originated from a v1 individual; B – monoaxial virginile “snag” which originated from a v1 individual. Legend: 1 – dead aboveground shoot of v1 individual; 2 – basal living part of dead aboveground shoot with reserve of dormant buds (upper part of xylopodium, future “stump”); 3 – renewal shoot of immature appearance which formed from dormant buds in the xylopodium; 4 – leaves of semi-mature (immature) type; 5 – xylopodium; 6 – “stump” or basal part of dead aboveground shoot; 7 – adventitious root; 8 – dead lateral branch in lower part of trunk (showing stem cleansing); 9 – border between annual growth sections; 10 – umbrella-shaped crown with plagiotropic shoots; 11 – dead branches in umbrella-shaped crown. Crosses – dead shoots
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