Jan Altman
Academy of Sciences of the Czech Republic, Institute of Botany, Department Member
- University of South Bohemia, Department of Ecology, Department Memberadd
Research Interests:
Research Interests:
Carbohydrate storage enables plants to both tolerate seasonally unfavourable conditions and recover from disturbance. Although short-term changes in storage levels due to disturbance are fairly well-known, less is known about long-term... more
Carbohydrate storage enables plants to both tolerate seasonally unfavourable conditions and recover from disturbance. Although short-term changes in storage levels due to disturbance are fairly well-known, less is known about long-term changes in storage levels, especially in response to cessation of repeated disturbance. Additionally, whereas it is presumably the total amount (pool) of storage carbohydrate reserves that is of importance, typically carbohydrate concentrations are measured instead, as a proxy. We assessed changes in carbohydrate concentrations and pools in storage organs and changes in above- versus below-ground biomass in response to mowing cessation in nine herbs from two meadows (dry and wet) at the (June) peak of vegetation development and the (October) growing season end one and three years after the change in the disturbance regime. We tested three hypotheses: (1) storage will increase with abandonment only in the first year after disturbance cessation, but not further increase subsequently, as high storage would hinder competitive ability; (2) storage will increase towards the end of the season in both disturbed and undisturbed plants; and (3) changes in carbohydrate concentrations are accurate predictors of changes in pools. Although species-specific changes in carbohydrate reserves occurred in the wet meadow, more general trends appeared in the dry meadow. There, plants accumulated higher carbohydrate reserves at the end of the season, especially in unmown plots. However, the reserves for plants in both disturbance regimes were the same at the growing season peak (June) in both examined years. The increase in storage of carbohydrates on unmown plots in October was manifested by increases of both storage organ biomass and carbohydrate concentration, whereas in mown plots it was due only to increased carbohydrate concentration. Although concentrations and pools represent different aspects of plant carbohydrate economy, concentrations well represent short-term responses to changed disturbance regimes.
Nest predation is assumed to be an important factor driving avian life histories. Altitudinal gradients offer valuable study systems to investigate how avian nest predation risk varies between bird populations. In this study, a hypothesis... more
Nest predation is assumed to be an important factor driving avian life histories. Altitudinal gradients offer valuable study systems to investigate how avian nest predation risk varies between bird populations. In this study, a hypothesis postulating an increase in avian nest survival rate with elevation as a result of decreasing predation pressure was experimentally tested along an altitudinal gradient (300-2250 m) in West-Central Africa. Three types of artificial nests (cup-shrub, cup-ground and bare-ground) were used along the altitudinal gradient. Overall, elevation had no effect on the daily survival rate (DSR) of the artificial nests. However, there was a significant elevation-nest type interaction. Daily survival rate for cup-shrub nests decreased significantly with elevation, but for cup-ground and bare-ground nests, elevation had no significant effect. We tested the effects of the same vegetation parameters (tree density, herb and shrub layer coverage, and canopy openness) on the DSR of different nest types to understand how different vegetation layers or combinations of them affect DSR. Daily survival rate for bare-ground nests significantly decreased with increasing canopy openness, and was positively influenced by coverage of herb layer and tree density. For cup-shrub nests, DSR increased significantly with increasing shrub layer coverage. Finally, for cup-ground nests, we found a positive effect of shrub coverage and canopy openness on DSR. In summary, we found that different forest vegetation layers affect predation risk of different nest types along elevations on Mt. Cameroon.
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In coppice-with-standards, once a common type of management in Central European lowland forests, selected trees (standards) were left to grow mature among the regularly harvested coppice stools to obtain construction wood. After the... more
In coppice-with-standards, once a common type of management in Central European lowland forests, selected trees (standards) were left to grow mature among the regularly harvested coppice stools to obtain construction wood. After the underwood was harvested, the forest canopy opened rapidly, giving standard trees an opportunity to benefit from reduced competition. Although this silvicultural system virtually disappeared after WWII, historical management cycles can still be traced in the tree-rings of remaining standards. Our research aims at answering the question whether tree-ring series of standard trees can be used to reconstruct past management practices. The study was carried out on 117 oak
standard trees from five sites situated in formerly coppiced calcareous oak-hornbeam and acidophilous oak forests in the Bohemian Karst Protected Landscape Area, Czech Republic.
The evaluation was based on the analysis of growth releases representing the response of the standards to coppicing events, and comparison to the archival records of coppice
events. Our results showed that coppicing events can be successfully detected by tree-ring analysis, although there are some limitations. Altogether 241 releases were identified (49%
of major releases). Large number of releases could be related to historical records, with the major ones giving better results. The overall probability of correct detection (positive predictive
power) was 58%, ranging from 50 to 67%, probability for major releases was 78%, ranging from 63 to 100% for different sites. The ability of individual trees to mirror past coppice events was significantly affected by competition from neighboring trees (their number and the sum of distance-weighted basal areas). A dendro-ecological approach to the study of forest management history can serve as an input for current attempts of coppice reintroduction and for conservation purposes.
standard trees from five sites situated in formerly coppiced calcareous oak-hornbeam and acidophilous oak forests in the Bohemian Karst Protected Landscape Area, Czech Republic.
The evaluation was based on the analysis of growth releases representing the response of the standards to coppicing events, and comparison to the archival records of coppice
events. Our results showed that coppicing events can be successfully detected by tree-ring analysis, although there are some limitations. Altogether 241 releases were identified (49%
of major releases). Large number of releases could be related to historical records, with the major ones giving better results. The overall probability of correct detection (positive predictive
power) was 58%, ranging from 50 to 67%, probability for major releases was 78%, ranging from 63 to 100% for different sites. The ability of individual trees to mirror past coppice events was significantly affected by competition from neighboring trees (their number and the sum of distance-weighted basal areas). A dendro-ecological approach to the study of forest management history can serve as an input for current attempts of coppice reintroduction and for conservation purposes.
Research Interests:
Research Interests:
Secondary woodlands in South Korea cover most mountains from low to middle elevations. While general patterns of forest succession are well understood, little is known about mechanisms of stand recovery after disturbance. We examined the... more
Secondary woodlands in South Korea cover most mountains from low to middle elevations. While general patterns of forest succession are well understood, little is known about mechanisms of stand recovery after disturbance. We examined the spatio-temporal variations in establishment, growth, size inequality, and mode of competition among trees in a 50-year-old post-logging Quercus mongolica-dominated stand. We further compared the growth and stem allometry of single trees, presumably of seed origin, with multi-stemmed trees resprouting from stumps. Q. mongolica formed the upper canopy 16–22 m tall, 88.3% of total stand basal area, and 36.2% of total stem density, with most trees established during the first post-logging decade (51.2% were resprouts). During the first three decades, the Q. mongolica recruits grew exponentially, and disproportionately more in diameter than few older reserved trees left after the last cutting. This substantially decreased size inequality. The reverse trend was observed from 1994 to 2004: larger trees grow more, indicating an increasing asymmetry of competition for light. Neighborhood analysis revealed that when target trees had more or larger neighbors, their exponential phase of growth was reduced and maximum size was decreased. After the 50 years of stand development, more than 70% of Q. mongolica showed growth decline as a result of competitive stress, and mortality was about 30%, concentrated in smaller size classes. Compared to single stems, resprouts within clones do not seem to compete less asymmetric as might be expected based on studies of clonal herbaceous plants and physiological integration within genets. As Q. mongolica was also negatively affected by competition from woody species currently prevailing in the lower tree stratum (Tilia amurensis, Acer mono, Fraxinus rhynchophylla, Acer pseudosieboldianum), we predict the stand will become increasingly dominated by these more shade-tolerant trees.
Research Interests:
Research Interests: Engineering, Physics, Chemistry, Climate Change, Conservation Biology, and 19 moreEast Asia, Biology, Biodiversity, Medicine, Multidisciplinary, Plant Diversity, Volcanic eruptions, Species Traits, Trees, Late Glacial, Species Richness, PLoS one, Republic of Korea, Early Holocene, Ecosystem, Shade tolerance, Leaf dry matter content, Litter Decomposition, and Vascular Plants
Research Interests:
We study nature of abandoned villages in Niokolo-Koba National Park and surrounded villages. We do ethnobotany, palaeoecology and ethnoarchaeology of abandoned villages areas as well as dynamic of savanna/deciduous tropical forest in... more
We study nature of abandoned villages in Niokolo-Koba National Park and surrounded villages. We do ethnobotany, palaeoecology and ethnoarchaeology of abandoned villages areas as well as dynamic of savanna/deciduous tropical forest in relation to the past human occupation. Special attention is paid to dominant large trees, which played crucial role in local human culture.