Lab 3 Flashcards
poikilohydric
is the lack of ability (structural or functional mechanism) to maintain and/or regulate water content to achieve homeostasis of cells and tissue connected with quick equilibration of cell/tissue water content to that of the environment.
epiphytic
Relating to a plant that grows on another plant but doesn’t feed from it.
Kubiak & Osyczka 2020: Introduction
The effect of abiotic and biotic factors on the diversity and distribution of epiphytic lichens in different ecosystems. EX: boreal, Mediterranean, temperate, deciduous.
Tree avenues (tree alley or allée)
Due to poikilohydric nature, specific physiology, and structural variety of lichen thalli, occurrence of particular epiphytic species depends on the properties of tree species and the climatic conditions where they grow.
Factors at the scale of the host-tree appear to be particularly important for epiphytes with narrow ecological amplitude.
Physicochemical bark properties, thickness, degree of splitting, pH value, water-holding capacity, and eutrophication, regulate the presence, richness, and biodiversity of lichens.
Attributes of a given tree can change as a tree ages and may be modified to a certain extent by natural environmental conditions and anthropogenic influences.
External factors related to stand characteristics, composition and age structure of tree species, tree density and canopy cover, moisture regime, and light availability, are also crucial for epiphytes.
Kubiak & Osyczka 2020: Methods
Conducted in NE Poland within the Olsztyn Lakeland mesoregion.
Selected five deciduous tree species:
- Acer platanoides – Ac (Norway maple),
- Fraxinus excelsior - Fr (ash),
- Tilia cordata – Ti (lime),
- Quercus robur - Qu (pedunculate oak),
- Ulmus laevis - Ul (European white elm)
Epiphytic lichens were studied on 100 trees (20 per species) from each habitat type:
(1) non-forested area – well-preserved stretches of tree avenues (ca 200 m in length) growing in similar topographical conditions and located at least 200m from the forest border.
(2) forest - best-preserved parts of forest sub-divisions (largely protected within the NATURA 2000 network) with uniform and undisturbed patches of vegetation corresponding to potential for this area, located at least 200 m from the nearest forest border.
Tree avenues along local roads with negligible traffic and situated at least 200 m from the nearest farm buildings were included in the study.
Lichens were identified in the field, when possible; however, most individuals were collected for detailed morphological and chemical examinations. … The nomenclature follows Index Fungorum (2018); the collected material is deposited in the OLTC herbarium
The effect of locality turned out to be insignificant (p > 0.05) for each dependent variable, locality was considered as a negligible factor and consequently two-way analysis of variance (tree species × habitat), followed by Tukey’s (HSD) test, was performed to verify significant differences in parameters across particular tree species and habitat types.
Kubiak & Osyczka 2020: Results
Significant differences in diversity indices between … trees were revealed (species number F = 10.73, p < 0.001; the Shannon index F = 12.95, p < 0.001).
Larsen et al. 2020: Introduction
Tree species composition is very important for lichen biodiversity.
Variation among tree species regarding bark properties and canopy structure offers different habitats for lichen communities.
For individual trees, age gradients along stems and branches also create a variety of conditions for corticolous organisms.
Larsen et al. 2020: Methods
Tree bark from seven Danish native angiosperm trees was examined by a floristic sample analysis of lichens.
Tree Species:
- Acer pseudoplatanus L.
- Alnus glutinosa
- Gaertn.
- Betula pendula Roth
- Fagus sylvatica L.
- Fraxinus excelsior L.
- Quercus robur L.
- Tilia cordata Mill.
All trees were grown in a common garden experiment established with two-year-old seedlings in 1973 at four sites: Matrup forests, Odsherred forest district, Det Petergaardske forest district and Vallø diocese.
As part of a study on tree biomass, six trees per tree species on each site were selected by stratified random selection and felled in March 2015.
Stem discs with a thickness of 3–4 cm were collected at different heights along the tree stems. … In total, 1956 stem discs were examined.
Bark was dried at 105 °C for 24 h to determine the dry weight as a part of the biomass study.
From each stem disc, all bark was carefully loosened from the cambium and collected in pieces as large as possible.
Bark was examined for the presence or absence of lichens.
Lichens were identified morphologically at ×10–30 magnification using keys in Smith et al.
Lichen species richness (S) and Shannon diversity (H´) values were calculated for each sample unit before omitting rare species and then means across sample units within tree species were calculated.
Differences in species richness and Shannon index values among tree species were tested by a Kruskal-Wallis test (R, version 3.3.2).
Larsen et al. 2020: Results
Lichen species diversity varied significantly across tree species.
Acer pseudoplatanus and Fraxinus excelsior had significantly higher species richness (S) and Shannon index (H´) values than all other tree species, except for the species richness of Alnus glutinosa .
Betula pendula and Fagus sylvatica showed a significantly lower presence and diversity of lichens
Ecology
the study of relationships between an organism and the environment.
Most ecologists are interested in describing relationships that apply to more than one organism.
These generalizations are commonly done at the level of the population.
population
is defined as a group of interbreeding organisms occupying a particular spatial area.
Therefore, it is important to define the population under study by identifying both the species and the area.
Since it is difficult to gather information from every individual in a given population, ecologists often will take multiple samples from within that population in an attempt to gather representative information about the population as a whole.
Urban ecology
is an emerging field that has its roots in landscape ecology.
And initially focused on practical problems related to urban planning as well as environmental protection and wildlife conservation in towns and cities.
The urban environment has many challenges that are less influential in more natural settings, such as higher temperatures, a high proportion of impervious surfaces, and contaminants such as heavy metals or other pollutants.
Lichens
Lichens are a unique group of organisms that are difficult to classify because they are actually symbiotic associations between at least one fungus (the mycobiont - usually an ascomycete fungus , but there are also a few basidiomycete species) and at least one of a green algae and/ or cyanobacteria (the photobiont).
Each species of lichen has a fungus species that is unique to it that provides the external structure, but the species of photobiont may occur in different lichens.
When a cyanobacteria is the photobiont partner , it is often a nitrogen fixing species like Anabaena or Nostoc.
Critical to water and nutrient balance in lichens is the ability to absorb, essential resources directly from the air and water.
Lack filtration systems (like vascular plants have) and the detoxification pathways common in insects. Therefore, Very sensitive to air pollution.
Photobiont and Mycobiont
The fungal hyphae form the tissues that gives the lichen its overall shape and structure, providing a stable moist environment and possibly some chemical substances for the photobiont.
The photobiont, usually located below the lichen’s surface, provides the food through photosynthesis.
If the lichen has a second photobiont, it is a cyanobacteria that is contained in pockets in the thallus or on the surface of the lichen.
The fungi and photobionts in a lichen can reproduce independently of each other (fungi usually sexually and algae asexually) but may reproduce asexually together as a symbiotic unit either by fragmentation or by forming specialized structures called soredia.
Soredia
Soredia are small groups of fungal hyphae that contain the photobiont(s) (algal cells) that are easily dispersed by air currents, for asexual reproduction.
Location of Lichen growth
Often called “pioneer plants” because they often grow on bare rock and are the first vegetation to appear in burnt areas or newly formed volcanic regions.
Lichens are extremely widespread, but are most abundant in the Arctic tundra, boreal forest, mountains, the Antarctic and the tropics. They commonly grow on rocks and the bark of trees.
They are amongst the slowest growing and oldest living organisms on earth; some species of lichen grow only 2- 3 cm in 1000 years and may be 4500 years old
