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Mount Usu / Sarobetsu post-mined peatland
From left: Crater basin in 1986 and 2006. Cottongrass / Daylily

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Conservation biology

1. I have chosen paper from your homepage with the title "Recovery of forest-floor vegetation after wildfire in a Picea mariana forest". After looking for another journal that contains different content with that journal, I found journal entitled “Effect of postfire logging on soil and vegetation recovery in a Pinus halepensis Mill. Forest of Greece” by Spanos et al. I have tried to find another journal, which was published earlier than 2013, but I found second journal was comparable with the first Journal I have chosen from your homepage. The reason why I have chosen these two journals is I can make comparisons and make sure that there are some contradictions that I can discuss. In these two journals, research has been conducted in the pine tree forests and observed temporally after forest fire.
2. First journal: Recovery of forest-floor vegetation after wildfire in a Picea mariana forest
This study has been done in P. mariana forest in boreal region. Wildfire in P. mariana forest is occurred naturally and caused by lightning. In the P. mariana forest, after wild fire happens, forest floor will be moderately burned out and semi-serotinous cone is produced by P. mariana for establishing seedlings. Aim of this research was to detect the trajectories of forest floor vegetation recovery in P. mariana forest after wildfire. Data was collected on the burned and unburned sites over time (2005 to 2009).
On the result, initial vegetation patterns and environments, temporal changes in vegetation, and habitat preferences were revealed. After wildfire in P. mariana forest, 29 vascular plant species (27 seed plants and 2 ferns) and over 13 non-vascular plant species were recorded on the 80 quadrats that had different fire severities. Those vascular plants consisted of 13 herbs, 12 shrubs, and 4 trees. The shrubs were visually survived throughout wildfire and recovered mostly by vegetative reproduction. The canopy openness was measured as well but it was not related to the parameters on plant community structure.
For the temporal changes in vegetation, total plant cover has increased from 10% in 2005 to 108% in 2009. But, for temporal changes specifically on the other species were varied, both on the understory plants and on the trees. For example, a forb Epilobium angustifolium that had peak of cover 2 years after the wildfire but then gradually decreased. Different with a sedge, Carex bigelowii, and a grass, Calamagrostis canadensis, that gradually increased over time. Moreover, all tree covers had gradually increased. Even though it was so, P. mariana slowly increased and also, B. neoalaskana and P. tremuloides that had low initial cover because these two species established from seeds. NDMS was also used for determining the relationships among environmental factors.
For the habitat preferences, the patterns of yearly fluctuations of unburned and burned sites were different. In the unburned sites, the fluctuation patterns of Sphagnum were stable but in the burned sites, the similarities were lower. But in case of the trees, both in the burned and unburned sites, the similarities gradually increased, which means tree covers were developed over time. Different cases with the herbs, their patterns were not synchronized. Then, shrubs established well with Spaghnum as indicated by NDMS. P. mariana established more in the unburned site and had higher similarities than any other trees, but P. mariana also didn’t have low establishment in the burned site.
On the discussion, along gradients of fire severity, revegetation patterns on the floor differed greatly between burned and unburned surface since the recovery on unburned surfaces was dependent on regeneration and that on burned surfaces on colonization. Moreover, along gradient of topography, species richness decreased with increasing slope gradients. Established plant life forms were varied (seeders and sprouters) and such differences in regeneration strategies between species or life forms determine the plant community structure. Regarding to the habitat preferences, the complete removal of moss and organic matter promoted the colonization of non-Sphagnum mosses and deciduous trees.
Second journal: Effect of postfire logging on soil and vegetation recovery in a Pinus halepensis Mill. Forest of Greece
Forest fire that happened in Pinus halepensis forest is caused by human activities for harvesting trees. After forest fire in that forest, plant cover and litter layer that are important for preventing soil erosion will be removed, soil processes get damaged, wildlife habitat destroyed and negatively affect vegetation recovery. But, in Greece, some people argue that forest fire has merits such as reduction of erosion, reduction of fuel loads, reduction of pest populations increased water infiltration and better condition for plant regeneration. This study aim was assessing the effect of post-fire logging on plant regeneration and soil erosion in a P. halepensis forest ecosystem. Data was collected in four plots: unburned (UB); burned but not logged (UL); burned, logged and use of tractors for log removal (LT); and burned, logged and use of mules for log removal (LM) at five dates on May 2002, November 2002, February 2003, October 2003 and March 2004.
On the result, Herbs and main woody plants one year after wildfire were recorded. There were 18 herbs and small herbs (3 resprouters and 15 seeders) and 6 main woody plants by 4 hectares sites. From that result, it showed that more herbs were established by seeds than by resprouting. For the soil condition, there were no effects on soil pH by fire or logging. And in the unlogged burned areas, the organic matter increased dramatically one year after forest fire.
For the temporal changes, tree regenerations were varied. Plant cover showed significant variations in the first two years after fire but significant reduction of the plant cover in February 2003. In detail, the tree species, A. unedo, was more successful in the unlogged burned site for six months after fire, but one year later, it was not. Another tree species, Cistus creticus, seedlings germinated in greater numbers in the unlogged burned site but in March 2003 no significant different with some other sites. Regeneration of P. lentiscus was found to be significantly better in unlogged burned site as well. The highest pine seedlings were found in the unlogged burned site, however seedlings in the logged site were developed a big root system.
On the discussion, burned unlogged plot had high rates of organic matter. It could be explained by the large amount of dead tree parts of the wind thrown trees. Also, there was no strong evidence that logging and mechanisms of log removal increased the sediment transfer. However, soil effects of different wood removal methods show that tractor skidding caused signify higher levels of soil disturbance and compaction.
For the emergence of the pine seedling, it was affected negatively by logging but not their survival. Post-fire logging affected negatively the establishment of pine seedlings. After a fire, P. halepensis seedlings emerge mainly during the first wet season. However, there was seedling emergence period shifting that possibly related to the environmental condition following the fire.
3. Contradictions between two journals are:
- In P. mariana forest, most established shrubs and herbs are sprouters. In contrast, in P. halepensis forest, most established shrubs and herbs are seeders. Based on the research by Campbell and Clarke (2006), it was concluded that post-disturbance persistence of shrub species relies on combination of the ability to resprout and accumulate seed banks in space or time. So, most established shrubs can be dominating by sprouters or seeders, depend on the ability to resprout and seed bank accumulation. Ability of resprouting after fire reduces the reliance on seed banks for persistence, however, in the long-term mortality must be balanced by seedling recruitment. If the ability of resprout is low, so ability of plant to be established by seed will get higher.
- In P. mariana forest, canopy openness was not related to the parameters on plant community structure. Meanwhile, in P. halepensis forest, pH was factor that had no effect by fire on the post-fire vegetation. Canopy effect and pH effect are relatively difficult to be understood because of many aspects that can be affecting those two factors. There are possibilities in some conditions when canopy openness and pH do not have relationship to the community structure after forest fire. If the gap between canopies is small, trees diversity in young pine-dominated forests seems to be difficult. However, event small gaps can be effective in creating size and age variation of the dominant species. Suitable substrate is the primary factor limiting seedling recruitment following gap logging (Rouvinen and Kouki, 2011). For the pH effect, most references showed that forest fire increase soil pH in the high temperature (Ekinchi, 2006; Ekichi, 2002). Burning of organic matter releases ash and charcoal on the ground. Ash contains the inorganic elements. Base cation in the ash leads to increased pH. But, still there is possibility that pH has no effect on the vegetation structure. If soil contains neo-formed calcite, it will still present even three 3 years after burning and maintained moderately alkaline soil pH. Fire-induced increase in pH is negligible in soils buffered by carbonates. Soil exchangeable capacity is decreased by fires due to loss of a high-density charged fraction such as organic matter (Certini, 2013).
- Total plant cover in P. mariana forest increased over time. Meanwhile, total plant cover in P. halepensis forest increased on the first two years and decreased afterward. In case of P. mariana forest, plant cover mostly determined surface albedo after the wildfire. The linear relationship between albedo and total plant cover indicate that the vertical development of plant cover by herbs and shrubs certainly contributes to increasing surface albedo. So, because surface albedo increased in the P. mariana forest total plant cover also increased (Tsuyuzaki et al. 2009). However, after forest fire, the replacement of the organic matter lost occurs via long-term plant production and litter inputs. The forest floor is reconstructed along with the re-development of vegetation, and related mostly to increasing plant cover. However, litterfall from resprouting Quercus coccifera was higher 3 years after fire and the decreased slightly to value of the mature vegetation (Cerda and Robichaud, 2009). Decreasing of litterfall may less contribute on supplying nutrient to the soil. The litter on the forest floor acts as input-output system of nutrient and the rates at which forest litter falls and subsequently decomposes contribute to the regulation of nutrient cycling and primary productivity, and to the maintenance of soil fertility in forest ecosystems (Wang et al. 2008).
Choosen Journals
  • Spanos I, Raftoyannis Y, Goudelis G, Xanthopoulou E, Samara T, Tsiontsis A. 2005. Effect of postfire logging on soil and vegetation recovery in a Pinus halepensis Mill. forest of Greece. Plant and Soil 278: 171-179
Arguments supporting journals:
  • Campbell ML, Clarke PJ. 2006. Seed dynamics of resprouting shrubs in grassy woodlands: Seed rain, predators and seed loss constrain recruitment potential. Austral Ecology 31, 1016–1026
  • Cerda A, Robichaud PR. 2009. Fire effects on soils and restoration strategies. Science Publishers p 241
  • Certini G. 2005. Effects of fire on properties of forest soils: a review. Oecologia 143: 1–10
  • Ekinchi H. 2006. Effect of Forest Fire on Some Physical, Chemical and Biological Properties of Soil in Çanakkale, Turkey. International Journal of Agriculture & Biology 1560-8530
  • Rouvinen S, Kouki J. 2011. Tree regeneration in artificial canopy gaps established for restoring natural structural variability in a scots pine stand. Silva Fennica 45(5)
  • Verma S, Jayakumar S. 2012. Impact of forest fire on physical, chemical and biological properties of soil: A review. Proceedings of the International Academy of Ecology and Environmental Sciences 2: 168-176
  • Wang Q, Wang S , Huang Y. 2008. Comparisons of litterfall, litter decomposition and nutrient return in a monoculture Cunninghamia lanceolata and a mixed stand in southern China. Forest Ecology and Management 255 1210–1218


Introduction to trans-disciplinary human development

Environmental conservation
The human disturbances that affect the ecosystem is, I think, a huge problem of our world. The role of human kind in the destruction of the nature is invaluable. Each years flower and animal species disappear because of our pollution. Here, we have modified the climate and now the global warming is coming much earlier than it should be.
I am interested in that topic because I feel responsible, we, as individual human being but also and especially as societies, have to change our way of life and way to save what we are going to destroy. Soon, there will be no more natural ecosystem other than salt (polluted) water.
I am thinking about join an NGO or any association that want to stop the pollution. There is so much to do. I am now enrolled in environmental courses and I may continue this way until I find my place in an enterprise / association that share my will.

Symbiosis in nature

Ecology is the scientific analysis and study of interactions among organisms and their environment, such as the interactions organisms have with each other and with their abiotic environment. Ecology is deeply related to environment. So, it is very difficult to study environmental science without the fundamental knowledge of ecology. This lecture should specialized in cutting-edge of environmental science concerning with ecological field. As fundamental ecology is a vast area, so it is very difficult to get knowledge about this field within this short time. However, we can get some fundamental knowledge of ecology that is related to environmental concern. This will help us to understand problem occurring in our environment. and finally interact with ecosystem. Without the knowledge in ecology, we cannot able to understand our environmental problem. So, the lectures should emphasize both in cutting-edge topics of environmental science and fundamental ecology.


Conservation biology

Debating the Intermediate Disturbance Hypothesis (IDH)
Paper 1: Fox JW. (in press) The intermediate disturbance hypothesis should be abandoned. TREE. DOI: 10.1016/j.tree.2012.08.014
This paper reviews studies which tried to support the IDH Empirical and theoretical refutation of the IDH. Through meta-analysis, it rejects the IDH through empirical and theoretical ways.
  • Empirical refutation: majority of studies aimed at proving the IDH did not succeed to find the peak at intermediate levels of disturbance. The papers states that less than 20% of studies (past and more recent ones) on diversity-disturbance studies found the IDH trend.
  • Theoretical refutation: the three mechanisms giving the humped shape of diversity distribution across disturbance levels in the IDH were criticized and proven flawed as follows.
    • IDH says that competitive exclusion is maximized at intermediate disturbance frequency and thus we are likely to find the most number of competing species at this level. Intense and frequent disturbances lead to no intolerant species while low disturbance does not lead to exclusion by better competitors. That mechanism is hereby being criticized as most studies who lent support to IDH were then conducted in conditions where the shape of diversity distribution is already likely to peak at intermediate disturbance levels and ignored the nonadditivity and nonlinearity or growth on temporal variation.
    • The second theory on IDH is that intermediate disturbance slows down competitive exclusion and high disturbance increases it. For this part, Fox criticizes Huston’s hypothesis on species diversity, particularly the disturbance-free control used that does not contrast correctly the existing natural scenarios. IDH is not false but important studies that found the same shape of distribution are biased so possibly cannot support it in the end. The mechanism of “bouncing back” of species also contributes in giving the peak at intermediate disturbance.
    • The basic theory here is that at intermediate frequency of disturbance, strong competitors or dominant species do not have time to settle before the next disturbance comes and sets all densities to low for all species again. Hutchinson’s paradox of the phytoplankton is here discussed and this paper advocates that the coexistence is mainly determined by relative fitness of species independently of environmental factors. That means the coexistence of different phytoplankton species at non equilibrium is rather explained by each species’fitness than the disturbance of the milieu.
In summary, the IDH should not be used as the reference theory to explain species’ coexistence because of theoretical flaws in the explanatory mechanisms but also based on the majority of empirical findings that failed to prove it right.
Paper 1: Mayor SJ, Cahill Jr JF, He F, Solymos P & Boutin S. 2012. Regional boreal biodiversity peaks at intermediate human disturbance. Nature Communications 3: 1142 | DOI: 10.1038/ncomms2145
This paper based its’ hypothesis on supporting the IDH and reports a large scale study to demonstrate it. They conducted a survey via 150m radius circle areas satellite imagery in 242 sites in boreal region in Canada, characterized the vegetation and measured disturbance by area altered by human land use.
They found that native species richness was highest at a level of 47,7% disturbance (percentage of land altered by human), the humped shape predicted by the IDH. When compared two by two, however, species composition at high disturbance is not significantly different from that at intermediate level.
When native and exotic species were treated separately though, natives species were found to follow this same trend while exotic species increase linearly without any peak at intermediate disturbance level. Besides, exotic species seem to increase while native ones decrease with disturbed area (native/exotic ratio)
Mayor et al. also found that biodiversity resists permanent disturbance such as infrastructures better than temporary disturbance like seasonally used agricultural fields. Other environmental parameters (climate, topography, stand age etc.) did not change the trend when taken into account, suggesting that the humped shape curve of diversity is due to human induced disturbance only or mainly.
Finally they concluded that this study supports IDH as IDH was originally defined for communities not biomes.
In short, this study tried to prove using a regional scale study that IDH has empirical foundation and other studies failed to prove it because they tried in insufficiently small scale. However, they also considered that
exotic species are not independent drivers of native species decline, implying that species interaction is important and might have affected this distribution. Finally, this paper admits that IDH is inconsistent and scale dependant and should not be used alone to apply directly in management decisions.
Contrasting points
Mayor et al based their studies or proving the IDH right and designed their experiment accordingly, considering the critics brought about IDH. Using a regional scale study, they succeeded to find the humped shape distribution of species diversity across disturbance levels that agrees with the IDH. They also found that the best fit model to explain that this natural trend in the boreal region is explained by disturbance. However they implicitly found that species’ interaction also plays a major role in shaping the tendency. That last point agrees with Fox in his theoretical refutation, saying that relative fitness of species is the most determinant factor in coexistence and therefore independently of disturbance shapes up the distribution.
So, one point for Mayor et al is that they could argue the empirical refutation of the IDH and prove that big scale studies can lend support to IDH even if majority of previous ones failed to do so.
On the other hand, the refutation of the IDH by Fox because of the likelihood to find the humped shape prior to the study is not proven wrong by Mayor et al. This study on boreal vegetation is indeed supported by the patch mosaic hypothesis but that also means species preference or better fitness to edges or center affects the diversity. Finally the similarity in the species composition areas with low, intermediate and high disturbance levels fails to show that co-occuring species are really determined by human disturbance but rather suggesting that is by their own potential to coexist.
I tend to support Mayor et al in refuting the IDH. The IDH is not false but cannot be used as a general theory to be applied in all ecosystems. Even Bongers et al (2009)* in their study in Ghanaian tropical forests found that IDH explains only why diversity changes across sites but in wet forest type the disturbance explained very weakly the species composition. In this study, analysis was done on large scale survey dataset, based on in situ inventory and in different types of forest along a wide range of moisture. Disturbance index was the percentage of pioneer species per plot, thus assumed to indicate the past disturbance events as well as present conditions. The theoretical expectations of IDH to find highest diversity at intermediate disturbance, especially with wet forest were not met both for species density and for diversity. This study also showed that density of pioneer species increased linearly with disturbance while that of shade tolerant ones decreased monotonically. All species combined however showed peak at intermediate level. That means that temperament and thus inherent characteristics of species do affect the distribution of diversity along disturbance gradient since they interact and succeed in the chain according to their temperament. This study also demonstrated that dry forests, more sensitive to disturbances, do show support to the IDH but contrary to the expectations whereas for wet forests, it is more difficult to prove it. Criticism about this study is the non consideration of dispersal limitation, the scale of disturbance (larger than the sampled plot or much localized fire). Percentage of pioneer indicates implicitly the level of disturbance which is basically different in wet and dry forests. One positive point about this study is the consideration of species temperament, which reflects fitness of the species to the environment. But, even if mathematically, they established that the disturbance index was nearly independent of the density of pioneer, the temperament itself became part of the factors biasing the measure of disturbance. Besides, the indication of disturbance through pioneer species might miss the temporal distinction of the coexisting mechanism in dry and wet forests.
In conclusion, the main idea in IDH is that diversity is driven primarily by the level of disturbance and that the highest level of diversity is found at intermediate level of disturbance. IDH is being supported by many studies like that of Mayor et al (2012) and Bongers et al (2009), to cite only large scale studies. However, the vast majority of studies who attempted to support it failed, leading to reinforce criticism about the foundation of the IDH. Also the mechanisms originally explaining the IDH were argued to be flawed by meta analysis (Fox 2012). Measuring disturbance or defining the “disturbance” is a key issue in debating whether IDH applies or not.
*Bongers F, Poorter L, Hawthorne W D, Sheil D. 2009. The intermediate disturbance hypothesis applies to tropical forests, but disturbance contributes little to tree diversity. Ecology Letters, 12 (8):798-805 |DOI: 10.1111/j.1461-0248.2009.01329.x


Conservation biology

Any ecological community existing on earth goes through several changes over time, replacing species within the community. This phenomenon is known as succession, in which primary succession occurs from a site with no occupation by a community, and secondary succession occurs from a site where an existing community was once removed. There are three main models considered by Connell and Slatyer (1977) explaining succession procedures; facilitation, tolerance, and inhibition pathways. Since each model captures a different aspect of succession, all three models are not necessarily conflicting models. The first common condition among all three models is that disturbance occurs causing a relatively large open space, in which resource is released. The succeeding process in which species behave differently determines the separate pathways.
Firstly, the facilitation model shows a positive effect towards the early stages of succession. The alteration of environmental conditions and resource availability creates a more suitable environment for later species, allowing later successional species to establish in that site. Out of all the species that arrive to the open site, only specific species specializing in early succession are capable of establishing in the site at first. Their establishment in result changes the environment less suitable for early species, allowing species of late succession to establish instead. Replacement of species occurs at this stage by modifying the environment so that early species facilitate the growth of later species to maturity, and eliminating earlier species in exchange. Facilitation model is thought to fit best in primary successions, where pioneer species establish in harsh earlier phases of succession, and thus demonstrates the well-known succession sequence. On the contrary, the other two models mentioned later on, have been tested in later species-rich stages. Connell and Slatyer regard the question of stability, in which succession is a balancing reaction which occurs in a stable system when disturbed. Only certain early species of succession are able to establish, dominate and modify the environment. This succession sequence continues until the residing species no longer largely modifies the environment for facilitation to occur for other species to invade and grow.
Secondly, the tolerance model explains how juveniles of many species establish in the early succession stages according to its growth rate and interspecific competition. Species tolerant to the environment at this stage would persist to survive. As obvious, this model would include climax species as being present at the earlier stages of succession, being a subset of the early species and further surviving throughout succession. Later species, therefore, are successful whether earlier species have preceded establishment or not, signifying that the conditions produced by earlier species, required in the facilitation model, are unnecessary or do not affect later species. As the succession sequence proceeds, the environment becomes less suitable for the recruitment of early species of succession, in which the change in environment has very little or no effect upon late species. This results in the growth of late successional species regardless of the presence of early species, eliminating earlier species. The tolerance model would continue the succession sequence until the restricted site can no longer be invaded. The sequence of species replacements result from different species having different strategies in resource usage, i.e. later species are tolerable to low resource levels than early species and can outcompete them and grow to maturity. In these two models of facilitation and tolerance, early species are displaced by later species due to competition among resources such as light and nutrients with the newcomers. The tolerance model states the appearance of both early and late species at the first stage after disturbance has occurs. The growth of the pioneer species, creating shade, allows less availability in resource for early-stage succession species (intolerant to shade). Little or no effect, however, is to be seen in those that are tolerant to shade (i.e. later species).
Lastly, the inhibition model is often defined as being the opposite model of the facilitation model. In inhibition, establishing species earlier in the successional stage would inhibit subsequent species from establishing and further grow to maturity in the same community. Similar to the tolerance model, any species that arrive to an open site are able to survive and establish themselves as adults in that site. Due to early occupants in the site, the environment becomes less suitable for both early and later succession species. The earlier colonists would thus exclude or inhibit the invasion of subsequent colonists under the conditions that the earlier species are undamaged and continuingly regenerating. Disturbance, however, continues to occur over time. In this model, later species of succession would establish in the community when earlier species are disturbed by severe conditions or predators once again. This model would only account for situations when disturbance persistently exists, where later species replace earlier ones by physical conditions, unlike the former two models affected by resource conditions. In these three models explaining succession, it is important to consider the fact that earlier species are not able to invade, establish,
and grow once the site is occupied. Species following the tolerance "pathway" would not be able to establish in a site if there were not enough room. Competition continually exists over time and species that are able to use resources most efficiently succeed and outcompete with others. The first-invading species inhibit growth and development of other species subsequent in succession, resulting in a type of incorporation between early and delayed succession species. Studies testing these proposing models of Connell and Slatyer have been made for the interference of succession mechanisms by removing species, sowing seeds and planting seedlings. The main objective of the proposal of these models was to suggest types of succession mechanisms that work between species in a certain forest.
As can be seen, different succession sequences support all three models. However, as each model being unique in its own way, it can be said that all three models are supported at only a particular stage. In other words, the entire succession sequence and patterns cannot be fully explained by one single model; i.e. facilitation is not the only process that underlies succession (facilitation does not always occur or is required for the establishment of later species or for the succession sequence in some cases). These three models therefore are not necessarily opposing models; a certain species would not necessarily undergo one type of succession sequence throughout its life history.
Results showing that both facilitation and inhibition occur in a succession sequence have been reported. These two "pathways" may not coexist at the same stage, but would be capable of occurring at different stages of the life cycle of invading species. The same can be said between the facilitation and tolerance model. In an experimental study of succession on Mount St. Helens, a perennial lupine Lupinus lepidus was examined for its effects on two common colonists (Anaphalis margaritacea and Epilobium angustifolium) of the Pumice Plains in Mount St. Helens. Lupine, being a nitrogen-fixing legume, was expected to facilitate the establishment of other species colonies, increasing the levels of nitrate, and also for its capability to supply shade in environmental conditions of high surface temperature and low moisture. Inhibitory effects of lupine were at the same time also expected, as large lupine patches only persisted in monocultures and because the spatial distributions of the two main colonists (Anaphalis margaritacea and Epilobium angustifolium) did not correlate with that of lupines. As a result, it was shown that Lupinus lepidus performed a combination of beneficial and disadvantageous effects (i.e. facilitative and inhibitory) on the establishment of the two common species of the Pumice Plains. This supports the proposal that a balance of facilitative and inhibitory effects exists in the influence of early species on later invading species. Depending on perspectives, the mechanisms of facilitation and inhibition act on different stages of the life history of succession species (i.e. inhibitory effects on seedling survival, while facilitative effects are observed in seedling growth of A. margaritacea and E. angustifolium in lupine patches). Similar results were seen in woody plant establishment in abandoned agricultural fields of New York. Different species at different life stages, supported all three of the succession models; the facilitation model being supported in increased seedling emergences and survivorship with herbs existing, tolerance seen in some cases of seed predation and seedling emergence, and the inhibition model supported in cases of decreased growth and survival of seeds and seedlings in the presence of herbs in the state of environmental stress.
As shown, the three models proposed by Connell and Slatyer are not conflicting hypotheses, but simply a classification of different possible outcomes which may occur at different circumstances. The three mechanisms of succession, facilitation, tolerance, and inhibition, do not oppose one another because of its capability to act on different stages of the life history of species in the community within the succession sequence.
  • Crawley, M. Plant Ecology. Blackwell Science 1997.
  • Schulze, E.D., Beck,E. and Muller-Hohenstein K. Plant Ecology. Springer 2005.
  • Finegan, B. 1984. Forest succession. Nature 312:109-114
  • Gill, D.S. and Marks, P.L. 1991. Tree and shrub seedling colonization of old fields in central New York. Ecological Monographs 61(2):183-205
  • McCook, L.J. 1994. Understanding ecological community succession: causal models and theories, a review. Vegetatio 110:115-147
  • Morris, W.F. and Wood, D.M. 1989. The role of lupine in succession on Mount St. Helens: facilitation or inhibition? Ecology 70(3):697-703
  • Pickett, S.T.A. Collins, S.L. and Armesto, J.J. 1987. A hierarchical consideration of causes and mechanisms of succession. Vegetatio 69: 109-114


Advanced Course in Regional Planning II

QUIZ I: Plant Community that makes below-ground competition more than above-ground competition.
In general, plants are likely to compete for three kinds of essential resource photosynthetically active radiation (PAR), water, and essential nutrients. Results from some studies have conclusion that belowground adult-juvenile competition is little or no importance for seedling regeneration. However, three line of evident and one piece of theory suggest that release from below-ground competition for nutrients may increase seedling growth and survival rates: field trenching experiments, pot experiments, field observations, and optimal foraging theory.
Below-ground competition have significant effect if plants growing on a community with nutrient-poor soil but not on nutrient-rich soil. This is suggested that, on nutrient-poor soil, seedling are competing with adult trees for nutrient as well as PAR, or root of plant competition in uptake water or nutrients was very high. The other experiments shown that many plant species can increase growth rates with nutrient additions.
One example of plant community with nutrient-poor soil is forest or green plant community in the dry-land ecosystem. In this community the light and carbondixide may be enough for their requirements. However, their requirements for water and soil nutrient are nor available. Therefore above-ground competition for light, and carbondioxide are not high, however below-ground competition is too hard because soil poor in water and nutrient contain. As we known that water and nutrient are important factor for physiological process in plant growth. Water is needed in the photosynthesis process. Water deficiency has direct effect on plant metabolism. In photosynthesis water storage affects carbon dioxide supply, the photochemical reactions which combine water and carbon dioxide, the chemical reduction and the translocation of photosynthates. Therefore in this community, below-ground competitive more than above-ground competition.
QUIZ II. Any herbivores in the field and their effects on plant growth (In this quiz I would like to explain about effect of any herbivores to the plant based on information that I get from some paper).
Herbivores have played and affect to the plant growth. Some studies shown this role. For examples: defoliation by herbivores is among the main factors limiting plant growth. Defoliation may lead to carbon accumulation if it remove a substantial part of nutrient reserves of a plant growing in a nutrient poor soil. Herbivores significantly affected floral trait and female fitness of plant.
1. Mollusc (Helix aspersa, Capaea hortensis, and Arianta arbustorum), and aphid species (Sitobion avenae) on 24 grassland plant species.Herbivory had significant and large effect on above-ground biomass after growing season. Invertebrate herbivores (in moderate and high soil fertility)fed selectively on early successional, fast- growing species, thus increasing the relative abundance of later successional, slow-growing species. This support that herbivory increases the rate secondary succession. Flowering and viable seed production of early successional ephemerals was also reduced by invertebrate herbivores across a wide range soil fertility.
2.Vertebrate herbivores : large and small mammal (rabbit) on Trientalis europeae
The effects of herbivory on standing biomasss were dramatic, significantly reducing above-ground biomass/production and expansion of the root zone. Above-ground biomass, below-ground production, soil elevation and expansion of the root zone decreased due to herbivore activity.Vertebrate grazers (mainly small rodent) feed on young shoot of Trientalis europaea in the spring. Vertebrate grazing affected all phases of the pseudo-annual life cycle of T. europaea. Grazing prevented flowering and fruiting, increased ramet mortality during summer and decreased tuber production. Futhermore, grazes ramets produced shorter stolonsand smaller tubers, which in turn had a lower winter survival and produced smaller ramets in the following growing season. The larger impact of grazing was due to the consumption of the whole of the single shoot of ramets of T. europaea. Althought regrowth was possible, secondary shoots were significantly smaller and assimilation was delayed.
III. Environmental factor that greatly influences plant community structure.
There are two factors that influence plant community structure: the abiotic factor (non-living) and the biotic factor (living). Examples of abiotic factors which affect to plants are temperature,, light, soil structure, water and nutrient supply. The biotic factors includes genetic potential and variation within species, plant/animal interaction, plant competition, mutualism and paratism. Each factor has influence specifically, and collectively determine plant community structure.
However, the greatly environmental factor that great influences plant community structure is light. Because the quality and quantity of light affects plant growth and development, and almost community are green plant. Visible light is essential to all green plants as the energy source for photosynthesis; infra-red and far-blue radiations play an important role in photoperiodism, and ultra-violet radiations, however, can be harmful to living organism.
The light requirements of different plan species result in the development of complex stratified communities. Green plant vary in their requirement for light and many species have morphological and phyological adaptations which maximise their growth efficiency under different light intensity. Morphological and physiological adaptation of plant influence plant community structure. Therefore light is a greatly factors that influence plant community structure.
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