Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Historia Plantarum (Theophrastus) wikipedia , lookup
Base-cation saturation ratio wikipedia , lookup
Ornamental bulbous plant wikipedia , lookup
Plant physiology wikipedia , lookup
History of the forest in Central Europe wikipedia , lookup
Hydroponics wikipedia , lookup
Indigenous horticulture wikipedia , lookup
Glossary of plant morphology wikipedia , lookup
第九集 檜木森林的共生現象 大片頭 30”Forest Story of Taiwan Within the forest it is actually not as quiet as the naked eye sees it Organisms both depend on and compete with one another for survival This is Yuanyang Lake Nature Reserve // situated on 110 Forest Road off the Northern Horizontal Highway As the towering cypress trees strive to survive at the same time many organisms are also quietly and passively // marking their own territories within the forest 小 片 頭 : 片 名 字 幕 : Symbiosis Within the Cypress Forest Situated at 1670 metres above sea level being influenced by its topography and the north-easterly monsoon Yuanyang Lake has a high level of precipitation and humidity It also possesses a vast area of natural and structurally complete // yellow cypress (扁 柏) forest As rain falls rainwater will pass through the cypress’ canopy leaves and branches and finally penetrate into the soil As rainfall stops the bottom layer of the forest begins to stir Turning over a piece of fallen leaf a snail is slowly moving around The forest’s humid and dim environment // is a favourite habitat for snails Within the forest plants which cannot survive on their own will live off other trees The humid environment of the cypress forest // has provided a suitable habitat for the growth of many invertebrates It has also nurtured many epiphytes // as they live on other trees to obtain nutrients Many fern and orchidaceae plants are common examples of plants which live on tree trunks and branches for survival and growth To be defined as an epiphyte firstly the plant has to be one which lives on a tree // and does not touch the ground and secondly is that it does not extract nutrients from its host On the other hand parasitic plants are different in that // they will extract nutrients from their hosts Therefore while epiphytes need to evolve // so that they can produce their own nutrients for growth this is not necessary in the case of parasitic plants because some of them will grow roots deep into the bark // of their host trees to draw and absorb nutrients This is the biggest difference between the two On a global scale epiphytic plants are mainly distributed in tropical and subtropical rainforests as well as fog forests (霧林) in mountain regions Since their habitat is a foggy and rainy environment they can easily obtain sufficient amounts of water and nutrients Because of Taiwan’s relatively high level of humidity their growth is most lush at altitudes between 700 or 800 metres // and 2000 metres above sea level Anywhere above 2000 meters above sea level is too cold Because the roots of epiphytes are exposed in the air therefore they cannot withstand coldness The region where they are more lush // is what we call the fog forest zone (霧林帶) which is situated at an altitude // where fog builds up every afternoon This increases the level of humidity in the air thereby providing epiphytes with water vapour The level of competition within a forest environment // is actually fiercer than what we would expect it to be Plants fight for their own space for survival as well as other factors that they need for growth such as nutrients water space and sunlight They fight for all these things because those are what plants need // for their survival and growth So imagine an area of one square metre within which more than ten species of land plants are growing Originally epiphytes could have also been a land plant But because it could not compete against other land plants // within that area it eventually chose the tree as its place for growth Within the forest epiphytes often establish many unique symbiotic relationships // with other animals and plants For terrestrial molluscs such as snails because their skin do not have stratum corneum (角質層) // to prevent water transpiration the acquisition of water is very important to them Some snails will choose to stay in areas with a build up // of water by epiphytes in order to replenish water Bryophyte is also a common type of non-vascular epiphyte // found in the cypress forest and is the food for snails The very tiny and green bryophyte is a type of green plant // which enjoys humid environments Its most distinctive difference from fern plants and other vascular plants is that since it is quite small and does not grow very tall it can still flourish as long as such micro-habitats // exist within the forest Bryophytes are further classified into mosses and liverworts They are mainly small in size // and like to grow in humid environments It is actually quite easy to differentiate // between mosses and liverworts If you look at their leaves the leaves of mosses do not split apart It is a whole piece of leaf // and does not split into two segments With liverworts their leaves will split into two or three segments This is a very distinctive difference between the two As we enter Yuanyang Lake Nature Reserve we can see a vast spread of bryophytes // creating a pleasant green scene It appears that every giant tree // has put on a green velvety jacket Mr Chang after we enter the fog forest (雲霧森林) we can see traces of bryophytes everywhere Within a tropical fog forest zone (霧林帶) in a mountain region bryophytes are very typical plants Because it is very humid therefore you can virtually see their traces on many places // such as rocks and tree trunks Sometimes we would call such places a “moss forest” (苔林) Bazzania (鞭蘚) is a type of liverwort // commonly seen within the cypress forest It is a creeper plant which looks like highways // supported by concrete columns below Therefore this creepy Bazzania (鞭蘚) can wiggle its way around the cypress forest while carrying out the process of photosynthesis above // and being kept well-ventilated below 錦苔 is another unique type of bryophyte // found in the cypress forest because it grows vertically and can hang upside down It can still live when it is hung upside down on this branch When it comes to peat mosses (泥炭苔) those that grow randomly in swamps are so adaptive that they can grow just as well wherever you dump them Therefore the cypress forest is like a kaleidoscope // with a large variety of lives In terms of its evolution bryophytes are considered to be quite an early plant Originally they did not have a vascular structure and were the first group of plants // that got washed up onto land from the ocean They then gradually evolved to become a vascular plant Bryophytes were the earliest pioneer plants // that settled on land after being washed up from the ocean With plants such as ferns gymnosperms whose seeds are exposed externally as well as angiosperms which are also called flowering plants they all have vascular structures // arranged as tubes gathered in bundles which assist in the transporting of water and other substances However since the simple structure of bryophytes lacks vascular bundles they have a lower ability to transport water // and will therefore lose water more easily This is also a factor which limits the size and height of their growth The moss forest (苔林) is a very humid environment In such an environment the level of humidity is very high Because it is an epiphyte that lives on the tree trunk when the humidity level in the air is very high it can absorb water vapour from the air for survival Since other organisms cannot obtain water in such a way they will not be able to survive in such an environment So bryophytes actually have quite strong life endurance We also have another saying that they are a type of organism // that can become wet by themselves In other words within an environment where changes in the level of humidity // fluctuate quite rapidly they are still able to survive They are different from ordinary plants and are very unique in that their leaves // do not have a waxy type of component Their simple double-layered cells means that // they can directly absorb water from the air But what happens when it does not rain They will wither when the environment gets too dry but they will not die When the presence of water vapour returns they can rapidly become alive again During times of drought organisms have their own different ways to conserve water For snails which eat bryophytes as food since the thick slime secreted from their skin is high in density the rate at which water is lost from their body can be reduced Apart from obtaining water via food that they eat snails can also directly absorb water as they press the skin // of their abdominal foot flatly onto humid surfaces The abundance of water vapour brought by rain and fog belts (雲霧帶) // provide bryophytes with a suitable habitat As bryophytes live on the towering cypress trees their chances of absorbing nutrients are thereby increased They also intercept a large amount of water // for this cypress forest Mr Chang so bryophytes actually play quite an important role // within the forest, right See how this bryophyte lives on the branch As we mentioned earlier it can absorb water from the air and can also intercept fog water droplets So if we consider the whole forest as a system bryophytes can help absorb water from the air like sponges So in terms of a forest ecosystem they would perform the function of helping to bring water in So because it lives on its host tree the tree can actually absorb the water that it brings in thereby forming a mutually beneficial relationship Yes if we look at it from such a perspective it is certainly mutually beneficial In the case of Cilan mountain a bryophyte with a dry weight of one gram can intercept // and hold 0.63 gram of water in an hour’s time This is more than half its own weight and is one and a half times more than // the yellow cypress’ (扁柏) ability to intercept and hold water The absorption power of bryophytes is even being // used for medical purposes The peat moss (泥炭苔) that is commonly seen at Yuanyang Lake was once used as a replacement for absorbent cotton // for the bandaging of wounds Because there are numerous amounts of transparent dead cells // within dried peat moss these are able to rapidly absorb large amounts of water thereby promoting the healing process of wounds Apart from the interception of water bryophytes also have another function within the forest Some bryophytes have a nitrogen-fixing ability A nitrogen-fixing ability means that // it can directly take nitrogen from the atmosphere and transform it into a form of nitrogen // that can be consumed by plants So if it has this ability then it can directly transform what used to be nitrogen // that could not be previously consumed into nitrogen that can now be consumed by the ecosystem So for both itself and the ecosystem this provides a channel for the input of nutrients Bryophytes can grow on rocks rotten wood as well as fallen woods and branches It will gradually grow to form a carpet-like “mat” // on which it will stabilise water and nutrients This often becomes the substrate on which other vascular plants grow Can you see this This is the seedling of a yellow cypress (扁柏) See how it is growing on top of the bryophyte This is a very interesting phenomenon // that we can see in a fog forest zone (霧林帶) Often it is very difficult to see such cypress seedlings // on the ground But we can easily spot them on top of bryophytes We would think that because bryophytes // are able to help such seedlings obtain water and nutrients so this place is sort of like a safe haven // for them to sprout and grow If they can gradually grow and extend their roots // deep into the soil they might be able to grow into a huge tree Therefore we are able to see a very important role // which bryophytes play in this place When seeds land on top of bryophytes their opportunities for growth are opened Some bryophytes can even provide insects and invertebrates // with a habitat and place for laying eggs For example the majority of snails lay eggs on top of bryophytes so as to avoid getting dried up or to reduce // the chances of getting preyed on by enemies Because of its ability to directly absorb water vapour // from the air bryophytes are not threatened // by the lack of water within the soil Therefore they can be distributed in places // where seed plants cannot survive Bryophytes often are the pioneers in opening up places // such as alpine rocks and land surfaces that are exposed We often say that bryophytes are pioneer plants For example as this island first emerges there were no organisms at all Volcanic eruption has washed it clean // and left it in a sterile condition As this island begins to grow the very first arrivals may be lichens followed by bryophytes Either way such lichens and bryophytes have a naturally exploitative characteristic which is their ability to decompose rocks They way by which they do this is to use a chemical substance acid to slowly decompose them Then other micro invertebrates will excrete matters // that slowly break down the particles on the rock surface thereby loosening up the rocks into a form // similar to that of soil As seeds of higher-level ferns or the spores of angiosperms // are scattered onto this surface it is easier for them to embed and sprout The bryophyte layer has also provided activity space // for many soil organisms thereby creating a higher level of organism diversity // within the cypress forest ecosystem So what sorts of organisms actually live in the bryophyte layer Dr Hou and her students are currently conducting a research // into soil organisms at Yuanyang Lake They will bake the bryophyte sample collected // to observe the organisms within Previously when we collected samples of soil organisms we directly dug up the soil which we then baked // in order to get the organisms to come out When we arrived at Yuanyang Lake although we wanted to dig up the soil but it was not possible because it was completely covered // by a thick layer of bryophytes The soil layer was only extremely thin // and was fully covered by bryophytes So we decided that we would dig up the bryophytes // together with the soil beneath Then we actually discovered that there were large quantities // of soil organisms within the bryophyte layer The most abundant springtails and mites play the role of // what we usually call engineers of the ecosystem Springtails mainly eat fungus while apart from predatory mites species such as the oribatid mite (甲螨) // will directly graze on fallen matters So either way they will release nutrients // that were previously fixed within fungus and fallen matters and allow them to return into the soil which will in turn get absorbed by plants There is no one to fertilise a natural forest It simply relies on its internal circulation of nutrients For example snails eat plants to survive and scrape on rocks to absorb // calcium carbonate for the formation of their own shells At the same time such an action will increase the rate // at which rocks are decomposed which in turn releases minerals // back into the land for absorption by plants This is similar to the endless cycle where micro-organisms decompose fallen leaves and branches // within the bryophyte layer resulting in the release of nutrients As leaves and branches fall onto the forest floor every year the process of decomposition needs to depend // on the function of micro-organisms such as bacteria and fungus to transform them into nutrients // which can be absorbed and consumed by plants However during such a process micro-organisms also want to take these nutrients // for their own consumption Therefore a slightly competitive relationship for nutrients // will exist between plants and micro-organisms This is when animals within the soil // come in to adjust micro-organisms by feeding on them to achieve the result of // the adjustment of microbial biomass This way micro-organisms will not be able to take away all the nutrients as their numbers are being adjusted by soil animals After micro-organisms get eaten such nutrients will be excreted in the form of animal faeces which will then be absorbed and consumed by plants again Within fog forests (雲霧森林) that have extremely high precipitation // and therefore severe washouts the outstanding ability of bryophytes to conserve water and nutrients // becomes even more important We believe that the bryophyte layer plays a vital role because under normal conditions // where the layer of soil is so thin organisms within the soil virtually // do not have any space to survive However the bryophyte layer acts like // an extra layer of carpet-like space So in fact soil organisms are not directly living within the soil layer They actually live within the bryophyte layer Above the bryophyte layer are live bryophytes while underneath it // lie dead bryophytes and other fallen matters Therefore soil animals can act in between these two layers So on a physical level bryophytes have provided an extra topsoil-like layer // for the soil beneath In fact it has created an even better environment // than that of topsoil As we walk into a forest and see how well organisms big and small // flourish delightfully under the sun you will discover and feel the hustle and bustle // of the world within the forest But if you also have a scientific sense you will find that things are ever moving and developing // within that world Bryophytes have shown us a micro-world which we cannot usually see with our naked eye // to which we should place special value As we can see the forest is filled with organisms // which usually get underestimated and neglected These are in fact major contributors in balancing // the entire forest ecology thereby adding vitality to the forest vitality Within the forest not one single matter is at a standstill Everyday old trees wither and die new seedlings spring up from the ground and organisms strive between one another for survival Within the forest organisms are closely linked to one another for survival and we are no exceptions as we are also living on the same piece of land // on which forests live We must constantly remind ourselves to treat every single life on this land // with a more humble heart