1、第 九 集 檜 木 森 林 的 共 生 現 象大片頭 30”Forest Story of TaiwanWithin the forestit is actually not as quiet as the naked eye sees itOrganisms both depend on and compete with one another for survivalThis is Yuanyang Lake Nature Reserve / situated on 110 Forest Road off the Northern Horizontal HighwayAs the towe
2、ring cypress trees strive to surviveat the same timemany organisms are also quietly and passively / marking their own territories within the forest小 片 頭 ： 片 名 字 幕 ： Symbiosis Within the Cypress ForestSituated at 1670 metres above sea levelbeing influenced by its topography and the north-easterly mon
3、soonYuanyang Lake has a high level of precipitation and humidityIt also possesses a vast area of natural and structurally complete / yellow cypress (扁柏) forestAs rain fallsrainwater will pass through the cypress canopy leaves and branchesand finally penetrate into the soilAs rainfall stopsthe bottom
4、 layer of the forest begins to stirTurning over a piece of fallen leafa snail is slowly moving aroundThe forests humid and dim environment / is a favourite habitat for snailsWithin the forestplants which cannot survive on their own will live off other treesThe humid environment of the cypress forest
5、 / has provided a suitable habitat for the growth of many invertebratesIt has also nurtured many epiphytes / as they live on other trees to obtain nutrientsMany fern and orchidaceae plants are common examples of plantswhich live on tree trunks and branches for survival and growthTo be defined as an
6、epiphytefirstly the plant has to be one which lives on a tree / and does not touch the groundand secondly is that it does not extract nutrients from its hostOn the other handparasitic plants are different in that / they will extract nutrients from their hostsTherefore while epiphytes need to evolve
7、/ so that they can produce their own nutrients for growththis is not necessary in the case of parasitic plantsbecause some of them will grow roots deep into the bark / of their host trees to draw and absorb nutrientsThis is the biggest difference between the twoOn a global scaleepiphytic plants are
8、mainly distributed in tropical and subtropical rainforestsas well as fog forests (霧林) in mountain regionsSince their habitat is a foggy and rainy environmentthey can easily obtain sufficient amounts of water and nutrientsBecause of Taiwans relatively high level of humiditytheir growth is most lush a
9、t altitudes between 700 or 800 metres / and 2000 metres above sea levelAnywhere above 2000 meters above sea level is too coldBecause the roots of epiphytes are exposed in the airtherefore they cannot withstand coldnessThe region where they are more lush / is what we call the fog forest zone (霧林帶)whi
10、ch is situated at an altitude / where fog builds up every afternoonThis increases the level of humidity in the airthereby providing epiphytes with water vapourThe level of competition within a forest environment / is actually fiercer than what we would expect it to bePlants fight for their own space
11、 for survivalas well as other factors that they need for growthsuch as nutrients water space and sunlightThey fight for all these things because those are what plants need / for their survival and growthSo imagine an area of one square metrewithin which more than ten species of land plants are growi
12、ngOriginally epiphytes could have also been a land plantBut because it could not compete against other land plants / within that areait eventually chose the tree as its place for growthWithin the forestepiphytes often establish many unique symbiotic relationships / with other animals and plantsFor t
13、errestrial molluscs such as snailsbecause their skin do not have stratum corneum (角質層) / to prevent water transpirationthe acquisition of water is very important to themSome snails will choose to stay in areas with a build up / of water by epiphytes in order to replenish waterBryophyte is also a com
14、mon type of non-vascular epiphyte / found in the cypress forestand is the food for snailsThe very tiny and green bryophyte is a type of green plant / which enjoys humid environmentsIts most distinctive difference from fern plants and other vascular plantsis that since it is quite small and does not
15、grow very tallit can still flourish as long as such micro-habitats / exist within the forestBryophytes are further classified into mosses and liverwortsThey are mainly small in size / and like to grow in humid environmentsIt is actually quite easy to differentiate / between mosses and liverwortsIf y
16、ou look at their leavesthe leaves of mosses do not split apartIt is a whole piece of leaf / and does not split into two segmentsWith liverwortstheir leaves will split into two or three segmentsThis is a very distinctive difference between the twoAs we enter Yuanyang Lake Nature Reservewe can see a v
17、ast spread of bryophytes / creating a pleasant green sceneIt appears that every giant tree / has put on a green velvety jacketMr Changafter we enter the fog forest (雲霧森林)we can see traces of bryophytes everywhereWithin a tropical fog forest zone (霧林帶) in a mountain regionbryophytes are very typical
18、plantsBecause it is very humidtherefore you can virtually see their traces on many places / such as rocks and tree trunksSometimes we would call such places a “moss forest” (苔林)Bazzania (鞭蘚) is a type of liverwort / commonly seen within the cypress forestIt is a creeper plant which looks like highwa
19、ys / supported by concrete columns belowThereforethis creepy Bazzania (鞭蘚) can wiggle its way around the cypress forestwhile 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 forestbecause it grows ver
20、tically and can hang upside downIt can still live when it is hung upside down on this branchWhen it comes to peat mosses (泥炭苔)those that grow randomly in swamps are so adaptivethat they can grow just as well wherever you dump themTherefore the cypress forest is like a kaleidoscope / with a large var
21、iety of livesIn terms of its evolutionbryophytes are considered to be quite an early plantOriginally they did not have a vascular structureand were the first group of plants / that got washed up onto land from the oceanThey then gradually evolved to become a vascular plantBryophytes were the earlies
22、t pioneer plants / that settled on land after being washed up from the oceanWith plants such as fernsgymnosperms whose seeds are exposed externallyas well as angiosperms which are also called flowering plantsthey all have vascular structures / arranged as tubes gathered in bundleswhich assist in the
23、 transporting of water and other substancesHowever since the simple structure of bryophytes lacks vascular bundlesthey have a lower ability to transport water / and will therefore lose water more easilyThis is also a factor which limits the size and height of their growthThe moss forest (苔林) is a ve
24、ry humid environmentIn such an environmentthe level of humidity is very highBecause it is an epiphyte that lives on the tree trunkwhen the humidity level in the air is very highit can absorb water vapour from the air for survivalSince other organisms cannot obtain water in such a waythey will not be
25、 able to survive in such an environmentSo bryophytes actually have quite strong life enduranceWe also have another saying that they are a type of organism / that can become wet by themselvesIn other wordswithin an environment where changes in the level of humidity / fluctuate quite rapidlythey are s
26、till able to surviveThey are different from ordinary plantsand are very unique in that their leaves / do not have a waxy type of componentTheir simple double-layered cells means that / they can directly absorb water from the airBut what happens when it does not rainThey will wither when the environm
27、ent gets too drybut they will not dieWhen the presence of water vapour returnsthey can rapidly become alive againDuring times of droughtorganisms have their own different ways to conserve waterFor snails which eat bryophytes as foodsince the thick slime secreted from their skin is high in densitythe
28、 rate at which water is lost from their body can be reducedApart from obtaining water via food that they eatsnails can also directly absorb water as they press the skin / of their abdominal foot flatly onto humid surfacesThe abundance of water vapour brought by rain and fog belts (雲霧帶) / provide bry
29、ophytes with a suitable habitatAs bryophytes live on the towering cypress treestheir chances of absorbing nutrients are thereby increasedThey also intercept a large amount of water / for this cypress forestMr Changso bryophytes actually play quite an important role / within the forest, rightSee how
30、this bryophyte lives on the branchAs we mentioned earlierit can absorb water from the airand can also intercept fog water dropletsSo if we consider the whole forest as a systembryophytes can help absorb water from the air like spongesSo in terms of a forest ecosystemthey would perform the function o
31、f helping to bring water inSo because it lives on its host treethe tree can actually absorb the water that it brings inthereby forming a mutually beneficial relationshipYesif we look at it from such a perspectiveit is certainly mutually beneficialIn the case of Cilan mountaina bryophyte with a dry w
32、eight of one gram can intercept / and hold 0.63 gram of water in an hours timeThis is more than half its own weightand is one and a half times more than / the yellow cypress (扁柏) ability to intercept and hold waterThe absorption power of bryophytes is even being / used for medical purposesThe peat m
33、oss (泥炭苔) that is commonly seen at Yuanyang Lakewas once used as a replacement for absorbent cotton / for the bandaging of woundsBecause there are numerous amounts of transparent dead cells / within dried peat mossthese are able to rapidly absorb large amounts of waterthereby promoting the healing p
34、rocess of woundsApart from the interception of waterbryophytes also have another function within the forestSome bryophytes have a nitrogen-fixing abilityA nitrogen-fixing ability means that / it can directly take nitrogen from the atmosphereand transform it into a form of nitrogen / that can be cons
35、umed by plantsSo if it has this abilitythen it can directly transform what used to be nitrogen / that could not be previously consumed into nitrogen that can now be consumed by the ecosystemSo for both itself and the ecosystemthis provides a channel for the input of nutrientsBryophytes can grow on r
36、ocksrotten woodas well as fallen woods and branchesIt will gradually grow to form a carpet-like “mat” / on which it will stabilise water and nutrientsThis often becomes the substrate on which other vascular plants growCan you see thisThis is the seedling of a yellow cypress (扁柏)See how it is growing
37、 on top of the bryophyteThis 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 groundBut we can easily spot them on top of bryophytesWe would think that because bryophytes / are able to help such seedlings o
38、btain water and nutrientsso this place is sort of like a safe haven / for them to sprout and growIf they can gradually grow and extend their roots / deep into the soilthey might be able to grow into a huge treeTherefore we are able to see a very important role / which bryophytes play in this placeWh
39、en seeds land on top of bryophytestheir opportunities for growth are openedSome bryophytes can even provide insects and invertebrates / with a habitat and place for laying eggsFor examplethe majority of snails lay eggs on top of bryophytesso as to avoid getting dried up or to reduce / the chances of
40、 getting preyed on by enemiesBecause of its ability to directly absorb water vapour / from the airbryophytes are not threatened / by the lack of water within the soilTherefore they can be distributed in places / where seed plants cannot surviveBryophytes often are the pioneers in opening up places /
41、 such as alpine rocks and land surfaces that are exposedWe often say that bryophytes are pioneer plantsFor exampleas this island first emergesthere were no organisms at allVolcanic eruption has washed it clean / and left it in a sterile conditionAs this island begins to growthe very first arrivals m
42、ay be lichens followed by bryophytesEither waysuch lichens and bryophytes have a naturally exploitative characteristicwhich is their ability to decompose rocksThey way by which they do this is to use a chemical substanceacidto slowly decompose themThen other micro invertebrates will excrete matters
43、/ that slowly break down the particles on the rock surfacethereby loosening up the rocks into a form / similar to that of soilAs seeds of higher-level ferns or the spores of angiosperms / are scattered onto this surfaceit is easier for them to embed and sproutThe bryophyte layer has also provided ac
44、tivity space / for many soil organismsthereby creating a higher level of organism diversity / within the cypress forest ecosystemSo what sorts of organisms actually live in the bryophyte layerDr Hou and her students are currently conducting a research / into soil organisms at Yuanyang LakeThey will
45、bake the bryophyte sample collected / to observe the organisms withinPreviously when we collected samples of soil organismswe directly dug up the soil which we then baked / in order to get the organisms to come outWhen we arrived at Yuanyang Lakealthough we wanted to dig up the soilbut it was not po
46、ssible because it was completely covered / by a thick layer of bryophytesThe soil layer was only extremely thin / and was fully covered by bryophytesSo we decided that we would dig up the bryophytes / together with the soil beneathThen we actually discovered that there were large quantities / of soi
47、l organisms within the bryophyte layerThe most abundant springtails and mites play the role of / what we usually call engineers of the ecosystemSpringtails mainly eat funguswhile apart from predatory mitesspecies such as the oribatid mite (甲螨) / will directly graze on fallen mattersSo either way the
48、y will release nutrients / that were previously fixed within fungus and fallen mattersand allow them to return into the soilwhich will in turn get absorbed by plantsThere is no one to fertilise a natural forestIt simply relies on its internal circulation of nutrientsFor examplesnails eat plants to s
49、urvive and scrape on rocks to absorb / calcium carbonate for the formation of their own shellsAt the same timesuch an action will increase the rate / at which rocks are decomposedwhich in turn releases minerals / back into the land for absorption by plantsThis is similar to the endless cyclewhere micro-organisms decompose fallen leaves and branches / within the bryophyte layer resulting in the release of nutrientsAs leaves and branches fall onto the forest floor every yearthe process of decomposi
