Earth Day 2016: Lichens and Mosses are Nature's Indicator of a Healthy Environment

Lichens are indicators of clean air, in the order of increasing pristine condition: crustose, foliose, fruiticose.  How do you rate the place you are living in?

Dr Abe V Rotor

Ecologists are learning from lichens and mosses as natural indicators, a sort of barometer, of environmental conditions.  They thrive best where the air is clean; temperature change is moderate, so with relative humidity, the vegetative cover undisturbed, the rivers and lakes full. From various observations and scientific researches, it is believed that lichens and mosses and their kind thrive best where man's intervention is least – or none at all.  

        

Top photo: Country lass poses with living specimens of lichens and mosses growing on ilang-ilang tree. Lower left photo: A closeup of lichens and mosses around a cast skin (exoskeleton) of cicada (kuliglig) which has just emerged. Right: A lichen-bryophyte complex found on cycad. Its species composition is unknown. It is a good subject of study. All these organisms are biological indicators of a good environment in Greater Lagro. They are Nature’s barometer of good climate and clean air.  

The Lichens – Earliest and longest known model of symbiosis  

A lichen is a group of two distinct genera of different kingdoms in the phylogeny of living organisms - alga (Kingdom Protista) and fungus (Kingdom Mycophyta) or in other cases bluegreen (Cyanophyta, Kingdom Monera) - living inseparably, a relationship developed through millions of years of evolution.  

Instead of each member developing its own adaptation, the two joined forces so to speak, in order for both to survive.  It is a perfect example of evolution through
cooperation, instead of competition as in most cases of evolutionary success.

The alga being photosynthetic manufactures food which it shares with the fungus.  The fungus on the other hand, being saprophytic, converts organic matter back into elemental forms which the alga again uses. Such a relationship consists of an enduring cycle - season in season out, year in year out, covering a span of hundreds if not a thousand years. Such a feat is among the wonders of the living world. If the
Redwood or Sequioa is the longest living individual which is estimated to be up to three thousands years, the lichen is the longest living union (mutualism). 

The key to such success through mutualism lies not only in highly efficient nutrient exchange, but gas exchange principally CO2 and O2, as well, more so, for their ability to transform rocks into living mass which they share with other living things in their own time and in the future. They are the precursors of succession in the living world. Which points out to another evolutionary tool - benevolence - the sharing of resources albeit destructive competition. 

Yet lichens are found in the most difficult areas like the Arctic and desert, on rock cliffs, even dilapidated and abandoned structures. Their resistance as well as vulnerability to changing environment has led scientists to use the lichen not only as environmental  indicator, but as pioneer organisms of a young ecosystem. 
How do you rate the place you are living in?

Left, crustose lichen; foliose lichen (leaf-like)

Young colony of squamous-foliose type of lichen on the trunk on acacia. Note its spreading and coalescing growth that will soon carpet a large area. Lichen is a closely knit association of algae and fungi in a state of symbiosis.

Fruticose lichen (right) hangs on  tree trunk. In spite of its epiphytic nature it does not harm its host because it is not parasitic. It shares however with the water and nutrients collected by the tree from rain and dust, as well as from the gradual wearing out of the bark tissues. 

Leave Nature Alone There is a simple old man living a hermit’s life close to the summit of Mt Pulag in Benguet.  It is reminiscent of the American philosopher Henry David Thoreau who lived by a pond (Walden Pond) deep in a woodland far away from town. Here on the country's second highest mountain, 'Tang Ben, when asked on how Nature is kept pristine, simply quipped with confidence and sparkle in his eyes. "Just leave Nature alone."  ~   

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Lichens are indicators of clean air, in the order of increasing pristine condition: crustose, foliose, fruiticose.  How do you rate the place you are living in?

--------------------------------------------------------It has been estimated that 6% of the Earth's land surface is covered by lichen. Lichens are informally classified by growth form into:

· crustose (paint-like, flat), e.g., Caloplaca flavescens
· filamentous (hair-like), e.g., Ephebe lanata
· foliose (leafy), e.g., Hypogymnia physodes
· fruticose (branched), e.g., Cladonia evansii, C. subtenuis, and Usnea australis
· leprose (powdery), e.g., Lepraria incana
· squamulose (consisting of small scale-like structures, lacking a lower cortex), 

                      e.g., Normandina pulchella
· gelatinous lichens, in which the cyanobacteria produce a polysaccharide that absorbs  and retains water.-----------------------------------------------------------

Bryophytes, Bridge of Evolution in the Plant Kingdom.


“Ah, but what good is a rock when it loses the essence on which life arises?”  avr

 

Imagine a lowly moss as a tree, and a liverwort as a large green carpet shaped like a liver. A hornwort has pinnacles in Gothic style. It is when you are small that you see small things big, and big things present themselves as giants.

Bryophytes are the dwarves of the plant kingdom, while the true or vascular plants are the giants. Mosses and liverworts are the early forms of plants, which botanists believe to have stopped evolving. What they were millions of years ago are what they appear today. They are living fossils.Observe a piece of rock covered with bryophytes. Under the magnifying lens you are looking at a miniature forest. It is thick and every space is taken by structures that look like stalks, leaves and other parts. On closer look these are not true organs because they lack vascular tissues, which in higher plants are for conduction of water and food and in providing support to the plant.

Since bryophytes are short-lived and seasonal, the soil deposit becomes thicker in each generation, while the borders extend to new frontiers. Soon whole trunks of tree, walls and rocks become covered like green carpet. As the bryophyte community reaches its peak and climax, more and more organisms become dependent on it. Insects frequent the place as a hunting ground for their prey. In turn predators of insects like amphibians and reptiles follow, then birds of prey – and a food web is formed.

Close-up of moss growing on a tree trunk. 

Feel the softness of a carpet of mosses on the wall or rock. It is thick and spongy. Now this is important because when it rains the carpet absorbs and stores water. In the night and in the morning dew precipitates and settles down making the surroundings cool.

Months, years pass. New plants rise out in the middle of the carpet. You are witnessing plant invasion. Soon the bryophytes will lose their dominance to ferns, and ferns to tracheophytes - annuals, biennials and trees. This is how an ecosystem is made together with its biodiversity.  This is how the La Mesa reservoir complex was made through thousands of years – a part of which is Lagro, the community in which we live today.

“What good is rock when it loses the essence from which life rises?”  Ask the lichen and the moss,  et al. ~

Luxuriant growth of moss; close-up of dewdrops clinging on moss.  

Two common bryophytes, liverwort (left) and moss in their reproductive stages. Bryophytes make a carpet of soil which is actually a combination of organic matter and minerals from weathered rock surface. Bryophytes produce acidic substances that break down compounds of calcium, phosphates and other materials. Through time with the process continuously repeated, soil builds up to the advantage of invading plants. A prototype ecosystem arises with the lichens and bryophytes taking the back seat. Biologist, Dr Anselmo S Cabigan examines lichens and brophytes growing on trees.