Oak Woodlands Seedlings Life
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Many oaks have a delicate covering of lace green living material, hanging down in curtains. A very common, abundant" plant", this lace lichen, or Ramalina menziesii, is a combination of fungus and algae. Often called "Spanish Moss", lace lichen is not a moss. In fact, the "Spanish Moss" of the south-eastern states in not a moss either. Their "Spanish Moss" is a member of the Bromeliad family of plants, a family that includes pineapples! Oaks often have real mosses, often growing as a carpet on the upper surfaces of large branches that are well shaded.
Lace lichen, like the green lichens on rocks in the tundra, does not hurt the host. In this case, Ramalina can provide a great benefit to the host oak, by capturing wind-borne nutrients. Jean Knops, and other researchers at Hastings, studied the nutrient balance in oak for many years. Ramalina plays a very important role. Nearby pairs of trees, one stripped of Ramalina, and one left with abundant Ramalina (see picture below) were set up with buckets and jugs to collect what fell to the root zone of each tree. When the first rains fell, the water from the trees covered with lichens was as dark as strong coffee, while the water from the trees stripped of lichens was clear. Why? Have you ever noticed that if you wash your new car and park it outdoors, it is soon covered with a fine film? This dry film, or "dry deposition" occurs just about everywhere. In some places, it can contain a mix of rubber tire particle, nitrogen, sulfur and carbon by-products of combustion, along with dust. Near the coasts, when oceans foam and churn, tiny bubble pop and launch a spray of natural nitrogen, bits of organic matter and thousands of particles of salt- sodium and chlorine. All these compounds blow inland all year. In places where nitrogen oxides and ozone in smog is abundant, these lichens die. In the San Jacinto mountains near Los Angeles, these lichens were once found at the base of the mountains and on the coastal plains. Now, they are only found at elevations on the mountain above the layer of smog that forms each day. Dry deposition collects on the surface of leaves and the lichen in the oaks. Lichen surface area can far exceed that of the leaves. Lichens can rapidly start photosynthesis and growth from a "dead" stop, often only a few minutes after rainfall starts. During the long, dry summer, Ramalina�s surface collects dry deposition, and these nutrients are then rinsed off into the soil below the tree in the first few rains. The amount of nitrogen thus captured by the tree�s root zone is significant, and all the soils in the Santa Lucia mountains are nitrogen deficient. In fact, plant growth in these foothills is moslty limited by the low levels of nitrogen. To demonstrate this, even a single pile of cattle droppings will stand out for years on a hillside as a relatively bright, dense green patch of annual grasses. The amount of nitrogen added to the soil under an oak tree is about 25% of what a farmer would put on soil in a cornfield, one of the most heavily fertlized soils in agriculture. Some of the nitrogen added to the soild comes from the bodies of the Ramalina. Bits fall off all the time, and the nitrogen in the bits of lichen that hit the ground is rapidly removed by bacteria or animals. In one 2 ac. "exclosure" on Hastings (where deer are excluded with a 8 foot tall fence), the lichens actually grow to the ground. There, as soon as they hit the ground, they turn black as the soil bacteria which live by breaking down organic matter, find the lichen. Outside the enclosure, animals quickly glean and eat every bit of lichen that falls. Deer, rabbits and other animals will pick up most bits of Ramalina that fall each day. Deer and other grazing animals (cows) will maintain a "browse line"- an amazingly even line about 5 feet up from the ground, below which very little Ramalina hangs uneaten. Even if an oak is cut down, the nitrogen content of the soil remains high and a green spot persists for many years in the soil where the oak once stood. �����Ramalina also has a very bizarre photosynthetic pathway that incorportes sulphur from the atmosphere. In fact, atmospheric chemists were unable to account for the global balance of suphur until they had studied Ramalina from Hastings. They found the odd chemical pathway that absorbs sulphur in Ramalina and then in many other lichens. In the northern latitudes, where the landscape is meters deep in lichens (reindeer food), the amount of sulphur stored in the bodies of the lichens is an important part of the total amount of sulphur removed each year from the atmosphere of the earth.
� � � � ����Ramalina adds a unique grace to the Sycamores at Hastings. � � More pictures below.... � � �
� ������Here, you can see that the blue oaks on the left has had all of the Ramalina removed. On the trees to the right,, all of the Ramalina remains undisturbed. Under each tree, at least three chemically clean white jugs with funnels were placed to collect water. Mineral content of the water was compared between trees with and without lichen. �����In addition, large black, plastic buckets were placed under the trees to compare how much biomass falls from the trees with and without lichens. These buckets were then cleaned out and contents sorted into leaves, woody debris, acorns, flowers, etc. One of the discoveries was that the western fence lizard, Scleoporus occidentalis, leaps from trees to the ground. The same leaping lizard would be found week after week in the same bucket, released, and then discovered again at a later date in the same bucket. � � For additional reading about the role of Ramalina in the mineral cycle of the California oak forests, here are some references from the work done at Hastings: Boucher, V. L. and T. H. Nash III. 1990. The role of the fruticose lichen Ramalina menziesii in the annual turnover of biomass and macronutrients in a blue oak woodland. Bot. Gaz. 151:114-118. Boucher, V.L. and T. H. Nash III. 1990. Growth patterns in Ramalina menziesii in California: coastal vs. inland populations. Bryologist 93:295-302. Gries, C., T. H. Nash III, and J. Kesselmeier. 1994. Exchange of reduced sulfur gases between lichens and the atmosphere. Biogeochemistry 26:25-93. Knops, J. M. H., T. H. Nash III and W. H. Schlesinger. 1996. The Influence of epiphytic lichens on the nutrient cycling of an oak woodland. Ecological Monographs 66:159-179. Knops, J. M. H., T. H. Nash, V.L. Boucher and W. H. Schlesinger. 1991. Mineral cycling and epiphytic lichens: implications at the ecosystem level. Lichenologist 23:309-321 Kuhn, U. 1997. Spurengasaustausch klimarelevanter reduzierter Schwefelverbindungen zwischen Biosphare und Atmosphare: COS Transfer der Flechten und anderer biotischer Kompartimente. Dissertation Doktor der Naturwissenchafaften. Johannes Gutenberg-Universitat in Mainz. Kuhn, U. and J. Kesselmeier. 1996. Lichens involved in the exchange of carbonyl sulfide between the biosphere and the atmosphere. In Borrell, P. M., Borrell, P. , Cvitas, T., Kelly, K., and W. Seiler.(eds.) Proceedings of EUROTRAC Symposium �96.189-196. Computational Mechanics Publications, Southhampton. Kuhn, U., C. Ammann, A. Wolf, F. X. Meixner, M. O. Andreae, and J. Kesselmeier. 1999. Carbonyl sulfide exchange on an ecosystem scale: soil represents a dominant sink for atmospheric COS. Atmospheric Environment. 33: 995-1008 Larson, D.W., U. Matthes-Sears, and T.H. Nash III. 1985. The ecology of Ramalina menziesii . I. Geographical variation in form. Canadian J. Bot. 63:2062-2068. Larson, D.W., U. Matthes-Sears, and T.H. Nash III.1986. The ecology of Ramalina menziesii . II. Variation in water relations and tensile strength across an inland gradient. Canadian J. Bot. 64:6-10. Matthes-Sears, U., and T. H. Nash III. 1986. A mathematical description of the net photosynthetic response to thallus water content in the lichen Ramalina menziesii . Photosynthetica 20:377-384. Matthes-Sears, U., T. H. Nash III, and D. W. Larson. 1986a. The ecology of Ramalina menziesii . III. In situ diurnal field measurements of two sites on a coast-inland gradient. Canadian J. Bot. 64:988-996. ___________. 1986b. The ecology of Ramalina menziesii . IV. Estimation of gross carbon gain and thallus hydration source from diurnal measurements and climatic data. Canadian. J. Bot. 64:1698-1702. ____________.1987. The ecology of Ramalina menziesii . VI. Laboratory response of net CO2 exchange to moisture, temperature, and light. Canadian J. Bot. 65:182-191. Rundel, P.W. 1974. Water relations and morphological variations in Ramalina menziesii Tayl. Bryologist 77:23-32. Back to Top |
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Ramalina needs
sunlight and water to grow. Given a little moisture and water, it will
start photosynthesis in a matter of a few seconds, from a "dead"
start. It can sit in the hot, dry summers of California, or in a museum
drawer, for very long periodds of time, and appear dead. But as soon is
it is wet and in the light, it springs back to life. It can grow about
30% a year and is one of the fastest growing "plants" of Hastings.
We don't know why it grows more abundantly on some trees and not others,
given an equal amount of open branches without leaves in the winter on
otherwise similar trees. Ramalina will do better on deciduous
trees than on evergreen trees (more light in the winter on deciduous trees).
It is clearly spread by wind and birds (hummingbirds incorporate bits
of it into their nests, as do orioles). Dead branches occur on almost
all trees, even healthy ones. These dead branches often have large clumps
of Ramamlina because there is so much more light on a dead
branch, as the leaves are gone. Sometimes heavy rains and strong winds
will make the clumps of lichen heavy and exert a great deal of force,
often breaking off the weakest dead branches in winter storms. But clearly,
the lichens persist and thrive in otherwise healthy trees for decades.
