Cálcio em Braun-Blanquet (1932)

Temperature Graphs.—In order to determine the amount of heat which plant communities actually receive, it is necessary to have a self registering apparatus in the habitat. [Nota de rodapé 1: For aquatic communities ordinary measurements have given useful suggestions. Next to calcium content, water temperature is one of the most important factors in the composition of aquatic communities. In the Bryum schleicheri-Philonotis seriata flora of the springs of Feldberg in the Black Forest B. schleicheri dominates where the water temperature is 4 to 5°C. in early summer, but P. seriata where it is 7 to 8°C. Otherwise the habitats are alike, and the companion flora identical.] The problem is complicated by the fact that, strictly speaking, each layer of vegetation has its own peculiar temperature requirement. The upper layers influence the lower, making the climate more equable. (Braun-Blanquet 1932:85)

Measuring Rainfall.—The characterization of climate according to rainfall is the business of the weather service. Daily precipitation is measured and from this are obtained the monthly and annual means and the number of rainy days and their distribution throughout the year. The last two points are of especial importance for biology. In uninhabited places, especially in high mountains, the total annual precipitation alone is taken by means of rain collectors. The ample collecting vessel, with windshield, is supplied with 6 kg. of calcium chloride to prevent freezing. A thin layer of oil poured over the contents prevents evaporation. Thus one annual measuring and emptying suffices. This “totalizer,” by acting as dust collector, also gives important data on soil formation (cf. p. 176). The establishment of rain collectors at high altitudes in the Pyrenees and the Alps has brought out the important fact that the total precipitation in mountains increases up to very great heights. (Braun-Blanquet 1932:114)

For a better understanding of the relations between lime content of the soil and vegetation it will be necessary to distinguish between direct and indirect action of calcium. (Braun-Blanquet 1932:182)

Indirect Action of Calcium.—Calcium affects in large measure the physicochemical conditions of the soil and thereby, indirectly, the vegetation. Lime affects the coagulation and aggregation of the soil colloids whereby coarse crumby structure, water conduction, temperature, and aeration of the soil are favorably influenced. (Braun-Blanquet 1932:182)

Upon this indirect action of calcium ions depend a number of phenomena which have not always been adequately distinguished from the direct action of lime. (Braun-Blanquet 1932:182)

Many cryptogamic communities are perhaps even more strictly limited to the occurrence of highly saturated calcium solutions. The lime-encrusting tufa builders, Eucladium verticillatum, Gymnostomum calcareum, Cratoneuron irrigatum, form broad carpets on rocky slopes and walls which are constantly wet with waters rich in lime. The C. commutatum-Arabis bellidifolia association in all its facies is one of the regular phenomena of cold, calcareous springs in the Alps. Motyka (1926) describes a number of lime-constant lichen communities of the Tatra, such as the Lecanora lamarckii association, the Verrucaria calciseda sub-association, and the L. reuteri association. He stresses particularly the unusually sharp line of division between the lime constant and lime-avoiding lichen associations. Similar communities inhabit the dolomite of the Swabian Alps, such as the V. calciseda community with its several variants of central Germany (Kaiser, 1926) and the Alps. (Braun-Blanquet 1932:184)

To what extent the indifferent and lime-favoring species can tolerate lime it is at present impossible to state. In one essential the observed facts and experimental investigations tally; the Ca ions (and perhaps Mg ions) seem to be the decisive factor in regard to lime constancy; the direct action of the supply of calcium ions cannot be replaced by the physical properties of the soil. The occurrence of calcicolous (lime constant) communities is strictly dependent upon solutions rich in calcium. (Braun-Blanquet 1932:184)

Instructions for the determination of the calcium content as calcium oxide, CaO, are given by Wiegner (1926) and by Mitscherlich (1923). (Braun-Blanquet 1932:185)

Serpentine.—Raw serpentine soil supports plants which are indifferent to lime as well as many lime-favoring and even lime constant species, such as Trisetum distichophyllum, Ranunculus parnussifolius, Oxytropis montana, Rhododendron hirsutum, Doronicum grandiflorum, and Leontopodium alpinum. The occurrence of lime plants may be connected with the presence of calcium in the serpentine. A substitution of Ca by Mg ions may also be possible. According to Angel, an analysis of serpentine from Steiermark gave these percentages. (Braun-Blanquet 1932:188)

Darwin was the first to call attention to the importance of earthworms in working over the soil. By their burrows, which penetrate to a maximum depth of 7 m., they open up the lower layers of the soil. They grind up large amounts of earth with their principal food, which is decomposing plant materials. The excreta of worms are deposited occasionally within their burrows but usually on the surface of the ground in little spiral heaps. This material, as D’Auchald has ascertained, is richer in nitric acid and calcium carbonate than the original earth. For this reason the soil reaction of the worm excreta shows a somewhat lower H ion concentration. Salisbury, too, found a higher carbonate content in worm excreta, and thus, as compared to the acid soil, a lower H ion concentration. (Braun-Blanquet 1932:233)

Adsorptively saturated humus is formed when aeration is good and in the presence of electrolytes, especially calcium ions, which neutralize the acid humus substances. The more lime in the soil the more humus is neutralized. The mild, saturated humus is relatively coarsely dispersed, crumbly, easily penetrated by plant roots, of dark brown to black color. It absorbs large amounts of water, without changing into a gelatinous form. Its favorable soil condition furthers the growth of minute living organisms and thereby the production of carbonic acid with its chain of consequences. This in turn leads, according to Wiegner (1926, p. 31), to a decrease in dispersity. Coagulated, saturated humus shows more or less neutral or weakly basic reaction. Its buffering capacity varies greatly; it may be low (mull forms of the Scandinavian forest soils) or very high (Caricetum firmae of the Alps). Adsorptively saturated humus soils support economically good, highly productive meadow and forest communities, such as the Caricetum ferruginei of the Alps with its many luxuriant herbs, the Seslerieto-Semperviretum, and notably the tall-herb communities of the Adenostylion. (Braun-Blanquet 1932:250)

The lichen peat is poorly developed. Waren has also investigated the relations existing between the chemical composition of peat and the vegetation of the bogs and has found that here calcium is of great importance. (Braun-Blanquet 1932:251)

The humus soils are first leached out with HCl, in order to decompose the calcium compounds, then with alkah, to dissolve the humus acids. The more or less dark-brown coloration of the solution is compared with commercial Acidum huminicum and given a humification number according to the relation of its color to that of the [253] commercial product. Melin and Oden were thus able to prove that the humification of the high-moor peat is considerably hastened by drainage. Humification increases rapidly from the upper levels downward, as the following table illustrates: (Braun-Blanquet 1932:252-3)

BRAUN-BLANQUET, Josias. 1932. Plant sociology: the study of plant communities. (Trans.: George D. Fuller; Henry S. Conard) New York: McGraw-Hill Book Company.