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Frost Damage of Cerrado Plants in Botucatu, Brazil, as Related to the Geographical Distribution of the Species

1977; Wiley; Volume: 9; Issue: 4 Linguagem: Inglês

10.2307/2388143

1744-7429

Ilse Silberbauer-Gottsberger, Wilfried Morawetz, Gerhard Gottsberger,

Forest ecology and management

A very severe frost with temperatures down to -6.00C in July 1975 in the region of Botucatu, Sio Paulo State, caused not only damage to crops but also to natural vegetation. The frost damage to woody plants was studied on 40 tree species and 10 shrub species. A frost-damage index for each individual was obtained, and the average index for each species calculated. Of the 50 species, 9 were not damaged, 9 were damaged slightly, 17 moderately, 13 substantially, and 2 totally. The average index of frost damage for species was 8.3 percent. In a 400 m2 plot where all the individuals were counted, the frost damage was only 5.8 percent per individual. It was shown that species which are less resistant to frost are less frequent in the area. In many cases a clear relation between the degree of frost damage of species and their geographical distribution could be seen. Species which are distributed more to the north and which in Sio Paulo have their most southern occurrence were nearly totally or substantially damaged. Species which occur also to the south of Sao Paulo State, but whose genus as a whole has its distribution center in northern, warmer regions, had notable damage too. Species which occur in the Brazilian Planalto Central, and which in some cases go even further south than the State of Sao Paulo, showed negligible or no damage. Of two species of the same genus, the more northern species was more damaged and less frequent than the southern species. Frost seems to be one of the selective factors influencing the floristic composition of the at its southern limit. TH.E PRESENT PAPER gives the results of a study of the damage to cerrado (semideciduous xeromorphic woodland) plants by frost, which was carried out in the municipality of Botucatu, Sao Paulo State, Brazil. The city of Botucatu is situated on the Serra (Cuesta) de Botucatu, which in places reaches about 950 m altitude. The plateau is principally formed of Botucatu sandstone, yielding in general a poor sandy soil. The southern side of the Serra forms a steep slope, whereas the northern and northeastern sides slope more gently. The area was originally covered by semideciduous, mesophyll forests, cerrados, and some strips of natural grasslands bordering gallervforests, these distributed in mosaic fashion. The natural vegetation, however, is now widely replaced by cropland and pastures. The climate of the Serra region at about 800 m altitude is characterized by an average yearly precipitation of about 1350 mm and an average temperature of 19.4?C. A rainy season from October to March, with 1100 mm average precipitation, alternates with a dry season from April to September with 250 mm average precipitation. The average monthly temperatures increase abruptly from July, the coldest month, with 17.50C, to September with 20.6?C, then more steadily to January with 21.7?C, and decrease slowly to March and then more abruptly to June and July. The absolute maximum of monthly temperatures for the years 1959 to 1968 was 34.5?C in September and 27.5?C in June. The absolute minimum in the same period was 10?C in October to May, decreasing to O.1?C in August (Tubelis, Nascimento and Foloni 1971). Corresponding values for the lower parts of the Serra, such as where the following observations were made, would be slightly different, but are not presently available. In July 1975, the region of Botucatu. like large parts of south and southeast Brazil, was exposed to the lowest temperatures in 57 years. The resulting frost not only caused damages to crops such as coffee, sugar cane, bananas, etc., but also to the natural vegetation. Frost is a more or less regular phenomenon in the State of Sao Paulo. Since 1892 about 26 frosts have been registered, 12 of which are dassified as severe, 3, including the last one, as very severe, and the rest as moderate (Anonymous 1975:4). BIOTROPICA 9(4): 253-261 1977 253 1 Current address: Botanisches Institut, Universitit Wien, Rennweg 14, A-1030 Wien, Austria. This content downloaded from 207.46.13.151 on Wed, 28 Sep 2016 04:24:43 UTC All use subject to http://about.jstor.org/terms The minimum temperature measured in open vegetation on July 18, the coldest day of the year, was 5.8?C at Fazenda Sao Manuel (a few km SW of city of Sao Manuel at about 700 m altitude). This fazenda is 12 km SW of the studied area at an altitude 150 m higher. The vegetation of the Serra de Botucatu plateau (highest elevation at Rubiao Junior, about 950 m) was damaged more than the surrounding lower region. Forest and vegetation showed significant symptoms of damage. Leaves died on most trees, causing a brown, dry appearance of forest and cerrado. Frost damaged the leaves, branches or even whole trees of many species. Some other species, however, showed no damage. About two months later, but still before the first rains, the old leaves had fallen, and new ones had sprouted that turned the landscape to a fresh, light green. MATERIAL AND METHODS The frost damage to woody species of the vegetation was studied in the municipality of Botucatu, in an area 18 km north of Botucatu and 14 km east of Sao Manuel, at 22045'S, 48025'W. It is situated on the northern spur of the Serra de Botucatu on a slight elevation, at an altitude of 550 m. The average temperature, therefore, is slightly higher than that of the city of Botucatu, whose climatic data were previously given. The whole study area of about 60 hectares is a remnant of natural vegetation, more or less undisturbed for at least the last five years. The varies from denser tree and scrub woodland form (low cerradao) on top of the elevation to a semi-open tree and scrub woodland form (cerrado sensm stricto) on one slope (Fig. 1), to a quite open scrub form (campo cerrado) on the opposite slope, which is separated from the first slope by a narrow valley with a low scrubby gallery forest. The area was visited twice: first, a few days after frost to see the actual frost damage to leaves and buds, and the second time two months later, to see where on the plants new buds had sprouted and what part of the trees had definitely died. In an area of approximately 1.5 hectares of sensmr stricto, 151 individuals of 50 different woody species were examined, including 40 tree species of the 45 tree species occurring in this part of and 10 shrub species. The number of tree species and the delimitation of what we call tree or shrub are based on a quantitative study of this (Silberbauer-Gottsberger and Eiten, in preparation). The families and species involved are given N ..:v ... .. .::SS.::e.R FIGURE 1. General view of the semi-open tree and scrub woodland (cerrado sensa stricto) at the end of the dry season. The tall trees in front are Sclerolobium aureum and Styrax tferuginea.