Day 268 - 24 Jun 96 - Page 25

     
     1        The climate is typical of rather damper savanna areas, with
     2        an average precipitation of 700-1600 millimeters and a very
     3        strong dry season during the southern winter, while average
     4        annual temperatures are 20-26 degrees Celsius.   The soils
     5        are dystrophic, with low pH and availability of calcium and
     6        magnesium, and high aluminium content.  They are always
     7        well-drained and in this the species-rich cerrado contrasts
     8        with the seasonally-inundated, species-poor, hydrologic
     9        savannas common north of the Amazon.
    10
    11        The typical pattern of vegetation in the cerrado landscape
    12        consists of cerrado (tree-savanna) on the well-drained
    13        interfluves and gallery forests following the watercourses.
    14          The tree-savanna itself is of very varied form, ranging
    15        from dense, grassy field with a sparse covering of shrubs
    16        to an almost closed woodland with a canopy height of 12-15
    17        metres.  It is often difficult to discover the cause of
    18        these differences in vegetation structure but fire is
    19        frequently an important factor.  The cerrado flora, like
    20        that of all savannas, is, of course, resistant to fire and
         has all the usual adaptations such as thick corky bark,
    22        lignotubers, tunicate leaf-basis, etc., but nevertheless
    23        too frequent burning causes destruction, particularly of
    24        trees and shrubs.
    25
    26        Traditionally the cerrado domain was an area of sparse
    27        population of Brazilian country-people (backwoodsmen) and
    28        Indians.  The domestic economy was largely based on
    29        low-density cattle-grazing in the cerrado vegetation,
    30        raising small crops in clearings in the gallery or
    31        deciduous forests, charcoal-burning (if there was an
    32        accessible market), and some hunting and fishing.  The
    33        native vegetation provided materials for housing (timber,
    34        palm thatch, etc.), seasonable fruits, fibre, firewood, and
    35        many other products for the rural economy.  All this has
    36        now changed, however, and during the last 20 or so years
    37        the cerrados have been extensively developed for
    38        agriculture with the active encouragement of the Brazilian
    39        government.  Such development is an important part of the
    40        policy to develop the empty centre of Brazil and
         incorporate it into the national economy.  The best known
    42        elements of the same policy were the building of the new
    43        capital city, Brasilia, right in the core of the cerrado
    44        area, and the construction of a vast system of national
    45        highways.
    46
    47        Encouragement for the agricultural development of the
    48        cerrados has consisted over the years in various forms of
    49        direct subsidy, extremely generous tax incentives, low
    50        interest loans with no indexing (practically a donation in
    51        an economy suffering from hyperinflation), guaranteed
    52        prices, etc.  As intended, such incentives have led to the
    53        establishment of a massive, highly mechanised, capital
    54        intensive system of agriculture.
    55
    56        Cerrado vegetation, with its small trees, is much more
    57        easily cleared than tall forest and the soil is of good
    58        structure for cultivation.  However, before cultivation can
    59        take place a heavy application of lime and fertilizer is
    60        necessary to counteract soil acidity and to get rid of the