Suchergebnisse

Response in growth of maize to temperature was studied under controlled conditions. The growth of plants was measured in terms of :
I. Growth characters
A. Stem, (1) surface area (πdh) (2) volume (πr2/h)
B. Leaves, (1) area, (2) dry weight
II. Growth attributes or physiological components of growth
A. Net assimilation rate (NAR)
B. Relative growth rate (RGR), (1) dry weight (R), (2) leaf area (RL)
C. α coefficient (R/RL)
III. Morphological components of growth
A. Leaf area ratio (LAR) : leaf area/total dry weight
B. Leaf weight ratio (LWR) : leaf weight/plant weight
C. Specific leaf area (SLA) : leaf area/leaf weight = 1/leaf thickness. The response was measured in terms of these characters and critically
analysed in relation to temperature and age of plants.

The present study deals with the productivity and photo-synthetic efficiency of a beechwood located in the belgian "Haute-Ardenne" ; this stand has an estimated dry biomass of 343 t/ha. The ecological productivity reachs 11,59 t/ha/year and the photosynthetic efficiency is 2,34 % according to the total radiant energy during the effective assimilation period. In connection with the total amount of radiant energy recorded throughout the year, the photosynthetic efficiency is only 1,18 %.

Biomass, water content and productivity of a 39 years old spruce stand have been studied during August 1966 at the «Plateau des Tailles» (Ardenne belge, 595 m above sea level) in a spot located close to the beechwood we previously dealed with. Total dry biomass was 166,4 t/ha ; out of this, the underground material is taking a part of 22,98 %. The annual productivity reachs 12,4 t/ha/year with a photosynthetic efficiency of 1,32 % if calculated on the basis of the total radiant energy throughout the year. According to the effective assimilation period only, the photosynthetic efficiency reachs a value of 1,88 %. These results are discussed with special reference to the values obtained in a beechwood.

Structure, dendrologie features and biomass of a 120 years old beechwood (Luzulo-Fagetum) have been studied during August 1966 at the « Plateau des Tailles » (Ardenne belge — 595 m above sea level). Ground vegetation is fairly well developed and its coverage is 89 % of the area ; canopy coverage reachs 68 %. Beech seedlings present a low vitality. The total dry biomass is 343 t/ha with a water content of 254 t/ha. On the whole, the herb layer contribution is 3,5 % of the dry biomass, while stocks and roots of trees stand for 18,6%.