Terrestrial Palaeoecology and Global Change

290 Valentin A. Krassilov. Terrestrial Palaeoecology
habit. The associated palynological assemblages of plicate-elaterifer-rimulate morphotypes
indicate a dominance of ephedroid and hirmerelloid components.
Two calculations were performed for the mid-Cretaceous biomes: one with the presentday
geography, the other with epicontinental seas (Fig. 114). Total mid-Cretaceous biomass
of the present-day continents would have been greater than the present-day biomass
(2421 Gt against 2039 Gt). The distribution would have been different, with a single
peak of biomass production at the high mid-latitudes (Fig. 115).
A reduction of terrestrial biomass with expansion of epicontinental seas and an adequate
increase in atmospheric CO 2
would have raised the mean global temperatures by no
more than 2°C relative to the present (an expected effect of doubling atmospheric CO 2
is
Fig. 115. Biomass (plant and soil carbon, Gt) distribution over latitudes.
A. Present-day distribution (generalized after UNESCO classification, 1973); (1) Equatorial and tropical
evergreen forests (451.7), (2) Tropical woodland, scrub and savanna (346.7), (3) Tropical semi-desert scrub
and steppe (46.7), (4) Mediterranean evergreen forest, scrub and woodland (159.9), (5) Temperate broadleaved
deciduous and mixed forest (390.6), (6) Temperate grassland, semi-desert (195.8), (7) Conifer rainforest
(19.7), (8) Boreal forest, taiga (327.5), (9) Tundra (178.7).
B. Mid-Cretaceous distribution (Fig. 114): (1) Xeromorphic scale-leaved biome (128), (2) Xeromorphic
serrato-scale leaved biome (275.4), (3) Mixed evergreen biome (lauro-coniferous of Mediterranean type)
(369.6), (4) Mixed deciduous biome with evergreen elements (sequoio-platanoid with laurophylls) (374.1),
(5) Coniferous biome of temperate rainforest type with Sequoia and Cupressinocladus (426.4), (6) Mixed
deciduous (parataxodio-platanoid) biome (109.7).