TY - JOUR

T1 - Revisiting factors affecting deciduousness in tropical rainforests at a study site in coastal lowland rainforest in NE Australia

AU - Heise-Pavlov, Sigrid

AU - Hüppe, Joachim

AU - Pott, Richard

PY - 2008/11/20

Y1 - 2008/11/20

N2 - The proportion of deciduous trees has been analysed in a marginally tropical coastal lowland rainforest between the Daintree River and Cape Tribulation, NE Queensland, Australia, in relation to the climate, soil fertility and evolutionary aspects. Due to the relatively low seasonality index of 0.676 and the low inter-annual variation of rainfall (0.238) in the study area we expected a lower proportion of deciduous canopy trees in this rainforest compared to the monsoonal tropical northern part of Australia with an extensive dry season (seasonality index between 0.91 and 1.01). The extremely low proportion of 6% deciduous species is, however, in contrast to the proportions in other areas with similar seasonality and may be attributable to 1. the relatively high rainfall of 85 mm on average during each of the three driest months, 2. extremely wet conditions and consequently high runoffs (up to 65 % of the annual rainfall) which decreases the water availability in the soil during the dry season and contributes to low soil fertility due to erosion and nutrient losses, and 3. the presence of a high proportion of old lineages and primitive families of angiosperms related to evolutionary aspects of the development of deciduousness in angiosperms. Most leaf-shedding trees in this area can be classified as brevi-deciduous, shedding their leaves for about 2 to 3 weeks at the onset of the dry season, suggesting that decreasing day length and temperature may trigger leaf abscission. Species with a brevideciduous habit may have evolved here at times when evergreen forests were restricted to refugia. Climatically similar conditions are found in rainforests of humid and subhumid regions of Eastern Madagascar reflected by a low canopy height which is also observed in the study area. Reduced growth rates seem to be a more advantageous strategy than a deciduous habit.

AB - The proportion of deciduous trees has been analysed in a marginally tropical coastal lowland rainforest between the Daintree River and Cape Tribulation, NE Queensland, Australia, in relation to the climate, soil fertility and evolutionary aspects. Due to the relatively low seasonality index of 0.676 and the low inter-annual variation of rainfall (0.238) in the study area we expected a lower proportion of deciduous canopy trees in this rainforest compared to the monsoonal tropical northern part of Australia with an extensive dry season (seasonality index between 0.91 and 1.01). The extremely low proportion of 6% deciduous species is, however, in contrast to the proportions in other areas with similar seasonality and may be attributable to 1. the relatively high rainfall of 85 mm on average during each of the three driest months, 2. extremely wet conditions and consequently high runoffs (up to 65 % of the annual rainfall) which decreases the water availability in the soil during the dry season and contributes to low soil fertility due to erosion and nutrient losses, and 3. the presence of a high proportion of old lineages and primitive families of angiosperms related to evolutionary aspects of the development of deciduousness in angiosperms. Most leaf-shedding trees in this area can be classified as brevi-deciduous, shedding their leaves for about 2 to 3 weeks at the onset of the dry season, suggesting that decreasing day length and temperature may trigger leaf abscission. Species with a brevideciduous habit may have evolved here at times when evergreen forests were restricted to refugia. Climatically similar conditions are found in rainforests of humid and subhumid regions of Eastern Madagascar reflected by a low canopy height which is also observed in the study area. Reduced growth rates seem to be a more advantageous strategy than a deciduous habit.

KW - Australia

KW - Deciduousness

KW - Evolution

KW - Primitive flowering plants

KW - Rain forest

KW - Seasonality

KW - Soil fertility

UR - http://www.scopus.com/inward/record.url?scp=57649100808&partnerID=8YFLogxK

U2 - 10.1127/0340-269X/2008/0038-0213

DO - 10.1127/0340-269X/2008/0038-0213

M3 - Article

AN - SCOPUS:57649100808

VL - 38

SP - 213

EP - 219

JO - PHYTOCOENOLOGIA

JF - PHYTOCOENOLOGIA

SN - 0340-269X

IS - 3

ER -