Leaf flushing phenology and herbivory in a tropical dry deciduous forest, southern India

Abstract

Patterns of leaf-flushing phenology of trees in relation to insect herbivore damage were studied at two sites in a seasonal tropical dry forest in Mudumalai, southern India, from April 1988 to August 1990. At both sites the trees began to flush leaves during the dry season, reaching a peak leaf-flushing phase before the onset of rains. Herbivorous insects emerged with the rains and attained a peak biomass during the wet months. Trees that flushed leaves later in the season suffered significantly higher damage by insects compared to those that flushed early or in synchrony during the peak flushing phase. Species whose leaves were endowed with physical defenses such as waxes suffered less damage than those not possessing such defenses. There was a positive association between the abundance of a species and leaf damage levels. These observations indicate that herbivory may have played a major role in moulding leaf flushing phenology in trees of the seasonal tropics.

Vegetative phenology of tropical montane forests in the Nilgiris, South India

“…According to our study in three montane forest sites, trees reach a peak in leaf flushing during the dry season before the onset of rains. This pattern was also observed in the deciduous forest trees from the same region (Murali & Sukumar, 1993). Similar dry season leaf flushing was also observed in other montane forest sites (Koptur et al, 1988;Sun et al, 1996).…”

“…In more seasonal forests such as tropical dry forests, rainfall is a crucial environmental factor that triggers the process of leaf flush or flower initiation (Reich & Borchert, 1984;Prasad & Hegde, 1986;Bullock & Solis-Magallenus, 1990;Murali & Sukumar, 1993) while Wright & van Schaik (1994) and Wright (1996) highlighted the influence of solar irradiance along with rainfall. Van Schaik (1993) proposed the insolationlimtation hypothesis, which predicts that unless limited by water availability, community-wide leafing and flowering phenology in tropical forests should coincide with the period of maximal insolation.…”

“…However, Borchert (1992) found that leafing and flowering events in tropical forest trees are more related to changes in water status of individual trees. The role of biotic factors such as herbivory on the evolution of timing of leafing events has also been examined in tropical forests (Aide, 1988;Lieberman & Lieberman, 1984;Murali & Sukumar, 1993).…”

“…Most of the studies on phenology were restricted to either lowland tropical moist forests (Medway, 1972;Frankie et al, 1974;van Schaik, 1986;Ashton et al, 1988;Bhat, 1992), which are extremely rich in species and aseasonal, or in dry forests (Prasad & Hegde, 1986;Bullock & Solis-Magallenus, 1990;Murali & Sukumar, 1993, 1994Borchert, 1994) where a strong seasonality exists and comparatively species poor. There are only a few studies on the phenology in montane cloud forests (Koptur et al, 1988;Sun et al, 1996;Berlin et al, 2000;Funch et al, 2002;Kudo & Suzuki, 2004).…”

<b>Vegetative and reproductive phenology of <I>Aquilaria malaccensis</I> Lam. (Agarwood) in Cachar District, Assam, India</b>

“…Flowering during the pre-monsoon season can be viewed as a strategy to make flowers more visible to pollinators and supply food sources during the poor periods of floral resources (Murali & Sukumar 1993). Species flowering during the pre-monsoon period can be capable of storing water in sufficient quantities to permit flowering even in the absence of rainfall (Borchert 1994).…”