Phenological differences in tree water use and the timing of tropical forest inventories: conclusions from patterns of dry season diameter change

Patterns of tree growth in relation to environmental variability in the tropical dry deciduous forest at Mudumalai, southern India

“…In particular, 100-200 mm stems constituted the modal frequency class with highest skewness values in all three intervals, lowest average growth rates in the first and third intervals, and highest kurtosis in the third interval (table 1), suggesting that competition affects growth most strongly in these saplings. The largest size classes in some common species appeared most sensitive to environmental stresses in the second interval, supporting earlier findings in other seasonal forests (Pelissier and Pascal 2000;Baker et al 2002).…”

“…Extreme shrinkage in large trees was excluded from analyses by conservative growth cutoffs; however, previous studies with dendrometers have shown that large trees, especially those with few neighbours, may experience greater seasonal drought stress and consequently shrink more than smaller trees (Pelissier and Pascal 2000;Baker et al 2002). Also, for some large trees in this forest with fire-adapted thick and fissured bark, measurement error may be up to 5 mm over the four-year interval.…”

“…However, an equally or more important resource gradient in the dry forests may be soil water availability, especially during seasonal droughts, and species may specialize or differentiate into guilds based on strategies to deal with seasonal drought stress (Baker et al 2002(Baker et al , 2003b. Hence, future attempts to separate dry tropical forest species into growth guilds might benefit from additional information on phenology, seasonal storage organs (including underground storage) and root growth strategies (Meinzer et al 1999;Enquist and Leffler 2001;Baker et al 2002Baker et al ,2003a, as well as factors associated with fire tolerance, such as root and stem coppicing, wood density and bark thickness (Gignoux et al 1997;Sukumar et al 2005).…”

“…Our results suggest that temporal variation of stem diameters in response to environmental variations such as seasonal drought, as well as its tolerance, can be considered as functionally plastic traits of tropical dry forest species. This may be mediated by seasonal expansion or shrinkage of elastic storage and transport tissues in the stem (Shell 1995;Baker et al 2002) that may facilitate rapid mobilization of water and nutrients between above-and below-ground organs of the plant Less commonly, in 100-200 mm dbh saplings of L. microcarpa increased densities may make this size class more vulnerable to unfavourable growth variations so that faster and less variable relative growth rates may be required to survive. Paradoxically, faster growth in medium saplings of K. calycina was associated with higher mortality due to elephants.…”

“…Previous studies using dendrometers to obtain daily, weekly or monthly measurements for up to two years in a range of forest types including dry lowland deciduous (Reich and Borchert 1984), moist semideciduous (Daubenmire 1972;Baker et al 2002Baker et al , 2003a, and wet evergreen forests (Breitsprecher and Bethel 1990;Pelissier and Pascal 2000) have demonstrated that intra-annual or seasonal diameter variations are generally positively associated with rainfall and soil water. However, longer term studies (without dendrometers) have suggested that on an annual basis the relationship between rainfall and growth might become negative as the average annual rainfall increases.…”