Phenology and water relations of tree sprouts and seedlings in a tropical deciduous forest of South India

Abstract

The phenology of sprouts (>1 year old, up to 1.5 m in height) and seedlings (<1 year old) of six woody species (four deciduous, one brevi-deciduous, and one evergreen) was examined during the dry season in a tropical deciduous forest of South India. Xylem water potential ( x ), leaf relative water content (RWC; % turgid weight), and xylem specific conductivity (K S ; kg s −1 m −1 MPa −1 ) of sprouts were measured on two occasions during the dry season. In addition, K S of seedlings (<1 year old) of one deciduous and one evergreen species was determined to allow comparison with sprouts. x of deciduous species was significantly higher at the second sampling date and was accompanied by a significant increase in K S and RWC, while the brevi-deciduous and evergreen species did not show any difference in x . Seedlings of Terminalia crenulata (deciduous) and Ixora parviflora (evergreen) had significantly lower K S compared to sprouts, while seedlings of all four deciduous species shed their leaves much earlier in the dry season than did conspecific sprouts. More favorable water relations of sprouts compared to seedlings during the peak of the dry season may explain the

Relationship between annual rainfall and tree mortality in a tropical dry forest: Results of a 19-year study at Mudumalai, southern India

“…Deciduous trees in tropical dry forest may also be more resistant to xylem cavitation (Maherali et al, 2004) or adapted to reduced leaf area index when soil water is deficient. Regeneration in fire-prone tropical dry forests is also mainly through sprouts (Sukumar et al, 1998(Sukumar et al, , 2005 that are less vulnerable to dry season water deficit as compared to seedlings (Saha et al, 2005). Thus, deciduous forest trees in the seasonal tropics may show a longer lag response to rainfall deficit before they wilt and die as compared to evergreen forest trees in the aseasonal tropics.…”

Linking the patterns in soil moisture to leaf water potential, stomatal conductance, growth, and mortality of dominant shrubs in the Florida scrub ecosystem

“…Soil moisture reductions lead to declines in gasexchange and leaf water potential, possibly leading to plant die-back or mortality, depending on the drought severity (Borchert 1994;Breshears et al 2005;Saha et al 2005;Gitlin et al 2006;Otieno et al 2006). For example, a 30% decrease in soil moisture, compared to the control, led to a mean decline of 53% in stomatal conductance (g s ) for isohydric (leaf water potential stable across seasons) Quercus ilex (Asensio et al 2007).…”