Soluble sugar composition of pond-cypress: A potential hydroecological indicator of ground water perturbations

Pond-cypress, a deciduous conifer, is a dominant canopy species in depressi onal wetlands of the southeastern Coastal Plain (SCP). Extensive premature decline and death of pond-cypress trees in central Florida have been attrib uted to hydroperiod alterations due to excessive withdrawals of ground wate r from the Floridan aquifer. One factor identified in the decline process i s basal decay, which may be related to the presence of Botryosphaeria rhodi na and Fusarium species (nonaggressive, facultative fungal pathogens). Thes e fungi have been cultured from sapwood tissue of declining pond-cypress as sociated with ground water mining, but not from pond-cypress away from grou nd water mining areas. In this experiment, differences in soluble (nonstruc tural) carbohydrate composition of branch tips were evaluated for one- and two-year old, nursery-grown (unsheltered) pond-cypress, following a year of growth under treatment conditions (control, fungal inoculation, water stre ss, and fungal inoculation plus water stress) in a growth chamber. Results from two methods of wet chemical analysis were compared (trimethylsilyl met hylglycoside Method A, and alditol acetate - Method B). Three pentoses (ara binose, rhamnose, and xylose) and three hexoses (galactose, glucose, and ma nnose) were identified in branch tips from both age classes. A fourth hexos e (fucose) also was identified in samples from the younger trees. The acidi c sugar, galacturonic acid, was identified in both age classes using Method A. Results suggest that prolonged water stress is correlated with greater relative concentrations of the neutral soluble sugars rhamnose (P = 0.02), xylose (P = 0.02), and galactose (P = 0.02), in addition to the acidic suga r galacturonic acid (P = 0.01), for Method A, and arabinose (P = 0.02) for Method B. These results also suggest that in the absence of water stress, t he fungal pathogen B. rhodina does not penetrate to the sapwood of the tree s, and that inoculation with this fungal pathogen is not correlated with di fferences in relative concentrations of nonstructural, soluble carbohydrate s, based on Method A analysis. Empirical evidence suggests that pond-cypres s trees in depressional wetlands respond similarly to anthropogenic perturb ations of ground water, but not to natural periods of drought in the absenc e of such perturbations. Therefore, pond-cypress appear to be integrators o f groundwater perturbations. Greater concentrations of the soluble sugars i dentified in this study in pond-cypress branch tips may be hydroecological indicators of such anthropogenic perturbations as unsustainable yield from the regional aquifer and adverse impacts from aquifer storage and recovery (ASR) activities in the SCP.