RELATIONSHIPS AMONG ABIOTIC PARAMETERS AND BREEDING EFFORT BY 3 AMPHIBIANS IN TEMPORARY WETLANDS OF CENTRAL PENNSYLVANIA

We monitored 35 temporary wetlands in a ridge region (Rothrock State Forest= 199l-R) of central Pennsylvania in 1991 and 15 temporary wetlands in each of three regions across a ridge (Rothrock State Forest=1992-R), plateau (Allegheny Front=1992-A), and valley (Barrens area, State Game Lands=1992-B) landscape in central Pennsylvania in 1992 in order to identify correlations among several abiotic variables and breeding success of three amphibians (wood frogs-Rana sylvatica, Jefferson salamanders-Ambystoma jeffersonianum, and spotted salamanders-A. maculatum). The number of egg masses deposited by A. jeffersonianum was correlated positively with pH (1991-R, 1992-R) and alkalinity (1991-R) and negatively with [Al] (1991-R). Egg deposition by A. maculatum was correlated positively with pH (1991-R) and pond volume (1991-R, 1992-B) and negatively with total cations (Na, K, Mg, Ca, specific conductance) (1991-R) and [Si] (1992-B). Egg deposition by R. sylvatica was correlated positively with pond volume (1991-R, 1992R) and dissolved organic carbon (1991-R). Three days following a rain event of 1.9 cm in April, 1991, the pH in four of nine ponds was significantly lower than three and five days prior to the rainfall. There were differences among some of the three regions in pond pH, [K], [Ca], [Al], [ortho-Pi] [dissolved organic carbon], alkalinity, [Zn], volume, and the number of egg masses of R. sylvatica and A. maculatum, suggesting that temporary ponds are rather heterogeneous in their abiotic and biotic characteristics. There are landscape scale patterns (ridge, valley, plateau) that are especially deserving of additional study. Amphibian breeding success in temporary ponds of central Pennsylvania can be predicted in part by abiotic conditions such as pH, [Al], [total cations], [dissolved organic carbon], [Si], and pond volume. Further work is needed to determine which of these variables are causally linked to amphibian breeding and why there is variation among sites and years in the degree of correlation among abiotic and biotic variables.