Microtopographic effects on growth of young bald cypress (Taxodium distichum L.) in a created freshwater forested wetland in southeastern Virginia

• Effects of initial soil amendments (compost and topsoil) and pit/mound microtopography on bald cypress (Taxodium distichum) growth in a ten year-old created tidal freshwater wetland were evaluated.
• Soil amendments had no significant effects after ten years, but the bald cypress trees showed a significant response to being planted in pits vs. mounds and their relative crown position was enhanced by competition from other woody species.
• Bald cypress growth in created wetlands would be enhanced by installation of microtopography and by planting viable cypress seedlings into shallow pits.

The purpose of this study was to determine the effects of soil treatments (ST) [fertilized sand (control) vs. added amendments of 78 Mg ha−1 compost (1×), 156 Mg−1 compost (2×), 15 cm of topsoil (TS), and 1 × compost + TS]; and restored microtopography (MT; level, pit and mound) on young bald cypress [Taxodium distichum (L.) Rich] tree growth in a created tidal freshwater wetland in southeastern Virginia. The crown class and position of each tree was classified according to the Kraft system ten years after establishment along with morphometrics of height (HT), trunk diameter at 10 cm above the soil surface (DIA 10), tree diameter at breast height (DBH at 1.3 m), and basal trunk swelling factor (D diff = DIA 10 − DBH). Additionally, competition effects of all planted and successional woody vegetation on the planted bald cypress were evaluated. There were no effects of soil treatments on the measured parameters, but there were strong overall experiment-wide effects of MT. Diameter at 10 cm (DIA 10) and basal swelling (D diff) were significantly (P < 0.05) greater in pits while overall height (p = 0.006) and DBH (p = 0.033) showed an even stronger response. Differentiation of individual tree crown classes and position was readily observable by year 10 and trees growing in pits were more likely to be in dominant and co-dominant positions (Kraft classes 1 and 2). The lack initial soil treatment effects (topsoil and compost additions) was surprising, but indicates that the overall quality of the site hydrology and initial soil substrate was high and therefore, microtopographic influences were dominant over the 10-year period studied. The results indicate that bald cypress plantings in created wetlands in this region would benefit from installed microtopography and that soil amendments per se may be less important.