Fire-mobilized nutrients from hydrophyte leaves favor differentially Typha domingensis seedling growth

In wetlands, altered disturbance regimes can change species composition and favor the expansion of invasive species. In Central Mexico, Typha domingensis expands after fires to colonize areas previously dominated by other natives, but the mechanisms are unknown. To explore if the invasion is facilitated by nutrient release after fire, we tested the effect of ash from Schoenoplectus americanus and T. domingensis plants on the growth of T. domingensis seedlings. Schoenoplectus ash had higher concentration of soluble phosphates (0.68 ± 0.23 mg/g) than Typha ash (0.36 ± 0.08 mg/g). At two months Typha seedlings were taller (48 ± 8 cm) in the treatment with Schoenoplectus ash added than in either the treatment with Typha ash (29 ± 7 cm) or in the control (25 ± 6 cm). Aboveground biomass (1.03 ± 0.42 g, 0.36 ± 0.17 g, 0.27 ± 0.11 g) and belowground biomass (0.65 ± 0.24 g, 0.32 ± 0.11 g, 0.27 ± 0.11 g) showed the same trends. Typha seedlings fertilized with Schoenoplectus ash had the lowest root:shoot ratios, but the largest rhizomes (dry weight 0.07 ± 0.03 g), followed by those fertilized with Typha ash (0.04 ± 0.01 g) and control plants (0.03 ± 0.01 g). These results show that T. domingensis responds to increased phosphate availability from ash of other species by growing larger and allocating more to storage tissues. We conclude that fire promotes the spread of Typha by facilitating seedling growth especially in areas dominated by S. americanus.

► In wetlands altered disturbance regimes can favor the expansion of invasive species.
► Invasion of Typha domingensis seedlings was facilitated by nutrient release after fire.
► Phosphorus in the ash increased Typha domingensis leave and root growth.
► Phosphorus content in ash is highly dependant on the species burned.