Fine Root Dynamics Following Single and Multiple Disturbances in a Subtropical Wet Forest Ecosystem

Silver, Whendee; Vogt, Kristiina

Live and dead fine root biomass and rates of root decomposition were studied prior to and immediately following a localized disturbance (experimental gap creation) and a landscape-level disturbance (Hurricane Hugo) in a lower montane subtropical wet forest in Puerto Rico. The effects of the hurricane on the previously disturbed environment (experimental gaps) were also examined to determine the effects of a multiple disturbance regime. A 40% decline in fine live roots occurred two months following gap creation. Six months following the hurricane, high fine root mortality resulted in a decline of 70-77% of the initial fine live root biomass in the experimental gaps; a similar decline occurred in the control forest. Root decay was slow and 48-65% of the fine root necromass still remained in trench plots after one year. Concentrations of Ca, Mg, K, P and N in fine roots (live plus dead) changed little over the course of one year. The loss of nutrients in live fine roots (kg ha-1) was equivalent to the loss of biomass. In the trench plot experiment, high root mortality resulted in lower concentrations of exchangeable cations in the soil, and a lower pH when compared to soil outside the trench plots. Concentrations of NO3-N were higher in the trench plot soils than in the surrounding soil environment and may have contributed to cation losses. Fine roots in this forest were not greatly diminished following localized disturbances and contributed to nutrient conservation. These root systems were more adversely affected by a. landscape-level disturbance and by a multiple disturbance regime. High root mortality following these disturbances may result in significant declines in nutrient availability.

Fine Root Dynamics Following Single and Multiple Disturbances in a Subtropical Wet Forest Ecosystem

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