The objective of this study was to examine the effects of flooding …

• Abstract
• Introduction
• Materials and Methods
• Results
• Discussion
• References
• Figures
• Tables

Biology Articles » Hydrobiology » Phosphorus Availability in an Artificially Flooded Southeastern Floodplain Forest Soil » Results

Results

- Phosphorus Availability in an Artificially Flooded Southeastern Floodplain Forest Soil

RESULTS 

 
General Soil Characteristics
Soils in the mesocosm field were slightly acid (pH = 4.9) sandy loams with an OM content of 91 g kg^-1, and a total N/P ratio of 7.3 (Table 1). On the basis of their contribution to total Hedley-extractable P (i.e., the sum of NaHCO₃ P_i and P_o, microbial P, NaOH I and II P_i and P_o, HCl P, and residual P fractions), dominant soil P fractions were microbial P (29%), NaOH I P_o (17%), and NaOH I P_i (14%) (Table 1). Total P estimated by the Hedley procedure (375.5 mg kg^-1) was comparable to that estimated by persulfate/peroxide digests (349.7 mg kg^-1) (Table 1).

Soil Phosphorus Pool Sizes and Phosphorus Availability
As indexed by daily supply to in situ AER, P availability was significantly greater in flooded versus control soils, and decreased significantly following drainage, in each of the five flooding treatments at some time during the 6-mo study (Fig. 2A–G). Total P supply to in situ AER was significantly greater in flooded versus control mesocosms regardless of treatment (Table 2).

Resin-extractable P_i increased significantly as a function of both nutrient addition and flooding in flooded-drained soils (Fig. 3E–G), and decreased significantly following drainage in flooded–drained soils receiving nutrient additions (Fig. 3F and G). Despite significant changes in resin-extractable P_i over time in flooded–drained soils, resin-extractable P_i was only occasionally significantly different in flooded versus control soils (Fig. 3). Remaining Hedley soil P fractions (water-soluble, NaHCO₃, NaOH I and II, HCl, and residual) did not differ significantly with either treatment or time (Wright, 1998). Thus we report only average values for these parameters (Table 1).

Microbial biomass P decreased significantly over time in two flooding treatments: FD (157.2 ± 39.8 kg P ha^-1 in June versus 57.9 ± 13.2 kg P ha^-1 in August) and +N (180.3 ± 7.4 kg P ha^-1 in June versus 39.7 ± 6.1 kg P ha^-1 in September) (Fig. 4E and G). Similar trends were observed in other flooding treatments, although they were not statistically significant (Fig. 4A, B, F). However, microbial biomass P was significantly lower in flooded versus control mesocosms during the first three months of flooding (Table 3). Microbial biomass P_o changed little over the course of the experiment (Wright, 1998).