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WETLAND SOILS

Substrate-Induced Respiration for Phosphorus-Enriched and Oligotrophic Peat Soils in an Everglades Wetland

^a Everglades Research & Education Center, Univ. of Florida, 3200 E. Palm Beach Rd., Belle Glade, FL 33430
^b Wetland Biogeochemistry Lab., Soil and Water Science Dep., Univ. of Florida, P.O. Box 110510, Gainesville, FL 32603

^* Corresponding author (alwr{at}ifas.ufl.edu).

	ABSTRACT

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
Nutrient enrichment may alter patterns of heterotrophic microbial activity (HMA) in wetland soils and influence organic matter decomposition dynamics. The response of the heterotrophic microbial community to C substrates (alcohols, amides, amino acids, aromatics, plant residues, and polysaccharides) was measured as CO₂ and CH₄ production in detritus and soil (0–10 cm) collected from P-enriched and oligotrophic areas of Water Conservation Area 2a (WCA-2a) of the Everglades. The wetland was characterized by decreasing P levels from peripheral to interior, oligotrophic areas. Denitrification and SO₄ reduction appeared to be the primary metabolic pathways at the P-enriched site, whereas the contribution of methanogenesis to organic matter decomposition was greater in the oligotrophic interior of the wetland. Methane production averaged 38 and 48% of the total CO₂ + CH₄ production for P-enriched and oligotrophic detritus, respectively. Basal CO₂ production of detritus was 36% higher at the P-enriched than the oligotrophic site, but CH₄ production was 43% greater at the oligotrophic site. All C substrates enhanced CO₂ and CH₄ production, indicating that labile organic C may be limiting in this wetland, and the types of C substrates used by the heterotrophic microbial community varied between P-enriched and oligotrophic sites. Substrate-induced respiration was 71 and 48% greater at the P-enriched than the oligotrophic site for detritus and soil, respectively. Nutrient loading, particularly P, promoted the development of a N-limited system near the periphery of the wetland, while the oligotrophic interior was characterized by P-limited conditions. Continued nutrient loading into oligotrophic areas of WCA-2a may enhance HMA and stimulate organic matter decomposition and nutrient regeneration, and further contribute to undesirable changes to the Everglades ecosystem.

Abbreviations: HMA, heterotrophic microbial activity • SIR, substrate-induced respiration • WCA-2a, Water Conservation Area 2a

	INTRODUCTION

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
The Florida Everglades ecosystem developed as relatively nutrient poor and supported vegetation adapted to these conditions. In the past century, the Everglades was drained and separated into hydrologic units where water movement and storage were controlled. Nutrient runoff from agricultural soils and altered hydrologic conditions have changed the Everglades ecosystem by increasing soil nutrient levels, particularly P, which promoted vegetation intrusions by cattail (Typha domingensis Pers.) into areas previously dominated by the indigenous sawgrass (Cladium jamaicense Crantz) (Davis, 1991; Childers et al., 2003).

In addition to contributing to changes in vegetation patterns in the Everglades, nutrient loading has altered soil biogeochemical properties (Newman et al., 2001; Wright and Reddy, 2001a, 2001b; Corstanje et al., 2007). The addition of limiting nutrients to ecosystems can alter the structure and function of the vegetation and soil microbial communities. The response of the microbial community, however, may be quicker and more sensitive to elevated nutrient levels than vegetation. Changes in vegetation patterns due to nutrient loading may take years to be observed (Chiang et al., 2000; Noe et al., 2002), while microbial processes may be altered after only a short exposure (McCormick and O'Dell, 1996; Corstanje et al., 2007). Thus, microbial processes and patterns may be suitable as sensitive early indicators of nutrient enrichment or changes in environmental conditions.

Organic matter decomposition and HMA in wetland soils depends on many factors, including available nutrients, organic substrates, and environmental factors such as temperature, pH, and redox potential (D'Angelo and Reddy, 1999). Available C may limit microbial activity in Everglades soils even though total C levels may be high (Amador and Jones, 1995; Wright and Reddy, 2001a). Carbon in wetland soils is present as lignocellulose, lignin, or other fractions with varying degrees of recalcitrance (DeBusk and Reddy, 1998). Organic matter in wetland soils often undergoes a short-term rapid breakdown of labile portions of the dissolved organic C pool followed by a longer term degradation of more recalcitrant fractions (Chrost, 1991). Decomposition of lignin, lignocellulose, and other plant residues produces polysaccharides and amino acids, which are utilized in microbial respiratory pathways (Chrost, 1991). Decomposition of these compounds by fermentative microorganisms produces alcohols, carboxylic acids, and inorganic nutrients. The exposure of the soil heterotrophic microbial community to broad classes of substrates enables characterization of microbial ecophysiology using measurements of their short-term response to C-substrate addition (Degens and Harris, 1997; Degens, 1999). Substrate-induced respiration is often used as a measure of microbial ecophysiology, as the response of HMA to added C substrates may indicate the catabolic diversity of soil heterotrophs (Degens and Harris, 1997).

Characterization of the metabolic activities of the heterotrophic microbial communities has been successfully utilized in understanding C flow in ecosystems (Degens, 1999; Corstanje et al., 2007). Eutrophication of Everglades wetlands has increased enzyme activity and C metabolism (Wright and Reddy, 2001b; Corstanje and Reddy, 2004), and altered organic matter decomposition dynamics (DeBusk and Reddy, 2003). Wetland soils at different trophic states may exhibit variable HMA, which ultimately influences organic matter dynamics by altering the metabolic pathways of decomposition. The objectives of this study were to determine the response of heterotrophic microbial communities to added C substrates and inorganic nutrients for P-enriched and oligotrophic detritus and soil in WCA-2a of the Everglades.

	MATERIALS AND METHODS

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Site Description and Sampling
The study was conducted in WCA-2a (44,700 ha) of the northern Florida Everglades. This wetland was historically P limited and vegetated by Cladium, periphyton, and open-water sloughs (Davis, 1991; Childers et al., 2003). External nutrient loading increased P concentrations in the soil and water column and contributed to the development of distinct gradients in soil P from primary water-inflow points extending into the interior of the wetland (DeBusk et al., 1994; Childers et al., 2003). Nutrient loading has been implicated as a factor in causing ecosystem shifts including changes in vegetation patterns from indigenous Cladium to Typha-dominated ecosystems, resulting in changes in organic matter accumulation rates, water quality, and biogeochemical processes (Reddy et al., 1993; DeBusk and Reddy, 2003).

Detritus and soil samples (0–10 cm) were collected in March 1999 at two sites along a nutrient-enrichment gradient 2.3 (P-enriched) and 10.2 km (oligotrophic) south of the S10-C water inflow structure of WCA-2a. Detritus consisted of recently deposited plant material while peat consisted of consolidated and decomposed organic matter. Sampling sites encompassed a range of soil P concentrations and vegetative zones, from Typha at the P-enriched site to Cladium–periphyton-dominated areas in the oligotrophic interior of the wetland. A total of nine soil cores (15-cm diameter) were taken at each site, with triplicate cores composited to yield three replicate samples per site. Detritus was collected from above the cored soil, and all samples were stored at 4°C until analysis.

Soil Characterization
Loss-on-ignition was determined as the mass loss of soil after ashing for 4 h at 550°C. Extractable organic C was measured by extraction with 0.5 mol L^–1 K₂SO₄ followed by analysis with a Dohrmann total organic C analyzer (Teledyne Tekmar, Mason, OH). Microbial biomass C was measured by fumigation–extraction (Vance et al., 1987) with an extraction efficiency factor of 0.37 for biomass C (Sparling et al., 1990). Microbial biomass P was calculated as the difference between the total P of 0.5 mol L^–1 NaHCO₃ extracts of chloroform-fumigated and unfumigated samples (Ivanoff et al., 1998). Soil total P was determined by ashing at 550°C (Anderson, 1976) and NaHCO₃–P by extraction with 0.5 mol L^–1 NaHCO₃ (Corstanje et al., 2007), followed by colorimetric analysis (USEPA, 1993, Method 365.4).

Basal and Substrate-Induced Respiration
Amendments (C substrates, plant residues, and inorganic N and P) were added to the soil and the response of heterotrophic microbial communities measured as CO₂ and CH₄ production. The C substrates were selected based on their common presence in soil and prior utilization for measurement of catabolic diversity of soil microbial communities (Degens and Harris, 1997; Degens, 1998). The classes of substrates tested were alcohols (glycerol and mannitol), amides (glucuronamide), amino acids (alanine, cysteine, aspartate, and glutamine), aromatics (inosine), and polysaccharides (glucose and maltose). The C substrates were added in excess of microbial requirements to prevent limitation to growth. All C substrates were dissolved in distilled water, adjusted to the pH of the soil (pH = 7), and applied on a C-equivalent basis (25 g C kg^–1 soil), followed by thorough mixing into the soil. In addition, standing dead Typha and Cladium tissue was collected from respective sites, ground past a 0.5-mm sieve, and applied on a C-equivalent basis. Inorganic N and P were utilized to assess the response of the heterotrophic microbial community to nutrient loading. Inorganic N was applied at 1.0 mmol L^–1 as NH₄Cl and inorganic P at 0.1 mmol L^–1 as NaH₂PO₄ in solutions buffered to pH 7.

For measurement of CO₂ production, 10 g of soil was incubated with amendments under N₂ in 120-mL glass bottles with 20-mL vials containing 3 mL of 0.5 mol L^–1 NaOH at 30°C. Vials containing NaOH were removed and capped at 2-d intervals for 14 d. For analysis, 1.0 mL of 3 mol L^–1 HCl was added to enclosed vials and resulting headspace CO₂ quantified by gas chromatography (Shimadzu GC-8A thermal conductivity detector at 25°C, Shimadzu Corp., Kyoto, Japan; Poropak N column at 20°C). Substrate-induced respiration was calculated as the slope of the regression of cumulative CO₂ production during the 14-d period.

For measurement of CH₄ production, 10 g of soil was incubated with amendments in 60-mL glass serum bottles under N₂ at 30°C. Every 2 d, aliquots of headspace were analyzed for CH₄ using a Shimadzu GC-8A fitted with a flame ionization detector (160°C) and a Carboxyn 1000 column (Supelco, Bellefonte, PA) at 110°C. Methane production rates were calculated as the slope of the regression of cumulative CH₄ production during 14 d. Incubations were also performed in the absence of C substrates and nutrients to determine basal respiration rates.

Data Analysis
No significant differences in the response of C substrates within groups were observed, so C substrates were grouped into alcohols, amides, amino acids, aromatics, plant residues, and polysaccharides for analyses and presentation. A completely randomized experimental design was used, with factors being amendment, sampling site, and soil depth. Data were analyzed using a three-way ANOVA model to determine significant main effects of amendment, sampling site, and depth using Fisher's LSD at P < 0.05 (CoHort Software, 2005). Individual treatment comparisons for each site and depth were made using a one-way ANOVA with the LSD at P < 0.05.

	RESULTS

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Biogeochemical Parameters
Soil moisture content averaged 94% and bulk density 0.09 g cm^–3, and neither was affected by P enrichment (data not shown). The loss-on-ignition averaged 86% and did not vary between sites or depths. The primary biogeochemical parameters that changed due to nutrient enrichment were P-related indicators such as total P, labile P, and microbial biomass P (Table 1), which were all higher at the P-enriched site. Nutrient enrichment was best illustrated by the range in total P from 1890 to 693 mg kg^–1 in detritus and 796 to 336 mg P kg^–1 in the underlying 0- to 10-cm soil.

View larger version (29K): [in this window] [in a new window]   Fig. 1. The contribution of CH4 production to total substrate-induced CO2 + CH4 production for P-enriched and oligotrophic detritus and soil (0–10 cm) from Water Conservation Area-2a of the Everglades.

	DISCUSSION

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
Short-term incubations measure the ability of soil microorganisms to rapidly utilize C substrates and indicate the presence of enzyme systems capable of substrate utilization (Degens and Harris, 1997; Degens, 1998). This short-term utilization indicates a previous exposure to these C substrates and indicates the types of C substrates typically present in soil. All added C substrates enhanced SIR in the 14-d incubation for both detritus and soil, indicating that a wide range of substrates are typically produced during the decomposition of Typha and Cladium residues in this wetland. The ability of the heterotrophic microbial community to rapidly utilize plant residues at rates similar to soluble C substrates also indicated a broad catabolic diversity and heterotrophic microbial community in this wetland ecosystem.

All C substrates enhanced CO₂ and CH₄ production; however, amides and plant residues stimulated CH₄ production the most at the P-enriched site. The highest CO₂ production rates for detritus occurred with polysaccharide amendment. Differences between the C substrates contributing only organic C and those contributing both organic C and N were generally not observed. The C substrates stimulated SIR at all sites and in detritus and the underlying soil, which suggested that HMA was limited by labile organic C. This result was not expected because both the detritus and the soil had at least 2290 mg extractable organic C kg^–1 (Table 1), suggesting that much of the extractable organic C pool in this wetland may not be directly available to soil microorganisms. Utilization rates of C substrates were generally greatest at the P-enriched site due to the effects of nutrient loading on stimulation of microbial biomass and elevated nutrient concentrations. Indeed, significant relationships between microbial biomass and microbial respiration were observed in other studies in the Everglades (DeBusk and Reddy, 1998; White and Reddy, 2000). Carbon dioxide and CH₄ production rates were higher in surface detritus than the underlying soil. Similar results were observed for other studies in the Everglades (Amador and Jones, 1995; Wright and Reddy, 2001a), as the most recently deposited material was more biologically active than the underlying soil.

Heterotrophic microbial activity at the oligotrophic site appeared to be limited by inorganic P in addition to labile organic C. Addition of P did not increase HMA at the P-enriched site; however, both CO₂ and CH₄ production at the oligotrophic site increased with P addition, suggesting no P limitation. In other studies, P addition had no impact on microbial respiration for high-P soils in the Everglades (Amador and Jones, 1995). Addition of inorganic N to detritus and soil from the P-enriched site enhanced HMA in some cases, suggesting a possible N limitation in areas of WCA-2a having elevated P levels (White and Reddy, 2003). Water Conservation Area 2a was historically P limited, but external nutrient loading has resulted in significant increases in soil P in areas adjacent to water-inflow points (Childers et al., 2003). The removal of the P limitation by external nutrient loading probably induced a N limitation, as evidenced by stimulation of CO₂ and CH₄ production from inorganic N addition.

At both P-enriched and oligotrophic sites, CO₂ production was generally higher than CH₄ production. The plant residue amendments were expected to show the least enhancement of SIR of all C-substrate treatments due to their more complex nature compared with soluble C substrates. Decomposition of plant residues requires the presence of numerous extracellular enzymes needed for the breakdown of large particles into smaller molecules that can be taken up by microbial cells (Chrost, 1991). Methane production in treatments receiving plant residues was comparable to other treatments, however, especially at the oligotrophic site. In fact, CH₄ production often exceeded CO₂ production when plant residues were added (Tables 2 and 3), indicating the ability of the heterotrophic microbial community to rapidly utilize plant residues.

Increases in NO₃ and SO₄ concentrations have occurred near water-inflow points in WCA-2a concomitant with P enrichment (DeBusk et al., 1994). The contribution of CH₄ production to total CO₂ + CH₄ production was greater at oligotrophic sites (Fig. 1), probably because higher nutrient levels at P-enriched sites near water-inflow points supported denitrification and SO₄ reduction, resulting in high CO₂ production rates (DeBusk et al., 1994; Childers et al., 2003). In contrast, nutrient-poor conditions and lower NO₃ and SO₄ levels at the oligotrophic site (DeBusk et al., 1994) promoted methanogenesis and higher rates of CH₄ production relative to CO₂ production. Methanogens are often outcompeted for C substrates by NO₃– and SO₄–reducing microorganisms due to differences in potential thermodynamic energy yields (Achtnich et al., 1995; Drake et al., 1996), hence the greater proportion of CH₄ to total SIR in oligotrophic than P-enriched areas. Thus, the catabolic diversity of heterotrophic microbial communities varied with nutrient enrichment, from metabolic pathways with CO₂ as the end product at the eutrophic site to pathways producing CH₄ as the end product at the oligotrophic site.

	CONCLUSIONS

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
Factors influencing HMA included C substrates and inorganic nutrients. The heterotrophic microbial community in WCA-2a possessed the ability to rapidly utilize a wide variety of C substrates, indicating that labile organic C was a limiting factor to HMA. Patterns of SIR varied between oligotrophic and P-enriched sites: CH₄ production had a greater contribution to total SIR in oligotrophic than P-enriched soils, indicating that external nutrient loading altered the metabolic pathways of organic matter decomposition. The diversity of heterotrophic microbial communities was also evident in that HMA was limited by inorganic N at the P-enriched site and by inorganic P at the oligotrophic site. Stimulation of the heterotrophic microbial community by inorganic nutrients, and the resulting increase in organic matter decomposition, has significant implications for management of the Everglades ecosystem. Continued external loading into WCA-2a and increased nutrient availability may alter pathways of organic matter decomposition and stimulate denitrification and SO₄ reduction at the expense of methanogenesis, decreasing total soil organic C storage in this wetland. The resulting regeneration of N and P from organic matter decomposition to floodwater may further exacerbate the harmful effects of nutrient enrichment on the Everglades ecosystem currently observed in P-enriched areas of WCA-2a.

	NOTES

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All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher.

Received for publication March 6, 2007.

	REFERENCES

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 

• Achtnich, C., F. Bak, and R. Conrad. 1995. Competition for electron donors among nitrate reducers, ferric iron reducers, sulfate reducers, and methanogens in anoxic paddy soil. Biol. Fertil. Soils 19:65–72.[CrossRef]
• Amador, J.A., and R.D. Jones. 1995. Carbon mineralization in pristine and phosphorus-enriched peat soils of the Florida Everglades. Soil Sci. 159:129–141.
• Anderson, J.M. 1976. An ignition method for determination of total phosphorus in lake sediments. Water Res. 10:329–331.
• Chiang, C., C.B. Craft, D.W. Rogers, and C.J. Richardson. 2000. Effects of 4 years of nitrogen and phosphorus additions on Everglades plant communities. Aquat. Bot. 68:61–78.[CrossRef][Web of Science]
• Childers, D.L., R.F. Doren, R.D. Jones, G.B. Noe, M. Rugge, and L.J. Scinto. 2003. Decadal change in vegetation and soil phosphorus patterns across the Everglades landscape. J. Environ. Qual. 32:344–362.[Web of Science]
• Chrost, R.J. 1991. Environmental control of the synthesis and activity of aquatic microbial ectoenzymes. p. 29–59. In R.J. Chrost (ed.) Microbial enzymes in aquatic environments. Springer-Verlag, New York.
• CoHort Software. 2005. CoStat Version 6.3. CoHort Software, Monterey, CA.
• Corstanje, R., and K.R. Reddy. 2004. Response of biogeochemical indicators to a drawdown and subsequent reflood. J. Environ. Qual. 33:2357–2366.[Abstract/Free Full Text]
• Corstanje, R., K.R. Reddy, J.P. Prenger, S. Newman, and A.V. Ogram. 2007. Soil microbial eco-physiological response to nutrient enrichment in a sub-tropical wetland. Ecol. Indic. 7:277–289.[CrossRef]
• D'Angelo, E.M., and K.R. Reddy. 1999. Regulators of heterotrophic microbial potentials in wetland soils. Soil Biol. Biochem. 31:815–830.[CrossRef]
• Davis, S.M. 1991. Growth, decomposition, and nutrient retention of Cladium jamaicense Crantz and Typha domingensis Pers. in the Florida Everglades. Aquat. Bot. 40:203–224.[CrossRef][Web of Science]
• DeBusk, W.F., and K.R. Reddy. 1998. Turnover of detrital organic carbon in a nutrient-impacted Everglades marsh. Soil Sci. Soc. Am. J. 62:1460–1468.[Abstract/Free Full Text]
• DeBusk, W.F., and K.R. Reddy. 2003. Nutrient and hydrology effects on soil respiration in a northern Everglades marsh. J. Environ. Qual. 32:702–710.[Web of Science]
• DeBusk, W.F., K.R. Reddy, M.S. Koch, and Y. Wang. 1994. Spatial distribution of soil nutrients in a northern Everglades marsh: Water Conservation Area 2a. Soil Sci. Soc. Am. J. 58:543–552.[Abstract/Free Full Text]
• Degens, B.P. 1998. Microbial functional diversity can be influenced by the addition of simple organic substrates to soil. Soil Biol. Biochem. 30:1981–1988.[CrossRef]
• Degens, B.P. 1999. Catabolic response profiles differ between microorganisms grown in soils. Soil Biol. Biochem. 31:475–477.[CrossRef]
• Degens, B.P., and J.A. Harris. 1997. Development of a physiological approach to measuring the catabolic diversity of soil microbial communities. Soil Biol. Biochem. 29:1309–1320.[CrossRef]
• Drake, H.L., N.G. Aumen, C. Kuhner, C. Wagner, A. Griebhammer, and M. Schmittroth. 1996. Anaerobic microflora of Everglades sediments: Effects of nutrients on population profiles and activities. Appl. Environ. Microbiol. 62:486–493.[Abstract]
• Ivanoff, D.B., K.R. Reddy, and S. Robinson. 1998. Chemical fractionation of organic P in Histosols. Soil Sci. 163:36–45.[CrossRef]
• McCormick, P.V., and M.B. O'Dell. 1996. Quantifying periphyton responses to P enrichment in the Florida Everglades: A synoptic-experimental approach. J. N. Am. Benthol. Soc. 15:450–468.[CrossRef]
• Newman, S., H. Kumpf, J.A. Laing, and W.C. Kennedy. 2001. Decomposition responses to phosphorus enrichment in an Everglades (USA) slough. Biogeochemistry 54:229–250.
• Noe, G.B., D.L. Childers, A.L. Edwards, E. Gaiser, K. Jayachandran, D. Lee, J. Meeder, J. Richards, L.J. Scinto, J.C. Trexler, and R.D. Jones. 2002. Short-term changes in phosphorus storage in an oligotrophic Everglades wetland ecosystem receiving experimental nutrient enrichment. Biogeochemistry 59:239–267.
• Reddy, K.R., R.D. DeLaune, W.F. DeBusk, and M.A. Koch. 1993. Long-term nutrient accumulation rates in the Everglades. Soil Sci. Soc. Am. J. 57:1147–1155.[Web of Science]
• Sparling, G.P., C.W. Feltham, J. Reynolds, A.W. West, and P. Singleton. 1990. Estimation of soil microbial C by a fumigation-extraction method: Use on soils of high organic matter content and a reassessment of the k_ec factor. Soil Biol. Biochem. 22:301–307.[CrossRef]
• USEPA. 1993. Methods for chemical analysis of water and wastes. Environ. Monitor. Support Lab., Cincinnati, OH.
• Vance, E.D., P.C. Brookes, and D.S. Jenkinson. 1987. An extraction method for measuring microbial biomass C. Soil Biol. Biochem. 19:703–707.[CrossRef]
• White, J.R., and K.R. Reddy. 2000. Influence of phosphorus loading on organic nitrogen mineralization of Everglades soils. Soil Sci. Soc. Am. J. 64:1525–1534.[Abstract/Free Full Text]
• White, J.R., and K.R. Reddy. 2003. Nitrification and denitrification rates of Everglades wetland soils along a phosphorus-impacted gradient. J. Environ. Qual. 32:2436–2443.[Web of Science][Medline]
• Wright, A.L., and K.R. Reddy. 2001a. Heterotrophic microbial activity in northern Everglades wetland soils. Soil Sci. Soc. Am. J. 65:1856–1864.[Abstract/Free Full Text]
• Wright, A.L., and K.R. Reddy. 2001b. Phosphorus loading impacts on extracellular enzyme activity in Everglades wetland soils. Soil Sci. Soc. Am. J. 65:588–595.[Abstract/Free Full Text]

This Article Abstract Figures Only Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Wright, A. L. Articles by Reddy, K. R. Search for Related Content PubMed Articles by Wright, A. L. Articles by Reddy, K. R. Agricola Articles by Wright, A. L. Articles by Reddy, K. R. Related Collections Wetlands and Aquatic Processes Soil Biology