Wetlands (2012) 32:919–929 DOI 10.1007/s13157-012-0325-5
ARTICLE
Vegetative Forage Quality and Moist-soil Management on Wetlands Reserve Program Lands in Mississippi K. Sarah Fleming & Richard M. Kaminski & Todd E. Tietjen & Michael L. Schummer & Gary N. Ervin & Kevin D. Nelms Received: 8 January 2012 / Accepted: 10 July 2012 / Published online: 25 July 2012 # Society of Wetland Scientists 2012
Abstract The Wetland Reserve Program (WRP) prescribes management of vegetation in moist-soil wetlands for waterfowl and other wildlife. This study used a block design on 18 sites in the Mississippi Alluvial Valley (MAV) in Mississippi to evaluate effectiveness of management prescriptions. Objectives were to determine appropriate timing of vegetation surveys and whether vegetation community metrics on private lands differed among management strategies (2008–2009): 1) active (e.g., annual soil disturbance), early drawdown of standing water (i.e., by 15 June), 2) active, late drawdown (≥3 weeks after early drawdown), and 3) passive, natural evaporation. A Vegetative Forage Quality Index K. S. Fleming (*) : R. M. Kaminski : M. L. Schummer Department of Wildlife, Fisheries and Aquaculture, Mississippi State University, Mississippi State, MS 39762, USA e-mail:
[email protected] T. E. Tietjen Southern Nevada Water Authority, Las Vegas, NV 89193, USA G. N. Ervin Department of Biological Sciences, Mississippi State University, Mississippi State, MS 39762, USA K. D. Nelms Natural Resource Conservation Service, 200 E Washington St, Greenwood, MS 38930, USA Present Address: K. S. Fleming Ducks Unlimited, Great Lakes/Atlantic Regional Office, 1220 Eisenhower Place, Ann Arbor, MI 48108, USA Present Address: M. L. Schummer Long Point Waterfowl, 115 Front Road, Port Rowan, ON N0E 1 M0, Canada
(VFQI) was developed to assess quality of plant communities as forage for waterfowl. The study examined VFQI, plant community diversity and richness, percent (%) occurrence of grass, % woody species, and mean number of plant life-forms among management categories (α00.10). Plant community metrics were measured June–October but only October metrics revealed differences in both years (p≤0.09). Active-early had the greatest VFQI, diversity, mean number of plant life-forms, and percent abundance of grasses in October 2008 and 2009 (p≤0.07). Results suggest that quality forage for waterfowl may be achieved through active management with early draw-down. Keywords Management . Moist-soil wetland . Vegetative Forage Quality Index . Waterfowl . Wetlands Reserve Program
Introduction Wetlands provide ecological, environmental, and economic benefits worldwide (Mitsch and Gosselink 2007). Despite increased knowledge of ecosystem services derived from wetlands, wetland loss in North America is ≥50 % in many regions and annual rate of loss in the United States exceeds 117,000 ha (Dahl 2006, Mitsch and Gosselink 2007). Wetland restoration in the United States has occurred on public lands (e.g., National Wildlife Refuges, Forests, and Parks) and on private lands primarily through the Food, Agriculture, Conservation, and Trade Act 1990 (i.e., Farm Bill; Mitsch and Gosselink 2007; Natural Resources Conservation Service [NRCS] 2007). Several important wetland conservation programs, including the Wetlands Reserve Program (WRP), exist within the 1990–present Farm Bills. Most WRP lands in the contagious United States are in the Mississippi Alluvial Valley (MAV) in Arkansas, Illinois, Kentucky, Louisiana, Mississippi, Missouri, and Tennessee, where >161,000 ha of wetlands previously converted to agriculture have been
920
enrolled in WRP (Ducks Unlimited 2006; King et al. 2006). The MAV is a focal area for WRP because drainage, deforestation, channelization, agriculture, and urbanization have substantially changed natural hydrology and decreased available habitat for wetland wildlife in this region (Reinecke and Heitmeyer 1988; Fredrickson et al. 2005; King et al. 2006). The WRP is a voluntary program, administered through NRCS, where landowners receive technical and financial assistance to protect, enhance, and restore previously converted wetlands (NRCS 2004; Haufler 2005). Wetlandconservation initiatives such as WRP, help meet habitat goals of the North American Waterfowl Management Plan (NAWMP) and Lower Mississippi Valley Joint Venture (LMVJV) by restoring habitats for waterfowl and other wildlife (Reinecke et al. 1989; Kushlan et al. 2002; King et al. 2006). A component of restoration and enhancement of WRP wetlands in the MAV includes development and management of moist-soil wetlands. Moist-soil wetlands generally are seasonally flooded, impounded basins which often contain early succession plant communities dominated by wetland grasses, sedges, and forbs (Fredrickson and Taylor 1982; Smith et al. 1989; Nelms 2007; Kross et al. 2008). Moist-soil management is frequently applied on WRP wetlands throughout the MAV and southern United States to provide forage and other habitat resources for waterfowl and other wetland wildlife (Fredrickson and Taylor 1982; Smith et al. 1989). A primary goal of moist-soil management on WRP sites is to increase production of grasses and sedges which provide energy dense seeds and tubers for migrating and wintering waterfowl (Fredrickson and Taylor 1982; Reinecke et al. 1989; Kaminski et al. 2003). Management of moist-soil wetlands in the MAV and elsewhere in North America includes passive and active management practices, combined with differential timing of spring-summer drawdown (Nelms 2007). However, the combined effectiveness of management intensities (i.e., passive vs. active) with timing of water drawdown (i.e., early and late season) have not been empirically tested in the MAV (Fleming 2010). Effectiveness of moist-soil management can be evaluated by monitoring and quantifying metrics of vegetative communities (Adamus et al. 1987; White 1987). Floristic Quality Assessment Indices (FQAI) are used to assess native vegetative communities, monitor restoration success, and evaluate broader ecological conditions of sites (Matthews et al. 2005; Bourdaghs et al. 2006; Ervin et al. 2006). Evaluating plant community characteristics of moist-soil wetlands is needed to determine effects of different management practices on conservation lands, and, thus to provide useful indicators of availability and quality of food and cover for waterfowl and other wetland wildlife. In our study, plant community metrics of moist-soil wetlands were evaluated from summer-autumn 2008 and
Wetlands (2012) 32:919–929
autumn 2009 on WRP lands subjected to active or passive management of vegetation and early or late season drawdown. Our objectives were to evaluate 1) potential forage quality of moist-soil plant communities for migrating and wintering waterfowl using plant community metrics (e.g., richness and diversity) and a Vegetative Forage Quality Index (VFQI), conceptually based upon a FQAI, (Andreas et al. 2004; Taft et al. 2006) among management strategies applied to private lands (2008–2009), and 2) seasonal dynamics of plant species richness, diversity, and VFQI to determine optimal timing to monitor these plant communities as a source of forage for waterfowl.
Methods Study Areas The 54 wetlands used in our study were on 18 private lands enrolled in WRP in the MAV in Mississippi. The wetlands were distributed across Grenada, Quitman, Sharkey, Sunflower, Tallahatchie, Tunica, and Yazoo counties (Fig. 1). Each WRP property had 3 to 22 moist-soil wetlands ranging in size from 0.4 to 67.8 ha each. Topography, wetland characteristics, and financial resources varied among landowners, and this influenced if areas were managed actively or passively. Fifty-one (94 %) wetlands had water control structures, which enabled landowners to manage hydrology within wetlands. Water for wetland flooding originated from different sources for each wetland including rivers, ditches, runoff, precipitation, and pumped ground water. None of the wetlands were connected through surface waters, and the distance among wetlands was at least 50 m. Therefore, wetlands were considered discrete, independent survey and analytical units. Vegetation in wetlands primarily consisted of native species adapted to seasonal flooding and drainage, such as grasses (Echinochloa muricata, Panicum rigidulum, Leersia spp.), forbs (Polygonum spp., Bidens aristosa), vines (Brunnichia ovata, Ipomoea spp.), sedges and rushes (Cyperus spp., Juncus spp.), and trees and shrubs (Quercus spp., Salix nigra, Cephalanthus occidentalis), including numerous truly aquatic species (Ludwigia peploides, Potamogeton spp; Fleming 2010; NRCS 2010; Schummer et al. 2012). Supplemental plantings of wildlife food (e.g., corn) also occurred but represented ≤5 % of the area in all wetlands. Wetland Management and Experimental Design Following inspection of the 54 wetlands during March–July 2008, management category was designated for wetlands as: 1) active vegetation management with draw-down by 15 June (i.e., active-early), 2) active vegetation management
Wetlands (2012) 32:919–929
921
Fig. 1 Locations of study counties (experimental blocks) and 18 study sites within Wetlands Reserve Program lands in the Mississippi Alluvial Valley region of Mississippi
with draw-down ≥3 weeks later (i.e., active-late), or 3) passive vegetation management with unregulated drawdown by evaporation and percolation into the groundwater. Moist-soil wetlands were assigned to the active vegetation management category when managers followed NRCS guidelines, which generally included a combination of at least monthly site inspections, annual soil disturbance (e.g., disking), and herbicide or mechanical control of plants with little or no known value as waterfowl forage (e.g., Sesbania exaltata; Hagy 2010). Passively managed wetlands received infrequent soil disturbance (≥5 years), limited or no control of undesirable plants, and no hydrological management (Brasher et al. 2007; Kross et al. 2008). Study wetlands were identified within the NRCS Mississippi WRP federal database. The aforementioned counties were designated as 6 experimental blocks which were distributed from north to south in the Mississippi MAV (Note: Tunica and Quitman were treated as a single block because surveyed properties spanned both counties). Only six active-early WRP sites existed in 2008; therefore, all were evaluated. An attempt was made to develop a balanced study design with the three management categories in each block. However, because of changes in management by landowners within and among study years, our final study design in 2008 contained five blocks with all three management categories, whereas one block had active-early and -
late but no passive site. In 2009, four blocks contained all three management categories, whereas two blocks had active-early and -late drawdown but no passive sites. In 2009, four blocks contained all three management categories, whereas two blocks included active-early and -late drawdown but no passive sites. For each management category, replicates were on a single property, and selection and geographical pairing of active-early, active-late, and passive sites were based on three criteria: 1) the three management types were located within the same block, 2) all three properties within a block were separated by 0.10). Pair-wise multiple comparisons were used to evaluate significant differences among management types, months, and management types×months (i.e., Tukey-tests). Evaluation of Management Effects on October Plant Communities As mentioned, analyses of 2008 and 2009 data revealed differences in plant community diversity and VFQI among management types only within October data sets (see Results). Therefore, October 2008 and 2009 data were used to test the effect of management on plant communities. The October plant communities contained potentially available forage and habitat for wintering waterfowl; thus, additional plant community metrics also were selected that may influence subsequent use of these wetlands by waterfowl. These metrics included: 1) COMP, 2) %WOODY and 3) %GRASS (Weller and Fredrickson 1974; Kaminski et al. 2003; Brasher et al. 2007; Kross et al. 2008). An ANOVA was used to test null hypotheses of no difference in October values of richness, diversity, VFQI, COMP, %WOODY, and %GRASS among active-early, active-late, and passive management (PROC MIXED SAS 9.2.2; Table 1). Management category was designated as a fixed effect, blocks and landowners nested within blocks as random effects, and year was a repeated measure. The VFQI data were log-transformed because of unequal variances. Pair-wise multiple comparisons were used to evaluate significant differences in October plant community metrics among management categories (i.e., Tukey-tests).
Results Seasonal Plant Community Dynamics Analysis of 2008 data revealed an interaction between management category and month for VFQI (F6, 153 02.33; p00.03) and diversity (F6, 153 01.82; p00.09). A difference among management categories was detected only for October 2008 VFQI (F2, 41.2 02.51; p00.09; Fig. 2) and diversity (F2, 29.5 0 3.81; p00.03; Fig. 3). There were no detectable differences in plant taxa richness among active-early (x 015.32±1.53 [SE]), active-late (x 016.22±1.50), and passively managed sites (x0 16.00±1.66; F2, 9.06 00.16; p00.85). For 2009 data, management category and month also interacted, and only October 2009 VFQI differed among management types (F2, 50.6 02.82; p00.07; Fig. 4). Effect of Management on October Plant Communities An effect of management was observed for VFQI (F2, 8.20 0 7.74; p00.01), diversity (F2, 9.39 04.54; p00.04), COMP
923
(F2, 9.72 04.71; p00.03), and %GRASS (F2, 8.70 03.63; p 00.07; Table 2). Mean diversity and %GRASS in active-early sites were ≥42 % greater, on average, than passively managed sites (p00.04; p00.09, respectively). Mean VFQI and COMP for active-early sites was ≥17 % greater, on average, than active-late and passively managed sites (p≤0.04, p≤0.08, respectively). No differences were detected for richness and %WOODY among management types (p≥0.14; Table 2).
Discussion Waterfowl require diverse and energy-dense plant foods during fall and winter to meet the nutritional requirements of the non-breeding season (Reinecke et al. 1989). The VFQI was developed to assess the ability of the WRP to meet the goal of providing quality foraging habitat for migrating and wintering waterfowl in the MAV. The VFQI and other plant community metrics were evaluated relative to active and passive vegetation management and early and late seasonal draw-down of surface water in WRP moist-soil wetlands. We think the VFQI may be a valuable tool to assess plant communities in WRP moist-soil wetlands because this index differed among management treatments and calculation of this metric included measures of forage quality and plant diversity (sensu Reinecke et al. 1989; Fleming 2010). Differences in plant community metrics were detected among management categories only for October vegetation data, which revealed active-early sites had greater VFQI, total percent of grass composition, greater plant life-form richness, and higher diversity than passively managed sites, whereas similar values existed between active-late and passive sites (Table 2). The NRCS guidelines and literature indicate active vegetation management and appropriate timing of draw-downs in moist-soil areas can promote seed production and diversity of early succession grasses, sedges, and other wetland plants, as well as waterfowl use (Fredrickson and Taylor 1982; Strader and Stinson 2005; Nelms 2007; Kross et al. 2008). The result indicating VFQI, total percent of grass composition, plant life-form richness and diversity were positively influenced by regular vegetation management and soil disking, coupled with early season water draw-down, supports NRCS management guidelines for producing quality foraging habitat for waterfowl. Natural and human induced soil disturbance (e.g., hydrological scouring, disking) in moist-soil wetlands vary in frequency and intensity (Fredrickson and Taylor 1982). Minimal and infrequent disturbances can have negligible effects on plant community diversity, but increased disturbances can result in predictable and beneficial changes in plant communities toward greater occurrence of early succession plants (Taft et al. 1997;
924
Wetlands (2012) 32:919–929
Table 1 Plant community metrics and summary statistics (x± SE; range) among management types for 54 moist-soil wetlands on the Wetlands Reserve Program lands, Mississippi, October 2008 and 2009 Year/metrics
2008 Vegetation Forage Quality Index (VFQI) Diversity Plant taxa richness per wetland x plant life-formsb per sample point % grasses % woody cover n 2009 Vegetation Forage Quality Index (VFQI) Diversity Plant taxa richness per wetland x Plant growth-formsb per sample points % grasses % woody cover n
Management typesa Active-early
Active-late
Passive
1.16±0.09 (0.66–1.86) 2.67±0.22 (0.66–4.57) 18.61±1.19 (8.00–29.00) 1.70±0.12 (0.30–2.62) 50.0±6.00 (10.00–100.00) 2.00±0.60 (0.00–8.00) 18
0.94±0.07 (0.18–1.50) 2.25±0.19 (0.02–3.49) 20.40±1.38 (2.00–31.00) 1.23±0.12 (0.54–2.51) 26.0 ±5.00 (0.00–78.00) 4.00±1.00 (18.00–85.00) 21
0.78±0.06 (0.43–1.24) 1.78±0.14 (0.85–2.70) 17.40±1.62 (6.00–27.00) 1.32±0.14 (0.64–1.91) 24.5 ±7.00 (0.00–92.00) 5.00±1.70 (0.00–18.50) 15
1.0±0.07 (0.40–1.64)
0.63±0.07 (0.12–1.34)
0.75±0.09 (0.28–1.38)
2.10±0.14 (0.44–3.43) 15.76±1.12 (5.00–26.00) 1.84±0.13 (0.29–2.52) 43.9±8.0 (0.00–100.00) 3.6±1.7 (0.00–25.50) 21
1.58±0.16 (0.67–3.44) 14.23±1.29 (1.00–24.00) 1.62±0.12 (0.06–2.56) 37.9±6.0 (0.00–92.00) 5.0±1.2 (0.00–22.00) 21
1.64±0.22 (0.48–2.70) 15.08±1.63 (6.00–26.00) 1.42±1.10 (0.68–1.92) 25.4±6.10 (0.00–78.00) 5.0±1.7 (0.00–18.50) 12
a
Management types were defined as 1) active-early: wetland management and draw-down by 15 June, 2) active-late: wetland management with draw-down ≥3 weeks later and 3) passive: draw-down by evaporation within wetlands with or without a water control structure. Active management was defined as managers following NRCS guidelines, which usually included a combination of at least monthly site inspections, annual soil disturbance (e.g., disking), and herbicide or mechanical control of plants with little or no known value as waterfowl forage.
b
Plant life-forms included grasses, sedges/rushes, aquatics, vines, woody vegetation, wildlife food crops, and broadleaves
A
A AB
AB
B
B
Fig. 2 Least-squared means (± SE) of logn transformed values of a Vegetative Forage Quality Index (VFQI) for 54 moist-soil wetlands on Wetlands Reserve Program lands in Mississippi, June–October 2008. Means followed by unlike letters in October 2008 differ (p
