Basic Information

Dataset ID:LKB2E8802A

Dataset Title (Identity):Spartina alterniflora decomposition in marsh sediments.

Dataset Contacts: Linda K. Blum ,

Dataset Originators (Authors): Linda K. Blum ,

LTER Core Areas: Primary Productivity, Organic Matter,

Collection Started (MM/DD/YY): 03/26/88 Collection Ended: 04/01/90

General Location Where Data Was Collected: Phillips Creek Marsh. West of farmer's irrigation pond.

Form of the Data: Column

Keywords: Spartina alterniflora, decay rate, decomposition,

Project Description and Goals

At present, little is known about decomposition rates and spatial variability in those rate within salt marsh sediments. Previous studies have in most cases examined the decomposition of dried plant roots buried a few cm below the marsh surface in both high and low marsh. Data from our studies of seagrass and cord grass decomposition in Chesapeake Bay (as well as Godshalk and Wetzel, 1978; Gallagher et al., 1984; Jesselyn and Mathieson, 1980) have shown that drying plant material significantly alters measured decay rates. Hackney (1987) found no differences in decay rates of dried Spartina alterniflora roots between high and low marsh, in areas with widely different Eh's, between sites with very different hydrologic regimes, or over a wide range of temperatures. The most significant difference reported by Hackney was within site variation. Before comparisons between sites along the Hog Island transect can be made, it is essential to understand within site variation in decomposition rates and to know the effects of temperature, hydrologic regime, Eh, and sampling frequency (see Singh et al, 1984 and Dickerman, 1986 on bias and random errors associated with sampling frequency) on the decay of fresh root material. Preliminary studies at Phillips Creek Marsh will also examine the vertical distribution and variation in decomposition rates which has not been reported in the literature previously.

METHOD

Litter bags will be collected, in triplicate, bimonthly; and implant bags (also in triplicate) will be collected monthly. Both will be sampled from mid-March through the end of September. At the time of collection soil temperatures and Eh will be measured for each depth.

After collection each bag will be separated separated into 10 cm increments to be analyzed separately. For each of these subsamples, the sediments are removed by washing. For litter bags the dead material is then separated from the live material and both portions are analyzed separately. For the implant bags the roots and rhizomes are separated from the mulch for analysis. These subsamples are then dried at 105o C. After cooling and weighing, samples are then ashed in a muffle furnace at 500 C. From these two determinations a % dry weight and % ash free dry weight remaining (AFDW) are calculated. Rates of decomposition and productivity can be calculated from these determinations. Relationships between rates of decomposition and productivity can then be compared through time and depth.

Future work will include a greenhouse study. This study will be designed to examine the rate of decomposition under different flooding regimes. The controlled conditions to be considered are continuous flooded, anaerobic conditions, well-drained aerobic conditions and alternating flooded and drained conditions. The details of this study will be worked out later and will begin later in the spring.

Project Methods

see above

Project Progress

05/01/89:

An intermediate length (one year) study of Spartina alterniflora decomposition was begun in March 1988. Root decomposition and root growth into the litter bags is being studied at depths ranging from the marsh surface to -40 cm using 50-cm long litter bags inserted vertically in the marsh sediment. Results from the first 7 months indicate different trends in the rates of weight loss between the creek bank and the marsh interior. Decomposition rates on the marsh surface have exceeded those of the buried plant material, but no clear differences in rates have been observed between litter buried 0-10cm and 30-40 cm below the surface. These results, along with measurements of sediment moisture and platinum electrode potential, suggest that variation in the rates of belowground decomposition may be related to differences in the degree of sediment aeration. We are currently testing this hypothesis in laboratory simulations with controlled drainage regimes.

Variables

Detailed Variable Information

DAYS - Days of incubation

• Units: Days

• Range: 0-736

• Format Information:
  
  • Start Column: 1
  • End Column: 3
  • Format: I
  • Width: 3
  • Decimals: 0
  • Line within Observation: 1

YEAR - Year Sampled

• Units: YY

• Range: 00-99

• Format Information:
  
  • Start Column: 5
  • End Column: 6
  • Format: I
  • Width: 2
  • Decimals: 0
  • Line within Observation: 1

MONTH - Month Sampled

• Units: MM

• Range: 1-12

• Format Information:
  
  • Start Column: 7
  • End Column: 8
  • Format: I
  • Width: 2
  • Decimals: 0
  • Line within Observation: 1

DAY - Day Sampled

• Units: DD

• Range: 1-31

• Format Information:
  
  • Start Column: 9
  • End Column: 10
  • Format: I
  • Width: 2
  • Decimals: 0
  • Line within Observation: 1

CRKSURF - Creek Bank,Surface Decomposition from Litter Bag

• Units: % AFDW

• Range: 0-150

• Format Information:
  
  • Start Column: 12
  • End Column: 18
  • Format: F
  • Width: 7
  • Decimals: 3
  • Line within Observation: 1

  Methods for Variable CRKSURF

  CRKSURF: MATERIALS AND METHODS Study Area The study area was located in the Phillips Creek marsh on the oceanside of the Delmarva Peninsula (Figure 3, Ray, 1989). This area is contained in the Nassawadox, Virginia 7.5 minute quadrangle at a latitude of approximately 37 o 27' 30'' and a longitude of approximately 75 o 50' (Figure 4, Ray, 1989). Phillips Creek is located near Brownsville, Virginia, headquarters of the Nature Conservancy, and is part of the Virginia Coastal Reserve Long Term Ecological Research (VCR/LTER) study area. The marsh area is located behind a relic sand ridge. The surrounding uplands are either farm lands or pine forest wood lots. The dominant marsh vegetation is Spartina alterniflora , with the tall form found along the creekbanks, an intermediate form found along the levee banks, and the short form in the marsh interior or marsh flat (taken from Harvey et al. 1987). Found along with the short form of Spartina is Salicornia virginica , usually indicative of higher salinities (W.E. Odum, personal communication). Farther inland in the high marsh are stands of Juncus roemerianus , and bordering the uplands are Spartina patens and Distichlis spicata . Areas near the levee bank and interior marsh (marsh flat) in the Spartina alterniflora are often riddled with burrows made by Uca and Sesarma , with several of these species found throughout the marsh. The areas appeared to be heavily grazed, with some areas completely bare and other areas sparsely vegetated with stalks of plants cropped off near the sediment surface. The underlying sediments are predominantly organic matter with clay to depths of 10-20 cm, at greater depths the organic content decreases and sand and clay increase (Barr 1989). Due to differences in classical marsh studies, descriptions of levee and interior marshes do not fit what has been observed for Phillips Creek Marsh. Therefore, each site was designated as Site I (Interior Marsh) and Site II (Creekbank Marsh). The differences between the two sites were related to Spartina height form and duration and frequency of tidal inundation. Two transects were established in the Phillips Creek area which were situated parallel to the creekbank along a contour interval (Figure 4, Ray, 1989). The first transect, Site II (creekbank), was situated within one meter of the creekbank in an intermediate form of S. alterniflora . The second transect, Site I (interior), was situated 4 meters inland in a short form of S. alterniflora . Site II (creekbank) is subjected to greater frequency and duration of tidal inundation, and Site I (interior) is not flooded with every tide. In May of 1988, elevations along each transect were determined with a long-range surveying transit (Appendix 1, Ray 1989). Both transects appear to be relatively uniform with respect to elevation, and approximately 22 cm difference in elevation separate the two sites. Mean elevation for the Site I is 13.95 m and 13.73 m for the Site II. Placing each transect along a marsh contour provides a control for tidal inundation, so that each point along a transect is subjected to similar tidal influences. Site I (interior) is flooded only at very high tides. Measurement of Decomposition Cores were collected from Site I on March 14, 1988, and returned to the lab where the organic matter consisting of live and dead roots and rhizomes, were rinsed free of sediments. All live material was removed and the dead root material (containing roots and rhizomes) separated into 12 gram ( q 0.5 gm, wet weight) portions. Each portion was placed in a nylon mesh litterbag (1 mm 2 mesh size) 40 cm long by 6.5 cm wide. The bags were sewn closed at 10 cm intervals as shown in Figure 5 (Ray, 1989). The design of these litterbags allow easier examination of the vertical distribution of belowground decomposition, rather than measuring decomposition at discrete intervals. Additional 12 g portions were weighed. These samples were dried and ashed without being placed in the marsh and used to calculate a wet weight:dry weight:ash-free dry weight ratio (Zieman, 1968). The litterbags were placed in the marsh on March 26, 1988. At Site II (creekbank), a flat spade was inserted in the sediment to approximately 60 cm depth and the bag slid into the sediment along the blade of the spade. The litter bag was placed vertically so that the top 10 cm section remained on the surface and the bottom of each bag was approximately 40 cm deep. The sediment was then pressed back in around each bag. In the interior marsh (Site I), cores were hand augered and a bag placed in each hole. Once again, the top 10 cm section was left exposed on the surface and the bag extended 40 cm below the surface. The sediment removed by coring was returned to the core hole beside the bag to ensure an environment similar to the pre-existing one. Sixty bags were inserted in the marsh at each site. Litterbags were collected in triplicate, and returned to the lab for processing. Ash-Free Dry Weight Determination (%AFDW) In the laboratory each decomposition bag was separated into 10 cm sections and washed free of sediments. All live roots growing into the decomposition bags were removed and handled separately (separate data set). Samples were dried in a mechanical convection oven at approximately 105 o C. After drying to a constant weight, approximately 24 hours, the samples were ashed in a muffle furnace at 500 o C for 6-8 hours. From the ash weight and the conversion factor from wet to dry weight, a percent ash free dry weight (AFDW) remaining was calculated for each 10 cm interval. References Barr, L.H. 1989. Sedimentation and fallout Cesium-137 cycling in a Virginia salt marsh. M.S. Thesis. Dept. of Environmental Sciences, Univ. of Virginia, Charlottesville, VA. Ray, M.W. 1989. Belowground decomposition and production dynamics in a Virginia salt marsh. M.S. Thesis. Dept. of Environmental Sciences, Univ. of Virginia, Charlottesville, VA. Zieman, J.C. 1968. A study of the growth and decomposition of the seagrass Thalassia testudinum . M.S. Thesis, Univ. of Miami, Coral Gables, FL.

CRKSSTD - Standard Deviation for variable CRKSURF

• Range: 0-
• Format Information:
  
  • Start Column: 20
  • End Column: 25
  • Format: F
  • Width: 6
  • Decimals: 3
  • Line within Observation: 1

CRKBELO - Mean decomp in Marsh sed (0-40cm) 1 Meter from Marsh Creek

• Units: % AFDW

• Range: 0-150

• Format Information:
  
  • Start Column: 27
  • End Column: 33
  • Format: F
  • Width: 7
  • Decimals: 3
  • Line within Observation: 1

  Methods for Variable CRKBELO

  CRKBELO: See methods description for variable CRKSURF

CRKBSTD - Standard deviation for variable CRKBELO

• Range: 0-
• Format Information:
  
  • Start Column: 35
  • End Column: 40
  • Format: F
  • Width: 6
  • Decimals: 3
  • Line within Observation: 1

INTSURF - Mean decomposition on Marsh surface, 5 M from Marsh Creek

• Units: % AFDW

• Range: 0-150

• Format Information:
  
  • Start Column: 42
  • End Column: 48
  • Format: F
  • Width: 7
  • Decimals: 3
  • Line within Observation: 1

INTSSTD - Standard deviation for variable INTSURF

• Range: 0-
• Format Information:
  
  • Start Column: 50
  • End Column: 55
  • Format: F
  • Width: 6
  • Decimals: 3
  • Line within Observation: 1

INTBELO - Mean decomp in Marsh Sed (0-40cm), 5 M from Marsh Creek

• Units: % AFDW

• Range: 0-150

• Format Information:
  
  • Start Column: 57
  • End Column: 63
  • Format: F
  • Width: 7
  • Decimals: 3
  • Line within Observation: 1

INTBSTD - Standard deviation for variable INTBELO

• Range: 0-
• Format Information:
  
  • Start Column: 65
  • End Column: 70
  • Format: F
  • Width: 6
  • Decimals: 3
  • Line within Observation: 1

Dataset Contacts

Linda K. Blum

Contact Information

Dataset Originators (Authors) - Details

Linda K. Blum

Contact Information

LKB2E8802 - Project Details

Students: Margit Waters Ray

Core Areas	Sampling Methods
Primary Productivity Organic Matter	Core

Voucher Specimen Location: destructive

Related Datasets

Project Description and Goals

At present, little is known about decomposition rates and spatial variability in those rate within salt marsh sediments. Previous studies have in most cases examined the decomposition of dried plant roots buried a few cm below the marsh surface in both high and low marsh. Data from our studies of seagrass and cord grass decomposition in Chesapeake Bay (as well as Godshalk and Wetzel, 1978; Gallagher et al., 1984; Jesselyn and Mathieson, 1980) have shown that drying plant material significantly alters measured decay rates. Hackney (1987) found no differences in decay rates of dried Spartina alterniflora roots between high and low marsh, in areas with widely different Eh's, between sites with very different hydrologic regimes, or over a wide range of temperatures. The most significant difference reported by Hackney was within site variation. Before comparisons between sites along the Hog Island transect can be made, it is essential to understand within site variation in decomposition rates and to know the effects of temperature, hydrologic regime, Eh, and sampling frequency (see Singh et al, 1984 and Dickerman, 1986 on bias and random errors associated with sampling frequency) on the decay of fresh root material. Preliminary studies at Phillips Creek Marsh will also examine the vertical distribution and variation in decomposition rates which has not been reported in the literature previously.

METHOD

Litter bags will be collected, in triplicate, bimonthly; and implant bags (also in triplicate) will be collected monthly. Both will be sampled from mid-March through the end of September. At the time of collection soil temperatures and Eh will be measured for each depth.

After collection each bag will be separated separated into 10 cm increments to be analyzed separately. For each of these subsamples, the sediments are removed by washing. For litter bags the dead material is then separated from the live material and both portions are analyzed separately. For the implant bags the roots and rhizomes are separated from the mulch for analysis. These subsamples are then dried at 105o C. After cooling and weighing, samples are then ashed in a muffle furnace at 500 C. From these two determinations a % dry weight and % ash free dry weight remaining (AFDW) are calculated. Rates of decomposition and productivity can be calculated from these determinations. Relationships between rates of decomposition and productivity can then be compared through time and depth.

Future work will include a greenhouse study. This study will be designed to examine the rate of decomposition under different flooding regimes. The controlled conditions to be considered are continuous flooded, anaerobic conditions, well-drained aerobic conditions and alternating flooded and drained conditions. The details of this study will be worked out later and will begin later in the spring.

Methods

see above

Progress

05/01/89:

An intermediate length (one year) study of Spartina alterniflora decomposition was begun in March 1988. Root decomposition and root growth into the litter bags is being studied at depths ranging from the marsh surface to -40 cm using 50-cm long litter bags inserted vertically in the marsh sediment. Results from the first 7 months indicate different trends in the rates of weight loss between the creek bank and the marsh interior. Decomposition rates on the marsh surface have exceeded those of the buried plant material, but no clear differences in rates have been observed between litter buried 0-10cm and 30-40 cm below the surface. These results, along with measurements of sediment moisture and platinum electrode potential, suggest that variation in the rates of belowground decomposition may be related to differences in the degree of sediment aeration. We are currently testing this hypothesis in laboratory simulations with controlled drainage regimes.

Impact on Site

CORING - approximately six cores/sampling interval (sample interval 2-3 weeks)

LITTER BAG PLACEMENT - cores will be removed and bags inserted, approximately 150 bags, diameter 2.5 cm, length 40-50 cm.

Need for Isolation

Litter bags must not be disturbed in any way

Products

Porposal with Nuttle, at least one publication, numbers for decomp./Org.Acc. monitoring

Related Projects

References

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