Research has identified the hyporheic zone as an important part of stream ecosystems. The hyporheic ... Analysis of plant growth and survival are being made in ...
HYPORHEIC ZONE DEVELOPMENT IN A RESTORED RIPARIAN AREA D. M. Andrewsa, C. D. Bartona, R. K. Kolkab, C. C. Rhoadesc Seedling Competition Plots
Results
• Research has identified the hyporheic zone as an important part of stream ecosystems. The hyporheic zone is the saturated subsurface sediment that lies directly beneath and beside streams where groundwater and surface water mix. • The importance of hyporheic zones to stream communities stems from the high activity of both chemical and biological reactions that occur within its reach. Riparian vegetation also plays a critical role in hyporheic zone development. Thus, subsurface hyporheic linkages and riparian vegetation are key components to understanding the structure and function of riparian and stream systems in restoration projects.
Channelized Reach of Wilson Creek
Wilson Creek Riparian Restoration
Treatment
Litter
SWD
LWD
Total
TC
6847 8625
605 2968
21 47
7473 11640
3053 4805
65 94
Tubex
7030
6344
148
13522
5649
98
Post Restoration: Pool
Project Objectives
Post Restoration: Riffle
The overall objective of this project is to demonstrate techniques to improve water quality in streams draining human-altered lands in central Kentucky. Techniques for the successful restoration of riparian vegetation communities will be developed, and the rate at which an active hyporheic zone develops will be evaluated. As part of the overall objective, this project expects to reconnect the stream to its historic floodplain causing an increase in floodplain flooding, and rise in groundwater levels that will create and support adjacent wetlands and floodplain ponds.
Methodology
18
Disturbed Stream Channel
17 13 3
I
12 4
5
6
7 8
9 16
D
H
15
E
14
G
1
F
2
11 10
Biogeochemical Plots Competition Plots
Restored Stream Channel
Table 1. Competition study design. Treatment Control H
Herbicide
Shelter
n
none Rodeo®
none none
3 3
Continental
Mesh®
3
C
none
T
none
Tubex®
C+H
Rodeo®
Continental Mesh®
3
T+H
Rodeo®
Tubex®
3
Nitrate-N
Water quality parameters, pH (7.89±0.36) and TDS (0.259±0.034 g/L), were similar within the surface and hyporheic waters within both the reference and restored areas. DO and EC were found to be lower in the hyporheic water as compared to the surface water (4 vs ~12 mg/L, and 300 vs 350 µS/cm respectively). At this time, no significant differences (at the 95% CI) were found between upstream and downstream nutrient concentrations (NO3-, NH4+, SO42-, Cl- , Na+, K+, Ca2+, Mg2+). Nitrate concentration was found to be gradually decreasing from upstream to downstream (Fig. 3.). Redox sensitive elements, Fe and Mn, were found to be at higher concentrations in the hyporheic water as compared to the surface water in both the forested and cane treatment plots (Fig. 4). Calculated P-values indicate significant differences in surface vs. subsurface Fe for both forested and cane plots, while Mn differences were observed only in the cane treatments (Table 3). Although the system is young, results indicate that development of the hyporheic zone has begun.
a
bc
b
c
b
Control
H
T
C
T+H
C+H
0
Survival
A
B
A
a
b
a
1 0.8
50
0.6 0.4
0
0.2 0 ASH
OAK
SYC
Element
Mn Fe
Surface vs Subsurface Waters
Total Organic Carbon 57. 00
0.35
56. 00
0.30
55. 00 54. 00
0.25
53. 00
0.20
52. 00
0.15
51. 00
0.10
50. 00
0.05
49. 00
0.00
48. 00
REF A
REF B
REF C
RES D
RES E
RES F
RES G
RES H
RES I
D/ S
Continental Mesh Tree Shelters
Study Sit e
Fig. 3. Surface water nutrient and carbon levels.
Tubex Tree Shelters
Fe Concentration in Forested vs Cane Plots 1.6
a)
1.4
1.2
1
Stream SSF
0.8
0.6
0.4
Forested Species Growth
0.2
0
Forested
Cane
Woody Debris Accumulation
Vegetation Type Mn Concentration in Forested vs Cane Plots
b)
Table 3. P-values for Fe & Mn.
3
Ammonium-N
0.40
Fe Concentration (mg/L)
The Restored Streambed
0.2
a
Nutrient Content In Reference vs Restored Areas at Wilson Creek
Water Quality
•Forest competition experimental plots (10- x 10-m) were planted American sycamore (Plantanus occidentalis), green ash (Fraxinus pennsylvanica var. subintegerrima), and pin oak (Quercus palustris) on 1.5-m centers (Table 1).
0.4
Fig. 2. Growth and survival of seedlings by species.
performed 16 months after planting and shelter installation; SWD = small woody debris (10 cm diameter); TC = total carbon per treatment; TN = total nitrogen per treatment.
Conclusions
1.4
1.2
Mn Concentration (mg/L)
During restoration: Pool & Riffle
Pre-restoration
0.6
40 30 20 10 0
-50
†Survey
• The riparian corridor was revegetated using giant cane (Arundinaria gigantea), native forbs, wetland herbaceous species; and bottomland forest species in spring 2004.
0.8
Growth
TN
No Shelter Continental
1
(ns)
100
-----------------------------------g m-2 -----------------------------------
• Previously channelized sections of Wilson Creek (Nelson Co., KY) were returned to its original meandering configuration in 2003.
Survival
Fig. 1. Growth and survival of seedlings by treatment.
Table 2. Debris, carbon and nitrogen retention in sheltered and non-sheltered treatments.
• Sections of Wilson Creek are thought to have been straightened in the late 19th or early 20th century, in order to maximize the amount of arable land in the valley bottom.
80 70 60 50
Survival
Growth (cm)
• The Wilson Creek riparian restoration site is located in central Kentucky’s Knobs Region on the western border of the Bluegrass section of the Interior Low Plateaus Physiographic Province. It is a tributary of the Rolling Fork in the Salt River watershed.
Within the competition plots, seedling survival was high (83-93%) and not significantly different for any of the treatments. There was a significant decrease in seedling growth in the non-shelter plots as compared to the plots with shelters (Fig. 1). Differences between shelter type without herbicide were not significant, but the addition of herbicide to the tubex plots resulted in increased growth. A comparison of seedlings, regardless of treatment, revealed that oaks had significantly lower growth and survival over the ash and sycamore (Fig. 2). In fact, oak exhibited a negative growth rate over the first two growing seasons. Frequent flooding that occurred during the 2004 growing season appeared to affect oak more so than the other species. Many of the original oak stems were knocked down by flooding waters, or debris carried within, and the resulting measurements were taken on re-sprouts. Examination of oak data by treatment revealed that both non-sheltered treatments had negative growth rates, while three of the four sheltered treatments exhibited positive growth rates similar to that of ash and sycamore. As such, shelters appeared to have physically protected seedlings during the flooding events. Interestingly, the shelters provided an unexpected benefit of debris retention within the plots. Both shelter types showed more debris than the non-sheltered treatments (Table 2). A stake that was hammered into the ground to support the shelter, was likely the reason for this retention as it was much less forgiving than the unprotected seedling stem which would fall over upon contact with floating material.
Growth (cm)
• Stream restoration offers the opportunity to return function to streams that are both ecologically and economically valuable. Almost all of Kentucky’s large streams have been impounded or channelized. Human disturbances to the physical, chemical and biological composition of smaller streams is also widespread throughout the state.
Experimental plots were established in the restored riparian area and in upstream reference areas to examine the effects of vegetation establishment and composition on soil and water quality attributes. Analysis of plant growth and survival are being made in the restoration plots on a quarterly basis. Seedling height and diameter are measured on all species planted in the forested plots, and %cover is utilized in the cane plots. The use of two tree shelters (tubex vs. continental mesh) with and without herbicide are being examined in the forested plots as potential methods for controlling competition and herbivory. Seasonal nutrient and carbon dynamics are measured within each of the plots using: litterfall traps; litter and woody debris accumulation surveys; litter decomposition bags; carbon dioxide flux; soil moisture; and soil physiochemical characterizations. Each plot is also being monitored using piezometers and wells to evaluate the biogeochemical conditions. Water samples are collected monthly from both the stream and the hyporheic zone in each plot. Field measurements of pH, electrical conductivity (EC), total dissolved solids (TDS), dissolved oxygen (DO), and temperature are performed using a YSI® environmental monitor. Water samples are analyzed in the laboratory for total organic carbon (TOC), NO3-, NH4+, SO42-, Cl- , Na+, K+, Ca2+, Mg2+, Fe, Mn, and Al.
Growth (cm)
Riparian Zone Establishment
Survival
Introduction
1
0.8
Stream SSF
0.6
0.4
0.2
0
Forested
Cane
Vegetation Type
Fig. 4. Surface vs. subsurface Fe (a) and Mn (b) concentrations.
Forested vs Cane Plots
Forested
Cane
Surface Waters
Subsurface Waters
0.11 0.0028
0.010 0.039
0.41 0.36
0.020 0.45
Success of restoration efforts center around how rapidly dense, close-canopy riparian vegetation develops to stabilize the site and curtail impacts to stream quality, and how quickly this restored riparian vegetation will take to modify the biogeochemistry of the stream corridor. Initial results show that the riparian species are growing and development of the hyporheic zone is occurring through carbon and nutrient accumulation and changes in subsurface redox conditions. Tree shelters appear to facilitate the development of these zones. a University
of Kentucky, Department of Forestry, USDA Forest Service, North Central Experimental Station C U.S. Forest Service, Rocky Mountain Research Station, b
