Transcript Design - Confex

Non-destructive Estimation of Net Primary Production in Urban Rain Gardens
M. R. Johnston and N. J. Balster, Department of Soil Science, University of WI, 1525 Observatory Drive, Madison, WI 53706
Most of the species of shrub planted in the rain gardens
have allometric equations derived from physical
dimensions such as stem diameter and crown area. These
allometries estimate aboveground biomass (Smith and
Brand, 1983; Golubiewski, 2006), whereas estimates of
belowground biomass are lacking. Similarly, the 19
species of prairie plants included in this study are
commonly planted within raingardens, yet these species
lack allometric equations for estimating biomass. In the
past, studies have approximated belowground production
beneath prairie vegetation from aboveground growth
(Reich et al., 2003), or have emphasized differences in
productivity at a landscape scale (Knapp et al., 1993). By
destructive sampling, we will establish allometric
equations between total, aboveground, and belowground
biomass for each species of shrub and wet-mesic prairie
vegetation. Moreover, we will regress plant biomass to a
suite of physical measurements, including stem diameter,
plant height, crown area, and canopy height.
Since we can easily measure indirect leaf area index (LAI)
in the rain gardens (with a light attenuation probe), we will
measure LAI as another possible predictor of biomass. For
each species of prairie and shrub, we will relate plant
aboveground biomass to indirect LAI (Turner et al., 2004),
asking also whether indirect LAI correlates best with leaf
biomass or total aboveground biomass (i.e., some of the
prairie species have photosynthetic stems). Through these
species-specific allometries, we will be able to estimate
aboveground, and thus belowground, biomass for a
community of species.
Preliminary Results
Harvesting one replicate of each prairie species a month after planting plugs provided preliminary
relationships among biomass, LAI, and canopy height. Here, we show initial data for the 19 species of
prairie planted in experimental rain gardens, labeled as in Table 1. We harvested a sample plant for
each shrub species at time of planting, but preliminary data on shrubs are not presented here.
Design
Plastic pots (open cylinders, diameter 36 cm and height 92 cm)
were filled with a mix of topsoil, sand, and compost. Planting took
place in late June, 2006. There are three replicate pots per
species of prairie (Table 1) and shrub (Table 2).
40
Prairie monocultures were planted with four individuals per pot,
using second-year plugs (Prairie Nursery, Brodhead, WI).
Shrubs were planted one individual per pot, using mature potted
plants (Watts Landscaping Service, Madison, WI).
All plants are growing under field conditions with minimal irrigation.
The pots are located near experimental rain gardens on the west
side of Madison, WI.
Prairie plants one month after planting, in
July 2006. The fourth pot of each species
was harvested for biomass.
Shrubs one month after planting, in July
2006.
Measurement
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
Scientific Name
Andropogon geradii
Asclepias incarnata
Aster novae-angliae
Baptisia bracteata
Boltonia asteroides
Carex vulpinoidea
Echinacea pallida
Echinacea purpurea
Eupatorium perfoliatum
Helianthus occidentalis
Liatris pycnostachya
Monarda fistulosa
Panicum virgatum
Parthenium integrifolium
Penstemon calycosus
Ratibida pinnata
Rudbeckia hirta
Solidago rigida
Veronicastrum virginicum
Common Name
Big bluestem
Red milkweed
New England aster
Cream indigo
False aster
Fox sedge
Pale purple coneflower
Purple coneflower
Boneset
Ox-eye sunflower
Prairie blazing star
Bergamot
Switch grass
Wild quinine
Longsepal beardtongue
Yellow coneflower
Black-eyed susan
Stiff goldenrod
Culver's root
Y = 8.62 X + 9.13
18
We will harvest all shrubs at the end of the growing season
(October, 2007). Each species of prairie vegetation will be
considered independently to account for the seasonal range in
peak productivity (harvested before, during, and after flowering).
25
2
13
20
19
15
11
15
1
16
8
10
7
10
9
6
4
0.0
0.5
1.0
1.5
2.0
2.5
3.0
LAI
Figure 1. Total aboveground biomass (g) and optical leaf
area index (LAI) for the 19 prairie species harvested one
month after planting.
Measure SLA by species three times over the season, using 6
leaves per prairie species and 9 leaves per shrub.
Harvest
3
17
12
0
Compute specific leaf area (SLA) from dry leaf mass (60 °C for 48
hours) and a leaf area meter with transparent conveyor belt (LiCor
LI-3000).
Measure indirect leaf area index (LAI) at the soil surface every two
weeks (LiCor LI-2000) beneath prairie vegetation.
R2 = 0.87
14
30
5
Record physical plant measurements, including heights, canopy
volume, and basal stem diameters.
Table 1. Prairie Mix Species List
5
35
Aboveground Biomass (g)
Rain gardens installed within the urban landscape have
included various vegetation types, such as a wet-mesic
prairie or typical landscaping shrubs. We evaluate the
performance of rain gardens by estimating plant
productivity and light interception for each vegetation type.
We seek simple predictors of biomass for each vegetation
type using dimensional analyses.
Methods
40
5
18
35
Aboveground Biomass (g)
Introduction
14
30
3
17
12
25
13
20
15
19
16
11
15
7
10
8
The Next Step
1
10
9
6 4
5
Y = 0.41 X + 6.28
R2 = 0.91
Clip aboveground biomass and separate into leaves, stems, fruit,
flowers. Hand sort and rinse live roots from soil carefully excavated
from pot. Hand sort roots and separate them into two groups: roots
which were part of the original plug and roots new since planting.
0
Dropped leaves from all pots will be collected every week and
factored into the biomass summations.
7
Establish allometric equations for aboveground,
belowground, and total biomass by species.
Apply these allometric equations for each species to
prairie and shrub vegetative communities in rain gardens.
0
20
40
60
80
Height (cm)
Figure 2. Aboveground biomass and canopy height for the
19 species of prairie harvested one month after planting.
2
R = 0.86
6
18
Scientific Name
Cornus sericea ‘isanti’
Ilex verticillata
Prunus aroniamelanocarpa
Salix purpurea ‘gracilis’
Viburnum trilobum
Viburnum dentatum
Common Name
Red-twig dogwood
Winter berry
Black chokeberry
Dwarf arctic willow
American cranberry
Arrowwood viburnum
4
13
3
5
14
3
1
2
17
12
15
2
16
1
8
10
11 19
7
6
9
References
Knapp, A. K., J. T. Fahnestock, S. P. Hamburg, L. B. Statland, T. R. Seastedt, and D. S. Schimel. 1993. Landscape patterns in soilplant water relations and primary production in tallgrass prairie. Ecology 74:549-560.
4
0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Optical LAI
Measuring aboveground biomass one
month after planting, Aster sp.
Hand-sorting belowground biomass one
month after planting.
Beginning in the spring of 2007, we will monitor
changes in the physical dimensions, LAI, and
productivity for each species of prairie and shrub.
We will harvest all plants to capture their peak
productivity and build allometric equations for each
species. These measurements, excepting harvest,
will be repeated in the experimental rain gardens.
We will select the best predictors of biomass for
each species by generating sets of equations. We
will apply these relationships to approximate
aboveground and belowground productivity in the
experimental rain gardens, where destructive
sampling is not preferable. Finally, rain garden
performance may be evaluated as a function of
differing vegetation types.
Y = 1.40 X + 0.59
Direct LAI
Table 2. Shrub Species List
We checked whether LAI measured with an
optical light attenuation probe represented actual
LAI when calculated from leaf biomass (Figure 3).
Although we will establish this relationship on a
species-basis, combined data from all 19 species
supports measuring indirect LAI in rain gardens
as a surrogate for direct LAI. Note that direct LAI
calculated for Solidago (number 18) is high
because this species grew the most leaf biomass
at time of harvest (Figure 2).
2
5
Objectives
Total aboveground biomass was positively related
to indirect LAI (Figure 1). In general, aboveground
biomass and canopy characteristics seemed to
change LAI. For example, Baptisia and Carex
(numbers 4 and 6) grew very little aboveground
since planting, Monarda (12) developed a tall,
open canopy, and Boltonia and Solidago (5 and
18) established dense canopies. Aboveground
biomass also related well with canopy height for
the 19 prairie species (Figure 2).
Figure 3. Leaf area index (LAI) by direct calculation and
optical light attenuation probe for the 19 prairie species
harvested one month after planting.
Reich, P. B., C. Bushena, M. G. Tjoelker, K. Wrage, J. Knops, D. Tilman, and J. L. Machado. 2003. Variation in growth rate and
ecophysiology among 34 grassland and savanna species under contrasting N supply: a test of functional group differences. New
Phytologist 157:617-631.
Smith, W. B., and G. J. Brand. 1983. Allometric biomass equations for 98 species of herbs, shrubs, and small trees. Research Note
NC-299, North Central Forest Experimental Station, USDA Forest Service, St. Paul, Minnesota, USA.
Turner, M. G., D. B. Tinker, W. H. Romme, D. M. Kashian, and C. M. Litton. 2004. Landscape patterns of sapling density, leaf area,
and aboveground net primary production in postfire lodgepole pine forests, Yellowstone National Park (USA). Ecosystems 7: 751-775.