connections and key scientific issues: a terrestrial perspective
TRANSCRIPT
Connections and Key Scientific Issues:
A Terrestrial Perspective
How do we get from Point A to Point B ?
Timing is everything
• Trajectories of change• Sequence and linkages
Timescale of change in terrestrial biogeochemistry and energy balance is longer than timescale of major climatic oscillations.
Spatial scales are generally finer.
Major need: Study systems that are clearly
changing, focus on linkages not single
processes
Scaling up: How can we make broad regional predictions from fine-scale measurements?
Williams and Rastetter 1999
y = 1.89x
R2 = 0.95
y = -0.44x2 + 2.16x
R2 = 0.92
0
0.5
1
1.5
2
2.5
3
3.5
4
0 0.5 1 1.5 2
LAI [m2 m-2]
Fo
liar
N [
g m
-2 g
rou
nd
are
a]Swedish heath Alaskan heath
Swedish shrub Alaskan shrub
Swedish wetland Alaskan wetland
Swedish peat Alaskan tussock
Linear (Swedish) Poly. (Alaskan)
B. Fertilized plots
0
50
100
150
200
250
300
350
400
1982 1983 1984 1989 1995 2000
Ap
ical
Gro
wth
, g
/m2/
y
A. Control plots
0
50
100
150
200
250
300
350
1982 1983 1984 1989 1995 2000
Ap
ical
gro
wth
, g
/m2/
y Forb apical
Evergreen apical
Deciduous apical
Graminoid apical
New elements: e.g., Winter C turnover
“Development” of prev. observed changes: e.g., Shrub abundance
Identification of feedbacks:
Surface Energy balanceC cycling/GH gases
Water
Nutrients
Scales of change: longer time scale, coarser space scale than climate oscillations.
A. Control Plots
0
50
100
150
200
250
1982 1983 1984 1989 1995 2000
g/m
2
Eriophorum
Betula
Ledum
Vaccinium
B. Fertilized plots
0100200300400500600700800900
1982 1983 1984 1989 1995 2000
g/m
2
A. Control plots
0
50
100
150
200
250
300
350
1982 1983 1984 1989 1995 2000
Ap
ical
gro
wth
, g
/m2/
y Forb apical
Evergreen apical
Deciduous apical
Graminoid apical
A. ANPP vs biomass
2000
1983
1984
19891995
0
100
200
300
400
500
0 200 400 600 800 1000Biomass, g/m2
AN
PP
, g
/m2/
y
Control
Fertilized
B. ANPP vs leaf mass
2000
1989
1984
1983
1995
0
100
200
300
400
500
0 50 100 150 200 250
Leaf mass, g/m2
AN
PP
, g
/m2
/y
C. ANPP vs. estimated leaf area
20001995
1983
1984
1989
0
100
200
300
400
500
0.00 1.00 2.00 3.00 4.00
Leaf area, m2/m2
AN
PP
, g
/m2
/y
Figure 4. Aboveground net primary production versus biomass, leaf mass, and leaf area in the long-term fertilizer experiment at Toolik Lake, Alaska. Open symbols represent data from control plots; filled symbols represent fertilized plots. For the fertilized plots, the year of harvest is indicated for each data point. Data from 1983-1995 are from Shaver et al. 2001; data from 2000 are unpublished.
