Within-stand Interactions of
Forest Structure and
Microclimate Variability in an
Old-Growth, Mixed-Conifer
Forest
Siyan Ma
Co-authors: Malcolm North, Jiquan Chen, Stephen Mather ,
Martin Jurgensen, and Brian Oakley
A Heterogeneous, Old-Growth,
Mixed-Conifer Forest
CC – Closed Canopy
(67.7%)
OC – Open Canopy
CECO – Ceanothus shrub
(4.7%)
(13.4%)
Changes in Forest Structure
before disturbances
After disturbances
Canopy cover influences within-stand
microclimate variability.
Canopy cover
Objectives
• examine heterogeneous forest and canopy structure in
multiple demonstrating scales
• quantify spatial variability of microclimatic variables
• explore spatial distributions of microclimatic variables
using empirical models
TeakettleHemispheric
Experimental
photos Forest
Microclimate Stations
Ta
RH
PAR
u
ri
CR10
datalogger
Tsf
Ts15
i = 1, 2, 3,…100 m
Ms
G
Stem Map
Microclimate Variables
• Daily means of each microclimate station
• Seasonal variability
• Spatial variability
?
Spatial variability in a whole year
• Spatial variability - Coefficient of Variation (CV, %)
• Spatial variability – seasonal patterns
Histograms of CV
• Different ranges of CV indicate spatial
variability of each variable.
• Most of variables have similar CV range.
• G has the greatest CV range.
Forest Structure in different
demonstrating scales
ri
i = 1, 2, 3,…100 m
Forest structure is “Heterogeneous”
within the area < 25 m radius.
120
(A)
100
DBH
(cm)
80
60
40
20
0
10000
(B)
Tree Density
(trees/ha)
8000
6000
4000
2000
0
1200
(C)
Basal Area
(m2/ha)
1000
800
600
400
200
0
0
20
40
60
Radius (m)
80
100
100
Closed canopy
Average
Canopy Cover (%)
80
Open canopy
60
40
20
0
0
20
40
60
Zenith (degree)
Tree density, dbh, and basal area may
80
100
The relationship between canopy
cover and forest structure
using stepwise regression.
CanopyCover = 72.545 - 0.004TD1 + 0.011TD3
- 0.053BA25 - 0.440DBH2
- 0.189DBH7 - 0.098DBH9
- 0.292DBH12 + 0.915DBH14
- 1.303DBH15
From Stem Map to Canopy Map
Table Linear regression models for predicting
microclimatic variables from topographic and foreststructure factors (EL – elevation, AS – aspect, and
CC -canopy cover), using photosynthetically active
radiation (PAR) and soil surface temperature (Tsf) in
May and August, and soil moisture (Ms) in June,
1999 and July, 2000 as examples.
Within-stand Spatial Distribution
Conclusions
• Microclimate spatial variability can be measured
using CV.
• CVs have seasonal patterns.
• Most of variables have similar spatial variability
except soil heat flux (G).
• Forest structure is “Heterogeneous” within the area
< 25 m radius.
• Spatial canopy distribution is related to forest
structure.
• Microclimate spatial distribution is predicable
using the relationship between microclimatic
variables and canopy distribution, topographic
factors, and other microclimatic variables.
Acknowledgements
Nathan Williamson
Rhonda Roberts
Eric Huber
Teakettle mapping Technicians (1999 ~ 2002)
The University of Toledo
USDA FS Pacific Southwest Research Station
USDA FS Southern Research Station
Michigan Technological University
Thanks for coming.
Questions ?