Download 118-129 Silver, WL and KA Vogt. 1993. Fine root dynamics following

… On Predicting Root Decomposition
Kim H. Ludovici
USDA Forest Service, SRS-4160
Abstract
Table 1.
Summary of literature review including root size and species, and decomposition rate constants (k-values)
when published.
Ref. #
Date
1955
1973
1982
1982
1983
1983
1983
1984
1984
1985
1986
1987
1988
1988
1991
1992
1993
1993
1993
1993
1994
1994
1994
1995
1996
1997
1997
1997
1997
1997
1998
1998
1998
1998
1999
2000
2000
2000
2000
2000
2001
2001
2001
2001
2001
2002
2002
2002
2002
2003
2004
2004
2005
2006
2006
2006
2006
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Determining what we know about root decomposition
means going back through the literature, to see what
has really been done, what assumptions have been
made, what species and environmental conditions
are included, and how the work was implemented. A
literature search for peer-reviewed publications
reguarding “tree and root and decomposition”
identified only 58 articles published in the past 40
years (Table 1). Of those 58, only 24 publications
included within-species manipulations and/or direct
tests of site effects on root decomposition rate (Table
2). Post-harvest decomposition (Fig. 1) is virtually
unstudied, even though large roots persist for many
years (Fig. 2), and contribute a sizable pool of C to
the developing forest (Fig. 3) Methodologies have
varied widely, but most often utilize live, excised
roots that are washed and dried prior to
decomposition (Fig. 4). Studies incorporating season
and root hydration (Fig. 5) suggest additional
sources of variability in root decomposition rates.
23
24
< 2 mm
< 1.5 mm
< 3 mm
< 2 mm
< 2 mm
< 19 cm
> 10 mm
< 2 mm
< 2 mm
< 5 mm
> 10 mm
cellulose
< 2 mm
< 5 mm
< 2 mm
< 1 mm
< 2 mm
< 2 mm
< 3 cm
< 5 mm
< 2 mm
< 3 mm
< 3 mm
< 2 cm
< 2 mm
< 2 mm
<10 mm
review
1 year
2 years
1 year
1 year
2 years
5.5 years
3 years
5 years
2 years
1 year
2 years
2 years
1 year
1 year
1 year
3.5 years
1 year
1 year
1 year
chrono
5 years
0.75 yr
1.5 years
3 years
2+ years
0.75 yr
1 time
1 year
< 2 mm 2.5 years
< 2 mm
1 year
< 2 mm 2 years
stumps 60 years
< 2 mm
1 year
< 10 mm 2 years
< 2 mm
0.15 yr
< .5 mm
0.25 yr
< 3 mm 0.5 year
< 10 mm 1 year
< 10 mm 1.5 years
> 2 mm
1 time
0.60 - 0.83
Species
Pinus
Pinus
Pinus, HW
Picea
Abies, Pinus, Pseud.
Quercus
mixed deciduous
Pinus
Pinus, Quercus, Acer
Pinus
Pinus
Acer
Pinus
Prestoea, Dacryodes
Acer
Pinus
Dacryodes
HW
HW
Fagus, Fraxinus
Picea
0.4 - 0.9
0.001 - 0.01
0.261 - 0.483
0.032 - 3.734
0.10 - 0.715
0.17 - 0.22
0.156 - 0.467
0.81 - 6.17
0.023 - 0.055
0.669 - 0.709
0.001 - 0.002
0.001 - 0.857
Spartina
Pinus
boreal forest
Festuca
Pinus, Alnus
Acacia
Gutierrezia
Liquidambar
4 species combined
Metrosideros
Picea, Pseud., Pinus
Pinus, Drypetes
Juglans, Quercus
Quercus, Pinus
Fagus
Quercus
Quercus, Fagus
HW
Pinus
published data
Picea, Pseud, Pinus
Acer
Pinus
Pinus
Quercus, Fagus
Dichrostachys
Acer, Pinus
Populus, Acer
Eucalyptus
Quercus
Pinus
Pinus, HW
Author
Orlov
Head
Yavitt & Fahey
McClaugherty et. al.
Alexander & Fairley
Fogel
Thompson & Boddy
McClaugherty et. al.
Persson
Aber et. al.
Gholz et. al.
Nambiar
Fahey et. al.
Hunt et. al.
Faber et. al.
Ruark & Proe
Bloomfield et. al.
Hendrick & Pregistzer
Ruark
Silver & Vogt
Fahey & Hughes
Fahey & Arthur
Scheu & Schauermann
Lohmus & Ivask
Arunachalam et. al.
Conn & Day
King et. al.
Kurka & Starr
Robinson et. al.
Steele et. al.
Lehmann & Zech
Mun & Whitford
Price & Hendrick
Singh
Ostertag & Hobbie
Chen et. al.
Gholz
Jose et. al.
Usman et. al.
Zeller et. al.
Dilustro et. al.
Dress & Boerner
Gaudinski et. al.
John et. al.
Silver & Miya
Chen et. al.
Dornbush et. al.
John et. al.
Ludovici & Richter
Dress & Boerner
Manlay et. al.
Rotkin-Ellman et. al.
King et. al.
Binkley et. al.
Fritz et. al.
Ludovici & Kress
Miller et. al.
Results
Discussion
Summarization across species,
ecotomes and methodologies suggest:
Scores
Soilsnot
0-20differ
cm
Root decomposition rate All
does
by soil depth
Soil temperature may, or may not be positively related to
decomposition rate
Root decomposition is affected by soil texture
Site fertility is not a predictor of decomposition rate
Soil biota are always important for root decomposition
Ambient temperature and CO2 level do not strongly impact root
decomposition rates
Decomposition is negatively related to root diameter
Nutrient concentrations in roots may or may not be related to
decomposition rate
Decomposition is negatively related to root lignin and carbohydrate
PC1
concentrations
Root decomposition rates vary widely between species
Research studies have been conducted on every continent,
and on many of the most economically important species. The
2 phase pattern of decomposition, often reported for fine roots,
supports the idea that root structure and complexity control
nutrient release rates from roots, however, most studies
include only roots < 5mm in diameter, and last only a year or
two (approximately the duration of a Master’s project).
Consideration that most decomposition work is conducted on a
small percentage of the root system (just 5 – 15% of the total
tree biomass), and has a duration far shorter than the lifespan
of a fine root, is necessary. Root decomposition and nutrient
release are also traditionally estimated from dried root tissues,
and while it is unlikely that roots dehydrate prior to
decomposition in-situ, the limited studies disagree on the
cause and effect.
PC2
Conclusions
Table 2.
Summary of root decomposition rate response to within-species manipulations and/or direct tests of site effects.
Ref
Soil
H2O
Soil
depth
Soil
temp
---
Soil
text
Soil Soil amb
fert biota temp
CO2
level
Root
size
--+
---
Root
nutrients
1
2
O
O
3
4
O
O
5
+
--6
O
O
7
+
--O+
--- O
8
O
----9
O
O
--10
+
O
--+
11
+O
+
13
14
+
+
--+
15
O
O
O
16
+
+
--+
17
O
O
--O
18
19
+
20
--21
O
22
+
+
--+
23
+
O
24
--O
Responses could be + (positive), --- (negative) or O (no significant response).
Root
lignin
+O
O
---
Root
carbo
Tree
species
---
O
O+
+
We are seriously over estimating the amount of root
decomposition that occurs over a forest rotation. Additional
studies are required to test the mechanisms of nutrient loss,
and the long-term decomposition rates of larger roots.
+
+
---
----+
---
O
+
+
---
---
+
100
90
A
J dry
J fresh
80
O dry
O fresh
70
Ja dry
Ja fresh
60
A dry
50
Large root decomposition
Carbon surrounding a stump
A fresh
40
1200
160
B
55
tap wt = 119.03e
Root supplied C
-0.059x
lateral wt = 58.715e
80
-0.1073x
2
R = 0.7269
40
1000
total soil C
45
2
R = 0.7962
120
35
800
25
15
0
600
5
0
20
40
60
80
Years since harvest
-5 0
10
20
30
40
50
Years since harvest
60
400
70
Ludovici et al. 2002 CJFR
Fig. 2. Biomass of mature loblolly pine root
systems recovered along a time chronosequence,
Durham, NC
200
Fig. 3. Carbon pools in decomposing roots and the soil
volume surrounding them, measured along a time
chronosequence, Durham, NC 2000
Ju
nA 97
ug
-9
O 7
ct
D 97
ec
-9
Fe 7
b9
A 8
pr
-9
Ju 8
nA 98
ug
-9
O 8
ct
D 98
ec
-9
Fe 8
b9
A 9
pr
-9
9
Introduction and Methods
16
17
18
19
20
21
22
kg/tree
Fig. 1 Photograph of recovered root material from 55 to 70-year-old loblolly pine
stumps that had been decomposing for (A) 5 years, (B) 20 years, (C) 10 years,
and (D) 55 years, on a Kanhapludult in the Piedmont region of North Carolina.
Reproduced from Ludovici et al. 2002
Root diam Duration
k-values
< 3 mm
review
< 1 cm
chrono
0.0415
< 5 cm
1 year
< 5 mm
2 years
< 2 mm
review
large
< 3 mm
0.193 - 0.696
< 2 mm
chrono
< 3 mm
1 year
< 5 mm
1 year
> 5 mm 2.5 years
< 10 cm 2 years 0.042 - 0.093
kg / tree
Quantification of root decomposition remains
controversial because researchers can not control
the process. The literature provides examples in
which researchers have limited the size, age and
species of roots used in studies, or controlled the
onset of decomposition. Others have controlled
ambient and/or soil conditions during root growth
and decomposition. Still, there is not one
quintessential root decomposition methodology that
can be utilized across species or ecotomes. Using
data from available publications, decay curves will
be generated with consideration given to tree
species, stand age, root size, temperature and
methodology.
Fig. 4. Photograph of a controlled environment
chamber used in root incubations.
Fig. 5. Graph of % biomass loss (A) and carbon
concentrations (B) in fine roots of Pinus taeda
decomposing in-situ.
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