wp coordinator meeting june 17/18 2010 wp3 progress report
TRANSCRIPT
WP coordinator meeting June 17/18 2010
WP3 progress report
Reference Land-use transitions
Response variable or main effect
Stratification or main contrast
Number of observations and studies
Main conclusions
Allen, 1985 forest to cropped, grazed or plantation
difference soil C %, weighted by sample size
temperate versus tropical, split soils into ´young´or ´old´ categories based on soil order
26 studies;205 paired comparisons
Magnitude of soil C losses vary geographically: losses were 50% greater on highly weathered tropical soils compared to younger soils in the tropics, or similar soils in the temperate zone
Mann, 1986 uncultivated to cultivated
regression of carbon content in cultivated soils on carbon content in paired uncultivated soils; analyzed both C% and samples adjusted to fixed depth
depth, soil orders and suborders
50 studies; 625 paired comparisons;estimated BD when lacking
Average losses for 0-15 cm are 20% and from depths from 0-30cm lose less than 20% with cultivation
Detwiler, 1986
forest to cultivated land, forest to pasture, and secondary forest
Change in percentage soil C (%); C= 100-((%Ct/%Co)*100)Where Ct = %C at some time t, and Co = unmanaged C %
Uncultivated soil C stocks are based on aggregated life zone estimates; land-use change effects are not partitioned geographically
28 studies, 128 observations
Fit spline models to change in %C over time for three land-use transitions. Forest to agriculture reduced C% by 40% in 5 years post-clearing, then reached new equilibrium (model explains 20.4% of variance). Forest to pasture reduces C% by 20%, which does not vary with pasture age. Shifting cultivation causes losses of 18-27% of C%.
Davidson & Ackerly, 1993
uncultivated to cultivated
percent change in C stock, (Xc-Xr)/(Xr)*100
Split data into fixed depth versus genetic horizon sampling schemes, analyzed depths separately
18 studies;56 paired comparisons; excluded studies without BD
27.2% (±2.9 SE) loss across all depths (range for subsets was 24 to 43%), losses decrease with depth; carbon losses are not proportional to initial C stocks; no apparent effect of clay%; rates of loss are greatest earliest post-conversion, but decrease with cultivation time.
McGrath et al 2001
primary forest, secondary forest, pasture, annual crops, plantations
ANOVA to test for differences in C% and stocks by land use
Restricted studies to Oxisols or Ultisols
39 studies; 71 plots No differences in soil C concentrations or stocks among land uses
Fearnside & Barbosa, 1998
forest to pasture in Brazilian Amazon
percent change in C stock, (Xc-Xr)/(Xr)*100
“typical” (no input) compared to “ideal” pasture management
7 studies; 10 observations; applied average changes in BD from 5 studies to correct for compaction
typical management reduces soil C by 17.8% (0-20 cm), while “ideal” management increases soil C by 15.0% (0-20 cm)
Paul et al 2002 afforestation absolute and percent change weighted by plantation age
age, type of study, site preparation, prior land use, climatic zone, clay content, and plantation species
43 studies; 204 observations; estimated BD when lacking
Age dependent decrease then increase in soil C stocks, which depended on depth; soil C decreased on sites converted from pasture, and increased on sites converted from cropping; higher rates of accumulation in tropical compared to temperature climates; Pinus species decreased soil C while other species increased it
Murty et al 2002
forest to cultivation; forest to pasture
percent change in C stock, (Xc-Xr)/(Xr)*100
54 studies; 216 observations; restricted studies to ≥ yrs in current land use; used studies with BD, and adjusted data to common mass when possible
22.1%±4.1% (SE) loss in soil C stock with conversion of forest to cultivated lands (BD-corrected data only); no significant change with forest to pasture, 6.4±7.0% increase (BD-corrected data only)
Guo & Gifford, 2002
forest to pasture; pasture to secondary forest; pasture to plantation; forest to plantation; forest to crop; crop to plantation; crop to secondary forest; pasture to crop; crop to pasture
ln(Xc/Xr); unweighted meta-analysis
Analyzed various subsets of the data to look for effects of precipitation, depth, plantation species, and age effects
74 studies; 537 observations; estimated BD when lacking
Increases or decreases depended on land use: forest to pasture conversion increases SOC by 8% (most of this was due to high sequestration rates in areas with rainfall 2000-3000 mm, which had 24% increase (18 to 30 CI)); pasture or forest to plantation decreased soil C, while converting cropped lands to plantations, secondary forests or pastures increased soil C
Reference Land-use transitions Response variable or main effect
Stratification or main contrast
Number of observations and studies
Main conclusions
Silver et al 2004 tropical secondary succession and tree plantations
regressed soil C stocks on stand age
previous land use and life zones : dry (<1000mm), moist (1,000-2,500mm), or wet (>2,500mm)
16 studies; 68 data points (not paired); adjusted data to common depth via regression equations
soil C increased with secondary forest age; rates of increase depended on prior land use, but varied little among life zones
Berthrong et al, 2009 afforestation, i.e. tree plantations established on former grasslands, pastures or agricultural lands
ln(Xc/Xr); unweighted meta-analysis
Species (pine, eucalypt) or other
71 studies; 153 pairs; estimated BD when lacking
‘Afforestation with Pinus decreased soil C stocks by 15%´; this was the only significant result for C
Laganiere et al, 2010 afforestation, percent change in C stock, (Xc-Xr)/(Xr)*100; weighted responses by sample size
By inclusion of organic layer, study design, plantation age, and soil size fraction, previous land use, climatic zone, clay content (above or below 33%), pH, tree species, site preparation
33 studies;200 observations excluded studies without BD
Increases in C stocks following afforestation depended on previous land use :26% increase for crop land, 3% for pastures (NS), and <10% for natural grasslands (NS)
Reference Land-use transitions
Response variable or main effect
Stratification or main contrast
Number of observations and studies
Main conclusions
Original 500 papers → 150 paper
Selection criteria:
-Only when carbon stocks were reported (bulk density !!)-Omit plots without obvious or logical reference sites-Only studies that reported data from reference land use that preceded current land use-If multiple paper on same sites: only one included-Studies excluded if plots in different land uses were sampled at diferent depths
-Final database: 92 studies with 974 paired observations.
Land-use transition Depth % Change Log ratio
Mean 95%CI Mean 95% CI
forest to crop (107) All -19.72 -25.67 to -13.43 -0.295 -0.369 to -0.222
forest to pasture (289) 7.21 4.01 to 10.37 0.036 0.006 to 0.066
forest to plantation (69) -6.11 -16.63 to 5.62 -0.154 -0.249 to -0.058
SC: forest to crop (54) -12.61 -18.13 to -6.97 -0.168 -0.242 to -0.099
SC: crop to forest fallow (26) 6.46 -0.07 to 13.28 0.049 -0.014 to 0.112
crop to pasture (7) 8.64 -2.11 to 19.15 0.073 -0.033 to 0.168
crop to plantation (48) 20.59 10.38 to 32.68 0.146 0.071 to 0.227
crop to secondary forest (26) 43.21 22.56 to 66.69 0.292 0.16 to 0.431
pasture to plantation (89) 8.20 2.83 to 13.52 0.050 -0.001 to 0.101
pasture to secondary forest (165)
11.54 6.94 to 16.43 0.074 0.032 to 0.115
forest to crop (32) 0-10 cm -29.36 -36.91 to -20.75 -0.398 -0.512 to -0.288
forest to pasture (98) 15.32 9.65 to 21.11 0.111 0.059 to 0.161
forest to plantation (13) -8.32 -22.35 to 4.316 -0.132 -0.321 to 0.023
SC: forest to crop (7) -10.96 -34.20 to 10.52 -0.187 -0.495 to 0.077
crop to plantation (17) 28.45 6.58 to 58.08 0.185 0.033 to 0.356
crop to secondary forest (11) 11.01 -0.95 to 22.92 0.087 -0.035 to 0.192
pasture to plantation (25) 4.62 -3.89 to 13.53 0.024 -0.057 to 0.104
pasture to secondary forest (18) 15.99 4.84 to 26.81 0.125 0.017 to 0.222
savanna to crop (7) -4.80 -12.38 to 2.81 -0.055 -0.142 to 0.027
savanna to plantation (7) -3.68 -18.75 to 8.61 -0.061 -0.256 to 0.082
Land-use transition Depth % Change Log ratio
Mean 95%CI Mean 95% CI
forest to crop (5) 0-100 cm -23.06 -48.23 to 7.73 -0.357 -0.721 to 0.002
forest to pasture (5) 10.11 -9.74 to 26.38 0.077 -0.126 to 0.234
forest to plantation (11) -10.70 -27.97 to 10.02 -0.171 -0.355 to 0.031
pasture to secondary forest (5) 9.90 -5.85 to 26.56 0.080 -0.061 to 0.225
savanna to crop (5) -15.06 -19.62 to -11.21 0.165 -0.222 to -0.116
Land-use transition Depth % Change Log ratio
Mean 95%CI Mean 95% CI
forest to pasture (0-30 cm)
< 4 yrs (N=20)
5-9 yrs (N=27)
10-19 yrs (N=32)
20-39 yrs (N=32)
> 40 yrs (N=14)
< 1500 mm (N=6)
1501-2000 mm (N=30)
2001-2500 mm (N=60)
2501-3500 mm (N=20)
>3500 (N=18)
low activity clay (N=106)
high activity clay (N=15)
allophanic (N=15)
pasture to secondary forest (0-30 cm)
5-9 yrs (N=9)
10-19 yrs (N=33)
20-39 yrs (N=12)
> 40 yrs (N=5)
1501-2000 mm (N=14)
2001-2500 mm (N=13)
2501-3500 mm (N=23)
>3500 (N=7)
low activity clay (N=21)
high activity clay (N=28)
allophanic (N=12)
forest to pasture (0-10 cm)
< 4 yrs (N=16)
5-9 yrs (N=18)
10-19 yrs (N=25)
20-39 yrs (N=25)
> 40 yrs (N=7)
< 1500 mm (N=5)
1501-2000 mm (N=27)
2001-2500 mm (N=36)
2501-3500 mm (N=13)
>3500 (N=17)
low activity clay (N=76)
high activity clay (N=12)
allophanic (N=9)
forest to pasture (10-50 cm)
1501-2000 mm (N=13)
2001-2500 mm (N=12
2501-3500 mm (N=24)
>3500 (N=40)
low activity clay (N=70)
allophanic (N=18)