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1984198420082008
Source: INPE and IBGESource: INPE and IBGE
What did we know about the biogeochemsitry of tropical forests in 1982?What did we know about the biogeochemsitry of tropical forests in 1982?
Several investigators published in Several investigators published in Plant and Soil 67 (1982) Plant and Soil 67 (1982) studies showing….studies showing….
• Stocks of N in tropical soil larger than stocks of N in the biomassStocks of N in tropical soil larger than stocks of N in the biomass
(opposite of Ca, Mg, Na, K)(opposite of Ca, Mg, Na, K)
• High input of N via biological fixationHigh input of N via biological fixation
• Suggesting open N cycle: high input and lossesSuggesting open N cycle: high input and losses
• N “equilibrium”: fragile and complex balance – land use would disruptN “equilibrium”: fragile and complex balance – land use would disrupt
such balancesuch balance
•Tropical forest richer in N than temperate forests Tropical forest richer in N than temperate forests
What do we know about the N biogeochemsitry of What do we know about the N biogeochemsitry of
terra-firmeterra-firme forests today? forests today?
Manaus – Cuieiras Reserva – INPA – LBA site Manaus – Cuieiras Reserva – INPA – LBA site
Source: Luizão et al. (2004); Nardoto et al. (2008)Source: Luizão et al. (2004); Nardoto et al. (2008)Source: Luizão et al. (2006); Nardoto et al. (2008)Source: Luizão et al. (2006); Nardoto et al. (2008)
Santarém Santarém FLONA – TapajósFLONA – TapajósIBAMAIBAMALBA site LBA site
Source: Silver et al. (2000)Source: Silver et al. (2000)
Santarém Santarém FLONA – TapajósFLONA – TapajósIBAMAIBAMALBA site LBA site
Source: Silver et al. (2000)Source: Silver et al. (2000)
Caxiuanã National Forest – Museu Goeldi – LBA site Caxiuanã National Forest – Museu Goeldi – LBA site
Source: Sotta et al. (2008)Source: Sotta et al. (2008)
NHNH44++ NONO33
--
NN22
OMOMMineralizationMineralization NitrificationNitrification
NN22O + NO + N22 + NO + NO
DenitrificationDenitrification
Biological fixationBiological fixationNHNH33
VolatilizationVolatilization
0‰0‰ 15 to 35‰15 to 35‰
0 to 33‰0 to 33‰
29‰29‰
-2 to +2‰-2 to +2‰
Isotopic Fractionation in the Nitrogen Cycle Isotopic Fractionation in the Nitrogen Cycle
Source: Högberg, 1997
15N15N
15N
15N15N
15N
Terra-Firme (sand soils)Terra-Firme (sand soils) Terra-Firme (sand soils)Terra-Firme (sand soils)
15N
14N
1515N-depletionN-depletion
δδ1515N N
14N14N
14N14N
14N
15N
15N
Gaseous N losses (Gaseous N losses (NONO + + NN22O)O)
15N
14N
14N
14N
1515N-enrichmentN-enrichment
δδ1515N N
15N
LeachingLeaching
15N15N 15N
14N14N
14N
14N
15N
Gaseous N losses (Gaseous N losses (NONO + + NN22O)O)
LeachingLeaching
Terra-Firme (clay soils)Terra-Firme (clay soils) Terra-Firme (clay soils)Terra-Firme (clay soils)
15N14N
Source: Michela Figueira
Source: Nardoto et al. (2008); Silver et al. (2000); Sotta et al. (2008)Source: Nardoto et al. (2008); Silver et al. (2000); Sotta et al. (2008)
Terra-firme LBA site: Manaus, Santarém and Caixuanã Terra-firme LBA site: Manaus, Santarém and Caixuanã
Maburu Hill Forest Reserve – GuyanaMaburu Hill Forest Reserve – Guyana(there is good science outside LBA…) (there is good science outside LBA…)
Source: Pons et al. (2007Source: Pons et al. (2007))
SantarémSantarém
SGCSGC
ManausManausRebioRebio
SamuelSamuel CaxiuanãCaxiuanãSotta et al. (2008)Sotta et al. (2008)
Source: Nardoto et al. (2008)Source: Nardoto et al. (2008)
See: Perez et al. (2006See: Perez et al. (2006)
Mabura - GuyanaMabura - GuyanaPons et al. (2007)Pons et al. (2007)
Terra-firme sites under clay soilsTerra-firme sites under clay soils
Terra-firme forest under the same precipitation regimeTerra-firme forest under the same precipitation regime(local scale) (local scale)
Terra-firme forest under the same soil type (texture)Terra-firme forest under the same soil type (texture) but with distinct annual rainfallbut with distinct annual rainfall
W.
Sch
roe
de
r
Forest x PastureForest x Pasture(disturbance of the equilibrium)(disturbance of the equilibrium)
Source: Mellilo, Neill, Cerri and others…..several referencesSource: Mellilo, Neill, Cerri and others…..several references
Source: “handsome” Source: “handsome” Davidson et al. (2008)Davidson et al. (2008)
What do we know about the N biogeochemsitry of tropical What do we know about the N biogeochemsitry of tropical
forests today?forests today?
• Terra-firmeTerra-firme forests are indeed N-rich systems with an “intense” N cycling forests are indeed N-rich systems with an “intense” N cycling viavia soil- soil-
plant-atmoshpere. They are richer than temperate forests, white-sand plant-atmoshpere. They are richer than temperate forests, white-sand
vegetation types , like vegetation types , like caatingascaatingas and and campinaras,campinaras, and also richer than savannas, and also richer than savannas,
like like cerradoscerrados
• Considering local scales this richness and “intensity” depends on the soil textureConsidering local scales this richness and “intensity” depends on the soil texture
• Considering a regional scale, besides soil texture, annual precipitation is another Considering a regional scale, besides soil texture, annual precipitation is another
important driver in the N richness and “intensity “ of important driver in the N richness and “intensity “ of terra-firmeterra-firme forests forests
• The replacement of The replacement of terra-firme terra-firme forests by pasture tend to impoverish the N cycleforests by pasture tend to impoverish the N cycle
and reduces its “intensity”and reduces its “intensity”
• As As terra-firmeterra-firme forests recover from disturbances the richness and intensity of the forests recover from disturbances the richness and intensity of the
N cycle tends to be restored. The degree of recovery is still unknownN cycle tends to be restored. The degree of recovery is still unknown
The big “gap”The big “gap”
• The major “fuel” of the nitrogen cycle of terra-firme forests is biological The major “fuel” of the nitrogen cycle of terra-firme forests is biological
nitrogen fixation. This is recognized since 1936, however, it appears that legumesnitrogen fixation. This is recognized since 1936, however, it appears that legumes
only fix nitrogen under special conditions. We do not understand why. We need aonly fix nitrogen under special conditions. We do not understand why. We need a
better understanding of N inputs to the forest better understanding of N inputs to the forest viavia BNF. BNF.
NN22 + 3H + 3H22 + energy 2NH + energy 2NH33
Future needsFuture needs
• Modelling efforts – Rainfor data - 82 sites (Jon Lloyd and colleagues)Modelling efforts – Rainfor data - 82 sites (Jon Lloyd and colleagues)
A maz onian ter ra- f irme f ores ts (non- f ix ers )
A ll Delta 15N = 3,7652+0,0002*x -2,4483*y -2,0097E-7*x *x +0,0012*x *y +2,787*y *y
5 4 3 2 1 0 -1
A maz onian ter ra- f irme f ores ts (non- f ix ers )
A ll Delta 15N = 3,7652+0,0002*x -2,4483*y -2,0097E-7*x *x +0,0012*x *y +2,787*y *y
5 4 3 2 1 0 -1
MAP (mm)
Clay (0-5cm)
Fol
iar 15
N
Source: Nardoto et al. (in prep.)Source: Nardoto et al. (in prep.)
N richnessN richness& intensity& intensity
