Changing enzymatic activities and mycorrhizal infections in a chronosequence of secondary and mature forests of eastern Amazonia

Cláudio José Reis de Carvalho1, Eric A. Davidson2, Tereza Primo dos

Santos3, Fábio Carneiro Dutra4, Bruno de Oliveira Serrão4

1Embrapa Amazônia Oriental; 2The Woods Hole Research Center, 3Instituto de Pesquisa Ambiental da Amazônia, 4Bolsista ITI/DTI, CNPQ-LBA

Amazônia Oriental The Woods Hole Research Center

The availability of N and P may limit rates of regrowth of secondary forests in Amazonia.

Age (years)

0 20 40 60 80 100

Bio

mas

s (M

g.ha

-1)

0

50

100

150

200

250

300

Primary forest

Losses of a 7-year-fallow Losses of a 7-year-fallow vegetation after burning vegetation after burning

(31 t/ha DM)(31 t/ha DM)

Losses in kg/ha and in Losses in kg/ha and in % of biomass% of biomass

Carbon 14378 (98%) Nitrogen 205 (96%) Potassium 39 (48%) Phosphorus 4 (47%) Calcium 107 (35%) Magnesium 18 (40%) Sulfur 14 (76%) Sodium 6 (30%)

Carbon 14378 (98%) Nitrogen 205 (96%) Potassium 39 (48%) Phosphorus 4 (47%) Calcium 107 (35%) Magnesium 18 (40%) Sulfur 14 (76%) Sodium 6 (30%)

Hölscher 1995

Losses of a 7-year-fallow Losses of a 7-year-fallow vegetation after burning vegetation after burning

(31 t/ha DM)(31 t/ha DM)

Losses in kg/ha and in Losses in kg/ha and in % of biomass% of biomass

Carbon 14378 (98%) Nitrogen 205 (96%) Potassium 39 (48%) Phosphorus 4 (47%) Calcium 107 (35%) Magnesium 18 (40%) Sulfur 14 (76%) Sodium 6 (30%)

Carbon 14378 (98%) Nitrogen 205 (96%) Potassium 39 (48%) Phosphorus 4 (47%) Calcium 107 (35%) Magnesium 18 (40%) Sulfur 14 (76%) Sodium 6 (30%)

Hölscher 1995

The highly weathered soils are nutrient poor, and numerous cycles of slash and burn can further impoverish nutrient stocks and lead to site degradation.

Site pHH20 Corg

(Mg.ha-1)

Norg

(Mg.ha-1)

PMehlich

(kg.ha-1)

Porg

(kg.ha-1)

Ptotal

(kg.ha-1)

Primary forest 4.36 (0.35) 47.4 (9.8) 3.42 (0.35) 6.81 (0.58) 247.84 (12.59) 715.63 (99.17)

Secondary forests

3 years 5.25 (0.16) 39.0 (7.2) 2.37 (0.75) 5.49 (1.28) 171.25 (78.49) 875.49 (224.27)

6 years 5.10 (0.24) 43.0 (4.4) 2.56 (0.55) 8.24 (1.44) 231.92 (33.00) 862.23 (147.35)

10 years 5.32 (0.16) 33.6 (6.3) 2.24 (0.88) 6.43 (1.56) 132.88 (48.54) 568.90 (134.58)

20 years 4.89 (0.41) 38.2 (6.3) 2.51 (0.54) 11.92 (7.67) 246.00 (107.92)

679.49 (185.03)

40 years 4.92 (0.25) 34.1 (8.1) 1.92 (0.68) 4.83 (0.37) 146.87 (25.42) 703.45 (45.57)

70 years 4.88 (0.29) 38.0 (6.7) 2.66 (1.02) 5.61 (0.40) 170.60 (71.01) 739.79 (71.79)

The mineralization of N and P from soil and litter by enzymatic activity and the acquisition of nutrients by mycorrhizae could be important for the recuperation of nutrient cycles during secondary forest succession.

These processes were studied in a secondary forest chronosequence (5, 8, 12, 22, 42, and 72 years), a recently abandoned black pepper plantation, and a remnant mature forest in the municipality of São Francisco do Pará.

• At the end of the rainy season (May), samples of soil and roots were

collected from the litter-soil interface and at 0-5, 5-15, and 15-30 cm

depths in mineral soil.

• Available P, total N, extractable NH4+ and NO3

-, urease and acid

phosphatase activity, and concentrations of total and readily extractable

glomalin were measured.

• The number of fungal spores and infections of mycorrhizae (VAM) were

counted in roots.

The number of spores and mycorrhizal infections decreased with increasing age of the forest, whereas the activity of acid phosphatase increased with forest age.

Site/Age (years)

Pepper 5 8 12 22 42 72 Forest

Sp

ore

s (N

º. 3

0g

-1)

0

20

40

60

80

100

Surface0-5cm5-15cm15-30cm

Site/Age (years)

Pepper 5 8 12 22 42 72 Forest

Infe

ctio

ns (

Nº.

cm

-1)

0

10

20

30

40

Surface0-5cm5-15cm15-30cm

Site/Age (years)

Pepper 5 8 12 22 42 72 Forest

g 4

-Nitr

ophe

nol.g

-1.h

-1

0

5000

10000

15000

20000

25000

Surface0-5 cm5-15 cm15-30 cm

The concentration of total and readily extractable glomalin tended to increase with forest

age.

E E

xtr.

Glo

ma

lin (

mg

.g-1

)

0

1

2

3

4

5

6

7

Site/Age (years)

Pepper 5 8 12 22 42 72 Forest

To

tal G

lom

alin

(m

g.g

-1)

0

2

4

6

8

10

12

14

Surface0-5cm5-15cm15-30cm

The concentration of NH4+ and NO3

- tended to increase with forest age, and

were significantly higher in the mature forest soil.

Site/Age (years)

Pepper 5 8 12 22 42 72 Forest

g N

-NH

4.g

-1.h

-1

0

20

40

60

80

100

120

140

160

180

Surface0-5cm5-15cm15-30cm

Site/Age (years)

Pimental 5 8 12 22 42 72 Floresta

NH

4-N

(m

g.kg

-1)

0

200

400

600

800

Surface0-5 cm5-15 cm 15-30 cm

Site/Age (years)

Pepper 5 8 12 22 42 72 Forest

NO

3-N

(m

g.k

g-1)

0

20

40

60

80

Surface0-5cm5-15cm15-30cm

2001 / 2002

fev abr jun ago out dez fev abr

Litte

r (k

g.ha

-1)

0

500

1000

1500

2000

25003 anos

2001 / 2002

fev abr jun ago out dez fev abr

Litte

r (k

g.ha

-1)

0

500

1000

1500

2000

2500Pimental

2001 / 2002

fev abr jun ago out dez fev abr

Litte

r (k

g.ha

-1)

0

500

1000

1500

2000

250010 anos

2001 / 2002

fev abr jun ago out dez fev abr

Litte

r (k

g.ha

-1)

0

500

1000

1500

2000

250040 anos

2001 / 2002

fev abr jun ago out dez fev abr

Litte

r (k

g.ha

-1)

0

500

1000

1500

2000

2500

70 anos

2001 / 2002

fev abr jun ago out dez fev abr

Litte

r (k

g.ha

-1)

0

500

1000

1500

2000

25006 anos

2001 / 2002

fev abr jun ago out dez fev abr

Litte

r (k

g.ha

-1)

0

500

1000

1500

2000

2500

Floresta primária

2001 / 2002

fev abr jun ago out dez fev abr

Litte

r (k

g.ha

-1)

0

500

1000

1500

2000

2500

20 anos

Site/Age (years)

Pepper 3 6 10 20 40 70 Forest

Bio

mas

s (M

g.ha

-1)

0

2

4

6

8

10

12

14Fine litter

Woody litter

Litterfall and decomposition

Site/Age (years)

Pepper 3 6 10 20 40 70 Forest

C/N

rat

io

10

12

14

16

18

20

22

24

The results indicate that some, but not all, of these indicators of nutrient mineralization and acquisition become similar to the mature forest within 8 years of secondary forest succession.