Biogeochemical processes in seasonally snow covered systems

Snow Distribution

Vegetation Water Source

Hydrochemistry

Biosphere-Atmosphere Gas Exchange

Snow DistributionVegetation communities are strongly linked to patterns of snow accumulationand melt by their influence on mass, chemical and energy exchanges, and bytheir sensitivity to snow thermal insulation and spring time inputs of meltwater, nutrients and latent heat.

Snow Distribution

1) Interception

Snow Distribution – Vegetation Effects

2) Wind Redistribution

Snow Distribution – Vegetation Effects

3) Wind Redistribution/ Energy Balance

Vegetation Water Source

Biomass ProductionAgricultureProtected Areas

Parks and Wilderness

Habitat

Snow Biogeochemistry; Hydrochemistry

Dissolved Organic Matter

Inorganic Nitrogen

0

40

80

120

160

Sn

ow

Dep

th (

cm)

-12

-8

-4

0

So

il T

emp

erat

ure

(oC

)

JAN FEB MAR APR MAY

DEEP

DEEP

SHALLOW

SHALLOW

-6 -5 -4 -3 -2 -1 0

Soil Temperature

CO

2 F

lux

(mg

C/m

2 /d

)

Relationship between temperature and soil heterotrophic activity

0

400

200

600

0

1

2

3

4

5

6

7

8

0 50 100 150

Julian Day

Gra

ms

N m

-2

Snowmelt Began

microbial biomass

0

1

2

3

4

5

6

7

8

0 50 100 150

Julian Day

Gra

ms

N m

-2

Snowmelt Began

microbial N

soil inorganic N

y = -0.0106x + 1.3327

R2 = 0.9919

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

0 20 40 60 80 100 120

Mean Daily CO2 Flux (mg C/m2)

Nit

rate

Lea

chat

e (g

N/m

2 )

Snow Cover Duration

Ov

er-

win

ter

Het

ero

tro

ph

ic

Ac

tivi

tyFrozen SoilLimits

Activity

Freeze-Thaw Cell Lysis Increases Carbon

Substrate

Absence of Freeze-Thaw

Decreases Carbon Substrate

Snow CoverLimits Primary

Production

Conceptual Model of How Snow Cover Controls Over-winter Heterotrophic Activity

y = -0.5381Ln(x) + 2.8147

R2 = 0.9171

y = -0.3725Ln(x) + 2.1949

R2 = 0.9232

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 100 200 300 400 500

CO2 Flux (mg C/m2/d)

Nit

rate

Lea

chat

e (g

N/m

2 /yr

)

Forest Sites

Meadow Sites

y = 0.0245x - 0.2965

R2 = 0.7627

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

40 45 50 55 60 65 70 75 80 85

Winter precip (cm)

N r

eten

tio

n (

kg/h

a)

Discharge (Montezuma) and DOC (DC5)1980 - 1996

0

5

10

15

20

25

Water Year

Dis

char

ge

(m3/

sec)

0

1

2

3

4

5

6

7

DO

C (

pp

m)

1980 1981 1982 1984 1985 1986 1993 1994 1995 1996

y = 0.0637x + 4.2667

R2 = 0.9065

5

10

15

20

25

30

35

100.0 150.0 200.0 250.0 300.0 350.0 400.0 450.0

Mean Daily CO2 Flux (mg C m-2 d-1)

DO

C L

each

ate

(g C

m-2

)

Heterotrophic activity vs. DOC export

y = 0.3994x + 0.8987

R2 = 0.836

y = 0.3697x - 0.3526

R2 = 0.6544

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

0 1 2 3 4 5 6 7 8 9 10Discharge (m3/sec)

DO

C C

on

cen

trat

ion

(p

pm

)

Vegetation communities are strongly linked to patterns of snow accumulation and melt by their influence on mass, chemical and energy exchanges, and by their sensitivity to snow thermal insulation and spring time inputs of meltwater, nutrients and latent heat.

Many snow models and parameterisations presume stationary plant communities as part of their regional calibrations.

It is now felt that the complex cumulative impacts of a changing environment have created a global need for focused studies of snow-vegetation interactions at several scales: plant, plant community, landscape, biome and global.

Discharge (Montezuma) and DOC (SN2)1980 - 1996

0

5

10

15

20

25

Water Year

Dic

har

ge

(m3/

sec)

0

1

2

3

4

5

6

7

DO

C (

pp

m)

1980 1981 1982 1984 1985 1986 1993 1994 1995 1996

y = 0.0245x - 0.2965

R2 = 0.7627

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

40 45 50 55 60 65 70 75 80 85

winter precip (cm)

N r

ete

nti

on

(k

g/h

a)

y = 1.0342x - 32.142

R2 = 0.9948

y = 0.1265x - 0.4547

R2 = 0.7326

0

5

10

15

20

25

30

30 35 40 45 50 55 60

Water yield (cm)

DO

C E

xpo

rt (

106 g

ram

s)