Changes in Nutrient Cycling and Availability due to Different Forest

Management Methods

K.W. Goyne 1, M.A. Albers 1, J. Kabrick 2, P. Motavalli 1, D. Gwaze 3, and M. Wallendorf 3

1 Univ. Missouri, Dept. Soil, Environ., Atmospheric Science

2 U.S.D.A. Forest Service, Northern Research Station

3 Missouri Department of Conservation, Resource Science Division

Overall Project Goals

• Elucidate landscape factors influencing nutrient status in MOFEP soils.

Overall Project Goals

• Quantify the effects of current MOFEP management practices on nutrient cycling and availability in soils with differing nutrient supply capacities.

Long-Term Team Goal

• Being able to model and predict changes in nutrient cycling and pools within MOFEP and other Ozark Highlands forests to ensure that forest management practices are sustainable.

Expected Benefits

• Results will either confirm that existing management practices minimally or negligibly impact soil nutrient status.

• Demonstrate that current management practices may not be suitable for all soil types.

• Improve MDC’s ability to make sound, scientifically-based management decisions.

Objective 1

• To quantify the landscape determinants (biotic and abiotic factors) of base cation supply and to rank them in order of importance across non-harvested forested landscapes within MOFEP.

• Hypothesis: Base cation supply is closely associated with (1) depth to bedrock, (2) soil parent material, and (3) forest plant community type.

Objective 1 - Approach

• Used soil characterization data collected from 117 pedons during the 1995-1996 soil-landscape analysis.– Soil texture, cation exchange capacity, base cation

concentration, etc.

• Data set was appended with biotic and abiotic site factors that may affect base cation supply.– Community type, slope position, aspect, parent material,

geologic strata, depth to bedrock, etc.

• Classification and Regression Tree (CART) Analysis was used to identify and rank important explanatory site factors related to base cation supply.

CART model — Ca and Mg in lower portion of the diagnostic subsurface horizon

CART model — Ca and Mg in lower portion of the diagnostic subsurface horizon

Node Size (%) DescriptionCa and Mg

(g m-2)100 All soil profiles 1122

Roubidoux or upper formation:1 32 -Shoulders, backslopes, footslopes or

floodplains276

2 12 -Summits 1014

Eminence formation:3 12 -Formed in pedisediments, residuum, or

alluvium752

Lower portion of the formation:4 22 -Formed in pedisediments, residuum, or

alluvium1594

5 22 Pedisediments over residuum from the Eminence of lower formation

2136

Tasks for this objective are ~ 85% complete.

Objective 2

• To conduct laboratory experiments and analyses investigating changes in total soil N (TN), potentially mineralizable N, the distribution of N in labile and stable pools, and exchangeable base cations that occur after even-aged and uneven-aged harvest in soils with differing nutrient status.

• Hypothesis: TN, potentially mineralizable N, and soil exchangeable base cations will decrease and the proportion of N in stable pools will increase with harvest intensity, effects will be greater in low nutrient soils.

Objective 2- Approach

• In August 2007, low, medium and high nutrient status soils were sampled in 10 cm increments from 0-30 cm within 9 MOFEP sites (486 samples).

• Within each site and soil type, 3 subsamples were randomly collected in areas harvested in 1996 and nearby no-harvest areas (paired sampling).

– Chosen to minimize variability of soil properties, vegetation, and climatic conditions that could mask treatment effects.

– Control sites sampled using paired technique as well.

B

B

B

B

B

B

MOFEP Site 3Clear Cut

/0 240 480 720 960120

Meters

Legend

B nutrientcycle3

Roads

Hydrology

Trails

CLASS_TYPE

drive

walk

Site Boundary

Clear Cut

TREAT

Clear cut

Int

NRCS Soils

Soil Map Units

15

27

31

41D

42D

45D

61C

63C

63D

63F

70F

71F

73C

73D

74D

74F

75D

75F

80C

80D

80F

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81F

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82F

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87G

89C

89D

Medium nutrient status map unit 82F

Low nutrient status map unit 80F

High nutrient status map unit 74F

B = location of field replicates; myriad solid colors = soil map units; cross hatching, red = intermediate cuts, black = clear cuts.

Objective 2- Approach

Objective 2- Approach

Potentially Mineralizable N (PMN)

• 84 day incubations of soil samples

• 30oC – optimum for N mineralizing bacteria

• Leaching conducted on days0, 1, 3, 7, 14, 21, 28, 42, 56,

70, and 84

• Leachates analyzed for inorganic N (NO3

- and NH4+)

Objective 2- Data

0 10 20 30 40 50 60 70 80 900

20

40

60

80

100

Cu

mu

lati

ve

Min

era

lize

d N

(m

g-N

kg

-1 s

oil)

Day

Low C Low T Medium C Medium T High C High T

Cumulative mineralized nitrogen in Even-Aged Management sites by Nutrient Status, 0-10 cm

Error Bars indicate one std. dev.

Objective 2- Data

0 10 20 30 40 50 60 70 80 900

20

40

60

80

100

Error Bars indicate one std. dev. Cu

mu

lati

ve

min

era

lize

d N

(m

g-N

kg

-1 s

oil)

Day

Low C Low T Medium C Medium T High C High T

Cumulative mineralized nitrogen in Uneven-Aged Management sites by Nutrient Status, 0-10 cm

Objective 2 – Characterization of N pools

• PMN incubations to continue into spring 2009.

•Total N combustion analysis in progress, anticipated completion January 2009.

•Labile and stable N (potassium permanganate extraction ) anticipated completion spring 2009.

• Water soluble N extractions completed by summer 2009.

Objective 2 – Base Cation and Soil Characterization Analyses

• Cation exchange capacity and exchangeable cations

• pH and exchangeable acidity

• Organic carbon content and particle size analysis

•60% completed by Soil Characterization Lab, anticipated completion December 2008.

Objectives 3 and 4 - Future Work

• To conduct laboratory column experiments investigating initial effects and longer-term effects of forest harvest management on leaching of N species and base cations from soils with differing nutrient status.

• To determine changes in soil solution chemistry and nutrient flux with emphasis on the loss and gains of N, base cations and acidity before and after even-aged and uneven-aged harvest conducted on soils with differing soil nutrient status.

Objectives 3 and 4 - Future Work

• Construction of cation and anion resin samplers has been initiated. Soil solution samplers will be created in Spring 2009.

Objectives 3 and 4 - Future Work

• Construction of cation and anion resin samplers has been initiated. Soil solution samplers will be created in Spring 2009.

• Using existing data, we will begin identifying sites in Summer 2009 to be sampled and instrumented.

B

B

B

B

B

B

MOFEP Site 3Clear Cut

/0 240 480 720 960120

Meters

Legend

B nutrientcycle3

Roads

Hydrology

Trails

CLASS_TYPE

drive

walk

Site Boundary

Clear Cut

TREAT

Clear cut

Int

NRCS Soils

Soil Map Units

15

27

31

41D

42D

45D

61C

63C

63D

63F

70F

71F

73C

73D

74D

74F

75D

75F

80C

80D

80F

81D

81F

82D

82F

83F

87G

89C

89D

Objectives 3 and 4 - Future Work

• Ground investigations and installation of samplers in late Summer and early Fall 2009.

Integration and Collaboration

• Collaboration with Dr. Chen and colleagues, sharing of data and integration of results, perhaps investigation of deep carbon quantity and distribution.

• Studies investigating changes in microbial or decomposer communities. – We have initiated development of a molecular technique to

assess nitrifying bacterial populations, specifically ammonia oxidizing bacteria.

• Studies investigating the effects of wildfires on soil carbon, nutrients and biotic communities.

Forest structure& composition

Water

Soil

Nutrients

Temperature

Rain

Wind

Air

Light

Geology/Parent material

Slope

Aspect

Elevation

Landform

Fauna(Birds, Mammals,Herps, Invertebrates)

Flora(ground flora, fungi, lichen)

Time Climate

Topography

Decomposers

PHYSICAL ENVIRONMENT SUB-MODELPHYSICAL ENVIRONMENT SUB-MODELHuman Impacts (Management)

Other Sub-models

Biotic Community

Wild Fire