Post on 16-Jan-2016
description
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
81D
81F
82D
82F
83F
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