Soils Geography: Warm Temperate and Tropical Soils Wade Grewe & Mario Guzman GEOG 4401/5401 Soils Geography Fall 2007 – Univ of Colorado, Boulder

Coweeta

Site Information 2,185 ha Founded in 1933 and mostly dedicated to forest hydrology research Elevation range from 679 to 1392 m Average annual temp. 13 °C Heavy precipitation but varying with elevation –178 low elevations and more than 250 cm/yr on higher slopes Negligible snow contributing less than 2%of total precip. Classified as warm temperate forest with four main types –Northern hardwoods, cove hardwoods, oak-chestnut, and oak- pine forests

Soil Characteristics Soil characteristics are variable over the basin Classified as either Inceptisols or Ultisols Relatively high in OM Moderately acidic Low cation exchange capacity –Properties typical for highly weathered Ultisols

Previous Land Use Alters Plant Allocation and Growth in Forest Herbs Jennifer M. Fraterrigo, Monica G. Turner, and Scott M. Pearson Examined forest stands that have developed after agricultural abandonment or logging at least 55 years ago and compared them to reference stands that showed little or no evidence of human disturbance

Soil Properties

Biomass

Growth

Results Growth in reference stands is strongly dependent on nutrient concentrations, no correlation between growth rate and soil nitrogen and phosphorus in farmed and logged stands implying no nutrient limitation. More allocation of biomass to stems in reference stands due to competition for light. Higher rate of growth in farmed stands may indicate more relaxed nutrient competition in former farms than logged stands.

Forest and Pasture Carbon Pools and Soil Respiration in the Southern Appalachian Mountains Paul V. Bolstad and James M. Vose Examined 4 forest sites and 4 pasture sites with similar variables like terrain, PM, and elevation to understand the impacts of land use activities on carbon cycling

Carbon Pools

Respiration is strongly and exponentially dependent on soil temperature. Average 20 cm depth –Forested: 11.8°C –Pasture: 13.0°C Predicted annual soil respiration –Forested: 13.8 Mg/ha/yr –Pasture: 11.8 Mg/ha/yr

Results Difference in flux is relatively small compared to the size difference in carbon pools –Possible explanation is that respiration from fine root turnover closes the gap because it is much more active than course root and both sites have similar amounts of fine roots.

Conclusion Land use activities impact the chemical and physical properties of soil which in turn effect biological and physical processes in ecosystems. Further understanding of these impacts will allow us to maintain productive and stable environments for generations to come.

References Coweeta LTER. Accessed 11/1/07 Bolstad, P., and Vose, J Forest and Pasture Carbon Pools and Soil Respiration in the Southern Appalachian Mountains. Forest Science 51: Fraterrigo, J.M., Turner, M.G. and Pearson, S.M Previous Land Use Alters Plant Allocation and Growth in Forest Herbs. Journal of Ecology 94:

Physical, Chemical and Biological Processes in the soil formation of Luquillo, Puerto Rico By Mario Guzman Soils Geography: Warm Temperate and Tropical Soils with Wade Grewe

Location

Physical Process Role of Evapotranspiration - Wu et al spatial distribution of evapotranspiration on different scales using remoting sensing data. - The derived aET ranged from 0 to 7.22 mm/day with a mean of 3.08+/-1.35 mm/day. - Simulated aET was highest in the low elevation forest and decreased progressively toward higher elevations. - Bowen ratio (ratio of sensible heat to latent heat) varied across different vegetation types and increased with elevation, reflecting differences of net solar radiation incident on the earth’s surface.

Chemical Processes: Sulfur transformations and pool sizes - Samples of A horizon soils collected along an elevational gradient in Luquillo were examined for their capacity to adsorb sulfate, form organic S and mobilize organic S. Soil Moisture, carbon, pH and S pool sizes are factors regulating Sulfur transformations. Sulfur is an essential micronutrient for all organisms. Important for biological productivity. Carbon and moisture content is directly proportional to organic S formation. While total amounts of sulfate were positively correlated with organic S mobilization rates.

Table I

Table II

Biological Processes: Heterotrophic soil respiration Fungal biomass have a greater influence on heterotrophic soil respiration in the pine plantation than bacterial biomass in the secondary forest in Luquillo. Suggesting that different microbial functional groups may regulate the decomposition processes under different vegetation types Heterotrophic soil respiration was more sensitive to total N than to carbon and soil moisture was a major factor influencing heterotrophic soil respiration in these forests. The carbon stock in global soils is twice the size of atmospheric carbon pool and 70% of the soil carbon is stored in forest soil. Important for carbon cycle. High correlation between heterotrophic soil respiration and the total soil nitrogen content suggests that nitrogen availability may also be critical to the decomposition process in wet tropical forests.

Conclusions Soil moisture is a key component in evapotranspiration, sulfur formation and transformation and heterotrophic soil respiration. Research has implications for global and domestic issues. Evapotranspiration important to the hydrologic cycle. Heterotrophic respiration important for carbon cycle. Sulfur transformation important component of nutrient cycling due to deforestation. Important to observe how a particular ecosystem responds to disturbances. Soil is the interface of evapotranspiration, respiration and is the body where sulfur formation and concentration. All effect soil formation, and is reflected in the soils. A lot of variation in soils of Luquillo. Solar radiation intensity influenced by orientation, elevation. Along with Soil moistue differing microbial communities fit certain niches.

References Li, Yiqing., Xu, Ming., and Zou, Xiaoming. Heterotrophic soil respiration in relation to environmental factors and microbial biomass in two wet tropical forests. Plant and Soil. 281: Springer, Stanko-Golden, K.M. and Fitzgerald, J.W. Sulfur Transformations and Pool Sizes in Tropical Forest Soils. Soil Biology and Biochemistry. Vol. 23, No. 11 pp , Pergamon Press, Wu, Wei., Hall, Charles A.S., Scatena, Frederick N., and Quackenbush, Lindi J. Spatial Modelling of Evapotranspiration in the Luquillo experimental forest of Puerto Rico using remotely-sensed data. Journal of Hydrology No. 328, , Elsevier, 2006.