Forest Soils

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Introduction

Forests represent the 31% of the total land area and support more than 1.6 million people around the world. At the same time, forests are important because they are home of 80% of the terrestrial biodiversity which include plants, animals and microorganisms [1]. The interactions of the terrestrial biodiversity are integrated in the food web process. Those processes include the transfer of energy, community interactions and nutrient cycling. These process are also linked with abiotic factors as soil, water and climate and determine the productive characteristic of each niche.

The most common soil definition is "Soils as a media for plant growth" [2]. However, soils have several functions that determine the ecological roles in the environment:

• Recycling system for nutrients and organic waste
• Modifier if the atmosphere
• Habitat for soil organisms
• Engineering medium
• System for water supply and purification

Soil formation is a pedogenic and biogeochemical process that is determined by space and time, and depends of the translocation, biocycling and transformation of materials deposited and degraded by organisms on the uppers soil layers. These processes are developed along time and space, and have as final product the formation of soils with different physical and chemical characteristics.

• Vegetation
• Terrestrial organism interaction
• Climate.

The early soil classification made by the USDA on 1938, classified forest soils in the Zonal soil Order, as Pedalfers, that are soils with the following suborder:

• Soils of forest-grassland trnasition
• Light-colored podzolized soils of timberland regions
• Lateritic soils of forested warm-temperature and tropical regions.

The Soil Science Society of America does not have a specific definition about forest soils. However, Comerford (2006) defined forest soils as a soil that has been developed under forest cover, or a forest that has been disturbed but once was covered by forest vegetation [3].

Physical environment

The physical characteristics observed in forest soils, are determined by the soil formation factors:

• Climate
• Organisms
• Parent Material
• Time
• Topography

Describe the physical and chemical characteristics of the environment, using as many sections/subsections as you require. If it is appropriate, you can divide the physical and chemical attributes of the environment into separate sections. Look at other topics available in MicrobeWiki. Which involve processes similar to yours? Create links where relevant.

Vegetation

Vegetation usually acelerate plant nutrient uptake. By doing this, it affect the biogeochemical process that occurs on the soil.

Microbial communities

Fungi

The microbial community in forest soil is dominated by fungi. Due that most of the organic compounds in forest soils stayed on the soil surface and there is plenty oxygen, fungi communities are able to extend their filaments called hyphae. Fungi are more efficient than bacteria, in terms of decomposing organic compounds. In fact, 50% of the decomposed material is transformed in fungi tissue. The formation of hyphae is what improve soil fertility by the formation of humus.

Bacterias

Bacterias have an important role in the nutrient cycling. The distribution of bacterias in forest soils is mostly determined by vegetation and soil chemical characteristics. For example, the study conducted by Hackl, E.(2004), compared the bacterial communities on six forests under different pine and oak vegetation. The results shown that Gram positive bacterial communities, especially actinomycetes, were more abundant under conifer forests than under oak coverage. This results suggest that bacterial communities are adaptive to the soil chemistry. Mangroves.

Microbial processes

What microbial processes define this environment? Describe microbial processes that are important in this habitat, adding sections/subsections as needed. Look at other topics in MicrobeWiki. Are some of these processes already described? Create links where relevant.

Decomposition

Microbial communities degrade most of the organic material that is settled on the forest soils. For these reason, most of forest soil have a fragile nutrient cycle. An example of these process can be seen when mature forest soil is disturbed, often the disturbance include, deforestation, fire and soil removal for agricultural activities. The first observation is that soil nitrate under natural conditions, does not represent a big part of the N pool, however, when is disturbed, nitrifier bacteria population increases, which increase soil fertility by the making nitrate more accessible for plants. That is one of the reason why poor farmers on the Tropics had adopt the slash and burn [1] practice to enhance soil fertility. However, at the long range the soil fertility is depleted due to the disruption of the nutrient cycle.

Current Research

Enter summaries of recent research here--at least three required

References

[Sample reference]

[1]

[Soil Genesis and classification|[2]]

Comerford|[3]

[2]

Hackl, E., Zechmeister-Boltenstern, S., Bodrossy, L., and Sessitsch, A. "Comparison of Diversities and Composition of Bacterial Populations Inhabiting Natural Forest Soils". Appl Enviro Microbiol. 2004 September; 70(9):(5057-5065)

Takai, K., Sugai, A., Itoh, T., and Horikoshi, K. "Palaeococcus ferrophilus gen. nov., sp. nov., a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney". International Journal of Systematic and Evolutionary Microbiology. 2000. Volume 50. p. 489-500.

Edited by Tito Lavaire, a student of Angela Kent at the University of Illinois at Urbana-Champaign.