**1. Introduction**

Alfisols are a soil order in USA "Keys of Soil Taxonomy" [1]. Alfisols are typically developed under mixed forests in temperate climates that maintain a low to moderate level of soil organic matter, a neutral to acidic pH and have a moderate degree of base saturation. One requirement of Alfisols is the presence of an argillic horizon, coupled with the requirement of having a base saturation greater than 35% in the argillic horizon control section [1]. In Missouri, Alfisols typically have aquic and udic moisture regimes and support deciduous forest vegetation [2]. Ultisols are a soil order in USA "Keys of Soil Taxonomy" that are similar to Alfisols with the exception that Ultisols have less than 35% base saturation in the control section [1].

The USDA-NRCS has developed the National Soils Information System based on a national soil survey composed of establishing soil characteristics using observations along soil delineation boundaries and determining map unit compositions

by field transects [3]. Three different geographic databases have been established having different mapping intensities: (i) State Soil Geographic database (STATSGO at a scale of 1:250,000, (ii) Soil Survey Geographic (SSURGO) at a scale ranging from 1:12,000 to 1:63,360, and (iii) National Soil Geographic (NATSGO) at a scale of 1:7,500,000. The STATSGO database is well-suited to represent soil data relative to specified soil associations (a soil association represents two or more different soils that appear in a regularly repeating landscape pattern) and are well-suited for regional, multi-state, river basin and multi-county resource planning, management, and monitoring. The SSURGO database provides detailed information about individual soils and is well-suited for landowners, municipal, and county planners for more local and site-specific resource planning, management, and monitoring. The NATSGO database establishes information and the identification of the Major Land Resource Area (MLRA) map and associated attribute data. The MLRA is a land area having a clearly defined composition of geography, geology, soils, climate, physiographic features, potential natural vegetation, water resources and land practices.

Ecological classification is predicated on the separation of a landscape into discrete and repeatable land parcels, wherein the individual land parcels provide information to guide land management. An ecological site is defined as "a distinctive type of land based on recurring soil, landform, geological, and climate characteristics that differs from other kinds of land in its ability to produce distinctive kinds and amounts of vegetation and in its ability to respond similarly to management actions and natural disturbances" [4]. As such, ecological sites provide a framework for connecting soils and landscapes to vegetational communities; after which, thoughtful and knowledgeable natural resource management may proceed with a full understanding of potential beneficial and negative consequences [5]. Once established, ecosystem site descriptions may be assembled to provide land management ranging from a woodlot to a landscape to an ecosystem.

In Missouri, ecosystem site identification/isolation and subsequent descriptions are prepared by a multiagency cooperation involving diverse disciplines within the Missouri Department of Conservation and the United States Department Agriculture-Natural Resource and Conservation Service (USDA-NRCS). Literature utilized by this multiagency cooperative project includes materials produced by the Missouri Department of Conservation, USDA-NRCS and other entities [6–12]. Eight soil and ecological factors are identified that significantly influence vegetation and site productivity: (i) landform, (ii) parent material, (iii) root restrictions, (iv) base saturation, (v) soil drainage, (vi) soil texture, (vii) flooding, and (viii) ponding.

These soil and ecological factors have been previously characterized by a 50+ year county-based soil survey program, resulting in a national database. Subsequently, land parcels having a commonality of these soil factors were correlated with historical and potential vegetation communities. Ecological site names are based on soil/substrate, landform and the historic plant community, with one example being "Loess Fragipan Upland Flatwoods". Based on a verification process, ecological sites are initially termed "provisional ecological sites", then with further review and data acquisition, the ecological sites are eventually termed "correlated ecological sites". In addition to soil, climate, local hydrology, and physiographic information, the final product contains additional information on species composition, canopy cover, biomass estimates, and ground cover information.

Products available to the public are termed "ecological site descriptions (ESD's) and provide additional information: (i) ecological site extent maps, (ii) physiologic features, (iii) landscape block diagrams, (iv) soil descriptions and interpretations, (v) ecological dynamics with state and transition models, (vi) plant lists, and (vii) site interpretations for forestry and wildlife management.

#### *Integrating Ecological Site Descriptions with Soil Morphology to Optimize Forest Management… DOI: http://dx.doi.org/10.5772/intechopen.97251*

Ecological site descriptions are not mapping units, rather they are taxonomic units. However, ecological site descriptions of an appropriate areal extent may be used as mapping units when the sites are highly patterned because of site topography, soil distribution, geology, and other attributes. The repeatable distribution of ecological sites provides for their useful application to manage land under the influence of livestock grazing, wildlife habitat, recreation, rural or urban development, forestry, and a multitude of other land uses. In general, we accept the definition proposed by Bestelmeyer et al. [13] and Briske et al. [14] to define an ecological site as landscape units that have similar characteristics of soil, topography, geological formations, and climate regimes that differ because of (i) the production and plant species composition under the disturbance of reference conditions associated with soil properties, the natural dynamics of vegetation and the ecosystem services provided, and (ii) the responses to management, processes of degradation, and restoration.

State and Transition Models attempt to explain how ecosystems transition from one state to another state. A state is a series of plant communities associated with specific soil properties that produce persistent attributes over time with structural and functional ecosystem characteristics [15]. The reference state is a state that provides the largest range of potential environmental services and typically is the "ideal" state. At its essence, researchers aim to understand how ecosystems function and respond to management or natural influences. Ecological resilience is the capacity to absorb and/or reorganize after a disturbance yet maintaining the site's structural integrity [15]. Thresholds are key biotic and abiotic factors and modified ecosystem functions that alter the ecosystem structure beyond the limits of ecological resilience resulting in a transition to a different state or limits recovery. Triggers are events, factors, processes and/or drivers that initiate a transition from one state to another.

The objectives of this project are to document the importance of combining soil survey information with ecological site descriptions to show relationships (i) between soil genesis-soil morphology with their resident plant communities, and (ii) and the actions of land management to alter the resident plant communities to a different plant community.
