**1. Introduction**

The ecosystem classification of land is about the theory and design of the ECL framework and implements and practices in different nations, continents, and global scales. Bailey had made his primary studies and contributions on ecological classification framework and application, representing his scientific collections of mapping on ecosystem classification of land for the United States, North America, and global continents in [1, 2]. The ecological sites were studied and monitored with environmental conditions, biological characters, and ecosystem services [3–6]. Ecologists and geographers had proposed and classified the land into simplified

ecosystems where the different plants, animals, and bacteria populations lived together. By processing into different scales, geographers and ecologists designed ECL framework, theory, and applications to depict the ecosystem as systemically organized, nested, and multiple layers in [7–9]. They are so complex and adapted a cycle crossing a threshold from one stable state to another depending on the seasonality, time, landscapes, and disturbances in Refs. [10, 11], which results in the academic argument where to draw a line based on prior selected criteria, how to identify ecological sites and classify the ecoregions in Refs. [1, 3, 8, 12–14]. Afterward, do we achieve our research goal?

From a philosophical perspective, ecological regionalization could be concerned as an objective that has a form with a perceptive logic; at other times, it is an inductive and subjective art that reflects a management consideration, which is dependent on the application of the ecoregion. However, with the ecological regionalization, the contributions of existing ecoregion schemes are inconsistent. In other words, it is getting study complete with errors remaining in [11, 15].

A large amount of vector or raster formats data made the quantitative and spatial analysis more useful and practical in the last two decades. The tree technique was used to explore the analysis of complex ecological data with nonlinear relationships and high-order interaction in 2000 [16]. Many studies and attempts to analyze the complex system of nature as dynamically organized and structured within and across the scales of space and seasonality had assisted ecological researchers to solve population richness and dynamics in [17], vegetation distributions in [18, 19], and ecosystem classification framework in Refs. [1, 2, 9, 14, 20–24]. Understanding how environmental variables influenced the vegetation pattern and distribution and successional order, many research works demonstrated a hierarchical paradigm in Refs. [1, 11, 15, 25].

From 1976 to 1998, Bailey started to identify the ecoregion boundaries and generated the ecoregions of the United States, North America, and the world's continents. He published his research works and had made significant progress in the 1990s. In 1993, Bailey classified the ecoregion into the top three level classes: Domain, Division, and Province. Then, applying the Köppen climate system of classification, he depicted the Domains with the synthetic description of the land surface form, climate, vegetation, soils, and fauna, seeing in [1–3]. Since Federal Geographic Data Committee (FGDC) in the United States accepted the National Hierarchy of Ecological Units (NHEU), ECOMAP in [26] was created with eight levels hierarchical approach to study the ecosystem classification of Land (ECL).

Bailey and Jensen published their work on the design and ecological mapping units with nine levels [27]. The Subregions below the Domain, Division, and Province were divided into Sections, Landtype Association, Landtype, Landtype Phase, and Ecological Site. Thus, NHEU and Bailey had driven a classified Ecosystem Classification of Land into the nested hierarchies at various scales, depending on management needs.

In the global context of ecosystem classification of land, we need to understand the landscape-scale processes more generally. The issue focuses on generalizing ecoregions, the landscape-scale variation, and the combination of abiotic and biotic factors. It had been extended to identify the circumstances in which generalizations can be made, where there are limits, and find a solution in Refs. [9, 10, 14, 24, 28, 29]. It was valuable to examine the hierarchies of ecosystem classification of Land {ECL} globally when we had working experiences and research cooperation that can be related in different countries or continents in Refs. [12, 14, 19, 30]. More recently, the ecosystem services and values have been concerned with the wise use of biodiversity and natural resources [6].

*Implement and Analysis on Current Ecosystem Classification in Western Utah of the United… DOI: http://dx.doi.org/10.5772/intechopen.100557*

In this chapter, we tried to compare the current two national ecosystem classification frameworks and assess any Domain related issue when it existed. We tried to find suitable abiotic and biotic factors, topographic features, climatic, and ecosystem services to generate deliverable lower-level ecosystem classification when these related research works were reported and published. However, this inconsistency in terminology is often confusing because similar terms may have different meanings or apply to different scales, and different terms may have the same meaning in [15]. Therefore, we will stick to our current references and literature for reviewing and discussing.

Two sets of ecoregions data of Western Utah of the United States, Yukon Territory of Canada were analyzed and validated. The Biogeoclimatic Ecosystem Classification (BEC) approach was referred to as an additional assessment in the discussion. Our focus was tried to explore lower level ecosystem classification in the different ecoregions of North America in Refs. [1, 2, 31–39].
