A Hierarchical Analysis On Ecosystem Classication of Land

Background: The ecosystem classication of land (ECL) has been studied for a couple of decades, from the beginning of the perfect organism system “top-down” approach to a reversed “bottom-up” approach, dening micro-ecological unit. After reviewing two study cases of the ecosystem classication of land, the ecosystem classication framework implements in different ecoregions were examined and analyzed. Results: Theoretically, Bailey’s upper levels ECL (1995) was applied to the United States, and world continents. China's Eco-geographic classication was most likely tted into Bailey’s Ecosystem Classication regime. With a binary decision tree analysis, it demonstrated that the top-level, Domain has an empty entity between the US and China ecoregion framework. Based on the biogeoclimate condition, vegetation distribution, landform, and plant species feature, classied HIIC1 into two subsections ( labeled as i, ii ), and delineated iia of QiLian Mountain East Alpine Shrub and Alpine Tundra ecozone into iia-1 and iia-2 zone. Conclusions: 1) The Plateau Domain 500 should be added into the top-level Bailey’s ecoregion framework, coordinately it includes HI and HII Divisions, and humid, dub-humid, semiarid, and arid provinces. 2) Two case comparisons recommend using a practical approach, objectively dened ecosystem classication for the lower-level ECLs in matter of time and project cost.

(GLMs) were used, the environmental variables such as mean monthly air temperature, precipitation, distribution area, Slop, and elevation became very signi cant to predict the species richness and community dynamics. Many studies and attempts to analyze the complex system of the land as dynamically organized and structured across the scales of space had assisted ecological researchers to solve population richness and dynamics (Allen and Angeler et al., 2014), vegetation distributions (Hou, 1983;Zhang and Zhou, 1992) and ecosystem classi cation framework (Bailey, 1995(Bailey, , 1996 Bailey started to identify and delineate the boundaries and the ecoregions of the United States, North America, and the world's continents from 1976 to 1998. His works were published and had made signi cant progress in the 1990s. In 1993, his work divided the ecoregion into the top three level classes as Domain, Division, and province. At the Domain level, applying the Köppen climate system of classi cation, Bailey (1983Bailey ( , 1995Bailey ( , and 1996  Chinese geographers and ecologists started to measure and study geographic regionalization and broad scale of ecological units, and had developed quantitative analysis methods for studying regional ecosystems (Zheng, 1999;. Detailed vegetation map, soil type map and grassland map, tree algorism to study the ecosystem complexity and nested multiple layers. This method was used to help actualize both categorical and continuous dependent variables under a supervised learning process for comparing the ecosystem classi cation between the United States and China. The algorism splits the selected classes into two or more homogeneous sets based on the most signi cant attributes, or charters making the groups as distinct as possible.
In the global context of ecosystem classi cation of land should be able to understand the landscapescale processes in a more general way. The issue is not whether we can generalize about landscape-scale variation, and combination of abiotic and biotic factors, but to identify the circumstances in which generalizations can be made, and where there are limits, and nd a solution (Hutchinson et  In this paper, we tried to compare the United States' and China's ecosystem classi cation frameworks and solve any Domain related issue. Two sets of study data between Western Utah of the United States and Qinghai-Tibet Plateau of China were examined in the upper levels, and discussed how to approach a deliverable lower-level ecosystem classi cation when time and project budget limited.

Methodology And Analysis
The Review of Two Cases of Upper-Level Ecosystem Classi cation of Land

Upper-Level Ecoregions between the United States and China
The ecosystem can be a complex system, which is changed and varied along with longitude, latitude, and elevation on the earth surface, and always adapted to the slop, and aspect and environmental variables in macroscales (Allen et al., 2014;Brodrick et al., 2019). Bailey (1995Bailey ( , 1996  States. Since they used the temperatures, water conditions, and landforms for the upper level of ECLs, there were similarities between these two ECLs. However, there were some failures to match each level class among the top three levels. At the top levels, China ECLs mainly used the accumulated temperature and the days of great than 10 0 C,and next level used aridity to classify as humid, dub-humid, semiarid, and arid (Labeled as A, B, C, D separately) and used landform types to classify plain, mountain and hills (Labeled as 1, 2, 3…etc.).
China's ecological geographic ecoregions had been classi ed and named ( Relatively, China's Eco-geographic classi cation is mostly tted into Bailey's Ecosystem Classi cation regime, and represents the top level of Eco-geographic regions for their scienti c needs. Zheng (1999) and  had provided the theory analysis and delineated the boundaries for 11 ecogeographic zones. The HI and HII eco-geographic zone in China did not properly t into any domain developed by Bailey. Bailey (1995, 1996   Ecoregions of the United States had been examined by Bailey (1995Bailey ( ,1996 in great detail at Domain, division, and Province. The rst case study used for lower-level was accomplished with upper 4 levels for the project in a 4.5-million-hectare area centered in western of ECOMAP (1993  "Bolson" is subsection and used as a special term in the lower level of ecosystem classi cation, described the terrain. DEM data (30m) was used in the model and generated 60 bolson segments (Fig.  2B). In the study area, the macrotterain, mesoterrain, microterrain units were generated in the model with algorisms to identify and delineate their boundaries. The protocols (Fig. 3A) were used to identify landscape units between ladtype association, landtype, and lantype phase one step at a time seperately.
The ecological sites (ESs), the 9th level, was designed to overcome the using important data on ESs, nested to ECOMAP; vegetation stands (VSs), the 10th and nest-grain level were subdivisions of individual polygons of ESs (Fig. 3B) based on differences in disturbance histories that have led to differing current vegetation structure and composition. The vegetation stands were de ned and described in terms of vegetation characteristics that represent ne-scale variations in regional climate, site-speci c moisture, nutrient regimes, and disturbance histories ( re, grazing and human activities).

The Study on Lower-Level of Ecosystem Classi cation of Land in China
In our second study case, Qinghai province is located western China, and the northeast part of Qinghai-Tibet Plateau. The latitude is from 31039'N to 39011'N, and the longitude is from 89025'E to 103004'E.
From south to north, there is almost a span of 8 degrees that equates to 800 km, and from east to west, there is a span of more than 14 degrees that equates to 1200 km (Zhou and Wang et al., 1987). The total area of Qinghai province is 720,000 km2.
Qinghai province is far away from the east-south coast of Mainland China, where the summer monsoon comes from the Paci c Ocean and brings the rainfall to the China continent. The warm and wet air mass only reaches the southeast province boundary and leaves the west part of the area dry in summer and cold in the winter. Geographically, Qinghai province is located in the subtropical and warm-temperate climate zone. However, the average elevation of the province is increased over 3000 m above sea level and the subtropical zone's evergreen broad-leaved forest and warm-temperate zone's deciduous broadleaved forest are total disappeared and replaced by the alpine shrub, alpine tundra, alpine steppe, and Mountains, which form major higher plateau in Qinghai ( Fig. 4 (a)).
The Qinghai province is within the 500 Plateau Domain as we examined and de ned, intersected with the HI, Plateau Sub-polar Division and HII, Plateau temperate Division (Fig. 3 (b)). The Qinghai province region is intersecting with 5 Sections in Table 3.   Table 3 and Fig. 5. Based on the biogeoclimate condition, vegetation distribution, landform, and plant species feature, three level biogeoclimate classi cations under Section were created, for example top layers i., ii., and 3 lower-levels' hierarchies of Subsection, Ecozone, and zone when applying ECOMAP classi cation framework.
Using DEM data and spatial analysis model (Zhang and Peterman et al., 2008), the lowest level of the ecological sites were classi ed, which was based on vegetation type, slope or aspect position (Fig. 5A).
By using objectively de ned algorism, the ecological sites map in the area of Haibei Alpine Meadow Ecosystem Station was generated. The map scales was changed from 1:3,000,000 (Subsection, ecozone, and zone) to 1:50,000 in mapping Ecological Sites. With the development in the GIS spatial analysis model ( Zhang et al., 2008), the Normalised temperature surface was generalized and integrated in the Vegetation Dynamic Simulation Model (VDMS). We simulated the alpine tundra vegetation dynamics in response to global warming with scenarios of global annual mean temperature increase of 1 o to 3 o C. Since the study area was with the features of the plain, lower hills, and glacier mountains, the ecological sites showed the relation with elevation, slope, aspect, temperature, and water condition (Table 4)   Based on the biogeoclimate condition, vegetation distribution, landform, and plant species feature, classi ed HIIC1 into two subsections ( labeled as i, ii ), and delineated iia of QiLian Mountain East Alpine Shrub and Alpine Tundra ecozone into iia-1 and iia-2 zone. Likewise, ia-1, HuangShui River watershed Forest, Temperate Steppe zone was classi ed under ia of QingHai East-North temperate Steppe ecorzone (Fig. 5).
The project in a dry domain area in western Utah of the United States, with 10 level classi cation would be more theoretical than practical. However, using objectively de ned algorism, it had demonstrated that the development in the GIS spatial analysis model ( Zhang et al., 2008) had signi cance valuable for conducting global warming research.

Discussions And Conclusions
By reviewing the upper level of ECLs in the United States, and China, we realized that ecosystem classi cation of land was very special methodology to explore and classify the ecoregions in different continents. Climatologists used relatively or multiple years' annual climate conditions to demonstrate the uniform climatic classi cations and applied them to ecological regionalization study. The differences of the geology and geomorphology on the earth caused uncertain changes within Domain, Division, Province, and Section, where we had to solve the issues in the next levels' classi cation (Cleland et (Bailey 1983(Bailey , 1995(Bailey , 1996. ECOMAP, de ned by the National Hierarchy of Ecological Unit (NHEU, 1993), had been set up to present as the "top-down" approach of Ecosystem Classi cation of Land in the United States. Theoretically, Western Utah's project had proved it was a cost matter and time consuming through a full ECL's eld survey and an intensive classi cation processing.
ECOMAP (1993) is a top-down regionalization that is hierarchically nested and explicitly geographic area. While hierarchical structures allow related land classi cation units to be used at scales appropriate to various needs, from national to local, a consequence of the top-down, nested hierarchically that dominates the NHEU is that perimeter of outer polygons created at lower levels have to be vertically integrated with the delineation of polygons occurring at upper levels. One consequence of this "top-down" process is that if the lowest levels are produced independently of higher levels, one should logically readjust (merge from the "bottom-up") the congruent polygon boundaries involved in all affected polygons created at higher levels when we understood and considered the content of whole (Bailey, 1983;West et al., 2005). In other words, we dissected wholes into parts on the basis of differences so that classes and units are arrived at by subdivision.
A top-down approach described by Rowe 1961, separated the ecosystem into components like organisms. We have simply pointed out that following a top-down nested hierarchy to its nest subdivisions counters common sense and practicality. Thus, a terrestrial ecosystem is a volume of earth space with organic contents, separated from its neighbors by reasonable divisions in the empirical continua of biota, soil, and physiography. However, ECL framework could be changed when selecting different biotic and abiotic criteria in two different continents or countries. Province and Section digital format data, and carried out a deliverable application associated with a scaled lower level ECLs such as ecological sites. The objectively de ned algorism and analysis generated internal function outputs in the algorism. The slope model, landform model were running based on objective needs, and vegetation, soil, and geology data could be considered as attribute data sources depended in the project.
Ecosystem regionalization is a scale-based approach to classifying land surface, combined with regional and continental data on climate, geomorphology, landform, lithology, and characteristic ora and fauna.
Also, we should have understood more on taking geology, landform, soils, vegetation, and climate into account to determine their biogeographical regions in different scales and ecosystem levels, while the boundaries of these ecoregions are still being studying and delineated in a global-wide scheme.

Authors' contributions
Author has contributed a lot to this manuscript, and approved the nal manuscript.

Funding
Final stage's research fund was supported by Instant Calling Spatial Arch lab, Burnaby, B.C. Canada.

Availability of data and materials
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Ethics approval and consent to participate Author con rmed that there is no ethical con ict

Consent for publication
Author has read the manuscript carefully and agreed to submit for publication.

Competing interests
Author declares that there are no competing interests.