Study on geographic basis in exploiting and using land for sustainable planning in Đa Lat city and its vicinities - Lam Đong province

: (1) Limitations, (2) Dominant factors; Level of suitability: (1) Very suitable (S1), (2) Medium suitable (S2), (3) Less suitable (S3), (4) Not suitable (N). 1.3.2.3. General land degradation evaluation The nature of soil degradation is the process of changing the properties of the soil leading to a reduction or loss of production capacity. The causes of degeneration are very diverse, complicated and associated with the conditions of soil generation, some places are mainly caused by nature and some are caused by humans, which are divided into different types according to the degenerating agent. (Nguyen Dinh Ky, 1987, 1990): (1) Potential soil degradation is the ability of natural fertility degradation of the soil due to natural processes. It is assessed by the soil degradation potential of soil-generated geographic conditions (including: basement rock/ age of basement rock, mantle rock, topographical and climate conditions, local hydrology) assuming no vegetation cover and human impact; (2) Current soil degradation is the current soil fertility degradation compared to the natural fertility due to the exploitation and use of humans. It is assessed by the degradation status of soil physicochemical and biological properties leading to a decrease in soil productivity; (3) General soil degradation is the result of forecasting the extent of soil degradation when used for specific purposes. It is assessed by the current fluctuation of soil degradation level based on potential soil degradation by space. 1.3.2.4. Soil geographic zoning - Percentile system inherited in the thesis: The study of natural geographic zoning in general does not have a common percentile system, each country, even each author, based on his/her experience to come up with a percentile system, to contribute a part to progress towards that common percentile system. According to Vu Tu Lap (2011), each generated land unit bears the mark of the basic natural geographic laws of zonal law and non-zonal law. The distribution of each land unit and their spatial combinations, the structure of the soil cover on the territory are necessarily subject to those laws. Therefore, when determining the natural geographic zoning units for any natural territory, it is required to analyze in detail and specifically the evolution of these laws. In Vietnam, the percentile system applies to the scale of the Vietnamese territory (1/1,000,000 scale) built by the Vietnam Soil Science Association, including 4 levels: Region - Sub – Region - Area - Zone (Ton That Chieu, 1996). Subsequent soil geographic zoning studies were primarily developed based on the inheritance of the above percentile system and zoning sign for different territories. The number of zoning units 10 may be more or less depending on the size and complexity of the studied territory. With small studied territories it is possible to divide the territory into sub-regional units. - Principles of soil geographic zoning: Include arising, aggregating and dominant factors, relative homogeneity, sharing the same territory. 1.3.3. Scientific grounds for assessing and aggregating land for sustainable planning and land use in Da Lat city and its vicinities 1.3.3.1. Basis for determining research boundaries and scope: Based on (1) the development history of Da Lat city through periods; (2) Planning to expand Da Lat City to 2030 and a vision to 2050; (3) Characteristics of natural conditions. 1.3.3.2. Some specific characteristics in land use and exploitation in Da Lat city and its vicinities Da Lat city and its vicinities have basic characteristics of the mountainous highland urban area, so the characteristics of land use and exploitation in the territory also show these characteristics, such as: - The differentiation of soil cover is diverse and complicated due to the influence of the non-zonal differentiation rules, especially the law of high- belt differentiation and tectonic-geomorphology differentiation, expressed through the system of feralite soils on different types of basement rocks and high belts, creating favorable conditions for the research area to develop a wide variety of agro-forestry crops and form large specialized annual and perennial tree-growing areas on the highlands. - The natural area of the territory is mainly forestry land and agricultural production land. However, the current forest cover in mountainous areas has been strongly reduced, which is mainly caused by deforestation to expand agricultural land. This is also the main conflict in land use exploitation in the research territory. Therefore, the identification of appropriate space, the arrangement of agricultural and forestry production types in a scientific way, not only resolve conflicts in land use exploitation among territorial spaces and meet the objectives of ensuring food security and economic development (providing raw materials for processing and export industries) but also protect land, water, forest resources and protect the natural environment for sustainable territorial development. - Due to the terrain of the plateau and mountains with high slope, the potential soil degradation processes (erosion, washout, landslides, etc.) are very great, areas that lose their forest cover or agricultural production lacking soil protection measures has led to serious soil degradation. - As an area with diverse and increasing types of non-agricultural land use. Therefore, in the orientation of sustainable development of territories, it is necessary to consider the structure and characteristics of specific types of non-agricultural land use in each of those territories. 1.3.3.3. General land evaluation for spatial orientation and sustainable land use solutions in Da Lat city and its vicinities According to the geographic approach, a general land evaluation based on the integration of the results of land classification and evaluation and soil degradation assessment by soil geographic zoning will determine the 11 sustainable land use type for land units in the territory, thereby providing spatial orientation and appropriate land use solutions as a scientific basis for sustainable planning and land use in Da Lat city and its vicinities. From the specific characteristics of land use exploitation in the studied territory, the natural land area as well as the conflicts and contradictions in the territory's land use structure mainly belong to agricultural production space and forestry space, the thesis focuses on researching, proposing orientations and solutions for sustainable land use for these two spaces. At the same time, analyzing the results of land use orientation for agricultural- forestry-urban production spaces by each soil sub-geographic region to propose priority development space orientations for each territory, aiming to organize a sustainable space in Da Lat city and its vicinities. 1.4. Research views and research methods 1.4.1. Research views: Use of specific research perspectives of the integrated natural geography including soil biological perspective, ecological perspective, historical perspective, system perspective, integrated perspective and sustainable development perspective. 1.4.2. Research Methods: Methods of inheritance and integration; Methods of survey and investigation; Methods of analyzing soil physical and chemical properties in the laboratory; Expert methods; Methods of assessing economic efficiency of land use types; Mapping and GIS method; Methods of land evaluation and classification; Methods of soil degradation assessment; Methods of soil geographic zoning. 1.5. Research procedure Figure 1.5 Diagram of research steps Study the geographical basis in land use exploition for sustainable planning in Da Lat city and its vicinities - Lam Dong province Define goals and missions Determine theoretical basis and research methods Characteristics of arising geographical conditions - degeneration of soil and land resources in the research area Geographic zoning for the research area Land ecaluarion and classification suitable for agriculture and forestry production Assess general soil degradation and determine the degree of degradation on land units Integrated land evaluation for sustainable land use Proposing orientations for organizing space for sustainable land use 12 Chapter 2. CHARACTERISTICS OF ARISING GEOGRAPHICAL CONDITIONS - DEGENERATION OF SOIL AND LAND RESOURCES IN DA LAT CITY AND ITS VICINITIES; 2.1. Arising conditions - soil degradation 2.1.1. Geographical location The research area is located in the north of Lam Dong province, including the administrative boundaries of Da Lat city and 4 adjacent districts: Lac Duong, Don Duong, Duc Trong and Lam Ha (referred to as Da Lat and its vicinities). The region has an average altitude above 850m above sea level, with geographical coordinates extending from 11 0 30'27” to 12 019'4” North latitude and from 108020'18” to 108043'39” East longitude. The total natural area is 415,101.9 ha, accounting for 42.4% of the province's total natural area. 2.1.2. Geological and mantle rock characteristics 2.1.2.1. Geological characteristics The long history of geological development has left the research area complex geological structure, including ancient sediments, intrusive rocks or ancient eruptions to basalt eruptions and quaternary and tertiary sediments which are younger, divided into 5 main rock groups, including: deposit and metamorphic rocks, granite intrusive rocks, neutral eruptions to weak acids, basalt eruptions and unconsolidated quaternary sediments. 2.1.2.2. Mantle rock characteristics In the law of forming Mantle rock (VPH) of the humid monsoon tropics, the feralitization process (iron and aluminum accumulation) with laterite and laterite - bauxite formations is a key trend. However, due to the natural conditions in which the basement rock and topography play the most important role, the research area has weathered products including: VPH saprolite, silicite, sialite, sialferite, ferosialite, alferite. 2.1.3. Topographic and geomorphological conditions The topography of the research area consists of mountainous areas (medium mountains, high mountains), highlands and plains. The popular terrain orientation is Northeast - Southwest. The terrain is clearly hierarchical, lower from the North to the South, including: High level: is the average high mountain range (1000 - 1500 m), completely up to the peaks above 2000m (Chu Yang Sin 2,405 m, Lang Biang 2,163 m); Low level are strong wavy hill-shaped plateaus, consisting of two different surfaces of about 500m. The above ground surface is 1500m high and the below surface is 850-1000m high. 2.1.4. Climate and hydrological characteristics 2.1.4.1. Climate characteristics The study area is characterized by a tropical monsoon tropical climate, strongly influenced by the monsoon tropical circulation and high belt. The differentiate of the terrain has divided into climatic regions with different characteristics, it can be divided into 2 regions: (1) Climate zone of Da Lat 13 plateau: There is a tropical monsoon climate, cool and cold, with an average temperature of 18.2 0 C, the average rainfall of 1865mm/ year and the dry season is 3 months long; (2) Climate zone of Lam Ha - Duc Trong - Don Duong: There is a warm-to-hot tropical monsoon climate, no cold season, the average annual temperature of 21.3 0 C, the coldest month’s temperature is 19.6 0 C, average annual rainfall is 1577.4 mm/year, dry season for 3-4 months. 2.1.4.2. Hydrological characteristics a. Surface water: Located in high mountainous terrain with strong rainfall, the network of rivers and streams in ther research area is quite rich. The two main rivers are Da Dang and Da Nhim Rivers. b. Groundwater: Groundwater reserves of the research area are distributed very unequally between regions and can be divided into the following water storage units: (1) The gap aquifers; (2)The cracked aquifers. 2.1.5. Characteristics of vegetation 2.1.5.1. Natural forest vegetation: including broad-leaved evergreen closed forest; mixed broad-leaved and coniferous forests; thin coniferous forest; bamboo forest; bush and grassland. 2.1.5.2. Artificial vegetation: plantation forest community; industrial forest community and other perennials; annual tree community. 2.1.6. Human activities in land exploitation and use The increase in mechanical population in recent years has put pressure on environmental resources - the need to use land for socio-economic development is great. Most of the area has been put into use, of which the group of agricultural land is 384,808.8 ha, accounting for 92.7% of natural land, including agricultural production land which is 157,058.8 ha, accounting for 37.8% of natural land and forestry land is 226,451.2 ha, accounting for 54.6% of the natural area; Non-agricultural land is 24,843.0 ha, accounting for 6.0% of natural area. There is also unused land which is 5,450.1 ha, accounting for 1.3% of natural area. In the agricultural land group of the region, there are 7 main types of land use for agro-forestry production, including: Types of annual land use (rice, crops (vegetables, flowers)); Types of perennial tree land use (coffee, tea, mulberry, fruit trees); Types of land use for forestry production (three-leaf pine). 2.2. Characteristics of land resources in Da Lat city and its vicinities 2.2.1. Processes of land generation: The process of washing and accumulating clay, the process of destroying clay minerals and accumulating aluminum iron, the process of accumulating humus and forming humus soil in mountains, the process of gleying. 2.2.2. Classification system and characteristics of major soil groups Land resources in the studied area are divided into 16 land units under 8 soil groups. In particular, the zonal soil group has absolute dominance with 86.2% of the natural area, including the red-yellow soil group 14 (accounting for 85.0% of the natural area), the groups of black soil, gray soil, soil exposing gravel and rock with negligible area; The azonal soil group in high rims of mountains with an area accounting for 6.3% of the natural area, including the group of red-yellow humus soil in mountains (6.1% of the natural area) and the group of humus soils in high mountains with very small area; The inland zonal soil group on the river alluvium accounts for 6.4% of the natural area, including the valley soil on sloping products (accounting for 3.7% of the natural area) and the alluvial soil group (accounting for 2.7% of the natural area). 2.2.3. Actual soil fertility The map of actual soil fertility reflects the soil fertility at the time of the study. On the basis of analyzing and combining component maps according to the norms with clear differentiation among soil types including: pHKCl, OM, Nts, P2O5dt, K2Odt, CEC by the method of scoring and calculating the average, it has divided the actual fertility of the studied area into 3 levels as follows: The land area with high fertility occupies a large proportion in the studied area, reaching 61.8% of the natural area; The land area with average fertility reaches 31.8% of the natural area; The land area with low fertility reaches 5.2% of the natural area. Chapter 3. EVALUATION, CLASSIFICATION OF LAND AND GENERAL SOIL DEGRADATIONIN DA LAT CITY AND ITS VICINITIES 3.1. Evaluation and classification of land for agricultural and forestry production in Da Lat city and its vicinities 3.1.1. Selection for promising types of land use Based on the results on surveying the current state of land use and evaluating economic efficiency of major types using agricultural - forestry production land in the studied area. The types that use dominant land in area and socio-economic efficiency have been selected for the evaluatin, including: wet rice, cash crops (vegetables and flowers), Robusta coffee, Arabica coffee, tea, mulberry trees, fruit trees, three-leave pines. 3.1.2. Establishing Land unit mapping 3.1.2.1. Selecting and decentralizing norms Based on the study of ecological requirements of evaluated land use types and actual land properties (including: soil, topography, climate, hydrology, irrigation) of the studied area, 12 norms have been selected to build land unit mapping, scale of 1/50,000: soil type, thickness of soil layers, mechanical composition, actual soil fertility, elevation, slope, average annual rainfall, average annual temperature, average rainfall of two months after harvest (January, February), distribution of drought areas, irrigation conditions. 3.1.2.2. Land unit mapping Land unit mapping of Da Lat city and its vicinities is built by overlaying thematic maps of 12 selected norms. Each land mapping unit 15 contains all the information presented in thematic maps and is distinguished from other units by the difference of at least one element. The aggregate results have identified 1,129 land mapping units (LMU), which are decentralized according to the area scale in Table 3.2. Table 3.2. Summary of land mapping units according to the area scale No. Area scale (ha) Area (ha) LMU quantity Ratio (%) 1 <10 182.7 176 0.1 2 10 - 100 1,352.6 39 0.3 3 100 - 500 181,487.8 693 44.3 4 500 – 1.000 100,111.3 146 24.4 5 > 1.000 126,968.7 75 31.0 Total land area 410,103.1 1,129 98.8 Rivers, streams, lakes 4,998.8 1.2 Total natural area 415,101.9 100.0 3.1.3. Determining ecological requirements of land use types Based on natural conditions in the studied area and referring to values of ecological requirements of tropical and subtropical crops of Sys Ir. C., (1993), and inheriting the relevant results of studies, the ecological requirements of land use types have been determined in 4 levels of suitability: S1 - very suitable, S2 - suitable , S3 - less suitable and N - not suitable 3.1.4. Results on evaluating and classifying land for agriculture and forestry production The evaluation and classification are done by comparing the characteristics of land units with ecological requirements of the selected land use types, according to 2 evaluation methods (limited conditions, dominant factors) and 4 levels of land suitability (S1, S2, S3, N) of FAO (section 1.3.2.1), based on the integration of Automated Land Evaluation Software ALES and geographic information system GIS. The result is that the land suitablity classification maps for different types of agricultural and forestry production land use in the studied area are built at 1/50,000 scale (Table 3.4). Table 3.4. Area of land suitability level by types of land use LUTs Area / Ratio Levels of suitablity Not suitable (N) Total natural land area Very suitable (S1) Suitable (S2) Less suitable (S3) 1. Rice Ha 5,336.9 16,256.0 7,467.3 381,042.9 410,103.1 % Natural land area 1.3 4.0 1.8 92.9 100.0 2. Cash crops (vegetables, flowers) Ha 8,588.3 71,999.1 14,953.7 314,562.0 410,103.1 % Natural land area 2.1 17.2 3.6 77.1 100.0 3. Robusta coffee Ha 2,417.8 29,308.9 56,677.1 321,699.3 410,103.1 % Natural land area 0.6 7.1 13.8 78.4 100.0 4. Arabica coffee Ha - 52,760.8 111,144.3 246,197.9 410,103.1 % Natural land area - 12.9 27.1 60.0 100.0 16 5. Tea Ha - 44,677.7 130,960.3 234,465.1 410,103.1 % Natural land area - 10.9 31.9 57.2 100.0 6. Mulberry trees Ha 14,798.4 30,910.2 25,753.0 338,640.6 410,103.1 % Natural land area 3.6 7.5 6.3 82.6 100.0 7. Fruit trees Ha 12,360.1 50,169.6 104,992.8 242,580.6 410,103.1 % Natural land area 3.0 12.2 25.6 59.2 100.0 8. Three- leave pines Ha 7,330.5 121,898.1 227,290.9 53,583.5 410,103.1 % Natural land area 1.8 29.7 55.4 13.1 100.0 3.2. Evaluation on integrated soil degradation in Da Lat city and its vicinities 3.2.1. Causes and specific soil degradation processes 3.2.1.1. Causes of soil degradation include: (1) Natural causes: The topography is steep, sharply divided; Concentrated season rain and profound division of rainy season and dry season; Drought; (2) Activities of exploiting and using land by human: Deforestation for agricultural land; Unsustainable cultivation on sloping land; Using chemical fertilizers and pesticides; Urbanization and infrastructure development; Activities of mining and mineral processing . 3.1.1.2. Processes of soil degradation include: Erosion, washout; Feralite - laterite forming clumps, laterite; Chemical degradation; Gley; landslide; Soil pollution. 3.2.2. Evaluation on soil degradation 3.2.2.1. Evaluation on potential soil degradation On such basis, analyzing and evaluating the factors and processes of soil generation - degradation of the studied area, allowing to select and decentralize norms for evaluating potential soil degradation, including 7 norms under 4 types as follows: Soil (basement rock/specimen, mantle rock and thickness of soil layers); Topography (topography morphology and topography slope); Climate (degree of drought); Potential erosion level. The combination of component maps corresponding to the evaluation norms allows the creation of potential soil degradation maps at the scale of 1/50,000 under 3 grades: Light degradation potential (TN1) occupies the smallest area of 30,579.3 ha, equivalent to 7.4% of total natural area; Average degradation potential (TN2) occupies an area of 135,007.3 ha, equivalent to 32.5% of total natural area; Strong degradation potential (TN3) occupies a very large area with 244,516.5 ha, equivalent to 58.9% of total natural area. 3.2.2.2. Evaluation on current soil degradation Based on the characteristics of the studied area, the norms are selected and decentralized to evaluate the current soil degradation, including: the humus content (OM%), the current state of indicator vegetation and the current erosion level. The combination of component maps corresponding to the evaluation 17 norms allows the creation of the current soil degradation map in the studied area at the scale of 1/50,000 under 3 grades: none or weak degradation (HT1) dominates with 250,168.4 ha, equivalent to 60.3% of the natural area; Average degradation (HT2) with114,133.0 ha, accounting for 27.5% of the natural area; Strong degradation (HT3) with 45,801.6 ha, accounting for 11.0% of the natural area 3.2.2.3. Evaluation on general soil degradation Based on the matrix of combination between potential soil degradation and current soil degradation, it is allowed to evaluate the level of general soil degradationin the studied area on a map with scale of 1/50,000 under 3 grades: Slight degradation (TH1) with an area of 92,684.8 ha, accounting for 22.3% of the natural area; Average degradation (TH2) with the largest area of 294,168.3 ha, accounting for 70.9% of the natural area; Strong degradation (TH3) with the smallest area of 23,249.9 ha, accounting for 5.6% of the natural area. Chapter 4. PROPOSAL OF SPATIAL ORIENTATION AND SUSTAINABLE LAND USE SOLUTIONS FOR DA LAT CITY AND ITS VICINITIES 4.1. Soil geographic zoning of Da Lat city and its vincinities 4.1.1. The specificity in the differentiation of soil cover The differentiation of soil cover by geographical latitude to form soil geographic zoning units is not clearly shown by the influence of azonal factors, of which the topography is the dominant factor that makes the differentiation. However, the general nature of the soil geographic zoning unit system is still determined by its sub-equatorial tropical monsoon climate factor. 4.1.2. Percentile system and norms of soil geographic zoning The percentile system used for soil geographic zoning maps of Da Lat city and its vinicities at a scale of 1/100,000 includes: soil geographic regional level and sub-regional level. In particular, each level has specific zoning norms as follows (Table 4.1). Table 4.1. The soil geographic zoning system No. Percentile level Zoning norms 1 Region The homogeneity of soil complexes differentiated by topography elevation, bioclimatology and characteristics of basement rock/speciment on the territory formed soil geographic regions. Of which, the dominant factordifferentiation is topography. 2 Sub-region The homogeneity of soil complexes differentiated according to topography and land use characteristics o