Xin TANG, Youhua MA*, Zhongxiang YU

1. Institute of Environment and Information Technology, Anhui Agricultural University, Hefei 230036, China;

2. Institute of Land and Resources Institute, Anhui Agricultural University, Hefei 230036, China

The first tea plant was discovered and used to produce tea by China.It is recorded that tea drinking can be dated back to ancient times. According to production data of Chinese tea plants issued by Ministry of Agriculture, grossoutput of tea exceeded 100 billion yuan in 2013 and gross yield of tea trees reached 1.95 million tons, increasing by 8% than that of last yield. It can be concluded that tea treeis an important Chinese traditional export product,making contribution to incomes of tea farmers[1].

However,there are two dominant problems during rapid development of tea tree, including blind expansion of tea garden and continuously decreasing of per unit area yield of tea tree. In China Tea Expo 2013, for example,some experts pointed out that tea tree surplus was severe in China, and it was necessary to make a scientific planning on growing area of tea tree.Meanwhile, yield and quality of tea trees do not match with advantageous natural conditions at all, and growing area in some regions in China should be finely controlled. Besides, it is crucial to make arrangements on tea tree planting,supported by advanced management technology[2]. Therefore, it is proposed to improve suitability and profits of tea tree planting, enhance tea tree quality and extend tea product exports in order to increase farmers’incomes[3].

The evaluation on planting suitability of tea trees is a final evaluation on suitability of tea trees growing in specific areas, aiming at fully making use of land resources and regional natural resources. Such evaluation based on GIS can achieveinformation and visualization ofinformation on global surface, and the evaluation model would make qualitative evaluations on whether a region is suitable for tea plants growth[4]by operational analysis, GIS and spatial analysis,providing references for practical production of tea.

Natural Conditions Suitable for Tea Tree Growth

Tea tree is an evergreen broad leaf plantmainly cultivated in tropical and subtropical climates and areas with acid soils[5]. It can be concluded that the cultivation of tea tree requires superior terrain,climate and soils.

Precipitation

The growth of tea trees requires higher precipitation in terms of total quantity in a year and specific quantity in different phases. For example, annual precipitation should be over 1 000 mm in suitable areas, and 1 500 mm would be best.The southern regionsof the Qin Mountains are suitable for tea tree cultivation for precipitation is abundant here under influence of monsoon climate[6].

Temperature

It is researched that the optimal daily mean temperature for tea tree growth is 16-25 ℃, at which growth rate and leaf area increase most rapidly. Furthermore, the temperature between 26 ℃and 30 ℃is also acceptable, when shoots grow slowly compared with the situation under the optimal temperature ranges. If the temperature rises over 30 ℃, shoot growth would slow down significantly,and shoots stop growth if temperature is over 35 ℃.

Altitude

The altitude decides tea quality.For example, teas growing in mountains are always better, due to abundant humidity, low air pressure, and long sunshine hour[8], as well as more UV-lights.

Sunlight

Tea trees are cultivated for its leaves and material accumulation mainly depends on photosynthesis.The hour and strength of sunshine have direct effects on tea quality and number. For instance, sunlight strength affects quality of tea and content of amino acid.If sunlight is strong,amino acid in fresh tea leaves keeps high, which is conductive to producing highly-qualified green teas[9].

Soils

Tea trees usually grow in acid soils,and it is believed that the pH values in the range of 6.0-6.5 are suitable for tea growth. It would be hard for tea tree to grow if pH value exceeds the range[10].Specifically,tea tree growth is under influences of physical environment, chemical environment and biological activities of soils. In general, soils characterized by loose texture, deep soil horizon, and abundant water are suitable for tea tree growth[11].

Application of GIS to Evaluation on Land and Crop Suitability

GIS (Geographic Information System)

A geographic information system is a system designed to capture,store,manipulate, analyze, manage, and present all types of spatial or geographical data,supported by computer hardware, software, and network. On basis of geographical spatial database, it uses geographic model to provide multi-spatial and dynamic geographic information for geographic research and decision-making. What’s more, GIS is capable of processing and analyzing spatial data, which directly reflects spatial and temporal changes of data,providing technological supports for evaluation on agricultural eco-environment[12].

The evaluation on crop suitability is a concluded evaluation on suitability of a crop growing region,which is conductive to making full use of natural resources and developing land potential to accomplish a high yield. Besides, based on the evaluation, it allows optimization of planting layout of crops to achieve sustainable development between regional economy and eco-environment[13].

The evaluation on suitability of growing tea trees utilizing GIS presents information and visual-based data, followed by data management and spatial analysis, providing references for evaluation on suitability of tea tree growth and regionalization[14].

The Application of GIS to evaluation on land and crop suitability

GIS is mainly applied to integrate qualitative research and quantitative research on grading agricultural lands.For example, the qualitative research is applied in adjustment and determination of agricultural land grading to improve the precision[15].Zhang Min explored land valuation,soil constituents and computed soil constituents on basis of land grading with GIS, which was taken as a valuation case of agricultural lands in Xinpu Town[16].

The application of GIS to evaluation on crop suitability mainly includes three aspects[17],as follows:

Application in agricultural regionalization GIS performs well in spatial data management and analyzing. For example, with GIS, suitability evaluation can be made on a specific land by spatial overlapping and analysis, and presented in the form of thematic maps.Su et al.[18]constructed a spatial analysis model oriented by regionalization index and divided the most suitable, suitable, less suitable and unsuitable areas for Citrus maxima in Guangxi, on basis of climate information in 30 years and basic geographic data(1∶250 000)from 90 meteorological stations in Guangxi, providing scientific references for rational distribution of Citrus maxima, and improving quality and yield of Citrus maxima.

Application in precisefertilization

Soil and Fertilizer Institute, Chinese Academy of Agricultural Sciences,constructs soil fertilizer information system(SOFISC)includeing soil fertility,fertilizer and nutrient data in 2 370 counties of 31 provinces,which can be sued for researchingsoil fertilizer information in different soil horizons and fertilization information.

Application in agricultural planting,management and decision making for government Wei et al.made use of computer and intellectualized agricultural information technology for management and decision making of wheat production[19].Yang et al.designed eco-agricultural monitoring and decision-making support system of tobacco planting in Honghe Hani and Yi Autonomous Prefecture[20].

International situation of GIS application in land and crop suitability evaluations

The suitability evaluation on land and crop based on GIS starts later in China, but develops and improves faster, with increasingly extending of application range. For example, it has been widely applied in urban planning,transportation and agricultural production. Lauru A.seffino conducted suit-ability evaluation on sugarcanes in Sao Paulo, Brazil on basis of Workflow-based Spatial Decision Support System[21]. Wang et al. constructed land suitability evaluation model with Arc/Info[22]for tropical crop in Sanya City, Hainan Province. These researches incorporate crop planting suitability with GIS and evaluation model.

Major Research Methods of Planting Suitability for Tea Trees with GIS

Overlapping analysis

Overlapping analysis is an important spatial analysis function of GIS.Specifically, different maps of evaluation factors are overlapped and analyzed to formula a general evaluation map. In terms of suitability evaluation of lands for tea tree planting,the overlapping analysis method analyzed evaluation factors covering precipitation, temperature, elevation, sunshine and soil for tea trees to obtain a general evaluation map,so that an optimal location can be selected for growing tea trees.Overlapping analysis targets analyzing interrelationship among spatial characteristics and exclusive properties of spatial objects correlated in spatial locations. Besides, overlapping analysis of multi-layer data produces new spatial relation and new relationship of property characteristics,as well as differences and changes of multi-layer data.

Wu selected raster data-based overlapping analysis in evaluating ecological suitability of tea garden in Guizhou and overlapped evaluation factors together, covering same measuring scale, projected coordinate system, unit size of the same grid, in order to conclude the results by model operation with grid units as evaluation units. Land use information obtained by remote sensing and land surveying to guarantee the data would be more objective and practical. Then, land suitability can be selected and evaluated with land use type as an entry point, on basis of land use status. Finally, the regions suitable for growing tea trees can be searched by GIS data searching and management. Nevertheless, it is usually hard to make a comprehensive and precision analysis because of inappropriate understanding of evaluation factors and weights in practice[23].Besides,the evaluation reliability would be affected also if property information of different factors is not unified.

Analytic hierarchy process

According to overlapping analysis,evaluation factors are just overlapped to represent the complex suitability evaluation, without a comprehensive conclusion. Analytic hierarchy process is one of methods widely applied in suitability evaluation for tea tree planting and it is a decision-making method integrating qualitative and quantitative aspects[24].The decision makers select some factors significantly influencing tea tree planting, such as terrain, soil,and climate, and determine relative weights of every property by self-experience. Subsequently, it is necessary to multiply weight of every property by corresponding score, and the results are added to obtain total value.The scheme with the highest total value would be chosen. Analytic hierarchy process is a systematic analysis method determining weights of evaluation factors developing from qualitative method,quantifying people’s thoughts and experience in order to check conclusionconsistency ofdecision-makers.Therefore, it actually divides related factors into objectives, principles, and indices, based on which qualitative and quantitative analyses can be conducted. The method firstly conducted further research on essence,influential factors and inherent relations of the complex decisions, followed by thoughtsquantificationof decision makers in order to provide references for multiobjective or multiprinciple complex problems. On basis of the merits, analytic hierarchy process is well applied in collaborative decisionmaking of land use and planning, although the theoretical functions are under suspicions[25].

Zhu made evaluation and analysis on weights of planting factors of tea trees in southeast of Shandong with analytic hierarchy process and selected weights of climate and terrain according to meteorological conditions for tea tree growth.In weights determination, the researcher constructed a judgment matrix, followed by multiplying values by others in every row to get a series of numbers, which can be taken as weight ratios of different factors.Finally, different weights are normalized and added to get a total weight.The weights of different factors can be obtained by values of different factors/total weight. It can be concluded that analysis of planting suitability of tea tree growth shows significant differences in Wulian County. For example,the suitability of tea trees performs better in middle and southwestern parts of Wulian County. The area of the most suitable region is smaller,scattering in the middle and northern parts, and the suitability of the north and south is the poorest. The rest regions are secondary in plantingtea trees[26].

Nevertheless, analytic hierarchy process also has shortages. At first,data input into GIS is unstable,imprecise and fuzzy. Secondly, indices with different dimensions should be normalized, but the results tend to be volatile upon normalization method.Linear transformation method is the most popular normalization method,but lacks a satisfied correction scheme in both theory and experience. Besides, it is still unsettled as for selection of land use measures as per specific region, and some problems are waiting to be resolved[25].

Multiple linear regression arithmetic

Traditional suitability evaluation is dominated by Delphi method. However,if few experts are interviewed, or experts’ opinions vary significantly,the evaluations would be not so reliable. What’s more, Delphi method is not suitable for computer modeling.Therefore, Tang et al. made use of multiple linear regression arithmetic to construct evaluation model[13]. The modeling just demands scores on suitability of sampling sites by experts and importance indices of different factors are produced by regression coefficient, which reduces frequency of artificially scoring and improves objectivity of evaluation. Meanwhile, the model ignores secondary factors, and reduces input data[11],which is conductive to modeling based on computers.

Assuming variables y and x0, x1,x2, …,xm-1,it can be concluded that y=a0x0+a1x1+…+am-1xm-1+am, of which a0,a1, …,am-1and am are regression coefficients;Y is the value of suitability of evaluation units,ranging from 0 to 1.It is notable that 1 represents “complete suitable”and 0 “totally unsuitable”.x0,x1, x2, ……, xm-1are values of evaluation factors, such as elevation, annual mean temperature and annual precipitation,a0,a1, ……,am-1and am are importance indices of the factors, representing contribution rates of different factors to suitability (y)[7].After modeling,an evaluation index system should be constructed in order to grade evaluation conclusions and achieve suitability in terms of quantitative and qualitative aspects[13].

Fuzzy comprehensive evaluation method

It is an effective way for resolving multi-factor or multi-index problems.Specifically, according to evaluation principle and measured values, it makes a comprehensive evaluation on grades of the objects based on fuzzy relation synthesis,and it divides the evaluation object and makes analysis on different grades to guarantee a more precise result[27-30].

On basis of GIS and fuzzy comprehensive evaluation method, Chen et al. made evaluation on suitability of lands for growing tea plants in Fujian by constructing evaluation factor collection, evaluation collection, and single-factor evaluation matrix and determining index weight as per evaluation by expert experience to make a comprehensive evaluation. Specifically,Chen made a coordinated evaluation on tea tree growth in Fujian in terms of eco-environment, social development and tea coordinated development,providing objective references for a long-term sustainable development strategy of tea industry and middle or long -term development planning. Besides, an objective evaluation on tea tree growth in Fujian provides references for concerning industries to recognize development environment and formulate self-development strategy and marketing countermeasures.

Conclusion and Expectation

Traditional suitability evaluation on tea tree growth is time and labor consuming in terms of evaluation process, mapping, area calculation, and statistical analysis, with low precision rate[32]. In contrast, as a platform of managing spatial database and property database,GIS integrates statistical model and evaluation methods,which makes it easier tomake aprecise and rapid evaluation on suitability of tea tree growth and overcome the shortage of subjective volition, simultaneously.Therefore,it is necessary to reinforce multi-zone model research and index selection, and further explore uncertainty of growing tea trees in order to incorporate differences of suitability grade for tea trees, which would provide scientific references for distribution of tea tree growth.

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