Characteristic Of Main Ecological Factors And Its Impacts On Quantity And Quality Of Flue-cured Tobacco In Chongqing

Tobacco is a special leaf economic crop, with both the yield and quality of equal importance. The growth and quality of tobacco leaves are related to the variety, cultivation management, baking technology, ecological environment and so on. Obviously, the ecological environment is the most important factor in determining the quality of tobacco leaves. Climate, terrain, geology, soil are the main factors that affect the yield, quality and characteristics of tobacco leaves, thus the understanding of the eco-environment conditions of Chongqing tobacco growing areas is necessary for showing the characteristics of Chongqing tobacco leaves. Chongqing tobacco growing areas are distributed in the mountainous area of Wuling and the Qin Ba Mountain, with complex geographic and geomorphic conditions, the significant difference of altitude, causing the complex spatial and temporal variability of the climate, terrain, soil and other ecological factors. However, the spatial distribution of Chongqing tobacco field is not clear, and its corresponding ecological factors, such as soil, geology, and terrain have not been fully acquired. In addition, due to the uneven and dispersive spatial distribution of meteorological observation stations in Chongqing, the existing climate observation data cannot reflect the climate conditions of the complex terrain of Chongqing tobacco growing areas. The lack of ecological factors data makes it difficult to make a comprehensive analysis of the impact of various ecological factors on the yield and quality of flue-cured tobacco(FCT), and to reveal the restrictive ecological factors on the quality of FCT, and then it restricts the layout of producing high-quality tobacco leaves in Chongqing, finally, it affects the characteristics and quality enhancement of Chongqing tobacco leaves.In order to tackle the above problems, this paper adopts geographic system technology and spatial analysis, under the unified coordinate system, climatic conditions, agricultural geological background investigation, soil properties survey and analysis are combined in Chongqing tobacco growing areas. Soil conditions, geological and climatic factors and the effects of ecological factors which forging the production of high-quality tobacco are studied under Chongqing complex terrain conditions. FCT yield is combined with the hierarchical structure, the data of overall quality to analyze the ecological characteristics of Chongqing tobacco growing areas and the main ecological factors affecting yield and quality of tobacco, it has been clear about the effects of climate factors on aroma types of FCT, revealing the relative importances of different ecological factors on the yield and quality of FCT in Chongqing tobacco growing areas. It provides scientific basis for the production planning and layout of the characteristic high-quality tobacco in Chongqing. The main results are as follows.(1) Digital elevation model construction and the spatial distribution of Chongqing tobacco growing areasThe topographic data in Chongqing tobacco producing areas were collected to construct the digital topographic map(digital elevation model, DEM). Through the digital topographic map, geology, topography and other basic geographic information in tobacco growing areas are obtained. Those tobacco growing counties,(township) towns, villages and groups(communities) are regarded the data acquisition unit, based on the Chongqing Municipal tobacco company’s annual tobacco acquisition data, the planting tobacco area units per year can be determined. Then, Chongqing tobacco acquisition database group(community) and spatial distribution maps are constructed.(2) It investigates the methods of obtaining the data under the complex terrain conditions in the Chongqing area, including the temperature, the number of sunshine hours(SH), and the solar radiation(SR). Furthermore it establishes and the grid meteorological data set, analyzes the main climatic factors of Chongqing tobacco growing areas in the fields of FCT(April-October). The earliest transplanting date of FCT in different altitude gradient regions is defined.Based on the meteorological observation data of various meteorological stations in China, the terrain correction model of climatic factors spatial interpolation is established, and the regional estimation method of sunshine, SRand temperature in Chongqing tobacco growing areas is discussed. Seven types of spatial interpolation models are used to evaluate the spatial interpolation and performance(accuracy) of the sunshine duration and SRin the Chinese mainland, it finds out that Thin Plate Spline(TPS) function enjoys the best performance in SH of spatial interpolation and then takes it as the optimal SH spatial simulation method. The geographic parameters(latitude, longitude, elevation) and TPS interpolation method are used to simulate SRinterpolation of multiple linear regression equation(MLR), as compared with the above-mentioned seven kinds of spatial interpolation models, it demonstrates the best performance. The linear regression(MLR), and the performance of the MLR model is better than the 7 spatial interpolation models by using the TPS(multiple). Based on the model of terrain correction, the regional estimation of the temperature of Chongqing tobacco growing areas was carried out by using the method of regional estimation of “multivariate regression equation plus residuals” with the adaptation of geographic parameters(latitude, longitude, elevation), with the release of ANUSPLIN 4.3 software in Australian National University in Canberra resources and environment Research Center, through the statistical relationship between rainfall data and geographic parameters(longitude, temperature and elevation) of the meteorological stations of precipitation, the regional rainfall is estimated in Chongqing tobacco growing areas.Based on the above optimal model, the grid meteorological data set of 1 km2 in Chongqing tobacco growing area was obtained, and the spatial distribution database of Chongqing tobacco growing area was established, and the climate characteristics of the temperature, SH and precipitation(April-October)in Chongqing tobacco growing county and town were analyzed. From April to October, the average monthly temperature in Chongqing tobacco growing areas is between 13.2℃-23.0℃, the total rainfall is 1047.2 mm, SH are 824.6h. Compared with the typical regions of the intermediate aroma type, the overall climate characteristics of Chongqing tobacco growing areas is characterized with suitable temperature, much precipitation, long sunshine time and too few SR, those factors are different in different tobacco growing counties, and different elevation gradients. China’s FCT growing Division offers the earliest transplanting date basis for daily temperature stability on the date of 13℃, the analysis of different altitude gradients of Chongqing in April and May reveals that the date of Chongqing tobacco transplanting delays with the rise of elevation, when elevation is less than 800 m, the earliest transplanting period is in early April, the areas 800-1200 m is 16-20 April, 1200-1400 m region for April 26-30, >1400 m region for 6-10May; It makes the earliest transplanting period at different altitudes clear, and provides scientific basis for real-time FCT transplanting date in different regions.(3) It obtains the ecological factors, such as geology, soli, gradient and so on in Chongqing tobacco growing areas, and then analyzes their characteristics and spatial distribution.On the basis of establishing Chongqing tobacco growing area group/ community distribution database with the help of Chongqing FCT purchase database, by overlaying with regional geological maps, soil maps, DEM, respectively, geological formations, soil types, elevation, slope and other factors are extracted in Chongqing tobacco growing areas. In 12 tobacco growing districts and counties of Chongqing, a total of 2777 soil samples are collected from the root level, the physical and chemical properties of soil are analyzed, and soil fertility status becomes clear. The results showed that there are 32 types of geologic strata in Chongqing, the number of geologic strata type in which the planting areas above 667 hm2 is 7, accounting for 90.48% in the total area of tobacco growing; including the formation of Daye group limestone dolomite, Liangshan formation of Permian Wujiaping limestone and dolomite, the Ordovician limestone of Tongzi formation mudstone, shale and limestone of Cambrian Niutitang Formation dolomite, Silurian Longmaxi shale siltstone interbedded limestone, Cambrian Loushanguan group dolomite limestone with sandstone shale, Silurian shale sandstone, the proportion of the FCT growing area accounts for the total are respectively 43.34%, 19.48%, 8.05%, 7.93%, 8.05%, 2.81% and 1.92%.The soil types in tobacco growing area mainly include yellow soil(70.0%),lime soil(rock)(19.4%), yellow brown soil(6.7%), purple soil(2.9%), and the rest are all less than 1%; yellow soil and lime soil(rock) mainly are developed from the Triassic and Permian limestone dolomite; from tobacco distribution on altitude and slope, the Chongqing tobacco growing area are mainly distributed in the altitude of 800-1400 m, accounting for about 73% but in recent years, there is a tendency for Chongqing tobacco growing area to move of high altitude areas; there are 28.11% tobacco growing soil distributing in slope 25 °-35 °, and 25.4% are located in the gentle plains whose slope is <5 °.In terms of the nature and fertility of tobacco growing soil, Chongqing tobacco soil is mainly acid soil, the acid and strong acid soil of p H<5.5 account for 50%. The soil organic matter content averages 25.7 g/kg, which is in a moderate range compared with other domestic tobacco growing areas. Soil nitrogen content is high, in order to avoid excessive amount of nicotine on the upper leaves result from the soil nitrogen in the late period, accurate control of the amount of nitrogen is proposed. Low, high and appropriate available P and available K all exists, therefore, the partition P and k fertilizer formula is suggested; Ca, Mg deficiency soil account for 68% and 41%. Available Cu, Zn, Fe, and Mn content are high, but the lack of B, molybdenum and Cl is common, the lack of soil account for 85.0%, 68.7% and 64.8%. Should be aimed at the above problems, in order to solve the above problems, tobacco growing soil should be improved and supplemented with some trace elements according to local conditions.(4) The probability of using chemical composition of tobacco leaves to discriminate those leaves into different Aroma Types were discussed, and found that total sugar, nicotine are the main indices to discriminate aroma type of FCT leaves.According to the acknowledged spatial distribution of flavor types, the chemical composition of tobacco leaves in159 typical counties were collected. SVMs for aroma type discrimination of FCT leaves were established to discriminate the above collected 159 samples of FCT leaves. The chemical composition characters among different aroma type groups were analyzed. Light flavor chemical parameters characteristic of tobacco samples show higher total sugar, reducing sugar, K2 O and derivative variables(potassium chlorine ratio, nitrogen-nicotine ratio and two sugar poor). Intermediate flavor show high nicotine content, total nitrogen and potassium chlorine ratio and low Cl content, sugar-nicotine ratio and nitrogen base ratio. Heavy flavor has a higher Cl ions, sugars and nitrogen bases than nicotine, and low nicotine, total nitrogen, K2 O and two sugar poor. We investigate the methods of classifying the flavor types by studying the chemical composition content in FCT, the total sugar and nicotine are especially important in classifying the light, intermediate and heavy types. It changes the traditional way of discriminating the flavor through the subjective smelling of professionals. It makes the objective and quantified classification of favor types possible.(5) Clarify the influence of climatic factors on the spatial distributions of aroma types of FCT, and find that SH is the first key climate factor to predict the regional araoma type.The classification and regression tree(CART) method is used to analyze the relationship between different flavor FCT spatial distribution and climatic factors. The results show that SH, average temperature and precipitation are key factors in distinguishing light, intermediate, and heavy tobacco leaf aroma samples, SH is the most important factor; typical light aroma type FCT growing areas are characterized with short SH, monthly mean temperature, while precipitation is higher; on the opposite of light aroma type FCT growing areas, heavy aroma type FCT growing areas has a larger number of SH, monthly mean temperature, but the precipitation is low; those three factors of the intermediate aroma type FCT growing areas are between those of the light type and heavy type; even though Chongqing FCT growing areas are regarded as intermediate type producing areas, but form the aspect of climatic factors, they are also inclined to the light type, which means, they have the characteristics of short SH, low average monthly temperature, and high precipitation. Compared with the meteorological conditions in light and heavy type tobacco growing areas, those characteristics are more inclined to the light type tobacco growing areas.(6) Using classification and regression tree model to analyze the importance of ecological factors in determining the FCT yield, the proportion of middle and first-class tobacco, and quality, the constraints of key ecological factors on the yield and quality of Chongqing FCT were clarified.Combining agricultural soil samples, tobacco group / community distribution, tobacco acquisition database(yield, the proportion of middle and first-class tobacco), and the above ecological factors of spatial data sets, 555 samples with complete data are screened, using the CART algorithm to analyze the relative importances of various ecological factors on tobacco yield, the proportion of middle and first-class tobacco. The ecological factors of relative importances on FCT yield per unit area in Chongqing tobacco growing areas is soil factor> climatic factor> topographical factor>geology type, the importance of each factor is demonstrated as follows: B> SH> Mn> Zn> altitude> Cu> available P> average temperature> lowest temperature> organic matter> temperature difference> Ca> precipitation> maximum temperature> available K> Cl> Mo> available N>geology type> Mg> Fe>p H. In soil factors, tobacco yield is under the distinct constraints of by soil trace elements B, Mn most, which is related to the great deficiency of B and Mn in large areas of Chongqing tobacco soil. Among climatic factors in the growing season places tobacco(April –September), the most obvious effect is sunshine. FCT pure unit area yield increases with the height above sea level increases, the basic altitude of 1000 m is a watershed, when the altitude is less than 1000 m, and FCT yield is lower.The relative importances of ecological factors on the middle and first-class FCT is as follows: sunshine> precipitation > Mn > Mg >Cl> Ca > B > temperature difference> available nitrogen > lowest temperature > altitude> the highest temperature >average temperature > P > Mo > Fe > p H >geology type > Cu > Zn > organic matter > available k, indicating that the ecological factors on the proportion of middle and first-class tobacco is climatic factor > soil factor > topographic factor>geology type. Among the climatic factors, SH, precipitation show the most obvious effect on flue- cured tobacco growing fields(April-September), and among the soil factors the soil trace elements and middle elements(soil Mn, Mg, Cl, Ca, B content) effect are the most obvious. The proportion of middle and first-class FCT increases with the increase of height above sea level, the basic altitude of 1,000 m is a watershed, when the altitude is less than 1000 m, and FCT yield is lower.(7) The relative importances of main ecological factors on the quality of FCT are analyzed and determined in Chongqing planting areaBy reference to the evaluation index system of the quality of FCT in China’s FCT growing Division, the synthesis scores about the flue-cured quality are calculated by index pulsing method, the quality of FCT is judged by the score. The middle part of tobacco leaves which are graded as C3 F are the samples being extracted. And the data of the obtained ecological factors are extracts, CART algorithm is used to analyze the relative importances of ecological factors on the overall quality of FCT. As a result, effects of ecological factors on the overall quality of FCT are in the order of climatic factors> soil factors> topographic factors> geological type. In the climatic factors, the effects on tobacco overall quality are in the order of sunshine> precipitation> average temperature> lowest temperature> maximum temperature> temperature difference; in soil factors the effects on tobacco overall quality are in the order of organic matter> available Fe> available B> available Mn> effective K> nitrogen>available phosphorus> p H> ammonium> exchange Mg> nitrate> effective molybdenum> Cl> available Cu> exchange Ca> available Zn, which further demonstrates the increasingly obvious influence of soil trace elements on the overall quality of FCT; the influence of and topographic factors and geological type on the overall quality of FCT is far less than that of climatic and soil factors.In summary, this paper through obtaining high-precise meteorological factors spatial data sets, combining FCT purchase database with geological and topographic factors, as well as collecting soil samples and determination of FCT samples and acquisitions, this paper offers an effective way to systematically analyze the main ecological factors influencing tobacco flavor, quality and yield. By the analysis of the relative importances of ecological factors on FCT flavor, quality and yield, it makes clear that SH, the average temperature and precipitation are the key climatic factors in discriminating FCT flavor, the SH is especially critical; the main ecological factor constrainting the quality are sunshine, precipitation, and soil organic matter, available B, Mn and others. These results provide a decision-making reference for the screening restrictive factors among many ecological factors that affect tobacco quality in Chongqing tobacco growing areas, for exploring the local ecological sources, optimizing the layout of growing areas and improving the quality of tobacco production level, we also attempt to provide a reference for conducting similar studies of other tobacco-growing areas.