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Chenzhou city is the most typical region of Nanling Hill Ecological Zone of flue-cured tobacco with of aroma style of burnt sweet and pure sweet in China and is the largest planting region of flue-cured tobacco in Hunan province. It is of significance to study the changes of climatic parameters with time because climate is the most important factor in determining the growth, yield and quality of flue-cured tobacco. In this study, the data of climatic parameters including cumulative sunshine hours(
*S*), mean temperature (
*T*) and cumulative precipitation (
*P*)
from 1952 to 2018 in Chenzhou were used to analyze their changes at the scales of year, whole field period and growing period of flue-cured tobacco. The results showed that at the scale of year, the cumulative
* S*, mean
*T* and cumulative
* P* were ranged from 1029.0 h to 2072.1 h, from 17.1
°C to 19.5
°Cand from 897.1 mm to 2244.6 mm, with the means of 1449.7 h, 18.1
°C and 1482.5 mm, respectively. At the scale of whole field period of flue-cured tobacco, the cumulative
*S*, mean
* T* and cumulative
*P* were ranged from 298.1 h to 807.2 h, from 21.2
°C to 23.9
°C and from 416.7 mm to 1102.7 mm, with the means of 514.8 h, 22.3
°C and 719.0 mm, respectively. At the scale of growing period of flue-cured tobacco, the annual cumulative
* S* were ranged from 70.0 h to 257.2 h, from 77.3 h to 322.5 h and from 131.2 h to 300.3 h in the periods of rooting, flourishing and maturing with the means of 127.8 h, 190.4 h and 197.2 h, respectively. The mean temperatures were ranged from 14.2
°C to 18.9
°C, from 22.2
°C to 26.1
°C, and from 25.8
°C to 29.6
°C with the means of 16.4
°C, 24.1
°C and 28.0
°C, respectively. The annual cumulative
* P* were ranged from 69.9 mm to 553.9 mm, from 133.1 mm to 485.6 mm and from 46.4 mm to 356.8 mm in the periods of rooting, flourishing and maturing with the means of 262.5 mm, 299.9 mm and 153.9 mm, respectively. At the year scale, cumulative
* S* annually decreased by 7.587 h, mean
* T* annually increased by 0.02
°C, while cumulative P changed irregularly with insignificantly increasing about by 0.184 mm annually. At the scale of whole field period of flue-cured tobacco, mean
*T* annually increased by 0.0195
°C, while both cumulative
*S* and
*P* changed irregularly with insignificantly decreasing by 1.64 h and 1.62 mm annually, respectively. At the scale of growing period of flue-cured tobacco, all climatic parameters changed irregularly except cumulative
*S* in significant positive compound function in the maturing period. Meanwhile, the slight decreasing tendency of cumulative sunshine hours and the slight increasing tendency of cumulative precipitation are disadvantageous while the slight increasing tendency of cumulative precipitation in the maturing period is positive for the growth and quality of flue-cured tobacco.

Chenzhou city, as the most typical region of Nanling Hill Ecological Zone of flue-cured tobacco with of aroma style of burnt sweet and pure sweet in China [^{4} hm^{2}) of the total planting area of flue-cured tobacco in Hunan [

Most studies have shown that climate is the most important factor in determining the growth, yield and quality of flue-cured tobacco [

Chenzhou is located in the southeast of Hunan province, between 112˚13' to 114˚14' in east longitude and 24˚53' to 26˚50' in north latitude with a total area of 1.94 × 10^{4} km^{2}. It belongs to subtropical monsoon humid climate with the mean of annual sunshine hours of 1510.3 - 1764.3 h, temperature of 15.4˚C - 18.3˚C, precipitation of 1320.3 - 1654.7 mm and frost-free season of 235 - 296 d [^{4} hm^{2} with the areas of 25.94 × 10^{4} hm^{2} for paddy fields and 5.02 × 10^{4} hm^{2} for dry fields [

The data of climatic parameters which include cumulative sunshine hours (S), mean temperature (T) and cumulative precipitation (P) from 1952 to 2018 were provided by national meteorological observation station in Chenzhou. The field-growing period of flue-cured tobacco in Chenzhou is generally from March 15 to July 15, in which the rooting period is from March 15 to April 30, the flourishing period is from May 1 to June 15, and the maturing period is from June 15 to July 15 [

Microsoft Excel 2016 and IBM Statistics SPSS 20.0 were used for data processing, modeling and mapping. The statistics information of climatic parameters was listed, such as the rangeability, average, skewness and kurtosis of climatic parameters. Besides, the linear tendency of cumulative S, mean T and cumulative P at the scales of year and whole field period were exhibited. And the optimal regression models of cumulative S, mean T, and cumulative P were used to explain the changing tendency in different growing periods of flue-cured tobacco. Moreover, the correlation analysis between climatic parameters at the scale of year, whole field period and growing period of flue-cured tobacco was done by pears on correlation coefficients.

At the scale of year, the annual cumulative S, mean T and cumulative P were ranged from 1029.0 h to 2072.1 h, from 17.1˚C to 19.5˚C and from 897.1 mm to 2244.6 mm, with the means of 1449.7 h, 18.1˚C and 1482.5 mm, respectively. At the scale of whole field period of flue-cured tobacco, the annual cumulative S, mean T and cumulative P were ranged from 298.1 h to 807.2 h, from 21.2˚C to 23.9˚C and from 416.7 mm to 1102.7 mm, with the means of 514.8 h, 22.3˚C and 719.0 mm, respectively. At the scale of growing period of flue-cured tobacco, the annual cumulative S were ranged from 70.0 h to 257.2 h, from 77.3 h to 322.5 h and from 131.2 h to 300.3 h in the periods of rooting, flourishing and maturing with the means of 127.8 h, 190.4 h and 197.2 h, respectively. The mean temperatures were ranged from 14.2˚C to 18.9˚C, from 22.2˚C to 26.1˚C, and from 25.8˚C to 29.6˚C, with the means of 16.4˚C, 24.1˚C and 28.0˚C, respectively. The annual cumulative P were ranged from 69.9 mm to 553.9 mm, from 133.1 mm to 485.6 mm and from 46.4 mm to 356.8 mm in the periods of rooting, flourishing and maturing with the means of 262.5 mm, 299.9 mm and 153.9 mm, respectively.

Time | Parameter | Min | Max | Mean | SD | CV% | Ske | Kur | |
---|---|---|---|---|---|---|---|---|---|

Year | S (h) | 1029 | 2072.1 | 1449.7 | 211.7 | 14.6 | 0.34 | 0.28 | |

T (˚C) | 17.1 | 19.5 | 18.1 | 0.6 | 3.28 | 0.60 | −0.31 | ||

P (mm) | 897.1 | 2244.6 | 1482.5 | 315.1 | 21.3 | 0.52 | −0.18 | ||

Whole field period | S (h) | 298.1 | 807.2 | 514.8 | 78.9 | 15.3 | 0.47 | 2.21 | |

T (˚C) | 21.2 | 23.9 | 22.3 | 0.7 | 3.0 | 0.39 | −0.44 | ||

P (mm) | 416.7 | 1102.7 | 719.0 | 157.1 | 21.9 | 0.32 | −0.24 | ||

Growing period | Rooting | S (h) | 70.0 | 257.2 | 127.8 | 35.0 | 27.4 | 1.03 | 2.24 |

Flourishing | 77.3 | 322.5 | 190.4 | 46.0 | 24.1 | 0.01 | 0.43 | ||

Maturing | 131.2 | 300.3 | 197.2 | 32.7 | 16.6 | 0.28 | 0.28 | ||

Rooting | T (˚C) | 14.2 | 18.9 | 16.4 | 1.1 | 6.9 | 0.10 | −0.63 | |

Flourishing | 22.2 | 26.1 | 24.1 | 0.9 | 3.8 | 0.11 | −0.36 | ||

Maturing | 25.8 | 29.6 | 28.0 | 0.8 | 2.9 | −0.06 | −0.12 | ||

Rooting | P (mm) | 69.9 | 553.9 | 262.5 | 87.6 | 33.4 | 0.46 | 0.97 | |

Flourishing | 133.1 | 485.6 | 299.9 | 78.0 | 26.0 | 0.16 | −0.20 | ||

Maturing | 46.4 | 356.8 | 153.9 | 62.3 | 40.5 | 0.88 | 1.30 |

Note: S, sunshine hours; T, temperature; P, precipitation; Ske, skewness; Kur, kurtosis. The same below.

C.V. (%) values of the climatic parameters at all the time scales showed that both cumulative S and P were all in moderate variation (10% - 100%), while mean T were all in weak variation (<10%) [

Figures 1-3 showed that annual changes of cumulative S, mean T and cumulative P from 1952 to 2018 in Chenzhou. S (^{2} = 0.488^{**}) with an annual decrease of 7.587 h. But ^{2} = 0.423^{**}) with an annual increase of 0.02˚C. However, P (^{2} = 0.000).

Figures 4-6 showed that changes of cumulative S, mean T and cumulative P in the whole field period of flue-cured tobacco from 1952 to 2018 in Chenzhou. Only the mean T (^{2} = 0.325^{**}) with an annual increase of 0.0195˚C, while both cumulative S (^{2} = 0.164; P = −1.6232a + 3941, R^{2} = 0.041).

Figures 7-9 and ^{a}, R^{2} = 0.268^{*}). In general, cumulative S showed an insignificant positive S function in the rooting period (R^{2} = 0.067), insignificant negative quadratic function in the flourishing period (R^{2} = 0.025). Mean T showed an insignificant positive cubic function in the rooting period (R^{2} = 0.180), insignificant positive power function in the flourishing period (R^{2} = 0.176) and insignificant negative inverse function in the maturing period (R^{2} = 0.049). Cumulative P showed an insignificant positive exponential function in the rooting period (R^{2} = 0.037) and insignificant positive inverse function in the periods of flourishing and maturing (R^{2} = 0.029, R^{2} = 0.014, respectively).

Parameter | Growing period | Model | R^{2} | |
---|---|---|---|---|

S | Rooting | S | S = e^{13964.259/a}^{−}^{2.220} | 0.067 |

Flourishing | Quadratic | S = −9.371 × 10^{−5}a^{2} + 559.714 | 0.025 | |

Maturing | Compound | S = 1352021.777 × 0.996^{a} | 0.268** | |

T | Rooting | Cubic | T = 2.085 × 10^{−9}a^{3} | 0.180 |

Flourishing | Power | T = a^{1.620} | 0.176 | |

Maturing | Inverse | T = −35907.895/a + 46.042 | 0.049 | |

P | Rooting | Exponential | P = 340417.270e^{−0.004a} | 0.037 |

Flourishing | Inverse | P = 2673230.106/a − 1046.993 | 0.029 | |

Maturing | Inverse | P = 1506088.953/a − 604.937 | 0.014 |

Time | Parameter | T | P | |
---|---|---|---|---|

Year | S | −0.251* | −0.384** | |

T | / | −0.100 | ||

Whole field period | S | 0.050 | −0.218 | |

T | / | 0.196 | ||

Growing period | Rooting | S | 0.344** | −0.259* |

T | / | 0.185 | ||

Flourishing | S | 0.380** | −0.404** | |

T | / | −0.256* | ||

Maturing | S | 0.307* | −0.231 | |

T | / | −0.471** |

Note: * and ** means correlation is significant in the levels of p = 0.05 and p = 0.01 (2-tailed), respectively.

At the scale of year, cumulative S was negatively significantly correlated with mean T and cumulative P (R = −0.251^{*}, p < 0.05; R = −0.384^{**}, p < 0.01), while no significant correlation was found between mean T and cumulative P. At the scale of whole field period, no significant correlation was found between the three climatic parameters. In the rooting period, cumulative S was positively significantly correlated with mean T (R = 0.344^{**}, p < 0.01) and negatively significantly correlated with cumulative P (R = −0.259^{*}, p < 0.05), while no significant correlation was found between mean T and cumulative P. In the flourishing period, cumulative S was positively significantly correlated with mean T (R = 0.380^{**}, p < 0.01) and negatively significantly correlated with cumulative P (R = −0.404^{**}, p < 0.01), while negative significant correlation was found between mean T and cumulative P (R = −0.256^{*}, P < 0.05). In the maturing period, cumulative S was positively significantly correlated with mean T (R = 0.307^{*}, p < 0.05) but not significantly correlated with cumulative P, while negative significant correlation was found between mean T and cumulative P (R = −0.471^{**}, p < 0.01).

Annual cumulative sunshine hours from 1956 to 2005 in China generally also showed a significant decreasing tendency (annually decreased by 0.012 - 0.023 h) [

As for the changes of climatic parameters during the whole field period of flue-cured tobacco, as literature showed that, during the whole field period of flue-cured tobacco from 1961 to 2010 in Hunan, annual cumulative sunshine hours generally also showed a significant decreasing tendency (annually decreased by 1.08 h), cumulative precipitation showed an insignificant increasing tendency (annually increased by 1.5 mm) [

For the whole field period of flue-cured tobacco, the mean of cumulative S was 514.8 h in Chenzhou, which is in the suitable grade for tobacco planting (500 - 600 h) but lower than the most suitable grade in Hunan (≥600 mm) [

Our study analyzed further the changes of climatic parameters from 1952 to 2018 in Chenzhou city of Hunan province, and the results showed that at the year scale, cumulative sunshine hours showed a significant linear decreasing tendency, mean temperature showed a significant linear increasing tendency, while cumulative precipitation changed irregularly with insignificant increasing tendency. At the scale of whole field period of flue-cured tobacco, mean temperature showed a significant increasing tendency but both cumulative sunshine hours and cumulative precipitation changed irregularly with insignificant decreasing tendency. At the scale of growing periods of flue-cured tobacco, all climatic parameters changed irregularly except cumulative sunshine hours in significant positive compound function in the maturing period. Meanwhile, the slight decreasing tendency of cumulative sunshine hours and the slight increasing tendency of cumulative precipitation were disadvantageous while the slight increasing tendency of cumulative precipitation in the maturing period is positive for the growth and quality of flue-cured tobacco. Further studies are needed to complete the evolution process, valuing research and model optimization of ecological environment in tobacco-growing area in Chenzhou city. Moreover, we should also pay attention to other climatic parameters so that we can make the forecasting application of models more precise.

This study was supported by Chenzhou Tobacco Company of Hunan Province (Grant No. 2019-45). We would like to express thanks to the contribution from all the participants in the data preparation and treatment.

The authors declare no conflicts of interest regarding the publication of this paper.

Kong, X.Z., Li, D.C., Li, W.J., Li, H.G. and Xiao, Y.S. (2020) Study on Climate Changes for Flue-Cured Tobacco Growth in Chenzhou City of Hunan Province. Agricultural Sciences, 11, 487-499. https://doi.org/10.4236/as.2020.115030