Analysis on the Conditions and Suitability of the Flowering of Osmanthus fragrans in Wenjiang District

Ren RONG

1.Chengdu Experimental Station of Agricultural Meteorology,Wenjiang 611135,China;2.Heavy Rain and Drought-Flood Disasters in Plateau and Basin Key Laboratory of Sichuan Province,Chengdu 610072,China

Wenjiang District has always been the country of flowers,andO.fragransis one of major planting flowers in Wenjiang.O.fragransis sweet smelting and beautiful,and can be used for people to enjoy leisure. What’s more,essence refined fromO.fragransflowers is widely applied in food industry and chemical industry.It is important material for making osmanthus sugar,osmanthus tea,osmanthus wine and osmanthus cake,and its product is special local product and knockout product in China.

At present,the researches aboutO.fragransin Wenjiang District only limit in analyzing meteorological conditions of abnormal flowering and the impact of meteorological disaster on florescence.So,to make up the deficiency,terrain,soil condition and meteorological data in Wenjiang District were analyzed in the research.Prerequisite and the climatic indicators for the first flowering ofO.fragranswere obtained,and suitability analysis of climatic condition during florescence was conducted.The research has important significances for people using fa vorable climate resources with purpose and plan,avoiding adverse climate condition,actively plantingO.fragrans,and developingO.fragransindustry in Wenjiang District andO.fragransleisure and tour.

Data Source and Method

Using statistical method[1-2],meteorological observation data at Wenjiang Meteorological Bureau during 1971-2014 and phenological observation data of early Yingui at Chengdu Experimental Station of Agricultural Meteorology during 2004-2014 were analyzed.

Suitability Analysis on Terrain,Soil and Climate in Wenjiang District

Wenjiang District is located in abdomen of Chengdu Plain,and belongs to alluvial plain of Minjiang River,with the average altitude of over 500 m.There is no mountain and hill,but many rivers.It is at upper reaches of Dujiangyan gravity irrigation district,with high groundwater level and water network discharging and irrigating freely.Soil is loam,pH is between 6.0 and 6.5[3],which shows subacidity.Its soil is fertile and is suitable for farming.

Wenjiang District belongs to central Asia tropical humid monsoon climate.It has clear four seasons and mild climate.It is not cold in winter and not hot in summer.Frost-free period is long,and there is rarely snow and ice.Rainfall is abundant,and humidity is large.There is more cloud and fog,and sunshine time is short.Rainfall mainly concentrates in July and August,and it is arid and rainless in winter and spring.Occurrence probability of disastrous weather is small.According to observation and statistics over the years,annual average temperature in Wenjiang District is 15.8℃;annual average rainfall is 896.1 mm;annual average sunshine hours is 1 104.5 h;average relative humidity is 84%,and average wind velocity is 1.3 m/s.Average temperature in January is 5.2℃,and extremely minimum temperature over the years is-5.1℃.Freezing days over the years is less than 10 days,and average temperature in July is 24.8℃.

Huang Yinget al.think thatO.fragransis sensitive to temperature,and temperature is an important factor ofO.fragransgrowth.O.fragranslikes warm,is suitable for growing in subtropical region,and only could endure short-time low temperature.The most suitable growth temperature is that annual average temperature is over 15℃;average temperature in January is between 3.0 and 5.5℃;extremely low temperature is not lower than-8℃.Neutral or slightly acidic sandy loam is the mostsuitable forO.fragransgrowth,which is humid,fertile,and has rich organic matter and good drainage.Alkaline soil and low-lying,too wet and dry barren land are not suitable for plantingO.fragrans.Suitable soil pH ofO.fragransis between 5.0 and 7.5,and it is the best between 5.5 and 6.5[4].

According to the research of Huang Yinget al.,by analyzing terrain,soiland climate characteristics in Wenjiang District,it is clear that geographicalenvironmentin Wenjiang District is good,and both soil quality and pH are within suitable ranges plantingO.fragrans,while annual average temperature,average temperature in January and extremely minimum temperature over the years are all suitable forO.fragransgrowth.It could even be said that natural conditions are unique,and are suitable for plantingO.fragrans.

Conditions and Climatic Indicators of First Flowering of Early Yingui in Wenjiang District

First weather conditions of the first flowering

Research of Huang Yinget al.thought that when autumn minimum temperature was lower than 17℃,which reached over 4 d,and the maximum temperature was over 26℃for several days,and it was accompanied with precipitation process,it was the prerequisite ofO.fragransflowering[1].Statistics on weather data during first flowering period of early Yingui and 10 days before flowering in Wenjiang District during 2004-2013 was shown as Table 1.Seen from Table 1,according to 100% of cumulative frequency,prerequisite suitable for first flowering of early Yingui in Wenjiang District was as below:in 10 days before flowering,cumulative days of daily minimum temperature less than 21℃was more than or equal to 2 days,and cumulative days of daily maximum temperature more than 28℃was more than or equal to 2 days,while rainfall days was more than or equal to 2 days.

Climatic indicators of first flowering

Statistics on phenology and weather data in 10 days before first flowering period of early Yingui in Wenjiang District during 2004-2013 was shown as Table 2.

(1)In 10 days before flowering,occurrence ranges of weather factors for first flowering of early Yingui in Wenjiang District were as below:average temperature changed between 20.7 and 24.8℃;average minimum temperature changed between 18.8 and 22.0℃;average maximum temperature changed between 24.3 and 29.9℃;average relative humidity changed between 75% and 88% ;cumulative rainfall changed between 9.6 and 115.0 mm;cumulative rainfall days changed between 3 and 9 days;cumulative sunshine changed between 5.6 and 80.3 hours.

(2)Statistical results showed thatclimatic indicators favorable for first flowering of early Yingui in Wenjiang District were as below:average temperature in continuous 10 days before flowering was less than or equal to 22.9℃;average minimum temperature was less than or equal to 20.2℃;average maximum temperature was more than or equal to 27.1℃;average relative humidity was more than or equal to 81% ;cumulative rainfall was more than or equal to 53.2 mm;cumulative rainfall days was more than or equal to 5.5 days;cumulative sunshine was more than or equal to 30.0 hours.

Table 1 Occurrence days and frequency of each-level meteorological indicator in 10 days before first flowering period of early Yingui

Table 2 Weather factors in 10 days before first flowering period of early Yingui

Table 3 Average weather factors in each ten days from first dekad of August to middle dekad of September

Analysis on Climatic Conditions Suitable for First Flowering of Early Yingui

Analysis on period favorable for first flowering

According to phenology data of early Yingui in Wenjiang District,first flowering period was from middle dekad of August to middle dekad of September.Means of meteorological factors over the years in each ten days from first dekad of August to middle dekad of September during 1971-2010 were shown as Table 3.Using climatic characteristics of first flowering,occurrence ranges of weather factors favorable for first flowering of early Yingui in Wenjiang District were obtained(Fig.1-Fig.7).

Seen from Fig.1-Fig.7,occurrence periods of dekad meteorological factors favorable for first flowering of early Yingui were as below:

(1)Dekad average temperature over the years from middle dekad of August to middle dekad of September and average minimum and maximum temperature from middle and latter periods of first dekad of August to latter period of middle dekad of September were all within favorable ranges of first flowering of early Yingui.

(2)From first dekad of August to middle dekad of September,dekad average relative humidity,dekad average rainfall,dekad average rainfall days,dekad average sunshine were all within favorable ranges of first flowering of early Yingui.

(3)The above dekad weather factors within favorable ranges of first flowering of early Yingui appeared from middle dekad of August to latter period of middle dekad of September,which showed that first flowering period could not appear from first dekad of August and last dekad of September according to current data and climate characteristics.It tallied with that the earliest first flowering date over the years was on August 13,while the latest first flowering date was on September 15.

Climaticindicatorsfavorable for first flowering in 10 days before flowering

According to prior climatic characteristics of first flowering,climatic indicators favorable for first flowering of early Yingui in Wenjiang District were obtained.By statistics on weather data in Wenjiang District from middle dekad of August to middle dekad of October during 1971-2010,occurrence years of climatic indicators favorable for first flowering of early Yingui was 37 years,with the frequency of 93%.Result showed that climatic indicators suitable for first flowering of early Yingui appeared in most of years in Wenjiang District,and only did adverse flowering conditions appear in very few years.Overall,autumn meteorological conditions in Wenjiang District were favorable for first flowering of early Yingui.

Analysis on meteorological conditions at first flowering stage

Research results of Wang Fengxiang et al.showed that 15-20℃of temperature is the most suitable for flowering.When temperature is lower than 15-20℃,flowering is slow,and sweet smell goes down;when temperature is higher than 15-20℃,flowering accelerates,and viewing period shortens[5].Ding Zhaohua et al.thought that it is required 80% of relative humidity when flowering. If encountering drought,it could affect flowering[6].Research result of Huang Yinget al.showed thatO.fragranslikes sunshine,and requires warm,humid and wellventilated environment.When sunshine is sufficient,there are more branches and leaves,and flowers are dense.When sunshine is too weak,O.fragransis at shade status for long time,and its growth is not good,with thin branch and sparse flower[4].

Table 4 Suitability statistics on weather factors at first flowering period of early Yingui

According to phenology observation and investigation data in Wenjiang District,first flowering period of early autumnO.fragransis from middle dekad of August to middle dekad of September,while first flowering period of late autumnO.fragransis from middle dekad of September to middle dekad of October.According to statistical analysis of the author,daily average temperature at first flowering period of earlyO.fragransis 22.9℃,which is higher than upper limit temperature(20.0℃)suitable for flowering.It makes flowering velocity accelerate slightly,and shortens viewing period at certain degree.Daily average sunshine is 3.8 hours,with suitable sunshine,which does not have adverse impact on flowering amount of earlyO.fragrans.At first flowering period of lateO.fragrans,daily average temperature is 18.2℃,which is the most suitable for flowering.Daily average sunshine is 1.8 hours,with less sunshine,which has certain adverse impact on first flowering amount of lateO.fragrans.During first flowering period of early and lateO.fragrans,daily average rainfall is between 1.7 and 6.5 mm,and relative humidity is 87%.Abundant water and humid air are favorable for flowering[7].

According to above opinions,combining actual situation in Wenjiang District,weather indicators suitable for flowering at first flowering stage were defined as below:first,suitable conditions were 15℃＜temperature≤20℃,75% ＜relative humidity≤85%,2.0 mm ＜rainfall≤5.0 mm,sunshine hours≥2.5 h.Second,more suitable conditions were temperature≤15℃or temperature＞20 ℃,71% ＜relative humidity≤75% or relative humidity＞85%,1.0 mm＜rainfall≤2.0 mm or 5.0 mm＜rainfall≤10.0 mm,1.5 h＜sunshine≤2.5h.Third,not very suitable conditions were 0 mm ＜rainfall≤1.0 mm,1.0 h＜sunshine hours≤1.5 h.Fourth,not suitable conditions were rainfall≤0 mm or rainfall＞10.0 mm,sunshine hours≤1.0 h.Statistics on phenology and weather data during 2004-2014 were shown as Table 4.

Seen from Table 4,according to current data in Wenjiang District,daily average temperature atflowering stage of early Yingui was between 19.7 and 27.1℃.Although daily average temperature in most of years was higher than upper limit(20.0℃)of that suitable for flowering,it was still suitable for flowering,and only flowering velocity accelerated slightly,and viewing period shortened.Daily average relative humidity was between 77% and 87%,and air was humid,which was suitable for flowering.In most of years,daily average rainfall was sufficient,which was suitable for flowering,and only flowering was less in two years,which was not suitable for flowering.Sunshine hours was between 1.1 and 4.0 hours,in which suitable in five years and more suitable in other five years.In most of years,sunshine was moderate,which was suitable for flowering,and quantity and quality of flower were better,and only one year was not suitable for flowering.Overall,meteorological conditions at first flowering stage of early Yingui were all favorable for flowering,and weather conditions not suitable for flowering did not appear.Seen from the above analysis,weatherconditions (light,temperature and water)in Wenjiang District could coordinate with first flowering stages of early and lateO.fragrans,could meet the requirements of flowering stages of early and lateO.fragrans,and were suitable for flowering ofO.fragrans.

Analysis on impacts of meteorological disasters

According to the research of author,during August-October of flowering period forO.fragrans,it is easy to suffer rainstorm,flood,drought,hail and gale,which directly affects yield and quality ofO.fragrans.Hail and autumn drought in Wenjiang District nearly have no adverse impact on flowering ofO.fragrans.Gale mainly has adverse impact on flowering of earlyO.fragrans,but rarely causes adverse impact on lateO.fragrans.Because occurrence frequencies of rainstorm and flood are higher,it is easy to cause adverse impact on flowering of early and lateO.fragrans.During July-August,the frequency of rainstorm and flood having serious impact is small,which is not conducive to flowering of earlyO.fragrans.Rainstorm has larger probability of causing adverse impact at flowering stage of earlyO.fragrans,and smaller probability of causing adverse impact at flowering stage of lateO.fragran[7].It is clear that weather disasters affecting flowering ofO.fragransin Wenjiang District mainly include rainstorm,flood and gale.In a word,occurrence probability of disastrous weather is small,and its impact probability on flowering of early and lateO.fragransis also small,which is conducive toO.fragransflowering.

Conclusions

(1)Terrain,soil and climate conditions in Wenjiang District are richly endowed by nature,and are suitable for plantingO.fragrans.

(2)Occurrence time of meteorological factors in each dekad in Wenjiang District within the range favorable for first flowering of early Yingui is from middle dekad of August to late period of middle dekad of September,which tallies with actual situation over the years.

(3)Meteorological conditions including light,temperature and water in Wenjiang District could coordinate with first flowering stages of early and lateO.fragrans,can meet the requirements of flowering periods of early and lateO.fragrans,and are suitable forO.fragransflowering.

(4)Meteorological disasters affectingO.fragransflowering in Wenjiang District mainly include rainstorm,flood and gale.Occurrence probability of disastrous weather is small,and its impact probability on flowering of early and lateO.fragransis also small,which is conducive toO.fragransflowering.

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