ارزیابی روند تغییرات پارامترهای آگروکلیمایی موثر بر رشد مرکبات مطالعه موردی: شمال ایران

هدف عمده این تحقیق ارزیابی روند تغییرات پارامترهای آگروکلیمایی موثر بر رشد مرکبات در شمال کشور می باشد. برای این منظور داده های روزانه دمای کمینه، بیشینه، بارش و ساعات آفتابی 6 ایستگاه همدیدی واقع در نوار شمالی کشور  از سازمان هواشناسی اخذ و از طریق آنها پارامترهای دیگر نظیر متوسط دما، دامنه دما، درجه روزهای رشد، مجموع واحد های حرارتی آفتابی و مجموع واحدهای حرارتی نوری در مقیاس ماهانه، فصلی و سالانه محاسبه گردید. در مرحله بعد،  از آزمون روند من کندال و روش خطی برای محاسبه روند تغییرات پارامترهای آگروکلیمایی ذکر شده در فوق در مقیاس ماهانه، فصلی و سالانه استفاده گردید. نتایج این تحقیق نشان دهنده وجود روند افزایشی معنی دار  در  دمای کمینه، بیشینه و متوسط، روند کاهشی معنی دار دامنه دما،  روند افزایشی معنی دار  درجه روزهای رشد، مجموع واحد های حرارتی آفتابی و مجموع واحدهای حرارتی نوری است. متغیر بارش در تعداد معدودی از ایستگاه ها در مقیاس ماهانه دارای روند معنی دار در سطح 5 درصد می باشد و در مقیاس فصلی و سالانه دارای روند معنی داری نمی باشد. نتایج این تحقیق همچنین نشان می دهند روند افزایشی دمای کمینه، بیشینه، مجموع واحدهای حرارتی نوری و حرارتی آفتابی و روند منفی دامنه دما در صورت تداوم تاثیر نامطلوبی بر کیفیت میوه مرکبات خواهد داشت.

The assessment of change Trend in Agro Climatological parameters that influence the growth of citrus Case study: Northern parts of Iran

> IntroductionCitrus fruits are ranking in the first place in the world with respect to production among fruits. They aregrown commercially in more than 50 countries around the world.Citrus fruit production recorded a handsome increase during the 1990s, and recently reached 100 million tonsannually. Considering the therapeutic value of these fruits and the general health awareness among the public,citrus fruit are gaining importance worldwide, and fresh fruit consumption is likely to increase.Climatic changes results essentially from man’s action on the ecosystems that degrade very quickly butrecovers very slowly and lose biodiversity.Climate change strongly influences desertification process by its impact on the vegetation, soil andhydrological cycle. Agriculture is interface of ecosystem and community. Agriculture is not only responsiblefor 20 percent of green house gas emissions into the atmosphere but also it becomes affected fromenvironmental conditions change. As a result, combining of agroclimatic studies and environmentalcondition is needed for a sound assessment of future climate change.The area of study in this research was the North of Iran. We have used information from six stations in the 0px > area including Gorgan, Noshahr, Rasht, Ramsar, Anzali and Babolsar. In the research, the timeseries(annual, seasonal and monthly period) of eight climatevariables including accumulated rainfall, meantemperature, min temperature, max temperature, min and max temperature difference (TD), Growing DegreeDay (GDD), Helio thermal Units (HTU) and Photo thermal Units (PTU) were Analyzed to ascertain theexistence of climate variability in the period 19762005 in the Northern part of Iran. Man Kendal test andlinear regression models (ttest) have been used for the trend detection in the time series of research variables.The Mann–Kendall method has been suggested by the World Meteorological Organization to assess the trendin environmental data timeseries. This test consists of comparing each value of the timeseries with theothers remaining, always in sequential order. The presence of a statistically significant trend is evaluatedusing the Z value. This Statistic is used to test the null hypothesis such that no trend exists. A positive ZIndicates an increasing trend in the timeseries, while a negative Z indicates a decreasing trend. To test foreither increasing or decreasing monotonic trend at p significance level, the null hypothesis is rejected if theabsolute value of Z is greater Than Z1−p/2 where Z1−p/2 is obtained from the standard normal cumulativeDistribution tables. In this work, the significance levels of p= 0.01 and 0.05 were applied, and the significantlevel (pvalue) was obtained for each analyzed timeseries. It is also possible to obtain a nonparametricestimate for the magnitude of the slope of trend. The ttest for trend detection is based on linear regression,and therefore checks only for a linear trend. There is no such restriction for the Mann Kendall test.Results and discussionThe results of this research indicated generally increasing trends in most of these variables (statisticallysignificant at p<0.01 or p<0.05) by Mann–Kendall test and linear regression models. However, the minimumand maximum temperature difference presented decreasing behavior. The study showed that most of thestations studied are going through a process of environmental warming. The results also suggest that thehistorical trends may be related to climate variability in northern part of Iran, which affects both semi tropicaland coastal part of the region.The decrease in the minimum and maximum difference is generally based on Wants' Hoff factor accompaniedby reduced quality of the citrus, while the increase in mean Temperature, GDD, HTU and PTU is satisfiedwith the plantation area of the citrus.ConclusionThis study investigated climatic variability in northern part of Iran based on Maximum, minimum and meanair temperatures, the difference between minimum and maximum temperature, rainfall, Growing Degree Day(GDD), Helio thermal Units (HTU) and Photo thermal Units (PTU). It emphasizes that the timeseries ofthese climatic variables in northern part of Iran presented an increasing trend (statistically significant atp<0.01 or p<0.05) for almost all stations.Moreover, the difference between minimum and maximum temperature trend is inverse, that is, decreasingover time, also statistically significant in most stations. The time behavior pattern of the temperature isphysically consistent with the behavior of the other climatic variables analyzed. The decrease in differencebetween minimum and maximum temperature is reduced generally, while the mean temperature, mintemperature, maximum temperature, HTU, GDD and PTU were increased.This study showed climate variability in most of the stations studied. ThisVariability affects not only the semitropical region of northern part of Iran but also the coastal part of theregion.