چکیده:
فنولوژی، شاخصی کلیدی در رشد و نمو گیاهان است و نقشی مهم در نظارت بر پوشش گیاهی دارد. در این پژوهش، مراحل اصلی فنولوژی پرتقال شامل تشکیل جوانة برگ و میوه، شکفتن جوانة برگ و میوه، میوهدادن و برگدادن، رشد میوه و برگدادن، رسیدن میوه و سیکل خواب با استفاده از سنجش از دور بررسی شد. منطقة مطالعهشده، یک باغ پرتقال در کشور ایران در جنوب شرقی استان فارس و در فاصلة 25کیلومتری شهر داراب در روستای فسارود است. بدین منظور دادههای مشاهداتی شامل دادههای فنولوژی و آبوهوایی در بازة زمانی دهساله (1385 تا 1395) جمعآوری شد. نخست تصاویر سنجندة مودیس برای سال 1385 تا 1395 با توجه به دادههای زمینی و نقشههای 1:25000 سازمان نقشهبرداری زمینمرجع شدند. این تصاویر برای محاسبة شاخصهای پوشش گیاهی سنجش از دوری شامل شاخص تفاضلی نرمالشدة پوشش گیاهی (NDVI)، شاخص وضعیت پوشش گیاهی (EVI) و شاخص شرایط دمایی (TCI) استفاده شد. درنهایت در ارزیابی عملکرد شاخصهای سنجش از دوری در مدلسازی مراحل فنولوژی، ضریب همبستگی میان این شاخصها و دادههای زمینی محاسبه شد. بیشترین مقدار ضریب همبستگی بین TCI وحداکثر دما برابر با 953/0 و کمترین ضریب همبستگی بین NDVI و حداکثر رطوبت برابر با 04/0 به دست آمده است. نتایج ضریب همبستگی حاکی است شاخصهای بهدستآمده از روش سنجش از دور با استفاده از تصاویر ماهوارهای بهخوبی تغییرات مراحل اصلی فنولوژیکی را نشان میدهد؛ از سوی دیگر برمبنای این شاخصها میتوان بدون برداشت زمینی و مشاهدة فیزیکی از روند تغییرات فنولوژی گیاه آگاه شد.
Extended Abstract Introduction Phenology is a key indicator in plant growth and plays an important role in monitoring vegetation. Monitoring seasonal variations in vegetation activities and crop technology over large areas is essential for many applications, including estimating initial net production time to model crop performance and supportive water supply decisions. On the other hand, extracting this important information requires a lot of time and money. The southeast of Fars Province in Iran has a very favorable climate and environmental conditions for citrus growth and thus the region is one of the most important citrus cultivation spots in Iran. Given the significance of citrus cultivation in the food production of the country as well as its important role in regional economics, planning in the field of citrus phenological information in this region solve many challenges in the agricultural sector in the region. In other words, knowing the plant phenological status in citrus orchards can play an important role in planning and managing climate change and ultimately the development of the agricultural sector of this province. In this regard, this study aims to estimate the main phenological stages of orange trees using remote sensing. Methodology In the proposed study, MODIS images (2006-2016) were employed. The images were downloaded for 10 days. The remotely sensed images were used to extract vegetation indices including NDVI, EVI, and TCI to modeling the phenology of the orange trees. Also, 1/25000 maps of Iran National Cartographic Center were used as the spatial reference for the images geo-referencing. The meteorological data including daily maximum and minimum temperature, relative humidity, and precipitation were collected from the Darab Agrometeorology station. The phenological data including the onset and end of each phonological period of orange trees which were being observed from 2006 to 2016 at the Agrometeorology Station was used in this study. In this study, the three most widely used remote sensing indices were investigated to evaluate the health and status of vegetation and temperature conditions. The normalized difference vegetation index, vegetation status, and temperature condition index were calculated to compare the results of the remote sensing and traditional harvesting of plant phenological stages. To observe the effect of moisture on vegetation, the charts of normalized maximum temperature, normalized maximum moisture, and normalized difference vegetation index were plotted for all the years. Discussion The phenological stages of citrus had 9 main phases and 97 sub-phases, out of which 6 main stages were presented to the researchers and were investigated. The 6 main phenological stages of oranges are as follows: Leaf bud and fruit formation, leaf bud and fruit flourishing, fruiting and leaf growth, fruit and leaf growth, fruit ripening, and sleep cycle. To interpret these stages, the charts of normalized maximum temperature and normalized temperature condition index obtained from the MODIS satellite images were plotted for all crop years. The variation of Tem max was correlated to the growing stages of orange trees. In the other words, the normalized temperature condition index obtained from the satellite images properly indicated the temperature variations. Moreover, the temperature change charts properly showed the changes in the duration of the phenological stages of orange trees. Conclusion To investigate the effect of temperature variations on different phenological stages of orange trees, the normalized maximum temperature and normalized difference vegetation index were plotted for all the crop years. At each point where the peak of the normalized maximum temperature was observed, the peak in the normalized difference vegetation index was also found at a very small distance. In other words, when the temperature increased, the conditions were favorable for increasing vegetation and the plant begins to grow. Finally, to evaluate the performance of remote sensing indices in expressing changes in temperature and vegetation conditions, the correlation coefficient between remote sensing indices and ground data was calculated in pairs. Since the study area was arable land and human factors were involved in plant growth, the resulting correlation coefficients were small. The results of calculating the correlation coefficients indicated that the indices obtained from remote sensing using satellite images can properly show the changes in the main phenological stages. 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خلاصه ماشینی:
(رجوع شود به تصویر صفحه) (رجوع شود به تصویر صفحه) شکل ٣: نمودارهاي تغييرات NDVI،TCI ، در بيان تغييرات حداقل رطوبت و حداقل دما و مراحل مختلف فنولوژي درخت پرتقال fig 3: Graphs of NDVI and TCI changes in expression of changes in minimum humidity and minimum temperature and corresponding stages of orange tree phenology در اين مرحله پيش از انجام مراحل اصلي پردازش ، براي نرمال سازي سري هاي زماني استفاده شده (نگاشت مقـادير به فضاي ٠ و ١) اقدام شده است .
ضريب همبستگي ميان شاخص هاي سنجش از دوري و شاخص هاي زميني Table 2: Correlation coefficient for remote sensing indices and ground indices (رجوع شود به تصویر صفحه) در مطالعۀ حاضر، سه شاخص پوشـش گيـاهي سـنجش از دوري (شـامل دو شـاخص بـراي مـدل سـازي شـرايط سبزينگي پوشش گياهي، NDVI و EVI و يک شاخص براي بيان شرايط دمايي پوشـش گيـاهي، TCI) بـا اسـتفاده از تصاوير ماهواره اي محاسبه شده است .
Graph of NDVI and EVI changes, in expressing maximum temperature changes and different stages of orange tree phenology درنهايت به منظور بررسي عملکرد شاخص هاي مختلف سنجش از دوري (EVI،NDVI و TCI) در بيـان تغييـرات در شرايط دما، رطوبت و بارندگي و پيرو آنها مدل سازي مراحل فنولوژي گياه (درختـان پرتقـال ) در منطقـۀ پـژوهش ، براي ايجاد مدل هاي خطي جداگانه بـه منظـور مـدل سـازي مقـادير عـددي هريـک از پارامترهـاي زمينـي يادشـده بـا شاخص هاي سنجش از دوري اقدام شد؛ بدين ترتيب براي هريـک از شـاخص هـاي سـنجش از دوري، يـک ضـريب (تأثير) در توليد مقادير پارامترهاي زميني محاسبه شد که در جدول ٣ آمده اسـت .