تحلیل و مدل‌سازی همبستگی بین LAI و شاخص‌های گیاهی حاصل از مشاهدات طیف‌سنجی

نوع مقاله : علمی - پژوهشی

نویسندگان

1 استادیار دانشگاه صنعتی خواجه نصیرالدین طوسی، دانشکدة مهندسی نقشه‌برداری

2 دانشجوی دکتری سنجش از دور، دانشگاه صنعتی خواجه نصیرالدین طوسی

3 دانشجوی کارشناسی ارشد سنجش از دور، دانشگاه صنعتی خواجه نصیرالدین طوسی

چکیده

بررسی خصوصیات انواع پوشش‌های گیاهی به‌عنوان یکی از پارامترهای مؤثر در تبادل انرژی بین جو و سطح زمین در مطالعات زیست‌محیطی، منابع طبیعی و کشاورزی اهمیت بسیاری دارد. امروزه فناوری سنجش ‌از ‌دور با ارائة اطلاعات طیفی گسترده و متنوع موجب تسهیل در مطالعة پوشش‌های گیاهی در سطح زمین و به‌ویژه تخمین پارامترهای بیوفیزیکی آنها شده است. یکی از مهم‌ترین پارامترهای فیزیکی به‌کار گرفته‌شده در تحلیل‌های مختلف مربوط به مطالعة پوشش‌های گیاهی، شاخص سطح برگ  (LAI) است. در پژوهش حاضر ضمن تحلیل و مدل‌سازی ارتباط بین LAI و شاخص‌های گیاهی مختلف، با استفاده از مشاهدات طیف‌سنجی آزمایشگاهی، به بررسی محدودیت‌های مدل ریاضی موجود در برآورد LAI، ارائة راهکارهایی به‌منظور افزایش دقت و صحت نتایج این مدل و همچنین طراحی یک شاخص جدید پرداخته شده ‌است. نتایج نشان دادند که از میان شاخص‌های گیاهی متداول، دو شاخص Simple Ratio و SAVI-2 دارای کمترین RMSE (حدود 08/0 در واحد LAI) بوده و شدت اشباع‌شدگی مدلی که برازش‌ داده‌اند از شاخص‌های دیگر کمتر است. دو شاخص مذکور کارایی بالاتری در تخمین LAI به‌ویژه در مناطق با تراکم پوشش گیاهی آنها زیاد، دارند و می‌توان با اطمینان بالایی در مدل‌سازی خطی برآورد LAI از آنها استفاده کرد.

کلیدواژه‌ها

عنوان مقاله [English]

Analyzing and Modeling of Correlation between LAI and Vegetation Indices using Spectroradiometric Observations

نویسنده [English]

  • A.A Abkar 1
1 Assistant Prof. of K.N. Toosi University of Technology
2
3
چکیده [English]

Investigation of various types of vegetation’s characteristics as an effective parameter in the energy exchange between the atmosphere and Earth's surface is very important in environmental, natural resources and agriculture studies. Nowadays, using remote sensing techniques with a wide range of valuable spectral information facilitate the study of vegetation, especially in estimation of the biophysical parameters. One of the most important biophysical parameters used in the various analyses related to the study of vegetation is Leaf Area Index (LAI). In this study, in addition to the analyzing and modeling of the relationship between LAI and vegetation indices (VIs)via spectrometry observations, the limitations of the mathematical model for estimation of LAI has been explored, some practical guidelines have been provided to improve the accuracy of the model as well as a new vegetation index has been designed. Finally, the results showed that through the conventional vegetation index, Simple Ratio (SR) and Second Soil Adjusted Vegetation Index (SAVI-2) have the minimum RMSE (about 0.08 in LAI unit) and the fitted models using their formulas in comparison with the other indices have the minimum rate of saturation. In other words, these indices are more efficient to estimation of the LAI; especially in high density vegetation area and can be used with high reliability in linear models for LAI estimation.

کلیدواژه‌ها [English]

  • Spectroradiometry
  • Leaf Area Index
  • Vegetation index
  • Sensitivity Analysis

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