Assessment of Rangeland Vegetation Condition from Time Series NDVI Data

Öz

The great spatial extent of rangelands has prompted a need for more efficient and cost effective management tools. Satellite based normalized difference vegetation index (NDVI) data offers improved and timely monitoring of rangeland vegetation. Since elevation is one of the factors affecting vegetation phenology, it should be considered when assessing vegetation status of rangelands.  In this study, rangeland condition was determined by classifying an elevation-normalized NDVI image (EN-NDVI) produced by a conditional rule approach based on elevation data representing active growing season of rangelands in whole project area.  A supervised classification algorithm was used to obtain four rangeland conditions called “very good”, “good”, “moderate” and “poor”.   The results revealed that the coverage of each range condition was; 10.02% “very good”,  20.55% “good”, 31.83% “moderate” and  37.60% “poor”. General classification accuracy and Kappa statistic values were 52.5% and 0.30 respectively.  

Anahtar Kelimeler

• Classification; Elevation; NDVI; Rangeland; SPOT-VEGETATION

Mera Vejetasyonu Durumunun Zaman Serisi NDVI Verileri ile Belirlenmesi

Öz

Geniş alanları kapsayan meraların daha etkin ve ekonomik yönetimi için yeni yöntemlerin geliştirilmesine gereksinim duyulmaktadır.Uydu verilerinden elde edilen normalleştirilmiş fark bitki indeksi (NDVI) verisi mera vejetasyonunun zamana bağlı olarak izlenmesine olanak verir. Yükselti vejetasyon gelişimini etkileyen önemli faktörlerden birisi olduğundan meraların vejetasyon durumunu belirlerken rakımın dikkate alınması gereklidir. Bu amaçla; çalışma alanındaki benzer yükseltiye sahip mera alanlarını temsil eden 10 yıllık (2000-2009) ortalama NDVI verisinden şartlı kural yöntemiyle yükseltiye göre normalleştirilmiş EN-NDVI verisi üretilmiştir. Daha sonra, EN-NDVI verisine kontrollü sınıflandırma yöntemi uygulanarak çalışma alanına ait dört farklı mera durum sınıfı elde edilmiştir. Bu sınıflar; “çok iyi”, “iyi”, “orta” ve “zayıf” olarak adlandırılmıştır. Sonuçlar, her bir mera durumu için kaplama alanının; “çok iyi” %10,02, “iyi” % 20,55, “orta” % 31,83 ve “zayıf” %37,60 şeklinde olduğunu göstermiştir. Yapılan değerlendirmede genel doğruluk  %52,5 ve  Kappa istatistiği 0,30 olarak bulunmuştur.

Anahtar Kelimeler

• Sınıflama; rakım; NDVI; mera; SPOT-VEGETATION

Kaynakça

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