Impact of mistletoe infestation on tree water status in Anatolian black pine trees in a semi-arid Mediterranean forest stand

Öz

Mistletoes can adversely affect the hydraulic functioning of their host trees by continuously extracting water and nutrients. This study investigated the effects of pine mistletoe (Viscum album subsp. austriacum) on water status in Anatolian black pine (Pinus nigra subsp. pallasiana) trees in a natural forest stand in Mediterranean Region, Türkiye, where mistletoe-infected and non-infected trees coexisted. Continuous stem radius change measurements were obtained throughout the 2024 growing period using automatic band dendrometers to compare maximum daily shrinkage (MDS) and tree water deficit (TWD) between infected and non-infected trees. Simultaneously, soil water potential was measured, and meteorological variables were recorded by a nearby station. Mistletoe-infected trees exhibited 92% higher TWD and 12% higher MDS compared to non-infected trees. In both groups, TWD and MDS were closely associated with meteorological variables. TWD showed significant correlations with soil water potential, global radiation, and vapor pressure deficit, while MDS was mainly related to air temperature, solar radiation, and soil water potential. Precipitation influenced MDS in non-infected trees but had no significant effect on infected trees. Moreover, correlation coefficients with environmental factors were consistently higher in infected trees. These findings indicate that pine mistletoe is associated with a marked deterioration in host water status, suggesting increased drought sensitivity and reduced physiological resilience under Mediterranean climatic conditions. Overall, this highlights the potential ecological risk posed by mistletoe infestation in drought-prone forest ecosystems.

Anahtar Kelimeler

• Drought stress
• Maximum daily shrinkage
• Pinus nigra
• Tree water deficit
• Viscum album parasitism

Yarı kurak bir Akdeniz orman ekosisteminde ökse otunun karaçam ağaçlarının su durumu üzerindeki etkisi

Öz

Ökse otları, konukçu ağaçtan sürekli su ve mineral madde alarak konukçu ağacın hidrolik işlevini olumsuz etkileyebilmektedir. Bu çalışma, çam ökse otunun (Viscum album subsp. austriacum) karaçam (Pinus nigra subsp. pallasiana) ağaçlarının su durumu üzerindeki etkilerini araştırmayı amaçlamaktadır. Araştırma, Türkiye’nin Akdeniz Bölgesi’nde, hem ökse otu ile enfekte olmuş hem de sağlıklı karaçam bireylerinin bir arada bulunduğu doğal bir meşcerede yürütülmüştür. 2024 yılı büyüme dönemi boyunca, enfekte ve sağlıklı ağaçlara kurulan otomatik şerit dendrometreler ile gövde yarıçapı değişiklikleri sürekli olarak kaydedilmiş; bu veriler kullanılarak maksimum günlük daralma (MGD) ve ağaç su açığı (ASA) parametreleri hesaplanmıştır. Eşzamanlı olarak toprak su potansiyeli ölçülmüş ve sahaya kurulan meteoroloji istasyonu aracılığıyla meteorolojik değişkenler izlenmiştir. Sonuçlar, enfekte ağaçların sağlıklı ağaçlara kıyasla %92 daha yüksek ASA ve %12 daha yüksek MGD değerlerine sahip olduğunu göstermiştir. Hem enfekte hem de sağlıklı ağaçlardaki ASA ve MGD değerlerinin meteorolojik değişkenlerle yakından ilişkili olduğu belirlenmiştir. ASA, toprak su potansiyeli, küresel radyasyon ve buhar basıncı açığı ile güçlü korelasyon gösterirken, MGD hava sıcaklığı, güneş radyasyonu ve toprak su potansiyeli ile ilişkili bulunmuştur. Yağış, sağlıklı ağaçların MGD’si üzerinde etkili olurken, enfekte ağaçlar üzerinde anlamlı bir etkisi gözlenmemiştir. Ayrıca, ağaç su durumu parametreleri ile çevresel faktörler arasındaki korelasyon katsayılarının enfekte ağaçlarda daha yüksek olduğu tespit edilmiştir. Bulgular, ökse otunun karaçam ağaçlarında su durumunu olumsuz etkilediğini, bu durumun Akdeniz iklim koşullarında enfekte ağaçların kuraklığa duyarlılığını artırabileceğini ve fizyolojik dayanıklılığını azaltabileceğini ortaya koymaktadır.

Anahtar Kelimeler

• Kuraklık stresi
• Maksimum günlük daralma
• Pinus nigra
• Ağaç su açığı
• Viscum album parazitizmi

Kaynakça

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