Detecting mistletoe infestation on Silver fir using hyperspectral images

Abstract

© iForest -Biogeosciences and Forestry IntroductionThe narrow ecological niche and the extensive exposure to pollution makes silver fir (Abies alba Mill.) a highly endangered species. It is currently the most damaged tree species in Croatian forests (Prpić & Seletković 2001, Potočić et al. 2008. In addition to insects and fungi, fir is increasingly attacked by mistletoe (Viscum album L. ssp. abietis [Weisb.] Abrom), which physiologically weakens the tree by its remarkable consumption of water (Fisher 1983, Lamont 1983, Ehleringer et al. 1986) and mineral nutrients (Watson 2001), thus predisposing the host to pest and disease attacks. Mistletoe is also considered an indicator of existing stress (Atzberger & Werner 1998, Smith et al. 2004, Moorthy et al. 2008, Wang & Li 2012. It has been reported that an excessive number of shrubs may even cause tree death (Plagnat & Brossier 1969, Cervera & Villaescusa 1977, Zuber 1983, Chéret et al. 1987, Tsopelas et al. 2004, Olivia & Colinas 2007. Morevover, mistletoe-infected trees have lower increment than uninfected trees (Klepac 1955, Uščuplić 1992, Uščuplić & Dautbašić 1998, Noetzli et al. 2003, Barbu 2009) and should therefore have a cutting priority as long as their timber still retains its commercial value. A high correlation between fir infestation and mistletoe distribution has been reported (Hofstetter 1988, Idžojtić et al. 2008, Barbu 2009) with an almost exponential trend in the mistletoe population increase (Noetzli et al. 2003). An increase in the intensity of mistletoe infestation was also noted, favoring its spread to healthy trees (Idžojtić et al. 2003). Tree health status can be determined in two ways: by ground and by remote sensing observations, of which color infrared (CIR) images are particularly important (Pernar 1997, Pernar et al. 2007a. In Croatia, forest damage over large areas has been assessed by means of CIR aerial imagery since 1988, though mistletoe could not be detected based on these images. Preliminary pilot tests aimed at assessing fir damage using multispectral digital images have been carried out in (Pernar et al. 2007b), confirming that mistletoe could be successfully detected using a high-resolution multispectral digital camera. In contrast, standard field methods for mistletoe detection are generally based on visual survey (using binoculars) of edge trees along roads or in clearings, from which only the upper crown is visible (Idžo-jtić et al. 2005), and therefore do not often reflect the real conditions in the field. For example, Diminić et al. (2011) suggests that ground analyses of mistletoe presence in the crowns of standing trees are not fully reliable.The limitations of standard field methods call for new approaches to assess tree health and quantify mistletoe infestation. The importance and efficiency of high-resolution multispectral and hyperspectral imagery for the goals mentioned above have been highlighted by Entcheva-Campbell et al. (2004), Somers et al. (2010) and Cho et al. (2012). By recording a high number of narrow ban...

Mistletoe, friend and foe: synthesizing ecosystem implications of mistletoe infection

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Mitigating the Mistletoe Menace: Biotechnological and Smart Management Approaches

“…Before this, several groups had developed other algorithms based on thermal imaging, hyperspectral lines, convolutional neural networks, canopy height, colorimetry, etc. [ 386 , 387 , 388 , 389 , 390 , 391 , 392 ]. If developments into these dimensions are studied further, the effective selection of conventional and biotechnological treatment approaches may lead to a productive synchrony with silviculture.…”

Biological Flora of Britain and Ireland:Viscum album

“…Therefore, early detection can be crucial for controlling Mistletoe. Ančić et al (2014) developed a technique for mapping the distribution and intensity of infection of subsp. abietis on Abies alba in Croatia using aerial hyperspectral scanning.…”