Assessment of the Health Status and Degradation Process of Forest Ecosystems

A special issue of Forests (ISSN 1999-4907). This special issue belongs to the section "Forest Health".

Deadline for manuscript submissions: closed (25 March 2022) | Viewed by 10450

Special Issue Editor

Department of Entomology, Phytopathology and Game Fauna, Forest Research Institute – Bulgarian Academy of Sciences, St. Kliment Ohridski Blvd. 132, 1756 Sofia, Bulgaria
Interests: forest health status; disturbances; invasive species
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Special Issue Information

In recent years, adverse phenomena of climate change such as prolonged droughts, floods, storms, etc., have occurred. Under such circumstances, forest stands are subject to more frequent and intense stresses and deterioration due to the combination of unfavourable climatic conditions and impact of harmful biotic factors, mostly insect pests and fungal pathogens. The monitoring of health status provides baseline data on the distribution, occurrence and harmfulness of biotic agents or abiotic factors. The assessment of harmful impact and spread of the most important insect pests and fungal pathogens is essential for making decisions about their control. It is necessary to take into account the severity of the infection and the prevalence of pests, as well as their specific impact on the affected forests. Among the abiotic factors responsible for the deterioration of forests, damage caused by wind, wet snow and ice have the most negative impact. Snow- and windthrow stem breakage often provokes bark beetle attacks. As a result, physiological weakening of trees observe and impact caused by invasive pests and pathogens can become devastating, covering vast areas of forests that pose a threat to economically important tree species. Remote sensing has great potential for vegetation mapping in complex landscapes due to the ultra-high-resolution imagery acquired. The new technology in combination with terrestrial survey techniques and methods have a huge research potential, especially in protected forest areas. They obtain information for the sizes of areas of deteriorated by biotic, abiotic and fire damages, health status of vegetation, observation the habitat in which pests and diseases are spreading out.

We encourage studies from all fields, including experimental studies and monitoring approaches to contribute to this Special Issue in order to promote knowledge and adaptation strategies for the assessment of health status and deterioration, preservation and management of forest ecosystems.

Prof. Dr. Margarita Georgieva
Guest Editor

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Keywords

  • forest health status
  • disturbances
  • monitoring of forest ecosystems, remote sensing
  • destructive pests and diseases
  • bark beetle outbreaks
  • invasive species
  • forest protection
  • forest fires

Published Papers (3 papers)

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Research

14 pages, 88103 KiB  
Article
Application of Remote Sensing Data for Assessment of Bark Beetle Attacks in Pine Plantations in Kirkovo Region, the Eastern Rhodopes
by Margarita Georgieva, Sevdalin Belilov, Stelian Dimitrov, Martin Iliev, Vladislav Trenkin, Plamen Mirchev and Georgi Georgiev
Forests 2022, 13(4), 620; https://0-doi-org.brum.beds.ac.uk/10.3390/f13040620 - 15 Apr 2022
Cited by 4 | Viewed by 2108
Abstract
Intensive forest afforestation with native pine species was developed in the 1960s on degraded and deforested lands in the region of the Eastern Rhodopes (south-eastern Bulgaria). Severe damage by wet snow was registered in the coniferous forests of the Rhodopes in March 2015. [...] Read more.
Intensive forest afforestation with native pine species was developed in the 1960s on degraded and deforested lands in the region of the Eastern Rhodopes (south-eastern Bulgaria). Severe damage by wet snow was registered in the coniferous forests of the Rhodopes in March 2015. In the following years, bark beetle attacks were registered on the broken and felled fresh wood. As a result, bark beetle infestation spots appeared in the pine plantations. In the period 2019–2021, damage caused by bark beetles was assessed in the region of State Forestry Kirkovo (the Eastern Rhodopes, south-eastern Bulgaria). An integrated approach using the data of the information system of the Executive Forest Agency (ISEFA), remote sensing data obtained by an “eBee SQ” unmanned aerial vehicle (UAV) equipped with a “Parrot Sequoia” multispectral camera, and subsequent terrestrial observations, was applied. ISEFA data showed that there was no serious damage caused by abiotic and biotic factors in the pine forests of SF Kirkovo until 2014. Snow damage in 2015 affected 513 ha of pine plantations, and bark beetle infestations reached up to 1316 ha in 2016. In 2019, a total of 226.87 ha of pine plantations were captured in three localities—Fotinovo, Kirkovo, and Kremen. The relative share of damage caused by bark beetles was greater in P. sylvestris plantations (15.3–23.0%), compared to damage in P. nigra (2.3%). Four different categories of normalised difference vegetation index (NDVI) were separated in bark beetle infestation spots—living trees, dead trees, grass and shrub vegetation, stones and rocks. The NDVI values in locations with living trees varied between 0.500 (spaces between tree crowns) and 0.700 (central part of the crown projection) (an average of 0.617). In the locations with dead trees, the average values of NDVI of lying trees was 0.273, and in standing trees, NDVI varied between 0.275 (central part of crown projections) and 0.424 (spaces between tree crowns). In the locations with grass and shrub vegetation, stones and rocks, the average NDVI was 0.436 and 0.329, respectively. In the field study, average defoliation of 31.2–32.3% was registered in P. sylvestris plantations, and 47.4% in P. nigra plantations. Defoliations mainly were caused by pine processionary moth (Thaumetopoea pityocampa) and fungal pathogens (Dothistroma septosporum and Lecanosticta acicola). The damage was caused by Ips acuminatus (in P. sylvestris only), and I. sexdentatus, Tomicus piniperda and T. minor (in P. sylvestris and P. nigra). Infestations by other xylophages, such as Phaenops cyanea, Rhagium inquisitor, and Pissodes spp., were also found on pine stems. Full article
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10 pages, 12372 KiB  
Article
Remote Sensing Assessment of the Expansion of Ips typographus Attacks in the Chuprene Reserve, Western Balkan Range
by Georgi Georgiev, Margarita Georgieva, Stelian Dimitrov, Martin Iliev, Vladislav Trenkin, Plamen Mirchev and Sevdalin Belilov
Forests 2022, 13(1), 39; https://0-doi-org.brum.beds.ac.uk/10.3390/f13010039 - 01 Jan 2022
Cited by 4 | Viewed by 1989
Abstract
The Chuprene Reserve was created in 1973 to preserve the natural coniferous forests in the Western Balkan Range in Bulgaria. The first infestations by European spruce bark beetle (Ips typographus) were registered in Norway spruce (Picea abies) stands in [...] Read more.
The Chuprene Reserve was created in 1973 to preserve the natural coniferous forests in the Western Balkan Range in Bulgaria. The first infestations by European spruce bark beetle (Ips typographus) were registered in Norway spruce (Picea abies) stands in the mid-1980s. The aim of this study is to assess the damages caused by I. typographus in the Chuprene Reserve using remote sensing techniques – unmanned aerial vehicle (UAV) images, airborne images, and satellite images of European Space Imaging (EUSI), combined with terrestrial verification. High-resolution images in four bands of the electromagnetic spectrum and in a standard RGB channel were taken in 2017 via a multispectral camera ‘Parrot Sequoia’, integrated with a specialized professional UAV system eBee ‘Flying Wing’. The health status of Norway spruce stands in the reserve was assessed with the normalized difference vegetation index, based on the digital mixing of imagery captured in the red and near infrared range. The dynamic of bark beetle attacks was studied in GIS on the basis of maps generated from photographic surveys, airborne images taken in 2011 and 2015, and satellite images from 2020. In the UAV-captured area (314.0 ha), the size of Norway spruce stands attacked by I. typographus increased from 7.6 ha (2.4%) in 2011 to 44.9 ha (14.3%) in 2020. The satellite images showed that on the entire territory of the Chuprene Reserve (1451.9 ha), I. typographus killed spruce trees on 137.4 ha, which is 9.6% of the total area. Full article
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17 pages, 8049 KiB  
Article
Spatial Patterns of ‘Ōhi‘a Mortality Associated with Rapid ‘Ōhi‘a Death and Ungulate Presence
by Ryan L. Perroy, Timo Sullivan, David Benitez, R. Flint Hughes, Lisa M. Keith, Eva Brill, Karma Kissinger and Daniel Duda
Forests 2021, 12(8), 1035; https://0-doi-org.brum.beds.ac.uk/10.3390/f12081035 - 04 Aug 2021
Cited by 13 | Viewed by 5443
Abstract
Effective forest management, particularly during forest disturbance events, requires timely and accurate monitoring information at appropriate spatial scales. In Hawai‘i, widespread ‘ōhi‘a (Metrosideros polymorpha Gaud.) mortality associated with introduced fungal pathogens affects forest stands across the archipelago, further impacting native ecosystems already under [...] Read more.
Effective forest management, particularly during forest disturbance events, requires timely and accurate monitoring information at appropriate spatial scales. In Hawai‘i, widespread ‘ōhi‘a (Metrosideros polymorpha Gaud.) mortality associated with introduced fungal pathogens affects forest stands across the archipelago, further impacting native ecosystems already under threat from invasive species. Here, we share results from an integrated monitoring program based on high resolution (<5 cm) aerial imagery, field sampling, and confirmatory laboratory testing to detect and monitor ‘ōhi‘a mortality at the individual tree level across four representative sites on Hawai‘i island. We developed a custom imaging system for helicopter operations to map thousands of hectares (ha) per flight, a more useful scale than the ten to hundreds of ha typically covered using small, unoccupied aerial systems. Based on collected imagery, we developed a rating system of canopy condition to identify ‘ōhi‘a trees suspected of infection by the fungal pathogens responsible for rapid ‘ōhi‘a death (ROD); we used this system to quickly generate and share suspect tree candidate locations with partner agencies to rapidly detect new mortality outbreaks and prioritize field sampling efforts. In three of the four sites, 98% of laboratory samples collected from suspect trees assigned a high confidence rating (n = 50) and 89% of those assigned a medium confidence rating (n = 117) returned positive detections for the fungal pathogens responsible for ROD. The fourth site, which has a history of unexplained ‘ōhi‘a mortality, exhibited much lower positive detection rates: only 6% of sampled trees assigned a high confidence rating (n = 16) and 0% of the sampled suspect trees assigned a medium confidence rating (n = 20) were found to be positive for the pathogen. The disparity in positive detection rates across study sites illustrates challenges to definitively determine the cause of ‘ōhi‘a mortality from aerial imagery alone. Spatial patterns of ROD-associated ‘ōhi‘a mortality were strongly affected by ungulate presence or absence as measured by the density of suspected ROD trees in fenced (i.e., ungulate-free) and unfenced (i.e., ungulate present) areas. Suspected ROD tree densities in neighboring areas containing ungulates were two to 69 times greater than those found in ungulate-free zones. In one study site, a fence line breach occurred during the study period, and feral ungulates entered an area that was previously ungulate-free. Following the breach, suspect ROD tree densities in this area rose from 0.02 to 2.78 suspect trees/ha, highlighting the need for ungulate control to protect ‘ōhi‘a stands from Ceratocystis-induced mortality and repeat monitoring to detect forest changes and resource threats. Full article
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