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Seyed Asaad Hosseini - One of the best experts on this subject based on the ideXlab platform.
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A new evaluation of the influence of climate change on Zagros oak forest Dieback in Iran
Theoretical and Applied Climatology, 2020Co-Authors: Hengameh Shiravand, Seyed Asaad HosseiniAbstract:Zagros forest, the second most important renewable source of cellulose for Iran, is one of the best known oak forest reserves worldwide. These vital ecosystems hold great environmental and ecological importance in protecting water resources in the climatic dry conditions of the country. In recent years, however, oak Dieback has decimated these forests. The purpose of our work is to evaluate and analyze the relationship of climate variables and the Dieback of the Zagros oak forest in Lorestan Province, Iran. Dieback is defined by Dieback indices, such as DVI, GEMI, IPVI, MSAVI2, NDVI, EVI, OSAVI, Sarvi2, SR, and VHI, which were obtained for 110 locations in the study area in the period between 2001 and 2017. On the other hand, daily climate variables influencing oak tree Dieback were extracted in the same time period. As a first step, the most important climate variables affecting oak tree Dieback were detected using the factor analysis method. Next, the so-called G* spatial correlation index was used to compute the covariance of Dieback indices with climate variables as well as the spatial patterns of the changes of these covariances. The results of factor analysis showed that three factors, namely, humidity, temperature, and precipitation, were the most significant variables affecting Dieback indices. Spatial autocorrelation patterns indicated that humidity played a major role regarding the widespread Dieback in the study area. The mismatch of areas of low humidity and Dieback indices, however, prompts that other factors, such as fungal diseases, affected the Dieback alongside climatic variables. A similar investigation relating temperature with Dieback indices indicated that changes in the match of spatial autocorrelation patterns of temperature and other Dieback indices were less than 30% in terms of matching area except for NDVI and EVI. The effect of temperature on Dieback indices was more limited to the southeast part of the study area. However, the covariance change pattern relating precipitation with Dieback indices was related to northwest areas. Among all studied Dieback indices, the NDVI was most correlated with all three factors of humidity, temperature, and precipitation, and temperature along humidity was found to play the most important role concerning the Dieback of the Zagros oak forest.
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an analysis of Dieback areas of zagros oak forests using remote sensing data case study lorestan oak forest iran
Modeling Earth Systems and Environment, 2020Co-Authors: Hengameh Shiranvand, Seyed Asaad HosseiniAbstract:The main purpose of the present study was to evaluate and analyze the Dieback-affected areas of middle Zagros oak forests in Lorestan, Iran. For this purpose, using programming tools, Dieback indices, such as DVI, GEMI, IPVI, MSAVI2, NDVI, EVI, OSAVI, Sarvi2, SR, and VHI, were derived from 110 points of oak forests in the underlying area, between 2001 and 2015. Finally, a 23 × 110 matrix (for each year) and a 345 × 110 matrix (for the total period) were developed as a database to detect the Dieback areas. Also, we applied cluster analysis to detect the Dieback areas and discriminant function analysis was subsequently used to validate the results of cluster analysis. After detecting Dieback areas, regression analysis was used for trend analysis of Dieback indices, followed with harmonic spectrum analysis for the identification of dominant fluctuations on these indices. The results showed that middle Zagros oak forest could be divided into four zones in terms of Dieback incidence, including areas without Dieback and small coefficient of variation, areas with moderate Dieback and large coefficient of variation, areas with very high Dieback rate and large coefficient of variation, and areas with very low Dieback rate and small coefficient of variation. According to the results obtained from trend analysis, Dieback indices demonstrated a significant downward trend in Dieback areas. Also, spectrum analysis revealed that dominant fluctuations on Dieback indices of middle Zagros oak forest were mostly short term (2–4 years).
Hengameh Shiravand - One of the best experts on this subject based on the ideXlab platform.
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A new evaluation of the influence of climate change on Zagros oak forest Dieback in Iran
Theoretical and Applied Climatology, 2020Co-Authors: Hengameh Shiravand, Seyed Asaad HosseiniAbstract:Zagros forest, the second most important renewable source of cellulose for Iran, is one of the best known oak forest reserves worldwide. These vital ecosystems hold great environmental and ecological importance in protecting water resources in the climatic dry conditions of the country. In recent years, however, oak Dieback has decimated these forests. The purpose of our work is to evaluate and analyze the relationship of climate variables and the Dieback of the Zagros oak forest in Lorestan Province, Iran. Dieback is defined by Dieback indices, such as DVI, GEMI, IPVI, MSAVI2, NDVI, EVI, OSAVI, Sarvi2, SR, and VHI, which were obtained for 110 locations in the study area in the period between 2001 and 2017. On the other hand, daily climate variables influencing oak tree Dieback were extracted in the same time period. As a first step, the most important climate variables affecting oak tree Dieback were detected using the factor analysis method. Next, the so-called G* spatial correlation index was used to compute the covariance of Dieback indices with climate variables as well as the spatial patterns of the changes of these covariances. The results of factor analysis showed that three factors, namely, humidity, temperature, and precipitation, were the most significant variables affecting Dieback indices. Spatial autocorrelation patterns indicated that humidity played a major role regarding the widespread Dieback in the study area. The mismatch of areas of low humidity and Dieback indices, however, prompts that other factors, such as fungal diseases, affected the Dieback alongside climatic variables. A similar investigation relating temperature with Dieback indices indicated that changes in the match of spatial autocorrelation patterns of temperature and other Dieback indices were less than 30% in terms of matching area except for NDVI and EVI. The effect of temperature on Dieback indices was more limited to the southeast part of the study area. However, the covariance change pattern relating precipitation with Dieback indices was related to northwest areas. Among all studied Dieback indices, the NDVI was most correlated with all three factors of humidity, temperature, and precipitation, and temperature along humidity was found to play the most important role concerning the Dieback of the Zagros oak forest.
Martin F. Jurgensen - One of the best experts on this subject based on the ideXlab platform.
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Evidence of damage from exotic invasive earthworm activity was highly correlated to sugar maple Dieback in the Upper Great Lakes region
Biological Invasions, 2018Co-Authors: Andrew J. Storer, Martin F. JurgensenAbstract:Sugar maple ( Acer sacharrum Marsh.) in the western Upper Great Lakes region has recently been reported with increased crown Dieback symptoms, prompting investigation of the Dieback etiology across the region. Evaluation of sugar maple Dieback from 2009 to 2012 across a 120 plot network in Upper Michigan, northern Wisconsin, and eastern Minnesota has indicated that forest floor disturbance impacts from exotic invasive earthworms was significantly related to maple Dieback. Other plot level variables tested showed significant relationships among Dieback and increased soil carbon, decreased soil manganese, and reduced herbaceous cover, each of which was also be correlated to earthworm activity. Relationships between possible causal factors and recent growth trends and seedling counts were also examined. Maple regeneration counts were not correlated with the amount of Dieback. The recent mean radial increment was significantly correlated with various soil features and nutrients. This study presents significant evidence correlating sugar maple Dieback in the western Upper Great Lakes region with earthworm activity, and highlights the need for considering the impacts of non-native earthworm on soil properties when assessing sugar maple health and productivity.
Allan N. D. Auclair - One of the best experts on this subject based on the ideXlab platform.
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Predicting forest Dieback in Maine, USA: a simple model based on soil frost and drought
Canadian Journal of Forest Research, 2010Co-Authors: Allan N. D. Auclair, Warren E. Heilman, Blondel Brinkmanb. BrinkmanAbstract:Tree roots of northern hardwoods are shallow rooted, winter active, and minimally frost hardened; Dieback is a winter freezing injury to roots incited by frost penetration in the absence of adequate snow cover and exacerbated by drought in summer. High soil water content greatly increases conductivity of frost. We develop a model based on the sum of z-scores of soil frost (December-February) and drought in summer (May-September) that accurately predicts timing and severity of Dieback on sugar maple (Acer saccharum Marsh.), Betula spp., Fraxinus spp., and red spruce (Picea rubens Sarg.) in Maine, USA, during 1920-1995. Discrepancies between predicted and actual Dieback relate largely to tree population dynamics. Extraordinary levels of Dieback on Betula during 1935-1950 occurred under low stress but in mature populations; under high climate stress during 1951-1975, younger surviving Betula proved resistant and showed little Dieback. Severe Dieback in Acer stands during 1975-1995 may relate to extensive partial cutting, leaving stands open to frost and high water tables. Widespread use of forwarder feller/buncher and wheeled skidders after 1960 commonly left hummocky, irregular surfaces subject to pooling and accelerated frost penetration. Silvicultural applications include modifying harvesting practices to minimize frost complications and use of the model to track and map climatic risk to avoid conditions and locales subject to Dieback.
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Patterns and general characteristics of severe forest Dieback from 1950 to 1995 in the northeastern United States
Canadian Journal of Forest Research, 2005Co-Authors: Allan N. D. AuclairAbstract:US national and state forest insect and disease surveys provide plentiful information on forest Dieback. These data, however, have not been quantified and analyzed systematically to address outstanding questions on the etiology of Dieback. This study quantified long-term (19501995) trends in the severity of Dieback on Acer saccharum Marsh., Fraxinus spp., Betula spp., and Picea rubens Sarg. in US northern hardwoods. A numeric index (010 scale) of the severity and extent of Dieback was applied using key words frequently found in the surveys. The 18 episodes identified showed considerable variability among species at the local scale, yet systematic, repetitive patterns of Dieback at the scale of the region and multidecadal time frame. Six Dieback characteristics were evident: episodes showed abrupt onset and subsidence, endured 13.6 years on average, were cyclical, with a frequency of 22.3 years between recurrence, and averaged about two-thirds of maximum possible severity. In contrast to the perception t...
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Principal Forest Dieback Episodes in Northern Hardwoods: Development of Numeric Indices of Areal Extent and Severity
Water Air and Soil Pollution, 1997Co-Authors: Allan N. D. Auclair, Peter D. Eglinton, Susan L. MinnemeyerAbstract:The incidence of forest Dieback in the Northern Hardwoods biome of Canada and the United States was determined for period from 1910 to 1990. Information from annual forest service pathology inventories in the two countries and other published literature was coded to estimate yearly the severity and areal extent of Dieback on white/yellow birch and sugar maple from 1910 to 1990. Principal Dieback episodes occurred as distinct waves coincident with maturation of the forest population in each of six regions. These episodes endured an average of 11 years. It is hypothesized that, once forest populations are mature, they are susceptible to extreme stresses such as freezing and drought which serve to synchronize the onset and subsidence of major Dieback episodes.
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The role of climate variability and global warming in the Dieback of Northern Hardwoods
Water Air and Soil Pollution, 1996Co-Authors: Allan N. D. Auclair, John T. Lill, Carmen RevengaAbstract:The severity of Dieback in Northern Hardwood Forests of Canada and the United States this century (1910–1990) was reconstructed from pathology records and compared to indices of extreme weather stresses in the region, and to changes in global temperatures and climatic variability over the same period. Thaw-freeze and root-freeze events in winter and early spring were key factors in triggering (and synchronizing) severe episodes of Dieback. Once trees were injured by freezing, forest Dieback correlated significantly with heat and drought stress. Freezing (but not drought) stresses in Northern Hardwoods correlated significantly (r = 0.70, p < 0.001) with increasing global mean annual temperatures and low values of the Pacific tropical Southern Oscillation Index. Major Diebacks did not occur early in the century at a time of notable freezing stress. Prior to 1940, the Northern Hardwoods consisted of relatively young populations of trees regrowing following extensive cutting and forest burning in the late 19th century (1860–1890). It appears that forest maturation is the key factor preconditioning trees to climatic injury, and Dieback. A simple projection of climate and forest maturation ages suggested the recurrence of major Dieback episodes on white/yellow birch, sugar maple and red spruce in the latter half of the 21st century (2045–2085).
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Extreme climatic fluctuations as a cause of forest Dieback in the pacific rim
Water Air and Soil Pollution, 1993Co-Authors: Allan N. D. AuclairAbstract:An overview of forest Diebacks in regions of the Pacific Rim strongly implicated extreme climatic fluctuations as a cause of Dieback in the absence of significant acidic deposition and O_3 pollution. There was strong circumstantial evidence that extreme moisture fluctuations had incited cavitation injury on Eucalyptus, Metrosideros and Nothofagus species with recent Dieback. The onset and intensification of crown Dieback on Metrosideros in Hawaii related directly to the incidence of extreme rainfall followed by prolonged (2 to 4 weeks) clear, hot, dry weather. Research needs to substantiate the role of an irreversible cavitation dysfunction of the xylem as a mechanism of persistent crown Dieback were discussed.
Richard Robinson - One of the best experts on this subject based on the ideXlab platform.
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impact of severe forest Dieback caused by phytophthora cinnamomi on macrofungal diversity in the northern jarrah forest of western australia
Forest Ecology and Management, 2010Co-Authors: Prue Anderson, Mark Brundrett, Pauline F Grierson, Richard RobinsonAbstract:Abstract The relative diversity and abundance of different functional groups of macrofungi were investigated in the northern jarrah forest, a mediterranean climate sclerophyllous forest dominated by eucalyptus trees in Western Australia. We sampled paired sites that were either severely affected by Dieback, a disease caused by Phytophthora cinnamomi which causes selective plant mortality, or unaffected by this type of forest decline. Macrofungi were sampled 3 times during the growing season along six 100 m × 2 m transects in these sites. Dieback-unaffected sites were found to have significantly different macrofungal floras than unaffected sites. Macrofungal abundance and diversity were approximately 1.5 times and 1.8 times greater respectively in Dieback-unaffected sites than in severely affected sites. Dieback-affected sites had a similar diversity of saprotrophic and ectomycorrhizal fungi, whereas more fungal taxa on Dieback-unaffected sites were mycorrhizal (>60%). Dung fungi were the most common saprophytes, especially in Dieback-affected sites, but abundance data greatly overestimated the importance of these relatively small fungi. We concluded that vegetation changes linked to Dieback had a negative effect on fungal community structure and biodiversity in the northern jarrah forest, in a similar manner to other forms of severe disturbance. Conversely, high tree mortality increased the abundance of wood decay fungi, at least in the short term. We expect that reductions in macrofungal species richness were indirectly linked to impacts on mycorrhizal host plants and saprotrophic substrates. Our data show that changes in vegetation composition had the greatest effect on ectomycorrhizal fungi, presumably due to their obligate symbiotic associations.