Proportion Of Dead Trees Research Articles

Taxonomic profiling of Nasutitermes takasagoensis microbiota to investigate the role of termites as vectors of bacteria linked to ironwood tree decline in Guam.

The ironwood tree (Casuarina equisetifolia, family Casuarinaceae), an indigenous agroforestry species in Guam, has been threatened by ironwood tree decline (IWTD) since 2002. Formation of bacterial ooze by the wilt pathogen from the Ralstonia solanacearum species complex and wetwood bacteria (primarily Klebsiella species) has been linked to IWTD. In addition, termite infestation of trees was statistically associated with IWTD. Termites are known carriers of a diverse microbiome. Therefore, we hypothesized that termites could be vectors of bacteria linked to IWTD. To investigate the potential role of termites as pathogen vectors, we employed next-generation 16S rRNA gene sequencing to describe the bacteria diversity of Nasutitermes takasagoensis (Family Termitidae) workers collected from 42 ironwood trees of different disease stages in Guam in association with tree-, plot-, and location-related factors. Nasutitermes takasagoensis workers account for the majority of termite infestations of ironwood trees. The bacterial phyla composition of N. takasagoensis workers was typical for wood-feeding higher termites consisting mainly of Spirochaetes and Fibrobacteres. However, Ralstonia species were not detected and Klebsiella species were rare even in termites collected from trees infected with Ralstonia and wetwood bacteria. Feeding experiments suggested that termites prefer to consume wood with low pathogen content over wood with high pathogen load. Termites were able to ingest Ralstonia but Ralstonia could not establish itself in healthy termite bodies. We concluded that N. takasagoensis workers are not vectors for Ralstonia spp. or the bacterial endophytes associated with wetwood (Klebsiella, Pantoea, Enterobacter, Citrobacter, and Erwinia) that were previously observed in IWTD-infested trees. The bacterial diversity in termite samples was significantly influenced by various factors, including Tree Health, Site Management, Plot Average Decline Severity, Proportion of Dead Trees in the Plot, Proportion of Trees with Termite Damage in the Plot, Presence of Ralstonia, and Altitude.

Rural parks as refugia of cavity nesters in an agricultural landscape: Which habitat features are important for cavity dwellers?

Parks as artificial non-forest tree stands that serve many useful functions for people can also act as refuges for specialised species that include, for example, cavity nesters. In 2017, (from March to end of May), using the example of 54 parks in the agricultural landscape of SE Poland, the importance of 9 basic habitat parameters was assessed (tree trunk diameter, health status of the trees, proportion of dead trees, management intensity, distance to the nearest forest, distance to a forest of >10 ha in area, park area, built-up area, area of tree cover surrounding the park), for the occurrence and richness of five cavity nesters. Rural parks serve refugia for cavity nesters in the agricultural landscape, such as Great Spotted and Syrian woodpeckers and secondary cavity nesters: European Starling, Eurasian Nuthatch and Eurasian Wryneck. The park size, as well as the presence of trees with large dimensions, were positively related to the occurrence and richness of most studied species. A small share of scattered built-up areas did not negatively affect the occurrence and richness of cavity nesters, and even positively affected the occurrence of Syrian woodpecker and Eurasian Wryneck. Only significant management intensity of the parks negatively influenced the Eurasian Wryneck occurrence, and richness of secondary cavity nesters and the whole cavity nester assemblage. The protection of parks with the characteristics listed above should also be taken into account when developing park management strategies, as such areas are important for species with greater ecological flexibility, and may support biodiversity in the agricultural landscape. The negative human impact on cavity nesters may be mitigated by the designation of ‘wild zones’ in the parks, which will save ecological valuable trees and at the same time ensure the safety of visitors.

Postfire tree mortality and fire resistance patterns in pine forests of Ukraine

Abstract The study was conducted in pure Scots pine (Pinus sylvestris L.) stands within the forest steppe physiographic region of Ukraine damaged by surface fires with different intensity. The aim of the research is to determine the effect of different fire intensity on pine stand and individual trees, considering tree morphometric parameters and type of damage. The intensity and duration of fire-related tree mortality was different in stands with different age. We found that tree fire resistance is driven by tree diameter, height of the rough bark, and natural degree of thickness. The proportion of dead trees one year after the spring fires in the middle-aged pine stands was 5 times lower and in mature pine stands even 10 times lower than after the summer fires. The critical damage to tree crowns in young pine trees causing their death is 80% of the needles burned. In the middle-aged pine trees, critical damage depended on the size of trees. The death of large, mature trees after smoldering summer fires was associated with the accumulation of a large stock of forest litter and duff near the tree-base, which contributed to the increased intensity of fire and its localization near the base part of the trees. Based on our findings, postfire tree mortality models have been developed for different age groups of pine stands.

Closing the Snack Bar: Developing Methods for Jackfruit Tree (Artocarpus heterophyllus Lamk.) Control in Brazil

ABSTRACT There are several techniques for the control and removal of invasive species that can be applied, and there is a demand among restoration practitioners for plant control methods. This study compared two methods for the control of jackfruit tree: mechanical method of trunk girdling and chemical method of herbicide injection into the trunk. It was evaluated both methods in terms of effectiveness in 10 plots (80 × 80 m). For the chemical method, triclopyr in concentrations of 2%, 6% and 8% was used. The progress of treatments was evaluated accordingly for the phytosanitary conditions. Method of trunk girdling proved to be ineffective and it had a low mortality rate (12%). The proportion of dead trees by chemical treatment was 100%. The results showed that chemical control of jackfruit trees was much faster and more effective.

Whitebark Pine in the National Parks of the Pacific States: An Assessment of Population Vulnerability

Whitebark pine (Pinus albicaulis) is a long-lived tree found in high-elevation forests of western North America that is declining due to the non-native white pine blister rust (Cronartium ribicola) and climate-driven outbreaks of mountain pine beetle (Dendroctonus ponderosae; MPB). The National Park Service established a monitoring program for whitebark pine in seven parks, including Sequoia & Kings Canyon, Yosemite, Lassen Volcanic, Crater Lake, Mount Rainier, Olympic, and North Cascades National Parks. Using these data, we summarized stand structure, presence of blister rust, and MPB prevalence to provide a baseline for future monitoring. Next, we used a stochastic, size-structured population model to speculate on future trends in the seven national park populations under conditions of increased MPB activity and ongoing blister rust infection observed in Crater Lake. We found that blister rust infected 29 to 54% of whitebark pine in all the parks except the two southernmost, Sequoia & Kings Canyon and Yosemite, where infections rates were 0.3% and 0.2%, respectively. The proportion of dead trees in Sequoia & Kings Canyon and Yosemite was low (0 to 1%), while they ranged from 10 to 43% in the other parks. Model projections suggested an average population decline of 25% in the parks over the next century using Crater Lake conditions, declines which are possible if blister rust continues to spread and climate change results in a significant increase in the frequency or severity of MPB outbreaks. Overall, our study describes conditions at seven western parks and illustrates potential rates of whitebark pine decline if pest outbreaks and/or blister rust infections worsen.

Forest structure determines spatial changes in avian communities along an elevational gradient in tropical Africa

AbstractAimTo test if tree species richness and forest structure drive spatial variation in avian communities along a tropical elevation gradient and to present information about the role of detailed forest parameters.LocationA 2,000‐m long elevational gradient of tropical forest on Mt. Cameroon, west‐central Africa.TaxonBirds and trees.MethodsWe performed bird censuses and vegetation mapping at the same plots across six forested sites at elevations of 350, 650, 1,100, 1,500, 1,850, and 2,200 m a.s.l., with 16 plots per elevation. We tested the effects of elevation, forest structure and tree diversity on the species richness, functional diversity and β‐diversity of birds (Bray–Curtis dissimilarity). We used conditional inference trees based on random forests (RF) to investigate these relationships across all elevation sites as well as within elevations.ResultsBoth tree and bird species richness declined monotonically with elevation. Vegetation structure correlated with elevation, and all vegetation attributes significantly differed among elevations. The RF explained 70% of the variance in avian species richness, with the most important predictors being elevation, proportion of dead trees, tree species richness and herb layer coverage. We found that elevation (and shrub layer) was a particularly important predictor of avian functional diversity. We identified no important predictor of bird species richness after standardization within elevations, and the proportion of dead trees was the sole important predictor of functional diversity. Within‐elevation β‐diversity in avian community composition was determined by the dissimilarity of the tree community and differences in leaf area index, solar radiation and spatial distance. The functional dissimilarity was best explained by leaf area index.Main conclusionsApart from elevation itself, spatial distance even within elevations correlated with compositional and functional variation among avian assemblages. Forest structural traits can have a significant influence on distribution of birds. Thus, gaps in the spatial distribution of species such as along elevations might be caused by fine‐scale recognition of suitable habitats.

Combined effects of drought stress and Armillaria infection on tree mortality in Norway spruce plantations

For the past two decades in the Czech Republic, Norway spruce (Picea abies) trees have been weakened by drought and subsequent attack by Armillaria root disease and bark beetles (Ips typographus, I. duplicatus, and Pityogenes chalcographus). We determined whether thinning of trees decreased mortality at 40 forest locations in the Czech Republic. The majority of the locations experienced long-term drought stress and very low groundwater levels. We also identified the species of Armillaria associated with the spruce decline and determined the reliability of visual detection of Armillaria infection.The mortality of trees at the 40 locations increased nearly linearly during the 5 years of the study. Sites were established in 2012, thinned or not thinned in October 2012, and were assessed in September and October in each year from 2012 to 2016. Thinning, with an intervention intensity of 30–40%, did not alter tree mortality at the locations. The proportion of dead trees was significantly greater in older than in younger stands in the last 3 years of the study.Among the trees that were suspected of being attacked by Armillaria based on visual inspection by foresters, 53% were confirmed (supported by statistical significance) to be infected by Armillaria spp. after morphological and genetic assessment. Among the trees with confirmed infections, 56% were infected by Armillaria ostoyae, 32% were infected by A. cepistipes, and 1% were infected by A. gallica (the rest could not be identified). Resinosis was positively associated with the occurrence of A. ostoyae. This species was more common on loamy flat locations, whereas A. cepistipes was more common on stony, sloped locations. The occurrence of Armillaria was negatively associated with increasing pH.Although our results indicate that spruce decline is strongly associated with the presence of Armillaria and that visual detection of Armillaria is reliable, management options for reducing Armillaria infection and damage appear to be highly limited. Forest managers should begin preparing to convert stands of Norway spruce to stands of other tree species that are better adapted to the local conditions and that are less susceptible to attack by Armillaria species.

Condition of Live Fire-Scarred Ponderosa Pine Twenty-one Years After Removing Partial Cross-Sections

Abstract Concern over the effects of removing fire-scarred partial cross-sections may limit sampling of live ponderosa pine to reconstruct fire history. We report mortality rates for ponderosa pine trees 20 to 21 years after removing fire-scarred partial cross-sections to reconstruct fire history. In 2015, following surveys every five years since 2000, we revisited 138 trees that were alive when we sectioned them in 1994/95 and 386 similarly sized, un-sectioned neighbor trees of the same species that were also alive in 1994/95. Between 1994/95 and 2015, a significantly greater proportion of sectioned than neighbor trees died, yielding average annual mortality rates of 3.3% versus 2.2%. However, many of the trees that died were likely killed by prescribed fires in 2002 and 2003 (64 sectioned plus neighbor trees). When we excluded these trees to assess the effect of fire-scar sampling rather than the effect of modern fires, the difference in proportion of dead trees was no longer significant and yielded ave...

Changes in soil nitrogen cycling in a northern temperate forest ecosystem during succession

Nitrogen (N) transformations in forest soils are fundamentally important to plant and microbial N nutrition and the N balance of forest ecosystems, but changes in the patterns and rates of N transformations during forest succession are poorly understood. In order to better understand how soil N cycling changes during ecosystem succession, we analyzed four years of soil N cycling measurements in a 90-year-old secondary forest undergoing dieback of early-successional, dominant canopy trees. We expected that tree mortality would decrease root biomass, leading to increased soil NH4 + availability, and that these changes would prompt fundamental shifts in the N cycle such as the initiation of significant nitrification and increased cycling of oxidized N compounds in gas phase and soil solution. As expected, indices of soil NH4 + and NO3 − availability increased with successional stage (defined as the proportion of dead trees), and were negatively correlated with the amount of fine root biomass. However, the standing amount of fine root biomass was not affected by tree mortality; increased soil NH4 + and NO3 − availability therefore more likely resulted from successional increases in N-mineralization than decreases in root N uptake. Nitrification (as indicated by NO efflux as a proxy) increased due to elevated substrate (NH4 +) availability, and the soil solution NO3 − concentration increased as a result. Soil N2O efflux was not affected by succession, nor was it related to other N cycling parameters. Collectively, these results indicate that recent successional advancement has accelerated soil N cycling and shifted the N economy of this ecosystem towards greater importance of NO3 −.

Wood-pastures in a traditional rural region of Eastern Europe: Characteristics, management and status

Wood-pastures are among the oldest land-use types in Europe and have high ecological and cultural importance. They are under rapid decline all over Europe because of changes in land use, tree cutting, and lack of regeneration. In this study we characterized the structure, condition and threats of wood-pastures in a traditional rural region in Romania. Forty-two wood-pastures were surveyed, as well as 15 forest sites for comparison. All wood-pasture sites were described via four groups of variables: condition, management, site, and landscape context. Forest sites were dominated by Hornbeam (Carpinus betulus) and Beech (Fagus sylvatica), whereas wood-pastures were dominated by Oak (Quercus sp.) and various species of fruit trees. Most wood-pastures contained trees classified as ‘ancient’ but no such trees were found in forests. The proportion of dead trees was positively related to forest cover within 300m around the wood-pasture. Models that included management, site and landscape-related variables best explained the prelevance of Oak, Beech, Hornbeam and Pear trees in wood-pastures. Large oaks and hornbeams were more likely to be dead or affected by uncontrolled pasture burning than small oaks and other tree species. Our results show that ancient wood-pastures are common in this rural region, and they may be more common in Eastern Europe than previously thought. There is an urgent need for research, legal recognition and conservation management of wood-pastures as distinct landscape elements for their cultural, ecological and agricultural importance.

Levels of dispersal and tail loss in an Australian gecko (Gehyra variegata) are associated with differences in forest structure

Corridors of natural habitat are often sought to maintain dispersal and gene flow among habitat patches. However, structural changes in natural habitat over space and time may influence connectivity. Here we investigate whether differences in forest structure and the frequency of potential retreat sites is associated with the genetic structure of a tree-dwelling Australian gecko (Gehyra variegata). We sampled 113 adult geckos from multiple state forest and adjacent reserve locations within the Pilliga forest, New South Wales, Australia. Individuals were genotyped at 14 microsatellite loci and levels of dispersal were inferred by the degree of genetic structuring observed in state forest and reserve. A greater proportion of dead trees and tree debris (features that are used as retreat sites by G. variegata) were present within the state forests than in the reserve locations (P < 0.05). This reduction in frequency of retreat sites in reserves was associated with significantly less genetic structuring of G. variegata, implying higher levels of dispersal. Tail loss was also significantly higher in G. variegata sampled in reserves than in the state forests. We conclude that dispersal characteristics in G. variegata are associated with structural changes to natural habitat and that this may influence rates of predation.

First Results of Monitoring of Stand Structure Changes in Unmanaged Beech Stands in NP Plitvice Lakes

Background and purpose: It is possible to monitor and study the natural growth and development of the forest ecosystems in the example of protected forest stands, which were excluded from management, and which are not under a negative influence of human activity. Therefore the aim of the research through the repeated measurements is to estimate the stand structure development on the Medveđak permanent experimental plot in the Plitvice Lakes national park area. In this paper we presented the first preliminary results of established monitoring, i.e. comparison of results of stand structure elements between two measurements (1998 and 2008). Furthermore, obtained results were compared with data from growth-yield tables for common beech stands similar characteristics as researched stand. In this case data from growth-yield tables present managed pure beech stands. Material and methods: The permanent experimental plot was set in 1998 in the natural stand of mountain beech forest (Lamio orvale-Fagetum sylvaticae Ht. 1938). It is in rectangular shape, dimensions 100×100m, with subplot 60×60 m and 30×30 m. The plot is founded according to the experimental plot setting methodology (Dubravac & Novotny, 1992 and Novotny, 1997) extended on the ICP Forest workgroup demand. Tree crown damage assessment was repeated in 2003, and in June 2008 another measurement of basic stand structural elements was done. Results and Conclusion: The results in this paper show the development of the observed structural elements of the pure beech stand in the natural conditions without the management activities. Obtained results of stand structure elements (N/ha, G/ha, V/ha) show discrepancies in relation to managed pure beech stand from growth-yield tables. Decrease in the number of trees, increase of the proportion of dead trees and proportion of significantly damaged trees in the monitoring period indicate the decrease of the stand vitality and health. Therefore, the question arises: Should protected forests today be absolutely left to the natural process of growth, development and dying? Since ten years is a brief period for research and conclusions about structural changes in the stand, further research efforts are necessary. They must be expanded with additional information and data from other permanent experimental plots which are also founded in other special purpose forests within project as well.

Effects of forest management on the abundance of insect pests on Scots pine

We compared the degree of needle damage and the abundance of common insect pests in Scots pine stands on the Finnish and Russian sides of the border on the Karelian Isthmus. The study areas have similar climatic and geological conditions, but the intensity of forest management has been much higher on the Finnish side of the border during the past 50 years. In Finland all stands are thinned once or twice during the rotation period, while there are no thinnings in the Russian side. The density of the Scots pine stands and the proportion of dead trees were significantly higher on the Russian side of the border. Needle damage caused by folivorous insects was about eight times higher in the non-managed forests of Russian Karelia compared to the managed Finnish forests. Shoot twigs damaged by pine shoot beetles ( Tomicus spp.) – the dominant bark beetle on Scots pine – and the number of egg clusters of the European pine sawfly ( Neodiprion sertifer) – the dominant defoliator, respectively – were also more abundant in samples collected from the trees on the Russian side of the border. There were, however, no differences in the number of aphid eggs or in the number of galls caused by Eversia resinella. Therefore, intensive forest management in Finland has changed the susceptibility of pine forests to insect pests compared to the situation in semi-natural forest on the Russian side of the border. However, these effects varied in accordance with the insect feeding guild. Especially bark beetles depending on recently dead trees benefit on unthinned forests where natural mortality of trees is high.

Quantitative assessment of vegetation structural attributes from aerial photography

Cover of vegetation understorey and overstorey was determined from aerial photography at 1:25 000 and 1:40 000 scales by a grid sampling technique. Models were developed relating values of aerial cover to field cover as determined by intensive field measurement. The influence of photo-scale, photo colour, the angle of the image, shadow, the hiatus between aerial and field sampling, crown width, crown height, proportion of dead trees, drought prior to aerial sampling, land type, previously cleared vegetation and incline on explanatory models was also examined. The only variables that could be clearly interpreted as influencing the models were vegetation height, photo-scale and land type. Only the latter two variables are useful for predictive models. The smaller the scale of photography the greater the exaggeration of the aerial image of tree crowns. This probable result of photo graininess would be most significant when tree crowns are small, an inverse surrogate of tree height. Two-phase models were developed for predicting basal area and biomass from aerial cover. In most instances models were successful for predicting overstorey and understorey cover and for predicting total basal area and biomass. The technique offers a powerful and cost-effective method of assessing vegetation change over long time periods in a way that no other technique can duplicate.

Wind and snow damage in a thinning and fertilisation experiment in Pinus sylvestris

Damage induced by wind and snow was examined in an experimental series with thinning and fertilisation established in 34–58 years old Scots pine (Pinus sylvestris L.) stands in northern Sweden during the period 1969–83. The experiment contained six treatments and 23 replications. The treatments were 25% and 60% thinning from below, 25% thinning from above, 30% thinning from below combined with N and NP fertilisation. Percentages represent basal area harvested at the first thinning. Differences in damage level were examined at the first reinventory, 4–8 years after thinning. The level of wind and snow‐induced damage was about 1% of the basal area during the period studied. Proportion of basal area damaged was not affected by the treatments, but there was more snow damage after thinning from above than after thinning from below. The proportion of trees damaged by snow and the proportion of dead trees were affected by treatment. The densest stands, the control and 25% thinning from above, were damaged the mo...

The effect of stand density on the susceptibility of Pinus sylvestris to Gremmeniella abietina

The susceptibility of a 20‐year‐old Scots pine stand to Scleroderris canker caused by Gremmeniella abietina was monitored in relation to stocking density. The data included five densities varying from 800 to 5 000 trees/ha. The degree of damage, as indicated by the proportion of brown needles and the number of dead trees, correlated positively with the stand density. The proportion of dead trees was low at densities below 1 100 trees/ha, but increased linearly with increasing density.

What Proportion of Standing Trees in Forests of the Northeast are Dead?

TRrrON, L. M. (USDA Forest Service, Northeastern Forest Experiment Station, P.O. Box 968, Burlington, VT 05402) AND T. G. SIccAMA (Yale School of Forestry and Environmental Studies, New Haven, CT 06512). What proportion of standing trees in forests of the Northeast are dead? Bull. Torrey Bot. Club 1 17: 163-166. 1990.-Based on 46 data sets, this paper documents standing dead trees as a proportion of total basal area and density of forest stands in the Northeast. Stands were grouped into six forest cover types ranging from coastal oak and pine types to montane spruce and fir. Over the wide diversity of stand histories, species, and sites studied, the proportion of dead trees was 3-43% of total basal area and 5-36% of total density. Montane spruce-fir stands characteristically had high proportions of standing dead trees, expressed as basal area and density. By quantifying the proportion of dead trees occurring in forests of the Northeast, this study provides a reference for evaluating overall forest vigor or decline.

A demographic analysis of mortality caused by the pine wood nematode (Bursaphelenchus xylophilus) and pine sawyer beetles (Monochamus alternatus) in pine forests in the Seto Inland Sea-side, Japan.

Demographic characteristics were examined in 51 study sites in naturally occurring pine populations in the Seto Inland Sea-side. The pine forests consisted on average of 51.4% Japanese red pine,Pinus densiflora, 28.9% Japanese black pine,Pinus thunbergii, and 19.7% hybrids of the two species, and occurred along an elevatinal gradient from denser, younger secondary forest regrowing after disturbance, to more mature stands at higher elevations. The proportion of dead trees did not vary much among taxa (range 24-31%). Mortality was caused primarily by the introduced pine wood nematodeBursaphelenchus xylophilus, and secondarily by its vector, the Japanese pine sawyer beetleMonochamus alternatus. While the nematode attacked individuals of all three pine taxa with equal frequency (3-8% mortality), the beetle caused the greatest proportional mortality inP. thunbergii (35%), less inP. densiflora (20%), and the least in hybrids (18%). Mortality caused by both the nematode and beetle was significantly correlated with the mean tree age, height and diameter of the dead trees.The majority (70.2%) of individuals in populations on Miyajima Island that had lived 60 or more years and survived without severe damage by nematodes and beetles were hybrids, although the proportion of hybrids in the seedlings (found only in seven out of the fifty-one study sites) was quite low (1.9%). Thus it seems that hybrids could be more long-lived and better adapted than their parental species to resist both the nematode and the beetle. IfB. xylophilus andM. alternatus populations continue to increase at their current levels they may have a drastic effect on the gene pools ofP. densiflora andP. thunbergii and on the structure and composition of Japanese pine forests.