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Biodiversity in dead wood
\"Fossils document the existence of trees and wood-associated organisms from almost 400 million years ago, and today there are between 400,000 and 1 million wood-inhabiting species in the world. This is the first book to synthesise the natural history and conservation needs of wood-inhabiting organisms. Presenting a thorough introduction to biodiversity in decaying wood, the book studies the rich diversity of fungi, insects and vertebrates that depend upon dead wood. It describes the functional diversity of these organisms and their specific habitat requirements in terms of host trees, decay phases, tree dimensions, microhabitats and the surrounding environment. Recognising the threats posed by timber extraction and forest management, the authors also present management options for protecting and maintaining the diversity of these species in forests as well as in agricultural landscapes and urban parks\"-- Provided by publisher.
Book
Do natural enemies explain fluctuations in low-density spruce budworm populations?
Understanding the causal pathways through which forest insect outbreaks are triggered is important for resource managers. However, detailed population dynamics studies are hard to conduct in low-density, pre-outbreak populations because the insects are difficult to sample in sufficient numbers. Using laboratory-raised larvae installed in the field across a 1,000 km east–west gradient in Québec (Canada) over an 11-yr period, we examined if parasitism and predation were likely to explain fluctuations in low-density spruce budworm (Choristoneura fumiferana; SBW) populations. Parasitism rates by the two main larval parasitoid species, Elachertus cacoeciae and Tranosema rostrale, peaked during different years. This suggests that temporal fluctuations in overall parasitism were partly buffered by compensatory dynamics among parasitoid species. Still, spatial covariance analyses indicate that the residual interannual variation in parasitism rates was substantial and correlated over large distances (up to 700 km). On the other hand, interannual variation in predation rates was not spatially correlated. Piecewise structural equation models indicate that temporal variation in parasitism and predation does not influence temporal variation in wild SBW abundance. Spatially, however, SBWs installed in warmer locations tended to show higher parasitism rates, and these higher rates correlated with lower wild SBW population levels. Overall, the results indicate that large-scale drops in parasitism occur and could potentially contribute to SBW population increases. However, during the period covered by this study, other factors such as direct effects of weather on SBW larval development or indirect effects through host tree physiology or phenology were more likely to explain large-scale variation in wild SBW populations.
Journal Article
Bug Bear
\"This bothersome bug wants a warm place to stay. Look out, grumpy bear-he might ruin your day! A hilarious tale of an uninvited guest\"--Back cover.
Book
A highly aggregated geographical distribution of forest pest invasions in the USA
Aim Geographical variation in numbers of established non-native species provides clues to the underlying processes driving biological invasions. Specifically, this variation reflects landscape characteristics that drive non-native species arrival, establishment and spread. Here, we investigate spatial variation in damaging non-native forest insect and pathogen species to draw inferences about the dominant processes influencing their arrival, establishment and spread. Location The continental USA, including Alaska (Hawaii not included). Methods We assembled the current geographical ranges (county-level) of 79 species of damaging non-indigenous forest insect and pathogen species currently established in the continental USA. We explored statistical associations of numbers of species per county with habitat characteristics associated with propagule pressure and with variables reflecting habitat invasibility. We also analysed relationships between the geographical area occupied by each pest species and the time since introduction and habitat characteristics.
Results The geographical pattern of non-native forest pest species richness is highly focused, with vastly more species in the north-eastern USA. Geographical variation in species richness is associated with habitat factors related to both propagule pressure and invasibility. Ranges of the non-native species are related to historical spread; range areas are strongly correlated with time since establishment. The average (all species) radial rate of range expansion is 5.2 km yr
-1
, and surprisingly, this rate did not differ among foliage feeders, sap-feeders, wood borers and plant pathogens.
Main conclusions Forest pest species are much more concentrated in the north-eastern region of the USA compared with other parts of the country. This pattern most likely reflects the combined effects of propagule pressure (pest arrival), habitat invasibility (pest establishment) and invasion spread. The similarity in historical spread among different types of organisms indicates the importance of anthropogenic movement in spread.
Journal Article
Tree by Tree
Tree by Tree is a warning and a toolkit for the future of forest recovery. Scott J. Meiners investigates the critical biological threats endangering tree species native to the forests of eastern North America, providing a needed focus on this plight. Meiners suggests that if we are to save our forests, the first step is to recognize the threats in front of us.
Meiners focuses on five familiar trees—the American elm, the American chestnut, the eastern hemlock, the white ash, and the sugar maple—and shares why they matter economically, ecologically, and culturally. From outbreaks of Dutch elm disease to infestations of emerald ash borers, Meiners highlights the challenges that have led or will lead to the disappearance of these trees from forests. In doing so, he shows us how diversity loss often disrupts intricately balanced ecosystems and how vital it is that we pay more attention to massive changes in forest composition.
With practical steps for the conservation of native tree species, Tree by Tree offers the inspiration and insights we need to begin saving our forests.
eBook
Forest Insect Population Dynamics, Outbreaks, And Global Warming Effects
Research in insect population dynamics is important for more reasons than just protecting forest communities. Insect populations are among the main ecological units included in the analysis of stability of ecological systems. Moreover, it is convenient to test new methods of analyzing population and community stability on the insect-related data, as by now ecologists and entomologists have accumulated large amounts of such data. In this book, the authors analyze population dynamics of quite a narrow group of insects – forest defoliators. It is hoped that the methods proposed herein for the analysis of population dynamics of these species may be useful and effective for analyzing population dynamics of other animal species and their effects and role in global warming. What can insects tell us about our environment and our ever-changing climate? It is through studies like this one that these important answers can be obtained, along with data on the insects and their behaviors themselves. The authors present new theories on modeling and data accumulation, using cutting-edge processes never before published for such a wide audience. This volume presents the state-of-the-art in the science, and it is an essential piece of any entomologist’s and forest engineer’s library.
eBook
Behavioral responses to resource heterogeneity can accelerate biological invasions
The abundance and spatial distribution of resources in a landscape and the behavioral response of individuals determines whether and how fast an invasive species spreads in an environment. Whether and how landscape manipulations can be used to slow invasive species is of great interest, in particular in forest ecosystems, where tree removal, thinning, and increasing tree diversity are discussed as management options. Classically, the focus is on availability and accessibility of resources; more recent considerations include individual-level behavioral movement responses to a spatially heterogeneous resource distribution. We derive a novel model for insect–host dynamics that includes three common behavioral aspects of foraging: higher movement rate in resource-poor areas, lower ovipositioning rate in resource-poor areas, and movement preference for resource-rich areas. We show that each of these basic mechanisms can increase the speed of invasion in a source–sink landscape above that in a homogeneous landscape with larger overall resource availability. We parameterize our model and illustrate our results with data for emerald ash borer, a recent highly destructive forest pest in North America. Our results highlight the importance of empirical work on movement behavior in different landscape types and near the interface between types.
Journal Article
Diversity, Stability, and the Forecast Challenge in Forest Lepidopteran Predictive Ecology: Are Multi-Scale Plant–Insect Interactions the Key to Increased Forecast Precision?
I report on long-term patterns of outbreak cycling in four study systems across Canada and illustrate how forecasting in these systems is highly imprecise because of complexity in the cycling and a lack of spatial synchrony amongst sample locations. I describe how a range of bottom-up effects could be generating complexity in these otherwise periodic systems. (1) The spruce budworm in Québec exhibits aperiodic and asynchronous behavior at fast time-scales, and a slow modulation of cycle peak intensity that varies regionally. (2) The forest tent caterpillar across Canada exhibits eruptive spiking behavior that is aperiodic locally, and asynchronous amongst regions, yet aggregates to produce a pattern of periodic outbreaks. In Québec, forest tent caterpillar cycles differ in the aspen-dominated northwest versus the maple-dominated southeast, with opposing patterns of cycle intensity between the two regions. (3) In Alberta, forest tent caterpillar outbreak cycles resist synchronization across a forest landscape gradient, even at very fine spatial scales, resulting in a complex pattern of cycling that defies simple forecasting techniques. (4) In the Border Lakes region of Ontario and Minnesota, where the two insect species coexist in a mixedwood landscape of hardwood and conifers, outbreak cycle intensity in each species varies spatially and temporally in response to host forest landscape structure. Much attention has been given to the effect of top-down agents in driving synchronizable population cycles. However, foliage loss, tree death, and forest succession at stem, stand, and landscape scales affect larval and adult dispersal success, and may serve to override regulatory processes that cause otherwise top-down-driven periodic, synchronized, and predictable population oscillations to become aperiodic, asynchronous, and unpredictable. Incorporating bottom-up effects at multiple spatial and temporal scales may be the key to making significant improvements in forest insect outbreak forecasting.
Journal Article
Beetle assemblages from an Australian tropical rainforest show that the canopy and the ground strata contribute equally to biodiversity
There remains great uncertainty about how much tropical forest canopies contribute to global species richness estimates and the relative specialization of insect species to vertical zones. To investigate these issues, we conducted a four-year sampling program in lowland tropical rainforest in North Queensland, Australia. Beetles were sampled using a trap that combines Malaise and flight interception trap (FIT) functions. Pairs of this trap, one on the ground and a second suspended 15-20 m above in the canopy were located at five sites, spaced 50 m or more apart. These traps produced 29 986 beetles of 1473 species and 77 families. There were similar numbers of individuals (canopy 14 473; ground 15 513) and species (canopy 1158; ground 895) in each stratum, but significantly more rare species in the canopy (canopy 509; ground 283). Seventy two percent of the species (excluding rare species) were found in both strata. Using IndVal, we found 24 and 27% of the abundant species (n≥20 individuals) to be specialized to the canopy and the ground strata, respectively, and equivalent analyses at the family level showed figures of 30 and 22%, respectively. These results show that the canopy and the ground strata both provide important contributions to rainforest biodiversity.
Journal Article
Plant-Pollinator Interactions over 120 Years: Loss of Species, Co-Occurrence, and Function
Using historic data sets, we quantified the degree to which global change over 120 years disrupted plant-pollinator interactions in a temperate forest understory community in Illinois, USA. We found degradation of interaction network structure and function and extirpation of 50% of bee species. Network changes can be attributed to shifts in forb and bee phenologies resulting in temporal mismatches, nonrandom species extinctions, and loss of spatial co-occurrences between extant species in modified landscapes. Quantity and quality of pollination services have declined through time. The historic network showed flexibility in response to disturbance; however, our data suggest that networks will be less resilient to future changes.
Journal Article