The Origin, Succession, and Predicted Metabolism of Bacterial Communities Associated with Leaf Decomposition.

Intraspecific variation in plant nutrient and defensive traits can regulate ecosystem-level processes, such as decomposition and transformation of plant carbon and nutrients. Understanding the regulatory mechanisms of ecosystem functions at local scales may facilitate predictions of the resistance and resilience of these functions to change. We evaluated how riverine bacterial community assembly and predicted gene content corresponded to decomposition rates of green leaf inputs from red alder trees into rivers of Washington State, USA. Previously, we documented accelerated decomposition rates for leaves originating from trees growing adjacent to the site of decomposition versus more distant locales, suggesting that microbes have a "home-field advantage" in decomposing local leaves. Here, we identified repeatable stages of bacterial succession, each defined by dominant taxa with predicted gene content associated with metabolic pathways relevant to the leaf characteristics and course of decomposition. "Home" leaves contained bacterial communities with distinct functional capacities to degrade aromatic compounds. Given known spatial variation of alder aromatics, this finding helps explain locally accelerated decomposition. Bacterial decomposer communities adjust to intraspecific variation in leaves at spatial scales of less than a kilometer, providing a mechanism for rapid response to changes in resources such as range shifts among plant genotypes. Such rapid responses among bacterial communities in turn may maintain high rates of carbon and nutrient cycling through aquatic ecosystems.IMPORTANCE Community ecologists have traditionally treated individuals within a species as uniform, with individual-level biodiversity rarely considered as a regulator of community and ecosystem function. In our study system, we have documented clear evidence of within-species variation causing local ecosystem adaptation to fluxes across ecosystem boundaries. In this striking pattern of a "home-field advantage," leaves from individual trees tend to decompose most rapidly when immediately adjacent to their parent tree. Here, we merge community ecology experiments with microbiome approaches to describe how bacterial communities adjust to within-species variation in leaves over spatial scales of less than a kilometer. The results show that bacterial community compositional changes facilitate rapid ecosystem responses to environmental change, effectively maintaining high rates of carbon and nutrient cycling through ecosystems

Main rotor-tail rotor intraction and its implications for helicopter directional control

Aerodynamic interference between the main and tail rotor can have a strong negative influence on the flight mechanics of a conventional helicopter. Significant unsteadiness in the tail rotor loading is encountered under certain flight conditions, but the character of the unsteadiness can depend on the direction of rotation of the tail rotor. Numerical simulations, using Brown's vorticity transport model, of the aerodynamic interaction between the main and tail rotors of a helicopter are presented for a range of forward and lateral flight trajectories. Distinct differences are predicted in the behavior of the system in left and right sideward flight that are consistent with flight experience that the greatest fluctuations in loading or control input are required in left sideways flight (for a counterclockwise rotating main rotor). These fluctuations are generally more extreme for a system with tail rotor rotating top-forward than top-aft. Differences are also exposed in the character of the lateral excitation of the system as forward flight speed is varied. The observed behavior appears to originate in the disruption of the tail rotor wake that is induced by its entrainment into the wake of the main rotor. The extent of the disruption is dependent on flight condition, and the unsteadiness of the process depends on the direction of rotation of the tail rotor. In intermediate-speed forward flight and right sideward flight, the free stream delays the entrainment of the tail rotor wake far enough downstream for the perturbations to the rotor loading to be slight. Conversely, in left sideward and quartering flight, the free stream confines the entrainment process close to the rotors, where it causes significant unsteadiness in the loads produced by the system

Temporal and Spatial Impact of Human Cadaver Decomposition on Soil Bacterial and Arthropod Community Structure and Function

As vertebrate carrion decomposes, there is a release of nutrient-rich fluids into theunderlying soil, which can impact associated biological community structure andfunction. How these changes alter soil biogeochemical cycles is relatively unknown and may prove useful in the identification of carrion decomposition islands that have long lasting, focal ecological effects. This study investigated the spatial (0, 1, and 5 m) and temporal (3–732 days) dynamics of human cadaver decomposition on soil bacterial and arthropod community structure and microbial function. We observed strong evidence of a predictable response to cadaver decomposition that varies over space for soil bacterial and arthropod community structure, carbon (C) mineralization and microbial substrate utilization patterns. In the presence of a cadaver (i.e., 0 m samples), the relative abundance of Bacteroidetes and Firmicutes was greater, while the relative abundance of Acidobacteria, Chloroflexi, Gemmatimonadetes, and Verrucomicrobia was lower when compared to samples at 1 and 5 m. Micro-arthropods were more abundant (15 to 17-fold) in soils collected at 0 m compared to either 1 or 5 m, but overall, micro-arthropod community composition was unrelated to either bacterial community composition or function. Bacterial community structure and microbial function also exhibited temporal relationships, whereas arthropod community structure did not. Cumulative precipitation was more effective in predicting temporal variations in bacterial abundance and microbial activity than accumulated degree days. In the presence of the cadaver (i.e., 0 m samples), the relative abundance of Actinobacteria increased significantly with cumulative precipitation. Furthermore, soil bacterial communities and C mineralization were sensitive to the introduction of human cadavers as they diverged from baseline levels and did not recover completely in approximately 2 years. These data are valuable for understanding ecosystem function surrounding carrion decomposition islands and can be applicable to environmental bio-monitoring and forensic sciences

Ecological integrity of boreal streams

Running waters provide a number of services for humans, such as drinking water and food resources and many freshwater animals are confined and specialised to this environment. However, this natural resource has become increasingly impacted by humans resulting in a substantial loss of biodiversity and services. To assess ecological integrity of streams a number of bioassessment schemes have been developed and most of these are based on community structure and composition. Although many of the biological metrics developed have been used successfully in bioassessment, it has been suggested that ecosystem functions, such as leaf-litter decomposition, should be incorporated in modern bioassessment schemes. In this thesis I compare a number of structural metrics with functional metrics along a nutrient gradient in nine boreal streams in south-central Sweden to assess the potential of ecosystem function as a biomonitoring tool. Leaf-litter breakdown (Alnus glutinosa (L.) Gaertner) was studied during four seasons and stable isotope (δ13C and δ15N) and stoichiometric ratios (C:N) of phytobenthos, CPOM, FPOM, invertebrates and fish were also analysed. My results indicate that leaf-litter breakdown is a relatively insensitive tool to assess ecosystem impairment compared to invertebrate metrics. However, δ15N in organic matter has been suggested as a potential tool to assess ecological integrity of streams and my results support this conjecture. A strong response in δ15N in organic matter with nutrient enrichment was revealed, suggesting that δ15N could serve as a simple tool to assess nutrient enrichment effects in boreal streams. I also found that leaf-litter associated fungi and invertebrates were positively correlated with leaf-litter breakdown rates and a nutrient gradient. Moreover, I found that certain dominating species, e.g. waterlouse (Asellus aquaticus (L.)), can have a strong influence on ecosystem processes. In this thesis I show that leaf-litter breakdown is not a simple low-cost biomonitoring tool as several field trips were necessary to assure adequate litter-bag recovery. Also natural factors, such as fluctuating water levels and heavy snow fall, resulted in substantial loss of litter bags thereby confounding data interpretation

DRSP : Dimension Reduction For Similarity Matching And Pruning Of Time Series Data Streams

Similarity matching and join of time series data streams has gained a lot of relevance in today's world that has large streaming data. This process finds wide scale application in the areas of location tracking, sensor networks, object positioning and monitoring to name a few. However, as the size of the data stream increases, the cost involved to retain all the data in order to aid the process of similarity matching also increases. We develop a novel framework to addresses the following objectives. Firstly, Dimension reduction is performed in the preprocessing stage, where large stream data is segmented and reduced into a compact representation such that it retains all the crucial information by a technique called Multi-level Segment Means (MSM). This reduces the space complexity associated with the storage of large time-series data streams. Secondly, it incorporates effective Similarity Matching technique to analyze if the new data objects are symmetric to the existing data stream. And finally, the Pruning Technique that filters out the pseudo data object pairs and join only the relevant pairs. The computational cost for MSM is O(l*ni) and the cost for pruning is O(DRF*wsize*d), where DRF is the Dimension Reduction Factor. We have performed exhaustive experimental trials to show that the proposed framework is both efficient and competent in comparison with earlier works.Comment: 20 pages,8 figures, 6 Table

The Effects of Potential Land Development on Agricultural Land Prices

We conduct a national-scale study of the determinants of agricultural land values to better understand how current farmland prices are influenced by the potential for future land development. The theoretical basis for the empirical analysis is a spatial city model with stochastic returns to future land development. From the theoretical model, we derive an expression for the current price of agricultural land in terms of annual returns to agricultural production, the price of recently developed land parcels, and expressions involving model parameters that are represented in the empirical model by nonlinear functions of observed variables and parameters to be estimated. We estimate the model of agricultural land values with a cross-section on approximately three thousand counties in the contiguous U.S. The results provide strong support for the model, and provide the first evidence that option values associated with irreversible and uncertain land development are capitalized into current farmland values. The empirical model is specified in a way that allows us to identify the contributions to land values of rents from near-term agricultural use and rents from potential development in the future. For each county in the contiguous U.S., we estimate the share of the current land value attributable to future development rents. These results give a clearer indication of the magnitude of land development pressures and yield insights into policies to preserve farmland and associated environmental benefits.