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The influence of fire interval on community structure in the Greater Yellowstone Ecosystem
No full textWith fires becoming more common in the intermountain West, understanding patterns of post-fire succession and the role of fire interval in shaping community responses has become critical. In 2016, the Berry Fire burned through 4 study grids which have been the focus of a long-term fire succession project started after the massive 1988 fire season. We investigated the effects of this fire with respect to the repeatability of post-fire succession patterns (i.e., does succession after the 2016 fire match patterns observed after the 1988 fire) and the role of burn interval in shaping community structure of small mammals, invertebrates, and plants. Preliminary results indicate that sites with short burn intervals had greater diversity and abundance across all three taxonomic groups, although these differences were not always significant. Whereas the dominant taxa (deer mice and ants) were the same 1 year after the 1988 and 2016 fires, we documented greater abundance of invertebrates and mammals and greater diversity of mammals after the 2016 fires. Taken together, these results highlight the importance of understanding fire regime (i.e., fire timing and intensity) in shaping these ecological communities into the future.
Featured photo by filarwilliams on Flickr. https://flic.kr/p/KYMiJ
Understanding wetland responses to climate change in the Greater Yellowstone Area
No full textWetlands in the Greater Yellowstone Area (GYA) support a high diversity of species. Increased temperatures associated with climate change are related to increased wetland drying in the GYA, potentially affecting the species using wetlands. The National Park Service Greater Yellowstone Inventory and Monitoring Network (GRYN) started monitoring wetlands in 2006, focusing on amphibian occupancy. Adding novel surveillance techniques to GRYN’s existing, long-term monitoring program offers an opportunity to observe more species. This may help us better understand how wetland species diversity may be affected by climate change and provide additional information to managers. In 2017, I outfitted four permanent wetlands with equipment collecting photographs, acoustic recordings, and ultrasonic recordings for approximately five days in June/July. When the equipment was deployed, I collected environmental DNA (eDNA) samples. Data from wildlife cameras, acoustic recorders, ultrasonic recorders, and eDNA for cataloging the biological diversity of wetlands is still being analyzed. Acoustic data and eDNA samples require additional processing; however, preliminary data is available for photographic data and ultrasonic data. Cameras detected elk at all sites, whereas bat detection varied by site.
Featured photo by Neal Herbert on Flickr. https://flic.kr/p/2gv8cS
Labor, Discipline, and Resistance: Transnational Migrant Workers ‘on the line’
No full textUnauthorized workers are foundational to neoliberal production regimes in the United States. The economic indispensability of such ‘disposable’ laborers in the era of flexible accumulation and the new energy they bring to labor activism promise to shape the emergence of the 21st century working class. This article explores the dynamics of labor discipline among undocumented workers, situating the current experiences of transnational migrants within a broader cultural history of the recruitment, disciplining, and exploitation of workers from vulnerable populations. Currently, conditions of illegality and deportability make transnational workers particularly vulnerable to labor rights violations and wage theft. The structure of immigration law, which frames and facilitates exploitation, serves the interests of capital and disciplines workers to perform their role as a subordinated class. Nonetheless, the confluence of labor militancy and immigrants’ rights activism over the past decade provides hope for social and political change based in solidarity and worker agency
Euler-Richardson method preconditioned by weakly stochastic matrix algebras: a potential contribution to Pagerank computation
No full textLet S be a column stochastic matrix with at least one full row. Then S describes a Pagerank-like random walk since the computation of the Perron vector x of S can be tackled by solving a suitable M-matrix linear system Mx = y, where M = I â Ï A, A is a column stochastic matrix and Ï is a positive coefficient smaller than one. The Pagerank centrality index on graphs is a relevant example where these two formulations appear. Previous investigations have shown that the Euler- Richardson (ER) method can be considered in order to approach the Pagerank computation problem by means of preconditioning strategies. In this work, it is observed indeed that the classical power method can be embedded into the ER scheme, through a suitable simple preconditioner. Therefore, a new preconditioner is proposed based on fast Householder transformations and the concept of low complexity weakly stochastic algebras, which gives rise to an effective alternative to the power method for large-scale sparse problems. Detailed mathematical reasonings for this choice are given and the convergence properties discussed. Numerical tests performed on real-world datasets are presented, showing the advantages given by the use of the proposed Householder-Richardson method
A new kind of companion matrix
No full textA new kind of companion matrix is introduced, for polynomials of the form c(λ) = λa(λ)b(λ)+c_0, where upper Hessenberg companions are known for the polynomials a(λ) and b(λ). This construction can generate companion matrices with smaller entries than the Fiedler or Frobenius forms. This generalizes Piers Lawrenceâs Mandelbrot companion matrix. The construction was motivated by use of Narayana-Mandelbrot polynomials, which are also new to this paper
Permutative nonnegative matrices with prescribed spectrum
No full textAn n à n permutative matrix is a matrix in which every row is a permutation of the first row. In this paper, the result given by Paparella in [P. Paparella. Realizing Suleimanova spectra via permutative matrices. Electron. J. Linear Algebra, 31:306â312, 2016.] is extended to a more general lists of real and complex numbers, and a negative partial answer to a question posed by him is given
On the distance signless Laplacian spectral radius of graphs and digraphs
No full textLet \eta(G) denote the distance signless Laplacian spectral radius of a connected graph G. In this paper,bounds for the distance signless Laplacian spectral radius of connected graphs are given, and the extremal graph with the minimal distance signless Laplacian spectral radius among the graphs with given vertex connectivity and minimum degree is determined. Furthermore, the digraph that minimizes the distance signless Laplacian spectral radius with given vertex connectivity is characterized
Upper bounds on Q-spectral radius of book-free and/or -free graphs
No full textIn this paper, we prove two results about the signless Laplacian spectral radius of a graph of order with maximum degree . Let denote a book, i.e., the graph consists of triangles sharing an edge. The results are the following: (1) Let and be a connected \{\}-free graph of order with maximum degree . Then with equality if and only if is a strongly regular graph with parameters (, , ). (2) Let , and let be a connected -free graph of order . Then q(G)\leq n+(s-t+1)^{1/t}n^{1-1/t}+(t-1)(n-1)^{1-3/t}+t-3.$
On skew-symmetric matrices related to the vector cross product in R^7
No full textA study of real skew-symmetric matrices of orders and , defined through the vector cross product in , is presented. More concretely, results on matrix properties, eigenvalues, (generalized) inverses and rotation matrices are established
Spectral Dynamics of Graph Sequences Generated by Subdivision and Triangle Extension
No full textFor a graph G and a unary graph operation X, there is a graph sequence \G_k generated by G_0=G and G_{k+1}=X(G_k). Let Sp({G_k}) denote the set of normalized Laplacian eigenvalues of G_k. The set of limit points of \bigcup_{k=0}^\infty Sp(G_k)\liminf_{k\rightarrow\infty}Sp(G_k) and are considered in this paper for graph sequences generated by two operations: subdivision and triangle extension. It is obtained that the spectral dynamic of graph sequence generated by subdivision is determined by a quadratic function, which is closely related to the the well-known logistic map; while that generated by triangle extension is determined by a linear function. By using the knowledge of dynamic system, the spectral dynamics of graph sequences generated by these two operations are characterized. For example, it is found that, for any initial non-trivial graph , chaos takes place in the spectral dynamics of iterated subdivision graphs, and the set of limit points is the entire closed interval [0,2]