Private Trees as Household Assets and Determinants of Tree-Growing Behavior in Rural Ethiopia

This study looked into tree-growing behavior of rural households in Ethiopia. With data collected at household and parcel levels from the four major regions of Ethiopia, we analyzed the decision to grow trees and the number of trees grown, using such econometric strategies as a zero-inflated negative binomial model, Heckman’s two-step procedure, and panel data techniques. Our findings show the importance of analysis at the parcel level in addition to the more common household-level. Moreover, the empirical analysis indicates that the determinants of the decision to grow trees are not necessarily the same as those involved in deciding the number of trees grown. Land certification, as an indicator of tenure security, increases the likelihood that households will grow trees, but is not a significant determinant of the number of trees grown. Other variables, such as risk aversion, land size, adult male labor, and education of household head, also influence the number of trees grown. In general, the results suggest the need to use education and/or awareness of the role and importance of trees and point out the importance of household endowments and behavior, such as land, labor, and risk aversion, for tree growing. Finally, we observed that, while tree planting is practiced in all four regions covered, there are variations across regions.trees as assets, tree growing, Ethiopia

Effect of selection on ancestry: an exactly soluble case and its phenomenological generalization

We consider a family of models describing the evolution under selection of a population whose dynamics can be related to the propagation of noisy traveling waves. For one particular model, that we shall call the exponential model, the properties of the traveling wave front can be calculated exactly, as well as the statistics of the genealogy of the population. One striking result is that, for this particular model, the genealogical trees have the same statistics as the trees of replicas in the Parisi mean-field theory of spin glasses. We also find that in the exponential model, the coalescence times along these trees grow like the logarithm of the population size. A phenomenological picture of the propagation of wave fronts that we introduced in a previous work, as well as our numerical data, suggest that these statistics remain valid for a larger class of models, while the coalescence times grow like the cube of the logarithm of the population size.Comment: 26 page

Macro-evolutionary models and coalescent point processes: The shape and probability of reconstructed phylogenies

Forward-time models of diversification (i.e., speciation and extinction) produce phylogenetic trees that grow "vertically" as time goes by. Pruning the extinct lineages out of such trees leads to natural models for reconstructed trees (i.e., phylogenies of extant species). Alternatively, reconstructed trees can be modelled by coalescent point processes (CPP), where trees grow "horizontally" by the sequential addition of vertical edges. Each new edge starts at some random speciation time and ends at the present time; speciation times are drawn from the same distribution independently. CPP lead to extremely fast computation of tree likelihoods and simulation of reconstructed trees. Their topology always follows the uniform distribution on ranked tree shapes (URT). We characterize which forward-time models lead to URT reconstructed trees and among these, which lead to CPP reconstructed trees. We show that for any "asymmetric" diversification model in which speciation rates only depend on time and extinction rates only depend on time and on a non-heritable trait (e.g., age), the reconstructed tree is CPP, even if extant species are incompletely sampled. If rates additionally depend on the number of species, the reconstructed tree is (only) URT (but not CPP). We characterize the common distribution of speciation times in the CPP description, and discuss incomplete species sampling as well as three special model cases in detail: 1) extinction rate does not depend on a trait; 2) rates do not depend on time; 3) mass extinctions may happen additionally at certain points in the past

Alternating model trees

Model tree induction is a popular method for tackling regression problems requiring interpretable models. Model trees are decision trees with multiple linear regression models at the leaf nodes. In this paper, we propose a method for growing alternating model trees, a form of option tree for regression problems. The motivation is that alternating decision trees achieve high accuracy in classification problems because they represent an ensemble classifier as a single tree structure. As in alternating decision trees for classifi-cation, our alternating model trees for regression contain splitter and prediction nodes, but we use simple linear regression functions as opposed to constant predictors at the prediction nodes. Moreover, additive regression using forward stagewise modeling is applied to grow the tree rather than a boosting algorithm. The size of the tree is determined using cross-validation. Our empirical results show that alternating model trees achieve significantly lower squared error than standard model trees on several regression datasets

Electrical Treeing in Silicone Rubber

Electrical treeing has been widely studied in a range of polymeric materials. In these investigations, the morphology and PD patterns associated with the growth of electrical trees in a model transparent silicone rubber were investigated using a new system recently developed at Southampton. With increasing voltage the trees became more complex in appearance but nevertheless grow more rapidly. As the tree evolves the PD pattern becomes more intense which may provide a method of monitoring the extent of treeing in opaque samples. Raman studies indicate that treeing and breakdown channels are hollow, carbonaceous entities, a finding consistent with other studies

Asymptotic distribution of two-protected nodes in ternary search trees

We study protected nodes in $m$-ary search trees, by putting them in context of generalised P\'olya urns. We show that the number of two-protected nodes (the nodes that are neither leaves nor parents of leaves) in a random ternary search tree is asymptotically normal. The methods apply in principle to $m$-ary search trees with larger $m$ as well, although the size of the matrices used in the calculations grow rapidly with $m$; we conjecture that the method yields an asymptotically normal distribution for all $m\leq 26$. The one-protected nodes, and their complement, i.e., the leaves, are easier to analyze. By using a simpler P\'olya urn (that is similar to the one that has earlier been used to study the total number of nodes in $m$-ary search trees), we prove normal limit laws for the number of one-protected nodes and the number of leaves for all $m\leq 26$

Trees that “Grow on You”: Naturalist Taxonomy and Ecopoetics of Interrelatedness in Murray Bail’s Eucalyptus

Investigating transcultural encounters between Europe and Australia in Murray Bail's Eucalyptus through an ecocritical lens, this essay re-evaluates the act of naming trees with regard to the status of the character symbolically called Holland. Critics have underlined how, in colonial contexts, the naturalist taxonomy of the environment partakes of the settlers' conquest of new colonies: Jamaica Kincaid's assertion 'to name is to possess' crystallises this cultural process of ecological imperialism. While I acknowledge this phenomenon, a re-appraisal of the naming practice in Eucalyptus allows us to transcend the legacy of polarised colonial and anthropocentric perspectives. Holland's status may be interpreted positively in view of Neil Evernden's concept of 'man-in-environment': if so, the act of naming represents the individual's constructive attempt at establishing a sense of place within a new territory. Bail's protagonists exemplify different stages in this process of interrelatedness between the human and non-human realms, one which resists a conventional subject-object relationship. Whereas the ambivalent Holland embodies a factual and existential naturalism, the imaginative approach to the treescape of his daughter Ellen and her storytelling suitor fully emancipates them from the commodifying effect of Holland's naming competition. Bail's aesthetics reflects the dissolving boundary between the self and environment: deployed in the suitor's fable-like stories and Bail's rich prose, the ecopoetic devices of anthropomorphism and zoomorphism defy the rational laws of Western realism. This ecopoetics of interrelatedness restores the agency of the eucalypts while negating the concept of a traditionally dominant human presence in the environment. In Eucalyptus, taxonomy reveals the reciprocal dynamics of a genuine interpenetration: Holland's 'bush garden' becomes a global space that combines European (symbolised by Holland and the stories) and Australian (the eucalypts) identities. Thus, Bail projects a creative site of transcultural dialogue at the level of the terrain through the complementary processes of physical and subjective interrelatedness

Modeling the Effect of Post-Dispersal Seed Predation on Tropical Tree Species in Panama

Palm trees provide a unique opportunity to study what conditions optimize the probability that a seed will grow successfully. The seeds of palm trees, endocarps, are large and easy to locate. When they don\u27t grow, predators leave marks on them that tell the story of their fate. The focus of my experiment is to determine how the current distribution pattern of parent palm trees in Panama Palm trees affects the the future distribution of seedlings. I have programmed a versatile model that takes the assumption that bruchid beetles are the sole predators acting on the seeds, and that these fall from the trees in an inverse logarithmic density pattern. The beetles are programmed to move to a random seed within an arbitrary distance of their start point. If no seeds are near enough to them, then they starve. I hypothesize that the beetles will decrease clumping within five generations.https://digitalcommons.usu.edu/fsrs2018/1010/thumbnail.jp