Survival and sprouting responses of Chihuahua pine after the Rodeo-Chediski fire on the Mogollon Rim, Arizona

Chihuahua pines ( Pinus leiophylla Schiede and Deppe var. chihuahuana Engelmann) were surveyed on 11 study plots on the Mogollon Rim in east central Arizona to compare characteristics of trees that sprouted from the base or root collar after the Rodeo-Chediski fire with those of trees that did not sprout. The differences in trees killed and top-killed by the fire versus those that survived were also assessed. Trees that sprouted were significantly smaller in height and diameter at breast height; they also experienced lower fire intensities than trees that did not sprout. Smaller trees had higher incidences of mortality than larger trees. These results indicate that, even though Chihuahua pine has fire resiliency, sprouting rates after fire are related to size of trees, age of trees, and burn intensity. Since Chihuahua pine is a rare species in the area studied, its ability to recover from and tolerate fire could prove advantageous for sustainability.     

Status of an invading mainland jackrabbit on Cerralvo island, Gulf of California

We report the first observations of the black-tailed jackrabbit ( Lepus californicus ) on Cerralvo Island, Baja California Sur, Mexico. Evidence suggests a self-sustaining population. Analysis of available records indicates no previous record of Lepus on the island. Introduction of the jackrabbit to the island appears to have occurred between 1960 and 1991.     

Effects of soil structure on burrow characteristics of five small mammal species

Burrows of small mammals can impact a variety of soil processes including organic turnover, aeration, and mineralization rates. The structure of burrows, depth, length, and complexity can influence the extent of the impact burrows have on soil processes. Soil properties, in turn, are thought to affect burrow structure. To increase our understanding of burrow-soil dynamics, we compared maximum depth, total volume, total length, volume:length ratio, and complexity of burrows of five small mammal species with bulk density of soil texture in multiple regression analyses. Burrows of Wyoming ground squirrels ( Spermophilus elegans ) were deeper, longer, and more complex as percentage of silt and clay increased and percentage of sand and bulk density decreased. Average maximum depth of montane vole ( Microtus montanus ) burrows increased as soils became sandier. Length and volume of deer mice ( Peromyscus maniculatus ) burrows increased with increases in bulk density and percentage of clay. Volume, length, and complexity of kangaroo rat ( Dipodomys ordii ) burrows were greater in soils with higher amounts of clay and silt. Townsend's ground squirrel ( Spermophilus townsendii ) burrows did not appear to be affected by the soil properties measured.     

Growth and demography of one population of the lizard Sceloporus mucronatus mucronatus

We report on growth and demography of Sceloporus mucronatus mucronatus , a lizard subspecies endemic to central Mexico. We characterize the life history of this subspecies, provide quantitative information relevant to conservation, and add to the growing literature on the diversity of life histories in the genus Sceloporus . We calculated body growth rates and fitted them to the Von Bertalanffy, the logistic-by-length, and the logistic-by-weight growth models. The Von Bertalanffy model provided the best fit, and we used it to analyze the growth pattern. Growth rates were similar during the 1st year of life in both sexes, but after that point males grew faster and reached maturity earlier (20 months) than females (31 months). We used a population projection matrix to model population dynamics during 2003–2004 and found a positive population growth rate (λ = 1.769). However, based on the projected stable size-class vector ( w ), this population does not appear to have reached stability, and it might be currently experiencing considerable interannual fluctuations. Elasticity values showed that the transition from the juvenile stage to the 1st adult stage was the vital rate that contributes the most to population growth rate, followed by fecundity and stasis of the 1st reproductive category. While total elasticities for demographic processes were similar, elasticities per size class showed the relatively high importance of small adults in comparison to juveniles and large adults. The restriction of this endemic subspecies to central Mexico, where human activities and consequent habitat destruction are increasing, demands further quantitative evaluation and monitoring of populations, even though our results indicate a potential for population growth.     

基于着陆器地基测量的火星定向参数确定

火星定向参数的精确测定对约束火星内部结构以及极区干冰变化的建模具有重要意义.基于未来的火星着陆任务,仿真分析了利用双程多普勒与距离测量方法直接跟踪着陆器,解算火星定向参数所能达到的精度.结果表明,通过双程多普勒和双程测距直接跟踪火星着陆器超过200个工作日,将显著提高火星岁差、章动以及日长变化参数的精度,约800个工作日后,岁差参数精度可较目前提高5–10倍,章动参数精度可达到10–30 mas,日长变化与钱德勒摆动参数精度可收敛至5–10 mas,这一精度水平可以满足研究火星内部结构与大气物质交换的需要.通过分析不同纬度着陆器的解算结果,发现高纬度的着陆器有必要进行距离测量,以保持岁差和章动参数的解算精度.此外,研究还发现,当火星星历误差小于75 m时,双程多普勒数据解算火星定向参数的精度不受影响,而对于双程测距数据来说,只有当火星历表精度优于0.15 m时,定向参数的解算结果才具有可信性.     

Nonparametric Quantile Regression‐Based Classifiers for Bankruptcy Forecasting

An improved classification device for bankruptcy forecasting is proposed. The proposed approach relies on mainstream classifiers whose inputs are obtained from a so‐called multinorm analysis, instead of traditional indicators such as the ROA ratio and other accounting ratios. A battery of industry norms (computed by using nonparametric quantile regressions) is obtained, and the deviations of each firm from this multinorm system are used as inputs for the classifiers. The approach is applied to predict bankruptcy on a representative sample of Spanish manufacturing firms. Results indicate that our proposal may significantly enhance predictive accuracy, both in linear and nonlinear classifiers. Copyright © 2013 John Wiley & Sons, Ltd.     

COMBINING SINGULAR SPECTRUM ANALYSIS AND PAR（p） STRUCTURES TO MODEL WIND SPEED TIME SERIES

Singular spectrum analysis （SSA） is a technique that decomposes a time series into a set of components, such as, trend, harmonics, and residuals. Leaving out the residual components and adding up the others, the time series can be smoothed. This procedure has been used to model Brazilian electricity consumption and flow series. The PAR（p）, periodic autoregressive models, has been broadly used in modelling energy series in Brazil. This paper presents an approach of this decomposition method, by fitting the PAR（p）, considering its multivariate version known as multivariate SSA （MSSA）. The method was applied to a vector of two wind speed series recorded at two locations in the Brazilian Northeast region. The obtained results, when compared to the univariate decomposition of each series, were far superior, showing that the spatial correlation between the two series were considered by MSSA decomposition stage.