Changes in forest structure and composition in a successional tropical dry forest

We describe changes in forest structure and floristic composition of three successional stages for Mata Seca State Park, in Minas Gerais, Brazil, through the measurement of all trees greater than 5 cm of diameter at breast height (DBH) of 18 permanent plots (6 per stage) for early, intermediate, and late successional stages of a tropical dry forest during a 5-year period. Using this information, we calculated the Importance Value Index (IVI), Holdridge Complexity Index, Jaccard Similarity Coefficient, and Shannon Diversity Index for each stage of succession. The floristic composition and structure of the successional stages expressed by the Holdridge Complexity Index, showed that complexity increases gradually as we advance through the successional stages, while the Shannon Diversity Index indicated that species diversity was higher in the intermediate stage of succession. The Jaccard Similarity Coefficients showed that the intermediate and late successional stages had high similarity, whereas the early successional stage had low similarity with these two successional stages. Mortality rates were higher in the early stage, especially in stems with smaller diameters (5-10cm). This information contributes to the dissemination of important knowledge for the conservation of the tropical dry forests of Brazil, which are the most threatened ecosystems in this country and, at the same time, the least studied

Changes in tree and liana communities along a successional gradient in a tropical dry forest in south-eastern Brazil

We investigated changes in species composition and structure of tree and liana communities along a successional gradient in a seasonally dry tropical forest. There was a progressive increase in tree richness and all tree structural traits from early to late stages, as well as marked changes in tree species composition and dominance. This pattern is probably related to pasture management practices such as ploughing, which remove tree roots and preclude regeneration by resprouting. On the other hand, liana density decreased from intermediate to late stages, showing a negative correlation with tree density. The higher liana abundance in intermediate stage is probably due to a balanced availability of support and light availability, since these variables may show opposite trends during forest growth. Predicted succession models may represent extremes in a continuum of possible successional pathways strongly influenced by land use history, climate, soil type, and by the outcomes of tree–liana interactions

Changes in tree and liana communities along a successional gradient in a tropical dry forest in south-eastern Brazil. Plant Ecology 201

Abstract We investigated changes in species composition and structure of tree and liana communities along a successional gradient in a seasonally dry tropical forest. There was a progressive increase in tree richness and all tree structural traits from early to late stages, as well as marked changes in tree species composition and dominance. This pattern is probably related to pasture management practices such as ploughing, which remove tree roots and preclude regeneration by resprouting. On the other hand, liana density decreased from intermediate to late stages, showing a negative correlation with tree density. The higher liana abundance in intermediate stage is probably due to a balanced availability of support and light availability, since these variables may show opposite trends during forest growth. Predicted succession models may represent extremes in a continuum of possible successional pathways strongly influenced by land use history, climate, soil type, and by the outcomes of tree-liana interactions

Aspectos ecológicos da aroeira (Myracrodruon urundeuva Allemão- Anacardiaceae): fenologia e germinação de sementes Ecological aspects of aroeira (Myracrodruon urundeuva Allemão - Anacardiceae): phenology and seed germination

Myracrodruon urundeuva Allemão, espécie arbórea conhecida como aroeira, constitui-se em um importante componente das Florestas Estacionais Deciduais do norte de Minas Gerais. Apesar disso, a aroeira vem sofrendo um processo de exploração intensa, de forma predatória, o que vem causando a devastação de suas populações naturais. Este trabalho teve como objetivo conhecer os padrões fenológicos reprodutivos e vegetativos, bem como a capacidade germinativa da aroeira, na Área de Preservação da COPASA em Juramento, MG. Foram feitas observações fenológicas quinzenais, no período de janeiro/2002 a novembro/2003, de 20 indivíduos arbóreos, sendo ainda coletadas sementes, submetidas a diferentes tratamentos de escarificação tegumentar (mecânico, térmico, químico e controle). A espécie apresentou as fenofases reprodutivas e vegetativas influenciadas diferencialmente pelas variáveis ambientais de precipitação e temperatura. Na estação seca ocorreram a floração, frutificação e queda foliar, e a estação chuvosa favoreceu o brotamento da espécie. A capacidade germinativa dos diásporos de aroeira variou entre os tratamentos utilizados, com potencial germinativo e velocidade de germinação altos no tratamento-controle, indicando ausência de dormência. Nesse sentido, estudos básicos sobre as espécies florestais ameaçadas podem ser precursores de modelos e mecanismos para manejo e recuperação de suas populações naturais.<br>Myracrodruon urundeuva Allemão, an arboreal species known as aroeira, is an important component of seasonal dry forests in northern Minas Gerais. In spite of that, aroeira is experiencing a process of predatory exploitation, causing the devastation of its natural populations. This study aimed to assess the reproductive and vegetative phenological patterns, and the germinating capacity of the species. The study was carried out at the COPASA Preservation Area in Juramento (MG), where phenological phases were systematically observed bimonthly, from Janurary/2002 to November/2003 in 20 arboreal individuals. Seeds were collected and submitted to different scarification treatments (mechanic, thermal, chemical and control). The reproductive and vegetative phenophases of the species are influenced by environmental conditions. During the dry season, flowering, fructification and leaf fall occur, whereas the wet season favors leaf growth. Besides, the germination of aroeira seeds varied among treatments, with higher germinating potential and germination velocity being verified in the control treatment, indicating the absence of dormancy. Therefore, basic studies on the ecology of threatened forest species are essential to generate models and mechanisms for the management and restoration of their natural populations

A Virally Encoded Chaperone Specialized for Folding of the Major Capsid Protein of African Swine Fever Virus

It is generally believed that cellular chaperones facilitate the folding of virus capsid proteins, or that capsid proteins fold spontaneously. Here we show that p73, the major capsid protein of African swine fever virus (ASFV) failed to fold and aggregated when expressed alone in cells. This demonstrated that cellular chaperones were unable to aid the folding of p73 and suggested that ASFV may encode a chaperone. An 80-kDa protein encoded by ASFV, termed the capsid-associated protein (CAP) 80, bound to the newly synthesized capsid protein in infected cells. The 80-kDa protein was released following conformational maturation of p73 and dissociated before capsid assembly. Coexpression of the 80-kDa protein with p73 prevented aggregation and allowed the capsid protein to fold with kinetics identical to those seen in infected cells. CAP80 is, therefore, a virally encoded chaperone that facilitates capsid protein folding by masking domains exposed by the newly synthesized capsid protein, which are susceptible to aggregation, but cannot be accommodated by host chaperones. It is likely that these domains are ultimately buried when newly synthesized capsid proteins are added to the growing capsid shell

Os caminhos da estatística e suas incursões pela epidemiologia The paths of statistics and its incursions through epidemiology

Neste trabalho, contempla-se o desenvolvimento da Estatística, desde suas origens probabilísticas até os atuais modelos de "dependência" no tempo e no espaço. Avalia-se a evolução do método quantitativo na abordagem epidemiológica, como também procura-se estabelecer limites das técnicas estatísticas habituais, discutindo-se suas suposições teóricas e sua adequação ao tratamento analítico das informações. Enfatizam-se a importância do desenvolvimento e/ou generalização de procedimentos que possam ajudar a superar as dificuldades metodológicas ainda encontradas em diversos estudos de inferência causal em Epidemiologia.<br>In this paper the development of Statistics is contemplated from its probabilistic fundamentals until the current studies of time and space "dependence". Some applications of the quantitative method in the epidemiologic approach are evaluated. An attempt is made to establish some limits to the current statistical techniques through the discussion of theoretical assumptions and their adequacy to analyse empirical data. The development (or generalization) of new procedures that could possibly help to overcome methodological difficulties that are still found in various analysis of causal inference in Epidemiology is emphasized

Functional recovery of secondary tropical forests

One-third of all Neotropical forests are secondary forests that regrow naturally after agricultural use through secondary succession. We need to understand better how and why succession varies across environmental gradients and broad geographic scales. Here, we analyze functional recovery using community data on seven plant characteristics (traits) of 1,016 forest plots from 30 chronosequence sites across the Neotropics. By analyzing communities in terms of their traits, we enhance understanding of the mechanisms of succession, assess ecosystem recovery, and use these insights to propose successful forest restoration strategies. Wet and dry forests diverged markedly for several traits that increase growth rate in wet forests but come at the expense of reduced drought tolerance, delay, or avoidance, which is important in seasonally dry forests. Dry and wet forests showed different successional pathways for several traits. In dry forests, species turnover is driven by drought tolerance traits that are important early in succession and in wet forests by shade tolerance traits that are important later in succession. In both forests, deciduous and compound-leaved trees decreased with forest age, probably because microclimatic conditions became less hot and dry. Our results suggest that climatic water availability drives functional recovery by influencing the start and trajectory of succession, resulting in a convergence of community trait values with forest age when vegetation cover builds up. Within plots, the range in functional trait values increased with age. Based on the observed successional trait changes, we indicate the consequences for carbon and nutrient cycling and propose an ecologically sound strategy to improve forest restoration success

Functional recovery of secondary tropical forests

One-third of all Neotropical forests are secondary forests that regrow naturally after agricultural use through secondary succession. We need to understand better how and why succession varies across environmental gradients and broad geographic scales. Here we present data on functional recovery, using community data on seven plant characteristics (traits) of 1016 forest plots from 30 chronosequence sites across the Neotropics. By analyzing communities in terms of their traits one can enhance understanding of the mechanisms of succession and assess ecosystem recovery

I do it for myself : A study on motivational differences between contracted and permanent employees in Sweden

Over the past decades outsourcing decades outsourcing has become an increasing trend.Firms decide to outsource in order to increase their profits or flexibility and many differentfunctions of the firm may be outsourced, one of them being the Human Resource (HR)function. When it comes to HR outsourcing, recruitment and selection are among the morecommon functions to be outsourced (Ordanini &amp; Silvestri, 2008:373). The motivation foroutsourcing of HR is to reduce cost and increase efficiency (Elmuti, Grunewald and Abebe,2010:177). Outsourcing of HR functions like recruitment can also have negative aspect, forexample lack of loyalty and high turnover (Fisher et al, 2008:202). Previous research hasinvestigated how commitment and loyalty is affected by HR outsourcing (Connelly &amp;Gallagher, 2004:963) and one aspect that has been touched upon but not dealt withexclusively is motivation and therefore this paper will explore it further. Using the following research question: How does motivation vary between individuals working at a company butare hired through a staffing firm versus hired directly by the company? This paper tries to both evaluate the existing literature and provide practicalimplications for managers. In order to explore this question and abductive research approachhas been used where the data and theory are intertwined and played of each other to achievethe purpose (Alvesson &amp; Sköldberg, 2009:4). The data collection consists of eight semistructuredinterviews, four with people hired directly by the company and four that are orhave previously been hired through a staffing company. The study found that the theoretical framework does for the most part explain themotivational behavior of both groups studied, and that the two groups are not alwaysmotivated in the same way. Those hired directly by the company are more interested inreceiving praise, relationships at work, and receiving small tokens of appreciation. The grouphired by staffing companies was more often motivated by an internal drive to satisfythemselves and did not value work relationships to the same extent. The research also showedthat the individual rather than the form of employment plays a big role when it comes to howpeople are motivated. It was also made apparent that education and work situation wereimportant factors influencing the respondent’s motivation