We introduce a new method to study the velocity distribution of galaxy systems, the Hellinger Distance (HD) -designed for detecting departures from a Gaussian velocity distribution. Testing different approaches to measure normality of a distribution, we conclude that HD is the least vulnerable method to type I and II statistical errors. We define a relaxed galactic system as the one with unimodal velocity distribution and a normality deviation below a critical value (HD<0.05). In this work, we study the gaussian nature of the velocity distribution of the Berlind group sample, and of the FoF groups from the Millennium simulation. For the Berlind group sample (z < 0.1), 67% of the systems are classified as relaxed, while for the Millennium sample we find 63% (z = 0). We verify that in multimodal groups the average mass of modes in high multiplicity (N 20) systems are significantly larger than in low multiplicity ones (N < 20), suggesting that groups experience a mass growth at an increasing virialization rate towards z=0, with larger systems accreting more massive subunits. We also investigate the connection between galaxy properties ([Fe/H], Age, eClass, g-r, R petro and µ petro ) and the gaussianity of the velocity distribution of the groups. Bright galaxies (M r -20.7) residing in the inner and outer regions of groups, do not show significant differences in the listed quantities regardless if the group has a Gaussian (G) or a Non-Gaussian (NG) velocity distribution. However, the situation is significantly different when we examine the faint galaxies (-20.7
-(Species accumulation curve and sampling sufficiency in tropical forests). The use of the species-area relationship, or the accumulation species curve, to determine sampling sufficiency in phytosociological studies is a current technique, despite of being a controversial issue. The definition of an optimum sample size is based on the idea that the larger the sample size, the greater the number of species in the sample, but the rate of increase becomes progressively smaller so the curve tends to a flat line. The point where the curve becomes horizontal is the minimal area to represent the plant community: the sampling sufficiency. This concept assumes that the plant community is a spacially discrete entity with fixed species composition. In tropical forests, the identification of communities boundaries is particularly difficult and, due to their high species richness, the species accumulation curves do not become flat, even with large sample sizes. The species accumulation curve is unsuitable to determine optimum sample size in tropical forests because these curves do not behave as expected, futhermore the concept of sampling sufficiency itself rests upon a problematic definition of plant community.Keywords -phytosociology, sampling sufficiency, species-accumulation curve, species-area relation RESUMO -(Curva de acumulação de espécies e suficiência amostral em florestas tropicais). O uso da relação espécie-área, ou curva de acumulação de espécies, para determinar a suficiência amostral em estudos fitossociológicos é uma técnica usual, porém controversa. A definição de um tamanho ótimo de amostra está baseado na idéia de que quanto maior o tamanho da amostra, maior o número de espécies que será encontrado, mas a uma taxa decrescente, até o ponto em que a curva estabiliza e torna-se horizontal. Esse ponto seria a área mínima necessária para representar a comunidade. Entretanto, esse conceito assume que a comunidade vegetal é uma entidade espacialmente discreta com composição de espécies fixa e definida. Em florestas tropicais, por sua vez, a definição dos limites das comunidades torna-se particularmente difícil e, devido à alta riqueza de espécies, a curva não apresenta estabilização mesmo com grandes tamanhos de amostra. Assim, a curva de acumulação de espécies é inapropriada como técnica de determinação do tamanho ótimo de amostra em florestas tropicais, por não apresentar o comportamento esperado. Além disso, o conceito de suficiência amostral em si está baseado numa definição problemática de comunidade vegetal.Palavras-chave -curva de acumulação de espécies, fitossociologia, relação espécie-área, suficiência amostral IntroduçãoA suficiência amostral é um conceito quantitativo (ou quasi-quantitativo) utilizado em estudos fitossociológicos para informar se a amostra utilizada é "representativa" da comunidade vegetal em estudo. A idéia de representatividade nesse caso está relacionada à indicação de que a composição florística e a densidade de árvores
5Autor para correspondência: talita_fontoura@uol.com.br RESUMO (Epífitas da floresta seca da Reserva Ecológica Estadual de Jacarepiá, sudeste do Brasil: relações com a comunidade arbórea) Investigamos a vegetação arbórea e a comunidade epífita da floresta seca para responder às seguintes perguntas: i) como a abundância e riqueza de epífitas ocorrem sobre os indivíduos das espécies arbóreas? ii) a abundância de forófitos depende do número de indivíduos das espécies arbóreas? iii) a abundância e riqueza de epífitas dependem do número e tamanho dos forófitos? iv) espécies arbóreas são selecionadas por espécies epifíticas? Nesta floresta, as espécies arbóreas mais abundantes é que hospedam a maioria das epífitas. Quatorze espécies arbóreas foram especialmente propensas a apresentar muitos grupos epifíticos e nove propícias a possuir várias espécies de epífitas mas não em alta abundância. O número de indivíduos arbóreos foi um bom parâmetro para estimar a abundância de forófitos e seu número foi considerado um bom parâmetro para estimar a riqueza de epífitas a ocorrerem nesta floresta seca. Quatro espécies arbóreas foram especialmente preferidas pelas duas espécies epífitas de maior abundância e freqüência na área, onde ocorreram com alta abundância. Entretanto, não houve seletividade de nenhuma espécie arbórea por epífitas raras que ocorreram na área. Palavras-chave : mata atlântica, restinga, comensalismo, redes de interação. ABSTRACT(Epiphytes from the dry forest of the Jacarepiá State Ecological Reserve, southeastern Brazil: interactions with the arboreal community) We investigated the arboreal vegetation and epiphytic community of a 'restinga' dry forest to answer the following questions: i) how does epiphyte abundance and richness occur on arboreal species? ii) does phorophyte abundance depend on the abundance of tree species? iii) does epiphyte abundance and richness depend on the size and abundance of phorophytes? iv) are arboreal species selected by epiphyte species? The most abundant arboreal species host most of the epiphytes. Fourteen arboreal species were especially prone to host ing many epiphyte groups and nine arboreal species were especially prone to hosting only high epiphyte richness. The abundance of arboreal species was a good surrogate to predict the number of phorophytes, and the number of phorophytes was a good surrogate to predict epiphyte abundance and epiphyte richness. Four arboreal species were especially preferred by the most abundant epiphyte species. Nevertheless, no rare epiphyte species had high abundance on any tree species.
The effectiveness of eight spectral reflectance indices for estimating chlorophyll (Chl) content in leaves of Eugenia uniflora L., a tropical tree species widely distributed throughout the world and a key species for ecosystem restoration projects, was evaluated. Spectral reflectance indices were tested using sun and shade leaves with a broad variation in leaf mass per area (LMA). Shortly after plants were exposed to chilling temperatures, there was a dramatic visible change in some sun leaves from green to red. Prior to testing Chl-related reflectance indices, the green and red leaves were separated according to the anthocyanin reflectance index (ARI). Slightly green to dark green leaves corresponded to an ARI value less than 0.11 (n = 107), whereas slightly red to red leaves corresponded to an ARI value greater than 0.11 (n = 35). To estimate leaf Chl, two simple reflectance indices (SR 680 and SR 705 ), two normalized difference indices (ND 680 and ND 705 ), two modified reflectance indices (mSR 705 and mND 705 ), a modified Chl absorption ratio index (mCARI 705 ) and an index insensitive to the presence of anthocyanins (CI re ) were evaluated. Good estimates of leaf Chl content were obtained using the reflectance indices tested regardless of the presence of anthocyanins and changes in LMA. Based on the coefficients of determination (r 2 ) and the root mean square errors (RMS c ) the best results were obtained with reflectance indices measured at wavelengths of 750 and 705 nm. Considering the performance of the models the best reflectance indices to estimate Chl contents in E. uniflora leaves with a broad variation in LMA and anthocyanin contents was SR 705 and mCARI 705 .
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.