ORCID Profile
0000-0002-7990-6715
Current Organisation
Universidade de Brasília
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Publisher: MDPI AG
Date: 28-04-2023
DOI: 10.3390/RS15092342
Abstract: Woody plant encroachment in grassy ecosystems is a widely reported phenomenon associated with negative impacts on ecosystem functions. Most studies of this phenomenon have been carried out in arid and semi-arid grasslands. Therefore, studies in tropical regions, particularly savannas, which are composed of grassland and woodland mosaics, are needed. Our objective was to evaluate the accuracy of woody encroachment classification in the Brazilian Cerrado, a tropical savanna. We acquired dry and wet season unmanned aerial vehicle (UAV) images using RGB and multispectral cameras that were processed by the support vector machine (SVM), decision tree (DT), and random forest (RF) classifiers. We also compared two validation methods: the orthomosaic and in situ methods. We targeted two native woody species: Baccharis retusa and Trembleya parviflora. Identification of these two species was statistically (p 0.05) most accurate in the wet season RGB images classified by the RF algorithm, with an overall accuracy (OA) of 92.7%. Relating to validation assessments, the in situ method was more susceptible to underfitting scenarios, especially using an RF classifier. The OA was higher in grassland than in woodland formations. Our results show that woody encroachment classification in a tropical savanna is possible using UAV images and field surveys and is suggested to be conducted during the wet season. It is challenging to classify UAV images in highly erse ecosystems such as the Cerrado therefore, whenever possible, researchers should use multiple accuracy assessment methods. In the case of using in situ accuracy assessment, we suggest a minimum of 40 training s les per class and to use multiple classifiers (e.g., RF and DT). Our findings contribute to the generation of tools that optimize time and cost for the monitoring and management of woody encroachment in tropical savannas.
Publisher: FapUNIFESP (SciELO)
Date: 2019
Publisher: Springer Science and Business Media LLC
Date: 22-03-2022
Publisher: CSIRO Publishing
Date: 2016
DOI: 10.1071/WF16085
Abstract: Open savannas and wet grasslands are present under the same seasonal macro-climate in central Brazil. However, in open savannas, temperatures during fires are higher than in wet grasslands. Grasses dominate both ecosystems and exhibit large variation in seed dormancy. We hypothesise that seeds of grass species from open savannas are more tolerant to heating than those of wet grasslands. Also, assuming that dormant seeds remain longer in the soil than non-dormant seeds – thus being more likely to burn – we expect that dormant seeds are more tolerant to heating than non-dormant seeds. We tested the effects of heating at 80 and 110°C for 2.5 and 5.0 min on the survival of seeds of 14 species, seven from each community, containing dormant and non-dormant species. Seeds of most species survived at 80°C, but seeds from open savannas maintained greater survival for 5 min than seeds from wet grasslands. Seeds of most species died at 110°C, but dormant seeds survived more than non-dormant seeds. We conclude that species with seed dormancy experience selection for covarying characteristics that allow tolerance to heating in hotter fires. Our findings suggest that both seed dormancy and habitat-specific fire temperatures may contribute to the evolution of seed fire tolerance in Neotropical savannas.
Publisher: Universidad Federal de Santa Maria
Date: 04-06-2020
Abstract: Dominância de espécies exóticas invasoras e compactação de substratos minerados são filtros ecológicos que geralmente restringem o estabelecimento e o crescimento de espécies nativas de plantas em jazidas mineradas. O entendimento dos mecanismos de atuação e a eliminação desses filtros são de grande importância para a restauração ecológica de ecossistemas. Visando melhorar a condição ecológica de uma jazida tratada com lodo de esgoto dominada por Urochloa brizantha (Braquiarão) e com a superfície compactada, dois tratamentos foram aplicados em parcelas experimentais para se analisarem os efeitos da atenuação desses filtros sobre o recrutamento de plantas: uso de herbicida para redução da dominância de U. brizantha e escarificação mecanizada da superfície compactada, aplicados in idualmente e combinados. A atenuação da dominância de U. brizanthae a descompactação da superfície minerada fomentaram o recrutamento de 29 espécies de plantas, 66% das quais descritas como espécies exóticas e invasoras do Cerrado. Os tratamentos aplicados in idualmente ou combinados resultaram na formação de biocenoses mais ricas em espécies e mais bio ersas em comparação às parcelas usadas como controle. A cobertura de U. brizantha se recuperou até o final do período chuvoso nas parcelas que receberam os dois tratamentos, mas o recrutamento de espécies que permaneceram sobre a cobertura de U. brizantha melhorou a condição ecológica nas parcelas experimentais.
No related grants have been discovered for Cassia Beatriz Rodrigues Munhoz.