Urban Forest Change Detection in Endayesus Area, Tigray, Ethiopia

Urban forests are one of the crucial ecosystems for sustainability, by which they provide carbon sequestration, microclimate regulation, recreation and other ecosystem services. To attain the benefits and ensure the livability of urban areas communities and governments have been putting efforts to increase coverage of urban forests. Based on that, this paper aimed to detect forest cover change and contribution of forestry practices in enhancing forest cover of Endayesus urban forest area. Aerial photos were obtained from Ethiopian mapping agency and planning office of Mekele city. Other data were collected from randomly selected 196 sample households and purposively selected 20 officials using questionnaire and interview checklists. Descriptive statistics, SPSS and GIS software were used for analysis and generating figurative and spatial outputs. The study confirmed forest cover in Endayesus increased by 1387.43% from 1965 to 2009. However, existence of bare and bush land use types exist substantially. Exclosing the catchment, plantations, public education and tree management activities contributed in improving forest cover of the area. There should have to be land cover/use plan prepared in a way to maximize the benefits of urban forests within the area based on established multiple criteria. In addition, further research is needed in modeling the possible damage to Mekele city under vegetated and non-vegetated scenarios of Endayesus area in different climatic conditions. Keywords: urban forest cover, vegetation cover and urban forestry activities DOI: 10.7176/JRDM/83-01 Publication date:March 31st 202

Modeling impacts of climate change on the geographic distribution and abundances of Tamarindus indica in Tigray region, Ethiopia

Tamarindus indica is a multipurpose dry land species in sub-Saharan that is traditionally used to build resilience into the farming system. The species is highly threatened and listed on the IUCN Red List. However, information on how climatic condition locally influences its ecological distribution is limited. This study investigates the current and future suitable habitat for the species in the Tigray region, in northern Ethiopia. A total of 220 species presence points and the number of T. indica within a 50 m × 50 m plot were collected. In addition, 19 bioclimatic variables, 3 topographic variables and soil data were used to model the impact of future climate conditions under two Representative Concentration Path Ways (RCP4.5 and RCP 8.5). MaxEnt-v-3.3.3 k, Diva-GIS-7.5, and GIS10.6 were used to model the current and future distribution. SPSSv-26 was also utilized to analyze the relationship between the species’ abundance and environmental variables. Results showed that the environmental variables determining most for the distribution of T. indica were mean diurnal range (Bio2 (56.9%)); temperature seasonality (Bio4 (10.3%)) and temperature annual range (Bio7 (9.2%)). The model suggested that the current distribution of T. indica covers an area of 9209 km2 (14.04%). This would have increased to 29,363 km2 (44.78%) and 11,046 km2 (16.85%) by 2070 under RCP4.5 and RCP8.5, respectively. Compared to the high-impact areas, new gains of suitable areas (net 25,081 km2) for the future distribution of the species were predicted in 2070-RCP4.5. Altitude, rainfall, temperature, silt contents of soils and soil pH have significant contributions (P-value<0.05) to the abundance of T. indica. However, altitude has a negative relationship with the abundance of T. indica. Additional studies to understand population trends and other threats are recommended

First Age-Estimation Model for Dracaena ombet and Dracaena draco subsp. caboverdeana

Research Highlights: The first model for crown age estimation was developed for Dracaena ombet Heuglin ex Kotschy and Peyr. and D. draco subsp. caboverdeana Marrero Rodr. and R. Almeida. Background and Objectives: Dracaena species are monocotyledon trees without annual tree rings. Most arborescent dragon tree species are endangered; thus, it is important to determine the age structures of these populations for proper conservation management strategies, and for modelling of population trends. For these reasons, it is necessary to develop a methodology of crown age estimation. Materials and Methods: Field data were collected in the Desa&rsquo;a Forest (Ethiopia) and in Santo Ant&atilde;o (Cape Verde Islands). Trees within each age class, as expressed by the number of branch orders, were measured. The diameter at breast height, tree height, stem height, number of branch orders, number of all leaf rosettes and number of flowering leaf rosettes within the crown were recorded for each sampled tree. The flowering probabilities were counted as input data for the model used. Results: The duration of the interval between flowering events was 5.23 years for D. ombet and 4.94 years for D. draco subsp. caboverdeana. The crown of the oldest tree of D. ombet with 18 branch orders was estimated to be 94.2 years old, and the crown of the oldest tree of D. draco subsp. caboverdeana with 22 branch orders was estimated to be 108.6 years old

Nanomaterial-based optical colorimetric sensors for rapid monitoring of inorganic arsenic species: a review

Abstract Health concerns about the toxicity of arsenic compounds have therefore encouraged the development of new analytical tools for quick monitoring of arsenic in real samples with improved sensitivity, selectivity, and reliability. An overview of advanced optical colorimetric sensor techniques for real-time monitoring of inorganic arsenic species in the environment is given in this review paper. Herein, several advanced optical colorimetric sensor techniques for arsenite (As+3) and arsenate (As+5) based on doping chromogenic dyes/reagents, biomolecule-modified nanomaterials, and arsenic-binding ligand tethered nanomaterials are introduced and discussed. This review also highlights the benefits and limitations of the colorimetric sensor for arsenic species. Finally, prospects and future developments of an optical colorimetric sensor for arsenic species are also proposed. For future study in this sector, particularly for field application, authors recommend this review paper will be helpful for readers to understand the design principles and their corresponding sensing mechanisms of various arsenic optical colorimetric sensors