Search Results (13)

Against the backdrop of intensified global climate change, the frequency and intensity of extreme weather events in mainland China continue to rise due to its unique topography and complex climate types. In-depth research on the trends and impacts of climate extremes can help develop effective adaptation and mitigation strategies to protect the environment and enhance social resilience. In this research, temperature data from 2029 meteorological stations for the period 1961–2021 were used to study 15 extreme temperature indices and 3 extreme composite temperature indices. Linear propensity estimation and the Mann–Kendall test were applied to analyze the spatial and temporal variations in extreme temperatures in China, and Pearson’s correlation analysis was used to reveal the relationship between these indices and atmospheric circulation. The results show that in the past 60 years, the extreme temperature index in China has shown a trend of decreasing low-temperature events and increasing high-temperature events; in particular, the increase in warm nights is significantly higher than that of warm days. In terms of spatial distribution, daily maximum temperature less than the 10th percentile (TX10P) and daily minimum temperature greater than the 90th percentile (TN90P) increased significantly in the warm temperate sub-humid (WTSH) region, north subtropical humid (NSH) region, and marginal tropical humid (MTH) region, whereas frost days (FD0) and diurnal temperature range (DTR) decreased significantly. In the extreme composite temperature index, extreme temperature range (ETR) showed a downward trend, while compound heatwave (CHW) and compound heatwave and relative humidity (CHW-RH20) increased, with the latter mainly concentrated in the WTSH and NSH regions. Correlation analysis with climate oscillation shows that Arctic Oscillation (AO), Atlantic Multiannual Oscillation (AMO), and El Niño–Southern Oscillation (ENSO) are positively correlated with extremely high temperatures, whereas North Atlantic Oscillation (NAO) and Pacific Decadal Oscillation (PDO) are negatively correlated. Full article

Archaea and bacteria communities play pivotal roles in tropical forest ecosystems’ functioning, especially nutrient cycling, plant phenology, and health. The objective of this study was to explore the diversity of archaeal and bacterial communities in forest soil ecosystem of Côte d’Ivoire and to identify abiotic factors that influence their composition. Using high-throughput amplicon sequencing targeting the V4V5 hypervariable region of the 16S ribosomal RNA gene, we analyzed 22 soil samples taken from the 2 main forest areas of Côte d’Ivoire, namely the semi-deciduous moist forest and the evergreen moist forest, both of which are located in the humid and sub-humid areas of the country. The analysis revealed that the biodiversity at the phyla level was congruent with previous studies. Richness and Shannon diversity indices revealed the dominance of bacteria over archaea in all studied soils. Moreover, the predominant bacterial community consisted of Proteobacteria (29.8%), Acidobacteria (15.5%), and Actinobacteria (14.2%), while the archaeal community was dominated by Thaumarchaeota (1.93%). However, at the genus level, patterns emerged. The most abundant and ubiquitous members at the genus level included Bradyrhizobium, Rhodoplanes, Bacillus (bacteria), and Nitrosophaera (archaea). While bacterial core microbiome members were found in almost all soils, Nitrososphaera genus were selective to sub-humid bioclimate and cropland land use. These patterns were correlated to the soils’ physicochemical characteristics, bioclimate, and land use. This study sheds light on the intricate relationships between abiotic factors and microbial communities in Côte d’Ivoire’s forest soils and helps to identify keys species for future soil management. Full article

Abiotic stress is a major cause of the declining crop yield worldwide, especially in tropical agricultural areas. Meeting the global food demand has become a serious challenge, especially in tropical areas, because of soil acidity, Al and Fe toxicity, drought and heat stress, and climate change. In this article, we reviewed several research and review papers from Google Scholar to list the different solutions available for the mitigation of abiotic stress, especially in tropical regions where several major crops, such as maize, sorghum, wheat, rice, soybean, and millet, are affected by abiotic stress and fertilizer input. In particular, Sub-Saharan Africa (SSA) has been affected by the low use of fertilizers owing to their high cost. Therefore, soil and plant researchers and farmers have developed many techniques to mitigate the effects of stress and improve the crop yield based on the agroecological zone and crop type. Nutrient management using chemical fertilizers alone or in combination with organic crops is a strategy recommended to cope with abiotic stress and increase the crop yield, particularly in developing countries. Notably, integrated soil fertility management has been effective in semi-arid areas under drought and heat stress and in subhumid and humid areas with high soil acidity and Fe toxicity in Africa. Recent advances in the molecular physiology of various crops considered a staple food in SSA have facilitated the breeding of transgenic tolerant plants with high yield. However, the feasibility and implementation of this technique in the African continent and most tropical developing countries are major issues that can be solved via adequate subsidies and support to farmers. This review can aid in the development of novel strategies to decrease hunger and food insecurity in SSA. Full article

Ethiopia is a developing nation that could highly benefit from securing food via improved smallholder poultry farming. To support farmer and breeding decisions regarding which chicken strain to use in which Ethiopian environment, G*E analyses for body weight (BW) of growing male and female chickens were conducted. Research questions were (1) if a G*E is present for BW and (2) which strain performs best in which environment in terms of predicted BW. Analyses were performed using predicted BW at four different ages (90, 120, 150, and 180 days) of five strains (Horro, Koekoek, Kuroiler, Sasso-Rhode Island Red (S-RIR), and Sasso) tested in five Ethiopian regions (Addis Ababa, Amhara, Oromia, South Region, and Tigray) that are part of three Agro-Ecological Zones (AEZ) (cool humid, cool sub-humid, and warm semi-arid). The indigenous Horro strain was used as a control group to compare four other introduced tropically adapted strains. The dataset consisted of 999 female and 989 male farm-average BW measurements. G*E was strongly present (p < 0.001) for all combinations of strain and region analyzed. In line with previous research, Sasso was shown to have the highest predicted BW, especially at an early age, followed by Kuroiler. Horro had the lowest predicted BW at most ages and in most regions, potentially due to its young breeding program. The highest predicted BW were observed in Tigray, Oromia, and Amhara regions, which are in the main part of the cool sub-humid AEZ. Full article

Land use of the sub-Himalayan region is not that intensive like the intensively land-managed region of Punjab, India. Land resources of the sub-Himalayas must be managed effectively for sustainable development by preparing carbon inventories and data banks. Such macro-level studies have not been conducted yet in the present study area, and thus were conducted to suggest sustainable land use management options. To achieve the present study’s desired goal, 33 tree-based land uses were identified from forested and agricultural landscapes of the sub-humid tropical region of West Bengal, India. Stratified random nested quadrat sampling was adopted for the study. The SOC, biomass, and carbon accumulation significantly differed. Mixed forests had the highest soil primary nutrients and carbon stock. Positive correlations were observed between SOC, total standing biomass, litter production, and ecosystem carbon. The sequence of land uses based on carbon stock was mixed-species forest > sole tree species stands in a forest landscape > tea plantations > homegardens. This baseline information can be used for developing prediction models for future interventions towards sustainable land management. The study, however, could not estimate the carbon fluxes in and out of the systems due to the absence of detailed land use land-cover databases. Full article

Understanding the relationship between topography, hydrological processes, and runoff source areas is essential in engineering design, such as predicting floods and implementing effective watershed management practices. This relationship is not well defined in the highlands with a monsoon climate and needs further study. The objective of this study is to relate topographic position and hydrological response in tropical highlands. The research was conducted in the Debre Mawi watershed in the northwest sub-humid Ethiopian highlands. In the monsoon rain phase of 2017 and 2018, groundwater depth, infiltration rate, and surface runoff were monitored at the upslope, midslope, and downslope positions. Surface runoff rates were measured in farmer fields through distributed V-notch weirs as estimates of positional runoff. Average water table depths were 30 cm deep in the downslope regions and 95 cm in the upslope position. The water table depth affected the steady-state infiltration rate in the rain phase. It was high upslope (350 mm h⁻¹), low midslope (49 mm h⁻¹), and zero downslope. In 2017, the average runoff coefficients were 0.29 for the upslope and midslope and 0.73 downslope. Thus, topographic position affects all aspects of the watershed hydrology in the humid highlands and is critical in determining runoff response. Full article

Morphology and forage productivity of 25 Tripsacum spp. materials were characterized under tropical conditions in Nayarit, Mexico. Treatments included: Tripsacum latifolium, T. australe var. Australe, Tripsacum spp., T. dactyloides (cv. Meridionale and Hispidum), T. bravum, T. manisuroides, T. zopilotense, T. andersonii, T. lanceolatum, T. floridanum, T. laxum, T. cundinamarceae, T. intermedium, T. maizar, and T. peruvianum. Five in row equidistant plants (1.5 m) and three rows (replicates) per species, were evaluated and fertilized using 100-60-00 (N-P-K units) per hectare per year. Variables included: plant mean height, leading flowered stem’s height, plant crown circumference, basal cover, tillers per crown, forage yield and growth rates. Data was analyzed through a completely randomized design including 25 treatments (species, varieties, and/or ecotypes) and LSD tests for mean separation. Differences (p < 0.01) were observed among morphological, productive variables, and species. Outstanding material included T. latifolium and T. australe (8.3 and 5.6 kg DM per plant). Forage production ranged (p < 0.01) from 22% to 1405%, in comparison with the local ecotype T. dactyloides. Morphology and forage productivity within Tripsacum is highly variable, according to the genetic diversity available within this native to Mexico genus, suggesting that Tripsacum agamic complex presents enormous forage production potential for its promotion under grazing for rain-fed systems. Full article

The sub-humid native rainforest in Yucatan is one of the most endangered in Mexico. Cattle production is one of the main causes of land use change and silvopastoral systems are a feasible alternative. This work compares the sustainable performance of silvopastoral (native and intensive) and monoculture cattle farms in the state of Yucatan using the Sustainability Assessment for Food and Agriculture (SAFA) framework. Questionnaires and semi-structured interviews were applied in 9 farms. Responses were fed to the SAFA Tool to obtain sustainability polygons. Percentages of SAFA themes positively and negatively valuated were calculated. Native farms had positive ratings for Participation, Land, Biodiversity and Cultural Diversity, whereas intensive excelled on Holistic Management. Native farms had limited ratings for Decent Livelihood. Native farms (and one intensive silvopastoral farm) had the highest percentages of themes positively valuated compared to monocultures (and one intensive silvopastoral farm), which scored the lowest. Positive evaluations identified native systems as an option for sustainable production; however, areas of opportunity in all farms were discovered. This is the first comparative study using SAFA to evaluate differences in farming systems in the Mexican tropics, providing valuable information to generate policies and incentives on sustainable livestock production, as well as for improving evaluation tools for local application. Full article

Moisture anomaly conditions within humid and subhumid tropics that are associated with different types of El Niño and La Niña phenomena are described and analyzed with a focus on their spatial distribution and seasonal variability. Five dryness indices (Keetch–Byram Drought Index, Weighted Anomaly Standardized Precipitation Index, Standardized Precipitation Index, Palmer Drought Severity Index, and Percent of Normal Precipitation) were derived from ECMWF (European Centre for Medium-Range Weather Forecasts) fifth generation reanalysis (ERA5) reanalysis and University Corporation for Atmospheric Research (UCAR) datasets for the period from 1979 to 2019. Cross-correlation analysis was used to evaluate the relationships between the El Niño Southern Oscillation (ENSO) and selected dryness indices. To describe the seasonal variability of the ENSO–surface moisture relationships, the composite maps of dryness indices in different seasons were analyzed. The results showed a significant heterogeneity of the ENSO-induced moisture anomaly conditions both within and across various geographical regions. Four main areas in humid and subhumid tropics with the maximum effects of El Niño/La Niña events on the surface moisture conditions were found: Southeast Asia and Australia, Eastern and South Africa, Northeastern and Eastern South America, and Central America. It was shown that the effects of La Niña were usually opposite to those of El Niño, while the responses to the two types of El Niño differed mostly in the moisture anomaly intensity and its spatial patterns. Full article

Most tropical regions in the world are vulnerable to climate variability, given their dependence on rain-fed agricultural production and limited adaptive capacity owing to socio-economic conditions. The Kalahandi, Bolangir, and Koraput districts of the south-western part of Odisha province of India experience an extreme sub-humid tropical climate. Based on the observed changes in the magnitude and distribution of rainfall and temperature, this study evaluates the potential impact of climate variation on agricultural yield and production in these districts. The study is conducted by taking into account meteorological data like rainfall and temperature from 1980 to 2017 and crop productivity data from 1980–81 to 2016–17. Additionally, climate variability indices like Monsoon Index, Oceanic Nino Index, and NINO-3 and NINO 3.4 are used. To analyse the data, various statistical techniques like correlation and multiple linear regression are used. The amount of monsoon rainfall is found to have a significant impact on crop productivity, compared to temperature, in the study area, and as a result the Monsoon Index has a determining impact on crop yield among various indices. Full article

The tropical multiuse tree Jatropha curcas L. (jatropha) is highly promoted as oilseed crop for biodiesel production and for climate change mitigation, but cultivation practices require further research. The objectives of this study were to assess the effects of varying plant spacings (2.0 m × 4 m compared to 1.5 m × 4 m), crop establishment methods (raising plantlets in a nursery prior to planting to the field compared to direct sowing) and genotypes on seed yield, seed quality and plant height, recorded at a dry-subhumid location in Madagascar (Ihosy) and at a humid location in Cameroon (Batchenga). Averaged across treatment variants and genotypes, seed yield and seed oil content were higher at the dry-subhumid site and in particular the narrower spacing reached higher seed yields per unit area than the wider spacing. At the humid site, plant growth was characterized by strong accumulation of biomass. The establishment method tested at the dry-subhumid site showed no significant differences in the recorded parameters. Our results encourage to re-think common practices in jatropha cultivation and underpin the importance of the correct choice of location, genotype and agronomic practices considering the interactions between all factors. Full article

Understanding the complex diversity of species and their potential uses in traditional agroforestry systems is crucial for enhancing the productivity of tropical systems and ensuring the sustainability of the natural resource base. The aim of this study is the evaluation of the role of home gardens and parklands, which are prominent tropical agroforestry systems, in the conservation and management of biodiversity. Our study quantified and compared the diversity of woody and herbaceous perennial species and their uses in traditional home gardens and parkland agroforestry systems under a sub-humid climate in western Ethiopia. A sociological survey of 130 household respondents revealed 14 different uses of the species, mostly for shade, fuelwood, food, and as traditional medicine. Vegetation inventory showed that the Fisher’s α diversity index and species richness were significantly higher in home gardens (Fisher’s α = 5.28 ± 0.35) than in parklands (Fisher’s α = 1.62 ± 0.18). Both systems were significantly different in species composition (Sørenson’s similarity coefficient = 35%). The differences occurred primarily because of the high intensity of management and the cultivation of exotic tree species in the home gardens, whereas parklands harbored mostly native flora owing to the deliberate retention and assisted regeneration by farmers. In home gardens, Mangifera indica L. was the most important woody species, followed by Cordia africana Lam. and Coffea arabica L. On the other hand, Syzygium guineense Wall. was the most important species in parklands, followed by C. africana and M. indica. The species diversity of agroforestry practices must be further augmented with both indigenous and useful, non-invasive exotic woody and herbaceous species, particularly in parklands that showed lower than expected species diversity compared to home-gardens. Full article

This study was aimed at quantifying soybean (Glycine max) nitrogen fixation under reduced tillage (RT) and conventional tillage (CT) in a tropical Ferralsol of the sub-humid zone of western Kenya, using the isotope ¹⁵N dilution method. Crop residue (CR) management was a superimposed treatment in soybean-maize rotation and intercropping systems. This study quantified N in abscised soybean leaves. Soybean-N derived from the atmosphere (%NDfA) ranged between 41–65%; it was higher (P < 0.05) in RT (55.6%) than in CT (46.6%). Total fixed-N under ‘RT + CR’ was more than in the other treatments by at least 55% in intercropping and 34% in rotation system. Nitrogen fixed in soybean aboveground parts was 26–48 kg N ha⁻¹ with intercropping and 53–82 kg N ha⁻¹ with rotation. Seasonal litter fall contained about 15 kg N ha⁻¹, with 54% NDfA. Annual nitrogen balances with soybean and maize grain removed were better in RT (−9 to −32 kg N ha⁻¹) than in CT (−40 to −60 kg N ha⁻¹). Application of P increased nodule weight (P < 0.05) by 3 to 16 times over the control. Soybean residues should be returned to the field after harvest to reduce soil N mining. We conclude that ‘RT + CR’ increases biological nitrogen fixation in soybean, over CT, and that phosphorus application is needed for better soybean nodulation in western Kenya. Full article