Living and Responding to Climatic Stresses: Perspectives from Smallholder Farmers in Hanang' District, Tanzania.

This study sought to assess how smallholder farmers have been living and responding to impacts of climate change in Hanang' District, Tanzania. Qualitative and quantitative data were collected using key informant interviews, household surveys, focus group discussions (FGDs) and field observations. Quantitative data from the questionnaire survey were analyzed using Statistical Package for Social Sciences (SPSS), whilst, qualitative data were exposed to content analysis. Rainfall and temperature trends were analyzed using Microsoft Excel and the significance of the trends determined using Mann-Kendall and CUSUM analysis. Most respondents (78%) revealed decreased rainfall amounts and changed onset, and 94% reported increased temperature. Farmers disclosed that droughts and floods are major climatic stresses in the area; this was substantiated by observed increasing and decreasing temperature and rainfall trends respectively. This corroborated with most respondents who perceived decreased rainfall amounts and changed onset, and reported increased temperature levels. Response strategies include crop diversification and drought-resistant crop varieties, migration, abandoning some crops, and short-cycle crops. However, smallholder farmers have been failing to effectively address climatic challenges. We argue that they are still heavily reliant on social, economic, and policy support to improve their adaptive capacity, particularly, transformative responses.

Seasonal variability of forest sensitivity to heat and drought stresses: A synthesis based on carbon fluxes from North American forest ecosystems.

Climate extremes such as heat waves and droughts are projected to occur more frequently with increasing temperature and an intensified hydrological cycle. It is important to understand and quantify how forest carbon fluxes respond to heat and drought stress. In this study, we developed a series of daily indices of sensitivity to heat and drought stress as indicated by air temperature (Ta ) and evaporative fraction (EF). Using normalized daily carbon fluxes from the FLUXNET Network for 34 forest sites in North America, the seasonal pattern of sensitivities of net ecosystem productivity (NEP), gross ecosystem productivity (GEP) and ecosystem respiration (RE) in response to Ta and EF anomalies were compared for different forest types. The results showed that warm temperatures in spring had a positive effect on NEP in conifer forests but a negative impact in deciduous forests. GEP in conifer forests increased with higher temperature anomalies in spring but decreased in summer. The drought-induced decrease in NEP, which mostly occurred in the deciduous forests, was mostly driven by the reduction in GEP. In conifer forests, drought had a similar dampening effect on both GEP and RE, therefore leading to a neutral NEP response. The NEP sensitivity to Ta anomalies increased with increasing mean annual temperature. Drier sites were less sensitive to drought stress in summer. Natural forests with older stand age tended to be more resilient to the climate stresses compared to managed younger forests. The results of the Classification and Regression Tree analysis showed that seasons and ecosystem productivity were the most powerful variables in explaining the variation of forest sensitivity to heat and drought stress. Our results implied that the magnitude and direction of carbon flux changes in response to climate extremes are highly dependent on the seasonal dynamics of forests and the timing of the climate extremes.

Plant growth-promoting bacteria in metal-contaminated soil: Current perspectives on remediation mechanisms.

Heavy metal contamination in soils endangers humans and the biosphere by reducing agricultural yield and negatively impacting ecosystem health. In recent decades, this issue has been addressed and partially remedied through the use of "green technology," which employs metal-tolerant plants to clean up polluted soils. Furthermore, the global climate change enhances the negative effects of climatic stressors (particularly drought, salinity, and extreme temperatures), thus reducing the growth and metal accumulation capacity of remediating plants. Plant growth-promoting bacteria (PGPB) have been widely introduced into plants to improve agricultural productivity or the efficiency of phytoremediation of metal-contaminated soils via various mechanisms, including nitrogen fixation, phosphate solubilization, phytohormone production, and biological control. The use of metal-tolerant plants, as well as PGPB inoculants, should hasten the process of moving this technology from the laboratory to the field. Hence, it is critical to understand how PGPB ameliorate environmental stress and metal toxicity while also inducing plant tolerance, as well as the mechanisms involved in such actions. This review attempts to compile the scientific evidence on this topic, with a special emphasis on the mechanism of PGPB involved in the metal bioremediation process [plant growth promotion and metal detoxification/(im)mobilization/bioaccumulation/transformation/translocation] and deciphering combined stress (metal and climatic stresses) tolerance.