Evaluating the effect of climate change on rice production in Indonesia using multimodelling approach.

Achieving global food security in the face of climate change is a critical challenge, particularly in vulnerable countries like Indonesia. To effectively address this challenge, a systems-based approach utilizing climate-hydrological-crop models has emerged as an integral approach. These models integrate climate, hydrological, and crop components to understand and predict the complex interactions within agricultural systems and their responses to climate variables. By employing this approach, policymakers, researchers, and stakeholders can gain comprehensive insights into the potential consequences of climate change on crop growth, water availability, soil fertility, and overall crop yield. However, challenges exist in the implementation of this approach, including data reliability; scarcity of complete long-term data; lack of experimental information about crop species, especially local varieties; inadequate research resources; lack of expertise concerning modeling approaches; lack of testing; inaccurate testing; calibration; and model uncertainties. Furthermore, to address limitations and challenges in implementing this approach, improving the availability and reliability of data, collection method, and data quality should be conducted to ensure the accuracy of simulation and prediction. Finally, climate-hydrological-crop models, alongside improved data collection and modelling techniques, serve as essential tools for guiding the development of effective adaptation measures to mitigate the impacts of climate change on rice production in Indonesia.

Thermodynamic sensitivity of ammonia oxidizers-driven N2O fluxes under oxic-suboxic realms.

In terrestrial ecosystems, the nitrogen dynamics, including N2O production, are majorly regulated by a complex consortium of microbes favored by different substrates and environmental conditions. To better predict the daily, seasonal and annual variation in N2O fluxes, it is critical to estimate the temperature sensitivity of different microbial groups for N2O fluxes under oxic and suboxic conditions prevalent in soil and wetlands. Here, we studied the temperature sensitivity of two groups of ammonia oxidizers, archaea (AOA) and bacteria (AOB), in relation to N2O fluxes through both nitrification and nitrifier-denitrification pathways across a wide temperature gradient (10-55 °C). Using square root theory (SQRT) and macromolecular rate theory (MMRT) models, we estimated thermodynamic parameters and cardinal temperatures, including maximum temperature sensitivity (TSmax). The distinction between N2O pathways was facilitated by microbial-specific inhibitors (PTIO and C2H2) and controlled oxygen supply environments (oxic: ambient level; and suboxic: ∼4%). We found that nitrification supported by AOA (NtA) and AOB (NtB) dominated N2O production in an oxic climate, while only AOB-supported nitrifier-denitrification (NDB) majorly contributed (>90%) to suboxic N2O budget. The models predicted significantly higher optimum temperature (Topt) and TSmax for NtA and NDB compared to NtB. Intriguingly, both NtB and NDB exhibited significantly wider temperature ranges than NtA. Altogether, our results suggest that temperature and oxygen supply control the dominance of specific AOA- and AOB-supported N2O pathways in soil and sediments. This emergent understanding can potentially contribute toward novel targeted N2O inhibitors for GHG mitigation under global warming.

Soil microbiome feedback to climate change and options for mitigation.

Microbes are a critical component of soil ecosystems, performing crucial functions in biogeochemical cycling, carbon sequestration, and plant health. However, it remains uncertain how their community structure, functioning, and resultant nutrient cycling, including net GHG fluxes, would respond to climate change at different scales. Here, we review global and regional climate change effects on soil microbial community structure and functioning, as well as the climate-microbe feedback and plant-microbe interactions. We also synthesize recent studies on climate change impacts on terrestrial nutrient cycles and GHG fluxes across different climate-sensitive ecosystems. It is generally assumed that climate change factors (e.g., elevated CO2 and temperature) will have varying impacts on the microbial community structure (e.g., fungi-to-bacteria ratio) and their contribution toward nutrient turnover, with potential interactions that may either enhance or mitigate each other's effects. Such climate change responses, however, are difficult to generalize, even within an ecosystem, since they are subjected to not only a strong regional influence of current ambient environmental and edaphic conditions, historical exposure to fluctuations, and time horizon but also to methodological choices (e.g., network construction). Finally, the potential of chemical intrusions and emerging tools, such as genetically engineered plants and microbes, as mitigation strategies against global change impacts, particularly for agroecosystems, is presented. In a rapidly evolving field, this review identifies the knowledge gaps complicating assessments and predictions of microbial climate responses and hindering the development of effective mitigation strategies.

Assessing the influence of environmental niche segregation in ammonia oxidizers on N2O fluxes from soil and sediments.

Understanding the environmental niche segregation of ammonia-oxidizing archaea (AOA) and bacteria (AOB) and its impact on their relative contributions to nitrification and nitrous oxide (N2O) production is essential for predicting N2O dynamics within an ecosystem. Here, we used ammonia oxidizer-specific inhibitors to measure the differential contributions of AOA and AOB to potential ammonia oxidization (PAO) and N2O fluxes over pH (4.0-9.0) and temperature (10-45 °C) gradients in five soils and three wetland sediments. AOA and AOB activities were differentiated using PTIO (2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide), 1-octyne, and acetylene. We used square root growth (SQRT) and macromolecular rate theory (MMRT) models to estimate cardinal temperatures and thermodynamic characteristics for AOA- and AOB-dominated PAO and N2O fluxes. We found that AOA and AOB occupied different niches for PAO, and soil temperature was the major determinant of niche specialization. SQRT and MMRT models predicted a higher optimum temperature for AOA-dominated PAO and N2O fluxes compared with those of AOB. Additionally, PAO was dominated by AOA in acidic conditions, whereas both AOA- and AOB-dominated N2O fluxes decreased with increasing pH. Consequently, net N2O fluxes (AOA and AOB) under acidic conditions were approximately one to three-fold higher than those observed in alkaline conditions. Moreover, structural equation and linear regression modeling confirmed a significant positive correlation (R2 = 0.45, p < 0.01) between PAO and N2O fluxes. Collectively, these results show the influence of ammonia oxidizer responses to temperature and pH on nitrification-driven N2O fluxes, highlighting the potential for mitigating N2O emissions via pH manipulation.

Measuring Responses of Dicyandiamide-, 3,4-Dimethylpyrazole Phosphate-, and Allylthiourea-Induced Nitrification Inhibition to Soil Abiotic and Biotic Factors.

Nitrification inhibitors (NIs) such as dicyandiamide (DCD), 3,4-dimethylpyrazole phosphate (DMPP), and allylthiourea (AT) are commonly used to suppress ammonia oxidization at different time scales varying from a few hours to several months. Although the responses of NIs to edaphic and temperature conditions have been studied, the influence of the aforementioned factors on their inhibitory effect remains unknown. In this study, laboratory-scale experiments were conducted to assess the short-term (24 h) influence of eight abiotic and biotic factors on the inhibitory effects of DCD, DMPP, and AT across six cropped and non-cropped soils at two temperature conditions with three covariates of soil texture. Simultaneously, the dominant contributions of ammonia-oxidizing archaea (AOA) and bacteria (AOB) to potential ammonia oxidization (PAO) were distinguished using the specific inhibitor 2 phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (PTIO). Our results revealed that AT demonstrated a considerably greater inhibitory effect (up to 94.9% for an application rate of 75 mg of NI/kg of dry soil) than DCD and DMPP. The inhibitory effect of AT was considerably affected by the relative proportions of silt, sand, and clay in the soil and total PAO. In contrast to previous studies, the inhibitory effects of all three NIs remained largely unaffected by the landcover type and temperature conditions for the incubation period of 24 h. Furthermore, the efficacy of all three tested NIs was not affected by the differential contributions of AOA and AOB to PAO. Collectively, our results suggested a limited influence of temperature on the inhibitory effects of all three NIs but a moderate dependence of AT on the soil texture and PAO. Our findings can enhance the estimation of the inhibitory effect in soil, and pure cultures targeting the AOA and AOB supported ammonia oxidization and, hence, nitrogen dynamics under NI applications.