Soil Carbon Dynamics Under Changing Climate A Research Transition from Absolute to Relative Roles of Inorganic Nitrogen Pools and Associated Microbial Processes:A Review

It is globally accepted that soil carbon （C） dynamics are at the core of interlinked environmental problems, deteriorating soil quality and changing climate. Its management remains a complex enigma for the scientific community due to its intricate relationship with soil nitrogen （N） availability and moisture-temperature interactions. This article reviews the management aspects of soil C dynamics in light of recent advances, particularly in relation to the availability of inorganic N pools and associated microbial processes under changing climate. Globally, drastic alterations in soil C dynamics under changing land use and management practices have been primarily attributed to the variation in soil N availability, resulting in a higher decomposition rate and a considerable decline in soil organic C （SOC） levels due to increased soil CO2 emissions, degraded soil quality, and increased atmospheric CO2 concentrations, leading to climate warming. Predicted climate warming is proposed to enhance SOC decomposition, which may further increase soil N availability, leading to higher soil CO2 effiux. However, a literature survey revealed that soil may also act as a potential C sink, if we could manage soil inorganic N pools and link microbial processes properly. Studies also indicated that the relative, rather than the absolute, availability of inorganic N pools might be of key importance under changing climate, as these N pools are variably affected by moisture-temperature interactions, and they have variable impacts on SOC turnover. Therefore, multi-factorial studies are required to understand how the relative availability of inorganic N pools and associated microbial processes may determine SOC dynamics for improved soil C management.

Effects of light availability on leaf attributes and seedling growth of four tree species in tropical dry forest

Background:In tropical dry forests,variation in understory light availability due to season and canopy tree density could be a governing factor in establishment and growth of tree seedlings.Species with varying life history traits are expected to respond differentially to such heterogeneity.We investigated the response of seedlings of four tree species in a tropical day forest in relation to spatiotemporal variability of light.We attempt to explore the role of leaf attributes in explaining intra-and inter-specific variations in relative growth rate.Four study sites,each with three contrasting canopy conditions,were selected along a soil moisture gradient.Seedlings of four tree species(viz.,Acacia catechu,Bridelia retusa,Lagerstroemia parviflora,and Shorea robusta),varying in life history traits,were monitored for seasonal variations in growth traits across canopy condition and sites for 2 years.Results:We observed a larger variation in leaf attributes for pioneer species.A.catechu showed highest mean values for leaf dry matter content,leaf nitrogen concentration,leaf phosphorus concentration,net stomatal conductance,net photosynthetic rate,and relative growth rate in high light conditions.S.robusta and B.retusa demonstrated highest mean values for all the leaf attributes(except leaf dry matter content)in low light conditions.However,intermediate values for leaf attributes were observed in L.parviflora which preferred moderate light conditions.Conclusions:Seasonal variations in light availability at the forest floor appear to play an important role in the establishment and growth of tree seedlings in seasonal dry forests.Leaf attributes can be used to explain intra-and inter-specific variation in response to light availability.Leaf attributes in combinations can be used to predict relative growth rate of tree species in tropical dry environment,which apart from soil moisture is also determined by light availability due to seasonal changes and canopy tree density.