Soil Carbon and Nutrient Accumulation under Forest Plantations in Jharkhand State of India

The decrease and degradation of the tropical forests affect not only the production of timber but also the global environment in a large scale. The ability of soil to sustain and its supply of nutrients to a growing forest are controlled by a complex of biogeochemical processes. The purpose of the present study aims to assess the degraded forest fringe areas, to promote plantations of various types and to evaluate their impacts on the soil nutrients and carbon content accumulation. The soil organic carbon (SOC) and nutrient content were evaluated and compared between plantations of mixed native species (MNS), some native tree species as Shorea robusta, Dalbergia sissoo, Dendrocalamus spp., certain agro‐forestry species and some exotic varieties. The impacts of the plantations on the SOC and the nutrients were firstly analyzed through comprehensive chemical analyses and the results were compared with the soil samples collected prior to plantation forestry. Significant changes were observed in SOC content, in nutrients, and in amounts of exchangeable cations. Soil carbon levels were highest under the MNS, Dendrocalamus and Tectona grandis stands and lowest under D. sissoo and Terminalia arjuna. Total N showed highest levels under Dendrocalamus and Pongamia pinnata and significantly higher in stands of native species; lowest total N level was observed in D. sissoo plantations. The C/N ratios of the soil varied between 9.2 and 13.5 among the exchangeable cations. Ca²⁺ recorded the maximum levels and Na⁺ showed the lowest levels.     

Geochemical characteristics of Tukureswari and Barbhita granitoid in Goalpara district,Assam

Late intrusive Tukureswari granitoids (TKG) and the Barbhita granitoids (BBG) of Goalpara district in western Assam constitute an important component of the continental crust of the Shillong Plateau. Thus, the geochemical study of these two granitoids involving their origin, classification and petrogenetic significance would be a contribution towards a better understanding of the evolution of continental crust of the Shillong Plateau.The major oxide and trace element geochemistry reveals several genetic issues on these two granitoids. The I-type affinity of the TKG is indicated from the geochemical features such as high TiO₂, P₂O₅ and K₂O contents, low normative corundum (< 1%), high Na₂O/K₂O ratios, and low concentrations of Ni, Co and Cr. Further, enriched LREE-LILE and HFSE depletion, as well as the normal calc-alkaline nature of arc affinity (e.g., enhanced LILE abundance and low HFSE/LILE ratios) of the TKG indicate subduction-related magmatism. TheTKG are also categorized as a deep-level pluton, being enriched in LREE and depleted in total REE and HFSE (Y, Nb, Ta, Zr, Hf). The high La/Nb ratio (1.9–8.6), negative Nb and Ti anomalies also suggest orogenic related magmatism.On the other hand, the geochemistry of the BBG reveal a high Niggli Si and Mg values, slightly high normative corundum values (2.16–3.41), high Th/Ta, Y/Nb, La/Nb, K₂O/Na₂O, and Rb/Sr ratios. It also shows ASI, K, Rb, and U contents, prominent depletion of Nb, Sr and Ti on the primitive mantle-normalized multi-element spider diagrams and a low concentrations of Cu, Cr, V and Na₂O (> 3.2%). All these geochemical characteristics provide strong evidences in support of a sedimentary parentage for Barbhita granitoids (BBG) and are dominantly of S-type.     

Plane symmetric gravitational collapse and linear equation of state

This paper examines the gravitational collapse in plane symmetry with a perfect fluid using a linear equation of state p=kρ. We find a class of collapse models satisfying the Einstein field equations and also the regularity as well as energy conditions. For a given initial data, the outcome of the collapse turns out to be a black membrane or a naked singularity depending upon the equation of state parameter. We conclude that this parameter plays a crucial role in determining the final fate of the collapse.     

Simulation of the nucleation and growth of simple clay minerals in weathering processes: The NANOKIN code

We present a numerical approach which accounts for nucleation, growth and/or resorption of particles of fixed composition in aqueous solutions, and which involves functionalities suited to the formation of simple clay minerals in weathering processes, such as: formation of non-spherical particles, heterogeneous/homogeneous nucleation, several growth laws, precipitation resulting from the dissolution of primary minerals. The overall model is now embedded into a new numerical code called NANOKIN, in which several optimization procedures have been introduced in order to allow long dynamics to be followed. NANOKIN was applied to the precipitation of Al- bearing minerals from aqueous solutions: halloysite, kaolinite and Ca-montmorillonite. It allowed us to propose a stable scheme for the competitive precipitation of halloysite and kaolinite under two different types of initial conditions: (1) a given initial super-saturation state of the aqueous solution; (2) progressive super-saturation resulting from the kinetic dissolution of the minerals from a granitic rock under weathering conditions. Both yield particle sizes in the micron range, but with distinct crystal size distribution functions. The interplay between kinetic and thermodynamic effects is discussed.