Patterns and determinants of soil CO2 efflux in major forest types of Central Himalayas, India.

Soil CO2 efflux (Fsoil) is a significant contributor of labile CO2 to the atmosphere. The Himalayas, a global climate hotspot, condense several climate zones on account of their elevational gradients, thus, creating an opportunity to investigate the Fsoil trends in different climate zones. Presently, the studies in the Indian Himalayan region are localized to a particular forest type, climate zone, or area of interest, such as seasonal variation. We used a portable infrared gas analyzer to investigate the Fsoil rates in Himalayan tropical to alpine scrub forest along a 3100-m elevational gradient. Several study parameters such as seasons, forest types, tree species identity, age of trees, distance from tree base, elevation, climatic factors, and soil physico-chemical and enzymatic parameters were investigated to infer their impact on Fsoil regulation. Our results indicate the warm and wet rainy season Fsoil rates to be 3.8 times higher than the cold and relatively dry winter season. The tropical forest types showed up to 11 times higher Fsoil rates than the alpine scrub forest. The temperate Himalayan blue pine and tropical dipterocarp sal showed significant Fsoil rates, while the alpine Rhododendron shrubs the least. Temperature and moisture together regulate the rainy season Fsoil maxima. Spatially, Fsoil rates decreased with distance from the tree base (ρ = - 0.301; p < 0.0001). Nepalese alder showed a significant positive increase in Fsoil with stem girth (R2 = 0.7771; p = 0.048). Species richness (r, 0.81) and diversity (r, 0.77) were significantly associated with Fsoil, while elevation and major edaphic properties showed a negative association. Surface litter inclusion presented an elevation-modulated impact. Temperature sensitivity was exorbitantly higher in the sub-tropical pine (Q10, 11.80) and the alpine scrub (Q10, 9.08) forests. We conclude that the rise in atmospheric temperature and the reduction in stand density could enhance the Fsoil rates on account of increased temperature sensitivity.

Mycorrhizal association and its relation with pteridophytes.

Mycorrhizal association is one of the earliest and diversely distributed symbiotic associations on the Earth. This association helped early terrestrial plants to colonize the land by improved supply of nutrients like phosphate, nitrogen and zinc. It also helped plants to tolerate unfavorable soil conditions with increased water retention capacity, resistance to drought and pathogens. In return, fungi benefitted with carbon as their food source from the plants. More than 80% of terrestrial plants including pteridophytes, gymnosperms and angiosperms are reported to form arbuscular mycorrhizal (AM) association. Plants with root systems appeared on land during the Devonian period and many of them like pteridophytes still exist today. Various molecular and fossil studies confirm that the plants belonging to Ordovician-Devonian are associated with fungi, which are very similar to genus Glomus. AM association is very common in pteridophytes and the growth of its sporophyte and gametophyte is directly affected in the presence of AM association. Pteridophytes as early land plants with root systems have a very significant place in the plant kingdom. They have evolved and adapted to fill various habitats and facilitated early terrestrialization of other land plants by providing suitable niche with the help of AM fungi. In spite of pteridophytes being a very important plant group in the land system, very few reports are available on fungal-pteridophyte association. The present review is an effort to gather information about AM association in pteridophytes that might help in unraveling the evolution and significance of plant and fungi association.

Taxonomic significance of megaspores in some species of Selaginella from Arunachal Pradesh in India.

The present study was carried out to record the color, size, and ornamentation of megaspores in 18 species of the family Selaginellaceae from Arunachal Pradesh using scanning electron microscope (SEM) and light microscope (LM). Electron microscopic study of the spore features revealed the type of ornamentation and microsculptural detail. SEM study on megaspore of Selaginella pentagona (S. pentagona), Selaginella tenuifolia, Selaginella semicordata, and Selaginella chrysorrhizos is presented for the first time. Variation in the megaspore ornamentation is noted at the interspecific level and intraspecific level in some cases. Examination of the megaspores under study found all the megaspores as trilete, with a size ranging from 116 to 560 µm in diameter. Taxonomic key is prepared to differentiate the species. Short descriptions of megaspores are provided and supported by photo plates. New features are recorded for seven species. The study contributes to the separation of species within the genus Selaginella based on the spore feature and brings forward the use of spore as a diagnostic tool in the taxonomy of the genus. These works contribute to the systematic of the family Selaginellaceae and provide useful information in the field of palynology. RESEARCH HIGHLIGHTS: Study on megaspore features of Selaginella species collected from Arunachal Pradesh, using SEM and LM. Taxonomic key is provided for each species based on megaspores features. New megaspore features are recorded for the seven species. The study brings forward the use of spore as a diagnostic tool in the taxonomy of the genus. These works provide useful information in the field of systematic and palynology.