Water Relations of the Indian Himalayan Treeline Species

Abstract

AbstractThis chapter deals with study the variation in water relation and drought-adaptive mechanisms of five Himalayan treeline species Quercus semecarpifolia Sm., Abies spectabilis D. Don., Betula utilis D. Don and Rhododendron campanulatum D. Don and R. arboreum Wall. growing at elevation ranging from 3200 to 3450 masl. Soil water potential, tree water potential, water potential components and leaf conductance were measured for 3 years (2016 to 2018). Across all seasons and years, the soils were mostly moist. Moderate stress was observed in summer and winter seasons. The treeline species were never severely stressed during the study period and the ΨPD was generally above −0.99 MPa. The magnitude of diurnal change across all species was maximum during the rainy season (−0.72 MPa to −0.82 MPa) except in Q. semecarpifolia. The diurnal pattern of water potential during winter seasons indicated that water potential can become severely low during 8.30 a.m. and 10.30 a.m. and ranged between −1.62 ± 0.09 MPa in R. campanulatum and − 2.10 ± 0.03 MPa in R. arboreum. All treeline species showed osmotic adjustment between winters and spring season which coincided with the commencement of the phenological activities in majority of tree species. A smaller adjustment occurred in all species during rainy to winter season also.KeywordsLeaf conductanceOsmotic adjustmentOsmotic potentialWater potential