Abstract
Water potential (predawn and mid day), water potential components (osmotic potential at full and zero turgor, relative water content), soil water potential and leaf conductance were measured for two adjacently growing tree species Shorea robusta Gaertn and Pinus roxburghii Sarg. at an elevation of 1370m. The stands were open and the density of S. robusta was 212 trees/ha and of P. roxburghii was 141trees/ha. Presence of high number of saplings indicates both the species were regenerating well in the site despite human disturbance. S. robusta maintained relatively high predawn water potential even in summers (above -0.50MPa) and P. roxburghii showed low predawn water potential in early summer and summer season (above-1.4 MPa). P. roxburghii maintained a relatively small daily change in water potential during early summer and summer season (0.33MPa and 0.27MPa) indicating greater ability of the species to close its stomata as drought intensifies. The values of osmotic potential at full and zero turgor remained more or less constant for S. robusta from monsoon to winter and then declined during early summer. P. roxburghii showed a gradual decline in osmotic potential values from monsoon to winter season. Chir-pine has the ability of invade and grow on sites that are water stressed which can be related to its capacity to show high osmotic adjustment.. The most negative values of soil water potential were in early summer in both years. The morning and afternoon conductance was lowest during early summer and highest in autumn season.
Highlights
Of the myriad environmental factors influencing distribution and growth of woody plants, water is of paramount importance and is usually the most limiting throughout the world
P. roxburghii showed a gradual decline in osmotic potential values from monsoon to winter season in osmotic potential at full turgor
ANOVA showed that osmotic potential and relative water content (%) varied significantly across species and season (P
Summary
Of the myriad environmental factors influencing distribution and growth of woody plants, water is of paramount importance and is usually the most limiting throughout the world. This situation exists even though global supplies of water are immense. The western Himalaya receive concentrated rainfall between end of June to mid of September This is followed by 8-9 months of prolonged drought which has a severe impact on adaptation of plants to drought and ecosystem processes.[2,3] The Himalayas are warming at a faster rate than the global average due to global warming.[4] The forest ecosystem of Himalaya can be seriously impacted by global climate change. The importance of drought in regulating the distribution of Himalayan species is not very well understood.[5]
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