Contrasting sap flow characteristics between pioneer and late-successional tree species in secondary tropical montane forests of Eastern Himalaya, India

Manish Kumar*, Yangchenla Bhutia, Gladwin Joseph, Jagdish Krishnaswamy

*Corresponding author for this work

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Abstract

The interactive role of life-history traits and environmental forcing on plant-water relations is crucial for understanding species response to climate change but remains poorly understood in secondary tropical montane forests (TMFs). Comparing contrasting life-history traits (pioneer vs late-successional species) in a biodiverse Eastern Himalayan secondary TMF, we investigated sap flow responses in co-occurring pioneer species, Symplocos racemosa (n=5) and Eurya acuminata (n=5), and late-successional species, Castanopsis hystrix (n=3), using modified Granier’s Thermal Dissipation probes. The fast-growing pioneers S. racemosa and E. acuminata) had 2.1- and 1.6-times higher sap flux density than the late-successional C. hystrix, respectively, and exhibited characteristics of long-lived pioneer species. Significant radial and azimuthal variability in sap flow (V) between species was observed and attributed to life history traits and the canopy’s access to sunlight. Nocturnal V (1800-0500 hr) was 13.8 % of daily V and is attributed to stem recharge for evening V (1800-2300 hr) and to endogenous stomatal controls for pre-dawn V (0000-0500 hr). Both the shallow-rooted pioneer species exhibited midday depression in V attributed to photosensitivity and diel moisture stress response. In contrast, deep-rooted C. hystrix transpired unaffected across the dry season likely accessing groundwater. Thus, the secondary broadleaved TMFs, with the dominance of shallow-rooted pioneers, are more prone to the negative impacts of drier and warmer winters than primary forests, which are dominated by deep-rooted species. The study provides an empirical understanding of life-history traits and microclimate modulating plant-water use in widely distributed secondary TMFs in Eastern Himalaya and highlights their vulnerability against warmer winters and reduced snowfall due to climate change.
Original languageEnglish
Article numbererad207
Number of pages21
JournalJournal of Experimental Botany
Early online date8 Jun 2023
DOIs
Publication statusE-pub ahead of print - 8 Jun 2023

Keywords

  • Sap flow
  • Transpiration
  • Pioneer species
  • late-successional species
  • Plant water relations
  • Secondary forests
  • Himalaya
  • Ecohydrology
  • Sensors

ASJC Scopus subject areas

  • Ecology
  • Water Science and Technology
  • Forestry
  • Earth-Surface Processes
  • Horticulture
  • Plant Science
  • Soil Science

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