Tropical Forest Plant Ecophysiology

pp 187-216

Influence of Seasonal Drought on the Carbon Balance of Tropical Forest Plants

  • Stephen S. Mulkey
  • , S. Joseph Wright

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Despite high annual rainfall, one of the principal determinants of resource availability in tropical forests is the seasonal occurrence of drought. Plant growth and reproduction in these forests are frequently coordinated with seasonal variation in rainfall (Richards, 1952). In this chapter, we review the role of seasonal drought in tropical plant demography and physiology, with particular emphasis on the relationships among water deficits, carbon balance, and plant survival. We begin with a review of physiological mechanisms permitting continued gas exchange during drought in tropical trees, understory shrubs, and herbs. Other drought responses of vines, hemiepiphytes, and epiphytes are considered in chapters by Holbrook and Putz (Chapter 13) and Medina (Chapter 2), and drought effects on tropical plant phenology are considered in detail by Wright (Chapter 15). Treefall gaps are a principal determinant of resource availability in the understory, and in the latter part of this review, we focus on the interaction between seasonal drought and gaps and their effect on plant demography and physiology. Central to this discussion is the role of declining plant water potentials in limiting carbon gain.