Photosynthesis and water relations of four oak species: impact of flooding and salinity

Abstract

As global climate changes, sea level rise and increased frequency of hurricanes will expose coastal forests to increased flooding and salinity. Quercus species are frequently dominant in these forest, yet little is known about their salinity tolerance, especially in combination with flooding. In this study, 1-year-old seedlings of Quercus lyrata Walt. (overcup oak), Q. michauxii Nutt. (swamp chestnut oak), Q. nigra L. (water oak), and Q. nuttallii Palmer (Nuttall oak) were chronically (simulating sea level rise) and acutely (simulating hurricane storm surge) exposed to increased flooding and salinity, individually and in combination. The four species demonstrated two response patterns of photosynthesis (A), conductance, and leaf water potential, apparently related to their relative flood tolerance. In Q. lyrata, Q. nuttallii, and Q. nigra (moderately flood-tolerant), A was not immediately reduced after the initiation of the freshwater flooding, but was reduced as the duration of flooding increased. In the second pattern, demonstrated by the weakly flood-tolerant Q. michauxii, A was immediately reduced by freshwater flooding with an increasing impact over time. Watering with 2 parts per thousand (ppt) saline water did not consistently reduce A, but flooding with 2 ppt reduced A of all species, similar to the response with freshwater flooding. Photosynthesis of all species was reduced by 6 ppt watering or flooding, with the latter treatment killing all species within 8 weeks. When acutely exposed to 30 ppt salinity, A was quickly and severely reduced regardless of whether the seedlings were watered or flooded. Acutely flooded seedlings exposed to high salinity died within 2 weeks, but seedlings watered with 30 ppt saline water recovered and A was not reduced the following spring. As saline flooding of coastal areas increases due to sea level rise, photosynthesis of these species will be differentially affected based primarily on their flood tolerance. This suggests that increased flooding associated with sea level rise will impact these tree species to a greater extent than small increases in soil salinity. High salinity accompanying storm surges will be very harmful to all of these species.& k w d :

Changes in photosynthesis and fluorescence in response to flooding in emerged and submerged leaves of Pouteria orinocoensis

“…After 45 d of flooding a severe reduction in P N and g s was observed in seedlings of P. orinocoensis. Flooding induced reductions in gas exchange of a great number of seedlings of tree species, such as Taxodium distichum, Quercus falcata, and Quercus lyrata (Pezeshky et al 1996), Quercus michauxii, Quercus nigra, Quercus nuttallii, and Q. lyrata after 4 months of freshwater flooding (McLeod et al 1999), and some grafts of Annona trees (Núñez-Elisea et al 1999). Stomatal closure can be critical for flood tolerance, since it often reduces carbon assimilation and may result in tree mortality (Núñez-Elisea et al 1999).…”

Photosynthetic and wood anatomical responses of Tamarixafricana Poiret to water level reduction after short‐term fresh‐ and saline‐water flooding

“…This reduction was not induced by a decline in carboxylation activity or electron transport, as Vc max and J max both did not vary by an increase in dark respiration. A decrease in the plant photosynthesis and growth has been reported in both glycophytes (Bongi and Loreto 1989;Mc Leod et al 1999;Centritto et al 2003;Loreto et al 2003) and halophytes (Ueda et al 2003;Parida et al 2004;Nandy Datta et al (2007), and is often the result of reduced stomatal conductance. An increase in stomatal resistance can be caused by feedback controls in response to the increase of intermediates or products of the Calvin cycle that accumulate because of the reduced growth under saline conditions (Lovelock and Ball 2002), or by an increase in the cellular concentration of Na + and/or Cl À .…”

Flooding effects on starch partitioning during early growth of two oak species

“…However, due to the low efficiency of ATP production by anaerobic processes, energy and carbon metabolism of trees are usually strongly affected by oxygen deprivation (Kreuzwieser et al 2004). Moreover, photosynthetic reductions are common features in woody species subjected to flooding stress (Dreyer 1994;McLeod et al 1999;Pezeshki 2001), that reduces availability of carbohydrate. Both changes in root internal carbon metabolism and carbohydrate starvation negatively affect root growth and survival.…”