Oak sprouts grow better than seedlings under drought stress

Abstract

(1-2) This study focused on the comparison of two contrasting forest regeneration types and their susceptibility to drought stress. Transpiration and biomass production were studied on young sessile oak trees Quercus petraea (Matt.) Liebl. regenerated as sprouts and seedlings, and grown in a coppice experimental site in the Czech Republic. Biomass production was estimated using destructive methods, while transpiration was derived from sap flow measurements and assessed according to the plant biometry and microclimatic conditions. Sprouts were characterized by a significantly higher diameter, height, leaf area and above-ground biomass and by a lower wood density as compared with seedlings of the same age. Moreover, the sap flow of sprouts was higher than that of seedlings, which was explained by the plant dimension. Transpiration, expressed as sap flow scaled to plant leaf area, did not differ between seedlings and sprouts when soil water was not limiting. However, during drought periods, when soil water potential dropped below -1.4 MPa, sprouts transpired significantly more than seedlings. Our results confirm that sprouts have access to a larger water pool via the old stump root system and are able to draw more water under drought. Moreover, sprouts seemed to be less susceptible to water limitations than seedlings of similar age. Less influence of drought on sprouts may partially explain their higher above-ground biomass production. Based on our results, coppice could be an appropriate management system to be adopted in sites characterized by frequent or extreme drought periods.

Analysis of growth of recruits of natural regeneration of Sorbus torminalis (L.) Crantz - a rare European forest tree species

“…Schüte (2001) reported that after 6-8 years root suckers are still not independent from the root system of the mother tree. This may explain the observation that suckers or sprouts are less susceptible to stress factors as shade or water deficit (Pietras et al 2016) and they have faster initial growth compared to seedlings. This finding is consistent with our observations.…”

Transpiration and water potential of young Quercus petraea (M.) Liebl. coppice sprouts and seedlings during favourable and drought conditions

“…Coppice sprouts have a fully functional root system of a previously established tree (Bond, Midgley 2001) which ensures them more stable water resources (Vilagrosa et al 2014). Therefore, coppice sprouts are minimizing the effect of water oscillations during the season by reaching the deeper soil layers (Vilagrosa et al 2014;Pietras et al 2016). Shallow roots and small root absorptive area were suggested as main reasons for lower transpiration rates of seedlings compared to sprouts (Pietras et al 2016).…”

“…Therefore, coppice sprouts are minimizing the effect of water oscillations during the season by reaching the deeper soil layers (Vilagrosa et al 2014;Pietras et al 2016). Shallow roots and small root absorptive area were suggested as main reasons for lower transpiration rates of seedlings compared to sprouts (Pietras et al 2016). Since seedlings rely on water in shallow soil layers where soil moisture availability is depleted rapidly (Gaines et al 2016), this may justify the lower transpiration rates of seedlings as compared to sprouts.…”

“…Sap flow was measured using commercially available EMS 62-type measuring sensors (EMS Brno, Czech Republic). The measuring principle is based on the stem heat balance method with external heating and internal temperature sensing (Lindroth et al 1995;Pietras et al 2016).…”

“…Drought affects growth, disturbs water relations and water use efficiency of plants (Pietras et al 2016), alters nutrient uptake and reduces photosynthesis ) and may lead to hydraulic failure and carbon starvation (McDowell 2011). It increases the susceptibility to abiotic and biotic stress factors (McDowell 2011;Ryan 2011).…”