Germination of acorns and development of oak seedlings (Quercus robur L.) following flooding

Abstract

Seeds and seedlings of Quercus robur, a characteristic tree species of the hardwood floodplain forests along the Rhine River, demonstrated high resistance to complete inundation under controlled conditions. In both experimental trials no significant difference between the different flooding periods (8, 10, and 12 weeks) could be established either for shoot emergence or for the measured morphological growth parameters. Flooding delayed the germination of submerged acorns till the end of inundation. However, seeds of the flooding treatments had significantly higher germination rates than the non-flooded acorns of the control. Likewise, dry weights of seedlings from the flooded seeds were significantly higher than those of seedlings from seeds not flooded. Aboveground growth in the 24-week growth period following flooding was reduced in favour of root development in either trial of the experiment. Restricted leaf development and reduced shoot elongation stalled the growth of young oaks in the seedling trial. The results confirm knowledge from earlier experiments about the flood tolerance of Quercus robur seed and seedlings. They also serve to explain why oak seedlings are widespread on the Rhine floodplain after mast years, but gradually disappear in successive years.Keywords: inundation; experiment; mortality; morphology; recovery; pedunculate oak 392 J. FOR. SCI., 53, 2007 (9): [391][392][393][394][395][396][397][398][399] Quercus robur revealed the least damage out of the six tested broadleaf tree species, demonstrating the best adaptation to flooding stress.In spring 1999, the meeting of flood waters from the Rhine and many of its tributaries along the upper part of the stream resulted in the worst flood of the last century. The extreme rise in the water level was caused by unusually mild and wet weather in the northern Alps. In the course of this event Kühne et al. (2005) observed high mortality and growth inhibition of Quercus robur grown from direct seeding and nursery plants at study sites situated between Speyer and Karlsruhe (Germany). In the experiment presented in this paper flood conditions of 1999 were simulated when acorns and seedlings from Quercus robur were entirely submerged under controlled conditions in growth chambers and germination of seeds and regeneration capacity of seedlings following flooding were investigated. Based upon field observations the following hypotheses were tested in this work: -Seeds begin to germinate only after flooding.-Germination rate decreases as the duration of inundation increases. -Inundation during the vegetation period results in leaf abscission and necrosis of the shoot. -Mortality of seedlings increases as the duration of inundation increases. MATERIAL AND METHODS SeedsSeeds were collected in a single-layered mature Quercus robur stand in southern Rhineland-Palatinate (Bellheim Forest District, Germany) in October 1999. The stand is subjected to annual floods from the Rhine River. Seeds were stored at 4°C until sowing. Prior to the commencement of t...

Using thermal time models to predict the impact of assisted migration on the synchronization of germination and shoot emergence of oak (Quercus robur L.)

“…Floods are not likely to be a particular problem for Q. robur, which occurs naturally in hardwood forests along floodplains. Q. robur acorns can survive soil water logging for up to 12 weeks although subsequent germination is delayed (Kühne and Bartsch 2007). As a result, the window between winter floods and summer droughts may be too narrow for seedlings to develop root systems that can tolerate the seasonal soil water deficits (Urbieta et al 2008).…”

Automation of the Acorn Scarification Process as a Contribution to Sustainable Forest Management. Case Study: Common Oak

“…Moreover, the drawbacks of natural regeneration include: (1) dependence on seed years; (2) unevenness of sowing, resulting in laborious and costly re-sowing; and (3) the lack of desired tree species, in the maternal stand. Natural regeneration usually ranges from several to several dozen percent of the total area [6,7]. Obtaining good quality natural regeneration in the case of the common oak (Quercus robur L.) is particularly difficult and requires from foresters vast knowledge and experience on the part of foresters.…”

Variability in commercial demand for tree saplings affects the probability of introducing exotic forest diseases

“…After sales, all remaining trees are discarded Demand variability, = 50 (Kormanik, Sung, Kormanik, Schlarbaum, & Zarnoch, 1998;Moustakas & Evans, 2015). Seedlings reach between 30 and 40 cm in average by the end of the growing season (Kühne & Bartsch, 2007;Mariotti, Maltoni, Jacobs, & Tani, 2015;Turcsán et al, 2016;Valkonen, 2008;Welander & Ottosson, 1998). We then assume that tree survival reaches 90%.…”