Effects of Drought Frequency on Growth Performance and Transpiration of Young Black Locust (Robinia pseudoacacia L.)

Hindawi Publishing Corporation International Journal of Forestry Research Volume 2014, Article ID 821891, 11 pages http://dx.doi.org/10.1155/2014/821891 Research Article Effects of Drought Frequency on Growth Performance and Transpiration of Young Black Locust (Robinia pseudoacacia L.) Dario Mantovani,1,2 Maik Veste,3 and Dirk Freese2 1 International Graduate School, Brandenburg University of Technology Cottbus-Senftenberg, Konrad-Wachsmann-Allee 6, 03046 Cottbus, Germany 2 Chair of Soil Protection and Recultivation, Brandenburg University of Technology Cottbus-Senftenberg, Konrad-Wachsmann-Allee 6, 03046 Cottbus, Germany 3 Centre for Energy Technology Brandenburg e.V. (CEBra), Friedlieb-Runge-Straße 3, 03046 Cottbus, Germany Correspondence should be addressed to Dario Mantovani; Received 19 November 2013; Revised 28 January 2014; Accepted 28 January 2014; Published 17 March 2014 Academic Editor: Kihachiro Kikuzawa Copyright © 2014 Dario Mantovani et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Black locust (Robinia pseudoacacia L.) is a drought-tolerant fast growing tree, which could be an alternative to the more common tree species used in short-rotation coppice on marginal land. The plasticity of black locust in the form of ecophysiological and morphological adaptations to drought is an important precondition for its successful growth in such areas. However, adaptation to drought stress is detrimental to primary production. Furthermore, the soil water availability condition of the initial stage of development may have an impact on the tree resilience. We aimed to investigate the effect of drought stress applied during the resprouting on the drought tolerance of the plant, by examining the black locust growth patterns. We exposed young trees in lysimeters to different cycles of drought. The drought memory affected the plant growth performance and its drought tolerance: the plants resprouting under drought conditions were more drought tolerant than the well-watered ones. Black locust tolerates drastic soil water availability variations without altering its water use efficiency (2.57 g L−1 ), evaluated under drought stress. Due to its constant water use efficiency and the high phenotypic plasticity, black locust could become an important species to be cultivated on marginal land. 1. Introduction Summer drought, as observed during extreme events in Central Europe in 2003 [1], is one of the major abiotic stress factors that limit plant growth and have drastic effects on the ecosystem productivity. The ongoing climate change amplifies the interannual climate variability and changes the seasonal distribution of rainfall in Central Europe [2]. Within Central Europe particularly the southern parts of Brandenburg and Poland will be highly vulnerable to climate change and a decrease in summer precipitation is forecasted. Consequently, drought periods during the growth season are to be expected [3]. In this region the reduced soil water availability (SWA), in combination with sandy soils, has led to negative effects on the productivity of the ecosystem [4]. An integrated concept of active species selection and an appropriate management of tree stands could mitigate the effect of the climatic stress to a certain extent. Therefore, it is important to assess the plasticity of the species to drought stress by understanding the plant response in terms of water consumption, growth performance, and production [5]. This is particularly important for short-rotation coppice (SRC) systems, where the primary production is driven mainly by the SWA [6, 7]. Black locust (Robinia pseudoacacia L.), as a drought tolerant species suitable for SRC, can be grown even on reclaimed post-mining sites, where the edaphic conditions are extreme [8]. Various studies emphasize the black locust morphological and ecophysiological adaptations in coping with long-term drought stress [9–11]. Hence, the ecological stress memory, defined by Walter et al. [12] as any response of a single plant after a stress experience, which improves the response of the same plant towards future stress experiences, 2 could be an important factor when evaluating the drought stress tolerance of the species. Depending on the drought stress severity, a reduction of the primary production due to these morphological and physiological adjustments is to be expected [13–15]. Stomatal closure is a typical temporary reaction to drought stress, leading to a reduced CO2 uptake and finally influencing carbon budgets and growth performances [16, 17]. Besides physiological adjustments, drought stress occurring during the tree development induces morphological adaptations from the roots to the crown, which will characterize the hydraulic architecture of the tree [18– 23]. As a consequence the transpiration of the plant will be influenced, along with its tolerance to drought stress [18–20]. Hence the recovering process after drought stress in terms of growth increment could be affected by the SWA at the initial stage of resprouting. In spite of the importance of this topic for coppicing practices, up to this date there is still a considerable informational gap: the effect of the drought occurring during the resprouting period on the drought tolerance, biomass production, and water use under drought stress has not been investigated. In our study, we aimed to assess the impact of drought cycles, applied during the resprouting phase on the drought resilience of black locust trees. We defined the physiological conditions in terms of plant water status at which the growth performance is compromised and analyzed the influence of drought applied during the resprouting phase on the hydraulic architecture of the tree, evaluating the relation between root system and the total transpiring surface. The effect of the different root weight: leaf area ratio was evaluated by analyzing (i) growth performance, (ii) transpiration rate, (iii) aboveground biomass production, and (iv) the water use efficiency under cyclic drought stress. The information gathered enlightened the importance of black locust as an appropriate tree for marginal land and the strong implication that the SWA during the resprouting phase has on the later drought tolerance and productivity of the species. 2. Material and Methods 2.1. Plants and Drought Stress Treatment. The study was carried out with three-year-old black locust trees in a lysimeter experiment, under a light transmissive rain-out shelter, arranged at the Brandenburg University of Technology Cottbus-Senftenberg. The water was supplied solely by an automatic irrigation system. The plant material was collected from a short-rotation plantation in the postmining area of Welzow-Süd, Brandenburg, Germany (N 51∘ 36󸀠 14󸀠󸀠 , E 14∘ 19󸀠 51󸀠󸀠 ), approximately 25 (...truncated)