Ecophysiology and biomass production of Robinia pseudoacacia


Black locust (Robinia pseudoaccacia L.) is an important tree species in Central and Eastern Europe. The native range of black locust is classified by a humid to sub-humid climate with normal annual precipitation of 1020 to 1830 mm. However, in Central Europe, Robinia pseudoacacia L. is known to be relatively drought tolerant compared to other temperate deciduous tree species. As a pioneer species the tree grows under a wide range of conditions and is used for reclamation of former open-cast lignite mining areas in Brandenburg and cultivated in short-rotation plantations for the production of bioenergy wood. In order to evaluate the growth and ecophysiological performance of Black locust to drought stress, we established several controlled experiments to study the morphological and ecophysiological adaptation of the tree under different water regimes and air temperatures and under field conditions.

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Influence of drought stress on photosynthesis, transpiration, and growth of juvenile black locust (Robinia pseudoacacia L.)

Nowadays, black locust (Robinia pseudoaccacia L.) is an important tree species in Central and Eastern Europe. The native range of black locust is classified by a humid to sub-humid climate with normal annual precipitation of 1,020 to 1,830 mm. However, in Central Europe, black locust is known to be relatively drought tolerant compared to other temperate deciduous tree species. As a pioneer species the tree grows under a wide range of conditions and is used for reclamation of former open-cast lignite mining areas in Brandenburg and cultivated in short-rotation plantations for the production of bioenergy wood. In order to evaluate the growth and ecophysiological performance of black locust to drought stress, a pot experiment was established at the Thünen-Institut, Hamburg. The photosynthetic performance was studied with a PAM 2100 chlorophyll fluorescence system and net CO2-exchange and transpiration were determined with a minicuvette system CMS 400. Under drought stress net photosynthesis and transpiration were reduced due to stomatal closure. The measured electron transport rate of the photosystem II showed an opposite trend to the net photosynthesis and increased also under drought stress and in- creasing temperature up 30 °C. This indicates a higher fraction of energy dissipation of electrons to photorespiration and the Mehler reaction to avoid photoinhibition under limited CO2-uptake under drought stress und high temperatures. To minimize transpiration on the plant level leaf area was drastically reduced during drought stress. The plants showed different adapta- tions and a high plasticity of the ecophysiological processes to cope with a long-term drought stress and high temperature, which allows growing also in drier regions.


Black locust (Robinia pseudoacacia L.) ecophysiological and morphological adaptations to drought and their consequence on biomass production and water use efficiency

Successful plantation efforts growing Robinia pseudoacacia L. (black locust) in the drier regions of Hungary and East Germany (Brandenburg), have demonstrated the potential of black locust as an alternative tree species for short-rotation biomass energy plantations. The response of black locust (Robinia pseudoacacia L.) to water limitation was investigated in a lysimeter experiment. Plants were grown under three different soil moisture regimes, with values set at 35%, 70%, and 100% of the soil water availability, namely WA35, WA70, and WA100. Their morphological adaptation and productivity response to water constraint were assessed together with their water-use efficiency. Furthermore, the ecophysiological adaptation at the leaf level was assessed in terms of net photosynthesis and leaf transpiration. During the growing season, plants in the WA35, WA70, and WA100 treatments transpired 239, 386, and 589 litres of water respectively. The plants subjected to the WA35 and WA70 treatments developed smaller leaves compared with the plants subjected to the WA100 treatment (66% and 36% respectively), which contributed to the total leaf area reduction from 8.03 m2 (WA100) to 3.25 m2 (WA35). The total above-ground biomass produced in the WA35 (646 g) and WA70 (675 g) treatments reached only 46% and 48% of the biomass yield obtained in the WA100 (1415 g). The water-use efficiency across all treatments was 2.31 g L−1. At vapour pressure deficit (VPD) values <1.4 kPa trees growing under the WA35 soil moisture regime showed a stomatal down-regulation of transpiration to 5.3 mmol m−2 s−1, whereas the trees growing under the WA100 regime did not regulate their stomatal conductance and transpiration was 11.7 mmol m−2 s−1, even at VPD values >2 kPa. Black locust plants can adapt to prolonged drought conditions by reducing water loss through both reduced transpiration and leaf size. However, under well-watered conditions it does not regulate its transpiration, and therefore it cannot be considered a water-saving tree species.


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

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.


Spatial and temporal variation of drought impact on black locust (Robinia pseudoacacia L.) water status and growth

Agroforst

Stimulated by the rising demand for bioenergy, forestry practices for energy production are of increasing importance worldwide. Black locust (Robinia pseudoacacia L.) is a suitable tree species for biomass production in short-rotation plantations in East Germany, especially on marginal land where insufficient water and nutrients are a limiting factor for tree growth. Our study aims to clarify the spatial and temporal variability of the black locust growth through the analysis of the plant water status, and to evaluate the effect of adverse edaphic conditions on growth performances, amplified by periods of summer drought. The study was carried out at two sites presenting comparable climatic but different edaphic conditions: (i) fertile agricultural soil; and (ii) heterogeneous unstructured soil from a reclaimed post-mining area. During the vegetation period, the growth rate decreased in both sites following the plant water status in terms of pre-dawn leaf water potential. Particularly in the post-mining area, due to the adverse edaphic conditions, below the critical pre-dawn water potential value of -0.5 MPa, the stem growth was drastically reduced during a period of summer drought. However, the trees could cope with the extreme soil and weather conditions in the post-mining site without perishing.

Read the paper iForest, 2015 


Carbon allocation, nodulation, and biological nitrogen fixation of black locust (Robinia pseudoacacia L.) under soil water limitation

Robinia

The pioneer tree black locust (Robinia pseudoacacia L.) is a drought-resistant tree and, in symbiosis with Rhizobium, able to fix dinitrogen from the atmosphere. It is, therefore, an interesting species for marginal lands where soil amelioration is sought in addition to economic gain. However, the interaction between soil water availability, carbon allocation and nitrogen fixation is important for a successful establishment of trees on marginal lands and has not yet been investigated for black locust. Two-year-old trees were grown under various soil water conditions and drought cycles. The stable isotopic composition of C (δ 13C) and N (δ 15N) of the leaves was used to identify i) the effective drought condition of the treatments and ii) the portion N accrued from the atmosphere by the biological nitrogen fixation. Drought-stressed plants significantly reduced their total aboveground biomass production, which was linearly linked to tree transpiration. The shoot:root ratio values changed from  2.2 for the drought-stressed to 4.3 for the well-watered plants. Our investigation shows that drought stress increases the nodule biomass of black locust in order to maintain biological nitrogen fixation and to counteract the lower soil nitrogen availability. The biological nitrogen fixation of drought-stressed trees could be maintained at relatively higher values compared to the well-watered trees. The average leaf nitrogen content varied between 2.8 % and 3.0 % and was not influenced by the drought stress. Carbon fixation, carbon allocation, and biological nitrogen fixation are to some extent balanced at low irrigation and allow Robinia to cope with long-term water constraints. The combination of black locust’s ecophysiological and morphological plasticity make it interesting as a biomass source for bioenergy and timber production, even in nutrient-limited and drought-affected areas of Europe.

  • Annals of Forest Research, 2015, PDF


Biological nitrogen-fixation by Robinia pseudoacacia

Rob-N

Because of its N2-fixation ability black locust plays generally an important role for the improvement of soil fertility. This effect is of particular interest in the post-mining landscapes. In order to estimate the N2-fixation potential of black locust at marginal sites leaf samples were taken from black locust trees in short rotation plantations planted between 1995 and 2007 in post mining sites south of Cottbus (Brandenburg, NE Germany). The variation of the natural 15N abundance was measured to evaluate the biological nitrogen fixation. The nitrogen derived from the atmosphere can be calculated using a two-pool model from the quotient of the natural 15N abundances of the N2-fixing plant and the plant available soil N. Because representatively determining the plant available soil N is difficult, a non-N2-fixing reference plant growing at the same site with a similar root system and temporal N uptake pattern to the N2-fixing plant is often used. In our case we used red oak (Quercus rubra) as a reference. The average nitrogen content in the leaves of black locust ranged from 3.1% (C/N 14.8) in 15 years old trees to 3.4% (C/N 14.4) in 3 year-old trees, respectively. A higher content of nitrogen was found in leaves of re-sprouted trees with 4.3% (C/N 11.5). The estimated percentage of nitrogen derived from the atmosphere (% NdfA) in black locust was 63% – 83% compared to 56% in seabuckthorn (Hippophaë rhamnoides) and 79% in common broom (Genista scuparia). The annual leaf biomass production of black locust varied between 1325 (2 years old trees) and 2576 kg/ha a (4 years old trees). The estimated leaf nitrogen fixed by Robinia was approx. 30.5 - 59.2 kg/ha a. From the results, we can conclude that the biological nitrogen fixation by Robina is an important factor for the nitrogen balance of short-rotation plantations on nutrient poor-soils.

       © Maik Veste 2017  -  Last update:  21JAN2017                            Impressum