Liu Z.X.,State Key Laboratory of Tree Genetics and Breeding |
Zhang H.X.,State Key Laboratory of Tree Genetics and Breeding |
Yang X.Y.,State Key Laboratory of Tree Genetics and Breeding |
Liu T.,State Key Laboratory of Tree Genetics and Breeding |
Di W.B.,Beijing Forestry Survey and Design Institute
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2014
As a salt-tolerant shrub/ tree species, Elaeagnus angustifolia L. is widely planted for afforestation in many marginal lands or environmentally harsh conditions in northern China. Although E. angustifolia is well known for its strong adaptation to harsh conditions, the underpinning physiological mechanisms associated with ion transport and homeostasis under high-salt conditions have not been revealed. Has it developed some physiological mechanisms to avoid the high Na+ in soil or sequester the Na+ in some specific tissues or organs? The use of E. angustifolia to answer these questions can greatly enhance our understanding of the general physiological mechanisms that plants deploy to combat the environmental challenges. To unravel the underlying physiological mechanisms responsible for the extra-ordinary adaptation to high salt in E. angustifolia, we used the well-controlled water culture experiment in greenhouse to investigate the biomass accumulation, and the absorption, transportation and allocation of multiple ions including K+, Na+, Ca2+ and Mg2+ in different plant tissues (roots, stems and leaves) of E. angustifolia seedlings upon being challenged by different NaCl concentrations (0, 100 and 200 mmol/ L) for 30 days. Interestingly, the root growth was stimulated to a different extent by salt stress. The biomass accumulation of E. angustifolia seedlings was not obviously affected by 100 mmol/ L NaCl stress, whereas it was significantly inhibited by 200 mmol/ L NaCl stress. Compared with non-salt control, the K+-Na+ selective transportation coefficients (SK, Na) and Ca2+-Na+ selective transportation coefficients (SCa, Na) of different plant tissues (roots, stems and leaves) under two salt concentrations were all significantly elevated, while the contents of K+, Ca2+ and Mg2+, and the ratios of K+ / Na+, Ca2+ / Na+ and Mg2+ / Na+ in the three plant tissues were all significantly decreased. The Na+ concentration and net Na+ accumulation in 200 mmol/ L NaCl-stressed seedlings'roots were 22.15 mg/ g DW and 1.87 mg/ plant, respectively, which were 16.20 and 20.06 times higher than that in the control roots, respectively. The concentration and the accumulating amplitude of Na+ in roots were more conspicuous than any of other two tissues, implicating that roots may contribute vitally to the observed salt-tolerance of E. angustifolia. The Na+ concentration in stems and leaves of 200 mmol/ L NaCl-stressed seedlings increased to 5.15 and 7.71 mg/ g DW, which were 7.22 and 9.58 times the content in corresponding control, respectively, and net Na+ accumulation in 200 mmol/ L NaCl-stressed seedlings'shoots was 3.29 mg/ plant (5.45 times as much as in control shoot). However, all seedlings stressed by two salt concentrations exhibited a normal growth, no typical salt-damaged symptoms like succulent shoot and abscised leaves in treated seedlings were observed, indicating that shoots (including stems and leaves) can tolerate high concentration's Na+ stress. In conclusion, our findings suggested that the salt-adaptation mechanisms of E. angustifolia are root salt-rejection and shoot salt-tolerance, which are primarily implemented by root growth stimulation, root Na+ accumulation and restriction, and shoot Na+ endurance, and are also correlated with a remarkably increased ability of K+ and Ca2+ selective transportation in roots, stems and leaves.
Zhang B.,CAS Institute of Geographical Sciences and Natural Resources Research |
Xie G.-D.,CAS Institute of Geographical Sciences and Natural Resources Research |
Gao J.-X.,Nanjing Institute of Environmental Sciences |
Yang Y.,Beijing Forestry Survey and Design Institute
Building and Environment | Year: 2014
Urban green spaces have been proven to significantly decrease ambient air temperature and mitigate heat islands created by urbanization. However, the environmental benefits of cooling provided by urban green spaces have rarely been measured. In this paper, we estimated the energy-savings and emission-reduction contribution of urban green spaces in Beijing, applying a empirical model. Our calculations suggest urban green spaces play a major role in reducing energy demand and increasing CO2 sequestration. Urbanized Beijing has 16,577ha of green space which could absorb 3.33×1012kJ of heat via evapotranspiration during the entire summer. The cooling effect reduced the air conditioning demand by 3.09×108kWh which amounts to a 60% reduction in net cooling energy usage in Beijing. The annual reduction in CO2 emissions from power plants associated with electricity saving would reach 243 thousand tons with an average of 61kg/(haday). Also, the cooling effect and the environmental benefits of urban green space in Beijing largely depend on the green space's structure and size. Urban managers and landscape planners should take advantage of this research to plan, design and manage green spaces in heat island areas. © 2014 Elsevier Ltd.
Li P.,CAS Beijing Institute of Geographic Sciences and Nature Resources Research |
Li P.,University of Chinese Academy of Sciences |
Xiao Y.,CAS Beijing Institute of Geographic Sciences and Nature Resources Research |
Yang Y.,Beijing Forestry Survey and Design Institute |
Zhang C.-S.,CAS Beijing Institute of Geographic Sciences and Nature Resources Research
Chinese Journal of Ecology | Year: 2014
Forest is the most important carbon pool of terrestrial ecosystems, of which the forest plantations become more and more crucial. We investigated the different-aged poplar plantations in Tianjin through field surveys and laboratory measurements, estimated the carbon stock in the tree layer, herb layer, litter layer and soils (0-100 cm). The results showed that the biomasses of the tree layer in the young, medium and matured poplar plantations were 43. 65, 56. 18 and 121. 59 t · hm-2, respectively. The proportions of different organs to the tree biomass were in the order of stem>root>branch>leaf in the young and medium age stands, and of stem>branch>root> leaf in the matured poplar plantations. The biomasses of the herb layer of the three age plantations were 4. 60, 2. 92 and 1. 58 t · hm-2, respectively, and that of the litter layer were 0. 46, 0. 35 and 0. 66 t · hm-2, respectively. The total ecosystem carbon storage values of the young, medium and matured poplar plantations were estimated to be 84. 34, 121. 03 and 121. 72 t C · hm-2, respectively. Among the carbon storage of the three age groups, plant communities accounted for 25. 85%, 22. 25% and 46. 58%, respectively, and soils accounted for 74. 15%, 77. 75% and 53. 42%, respectively. The carbon storage values of the tree layer in the young, medium and matured poplar plantations were 20. 04, 25. 78 and 55. 95 t C · hm-2, respectively. The carbon storage values of the herb layer in the three age groups were 1. 63, 1. 05 and 0. 57 t C · hm-2, respectively, and that of the litter layer were 0. 14, 0. 10 and 0. 19 t C · hm-2, re-spectively. The soil organic carbon storage values (0-100 cm) in the three age groups were 62-53, 94. 10 and 65. 03 t C · hm-2, respectively. The proportions of the carbon storage in the 0-30 cm soil layer to that of the total soil layer were 33. 91%, 37. 64% and 44. 16%, increasing with the stand age. It was showed that the ecosystem carbon storage of the poplar plantations in Tianjin increased with the increasing stand age. Nowadays, the young poplar plantations account for a large proportion of the total forest plantations in Tianjin. Thus, the poplar plantations in Tianjin would have a huge carbon sequestration potential in the future. © 2014, Editorial Board of Chinese Journal of Ecology. All rights reserved.
Zhang X.-Q.,Chinese Academy of Forestry |
Lei Y.-C.,Chinese Academy of Forestry |
Chen X.-M.,Chinese Academy of Forestry |
Wang J.-Z.,Beijing Forestry Survey and Design Institute
Beijing Linye Daxue Xuebao/Journal of Beijing Forestry University | Year: 2010
Stand basal area is an important variable in forecasting stand growth and yield. A stand basal area growth model is a major component in stand variable modeling. A forecast combination combines information and disperses errors from different models and, as well, improves the accuracy of prediction. In this study, weights of different models were determined with minimum error variance. Based on periodic data of Chinese pine (Pinus tabulaeformis) stands from the mountain areas of Beijing, a forecast combination was used to estimate stand basal area from both stand-level and tree-level models. The results showed that the forecast combination for predicting stand basal area outperformed both stand-level and tree-level models. It also improves the compatibility of stand basal area growth models.
Zhang X.,Chinese Academy of Forestry |
Lei Y.,Chinese Academy of Forestry |
Pang Y.,Chinese Academy of Forestry |
Liu X.,Chinese Academy of Forestry |
Wang J.,Beijing Forestry Survey and Design Institute
Climatic Change | Year: 2014
Tree mortality in response to climate change induced drought has emerged as a global concern. Small changes of tree mortality rates can profoundly affect forest structure, composition, dynamics and ecosystem services such as carbon sequestration. Our analyses of longitudinal data from natural stands (82 plots) in Beijing showed that tree mortality rates have increased significantly over the two decades from 1986 to 2006. In contrast, recruitment rates decreased significantly over this period. The increase in overall mortality rates resulted from an increase in tree deaths dominantly attributed to changes in temperature and precipitation resulting in drier conditions across latitudes, elevations, tree species, and tree sizes. In addition, the results showed that mortality rates of Chinese pine (Pinus tabuliformis) (β 1 = 0.0874) as a result of climate change induce drought were much smaller than oak (Quercus) (β 1 = 0.1583). © 2014 Springer Science+Business Media Dordrecht.