Selection And Evaluation On Superior Plant Materials For Drought Resistant And Water-Saving In Beijing

Beijing is a city short of water severely. And the water shortage problem will be further deteriorated with the increase of forest and green space cover rates. To solve this problem, it is the key factor to select and apply plant species with characteristics of drought resistance and water-saving in Beijing. In this paper, according to present situation of the green space construction and the shortage of urban water resource in Beijing, the common 63 landscape plant species in Beijing (6 evergreen conifers, 16 deciduous trees, 20 shrubs, 5 wood ground cover plants and 9 herb ground cover plants, 7 climbers) were used to examined their anatomical characteristics (the leaves anatomical structure: thickness of both upper and lower epidermis cuticle, the thickness of both upper and lower epidermis, thickness of leaf, layers and thickness of spongy tissue, layers and thickness of the palisade tissue, width of spongy tissue cell and palisade cell, the ratio of thickness of palisade tissue versus thickness of spongy tissue, cell tense ratio, spongy ratio, stomatal density and size, etc), physiological characteristics (long-term and instantaneous water use efficiency in spring, summer and autumn and relationships betweenδ13C with soil temperature, humidity and the other weather variables) as well as responses of plant seedlings to water stress. Some potentially drought resistant greenism plant species with high ornamental value were selected by multi-objective, multi-plant comprehensive selection, and the indicators of selecting drought resistant and water-saving plants were also evaluated. Evaluation indicator system of Beijing urban landscape plants with characteristics of drought resistance and water-saving was established based on this. Main conclusions are as follows:(1) The differences of drought resistance characteristics among four kinds of greenism plant species were preliminarily identified by analyzing the leaf anatomical indicators. The order of drought resistant capability in evergreen trees was Platycladus orientalis>Sabina chinensis, Pinus tabulaeformis > Pinus bungeana>Pinus armandi>Cedrus deodara; while, that in the 16 kinds of hardwood plants was S. matsudana f.Umbraculifera>Magnolia denudate, Eucommia ulmoides, Diospyros kaki, Acer truncatum>Sophora japonica, Koelreuteria paniculata, Populus tomentos, Robinia pseudoacacia, Ailanthus altissima, Crataegus pinatifida, Fraxinus chinesis, Tilia mandshurica and Catalpa bungei>Ginkgo biloba and Liriodendron chinense×L.tulipifera; and the sequence of drought resistant capability for shrubs was Hippophae rhamnoides>groupⅠof shrubs with greater drought resistant capability (Cotinus coggygria, Lonicera maackii, S. leaucopithecia, Sorbaria sorbifola, Syringa oblata, Philadephus pekinensis, Chaenomeles speciosa, Malus'Red jude', Amorpha fruticosa, Kerria japonica var.pleniflora, Buddleja lindleyana and Prunus cerasifera f. atropurea)>groupⅡof shrubs with relatively weaker drought resistant capability (Abelia chinensis, Prunus persica f.duplex, Prunus triloba, Weigela coraeensis and Viburnum sargentii)>Euonymus japonicus and Weigela florida cv.Red Prince; the order in wood cover ground plants was Cotoneaster horizontalis>Ligustrum×vicaryi>Berberis thunbergii cv. Atropurpurea, Caryopteris clandonensis'Worcester Gold'and Rosa chinensis, and that in herb cover ground plants, Sedum spectabile>Hemerocalis fulva>Tagetes patula and Corepsis grandiflora>Monarda didyma, Veronica didyma, Hosta plantaginea, Orychophragmus viloaceus and Viola philippcia; in the climbers, Euonymus var.microphyllus>Lonicera japonica, Wisteria sinensis, Campsis radicans>Parthenocissus quinquefolia and Celastrus orbiculatus>Polygonum aubertii.(2) The results inδ13C value of different plants during the 3 different season showed thatδ13C value in evergreen trees differed significantly among tree species and did not vary among seasons; whileδ13C value in deciduous hardwood trees, shrubs, ground cover and climber plants in spring were greater than that in summer and autumn, and differed significantly among seasons and plant species (except wood ground cover species). As there was a positive relationship between water use efficiency andδ13C value, the above results indicated that water use efficiency in deciduous hardwood trees, shrubs, ground cover and climber plants in spring was larger than that in summer and autumn, with the smallest in summer. The result of instantaneous water use efficiency was consistent with that of long term water use efficiency, that is, instantaneous water use efficiency in spring was greater than that in summer.(3) Comprehensive analysis ofδ13C, photosynthetic rate and instantaneous water use efficiency of different plants during the 3 seasons showed that water use efficiency of Sabina chinese was higher than that of Platycladus orientalis, higher water use efficiency suggesting stronger water saving characteristics. And water-saving capability of Pinus bungeana and Pinus tablaeformis were greater, and Cedrus deodara was the opposite, Drought resistance capability of Ginkgo biloba and Liriodendron chinense×L.tulipifera was weaker, but their WUE was higher, Salix matusdana f. Umbraculifera was a kind of plant with deep roots and strong drought resistant capability. Fraxinus chinese, Magnolia denudate, Diospyros kaki, Eucommia ulmoides and Acer truncatum were greater water-saving landscape plants, while Sophora japonica, Populus tomentosa, Ailanthus altissima and Crataegus pinatifida were lower water-saving landscape plants, and the rest species were in the middle level. For shrubs, Lonicera maackii, Weigela florida cv.Red Prince, Weigela coraeensis and Viburnum sargentii were higher water - saving landscape shrubs with higher long term water use efficiency, but drought resistant capability and water use efficiency of Euonymus japonicus were lower; In wood ground cover plants, Cotoneaster horizontalis and Ligustrum×vicaryi were better at water saving, next was Rosa chinensis; Sedum spectabile with special structure and CAM metabolic pathway showed the strongest drought resistance and water- saving capabilities, water use efficiency in Hosta plantaginea and Veronica didyma were higher; Drought resistance and water-saving of Lonicera japonica and Wisteria sinensis were higher among the climbers, Polygonum aubertii was the opposite.(4) The water stress experiment on typical plants among four types of plant species showed that the adaptability to drought in Fraxinus chinese was better than that in Ginkgo biloba, Sabina Chinese, with Cedrus deodara the weakest, for shrubs, Viburnum sargentii was stronger than Buddleja lindleyana, Prunus persica and Weigela florida cv.Red Prince; drought resistance of Ligustrum×vicaryi was the strongest among the ground cover plants; For climbers, the adaptability to drought in Euonymus var.microphyllus was better than that in Polygonum aubertii. Thus, it can be concluded that the drought adaptability of seedlings was consistent with the above results except that in V. sargentii.(4) Evaluating indicators system of drought-resistant and water-saving urban landscape plants in Beijing was established. The grey correlative degree analysis showed that the indicators that highly associated with drought-resistant and water-saving plants in various groups were very close, mainly includingδ13C value in spring, summer and autumn, the thickness of leaves, specific leaf area, stomatal density, stomatal long diameter, the size of a single stoma, cell tense ratio and spongy ratio of leaves, The conclusion reflected that these indicators contributed more than the others to drought-resistant and water-saving capability. The grey correlative degree analysis showed the drought adaptability of seedlings to water stress was consistent with actual drought resistant capability of seedlings.