Study On Water Adaptability Of Tree Species Of Water Conservation Forest

The chief function of water resource conservation forest contains three parts, water conservation, soil and water conservation and improvement of water quality. The water resource conservation system should be a comprehensive protective forest system whose main objectives are water conservation, soil and water conservation. At the same time it gives attention to commercial timber forest. With the development of modern society and the growth of population and economic, water resources shortage has been becoming a global problem which attracted the attention all over the world. And more and more attention is being paid to water resource conservation forest which main objective is water conservation.Water adaptability of 3-year-seedlings was investigated using pot experiment of 12 tree species in this paper. The 12 tree species included Populus alba×Populus berolinensis, Fraxinus maudshurica, Syringa oblate, Betula platyphylla, Ulmus pumila, Syringa amurensis, Tilia amurensis, Juglans mandshurica, Salix matsudana, Phellodendron amurense, Picea koraiensis Nakai, Pinus sylvesris L.var.mongolica Litvin. The research contained three parts: (1) Photosynthetic and water consuming characteristics of the tree species of water conservation forest was researched in Heiiongjiang Province (2) Wilting coefficient of tree species in water conservation forest was determined and drought-resistance of different tree species was compared. Also, drought-resistance mechanism under simulated drought stress was researched using Populus alba×Populus berolinensis as experimental material. (3)Waterlogging adaptability of tree species was studied and waterlogging-resistance of different tree species was compared Mechanism of waterlogging harm was probed into and waterlogging-resistance indices had been screened.Through the analyses of the photosynthetic and water consuming characteristics of the trees the results showed that net photosynthesis rate per day from May to September decreased as follow sequence: Salix matsudana＞Populus alba×Populus berolinensis＞Syringa oblata＞Ulmus pumila＞Betula platyphylla＞Fraxinus maudshurica＞Juglans mandshurica＞Syringa amurensis＞Phellodendron amurense; Transpiration rate per day as follows: Salix matsudana＞Ulmus pumila＞Populus alba×Populus berolinensis＞Phellodendron amurense＞Syringa oblata＞Fraxinus maudshurica＞Betula platyphylla＞Juglans mandshurica＞Syringa amurensis＞Tilia amurensis; Water consumption every year per plant: Populus alba×Populus berolinensis＞Salix matsudana＞Betula platyphylla＞Syringa oblata＞Ulmus pumila＞Fraxinus maudshurica＞Syringa amurensis＞Tilia amurensis＞Juglans mandshurica＞Phellodendron amurense; Water use efficiency per day: Populus alba×Populus berolinensis＞Syringa oblata＞Betula platyphylla＞Salix matsudana＞Syringa amurensis＞Tilia amurensis＞Ulrnus pumila＞Fraxinus maudshurica＞Juglans mandshurica＞Phellodendron amurense. Fluorescence parameters of different tree species vary regularly,ΦPSII and Fv/Fm were higher in the morning and evening while lower at noon, which wais converse to the changes of PAR and air temperature per day. Fo was lower in the morning and evening while higher at noon. The seasonal varieties of fluorescence parameters of different tree species were quite different.The study from the aspect of drought adaptability mechanism showed that the wilting coefficients of tree species from strong to weak were as follows: duglans mandshurica, Phellodendron amurense, Salix matsudana, Betula platyphylla, Tilia amurensis, Populus alba×P opulus berolinensis, Fraxinus maudshurica, Syringa amurensis, Picea koraiensis Nakai, Ulmus pumila, Syringa oblata and Pinus sylvesris L.varmongolica Litvin. Populus alba×Populus berolinensis presented strong drought resistance and moderate drought was favorable to photosynthesis, in given soil moisture content (40.1%～20.2%), the rate of photosynthesis decreased with the soil moisture and the decreased degree was smaller. The rate of photosynthesis decreased tempestuously when the soil moisture lowered to 15.5%. The light saturation point of Poplar reduces with the reducing of soil moisture content. There would be a series of changes in physiology and biochemistry in Poplar under drought stress so that its drought-resistance was stronger. Drought stress would lead to the reduction of chlorophyll content. SOD activity increased at the beginning of soil slight drought and decreased with soil water stress degree ascending and days prolonging. Freeproline and carotenoind and electrolyte matter content increased slightly and soluble sugar increased obviously. The indices which could make the drought resistance of Poplar much stronger are the accumulation of soluble sugar, praline and carotenoid, smaller descending range of SOD and unobvious changes of MDA and membrane permeability. In terms of that we could take them as drought-resistance indices.The study from the aspect of water-logging adaptability mechanism showed that the waterlogging-resistances of tree species from the best to the worst were as follows: Populus alba xPopulus berolinensis and Salix matsudana＞Tilia amurensis＞Pinus sylvesris L.varmongolica Litvin＞Betula platyphylla, Ulmus pumila and Picea koraiensis Nakai＞Syringa amurensis＞Fraxinus maudshurica＞Syringa oblate. Water-logging leaded to the descend of photosynthetic rate and the decrease of chlorophyll content, but there was no direct relation between them. There is few changes of transpiration rate, stomatal conductance and Fv/Fm in the trees which has good waterlogging-resistance. In the late stage of waterlogging, Fo variation of tree species of good waterlogging-resistance keet stable, and Fo of the tree species of middling waterlogging-resistance decreased, while that of the tree species of bad waterlogging-resistance increased. Under the waterlogging condition, the Photochemical Quenching(qP), practice photosynthetic rate(ΦPSII) and net photosynthetic rate of tree species changed in the same step. Although practice photosynthetic rate(ΦPSII) and net photosynthetic rate of tree species of good waterlogging-resistance decreased, qN of them increased. There should be a series of changes in physiology and biochemistry in seedlings after waterlogging stress, which helps adapt to waterlogging stress. Tree species whose leaf water content increased at the beginning of wateriogging had better waterlogging-resistance. There was much relationship between the variation of carotenoid contents and waterlogging-resistance of tree species whose waterlogging-resistance was strong. Its waterlogging-resistance increased a lot and with less reduction of boiling conductivity after being subjected to longtime water stress it became stronger. But there is no comparability between conifer and broadleaf trees. Proline content increased gradually with days prolonging. The praline content of Poplar whose waterlogging-resistance was strong increased obviously while much less in Salix matsudana instead。Soluble protein contents of the tree species which had good waterlogging-resistance increased gradually or kept a high level and that of the tree species of middling wateriogging-resistance kept stable or decreased gradually after the decline at the beginning of waterlogging, while soluble protein contents of the tree species which had bad waterlogging-resistance decreased gradually after increased. SOD activity of the tree species which had good waterlogging-resistance increased while that of the ones whose waterlogging-resistance was worse decreased after being subjected to longtime water stress, except for Syringa oblata of the worst waterlogging-resistance.Different tree species have different waterlogging-resistance and different indexes have different influences on waterlogging. Taking every aspect into consideration show that the variation of photosynthetic rate, Fo, Fv/Fm, carotenoind content, boiling conductivity, proline content, soluble protein contents and SOD activity make direct effect on the waterlogging-resistance of tree species. They all can be taken as waterlogging-resistance indexes. The study on water-logging adaptability shows the water-logging adaptability mechanism of forest trees and fixes the factors that can reflect trees' waterlogging-resistance.Basing on the test results, electable tree species could be provided for the water conservation forests in different habitats and their different purposes of management. (1)From the aspect of water conservating, the tree species which has lower transpiration rate, less water consumption per year and higher water use efficiency was needed, such as Betula platyphylla, Fraxinus maudshurica, Syringa amurensis, Tilia amurensis, Juglans mandshuricam, Phellodendron amurense, Pieea koraiensis Nakai and Pinus sylvesris L.var.mongolica Litvin. (2)Salix matsudana and Populus alba×Populus berolinensis who have good photosynthetic ability and great growth increment are fast-growing tree species, with Ulmus pumila and Syringa oblate second to them. (3)The ones which have stronger drought-resistance are Pinus sylvesris L.var.mongolica Litvin, Syringa oblate, Ulmus pumila, Picea koraiensis Nakai, Syringa amurensis, Fraxinus maudshurica, Populus alba×Populus berolinensis, Tilia amurensis and Betula platyphylla. (4)The water conservation forests around the reservoir and on the riverside and catchment are always under the condition of water-logging. The tree species which have stronger waterlogging-resistance are Populus alba×Populus berolinensis, Salix matsudana and Tilia amurensis.There had been a comprehensive research on photosynthetic characteristic, fluorescence characteristic, water consuming characteristic and water adaptability mechanism of some different tree species in water conservation forest under different water conditions in this paper. The water-logging adaptability mechanism of trees had showed and the factors that can reflect trees' waterlogging-resistance had fixed. The results of the research not only provide the evidence for the construction of water conservation forest in Heilongjiang Province. but also enrich the water physiology of trees.