Study On Eco-physiological Characteristics And Ecological Benefits Of Ten Main Garden Tree Species In Hohhot

The characteristics of growth, water and photosynthesis eco-physiological, carbon fixation and oxygen release, energy absorbed through transpiration and dust-retention ability of ten main garden tree species in Hohhot were reseached. On the basis of the analysis, water adaptability and ecological benefits of tree species were recognized as the garden trees'evaluation principles of applicability in our region. And by means of them tested tree species were classified and evaluated. The results had provided theoretical basis and technical reference for choosing garden trees in our city. The main results were as follows:1. Use the maximum of the osmotic potentials at the initial loss turgor in twig growth period to compare drought resistances of ten tree species. The drought resistances of conifers from strong to weak was Platycladus orientalis, Juniperus rigida, Pinus tabulaeformis, Picea meyeri Rehd. et Wils.The order of broadleaved tree species from strong to weak was: Syringa oblata, Populus alba var.pyramidalis, Prinus triloba, Sorbaria kirilowii, Sophora japonica, Ailanthus altissima.2. The research of absorbing water capacity indicates, the order of conifers was Platycladus orientalis>Pinus tabulaeformis>Juniperus rigida>Picea meyeri Rehd. et Wils, the order of broadleaved tree was Sorbaria kirilowi>Ailanthus altissima>Syringa oblata >Prunus triloba >Populus alba var.pyramidalis>Sophora japonica.3. On the condition of suitable temperature, humidity, CO2 and saturated light intensity, the relationship between the net photosynthetic rate and relative transpiration rate was y=a+b(1-e-bx) and y=k/(1+ae-bx) respectively. The conifers order of the water saturated deficit at 0 net photosynthetic rate was Platycladus orientalis>Juniperus rigida >Pinus tabulaeformis>Picea meyeri Rehd. et Wils,the order of broadleaved tree was Populus alba var.pyramidalis>Ailanthus altissima>Prunus triloba>Syringa oblata> Sophora japonica>Sorbaria kirilowii.4. The daily course curve of net photysynthetic rate and transpiration rate was double peak or single peak type. The order of the average of net photosynthetic rate in growth season was Prunus triloba>Populus alba var.pyramidalis>Sophora japonica> Syringaoblata>Ailanthus altissima>Sorbaria kirilowii>Platycladus orientalis>Picea meyeri Rehd. et Wils>Juniperus rigid >Pinus tabulaeformis. The order of the average of transpiration rate in growth season was Prunus triloba>Syringaoblata>Sophora japonica>Populus alba var.pyramidalis>Ailanthus altissima>Sorbaria kirilowii>Platycladus orientalis>Pinus tabulaeformis>Picea meyeri Rehd. et Wils>Juniperus rigida.5. The order of the annual fixed carbon and releasing oxygen capacity of broadleave trees was Populus alba var.pyramidalis>Sophora japonica>Ailanthus altissima>Prunus triloba > Syringaoblata > Sorbaria kirilowii, confier trees was Platycladus orientalis>Juniperus rigid>Picea meyeri Rehd. et Wils>Pinus tabulaeformis. The annual average fixed carbon and releasing oxygen of broadlevae trees were 86.40㎏·stock-1·a-1 and 73.13㎏·stock-1·a-1, and confier trees were 51.75㎏·stock-1·a-1 and 37.63㎏·stock-1·a-1. The order of the annual transpiration of broadleave trees was Populus alba var.pyramidalis > Sophora japonica > Ailanthus altissima > Prunus triloba >Syringaoblata>Sorbaria kirilowii,confiertrees was Platycladus orientalis>Juniperus rigida>Pinus tabulaeformis>Picea meyeri Rehd. et Wils. The annual transpiration of broadlevae trees was 18.32 t·stock-1·a-1, and confier trees was 9.94 t·stock-1·a-1.6. The order of the average of dust absorption of broadleaved trees was Populus alba var.pyramidalis>Ailanthus altissima>Sophora japonica>Sorbaria kirilowii>Syringa oblata>Prunus triloba,and confier trees was Juniperus rigida>Platycladus orientalis>Picea meyeri Rehd. et Wils>Pinus tabulaeformis. The average amount of dust absorption in one week of confier trees was 4.5 times as big as broadleave trees.7. According to water adaptability comprehensive index, tested tree species were classified to four groups by Cluster Analysis. The result showed that Platycladus orientalis had the most adaptive to water. Juniperus rigida, Pinus tabulaeform and Picea meyeri Rehd. et took the second place. Prunus triloba, Populus alba var.pyramidalis and Ailanthus altissima were in the middle. Syringaoblata, Sorbaria kirilowii and Sophora japonica had the least water adaptability.According to the main ecological benefits indexes, the tested species trees were classified to four groups by Cluster Analysis. Ecological benefits of Populus alba var.pyramidalis was the highest. Juniperus rigida took the second place. Sophora japonica, Ailanthus altissima and Platycladus orientalis were in the middle. Pinus tabulaeformis, Picea meyeri Rehd.et, Syringaoblata, Prunus triloba and Sorbaria kirilowii had the smallest ecological benefits.