Carbon-Fixation and Oxygen-Release Potential of Six Greening Tree Species on a Large-Scale Pig Farm

The physiological indices of six greening tree species on a large-scale Pig Farm of Fuxin city were measured by the LI-6400 portable photosynthesis system,and their carbon-fixation and oxygen-release potentials were evaluated.The results indicated that the daily curves of the net photosynthetic rates of the six tree species were mainly a double-peak type,with the first peak appearing between 7:00-9:00,the second one between 14:00-16:00,and an apparent photosynthetic siesta phenomenon at noon.The net photosynthetic rates of Populus alba berolinensis and Populus simonii Car seasonally varied as single-peak curve and arrived at the peak in June and July,respectively.And that of Pyrus ussuriensis Miaxim.fand Pyrus ussuriensis Maxim.varied as a double-peak curve,with a valley August.The net photosynthetic rates of Passer montanus saturatus Stejneger and Syringa oblata Lindl also seasonally varied as a double-peaks curve,with a significant reduction in June.The potentials of the six tree species on fixing carbon and releasing oxygen were high in the months of June,July and August,weaker in September,and weakest in May.The order of their potentials on fixing carbon and releasing oxygen was Pyrus ussuriensis Miaxim.f Passer montanus saturatus Stejneger Pyrus ussuriensis Maxim. Populus simonii Carr. Populus alba berolinensis Syringa oblata Lindl.Pyrus ussuriensis Miaxim.f.,Passer montanus saturatus Stejneger and Populus simonii Carr.were suitable greening tree species for widely planting on the large-scale pig farm.