Effect Of Crown Thinning On Photosynthesis Of Pinus Koraiensis In The Understory

The broad-leaved and Korean-Pine Forest of Northeast Eastern Mountain is the richest and most diverse forest ecosystem of North temperate Eurasia, containing extremely rich flora and fauna, is our precious forest resources. Pinus koraiensis is the dominant tree species of broad-leaved and Korean-Pine Forest, and is shade-tolerant tree specie. Understorey seedlings are slow growing. Whether reasonable crown thinning intensity play an active role in the growth of pine, Requiring scientific evidence.Relevant Study will provide the basic data for the development of operating model and realization of Sustaining Development for Pinus Koriensis Forests.A survey was conducted to study the effects of different crown thinning intensities on Pinus koraiensis forests using 15-year-old and 30-year-old Pinus koraiensis in Changbai With international advanced portable Photosynthetic measuring system. We measured the main photosynthetic parameters including the apparent quantum yield,the dark respiratory rate and the maximum rate of photosynthesis of Pinus koraiensis from May to October. The experimental study canopy density 0 (clear cutting),0.2,0.4,0.6, and 0.8 (control) the effect of differences between the obtained results are as follows:1. Effect of crown thinning on seasonal dynamics of photosynthetic parameters of Pinus koraiensis in the understory(1) Crown thinning changes the seasonal trends of the apparent quantum yield of 15-year-old and 30-year-old Pinus koraiensis in the understory.Crown thinning intensities change the seasonal trends of the apparent quantum yield of 15-year-old Pinus koraiensis shade conifer needles.15-year-old Pinus koraiensis sun and shade conifer needles showed a decrease from May to July and first decreased and then increased from August to October in check community forest. canopy density 0 (clear cutting), 0.2,0.4 shade conifer needles all showed a decrease from May to July and First increased and then decreased from August to October. Canopy density of 0.6 showed a decreasing trend from May to July and August to October; Only the higher upbringing density (canopy density 0) changed the seasonal trend of the apparent quantum yield (decrease from May to July, First increased and then decreased from August to October).30-year-old Pinus koraiensis sun and shade conifer needles showed a decrease from May to August and a increase from September to October, canopy densities Pinus koraiensis sun and shade conifer needles showed a decrease from May to July,but show different trends from August to October, canopy density 0 First decreased and then increased, canopy density0.2 shade conifer needles First increased and then decreased,sun conifer needles decrease from May to August and decrease from September to October, canopy density0.4 First increased and then decreased, canopy density0.6 increased.(2) Crown thinning changes the seasonal trends of the maximum net rate of 15-year-old and 30-year-old Pinus koraiensis in the understory.The maximum net rate of 15-year-old canopy density0,0.2,0.4,0.6,0.8 Pinus koraiensis sun conifer needles Seasonal changes were first increase and then decrease from May to July and August to October,both decreases from May to July and August to October, first increase and then decrease from May to July,first decrease and then increase from August to October, decrease from May to July,first decrease and then increase, first increase and then decrease from May to July,decrease from August to October; shade conifer needles were first decrease and then increase from May to July,first increase and then decrease from August to October, both decreases from May to July and August to October, decrease from May to July,first decrease and then increase from August to October, both decreases from May to July and August to October, first increase and then decrease from May to July,decrease from August to October. the maximum net rate of photosynthesis of 30-year-old canopy density0,0.2,0.4,0.6,0.8 Pinus koraiensis sun conifer needles Seasonal changes were both decreases from May to July and August to October, first decrease and then increase from May to July and August to October, both decreases from May to July and August to October, first increase and then decrease from May to July,decrease from August to October, first increase and then decrease from May to July,decrease from August to October; shade conifer needles were first increase and then decrease from May to July,decrease from August to October, first increase and then decrease from May to July and August to October, first increase and then decrease from May to July and August to October, both decreases from May to July and August to October, decreases from May to July,first decrease and then increase from August to October.(3) Crown thinning changes the seasonal trends of the dark respiratory rate of 15-year-old and 30-year-old Pinus koraiensis in the understory.The dark respiratory rate of 15-year-old canopy density0,0.2.0.4.0.6.0.8 Pinus koraiensis sun conifer needles Seasonal changes were both decreases from May to August and from September to October, decrease from May to August,increase from September to October, decrease from May to July,decrease from August to October, decrease from May to July,first decrease and then increase from August to October, decrease from May to July,first decrease and then increase from August to October; shade conifer needles were decrease from May to July,increase from August to October, decrease from May to August,increase from September to October, decrease from May to July,increase from August to October, decrease from May to July,increase from August to October, decrease from May to September,increase in October.the dark respiratory rate of photosynthesis of 30-year-old canopy density0,0.2,0.4,0.6,0.8 Pinus koraiensis sun conifer needles Seasonal changes were decrease from May to September,increase in October, decrease from May to August,increase from September to October, decrease from May to July,increase from August to October, decrease from May to July,first decrease and the increase from August to October, decrease from May to July,first decrease and the increase from August to October; shade conifer needles were decrease from May to September,increase in October, decrease from May to August,increase from September to October, decrease from May to August increase from September to October, decrease from May to July,first decrease and the increase from August to October, decrease from May to July,increase from August to October. The dark respiratory rate of photosynthesis of Canopy densities is largely unlike to check community forest except canopy density 0.6 sun conifer needles.2. Effect of crown thinning on photosynthesis of Pinus koraiensis in the understory(1) Crown thinning had significant effects on the apparent quantum yield of Pinus koraiensis in the understory.The average apparent quantum yield of The growing season 15-year-old Pinus koraiensis distribution between0.064-0.101 molmol-1,lower(0.6),middle(0.4),higher upbringing density(0.2,0) improve it 38.6%～40.6%,32.4%～54.9%,37.8%～39.2%and12.0%～12.7%. The average apparent quantum yield of The growing season 30-year-old Pinus koraiensis distribution between0.052-0.082molmol-1, higher upbringing density improve it26.9%～35.7%,shade conifer needles were similar to check community forest (2.5%～9.0%) middle upbringing density Reduced it 20.6%-23.7%, sun conifer needles were similar to check community forest (-5.0～9.1%)(2) Crown thinning had significant effects on the maximum net rate of Pinus koraiensis in the understory.The average maximum net rate of The growing season 15-year-old Pinus koraiensis distribution between10.170～16.139μmolCO2m-2s-1, higher upbringing density(0.2,0) improve it 41.4%～54.3%and38.6%～58.7%; middle upbringing density improve it 16.9%～35.0%; lower upbringing density were similar to check community forest (-1.2%～7.8%).The average maximum net rate of The growing season 30-year-old Pinus koraiensis distribution between 8.622～17.444μmolCO2m-2s-1, higher upbringing density improve it 14.1%～18.6%and24.6%～49.2%; middle upbringing density reduced it 12.3%～26.2%; lower upbringing density were similar to check community forest (-8.5%～0.9%)(3) Crown thinning had significant effects on the dark respiratory rate of Pinus koraiensis in the understory.The average the dark respiratory rate of The growing season 15-year-old Pinus koraiensis distribution between 1.272～2.036μmolCO2m-2s-1, higher upbringing density reduced shade conifer needles 16.2%～19.9%, sun conifer needles were similar to check community forest (-3.7%～16.7%);middle upbringing density improve sun conifer needles and shade conifer needles28.1%～44.4%; lower upbringing density improve it (22.9%～34.6%).The average the dark respiratory rate of The growing season 30-year-old Pinus koraiensis distribution between 1.255～1.625μmolCO2m-2s-1 middle and higher upbringing density sun conifer needles were similar to check community forest (1.4%～1.2%),lower upbringing density reduced 16.8%;Crown thinning intensities reduces the dark respiratory rate of shade conifer needles 18.2%～28.4%。as a result, crown thinning reduced The average the dark respiratory rate of The growing season30-year-old Pinus koraiensis shade conifer needles largely more than check community forest,but,had less effects on the dark respiratory rate of Pinus koraiensis sun conifer needles.