| Platycladus orientalis（L.）Franco is a coniferous evergreen tree that originated in China,and is widely distributed in many parts of the country because of its barren resistance,drought resistance,and strong adaptability.The semimature Platycladus orientalis plantation after canopy closure needs thinning measures such as cutting and irrigation,plant fixation,and thinning,which will produce a large number of forest thinning shreds that are not easy to decompose.Platycladus orientalis has a high content of lignocellulose and other macromolecules,and the natural decomposition of thinning shreds is very slow.There are hidden dangers of forest fire and diseases and insect pests stacked in the forest,which will cause nutrient loss if brought out artificially.It can be seen that the efficient and harmless treatment of these organic wastes is of great significance.Composting is an important technical means to deal with organic waste,but the research on composting forest thinning shreds is still very scarce.It is of great significance to explore the technical means and fertilizer efficiency verification of in-situ composting of Platycladus orientalis in the forest.The process and quality of four kinds of compost（adjusting C/N and C/P+0.2%priming;adjusting C/N and C/P+0.2%common compost;only adjusting C/N and C/P;raw material crushing of thinning shreds）were studied by selecting two different additives（priming,Vitex,and cow dung compost）;Four different forest types（semimature Platycladus orientalis and Pinus tabuliformis Carr.plantation after thinning,thinning and non-thinning young Platycladus orientalis plantation）were selected to further design the fertilizer efficiency verification of compost products of four kinds of Platycladus orientalis thinning shreds.The fertilizer rates of 300 g·m-2,600 g·m-2,900 g·m-2,and 1200 g·m-2were applied back to the forest land,and the fertilization method was surface ring application（within 0.5m radius）.Within a 1.5-year cycle,the optimal fertilization combination of Platycladus orientalis thinning compost was selected from three aspects:forest soil（nutrients and microorganisms）,forest growth（height,diameter,and volume）,and understory regeneration.The main results are as follows:（1）In this study,the thinning shreds of Platycladus orientalis were collected as composting raw materials.After they were crushed,the moisture content was adjusted to 70%,C/N to 40,and C/P to 100.After that,the additive was added according to 0.2%of the mass of the pile.After mixing,the pile was covered with plastic agricultural film.After reaching the temperature peak in the 6th week,the reactor was turned over once.The whole composting cycle of this study was 8 weeks.（2）The peak temperature of the priming compost reached 51℃,and the common compost had a great influence on the variation of water content and EC value.At the end of composting,the lignin decomposition rate of priming compost reached 25.5%.The hemicellulose decomposition of common compost was 1.9 times that of only adjusting C/N and C/P compost and 3.2 times that of the control group.The contents of organic matter and total nutrients in the priming compost were significantly increased,and the total nutrient content reached 5.8%.The germination index of each compost ranged from 60%to 81%.Except for the control group,the C/N of other treatments decreased below 25.（3）After half a year of fertilization,the soil nitrogen content of Pinus tabulaeformis plantation with priming compost was 1.5 times that without fertilization.The contents of available phosphorus in 0～20 cm and 20～40 cm soil layers were 47.2 and 20.4 mg·kg-1higher than those in the control group,respectively;The microbial biomass carbon content in 0～20 cm soil layer was 1.4 times that of no fertilization.One year after fertilization,the soil became sour;the effect of compost on urease activity in the 0～20 cm soil layer was greater than that in the 20～40 cm soil layer.After fertilization for 1.5years,the number of fungi in the 0～20 cm soil layer of the priming compost was 2.2 times that of only adjusting C/N and C/P compost,and 2.8 times that of the non-fertilization in the 20～40 cm soil layer;common composting can effectively stimulate the accumulation of soil bacteria and soil alkaline phosphatase activity in Pinus tabulaeformis plantation.The average height of Pinus tabulaeformis after1.5 years of fertilization was 3 times that without fertilization;common promoted the growth of DBH of trees,and the average increment of DBH was 2.5 cm.The renewal effect of priming compost was better than that of common compost.（4）After half a year of fertilization,the available phosphorus in the soil of Platycladus orientalis plantation increased by 56.4 and 54.6 mg·kg-1respectively under high fertilization.After 1.5 years of fertilization,the soil with the low amount of fertilizer was the most neutral;in 0～20cm soil layer,the soil microbial biomass carbon of common compost under low fertilizer application was 1.9 times that of non-fertilizer application,and the soil microbial biomass nitrogen of priming compost was 2.12 times that of common compost;the soil invertase activity of Platycladus orientalis was 3 times higher than that of non-fertilization under medium and high application rates of detonator fertilizer;the primary compost was more conducive to the growth of soil bacteria.High fertilization stimulated the growth of tree crown in a short time,but it was not conducive to the growth of tree height;the average DBH growth of Platycladus orientalis was 1.5 cm when the medium fertilizer amount was applied to the priming compost;the single tree volume and stand volume increased fastest when the amount of fertilizer was low.The effect of medium and high fertilizer applications was better than that of low fertilizer applications.（5）The effect of compost on soil pH of thinning and non-thinning Platycladus orientalis plantation occurred during 1～1.5 years;the soil total nitrogen of the thinning+fertilization group was significantly different from that of other fertilization treatments;After 1.5 years of fertilization,the available phosphorus content of thinning+no fertilization group was the highest in both soil layers;fertilization without tending would reduce the accumulation of soil available potassium in Platycladus orientalis plantation.The stimulation of tending compost on the diameter growth of Platycladus orientalis could last for 0.5 years;the effect of thinning on the single tree volume accumulation of Platycladus orientalis plantation was greater than that of fertilization.The renewal effect of forest tending compost could last for 1 year.In conclusion,composting reduced the natural decomposition cycle of forest thinning shreds to 2～3 months,and additives effectively accelerated the decomposition of organic matter and improve the quality of compost;the primary compost had the best fertilization effect on Pinus tabulaeformis plantation;when the primary compost was applied at the rate of 600 g·m-2,the effect of fertilization on Platycladus orientalis plantation was the best;the fertilizer effect of thinning compost on young Platycladus orientalis plantation could last for 0.5 years,and then it was mainly affected by tending.This paper studied the composting technology of integrated Platycladus orientalis thinning forest land,studied the process,maturity,and quality of composting products with different additives,and determined the time effect and optimal fertilization combination of additive Platycladus orientalis thinning composting by verifying the composting fertilizer effect.The study is of significance to explore the composting,nutrient cycling,and forestry production of Platycladus orientalis. |
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