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The Effect Of Thinning On Soil Hydrological And Physicochemical Properties In Three Plantations

Posted on:2021-01-17Degree:MasterType:Thesis
Country:ChinaCandidate:K L DongFull Text:PDF
GTID:2370330605957079Subject:Forest science
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Cunninghamia lanceolate,Pinus elliottii and Cryptomeria fortunei take a quite important role in plantation of South China,while its comprehensive benefits were limited by the problems including mono-specie and over dense,which should be improved urgently.For above issue,tending and thinning is a crucial pathway to adjust the composition structure,hierarchical structure and age structure,which through eliminated the stands with weak growth and poor genetic quality then improving the quality and structure of coniferous plantation.With such process,the hydrological effect and soil physical and chemical properties also were ameliorated under these forest.Additionally,the near natural forest management could be realized by replant the precious native broad-leaved trees in the coniferous plantation.At present,the national policy named "Accurate improvement of forest quality project"was implementing,while tending and thinning was considered as an important technical mean in the policy.For accurately understand the influence of the technical mean to the ecosystem process in pure coniferous plantation.Fixed tending(T)and control(CK)plots were set in three pure coniferous plantations including Cunninghamia lanceolate with 16a,Pinus elliottii with 14a and Cryptomeria fortunei with 12a,where were located in Jiangxi,Hunan and Sichuan,China,respectively.From 2016 to 2019,The growth of trees,the soil physical properties,the soil enzymes and the soil and water loss were regularly investigated and their differences between tending sample plots and control sample plots were compared,systematically.The main resulted are as follows:(1)Thinning could effectively improve the hydrological effects of forest soil and reduce soil erosions:After tending,the hydrological indicators were significantly decreased in Cunninghamia lanceolate,Pinus elliottii and Cryptomeria fortunei.plantations(P<0.05),from 2016-2019.Among of these indexes,the surface runoff were decreased by 2.29,2.18 and 1.71 mm in above three plantations,respectively;the net water volume were decreased by 45.84,43.61 and 34.35 kg·L-1,respectively;the net mud volume were decreased by 92.09,108.02 and 54.16 kg·L-1,respectively;the runoff coefficient were decreased by 0.16,0.18 and 0.10%,respectively;and the scour volume were decreased by 4.60,11.43 and 2.71%respectively;However,the weak fluctuation of these indicators were not significantly in CK at the experiment period(P>0.05).(2)Thinning could improve the structure of surface soil and enhance the ventilation and permeability of soil:From 2016 to 2019,The soil bulk density(0-20cm)in tending sample plots of Cunninghamia lanceolate,Pinus elliottii and Cryptomeria fortune were decreased significantly than CK(P<0.05)and it were decreased by 0.43,0.21 and 0.19 g·cm-3,respectively;the soil capillary porosity were increased by 11.76,19.57 and 8.63%,respectively;the non-capillary porosity were increased by 5.26,4.27 and 4.03%,respectively;the forest water storage capacity were increased by 263.34,102.51 and 237.67 t·hm-2,respectively,and it were increased significantly than 2016,while the these differences between two soil layers(0-20cm and 20-40cm)of the CK plot and 20-40 cm soil layer of the tending plot was weak(P>0.05).(3)Thinning could vary the restoration of forest land capacity and increase the content of soil nutrients:From 2016 to 2019,the soil pH values of 0-20cm soil layer in tending plots of Cunninghamia lanceolate Pinus elliottii and Cryptomeria fortune were increased significantly(P<0.05),which were increased by 0,35,0.20 and 0.21 respectively,and with the decrease of soil acidity,while deeper than 20cm of soil layer,the differences of pH value between T and CK were was not significantly(P>0.05);the varities of soil chemical indexes were significant,among of them,the total nitrogen content were increased by 0.46,0.56,1.99 g·kg-1 respectively,the total potassium content were increased by 1.66,2.05,2.12 g·kg-1,respectively,the total phosphorus content were increased by 0.16,0.19,0.35 g·kg-1,respectively,the hydrolytic nitrogen contents were increased by 0.079,0.03 and 0.195 g·kg-1,respectively,the available potassium contents were increased by 0.044,0.053,0.040 g·kg-1,respectively,the available phosphorus contents were increased by 0.0032,0.0033 and 0.0221 g·kg-1,respectively.While the varieties of nutrient contents in 20-40cm soil layers between T and CK were not obviously in 4 years Meanwhile,the trends of decrease of soil nutrient contents were detected in two soil layers of CK at the past five years,while them is not significant(P>0.05).(4)Thinning could promote the activities of soil enzymes:After 4 years of tending,the catalase activities were increased by 0.29,0.25 and 0.66 ml·h-1·g-1 in Cunninghamia lanceolate Pinus elliottii and Cryptomeria fortune.than their control plots,respectively;urease activities were increased by 0.19,0.07 and 0.16 mg·g-1·24h-1,respectively;Acid phosphatase activities were increased by 1.94,1.22,0.62 mol·g-1·24 h-1,respectively;Meanwhile,the significant differences of acid phosphatase activities between T and CK plots in each experiment areas.(P<0.05).(5)Thinning could accelerate the growth of the stands:In T plots,the mean DBH,mean height and the growth of stock volume were obviously increased than CK,these indexes were increased 2.29 cm,2.34 m and 49.11 m3/hm2 for Cunninghamia lanceolate,2.1 cm?0.8 m and 44.44 m3/hm2 for Pinus elliottii,1.8 cm,3.45 m and 88.72 m3/hm2 for Cryptomeria fortune,among these indexes,DBH and stock volume were shown significant differences than CK(p<0.05).while for height of stands,there had week differences(P>0.05),except Cryptomeria lanceolate(P<0.05).For coniferous plantation,above results indicated that the soil structure,the enzyme activities and the forest growth were improved by thinning.Additionally,the thinning management could increase and decrease the soil nutrient and soil erosion,respecitively.
Keywords/Search Tags:Tending thinning, Soil, Hydrological effect, Physical and chemical properties, Cunninghamia lanceolate, Pinus elliottii, Cryptomeria fortune
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