【作者】 张海涛；

【导师】 宫渊波；

【作者基本信息】 四川农业大学 ， 水土保持与荒漠化防治， 2017， 博士

【摘要】 我国人工林在经营过程中,由于长期纯林经营或经营措施不当等因素,普遍存在的生物多样性丧失严重,生产效率低下、生态功能普遍不高、水土流失严重等生态安全问题。采用珍贵乡土用材树种改造现有低产低效人工林是提高人工林生产效益和生态防护功能的重要途径。但在进行人工林改造过程中由于采用不同的改造模式或进行不同方式的整地技术,不可避免的导致改造初期水土流失加剧和土壤抗蚀性下降的现象。本文以川南低山丘陵区马尾松低效人工林为研究对象,采用设置4种不同大小林窗以及林窗内建立5个人工径流小区的方法,从枯落物持水功能、土壤抗蚀性变化以及地表产流产沙等方面入手,对马尾松低效林不同模式改造初期坡面产流产沙特征及演变过程、枯落物持水、土壤抗蚀性变化及相应的土壤水土保持功能进行了系统研究,探索马尾松低效林不同改造模式下林地水土保持功能演变规律,以期为当地低效人工林改造和更新,及森林可持续经营提供理论和技术支撑。经过试验取得以下研究结果:(1)、试验区降雨多集中于6～9月份,年均降水总量约1000mm。试验期2.5a内最小降雨量为1.2mm,最小产流降雨量为6.9 mm,最大降雨量为93.8 mm。径流小区试验开始一年后,各小区径流系数下降幅度超过30%,皆伐小区达到50%左右。降雨量与地表径流量相关系数在0.905以上。(2)、2012年下半年径流小区产沙次数均超过2013年和2014年全年产沙次数,产沙降雨由最初超过50%降至20%左右。5个径流小区产沙量大小与受人为扰动程度一致,Ⅲ号皆伐小区最高,Ⅰ号最低。冬季由于降雨量较少,无产沙现象发生。试验初始阶段各径流小区侵蚀模数均在6000t/km2·a以上,2014年时降至700t/km2·a以下。(3)、选取中雨、大雨、暴雨3种类型共计9次典型次降雨,对比不同次降雨条件下径流小区产流、产沙特征。2014年Ⅰ～Ⅴ号径流小区各雨量级次降雨产流量分别比 2012 年降低-6.44%,-10.51%,20.95%,13.28%,12.73%;产沙总量降低 58.4%,56.38%,77.72%,78.16%,79.68%。降雨量与产流量之间线性关系拟合程度较好,R2为0.9536;与产沙量拟合后R2为0.4647。表明坡面径流大小主要受降雨量影响,而产沙量大小则是由多种因素共同决定。产流量与产沙量拟合后R2达到0.6356,说明二者存在较密切关系。(4)、不同大小林窗未分解层枯落物比例大小为CK>L30>L20>L40>QK>L10,已分解层的比例大小排序为L20>L10>L40>QK>L30>CK。枯落物最大持水总量大小排序为L30>QK>L10>L20>L40>CK。林窗和QK两种改造措施下枯落物有效拦蓄量处于8.85t/hm2～11.14t/hm2之间,均高于CK(7.64t/hm2),有效拦蓄量大小排序为L30>QK>L10>L20>L40>CK。枯落物层持水量与浸水时间存在以下关系:w=alnt+b[249],R2均在0.86以上。4种不同大小林窗改造模式下枯落物吸水速率大小排序为未分解层>半分解层>已分解层;QK大小排序为半分解层>未分解层>已分解层;CK大小排序为半分解层>已分解层>未分解层。(5)、CK在6种类型样地中土壤持水能力表现最佳;表层土壤(0～20cm)最大持水量和田间持水量等指标均好于第二层(20～40cm)。两种改造模式土壤总孔隙度和毛管孔隙度两项指标均比CK样地土壤低,非毛管孔隙度则高于CK。表层土壤毛管孔隙度大于第二层,非毛管孔隙度对比后结果则相反。表层土壤容重大小排序为L30-1(1.50g/cm3)>L40-1(1.37g/cm3)>L20-1(1.36g/cm3)>L10-1(1.34g/m3)>CK-1、QK-1(1.33g/cm3);第二层容重大小排序为 L20-2(1.58g/cm3)>L10-2、QK-2(1.50g/cm3)>L30-2(1.45g/cm3)>CK-2(1.40g/cm3)>L40-2(1.39g/cm3)。随着改造时间推移,规格小于30m的林窗2～5mm粒径团聚体比例呈现上升趋势,0.5～1mm和1～2mm粒径团聚体比例呈下降趋势。各粒级水稳性团聚体比例多数都随时间推移而减小。CK样地的土壤平均重量直径(MWD)均显著高于其他样地。0～20cm 土层MWD值随林窗面积增大而减少。各样地间MWD差异不显著。除L10样地0～20cm 土层团聚体破坏率有小幅下降以外,其余样地该指标均有不同程度增加。与CK相比,不同改造模式表层土壤有机质含量明显降低,但下层变化幅度不大,从改造模式看,皆伐模式低于林窗,大林窗低于小林窗。不同类型样地土表层土壤有机质含量差异极显著,而第二层土壤除CK与L10和L40与QK之间有机碳含量差异不显著以外,其余为极显著。(6)、选取土壤不同层次最大持水量、土壤总孔隙度、毛管孔隙度、非毛管孔隙度、容重、平均重量直径、团聚体破坏率、可蚀性因子K、有机碳含量等9个指标,采用主成分分析法得到两个主成分回归方程:F1=0.01X1+0.127X2+0.182X3-0.245X4+0.1 14X5+0.136X6-0.179X7-0.178X8+0.1 11X9;F2=0.346X1+0.068X2-0.071X3+0.408X4-0.502X5+0.067X6+0.044X7+0.041X8+0.092X9。并推算出水土保持功能综合评价指数F=0.797F1+0.203F2。结果显示CK综合指数最高,L10和L20分列二、三位,且两者水土保持功能差别不大,好于L30、L40和QK样地。综上所述:马尾松低效人工林改造初期随着植被的恢复,地表产流、产沙明显降低。但土壤持水能力、水稳性团聚体、有机质含量及土壤抗蚀性等均呈下降趋势,且随干扰程度的增加而加剧,这符合林分改造初期的客观规律,表明选择合适的改造模式及造林整地方法是减少水土流失和控制土壤抗蚀降低的重要措施。不同改造模式亦会随着林木的生长和森林生态系统的自我完善,其水土保持效益会明显提高。但因本研究时间较短,林窗水土保持功能长期演变规律需未来进一步研究。更多还原

【Abstract】 China is a large country of plantation resources,but in the process of plantation management,due to long-term pure forest management or improper operating measures and other factors,the prevalence of serious loss of biodiversity,low production efficiency,ecological function is generally not high,serious soil erosion ecological security issues.The use of precious native timber tree species to transform existing low and low efficiency plantations is an important way to improve the production efficiency and ecological protection of plantations.However,in the process of artificial forest transformation,due to the use of different transformation mode or different ways of soil preparation technology,inevitably lead to the initial soil erosion and soil erosion increased the phenomenon of decline.Therefore,it is an important content to be concerned about the process and mechanism of soil erosion and the law of soil erosion and its evolution law,which is different from the different transformation and regeneration mode or land preparation method in the early stage of transformation.In this paper,the low-efficiency artificial forest of Pinus massoniana in hilly area of southern Sichuan was used as the research object,and 4 methods of setting up 5 artificial trees were established.The characteristics of runoff and sediment yield and the evolution process of the slope on the early stage of the transformation of different provenances of Pinus massoniana were studied from the aspects of water holding function of litter,soil erosion resistance and surface runoff and sediment yield.The change of soil erosion and the corresponding soil water and soil conservation function were systematically studied,and to explore the evolution rule of soil and water conservation in different landforms of low efficiency forest of Pinus massoniana,in order to provide theoretical and technical support for the transformation and renewal of local inefficient plantation and sustainable management of forest.The following results were obtained:(1)Local rainfall and more concentrated in Jun～Sep,the average annual rainfall was about 1000mm.The minimum rainfall was 1.2 mm,the minimum rainfall was 6.9 mm and the maximum rainfall was 93.8 mm.A year after the start of the runoff plot test,the runoff coefficient of each plot decreased by more than 30%,and the cutting area was even about 50%.The correlation coefficient between rainfall and surface runoff is above 0.905.(2)In the second half of 2012,the number of runoff in the runoff area exceeded that of 2013 and 2014,and the sediment rainfall decreased from about 50%to about 20%.The size of sediment concentration in 5 runoff towns was consistent with the degree of human disturbance,and the highest level of Ⅲ was the highest.Winter due to less rainfall,no sediment occurred.At the initial stage of the experiment,the erosion modulus of each runoff area is above 6000 t/km2·a,and in 2014,it was reduced to 700t/km2 · a.(3)A total of nine typical singal rainfalls were selected for the three types of rainfall,and the characteristics of runoff and sediment yield were compared under the secondary rainfall conditions.The total rainfall output was reduced by-6.44%,10.51%,20.95%,13.28%and 12.73%respectively.The total sediment yield decreased by 58.4%,56.38%and 77.72%,78.16%,79.68%.The linear relationship between rainfall and runoff was better,R2 was 0.9536,and after sedimentation’s R2 was 0.4647.Indicating that the runoff size of the slope was mainly affected by rainfall,and the size of sediment production is determined by a variety of factors.The yield and sediment yield reached R2 was 0.6356 after fitting,indicating that there was a close relationship between the two factors.(4)The proportion of litter size of non-decomposed layer was CK>L30>L20>L40>QK>L10,the proportion of decomposed layer was L20>L10>L40>QK>L30>CK.Litter maximum water holding capacity of the order of L30>QK>L10>L20>L40>CK.The effective storage volume was ranked L30>QK>L10>L20>L40>CK,and the effective storage of litter was between 8.85 t/hm2 and 11.14 t/hm2.Litter layer water holding capacity and flooding time there are the following relationship:w = alnt+b,R2 were more than 0.86.Four patterns litter absorption rate is undecomposed layer>semi-decomposing layer>decomposed layer QK was a semi-decomposing layer>undecomposed layer>decomposed layer;CK was a semi-decomposing layer>decomposed layer>undecomposed layer(5)The water holding capacity of CK was the best among the six types of plots.The maximum water holding capacity and field water holding capacity of surface soil(0～20cm)were better than those in the second layer(20～40cm).The soil total porosity and capillary porosity were lower than those of CK plots,and the non-capillary porosity was higher than that of CK.The porosity of the topsoil is greater than that of the second layer,and the non-capillary porosity is opposite.The surface soil bulk density ranking was L30-1(1.50g/cm3)>L40-1(1.37g/cm3)>L20-1(1.36g/cm3)>L10-1(1.34g/cm3)>CK-1,QK-1(1.33g/cm3),and the second layer bulk density ranking was L20-2(1.58g/cm3)>L10-2,QK-2(1.50g/cm3)>L30-2(1.45g/cm3)>CK-2(1.40g/cm3)>L40-2(1.39 g/cm3).With the transformation time,the ratio of 2～5mm particle aggregated with diameter less than 30m showed an increasing trend,and the proportion of 0.5～1mm,and 1～2mm aggregated decreased.The proportion of water-stable aggregates of each particle size decreased with time.The soil average weight diameter(MWD)of CK plots was significantly higher than that of other plots.The MWD of 0～20cm soil layer decreased with the increase of the gap.The difference between MWD was not significant.In addition to L10 sample 0～20cm soil aggregate agglomeration rate decreased slightly,the remaining samples of the indicators have increased to varying degrees.Compared with CK,the content of soil organic matter in the surface of the different transformation mode was significantly lower,but the change of the lower layer was not significant.From the model of transformation,the clear cutting mode was lower than that of the gap.The content of soil organic matter in different types of soils was very different,while the difference of organic carbon content between CK and L10 and L40 and QK was not significant.(6)The effects of maximum soil water holding capacity,soil total porosity,capillary porosity,non-capillary porosity,bulk density,average weight diameter,agglomeration rate,erasable factor K and organic carbon content were selected.The law yields two principal component regression equations:F1=0.01X1+0.127X2+0.182X3-0.245X4+0.114X5+0.136X6-0.179X7-0.178X8+0.111X9;F2=0.346X1+0.068X2-0.071X3+0.408X4-0.502X5+0.067X6+0.044X7+0.041X8+0.092X9。And the comprehensive evaluation index of soil and water conservation function is calculated:F = 0.797Fi + 0.203F2.The results showed that the soil and water conservation functions of L10 and L20 were not much better than those of L30,L40 and QK plots.The comprehensive analysis showed that the surface runoff and sediment yield were obviously decreased with the restoration of vegetation in the early stage of plantation.But the soil water holding capacity,water stable aggregates,organic matter content and soil corrosion resistance all decreased,and increased with the increase of interference degree,which accorded with the objective law of the early stage of forest transformation,indicating that the appropriate transformation mode And afforestation method is an important measure to reduce soil erosion and reduce soil erosion.Different transformation mode will be with the growth of trees and forest ecosystems self-improvement,the soil and water conservation benefits will be significantly improved.However,due to the short time of this study,the long-term evolution of soil and water conservation function of the gap can be further studied in the future.更多还原