【作者】 张龙；

【导师】 方向文；

【作者基本信息】 兰州大学 ， 林学， 2024， 硕士

【摘要】 自“退耕还林”工程实施以来,柠条锦鸡儿（Caragana korshinskii）作为黄土高原旱区林木植被恢复的主要树种,广泛用于造林。然而,前期由于技术限制,对种植密度难以确定,所造林分密度普遍偏高,造成了土壤水分的过度消耗、深层土壤旱化。间伐是一种传统的降低植株密度的手段,能够有效缓解林木对土壤水分的过度消耗,促进林木的体质增效。但对柠条锦鸡儿林如何间伐,以此缓解土壤旱化,改善林木光合水分生理尚不清楚。本论文以榆中县北山地区1993年人工栽植的柠条锦鸡儿林为研究对象,对其进行未间伐、轻度间伐（隔2株伐1株）、重度间伐（隔1株伐2株）和皆伐（全部砍伐）为处理,探究不同间伐强度对灌木水分生理和光合生理的影响。取得的主要结果如下:1、间伐处理恢复了浅层土壤含水量。研究发现,间伐两年后,与未间伐处理相比,轻度间伐、重度间伐和皆伐处理中0-200 cm土层土壤含水量提升了0.22%、0.33%和0.36%;和未间伐处理相比,200-500 cm土层中,轻度间伐处理的土壤含水量没有变化,重度间伐和和皆伐处理分别提高了0.17%和0.06%。2、间伐处理提升了柠条锦鸡儿光合水分生理。研究发现,间伐2年后,植株叶的凌晨水势和正午水势随着间伐强度的增加而增加,未间伐植株叶的凌晨水势和正午水势为-1.46 MPa和-2.35 MPa,轻度间伐处理后分别增加了0.1 MPa和0.17 MPa,重度间伐后分别增加了0.26 MPa和0.27 MPa;叶片最大水分传导速率随着间伐强度的增加而增加,未间伐植株叶最大水分传导速率为7.09mmol m^-2 s^-1 MPa^-1,轻度间伐和重度间伐处理后最大水分传导速率增加了1.45mmol m^-2 s^-1 MPa^-1和3.7 mmol m^-2 s^-1MPa^-1;最大光合速率随着间伐强度的增加而增加,未间伐处理植株最大光合速率为6.76μmol m^-2 s^-1 MPa^-1,轻度间伐和重度间伐处理后最大光合速率分别提升了1.35μmol m^-2 s^-1 MPa^-1和2.91μmol m^-2 s^-1 MPa^-1。3、间伐处理增加了柠条锦鸡儿的营养生长和生殖生长。研究发现,间伐两年后,新枝长度与生物量随着间伐强度的增加而增加,未间伐植株当年生枝长和生物量分别为3.74 cm和0.23 g/枝,轻度间伐处理后分别增加了0.89 cm和0.03 g/枝,重度间伐处理后分别增加了3.4 cm和0.11 g/枝;种子生物量和繁殖分配比随着间伐强度的增加而增加,未间伐植株种子生物量和繁殖分配比分别为5.00 g/枝和24.71%,轻度间伐处理后分别增加了11.87 g/枝和21.03%,重度间伐处理后分别增加了16.55 g/枝和34.03%。4、间伐处理增加了林下草本的优势度指数和物种丰富指数。未间伐处理的优势度指数为和物种丰富指数分别为0.55和0.80,轻度间伐处理后基本不变,重度间伐处理后分别增加了0.07和0.04,皆伐处理后分别增加了0.1和0.16。以上的研究结果表明,间伐能够促进柠条锦鸡儿林浅层土壤水分的恢复,缓解植株的水分亏缺,改善植株的光合水分生理,增强了植株的营养生长和生殖生长。本研究结果为黄土高原半干旱地区柠条锦鸡儿营林提供了科学指导,也为黄土高原人工植被恢复可持续发展提供了理论依据。更多还原

【Abstract】 Since the implementation of the"Grain for Green"project,Caragana korshinskii has been widely used for reforestation as a major species for vegetation restoration in the arid regions of the Loess Plateau.However,due to technical limitations,the reasonableness of planting density was not fully considered in the early stages,leading to generally high afforestation density,which caused excessive soil moisture consumption and deep soil desiccation.Thinning is a traditional method to reduce plant density,effectively alleviating the excessive consumption of soil moisture by shrublands and promoting rejuvenation and renewal.However,the appropriate thinning method for C.korshinskii to alleviate soil desiccation and improve plant photosynthesis and water physiology remains unclear.This study focuses on C.korshinskii plantations established in 1993 in the Beishan area of Yuzhong County,implementing treatments of no thinning,light thinning（removal of 1 in 3 plants）,heavy thinning（removal of 2 in 3 plants）,and clear-cutting（removal of all plants）.The study aims to explore the effects of different thinning intensities on soil moisture content and the water and photosynthetic physiology of C.korshinskii,revealing the regulatory role of thinning on the vegetative and reproductive growth of C.korshinskii shrublands.The main findings are as follows:Thinning treatments restored shallow soil moisture content.Two years after thinning,compared to the no-thinning treatment,the soil moisture content in the 0-200 cm layer increased by 0.22%,0.33%,and 0.36%for light,heavy,and clear-cutting treatments,respectively.In the 200-500 cm layer,soil moisture content decreased by 0.08%in the light thinning treatment but increased by 0.17%and 0.06%in the heavy and clear-cutting treatments,respectively.Thinning treatments improved the water physiology and photosynthesis of C.korshinskii.Two years post-thinning,the pre-dawn and midday leaf water potentials increased with thinning intensity.The pre-dawn and midday leaf water potentials were-1.46 MPa and-2.35 MPa for the no-thinning treatment,increased by 0.1 MPa and0.17 MPa for light thinning,and by 0.26 MPa and 0.27 MPa for heavy thinning.The maximum leaf water conductance increased with thinning intensity,from 7.09 mmol m^-2 s^-1 MPa^-1 for no thinning,to increases of 1.45 mmol m^-2 s^-1 MPa^-1 and 3.7 mmol m^-2 s^-1 MPa^-1 for light and heavy thinning,respectively.The maximum photosynthetic rate also increased with thinning intensity,from 6.76μmol m^-2 s^-1 MPa^-1 for no thinning,to increases of 1.35μmol m^-2 s^-1 MPa^-1 and 2.91μmol m^-2 s^-1 MPa^-1 for light and heavy thinning,respectively.Thinning treatments increased both vegetative and reproductive growth of C.korshinskii.Two years post-thinning,new shoot length and biomass increased with thinning intensity.For no-thinning,the shoot length and biomass were 3.74 cm and0.23 g/shoot,increased by 0.89 cm and 0.03 g/shoot for light thinning,and by 3.4 cm and 0.11 g/shoot for heavy thinning.Seed biomass and reproductive allocation also increased with thinning intensity,from 5.00 g/shoot and 24.71%for no-thinning,to11.87 g/shoot and 21.03%for light thinning,and 16.55 g/shoot and 34.03%for heavy thinning.Thinning treatments increased the dominance index and species richness index of understory herbs.For no-thinning,the dominance index and species richness index were 0.55 and 0.80,respectively.For light thinning,they decreased by 0.02 and 0.06;for heavy thinning,they increased by 0.07 and 0.04;and for clear-cutting,they increased by 0.1 and 0.16.These results indicate that thinning,as a traditional forestry management measure,can promote the recovery of shallow soil moisture,alleviate plant water deficits,improve plant water physiology and photosynthesis,and enhance both vegetative and reproductive growth,thereby rejuvenating shrublands.This study provides scientific guidance for the sustainable management of C.korshinskii plantations in the semi-arid regions of the Loess Plateau and offers theoretical support for the sustainable development of artificial vegetation restoration on the Loess Plateau.更多还原