【作者】 刘梦云；

【导师】 常庆瑞；

【作者基本信息】 西北农林科技大学 ， 土地资源与空间信息技术， 2011， 博士

【摘要】 为探讨黄土高原大规模的生态修复对土壤碳收支的影响,本研究以乔、灌、草和农田等不同植被类型,植被恢复的不同阶段,纯林和混交林等不同林分结构为对象,在野外调查和室内试验分析基础上,通过测定其典型剖面土壤及其团聚体有机碳的组分、数量变化及相互关系,研究其有机碳组分的变化趋势,探索生态恢复对土壤有机碳固定的影响,为黄土高原土地利用和生态环境建设规划提供依据。主要研究结果如下:1.植被恢复对土壤有机碳和总碳的影响(1)植被类型对土壤有机碳和总碳的影响较大。林地和草地可较大幅度地提高土壤碳含量,其中,灌木林地和天然草地在整个剖面上能积累更多碳。不同植被类型土壤有机碳和总碳的差异以0-5 cm土层尤为显著,林地和草地土壤有机碳含量高出耕地70%-107%,其土壤总碳高出耕地34%-66%。(2)不同植被恢复阶段土壤有机碳和总碳存在一定差异。沙棘林对土壤碳的积累效果最明显,其中在幼年期(15、16年)-成年期(20年)有机碳和总碳增加迅速,分别增加94%、158%;成年期-过熟期(26年)逐渐降低,总碳和有机碳分别减少32%、43%。刺槐林土壤碳随林龄增加而持续缓慢增加,22-28的6年间总碳增加14%,22-41的19年间有机碳增加68%。油松林有机碳和总碳变化速率介于沙棘林和刺槐林之间,30年以前(幼年-青年-成年期)随生长年限的增加而缓慢增加,30年后(成年-过熟期)则有所降低。(3)林分结构对土壤有机碳和总碳的累积存在较大影响。混交林对碳的积累效果明显优于纯林,土壤有机碳含量高出纯林16%-160%,其中侧柏-刺槐混交林高于纯林123%-160%,而油松-沙棘-刺槐混交林低于部分纯林;混交林土壤总碳含量高出纯林8%-115%,其中侧柏-刺槐混交林高于纯林74%-115%,而油松-沙棘-刺槐混交林分别低于沙棘和刺槐纯林15%和10%。2.植被恢复对土壤团聚体及其碳含量的影响(1)植被恢复可以较大程度地影响土壤团聚体及其碳含量。植被恢复可提高大粒径团聚体的含量,天然草地和灌木林地提高效果突出,而传统耕作会破坏大粒径团聚体。其中0-5cm土层,草地和林地土壤平均重量直径与耕地相比提高417%-811%,团聚体总量高于耕地29%-51%;耕地团聚体的48%为0.25-0.5mm粒级,草地和林地0.25-0.5mm团聚体所占比例均<20%,而其0.5-2mm团聚体所占比例均大于50%。植被恢复可以有效提高各粒级团聚体有机碳含量,尤以灌木林地最为显著;各植被类型土壤均表现为,0.25-0.5mm粒级有机碳含量最低,而2-5、1-2mm粒级有机碳较高。其中以0.5-1mm (林地和草地高于耕地53%-129%)和0.25-0.5mm(林地和草地高于耕地194%-196%)两个粒级差异较大。(2)不同植被恢复阶段土壤团聚体及其碳存在一定差异。刺槐林随恢复年限增加,团聚体增加明显,从28-41年的13年间,团聚体增加64%-143%。沙棘林和油松林幼年-青年期团聚体增加,成年期以后随恢复年限增加有所降低,油松在26-36年的10年间,团聚体降低43%-57%;沙棘林在16-26年的10年间降低36%-90%。不同植被恢复阶段,都以2-5mm、1-2mm和0.5-1mm三个粒级团聚体颗粒态有机碳含量较高。0-5 cm土层各粒径团聚体有机碳含量,油松林表现为16-26年间下降14%-36%,26-36年间除1-2mm粒径无变化外,其他各粒径均有小幅度增加,2-5mm粒级增加33%;28-41的13年间刺槐林各粒径团聚体有机碳含量增加23%-71%;而沙棘林16-26的10年间,各粒径团聚体有机碳含量基本上表现为先增加后减少,16-21的5年间增加46%-126%,而21-26的5年间下降24%-52%。(3)不同林分结构造成土壤团聚体及其碳存在一定差异。除刺槐混交林外,其他混交林土壤团聚体含量都低于其纯林。混交林可有效提高土壤各粒径团聚体有机碳含量。0-5 cm土层,侧柏纯林低于其混交林40%-58%,沙棘纯林低于油松-沙棘-刺槐混交林23-39%,油松纯林高于其混交林8%-57%,但低于油松-沙棘-刺槐混交林7%-30%,刺槐纯林低于其混交林1%-51%。3.植被恢复对土壤活性碳组分的影响(1)不同植被类型土壤活性碳组分存在较大差异。植被恢复可明显提高土壤活性碳组分及其分配比例,灌木林地和天然草地尤为显著。其中易氧化态有机碳含量高出耕地179%-204%,轻组有机碳含量高出耕地250%-1303%,粗颗粒态有机碳含量高出耕地865%-1409%,细颗粒态有机碳含量高出耕地65%-239%,可溶性有机碳含量高出耕地86%-155%。(2)不同植被恢复阶段土壤活性碳组分的变化较大。幼-青年期沙棘林和成年期刺槐林效果突出。其中沙棘林从幼年-青年,各碳组分积累明显,易氧化态有机碳含量增加25%-67%,轻组有机碳含量增加82%,粗颗粒态有机碳含量增加128%,细颗粒态有机碳含量增加57%,可溶性有机碳含量增加90%;成年-过熟期则迅速降低,易氧化态有机碳含量降低31%,轻组有机碳含量降低58%,粗颗粒态有机碳含量降低65%,细颗粒态有机碳含量降低40%,可溶性有机碳含量降低35%。刺槐林各碳组分随生长年限的增加各碳组分持续增加,其中22-41年的青年-成年期,易氧化态有机碳含量增加约60%,轻组有机碳增加18%-137%,粗颗粒态有机碳含量增加67%-210%,细颗粒态有机碳含量增加27%-243%,可溶性有机碳含量增加69%。而油松林的各活性有机碳组分变化速率介于沙棘林和刺槐林之间,基本以30年为界限先缓慢增加后缓慢降低。(3)不同林分结构土壤活性碳组分存在很大差异。混交林可有效提高各活性有机碳含量,混交林易氧化态有机碳含量高于纯林16%-304%;混交林轻组有机碳含量高于纯林17%-1399%,而沙棘混交林低于沙棘纯林7%-42%;混交林粗颗粒态有机碳含量高于纯林7%-639%,而刺槐-沙棘混交林低于沙棘纯林8%,油松-沙棘-刺槐混交林低于纯林21%-54%;混交林细颗粒态有机碳含量高于纯林16%-633%,却低于沙棘纯林5%- 53%;混交林可溶性有机碳含量高于纯林17%-170%,沙棘混交林略低或等于沙棘纯林。4.各碳组分之间的关系易氧化态、轻组、颗粒态有机碳组成物质及其物质来源基本一致,而重组与稳态有机碳基本一致,可溶性有机碳主要来源于易氧化态、细颗粒态有机碳;可溶性有机碳的增加可以减少无机碳的含量;碱性磷酸酶、蔗糖酶和脲酶活性直接与土壤活性碳组分的转化有关,而过氧化氢酶活性可反映土壤碳总量特征。土壤总碳、各有机碳组分与团聚体及其各粒级碳相关性说明,有机碳及其组分主要集中在1-2mm和0.5-1mm水稳性团聚体内;土壤碱性磷酸酶、蔗糖酶活性促进了团聚体的形成,尤其是1-2mm、0.5-1mm两个粒级团聚体。更多还原

【Abstract】 To explore the influence of mass ecological restoration on soil carbon balance in the Loess plateau, this study as the objects of different plant types-arbor, shrub, grass and wheat, different vegetation restoration stages and different plantation structures of pure and mixed forests, on the base of field investigation and laboratory analysis, by measure the typical soil and it’s aggregates carbon fractions and their relationship, had been done to research the trend of carbon variations. The main research results as follows:1. Effects of vegetation restoration on soil organic carbon(SOC) and total carbon(STC)(1) Vegetation restoration could influence on SOC and STC greatly.Soil carbon content could be improved greatly in forestland and grassland, especially in shrub forestland and natural grassland in the whole profile. The obvious difference of SOC and STC was in 0-5 cm layer, SOC under forestland and grassland was markedly higher than that under farmland by 70%-107%, their STC by 34%-66%.(2) There were some difference on SOC and STC during vegetation restoration stages.During short time planting Hippophae reamnoides, soil carbon could been increased distinctly, while long time planting Robinia pseudoacacia, soil carbon could been enhanced notably. The obvious differences of SOC and STC during different stages were in 0-5 cm layer, with the extension of planting time, STC and SOC increased very slowly under Robinia pseudoacacia but constantly(22-28 year STC increased by 14%, 22-41 year SOC increased by 7%-68%). SOC and STC under Hippophae reamnoides increased promptly during 15-21 years(STC and SOC increased by 94% and 158% individually), while that during 21-26 years decreased obviously(STC and SOC decreased by 32%, 43% individually). The rate of change of SOC and STC under Pinus tabuliformis was between those under Robinia pseudoacacia and under Hippophae reamnoides, 30 years ago SOC and STC slowly increased with the etension of planting time, while 30 years later they decreased slowly.(3) The accumulation of SOC and STC were influenced greatly by plantation structure.The accumulation of carbon under mixed forestland was more than that under pure forestland. The obvious difference of SOC and STC was in 0-5 cm layer, SOC content under mixed forestland was higher than that under their pure forestland for 16%-160%, except that under the mixed forestland of Pinus tabuliformis-Hippophae reamnoides-Acer mono Maxim was lower than that under Hippophae reamnoides pure forestland for 3%, that under mixed forestland of Pinus tabuliformis-Hippophae reamnoides-Robinia pseudoacacia was lower than that under Hippophae reamnoides and Robinia pseudoacacia pure forestland for 19%, 21% individually. STC content under mixed forestland was higher than that under their pure forestland for 8%-115%, except that under mixed forestland of Pinus tabuliformis-Hippophae reamnoides-Robinia pseudoacacia was lower than that under Hippophae reamnoides and Robinia pseudoacacia pure forestland for 15% and 10% individually.2. Effects of vegetation restoration on soil aggregates and their organic carbon content(1) Vegetation restoration could affect soil aggregates and their carbon concent greatly.Vegetation restoration could improve effectively big size aggregate content, especially by shrub forest and natural grass, while big size aggregates could been destroyed by conventional tillage. The obvious difference of >0.25 size aggregate content was in 0-5 cm layer, soil MWD under forestland and grassland was higher than that under farmland by 417-811%, total big size aggregate content were higher than that under farmland by 29%-51%. 48% aggregates under farmland was in 0.25-0.5mm size, that under grassland and forestland was less than 20% in 0.25-0.5mm size, while more than 50% aggregate was in 0.5-2mm size.Vegetation restoration also could improve effectively soil aggregate organic carbon content of big size, especially by shrub forest. For each plant type, among aggregate of >0.25mm size, aggregate organic carbon content in 0.25-0.5mm size was the lowest, while that in 2-5mm and 1-2mm size was higher. The obvious difference of aggregate organic carbon content was in 0-5 cm layer, the difference of aggregate organic carbon in 0.5-1mm size (that under forestland and grassland markedly higher than that under farmland for 53%-129%) and 0.25-0.5mm(that under forestland and grassland markedly higher than that under farmland for 194%-196%) were more obvious than others among different plant types.(2) There were certain different in soil aggregates and their organic carbon during different vegetation restoration stages.During short time of planting Pinus tabuliformis, it’s soil aggregates could been increased distinctly. While long time of planting Robinia pseudoacacia, it’s soil aggregates could been enhanced greatly. The obvious difference of aggregate content was in 0-5 cm layer, aggregate content under Pinus tabuliformis forestland during 16-36 years decreased with the extension of planting time, during 16-26 years soil aggregates in 2-5mm, 1-2mm and 0.5-1mm decreased by 41%-79%, during 26-36 years soil aggregates in 1-2mm, 0.5-1mm and 0.25-0.5mm decreased by 43%-57%. during 28-41 years under Robinia pseudoacacia forestland increased differently by 64%-143% (except >5mm size). That under 16-26 years Hippophae reamnoides forestland decreased 36%-90% (except 0.25-0.5mm).During vegetation restoration years, aggregate organic carbon in 2-5mm, 1-2mm and 0.5-1mm size were higher than that in other sizes. 0-5cm layer, aggregate organic carbon content under 16-26 years’Pinus tabuliformis forestland decreased by 14%-36%, that under that of 26-36 years increased a little bit. That under 28-41 years Robinia pseudoacacia forestland increased differently by 23%-71%. That under 16-26 years Hippophae reamnoides forest increased firstly and then decreased, that of 16-21 years increased by 46%-126%, 21-26 years decreased by 24%-52%.(3) Soil aggregates and their carbon were influenced greatly by plantation structure. >0.25mm aggregate content under pure forest was higher than that under mixed(except that under Robinia pseudoacacia pure forest). While aggregate organic carbon was on the contrary, in the 0-5 cm layer, that under Biota orientalis pure forest was lower than that under it’s mixded by 40%-58% (except that in >5mm size higher by 30%); that under Hippophae reamnoides pure forest was lower than that under mixed Pinus tabuliformis-Hippophae reamnoides-Robinia pseudoacacia forest by 23%-39% (except that in 0.25-0.5mm size higher by 21%); that under Pinus tabuliformis pure forest was lower than that under mixed forest of Pinus tabuliformis-Hippophae reamnoides-Robinia pseudoacacia by 7%-30%; that under Robinia pseudoacacia pure forest was lower than that under it’s mixed by 1%-51%.3. Effects of vegetation restoration on soil labile organic carbon(LOC)(1) Different plant type leaded to the big difference on soil LOC.Soil LOC fractions’content and their proportions under forestland and grassland were higher than those under farmland in the 0-100 cm profile, especially under shrub forestland and natural grassland. The obvious difference of soil LOC was in 0-5cm layer, compared to farmland, EOC of forestland and grassland was higher by 179%-204%, LFOC of those was higher by 250%-1303%, CPOC of those was higher for 865%-1409%, FPOC of those was higher by 65%-239%, DOC was higher by 86%-155%.(2) Soil LOC during different vegetation restoration stages varied greatly.During short time of planting Hippophae reamnoides, soil LOC could been increased distinctly. While long time of planting Robinia pseudoacacia, soil LOC could been improved greatly. The obvious difference of soil LOC was in 0-5 cm layer, soil LOC under Robinia pseudoacacia forestland increased very slowly with the extension of planting time but constantly increased, EOC increased by 60%, LFOC increased by 18%-137%, CPOC increased by 67%-210%, FPOC increased by 27%-243%, DOC increased by 69%. In 0-5 cm layer, soil LOC under Hippophae reamnoides forestland increased promptly during 15-21 years, EOC increased by 25%-67%, LFOC increased by 82%, CPOC increased by 128%, FPOC increased by 57%, DOC increased by 90%; while those of during 21-26 years decreased obviously, EOC decreased by 31%, LFOC decreased by 58%, CPOC decreased by 65%, FPOC decreased by 40%, DOC decreased by 35%.The rate of change of soil LOC under Pinus tabuliformis forestland was between that under Robinia pseudoacacia and that under Hippophae reamnoides, 30 years ago with the etension of planting time, LOC slowly increased, while 30 years later they decreased slowly.(3) There were obvious difference on soil LOC among different plantation structure.Compared to pure forestland, mixed forestland could boost effectively soil LOC, for example, in the 0-5 cm layer, EOC increased by 16%-304%, LFOC increased by 17%-1399% (while that under mixed forest of Hippophae reamnoides was lower than that under it’s pure forest by 7%-42%), CPOC increased by 7%-639% (while that under mixed forest of Robinia pseudoacacia-Hippophae reamnoides was lower than that under Hippophae reamnoides pure forest by 8%,that under mixed forest of Pinus tabuliformis-Hippophae reamnoides-Robinia pseudoacacia was lower than that under their pure forest by 21%-54%), FPOC increased by 16%-633% (while was lower than that under Hippophae reamnoides forest by 5%-53%), DOC increased by 17%-170% (while that under mixed Hippophae reamnoides forest was lower than that under it’s pure forest for 10%).4. The relationship among different carbon fractionsThe correlation coefficients among carbon fractions showed: the composition of the substance and its material source of EOC, LFOC and POC were basically the same, while those of heavy fraction organic carbon and stable organic carbon were basically the same, DOC mainly came from EOC and FPOC, the increase of DOC could decrease soil inorganic carbon content. Alkaline-phosphatase, Invertase and Urease activities related directly with the transformation of soil LOC and their availibility; while Catalase activity could reflect the characteristics of soil carbon amount.The correlations between STC, organic carbon fractions and aggregates, aggregate organic carbon showed: organic carbon fractions were mainly concentrated in aggregates of 1-2mm and 0.5-1mm; in addition, the correlation coefficients between 1-2mm, 0.5-1mm size aggregate and four enzyme activities were higher than those of other sizes, this also could indirectly explain that soil enzyme activity would affect the formation of aggregate.更多还原