【作者】 王文波；

【导师】 赵雨森；

【作者基本信息】 东北林业大学 ， 水土保持与荒漠化防治， 2010， 博士

【摘要】 有机酸在森林生态系统中普遍存在,尽管其含量较低,但其具有活性基团,所以在森林生态系统中发挥着重要作用。本文以我国东北地区落叶松、水曲柳、红松、白桦等主要树种为对象,以东北林区地带性森林暗棕壤为基础,通过室内淋洗L层和F层凋落物,研究了东北林区4个主要林分凋落物释放有机酸的种类和数量变化；通过模拟凋落物释放优势有机酸的含量,进行有机酸/盐添加试验,研究了优势有机酸/盐对东北林区地带性森林暗棕壤难溶性磷素有效性的影响,以及有机酸/盐对水曲柳幼苗生理特性、生长、生物量积累和分配的影响,得到以下主要结论：(1)建立了一种森林凋落物淋洗液中有机酸分析测定的气相色谱法,经回收率、检出限、精密度检验,该方法符合分析要求。森林凋落物可溶出多种有机酸,出现频率较多的主要包括草酸、丙二酸、反丁烯二酸、丁二酸、酒石酸、顺丁烯二酸、苹果酸、柠檬酸等。已定性的有机酸中,柠檬酸含量最大,其次为草酸、丁二酸、反丁烯二酸,再次为苹果酸、丙二酸、酒石酸,顺丁烯二酸含量最低。对于某一种有机酸,落叶松和水曲柳凋落物淋溶的数量相对较多,白桦和红松相对较少。(2)用浸提方式研究有机酸/盐对暗棕壤的磷释放效应时,草酸、柠檬酸和苹果酸均有最佳的浸提时间,均为12h,此时磷释放量最大。浸出液中磷的测定,主要有“土显法”和“水显法”两种,通过研究正常显色时间时不同浓度有机酸对磷标准溶液显色的影响、有机酸和有机盐浸提暗棕壤后待测液显色的时间序列,发现,“水显法”测定效果强于“土显法”,因此研究有机酸/盐对暗棕壤磷的释放效应时,采用“水显法”测定浸出液和淋洗液中的磷,≤5mmol/L有机酸/盐浸提或淋洗时,采用“水显法”直接测定,10和20mmol/L有机酸/盐浸提时则分别稀释2倍和4倍后测定,显色时间均定为15min。(3)一次性浸提时,草酸、柠檬酸、苹果酸、草酸盐、柠檬酸盐和苹果酸盐显著促进暗棕壤A1层磷的释放,磷释放量随其浓度增加而增大,但B层土壤磷的释放效应相对较弱。草酸盐、柠檬酸盐和苹果酸盐分别比同浓度草酸、柠檬酸和苹果酸具有更高的解磷效率,因此推断有机酸/盐促进暗棕壤磷素养分释放的主要机理在于有机酸阴离子反应。三种有机酸/盐对A1层和B层暗棕壤磷的释放效应表现为：柠檬酸＞苹果酸＞草酸、柠檬酸盐＞苹果酸盐＞草酸盐,这主要与三种有机酸的化学结构、离解常数、有机酸配体和金属形成络合物的稳定性大小有关。(4)有机酸/盐对A1层暗棕壤中磷的释放不是一次就能完成的,第1次以后的连续9次浸提仍有一定的解磷效果,这说明有机酸/盐对土壤磷的释放是连续的,具有累加性,尽管每次磷释放量可能不多,但经过有机酸/盐多次浸提的累加效应,就能释放出数量可观的磷。淋洗实验同样证实,柠檬酸盐溶液明显促进暗棕壤A1层磷的活化释放,随淋洗时间延长磷的累积释放量增大。(5)外源有机酸和有机盐均提高水曲柳幼苗的光合作用水平,包括光响应曲线和光合日进程,均以5.0mmol/L浓度处理时影响最显著,其他浓度处理增幅较小,作用规律不明显。三种有机酸和有机盐对水曲柳幼苗光合作用的影响强弱,表现为：柠檬酸＞苹果酸＞草酸、柠檬酸盐＞苹果酸盐＞草酸盐、草酸盐＞草酸、柠檬酸盐＞柠檬酸、苹果酸盐＞苹果酸。(6)有机酸和有机盐对水曲柳幼苗的多种生理指标产生重要影响,包括ALA合成速率、PBG合成酶活性、叶绿素含量、可溶性蛋白含量、可溶性糖含量、Rubisco初始活性和总活性、根系活力等,0.2-50.0mmol/L三种有机酸和有机盐处理均对上述几种生理特性有促进作用,且都以5.0mmol/L浓度时影响最显著,其中叶绿素a和叶绿素b含量变化较明显,类胡萝卜素含量变化较平缓,Rubisco活化率影响规律不明显。三种有机酸与有机盐对上述几种生理特性的影响强弱,表现为：柠檬酸＞苹果酸＞草酸、柠檬酸盐＞苹果酸盐＞草酸盐、草酸盐＞草酸、柠檬酸盐＞柠檬酸、苹果酸盐＞苹果酸。(7)不同浓度有机酸/盐均促进水曲柳幼苗的生长,增加了叶面积、苗高和基径,其中5.0mmol/L浓度处理时增加效果最显著,其余浓度处理增幅较小。三种有机酸和有机盐的影响强弱表现为：柠檬酸＞苹果酸＞草酸、柠檬酸盐＞苹果酸盐＞草酸盐、草酸盐＞草酸、柠檬酸盐＞柠檬酸、苹果酸盐＞苹果酸。(8)不同浓度有机酸/盐有利于水曲柳幼苗叶片的光合作用、叶绿素合成及土壤中养分元素的活化释放,因而有利于水曲柳幼苗的生物量积累,0.2-50.0mmol/L草酸/盐、柠檬酸/盐、苹果酸/盐处理后,根、茎、叶、地上部分和单株生物量均有所增加,各浓度间的影响均以5.0mmol/L浓度处理时效果最显著。各器官生物量增加的比例呈现出不同的规律,整体看,根和叶生物量增幅较大,茎生物量变化较小,但也略有增加。三种有机酸和有机盐对各器官生物量的影响大小表现为：柠檬酸＞苹果酸＞草酸、柠檬酸盐＞苹果酸盐＞草酸盐、草酸盐＞草酸、柠檬酸盐＞柠檬酸、苹果酸盐＞苹果酸,在各处理浓度时此规律均比较明显。(9)不同浓度有机酸和有机盐作用下水曲柳幼苗生物量分配趋势与对照完全一致,其生物量主要分配到根系部分,根生物量明显高于地上部分生物量,更高于叶或茎生物量,这和树种本身的特点有关。从不同浓度有机酸和有机盐对生物量分配的影响看,根生物量比例增加,茎生物量比例降低,叶生物量比例变化规律不明显,地上部分生物量比例降低,根茎比提高,其中均以5.0mmol/L浓度时影响最显著。三种有机酸和有机盐对各器官生物量分配的影响,强弱均表现为：柠檬酸＞苹果酸＞草酸、柠檬酸盐＞苹果酸盐＞草酸盐、草酸盐＞草酸、柠檬酸盐＞柠檬酸、苹果酸盐＞苹果酸。更多还原

【Abstract】 Organic acids were ubiquitous in forest ecosystems.There was active-COOH in organic acids’structure,so they played a central role in forests and forest soils.In the paper, based on Larix olgensis, Fraxinus mandshurica, Pinus koraiensis,Betula platyphylla and dark brown forest soil, kinds and content of organic acids in 4 kinds of litter leachates were researched by leaching L and F layer litters; by simulating organic acids concentrations in forest litter leachates and application experiment,effects and mechanism of exogenous organic acids/salts on P availability of dark brown forest soils,effects of exogenous organic acids/salts on physiological characteristics,growth,biomass accumulation and biomass allocation of Fraxinus mandshurica seedlings were researched.The results were as follows:(1)A capillary gas chromatography procedure was established to determine organic acids in forest leachates,and the method was satisfactory by feasibility test.Some low-molecular-weight organic acids could be leached from forest litters,including oxalic,malonic,fumaric, succinic,maleic,malic,tartaric and citric and so on.Contents of citric were greater than any other organic acids,followed by oxalic,succinic and fumaric,contents of malic,malonic and tartaric were lower,and contents of maleic were fewest in all samples.As to the same organic acid,the contents in leachates of Larix olgensis and Fraxinus mandshurica were greater than of Pinus koraiensis and Betula platyphylla.(2)Effects of exogenous organic acids/salts on P availability of dark brown forest soils following extractions,there were optimal extraction time(12h) to oxalic, citric and malic.As to P determination in extraction,"soil coloration method" and "water coloration method" both could be used.By studying the effects of different concentration of organic acids on coloration of phosphorus standard solutions,and organic acids added to A1 and B horizon soils, it founded that,"water coloration method" was better,so it was chosen to determine P in extraction and leachate.When concentration of organic acids/salts were lower than 5mmol/L,P could be determined directly,concentration were 10 and 20mmol/L,P should be diluted to 2 and 4 times respectively,and coloration time was all 15min.(3)Oxalic acid/salts substantially stimulated soil P release of A1 horizon following one-time extraction,showing a linear relationship.But its effect on B horizon soil was relatively negligible.Organic salts had a much higher soil-P-release effect than corresponding organic acids the same in concentration,therefore,the mechanism of organic acids/salts triggering P release were assumed to be dominated by reactions of organic anion.P release from A1 and B horizons by organic acids/salts followed the series:citric>malic>oxalic,citrate>malate>oxalate, and it was related to structures,dissociation constants of organic acids and stabilities of organic ligand-metal.(4)Soil P release from A1 horizon under different concentrations of organic acids/salts could not be finished following one-time extraction,and P could be released following latter nine-time extractions,so the effects of organic acids/salts on P release was somewhat cumulative.P release following one-time extraction was not much,but P release following sequential extractions would be very conspicuous.Leaching experiment also proved that,citrate stimulated soil P release of A1 horizon,and P cumulative release were higher with longer leaching times.(5)Exogenous organic acids/salts could improve photosynthesis level of Fraxinus mandshurica seedlings,including photosynthesis curve and dynamic,of which 5.0mmol/L concentration had better capacity than other concentrations.Effects of organic acids/salts on photosynthesis followed the series:citric>malic>oxalic,citrate>malate>oxalate,oxalate>oxalic, citrate>citric and malate>malic.(6)Organic acids/salts had important impacts on some physiological characteristics of Fraxinus Mandshurica seedling,including activity of ALA biosynthesis rate,activity of PBG synthase,chlorophyl content,soluble protein concentration,soluble sugar content,Rubisco initial activity,total activity and root activity.Organic acids/salts of 0.2 to 50.0mmol/L concentration were all profitable to the characteristics above,and 5.0mmol/L concentration had best effect.To effects on chlorophyl content,chlorophyl a and chlorophyl b contents varied more than carotenoid content.Rubisco activity ratio did not show obvious rule.Effects of organic acids/ salts on physiological characteristics above followed the series:citric>malic>oxalic,citrate> malate>oxalate,oxalate>oxalic,citrate>citric and malate>malic.(7)Organic acids/salts were helpful to increase growth of Fraxinus mandshurica seedlings, leaf area,height and collar diameter under organic acids/salts treatments were all higher than distilled water.Growth of 5.0mmol/L concentration organic acids/salts were higher than other concentrations.Effects of organic acids/salts on growth of Fraxinus mandshurica seedlings followed the series:citric>malic>oxalic,citrate>malate>oxalate,oxalate>oxalic,citrate>citric and malate>malic.(8)Organic acids/salts increased photosynthesis level,chlorophyl contents of Fraxinus mandshurica seedlings and nutrient availability in soils,so they also were helpful to increase biomass accumulation.Organic acids/salts of 0.2 to 50.0mmol/L concentrations all increased root,stem,leaf,aboveground,underground and total biomass,and 5.0mmol/L concentration had best effect.Increase scope of different organs showed different rules:increase percents of root and leaf biomass were bigger than that of stem.Effects of organic acids/salts on biomass accumulation of Fraxinus mandshurica seedlings followed the series:citric>malic>oxalic, citrate>malate>oxalate,oxalate>oxalic,citrate>citric and malate>malic,and it was obvious with all concentration treatments. (9)Trends of biomass allocation of Fraxinus mandshurica seedlings under different concentrations of organic acids/salts were same as distilled water treatment.The biomass mostly were distributed to root,i.e.underground,so root biomass were higher than aboveground biomass,and much higher than leaf or stem biomass,which was related to tree species.To the effects of organic acids/salts on biomass allocation of Fraxinus mandshurica seedlings,root and underground biomass percents increased,stem biomass percent decreased,leaf biomass percent showed no obvious rule,aboveground biomass percent decreased,ratio of root to stem increased, and 5.0mmol/L concentration had best effect.Effects of organic acids/salts on biomass allocation of different organs followed the series:citric>malic>oxalic,citrate>malate>oxalate, oxalate>oxalic,citrate>citric and malate>malic.更多还原