桉树人工林土壤酚酸物质积累机制及其环境行为

Phenolic acid is one of the main components of allelochemicals in soil, which is considered as one toxic factor to result in continuous cropping obstacle in agricultural and forestry crops. But some studies have shown no accumulation and toxicity in continuous plantation. In this subject, the accumulation rule and environment behavior of soil phenolic acids will be studied in continuous pure eucalyptus plantations (including 1st generation, 2nd generation and 3rd generation ) and the three mixed forests (including fast-growing Eucalyptus mixed with Acacia mangium, Erythrophleum fordii, Dalbergia odorifera, respectively). .HPLC will be used to detect phenolic acids content and types in different organs of trees, rhizosphere and non-rhizosphere soils in the above forest stands so that accumulative differences can be compared between the different forest soils the accumulation mechanism. The environmental behaviors of phenolic acids such as adsorption, desorption and maintenance are studied for explore their accumulation mechanism through exogenous application. Furthermore, the relations between phenolic acids and important chemical properties and microbes in soil are analyzed and the effects of phenolic acids on growth of eucalyptus seedlings, physiological, nutrient absorption process are evaluated too. From the above researches, we hope to get more information to reveal the environmental behavior of phenolic acids in soil ecological system of eucalyptus plantations and their biological effects on eucalyptus, so as to provide the scientific basis for evaluating the phenolic acid roles in eucalyptus plantation correctly. And the theoretical reference and technical support based on chemical ecology view will be prepared for the reasonable management model and suitable mixed species for short rotation eucalyptus plantation.

酚酸是土壤化感物质的主要成份之一，虽然被认为是导致农林作物连作障碍的致毒因子之一，但也有研究表明连栽林地并未产生酚酸的积累并产生毒害作用。本课题以连栽桉树人工林纯林（1代、2代、3代）及速生桉与马占相思、格木、降香黄檀的3种混交林作为研究对象，对土壤中酚酸物质的积累规律及环境行为进行研究。采用HPLC检测不同林分中林木不同器官、根际及非根际土壤酚酸物质的含量和种类，分析其在不同林地土壤中累积的差异，并通过对酚酸物质在土壤中有吸附、解吸、滞留行为研究其累积机制，进一步分析酚酸物质与土壤重要理化性质、微生物间的相互关系，评价其对桉树幼苗生长、生理、养分吸收等过程的影响，揭示酚酸物质在桉树人工林土壤生态系统中的环境行为及其对桉树的生物学效应，从而为正确评价酸酸物质在桉树人工林地的作用提供科学依据，也为从化学生态学的角度提出短轮伐期桉树人工林合理的经营模式及适宜的混交树种提供理论参考及技术支持。

本项目已完成桉树多代连栽林地以及混交林土壤中的对羟基苯甲酸、香草酸、阿魏酸、香豆酸、苯甲酸、水杨酸和肉桂酸7种酚酸物质的季节动态变化特征及其累积机制、酚酸物质对桉树纯林及混交林地土壤生物化学性质的影响、不同腐殖酸肥料对桉树酚酸分泌的初步研究。主要研究结论如下：.1. 1代桉树纯林林间土壤和根际土壤中的酚酸物质均高于2代桉树纯林，因此，在2代桉树纯林中并未出现酚酸物质的积累现象。对羟基苯甲酸、香豆酸和香草酸是桉树纯林及其与马占相思、降香黄檀混交林土壤中含量较高的酚酸物质，而肉桂酸在各林地内的含量极低。.2. 在外源酚酸添加的情况下，混交林土壤的解吸能力在低浓度条件时极低，不会对林地内的其它物种造成化感效应，而桉树纯林则与之相反，桉树混交林能够有效降低林间土壤中的酚酸物质含量，从而减少化感效应的产生。.3. 酚酸对两种桉树纯林、桉树与降香黄檀混交林林分土壤pH、养分有效性、酶活性及微生物数量绝大多数存在显著抑制作用，巨尾桉2代萌芽混交降香黄檀可改善土壤理化性质，是合理的伴生树种。.4. 对羟基苯甲酸对纯林土壤pH产生的降低影响最显著；水杨酸对混交林土壤pH产生的降低影响最显著。.5. 外源酚酸对桉树纯林和混交林土壤的处理中，水杨酸、对羟基苯甲酸、苯甲酸、香草酸对纯林土壤养分有效性作用较显著；除上述4种酚酸外，阿魏酸对混交林土壤也有较显著的影响。.6. 对纯林土壤中脲酶影响最显著的酚酸为水杨酸，对酸性磷酸酶影响显著的仅苯甲酸，对多酚氧化酶影响最显著的为香草酸。对混交林酸性磷酸酶影响最显著的酚酸为水杨酸，对多酚氧化酶活性影响最显著的是香草酸，苯甲酸对混交林脲酶活性抑制作用最大。.7. 对真菌数量抑制作用最显著为阿魏酸，对纯林土壤细菌影响最显著的为阿魏酸，对混交林土壤细菌影响最显著的为苯甲酸。.8. 腐植酸肥料处理的盆栽基质中香豆酸和苯甲酸含量降低，常规复合肥的处理则提高了阿魏酸、香豆酸及水杨酸在土壤中的积累量。