桉树与红锥混交对土壤水解酶活性及其化学计量特征的影响

Effects of mixing Eucalyptus and Castanopsis hystrix on soil hydrolytic enzyme activities and ecoenzymatic stoichiometry

为从土壤酶活性及其化学计量特征的角度,揭示桉树与珍贵乡土树种混交后土壤养分的响应机制,该文以广西凭祥热林中心青山实验场的桉树纯林、红锥纯林和桉树×红锥混交林为研究对象,采用随机区组试验设计,通过测定土壤碳(C)、氮(N)、磷(P)水解酶[β-1,4-葡萄糖苷酶(BG)、β-1,4-N-乙酰葡糖氨糖苷酶(NAG)、亮氨酸氨基肽酶(LAP)和酸性磷酸酶(ACP)]的活性及土壤理化性质,分析桉树与红锥混交对土壤养分状况的影响。结果表明:(1)桉树与红锥混交在0~10 cm和10~20 cm土层均显著提高pH值、有效氮(AN)和有效磷(AP)的含量以及LAP酶活性,显著降低BG和ACP酶活性,但对NAG酶活性影响不显著。(2)SOC和TN与除酶C∶N外的其他土壤水解酶活性及其化学计量比呈现不同程度的显著正相关。(3)在0~10 cm和10~20 cm土层,三种林分间土壤水解酶活性均具有显著差异,SOC和AN含量是土壤水解酶活性产生差异的驱动因子。(4)桉树纯林、桉树×红锥混交林和红锥纯林在0~20 cm土层土壤酶C∶N∶P分别为1∶1.08∶1.37、1∶1.16∶1.34和1∶1.07∶1.31,均与全球生态系统酶C∶N∶P(1∶1∶1)相偏离,表明三种林分的土壤微生物相对于C、N更容易受到P限制。桉树×红锥混交林的酶C∶P和酶N∶P均高于桉树纯林,而酶C∶N低于桉树纯林,表明桉树与红锥混交在一定程度上缓解了土壤受到P限制的情况,但并未改善土壤N限制。该研究结果为桉树×红锥混交林土壤养分管理以及桉树人工林养分循环的改善提供了科学的理论依据。

In order to study the effects of mixed Eucalypts with precious native plant species on soil nutrient status from the perspectives of soil enzyme activities and stoichiometric characteristics,we measured the activities of soil C,N,and P hydrolase,includingβ-1,4-glucosidase(BG),β-1,4-N-acetylglucosaminidase(NAG),leucine aminopeptidase(LAP)and acid phosphatase(ACP),and physicochemical properties in pure Eucalyptus plantations,pure Castanopsis hystrix plantations and mixed Eucalyptus and Castanopsis hystrix plantations using a randomized block method in the Qingshan Experimental Field of Tropical Forestry Experiment Centre of Chinese Academy of Forestry,Pingxiang,Guangxi.The results were as follows:(1)Soil pH,AN,AP and the activities of LAP were significantly increased in the mixed plantations at both 0-10 cm and 10-20 cm soil layers,and the activities of BG and ACP were significantly reduced on the above layers,but had nosignificant effects on the activity of NAG.(2)SOC and TN had significant positive correlation with the soil hydrolase activities and their stoichiometric ratios except enzyme C∶N.(3)There were significant differences in soil hydrolase activities among the three plantations at both 0-10 cm and 10-20 cm soil layers,as well as SOC and AN were the dominant factors affecting soil enzymatic activity.(4)The soil ecoenzymatic C∶N∶P stoichiometry of the pure Eucalyptus plantations,mixed Eucalyptus and Castanopsis hystrix plantations and pure Castanopsis hystrix plantations were 1∶1.08∶1.37,1∶1.16∶1.34 and 1∶1.07∶1.31 at 0-20 cm soil layer respectively,which were inconsistent with the 1∶1∶1 global pattern of C∶N∶P stoichiometry,which suggests that the soil microbe of the three stands were more easily restricted by phosphorus than carbon and nitrogen.Additionally,the values of enzyme C∶P and enzyme N∶P of the mixed Eucalyptus and Castanopsis hystrix plantations were both higher than that of the pure Eucalyptus plantations,while its enzyme C∶N was lower than that of the pure Eucalyptus plantations,which indicated that the limitation of P was alleviated in the mixed Eucalyptus and Castanopsis hystrix plantations to some extent,but did not improve the limitation of N.This study can provide scientific basis for soil nutrient management and the improvement of the nutrient cycle of the mixed Eucalyptus and Castanopsis hystrix plantations.