添加生物质炭对桉树人工林土壤磷组分及转化的影响

Effects of biochar addition on soil phosphorus composition and transformation in Eucalyptus plantation

为改善我国亚热带桉树人工林土壤磷(P)供应不足的状况,该研究利用生物质炭(BC)作为土壤改良剂,以桉树人工林(林龄为15年)土壤为研究对象,通过室内培养试验,分别加入不同用量[0(CK)、2%、5%、10%和20%]的BC,重点探究不同用量BC对土壤P组分及转化的影响及其与土壤理化性质之间的关系。结果表明:(1)与CK相比,20%的BC添加量显著提高了土壤硝态氮(NO_(3)^(-)-N)、全磷(TP)、微生物生物量磷(MBP)含量和pH值(P<0.05),而2%、5%和10%的BC添加量仅显著提高了MBP和pH值(P<0.05),对其他土壤理化指标无显著影响。(2)与CK相比,2%的BC添加量显著提高了易利用性磷(LP)(P<0.05),5%和10%的BC添加量显著提高了速效磷(AP)和LP(P<0.05),20%的BC添加量显著提高了AP、LP和难利用性磷(OP)(P<0.05),但中等程度利用性磷(MP)在4种BC添加量下均无显著变化。(3)与C、N和P转化相关的β-葡萄糖苷酶(BG)、β-N-乙酰氨基葡萄糖苷酶(NAG)、蛋白酶(LAP)和酸性磷酸酶(ACP)活性均在10%和20%的BC添加量下显著高于CK(P<0.05)。(4)相关分析结果表明,ln(BG)和ln(NAG+LAP)均与ln(ACP)呈显著正相关(P<0.05);冗余分析(redundancy analysis,RDA)表明,pH、TN和TP是驱动桉树人工林土壤P组分变化的最主要因素;结构方程模型(structural equation model,SEM)进一步表明,pH、C∶P和N∶P是驱动土壤P转化的最关键因子。综上所述,不同用量BC主要通过影响土壤理化性质提高与C、N循环相关的酶活性,并在一定程度上改善桉树人工林土壤的P供应潜力,其中以高浓度BC添加量(20%)的效果最佳。该研究对指导我国桉树人工林土壤养分管理及促进林业可持续发展具有重要意义。

In order to improve the phosphorus(P)deficiency in the soil of Eucalyptus plantations in subtropical China,we used biochar(BC)as a soil amendment to investigate the soil of Eucalyptus plantations(15 years old).Meanwhile,we added the different amounts[0(CK),2%,5%,10%and 20%]of BC through the laboratory culture experiment to evaluate the effects of different amounts of BC on P components and transformation in soil and its relationship with soil physicochemical properties.The results were as follows:(1)Compared to CK,the nitrate nitrogen(NO_(3)^(-)-N),total phosphorus(TP),microbial biomass phosphorus(MBP)and pH values were significantly increased at 20%BC addition,respectively(P<0.05),the MBP and pH values were significantly increased at 2%,5%,and 10%BC addition,respectively(P<0.05),while no marked difference was found in other soil physicochemical properties.(2)Compared to CK,the labile P(LP)was significantly increased at 2%of BC addition(P<0.05),the available P(AP)and LP were significantly increased at 5%and 10%of BC additions,respectively(P<0.05).Moreover,the AP,LP and occluded P(OP)were significantly increased at 20%BC addition(P<0.05),whereas the moderately available P(MP)had no significant change under the four BC additions.(3)The total activities ofβ-glucosidase(BG),β-N-acetylglucosaminidase(NAG),L-leucine aminopeptidase(LAP),and acid phosphatase(ACP)involved in C,N and P transformations increased significantly at 10%and 20%BC additions than those in CK(P<0.05).(4)Correlation analysis showed that ln(BG)and ln(NAG+LAP)were positively correlated with ln(ACP),respectively(P<0.05).In addition,redundancy analysis(RDA)indicated that pH,TN and TP appeared to be the primary drivers of variations in soil P components of Eucalyptus plantations.Furthermore,structural equation model(SEM)revealed that the pH,C:P and N:P of soil were the most critical factors driving P transformation.In conclusion,our findings suggest that different amounts of BC improve the enzyme activities related to C,N cyclings by affecting soil physicochemical properties and improving the P supply potential of soil in Eucalyptus plantations.Notably,20%BC addition had the optimum effect.This study provides critical theoretical guidance for gaining knowledge on soil nutrient management in Eucalyptus plantations and facilitating the sustainable development of forests in subtropical China.