林业废弃物生物炭对桉树人工林土壤磷素形态转化的影响及其微生物学机制

Phosphorus as one of the essential nutrient elements for growth and development of plants plays an important role in promoting tree growth and forest productivity. Soil (red soil) weathering and leaching processes are severe in the main Eucalyptus planting areas of South China as well as phosphorus adsorption, leading to a low phosphorus use efficiency. Therefore, to activate soil insoluble phosphorus is crucial for improving phosphorus bioavailability and utilization efficiency. Biochar is characteristics of contribution to soil structure and soil nutrient content. In this project, the soils from continuous planting plantations of Eucalyptus will be taken as the object, through combining experiments of simulation, pot and field with Hedley phosphorus fractionation method, 31P nuclear magnetic resonance (NMR) and real-time quantitative fluorescence PCR, the dynamic characteristics of soil phosphorus forms, adsorption, desorption and fixation will be studied, change rules in and relationships between soil phosphorus fractions and microbial community will be detected, following importation of the biochar made by the forestry waste of Eucalyptus, for elucidating the processes of biochar influencing on transformation forms of soil phosphorus and revealing the microbial mechanisms of biochar mediating phosphorus activation, so that the scientific evidences will be provided with rationaluse of biochar resources, enhance of soil phosphorus bioavailability and utilization efficiency, reduction of environmental pollution and promotion of sustainable management of Eucalyptus plantations.

磷是植物生长发育的必需营养元素之一, 对促进林木生长, 提高森林生产力具有十分重要的作用。我国南方桉树主要种植区土壤（红壤）风化淋溶及其对磷素吸附作用强烈，导致磷肥利用效率极低。因此，活化土壤难溶性磷，是提高磷素生物有效性和利用效率的关键因素。生物炭具有改良土壤、提高土壤养分含量的作用。本项目以连栽桉树人工林土壤为研究对象，通过模拟培养试验、盆栽试验和田间小区试验，同时结合Hedley磷素分级方法、31P磷核磁共振和实时定量荧光PCR等技术，研究林业（桉树）废弃物生物炭输入条件下土壤磷素赋存形态、吸附与解吸特性以及固定作用的动态特征，探索土壤磷素组分和微生物功能群群落的变化规律及其相互关系，以阐明生物炭对桉树人工林土壤磷素形态转化的影响过程，揭示生物炭调控磷素活化的微生物学机制，为合理利用生物炭资源，提高土壤磷素的生物有效性和利用效率，减少环境污染，促进桉树人工林可持续经营提供科学依据。

磷是桉树生长发育的必需营养元素之一。我国南方桉树主要种植区土壤磷素含量低，加上土壤风化淋溶及其对磷素吸附作用强烈，导致磷肥利用效率极低。因此，活化土壤难溶性磷，是提高磷素生物有效性和利用效率的关键因素。本项目以连栽桉树人工林土壤为研究对象，研究林业（桉树）废弃物生物炭输入条件下土壤磷素赋存形态、吸附与解吸特性以及固定作用等动态特征。研究结果主要如下：.（1）桉树废弃物生物炭的转化率在24.4%—41.1%之间，随裂解温度（300℃—700℃）的升高而降低，其全磷、HCl-P和Residual-P含量表现出相同的变化趋势，但其pH值和NaHCO3-Pi、NaOH-Pi含量则呈现相反的变化趋势，其对磷素的吸附能力较强随裂解温度的升高而逐渐增强。.（2）与不添加生物炭相比，添加生物炭能够增加土壤全磷、全钾和有效钾含量，促进促进土壤磷素化学形态的转化，提高土壤磷素有效性及其含量，促进桉树幼树生长，进而提高桉树生物量和氮、磷、钾养分的吸收和积累能力。.（3）与不添加生物炭相比，添加生物炭能有效中和土壤酸度，提高土壤pH值，使土壤酸性磷酸酶活性下降，但显著提高了土壤微生物生物量碳、氮、磷（SMBC、SMBN、SMBP）含量，有效降低SMBC/SMBN、SMBC/SMBP和SMBN/SMBP，有利于促进土壤微生物对N、P养分的固持与周转，从而改善土壤对N、P养分的供应。.综上所述，添加桉树废弃物生物炭能够提高土壤pH值，增加土壤养分含量，显著影响土壤磷素化学形态、微生物生物量碳、氮、磷含量及磷素转化，有利于促进土壤微生物对N、P养分的固持与周转，进而提高土壤对N、P养分的供应能力。