IMHE OpenIR  > 山地表生过程与生态调控重点实验室
贡嘎山东坡峨眉冷杉林土壤有机磷的生物有效性
Alternative TitleBioavailability of soil organic phosphorus in the Abies fabri (Mast.) Craib forest on Mt. Gongga
何晓丽
Subtype博士
Thesis Advisor吴艳宏
2018
Degree Grantor中国科学院大学
Place of Conferral北京
Degree Discipline自然地理学
Keyword有机磷形态 生物有效磷 垂直分异 季节变化 淋溶作用
Abstract磷是重要的生命元素和营养元素,对林线和植被带谱的形成,生态系统初级生产力的提升等具有重要作用。随着成土过程进行,土壤中生物有效磷含量逐渐降低,有机磷含量逐渐增加,最后保留在土壤中的磷主要为闭蓄态磷和有机磷。此外,对大多数高山和亚高山森林土壤的研究表明,有机磷占总磷的比重较高。因此,土壤有机磷的生物地球化学循环过程对山地生态系统中生物有效性磷供给的影响日益增大。虽然土壤有机磷的海拔异质性已被认为是控制磷生物有效性甚至林线形成的重要因素之一,但目前关注海拔梯度上土壤有机磷形态的赋存特征及其生物有效性的研究仍不足。于2016年5月在贡嘎山东坡海拔2628 m(样点 1)、2781 m(样点 2)、3044 m(样点 3)和3210 m(样点 4)的峨眉冷杉林冠下共设置4个采样点,每个采样点选择坡度较小区挖掘6个土壤剖面。在调查土壤基本理化特征的基础上,揭示了土壤有机磷和生物有效磷的赋存特征及其影响因素,明确了山地森林土壤中有机磷形态的生物地球化学循环过程,并定量评估了土壤有机磷对生物有效磷的贡献。主要研究结果和结论如下:(1)贡嘎山东坡峨眉冷杉林土壤有机磷形态呈现明显的空间变化。土壤总有机磷(TOP)储量随海拔升高有增大趋势,但最小储量在2781 m样点,为824.69 kg ha-1。该分布模式主要是由于随海拔升高,土壤温度降低,有机磷矿化速率减慢,导致有机磷在高海拔地区累积。此外,淋溶过程也对其赋存特征产生明显干扰。活性有机磷(LOP)浓度和储量随海拔升高有增大趋势,其赋存特征的主要影响过程为有机磷矿化。A层和B层中活性有机磷(MLOP)浓度随海拔升高有降低趋势,但其O层和C层的浓度在海拔梯度上均不存在显著性差异(p < 0.05);MLOP储量在4个样点间不存在显著性差异(p < 0.05);其赋存特征主要受淋溶过程影响,随无定型铁(Feox)向下迁移。中稳性有机磷(MROP)浓度和储量随海拔升高有增大趋势,且占TOP比重最高,是受淋溶影响最大的有机磷形态,主要随土壤有机质(SOM)和无定型铝(Alox)向下迁移。高稳性有机磷(HROP)浓度随海拔升高有降低趋势,其储量在4个样点间不存在显著性差异(p < 0.05),其赋存特征由土壤pH值控制。(2)贡嘎山东坡亚高山土壤生物有效磷呈显著的垂直分异和季节变化特征。土壤生物有效磷含量(Bio-PL)及生物有效磷供给量(Bio-PS)均随海拔升高呈增大趋势,低海拔地区生物有效磷因淋溶大量流失是形成这种梯度变化的主要原因。随土层深度增加,Bio-PL库及Bio-PS显著降低,O层Bio-PL库约占土壤剖面的75%且该层的Bio-PS全年均为正值。O层中较高的有机磷含量和较强的磷酸酶活性是O层生物有效磷富集的重要原因。2781 m样点O层Bio-PS在9月最高,而3 044 m和3 210 m样点的Bio-PS在5–6月和9月出现两个高值。各样点矿质土层的Bio-PS全年多低于0,在8月时最低。Bio-PS的季节变化主要受生物吸收及径流流失控制。(3)基于贡嘎山东坡峨眉冷杉林构建了山地森林土壤有机磷形态赋存特征的概念模型。TOP储量随海拔升高呈增加趋势,但其最小储量在2781 m样点而不是在2628 m样点。不同海拔淋溶强度不同是对土壤TOP赋存特征造成以上干扰的重要原因。由于土壤生物有效磷随淋溶过程大量流失,一方面生物通过微生物量磷(MBP)直接获取生物有效磷;另一方面,通过刺激磷酸单酯酶活性矿化LOP以获得足够的生物有效磷。MLOP和MROP是随淋溶迁移最主要的有机磷形态,两者依赖SOM和矿物(Feox和Alox)的垂向迁移。HROP是最稳定的有机磷形态,受淋溶作用较小。(4)定量评估了矿质土壤表层无机磷和有机质层有机磷对生物有效磷的贡献。随海拔升高,矿质土壤表层无机磷对生物有效磷的贡献率依次为50%、67%、83%和0%。由2628 m样点至3044 m样点这种随海拔升高逐渐增强的梯度变化模式是由于低海拔地区淋溶过程强烈导致无机磷大量流失;而在3210 m样点,土壤温度最低、含水量最少,导致风化作用最弱,进而造成无机磷对生物有效磷的贡献率最低。随海拔升高,有机质层中LOP对生物有效磷的贡献率依次为44%、42%、40%和70%。由2628 m样点至3044 m样点这种随海拔升高逐渐减弱的梯度变化模式是因为随海拔升高,温度降低,MBP和磷酸酶活性均有减小趋势。然而,在3210 m样点无机磷对生物有效磷供应不足的情况下,生物对有机磷的矿化增强以维持生态系统中生物有效磷的充足供给。
Other AbstractPhosphorus (P) is a crucial nutrient for life. It plays an important role in regulating the function and primary productivity of terrestrial forest ecosystems. With the process of soil formation, the content of bioavailable P in soil gradually decreases and the trend of organic P is opposite. Finally, the P fractions that remain in ecosystems are mainly occluded P and organic P. In addition, studies on most alpine and sub-alpine forest soils have shown that organic P represents the majority of total P, indicating that its biogeochemical cycling becomes increasingly important for the bioavailability of P. Although the altitudinal heterogeneity of soil organic P has been identified as a considerable factor controlling P bioavailability or even the timberline, few studies focus on the variations in soil organic P along altitudinal gradients.Four altitudes (2628 m, 2781 m, 3044 m and 3210 m a.s.l.) were selected for sampling in May 2016 in the Abies fabri (Mast.) Craib forest on Mt. Gongga, Southwest China. Six soil profiles were randomly set up for each site with a distance larger than 10 m between them. The general properties of the Abies fabri (Mast.) Craib forest were studied. The distribution of organic P fractions and bioavailable P in profiles along the altitudinal gradient were deciphered. In addition, the factors impacting the spatial and temporal distribution of organic P fractions and bioavailable P in subalpine soils were clarified. Based on these results, a conceptual model was proposed to describe the altitudinal distribution of different soil P fractions in montane ecosystems. Finally, the contribution of soil organic P fractions to bioavailable P was quantitatively assessed. The main results and conclusions are as follows: (1) Organic P fractions in the subalpine soil on the eastern slope of Gongga Mountain showed obvious spatial and temporal variations. The concentration and stock (in the O horizon and the 0–50 cm mineral soil horizon) of total organic P (TOP) and moderately resistant organic P (MROP) increased roughly along the altitude, with their minimum stocks at 2781 m a.s.l. Different from the TOP and MROP, the concentrations and stocks of labile organic P (LOP) markedly increased as the elevation increased. The stocks of moderately labile organic P (MLOP) and highly resistant organic P (HROP) did not vary significantly between the four sites (p < 0.05). The maximal stocks of MLOP and HROP were found in the B and A horizons, respectively. The distribution pattern of TOP was likely related to the decrease of mineralization rate caused by the decreasing temperature upslope, while it was also disturbed by the leaching process. In addition, apart from the LOP, the altitudinal distributions of other P fractions were also regulated by this process. The MLOP and MROP were the main organic P fractions that were migrated with the translocation of organic compound (fulvic acids) and minerals (Feox and Alox). The leaching loss for the two organic P fractions likely occurred due to the undeveloped placic horizon in the early stage of soil development. The HROP was the most stable organic P fraction that was not severely influenced by the leaching in this gradient.(2) Bioavailable P in the subalpine soil on the eastern slope of Gongga Mountain showed obvious spatial and temporal variations. The concentrations and stocks of Bio-PL as well as Bio-PS increased with altitude. The leaching process was more intensified in lower altitudes. This altitudinal pattern of bioavailable P was likely related to a lager loss of bioavailable P in lower altitudes (especially at the 2 781 m site) as shown by increasing soil moisture downward. The concentrations and stocks of Bio-PL decreased with soil depth. The stock of Bio-PL in the O horizon accounted for the largest proportion of the total Bio-PL stock, with an average of 75%. The Bio-PS in the O horizon was larger than 0 mg kg-1 d-1 in the whole year. Thus, most soil bioavailable P was stored in the O horizon. The higher organic P content and phosphatase activity in the O horizon were the most important factors for this vertical distribution of bioavailable P in soil profiles. Bio-PS in the O horizon at the 2 781 m site was higher in September. For both of the 3 044 m and 3 210 m site, Bio-PS in the O horizon were higher in May~June and September. Bio-PS in the mineral horizons at the four sites was smaller than 0 mg kg-1 d-1 in most months. The minimum Bio-PS for both A and B horizon were in August at the 2 781 m site, which were -1.143 and -0.943 mg kg-1 d-1, respectively. Biological assimilation and loss with runoff were the main factors controlling the seasonal changes of soil bioavailable P.(3) A conceptual model was proposed to describe the altitudinal distribution of different soil P fractions in montane ecosystems. The TOP stocks showed a rough increase along the altitudinal gradient, which would be explained as the soil temperature decreased, and thus, enzyme activities occurred with increasing elevation. However, the variations in soil temperature alone could not completely explain the altitudinal TOP change because the minimum TOP stock was at the 2781 m site. The leaching process during heavy rainfall was considered to interfere in the altitudinal pattern of soil TOP. Apart from the LOP, the altitudinal distributions of other P fractions were also disturbed by the leaching process. Because of the large bioavailable P loss caused by the leaching, organisms in ecosystems have developed effective strategies to adapt to the low supply of bioavailable P. The microbial biomass P (MBP) was the main contributor to LOP and bioavailable P. In addition, greater phosphomonoesterase activities were observed at the 2781 m site, which facilitated LOP mineralization and thus compensated for the bioavailable P pool in soils. The MLOP and MROP were the main organic P fractions that were migrated with leaching. The vertical distribution of MLOP and MROP were changed as a result of the leaching of soil organic matter (SOM) and the amorphous Fe and Al. Most of the two organic P fractions accumulated in the B horizon, but a small amount still flowed out of the montane ecosystem. The young age and incompletely placic horizon probably caused the leaching loss. The HROP was the most stable organic P fraction and mainly retained in the O and surface mineral horizons. It was not severely influenced by the leaching in this gradient.(4) The contributions of inorganic P and organic P fractions to bioavailable P were quantitatively assessed. The contributions of inorganic P to bioavailable P in the surface mineral soils were 50%, 67%, 83% and 0%, respectively from the 2628 m site to the 3210 m site. This increasing pattern from 2628 m site to the 3044 m site was likely influenced by the more intensive leaching of inorganic P at lower altitudes. As the rate of weathering declined significantly at the 3210 m site which was caused by the decrease of soil temperature and moisture with altitudes, the sharp decline in contribution of inorganic P to bioavailable P was observed. The contributions of LOP to bioavailable P in the organic horizon were 44%, 42%, 40% and 70%, respectively from the 2628 m site to the 3210 m site. This decreasing pattern from 2628 m site to the 3044 m site could be explained as the soil temperature decreased, and thus, enzyme activities occurred with the increasing elevation. In addition, in the case of an insufficient supply of inorganic P to bioavailable P at the 3210 m site, the more contribution of organic P was occurred in this ecosystem. 
Pages130
Language中文
Document Type学位论文
Identifierhttp://ir.imde.ac.cn/handle/131551/24779
Collection山地表生过程与生态调控重点实验室
Affiliation中国科学院成都山地灾害与环境研究所
First Author Affilication中国科学院水利部成都山地灾害与环境研究所
Recommended Citation
GB/T 7714
何晓丽. 贡嘎山东坡峨眉冷杉林土壤有机磷的生物有效性[D]. 北京. 中国科学院大学,2018.
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