Vertical patterns of phosphorus concentration and speciation in three forest soil profiles of contrasting climate
Vertical patterns of phosphorus concentration and speciation in three forest soil profiles of contrasting climate
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DOI：
10.1016/j.gca.2021.07.002
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发表时间：
2021-10
影响因子：
5
通讯作者：
Zhuo‐Jun Zhang;Zhiqi Zhao;Cong-Qiang Liu;O. Chadwick;C. Liang;Yongfeng Hu;K. Vaughan;M. Zhu
中科院分区：
文献类型：
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作者：
Zhuo‐Jun Zhang;Zhiqi Zhao;Cong-Qiang Liu;O. Chadwick;C. Liang;Yongfeng Hu;K. Vaughan;M. Zhu
土壤中磷的有效性控制着陆地生态系统的关键功能和性质。土壤剖面中磷浓度和形态的垂直分布模式提供了成壤过程如何重新分配和转化磷从而改变土壤中磷有效性的历史记录，然而，这一点仍然知之甚少。采用精细采样间隔、PK边缘X射线吸收近边缘(XANES)光谱和化学提取等方法，测定了3个气候条件不同的森林土壤剖面的格局。在这种反差的气候下，这些图案的主要特征依然存在。总磷浓度从A层向B层递减，在B层达到最小，然后向上C层增加，但在下C层随深度变化不大。钙结合无机磷(Ca-PI)和有机磷(Po)在A层呈下降趋势，而Fe和Al结合态PI[(Fe+Al)-PI]呈下降趋势，这是因为灰尘输入和有机质积累量均随深度增加而下降。由于强烈的风化作用，B层以(Fe+Al)-PhI为主，CA-PhI可忽略不计。从下B层到上C层，Ca-P i比例明显向下增加，(Fe+Al)-P i比例下降。由于土壤的低透水性，向下淋溶的Ca~(2+)和P~(2+)在C层上部形成新的Ca-Pisem。在下部C层，由于化学风化作用减弱，Ca-Pi值增加，(Fe+Al)-Pidecrease值随深度增加。在磷的生物有效性方面，封闭磷(POCC)的比例随着深度的增加呈增加和减少的趋势，在B层最高，而非封闭磷(Pn-OCC)没有一致的趋势。虽然可以通过考虑不同成壤过程的相对重要性来理解P垂直格局，但气候会影响这些过程的强度，从而影响格局的细节。当深度整合时，更温暖/更潮湿的气候导致Ca-PiC和Pn-Oc的比例下降，但P的损失和Po、(Fe+Al)-PI和POCC的比例增加。无论土壤深度和气候条件如何，土壤中Ca-PiI和(Fe+Al)-Piover总PI的相对比例与土壤pH值和风化程度(化学变化指数，CIA)有很好的相关性，而PoS浓度则与土壤中的Fe、Al和有机碳浓度相关。相关分析表明，土壤化学/矿物学主要控制土壤的富集度，土壤地球化学/矿物学和生物活性共同控制土壤的富集度。Pocc与CIA相关，因此主要受土壤矿物学控制，但Pn-occ与土壤性质相关性较弱，可能是由于其易受粉尘输入、淋溶、生物活性和对矿物的吸附等综合影响。上述定量关系有助于预测不同土壤中磷的形态和有效性。我们进一步表明，土壤剖面、气候和CIA梯度是研究土壤成土过程中磷转化的有用工具，特别是对于Pipool。本研究对气候和土壤变量对森林土壤磷动态的控制进行了综合和综合。
Phosphorus (P) availability in soils controls critical functions and properties of terrestrial ecosystems. Vertical distribution patterns of P concentration and speciation in soil profiles provide historical records of how pedogenic processes redistribute and transform P and thus change its availability in soils, which, however, remain poorly understood. We determined the patterns in three forest soil profiles of contrasting climate, using fine sampling intervals, PK-edge X-ray absorption near edge (XANES) spectroscopy and chemical extractions. The major features of the patterns persist under the contrasting climate. The total P concentration decreases from A to B horizons, reaches a minimum in the B horizons, and then increases towards the upper C horizons, but with little variations with depth in the lower C horizons. Both calcium-bound inorganic P (Ca–Pi) and organic P (Po) decrease and Fe- and Al-bound Pi[(Fe + Al)–Pi] increases in proportion downward in the A horizons because dust inputs and accumulation of organic matter both decline with increasing depth. Ca–Piis negligible and (Fe + Al)–Piis dominant in the B horizons due to strong weathering. There is a strong downward increase in Ca–Piproportion and decrease in (Fe + Al)–Piproportion from the lower B to the upper C horizons. New Ca–Piseems to form in the upper C horizons where downward leaching Ca2+and phosphate accumulate due to the low water permeability of the soils. In the lower C horizons, Ca–Piincreases and (Fe + Al)–Pidecreases with increasing depth due to decreasing chemical weathering. Regarding P bioavailability, the proportion of occluded P (Pocc) shows an increasing and decreasing trend with increasing depth, being the highest in the B horizons; however, there are no consistent trends for non-occluded P (Pn-occ). While the P vertical patterns can be understood by considering the relative importance of different pedogenic processes, climate affects the intensities of these processes and thus the details of the patterns. When depth-integrated, warmer/wetter climate results in decreases in the proportions of both Ca–Piand Pn-occbut increases in the P loss and the proportions of Po, (Fe + Al)–Pi, and Pocc. Regardless of soil depth and climate, the Pispeciation, i.e., the relative proportions of Ca–Piand (Fe + Al)–Piover total Pi, correlates well with soil pH and weathering degree (Chemical Index of Alteration, CIA), and the Poconcentration correlates with pedogenic Fe and Al and organic carbon concentration. The correlations suggest that the Pispeciation is primarily controlled by soil geochemistry/mineralogy, and the Poconcentration by both soil geochemistry/mineralogy and biological activities. Pocccorrelates with CIA, and thus is mainly controlled by soil mineralogy; but Pn-occcorrelates weakly with soil properties, probably due to its susceptibility to combined influences of dust inputs, leaching, biological activities, and adsorption on minerals. The above quantitative relationships may help predict P speciation and availability in diverse soils. We further show that soil profiles, and climate and CIA gradients are useful tools for studying P transformations, particularly for the Pipool, during pedogenesis. This study provides an integration and synthesis of controls of climatic and edaphic variables on P dynamics in forest soils.