温带森林土壤游离氨基酸含量动态及测定方法研究
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摘要
近年来,传统矿质氮营养理论遭遇了新观念的挑战,越来越多的研究证实有机氮(特别是氨基酸氮)也是重要的植物氮源。研究土壤氨基酸在生态系统氮循环中的作用对于重新认识森林生态系统中氮的有效性,完善再认识森林生态系统氮循环过程,提高森林生态系统氮营养管理水平,研究森林生态系统氮营养对全球变化的影响及森林演替与退化森林生态系统恢复都具有重要的意义。本研究以我国温带原始红松林与白桦次生林下土壤及凋落物为研究对象,系统研究凋落物、土壤A1层、根际土壤中游离氨基酸含量动态与转化特征,并对游离氨基酸、可溶性有机氮、土壤蛋白水解率的测定条件进行详细研究,主要结果如下：
(1)原始红松林、白桦次生林土壤游离氨基酸含量范围分别为8.44-151.66μgN·g-1和7.61-56.15μgN·g-1；两种林型各土层游离氨基酸含量均表现为：7月,根际土壤>土壤A1层；8月,凋落物层>根际土壤>土壤A1层；10月,凋落物层>新鲜凋落物>根际土>土壤A1层。土壤(根际土与土壤A1层)游离氨基酸与pH值、全氮、碱解氮相关,凋落物游离氨基酸与pH值、全氮相关。
(2)原始红松林、白桦次生林土壤游离氨基酸净生产速率分别为-3.97μgN(g-d)-1-3.25μgN(g·d)-1和-0.54μgN(g·d)-1-1.93μgN(g·d)-1;两种林型游离氨基酸生产率因土层深度而异,均变现为：凋落物层>根际土>土壤A1层；总体上,土壤与凋落物游离氨基酸含量均表现为：原始红松林>白桦次生林(除10月凋落物)。
(3)原始红松林、白桦次生林土壤原始蛋白水解率大小分别为73.78-158.53μmolAA·g-1·5h-1和63.60-114.13μmolAA·g-1·5h-1;其潜在蛋白水解率大小分别为96.80-222.05μmolAA·g-1·5h-1和92.20-233.57μmolAA·g-1·5h-1;两种林型土壤原始蛋白水解率、潜在蛋白水解率因土层深度而异,均变现为：凋落物层>根际土>土壤A1层；蛋白水解潜力表现为：原始红松林>白桦次生林。
(4)KCl浸提土壤游离氨基酸含量显著高于水浸提,但二者对凋落物的浸提效果没有明显规律。甲苯与TCA加入后,KCl与水浸提土壤游离氨基酸含量均增加,其中对水浸提效果影响显著。30min内,土壤游离氨基酸含量随振荡时间增加,而后增加效果不明显。3种浸提液对土壤可溶性有机氮含量的影响表现为：硫酸钾>蒸馏水>氯化钾,但对凋落物的浸提效果没有明显规律。
(5)蛋白水解率测定时所使用的3种缓冲溶液对土壤蛋白水解率的影响表现为：用蒸馏水配制成的缓冲液>缓冲液与KCl盐溶液相混合形成的缓冲液>由KCl溶液配制成的缓冲液；振荡时间对3种缓冲液处理蛋白水解率的影响均表现为：5h>lh,且缓冲液与KCl盐溶液相混合形成的缓冲液>由KCl溶液配制成的缓冲液>用蒸馏水配制成的缓冲液；TCA作用时间对土壤原始蛋白水解率、潜在蛋白分解率的影响均表现为：1h>5min,其中原始蛋白水解率缓冲液与KCl盐溶液相混合形成的缓冲液1>由KCl溶液配制成的缓冲液>用蒸馏水配制成的缓冲液,潜在蛋白水解率除用蒸馏水配制成的缓冲液处理外,其他缓冲液差异不显著；TCA浓度对土壤蛋白水解率的影响表现为：随TCA浓度增加而土壤蛋白水解率下降,至0.55mol·L-1后下降停滞。
Free amino acid was one of the important nitrogen sources, and significant in plant nitrogen nutrition, it played a critical role in soil-N cycling in nitrogen cycling in forests and forest soils, became more and more important in evaluating nitrogen nutrition in soils, so it was of great significant to study free amino acid in forest soils. In this paper we studied content and seasonal dynamic of free amino acid, correlation between free amino acid and other N forms in soil and soil property, fate of free amino acid, net amino acid N production, net soluble organic N production, net N mineralization and net nitrification, gross proteolysis, and facts of impacting free amino acid, soluble organic nitrogen and gross proteolysis experiment analysis in Dark Brown Soil in primitive korean pine forest and its secondary broadleaved forest in northeast China, which were typical forests in temperate mixed forest.The main results were as follows:
(1) The free amino acids content range was respectively78.44-151.66μgN-g-1and7.61-56.15μgN-g-1in primitive korean pine forest and white birch secondary forest soil; the size order of free amino acids content of every soil layer is rhizosphere soil>soil Al layer in July, fermentation litter layer> rhizosphere soil>soil Al layer in August and Fermentation litter layer>Fresh litter layer> rhizosphere soil>soil Al layer in October in primitive korean pine forest and white birch secondary forest soil. Correlation analysis showed that free amino acid content was correlation with pH, total nitrogen content and alkali-hydrolyzable content in soil Al layer and rhizosphere soil, and the free amino acid of litter layer was correlation with pH and total nitrogen content.
(2) The net free amino acids production rate range was respectively-3.97μgN·(g·d)-1～3.25μgN·(g·d)-1and-0.54μgN·(g·d)-1～1.93μgN·(g·d)-1in primitive korean pine forest and white birch secondary forest soil; the free amino acids content varied with the depth of soil layer, was shown as:Fermentation litter layer>rhizosphere soil>soil Al layer; the free amino acids content in the two forests were generally shown as primitive korean pine forest>white birch secondary forest(except fermentation litter layer in October).
(3) The native proteolysis range was respectively73.78～158.53μmolAA·g-1·5h-1and63.60-114.13μmolAA·g-1·5h-1in primitive korean pine forest and white birch secondary forest soil; and the potential proteolysis range was respectively96.80～222.05μmolAA·g-1·5h-1和92.20～233.57μmolAA·g-1·5h-1; the native proteolysis and potential proteolysis varied with the depth of soil layer, were both shown as:Fermentation litter layer>rhizosphere soil>soil Al layer; native potential was manifested as primitive korean pine forest>white birch secondary forest.
(4) The free amino acids content that was extracted with KCl solution significantly greater than that extracted with distilled water in mineral soil, but the effect of extracting agent on the free amino content had not obvious rule in litter layer. The free amino acid content of soil that determined with three treatments that were added toluene and TCA separately and simultaneously were all increased, but that was only significant on that extracted with distilled water. The free amino acids content increased with oscillation time within thirty minutes, and it was no significant increase after thirty minutes. The order of soluble organic nitrogen content extracted from soil with different soil extractant was shown as potassium sulfate>distilled water>potassium chloride, and the difference was significant in three treatments with three soil extractants in mineral soil layer, but it is complex in litter layer, and the difference was not significant in three treatments with three soil extractants.
(5) The impact of three buffer solution on soil proteolysis was shown as treatment1(buffer solution prepared with distilled water)> treatment2(mixed solution by buffer solution and KCl solution)> treatment3(buffer solution prepared with KCl solution); the impact of oscillation time on soil proteolysis was shown as5h>lh, and the soil proteolysis size order was treatment2(mixed solution by buffer solution and KCl solution)> treatment3(buffer solution prepared with KCl solution)>treatment1(buffer solution prepared with distilled water); the impact of TCA action time on soil native proteolysis and potential proteolysis was shown as1h>5min, and the size order of soil native proteolysis was treatment2(mixed solution by buffer solution and KCl solution)> treatment3(buffer solution prepared with KCl solution)>treatment1(buffer solution prepared with distilled water), potential proteolysis was not significant except treatment1(buffer solution prepared with distilled water).The soil gross proteolysis decreased with the concentration of adding TCA, and the decrease of soil gross proteolysis stoped when the concentration of TCA was0.55mol·L-1.
(1)原始红松林、白桦次生林土壤游离氨基酸含量范围分别为8.44-151.66μgN·g-1和7.61-56.15μgN·g-1；两种林型各土层游离氨基酸含量均表现为：7月,根际土壤>土壤A1层；8月,凋落物层>根际土壤>土壤A1层；10月,凋落物层>新鲜凋落物>根际土>土壤A1层。土壤(根际土与土壤A1层)游离氨基酸与pH值、全氮、碱解氮相关,凋落物游离氨基酸与pH值、全氮相关。
(2)原始红松林、白桦次生林土壤游离氨基酸净生产速率分别为-3.97μgN(g-d)-1-3.25μgN(g·d)-1和-0.54μgN(g·d)-1-1.93μgN(g·d)-1;两种林型游离氨基酸生产率因土层深度而异,均变现为：凋落物层>根际土>土壤A1层；总体上,土壤与凋落物游离氨基酸含量均表现为：原始红松林>白桦次生林(除10月凋落物)。
(3)原始红松林、白桦次生林土壤原始蛋白水解率大小分别为73.78-158.53μmolAA·g-1·5h-1和63.60-114.13μmolAA·g-1·5h-1;其潜在蛋白水解率大小分别为96.80-222.05μmolAA·g-1·5h-1和92.20-233.57μmolAA·g-1·5h-1;两种林型土壤原始蛋白水解率、潜在蛋白水解率因土层深度而异,均变现为：凋落物层>根际土>土壤A1层；蛋白水解潜力表现为：原始红松林>白桦次生林。
(4)KCl浸提土壤游离氨基酸含量显著高于水浸提,但二者对凋落物的浸提效果没有明显规律。甲苯与TCA加入后,KCl与水浸提土壤游离氨基酸含量均增加,其中对水浸提效果影响显著。30min内,土壤游离氨基酸含量随振荡时间增加,而后增加效果不明显。3种浸提液对土壤可溶性有机氮含量的影响表现为：硫酸钾>蒸馏水>氯化钾,但对凋落物的浸提效果没有明显规律。
(5)蛋白水解率测定时所使用的3种缓冲溶液对土壤蛋白水解率的影响表现为：用蒸馏水配制成的缓冲液>缓冲液与KCl盐溶液相混合形成的缓冲液>由KCl溶液配制成的缓冲液；振荡时间对3种缓冲液处理蛋白水解率的影响均表现为：5h>lh,且缓冲液与KCl盐溶液相混合形成的缓冲液>由KCl溶液配制成的缓冲液>用蒸馏水配制成的缓冲液；TCA作用时间对土壤原始蛋白水解率、潜在蛋白分解率的影响均表现为：1h>5min,其中原始蛋白水解率缓冲液与KCl盐溶液相混合形成的缓冲液1>由KCl溶液配制成的缓冲液>用蒸馏水配制成的缓冲液,潜在蛋白水解率除用蒸馏水配制成的缓冲液处理外,其他缓冲液差异不显著；TCA浓度对土壤蛋白水解率的影响表现为：随TCA浓度增加而土壤蛋白水解率下降,至0.55mol·L-1后下降停滞。
Free amino acid was one of the important nitrogen sources, and significant in plant nitrogen nutrition, it played a critical role in soil-N cycling in nitrogen cycling in forests and forest soils, became more and more important in evaluating nitrogen nutrition in soils, so it was of great significant to study free amino acid in forest soils. In this paper we studied content and seasonal dynamic of free amino acid, correlation between free amino acid and other N forms in soil and soil property, fate of free amino acid, net amino acid N production, net soluble organic N production, net N mineralization and net nitrification, gross proteolysis, and facts of impacting free amino acid, soluble organic nitrogen and gross proteolysis experiment analysis in Dark Brown Soil in primitive korean pine forest and its secondary broadleaved forest in northeast China, which were typical forests in temperate mixed forest.The main results were as follows:
(1) The free amino acids content range was respectively78.44-151.66μgN-g-1and7.61-56.15μgN-g-1in primitive korean pine forest and white birch secondary forest soil; the size order of free amino acids content of every soil layer is rhizosphere soil>soil Al layer in July, fermentation litter layer> rhizosphere soil>soil Al layer in August and Fermentation litter layer>Fresh litter layer> rhizosphere soil>soil Al layer in October in primitive korean pine forest and white birch secondary forest soil. Correlation analysis showed that free amino acid content was correlation with pH, total nitrogen content and alkali-hydrolyzable content in soil Al layer and rhizosphere soil, and the free amino acid of litter layer was correlation with pH and total nitrogen content.
(2) The net free amino acids production rate range was respectively-3.97μgN·(g·d)-1～3.25μgN·(g·d)-1and-0.54μgN·(g·d)-1～1.93μgN·(g·d)-1in primitive korean pine forest and white birch secondary forest soil; the free amino acids content varied with the depth of soil layer, was shown as:Fermentation litter layer>rhizosphere soil>soil Al layer; the free amino acids content in the two forests were generally shown as primitive korean pine forest>white birch secondary forest(except fermentation litter layer in October).
(3) The native proteolysis range was respectively73.78～158.53μmolAA·g-1·5h-1and63.60-114.13μmolAA·g-1·5h-1in primitive korean pine forest and white birch secondary forest soil; and the potential proteolysis range was respectively96.80～222.05μmolAA·g-1·5h-1和92.20～233.57μmolAA·g-1·5h-1; the native proteolysis and potential proteolysis varied with the depth of soil layer, were both shown as:Fermentation litter layer>rhizosphere soil>soil Al layer; native potential was manifested as primitive korean pine forest>white birch secondary forest.
(4) The free amino acids content that was extracted with KCl solution significantly greater than that extracted with distilled water in mineral soil, but the effect of extracting agent on the free amino content had not obvious rule in litter layer. The free amino acid content of soil that determined with three treatments that were added toluene and TCA separately and simultaneously were all increased, but that was only significant on that extracted with distilled water. The free amino acids content increased with oscillation time within thirty minutes, and it was no significant increase after thirty minutes. The order of soluble organic nitrogen content extracted from soil with different soil extractant was shown as potassium sulfate>distilled water>potassium chloride, and the difference was significant in three treatments with three soil extractants in mineral soil layer, but it is complex in litter layer, and the difference was not significant in three treatments with three soil extractants.
(5) The impact of three buffer solution on soil proteolysis was shown as treatment1(buffer solution prepared with distilled water)> treatment2(mixed solution by buffer solution and KCl solution)> treatment3(buffer solution prepared with KCl solution); the impact of oscillation time on soil proteolysis was shown as5h>lh, and the soil proteolysis size order was treatment2(mixed solution by buffer solution and KCl solution)> treatment3(buffer solution prepared with KCl solution)>treatment1(buffer solution prepared with distilled water); the impact of TCA action time on soil native proteolysis and potential proteolysis was shown as1h>5min, and the size order of soil native proteolysis was treatment2(mixed solution by buffer solution and KCl solution)> treatment3(buffer solution prepared with KCl solution)>treatment1(buffer solution prepared with distilled water), potential proteolysis was not significant except treatment1(buffer solution prepared with distilled water).The soil gross proteolysis decreased with the concentration of adding TCA, and the decrease of soil gross proteolysis stoped when the concentration of TCA was0.55mol·L-1.
引文
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