The Studies Of Dynamic On Free Amino Acid Of Different Forest Types In Cold-temperate Forest Soil

At present, the study of amino acid in soil have been more and more people’s attention, especially the research of free amino acid, and the amino acid has a significant impact on the supply of soil nitrogen and carbon nitrogen cycle. Therefore, it is very important to study the difference of amino acid composition and concentration in different forest ecosystems and different soil layers, we selected the litter layer and mineral layer of four typical kinds of forest lying in the boreal forest of Great Xing’an Mountains as our plots in this study, to investigate dynamic changes of the variation of the type and content of free amino acid in different soil layer, as well as the influence of different forest types on free amino acid content in the boreal forest of Great Xing’an Mountains, this studies showed that different forest types have generated varying degrees effect on the content and type of soil free amino acid accounting for various stand climatic environment, edaphic conditions, and understory associated trees, the study has important significance for soil free amino acid in Cold-temperate forest in nitrogen supply capacity and stabilizing productivity of soil different forest ecological system.The major findings are as follows:(1) In the four forest types of Cuckoo-Betula forest, Cuckoo-Larix gmelinii forest, Ledum palustre Larch and Pinus pumila forest., from June to August, the total content of free amino acid nitrogen showed a trend of the inverted " V" sharp, and all showed the lowest in August and the highest in July, between different soil layers in addition to litter layer and the 0-5 cm of mineral layer of Cuckoo-Larix gmelinii forest and the 5-20 cm of mineral layer in Ledum palustre Larch showed the highest in July, and others are in line with the trend of four forest types except the August slightly higher than the June.(2) In June, July and August all the soil layers in four forest types of free amino acid nitrogen content showed the same rule:the size order of free amino acid nitrogen content of every soil layer is litter layer> mineral layer, the 0-5 cm of mineral layer> the 5-20 cm of mineral layer, the content of free amino acid rang from 13.19 to 77.64 ugN/g, the maximum value appeared the litter layer of Cuckoo-Larix gmelinii forest in July, and the minimum appeared the 5-20 cm of mineral layer of Ledum palustre Larch in June. The free amino acid of content n Ledum palustre Larch litter layer had significant difference with mineral layer (P<0.05); the three soil layers had significant difference with each other in Cuckoo-Larix gmelinii forest; in the June and July, the different levels of soil layers were significantly different in the Cuckoo-Larix gmelinii forest and Ledum palustre Larch, in August the former had significant difference between litter layer and mineral mineral (P<0.05), the latter is a significant difference between mineral soil (P<0.05).(3) The kinds of amino acid were detected in the four species of forest types, neutral amino acid,alkaline and acidic amino acid, sulfur-containing amino acid also showed seasonal dynamic changes, but also into the "V" shape changes, that is the lowest in July highest in August, neutral amino acid content was the highest, followed by alkaline and acidic amino acid, and sulfur-containing amino acid was lowest, besides in the four forest types the content of acidic amino acid is greater than alkaline amino acid in June, July and August, amino acids accounted for the total free amino acid of neutral amino acid was 45.00%-65.09%, alkaline amino acid was 6.22%-20.64%, acidic amino acid was 14.02%-27.74%, sulfur-containing amino acid was 2.21%-14.54%.(4) The composition of different tree species also had the influence on the content of free amino acid nitrogen, for the determination of free amino acid nitrogen content showed Cuckoo-Betula forest>Cuckoo-Larix gmelinii forest> Ledum palustre Larch>Pinus pumila forest.(5) In the four types of forest, not only the total content of amino acid nitrogen showed obvious seasonal dynamic change in June, July and August, but also the amino acid content of each species is also in line with the law, the larger content of amino acids are mostly similar to Asp, Gly, Glu, Lys, Thr, Tyr, the total amino acid content between the forest types in different months of variance analysis results showed that:in addition to Pinus pumila forest seasonal difference was not significant, but the other three forest types are expressed as June was significant difference with July and August (P<0.05).(6) The types of amino acid detected under different forest types were mostly similar, Arg was not detected in the four forest types, the species and contents of amino acids in the same forest type were different in different soil layers, and most of them were detected by litter layer, the amino acid species were also different months.