A Study On The Decomposition Of Fallen Trees Of Larix Gmelinii And Betula Platyphylla Forests In Daxinganling Mountains

In forest ecosystem, fallen trees contain a large quantity of nutrient matters, which function in woodlands and benefit trees like long-term chemical fertilizer. The process of organs decomposing and nutrient emissing in fallen trees, with diverse rates in different periods, plays a critical role in improving forest productivity, restoration and regeneration. Up to now, few reports are found in studying nutrient content in fallen trees of Daxinganling Mountains. Therefore, detailed investigation and statistical analysis on the decomposition, nutrient content and its dynamics along with decomposition of fallen trees of Larix gmelinii were carried out in Daxinganling Mountains. Main conclusions are following:(1) Along with decomposition grades increasing, density of fallen trees decreased linearly.(2) The decomposition time of Larix gmelinii was notably longer than of Betula platyphylla, which means, the former decomposition rate was lower than the later.(3) The difference in nutrient content between Larix gmelinii and Betula platyphylla was quite significant.(4) Basically, fallen trees of Larix gmelinii contained a large number of C (carbon), with a sequence of:native forests> half cutting forests> clear cutting forests, the same with Betula platyphylla. However, N (nitrogen) content in fallen trees of Larix gmelinii showed as:half cutting forests>native forests>clear cutting forests, and the difference aomong types was quite tiny. Inversely, the sequence of N content: native forests> half cutting forests> clear cutting forests was found in Betula platyphylla, with a notable difference among the three types. The sequence of P (phosphorus) content in Larix gmelinii was same to its C content. But, it turned dissimilar and complex in Betula platyphylla, which displayed as:when in degrade i and ii, clear cutting forests were obviously lower than the native and half cutting ones, then increased rapidly with the decomposition grades increasing from iii to v, finally, it got the similar P content with the other two types of forest managements. In a word, P content changed significantly with decomposition grades in clear cutting forests. K (potassium) content, which rose and fell irregularly with decomposition grades, was higher in Larix gmelinii than in Betula platyphylla. No significant correlation ship was found between K content and decomposition grades of the two species.(5) Along with decomposition grades increasing, surface soil temperature around fallen trees dropped gradually. In other words, the more thoroughly fallen trees decomposed, the lower around soil temperature would be. Besides, there existed a dramatic drop from grade i to iii. After then, it became smooth and steady.(6) Species of micro creatures were influenced by decomposition grades.