Studies On Decomposition Of Fine Roots Of Castanopsis Carlesii And Cunninghamia Lanceolata In Wanmulin Natural Reserve

Although abundant oversea researches had reported that fine roots play an important role in nutrient cycling and energy flow in forest ecosystem in late 70's and early 80's, our nation ecologists don't fully understand its ecological and environmental functions and so not pay much attention to it until now. Based on soil degradation caused by continuous mono-culture with Chinese fir, a large number of researches on mixed forests of Chinese fir and broadleaf trees have been carried out which are involved in community function, ecosystem function and interactions of Chinese fir and other species while lack of intensive study on mechanism of maintaining long-term fertility in point of fine roots. This research was carried out in Wanmulin Natural Reserve of Fujian province and mainly focused on the decomposition of fine roots of Chinese fir (Cunninghamia lanceolata) and Castanopsis carlesii with litter bag and arenaceous tube. This article has deeply researched into the phase of weight loss of fine roots, dynamic and process of nutrient release , decomposition dynamic of organic components and their variances. We get these results as follows:1. This research has indicated that weight loss of fine roots of 0-1 mm and 1-2mm of Castanopsis carlesii decomposed in Castanopsis carlesii stand are higher than that of in Chinese fir stand. Data shows that: when fine roots of Castanopsis carlesii decomposed in Chinese fir stand, soil attributes and micro-climate surroundings in situ have certain effects on decomposition speed which leaded to the decomposition speed in Chinese fir stands lower than that in Castanopsis carlesii stand, and resulted in their variances of weight loss phase.2. This research has also showed that there exist strong variances of weight loss of fine roots of 0-1 mm and 1-2mm of Chinese fir when decomposed in Chinese fir stand and in Castanopsis carlesii stand. Data indicates that: adaptation of soil microbes and animals is probably responsible for the higher decomposition speed of fine roots of 0-1 mm of Chinese fir when decomposed in Chinese fir stand than that of in Castanopsis carlesii stand. For fine roots of 1-2mm of Chinese fir, its decomposition speeds have some differences compared with 0-1 mm fine roots and these differences need further insight research.3. This research, as well, has showed that fine roots of Castanopsis carlesii and Chinese fir have some interactions during the course of decomposition with mixed samples, which were either inter-promoting or inter-impeding. Data shows that: mixed fine roots of 0-1 mm of Castanopsis carlesii and Chinese fir, compared with their pure samples, impeded thedecomposition of Castanopsis carlesii, while promoted the decomposition of Chinese fir. On the contrary, mixed fine roots of l-2mm promoted the decomposition of Castanopsis carlesii, but constrained the decomposition of Chinese fir.4. Soil microbes have some different functions when fine roots of 0-1 mm and l-2mm of Castanopsis carlesii decomposed in Castanopsis carlesii stand and Chinese fir stand. When fine roots were cut up by man work, soil microbes decomposed fine roots fast in former time, while in later, weight loss is similar to that of with litter bag. When fine roots decomposed in different forest stands, weight losses have no significant difference because of shielding from soil animals by arenaceous tube which indicate that soil animals have certain influences on fine roots decomposition.5. Soil microbes also have some different functions when fine roots of 0-1 mm and l-2mm of Chinese fir decomposed in Chinese fir stand and Castanopsis carlesii stand. When fine roots of Chinese fir decomposed in Chinese fir stand, weight loss in each decomposition phase was higher than that with litter bag which indicate that fine roots cut-up by man work is stronger than broke-up by soil animals. When fine roots of Chinese fir decomposed in Castanopsis carlesii stand, weight loss in each decomposition phase was lower than that with Utter bag which indicate that fine roots cut-up by man work is weaker than broke-up by soil animals. All of these show that activity of soil animals of Chinese fir stand is weaker than that of Castanopsis carlesii stand.6. Functions of soil microbes on mixed fine roots of 0-1 mm and l-2mm of Chinese fir and Castanopsis carlesii exist a certain variances. During the course of decomposition, different fine roots have a strong inter-impeding effect, and such effect is stronger than that of with litter bag. The weight loss of mixed fine roots of Chinese fir and Castanopsis carlesii of 0-1 mm and l-2mm is lower than that of Chinese fir and Castanopsis carlesii pure fine roots,, and meantime lower than that of litter bag.7. The release of C, N> ?> K nutrient contents obeys a general principal in this research ,namely, N increasingly accumulated or formerly accumulated then released, C, P> K and C/N gradually decreased with different pattern. Among them, the change of concentration of N was decided by C/N. bigger the C/N, more likely to accumulate the N, especially when C/N is bigger than a threshold number. K has a strong eluviation which accounts for its fastest release speed. Simulating the dynamic of leftover of nutrient substances with Olson negative exponent equation, coefficients are all above 0.90.8. During the course of decomposition, the relative percentage of hydro-dissolved substances and semi-celluloses decreased gradually, phenol-dissolved substances, coarse proteins andcelluloses formerly mounted then decreased, while lignin increasingly accumulated comparatively which indicate that hydro-dissolved substances and semi-celluloses easily and fast decomposed in the initial stages of decomposition, and that phenol-dissolved substances, coarse proteins and celluloses are more difficult to decompose and therefore formerly accumulated then decomposed comparatively. Lignin, as a complex substance, is most difficult to decompose in soil and finally take part in the formation of humus. The decomposing speed of lignin, as a matter of fact, is the determinant factor of weight loss speed of fine roots.