Fine Root Production And Turnover Of Sabina Vulgaris And Artemisia Ordosica In Mu Us Sandland

In order to study the effect of fine roots in the material cycle of sandland ecosystem, the fine root production and turnover of natural Sabina vulgaris and Artemisia ordosica that distribute at Research Center of Development and Management in Mu Us Sandland was dynamicly surveyed by sequential root coring from 2005 to 2006. The results show that:1. The total fine root biomass of Sabina Vulgaris accounted for 60.10% of its'total root biomass, annual average fine root biomass(≤2mm in diameter) of it were 14.480 t·hm^-2, living fine root biomass was 52.72% of the fine root biomass. The total fine root biomass of Artemisia ordosica was 73.04% of its'total root biomass, annual average fine root biomass(≤2mm in diameter) of it were 1.027t·hm^-2, living fine root biomass of its accounted for 53.57% of all fine root. Fine root biomass of Sabina Vulgaris was 14.11 times as high as that of Artemisia ordosica ( P< 0.05). Fine root was mostly distributed in the soil layers of 0⁴5cm,βof its was around 0.96. Root Length Density (RLD) and Root Area Index (RAI) of fine root appeared similar rule on depth, and annual average maximum values happened in 0¹5cm, the values reduced with the depth. The curves of fine root biomass of Sabina Vulgaris and Artemisia ordosica showed two peaks.2. Nutrient concentrations of C, N, P, K, Ca and Mg elements of fine root were constantly changeable. The standing crop of C, N, P,K, Ca and Mg elements of S. Vulgaris fine root basically showed the reverse S-shape and V-shape in 2005 and 2006 respectively. The standing corp of C, N, P, K, Ca and Mg elements of A. ordosica fine root showed the reverse S-shape basically. Ash content of S.Vulgaris fine root was single peak, the curve of A. ordosica ash content showed the reverse S-shape, the change tendency of S. Vulgaris and A. ordosica gross caloric value (GCV) was opposite from ash. The standing crop of total ashes, GCV and the ash-free caloric values(AFCV) of two plant species fine root changed with season, S. Vulgaris respectively showed the S-shape amd V-shape in 2005 and 2006 the reverse S-shape was showed by A. ordosica. and A. ordosica fine root3. The decomposition constant of S.Vulgaris were 0.0004d^-1, was 44.44% compared with A. ordosica. The annual fine root decomposition rate of S. Vulgaris and A. ordosica were 17.6% and 41.8%. It will take 1639d and 544d to decompose to the half of fine root, 7396d and 3102d to decompose to 95% of fine root for S. Vulgaris and A. ordosica. In the process of its'fine root decomposition, nutrient concentrations of C and P elements of fine root showed a decreasing tendency of the wave-shape staggered increasing and decreasing, nutrient concentrations of K showed a rapidly decreasing, the N and Ca were an increasing and Mg showed an wave-shape increasing. The dynamic change tendency of its'C/N and C/P showed the same change, the change difference was significant (P﹤0.05). the change tendency of lignin content showed single peak, the content of cellulose was the wave-shape starggered increasing and decreasing. C, P, K and Mg were released, the release rate of S. Vulgaris was bigger than A. ordosica.4. The differences of Fine Root Production and Turnover rate of two plant species were 2～3 times from two different calculation methods. annual fine root production of S. Vulgaris and A. ordosica were 5.868 t·hm^-2·a^-1 and 0.428 t·hm^-2·a^-1, Annual fine root mortality of its were 5.309 t·hm^-2·a^-1 and 0.357 t·hm^-2·a^-1,fine root annual decomposition residue were 4.534 t·hm^-2·a^-1 and 0.250 t·hm^-2·a^-1, Annual turnover rates of fine root were 0.788 times·a^-1 and 0.892 times·a^-1.annual nutrient return of S. Vulgaris and A. ordosica fine root were in the following order: C>Ca>N>K>Mg>P and C>K>Ca>N>P>Mg respectively,the ratio of its'nutrient return were in the following order: K>C>P>N>Ca>Mg and K>C>P>N>Mg>Ca respectively. During the decomposition process, C, N, P, K and Mg elements were released and Ca was accumulated. The Release Amount of fine root decomposition of S.Vulgaris and A. ordosica was in the following order: C>K>P>N>Mg and C>K>N>P>Mg. annual Net Energy production of S.Vulgaris fine root was almost 11.23～16.58 times of A. ordosica fine root. Annual energy return of S. Vulgaris was 11.23～16.58 times of A. ordosica. Annual energy Release of S.Vulgaris fine root was almost 9.21～20.27 times of A. ordosica fine root. Annual energy release of S.Vulgaris fine root was 4.49～9.88 times of A. ordosica, the ratios of its'energy return were 51.70% and 57.86%.5. Fine root production dynamic of S. vulgaris communities was significant positive correlation with soil water content in 0¹5cm (P< 0.05) and air relative humidity (P< 0.01), the correlation coefficient of A. ordosica fine root production dynamic which didn't reach significant level with surface soil sater content. The fine root decomposition of S.Vulgaris and A. ordosica was related to micro-climate factors besides the influences of its'characteristics. The fine root decomposition of its was significant positive correlation with sample plot temperature ( P< 0.05)and extremely significant negative correlation with relative humidity, dew point temperature and absolute humidity(P﹤0.01). the fine root decomposition of two plant species was not correlation with soil water content.In a word, the study offered a theoretical basis for research on the important effects of nutrient cycling and carbon balance in semi-arid area sandland ecosystem, through analyzing fine root production and turnover mechanism of main plant communities in Mu Us sandland comprehensively and systematically. It is significance to reveal the degradation mechanism of plantation on sandland, maintain measures, select and collocate tree species.