Fine Root Dynamics Of Larix Princpis-rupprechtii In Guandi Mountains

Fine roots (usually diameter<2mm) is the most active components in the underground ecosystem, always being growth, aging, death and decomposition of the dynamic process (called the fine root turnover) constantly, fine root turnover is one of the key of carbon nutrient cycling processes and terrestrial ecosystems. However, due to limitations of fine roots deep in the ground and research methods, our knowledge of the laws of fine root turnover is still very lacking.In this study, we use the root window glass method (size,20×30cm), to Larch Forests for the study, to explore the structure of the forest fine root turnover, reveal the relationship between fine root turnover and environmental factors. The main results are as follows:1. Fine roots seasonal dynamics of total root length:Fine root production and death has obvious seasonal dynamics. Fine root production showed two peaks, the largest production appears in the summer months of July,0.86±0.46mm·cm-2·month-1. Spring and summer fine root production accounts for77.51%of annual production, the fall and winter production accounted for only22.49%of all.Fine root death mainly occurs in autumn and summer, the amount of death accounted for43.64%and38.11%of all deaths. The maximum fine root death appears in the autumn (September),0.43±0.12mm· cm-2·month-1.2. The relationship between fine roots seasonal dynamics and soil environmental factors:soil temperature (r=0.66) and soil moisture (r=0.5) were impact the fine root production, but the effect is not obvious (p>0.05). Soil available nitrogen (r=0.91, p<0.05), ammonium nitrogen (r=0.89, p<0.05), nitrate (r=0.88, p<0.05) were significantly affected the production of fine roots.Soil temperature (r=0.42), soil moisture (r=0.32), soil nutrient impact the fine root death, but it is not obvious (p>0.05). Multiple linear analysis showed that the combined effects of soil temperature, moisture, organic matter, available nitrogen which can explain84%of fine root mortality variation.3. The relationship between fine roots seasonal dynamics in different soil depth and soil factors:The differences of fine root production and mortality was not significant in different soil depth (p>0.05), the same soil depth, the difference of fine root production and mortality were significantly (p<0.01). Fine root production is mainly concentrated in the soil surface depth (0～20cm), surface production accounts71.44%of all production. In the10～20cm soil depth, the maximum fine root production appears in spring (May); in the20～30cm soil depth, it produced the largest production in summer (July). The max death of fine roots occurs in autumn (September). Fine root death occurs mainly at the surface, the surface (0-20cm) accounted for70.35%of all, bottom accounted for only29.65percent.Different depths of fine root production and soil ammonium, nitrate, available nitrogen was significantly correlated (p<0.05), the combined effect of the three can explain78%to90%of the fine root production variance. Different depths of soil factors impact the fine root mortality, but the effect is not obvious (p>0.05).4. The relationship of the fine roots seasonal dynamics in different diameters and soil factors:The differences of Larch fine root production in different diameters was not significant, the difference of death was obvious. Fine root production and mortality are mainly concentrated in0.3～0.7mm diameter of fine roots. The fine root production and mortality in different diameters have obvious seasonal dynamics, the fine root production is the largest in the summer, the maximum fine root mortality was in the fall. Soil moisture, available nitrogen, organic matter can explain88%to97%of fine root production variation and73%to88%of mortality variation.5. The fine root turnover of different soil depths and different diameters:It has the trend that fine root turnover has decreased with increasing soil depth. The fine root turnover of the soil subsurface (10～20cm) was the largest (2.08a1), bottom turnover (1.55a-1)was the least, surface turnover (1.73a-1) was center. Larch’s fine root turnover was different in different diameters, fine root turnover increases as the diameter decreases. Fine root turnover was maximum (2.65a-1) in0.3～0.7mm diameter, fine root turnover (1.26a-1) min in1～2mm diameter.