| Closing hillsides to facilitate afforestation, promoting forest update with its self-recovery ability, was one of the most efficient methods to recovery vegetation in limestone area. In this paper, I studied the recovery processes by selecting stands of different ages since hillside closing in Qiaomu village, Qingyang county, Anhui province. I addressed the following research:the fine root biomass and their distribution characteristics; the N, P, K, Ca, Mg element content and the change trend of C/N. Study aimed to discuss the biomass and the change trend of fine root under different cultivating ages, and to provide theoretical reference basis for he limestone mountain afforestation management. The main results were as follows:1. The fine root biomass of 0 year,5 years,10 years,20 years and 30 years were 2.9711 t/hm2,6.6287 t/hm2,2.3063 t/hm2,13.1322 t/hm2 and 2.8316 t/hm2. The closing ages had significant effect on fine root biomass, the change trend was 5 years> 20 years> 0 year> 30 years>10 years. The 5 years stand had maximum fine root biomass. The value of 5 years and 20 years were bigger than 0 years.2. The fine root biomass showed significant vertical distribution characteristics in deferent closing ages, most of fine root biomass was distributed in top layer(Ocm-10cm) and decreased with the layer down. The distribution of 0 year stands in three layers(0cm-10cm, llcm-20cm,21-30cm) was 42.0%,33.9%,24.1%; that of 5 years was 7.16%,27.20%,15.64%; that of 10 years was 58.48%,26.92%,14.59%; that of 20 years was 57.74%,27.09%,15.17%; that of 30 years was 52.54%,31.83%,15.63%.3. The change of fine root biomass in deferent closing ages was bimodal pattern and the peak and valley were occurred at spring and autumn.4. The contents of N, P, K, Ca and Mg in fine root were decreased with the depth down. The maximum appeared in the top layer. The content of nutrient in live fine root was bigger than that in dead ones, which indicated that the nutrient had been transformed. The trend of N content in fine root was 20 years (11.28mg/g)>10 years (10.69mg/g)>0 year (9.36mg/g)>30 years (8.72mg/g)>5 years (7.17mg/g). The trend of P content in fine root was 20 years (1.10mg/g)>0 year (0.77mg/g)>10 years (0.66mg/g)> 30 years (0.55mg/g)>5 years (0.52mg/g). The trend of K.content in fine root was 10 years (8.38mg/g)>0 year (8.23mg/g)>5 years (7.70mg/g)>20 years (7.52mg/g)>30 years (5.88mg/g). The trend of Ca content in fine root was 10 years (51.43mg/g)>20 years (49.58mg/g)>0 year (29.67mg/g)>5 years (28.10mg/g)>30 years (27.62mg/g). The trend of Mg content in fine root was 10 years (3.23mg/g)>20 years (3.14mg/g)>5 years (2.25mg/g)>0 year (2.06mg/g)>30 years (1.49mg/g). The trend of C/N was 5 years (49.64)> 0 years (40.72)> 30 years (40.05)>20 years (33.24)> 10 year (32.53).5. The fine root biomass and fine root nutrient in the whole closing model indicated that the best management was closing the hill for 10-20 years. During this period, the fine root biomass and fine root nutrients increased fast, so was the fine root turnover. After this period, if appropriate management was taken, the production of forest will be higher. |
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