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Zheng J.,Fujian Forestry Vocational Technical College | Huang J.,State Key Laboratory of Humid Subtropical Montane Ecology | Huang J.,Fujian Normal University | Wang Z.,State Key Laboratory of Humid Subtropical Montane Ecology | And 7 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2012

Fine roots (<2mm), as the most dynamic component of root system, play an important role in energy flow and nutrient cycling in the forest ecosystems, which send enormous carbon belowground through root turnover. Fine root survivorship in a plantation of Phoebe bournei (Hemsl.) Yang in Xihou, Wangtai, Fujian province, was monitored by the minirhizotron method for two consecutive years. Fine root longevity was estimated by the Kaplan-Meier method and differences among single factors, including root diameter (<0. 3mm, 0. 3-0. 6mm, 0. 6-1mm, 1-2mm), root order (first order, higher order), season of birth (spring, summer, autumn and winter), and soil depth (<20cm, 20-40cm), were tested by the Log-rank test. The chemical properties of different root diameter (<0. 3mm, 0. 3-0. 6mm, 0. 6-1mm, 1-2mm) were also determined. The objective of this study was to understand whether the more rapidly the fine roots grow, the shorter their lifespans. The mean and median root lifespans of Phoebe bournei (Hemsl.) Yang were (121±3)d and (89±1)d, respectively. Root growth was highly dynamic during the year, with 82. 36% of new roots born in spring. Fine root longevity was significantly affected by the season of birth (P<0. 01); the mean and median lifespans were (218±23)d and (175±65)d for roots born in summer, (121±3)d and (89±1)d for those born in spring, and (93±3)d and (46±6)d for those born in autumn and winter, respectively. While soil depth had no significant effect on the median fine - root longevity ((89±3)d amd (89±2)d respectively in the lower and upper soil layer) (P>0. 05), mean root lifespan in the lower layer ((126±4)d) was higher than that in the upper layer ((116±5)d). Mean root lifespan increased significantly with root diameter (P<0. 01); the mean root lifespan was (109±4)d, (123±5)d, (139±11)d and (185±25)d, and the median root lifespan was (89±0)d, (89±1)d, (123±13)d and (130±13)d, respectively, for root diameter classes of <0. 3mm, 0. 3-0. 6mm, 0. 6-1mm and 1-2mm. Root lifespan was significantly affected by root order (P<0. 05). Mean root lifespan and median root lifespan of the first root order were (120±4)d and (89±1)d, respectively, while those of the higher order were (137±7)d and (123±1)d, respectively. The root carbon content ranged from 455. 2g/ kg to 475. 6g/ kg and the root C/ N ratio rangeed from 20. 04 to 42. 62, both increased significantly with root diameter (P<0. 01). Whereas, both the nitrogen (from 11. 16 g/ kg to 22. 71 g/ kg) and phosphorus content (from 0. 38 g/ kg to 0. 97g/ kg) were decreased significantly with root diameter (P<0. 01). It is evidenced from the above that the smaller the root diameter, the higher the root physiological activity, and the shorter the root lifespan. It's concluded that the fine-root longevity of the Phoebe bournei (Hemsl.) plantation was affected by the morphological (root diameter and root order) and chemical traits, and the season of birth. Source

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