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Dongtai, China

Xu Y.,Nanjing Forestry University | Xu K.,Nanjing Forestry University | Yu S.-Q.,Nanjing Forestry University | Ruan H.-H.,Nanjing Forestry University | And 4 more authors.
Chinese Journal of Ecology | Year: 2014

Nitrogen deposition is a hot topic issue of global change. Understanding the response patterns and feedback mechanisms of forest ecosystems associated with this continued, increased nitrogen deposition and rapid nitrogen cycle is vital for the maintenance of forest ecosystem health and productivity. Increasing nitrogen deposition may alter the distribution structure of fine roots, such as vertical distribution and diameter size distribution formed in the long-term evolution process. We conducted an experiment to examine the allocation of fine root biomass and its response to nitrogen deposition in poplar plantations with different stand ages in the coastal plain of Dongtai, Jiangsu. The randomized block design was used with five nitrogen deposition concentration treatments, i. e. N0(0 g N·m-2 · a-1), N1(5 g N · m-2 · a-1), N2(10 g N·m-2 · a-1), N3(15 g N · m-2 · a-1), and N4(30 g N · m-2 · a-1) in the field. The results showed that: (1) The fine root biomass was obviously enriched in the surface soil, with 70% -80% of fine root biomass allocated to the 0-20 cm soil layer. With the increase of exogenous nitrogen, the proportion of fine root biomass at the 0-10 cm soil layer increased in the young plantation (4 years old), while reduced in the mid-aged and mature plantations (8 and 15 years old, respectively) to some extent. (2) Fine root biomass was mainly distributed in the diameter class of 0-0. 5 and 0. 51. 0 mm, and about 50% of the fine root biomass (<2. 0 mm) was allocated in the diameter class of 0-0. 5 mm. Exogenous nitrogen increased the proportion of very fine root biomass (00. 5 mm), especially in the young plantation. (3) In the 30-40 cm soil layer, fine root biomass was allocated with a greater proportion in 0-0. 5 mm diameter class in the mature plantation than in the young and mid-aged plantations, which showed that small fine roots had a decreasing trend with the increase age. (4) Four factors (plantation age, soil layer, diameter class, and nitrogen concentration) in combination explained 66. 3% of variation of fine root biomass. Plantation age, soil layer, and diameter class respectively explained 17. 6%, 16. 1%, and 10. 4% of variation, with significant effects (P<0. 01), and the increase of nitrogen deposition only explained 0. 24% of variation of fine root biomass, with no significant effect (P>0. 05). © 2014, Editorial Board of Chinese Journal of Ecology. All rights reserved.

Wang G.-B.,Nanjing Forestry University | Zhao X.-L.,Dongtai Forest Farm | Wang M.-H.,Nanjing Forestry University | Ruan H.-H.,Nanjing Forestry University | And 2 more authors.
Chinese Journal of Applied Ecology | Year: 2013

Soil readily oxidizable carbon (ROC) is a sensitive index to indicate the early changes of soil organic carbon (SOC), and has important value to research the stability and dynamics of SOC pool under the backgrounds of human disturbance and global climate change. To further understand the effects of land use change on soil ROC, an investigation was conducted on the soil ROC content and related factors in four different land use types (grassland, farmland, poplar-agriculture system and pure poplar plantation) in a coastal area of northern Jiangsu Province, East China. The soil ROC content was in the order of grassland < farmland < poplar-agriculture system < pure poplar plantation, and the difference was most significant in 0-10 cm soil layer. The ROC and ROC/SOC ratio decreased with increasing soil depth, and had significant differences between different soil layers in any one of the land use types. The soil ROC in the four different land use types had the same seasonal variation trend, with the maximum in summer, followed by in winter and autumn, and the minimum in spring. The soil ROC was significantly negatively correlated with soil pH and soil bulk density, positively correlated with SOC, soil water soluble organic carbon (WSOC), total nitrogen (TN), C/N ratio, and Mg, but less correlated with soil moisture and soil total phosphorus (TP). The results indicated that land use change had significant effects on the spatial distribution characteristics of soil ROC, and soil bulk density, pH value, TN, and SOC were the main factors inducing the differences of soil ROC content between different land use types.

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