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Table of Content
    Volume 36 Issue 2
    01 February 2012

    The landscape at south margin of the Gurbantonggut Desert in winter. The thickness of snow-cover is about 20–30 cm. It is dominated by Haloxylon ammodendron and Haloxylon persicum and possesses plenty of herbaceous plants in spring. Fan et al. investigated the responses of the herbaceous layer to the changes of snow cover depth (Pages 126–135 of this issue). (Photographed by MA Jian)

      
    Research Articles
    Response of Betula luminifera leaf litter decomposition to simulated nitrogen deposition in the Rainy Area of West China
    TU Li-Hua, HU Hong-Ling, HU Ting-Xing, ZHANG Jian, LUO Shou-Hua, and DAI Hong-Zhong
    Chin J Plan Ecolo. 2012, 36 (2):  99-108.  doi:10.3724/SP.J.1258.2012.00099
    Abstract ( 1457 )   PDF (550KB) ( 1395 )   Save
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    Aims Our objective was to determine the effect of simulated increased nitrogen (N) deposition on decomposition of Betula luminifera leaf litter, under a high wet-nitrogen deposition background.
    Methods From January 2008 to February 2009, a field experiment of simulated N deposition was conducted in a B. luminifera plantation in the Rainy Area of West China. The levels of nitrogen deposition were control (CK), low, medium and high N (0, 5, 15 and 30 g N·m–2·a–1, respectively). A field experiment using the litterbag method was conducted on the decomposition of leaf litter of B. luminifera. In the end of each month, NH4NO3 was added into N-treated plots.
    Important findings Despite the high background N deposition, there were significant effects of simulated increased N deposition on B.luminifera leaf litter. N treatments significantly slowed the decomposition of B. luminifera leaf litter through inhibiting the decay of lignin and cellulose. The time of 95% mass loss (T95%) of B. luminifera leaf litter was increased by 1.14–1.96 a from 2.65 a (T95% of CK) caused by simulated N deposition. Simulated N deposition significantly increased the remaining amount of carbon, N, phosphorus, potassium, and magnesium after one year of decomposition. However, calcium release rate was stimulated by simulated N deposition in all three N treatments. The initial chemical characteristics of litter determined the response direction of litter decomposition to simulated N deposition, as well as the nutrient release pattern during litter decomposition.

    Effects of forest litter layer on regeneration of Populus cathayana natural population in Xiaowutai Mountains in China
    LI Xiao-Feng, XU Xiao, WANG Bi-Xia, HUANG You-You, WANG Zhi-Feng, and LI Jun-Yu
    Chin J Plan Ecolo. 2012, 36 (2):  109-116.  doi:10.3724/SP.J.1258.2012.00109
    Abstract ( 1310 )   PDF (553KB) ( 1455 )   Save
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    Aims Populus cathayana, a typical riparian tree in northern China, can produce substantial seeds and numerous clones. Several studies in the last few years indicated that the proportion of seedlings and clones in the population was correlated with factors such as river flooding, soil substrates and slope gradient. Our objective was to investigate the regeneration mode of Populus cathayana located in high-elevation woodland of Xiaowutai Mountains, revealing why there was such a phenomenon.
    Methods From 2010 to 2011, we excavated 1 284 small P. cathayana saplings along an elevational gradient in high-elevation woodland of Xiaowutai Mountains to determine their method of origin. The influence of allelopathy and mechanical effects of litter layer on seedling regeneration was investigated by a series of controlled experiments.
    Important findings Regeneration was overwhelmingly from clonal propagation. Litter layer had a negative effect on recruitment from seed. Under treatment of different concentrations of litter layer aqueous extracts, seed germination exhibited significant differences. Compared with the control treatment, 50 mg·mL–1 solution decreased seed germination by 41% and root length by 95%, and 100 mg·mL–1 solution completely inhibited germination. Furthermore, litter layer inhibited roots of seedlings from absorbing water and rapidly caused seedling death. Therefore, litter layer prevents seedling recruitment, and clonal propagation was the only effective regeneration mode of P. cathayana in the population.

    Dynamics of stand biomass and volume of the tree layer in forests with different restoration approaches based on tree-ring analysis
    ZHANG Yuan-Dong, LIU Yan-Chun, LIU Shi-Rong, and ZHANG Xiao-He
    Chin J Plan Ecolo. 2012, 36 (2):  117-125.  doi:10.3724/SP.J.1258.2012.00117
    Abstract ( 1605 )   PDF (541KB) ( 1490 )   Save
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    Aims Our objectives were to (a) explore potential applications of tree-ring analysis for evaluating biomass dynamics of different forest restoration approaches in Western Sichuan, (b) compare aboveground biomass and stem volume with differently restored forests, and (c) identify the appropriate management approaches for different management aims.
    Methods We intensively surveyed three replicated plots for each restoration approach and cored and measured all living trees with diameter at breast height (DBH) ≥ 5 cm using dendroecological methods. Dynamics of aboveground biomass and stem volume were calculated by means of allometric relationships and one-way tree volume models based on continuous variation of DBH.
    Important findings Forests in all three restoration approaches entered into an accelerated growth phase after 20 years, when significant differences in average DBH were observed among different forest types. Planted spruce (Picea asperata) forest (PSF) showed faster growth in mean DBH than secondary birch (Betula spp.) forest (SBF) and secondary coniferous and broad-leaved mixed forest (SMF). In the process of recovery, SMF had the highest aboveground biomass and stand volume; its biomass was significant higher than that of PSF (p < 0.05) throughout and higher than SBF after 20 years. SBF had a higher aboveground biomass compared with that for PSF during 1–25 years and a lower value after 25 years. Before 20 years, the stand volume of SBF was higher than that of PSF, but PSF had higher volume after 20 years. Before 30 years, the aboveground net primary productivity for three forest types ranked SMF>SBF>PSF. After 30 years, the order changed to SMF>PSF>SBF. Results indicated that SMF had an advantage in both biomass and stand volume accumulation among the three restoration approaches.

    Response of the herbaceous layer to snow variability at the south margin of the Gurbantonggut Desert of China
    FAN Lian-Lian, MA Jian, WU Lin-Feng, XU Gui-Qing, LI Yan, and TANG Li-Song
    Chin J Plan Ecolo. 2012, 36 (2):  126-135.  doi:10.3724/SP.J.1258.2012.00126
    Abstract ( 1437 )   PDF (581KB) ( 1359 )   Save
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    Aims The herbaceous layer is an important component of the plant community of China’s Gurbantonggut Desert, and it primarily depends on early spring snow-melt water for germination and development. However, few studies have shown how the herbaceous layer responds to variability of precipitation. Generally, snow thickness changes in accordance to variability of precipitation. Therefore, our objective was to determine how snow thickness affects the ecological and physiological traits of the herbaceous layer in a typical arid zone.
    Methods We used five treatments of snow thickness (0, 50%, 100%, 150% and 200%), and natural snow thickness (100%) was the control. We investigated species number, coverage, density and height of plants in 1 m × 1 m quadrats and used the harvest method to measure aboveground biomass of both the herbaceous layer and the dominant species (Nepeta micrantha).
    Important findings Seedling density of the herbaceous layer was positively correlated with the amount of snow, but average height was negatively correlated with it. Also, total aboveground biomass and number of species showed no significant differences among treatments. Plant height and aboveground biomass of the individual dominants were negatively correlated with the amount of snow. For other species in the layer, the average height was also negatively correlated with the snow thickness. The number of seeds germinating and the abundance of herbaceous plants increased with the amount of snow, but species richness was not influenced by snow thickness. Our results suggested that although melted snow is the main water source for herbaceous plants, they have developed a strong buffering capacity against variation in the snow thickness. Therefore, species diversity and net primary productivity of the herbaceous layer can be stable even under strong variation of snow accumulation.

    Variations in leaf functional traits of Stipa purpurea along a rainfall gradient in Xizang, China
    HU Meng-Yao, ZHANG Lin, LUO Tian-Xiang, and SHEN Wei
    Chin J Plan Ecolo. 2012, 36 (2):  136-143.  doi:10.3724/SP.J.1258.2012.00136
    Abstract ( 1588 )   PDF (479KB) ( 1624 )   Save
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    Aims Stipa purpurea is the dominant species in alpine arid and semi-arid grasslands on the Tibetan Plateau. Our objectives are to determine if this species exhibits a strategy shift in its specific leaf area (SLA) to nitrogen (N) concentration relationship along a rainfall gradient and to detect possible effects of environmental factors on related leaf traits.
    Methods We investigated variations in leaf traits of S. purpurea associated with climatic and soil factors along an east-west transect with a rainfall gradient (69–479 mm) but similar altitudes (4 300–4 700 m). Five locations from east to west are Damxung, Namco, Gêrzê, Mount Qomolangma and Rutog. We measured SLA, mass- and area-based leaf N concentration (Nmass, Narea), leaf density and thickness and soil total N along the transect.
    Important findings In pooled data, SLA and Nmass varied little with the growing season mean temperature and precipitation and the soil total N concentration. The SLA-Nmass relationship in S. purpurea did not shift between the semi-humid areas (ratio of rainfall to evaporation > 0.11) and the arid and semi-arid areas (ratio < 0.11), although there was a positive correlation between SLA and Nmass across the five locations. Variation in SLA was mainly determined by leaf density in the semi-humid areas and by leaf thickness in the arid and semi-arid areas; both were negatively correlated with SLA. With increasing temperature or declining precipitation, leaf density decreased and leaf thickness increased, leading to non-significant relationships between SLA and climatic factors. The increase of leaf density in the semi-humid areas was correlated with the increase of Narea, but the increase of leaf thickness in the arid and semi-arid areas did not lead to change of Narea, resulting in unchanged Narea along the rainfall gradient. A positive correlation was detected between aboveground biomass and Narea in S. purpurea, indicating that increased Narea may increase plant productivity. Our findings suggest that alpine plants in arid and semi-arid areas may maintain a constant Narea by increased leaf thickness in order to achieve a similar photosynthetic productivity and water use efficiency compared to the relatively humid areas. The relative impacts of leaf density and leaf thickness on SLA shifted between the semi-humid areas and the arid and semi-arid areas, which may provide insight in detecting the threshold of water limitation in alpine grasslands.

    Regenerative condition and analysis of spatial distribution pattern of two relic plants in Mao’ershan Mountain, China
    LI Lin, WEI Shi-Guang, HUANG Zhong-Liang, CAO Hong-Lin, and MO De-Qing
    Chin J Plan Ecolo. 2012, 36 (2):  144-150.  doi:10.3724/SP.J.1258.2012.00144
    Abstract ( 1421 )   PDF (387KB) ( 1391 )   Save
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    Aims Current knowledge about tree distributions in species-rich communities is almost exclusively derived from tropical rain forests. The Natural Reserve of Mao’ershan Mountain has complicated landforms and high biodiversity, including relic plants. Our objective was to analyze distribution patterns and regeneration conditions of two relic plants to find survival conditions and coexistence mechanisms.
    Methods Using a stem map of two 1 hm2 permanent plots at different altitudes in the Mao’ershan Mountain Natural Reserve, we analyzed the distribution pattern, regeneration condition and size distribution of two relic plants: Tsuga chinensis var. tchekiangensis and Fagus longipetiolata. Spatial patterns were analyzed by R program. Confidence intervals were generated from 999 Monte Carlo simulations under the null hypothesis of complete spatial randomness.
    Important findings Regeneration conditions and size distribution of both species determined no new individuals had appeared in six years. Diameter at breast height (DBH) classes for 2002 and 2008 were inverse J type for F. longipetiolata and normal distribution for T. chinensis var. tchekiangensis. Both species have regeneration problems. There were fewer individuals of T. chinensis than F. longipetiolata. Continuously sampling data to analyze spatial point pattern using the relative neighborhood density showed that both species had different distribution patterns at different scales. Fagus longipetiolata were significantly aggregated at scales <11 m, as did T. chinensis at scales from 2 to 20 m. Fagus longipetiolata was widely distributed in its plot, while T. chinensis was distributed in the southwest of the plot. Integrative measures should be adopted to protect both relic species from regeneration difficulties, such as local protection, artificially aided regeneration and ex-situ conservation to increase their populations and enlarge their areas of distribution.

    Selection of optimum quadrat size and number for estimating aboveground volume of cultivated cultivated Dipsacus asperoides
    ZHU Shou-Dong, LIU Hui-Ping, HUANG Lu-Qi, WANG Xin-Cun, ZHANG Xiao-Bo, XUE Xiao-Juan, MU Xiao-Dong, and CHENG Jie
    Chin J Plan Ecolo. 2012, 36 (2):  151-158.  doi:10.3724/SP.J.1258.2012.00151
    Abstract ( 1313 )   PDF (484KB) ( 1254 )   Save
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    Aims In the traditional Chinese medicine resources survey process, quadrat size and number must be determined before surveying. Our objective is to determine how to select the optimal quadrat size and number for Dipsacus asperoides.
    Methods We examined D. asperoides cultivated in Longli, Qiannan Autonomous Prefecture, Guizhou Province. We first calculated aboveground volume of D. asperoides by a segment model. Then we selected the optimal quadrat size and number by using the quadrat-based transect survey method, and calculated the optimal quadrat number by the variance method.
    Important findings When only considering of the relative mean of aboveground volume and relative time costs, 25 m × 25 m is the optimal size. But when further considering quadrat boundary effects and variation in relative mean of the aboveground volume, the optimal size is 25 m × 50 m. If the expected confidence level is 0.9, the absolute margin of error is 0.12, the population variance S2 obtained conventionally is 0.25 and the optimal quadrat number is 25. This study sampled 25 quadrats of 25 m × 50 m within the entire area of the cultivated garden (72 696.24 m2). The total aboveground volume of D. asperoides with approximately 90% confidence located in the extent is [1 909.798 m3, 2 214.762 m3]. Results showed that the optimal quadrat size from the nested quadrats method and the segment model are useful in estimating the aboveground volume of cultivated D. asperoides, and they can provide a reference for other surveys.

    Dynamics of nitrogen and phosphorus concentrations and nitrate reductase and acidic phosphatase activities in Imperata cylindrica on copper mine tailings
    SHEN Zhang-Jun,SUN Qing-Ye, and TIAN Sheng-Ni
    Chin J Plan Ecolo. 2012, 36 (2):  159-168.  doi:10.3724/SP.J.1258.2012.00159
    Abstract ( 1332 )   PDF (457KB) ( 1286 )   Save
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    Aims Our objective was to study self-regulation of nitrogen (N) and phosphorus (P) nutrient use by Imperata cylindrica at different growth stages on copper mine tailings.
    Methods We obtained samples from two different nutrient habitats: copper mine tailings and farmlands. We investigated N and P distributions, N P, nutrient resorption rate, nitrate reductase and acidic phosphatase ∶ activities in I. cylindrica organs.
    Important findings The N and P distributions in I. cylindrica differed by growth period. During the initial stage of growth, N and P in both populations were mainly in the rhizomes. At bud and mature times, N and P concentrations were highest in leaves and lowest in roots and rhizome. At the decay period, N and P concentrations in senescent leaves were (9.19 ± 0.80) and (0.05 ± 0.03) mg·g–1, respectively, which were significantly lower than for the control farmland. The N and P resorption efficiencies of I. cylindrica leaves in the tailings were 49.54%–65.22% and 74.71%–98.71%, respectively, with P in senescent leaves resorbed completely. However, values for the farmland system were 18.18%–52.81% and 71.39%–84.07%, respectively. These results indicated that the poor nutrition condition of the tailings can increase I. cylindrica nutrient resorption efficiency. Nitrate reductase activity of I. cylindrica leaves in the tailings was significantly higher than in the farmlands (p < 0.05); this is useful to regulate I. cylindrica nitrogen metabolism activities. But with plant growth, the differences gradually disappeared. At the same growth period, acidic phosphatase activity of I. cylindrica leaves between the tailings and the farmlands were not significantly significant (p > 0.05). With plant growth, the acidic phosphatase activities increased, which was conducive to decompose organophosphate in senescent leaves and increase P resorption efficiencies.

    Effects of different ratios of straw to N-fertilizer on growth of Malus hupehensis seedling and its absorption, distribution and utilization of nitrogen
    yuan-mao jiang fu-tian peng shao-chong wei
    Chin J Plan Ecolo. 2012, 36 (2):  169-176.  doi:10.3724/SP.J.1258.2012.00169
    Abstract ( 1251 )   PDF (368KB) ( 1324 )   Save
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    Aims The study was to explore the effects of different ratios of straw to N-fertilizer on growth of Malus hupehensis seedlings and 15 N absorption, distribution and utilization in them.
    Methods Using 15N trace technique, we measured growth parameters (plant height, basal stem diameter and dry weight) and 15N parameters (absorption, N derived from fertilizer, distribution and utilization) of two-year-old M. hupehensis seedlings and C/N ratio in soil organic matter under different straw-nitrogen fertilizer treatments.
    Important findings Seedlings grew best under the condition of 45 : 1 of soil to straw and 300 mg·kg–1 N addition, showing the greatest height, basal stem diameter and total dry weight: 85.33 cm, 8.05 mm and 74.68 g, respectively. Total nitrogen, the 15N uptake and 15N utilization were also greatest: 0.938 g, 29.2 mg and 9.7%, respectively. The root/shoot ratio of seedlings without addition of straw (the control treatment) was 1.54, higher than those of other treatments. The 15N derived from fertilizer (Ndff) values of the aboveground parts for all the treatments were higher than those of the belowground parts, and the control showed the highest Ndff values in both aboveground and belowground parts, which were 7.94% and 4.69%, respectively. The 15N distribution ratios of the aboveground parts were higher than those of belowground parts in all treatments except the control. Straw additions could obviously increase the contents of organic matter and total nitrogen in soil and increase C/N ratio of soil organic matter. The correlation analysis showed that the C/N ratio of soil organic matter was significantly negatively correlated with the Ndff value of the belowground parts, as well as in the whole plant. Our findings suggest that it is better to apply nitrogen at rates between 200 and 300 mg·kg–1 when corn straw is added into orchard soil.


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