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Table of Content
    Volume 40 Issue 3
    10 March 2016

    The scenery of desert vegetation on the northern slope of the Qilian Mountains (Photographed by ZHAO Cheng-Zhang). Du et al. used the standardized major axis estimation method and analyzed the trade-off relationships between twig and leaf of Zygophyllum xanthoxylum in this area and discussed how Z. xanthoxylum modulated twig and leaf traits with size-dependence in different light environment (Pages 212–220 of this issue).

      
    Research Articles
    Effects of clipping and fertilization on the temporal dynamics of species diversity and functional diversity and their relationships in an alpine meadow
    Bin-Bin KONG, Xin-Hua WEI, Jia-Li DU, Ying-Nian LI, Zhi-Hong ZHU
    Chin J Plan Ecolo. 2016, 40 (3):  187-199.  doi:10.17521/cjpe.2015.0343
    Abstract ( 594 )   HTML ( 3 )   PDF (1267KB) ( 1189 )   Save
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    Aims

    Strong disturbance and environment stress have significant influence on species diversity (SD) and functional diversity (FD) in plant community. However, the changes in SD, FD and their relationships over time remain controversial. Previous studies showed that the SD-FD relationship along disturbance gradients can represent positive correlation, negative correlation and/or sigmoid curve, respectively. Our aim here is to explore the temporal dynamics patterns of SD and FD in a community experienced disturbance. Particularly, we explored how specific disturbance factor and/or disturbance intensity affect the SD-FD relationship over time.

    Methods

    The experiment was conducted in the alpine Kobresia humilis meadow at Haibei Research Station of the Chinese Academy of Sciences with clipping (unclipping, stubbled 3 cm and 1 cm) and fertilizing (12.75 g·m-2·a-1 urea + 3.06 g·m-2·a-1 ammonium phosphate) treatments from 2007 to 2013. GLMRMANOVA regression analysis and ANCOVA were used for analyzing the effects of different treatment factors and their interaction on SD, FD, the patterns of temporal dynamics of SD and FD and their relationship over time.

    Important findings

    SD and FD significantly increase with increasing clipping intensity. In contrast, fertilization decreased SD and increased feebly FD. During the experiment period, SD declined with time while FD increased. The SD-FD relationship was positively correlated in unclipped and moderate clipped plots, but was not correlated in heavy clipped plots. The slope of SD(x)-FD(y) relationship declined with the increase in clipping intensity. In contrast, fertilization did not change the shape and slope of the SD(x)-FD(y) relationship. The effects of the interaction of clipping and fertilization on SD and FD were not significant, and the slope changes along clipping gradients were identical in fertilized and unfertilized plots. These results suggest that clipping disturbance may induce trait divergence rather than trait convergence in this meadow community, while the strong interspecific competition resulted from fertilizing may not significantly intensify the trait divergence. These findings were inconsistent with the predictions of plant community assembly theory. Compared with fertilizing disturbance, clipping disturbance should play a more important role in shaping the SD-FD relationship.

    Spatial patterns of species diversity in the herb layer of early post-fire regeneration in mixed Pinus yunnanensis forests
    Jie HAN, Ling-Xiao YING, Gui-Xiang LI, Ze-Hao SHEN
    Chin J Plan Ecolo. 2016, 40 (3):  200-211.  doi:10.17521/cjpe.2015.0161
    Abstract ( 549 )   HTML ( 4 )   PDF (1383KB) ( 1010 )   Save
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    Aims

    Herb layer plays an important role in maintaining ecosystem functioning of forests. The aims of this study were to determine the pattern of species diversity in early post-fire regeneration of the herb layer in mixed Yunnan pine forests and to identify the effects of topography, fire severity, pre-fire vegetation and herb species life-history feature on post-fire regeneration.

    Methods

    We conducted field investigations of post-fire regeneration by randomly setting 47 transects of 10 m × 100 m in a burned forest stand in Qinfeng Township, Lufeng County, Yunnan Province, from September to October, 2013. The Two-Way Indicator Species Analysis (TWINSPAN) was used to classify the herb community types from the 47 transects, and species richness and two indexes of β-diversity were used to analyze herb species diversity and compositional change within sampling transects. Generalized linear model and hierarchical variation partitioning were applied to estimate factors affecting the pattern of herb species diversity of the post-fire communities.

    Important findings

    Four herb community types were identified for the 47 transects, which are differentiated by topographic features and fire severities. The species richness in the herb layer of early post-fire regeneration was primarily affected by elevation, topography, fire severity and the pre-fire forest canopy. Specifically, the species richness decreased with increasing elevation, and was positively correlated with biomass of the standing trees and steepness of site slope and negatively correlated with slope position. However, the species richness of herbs was not correlated with fire severity significantly. The within community β-diversity of the post-fire herb layer had a positive correlation with both basal area of pre-fire canopy trees and fire severity. Moreover, the β-diversity was lower at higher elevations. The results also highlighted the differences between annual and perennial species in their distribution patterns.

    Plant size differences with twig and leaf traits of Zygophyllum xanthoxylum in the northern slope of Qilian Mountains, China
    Jing DU, Cheng-Zhang ZHAO, Qing-Hua SONG, Yuan-Chun SHI, Ji-Wei WANG, Jing CHEN
    Chin J Plan Ecolo. 2016, 40 (3):  212-220.  doi:10.17521/cjpe.2015.0255
    Abstract ( 474 )   HTML ( 0 )   PDF (861KB) ( 940 )   Save
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    Aims

    Understanding the effects of plant size on the trade-off between twigs and leaves is important for revealing strategies of plants forming different canopy structure, making full use of space resources, and enhancing their photosynthetic efficiency and competitiveness with adjusting plant configuration. Our objective was to study how twig and leaf traits of Zygophyllum xanthoxylum depended on size in the northern slope of Qilian Mountains, China.

    Methods

    The study was conducted in a desert grassland on the northern slope of the Qilian Mountains, Gansu Province, China. A transect was laid out horizontally along latitudinal direction, and three sample plots were set up along the transect at the interval of 50 m. Community traits were investigated by using double diagonal method, and all individuals of Z. xanthoxylum were used for measurement of the height, canopy, single leaf area, leaf numbers, twig length, cross-sectional area of twig, and bifurcation angle. Total of 90 plants were divided into different size classes based on the volume: d (the cube root of plant volume) ≤ 60 cm, 60 cm < d ≤ 120 cm, and d > 120 cm. Twig and leaf traits were log-transformed, and the standardized major axis (SMA) estimation method was used to examine the allometric relationships of twig length with leaf area or leaf number.

    Important findings

    With the increase of plant size, the height, individual leaf area, twig length, and twig cross-sectional area of Z. xanthoxylum increased gradually (p < 0.01), while the bifurcation angle and leaf number decreased gradually (p < 0.01). An isometric or allometric relationship was found between twig length and leaf area in all plant size, whereas an allometric relationship was found between twig length and leaf number. The allometric slope between twig and leaf area was significantly decreased with the increase of plant size, the y-intercepts between twig and leaf number was significantly decreased too. To improve the efficiency of resource utilization, small individuals of Z. xanthoxylum tend to have a large number of leaves on short twigs, and large individuals have relatively few leaves on thick and long twigs. The increase of leaf area and the decrease of leaf number influenced the resource allocation pattern of twigs.

    Effects of air temperature and relative humidity on equilibrium moisture content and time-lag of forest land surface dead fine fuels
    Hai-Qing HU, Xin LU, Long SUN, Zhi-Lin QU, Yu LIANG, Hai-Yang LI
    Chin J Plan Ecolo. 2016, 40 (3):  221-235.  doi:10.17521/cjpe.2015.0243
    Abstract ( 518 )   HTML ( 0 )   PDF (1359KB) ( 763 )   Save
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    Aims

    This study was conducted to determine the effects of air temperature and relative humidity on the equilibrium moisture content (EMC) and time-lag of forest dead fine fuels by taking Larix gmelinii leaves, Betula platyphylla leaves and mixture of L. gmelinii and B. platyphylla leaves as examples.

    Methods

    Measurements were made on moisture content of fuels under different air temperature and humidity conditions (a total of 20 temperature by relative humidity combinations). Equations describing the dynamics of moisture content of fine-grain fuels in three types of forests were developed and the EMC and time-lag were estimated. The moisture-time mode, EMC-temperature and EMC-relative humidity models, time-lag-temperature and time-lag-relative humidity models for fine-grain fuels were also established.

    Important findings

    Data were fit by four EMC models. The Van Wanger model gave the best fit with small errors (both mean absolute error (MAE) and root mean square error (RMAE) within 0.01); the performance of Nelson model was worst. Further analysis revealed that both air temperature and relative humidity significantly affected EMC and time-lag. Air temperature was negatively correlated with EMC and time-lag, whereas relative humidity was positively correlated with EMC and time-lag. Using the time-lag-relative humidity model overestimated the time-lag. There are some uncertainties and limitations remaining in the current analysis, and further research is needed on both desorption and absorption processes of fine fuels, with broader range of fuel types and more influencing factors.

    Characteristics of soil organic carbon mineralization at different temperatures in severely eroded red soil
    Xi Qiu, Mao-Kui LÜ, Jin-Xue HUANG, Wei LI, Ben-Jia ZHAO, Hao ZHANG, En-Xi WANG, Jin-Sheng XIE
    Chin J Plan Ecolo. 2016, 40 (3):  236-245.  doi:10.17521/cjpe.2015.0364
    Abstract ( 499 )   HTML ( 1 )   PDF (1444KB) ( 688 )   Save
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    Aims It is crucial to study the soil organic matter decomposition and its temperature sensitivity for in-depth understanding of soil organic carbon (SOC) dynamic changes in severely eroded red soil. Methods We selected the severely eroded red soil on the bare land from Hetian town of Changting County as the research object. To study the influences of temperature on SOC mineralization and their temperature sensitivity (Q10), the SOC mineralization rate, the associated soil microbial biomass carbon (MBC), and dissolved organic carbon (DOC) under different incubation temperatures (10, 20 and 30 °C) were measured.Important findings The results showed that the incubation temperature significantly influenced the SOC mineralization. The mineralization ratio and the cumulative SOC mineralization rate increased with temperature. During the incubation period, the cumulative SOC mineralization was positively and significantly correlated with the soil MBC, and negatively correlated with soil DOC, indicating that soil microbes and C availability can significantly influence the SOC mineralization. During the 180 days incubation period, the accumulation mineralization rate of the severely eroded red soil was as high as 22.2%-33.3% under the conditions of the SOC content being only 1.54 g·kg-1, which indicates that the eroded red soil is easily mineralized. For the severely eroded red soil, its SOC temperature sensitivity (Q10) value was 1.41 at low temperatures (10-20 °C), but decreased to 1.06 at high temperatures (20-30 °C). The relatively low Q10 value at low temperatures was partly attributed to the low soil SOC quality. Furthermore, the long-time exposure to sunshine for the severely eroded red soil in the summer leads to the soil microbial adaptability to high temperature. As a result, its Q10 value is close to 1 at high temperatures. This study implies that it is of great significance to restore vegetation to minimize loss SOC caused by mineralization of the eroded red soil under climate changes in the future.
    Effects of light heterogeneity on leaf anatomical structure in Buchloe dactyloides
    Chen-Song HAO, Qing-Kai WANG, Xiao-Ling SUN
    Chin J Plan Ecolo. 2016, 40 (3):  246-254.  doi:10.17521/cjpe.2015.0377
    Abstract ( 539 )   HTML ( 0 )   PDF (1182KB) ( 730 )   Save
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    Aims

    Essential resources for plant growth are usually patchily distributed. During the process of propagation, interconnected ramet pairs of stoloniferous plant buffalograss (Buchloe dactyloides) may therefore experience contrasting resource supply such as light. Under heterogeneous light supply, anatomical structure of newly developed leaves is regulated by the light condition of mature leaves. However, little is known about whether leaf anatomical structure of clonal ramets is affected by the light environment of interconnected ramets in clonal plants under heterogeneous light supply.

    Methods

    Two light levels were set, with high light (natural sunlight) and low light (shade, 10% natural sunlight). Interconnected ramet pairs of buffalograss were exposed to homogeneous or heterogeneous light conditions.

    Important findings Main vein diameter, bundle sheath cell number, leaf thickness and adaxial/abaxial mesophyll thickness of shaded ramets were remarkably decreased in spatially heterogeneous light environment; while no signifiacnt difference of these parameters was observed between ramets developed under homogeneous high light and low light conditions. Under heterogeneous light supply, adaxial/abaxial mesophyll thickness and abaxial stomatal size in unshaded elder daughter ramets (EDR) were remarkably increased, while adaxial/abaxial mesophyll thickness, stomatal density and size, leaf thickness, and bundle sheath cell number in unshaded younger daughter ramets (YDR) were reduced. Ramets under homogeneous high light conditions had higher stomatal density and larger stomata than those under homogeneous low light conditions. Adaxial/abaxial mesophyll thickness, stomatal density and size in buffalograss ramets were significantly affected by the light conditions of interconnected ramets.

    Conclusions

    Unshaded EDR benefit from their connection to shaded YDR, while unshaded YDR experience marked cost due to its connection to shaded EDR. The plastic decrease of shaded ramets under heterogeneous light may be associated with its reduced survival cost, and elevated survival rate under shading.

    Relationships between xylem structure and embolism vulnerability in six species of drought tolerance trees
    Rong LI, Wei DANG, Jing CAI, Shuo-Xin ZHANG, Zai-Min JIANG
    Chin J Plan Ecolo. 2016, 40 (3):  255-263.  doi:10.17521/cjpe.2015.0260
    Abstract ( 584 )   HTML ( 4 )   PDF (1147KB) ( 958 )   Save
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    Aims

    The study of embolism vulnerability to drought has become a hot and key topic under global climate change. The objective of the study was: 1) to identify the relationship between xylem structure and embolism vulnerability; 2) to define the differences in resistance of embolism in xylem structure of each species; and 3) to establish drought tolerance indexes in xylem structure of six species.

    Methods

    Drought tolerance trees of Robinia pseudoacacia, Hippophae rhamnoides, Ulmus pumila, Corylus heterophylla, Salix matsudana, Acer truncatum were studied. Cochard Cavitron centrifuge was used to establish embolism vulnerability curves and to calculate xylem vulnerability value. Staining and silicone injection techniques were used to to measure xylem structure of drought tolerance trees including vessel diameter, conduit wall span, number of vessels per unit area, contact faction, vessel length and wood density.

    Important findings

    The results showed: 1) xylem embolism vulnerability of the six species ranked as Robinia pseudoacacia > Ulmus pumila > Hippophae rhamnoides > Salix matsudana > Acer truncatum > Corylus heterophylla; 2) the vulnerability curves is “r” shape for Robinia pseudoacacia, Hippophae rhamnoides, Ulmus pumila and is “s” shape for Corylus heterophylla, Salix matsudana, Acer truncatum, respectively; 3) the xylem vulnerability values is significantly different in trees of “r” shape and “s” shape (p < 0.01). Furthermore, linear analysis showed that the different effects between the xylem structure of the species was closely related to the vulnerability in the following order: the maximum effect was from wood density (t = 0.702), the medium effect was from vessel diameter (t = 0.532), and the minimum effect was from vessel length (t = 0.01).

    Review
    Research on ecological stoichiometry in bamboos: From biological basis to applications in silviculture of bamboo forests
    Qing-Pei YANG, Ming OUYANG, Guang-Yao YANG, Qing-Ni SONG, Chun-Lan GUO, Xiang-Min FANG, Xin CHEN, Lan HUANG, Fu-Sheng CHEN
    Chin J Plan Ecolo. 2016, 40 (3):  264-278.  doi:10.17521/cjpe.2015.0298
    Abstract ( 645 )   HTML ( 0 )   PDF (1128KB) ( 1051 )   Save
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    Bamboo ecology and nutrient management require guidance of a set of theoretical principles. By focusing on the contents of multiple nutrient elements and their ratios and summarizing recent research findings in biology, ecology and silvics of bamboos, this paper seeks to establish the bamboo ecological stoichiometry (BES) in order to support the sustainable development of bamboo forests. It is considered that: (1) bamboos have the ubiquitous characteristics of stoichiometry, with average leaf C:N:P of 380:16:1, which complies to the “homeostasis hypothesis”; (2) the internal factors such as organs, ages and development stages and the external factors such as soil, climate and harvest can all affect the characteristics of bamboo stoichiometry; (3) changes in the ecological stoichiometry of bamboos affect the bamboo biological and ecological processes including photosynthesis, nutrients uptakes, flowering, shootings and growth, community dynamics, and qualities of bamboo products; (4) the principles of BES have been preliminarily used to guide the nutrient diagnosis, balanced fertilization, and production of high-quality and high-yield bamboos. As a new tool, BES can be further improved to integrate biology and silviculture under the background of ecological and environmental protection and food safety. Future research should place more emphasis on elucidating the ecological homeostatic mechanisms for more bamboos, as well as on understanding the stoichiometric principles in producing high-quality bamboo shoots, the bamboo-soil stoichiometric interaction processes, the nutrient diagnosis and stoichiometric balanced fertilization, and the optimal ecosystem management of bamboo forests.


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