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Table of Content
    Volume 41 Issue 12
    10 December 2017
    The scenery of subtropical evergreen forest in Zhujiajian-Putuoshan Islands, Zhejiang (Photographed by ZHAO Hai-Ping). Liu et al. used 93 woody plant species in forests of Putuoshan Island to test species associations, analyse the effect of random process on species associations, and explore the process of community assembly (Pages 1219–1227 of this issue).
      
    Research Articles
    Patterns of species associations in woody plants in forest communities of Putuoshan Island, Zhejiang, China
    LIU Xiang-Yu, HE Dong, TIAN Wen-Bin, SONG Yan-Jun, YIN Fang, XU Ming-Shan, CHENG Jun-Yang, YAN En-Rong
    Chin J Plan Ecolo. 2017, 41 (12):  1219-1227.  doi:10.17521/cjpe.2017.0170
    Abstract ( 646 )   HTML ( 96 )   PDF (1289KB) ( 1081 )   Save
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    Aims Interspecific associations can reflect how species are assembled into communities. The objectives of this study were to examine the patterns of woody species co-occurrence and to determine how species’ abundance would affect species associations. Methods Data from a total of 23 plots were used to test the interspecific associations of 93 woody plant species in forest communities of Putuoshan Island in Zhejiang Province. We compared the observed species associations with the expected patterns at random, and correlated interspecific association intensities with co-dominance propensity of species pairs. Important findings Species distribution co-varied among plots at the spatial scale of either 10 m × 10 m or 20 m × 20 m, but the majority of the 4 278 species pairs were not significantly associated. Interspecific association intensities were positively correlated with co-dominance propensity of species pairs, indicating that species abundance is a key factor affecting the interspecific co-occurrence. The observed values of variance ratio and the proportion of significantly associated species pairs consistently fell outside of the 2.5th-97.5th percentiles of random expectations (i.e. randomly permuting species across plots), suggesting that deterministic processes also play a role in species associations on the Putuoshan Island. We conclude that the pattern of woody species co-occurrence on Putuoshan Island are structured by both niche and stochastic processes.
    Changes in leaf nitrogen and phosphorus stoichiometry of woody plants along an altitudinal gradient in Changbai Mountain, China
    YANG Lei, SUN Han, FAN Yan-Wen, HAN Wei, ZENG Ling-Bing, LIU Chao, WANG Xiang-Ping
    Chin J Plan Ecolo. 2017, 41 (12):  1228-1238.  doi:10.17521/cjpe.2017.0115
    Abstract ( 639 )   HTML ( 28 )   PDF (900KB) ( 844 )   Save
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    Aims Leaf is the organ of plant photosynthesis, and it is important to understand the drivers for the variations of leaf nitrogen (N) and phosphorus (P) stoichiometry along geographical and climatic gradients. Here we aimed to explore: 1) the changes in leaf nitrogen (N) and phosphorus (P) stoichiometry of woody plants along an altitudinal gradient in Changbai Mountain, and 2) the relative contribution of climate, plant characteristics, and phylogeny to the changes in leaf N, P concentration and N:P.

    Methods We measured leaf N and P concentration, and N:P of 48 woody species in 14 plots along an altitudinal gradient in Changbai Mountain. General linear models (GLMs) and variation partitioning analyses were used to explain leaf N and P stoichiometry with parameters related to plant functional groups, climate and phylogenetic groups.

    Important findings Leaf N concentration and N:P decreased with altitude, and were positively correlated with mean annual temperature (MAT) but negatively correlated with mean annual precipitation (MAP). Leaf P concentration had no significant relationship with altitude. Leaf N, P concentration and N:P were significantly different among different plant functional groups. Leaf N concentration of shrubs was higher than that of trees, but leaf P concentration and N:P did not differ significantly between shrubs and trees. Leaf N, P concentration and N:P of broad-leaved plants were significantly higher than those of coniferous plants. Similarly, leaf N, P concentration and N:P of deciduous plants were significantly higher than those of evergreen plants. The effects of climate on leaf N, P concentration and N:P were significant but very weak, with MAT and MAP together explaining 1.50%-2.98% of the variations. Phylogenetic groups explained 30.36%-54.38% of the variations, suggesting the critical effect of phylogeny. Our study also showed that the synergistic effect of climate and species composition (phylogeny) on leaf N and P stoichiometry was neglectable, at least along the altitude gradient of Changbai Mountain. More comparative studies between altitudinal and latitudinal gradients are needed to better understand the drivers of the changes in leaf stoichiometry along an environmental gradient.

    Main factors driving changes in soil respiration under altering precipitation regimes and the controlling processes
    YANG Qing-Xiao, TIAN Da-Shuan, ZENG Hui, NIU Shu-Li
    Chin J Plan Ecolo. 2017, 41 (12):  1239-1250.  doi:10.17521/cjpe.2017.0208
    Abstract ( 742 )   HTML ( 26 )   PDF (1290KB) ( 1092 )   Save
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    Aims Our objective was to determine the effects of changes in global pattern of precipitation on soil respiration and the controlling factors. Methods Data were collected from literature on precipitation manipulation experiments globally and a meta-analysis was conducted to synthesize the responses of soil respiration to changes in precipitation regimes. Important findings We found that an increased precipitation stimulated soil respiration while a decreased precipitation suppressed it. When changes in rainfall were normalized to the average treatment level (41% of the current annual precipitation), the level of increases in soil respiration with increased precipitation (49%) were higher than that of decreases with decreased precipitation (21%), showing an asymmetric responses of soil respiration to increases and decreases in precipitation. Soil moisture occurred as the most predominant factor driving the changes in soil respiration under altered precipitation. Changes in soil moisture affected soil respiration directly and indiscreetly by changing aboveground/belowground net primary productivity and microbial biomass carbon, which collectively contributed 98% of variations in soil respiration. In addition, the responses of soil respiration to altered precipitation varied with background temperature and precipitation. The sensitivity of soil respiration increased with local mean annual temperature when precipitation was reduced, while remaining unchanged when precipitation was increased. Meanwhile, the sensitivity of soil respiration to either increases or decreases in precipitation decreased with increasing local mean annual precipitation. Under future altered precipitation regimes, the sensitivity of soil respiration to changes in precipitation is likely dependent of local environment conditions.
    Accumulation of humic acid and fulvic acid during root humification of three diameters of two dominant subalpine trees in western Sichuan, China
    LIU Qun, ZHUANG Li-Yan, YANG Wan-Qin, NI Xiang-Yin, LI Ting-Ting, XU Zhen-Feng
    Chin J Plan Ecolo. 2017, 41 (12):  1251-1261.  doi:10.17521/cjpe.2017.0169
    Abstract ( 362 )   HTML ( 18 )   PDF (1094KB) ( 378 )   Save
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    Aims Plant roots store large amount of terrestrial carbon, but little is known about humus formation processes during the decomposing root litter. Compared with coarse roots, fine roots have greater nutrients, which may be favorable to humus formation. The objective of the study was to examine how root diameters affect their humus formation processes. Methods In this study, in order to examine the accumulation of humic acid and fulvic acid of three root diameter classes (0-2, 2-5 and 5-10 mm) of two subalpine tree species (Abies faxoniana and Picea asperata) on the eastern Qinghai-Xizang Plateau of China, a two-year field experiment was conducted using a litter-bag method. Air-dried roots of A. faxoniana and P. asperata were placed in litterbags and incubated at 10 cm of soil depth in October 11th, 2013. Duplicate litter bags were collected in May (late winter) and October (late in the growing season) of 2014 and 2015, respectively. Concentrations of humic acid and fulvic acid were measured, and net accumulations were calculated for different periods. Important findings The concentrations of humic acid and fulvic acid were significantly influenced by root diameter that humic acid and fulvic acid decreased with increase in root diameter. Root diameter had significant effects on the net accumulation of humic acid, but not for the accumulation of fulvic acid. However, there were no significant differences in both humic acid and fulvic acid between A. faxoniana and P. asperata roots. Regardless of tree species, humic acid degraded during the winter but accumulated during the growing season. After two years of decomposition, the net accumulations of humic acid in 0-2, 2-5 and 5-10 mm roots were 8.0, 10.8 and 7.6 g·kg-1 for P. asperata and 15.2, 8.0 and 7.8 g·kg-1 for A. faxoniana, respectively. Conversely, the degradation of fulvic acid in 0-2, 2-5 and 5-10 mm roots were 178.0, 166.0 and 118.0 g·kg-1 for P. asperata and 170.0, 160.0 and 128.0 g·kg-1 for A. faxoniana, respectively. Our results suggest that diameter-associated variations in substrate quality could be an important driver for root litter humification in this subalpine forest. Moreover, diameter effect is dependent on decomposition period in this specific area.
    Water-use process of two desert shrubs along a precipitation gradient in Horqin Sandy Land
    CHEN Ding-Shuai, DONG Zheng-Wu, GAO Lei, CHEN Xiao-Min, PENG Xin-Hua, SI Bing-Cheng, ZHAO Ying
    Chin J Plan Ecolo. 2017, 41 (12):  1262-1272.  doi:10.17521/cjpe.2017.0219
    Abstract ( 414 )   HTML ( 16 )   PDF (1149KB) ( 712 )   Save
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    Aims The determination of the source of plant water is an important research on the plant-water relationship in arid and semiarid regions and helps to understand the adaptation strategy of desert species to the dry environment. Plant water use pattern affects plant community composition and ecosystem water budget. This study aims to investigate the water use patterns of Caragana microphylla and Artemisia halodendron, two typical shrub species, under altered rainfall conditions in Horqin Sandy Land. Methods Water treatments include ambient rainfall (natural rainfall), 50% increase in rainfall (enhanced rainfall) and 50% decrease in rainfall (reduced rainfall) by artificially intercepting and redistributing natural rainfall. Stable hydrogen and oxygen isotope ratios (δD and δ18O) were measured for xylem water, rainfall, and soil water in different soil layers (0-120 cm depth). The possible ranges of potential water sources used by C. microphylla and A. halodendron were calculated using the IsoSource model. Important findings 1) Alteration of ambient rainfall mainly affected the soil water condition in the shallow soil (0-30 cm). Increase in rainfall significantly increased the above- and below-ground biomass, and δ18O values of soil water declined with soil depth. 2) Under the enhanced rainfall treatment, A. halodendron mainly used the soil water in the shallow soil (0-40 cm) and C. microphylla was able to extract water from multiple soil layers. Under the reduced rainfall treatment, both species increasingly relied on extracting water from deeper soil layers, 60-80 cm for A. halodendron and 60-120 cm for C. microphylla. 3) For the natural rainfall treatment, in the wet season, the upper soil water was recharged by rainfall, C. microphylla and A. halodendron extract the shallow soil water (0-60 cm). However, in the dry season, soil water content was dramatically reduced, and main water sources for C. microphylla shifted from topsoil to deeper soil, and A. halodendron can use multiple layers of soil water. In summary, A. halodendron is more capable of exploring deeper soil moisture under reduced rainfall in comparison with C. microphylla, and is likely to be more adaptive to this water-limiting desert environment.
    Exploring the influence of soil types underneath the canopy in winter wheat leaf area index remote estimating
    GAO Lin, WANG Xiao-Fei, GU Xing-Fa, TIAN Qing-Jiu, JIAO Jun-Nan, WANG Pei-Yan, LI Dan
    Chin J Plan Ecolo. 2017, 41 (12):  1273-1288.  doi:10.17521/cjpe.2017.0231
    Abstract ( 490 )   HTML ( 16 )   PDF (6506KB) ( 1125 )   Save
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    Aims Remote sensing is an effective and nondestructive way to retrieve leaf area index (LAI) from plot, regional and global range. Soil background is one of the confounding factors limiting remotely estimating LAI. And soil type contains a large proportion of soil background information, which can influence the optical properties of vegetation canopy and soil. However, our knowledge on the effects stemmed from soil types underneath the canopy on LAI remote estimating have been in shortage. Thus, this study aims to explore the influences of soil types underneath the canopy on winter wheat LAI remote estimating. Methods We analyzed the sensitivity variation of eight spectral indices, named normalized difference vegetation index (NDVI), modified soil-adjusted vegetation index (MSAVI), modified chlorophyll absorption ratio index 2 (MCARI2), red edge inflection point (REIP), red edge amplitude (Dr), red edge area (SDr), red edge symmetry (RES), normalized difference spectral index (NDSI), to LAI in different soil types, and then we identified some spectral intervals or parameters that were insensitive to soil type variations underneath the canopy. We also compared the accuracy of two commonly used regression models, partial least squares regression (PLSR) and random forest regression (RFR), in estimating LAI for different soil types. We also explored the problems arising from applying the regression model developed in single soil type area to complex soil types area in retrieving LAI. Important findings This paper demonstrates the effects of soil types underneath the canopy on LAI retrieving. 1) The sensitivity of spectral indices to LAI is significantly different due to the soil type variation, but REIP has the least effects from soil type variation among the eight spectral indices. Meanwhile, the band selection algorithm of lambda-by-lambda not only chooses the most sensitive spectral interval for LAI, but also provides a feasible way to construct the spectral index that exhibits strong resistances to the effects of soil types underneath the canopy. 2) The accuracy of LAI estimation by regression models differs under soil type considered or not. So we suggest that in small scale researches, especially in a field scale, the ability of regression models in explaining variables is the priority consideration, while the PLSR is superior to RFR in this respect. Under the premise of unknown priori knowledge of land surfaces, the RFR is more suitable for retrieving LAI than PLSR, but land surface priori knowledge is still necessary. These findings provide the theoretical basis and methods for developing remotely sensing estimating LAI models adapted to various land surfaces. Further analysis is needed in applying the findings in more crop types, cultivars and growth stages.
    Modeling study on photosynthetic-light response curves of a C4 plant, maize
    Li Yi-Bo, SONG He, ZHOU Li, XU Zhen-Zhu, ZHOU Guang-Sheng
    Chin J Plan Ecolo. 2017, 41 (12):  1289-1300.  doi:10.17521/cjpe.2017.0158
    Abstract ( 624 )   HTML ( 26 )   PDF (1078KB) ( 1133 )   Save
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    Aims A light response curve can reflect a plant’s ability to utilize light, which is also a key tool in determining the relationship between photosynthetic capacity and environmental factors; however the model accuracies concerning the light response curve remain elusive. The objectives of this study were to compare and assess the model accuracies related to a light response curve and the effects of drought. Methods A field rain shelter was used to control the soil water conditions. To obtain photosynthesis parameters from the light response curve and the drought effects, the relevant models (including the rectangular model, non-rectangular hyperbolic model, modified rectangular hyperbolic model, exponential model, quadratic function model, and a newly modified model) were applied to fit the light response curves. The validity of each model was tested by analyzing the differences between the fitted values obtained by the models and the measured values. Important findings The newly modified model has been proved to performing relatively better in accurately describing the light response curve patterns, and credibly obtaining the crucial photosynthetic parameters such as the maximum net photosynthetic rate, light saturation point, light compensation point, and dark respiration rate, especially under high radiation conditions.

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