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Table of Content
    Volume 43 Issue 6
    20 June 2019
    Modeling phosphorus effects on the carbon cycle in terrestrial ecosystems
    HUANG Mei, WANG Na, WANG Zhao-Sheng, GONG He
    Chin J Plant Ecol. 2019, 43 (6):  471-479.  doi:10.17521/cjpe.2019.0021
    Abstract ( 1751 )   Full Text ( 186 )   PDF (1130KB) ( 1851 )   Save
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    Climate warming has significantly alerted the terrestrial carbon dynamics, resulting in enhanced vegetation productivity, especially in the northern hemisphere. However, most of the prior modeling studies have neglected the effects of nutrient availability, such as the phosphorus limitation, on carbon processes, which potentially leads to an overestimation of the capacity of terrestrial ecosystems to sequester additional carbon. Here, we reviewed recent progress in phosphorus limitation and its interactions with carbon dynamics in the context of climate change, with a focus on the process-based modeling approach. We comparatively analyzed quantitative representations of phosphorus-associated biological processes in some models (i.e., Carnegie-Ames-Stanford Approach (CASA), Community Land Model (CLM), and Jena Scheme for Biosphere-Atmosphere Coupling in Hamburg (JSBACH)), such as photosynthesis and distribution of assimilates, phosphorus uptake by plants, the transformation of phosphorus pools in soil, phosphorus inputs and outputs, etc. We also discussed the key characteristics of these models and summarized the mathematical representations of the terrestrial phosphorus cycle. In addition, we identified and discussed the limitations, uncertainties and future needs in process-based modeling in terms of nutrient and carbon dynamics. Our study highlighted the importance of including phosphorus limitation in regional carbon estimation and provided deep insights related to biogeochemical modeling at broad scales.

    Research Articles
    C, N and P stoichiometric ratios in mixed evergreen and deciduous broadleaved forests in Shennongjia, China
    LIU Lu, GE Jie-Lin, SHU Hua-Wei, ZHAO Chang-Ming, XU Wen-Ting, SHEN Guo-Zhen, XIE Zong-Qiang
    Chin J Plant Ecol. 2019, 43 (6):  482-489.  doi:10.17521/cjpe.2019.0064
    Abstract ( 1539 )   Full Text ( 140 )   PDF (1148KB) ( 1077 )   Save
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    Aims Ecological stoichiometry focuses on the balance of chemical elements in ecological processes, in which the stoichiometric ratios of carbon (C), nitrogen (N) and phosphorus (P) are important features of ecological functions. The objectives of this study were to determine the stoichiometric characteristics in different organs and components of mixed evergreen and deciduous broadleaved forests, and to examine the discrepancy in stoichiometric ratios among different components of the ecosystem and plant organs. Methods We measured the concentrations of C, N and P in different plant organs, litter and soil in a mixed evergreen and deciduous broadleaved forest in Shennongjia of Hubei Province, China, and computed the stoichiometric ratios using the biomass-weighted mean method. Important findings The C concentration, C:N and C:P of different components were ranked in the order of plant community > litter > soil, and concentrations of N and P and N:P in the order of litter > plant community > soil. There were little differences in C concentration among various organs, with the coefficient of variation (CV) much lower and less variable than that for N and P concentrations. Both N and P concentrations were highest in leaves with the lowest CV value; N:P was highest in the bark, but with the lowest CV value in branches. Additionally, there were considerable differences in N and P concentrations in leaves between evergreen and deciduous species. Compared with other forest types, this forest had lower C:P and N:P ratios in plant community, higher C:P and N:P ratios in litter, and the C, N and P stoichiometric ratios in soils were consistent with, and the C:N ratio in ecosystem was lower than, that in subtropical evergreen broadleaved forests. Our findings demonstrated the patterns of differences among components in stoichiometry using the integral biomass-weighted mean method differ from that using the arithmetic mean method in selective organs. Furthermore, the distribution and homeostasis of C, N and P concentrations and their stoichiometric ratios could be closely related to the physiology of different organs.

    Spatio-temporal characteristics of vegetation water use efficiency and its relationship with climate factors in Tianshan Mountains in Xinjiang from 2000 to 2017
    Aizezitiyuemaier MAIMAITI, Yusufujiang RUSULI, HE Hui, Baihetinisha ABUDUKERIMU
    Chin J Plant Ecol. 2019, 43 (6):  490-500.  doi:10.17521/cjpe.2019.0006
    Abstract ( 1497 )   Full Text ( 100 )   PDF (6216KB) ( 853 )   Save
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    Aims Water use efficiency (WUE) is a key index to measure the coupling degree of carbon and water cycle in ecosystems. The WUE of vegetation in Tianshan Mountains in Xinjiang and the north and south sites of the main oasis was estimated and then the spatio-temporal distribution of vegetation WUE was analyzed to explore its influencing factors, which will be of great significance to the protection of ecosystem and the rational utilization and development of agricultural water resources in this region. Methods This study used data from moderate-resolution imaging spectroradiometer (MODIS), meteorological and land use type data to estimate the vegetation WUE. The spatio-temporal characteristics of vegetation WUE were analyzed in Tianshan Mountains in Xinjiang over the last 18 years, and the relationship of WUE with climatic factors was evaluated. Important findings The results indicated that: (1) From 2000 to 2017, the average annual vegetation WUE for Tianshan Mountains in Xinjiang was 1.11 g·mm -1·m -2, ranging from 0.84 to 1.34 g·mm -1·m -2. As a whole, the annual decrease trend of vegetation WUE was 0.014 1 g·mm -1·m -2·a -1, and vegetation WUE showed a strong vertical zonality in Tianshan Mountains in Xinjiang, as indicated by the decrease with the altitude above 1 000 m. (2) The vegetation WUE in Tianshan Mountains in Xinjiang showed a unimodal change pattern with significant seasonal difference, in order of summer > spring > autumn > winter. (3) Correlation analysis and statistical results indicated that the dynamic change of vegetation WUE in Tianshan Mountains in Xinjiang was closely related to temperature and rainfall. The regions with vegetation WUE changes resulting from non-climate factors accounted for 39.26% in Tianshan Mountains in Xinjiang. However, the factors of temperature and precipitation contributed to the change of vegetation WUE as 33.23% and 8.57%, respectively. On the other hand, the combination of temperature and precipitation with heavy impact and light impact contributed to WUE by 5.63% and 13.13%, respectively. Overall, temperature played the most important role among all climate factors in the changes in vegetation WUE. (4) The WUE of paddy field and dryland decreased continuously with time, and these areas were mainly affected by non-climatic factors, suggesting the irrationality in local human activities.

    Effects of water and nutrient additions on functional traits and aboveground biomass of Leymus chinensis
    ZHAO Dan-Dan, MA Hong-Yuan, LI Yang, WEI Ji-Ping, WANG Zhi-Chun
    Chin J Plant Ecol. 2019, 43 (6):  501-511.  doi:10.17521/cjpe.2019.0041
    Abstract ( 1352 )   Full Text ( 120 )   PDF (1297KB) ( 1239 )   Save
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    Aims The research on the response of plant functional traits to environmental change, such as precipitation change and nutrient additions is very important to understand how plant species adapt to variable environments. Methods We conducted a pot experiment with a gradient of water treatments (increase precipitation by 50%, HW; decrease precipitation by 50%, LW; take 498 mm precipitation as control, MW) and nutrient additions (without nutrient addition, CK; nitrogen (N) addition, NA; phosphorus (P) addition, PA; nitrogen and phosphorus additions, N+P). We investigated 11 plant functional traits and aboveground biomass of Leymus chinensis. Important findings The effects of moisture on plant height, tillers, stem biomass, leaf biomass, leaf area, leaf mass, net photosynthetic rate, transpiration rate, water use efficiency were significant. The effects of fertilizers on tillers, stem biomass, net photosynthetic rate, transpiration rate, water use efficiency were significant. And the combination of fertilizers and moisture had a significant influence on tillers, stem biomass, transpiration rate and water use efficiency (two-way ANOVA). The pattern of functional traits in response to precipitation differed between plants with varied fertilizer additions. Tillers and leaf area were increased in treatments with HW under N and N+P additions, but not changed under CK and P addition. Stem biomass increased along the precipitation gradients under CK, N addition and P addition, but did not change under N+P additions. Specific leaf area with HW was significantly higher than that of MW under N addition, but not changed under other nutrient addition. Short-term nutrient additions significantly affected photosynthetic physiological traits of L. chinensis, but it had no significant effect on morphological traits under the same precipitation. The aboveground biomass of L. chinensis increased with the increase of precipitation, and reached the highest level of 522.55 g·m -2 with HW treatment under N addition. In conclusion, our results indicate that the functional traits in L. chinensis respond to precipitation addition and the patterns of responses differ under different nutrient additions, reflecting the adaptation to changes in water and nutrient availability.

    Characteristic environmental factors in peatlands facilitate the formation of persistent Sphagnum spore banks
    FENG Lu, BU Zhao-Jun, WU Yu-Huan, LIU Sha-Sha, LIU Chao
    Chin J Plant Ecol. 2019, 43 (6):  512-520.  doi:10.17521/cjpe.2019.0082
    Abstract ( 683 )   Full Text ( 95 )   PDF (1113KB) ( 667 )   Save
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    Aims To test the effects of environmental factors in peatlands on the persistence of Sphagnum spore germinability. The results may help to understand the mechanisms behind the formation of Sphagnum spore banks in peatlands. They can also provide valuable insights for restoration of degraded peatlands. Methods We determined the initial germination percentage in spores of two Sphagnum species (hummock- forming Sphagnum capillifolium and hollow-forming S. flexuosum) and then stored them for 60 days, either dry, in ultrapure water, peatland surface water or Sphagnum water leachate. We varied oxygen concentration by injecting air at three concentrations during the storage experiment. After retrieval from experimental storage, spore germinability was assessed. Important findings Spore germinability was lower after air-injection than under oxygen-deficiency. Spore germinability was higher after storage in the peatland surface and Sphagnum leachate water, having high concentrations of allelochemicals, than in ultrapure water, under oxygen-deficiency. Path analysis showed that dissolved oxygen is the main factor negatively affecting Sphagnum spore persistence in peatlands. Nitrogen (TN) and phosphorus (TP) also affect spore persistence negatively. These results indicate that once dispersed onto Sphagnum substrates or waterlogged hollows, Sphagnum spores can remain viable longer than when exposed to dry conditions or in water without allelochemicals. Extreme longevity of Sphagnum spores and other plant propagules may be attributed to the oxygen-deficient, nutrient-poor and allelopathic substrates in peatlands.

    Seasonal dynamics of non-structural carbohydrate content in branch of Quercus variabilis growing in east Qinling Mountain range
    ZHANG Yi-Ping, HAI Xu-Ying, XU Jun-Liang, WU Wen-Xia, CAO Peng-He, AN Wen-Jing
    Chin J Plant Ecol. 2019, 43 (6):  521-531.  doi:10.17521/cjpe.2018.0325
    Abstract ( 854 )   Full Text ( 93 )   PDF (1382KB) ( 887 )   Save
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    Aims Measure of non-structural carbohydrate (NSC) reserves indicates tree carbon surplus or shortage stored. Branches connect NSC sources (leaves) and NSC sinks (stemwood, root) of woody plants. Therefore, the seasonal dynamics of NSC concentration in branches will be of important implications for understanding and modeling plant carbon allocation. Methods We conducted a field survey monitoring branch NSC concentrations of Chinese cork oak (Quercus variabilis). We also synchronously observed the leaf phenology of the trees in uneven-aged secondary oak forests at its upper and lower distribution limits (650 m to 970 m) in east Qinling Mountain ranges. Sampling intervals were set semimonthly/monthly during the leaf unfolding period (March to May), and monthly/bimonthly during the tree’s full growing season (June to November) from May 2016 to May 2017. Important findings (1) The NSC measures in the tree branches had weak seasonal changes at both sites. However, the soluble sugar (SS) concentrations at the upper elevation site and the starch (S) concentrations at the lower site had significant seasonal changes. The relative stable NSC levels vs. larger seasonal oscillations of soluble sugar and starch may be explained by the mutual conversion between soluble sugar and starch in the tree branches. (2) Soluble sugar was the major contributor to the total NSC in oak branches, accounting for approximately 61% of it. Here the soluble sugars performed as quick C whereas starch acted mostly as reserved C for future use, it could be inferred that the Q. variabilis, a warm temperate deciduous tree species, developed this feature as its life strategy to survive in warm temperate climate. (3) Soil water availability was positively related to the NSC measures at the high elevation site, while vapor pressure deficit (VPD) was negatively related to the NSC at the low elevation site, indicating the oak may be more drought-susceptible to water stress at lower elevation. (4) The maximum and the minimum concentrations of NSC in tree branches were observed before bud break (late March, approximately 11%) and when full leaf expansion (late April, approximately 11%), respectively. These extremes of NSC could be partly explained by the simultaneous leaf phenological dynamics. Considering the fact of carbon supply for bud break and leaf development via branches rather than by photosynthesis, it was reasonable that the NSC concentration in branches of Q. variabilis reached its maximum before the bud break, and did not change significantly with elevation. Not surprisingly, the significant differences in branches NSC with elevation only occurred during bud break in spring, as a later phenology occurred at higher elevation. In conclusion, this study confirms that the leaf phenology of Q. variabilis directly affects the branches seasonal patterns of NSC, particularly in the spring. The relationship between the carbon budget of the oak branches and its aboveground phenology should be more emphasized for further comprehension on the NSC metabolism.

    Seasonal dynamics of soil microbial biomass carbon, nitrogen and phosphorus stoichiometry across global forest ecosystems
    LI Pin, Muledeer TUERHANBAI, TIAN Di, FENG Zhao-Zhong
    Chin J Plant Ecol. 2019, 43 (6):  532-542.  doi:10.17521/cjpe.2019.0075
    Abstract ( 2130 )   Full Text ( 155 )   PDF (1360KB) ( 1014 )   Save
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    Aims Soil microorganisms in forest ecosystems play vital roles in regulating above- and belowground ecosystem processes and functions such as soil nutrient cycling, litter decomposition, net ecosystem productivity, and ecosystem succession. We aim to investigate broad-scale seasonal patterns of soil microbial biomass carbon (C), nitrogen (N) and phosphorus (P) stoichiometry. Methods By synthesizing 164 samples of soil microbial biomass C, N and P content derived from the published literature, we investigated global seasonal patterns of soil microbial C, N, P content and their ratios across three vegetation types of global forests. Important findings Soil microbial biomass C, N and P content in temperate and subtropical forests were lower in summer and higher in winter. Soil microbial biomass C, N and P content in tropical forests were lower than those in temperate and subtropical forests in four seasons. Soil microbial biomass C and N content in tropical forests were relatively the lowest in autumn, and soil microbial biomass P content was relatively constant in all seasons. The soil microbial biomass C:N of temperate forest was significantly higher than that of other two forest types in spring, and that of tropical forest was significantly higher than that of other two forest types in autumn. Soil microbial biomass N:P and C:P in temperate forests remained relatively constant in four seasons, while those in tropical forests were higher than those in other three seasons in summer. The soil microbial biomass C content, N content, N:P and C:P of broad-leaved trees were significantly higher than those of conifers in four seasons, while the soil microbial biomass P content of conifers was significantly higher than that of broad-leaved trees in four seasons. There was no significant difference in soil microbial biomass C:N between broad-leaved and coniferous trees in both spring and winter, but the soil microbial biomass C:N of coniferous trees was significantly higher than that of broad-leaved trees in summer and autumn. For the change of soil microbial biomass, season is not but forest type is the main significant factor, suggesting that the seasonal fluctuation of soil microbial biomass changes with the inherent periodic change of trees. Asynchronous nutrient uptake by plants and soil microorganisms is a trade-off mechanism between nutrient retention and ecological function maintenance.

    Diversity and potassium-solubilizing activity of rhizosphere potassium-solubilizing bacteria of invasive Solidago canadensis
    YAN Ya-Nan, YE Xiao-Qi, WU Ming, YAN Ming, ZHANG Xin-Li
    Chin J Plant Ecol. 2019, 43 (6):  543-556.  doi:10.17521/cjpe.2019.0045
    Abstract ( 1259 )   Full Text ( 134 )   PDF (1756KB) ( 1149 )   Save
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    Aims Solidago canadensis, an invasive herbaceous species, has a strong capacity of potassium enrichment, that may relate to its influence on soil microbial community. Rhizosphere potassium-soluble bacteria can convert mineral potassium into soluble forms being able to be used by plants. It is not known how invasion of S. canadensis may affect diversity and potassium-solubilizing activity of the potassium-solubilizing bacteria. Methods We compared S. canadensis and its coexisting native plant Imperata cylindrica in the reclaimed Hangzhou Bay wetland, Zhejiang Province. We compared the potassium contents of soil and the plant tissues of S. canadensis and Imperata cylindrica which coexists with the invasive species, the effect of potassium supply level on biomass accumulation of plants, and the quantity, diversity and potassium-soluble activity of the rhizosphere potassium-solubilizing bacteria. Important findings The potassium contents in stem and leaf of S. canadensis were significantly higher (1.59 and 7.33 times respectively) than that of I. cylindrica, the contents of available potassium in the 0-10 cm soil layer where the two species grew were significantly different, but not in the 10-20 cm soil layer. Potassium application experiments showed significant biomass increase in both S. canadensis and I. cylindrica, and tissue potassium concentrations as well. Potassium-dissolving medium culture results showed that the number of potassium-‌solubilizing bacteria of S. canadensis rhizosphere was 2.51 times higher than that of I. cylindrica. The strains with potassium-dissolving rings were identified, and the amount of released potassium was determined. Among the 15 strains of potassium-solubilizing bacteria isolated from the rhizosphere soil of S. canadensis, nine efficiently dissolved potassium, and the content of K + in the treatment solution was 85.11%-192.54% higher than that in the control. Strain H2-20 had the strongest ability with the dissolved K + of 10.657 mg·L -1. The potassium- solubilizing effect of rhizosphere potassium-solubilizing bacteria of S. canadensis was significantly higher than that of I. cylindrica. According to 16S rDNA identification, the 15 strains of bacteria associated with S. canadensis were of 11 genera, and 6 of them had been reported to have the potassium-solubilizing ability. Our results suggest that potassium-solubilizing bacteria in the rhizosphere of S. canadensis is abundant, and may play an important role in potassium enrichment.

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