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Table of Content
    Volume 42 Issue 3
    20 March 2018
    Landscapes of typical steppe of Xilinhot (Upper left, photographed by BAI Yong-Fei), meadow steppe of Ulgai (Upper middle, photographed by BAI Yong-Fei), desert of Alxa Right Banner (Upper right, photographed by LIANG Cun-Zhu), Nei Mongol, Warm temperate meadow of Wuxi, Chongqing (Lower left, photographed by WU Yan), temperate mountain meadow of Bortala, Xinjiang (Lower middle, photographed by BAI Yong-Fei), alpine meadow of Haibei, Qinghai (Lower right, photographed by BAI Yong-Fei). This specia [Detail] ...
      
    Editorial
    Carbon sequestration of Chinese grassland ecosystems: stock, rate and potential
    Yong-Fei BAI, Shi-Ping CHEN
    Chin J Plan Ecolo. 2018, 42 (3):  261-264.  doi:10.17521/cjpe.2018.0031
    Abstract ( 559 )   HTML ( 82 )   PDF (717KB) ( 769 )   Save
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    Research Articles
    Spatial distributions of biomass and carbon density in natural grasslands of Hebei, China
    CEN Yu, WANG Cheng-Dong, ZHANG Zhen, REN Xia, LIU Mei-Zhen, YANG Fan
    Chin J Plan Ecolo. 2018, 42 (3):  265-276.  doi:10.17521/cjpe.2015.0300
    Abstract ( 762 )   HTML ( 40 )   PDF (2318KB) ( 817 )   Save
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    Aims Grassland is an important component of the global terrestrial ecosystem and plays a significant role in the global carbon cycle. Knowledge of the spatial distribution of biomass and carbon density and their constraining environmental factors in different types of grasslands is crucial for revealing the variations of grassland carbon pool and understanding the grassland ecosystem carbon sequestration in China. The objective of this study was to determine the spatial patterns of biomass and carbon density distribution in natural grasslands of Hebei Province, China.

    Methods The aboveground biomass, root biomass, litter mass, and their carbon densities were investigated in 390 grassland plots from 78 sites representative of six different types of natural grasslands based on vegetation, soil and climate from 2011 to 2013. The grassland types include temperate steppe, temperate meadow, temperate mountain meadow, low-land saline meadow, warm-temperate tussock and warm-temperate shrub tussock.

    Important findings There were significant differences (p < 0.05) in the total biomass among the six grassland types, with the highest value of 2770.2 g·m-2 in the low-land saline meadow and lowest value of 747.6 g·m-2 in the temperate steppe. The low-land saline meadow also had the highest value in the aboveground biomass (285.0 g·m-2), followed by the warm-temperate shrub tussock (235.1 g·m-2) and the temperate mountain meadow (203.1 g·m-2); the lowest value in aboveground biomass was found in the temperate steppe (110.6 g·m-2). The litter mass was largest in the lowland saline meadow (584.0 g·m-2), followed by the temperate mountain meadow (187.9 g·m-2) and the warm-temperate shrub tussock (91.0 g·m-2). The values of root biomass were 1.9-4.3 times greater than that of aboveground biomass across the six types of grasslands, resulting in average root:shoot ratio of 3.1. The root biomass was largest in the lowland saline meadow (1901.3 g·m-2), and smallest in the temperate steppe with only 1/3 of that in the former. In terms of carbon density, lowland saline meadow also displayed the largest values among all the types of grasslands. The values of carbon density in the aboveground vegetation, litter and root were respectively 132.7, 81.2, and 705.9 g C·m-2. In all grassland types, the biomass of aboveground vegetation and root, litter mass, and total biomass decreased initially and then increased with elevation (p < 0.05). With the increasing accumulative temperatures >10 °C, the root biomass and the total biomass decreased initially and then increased (p < 0.01). In this study, the warm-temperate shrub tussock mostly distributes in the rocky mountain area where the soil layer is very thin, leading to the lower biomass relatively to the temperate meadow. Therefore, climate, soil and geographical factors should be comprehensively considered when comparing the biomass among different grassland types in large area.

    Carbon stock and seasonal dynamics of carbon flux in warm-temperature tussock ecosystem in Shandong Province, China
    LI Yong-Qiang, DONG Zhi, DING Chen-Xi, WANG Ya-Mei, JIA Ji-Wen, ZHANG Jia-Nan, JIAO Shu-Ying
    Chin J Plan Ecolo. 2018, 42 (3):  277-287.  doi:10.17521/cjpe.2015.0329
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    Aims The project was to analyze the carbon stock, seasonal dynamics of carbon flux and the responses of net ecosystem CO2 exchange (NEE) to various environmental factors of Zoysia japonica warm tussock ecosystem in Shandong Province.

    Methods We used field sampling and fixed-point observation-static chamber method (LI-840 infrared analyzer).

    Important findings (1) The average carbon density (carbon stock per area) of Z. japonica warm tussock ecosystem in Yaoxiang small watershed was about 2.74 Mg C·hm-2 and the order of carbon density was as follows: soil carbon (89%) > vegetation carbon (9%) > litter carbon (2%), the total amount of carbon stock of warm tussock in Shandong Province was about 15.88 Tg C. (2) The NEE seasonal dynamics of Z. japonica warm tussock ecosystem was low in summer but high in winter. This ecosystem functioned as carbon source (i.e., CO2 emissions) during the non-growing seasons (October to March of next year), but acted as carbon sink (net absorption of CO2) during the growing seasons (April to September). The average carbon sequestration rate during the peak months was -2.58- -4.46 μmol CO2·m-2·s-1. The annual average NEE of small watershed warm tussock was respectively -0.43 and -0.31 μmol CO2·m-2·s-1 in the year of 2012 and 2013, indicating this ecosystem exhibited carbon sink effect. (3) The photosynthetic active radiation (PAR), atmospheric temperature (Ta), vapor pressure deficit (VPD) and the temperature and water content of 10 cm soil depth were the major factors regulating NEE dynamics in Z. japonica warm tussock ecosystem, but drivers of NEE dynamics in different months were different and had the interaction effects between factors. Principal component analysis indicated that the seasonal dynamics of NEE was mainly controlled by the temperature, moisture and light intensity.

    Distribution and storage of soil organic carbon across the desert grasslands in the southeastern fringe of the Tengger Desert, China
    YANG Hao-Tian, WANG Zeng-Ru, JIA Rong-Liang
    Chin J Plan Ecolo. 2018, 42 (3):  288-296.  doi:10.17521/cjpe.2017.0068
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    Aims The complexity of environments and high spatial heterogeneity of desert ecosystems are important factors contributing to the uncertainty in the estimation of soil organic carbon storage.

    Methods Ten types of desert grassland communities in the southeastern fringe of the Tengger Desert, China were investigated. The content and vertical distribution of soil organic carbon (SOC) content in seven soil depths (0-5, 5-10, 10-20, 20-30, 30-50, 50-70 and 70-100 cm) and the underlying drivers were examined. Soil organic carbon density (SOCD) of four soil profiles (0-5, 0-20, 0-50 and 0-100 cm) were quantified.

    Important findings We found significant differences in SOC content among the 10 vegetation communities, and the shrub community type was an important factor affecting SOC content. Two types of trends in SOC content changes with soil depth were observed: 1) monotonic decrease, 2) increase followed by decrease. The SOC content was significantly positively correlated with clay content, total N, total P and conductivity, but negatively correlated with sand content. There were significant differences in SOCD for soil profiles of 0-5, 0-20, 0-50 and 0-100 cm among different communities, of which the mean values of SOCD were 0.118, 0.478, 1.159 and 1.936 kg·m-2, respectively. Our results show that SOCD is far below the mean value of global or national grasslands. Using the average values of SOCD across either global or national grasslands (including the grassland in this study) to estimate the SOC storage of desert ecosystems may lead to the overestimation or underestimation. Using the SOCD of specific communities may greatly increase the accuracy of SOC storage estimation in desert grasslands.

    Spatial distribution and influencing factors of soil organic carbon among different climate types in Sichuan, China
    WANG Li-Hua, XUE Jing-Yue, XIE Yu, WU Yan
    Chin J Plan Ecolo. 2018, 42 (3):  297-306.  doi:10.17521/cjpe.2017.0061
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    Aims Spatial distribution and influencing factors of soil organic carbon (SOC) content among different climate types were studied to gain new insights into the estimation and dynamics of SOC.

    Methods The study areas are located in the mountain meadow in Guanyuan City, Ya’an City, Liangshan Prefecture of Sichuan Province, China. Plant populations were recorded according to species, number, coverage, meantime, and soil samples (0-10, 10-20, 20-30 cm) were collected and analyzed for SOC content, the carbon content of root, soil pH value, and soil total nitrogen. The diversity indices for plant community diversity (Shannon-? Wiener index) was also calculated to analyze their relationships with SOC content among different climate types.

    Important findings Results showed that: (1) SOC in three sites was significantly different and was in the order of Ya’an > Liangshan Prefecture > Guanyuan, and decreased with soil depth. (2) The percentage of SOC content in each vertical layer out of total SOC was lower in the 0-10 cm layer at Ya’an site than at the other two sites, but was higher than the other two sites in the 10-20 cm layer. (3) At Guanyuan site, SOC content in 10-20 cm was significantly positively correlated with plant species richness index and SOC content in 20-30 cm was negatively correlated with plant Shannon-Winner index, while soil pH value and soil total nitrogen were significantly positively correlated with SOC content in each layer. At Ya’an site, SOC content in each layer only had positive correlation with soil pH value, but not with other examined factors. At Liangshan Prefecture site, SOC content in each layer only had positive correlation with soil nitrogen content, but not with other examined factors. (4) Principal component analysis showed that, at Guanyuan, Ya’an and Liangshan Prefecture sites, the total contents of SOC were dominantly affected by climate, followed by vegetation type.

    Carbon and nitrogen traits of typical shrubs in grassland of northern Xinjiang, China
    ZHANG Jing, LIU Yun-Hua, SHENG Jian-Dong, CHAI Qiang, LI Rui-Xia, ZHAO Dan
    Chin J Plan Ecolo. 2018, 42 (3):  307-316.  doi:10.17521/cjpe.2015.1086
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    Aims

    Shrub is an important vegetation type for maintaining ecosystem stability in arid and semiarid zones. We investigated typical shrub species in grassland of northern Xinjiang, and analyzed their carbon (C) and nitrogen (N) contents in leaves, branches and stems, in order to accurately estimate the C and N pools in shrubland, and to obtain basic data for C and N cycling study.

    Methods Leaf, branch and stem samples of 13 shrub species were collected in northern Xinjiang, and determined for C and N contents.

    Important findings In northern Xinjiang, the typical shrub species include Nitraria spp., Convolvulus tragacanthoides, Reaumuria songarica, Anabasis spp., Caragana spp., Ephedra spp., Calligonum mongolicum, Haloxylon spp., Spiraea hypericifolia, Krascheninnikovia spp., Nanophyton erinaceum, Kalidium spp., and Salsola spp. These shrubs belong to the families of Rosaceae, Leguminosae, Ephedraceae, Tamaricaceae, Zygophyllaceae, Polygonaceae, Convolvulaceae, and Chenopodiaceae, respectively. The C contents in different organs ranked in the order of stems (45.76 ± 3.43)% > branches (44.27 ± 4.51)% > leaves (39.15 ± 5.91)%, and the N contents ranked in the order of leaves (2.21 ± 0.59)% > branches (1.55 ± 0.44)% > stems (1.34 ± 0.35)%; the C:N followed the order of stems (36.74 ± 10.80) > branches (31.07 ± 10.43) > leaves (18.94 ± 5.82). The contents of C and N as well as C:N within organs were significantly different among shrub species of different families (p < 0.05); the C contents in different organs in the species of Rosaceae were significantly greater (p < 0.05); the N contents in leaves and stems in the species of Leguminosae were significantly greater (p < 0.05); the N content in branches in the species of Ephedraceae was significantly greater (p < 0.05); the values of C:N in leaves and branches in Convolvulus tragacanthoides were significantly greater (p < 0.05); the value of C:N in stems in the species of Rosaceae was significantly greater (p < 0.05), those in those of other families. The average values in the aboveground tissues across the shrub species studied was (43.77 ± 4.43)% for the C content, (1.56 ± 0.45)% for the N content, and 31.78 ± 10.12 for C:N. The degree of variation was low for the C content, with average coefficient of variation of only 10%, in contrast to the average coefficient of variation of 27% for the N content and 32% for C:N.

    Dynamic responses of aboveground biomass and soil organic matter content to grassland restoration
    ZHANG Lu, HAO Bi-Tai, QI Li-Xue, LI Yan-Long, XU Hui-Min, YANG Li-Na, BAOYIN Taogetao
    Chin J Plan Ecolo. 2018, 42 (3):  317-326.  doi:10.17521/cjpe.2017.0046
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    Aims Based on a long-term observation experiment set up in 1983, which was designed to test how different restoration measures would affect the aboveground biomass and soil organic matter content in a degraded Leymus chinensis steppe in Nei Mongol, under the enclosure protection from interference. Our restoration measures included shallow plowing, harrowing and natural restoration.

    Methods This experiment used the quadrat method (five replicates) to survey the aboveground biomass and the potassium dichromate oxidation volumetric method to analyze soil organic matter content.

    Important findings Results showed that the changes of aboveground biomass in the early period (1983-1991) were significantly higher under shallow plowing treatment than under natural restoration, while those under the harrowing treatment were not significantly different from those under the rest two treatments. In the middle period (1991-2006), there the three treatments had no significant different changes of aboveground biomass. In the late period (2006-2014), the changes of aboveground biomass were in the order of natural restoration > harrowing > shallow plowing, while the difference was significant between natural restoration and shallow plowing. The changes of soil organic matter content in the 0-10 cm soil layer in the early period was significantly different under different treatments and was in the order of shallow plowing > harrowing > natural restoration. Compared to the initial value (1983), natural restoration, harrowing, and shallow plowing treatments increased soil organic matter content by 21%, 45%, and 37% respectively. In middle and late period, natural restoration increased soil organic matter content significantly more than shallow plowing did, while harrowing treatment result was between the two treatment results and was not significantly different from natural restoration and shallow plowing. Natural restoration, harrowing, shallow plowing increased soil organic matter content by 61%, 46%, and 57% respectively in the middle period and by 67%, 51%, 62% in the later period. The changes of soil organic matter content in the 10-30 cm soil layer in the early period was significantly different under different treatments and was in the order of shallow plowing > natural restoration > harrowing. In middle and late periods, there was no significant difference among treatments. In summary, different improvement measures should be chosen according to the objectives of recovery. On a short time scale, shallow plowing is beneficial to the rapid restoration of productivity and soil organic carbon content in the degraded Leymus chinensis steppe, while the benefit of natural restoration and harrowing is more obvious on a longer time scale.

    Effects of enclosure on carbon density of plant-soil system in typical steppe and desert steppe in Nei Mongol, China
    YAN Bao-Long, WANG Zhong-Wu, QU Zhi-Qiang, WANG Jing, HAN Guo-Dong
    Chin J Plan Ecolo. 2018, 42 (3):  327-336.  doi:10.17521/cjpe.2017.0067
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    Aims As an immense carbon (C) stock, grassland ecosystem plays a crucial role in global C cycling. The objective of this research was to reveal the effects of enclosure on C density of the plant-soil system by comparing the aboveground biomass (AGB), belowground biomass (BGB) and soil C density in enclosure plots with those in grazing plots in the typical steppe (TS) and desert steppe (DS) in Nei Mongol, China.

    Methods At each of the 19 study sites, we set up a 100 m × 100 m plot and 5 quadrats (1 m × 1 m) along the diagonal transect within each plot. At each quadrat, AGB was harvested first and then a soil core (0-100 cm depth, 7 cm inner diameter) was taken for BGB and soil C content measurement. Each soil core was divided into 7 depth increments (0-5 cm, 5-10 cm, 10-20 cm, 20-30 cm, 30-50 cm, 50-70 cm, 70-100 cm).

    Important findings (1) Enclosure significantly increased C density of AGB and BGB in TS. In DS, enclosure significantly increased C density of AGB, but had no significant effect on the C density of BGB. (2) Enclosure significantly increased soil C density in TS, but had no significant impact in DS although there was an increasing trend. (3) For all increments along the soil profile, enclosure significantly increased BGB and soil C density compared to grazing plots in TS, but this effect was not found in DS. (4) Enclosure increased C density of the plant-soil system by 2.2 and 1.6 times in TS and DS, respectively. 65% and 89% C was stored in soil in TS and DS, respectively, and BGB C stock accounted for more than 90% of total biomass C in both TS and DS. Enclosure is an effective approach to improve C sequestration in grassland ecosystems.

    Spatial patterns and drivers of root turnover in grassland ecosystems in China
    Yuan-Feng SUN, Hong-Wei WAN, Yu-Jin ZHAO, Shi-Ping CHEN, Yong-Fei BAI
    Chin J Plan Ecolo. 2018, 42 (3):  337-348.  doi:10.17521/cjpe.2017.0241
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    <i>Aims</i> Root turnover rate is a key indicator of ecosystem functions and services. It is also a core parameter for estimating net primary productivity and carbon sequestration potential. However, few studies have examined the patterns and drivers of root turnover at regional and global scales, especially for the widely distributed grassland ecosystems in China. Our objective is to determine: 1) the spatial patterns of root turnover rate for grassland ecosystems in China; and 2) the mechanisms and relative contributions of abiotic and biotic factors driving the root turnover process.

    <i>Methods</i> Root turnover data used in this study were derived from two sources. One was obtained from the sample- to-sample plot survey by Grassland Carbon Sequestration Project. The other was extracted from 43 published literatures on root turnover of grasslands in China from 1983 to 2016. These publications were collected from the ISI Web of Science or Chinese literature database. For studies in which climatic variables were not reported, climate information was extracted from the World Climate Database based on site coordinates. Soil properties were collected from Harmonized World Soil Database Version 1.1 supplied by Food and Agriculture Organization of the United Nations.

    <i>Important findings </i> Our results showed that root turnover rate was significantly negatively correlated with latitude in China. The national scale pattern of root turnover was influenced by climatic variables (mean annual temperature and mean annual precipitation) and soil properties (gravel content, bulk density, and pH value). These variables together explained 44% of the variation in root turnover rate, with the relative contribution being 57% for climatic variables and 43% for soil properties. However, the regional scale patterns and drivers of root turnover for grasslands in China were different from those at the global scale.

    Effects of litter removal and addition on ecosystem carbon fluxes in a typical steppe
    ZHANG Su-Yan, JIANG Hong-Zhi, WANG Yang, ZHANG Yan-Jie, LU Shun-Bao, BAI Yong-Fei
    Chin J Plan Ecolo. 2018, 42 (3):  349-360.  doi:10.17521/cjpe.2016.0083
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    Aims Our objectives were to investigate: 1) How does litter affect the ecosystem carbon fluxes in mature and degraded community ecosystems? and 2) What are the effects of litter on the ecosystem carbon fluxes of the two ecosystems?

    Methods The study was carried out at Baiyinxile Ranch experiment site, which is located in the semiarid agriculture-pasture transition region in southeastern Nei Mongol, China. The treatments were litter removal (50% and 100%) in mature community and litter addition (50% and 100%) in degraded community. We measured net ecosystem CO2 exchange (NEE) by the chamber method during the growing season of 2013 and 2014.

    Important findings Our results showed that there were significant seasonal changes of NEE in both mature and degraded community. After the consecutive treatments for two years, in mature community, the 50% litter removal significantly increased NEE and the 100% litter removal significantly reduced the NEE, while litter removal had no significant effect on the ecosystem gross primary productivity (GEP) and ecosystem respiration (ER). In the degraded community, litter addition significantly increased NEE and GEP and had no effect on ER. Meanwhile, neither litter removal nor litter addition had significant effect on the total ecosystem respiration (ER). In both communities, the correlation between GEP and soil temperature at 10 cm was significantly positive (p < 0.05). However, the changes of GEP and NEE under litter treatments was contrary to the changes of soil temperature, and consistent with the changes of soil moisture content at 10 cm depth. We concluded that the mechanism underlying the effects of litter removal and addition on the carbon flux of ecosystem was mainly attributed to soil moisture and above ground biomass.

    Net ecosystem carbon exchange characteristics in Stipa breviflora desert steppe with different stocking rates
    JIN Yu-Xi, LIU Fang, ZHANG Jun, HAN Meng-Qi, WANG Zhong-Wu, QU Zhi-Qiang, HAN Guo-Dong
    Chin J Plan Ecolo. 2018, 42 (3):  361-371.  doi:10.17521/cjpe.2017.0066
    Abstract ( 286 )   HTML ( 22 )   PDF (1613KB) ( 220 )   Save
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    Aims Grassland ecosystem is the largest terrestrial ecosystem type in China. The dynamic changes in carbon cycle play an important role in global carbon budget balance. Grazing is the main use of grassland ecosystem. Different grazing intensity has different effects on the grassland ecosystem.

    Methods In the growing seasons (May to October) from 2014 to 2016, we used portable optical LI-6400 and the method of static chamber to measure net ecosystem carbon exchange in Stipa breviflora desert steppe with 3 different stocking rates (CK, no grazing control; LG, lightly grazing; HG, heavily grazing). At the same time, the soil temperature and moisture of 10 cm depth were also measured. The effects of stocking rate and hydrothermal factors on the carbon exchange were discussed.

    Important findings Stocking rate had a significant impact on net ecosystem carbon exchange. With the increase of stocking rate, the net ecosystem carbon exchange, ecosystem respiration, gross ecosystem productivity decreased by 48.6%, 35.3% and 40.4% respectively. Heavily grazing significantly reduced grassland carbon sequestration, but lightly grazing had no significant effect. The inter-annual changes in net carbon exchange was mainly controlled by precipitation. Throughout the growing season, Stipa breviflora desert steppe were carbon sinks. The contribution of soil temperature to the variations of net ecosystem carbon exchange was higher than that of soil moisture.

    Effects of fencing on ecosystem carbon exchange at meadow steppe in the northern slope of the Tianshan Mountains
    HU Yi, ZHU Xin-Ping, JIA Hong-Tao, HAN Dong-Liang, HU Bao-An, LI Dian-Peng
    Chin J Plan Ecolo. 2018, 42 (3):  372-381.  doi:10.17521/cjpe.2016.0049
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    Aims The carbon exchange between ecosystems and the atmosphere and its response to environmental factors is the focus of current research. The aim of this study was to examine the effects of fencing on ecosystem carbon exchange at meadow steppe in the northern slope of Tianshan Mountains.

    Methods The static box method with a LI-840 CO2/H2O infrared analyzer was used to evaluate daily and seasonal changes of ecosystem carbon exchange and their relationship with environmental factors in the inside fence and outside fence after 9 years fencing.

    Important findings We found the ecosystem carbon exchange inside the fence was significantly (p < 0.05) higher than that in outside the fence. The ecosystem carbon exchange had obvious daily and seasonal variation both in inside and outside the fence, which showed a unimodal curve during the plant growing season. The minimum net ecosystem CO2 exchange (NEE) in the inside and outside of the fences were -7.62 and -6.63 μmol·m-2·s-1, respectively; the maximum ecosystem respiration (ER) were 8.55 and 7.04 μmol·m-2·s-1, respectively; and the maximum gross ecosystem productivity (GEP) were -14.66 and -13.89 μmol·m-2·s-1, respectively. Due to the protection of fence, the vegetation in the fence was flourished with higher photosynthesis, and thus resulted in lower NEE. Meanwhile, organic carbon input enhanced ecosystem respiration. Besides, the ecosystem carbon exchange significantly correlated with the air temperature and soil temperature of 0 to 10 cm depth, and the correlation with the air temperature was higher than soil temperature of 0 to 10 cm depth. Also, the correlation in the inside of the fence was higher than that in the outside of the fence. Ecosystem carbon exchange had correlation with soil water content, but the correlation was slightly lower than that with soil temperature.

    Soil respiration features of mountain meadows under four typical land use types in Zhaosu Basin
    WANG Xiang, ZHU Ya-Qiong, ZHENG Wei, GUAN Zheng-Xuan, SHENG Jian-Dong
    Chin J Plan Ecolo. 2018, 42 (3):  382-396.  doi:10.17521/cjpe.2017.0050
    Abstract ( 328 )   HTML ( 11 )   PDF (2022KB) ( 271 )   Save
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    Aims Our objective was to explore the effects of different land use types on soil respiration rates in the mountain meadows of Tianshan Mountain, Zhaosu Racecourse, Xinjiang, China from 2015 to 2016.

    Methods Four impermanent plots with different land use types (legume-grass mixture, LG; reseeding grassland, RG; natural grassland, NG; cropland, CR), which were established in 2013, were selected. The soil respiration rates in the growing seasons of two consecutive years (from April to September in 2015 and 2016) were measured using LI-8100A Soil Respiration System. Soil temperatures at 5 cm depth and soil water content at 0-10 cm depth were measured simultaneously. We also investigated soil biological properties including soil microflora structures, soil microbial biomass carbon, and soil enzyme activity. The hydrothermal and soil biological impacts on soil respiration rates were analyzed using the relationship among soil hydrothermal factors, soil microflora factors, and soil enzyme activities.

    Important findings We found that: 1) in 2015, the temporal variation of soil respiration showed double peaks in NG and RC plots, but showed a single peak in RG and LG plots, and it reached the maximum in August in all plots. This temporal pattern was different in 2016. Soil respiration reached the maximum at the end of June in RG and LG, and at the end of July in NG and CR. 2) For the whole study period, the average soil respiration rate was in the order of: NG > RG > CR > LG. 3) Soil respiration rate was positively correlated with soil temperature, and negatively correlated with soil volumetric water content. The temperature sensitivity of soil respiration (Q10) was in the order of: NG > CR > RG > LG. 4) Bacteria were dominant among soil microbes in all type of plots, followed by actinomycetes and fungi were the least abundant. The total soil microbial biomass was in the order of: NG > RG > CR > LG, which was consistent with the average soil respiration rate. The fitting analysis showed that soil respiration was positively correlated with the abundance of actinomycetes in RG (p < 0.05), and was positively correlated with the abundances of bacteria and actinomycetes in LG (p < 0.05). 5) The average microbial biomass carbon was in the order of: CR > NG > LG > RG. Fidelity analysis showed that soil respiration rate was significantly positively correlated with microbial biomass carbon in GR and CR (p < 0.05). 6) Among the examined enzymes, only protease and sucrase had a correlation with soil respiration, with sucrase having a greater effect. Changing the degraded mountain meadow to legume-grass mixture and reseeding grassland could decrease soil respiration rates, potentially benefiting carbon sequestration.

    Responses of ecosystem carbon exchange to multi-level water addition in an alpine meadow in Namtso of Qinghai-Xizang Plateau, China
    GENG Xiao-Dong, Xu Ri, LIU Yong-Wen
    Chin J Plan Ecolo. 2018, 42 (3):  397-405.  doi:10.17521/cjpe.2015.0395
    Abstract ( 362 )   HTML ( 13 )   PDF (1210KB) ( 606 )   Save
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    Aims Alpine meadow is widely distributed in the Qinghai-Xizang Plateau, playing an important role in regulating the regional carbon budget. Over the Qinghai-Xizang Plateau, precipitation generally shows an increasing trend during past the several decades, and is projected to increase during the 21st century. Alpine meadow is very susceptible to such climate change, but it remains unclear how its ecosystem carbon exchange responses to precipitation change. In this study, we aim to clarify the effects of altered precipitation on ecosystem carbon exchange in the alpine meadow by conducting a manipulative field experiment.

    Methods We conducted a precipitation manipulation experiment at an alpine meadow site in the Namtso area of central Qinghai-Xizang Plateau during 2013 to 2014. A total of six treatments were established, with levels of water addition set for 0%, 20%, 40%, 60%, 80% and 100%, respectively, of equivalent increases in precipitation. We investigated the effects of water addition on gross ecosystem production (GEP), ecosystem respiration (ER), net ecosystem carbon exchange (NEE), and environmental conditions during the growing season.

    Important findings The increasing water addition substantially increased soil moisture, but had no significant effect on soil temperature. Both GEP and NEE significantly increased with water addition equivalent to 20% of increases in precipitation, but were suppressed with further increases in the level of water addition. No significant difference was detected in ER across the water addition treatments. Our study suggests that: 1) The change in soil moisture significantly affected NEE and GEP but had a weak effect on ER in the alpine meadow; 2) CO2 sequestration in the alpine meadow could be stimulated by moderate increases (e.g. 20%-40%) in precipitation.


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