Table of Content

18 June 2018, Volume 29 Issue 6

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Spatial pattern of plant community in original karst tiankeng: A case study of Zhanyi tiankeng in Yunnan, China

SHUI Wei, CHEN Yi-ping, JIAN Xiao-mei, JIANG Cong, WANG Qian-feng, GUO Ping-ping

2018, 29(6):  1725-1735.  doi:10.13287/j.1001-9332.201806.010

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Damaosi is one of original karst tiankengs with underground virgin forest in Yunnan Pro-vince. The spatial point pattern analysis and the woody individual spatial structure parameters, including the uniform angle index, mingling degree and storey index, were used to estimate spatial pattern of the tiankeng’s underground forest community. We also analyzed the intraspecific spatial distribution characteristics and interspecific spatial association on the basis of the individual relative position information of plant community. The results showed that the spatial distribution of plant community in Damaosi tiankeng was random. Plant species in the forest were moderately mixed. The vertical stratification of this forest was relatively simple, with stable structure and mature development characteristics of climax forest community. The populations in this community were mainly clustered in spatial distribution, negatively correlated between species and stronger negative correlation on the same vertical level. The larger the difference in the vertical level, the smaller the space competition was. The negative correlation in space became weaker with the increases of spatial scale. Tiankeng ecosystem was one type of precious natural habitats and plant refuges with high ecological stability. The stable structure of tiankeng plant community had important implications for the ecological resto-ration in karst areas.

Interspecific association and functional group classification of the dominant populations in shrub layer in secondary forest of Pinus tabuliformis in Qinling Mountain, China.

CHEN Qian, CHEN Jie, ZHONG Jiao-jiao, JI Liu-ting, KANG Bing

2018, 29(6):  1736-1744.  doi:10.13287/j.1001-9332.201806.004

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We analyzed the interspecific association among 20 dominant populations in shrub layer in secondary natural forest of Pinus tabuliformis in Qinling Mountain, China, with χ²-test, the association coefficients and the percentage of common occurrence. The results showed that the species pairs with significant positive associations accounted for only 7.4% of the total 190 species pairs. The species pairs such as Lespedeza bicolor and Elaeagnus pungens, Toxicodendron vernicifluum and Pinus tabuliformis, Euonymus alatus and Cerasus tomentosa had extremely significant positive correlations, whereas most of the species pairs showed weak interspecific association. The ratio of positive and negative correlations was less than 1. The results suggested that the interspecific association was relatively weak. Species were with certain independence among dominant populations. Community structure was at an unstable mid-stage with dynamic succession. According to the interspecific association and cluster analysis, combined with biological and ecological characters, the 20 dominant populations in shrub layer were classified into four functional groups. The ecological requirement and resource use pattern of species within the same functional groups were similar, exhibiting a close connection between the shrub species. The connection between different functional groups was relatively loose.

Construction of empirical models for leaf area and leaf dry mass of two broadleaf species in Xiaoxing’an Mountains, China.

WANG Yan-jun, JIN Guang-ze, LIU Zhi-li

2018, 29(6):  1745-1752.  doi:10.13287/j.1001-9332.201806.014

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Rapid and accurate measurement of leaf area (LA) and leaf dry mass (LM) is one of the basic requirement for leaf geometry and plant functional studies. It is important not only for studying leaf morphology and biomass estimation, but also for understanding the response mechanism of vegetation to climate change. In this study, we took two temperate deciduous broad-leaved tree species, Ulmus laciniata and Acer tegmentosum, as the study objects, constructed empirical models between LA or LM and leaf structure parameters (e.g., leaf length, L; leaf width, W) to reveal the interspecific variability in the selection of empirical model formats (linear or non-linear) and independent variables. We evaluated the forecast accuracy of these empirical models in predicting LA and LM for each species. The results showed that the optimal empirical models for predicting LA were LA=0.614L^1.468W^0.464 and LA=0.865(LW)^0.933, and for predicting LM were LM=0.003L^1.537W^0.365 and LM=0.001L^2.318 for U. laciniata and A. tegmentosum, respectively. The forecast accuracies of empirical models in predicting LA were 88% and 96%, and for LM were 73% and 83% for U. laciniata and A. tegmentosum, respectively. In addition, based on the empirical models for predicting LA and LM, the specific leaf area also could be indirectly measured under non-destructive conditions, with the forecast accuracies being 83% and 90% for U. laciniata and A. tegmentosum, respectively. These results provide a technical support for the efficient measurement of leaf traits and their dynamics.

Effects of N-fixing tree species (Alnus sibirica)on amino sugars in soil aggregates of Larix kaempferi plantation in eastern Liaoning Province, China.

JING Yan-li, LIU Shi-rong, YIN You, YAO Rong-sheng, ZHANG Shao-qiang, MAO Ri-xin

2018, 29(6):  1753-1758.  doi:10.13287/j.1001-9332.201806.020

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Soil microbial residues are important components of soil stable carbon (C) pools. How N-fixing tree species influence microbial residues in soil aggregates in larch plantations is still unclear. To determine the effects of N-fixing tree species on the distribution of microbial residues in different aggregates, we compared the distribution of amino sugars, biomarker of microbial residues, among aggregates in a pure larch (Larix kaempferi) plantation and a mixed plantation of larch (Larix kaempferi) and alder (Alnus sibirica) in eastern Liaoning Province. The results showed that alder did not affect the distribution of amino sugars, but significantly increased amino sugars content in soil aggregates. The total amino sugars in different soil aggregates were enriched by 130%-170% in the mixed larch plantation compared with those in pure larch plantation. The contributions of glucosamine, galactosamine and muramic acid to the increases of total amino sugars caused by alder introduction were 66.5%-66.9%, 30.0%-30.6% and 2.5%-3.2%, respectively. Alder introduction significantly accelerated the glucosamine/muramic acid ratios in >2000 μm and <250 μm aggregates, but not in 250-2000 μm aggregates. Moreover, alder introduction increased the microbial contribution to soil organic C in all aggregates, but did not influence this contribution among aggregates, indicating that the effects of alder introduction on microbial contribution to aggregates were homogeneous.

Effects of drought and rewatering on growth and photosynthetic physioecological characteristics of Xanthoceras sorbifolia.

XIE Zhi-yu, ZHANG Wen-hui

2018, 29(6):  1759-1767.  doi:10.13287/j.1001-9332.201806.007

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An experiment was conducted to examine the effects of drought and rewatering on growth and photosynthetic physioecological characteristics of Xanthoceras sorbifolia, with 2-year-old seedlings as test materials. There are three treatments, i.e., light drought stress (soil water content 14.3%-16.2%), moderate drought stress(10.6%-12.5%) and severe drought stress (6.8%-8.7%), with the control (21.8%-23.7%). The results showed that with the increases of drought stress, the dry mass per plant, height, basal diameter, leaf number, and leaf area significantly decreased, and length of the main root and the secondary root increased. The gas exchange parameters gradually decreased with the increases of drought stress. The level of P_n was caused by stomatal factors from 10:00 to 14:00 and by non-stomatal factors after 14:00. Apparent CO₂ use efficiency (CUE) of X. sorbifolia was obviously increased under the moderate and severe drought stress. With the increases of drought stress, F_v/F_o, F_v/F_m, q_P, ETR and Ф_PSⅡ gradually decreased, and NPQ gradually increased. The changes of all those characters after rewatering were contrary to those after drought. After rewatering for eight days, F_v/F_o, F_v/F_m, q_P, ETR, Ф_PSⅡ were significantly higher than that of drought stress treated for 30 days. With the increases of drought stress, SOD and POD activities and MDA content gradually increased, but CAT activity decreased, showing the contrary changes after rewatering. After rewatering, the root activity under drought stress increased. X. sorbifolia was strongly resistant to heavy drought stress, and thus could be widely used as energy or garden plants in garden landscaping in North China.

Application of near-surface remote sensing in monitoring the dynamics of forest canopy phenology.

LIU Fan, WANG Chuan-kuan, WANG Xing-chang

2018, 29(6):  1768-1778.  doi:10.13287/j.1001-9332.201806.016

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Near-surface remote sensing is an important technique for in-situ monitoring of forest phenology and a robust tool for scaling of the phenology with a high temporal resolution and mode-rate spatial coverage. Here, we first reviewed the methods of near-surface remote sensing with three major optical sensors (i.e., radiometer, spectrometer, and digital camera) for monitoring forest phenology. Second, we analyzed sources of uncertainties from distinguishing the phenophases by using the data obtained at the Maoershan flux site in the temperate forest. We found that the error was mainly attributed to the extracting method. Third, we analyzed the linkage of near-surface remote sensing with other methods and its intrinsic problems. Finally, we proposed four priorities in the research of this field: 1) linking optical (or canopy structural) phenology with functional phenology (physiological and ecological processes); 2) integrating the regional networks of canopy phenology for global networking observation and data sharing of canopy phenology; 3) integrating multi-source and multi-scale phenological data with the help of near-surface remote sensing; 4) developing phenology models based on near-surface remote sensing in order to improve the phenology simulation in the dynamic global vegetation models.

Responses of soil and aggregate-associated organic carbon mineralization to throughfall reduction in a Pinus massoniana plantation.

YANG Yu-jing, LIU Shi-rong, CHEN Lin, WANG Hui

2018, 29(6):  1779-1786.  doi:10.13287/j.1001-9332.201806.006

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To examine the effects of altered precipitation pattern on the mechanism of forest soil carbon (C) emission under climate change scenarios, we established plots with 50% reduction in throughfall in a subtropical Pinus massoniana plantation. The effects of throughfall reduction on the mineralization of both soil and aggregate-associated organic C were quantified by laboratory incubation at constant temperature. The results showed that the cumulative mineralization of organic C in the 1-2 mm aggregates was higher than that in other sizes of aggregates. In the dry and wet seasons, the surface soil water content in the throughfall reduction plots was 82.1% and 82.7% of that in the control, but the mass fractions of 0.106-0.25 mm soil aggregates in the throughfall reduction plots increased by 1.8% and 4.2% than the control, respectively. The throughfall reduction treatment significantly reduced the mineralization rate of labile C pools (k₁) of soil and micro-aggregates in the dry season, increased the mineralization rate of recalcitrant C pool (k₂) of soil and <1 mm aggregates, and had no significant effects on the cumulative mineralization of soil organic C. Results from the correlation analyses revealed significant and positive correlations between k₁ of soil and that of the micro-aggregates and between k₂ of soil and that of the 0.25-1 mm aggregates. Under the influence of aggregate structure, water condition and soil organic carbon content, the throughfall reduction suppressed the mineralization of labile organic C while stimulated that of recalcitrant organic C.

Turbulence micro-meteorological characteristics over the plantation canopy.

ZHANG Gong, ZHENG Ning, ZHANG Jin-song, MENG Ping

2018, 29(6):  1787-1796.  doi:10.13287/j.1001-9332.201806.017

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Based on the eddy-covariance system monitoring during leaf germination (15^th March to 15^th April 2015) and leaf forming (15^th July to 15^th August), the turbulence characteristics, turbulence intensity, normalized standard variance of turbulent wind speed and bulk transfer coefficient over forest plantation canopy in the Xiaolangdi Ecosystem Location Research Station were analyzed, aiming to deepen the understanding of the micro-meteorological characteristics of the forest ecosystem and provide scientific basis for the further studies of energy balance and material exchange. Results showed that turbulence spectrum of the plantation had a peak frequency in the low frequency zone and the inertial subarea had an obvious dissipation tendency, which was basically in accor-dance with the law of -5/3. Turbulence intensity was significantly affected by canopy structure. When the turbulence was strong, the wind speed was less than 3 m·s^-1 in spring and less than 2 m·s^-1 in summer. Normalized standard variance of turbulent wind speed in horizontal direction was better than that in vertical direction, which conformed to the similarity law of 1/3 power. The ratio of normalized standard deviation and the friction velocity in u, v, w components of canopy wind speed was 2.55, 2.06 and 1.30 in spring, 2.61, 2.45 and 1.21 in summer, respectively. The bulk transfer coefficient decreased with the increases of stability, with a difference of 1-2 orders of magnitude or more between unstable and stable conditions. Canopy structure had direct influence on the turbulence of the wind speed in each direction, and thereby changed the diffusion direction of the canopy material and energy.

Diversity of bryophytes in urban area of Nanjing, China

JING Lei, LU Jian-guo, XIA Wen

2018, 29(6):  1797-1804.  doi:10.13287/j.1001-9332.201806.003

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Bryophytes are morphologically special higher plants, with unique ornamental values and a wide application prospect. Its species richness was just secondary to angiosperms. To more effectively utilize bryophytes for greening and landscape construction, 77 plots in 10 green spaces were investigated in urban area of Nanjing. 55 species belonging to 36 genera and 21 families were recorded, among which Pottiaceae and Thuidiaceae were widely distributed. The species richness in green space gradually reduced from the center to the surrounding areas of the city. The 10 green spaces could be clustered into three groups based on bryophyte diversity, habitats, human distur-bance frequency, green space areas. Results from Canonical correspondence analysis (CCA) showed that canopy density, humidity, and substrate types were the major environmental factors the distribution of bryophytes. In Nanjing, most bryophytes preferred to grow in moderate humidity and open areas.

Landscape pattern change and simulation in the Sanjiang Plain based on the CLUE-S model.

LI Zhen, LIU Miao, XUE Zhen-shan, HU Yuan-man, LYU Xian-guo, LI Yue-hui

2018, 29(6):  1805-1812.  doi:10.13287/j.1001-9332.201806.030

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The Sanjiang Plain is one of the most concentrated and contiguous area of marshes, which plays an irreplaceable role in maintaining regional ecological security. Based on the 3S technology, we examined the changes in land use and landscape pattern of the Sanjiang Plain from 1980 to 2010. The results showed that marshland area lost 7135 km², with a loss rate of 59.1%. The paddy area increased 18010 km², with a growth rate of 610.1%. The results of landscape indices analysis showed that the number of patches increased, the landscape fragmentation became stronger, the landscape heterogeneity increased, and the different landscape types became homogenized. The CLUE-S model was validated based on the five different periods of land use maps during 1980-2010. The Kappa index between the simulation and actual measurement at the time scale of 30 years was 0.71, indicating that the model was suitable for 30 years simulation in the study area. The future wetland changes in the Sanjiang Plain from 2010 to 2030 was simulated with validated CLUE-S models, including historical development scenario, planning scenario, and ecological restoration scenario. The simulation results showed that the marsh land would decrease 2515.44 km² and the paddy area would increase 19656.24 km² in the historical development scenario. The marsh land would decrease 303.28 km², but the paddy area would increase 1392.08 km² in the planning scenario. The marsh land would increase 3585.61 km² and the paddy area would increase 289.72 km² in the ecological restoration scenario. The landscape patterns of the three scenarios were estimated using landscape indices. The results showed that the landscape pattern fragmentation would become more and more serious in the historical development scenario. The landscape pattern would have no signifi-cant changes in the planning scenario. The wetland area and connectivity would increase, the different landscape types would become balanced, and the landscape pattern would be gradually optimized in the ecological restoration scenario.

Multi-scale effects of urban landscape pattern on plant diversity in Xuzhou City, Jiangsu Province, China.

LI Zu-zheng, YOU Hai-mei, WANG Zi-yi

2018, 29(6):  1813-1821.  doi:10.13287/j.1001-9332.201806.018

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The changes of urban surface landscape will lead to damage, fragmentation, and losses of biodiversity, resulting in urban biodiversity decline. In order to explore the responses of urban plant diversity to the changes of landscape pattern, we chose the urban area surrounded by round-city highway as research object, set 36 plots in different directions with the Gupeng Square as the center, investigated the plant group in each of the plots through coverage rank method of Braun-Blanquet, and examined the features of plant species diversity in Xuzhou’s greenlands. Meanwhile, we divided the landscape of the research area into seven categories: buildings, grasslands, forest lands, waste lands, water areas, roads and farmlands with the help of Erdas, GIS software and Landsat TM remote sensing images from 2005 to 2015 as basic data source. The features of landscape pattern in the research area were analyzed by Fragstats software. We set nine different buffer districts within each of the sample plot by applying the space analyzing function of GIS, calculated 39 landscape pattern metrics using Fragstats, and explored the features of how plant diversity responsed to landscape pattern. After that, the landscape pattern metrics with significant influence on the plant diversity of urban greenlands under different extents were selected by redundant analysis (RDA). The results showed that the plant diversity had obvious temporal and spatial scale effects in responses to landscape pattern and landscape elements. In 2005, the patch area and shape metrics of unused land and farmland could better explain plant diversity in 800 m buffer zone. The patch fragmentation and connectivity metrics of construction land had significant impacts on plant diversity within the extent of 800-2000 m. In 2015, grassland and forest landscapes better explained plant diversity in the 800 m buffer zone while construction sites and unused land had a remarkable impact on plant diversity in the extent of 1000-2000 m. The current plant diversity was more strongly influenced by the 2005 landscape type metrics, indicating that the plant diversity lagged in its response to the changes of landscape pattern. The pattern metrics of landscape level were more consistent with the landscape-class level metrics, indicating that the interaction between species and spatial scale was more dependent on the landscape type. This study would provide effective decision-making information for Xuzhou City planning and construction as well as effective protection of urban green space biodiversity.

Effects of precipitation changes on the precipitation use efficiency and aboveground productivity of alpine steppe-meadow on northern Tibetan Plateau, China.

WANG Zhi-peng, ZHANG Xian-zhou, HE Yong-tao, SHI Pei-li, ZU Jia-xing, NIU Ben, LI Meng

2018, 29(6):  1822-1828.  doi:10.13287/j.1001-9332.201806.009

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Total amount, distribution pattern and occurrence time of precipitation determine the water condition of alpine vegetation growth on the Tibetan Plateau, China. Precipitation use efficiency (the ratio of aboveground productivity to precipitation, PUE) is an effective indicator for the relationship between precipitation and vegetation productivity. In this study, we calculated aboveground net primary productivity (ANPP) of an alpine steppe-meadow in northern Tibetan Plateau from 2000 to 2016 based on the correlation model between long-term monitoring biomass data and enhanced vegetation index (EVI) in Damxung. Meteorological data during the same period was also analyzed. Growing season precipitation (GSP) represented the amount of precipitation, improved precipitation concentrated index (PCI) indicated their distribution pattern in the growing season, and precipitation centroid (PC) represented the time of precipitation occurrence. Structural equation model was used to explore the effects of climatic factors on PUE and ANPP, with the consideration of growing season temperature (GST). Results showed that ANPP of this alpine steppe-meadow was mainly controlled by precipitation during the growing season. GSP and ANPP showed significantly positive correlation, whereas the correlation of GST with PUE and ANPP was not significant. PCI and PUE showed significantly positive correlation, which indicated that concentrated distribution of precipitation was beneficial to the increase of PUE. Indirect coefficient between PCI and ANPP was greater than direct coefficient, indicating that PCI influenced ANPP through PUE. Changes of precipitation concentrated time did not show significant effect on PUE and ANPP. Our results suggested that under the rapid climate warming on the Tibetan Plateau, future changes of precipitation and their concentration would have important impacts on aboveground productivity of the alpine grassland.

Responses of net ecosystem carbon exchange to diffuse radiation in an alpine meadow on the Qinghai-Tibetan Plateau, China.

CHEN Zhi-guang, ZHANG Xiang, LIU Xiao-qin, ZHANG Li-feng, TANG Yan-hong, DU Ming-yuan, GU Song

2018, 29(6):  1829-1838.  doi:10.13287/j.1001-9332.201806.011

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Qinghai-Tibetan Plateau, one of the regions on the earth that receives the most solar radiation, is the world’s highest alpine meadow ecosystem, with significance to regional and global carbon cycles. To examine the effects of solar radiation on ecosystem carbon dynamics in an alpine meadow, the net ecosystem CO₂ exchange (NEE), solar radiation, diffuse radiation, and related environmental variables were measured using eddy-covariance technique and micro-meteorological system. Sky conditions were divided into three categories of clear days (CI≥0.7), cloudy days (0.3<CI<0.7) and overcast days (CI≤0.3) by clearness index (CI, defined as the ratio of solar radiation observed at meadow to the top of the earth’s atmosphere). We analyzed the changes in NEE and the effects of related factors on it under different CI. The results showed that the maximum NEE (-0.63 mg CO₂·m^-2·s^-1) appeared in photosynthetic photon flux density (PPFD) of approximately 1400 μmol·m^-2·s^-1, corresponding the CI of 0.6-0.7 in cloudy days, which was higher than the maximum NEE in clear days (-0.57 mg CO₂·m^-2·s^-1) (negative and positive NEE represented carbon uptake and emission, respectively, here absolute value was used to describe NEE). With the increases of diffuse radiation, NEE increased logarithmically when CI<0.6, reached the highest value when CI ranged from 0.6 to 0.7, and then decreased when CI≥0.7, indicating that photo-inhibition might occur under high solar radiation conditions and increasing diffuse radiation would improve carbon sequestration of alpine meadow. Ecosystem respiration (R_e) increased exponentially with the increases of air temperature (T_a). The maximum NEE was found at the air temperature of about 15 ℃ from the relationship of NEE and air temperature, but NEE tended to decrease with increasing air temperature when T_a>15 ℃. Under clear sky day conditions, R_e increased with increasing CI due to the increases of air temperature, with negative effects on NEE. NEE increased with the increases of VPD up to 0.6 kPa, then slowly decreased when VPD>0.6 kPa, illustrating that NEE was reduced due to the relatively high VPD. Our results suggested that strong solar radiation on clear days would not increase carbon uptake capacity of alpine meadow, while cloudy days with clearness index of 0.6-0.7 would help increase carbon sequestration on the Qinghai-Tibetan Plateau.

Effects of grassland management on soil nutrients and their spatial distribution on the Qinghai-Tibetan Plateau, China

CAO Jian-jun, WANG Xue-yan, LI Meng-tian, YANG Shu-rong, XU Xue-yun, GONG Yi-fan

2018, 29(6):  1839-1845.  doi:10.13287/j.1001-9332.201806.002

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After grasslands were contracted to individual households on the Qinghai-Tibetan Pla-teau, two grassland management patterns were formed, i.e., the single-household management pattern (SMP) and the multi-household management pattern (MMP). The soil nutrients and their spatial distributions under those two patterns were compared in the Nagchu Prefecture of Tibet. The results showed that the soil organic carbon, total nitrogen, and total phosphorus under the MMP (84.31, 6.87 and 0.59 g·kg^-1) were all significantly higher than those under the SMP (73.57, 6.07 and 0.54 g·kg^-1). On the vertical dimension, the variation coefficient of soil total phosphorous between 0-15 cm layer and 15-30 cm layer under SMP had no significant difference, while that of soil pH, soil organic carbon and total nitrogen in 15-30 cm layer were all higher than 0-15 cm layer under both patterns. On the horizontal dimension, the variation coefficients of soil organic carbon and total nitrogen under SMP were significantly higher than those under MMP, with the estimated values for the former being 25.7% and 23.5%, and for the latter being 19.3% and 18.6%, respectively. Compared with the MMP, the uneven distribution of nutrients could easily lead to soil nutrient loss under the SMP.

Population spatial patterns of grassland plant communities in different slope aspects in the loess hilly area, China.

CHEN Zheng-xing, GAO De-xin, ZHANG Wei, HAN Xin-hui, ZHONG Ze-kun, QIAO Wen-jing, DAI Yin-yue, YANG Gai-he

2018, 29(6):  1846-1856.  doi:10.13287/j.1001-9332.201806.001

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We investigated the species composition and diversity of four grassland communities with different slope aspects in the loess hilly area of China. The power law was used to analyze spatial heterogeneity of the community and spatial pattern of the population. The results showed that Artemisia sacrorum was the dominant species and occurred in each site. Other species had different status and contributed differently to the spatial pattern of communities. Moreover, the spatial patterns of communities responded differently to various slope aspects, with the degree of aggregation ranked as sunny > half-sunny > half-shady > shady. The spatial heterogeneity index of community was positively correlated with the Simpson diversity index, but was negatively correlated with Margalef richness, Shannon diversity and Pielou evenness. The relative spatial heterogeneity index of the dominant species (A. sacrorum), sub-dominant species (Lespedeza dahurica and Stipa bungeana), and a few associated species (Artemisia scoparia, Melica scabrosa) were larger than that of the community, which resulted in cluster distribution. However, the relative spatial heterogeneity index of most associated species (Phragmites communis, Sonchus arvensis, and Bothriochloa flaccidum) showed the similar trends with the distribution of the community. In contrast, the relative spatial heterogeneity index of Cephalanoplos segetum, Gueldenstaedtia multiflora and Artemisia giraldii was lower than that of the community. These differences reduced the aggregation degree of the community. In summary, the aggregation degree of community was determined by dominant species, sub-dominant species and occasional species. Specifically, the dominant species, sub-dominant species and some associated species could promote the aggregation of the community, but occasional species would reduce the cluster distribution.

Effect of row spacing on physiological characteristics and yield of intercropped peanut with wheat.

LIU Zhao-xin, LIU Ting-ru, LIU Yan, YANG Jian-qun, ZHEN Xiao-yu, LI Xin-xin, YANG Dong-qing, LI Xiang-dong

2018, 29(6):  1851-1959.  doi:10.13287/j.1001-9332.201806.028

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Using two peanut varieties Shanhua108 (early-maturing variety) and 780-15 (late maturing variety), a field experiment was conducted to investigate the influences of row-spacing of wheat (25 cm, 30 cm, 40 cm+20 cm) and two peanut cropping patterns (intercropped peanut with wheat, summer-sowing peanut) on yield components, photosynthetic characteristics, antioxidant system, and dry matter accumulation and transportation. The results showed that wide spacing form of wheat and wide-narrow row planting pattern increased the pod yield, kernel yield, leaf area index, total dry matter accumulation and photosynthetic capacity, as well as SOD, POD and CAT activities, but decreased the MDA content. There are no obvious differences of wheat yield between the two row-spacing. Intercropping system increased peanut yield compared with summer-sowing peanut, which were much higher for wide-narrow row planting pattern than row spacing of 25 cm or 30 cm. The wide-narrow row planting pattern increased the pod yield and kernel yield by 6.3%, 13.3% and 7.7%, 16.5% for Shanhua108 and 780-15 than those of row spacing of 30 cm, respectively. Wide-narrow row planting could enlarge photosynthetic area, improve the net photosynthetic rate, and increase total dry matter accumulation. Meanwhile, it could alleviate the contradictionbetween the plant individual and group, delay the senescence, and increase peanut yield.

Effects of ultrasound on the germination and seedling growth of three aged forage seeds.

LIU Xu, CHEN Zhao, LIU Qian, GAO Ya-ni, ZHOU Wen-nan, CUI Xue-wen, WANG Quan-zhen

2018, 29(6):  1857-1866.  doi:10.13287/j.1001-9332.201806.008

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To examine the effects and physiological mechanisms of ultrasound treatment on the germination and seedling growth of naturally aged seeds, an [L₉(3⁴)] orthogonal matrix experiment was carried out, which included ultrasound time, ultrasound temperature, output power and seed soaking time with tall fescue Festuca arundinacea stored for one year and five years at room temperature, perennial ryegrass (Lolium perenne, stored for five years), and Russian wildrye (Psathyrostachys juncea, stored for six years) as test materials. The results showed that ultrasound temperature was the most important factor for the germination of aged seeds. The appropriate ultrasound treatment promoted germination percentage and significantly enhanced root and shoot length in aged seeds of tall fescue (stored for five years) and Russian wildrye. The positive effect of ultrasound was not significant on the germination of aged seeds of tall fescue (stored for one year) and perennial ryegrass, but was significant on the root length. Ultrasound treatment reinvigorated aged seeds by increasing superoxide dismutase (SOD) and peroxidase (POD) activities and reducing malondialdehyde (MDA) content. A regression model analysis was performed to determine the final optimal ultrasound condition for aged grass seeds that resulted in ultrasound time of 22 min, at 26 ℃, output power of 254.29 W and a seed soaking time of 2.89 h.

Carbon sequestration characteristics and regional differences of typical warm and tropical grasslands in Henan Province, China.

ZHAO Wei, LI Lin, WANG Yan-jie, LI Ya-ge, WANG Yan-fang, WANG Xin

2018, 29(6):  1867-1875.  doi:10.13287/j.1001-9332.201806.005

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In this study, we examined the vegetation and soil carbon density characteristics and carbon distribution differences of four typical grasslands in two climatic zones, including warm-tempe-rate tussock (WT), warm-temperate shrub tussock (WS), tropical tussock (TT), and tropical shrub tussock (TS) in Henan Province. The results showed that the average aboveground biomass of grasslands was significantly higher in Northwest Henan (327.4 g·m^-2) than that in South Henan (221.4 g·m^-2), whereas the average root biomass in Northwest Henan (1.58×10³ g·m^-2) was significantly lower than that in South Henan (1.94×10³ g·m^-2). The average aboveground carbon density of grasslands in Northwest and South Henan was 113.75 and 77.35 g C·m^-2, respectively. The aboveground carbon density of WT in Northwest Henan was higher than that of WS, though not statistically significant. The living biomass carbon density of TT was significantly lower than that of other grasslands in Southwest Henan. The average underground carbon density of grasslands in Northwest and South Henan were 6.35×10³ and 5.14×10³ g C·m^-2, respectively. In Northwest Henan, there was no difference between WT and WS for both the root and soil carbon density. In South Henan, the root carbon density of TS was significantly lower than other grasslands, while the soil carbon density of TT was significantly higher than other grasslands. The average carbon density of grassland ecosystem in Northwest and South Henan was 6.46×10³ and 5.22×10³ g C·m^-2, respectively. Soil was the main contributor of ecosystem carbon storage and accounted for about 78%-90% of total grassland ecosystem carbon density. In addition, there were no significant differences in the ecosystem carbon density between WT and WS in Northwest Henan, while TT possessed significantly higher ecosystem carbon density (9.70×10³ g C·m^-2) compared with other grasslands in Southern Henan. Our results provide basic data for accurately calculating ecosystem carbon storage and assessing carbon sequestration potential of different grasslands in Henan Province.

Spatial-temporal distribution of vegetation net primary productivity and its driving factors from 2000 to 2015 in Shaanxi, China.

WANG Zhao, LI Deng-ke

2018, 29(6):  1876-1884.  doi:10.13287/j.1001-9332.201806.029

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Using MOD17A3 NPP time series data, surface cover type data, weather data, MOD16 evapotranspiration products and terrain data, the temporal and spatial variability of vegetation net primary productivity (NPP) in Shaanxi Province from 2000 to 2015 was analyzed, and its response to each influencing factor were discussed. The results showed that the NPP of Shaanxi had a significant upward trend in the past 16 years with a slope of 5.02 g C·m^-2·a^-1. The annual average of NPP was 344 g C·m^-2·a^-1 with a range from 247 to 390 g C·m^-2·a^-1. The NPP at 61.2% area of Shaanxi Province showed a significant increasing trend, which were mainly distributed at northern part of Shaanxi, Weibei area and western part of Qinba Mountain. There was a decrease trend of NPP for the area around Xi’an and Baoji City, accounting for only 2.5% of the whole province. During the study period, the variation of annual mean temperature and annual precipitation in Shaanxi showed no significance. The temperature showed a increase trend and the precipitation showed a decrease trend, implying a drier and warmer climate trend in Shaanxi Province. The areas with significant correlation between NPP and precipitation and temperature accounted for 9.4% and 1.5% of the total area of the province. The frequent intervention of human activities reduced the impact of climate on the changes of NPP, so human activity had gradually become the dominant factor. NPP in northern Shaanxi and Guanzhong areas was significantly correlated with evapotranspiration. The increases of NPP in these areas would have great influence on the water and heat balance. The average NPP at different land cover was farmland > forestland > grassland > garden, increasing rate of NPP at different land cover was garden > grassland > forestland > farmland, and proportional changes of NPP was grassland > garden > forestland > farmland. The increasing percentage of NPP at three gradient ranges were 14.6% (0°-5°), 25.7% (5°-25°) and 35.9% (>25°), respectively.

Impacts of adaptive measures to climate changes on climatic potential productivity of maize in northeast China.

CHU Zheng, GUO Jian-ping

2018, 29(6):  1885-1892.  doi:10.13287/j.1001-9332.201806.013

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To understand how would the maize production in northeast China adapt to climate change, we adopted two strategies, inclduing using stress resistant varieties and delayed sowing date, combined with the daily meteorological data of RCP4.5 scenario and RCP8.5 scenario from 2010 to 2099 simulated by regional climatic model, to analyze the changes of climatic potential productivity of maize under different climate change scenarios. The results showed that in 2010-2099, the spatial characteristics of climatic potential productivity of maize in northeast China decreased from southeast to northwest. The climatic potential productivity of maize under RCP4.5 scenario was higher than that under RCP8.5 scenario, while years with the lowest values under RCP8.5 scenario was more than that under RCP4.5 scenario. The climatic potential productivity for stress resistant varieties of maize was higher than the original varieties. Under RCP4.5 scenario, the heat resistant variety had higher productivity. Under RCP8.5 scenario, the drought resistant variety performed better. The variety with both heat and drought resistance characters achieved the highest productivity under both scenarios. Under RCP4.5 scenario, yield increased with postponed sowing, with 30-40 days delay achieving the highest yield. Under RCP8.5 scenario, yield reduction occurred in some areas. Such a result indicated that the appropriate delay in sowing is conducive to improve the maize productivity, with differences among regions.

Spatial variability of nutrients and heavy metals in paddy field soils based on GIS and Geostatistics.

YANG Zhi-jiang, CHEN Xiao-min, JING Feng, GUO Bi-lin, LIN Gao-zhe

2018, 29(6):  1893-1901.  doi:10.13287/j.1001-9332.201806.036

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Based on a grid (25 m × 25 m) equidistant sampling, the spatial variability of pH, organic matter, total nitrogen, available phosphorus, CEC and three typical heavy metal elements Cd, As and Pb in soil tillage layer (0-20 cm) were analyzed by using GIS and Geostatistics in the paddy field of 3.56 hm² in Beishan Town, Changsha County, Hunan Province. The results showed that soil pH value and Pb content showed weak variation, and other indexes showed moderate variation. The order of variation was following available phosphorus ＞ Cd ＞ total nitrogen ＞ organic matter ＞ CEC ＞ As ＞ Pb ＞ pH. Results of the semi-variance test showed that the best fitting model of the semi-variance function of organic matter, available phosphorus and As was exponential, and the best semi-variance function of pH, total nitrogen, CEC, Cd, Pb was spherical. All the indicators had a strong spatial correlation except for CEC, which showed moderate spatial correlation. Kriging interpolation analysis showed that pH, total nitrogen, CEC, Pb were plaque distribution, while organic matter, available phosphorus, Cd and As were block and banded distribution. Vegetation, topography and human activities were the main factors driving the variation of soil nutrients and heavy metals in the study area. The correlation between soil nutrients and heavy metals content was significant, among which pH and organic matter, Cd and Pb reached a very significant correlation level.

Effects of Myospalax baileyi disturbance on plant community at alpine meadow in Three Rivers Headwater Region, China.

YU Hai-ling, FAN Jiang-wen, LI Yu-zhe, SHI Wen-jiao

2018, 29(6):  1902-1910.  doi:10.13287/j.1001-9332.201806.038

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Plateau zokor (Myospalax baileyi) is one of the major rodent species at the alpine meadow in Three Rivers Headwater Region. They eat plant roots, excavate many tunnels and deposit soil on the surface, which result in many exposed mounds to cover the aboveground part of plants. Here, taking plateau zokor mound density in a plot as their disturbance degree, we selected seven plots with different plateau zokor mound densities and one control plot which was not disturbed by plateau zokor to explore the effects of M. baileyi disturbance on community composition, species diversity and productivity. The results showed that, with the increases of available mound density, the dominant species were changed from Cyperaceae and Gramineae species to forb species, including Poly-gonum viviparum, Potentilla anserine, and Polygonum sibiricum. The community coverage and height were significantly decreased. Light or intermediate disturbance by plateau zokor improved species diversity, whereas the evenness index showed no significant change. The changes of community productivity did not support the ‘intermediate disturbance hypothesis’. With the increases of plateau zokor disturbance, the aboveground biomass, belowground biomass, total biomass of community significantly decreased. Our findings revealed the effects of plateau zokor’s activity on plant community at alpine meadow and presented important information for the management and restoration of degraded grassland and the sustainable utilization of grassland in Three Rivers Headwater Region.

Soil physical properties and its effects on wheat yield in typical dark loessial soil on Weibei Plateau, China.

HE Li-yan, DU Hao-hui, WANG Xu-dong

2018, 29(6):  1911-1918.  doi:10.13287/j.1001-9332.201806.022

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Based on the investigations of fertilizer application rates, wheat yield and soil properties (soil compaction) of dark loessial soil on Weibei Plateau in 2015, soil samples from 0-50 cm depth were collected in 61 winter wheat fields. The variability of soil compaction, bulk density, water-stable aggregates and their partial correlations with wheat yield and partial factor productivity were analyzed. The results showed that soil compaction and water-stable aggregates in 0-50 cm depth had weak variability, with the variation coefficients of 9.9% and 4.9%, respectively. Soil bulk density had moderate variability, with the variation coefficient of 27.5%. Wheat yield and fertilizer partial factor productivity were negatively correlated with soil compaction, which were more closely correlated in soil depths of 0-10 cm, 10-20 cm and 20-35 cm. Results from multiple regression showed that wheat yield was determined by soil compaction and organic matter. The improvement of soil organic matter and reduction of soil compaction in top soil (0-20 cm) and plough pan layer (20-35 cm) would be the key strategies to enhance wheat yield in dark loessial soil on Weibei Plateau.

The interactive effects of water and nitrogen addition on ammonia volatilization loss and yield of winter wheat.

WANG Lei, DONG Shu-ting, LIU Peng, ZHANG Ji-wang, ZHAO Bin, ZHENG Feng-xia

2018, 29(6):  1919-1927.  doi:10.13287/j.1001-9332.201806.026

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An experiment with winter wheat of Shimai 15 and treatments of two types of fertilizers (organic manure, M; urea, U), two amounts of nitrogen application (180 kg·hm^-2, M₁U₁; 90 kg·hm^-2, M₂U₂), two irrigation levels (500 mm, W₁; 250 mm, W₂) was carried out in the lysimeters in 2015-2017. The results showed that ammonia volatilization was substantial after fertilization and irrigation. The dynami of ammonia volatilization during two years was similar. The process of ammonia volatilization after fertilization lasted for seven days. In 2015-2016, the total amount of ammonia volatilization ranged from 13.36 to 46.04 kg·hm^-2, and the loss rate of ammonia nitrogen ranged from 8.9% to 41.1%. The total amount of ammonia volatilization in 2016-2017 ranged from 14.78 to 52.99 kg·hm^-2, and the ammonia nitrogen loss rate ranged from 9.2% to 45.8%. During the two years, the highest loss of ammonia volatiles occurred in W₂U₁, the highest loss rate of ammonia volatilization occurred in W₂U₂. Ammonia volatilization loss rate significantly decreased under appropriate water and nitrogen management. Ammonia loss under the application of urea was about 2-3 times of organic manure. The highest yield occurred in W₁M₁ during the two growing seasons. The type of fertilizer, the amount of irrigation and nitrogen applied interactively affected the yield of winter wheat. As for the increases of production, organic manure was better than urea. Under the experimental condition, the best treatment was irrigation amount of 500 mm and application of organic manure with about 180 kg·hm^-2 of N fertilizers, which could be applied in practice for wheat production in Huang-Huai-Hai region.

Effects of returning straw with nitrogen application on soil water and nutrient status, and yield of maize

HOU Xian-qing, WU Peng-nian, WANG Yan-li, LI Pei-fu, WANG Xi-na, LI Rong

2018, 29(6):  1928-1934.  doi:10.13287/j.1001-9332.201806.023

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The study focused on the problems of lean soil and low fertility in arid area of central Ningxia. To explore the optimum rate of nitrogen (N) fertilizer application under straw returning, taking the treatment with straw return and no nitrogen fertilization as control, we investigated the effects of three N application levels (150, 300, 450 kg·hm^-2) with return of total maize straw (9000 kg·hm^-2) on soil water and nutrient status and maize yield. The results showed that the soil water storage (0-100 cm) at 300 and 450 kg N·hm^-2 in middle and late growing period of maize was significantly increased by 10.1% and 9.0%. The enhancement of soil fertility was highest at 300 kg N·hm^-2, with significant increases of the contents of soil organic matter, total N, alkali-hydrolyzable-N, available P, and available K by 12.8%, 31.6%, 11.6%, 20.6% and 74.2%, respectively. The enhancement of maize grain yield was highest at 300 and 450 kg N·hm^-2, with the value being 32.1% and 23.7%, respectively. The net income at 300 and 450 kg·hm^-2 N was significantly increased by 31.8% and 16.8%, respectively. Our results showed that straw returning plus proper quantity of N fertilizer could improve soil water and fertilizer status and enhance maize yield and net income in arid area of central Ningxia. The treatment of straw returning with 300 kg·hm^-2 N was the best one.

Effects of plastic film mulching patterns on maize grain yield, water use efficiency, and soil water balance in the farming system with one film used two years.

XIE Jun-hong, ZHANG Ren-zhi, LI Ling-ling, CHAI Qiang, LUO Zhu-zhu, CAI Li-qun, QI Peng

2018, 29(6):  1935-1942.  doi:10.13287/j.1001-9332.201806.027

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The aim of this study was to develop cost-saving and efficiency-improving technologies in whole plastic mulching and double ridge-furrow maize in semi-arid region of Loess Plateau. The objective was to investigate soil water balance in farming system with one film used two years. A field experiment was conducted to investigate the effects of different mulching and tillage patterns under one film used two years conditions on the yield, economic benefits, and water use efficiency of maize. There are four treatments: Ridge-furrow planting with complete plastic film mulching, F₁M; flat-planting with complete plastic film mulching, F₂M; flat-planting with half plastic film mulching, F₃M; and flat-planting without mulching, F₄M, the control. The results showed that the F₁M and F₂M treatments had significant effects on the improvement of the production and efficiency compared with the control. The F₁M and F₂M treatments improved biomass by 32.8% and 32.9%, enhanced grain yield by 60.0% and 51.7%. Water use efficiency and rainfall use efficiency in F₁M and F₂M treatments were increased by 59.8%, 35.9% and 87.6%, 64.4%, respectively. Furthermore, gross output value and input-output ratio of F₁M and F₂M treatments under every new plastic film mulched pattern were enhanced by 51.0%, 41.2% and 15.1%, 16.2%, respectively. The production pattern on cost-saving and efficiency-increasing of the system on double ridge-furrow and flat planting with one film used two years, this pattern increased gross output value by 40.8%, 42.2%, and increased input-output ratio by 40.3%, 42.2%, respectively. Under the condition of low precipitation (606.5 mm), total water consumption of ridge-furrow and flat planting under the system of one film used within two years was 731.3 mm and 746.8 mm, the soil moisture deficit was 124.8 mm and 140.3 mm, with enhancement of 22.7% and 38.0%, respectively. The total water consumption of ridge-furrow and flat planting treatments was reduced by 28.6% and 30.0%, and the fallow efficiency was improved by 178.9% and 148.3%. In conclusion, whole plastic mulching with double ridge-furrow and flat planting farming system had positive effects on yield and water use efficiency in semi-arid region of Loess Plateau. Combined with the technology of one film used within two years, this cropping system could be cost saving and efficiency increasing. However, the water deficit under low water condition should be seriously considered in practice.

Effects of drought stress at different growth stages on photosynthetic efficiency and water consumption characteristics in sweet potato.

ZHANG Hai-yan, XIE Bei-tao, DUAN Wen-xue, DONG Shun-xu, WANG Bao-qing, ZHANG Li-ming, SHI Chun-yu

2018, 29(6):  1943-1850.  doi:10.13287/j.1001-9332.201806.024

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To investigate the effects of drought stress on the growth of sweet potato, photosynthesis, yield, and water consumption characteristics were investigated in field-grown sweet potato plants (Jishu 21, a drought-tolerant cultivar) at different growth stages in 2014-2015. There were five drought treatments, including the whole growth period (DS), the early stage of growth (rooting and branching period, DS₁), the middle stage of growth (storage root initiation period, DS₂), and the late stage of growth (storage root bulking period, DS₃), and a normal irrigation treatment (WW) as control. The results showed that sweet potato plants in DS significantly decreased in dry mass, biomass, and harvest index during two years. The biomass of sweet potato under DS, DS₁, DS₂ and DS₃ was decreased by 31.3%, 21.2%, 19.6% and 7.7%; the harvest index was decreased by 19.9%, 14.5%, 14.1% and 6.5%, and the dry mass was decreased by 45.3%, 33.1%, 31.3% and 14.2%, respectively. The leaf area index in DS, DS₁, DS₂ and DS₃ was decreased by 77.1%, 60.1%, 39.2% and 17.1% at 100 days after transplanting (DAT), and the net photosynthesis was decreased by 56.7%, 26.6%, 18.7% and 9.5% at 90 DAT, respectively. Plants under drought stress reduced diurnal evaporation, transpiration rate, water consumption, daily water consumption, and soil water use efficiency, but increased irrigation water use efficiency. Drought stress decreased leaf area index, P_n, biomass and the allocation of biomass to storage root, resulting in a significant reduction of yield. The early drought and the long stress duration had significant impacts on leaf area index, P_n, biomass and harvest index, leading to a greater reduction in yield and water use efficiency. Therefore, drought stress at the early growth stages of sweet potato should be avoided during cultivation.

Effects of consecutive application of composted sewage sludge on active organic nitrogen fractions in the sandy fluvo-aquic soil.

GUO Kang-li, ZHENG Jiang, JI Zheng-yu, LIU Xiao, ZHU Xing-juan, JIANG Hui-min, YANG Jun-cheng, ZHANG Jian-feng

2018, 29(6):  1960-1968.  doi:10.13287/j.1001-9332.201806.025

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A field experiment was conducted with sandy fluvo-aquic soil under wheat-maize rotation system during 2012 to 2016 in Henan Province, with four treatments: Chemical fertilizer (CK), composted sewage sludge (CS) 15 t·hm^-2(CS₁), 30 t·hm^-2(CS₂), 45 t·hm^-2(CS₃). We investigated the effects of CS on soil active organic nitrogen and its allocation ratio. Results showed that CS significantly enhanced soil water content, decreased soil pH, increased contents of soil organic carbon and total nitrogen (TN) and available nutrients. Soil TN was increased by 93.1%-284.3%. The CS₃ treatment significantly improved the content of light fraction organic nitrogen (LFON), particulate organic nitrogen (PON) and microbial biomass nitrogen (MBN). CS treatments promoted the allocation of PON/TN and MBN/TN. with an enhancement of 12.3% and 539.9% in the CS₂ treatment, respectively. The distributions of LFON/TN and DON/TN were decreased by 17.3%-40.1% and 38.5%-71.3%, respectively. The contribution of soil active organic nitrogen fractions to TN was: PON>LFON>DON>MBN. Results from the principal component analysis showed that organic nitrogen and their distribution had high load value in CS₂ and CS₃ treatments. Results from redundancy analysis showed that positive correlations existed between the soil physicochemistry, enzymatic activity and soil active organic nitrogen as well as their distribution. In summary, CS had positive impacts on soil organic matter, soil properties, and the formation of active organic nitrogen. The rates of 30 and 45 t·hm^-2 CS application had significant effects on soil fertility, which could be an effective way to improve sandy fluvo-aquic soil quality.

Food utilization and excretion mechanism of Cd in gypsy moth larvae fed on Cd-enriched Populus alba×P. berolinensis leaves

JIANG Dun, DI Gui-qiu, YAN Shan-chun

2018, 29(6):  1969-1974.  doi:10.13287/j.1001-9332.201806.039

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To investigate the eco-physiological responses of phytophagous insects to host plants exposed to heavy metal stress, the gypsy moth (Lymantria dispar) larvae were reared with leaves of Populus alba×P. berolinensis grown in Cd-contaminated soil to analyze their food utilization and mechanisms underlying Cd excretion. Our results showed that after feeding on Cd-stressed poplar leaves, Cd concentrations and contents in the 3rd-6th instar larvae were significantly higher than those in control. The Cd concentrations significantly decreased with the larval age, whereas it was reverse for Cd contents. Cd concentrations in the larval faces and exuvia were significantly higher than those in control. Food digestion/consumption rate and conversion rate of the 3rd-5th instar larvae in the Cd-treatment group were significantly higher and lower than those in the control, respectively. Food utilization rate of the Cd-stressed 3rd-4th instar larvae were not significantly different from that of the control larvae with the same age. In contrast, the Cd-stressed 5th instar larvae showed a significantly lower food utilization rate than the control. These results indicated that gypsy moth larvae could remove some Cd from their bodies through effective excretion (e.g. feces and exuvia), with the mature larvae being more effective than the juveniles. The increases of larval body mass seemed to have a “dilution effect” on its Cd concentration. Under Cd stress, the gypsy moth larvae might maintain a certain level of food utilization rate for growth and development via a modulation of food consumption/conversion rates, but Cd-stress would still reduce the larval food utilization rate when it was beyond a certain threshold.

Spatiotemporal dynamics and driving forces of soil bacterial communities on the dam of Shibahe copper mine tailings in Shanxi, China.

LI Cui, JING Ju-hui, LIU Jin-xian, CHAI Bao-feng

2018, 29(6):  1975-1982.  doi:10.13287/j.1001-9332.201806.040

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The maintaining mechanism of community diversity is the core of community ecology. The mine tailing is a good field for studying on the underlying mechanism of community diversity, as a kind of original bare land with heavy metal pollution, where the physicochemical characteristics of soil change with the restoration periods. We examined the driving forces for bacterial community diversity based on the investigation of edaphic factors, plant community, and bacterial communities in Shibahe copper mine tailing, Shanxi. The results showed that nutrient contents in soil increased with restoration periods. The seasonal dynamics of soil nutrient in different restoration time were different. Shannon diversity and richness of bacterial community showed an increasing trend, indicating community stability was improved with restoration. Influenced by plant community, the seasonal changes of those indices differed with restoration. Results from the RDA analysis showed that the diversity and structure of bacterial communities were determined by environmental factors (edaphic, plant and heavy metals). Results from the structure equation models further confirmed that soil nutrients (TC, TN, NO₃^--N, NO₂-N), plant community, and soil enzyme activities jointly drove bacterial community assembly on the copper mine tailings.

Analysis of chlorophyll and photosynthesis of a tomato chlorophyll-deficient mutant induced by EMS.

YANG Xiao-miao, WU Xin-liang, LIU Yu-feng, LI Tian-lai, QI Ming-fang

2018, 29(6):  1983-1989.  doi:10.13287/j.1001-9332.201806.021

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We analyzed the growth, leaf chlorophyll content, and photosynthetic parameters of a tomato leaf yellowing mutant (Y55) induced by ethyl methane sulfonate (EMS) from the cultivar “Heinz 1706” (WT). Results showed that the plant height, stem diameter, and fresh mass of Y55 significantly . The contents of chlorophyll a, chlorophyll b, carotenoid, total chlorophyll and the chlorophyll a/b ratio of the mutant were significantly lower than those of WT. The contents of all precursor materials of chlorophyll synthesis, especially porphyrinogen III and those involved in the chlorophyll biosynthesis pathway, were significantly lower in Y55 than those in WT. Moreover, the net photosynthesis (P_n), transpiration rate (T_r), intercellular CO₂ concentration (C_i), and conductance to H₂O (g_s) significantly in Y55. The maximum photosynthetic rate, CO₂ saturation and compensation point, and light saturation and compensation point. The F_v/F_m significantly, whereas the F_o significantly in Y55. The photosynthetic electron production and electron transport rates of PSII and PSI also significantly decreased. The total photosynthetic pigment molecules (N_o) and the minimum average lifetime of photosynthetic pigment molecules in the excited state (τ_min) significantly in Y55. All these results suggest that blocking the synthesis of porphyrinogen III ould decrease the chlorophyll content in the mutant Y55. Furthermore, the reduced amount of leaf pigment could affect photosynthesis in leaves and slow down the growth of mutant plants.

Construction of ecological security pattern in the agro-pastoral ecotone based on surface humid index: A case study of Hangjin Banner, Inner Mongolia Autonomous Region, China.

PENG Jian, JIA Jing-lei, HU Yi-na, TIAN Lu, LI Hui-lei

2018, 29(6):  1990-1998.  doi:10.13287/j.1001-9332.201806.015

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The construction of regional ecological security pattern can effectively protect regional ecological security and achieve regional sustainable development, which has become one of the key topics in landscape ecology. The construction of regional ecological security pattern is particularly important for the Inner Mongolia Plateau, which is characterized by relatively fragile ecological environment and single land cover type. Considering regional natural environment characteristics, five typical ecosystem services, such as food supply, carbon fixation and oxygen release, soil conservation, water yield and habitat conservation, were selected to assess the importance of natural habitats with Hangjin Banner of Inner Mongolia Autonomous Region as a case study area. Based on comprehensive consideration of single ecosystem service quality and landscape multi-functionality, ecological sources were identified. The basic ecological resistance surface based on the land cover was revised by the surface humid index. The minimum cumulative resistance model was used to identify the ecological corridors, to construct the ecological security pattern of Hangjin Banner. The results showed that the ecological source of Hangjin Banner was 6781.70 km², accounting for 35.9% of the whole area, which mainly located in the northern Hetao Plain and southern Ordos steppe zone. The total ecological corridor length of Hangjin Banner was 498.51 km, which was divided into two groups from north to south by Kubuqi Desert. Based on the arid and ecologically fragile characteristics in the agro-pastoral ecotone in northern China, this study constructed regional ecological security pattern to provide decision-making guidelines for local economic development and ecological conservation.

Effects of storage temperature and time on the contents of different nitrogen forms in fresh soil samples.

WU Yue, MA Hong-liang, PENG Yuan-zhen

2018, 29(6):  1999-2006.  doi:10.13287/j.1001-9332.201806.035

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Soil nitrogen forms and contents are of great importance in ecological studies. The storage methods of soil samples have great effects on the accuracy of determination of nitrogen contents. We aimed to select a reasonable storage method for soil samples with forest soil of Castanopsis faberi fore-st at Wanmulin Nature Reserve in Jian’ou City as an example. The contents of soil ammonium, nitrate, total nitrogen, soluble organic nitrogen, amino acid nitrogen and microbial biomass nitrogen were measured in soil samples under the storage conditions of different temperature (at 25, 4 and -20 ℃) and different times (0, 7 and 30 days). The nitrogen contents during the process of cultivating under the room temperature after being frozen were also measured. The results showed that the contents of all nitrogen forms except for amino acid nitrogen were increased in the soil samples that stored at the room temperature for seven days. There were no significant differences between the contents of all the tested nitrogen forms in the refrigerated or frozen samples and the fresh soil samples. The changes of nitrogen content in soil samples at refrigerated and frozen storage were more stable than those at room temperature storage. The low temperature storage could stimulate soil mineralization. Hence, after stored for 30 days, contents of all the tested nitrogen forms in the refri-gerated and frozen storage soil samples were significantly higher than those in the fresh samples except for the soluble organic nitrogen, whereas there was no significant difference between the refrigerated and frozen storage methods. Therefore, fresh samples should be promptly processed when taken back to the laboratory. If the samples needed to storage, it should not be stored more than half a month. If the samples need a longer storage time, it must be placed in lower temperature (at -40 or -80 ℃). Pre-incubation treatment was required when the low temperature storage soil sample was subjected to an experiment. In the process of pre-incubation, the contents of all the tested nitrogen form in soil samples gradually approached the level of fresh soil sample with the increases of incubation time except for that of nitrate which decreased firstly and then increased rapidly. After incubation for about one week, the nitrogen content of soil sample returned to the level that was close to that of the fresh soil. In combination with studies previously reported, soil samples collected from field and air dried samples needed a pre-incubation for 5-14 days, and the pre-incubation time for the cold storage sample should not be less than one week.

Difference analysis in estimating biomass conversion and expansion factors of masson pine in Fujian Province, China based on national forest inventory data: A comparison of three decision tree models of ensemble learning.

OU Qiang-xin, LI Hai-kui, LEI Xiang-dong, YANG Ying

2018, 29(6):  2007-2016.  doi:10.13287/j.1001-9332.201806.019

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Biomass conversion and expansion factors (BCEFs) are important parameters for estimating carbon storage in forest biomass. Clarifying the source of differences in estimating BCEFs could reduce uncertainties in forest biomass carbon estimation. The decision tree models of ensemble learning can be used to properly figure out the source of differences in estimating BCEFs. However, the comparison of different decision tree models for analyzing differences in estimating BCEFs has never been reported. In this study, three models [the boosted regression trees (BRT), random forest(RF), and Cubist] and data of 331 masson pine plots from the 8^th Chinese National Forest Inventory for Fujian Province were used to analyze the differences in estimating BCEFs (including above- and below-ground). The results showed that BCEFs were following right-skewed distribution, with the mean, minimum and maximum value being 0.69 t·m^-3, 0.67 t·m^-3 and 0.71 t·m^-3, respectively. All three models performed well in BCEFs prediction and fitting, and could explain more than 92.8% variations of BCEFs. All three models showed that average DBH and volume were the top two highest relative importance predictors. BCEFs decreased with the increases of average DBH and volume. Stand characteristics factors, such as average DBH, volume, average age and average height, had great influence on BCEFs. Both soil factors and topographic factors had little influence on BCEFs. Using a few variables (such as average DBH, volume, average age and avera-ge height) which contained more BCEFs prediction information could have preferable forecasting precision when building BCEFs models. Moreover, widely representative samples with different average tree ages, average DBH and volume should be chosen to calculate BCEFs when applying constant BCEFs.

Parameter estimation and verification of DSSAT-CROPGRO-Tomato model under different irrigation levels in greenhouse.

ZHAO Zi-long, LI Bo, FENG Xue, YAO Ming-ze, XIE Ying, XING Jing-wei, LI Chang-xin

2018, 29(6):  2017-2027.  doi:10.13287/j.1001-9332.201806.012

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Based on the greenhouse experiment in Shenyang, the growth, development, and yield formation of tomato under different irrigation levels were simulated by growth model DSSAT-CROPGRO-Tomato. The optimal scheme of parameter estimation and model validation was determined. There were four treatments in this experiment. Irrigation upper limit of whole growth season was set as field capacity, while the lower limit was 50% (W₁), 60% (W₂), 70% (W₃), and 80% of field capacity (CK), respectively. The relevant genetic coefficients were estimated by DSSAT-GLUE, a program package for parameter estimation in DSSAT. The differences between simulated and observed values of phenological phase, canopy height, shoot dry matter, tomato fresh mass, leaf area index (LAI), and soil moisture were analyzed to determine the accuracy of simulation. The results showed that the estimated value of genetic parameter of tomato (thermal time for final pod load appeared greater variability under optimal genetic coefficient of tomato, PODUR) had large variability, with the coefficient of variation being 11.5%. When the CROPGRO-Tomato model was applied to the greenhouse in different regions, the PODUR should be estimated adequately. Otherwise, the accuracy of simulation would be affected. In the process of model application, the observation data of sufficient irrigation treatment should be selected for estimating genetic parameters, which could improve the simulation precision. The absolute relative error and standard root mean square error were 8.7% and 10.5%, respectively. The simulation results of LAI and soil moisture showed that the higher the irrigation level was, the higher accuracy of simulation was. By leave-one-out cross validation, the overall error validation ranged from 10.5% to 12.5%. Our results indicated that the growth, development, and yield formation of tomato could be accurately simulated by DSSAT CROPGRO-Tomato model under different irrigation conditions in Shenyang greenhouse.

The effects of climate change on isoprene emission rate from leaves of Pleioblastus amarus in different regions.

XU Tian-ying, WU Jian-guo, WANG Li

2018, 29(6):  2028-2042.  doi:10.13287/j.1001-9332.201806.031

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Based on the RCP2.6, RCP4.5, RCP6.0 and RCP8.5 climate change scenarios produced by the global climate model NorESM1-M and plant isoprene emissions model, the effects of climate change on the isoprene emission rate from leaves of Pleioblastus amarus in Yixing City of Jiangsu Province, Longmen County of Guangdong Province, Yulong Naxi Autonomous County of Yunnan Province and Wanyuan City of Sichuan Province were simulated. The differences of isoprene emission rate from leaves of P. amarus distributed in four regions were compared under future climate change scenarios. The results showed that mean annual air temperature would increase, annual precipitation and radiation intensity would greatly fluctuate, with the coexistence of increasing and decreasing trends in the four regions. In the baseline scenario, daily mean emission rate of isoprene from leaves of P. amarus was 71-470 μg·g^-1·d^-1, and annual mean value was 25954-171231 μg·g^-1·a^-1. The daily and annual emission rates in the four regions decreased with the order of Longmen, Yixing, Wanyuan and Yulong. Compared with the baseline scenario, daily mean emission rate of isoprene from leaves of P. amarus was about 4-45 μg·g^-1·d^-1 higher in future climate change scenario, and which was about 23, 29, 4, and 14 μg·g^-1·d^-1 higher than that in baseline in Yixing, Longmen, Yulong and Wanyuan, respectively. In addition, the emission rate of isoprene from leaves of P. amarus was more than 5% higher in the future climate change scenario than that in the baseline scenario, which was higher in Wanyuan and Yixing (>13%) than and lower in Longmen and Yulong (>5%). All the four regions reached the highest rate under RCP8.5 scenario (increased by about 11%-18%). Compared with the baseline scenario, annual emission rate of isoprene in the future climate change scenario was about 1500-17000 μg·g^-1·a^-1, and which was about 8560-13208 μg·g^-1·a^-1 higher in Yixing, 10862-16131 μg·g^-1·a^-1 higher in Longmen, 1574-3028 μg·g^-1·a^-1 higher in Yulong, 5288-8532 μg·g^-1·a^-1 higher in Wanyuan. In addition, the increasing rate of annual isoprene emission rates was 6%-14%. The rates in Yixing (8%-12%) and Wanyuan (8%-14%) were higher than that in the other two regions, the rate in Yulong (6%-12% increase) was the lowest, with all four regions increasing substantially (9%-14%) under RCP8.5 scenario. The results suggested that climate change would have different effects on the rate of isoprene emissions from leaves of P. amarus distributed in diffe-rent regions.

Distribution characteristics of dissolved inorganic carbon in soil of typical estuarine wetlands in Jiaozhou Bay, China.

WANG Xiao-tong, KONG Fan-long, XI Min, LI Yue, SUI Xiao-min

2018, 29(6):  2043-2050.  doi:10.13287/j.1001-9332.201806.037

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We examined the dissolved inorganic carbon (DIC) content, ion content, and soil physi-cal and chemical properties in Dagu River and Yanghe River estuary wetland of Jiaozhou Bay. Soil samples were collected by stratified sampling in the mudflat paralleled to the coastal zone and the river flat perpendicular to the coastal zone. Duncan method and Pearson correlation analysis were used to investigate the characteristics of soil DIC distribution and its driving factors. The results showed that the scouring action of water bodies led to the lowest content of soil DIC in the river estuary of mudflat, which showed an increasing trend with the increases of distance from the estuary. In river flat, the soil DIC content first decreased and then increased with the distance from the sea, which was influenced by human activities. Invasion of Spartina alterniflora significantly decreased soil DIC content, with its root transformation being the main reason for such decreases. The farming activities changed the environmental factors of aquaculture pond, and then changed the distribution of soil DIC. The surface soil of the pond had higher DIC content than that of the mudflat, while the other soil layers had lower DIC content than that of the mudflat. Soil DIC content was significantly positively correlated with soil salt content and total inorganic carbon content, and negatively correlated with soil pH.

Suitability of various benthic biotic indices in assessing the coastal ecological quality in Fujian Province, China

WU Hai-yan, FU Shi-feng, CAI Xiao-qiong, CHEN Qing-hui

2018, 29(6):  2051-2058.  doi:10.13287/j.1001-9332.201806.032

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Three benthic biotic indices, AZTI marine biotic index (AMBI), benthic opportunistic polychaetes amphipods (BOPA), and benthic polychaetes amphipods (BPA), combined with Shannon diversity index (H) were applied in ecological quality status (EQS) assessment, to investigate their suitability at four bays and an estuary in Fujian Province. The results showed that there were substantial differences in the performance of these indices. There were only four sites with the same assessment grades using different indices, accounting for 8.7% of the applied sites. AMBI classified 76.1% of the sites as “Good”, while 89.1% of the sites were classified as “High” using BOPA. The assessment results of BPA and H showed obvious gradient changes. For the bay areas, all the BOPA, BPA and AMBI values had no significant correlation with dissolved inorganic phosphate (DIP) and dissolved inorganic nitrogen (DIN) concentrations, suggesting that these indices did not respond to eutrophication pressure. The H value was significantly and negatively correlated with DIN concentration. For the estuarine area, the three indices, i.e . BOPA, BPA and AMBI, had significantly positive correlations with DIN and DIP, and there was no clear spatial variation in the assessment grades of these indices with the distance toward sea. The results suggested that BOPA, BPA and AMBI would overestimate the EQS and would show no response to the eutrophication pressure in estuarine area. Similar to the result from the bay areas,H value in the estuary area was significantly and negatively correlated to DIN. Meanwhile, the assessment grades of the seven sections in the estuary tended to increase with the distance toward the sea. In summary, our results suggested that BOPA, BPA and AMBI would not be suitable for the EQS assessment for Fujian coastal area, while H would be more suitable as it could respond to the main anthropogenic pressures.

Effects of light intensity and photoperiod on the embryonic development of Sepia pharaonis.

ZHOU Shuang-nan, LYU Teng-teng, CHEN Qi-cheng, PENG Rui-bing, HAN Qing-xi, JIANG Xia-min

2018, 29(6):  2059-2067.  doi:10.13287/j.1001-9332.201806.033

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We investigated the effects of lumination on hatching of fertilized eggs of Sepia pharaonis, to reveal the best light conditions for its embryonic development. A single-factor experiment was carried out to examine the effects of different light intensities (10, 30, 50, 70, 90 μmol·m^-2·s^-1) and different photoperiod L:D (24 h:0 h, 18 h:6 h, 12 h:12 h, 6 h:18 h, 0 h:24 h) on the embryonic development. The results showed that the effects of light intensity on the hatching rate, fractured yolk sac rate, incubation period, mass of newly hatched larvae and mantle length was significant. There was no significant effect on hatching period and survival rate after hatching 7 days. With the increases of light intensity, the hatching rate, incubation period, mass of newly hatched larvae and mantle length first increased and then decreased, while the fractured yolk sac rate gradually increased. The optimum light intensity was 30 μmol·m^-2·s^-1. Exposed to this light intensity, the hatching rate, fractured yolk sac rate, incubation period, hatching period, mass of newly hatched larvae, mantle length and survival rate after hatching 7 days were (90.0±4.1)%, (7.3±1.5)%, (25.50±0.35) d, (8.10±0.89) d, (0.213±0.011) g, (1.013±0.022) cm, (97.1±4.0)%, respectively. The effects of photoperiod on the hatching rate, incubation period, hatching period were significant, but there was no significant effect on fractured yolk sac rate, mass of newly hatched larvae, mantle length and survival rate after hatching 7 days. With the increases of illumination time, the hatching rate and hatching period first increased and then decreased. The optimum photoperiod was L:D (12 h:12 h). When exposed to this photoperiod environment, the hatching rate, fractured yolk sac rate, incubation period, hatching period, mass of newly hatched larvae, mantle length and survival rate after hatching 7 days were (88.7±1.8)%, (8.7±1.8)%, (25.00±0.50) d, (7.00±3.20) d, (0.209±0.005) g, (0.998±0.026) cm, (96.8±7.1)%, respectively. In conclusion, embryo hatchability of S. pharaonis preferred to low light intensity (30 μmol·m^-2·s^-1) and normal photoperiod L:D (12 h:12 h). In production practice, sunproof measures should be taken to keep the eggs in weak light condition.

Plant anti-herbivore defense priming: Concept, mechanisms and application.

WANG Jie, SONG Yuan-yuan, HU Lin, YANG Ming-yu, ZENG Ren-sen

2018, 29(6):  2068-2078.  doi:10.13287/j.1001-9332.201806.034

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Plant anti-herbivore defense priming refers to the increased readiness of anti-herbivore defense after the initial exposure to a series of biotic or abiotic factors. The primed plants can respond to herbivory more quickly and strongly and thereby show enhanced resistance to insect herbivory. It is a newly recognized strategy of plant defense against insect herbivores. Insect feeding, secretion, oviposition, herbivore-inducible plant volatiles (HIPVs), beneficial microorgani-sms, certain plant nutrient elements, heavy metals and some chemical compounds have been found to be able to prime plant defense. The defense priming is highly efficient, durable, environmental friendly, and even trans-generational. This review summarized current research progress on the plant anti-herbivore defense priming in recent years, and analyzed general characteristics, priming agents and potential mechanisms involved, and proposed the future development and the perspective of practical application in the field. Moreover, the unresolved questions and the research directions in this field were also discussed. Appropriate management of plant defense priming would minimize use of insecticide and serve as an important approach of integrated pest management.