Table of Content

18 April 2018, Volume 29 Issue 4

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Special Features of Hydrological Variability and Inconsistency

Gene method for inconsistent hydrological frequency calculation. I: Inheritance, variability and evolution principles of hydrological genes

XIE Ping, WU Zi-yi, ZHAO Jiang-yan, SANG Yan-fang, CHEN Jie

2018, 29(4):  1023-1032.  doi:10.13287/j.1001-9332.201804.017

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A stochastic hydrological process is influenced by both stochastic and deterministic factors. A hydrological time series contains not only pure random components reflecting its inheri-tance characteristics, but also deterministic components reflecting variability characteristics, such as jump, trend, period, and stochastic dependence. As a result, the stochastic hydrological process presents complicated evolution phenomena and rules. To better understand these complicated phenomena and rules, this study described the inheritance and variability characteristics of an inconsistent hydrological series from two aspects: stochastic process simulation and time series analysis. In addition, several frequency analysis approaches for inconsistent time series were compared to reveal the main problems in inconsistency study. Then, we proposed a new concept of hydrological genes origined from biological genes to describe the inconsistent hydrolocal processes. The hydrologi-cal genes were constructed using moments methods, such as general moments, weight function moments, probability weight moments and L-moments. Meanwhile, the five components, including jump, trend, periodic, dependence and pure random components, of a stochastic hydrological process were defined as five hydrological bases. With this method, the inheritance and variability of inconsistent hydrological time series were synthetically considered and the inheritance, variability and evolution principles were fully described. Our study would contribute to reveal the inheritance, variability and evolution principles in probability distribution of hydrological elements.

Gene method for inconsistent hydrological frequency calculation. Ⅱ: Diagnosis system of hydrological genes and method of hydrological moment genes with inconsistent characters

XIE Ping, ZHAO Jiang-yan, WU Zi-yi, SANG Yan-fang, CHEN Jie, LI Bin-bin, GU Hai-ting

2018, 29(4):  1033-1041.  doi:10.13287/j.1001-9332.201804.010

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The analysis of inconsistent hydrological series is one of the major problems that should be solved for engineering hydrological calculation in changing environment. In this study, the diffe-rences of non-consistency and non-stationarity were analyzed from the perspective of composition of hydrological series. The inconsistent hydrological phenomena were generalized into hydrological processes with inheritance, variability and evolution characteristics or regulations. Furthermore, the hydrological genes were identified following the theory of biological genes, while their inheritance bases and variability bases were determined based on composition of hydrological series under diffe-rent time scales. To identify and test the components of hydrological genes, we constructed a diagnosis system of hydrological genes. With the P-Ⅲ distribution as an example, we described the process of construction and expression of the moment genes to illustrate the inheritance, variability and evolution principles of hydrological genes. With the annual minimum 1-month runoff series of Yunjinghong station in Lancangjiang River basin as an example, we verified the feasibility and practicability of hydrological gene theory for the calculation of inconsistent hydrological frequency. The results showed that the method could be used to reveal the evolution of inconsistent hydrological series. Therefore, it provided a new research pathway for engineering hydrological calculation in changing environment and an essential reference for the assessment of water security.

Correlation coefficient-based principle and method for the classification of jump degree in hydrological time series

WU Zi-yi, XIE Ping, SANG Yan-fang, GU Hai-ting

2018, 29(4):  1042-1050.  doi:10.13287/j.1001-9332.201804.012

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The phenomenon of jump is one of the importantly external forms of hydrological variabi-lity under environmental changes, representing the adaption of hydrological nonlinear systems to the influence of external disturbances. Presently, the related studies mainly focus on the methods for identifying the jump positions and jump times in hydrological time series. In contrast, few studies have focused on the quantitative description and classification of jump degree in hydrological time series, which make it difficult to understand the environmental changes and evaluate its potential impacts. Here, we proposed a theatrically reliable and easy-to-apply method for the classification of jump degree in hydrological time series, using the correlation coefficient as a basic index. The statistical tests verified the accuracy, reasonability, and applicability of this method. The relationship between the correlation coefficient and the jump degree of series were described using mathematical equation by derivation. After that, several thresholds of correlation coefficients under different statistical significance levels were chosen, based on which the jump degree could be classified into five levels: no, weak, moderate, strong and very strong. Finally, our method was applied to five diffe-rent observed hydrological time series, with diverse geographic and hydrological conditions in China. The results of the classification of jump degrees in those series were closely accorded with their physically hydrological mechanisms, indicating the practicability of our method.

Hydrologic variability and sensitivity based on Hurst coefficient and Bartels statistic

LEI Xu, XIE Ping, WU Zi-yi, SANG Yan-fang, ZHAO Jiang-yan, LI Bin-bin

2018, 29(4):  1051-1060.  doi:10.13287/j.1001-9332.201804.009

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Due to the global climate change and frequent human activities in recent years, the pure stochastic components of hydrological sequence is mixed with one or several of the variation ingredients, including jump, trend, period and dependency. It is urgently needed to clarify which indices should be used to quantify the degree of their variability. In this study, we defined the hydrological variability based on Hurst coefficient and Bartels statistic, and used Monte Carlo statistical tests to test and analyze their sensitivity to different variants. When the hydrological sequence had jump or trend variation, both Hurst coefficient and Bartels statistic could reflect the variation, with the Hurst coefficient being more sensitive to weak jump or trend variation. When the sequence had period, only the Bartels statistic could detect the mutation of the sequence. When the sequence had a dependency, both the Hurst coefficient and the Bartels statistics could reflect the variation, with the latter could detect weaker dependent variations. For the four variations, both the Hurst variability and Bartels variability increased with the increases of variation range. Thus, they could be used to measure the variation intensity of the hydrological sequence. We analyzed the temperature series of different weather stations in the Lancang River basin. Results showed that the temperature of all stations showed the upward trend or jump, indicating that the entire basin had experienced warming in recent years and the temperature variability in the upper and lower reaches was much higher. This case study showed the practicability of the proposed method.

Comprehensive weighted recognition method for hydrological abrupt change: With the runoff series of Jiajiu hydrological station in Lancang River as an example

GU Hai-ting, XIE Ping, SANG Yan-fang, WU Zi-yi

2018, 29(4):  1061-1070.  doi:10.13287/j.1001-9332.201804.016

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Abrupt change is an important manifestation of hydrological process with dramatic variation in the context of global climate change, the accurate recognition of which has great significance to understand hydrological process changes and carry out the actual hydrological and water resources works. The traditional method is not reliable at both ends of the samples. The results of the methods are often inconsistent. In order to solve the problem, we proposed a comprehensive weighted recognition method for hydrological abrupt change based on weighting by comparing of 12 commonly used methods for testing change points. The reliability of the method was verified by Monte Carlo statistical test. The results showed that the efficiency of the 12 methods was influenced by the factors including coefficient of variation (Cv), deviation coefficient (Cs) before the change point, mean value difference coefficient, Cv difference coefficient and Cs difference coefficient, but with no significant relationship with the mean value of the sequence. Based on the performance of each method, the weight of each test method was given following the results from statistical test. The sliding rank sum test method and the sliding run test method had the highest weight, whereas the RS test method had the lowest weight. By this means, the change points with the largest comprehensive weight could be selected as the final result when the results of the different methods were inconsistent. This method was used to analyze the daily maximum sequence of Jiajiu station in the lower reaches of the Lancang River (1-day, 3-day, 5-day, 7-day and 1-month). The results showed that each sequence had obvious jump variation in 2004, which was in agreement with the physical causes of hydrological process change and water conservancy construction. The rationality and reliability of the proposed method was verified.

Stochastic characteristics of daily precipitation and its spatiotemporal difference over China based on information entropy

LI Xin-xin, SANG Yan-fang, XIE Ping, LIU Chang-ming

2018, 29(4):  1071-1078.  doi:10.13287/j.1001-9332.201804.013

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Daily precipitation process in China showed obvious randomness and spatiotemporal variation. It is important to accurately understand the influence of precipitation changes on control of flood and waterlogging disaster. Using the daily precipitation data measured at 520 stations in China during 1961-2013, we quantified the stochastic characteristics of daily precipitation over China based on the index of information entropy. Results showed that the randomness of daily precipitation in the southeast region were larger than that in the northwest region. Moreover, the spatial distribution of stochastic characteristics of precipitation was different at various grades. Stochastic characteri-stics of P₀(precipitation at 0.1-10 mm) was large, but the spatial variation was not obvious. The stochastic characteristics of P₁₀(precipitation at 10-25 mm) and P₂₅(precipitation at 25-50 mm) were the largest and their spatial difference was obvious. P₅₀(precipitation ≥50 mm) had the smallest stochastic characteristics and the most obviously spatial difference. Generally, the entropy values of precipitation obviously increased over the last five decades, indicating more significantly stochastic characteristics of precipitation (especially the obvious increase of heavy precipitation events) in most region over China under the scenarios of global climate change. Given that the spatial distribution and long-term trend of entropy values of daily precipitation could reflect thespatial distribution of stochastic characteristics of precipitation, our results could provide scientific basis for the control of flood and waterlogging disaster, the layout of agricultural planning, and the planning of ecological environment.

Synthetic duration curve method for the design of the lowest navigable water level with inconsistent characters in dry seasons

ZHAO Jiang-yan, XIE Ping, SANG Yan-fang, XU Qiang-qiang, WU Zi-yi

2018, 29(4):  1079-1088.  doi:10.13287/j.1001-9332.201804.014

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Under the influence of both global climate change and frequent human activities, the variability of second-moment in hydrological time series become obvious, indicating changes in the consistency of hydrological data samples. Therefore, the traditional hydrological series analysis methods, which only consider the variability of mean values, are not suitable for handling all hydrological non-consistency problems. Traditional synthetic duration curve methods for the design of the lowest navigable water level, based on the consistency of samples, would cause more risks to navigation, especially under low water level in dry seasons. Here, we detected both mean variation and variance variation using the hydrological variation diagnosis system. Furthermore, combing the principle of decomposition and composition of time series, we proposed the synthetic duration curve method for designing the lowest navigable water level with inconsistent characters in dry seasons. With the Yunjinghong Station in the Lancang River Basin as an example, we analyzed its designed water levels in the present, the distant past and the recent past, as well as the differences among three situations (i.e., considering second moment variation, only considering mean variation, not considering any variation). Results showed that variability of the second moment changed the trend of designed water levels alteration in the Yunjinghong Station. When considering the first two moments or just considering the mean variation, the difference ofdesigned water levels was as bigger as -1.11 m. When considering the first two moments or not, the difference of designed water levels was as bigger as -1.01 m. Our results indicated the strong effects of variance variation on the designed water levels, and highlighted the importance of the second moment variation analysis for the channel planning and design.

Correlation coefficient-based classification method of hydrological dependence variability: With auto-regression model as example

ZHAO Yu-xi, XIE Ping, SANG Yan-fang, WU Zi-yi

2018, 29(4):  1089-1097.  doi:10.13287/j.1001-9332.201804.015

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Hydrological process evaluation is temporal dependent. Hydrological time series including dependence components do not meet the data consistency assumption for hydrological computation. Both of those factors cause great difficulty for water researches. Given the existence of hydrological dependence variability, we proposed a correlationcoefficient-based method for significance evaluation of hydrological dependence based on auto-regression model. By calculating the correlation coefficient between the original series and its dependence component and selecting reasonable thresholds of correlation coefficient, this method divided significance degree of dependence into no variability, weak variability, mid variability, strong variability, and drastic variability. By deducing the relationship between correlation coefficient and auto-correlation coefficient in each order of series, we found that the correlation coefficient was mainly determined by the magnitude of auto-correlation coefficient from the 1 order to p order, which clarified the theoretical basis of this method. With the first-order and second-order auto-regression models as examples, the reasonability of the deduced formula was verified through Monte-Carlo experiments to classify the relationship between correlation coefficient and auto-correlation coefficient. This method was used to analyze three observed hydrological time series. The results indicated the coexistence of stochastic and dependence characteristics in hydrological process.

Reviews

Fitness of sexual reproduction of Toona ciliata var. pubescens natural populations and their sexual reproduction and regeneration

HUANG Hong-lan, ZHANG Lu, JIA Li-ming, LIANG Yue-long, CAI Jun-huo

2018, 29(4):  1098-1106.  doi:10.13287/j.1001-9332.201804.001

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To examine the reproduction fitness coefficients and individual-level fitness of Toona ciliata var. pubescens, their sexual reproduction and natural regeneration were investigated during 2006-2016, with four natural populations in Jiulianshan National Reserve as test objects. The results showed that there were only 2-10 trees for the natural populations of T. ciliata var. pubescens with a small initial number of fruiting plants (3-9 trees), which were from the initial fruiting plants or their first/second generation. The sexual reproduction of these isolated populations were significantly different, and their seed production capacities tended to decline over time. With the maturing of communities, soil seed banks and seed germinations were extremely poor, and the number of trees that could be growing to mature stage was nearly zero. The optimum maturity age of T. ciliata var. pubescens was about 40 a, and the fitness coefficients (2.0-2.8) rapidly increased in early development stage, but then was sharply reduced (0.3-0.5), and then gradually dropped to almost 0. There were significant differences in the fitness at individual level (0-14 tree·cm^-2) among different populations, but their values were low (close to zero). Based on the existing reproduction rate, the actual values of sexual reproduction and regeneration fitness were much lower than the predicted ones. Due to the low level of genetic fitness, the sexual reproductive ability of different populations all showed decreasing trends. The natural sexual regeneration ability tended to decline, while the fitness of T. ciliata var. pubescens further decreased. All those factors suggested higher investment risks. Therefore, the systems of sexual reproduction became unbalanced and deteriorating. We proposed that more studies, including breeding mating, pollination, seed setting, and genetic diversity evaluation, are needed. Moreover, we should provide suitable forest environment through cleaning up litter in the fruiting stage and applying appropriate thinning during the transition period from seedling to young tree growth.

Seasonal divergence in the responses of vegetation growth to PDO in Tibetan Plateau, China

SHI Fang-zhong, LI Xiao-yan, WU Xiu-chen, LIU Wen-ling, PEI Ting-ting, KONG Dong-dong, JIANG Zhi-yun, ZHANG Yu

2018, 29(4):  1107-1116.  doi:10.13287/j.1001-9332.201804.002

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Regional-scale normalized difference vegetation index (NDVI) derived from satellite remote sensing observations and gridded climate data were used to study the seasonal responses and underlying mechanisms of vegetation growth over Tibetan Plateau to Pacific Decadal Oscillation (PDO) at period of 1982-2015, by performing Spearman correlation analysis and enhanced multivariate regression model: structural equation model (SEM). The results showed that there was significant negative correlation between PDO index and mean growing-season (April-October) NDVI over Tibetan Plateau; however, marked seasonal divergence in the relationship between PDO and vegetation growth existed among different seasons. It characterized with stronger negative correlation between PDO and NDVI in autumn than in summer, and winter PDO had significant effect on consequent summer vegetation growth. Additionally, it showed great divergence in control processes of PDO on vegetation growth among different seasons, with significant control of PDO on both temperature and precipitation in summer, and significant control of PDO on temperature only in autumn.

Responses of sap flow to natural rainfall and continuous drought of tree species growing on bedrock outcrops

ZHANG Hui-ling, DING Ya-li, CHEN Hong-song, WANG Ke-lin, NIE Yun-peng

2018, 29(4):  1117-1124.  doi:10.13287/j.1001-9332.201804.021

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This study focused on bedrock outcrops, a very common habitat in karst region of southwest China. To reveal the responses of plant transpiration to natural rainfall and continuous drought, two tree species typical to this habitat, Radermachera sinica and Triadica rotundifolia, were selected as test materials. A rainout shelter was used to simulate continuous drought. The sap flow dynamics were monitored using the method of Granier’s thermal dissipation probe (TDP). Our results showed that sap flow density increased to different degrees after rain in different stages of the growing season. Sap flow density of the deciduous species T. rotundifolia was always higher than that of the semi-deciduous species R. sinica. After two months without rainfall input, both species exhibited no obvious decrease in sap flow density, indicating that rainfall was not the dominant source for their water uptake, at least in the short-term. Based on the regression relationships between sap flow density and meteorological factors before and after rainfall, as well as at different stages of continuous drought, we found that the dynamics of meteorological factors contributed little to plant transpiration. The basic transpiration characteristics of both species were not changed in the circumstance of natural rainfall and short-term continuous drought, which would be closely related to the special water storage environments of bedrock outcrops and the reliance on deep water sources by tree species.

Ecophysiological responses of Camellia japonica (Naidong) to different light and water conditions

LIU Cui-ju, GUO Xiao, WANG Kui-ling, LIU Qing-chao, SUN Ying-kun, JIANG Xin-qiang, LIU Qing-hua

2018, 29(4):  1125-1132.  doi:10.13287/j.1001-9332.201804.005

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Camellia japonica (Naidong), a Tertiary relict species with abundant morphological characteristics and special genetic characteristics, is the northernmost distributed population of C. japonica. The seedlings of Naidong were subjected to two light regimes (65%, 15% of full sunlight, respectively) and three water supply regimes (75%, 50% and 25% of field capacity, respectively). Our objectives were to reveal the ecophysiological responses of Naidong under different drought and shade conditions and to examine the four existing hypotheses explaining the responses of Naidong seedlings to the interactions of shade and drought. The results showed that 15% of full sunlight reduced the growth of seedlings. Compared with those under 65% of full sunlight condition, the net photosynthetic rate, transpiration rate and chlorophyll content of seedlings under 15% of full sunlight condition were decreased by 63.3%, 82.9% and 17.5%, respectively. In contrast, the specific leaf area, leaf water content and maximal quantum yield under 15% of full sunlight condition were enhanced by 60.3%, 8.3% and 6.4%, respectively. Drought limited the growth of seedlings,decreased their height and basal diameter. The net photosynthetic rate, transpiration rate and stomatal conductance of seedlings significantly decreased with the increases of drought stress, with their minimum values being 0.83 μmol·m^-2·s^-1, 0.30 μmol·m^-2·s^-1 and 11.56 mmol·m^-2·s^-1, respectively. With the increases of drought stress, the contents of peroxidase and catalase showed a general declining trend, but the contents of malondialdehyde and proline significantly increased. The treatment 15% of full sunlight alleviated the negative effects of drought on Naidong seedlings, which supported the above-ground facilitation hypothesis. Our results indicated that Naidong seedlings could respond and acclimate to environmental changes through various mechanisms, and the seedlings might normally grow under broad ranges of light and water stresses. In addition, providing ideal light and water conditions for the Naidong seedlings could facilitate its application in gardening.

Effects of gap and growth substrate on nitrogen and phosphorus contents of bryophytes in an alpine forest

TANG Guo-qing, WU Fu-zhong, YANG Wan-qin, WANG Zhuang, WANG Qin, LIANG Zi-yi, CHANG Chen-hui, LI Jun

2018, 29(4):  1133-1139.  doi:10.13287/j.1001-9332.201804.003

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Bryophyte plays an important role in nutrient enrichment and cycling in the forest ecosystems. The role of bryophyte in nitrogen (N) and phosphorus (P) cycles might be affected by forest regeneration and growth substrate. To understand the role of bryophyte in N and P cycling in the forest ecosystem, we measured the contents of N and P in the bryophytes that grew on different positions (gap center, gap edge, and closed canopy) and growth substrates (standing tree, fallen log, snag, large dead branch, stump and forest floor) in an alpine forest ecosystem. The results showed that the N content in the bryophyte on the forest floor was 3.12 mg·g^-1, which was significantly lower than those on other growth substrates. Although N content in the bryophyte on the snag reached up to 17.41 mg·g^-1, no significant differences of N contents in the bryophytes were observed among standing tree, fallen log, large dead branch and snag. The highest and lowest P contents was 1.09 mg·g^-1 in the bryophyte on the forest floor and 0.61 mg·g^-1 in the bryophytes on the snag, respectively. Furthermore, P content in the bryophyte on the forest floor was significantly higher than that on other growth substrates, but no significant differences of P contents in the bryophytes were detected among standing tree, fallen log, large dead branch and stump. The gap position significantly affected N and P contents in the bryophytes, with the N and P contents in the bryophytes on fallen log and large dead branch at gap center being significantly higher than those at the gap edge. The effects of coarse woody debris (CWD) on the N and P contents in the bryophyte depended on its types and decay classes, with their interaction having much stronger effects on N and P contents in the bryophytes. The N contents in the epiphytic bryophytes on fallen logs with V decay class were significantly higher than those with other decay classes. Similarly, the N contents in the epiphytic bryophytes on large dead branches with III decay class were significantly higher than those with other decay classes. Meanwhile, the P contents in the bryophytes on fallen logs with Ⅱ decay class were significantly higher than those with other decay classes. Moreover, the P contents in the epiphytic bryophytes on the snags with Ⅳ decay class were significantly higher than those with other decay classes. In conclusion, both forest gap regeneration and CWD decay process can affect the N and P contents in the bryophytes, and thereafter manipulate the nutrient cycles in the forest ecosystems.

Coupling mode of irrigation and shading for good quality and proper yield of Coffea arabica in dry-hot region

LIU Xiao-gang, LI Yi-lin, QI Yun-tao, CHENG Jin-huan, YANG Qi-liang, LIU Yan-wei

2018, 29(4):  1140-1146.  doi:10.13287/j.1001-9332.201804.004

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In a field experiment with three levels of irrigation, i.e., CI, DI₇₅ and DI₅₀(100%, 75% and 50% full irrigation) and four levels of shade, i.e., T₁₀₀, T₇₀, T₅₅ and T₄₀(100%, 70%, 55% and 40% natural radiation), the effects of irrigation and shading levels on growth, yield and quality of Coffea arabica were examined. The comprehensive benefit evaluation model was established under different irrigation and shading levels. The results showed that DI₇₅ treatment increased the contents of fat and chlorogenic acid in dry bean by 6.0% and 10.2%, DI₅₀ treatment significantly increased the content of caffeine of dry bean, but reduced water use efficiency. Compared with T₁₀₀, T₇₀ treatment increased the yield of dry bean and water use efficiency by 27.2% and 26.8%, respectively, and increased total sugar and chlorogenic acid content in dry bean by 6.3% and 5.5%. T₅₅ and T₄₀ treatments significantly reduced the yield of dry bean, water use efficiency, and the contents of caffeine and chlorogenic acid of dry bean. Compared with CIT₁₀₀, DI₇₅T₇₀ treatment increased dry bean yield and water use efficiency by 28.0% and 44.5%, and increased the contents of total sugar, protein, fat and chlorogenic acid of dry bean by 12.2%, 14.7%, 6.6% and 10.0%, respectively, but reduced the concentration of caffeine by 8.3%. The comprehensive benefit of yield and quality of DI₇₅T₇₀ treatment (75% full irrigation, 70% natural radiation) was the best, which could implement good quality and proper yield of C. arabica.

Effects of mulching management on biomass of Phyllostachys praecox and soil fertility

ZHAI Wan-lu, YANG Chuan-bao, ZHANG Xiao-ping, GAO Gui-bin, ZHONG Zhe-ke

2018, 29(4):  1147-1155.  doi:10.13287/j.1001-9332.201804.006

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We analyzed the dynamics of stand growth and soil nutrient availability during the degradation processes of Phyllostachys praecox plantation, taking the advantage of bamboo forest stands with different mulching ages (0, 3, 6, 9 and 12 a). The results showed the aboveground and belowground biomass of bamboo forest reached the maximum value when they were covered by three years, which was significantly increased by 14.6% and 146.6% compared with the control. The soil nutrient content was affected by the mulching age and soil layer. Soil nutrients gradually accumulated in upper layer. Soil organic carbon and total nitrogen content were increased with the increases of coverage years. The soil total phosphorus content at different soil layers showed a trend of decreasing first and then increasing. It was the lowest level in the surface layer (0-20 cm) and the bottom (40-60 cm) in 6 years, and the subsurface (20-40 cm) soil reached the lowest level in three years. The total potassium content kept increasing in 0-20 cm soil layer, but decreased during the first three years of mulching and then increased in 20-60 cm soil layer. The comprehensive index of soil fertility quality was greatly improved after nine years mulching, with fertility of subsurface soil being better than that of surface and bottom soils. There was no relationship between the soil fertility index and biomass of different organs in bamboo in the different mulching ages. In the subsurface, however, nitrogen content was negatively related to leaf biomass and potassium was negatively correlated with the biomass of leaves and whip roots. Our results indicated that excessive accumulation of soil nutrients seriously inhibited the propagation and biomass accumulation of P. praecox after long-term mulching management and a large amount of fertilizer, which further aggravated the degradation of bamboo plantation.

Prediction of the suitable distribution and responses to climate change of Elaeagnus mollis in Shanxi Province, China

ZHANG Yin-bo, GAO Chen-hong, QIN Hao

2018, 29(4):  1156-1162.  doi:10.13287/j.1001-9332.201804.011

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Understanding the responses of the habitats of endangered species to climate change is of great significance for biodiversity conservation and the maintenance of the integrity of ecosystem function. In this study, the potential suitable distribution habitats of Elaeagnus mollis in Shanxi Province was simulated by the maximum entropy model, based on 73 occurrence field records and 35 environmental factors under the current climate condition. Moreover, with the Fifth Assessment Report of Intergovernmental Panel on Climate Change, the dynamics of distribution pattern was analyzed for E. mollis under different climate scenarios. The results showed that the area under the receiver operating characteristic curve (AUC) value was 0.987, indicating that the data fitted the model very well and that the prediction was highly reliable. Results from the Jackknife test showed that the main environmental variables affecting the E. mollis distribution were the precipitation seasonality, the range of annual temperature, annual mean temperature, isothermality, annual precipitation, and pH of topsoil, with the cumulative contribution reaching 94.8%. At present, the potential suitable habitats of E. mollis are mainly located in two regions, the southern of Lyuliang Mountain and Zhongtiao Mountain in Shanxi Province. Under different climate scenarios, the total suitable area of E. mollis would shrink in 2070s. In RCP 2.6 the suitable area would firstly increase and then decrease, while in RCP 4.5 and RCP 8.5 it would response sensitively and first decrease and then increase. Its spatial distribution in two suitable regions would show divergent responses to climate change. The distribution in southern Lyuliang Mountain would fluctuate slightly in latitudinal direction, while that in Zhongtiao Mountain would migrate along elevation.

Seasonal dynamics of soil microbial community and enzyme activities in Hippophae rhamnoides plantation

LUO Rong, YANG Miao, YU Xuan, MA Zi-tong, HAO Ru-qian, YANG Lin

2018, 29(4):  1163-1169.  doi:10.13287/j.1001-9332.201804.035

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We investigated the effects of forest age and season on soil microbial community structure and enzyme activities in Hippophae rhamnoides plantation. The results showed that the amounts of total PLFAs, bacterial PLFAs, and fungal PLFAs increased with the increases of forest age. The highest values presented in mature plantation (CL). Soil enzyme activities showed the same trend as soil microbial communities. The total PLFAs, bacteria PLFAs, and fungal PLFAs exhibited significantly positive correlations with soil pH, total nitrogen, and available phosphorus. In conclusion, forest age and season has significant impacts on soil microbial community structure and enzyme activities. H. rhamnoides plantation is a suitable afforestation model, which would help improve soil fertility.

Dynamics and driving forces of main vegetation types in the Saihanba Nature Reserve, Hebei Province, China

WEI Shi-kai, FAN Shun-xiang, ZHANG Yu-zhen, HUANG Xuan-rui, ZHANG Zhi-dong

2018, 29(4):  1170-1178.  doi:10.13287/j.1001-9332.201804.008

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To explore the changes of vegetation landscape pattern and its driving mechanism in Saihanba Nature Reserve, we analyzed vegetation type changes from 1989 to 2013 and the driving factors using random forest and Logistic regression models in conjunction with land dynamic degree indicator, based on three Landsat TM imageries obtained in 1989, 2000 and 2013. The results showed that the proportion of shrubland was always small in this area from 1989 to 2013. During 1989-2013, the proportion of shrubland rapidly decreased and plantation area significantly increased, while the area of grassland and natural secondary forest slightly changed. Key driving factors for the vegetation dynamics were dependent on vegetation type and time. The change of each vegetation type from 1989 to 2000 was significantly influenced by social factors, i.e. distance to road and total investment of afforestation. Since the implementation of the Natural Forest Protection Project and establishment of Saihanba Nature Reserve, the role of natural factors including elevation and aspect gradually became more important during the 2000-2013. The vegetation landscape dynamics were primarily determined by social activities, while the distribution patterns of vegetation types were probably controlled by natural factors in the study area.

Environmental selection and dispersal limitation drive the assemblage of bacterial community in temperate forest soils

MA Zhuan-zhuan, QIAO Sha-sha, CAO Miao-wen, ZHOU Yong-na, LIU Jin-xian, JIA Tong, LI Cui, CHAI Bao-feng

2018, 29(4):  1179-1189.  doi:10.13287/j.1001-9332.201804.039

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Environmental selection and dispersal limitation are two basic processes underlying community assembly. The relative importance of those two processes differs across scales, community identities, and community types. The processes responsible for structuring microbial communities in soil of temperate subalpine forest are poorly understood. Here, we investigated the relationship between soil bacterial community structure and environmental factors, and quantified the relative role of edaphic factors, vegetation, and spatial variables in shaping the structure of six soil bacterial communities (LpMC1, LpMC2, PwMC, PmMC, PtMC, and BMC) in five forest types including Larix principis-rupprechtii, Picea wilsonii, Picea meyeri, Pinus tabulaeformis, and Betula platyphylla in Pangquangou Nature Reserve by using PCR-DGGE technology. Our results showed that the structure and biodiversity of bacterial communities were significantly different among six communities. The biodiversity of bacterial community were higher in LpMC2 and PtMC, lowest in PmMC, and highest in LpMC1. Soil environmental factors, such as pH, soil water content, total carbon, total nitrogen, soil organic matter, available phosphorous, and soil enzymes, were significantly correlated with biodiversity and structure of soil bacterial community. The beta diversity of bacterial communities were significantly correlated with geographic distance, indicating the influence of dispersal limitation on the structure of bacterial community. The order of driving force on the structure of bacterial community was edaphic factors (0.27), spatial factor (0.19) and vegetation (0.15) in six samples. Using regional soil microbes from 10 samples around reserve as source community, results from the microcosm experiments showed that the edaphic factors were the predominant driving factors (0.35) on structure of artificial dispersal bacterial community, while the high diversity of source microbial community affected the structure of microcosm soil. In summary, at local scale, environmental selection predominantly determined the structural and biodiversity of soil bacterial communities in temperate subalpine forest, while dispersal limitation played a significant role. Such a result indicated that deterministic processes and stochastic processes played important roles in shaping the structure of soil bacterial community at local scale, with the former having the leading role. The composition of dispersal soil bacteria community was source-dependent but also modulated by local environmental selection.

Effects of crude toxin from Alternaria alternata on the growth and physiological metabolism of chrysanthemum ‘Jinba’ seedlings

ZHANG Kai-kai, ZHAO Shuang, CHEN Hui-jie, Ni Jia-qi, JIANG Xiao-fan, CHEN Fa-di, FANG Wei-min

2018, 29(4):  1190-1196.  doi:10.13287/j.1001-9332.201804.040

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The chrysanthemum black spot caused by Alternaria alternata significantly reduced the quality and yield of chrysanthemum. The crude toxin secreted by A. alternata in the metabolic process have elopathic effects on plants, which is the main pathogenic factor for the occurrence of chrysanthemum black spot. The pathogenic fungi A. alternate was isolated from chrysanthemum black spot leaves, The effects of crude toxin on plant height, stem diameter, root length, resistant material content, membrane relative permeability, polyphenol oxidase (PPO), peroxidase (POD), phenylalanine ammonia-lyase (PAL) in different treatments of chrysanthemum ‘Jinba’ seedlings were investigated. The results showed that the crude toxin of A. alternata had an inhibition effect on plant height, stem diameter and root length. The toxin concentration was positively correlated with the inhibitory effect. 14 days after crude toxin treatment, plant height, stem diameter and root length were significantly inhibited, with an reduction of 28.9%, 21.4% and 23.3%, respectively. The cell membrane permeability of leaf increased with the toxin concentration. Under the same toxin concentration, the cell membrane permeability first increased and then decreased with the treatment duration. The contents of soluble protein, malondialdehyde (MDA) and proline in leaves were significantly increased after treatment with the toxin solution. The increases of PAL, POD and PPO were the most significant in 10 times A. alternatacrude toxin treatment. The pathogenicity of A. alternate crude toxin to the chrysanthemum ‘Jinba’ seedlings was mainly through inhibi-ting the normal growth of roots and stems, destructing the root cell membrane permeability and increasing the contents of MDA, normal soluble sugar and proline, and promoting the activities of PAL, POD, PPO in leaf tissues.

Effects of plastic film mulching and nitrogen application rate on net global warming potential in semiarid rain-fed maize cropland

LIU Jian-can, WANG Ze-lin, YUE Shan-chao, LI Shi-qing

2018, 29(4):  1197-1204.  doi:10.13287/j.1001-9332.201804.028

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A one-year field experiment was conducted to evaluate the effects of plastic film mulching (FM) and nitrogen application rates applied to rain-fed maize fields on net global warming potential (Net GWP) and greenhouse gas intensity (GHGI) at the Changwu Agricultural and Ecological Experimental Station. Both GWP and GHGI were affected by the plastic film mulching and nitrogen application rate. Under the FM treatment, maize yield ranged from 1643 to 16699 kg·hm^-2, the net GWP (CO₂-eq) ranged from 595 to 4376 kg·hm^-2·a^-1, and the GHGI (CO₂-eq) ranged from 213 to 358 kg·t^-1. The grain yield of maize, net GWP and GHGI for the UM (no mulching) treatment were 956 to 8821 kg·hm^-2, 342 to 4004 kg·hm^-2·a^-1 and 204 to 520 kg·t^-1, respectively. The results suggested that plastic film mulching could simultaneously improve grain yield and decrease GHGI in rain-fed cropland along with nitrogen fertilizer of 250 kg·hm^-2.

Effects of phosphorus application rates and depths on P utilization and loss risk in a maize-soybean intercropping system

ZHAO Wei, SONG Chun, ZHOU Pan, WANG Jia-yu, XU Feng, YE Fang, WANG Xiao-chun, YANG Wen-yu

2018, 29(4):  1205-1214.  doi:10.13287/j.1001-9332.201804.026

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In order to explore the advantage of intercropping on phosphorus (P) efficient utilization and the reduction of soil P loss, a field experiment in a maize-soybean intercropping system, which included three P application (P₂O₅) rates (CP: 168 kg·hm^-2; RP₁: 135 kg·hm^-2; RP₂: 101 kg·hm^-2) and three P application depths (D₁: applied in 5 cm depth; D₂: applied in 15 cm depth; D₃: 1/2 of P fertilizer applied in 5 cm depth and another 1/2 in 15 cm depth) was carried out to analyze the effects of P application rates and depth on crop aboveground biomass, grain yield, crop P uptake, soil total and available P contents, and soil P adsorption-desorption characteristics. Compared with control treatment, the aboveground biomass, grain yield, crop P uptake, soil total P, and available P content were increased significantly by P application, regardless of P rate and application depth. Under the same application depth, RP₁ had similar grain yield but higher crop P uptake compared with CP, and thus higher P apparent utilization efficiency. Under the same P application rate, the application depth of D₂ had the highest crop aboveground biomass, grain yield, P uptake, soil total P, and available P. According to the characteristic of soil P adsorption-desorption, the treatment with the rate of RP₁ and the depth of D₂ had the strongest soil P retention capacity, which had advantage in alleviating P loss. These results suggested that reducing application rate but increasing application depth of P fertilizer could improve P use efficiency and reduce soil P loss without sacrifice in crop production in maize-soybean relay intercropping system.

Effect of exogenous α-naphthaleneacetic acid on carbon metabolism of soybean under drought stress at flowering stage

XING Xing-hua, XU Ze-jun, QI Yu-jun, WANG Xiao-jun, SUN Dong-lei, BIAN Neng-fei, WANG Xing

2018, 29(4):  1215-1224.  doi:10.13287/j.1001-9332.201804.022

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With pot experiment, two soybean (Glycine max) varieties, Jindou 21 (drought-tole-rant) and Xudou 22 (drought-sensitive), were used to examine the effects of α-naphthaleneacetic acid (NAA) on carbon metabolism of soybean under drought stress at flowering stage. The results showed that under drought stress, compared to Xudou 22, Jindou 21 had smaller decrease in net photosynthetic rate (P_n), smaller increase in photorespiration rate (P_r) and soluble sugar content of leaves, while a greater increase in the activities of sucrose phosphate synthase (SPS) and sucrose synthetase (SS) (synthesis) of leaves and sucrose content of roots. NAA treatment increased P_n and decreased P_r under drought stress, and thus obviously alleviated the growth inhibition of drought stress on plants. NAA treatment reduced the activities of starch-degrading enzymes, acid invertase (AI) and SS (cleavage), thereby inhibited the accumulation of soluble sugar induced by drought stress. In addition, NAA treatment increased SPS and SS (synthesis) activities of leaves, sucrose content of roots and shoot-root ratio, indicating that NAA treatment improved the transportation of sucrose from leaf blade to root under drought stress. In conclusion, exogenous NAA could enhance drought tolerance in soybean by regulating carbon metabolism.

The inversion of nitrogen balance index in typical growth period of soybean based on high definition digital image and hyperspectral data on unmanned aerial vehicles

LI Chang-chun, CHEN Peng, LU Guo-zheng, MA Chun-yan, MA Xiao-xiao, WANG Shuang-ting

2018, 29(4):  1225-1232.  doi:10.13287/j.1001-9332.201804.020

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Nitrogen balance index (NBI) is one of the important indicators for crop growth. The high and low status of nitrogen can be quickly monitored by measuring NBI, which can provide accurate information of agricultural production and management. The relationship between NBI and original spectrum and derivative spectrum of infrared and near infrared wavelength from flowering to maturity stage was analyzed based on high definition digital image and hyperspectral data on unmanned aerial vehicles. Then, the sensitive bands were selected and the vegetation indexes were calculated. The inversion models of NBI were constructed by empirical model method. The optimal inversion model was obtained by analysing the determination coefficient (R²) and the root mean square error (RMSE) of validating model. The results showed that the correlation between NBI and derivative spectral reflectance was more stronger than that between it and original spectral reflectance. All the 14 vegetation indices selected in this study, except the derivative spectral photochemical reflectance index, had significant correlation with NBI. The NBI inversion models were constructed based on those 13 vegetation indices and the accuracy was analyzed. The inversion model constructed by derivative spectral difference vegetation index had the highest accuracy, with the R² and RMSE being 0.771 and 3.077 respectively. The soybean NBI distribution maps of the whole growing stages generated by this model could reflect the soybean growth state. Estimation of NBI using the high definition digital image and hyperspectral data obtained by unmanned aerial vehicle, as shown by our results, could be a real-time, dynamic, non-destructive and effective way to monitor the nitrogen status of soybean. It’s a simple and practical method for precise management of nitrogen in soybean.

Effects of irrigation regimes on photosynthesis, water use efficiency and grain yield in winter wheat

MA Fu-ju, YANG Cheng, ZHANG De-qi, YUE Jun-qin, WANG Han-fang, SHAO Yun-hui, FANG Bao-ting, LI Xiang-dong

2018, 29(4):  1233-1239.  doi:10.13287/j.1001-9332.201804.030

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The effects of different irrigation regimes on photosynthesis, plant growth, water use efficiency (WUE), and grain yield in winter wheat were examined in a common garden with rainout shelter during 2013-2014 and 2014-2015 growing seasons. The experiment consisted of two irrigation timings, jointing stage (J) and anthesis (F), and three irrigation levels, 0, 37.5 and 75 mm, which generated nine irrigation combinations, i.e. J₀F₀, J₀F₁, J₀F₂, J₁F₀, J₁F₁, J₁F₂, J₂F₀, J₂F₁ and J₂F₂. All plots received 75 mm irrigation at grain filling stage. The results showed that water stress at jointing stage significantly reduced leaf area after jointing stage and the net photosynthetic rate (P_n) at anthesis. Post-anthesis flag leaf P_n was significantly affected by irrigation at anthesis. Water stress at jointing stage followed irrigation at anthesis or that at anthesis followed irrigation at grain filling stage increased dry matter accumulation of wheat plants. Higher amount of irrigation at jointing stage led to higher water consumption in the entire growing period. High amount of irrigation during the entire growing period resulted in high water consumption and grain yield with an exception of J₁F₂ treatment. Among all the treatments, the J₁F₂ treatment had superior grain yield and WUE. Sufficient water supply at anthesis resulted in high flag leaf P_n after flowering in J₁F₂. Irrigation at anthesis for J₁F₂ enhanced wheat dry matter accumulation and kernel numbers per spike, and consequently high yield. Small amount of irrigation at jointing stage reduced wheat water consumption at middle and late growth stages. The wheat WUE in treatments with small amount of irrigation at jointing stage (J₁F₂) was higher than in other treatments. In this study, J₁F₂ was the best irrigation regime for winter wheat.

Effects of combined application of chemical fertilizer and organic manure on wheat yield and leaching of residual nitrate-N in dryland soil

MA Chen, LIU Yan-ni, LIANG Lu, ZHAI Bing-nian, ZHANG Hao-qing, WANG Zhao-hui

2018, 29(4):  1240-1248.  doi:10.13287/j.1001-9332.201804.023

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The effects of optimum nitrogen (N) fertilization rate with and without adding manure on wheat yield and leaching of residual nitrate-N in soil profile were examined in Weibei dryland, Shaanxi with a field experiment combined different N fertilization rates (0, 75, 150, 225, 300 kg N·hm^-2) and organic manure (0 and 30 t·hm^-2). The results showed that, compared to chemical N fertilizer, combined application of inorganic fertilizer and organic manure increased winter wheat yield by 14.7% when N fertilization rate was reduced by 27.1%. The highest yield was obtained when 150 kg·hm^-2 of N rate was combined with the manure (N₁₅₀+M). The combination of N fertilizer and manure promoted N uptake of wheat grain and increased N use efficiency by 20.2%. The highest N use efficiency was recorded in the N₁₅₀+M treatment. In addition, the lea-ching of residual nitrate-N during the wheat growing season and the leaching of nitrate-N during summer fallow were decreased. When N application rate was lower than 115 kg·hm^-2, N fertilizer combined with organic manure reduced the amount of nitrate-N leaching in summer fallow. We recommend the combined application of organic manure with about 150 kg·hm^-2 of N fertilizers in Weibei dryland to guarantee high winter wheat yield, N use efficiency, and reduce excessive residue of fertilizer N in the soil.

Soil moisture variation under different water and fertilization managements in apple orchard of Weibei dryland, China

ZHAO Zhi-yuan, ZHENG Wei, LIU jie, MA Peng-yi, LI Zi-yan, ZHAI Bing-nian, WANG Zhao-hui

2018, 29(4):  1249-1258.  doi:10.13287/j.1001-9332.201804.027

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To evaluate the variations of soil moisture under different water and fertilizer treatments in apple orchard in the Weibei dryland, a field experiment was carried out in 2013-2016 at Tianjiawa Village, Baishui County, Shaanxi Province. There were three treatments, i.e., farmers traditional model (only addition of NPK chemical fertilizer, FM), extension model (swine manure and NPK chemical fertilizer combined with black plastic film in tree row space, EM), and optimized model (swine manure and NPK chemical fertilizer combined with black plastic film in tree row space and planting rape in the inter-row of apple trees, OM). The results showed that OM treatment significantly increased soil water storage capacity in 0-200 cm soil layer. Water content of 0-100 cm soil layer was increased by 5.6% and 15.3% in the dry season compared with FM and EM treatment, respectively. Moreover, the soil water relative deficit index of OM was lower than that of EM in 200-300 cm soil layer. The rainfall infiltration in the dry year could reach 300 cm depth under OM. Meanwhile, OM stabilized soil water content and efficiently alleviated the desiccation in deep soil layer. Compared with FM and EM, the 4-year average yield of OM was increased by 36.6% and 22.5%, respectively. In summary, OM could increase water use efficiency through increasing the contents of available soil water and improving the soil water condition in shallow and deep layers, which help alleviate the soil deficit in deep layer and increase yield.

Nitrogen mineralization rate in different soil layers and its influence factors under plastic film mulched in Danjiangkou Reservoir area, China

YU Xing-xiu, XU Miao-miao, ZHAO Jin-hui, ZHANG Jia-peng, WANG Wei, GUO Ya-li, XIAO Juan-hua

2018, 29(4):  1259-1265.  doi:10.13287/j.1001-9332.201804.025

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The objective of this study was to investigate the rate of nitrogen mineralization in various soil layers (0-10, 10-20, and 20-30 cm) and its influencing factors under plastic film mulching ridge-furrow in a corn field of Wulongchi small watershed, Danjiangkou Reservoir Area. Results showed that the rate of soil ammonification decreased with soil depth during the entire maize growth period. The rate of nitrification in seedling, jointing, and heading stages decreased in the following order: 10-20 cm > 0-10 cm > 20-30 cm, while it increased with soil depth in maturation stage. The rate of soil nitrogen mineralization decreased with the increases in soil depth in the seedling, jointing and heading stages, whereas an opposite pattern was observed in maturation stage. Compared with non-filming, film mulching promoted the soil ammonification process in 0-10 cm and the soil nitrification and nitrogen mineralization processes in jointing, heading, and maturation stages in both 0-10 and 10-20 cm. However, the rates of soil nitrification and nitrogen mineralization under film mulching were much lower than those under non-filming in seedling stage. The stepwise regression analysis indicated that the main factors influencing soil nitrogen mineralization rate varied with soil depth. Soil moisture and total N content were the dominant controller for variation of soil nitrogen mineralization in 0-10 cm layer. Soil temperature, moisture, and total N content were dominant controller for that in 10-20 cm layer. Soil temperature drove the variation of soil nitrogen mineralization in 20-30 cm layer.

Effect of nitrogen and phosphorus addition on soil enzyme activities: A meta-analysis

FAN Zhen-zhen, WANG Xin, WANG Chao, BAI E

2018, 29(4):  1266-1272.  doi:10.13287/j.1001-9332.201804.024

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We conducted a meta-analysis to analyze the effects of nitrogen (N) and combined N and phosphorus (N+P) addition on soil enzyme activities, which being involved in soil carbon (C), N, and P cycles as well as oxidative processes. Nitrogen addition significantly increased the activities of soil C acquisition enzymes, N acquisition enzymes, and P acquisition enzymes by 6.9%, 5.6% and 10.7%, respectively, while the enhancement was much stronger under N+P treatment with 13.4%, 37.4% and 13.3%, respectively. In contrast, both N addition and N+P addition decreased the activities of oxidative enzymes by 6.1% and 0.4%, respectively. The effect sizes of N and N+P addition on soil enzyme activities varied with ecosystem types, N fertilizer types, N addition rates, and the duration of fertilization experiments. Our results suggested that the changes in soil microbes and their enzymes under increasing N deposition and P addition would have profound impacts on soil biogeochemical processes and functions.

Effects of biochar and sheep manure on rhizospheric soil microbial community in continuous ratooning tea orchards

LI Yan-chun, LI Zhao-wei, LIN Wei-wei, JIANG Yu-hang, WENG Bo-qi, LIN Wen-xiong

2018, 29(4):  1273-1282.  doi:10.13287/j.1001-9332.201804.036

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Long-term continuous ratooning of tea could lead to serious soil acidification, nutritional imbalance, and the deterioration of the rhizosphere micro-ecological environment. Understanding the effects of biochar and sheep manure on the growth of tea plants and the rhizosphere microbial community structure and function would provide theoretical basis to improve the soil micro-ecological environment of continuous ratooning tea orchards. Biolog technology combined with phospholipid fatty acid (PLFA) approaches were employed to quantify the effects of biochar (40 t·hm^-2) and sheep manure on the growth of 20 years continuous ratooning tea plants, soil chemical properties, and the soil microbial community structure and function. The results showed that after one year treatment, biochar and sheep manure both improved soil pH and nutrition, and significantly enhanced tea production. Compared with the routine fertilizer application (CK), the biochar and sheep manure treatments significantly increased the carbon metabolic activity (AWCD) and microorganism diversity in the rhizosphere soils, and increased the relative utilization of the carbon sources such as amines, carbohydrates, and polymers. The total PLFA concentrations in the biochar and sheep manure treatments were significantly increased by 20.9% and 47.5% than that in the routine fertilizers application. In addition, sheep manure treatment significantly decreased the saturated/monosaturated fatty acids In conclusion, biochar and sheep manure could alleviate soil acidification, enhance soil nutrition and the growth of tea plants. Both management strategies could increase the soil microbial activity and biomass, enhance the diversity, and improve the microbial community structure, which could be taken as effective measures to regulate the rhizosphere micro-environment of tea plants.

Effects of trampling disturbance on soil organic carbon fractions and mineralization potential of biological soil crusts in the Loess Plateau Region, China

YANG Xue-qin, XU Ming-xiang, ZHAO Yun-ge, GAO Li-qian, BAO Tian-li, REN Wei, YANG Qiao-yun

2018, 29(4):  1283-1290.  doi:10.13287/j.1001-9332.201804.032

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The experiment was conducted in the plots that had been enclosed for nearly 20 years in the hilly Loess Plateau region. The effects of trampling disturbance on the biological soil crust (biocrust) coverage, soil organic carbon (SOC), soil easily oxidizable carbon (SEOC), SOC mineralization amount and mineralization rate were investigated. The biocrust SOC mineralization potential after disturbance in different soil layers were simulated by a first-order kinetic equation. The results showed that the coverage of cyanobacteria biocrust and moss biocrust significantly decreased with the increases of disturbance intensity. Compared to no disturbance, the cyanobacteria coverage declined by 264%-339% and moss coverage declined by 46%-127%. Compared to no disturbance, SOC content in biocrust layer significantly decreased by 211%-300%. No significant difference was found among the five disturbance intensities. Disturbance increased SEOC content in biocrust layer, and the variation amounted to 1.5-3.4 g·kg^-1, with 30%, 40% and 50% distur-bance differed significantly to no disturbance. Disturbance significantly increased biocrust SOC mineralization cumulative amount. However, SOC mineralization rate did not show any significant change. The SOC mineralization cumulative amount under 40% disturbance intensity increased by 77% compared to that under no disturbance. Disturbance significantly increased SOC mineralization potential in biocrust layer, but with no influence in 0-2 cm and 2-5 cm soil layers. The 40% disturbance intensity significantly increased SOC mineralization potential by 4.7 g·kg^-1. The results of principal component analysis showed that SOC, SEOC, SMC and mineralization rate explained 76.7% of the variation of SOC mineralization potential in biocrust layer. Disturbance might be a main factor driving the increases of biocrust SOC mineralization potential in this area.

Comprehensive method for evaluating soil quality in cotton fields in Xinjiang, China

ZHENG Qi, WANG Hai-jiang, LYU Xin, DONG Tian-yu, SHI Xiao-yan, LIU Yue

2018, 29(4):  1291-1301.  doi:10.13287/j.1001-9332.201804.029

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To evaluate the soil quality in the main cotton growing regions of Xinjiang, 11 soil quality indices were measured in representative locations: Hami, Bole, Changji, Shihezi, Aksu, Kashgar and Kuitun. The indices included soil pH, salt, organic matter, total N, available P and available K for soil physicochemical properties, and Cr, Cu, Zn, As, and Pb for soil heavy metal pollution. Based on these indices, a comprehensive soil quality index (SQI) was developed to analyze the soil quality in the cotton fields of Xinjiang. The results showed that the soils in Xinjiang’s cotton fields were alkaline, with an average pH of 7.87. The soils were mildly saline, with an average salt content of 3.44 g·kg^-1. Soil organic matter and total N concentrations were generally low, whereas available P and available K concentrations were relatively high. Soil available P concentrations were significantly higher than that of the second national soil survey, whereas soil pH, salt content, organic matter, and total N were less. Soil available K was greater in some regions but lower in others compared with the second national soil survey. The average heavy metal concentrations were as follows: Cr, 45.88 mg·kg^-1; Cu, 40.66 mg·kg^-1; Zn, 68.30 mg·kg^-1; As, 12.88 mg·kg^-1; and Pb, 16.68 mg·kg^-1. These values were all below the national standards. However, the Cu, Zn, and As concentrations were greater than the background values in Xinjiang, indicating the accumulation of those elements in the soils. When the Nemerow comprehensive pollution index (PN) of heavy metals was less than 0.5, the comprehensive soil quality improved as the soil physicochemical properties improved. Soil organic matter, total N, Cu, Zn, As and Pb were the main variables affecting soil quality in the main cotton cropping regions of Xinjiang. The cotton growing areas in Xinjiang generally had medium soil quality. Changji and Kuitun had the highest SQI (0.52) whereas Aksu had the lowest value (0.31). Soil quality was generally highest in northern Xinjiang, followed by western area, and then southern area.

Simulation for balanced effect of soil and water resources on cultivated land in Naoli River Basin, Northeast China under the RCPs climate scene

ZHOU Hao, LEI Guo-ping, YANG Xue-xin, ZHAO Yu-hui, ZHANG Ji-xin

2018, 29(4):  1302-1312.  doi:10.13287/j.1001-9332.201804.019

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Under the scenarios of climate change, balancing the land and water resources is one of the key problems needed to be solved in land development. To reveal the water dynamics of the cultivated land in Naoli River Basin, we simulated the future scenarios by using the future land use simulation model based on Landsat Satellite images, the DEM data and the meteorological data. Results showed that the growth rate of cultivated land gradually decreased. It showed different changing characteristics in different time periods, which led to different balancing effect between land and water resources. In 1990, the water dynamics of the cultivated land resources was in good state, At the same time, the adjustment of crops structure caused the paddy fields increased dramatically. During 2002 to 2014, the cultivated land that in moderate and serious moisture shortage state increased slightly, the water deficit was deteriorating to a certain degree, and maintained sound development of water profit and loss situation gradually. By comparing the simulation accuracy with different spatial resolutions and time scales, we selected 200 m as the spatial resolution of the simulation, and simulated the land use status in 2038. The simulation results showed that the cultivated land’s water profit and loss degree in the river basin showed significant polarization characteristic, in that the water profit and loss degree of the cultivated land would be further intensified, the area with the higher grades of moisture profit and loss degree would distribute more centralized, and partially high evaluated grades for the moisture shortage would expand. It is needed to develop the cultivated land irrigation schemes and adjust the cultivated land in Naoli River Basin to balance soil and water resources.

Effects of different salinity levels on nitrification processes in sediments of Minjiang River Estuary, China

SUN Qi-yuan, LI Jia-bing, LAI Yue-ting, ZHANG Dang-yu, QIU Wen-kang, WU Chun-shan

2018, 29(4):  1313-1320.  doi:10.13287/j.1001-9332.201804.038

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Two estuary wetlands in Minjiang River, Shanyutan and Daoqingzhou, were selected as the research objects. Wetland sediments were collected to examine the effects of different salinity levels on nitrification processes in the wetland with a culture experiment. The results showed that the nitrification rate of sediment in Minjiang River estuary wetland was generally low. The highest nitrification rate of sediment in the Shanyutan wetland was 0.193 mg·kg^-1·d^-1, while that in the Daoqingzhou wetland did not exceed 0.050 mg·kg^-1·d^-1. In the low salinity level (5), the decrease of nitrification rate was attributed to the restraint of nitrifying bacteria activities. The nitrification rate slightly increased with the increases of salinity (10), but was still lower than the initial value. This would be owed to the fact that the inhibitory effect of salinity on the activities of aerobic bacteria was strengthened, which reduced the rate of NH₄⁺-N production, and thus resulted in a decrease of the contribution of aerobic ammonification bacteria to the apparent nitrification rate. There were regional variations in the responses of sediment nitrifying activity to salinity. In saltwater wetland (Shanyutan wetland), the adaptability of microbes in sediment to salinity was stronger, so that the nitrification activity in high salinity conditions was still higher. While in the freshwater wetland (Daoqingzhou wetland), the adaptability of the sediment to the salinity change was relatively lower, with a lower nitrification activity of the sediment in high salinity than in middle salinity. Acidic condition was the main reason for the low nitrification in the sediments of Minjiang estuary wetland. The nitrification rate and nitrification activity of the two wetlands increased first and then decreased with the duration of the culture experiment, which was driven by combined effects of initial NH₄⁺-N concentration, oxygen content and denitrifying.

Influences of municipal sludge applied in slope vegetation restoration on surface water environment

ZHEN Chen-guang, LENG Ping-sheng, LIU Li-juan, DOU De-quan, HU Zeng-hui

2018, 29(4):  1321-1327.  doi:10.13287/j.1001-9332.201804.018

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The application of municipal sludge in ecological restoration has a good prospect for avoiding the food chain of grain crops, but its influences on surface water environmental are unclear. The municipal sludge and construction waste were mixed with 1:1 (V/V) as growth media, which were covered over simulation coal gangue slopes. Eight native woody species were sowed in the mixed media. The plant growth and coverage, as well as conductivity, pH, the concentrations of nitrogen (N), phosphorus (P), potassium (K), heavy metal and polycyclic aromatic hydrocarbon (PAHs) of surface and underground runoff of the slopes in the growing season were investigated. The results showed that plants grew well on the mixed media. The average plant coverage reached 60%. The pH of the surface and underground runoff changed little and near to neutral. The conductivity, N, P, K, heavy metal and PAHs contents of the slope runoff were high. The N and P contents in the growing season were above the National Standards of Surface Water Quality (GB 3838-2002) V. The contents of heavy metal were the highest in July. The contents of As lied at the GB IV-V, whereas other heavy metal contents up to GB II-IV. With strong rain leaching in the summer as well as the absorption, degrading and fix effect of plant-soil system on chemical substrates, the conductivity and N, P, K, heavy metal and PAHs contents of the slope runoff significantly decreased. The contents of heavy metal in late stage of growing season arrived at GB Ⅱ-Ⅲ. The contents of PAHs reduced by about 50%. The direct application of municipal sludge in ecological restoration of coal gangue slope were beneficial to plant growth. The plant-soil system might gradually decrease the harmful substance concentrations in the growth media. The negative influences on surface water environment mainly came from eutrophication of N and P. Generally, the environmental safety is manageable.

Cadmium adsorption by biochar prepared from pyrolysis of silk waste at different temperatures

JI Hai-yang, WANG Yu-ying,LYU Hao-hao, LIU Yu-xue, YANG Rui-qin, YANG Sheng-mao

2018, 29(4):  1328-1338.  doi:10.13287/j.1001-9332.201804.034

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In this study, biochars (BC300, BC500 and BC700) were produced from silk waste through pyrolysis under oxygen-limited condition at 300, 500 and 700 ℃, respectively. The physicochemical properties of biochar were detected by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometer (XRD) and specific surface area analyzer. The Cd²⁺ adsorption capacities of biochars were investigated. Results showed that BET surface area, pH, and ash were increased with the increases of pyrolysis temperature. SEM images showed that the surfaces of biochars were rough and irregular. XRD and FT-IR results showed that all the silk waste biochars obtained at different temperatures contained calcite. pH had limited influence on the removal efficiency of biochar for Cd²⁺. Langmuir isotherm fitted the experimental data quite well. The Langmuir monolayer adsorption capacity of BC300, BC500, and BC700 were 25.61, 52.41, and 91.07 mg·g^-1, respectively. The adsorption of Cd²⁺ onto the biochars obeyed a pseudo second-order kinetic model, with the BC700 showing the best removal efficiency. Further-more, the effects of the ionic strength and coexisting cations on Cd²⁺ removal were investigated. The results showed that the removal of Cd²⁺ was decreased with the increases of NaCl. Among the coexisting cations, the removal of Cd²⁺ was decreased by Ca²⁺ and Mg²⁺, while K⁺ had limited effect on the removal of Cd²⁺. In conclusion, the biochar derived from silk waste pyrolysis is a potential attractive adsorbent for the removal of Cd²⁺ from water.

Feeding ecology of Conger myriaster and structure of the food webs in artificial reef zone, Laoshan Bay, China

LIU Hong-yan, SUN Tong-tong, ZENG Xiao-qi, ZHANG Pei-dong, LI Wen-tao, ZHANG Xiu-mei

2018, 29(4):  1339-1351.  doi:10.13287/j.1001-9332.201804.031

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Based on cage net and longline fishing surveys in Laoshan Bay, China, from April 2015 to January 2017, a total of 279 Conger myriaster stomach samples were analyzed to study their feeding ecology, including diet composition, feeding type, feeding grade, feeding intensity, trophic niche, and trophic level. The stomach content analysis of nine key fish species (including Sebastes schlegelii, Hexagrammos otakii, Hexagrammos agrammus, Sebastiscus mamoratus, Lateolabrax maculatus, etc.), were conducted to examine the food webs in artificial reef zone. The results showed that the diet of C. myriaster consisted of more than 30 species belonging to seven orders, in which shrimps were the most dominant prey species, followed by fishes and cephalopods. The dominant species in the diet of C. myriaster were H.otakii, Enedrias fangi, Trachypenaeus curvirostris, Ammodytes personatus and Alpheus japonicas. The diet composition of C. myriaster varied with season and anal length. Fishes and shrimps were the two important groups throughout the years. Cephalopods were predominant in spring. Cephalopods and crabs were predominant in Autumn. Fish eggs were eaten mostly during winter. Fish eggs and T. curvirostris were the dominant prey groups of the C. myriaster with anal length ≤120 mm, whereas A. personatus and A. japonicas were the dominant prey groups of the C. myriaster with anal length 120-130 mm, H.otakii and E.fangi were the dominant prey of the C. myriaster with anal length ＞130 mm. The percentage of empty stomach of C. myriaster varied significantly with season, but the mean stomach fullness index did not. The percentage of empty stomach and mean stomach fullness index did not differ significantly among different anal length groups. The trophic levels of the key fish species were higher than level 3, with C. myriaster at the top of food webs (with a trophic level of 4.636). Decapoda, crabs, amphipoda and molluscs were the main prey of key fish species, while Crustaceans, E. fangi, H. otakii and A. personatus were the main preys of L. maculatus and C. myriaster.

Distribution of Larimichthys polyactis and its relationship with environmental factors in offshore water of southern Zhejiang

DAI Li-bin, TIAN Si-quan, PENG Xin, GAO Chun-xia, YE Shen, DU Xiao-xue, LIUPan

2018, 29(4):  1352-1358.  doi:10.13287/j.1001-9332.201804.033

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Based on data collected from four trips of trawl surveys in offshore water of southern Zhejiang in 2015-2016, a generalized additive model was used to analyze the distribution of small yellow croaker (Larimichthys polyactis) and its relationship with environmental factors. The results showed that the highest resource abundance occurred in the summer trip, primarily in Yushan fishing ground with an average density of 500.74 kg·h^-1·km^-2. Environmental factors influencing the density and distribution of small yellow croaker changed with season. The effect of environmental factors on the resource density of small yellow croaker was not significant in autumn. In spring, the small yellow croaker mainly distributed in waters with high salinity, while both sea bottom temperature and salinity had negative correlation with resource density of small yellow croaker in summer, and the fish habited in Yushan waters with middle temperature and high salinity. In winter, water temperature had a positive relationship with resource density of small yellow croaker which primarily distributed in waters of outside stations with suitable temperature. Generally, the distribution characteristic of small yellow croaker accorded to its migration habit. It was hard to explain the relations between environmental factors and resource density of small yellow croaker, which needed to further study. The results are helpful for understanding the living behavior and the conservation and management of the small yellow croaker stock in offshore water of southern Zhejiang.

Effects of ibuprofen concentration on life table demography of Moina macrocopa under different densities of Scenedesmus obliquus

GU Jing, XI Yi-long, HU Xiao-yan, JIANG Hui

2018, 29(4):  1359-1366.  doi:10.13287/j.1001-9332.201804.037

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The cladoceran Moina macrocopa was used as test animal to investigate the effects of ibuprofen concentrations (0, 0.45, 0.9, 1.8, 3.6, 7.2 and 14.4 mg·L^-1) on its life table demographic parameters under low (0.5×10⁶ cells·mL^-1), medium (1.0×10⁶ cells·mL^-1), and high (2.0×10⁶ cells·mL^-1) densities of Scenedesmus obliquus. The results showed that at low and high food levels, ibuprofen concentration significantly affected the intrinsic rate of population increase and the life expectancy of M. macrocopa, respectively. At all the three food levels, however, ibuprofen concentration did not significantly affect the generation time, net and gross reproduction rate of M. macrocopa. Compared with the controls, the intrinsic rate of population increase of M. macrocopaexposed to ibuprofen at 0.45, 0.9, 3.6 and 14.4 mg·L^-1 was significantly decreased at low food level. At high food level, the life expectancy at hatching of M. macrocopa exposed to ibuprofen at 3.6 and 14.4 mg·L^-1 was significantly increased. The results indicated that at low food level, certain concentrations of ibuprofen had negative effect on the population growth of M. macrocopa, which disappeared at medium and high food levels. At high food level, ibuprofen had positive effect on the survival of M. macrocopa, which disappeared at low and medium food levels. The effects of ibuprofen concentration on demographic parameters of M. macrocopa were dependent on food levels.

FQA: A method for floristic quality assessment based on conservatism of plant species

CAO Li-juan, HE Ping, WANG Mi, XU Jie, REN Ying

2018, 29(4):  1367-1372.  doi:10.13287/j.1001-9332.201804.007

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FQA, which uses the conservatism of plant species for particular habitats and the species richness of plant communities, is a rapid method for the assessment of habitat quality. This method is based on species composition of quadrats and coefficients of conservatism for species which assigned by experts. Floristic Quality Index (FQI) that reflects vegetation integrity and degradation of a site can be calculated by a simple formula and be used for space-time comparison of habitat quality. It has been widely used in more than ten countries including the United States and Canada. This paper presented the principle, calculation formulas and application cases of this method, with the aim to provide a simple, repeatable and comparable method to assess habitat quality for ecological managers and researchers.