Table of Content

18 October 2017, Volume 28 Issue 10

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Black carbon content and distribution in different particle size fractions of forest soils in the middle part of Great Xing’an Mountains, China.

XU Jia-hui, GAO Lei, CUI Xiao-yang

2017, 28(10):  3111-3118.  doi:10.13287/j.1001-9332.201710.014

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Soil black carbon (BC) is considered to be the main component of passive C pool because of its inherent biochemical recalcitrance. In this paper, soil BC in the middle part of Great Xing’an Mountains was quantified, the distribution of BC in different particle size fractions was analyzed, and BC stabilization mechanism and its important role in soil C pool were discussed. The results showed that BC expressed obvious accumulation in surface soil, accounting for about 68.7% in the whole horizon (64 cm), and then decreased with the increasing soil depth, however, BC/OC showed an opposite pattern. Climate conditions redistributed BC in study area, and the soil under cooler and moister conditions would sequester more BC. BC proportion in different particle size fractions was in the order of clay>silt>fine sand>coarse sand. Although BC content in clay was the highest and was enhanced with increasing soil depth, BC/OC in clay did not show a marked change. Thus, the rise of BC/OC was attributed to the preservation of BC particles in the fine sand and silt fractions. Biochemical recalcitrance was the main stabilization mechanism for surface BC, and with the increasing soil depth, the chemical protection from clay mineral gradually played a predominant role. BC not only was the essential component of soil stable carbon pool, but also took up a sizable proportion in particulate organic carbon pool. Therefore, the storage of soil stable carbon and the potential of soil carbon sequestration would be enhanced owing to the existence of BC.

Effects of warming and precipitation exclusion on soil N₂O fluxes in subtropical forests.

TANG Cai-di, ZHANG Zheng, CAI Xiao-zhen, GUO Jian-fen, YANG Yu-sheng

2017, 28(10):  3119-3126.  doi:10.13287/j.1001-9332.201710.026

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In order to explore how soil warming and precipitation exclusion influence soil N₂O fluxes, we used related functional genes as markers, and four treatments were set up, i.e., control (CT), soil warming (W, 5 ℃ above the ambient temperature of the control), 50% precipitation reduction (P), soil warming plus 50% precipitation reduction (WP). The results showed that precipitation exclusion reduced soil ammonium nitrogen concentration significantly. Soil warming decreased soil N₂O flux and soil denitrification potential significantly. Soil microbial biomass nitrogen (MBN) in warming treatment (W) and precipitation exclusion treatment (P) was significantly lo-wer than that in the control. The amoA gene abundance of AOA was negatively correlated with MBN and ammonium nitrogen contents, but neither soil nitrification potential nor soil N₂O flux was correlated with the amoA gene abundance of AOA. Path analysis showed that the denitrification potential affected soil N₂O flux directly, while microbial biomass phosphorus (MBP) and warming affected soil N₂O flux indirectly through their direct effects on denitrification potential. Temperature might be the main driver of N₂O flux in subtropical forest soils. Global warming would reduce N₂O emissions from subtropical forest soils.

Estimation of vegetation carbon storage and density of forests at tree layer in Tibet, China

LIU Shu-qin, XIA Chao-zong, FENG Wei, ZHANG Ke-bin, MA Li, LIU Jian-kang

2017, 28(10):  3127-3134.  doi:10.13287/j.1001-9332.201710.023

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The estimation of vegetation carbon storage and density of forests at tree layer in Tibet Autonomous Region was calculated based on the eighth forest inventory data using the biomass inventory method, as well as other attributes like tree trunk density and carbon content of different species. The results showed that the total carbon storage at tree layer in Tibet forest ecosystem was 1.067×10⁹ t and the average carbon density was 72.49 t·hm^-2. The carbon storage at tree layer of different stands was in the order of arbor forest > scattered wood > sparse forest > alluvial tree. The carbon storage of different forest types at tree layer were in the order of shelterbelt > special-purpose forest > timber forest > firewood forest. The proportion of the first-mentioned two was 88.5%, and the average carbon density of different forest types at tree layer was 88.09 t·hm^-2. The carbon sto-rage and its distribution area at tree layer in different forest groups were in the same order, followed by mature forest > over mature forest > near mature forest > middle aged forest > young forest. The carbon storage in mature forests accounted for 50% of the total carbon storage at tree layer in diffe-rent forest groups. The carbon storage at tree layer in different forest groups increased first and then decreased with the increase of stand ages.

Vertical variation in stoichiometric relationships of soil carbon, nitrogen and phosphorus in five forest types in the Maoershan region, Northeast China

ZHANG Tai-dong, WANG Chuan-kuan, ZHANG Quan-zhi

2017, 28(10):  3135-3143.  doi:10.13287/j.1001-9332.201710.025

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Five forests under diverse site conditions but under identical climate in the Maoershan region of Northeast China were sampled for measuring contents of soil carbon (C), nitrogen (N), and phosphorus (P), soil bulk density, and soil thickness by soil profile horizons. The stands included two plantations (i.e., Pinus koraiensis and Larix gmelinii plantations) and three broadleaved forests (i.e., Quercus mongolica stand, Populus davidiana - Betula platyphylla mixed stand, and hardwood stand). Our aim was to examine vertical distribution of the content, density, and stoichio-metry of soil C, N and P for the five forest types. The results showed that the contents and densities of soil C, N and P differed significantly among the forest types, with the maxima of the soil C and N at both O- and A-horizons occurring in the hardwood stand. The contents of C and N decreased significantly with increasing soil depth in all the stands. P content decreased significantly only in the broadleaved stands, and P content had no significant difference among different soil layers in the coniferous stands. The soil C/N at the A-horizon, N/P at the O-horizon, and the C/P at A- and B-horizons were significantly different among the forest types. The soil C and N linearly correlated significantly across all the forest types without significant differences in the slopes and intercepts, and the soil N and P, or the soil C and P correlated significantly only in the broadleaved stands. This result suggested that the C-N coupling relationship tended to converge across the forest types, and the N-P and C-P relationships varied with forest types.

Evaluating fire behavior simulators in southwestern China forest area.

ZHAO Fan, SHU Li-fu, ZHOU Ru-liang, XIAO Xiang-ming, WANG Ming-yu, ZHAO Feng-jun, WANG Qiu-hua

2017, 28(10):  3144-3154.  doi:10.13287/j.1001-9332.201710.012

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As an important technical reference for efficient prevention and fighting against forest fire, forest fire behavior parameters are mainly obtained from fire behavior simulators in some deve-loped countries. This study selected two simulators, the Farsite from USA and the Prometheus from Canada, which were both widely used in local area. Through comparing simulated results and relative data of the ‘3·29 Fire’ occurred in Anning City, Southwestern China, we tried to evaluate accuracy of the simulators in a quantitative way. The results indicated that, in the simulation of peri-meter, the precision of Farsite under Scott fuel model was the highest, while Prometheus was the lowest, but the difference was not significant. The difference in simulative perimeter between Farsite and Prometheus mainly concentrated in the distribution area of Pinus yunnanensis. In the simulation of rate of spread (ROS), the mean ROS results of Farsite under both fuel models were close to the actual situation, while the results of Prometheus were far away from the actual situation. The diffe-rent simulative area of ROS between Farsite and Prometheus mainly concentrated in the distribution area of P. yunnanensis. In the simulation of fireline intensity (FLI), the mean FLI results of Farsite under both fuel models were similar, and Prometheus obtained significantly different FLI results from Farsite, while the different simulative area of FLI between Farsite and Prometheus mainly concentrated in the distribution area of Quercus.

Addition effects of co-expansion of two bamboos on plant diversity in broad-leaved forests

YANG Qing-pei, GUO Ying-rong, LAN Wen-jun, SONG Qing-ni, YANG Guang-yao

2017, 28(10):  3155-3162.  doi:10.13287/j.1001-9332.201710.007

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The effects of Phyllostachys edulis and Oligostachyum oedogonatum expansion on species diversity of broad-leaved forests were investigated in Wuyishan National Nature Reserve, Jiangxi Province, China. Ph. edulis and/or O. oedogonatum expansion changed community structure and species composition. The co-expansion of the two bamboos in high intensity (Ph. edulis was 30-50 ind·100 m^-2, O. oedogonatum was 300-500 ind·100 m^-2) changed the density ratio of arbor and shrub from 2:8 to 1:9, and density ratio of bamboo and tree from 0:10 to 9:1. The main effects of Ph. edulis and O. oedogonatum on the species diversity were significant. Ph. edulis mainly influe-nced arbor layer, while O. oedogonatum influenced shrub layer more, and the interaction effect of two bamboos was not remarkable. There existed addition effects between Ph. edulis and O. oedogonatum on species diversity. The co-occurrence of two bamboos in high intensity decreased the Shannon index of community by 91.3%. Ph. edulis and O. oedogonatum did not compete obviously unless in high density. It was addition effect rather than interaction effect that changed the community structure and reduced species diversity when broad-leaved forest suffered invasion by Ph. edulis and O. oedogonatum.

RS estimation of inventory parameters and carbon storage of moso bamboo forest based on synergistic use of object-based image analysis and decision tree.

DU Hua-qiang, SUN Xiao-yan, HAN Ning, MAO Fang-jie

2017, 28(10):  3163-3173.  doi:10.13287/j.1001-9332.201710.019

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By synergistically using the object-based image analysis (OBIA) and the classification and regression tree (CART) methods, the distribution information, the indexes (including diameter at breast, tree height, and crown closure), and the aboveground carbon storage (AGC) of moso bamboo forest in Shanchuan Town, Anji County, Zhejiang Province were investigated. The results showed that the moso bamboo forest could be accurately delineated by integrating the multi-scale ima-ge segmentation in OBIA technique and CART, which connected the image objects at various scales, with a pretty good producer’s accuracy of 89.1%. The investigation of indexes estimated by regression tree model that was constructed based on the features extracted from the image objects reached normal or better accuracy, in which the crown closure model archived the best estimating accuracy of 67.9%. The estimating accuracy of diameter at breast and tree height was relatively low, which was consistent with conclusion that estimating diameter at breast and tree height using optical remote sensing could not achieve satisfactory results. Estimation of AGC reached relatively high accuracy, and accuracy of the region of high value achieved above 80%.

Growth characteristics of different tree species in shelterbelts in the depression area of Hebei Province, China.

ZHANG Jie-ming, YU Xin-xiao, JIA Guo-dong, LIU Zi-qiang, LU Wei-wei

2017, 28(10):  3174-3180.  doi:10.13287/j.1001-9332.201710.005

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This research investigated shelterbelt structure indices using the standard sampling met-hod, to study the dynamic changes of different tree species including Ulmus pumila, Populus simonii and Pinus tabuliformis in the depression area in Xiaobazi Township of Fengning County, Hebei Province, China. The results showed that the average age of U. pumila, P. simonii and P. tabuliformis pure forests was 10 years in this area. The average DBH and tree height of P. simonii pure forest were 2.3 times and 3.8 times as those of U. pumila pure forest, as well as, 2.3 times and 3.0 times as those of P. tabuliformis pure forest, respectively. The average DBH, tree height, LAI and height of first live branch of P. simonii pure forest were significantly larger than those of U. pumila pure forest and P. tabuliformis pure forest. Compared with P. simonii mixed forest, the stand density of P. simonii pure forest was 10.8% higher, average DBH of pure forest was 5.2% lower, and average tree height was 11.3% lower. Compared with U. pumila mixed forest, the stand density of U. pumila pure forest was 6.6% higher, average DBH and tree height of pure forest were 7.8% and 14.2% lower. Compared with P. tabuliformis mixed forest, the stand density of P. tabuliformis pure forest was 4.9% larger, but average DBH and tree height were 29.3% and 31.8% lower, respectively. The average DBH, tree height of different forest types showed significant negative correlation with the stand density. Average LAI showed significant positive correlation with density and height of first live branch, and significant negative correlation with the DBH, tree height. There was a significant positive relationship between the average height of first live branch and stand density. The increments of DBH and tree height of coniferous and broad-leaved mixed forest were significantly higher than those of coniferous pure forest. The comprehensive growth potential of the shelterbelts tended to increase, and the lateral growth potential on the whole exhibited a declining trend.

Effects of forest structure on natural regeneration of Excentrodendron hsienmu population in Southwest Guangxi, China

OU Zhi-yang, PANG Shi-long, TAN Zhang-qiang, ZHENG Wei, HE Qin-fei, SHEN Wen-hui

2017, 28(10):  3181-3188.  doi:10.13287/j.1001-9332.201710.001

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The effects of forest vertical structural variables (crown index, tree height, and large and small tree proportions) and density variables (basal area, adult tree density, shrub density, shrub coverage, and Excentrodendron hsienmu proportion in the forest canopy) on the natural rege-neration of the typical E. hsienmu populations in the karst mountains of Southwest Guangxi, China were studied. The results showed that the average regeneration density of E. hsienmu populations was 1742-3861 trees·hm^-2 and relatively low. Forest vertical structure and density variables did not significantly affect the number of E. hsienmu seedlings, but significantly affected seedling ground diameter and height to some extent. Among the vertical structure variables, a significant nega-tive correlation was observed between crown index and seedling height, but the association between crown index and seedling ground diameter was not significant. The large tree proportion and tree height were significantly negatively correlated with both seedling ground diameter and height. However, the proportion of small trees was significantly positively related to both seedling ground diameter and height. Among the density variables, adult tree density showed a significant positive correlation with both seedling ground diameter and height. A significant negative association was observed between the proportion of E. hsienmu and seedling ground diameter. Multiple regression analysis indicated that the model based on stand structure factors showed a poor fitness with regard to the number of E. hsienmu seedlings (P>0.05), and the quantitative distribution of E. hsienmu seedlings was affected to some extent by vertical structural variables. The stand structure factor model fitted well for the diameter and height of the seedlings (P<0.01). Seedling ground diameter was mainly affected by adult tree density, and seedling height was mainly determined by the combined effects of adult tree density and basal area.

Compatible biomass models of natural spruce (Picea asperata).

WANG Jin-chi, DENG Hua-feng, HUANG Guo-sheng, WANG Xue-jun, ZHANG Lu

2017, 28(10):  3189-3196.  doi:10.13287/j.1001-9332.201710.018

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By using nonlinear measurement error method, the compatible tree volume and above-ground biomass equations were established based on the volume and biomass data of 150 sampling trees of natural spruce (Picea asperata). Two approaches, controlling directly under total aboveground biomass and controlling jointly from level to level, were used to design the compatible system for the total aboveground biomass and the biomass of four components (stem, bark, branch and foliage), and the total-ground biomass could be estimated independently or estimated simultaneously in the system. The results showed that the R² of the one-variable and bivariate compatible tree volume and aboveground biomass equations were all above 0.85, and the maximum value reached 0.99. The prediction effect of the volume equations could be improved significantly when tree height was included as predictor, while it was not significant in biomass estimation. For the compatible biomass systems, the one-variable model based on controlling jointly from level to level was better than the model using controlling directly under total above-ground biomass, but the bivariate models of the two methods were similar. Comparing the imitative effects of the one-variable and bivariate compatible biomass models, the results showed that the increase of explainable variables could significantly improve the fitness of branch and foliage biomass, but had little effect on other components. Besides, there was almost no difference between the two methods of estimation based on the comparison.

Compatible biomass models of natural spruce Picea asperata

LI Yu-ran, WANG Xing-chang, WANG Chuan-kuan, LIU Fan, ZHANG Quan-zhi

2017, 28(10):  3197-3207.  doi:10.13287/j.1001-9332.201710.008

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Plant temperature is an important parameter for estimating energy balance and vegetation respiration of forest ecosystem. To examine spatial variation in diurnal courses of stem temperatures (T_s) and its influencing factors, we measured the T_s with copper-constantan thermocouples at different depths, heights and azimuths within the stems of two broadleaved tree species with contrasting bark and wood properties, Betula platyphylla and Fraxinus mandshurica. The results showed that the monthly mean diurnal courses of the T_s largely followed that of air temperature with a ‘sinusoi-dal’ pattern, but the T_s lagged behind the air temperature by 0 h at the stem surface to 4 h at 6 cm depth. The daily maximal values and ranges of the diurnal course of T_s decreased gradually with increasing measuring depth across the stem and decreasing measuring height along the stem. The circumferential variation in T_s was marginal, with slightly higher daily maximal values in the south and west directions during the daytime of the dormant season. Differences in thermal properties (i.e., specific heat capacity and thermal conductivity) of both bark and wood tissue between the two species contributed to the inter-specific variations in the radial variation in T_s through influencing the heat exchange between the stem surface and ambient air as well as heat diffusion within the stem. The higher reflectance of the bark of B. platyphylla decreased the influence of solar radiation on T_s. The stepwise regression showed that the diurnal courses of T_s could be well predicted by the environmental factors (R² > 0.85) with an order of influence ranking as air temperature > water vapor pressure > net radiation > wind speed. It is necessary to take the radial, vertical and inter-specific varia-tions in T_s into account when estimating biomass heat storage and stem CO₂ efflux.

Estimating in situ maximum net photosynthetic rate of Larix olgensis based on abscised mea-surement.

LIU Qiang, LI Feng-ri, PENG Wei

2017, 28(10):  3208-3216.  doi:10.13287/j.1001-9332.201710.020

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The data of needle in situ maximum net photosynthetic rate (SP_{n max}) and abscised maximum net photosynthetic rate (AP_{n max}) were measured for the 15 year-old planted Larix olgensis stand in the Maoershan Forest Farm, Heilongjiang Province, China. The change pattern between AP_{n max} and abscised time (t_a) was analyzed and the functional relationship between SP_{n max} and AP_{n max} with t_a was also established. Finally, the prediction model of SP_{n max} for planted L. olgensis trees was developed by analyzing the effect of tree size and environmental factors on the decline of AP_nmax. The results showed that needle AP_{n max} decreased with the increase of t_a without restoring water supply. The higher vapor pressure deficit (VPD) and the leaf temperature (T_leaf) would lead to faster and lager reduction of AP_{n max}. Taking VPD and t_a as the independent variables of the linear regression model had the best goodness-of-fit for SP_{n max}(R_a² were 0.774 and RMSE was 20.73). The model prediction precision decreased with the increase of t_a, but after 20 min it would be stabilized at 97%. Overall, estimating SP_{n max} of L. olgensis trees by developing regression model based on abscised measurement not only had a well predictive ability but also had a stable predictive precision, and greatly improved the efficiency of field measurement. The results of this study could be suitably applied to measure SP_{n max} in practice.

Characteristics of canopy stomatal conductance of Platycladus orientalis and its responses to environmental factors in the mountainous area of North China.

LIU Wen-na, JIA Jian-bo, YU Xin-xiao, JIA Guo-dong, HOU Gui-rong

2017, 28(10):  3217-3226.  doi:10.13287/j.1001-9332.201710.027

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Canopy stomatal conductance (g_s) is an important biological parameter to measure water vapor flux in canopy-atmosphere interface. Exploring characteristics of canopy stomatal conductance and its responses to environmental factors can offer theoretical evidence for conducting mechanism-based study of vapor exchange process in forest canopy. SF-L thermal dissipation probe was adopted to measure sap flow density (J_s) of Platycladus orientalis in 2014. The environmental factors including photosynthetically active radiation (PAR), vapor pressure deficit (VPD) and air temperature (T) were simultaneously observed. The canopy stomatal conductance was calculated, and the responses of g_s to environmental factors were analyzed. The results showed that the daily variation of sap flow density was of two-peak pattern curve, and the J_s in growing season was higher than in non-growing season. And the bigger DBH was, the higher J_s would be. The daily variation of canopy stomatal conductance was similar to the canopy transpiration of per leaf area (E_L), which was of two-peak pattern curve. The g_s and E_L in growing season were higher than those in non-growing season. The canopy stomatal conductance and air temperature presented parabolic relation, and g_s reached peak valley at around 10 ℃. Taking the value of 400 μmol·m^-2·s^-1 as the PAR thre-shold, when PAR was under this threshold, g_s was positively correlated with PAR. When PAR was beyond this threshold, the correlation between g_s and PAR would be small. The relationship between canopy stomatal conductance and vapor pressure deficit was negative logarithmic function. As VPD increasing, g_s decreased gradually. Higher air temperature and photosynthetically active radiation, and lower vapor pressure deficit contributed to higher canopy stomatal conductance of P. orientalis and could promote greater canopy transpiration.

Effect of trampling disturbance on soil infiltration of biological soil crusts

SHI Ya-fang, ZHAO Yun-ge, LI Chen-hui, WANG Shan-shan, YANG Qiao-yun, XIE Shen-qi

2017, 28(10):  3227-3234.  doi:10.13287/j.1001-9332.201710.011

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The effect of trampling disturbance on soil infiltration of biological soil crusts was investigated by using simulated rainfall. The results showed that the trampling disturbance significantly increased soil surface roughness. The increasing extent depended on the disturbance intensity. Soil surface roughness values at 50% disturbance increased by 91% compared with the undisturbed treatment. The runoff was delayed by trampling disturbance. A linear increase in the time of runoff yield was observed along with the increasing disturbance intensity within 20%-50%. The time of runoff yield at 50% disturbance increased by 169.7% compared with the undisturbed treatment. Trampling disturbance increased soil infiltration and consequently decreased the runoff coefficient. The cumulative infiltration amount at 50% disturbance increased by 12.6% compared with the undisturbed treatment. Soil infiltration significant decreased when biocrusts were removed. The cumulative infiltration of the treatment of biocrusts removal decreased by 30.2% compared with the undisturbed treatment. Trampling disturbance did not significantly increase the soil loss when the distur-bance intensity was lower than 50%, while the biocrusts removal resulted in 10 times higher in soil erosion modulus. The trampling disturbance of lower than 50% on biocrusts might improve soil infiltration and reduce the risk of runoff, thus might improve the soil moisture without obviously increa-sing the soil loss.

Effects of grazing and mowing on extractable carbon and nitrogen in typical grassland of Inner Mongolia, China

DUN Sha-sha, CAO Ji-rong, JIA Xiu, PANG Shuang

2017, 28(10):  3235-3242.  doi:10.13287/j.1001-9332.201710.003

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Relying on a long-term field manipulated grazing experiment of typical grassland in Inner Mongolia, China, we investigated the responses of soil organic carbon, total nitrogen, extractable carbon and nitrogen, and microbial biomass carbon and nitrogen to livestock grazing and grass mo-wing. The results showed that grazing decreased extractable organic carbon by 11.4%-37.1%, while mowing increased extractable organic carbon by 5.8%. Grazing and mowing increased extrac-table nitrogen by 10%-340% and 10%-240%, respectively. Grazing intensity less than 6.0 sheep·hm^-2 favored the maintenance of microbial biomass carbon, and heavy grazing intensity, i.e., 7.5 and 9.0 sheep·hm^-2, decreased microbial biomass carbon. Mowing consistently increased microbial biomass carbon and nitrogen by 31.0% and 9.8%, respectively. Path analysis showed that soil organic carbon, extractable total nitrogen and total nitrogen were the dominant controls of microbial biomass carbon with soil organic carbon and total extractable nitrogen as the direct influencing factors. Soil pH, extractable organic carbon, soil organic carbon and total extractable nitrogen were the dominant controls of microbial biomass nitrogen with soil organic carbon and total extractable nitrogen as the direct factors. Mowing, light grazing and moderate grazing were beneficial to maintaining or improving soil function, and heavy grazing would cause soil degradation.

Fractal features of soil particle size in the process of desertification in desert grassland of Ningxia, China.

YAN Xin, AN Hui

2017, 28(10):  3243-3250.  doi:10.13287/j.1001-9332.201710.024

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The variation of soil properties, the fractal dimension of soil particle size, and the relationships between fractal dimension of soil particle size and soil properties in the process of desertification in desert grassland of Ningxia were discussed. The results showed that the fractal dimension (D) at different desertification stages in desert grassland varied greatly, the value of D was between 1.69 and 2.62. Except for the 10-20 cm soil layer, the value of D gradually declined with increa-sing desertification of desert grassland at 0-30 cm soil layer. In the process of desertification in de-sert grassland, the grassland had the highest values of D, the volume percentage of clay and silt, and the lowest values of the volume percentage of very fine sand and fine sand. However, the mobile dunes had the lowest value of D, the volume percentage of clay and silt, and the highest value of the volume percentage of very fine sand and fine sand. There was a significant positive correlation between the soil fractal dimension value and the volume percentage of soil particles <50 μm, and a significant negative correlation between the soil fractal dimension value and the volume percentage of soil particles >50 μm. The grain size of 50 μm was the critical value for deciding the relationship between the soil particle fractal dimension and the volume percentage. Soil organic matter (SOM) and total nitrogen (TN) decreased gradually with increasing desertification of desert grassland, but soil bulk density increased gradually. Qualitative change from fixed dunes to semi-fixed dunes with the rapid decrease of the volume percentage of clay and silt, SOM, TN and the rapid increase of volume percentage of very fine sand and fine sand, soil bulk density. Fractal dimension was significantly correlated to SOM, TN and soil bulk density. Fractal dimension 2.58 was a critical value of fixed dunes and semi-fixed dunes. So, the fractal dimension of 2.58 could be taken as the desertification indicator of desert grassland.

Effects of short-term elevated CO₂ concentration and drought stress on the rhizosphere effects of soil carbon, nitrogen and microbes of Bothriochloa ischaemum.

XIAO Lie, LIU Guo-bin, LI Peng, XUE Sha

2017, 28(10):  3251-3259.  doi:10.13287/j.1001-9332.201710.009

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A water-control pot experiment was conducted in climate-controlled chambers to study soil carbon, nitrogen and microbial community structure and their rhizosphere effects in the rhizosphere and non-rhizosphere soil of Bothriochloa ischaemum at elevated CO₂ concentrations (800 μmol·mol^-1) under three water regimes, i.e., well watered (75%-80% of field capacity, FC), moderate drought stress (55%-60% of FC), and severe drought stress (35%-40% of FC). The results showed that elevated CO₂ concentration and drought stress did not have significant impacts on the content of soil organic carbon, total nitrogen or dissolved organic carbon (DOC) in the rhizosphere and bulk soils or their rhizosphere effects. Elevated CO₂ concentration significantly decreased dissolved organic nitrogen (DON) content in the rhizosphere soil under moderate drought stress, increased DOC/DON, and significantly increased the negative rhizosphere effect of DON and positive rhizosphere effect of DOC/DON. Drought stress and elevated CO₂ concentration did not have significant impacts on the rhizosphere effect of total and bacterial phospholipid fatty acids (PLFA). Drought stress under elevated CO₂ concentration significantly increased the G⁺/G^- PLFA in the rhizosphere soil and decreased the G⁺/G^- PLFA in the bulk soil, so its rhizosphere effect significantly increased, indicating that the soil microbial community changed from chemoautotroph microbes to heterotrophic microbes.

Diurnal variation characteristics of leaf water potential of Spinifex littoreus on the nebkhas in different succession periods on the coast of Pingtan Island, Fujian Province, China.

YANG Xian-ji, DU Jian-hui, QIN Jing, CHEN Zhi-hua, YANG Lin, SONG Shuang

2017, 28(10):  3260-3266.  doi:10.13287/j.1001-9332.201710.010

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Diurnal variation and its influencing factors of leaf water potential (ψ_l) of Spinifex littoreus on the nebkhas in two succession periods were measured on the coast of Pingtan Island, Fujian Province. The results showed that the diurnal variation of ψ_l of S. littoreus mainly demonstrated a ‘W’ curve pattern, with a temporary rise at midday. The mean ψ_l of S. littoreus on the nebkhas at developing stage was higher than that at stabilizing stage, and recovered better during the night. ψ_l of S. littoreus was positively related to the atmospheric water potential (ψ_a) and relative humidity, negatively related to air temperature, but had no significant correlation with the soil water potential at different depthes. ψ_l of S. littoreus on the interdune depression at developing stage was higher than that on the windward slope and on the leeward slope from 10:00 to 16:00, and that on the windward slope was lower than that on the leeward slope all day long except at 10:00 and at 12:00. The variation of ψ_l of S. littoreus on the leeward slope was higher than that on the windward slope, and the minimal variation was found on the interdune depression, without statistical significance. ψ_l of S. littoreus on the windward slope was positively correlated with ψ_a and relative humidity, while negatively correlated with air temperature. ψ_l of S. littoreus on the leeward slope and the interdune depression were correlated with meteorological factors, but they had no significant relationship.

Effects of hydrogen sulfide on root architecture, leaf reactive oxygen and photosynthetic characteristics of Malus hupehensis under waterlogging

WEI Guo-qin, CAO Hui, SUN Yu-gang, DENG Bo, ZHANG Wei-wei, YANG Hong-qiang

2017, 28(10):  3267-3273.  doi:10.13287/j.1001-9332.201710.006

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The root architecture, leaf reactive oxygen species and photosynthetic characteristics of potted Malus hupehensis seedlings were investigated after 10 days of waterlogging under five concentrations of hydrogen sulfide (H₂S) donor sodium hydrosulfide (NaSH,0, 0.02, 0.05, 0.1, 0.2 mmol·L^-1) and NaSH with scavenger hypotaurine (HT). The results showed that the root length, root surface-area, root volume, root diameter, root top number, fractal dimension, first lateral roots and root activity all increased, the leaf superoxide anion (O₂^-·) accumulation and hydrogen pero-xide (H₂O₂) content both decreased, the leaf P_n, T_r, g_s, WUE and CUE all raised, the plant height and biomass both increased when the 0.02-0.1 mmol·L^-1 NaHS were added to the waterlogging environment. Adding 0.1 mmol·L^-1 NaHS showed the best effects. All these parameters dropped back to the level of waterlogging alone when NaHS concentration was 0.2 mmol·L^-1 or HT was added to the 0.1 mmol·L^-1 NaHS solution. These suggested that applying an appropriate amount of H₂S could effectively alleviate the inhibition of soil waterlogging on the root growth of M. hupehensis and relieve the effects of waterlogging stress on photosynthesis and plant growth by reducing the production of reactive oxygen species and increasing CUE.

Effects of exogenous salicylic acid on seed germination and physiological characteristics of Coronilla varia under drought stress.

MA Le-yuan, CHEN Nian-lai, HAN Guo-jun, LI Liang

2017, 28(10):  3274-3280.  doi:10.13287/j.1001-9332.201710.004

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This research investigated the effects of different concentrations (0, 0.5, 1.0, 2.0 mmol·L^-1) of salicylic acid on the seed germination and physiological characteristics of legume forage Coronilla varia (cultivar ‘Lvbaoshi’) under PEG-6000 (concentration 8% and 12%) simulated drought stress. The results showed that under drought stress, 0.5-1.0 mmol·L^-1salicylic acid significantly increased germination percentage, germination vigour, germination index, vitality index and bud length of C. varia. Under the stress of 12% PEG, the dry mass of C. varia seedlings processed by 1.0 mmol·L^-1 salicylic acid was significantly higher than that under drought stress. 0.5-1.0 mmol·L^-1 salicylic acid processing significantly increased proline, soluble protein content, the activities of catalase, peroxidase and superoxide dismutase of C. varia seedlings under drought stress, but cell electrolyte permeability, H₂O₂ content and O₂^-· production rate of seedlings were significantly decreased. 1.0 mmol·L^-1 salicylic acid produced the best results. When the concentration of salicylic acid was beyond 2.0 mmol·L^-1, no mitigation effect was observed on the seed germination and growth of seedlings under drought stress. It was concluded that salicylic acid at appropriate concentrations could effectively improve osmotic regulation, antioxidation and mitigate the damage of drought stress so as to promote the growth of C. varia seedlings.

Chilling damage comprehensive assessment methods for rice

YANG Fei-yun, ZHANG Yu-shu, LI Wen-ke, LYU Hou-quan, LUO Jiang-mei

2017, 28(10):  3281-3288.  doi:10.13287/j.1001-9332.201710.021

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Based on the grey correlation analysis method, the chilling damage inducing factors and yield structure traits of rice in different growth stages, and the yield structure traits and final yield of rice were regarded as two grey systems. By seeking the grey relations of the grey systems and using the multi-level grey correlation analysis method, the comprehensive assessment model of rice chil-ling damage was constructed, and the comprehensive assessment indices of chilling damages in sepa-rate stages were established. The rice chilling damages at 27 stations in Northeast China from 1961 to 2015 were assessed separately. The results showed that there was a good corresponding relationship between the chilling damage and the rice yield. The low temperature during the vegetative growth stage, the vegetative growth and reproductive stage, the pollination stage or the grain filling stage significantly decreased the panicle number per plant, the average panicle grain number or the thousand-kernel mass, and increased the empty grain rate. A good correspondence existed between temperature and rice yield in the typical chilling damage years.

Hyper-spectral characteristics and estimation model of leaf chlorophyll content in cotton under waterlogging stress

XU Dao-qing, LIU Xiao-ling, WANG Wei, CHEN Min, KAN Hua-chun, LI Chang-feng, ZHENG Shu-feng

2017, 28(10):  3289-3296.  doi:10.13287/j.1001-9332.201710.013

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In order to rapidly monitor chlorophyll content in cotton functional leaf, and establish the quantitative relationship between chlorophyll content and spectral characteristic parameter of single cotton leaf, cotton was pot cultivated in a rain-shelter and subjected to waterlogging at squaring stage. Cotton leaf samples were taken and measured every 3 days after waterlogging. The correlation between chlorophyll content and spectral characteristic parameter was synthetically analyzed, and then the estimation model of chlorophyll content was established and verified. The results showed that the chlorophyll content decreased with increasing waterlogging stress. The original spectral reflectance and first-order differential spectral reflectance was negatively correlated with the chlorophyll content in the band near 580 and 697 nm. The estimation model established by difference vegetation index and normalized difference vegetation index performed better than that established by linear model of single band. Furthermore, the estimation model with (DR₆₉₇-DR₇₃₈)/(DR₆₉₇+DR₇₃₈) as the independent variable fitted the best with the correlation coefficient of 0.814, which could be utilized to estimate chlorophyll content of single leaf under waterlogging stress.

Effect of mineral N fertilizer reduction and organic fertilizer substitution on soil biological properties and aggregate characteristics in drip-irrigated cotton field.

LI Rui, TAO Rui, WANG Dan, CHU Gui-xin

2017, 28(10):  3297-3304.  doi:10.13287/j.1001-9332.201710.029

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A four-year field study was conducted to determine how soil biological properties and soil aggregate stability changed when organic fertilizer and biofertilizer were used to reduce chemical fertilizer application to a drip-irrigated cotton field. The study consisted of six fertilization treatments: unfertilized (CK); chemical fertilizer (CF, 300 kg N·hm^-2; 90 kg P₂O₅· hm^-2, 60 kg K₂O·hm^-2); 80% CF plus 3000 kg·hm^-2 organic fertilizer (80%CF+OF); 60% CF plus 6000 kg·hm^-2 organic fertilizer (60%CF+OF); 80% CF plus 3000 kg·hm^-2 biofertilizer (80%CF+BF); and 60% CF plus 6000 kg·hm^-2 biofertilizer (60%CF+BF). The relationships among soil organic C, soil biological properties, and soil aggregate size distribution were determined. The results showed that organic fertilizer and biofertilizer both significantly increased soil enzyme activities. Compared with CF, the biofertilizer treatments increased urease activity by 55.6%-84.0%, alkaline phosphatise activity by 53.1%-74.0%, invertase activity by 15.1%-38.0%, β-glucosidase activity by 38.2%-68.0%, polyphenoloxidase activity by 29.6%-52.0%, and arylsulfatase activity by 35.4%-58.9%. Soil enzyme activity increased as the amount of organic fertilizer and biofertilizer increased (i.e., 60%CF+OF > 80%CF+OF, 60%CF+BF > 80%CF+BF). Soil basal respiration decreased significantly in the order BF > OF > CF > CK. Soil microbial biomass C and N were 22.3% and 43.5% greater, respectively, in 60%CF+BF than in CF. The microbial biomass C:N was significantly lower in 60%CF+BF than in CF. The organic fertilizer and the biofertilizer both improved soil aggregate structure. Soil mass in the >0.25 mm fraction was 7.1% greater in 80%CF+OF and 8.0% greater in 60%CF+OF than in CF. The geometric mean diameter was 9.2% greater in 80%CF+BF than in 80%CF+OF. Redundancy analysis and cluster analysis both demonstrated that soil aggregate structure and biological activities increased when organic fertilizer and biofertilizer were used to reduce chemical fertilizer application. In conclusion, the organic fertilizer and the biofertilizer significantly increased SOC, soil enzyme activity, and soil microbial biomass C and N. The organic fertilizers also improved soil aggregation. Therefore, soil quality could be improved by using these fertilizers to reduce chemical fertilizer application, especially under drip-irrigation.

Spatio-temporal variation of water requirement and meteorological impact factors of cotton in North Xinjiang, China.

LUO Na-na, BATUR Bake

2017, 28(10):  3305-3313.  doi:10.13287/j.1001-9332.201710.028

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Based on daily data of 25 meteorological stations in North Xinjiang during 1961-2013, the FAO Penman-Monteith equation and crop coefficient method were used to estimate water requirements as well as irrigation water demands of cotton during all growth stages. The results suggested that cotton water requirement in each growth period had been decreasing in the past 53 years. Besides, crop water demand declined most significantly at the blossing and boll-forming stage, with change rate of -0.15 mm·a^-1. Furthermore, there were various multiscale cycle changes during the growth period. the water demand of crops in each growth period roughly changed as ‘high-low-high’ in the large periodic scale around 30 a and, as ‘low-high-low’ in the 15-17 a of the mesoscale cycle, but had no obvious cyclical characteristics on the interannual scale. Average crop water demands decreased roughly from west to east across North Xinjiang. The mutation results showed that the crop water demand decreased significantly in each growth period, especially in the northwest and southwest of North Xinjiang. In addition, cotton water demand was positively correlated with ave-rage wind speed, sunshine hours and average temperature during each growth period, and negatively correlated with relative humidity. The results would provide basic data for timely quantitative irrigation and improving water use efficiency of cotton in North Xinjiang.

Development of a new type of biological organic fertilizer and its effect on the growth promotion of tomato.

LIU Qiu-mei, CHEN Xing, MENG Xiao-hui, YE Qi, LI Tuo, LIU Dong-yang, SHEN Qi-rong

2017, 28(10):  3314-3322.  doi:10.13287/j.1001-9332.201710.039

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The objective of this study was to improve the ability of sporulation production of Trichoderma guizhouense NJAU4742 under solid-state fermentation by using rice straw and amino acids as resources, and the fermentation products were used as inoculants of the organic fertilizers adding with different ratios of amino acids solution to develop a new type of biological organic fertilizer. The results indicated that the optimal condition for sporulation by T. guizhouense NJAU4742 was soaking in 30 times diluted amino acid solution for one whole night, with initial pH 3.5, 75% of moisture content and 30% of corn powder, under which the sporulation reached to 2.40×10¹⁰ CFU·g^-1. The fermentation products were inoculated at 2% into the mature organic fertilizer containing 20% of amino acids solution, and the sporulation and IAA content were 6.40×10⁹ CFU·g^-1 and 38.66 mg·kg^-1, which were 1142.30 and 1.42 times higher than that of CK after 7 days, respectively. Pot experiment showed that biological organic fertilizer could significantly promote the growth of tomato, and the height of the tomato increased by 98.8% and 23.8%, respectively, compared with CK. The stem diameters of AT (amino acids + mature organic fertilizer + T. guizhouense NJAU4742) and AA (amino acids + mature organic fertilizer) were increased by 58.9% and 10.3%, respectively, compared with CK. As for the chlorophyll, leaf length and leaf width, the values also increased significantly. The highest spore content was obtained by using amino acids and rice straw as substrates under solid-state fermentation (SSF), which overcame the difficulties of producing new type of biological organic fertilizer during the large-scale industrial production. Biological organic fertilizer and amino acids organic fertilizer could significantly promote the growth of tomato compared with the chemical fertilizer, and had a good application prospect in intensive agriculture.

Effects of different rootstocks on the weak light tolerance ability of summer black grape based on 4 photo-response models

HAN Xiao, WANG Hai-bo, WANG Xiao-di, SHI Xiang-bin, WANG Bao-liang, ZHENG Xiao-cui, WANG Zhi-qiang, LIU Feng-zhi

2017, 28(10):  3323-3330.  doi:10.13287/j.1001-9332.201710.030

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The photo response curves of 11 rootstock-scion combinations including summer black/Beta, summer black/1103P, summer black/101-14, summer black/3309C, summer black/140Ru, summer black/5C, summer black/5BB, summer black/420A, summer black/SO4, summer black/Kangzhen No.1, summer black/Huapu No.1 were fitted by rectangular hyperbola mo-del, non-rectangular hyperbola model, modified rectangular hyperbola model and exponential model respectively, and the differences of imitative effects were analyzed by determination coefficiency, light compensation point, light saturation point, initial quantum efficiency, maximum photosynthetic rate and dark respiration rate. The result showed that the fit coefficients of all four models were above 0.98, and there was no obvious difference on the fitted values of light compensation point among the four models. The modified rectangular hyperbola model fitted best on light saturation point, apparent quantum yield, maximum photosynthetic rate and dark respiration rate, and had the minimum AIC value based on the akaike information criterion, therefore, the modified rectangular hyperbola model was the best one. The clustering analysis indicated that summer black/SO4 and summer black/420A combinations had low light compensation point, high apparent quantum yield and low dark respiration rate among 11 rootstock-scion combinations, suggesting that these two combinations could use weak light more efficiently due to their less respiratory consumption and higher weak light tolerance. The Topsis comparison method ranked summer black/SO4 and summer black/420A combinations as No. 1 and No. 2 respectively in weak light tolerance ability, which was consistent with cluster analysis. Consequently, summer black has the highest weak light tolerance in case grafted on 420A or SO4, which could be the most suitable rootstock-scion combinations for protected cultivation.

Comparison of the potential geographical distribution of foxtail millet (Setaria italica) predicted by different models.

GAO Bei, HU Ning, GUO Yan-long, GU Wei, ZOU Ji-ye

2017, 28(10):  3331-3340.  doi:10.13287/j.1001-9332.201710.015

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Foxtail millet is one of the main food crops in arid and semi-arid areas of China. Due to its strong anti-adversity, wide adaptability and resistance against drought and barren, the foxtail millet is treated as an important strategic crop reserve for the future drought situation. In this study, data from 157 geographical distributions were used to choose 10 climatic indices, 7 soil indices and 3 topographical indices, which were based on the relationship between the foxtail millet production and the environmental factors. Four species distribution models, including maximum entropy model (MaxEnt), ecological niche factor analysis (ENFA), random forest (RF) and generalized additive model (GAM), were applied to analyze the potential geographic distribution of foxtail millet in China. The results showed that all four models did a good job in simulating the potential geographic distribution for foxtail millet and the MaxEnt model was the best one. Precipitation and temperature were most sensitive to the distribution of foxtail millet among all selected environmental factors. The outputs of models, together with the ArcGIS spatial analyst module, displayed that the total potential suitable growing regions for the foxtail millet, including the highly and moderately suitable gro-wing regions, occupied 55.68×10⁴ km², which were much larger than the actual foxtail millet gro-wing area. The potential suitable growing regions were mainly located in northeast China, including the Northeast Plain, south of Changbai Mountain and Mudanjiang River basin, north China, including north of the Huaihe River, central China, including east of Hanjiang River and north of Dabie Mountains, northwest China, including Loess Plateau, the southern Ordos Plateau, the eastern Qilian Mountains, the eastern Tianshan Mountains and the Altai Mountains, and southwest China, including north of Chongqing and the western Guizhou Province.

Carbon balance of household production system in the transition zone from the Loess Plateau to the Qinghai-Tibet Plateau, China

WU Chao-chao, GAO Xiao-ye, HOU Fu-jiang

2017, 28(10):  3341-3350.  doi:10.13287/j.1001-9332.201710.002

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The transition zone from the Loess Plateau to the Qinghai-Tibet Plateau is one of the regions with most dramatic changes in agricultural production mode and most sensitive response to the carbon balance effect. This paper analyzed the carbon balance of the agriculture system along the altitude gradient in Tongwei, Weiyuan and Xiahe counties. The results showed that with the increase of altitude, the carbon emission, carbon fixation and carbon sink capacity of crops per unit area decreased accordingly, while the average carbon emission, carbon fixation and carbon source capacity of each household in livestock system increased. The integrated crop-livestock production system changed from carbon sink to carbon source. The average carbon emission of each household rose with altitude, but the carbon fixation was the opposite. The change of percentage ofhousehold in the transition zone from the Loess Plateau to the Qinghai-Tibet Plateau with carbon balance could be fitted with Logistic equation. In the crop system of Tongwei, Weiyuan and Xiahe with the altitude increase, carbon emission at the inflection point where the household percentage accounted for 50.0% was 1491, 857 and 376 kg CE·household^-1, and carbon fixation was 6187, 3872 and 778 kg CE·household^-1, respectively. For the livestock system, carbon emission was 2218, 3725 and 49511 kg CE·household^-1, and carbon fixation was 138, 230 and 2706 kg CE·household^-1, respectively. For the integrated crop-livestock system, carbon emission was 3615, 4583 and 49918 kg CE·household^-1, and carbon fixation was 6289, 4113 and 3819 kg CE·household^-1, respectively, which could be the key point for the regulation of regional carbon balance.

Effects of lime-ammonium bicarbonate fumigation and biofertilizer application on Fusarium wilt and biomass of continuous cropping cucumber and watermelon.

SHEN Zong-zhuan, SUN Li, WANG Dong-sheng, LYU Na-na, XUE Chao, LI Rong, SHEN Qi-rong

2017, 28(10):  3351-3359.  doi:10.13287/j.1001-9332.201710.036

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In this study, the population size of soil microbes was determined using plate counting method after the application of lime-ammonium bicarbonate and ammonium bicarbonate fumigation. In addition, biofertilizer was applied after soil fumigation and population of Fusarium oxysporum, Fusarium wilt disease control efficiency and plant biomass were determined in the cucumber and watermelon continuous cropping soil. The results showed that the population of F. oxysporum in cucumber mono-cropped soil fumigated with lime-ammonium bicarbonate or ammonium bicarbonate was decreased by 95.4% and 71.4%, while that in watermelon mono-cropped soil was decreased by 87.3% and 61.2%, respectively compared with non-fumigated control (CK). Furthermore, the greenhouse experiment showed that biofertilizer application, soil fumigation and crop type showed significant effects on the number of soil F. oxysporum, Fusarium wilt disease incidence, disease control efficiency and plant biomass based on multivariate analysis of variance. In the lime-ammonium bicarbonate fumigated soil amended with biofertilizer (LFB), significant reductions in the numbers of F. oxysporum and Fusarium wilt disease incidence were observed in both cucumber and watermelon cropped soil compared to non-fumigated control soil applied with organic fertilizer. The disease control rate was 91.9% and 92.5% for cucumber and watermelon, respectively. Moreover, LFB also significantly increased the plant height, stem diameter, leaf SPAD, and dry biomass for cucumber and watermelon. It was indicated that biofertilizer application after lime-ammonium bicarbonate fumigation could effectively reduce the abundance of F. oxysporum in soil, control Fusarium wilt disease and improve plant biomass in cucumber and watermelon mono-cropping systems.

Diversity of soil nematode communities in the subalpine and alpine forests of western Sichuan, China.

CHEN Ya, YANG Wan-qin, WU Fu-zhong, YANG Fan, LAN Li-ying, LIU Yu-wei, GUO Cai-hong, TAN Bo

2017, 28(10):  3360-3368.  doi:10.13287/j.1001-9332.201710.037

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In order to understand the diversity of soil nematodes in the subalpine/alpine forests of the eastern Qinghai-Tibet Plateau, soil nematodes in the primary forest, mixed forest and secondary forest of Abies faxoniana were extracted by elutriation and sugar-centrifugation method in July 2015, and the composition and structure characteristics of soil nematode communities were studied in the three forests at different altitudes. A total of 37950 soil nematodes were collected, which belonged to 20 families and 27 genera, and the mean density was 4217 ind·100 g^-1 dry soil. Filenchus was the dominant genus in the primary forest, and Filenchus and Pararotylenchus in the mixed forest and secondary forest, respectively. The individual number of each dominant genus was significantly affected by forest type. All nematode individuals were classified into the four trophic groups of bacterivores, fungivores, plant-parasites and omnivore-predators. The fungivores were dominant in the primary and secondary forest and the bacterivores in the mixed forest. The number of soil nematode c-p (colonizer-persister) groups of c-p 1, c-p 2, c-p 3 and c-p 4 accounted for 6.1%, 51.1%, 30.0% and 12.7% of the total nematode abundance, respectively. The maturity index (MI), the total maturity index (∑MI) and the plant parasitic index (PPI) of soil nematodes decreased gradually with the increase of altitude. The nematode channel ratio in the mixed forest was higher than 0.5, but that in the primary forest and secondary forest was below 0.5. The forest type significantly affected the soil nematode maturity index and channel ratio, but the forest type, soil layer and their interaction had no significant effect on the diversity index. There were obvious diffe-rences in the composition, nutrient structure and energy flow channel of soil nematodes in the subalpine/alpine forests of western Sichuan, providing an important reference for understanding the function of soil nematodes in soil processes of this region.

Ecological risk assessment of Taihu Lake basin based on landscape pattern

XIE Xiao-ping, CHEN Zhi-cong, WANG Fang, BAI Mao-wei, XU Wen-yang

2017, 28(10):  3369-3377.  doi:10.13287/j.1001-9332.201710.016

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Taihu Lake basin was selected as the study site. Based on the landscape data of 2000, 2005, 2010 and 2015, the Markov and CLUE-S models were used to simulate the landscape types with different scenarios in 2030, and landscape ecological risk index was constructed. The shift of gravity center and spatial statistics were used to reveal landscape ecological risk of Taihu Lake basin with temporal and spatial characteristics. The results showed that the ecological risk mainly was at medium and low levels in Taihu Lake basin, and the higher ecological risk areas were mainly distributed at the Taihu Lake area during 2000 to 2015, and the low ecological risk was transferred from the southwest and south of Taihu Lake to the developed areas in the northern part of Taihu Lake area. Spatial analysis showed that landscape ecological risk had negative correlation with natural factors, which was weakened gradually, while the correlation with socioeconomic factors trended to become stronger, with human disturbance affecting the landscape ecological risk significantly. The impact of socioeconomic factors on landscape ecological risks differed in different urbanization stages. In the developing area, with the economic development, the landscape was increasingly fragmented and the ecological risk was correspondingly increased. While in the developed area, with the further development of the economy, the aggregation index was increased, and fragmentation and separation indexes were decreased, ecological construction was restored, and the landscape ecological risk began to decline. CLUE-S model simulation showed that the ecological risk of Taihu Lake basin would be reduced in future, mainly on the low and relatively low levels. Taihu Lake area, both in history and the future, is a high ecological risk zone, and its management and protection should be strengthened.

Optimum population analysis of Jilin Province, China based on comprehensive carrying capacity.

LI Xiu-xia, MENG Mei

2017, 28(10):  3378-3384.  doi:10.13287/j.1001-9332.201710.022

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The regional moderate population model was constructed using state-space method, and the weights of relevant factors were obtained using principal component analysis. The optimum population of Jilin Province during 2005-2014 was calculated and the causes for its formation were discussed. The results showed that the optimum population of Jilin Province was in deficit from 2005-2014, and the imbalance existed between the population, resources and environment. The resources carrying population was significantly higher than the economic carrying and the ecological carrying population, indicating that the economic development of Jilin Province was established at the expense of destroying the environment. Moreover, the land resources carrying population was substantially higher than the water and energy carrying population, which was at a deficit, indicating that the economic development of Jilin Province was based on the depletion of energy and water resources. In the future, water resources carrying capacity should be improved according to the local conditions, the energy efficiency should be enhanced via the development of new energy sources, the extensive and consumption-based resource utilization should be transformed to the intensive and low-carbon type, and the production mode and consumption patterns should be changed to protect the ecological environment.

Effects of urban wetlands with different shapes on the temperature and humidity of ambient environment.

JI Peng,ZHU Chun-yang, SHENG Yun-yan

2017, 28(10):  3385-3392.  doi:10.13287/j.1001-9332.201710.017

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To quantify the effects of urban wetlands on temperature and humidity of ambient environment, five urban wetlands with different shapes and surroundings were selected in Daqing City, and the air temperature and relative humidity were investigated in spring, summer and autumn using small-scale quantitative measurement method. The results indicated that the urban wetlands with different shapes all could decrease the temperature and increase the humidity, with the effect being strongest in summer, followed by in spring, and the smallest effect in autumn. The shape of the urban wetland had significant effect on temperature and humidity, which decreased in the order of irregular-shaped wetland > regular-shaped wetland (subcircular-shaped wetland, subcuboid-shaped wetland) > long-shaped wetland. The diurnal variation of temperature and humidity was influenced by the ambient temperature, namely the effect of wetlands was weak in morning and evening, but strong at noon. The maximum effect occurred at12:00-14:00 in spring and autumn, and at 14:00-16:00 in summer.

Characterization of microbial community in produced water from a petroleum reservoir subjected to alkali-surfactant-polymer ASP flooding

HAO Qin-qin, SHI Rong-jiu, HAO Jin-sheng, ZHAO Jin-yi, LI Guo-qiao, ZHAO Feng, HAN Si-qin, ZHANG Ying

2017, 28(10):  3393-3402.  doi:10.13287/j.1001-9332.201710.038

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Injection of alkali, surfactant and polymer (ASP) into oil reservoir can substantially increase oil recovery compared with water-flooding strategy. However, the effects of these agents on the microbial diversity and community structure, which is important for water management and corrosion control in oil industry, are hitherto poorly understood. Here, we disclosed the microbial diversity and community structure in the produced water collected from four producing wells of an ASP-flooded oilfield at Daqing, China, using high-throughput sequencing technique. Results showed that the average pH in produced water was as high as 9.65. The microbial diversity varied from well to well, and the Shannon diversity index was between 2.00 to 3.56. The Proteobacteria (85.5%-98.3%), γ-proteobacteria (83.7%-97.8%), and alkaliphilic Nitrincola (51.8%-82.5%) were the most dominant phylogenetic taxa at the phylum, class, and genus levels, respectively. A total of 12 potentially sulfide-producing genera were detected, and the most abundant taxon was Sulfurospirillum (0.4%-7.4%). The microbial community of ASP-flooded petroleum reservoir was distinct, showing an alkaliphilic or alkalitolerant potential; a reduced diversity and more simple structure were observed compared with those of the water-flooded petroleum reservoirs that were previously reported.

Predatory and control ability of Orius minutus to the diamondback moth (Lepidoptera: Plutellidae).

SUN Li-juan, YI Wei-xian, ZHENG Chang-ying

2017, 28(10):  3403-3408.  doi:10.13287/j.1001-9332.201710.032

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In order to make clear the suitability of eggs of Plutella xylostella as foodstuff of Orius minutus and the predatory and control ability of the bug to P. xylostella, the influence of praying on eggs of P. xylostella on development and reproduction of O. minutus was studied indoors with Myzus persicae as reference. The predation functional response was included to evaluate the control ability of O. minutus to P. xylostella. The results showed that O. minutus could finish its generation and reproduce offspring when fed on eggs of P. xylostella. The developmental durations of nymphal bugs (♀: 12.3 d, ♂: 12.2 d), the length of body of adult bugs [♀: (2.13±0.01) mm, ♂: (1.91±0.00) mm], the width of body of adult bugs [♀: (0.87±0.01) mm, ♂: (0.71±0.01) mm], the fecundity per female (12.7±1.1), the pre-oviposition period [(5.1±0.6) d] and the oviposition period [(3.7±0.4) d] all had no significant difference from those of treatment group of M. persicae; the longevity of adult bugs [♀: (10.7±1.4) d, ♂: (9.1±1.3) d] was longer than that of treatment group of M. persicae [♀: (8.5±0.5) d, ♂: (6.4±0.3) d]; the survival rate of nymphal bugs [(65.0±6.8)%] was lower than that of treatment group of M. persicae [(80.0±8.2)%], and the percentage of females was low. The predation functional responses of O. minutus to P. xylostella were all in accord with HollingⅡ equation. The largest amounts of caught per day (N_max) of the 1st, 2nd, 3rd, 4th and 5th instar nymphal bugs to eggs of P. xylostella were 7.5, 16.3, 23.3, 29.1 and 38.7, respectively; the N_max of the female and male adult to eggs of P. xylostella was 39.0 and 26.9, respectively; the N_max of the 5th instar nymph to lower instar larva of P. xylostella was 41.3; and the N_max of the female and male adult to lower instar larva of P. xylostella was 40.8 and 23.9, respectively. Single female and male pray eggs of P. xylostella up to (711.3±58.1) and (535.4±30.6), lower instar larvae of P. xylostella up to (371.9±52.0) and (253.9±32.3) during their whole lifetime, respectively. O. minutus could be reared with eggs of P. xylostella, and O. minutus has a good ability to control P. xylostella.

Inter-decadal variation of spatial aggregation of Trichiurus japonicus in East China Sea based on spatial autocorrelation analysis

YUAN Xing-wei, LIU Zun-lei, JIN Yan, CUI Xue-sen, ZHOU Wei-feng, CHENG Jia-hua

2017, 28(10):  3409-3416.  doi:10.13287/j.1001-9332.201710.040

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Marine fish shows high heterogeneity in spatial aggregation. We analyzed the inter-deca-dal variations of stock density for Trichiurus japonicus in East China Sea (ECS) using geo-statistical approaches such as spatial autocorrelation and hotspot analysis, based on the data of T. japonicus from both bottom trawl fishery and research surveys in the open waters of ECS during 1971 to 2011, combined with the sea surface temperature (SST) and surface salinity data in the PN section in August. The global spatial autocorrelation statistics showed that Moran’s I firstly decreased and then went up, indicating that the spatial aggregation patterns of T. japonicus was weakened in the beginning and then increased during 1971 to 2011. The surface salinity in the PN section displayed the opposite trend during the same period. The local spatial autocorrelation statistics showed that the population firstly moved to the southern ECS and then to the northern ECS except in 1971 in which the population concentrated in the middle of ECS because of the restriction of offshore fishing ground. The movement of hotspot areas of T. japonicus adaptively varied with the first EOF mode of SST in summer (sumEOF1), which indicated that the hotspot areas first moved southeastward with decreasing sumEOF1, and moved northeastward with increasing sumEOF1, but all of the hotspot areas were close to the northward branch of the Kuroshio Current.

Effects of biochar application on the abundance and structure of ammonia-oxidizer communities in coal-mining area.

LIU Yuan, ZHU Ji-rong, WU Yu-chen, SHU Liang-zuo

2017, 28(10):  3417-3423.  doi:10.13287/j.1001-9332.201710.034

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As a new type of soil amendment, biochar can effectively improve soil fertility, structure and soil nitrogen transformation. We studied the effects of biochar application on soil properties, abundance and community structure of ammonia oxidizer in coal-mining area. The results showed that the biochar application significantly increased contents of soil NH₄⁺-N, total nitrogen, available phosphorus and potassium. Compared with the control, no change in the abundance of ammonia-oxidizing archaea (AOA) was found under biochar treatment, but there was a significant increase in the abundance of ammonia-oxidizing bacteria (AOB). The analysis of T-RFLP profiles showed that biochar significantly increased the diversity indexes of AOA and AOB, and altered the community structure of both AOA and AOB. Improved soil nutrients as well as increased abundance and diversity of ammonia-oxidizing community to some extent indicated the potential of biochar application in reclamation of coal-mining area soil.

Advances in trace platinum group elements speciation and preconcentration of chelate resins in seawater.

LIU Kai, GAO Xue-lu, LI Li

2017, 28(10):  3424-3432.  doi:10.13287/j.1001-9332.201710.031

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The content and occurrence of platinum group elements have a close relation with their biogeochemical behavior and ecological risk in seawater. However, the determination of the PGE content and morphology in seawater is difficult. The characterization of chelating resins for specific elements and specific ligand structures provides a potential for breakthrough in this problem. This review reported the major speciation of PGEs in seawater, discussed the adsorbing mechanism of resin, and compared the adsorption capacity of different types of chelate resin. Finally, some conclusions were drawn. First, the inorganic complexes of PGEs in seawater were mainly composed of [MCl₃OH^2-]/[MCl₄^2-](M=Pt,Pd) and M(OH)₃^{3-n(n=3-6) (M=Rh); Second, chelate resins had certain recognition for different complex morphology of PGEs; Third, nitrogen-sulfur chelate resin was the ideal resin for studying PGEs in seawater under practical conditions.}

Remote sensing monitoring and screening for urban black and odorous water body: A review.

SHEN Qian, ZHU Li, CAO Hong-ye

2017, 28(10):  3433-3439.  doi:10.13287/j.1001-9332.201710.033

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Continuous improvement of urban water environment and overall control of black and odorous water body are not merely national strategic needs with the action plan for prevention and treatment of water pollution, but also the hot issues attracting the attention of people. Most previous researches concentrated on the study of cause, evaluation and treatment measures of this phenomenon, and there are few researches on the monitoring using remote sensing, which is often a strain to meet the national needs of operational monitoring. This paper mainly summarized the urgent research problems, mainly including the identification and classification standard, research on the key technologies, and the frame of remote sensing screening systems for the urban black and odorous water body. The main key technologies were concluded too, including the high spatial resolution image preprocessing and extraction technique for black and odorous water body, the extraction of water information in city zones, the classification of the black and odorous water, and the identification and classification technique based on satellite-sky-ground remote sensing. This paper summarized the research progress and put forward research ideas of monitoring and screening urban black and odorous water body via high spatial resolution remote sensing technology, which would be beneficial to having an overall grasp of spatial distribution and improvement progress of black and odorous water body, and provide strong technical support for controlling urban black and odorous water body.

Research advance on molecular ecology of asymbiotic nitrogen fixation microbes.

XU Peng-xia, HAN Li-li, HE Ji-zheng, LUO Feng, ZHANG Li-mei

2017, 28(10):  3440-3450.  doi:10.13287/j.1001-9332.201710.035

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Nitrogen is the main limiting factor in the productivity of ecological system, and biological nitrogen fixation is the main nitrogen source in the natural ecosystem. Biological nitrogen fixation includes 3 types: symbiotic, associate and free-living nitrogen fixation. Associate and free-living nitrogen fixations are collectively called asymbiotic nitrogen fixation. Compared with symbiotic system, asymbiotic nitrogen fixation rate is lower, but asymbiotic nitrogen fixation microorganisms can survive and fix nitrogen without forming symbiotic structure with plants, therefore play an important role in nitrogen cycling, especially nitrogen input in ecosystems, due to their wide distribution and high adaptability to different environments. In this review, we mainly introduced the research progress of asymbiotic nitrogen fixation microorganisms in terms of diversity, distribution characteristics, the factors influencing asymbiotic nitrogen fixation efficiencies in soils and phyllosphere, and also highlighted the existing problems and future perspectives in this research field.