Table of Content

10 May 2019, Volume 38 Issue 5

Previous Issue    Next Issue

Grazing affected metabolic characteristics of rhizospheric fungi community of Populus euphratica Oliv. with different diameters.

WANG Wen-juan, WANG Jian-ming, ZHANG Tian-han, QU Lai-ye, LI Jing-wen

2019, 38(5):  1267-1275. 

Asbtract ( 618 )   PDF (958KB) ( 270 )  

Grazing is one of the most important anthropogenic activities in drylands, which could influence the structure and components of soil microbial community. It is critical to understand the effects of grazing on metabolic characteristics of fungi community that is closely related with nutrient cycling and ecosystem stability in drylands. We selected three levels of grazing intensity: heavy grazing (HG), moderate grazing (MG) and light grazing (LG). We set five diameter classes of trees \[A (0-10 cm), B (10-20 cm), C (20-30 cm), D (30-40 cm) and E (>40 cm)\] with each grazing level in Ejina Oasis to explore metabolic characteristics and diversity of rhizospheric fungi community in Populus euphratica Oliv. forest by BiologFF microplate. Theresults showed that diameter class size had significant effect on fungi community metabolism, accounting for 7.8% of variance. The fungi community metabolic activities gradually decreasedalong with increasing grazing intensity (AWCD_LG>AWCD_MG>AWCD_HG). There was no obvious difference under different diameter classes in LG site while significant differences were observed in MG and HG site. This result indicated that the effects of grazing intensity on P. euphratica were dependent on tree diameters, thus leading to diverse responses of fungi community. While there was no interactive effect between grazing intensity and diameter on metabolic activities of fungi community but they interacted to affect diversity, indicating that grazing intensity didn’t change the metabolic intensity of fungi community but changed the community structure. In addition, the effects of grazing intensity and diameter class of trees on fungi community metabolic characteristics were mainly due to alteration of fungi principally using the small molecular carbon sources.

 

Effects of nitrogen addition on the quantitative characteristics and photosynthesis of different plant functional groups in an alpine meadow of Qinghai-Tibetan Plateau.

SHEN Hao, DONG Shi-kui, LI Shuai, XU Yu-dan, HAN Yu-hui, ZHANG Jing

2019, 38(5):  1276-1284. 

Asbtract ( 530 )   PDF (1606KB) ( 227 )  

The effects of nitrogen deposition on plant communities, especially on the alpine meadow with relatively fragile habitats, have been hot topic in ecology. To better understand the effects of nitrogen deposition on the eco-physiology of different plant functional groups in the alpine meadow of Qinghai-Tibetan Plateau, we conducted a field experiment under different nitrogen addition levels (0, 8, 24, 40, 56, 72 kg·hm^-2·a^-1) to simulate natural nitrogen deposition. We classified the plant species into three functional groups, including grass, sedge, and forb. Results showed that: (1) The effects of nitrogen deposition on three functional groups were different. Nitrogen addition increased the abundance and height of sedge, but had no effects on that of grass and forb (P>0.05). Aboveground biomass of grass showed non-linear response to nitrogen addition, while the aboveground biomass of sedge and forb significantly decreased with the increases of nitrogen addition level. (2) Net photosynthetic rate of grass showed nonlinear response to nitrogen addition, while that of sedge and forb significantly decreased with the increases of nitrogen addition level. Nitrogen addition significantly increased the stomatal conductance (G_s) and transpiration rate (T_r) of all the three functional groups. (3) The net photosynthetic rate was significantly positively correlated with aboveground biomass of the three functional groups (P<0.05). In conclusion, short-term high nitrogen deposition will decrease the accumulation of plant aboveground biomass through reducing the photosynthetic capacity, and thus inhibiting plant growth in alpine meadow of Qinghai-Tibetan Plateau.

Relationship between Cephalcia kunyushanica occurrence and stand factors of Pinus densiflora pure forests.

HU Rui-rui, LIANG Jun, XIE Xian, HUANG Yong-huai, YUAN Xiao-wen, WANG Jun, ZHANG Ying-jun, ZHANG Xing-yao

2019, 38(5):  1285-1291. 

Asbtract ( 337 )   PDF (569KB) ( 195 )  

To understand the relationship between stand factors of Pinus densiflora pure forest and Cephalcia kunyushanica occurrence, and thus to provide theoretical guidance for P. densiflora pure forest management as well as the prevention and control of C. kunyushanica, we investigated seven stand indices of stand density, canopy cover, herb coverage, tree height, height under branch, diameter at breast height (DBH) and crown size as well as the nest number of C. kunyushanica in P. densiflora pure forests with relatively consistent stand age (34±2 years old) in the Kunyushan Mountains. The plots were divided into four groups according to the distribution range of the pest severity index (PSI). The differences of stand factors in four groups were examined by means of variance analysis and multiple comparison. Stepwise regression was used to select key factors affecting C. kunyushanica. The relationship between the critical stand factors and the PSI was further clarified by partial correlation analysis and oneway ANOVA. The results showed that all the seven stand factors were significantly different among the four groups. Crown size, height under branch and stand density were the key factors affecting the PSI among the seven factors following results from stepwise regression. Then, the prediction equation of pest severity index was established. The effects of crown size and height under branch on PSI were significant and positive (P<0.01), while stand density had a negative effect (P<0.01). However, the key factors affecting the insect pest index may be inconsistent in different forests. Forest structure should be adjusted according to the critical factors to achieve the goal of controlling the epidemic of insect pests.

Niche dynamics of main populations of old-tree communities in Jiuhua Mountain Scenic Area of Anhui Province.

DONG Dong, XU Xiao-tian, ZHOU Zhi-xiang, HE Yun-he, WANG Cun-zhi, SHI Fang-ke, GAO Lu-lu

2019, 38(5):  1292-1304. 

Asbtract ( 542 )   PDF (1250KB) ( 243 )  

The niche characteristics and its dynamic changes of old-tree communities were investigated in this study. Results from this study help improve our understanding the utilization and adaptation of different species to environmental resources and provide a scientific basis for the conservation and management of old-tree communities. Based on the dynamic monitoring of the fixed plots of old-tree communities in Jiuhua Mountain from 2007 to 2017, we analyzed the changes of species importance values, niche breadth and niche overlap of main populations in old-tree communities. The results showed that there were 230 species in the plots in 2007. In 2017, 39 species disappeared from the community, and another 12 species entered the community. For the importance value, old-tree populations such as Cyclobalanopsis myrsinaefolia, Liquidambar formosana,Cornus controversaand Sassafras tzumu were enhanced, but the dominant position of Pinus massoniana,Pseudolarix amabilis and Magnolia denudategradually decreased during the past decade. In terms of niche breadth, C. myrsinaefoliawas still the largest species in the hierarchy, but the broadest species of shrub layer niche were replaced by C. myrsinaefolia and Hedera nepalensisvar. sinensis. The utilization of environmental resources by C. myrsinaefolia was enhanced. The niche breadth of M. grandiflora, C. lanceolata, P. massonianabecame narrower, indicating that a decline of their ability to use resources and adapt to the environment. BrayCurtis cluster analysis divided the dominant species in each community into three groups. C. controversa, C. myrsinaefolia, L. formosana and M. denudate were clustered in one group, with similar niche breadths. The proportion of species with an overlap value of more than 0.2 increased significantly in the past decade, indicating that species competition for similar resource was more intense, or that they might utilize resources from different approaches to form a relatively stable and competitive dynamic balance. The populations of C. myrsinaefolia, L. formosana, C. controversawere relatively stable in the community, but the dominant position of P. massoniana and P. amabilis may be replaced by other tree species with strong environmental adaptability in old-tree communities of Jiuhua Mountain Scenic Area.

The effect of plot size on shrub plant diversity in a karst desertification area, central Guizhou Province, China.

ZHANG Xi, HUO Da, XIANG Kai-xuan, HOU Yi-ju, XIE Tao, CUI Ying-chun

2019, 38(5):  1305-1313. 

Asbtract ( 458 )   PDF (834KB) ( 218 )  

Stony desert shrub forests with similar habitat factors and vegetation development were investigated using twelve 200 m² (20 m×10 m) plots, including ninety-six 25 m² (5 m×5 m) subplots in central Guizhou karst desertification area. We assessed the impacts of plot size on plant diversity using the improved nest method, to provide a scientific framework for determining the minimum sampling plot size. Our results showed that an increase in the ordered sampling area in stony desert shrub forest caused the increase of the values of Patrick index, Gleason index and Margalef index, while caused the values of Shannon index, Pielou index and Alatalo index to increase first and then decrease. There was a significant difference in the values of six plant diversity indices among the different plot sizes. Simpson index and McIntosh index increased first and then decreased, but there was no significant difference between the two indices for the plot sizes. We classified the eight diversity indices into two groups according to the information retention rate ≥80%: for the 100 m² plot size, the Patrick index that reflects the number of species was selected, and for the 25 m² plot size, the Gleason index, Margalef index, Simpson index, Shannon index, Pielou index, Alatalo index and McIntosh index that reflect plant diversity and evenness were selected. The Connor & McCoy model, with eight plant diversity index values, had a better fitting effect, the de Caprariis model and MichaelsMenton model had a worse fitting effect, and the Arrhenius model and Logistic model with Patrick index and Margalef index had a better fitting effect. There was a significant correlation between the eight plant diversity indices and the average height of shrubs and the average coverage of herbs, but no significant correlation between these indices and the average height of herbs across the 96 subplots. Results of principal component analysis showed that the contribution rates of site elements, stand density and stand spatial properties to the shrub diversity were 4.3%-11.7%, 35.4%-67.9%and 20.4%-60.2%, respectively. The shrub diversity was mainly affected by forest structure and development level.

Water content of surface ground fuel in Larix gmelinii-Betula platyphylla mixed forest of Nanwenhe, Daxing’an Mountains.

HU Hai-qing, LUO Bi-zhen, LUO Si-sheng, SUN Long

2019, 38(5):  1314-1321. 

Asbtract ( 356 )   PDF (667KB) ( 220 )  

To provide a basis for improving the prediction accuracy of surface ground fuel moisture content, we monitored the dynamics of water content of the surface ground fuel and the meteorological factors in Larix gmelinii-Betula platyphylla mixed forests in both shady slope and sunny slope in Nanwenghe National Natural Reserve of Daxing’an Mountains with different fire prevention periods. The direct estimation method based on equilibrium moisture content and timelag was used to analyze the effects of different fire prevention periods and slope aspects on the accuracy of the prediction model for estimating surface ground fuel moisture content. The results showed that water content of ground fuel differed with fire prevention periods and slope aspects, being greater in autumn than in spring and greater in the sunny slope than in the shady slope. In the predicted models of surface ground fuel moisture content, prediction accuracy for autumn fire prevention period was better than that for spring fire prevention period, and that for the sunny slope was better than for the shady slope. The effects of slope aspects and fire prevention periods on water content of surface ground fuel should be taken into account to establish different prediction models in forest fire risk prediction, which will help improve the accuracy of fire risk prediction.

Assessing the feasibility of tree-medicinal plant intercropping system of Cinnamomum migao and Aomum villosumtbased on allelopathy.

CHEN Jing-zhong, LIU Ji-ming, XIONG Xue, HUANG Xiao-long, TONG Bing-li, WEN An-lai

2019, 38(5):  1322-1330. 

Asbtract ( 403 )   PDF (965KB) ( 179 )  

To realize the rational utilization of land resources and reduce cost of field management, the feasibility of a Cinnamomum migao and Aomum villosumt intercropping system was evaluated from the perspective of allelopathy, which would provide theoretical support for intercropping under C. migao plantations. In this study, seeds and seedlings of A. villosumt were treated by different concentrations of aqueous extracts of pericarps and leaves from C. migao to assess the allelopathic effects onA. villosumt. The results showed that pericarp and leaf aqueous extracts of C. migao at high concentration (50 mg·mL^-1) had significant inhibitory effects on the A. villosumt seeds. The total biomass and seedling height of A. villosumt were promoted by low concentration but were inhibited by high concentration of aqueous extracts of pericarp and leaves of C. migao. At the treatment of pericarp aqueous extract, soluble protein, free proline and MDA contents decreased, while soluble sugar content, soil polyphenol oxidase activity, and urease activity increased. At the treatment of leaf aqueous extract, MDA content, SOD activity and urease activity increased, while free proline content decreased. In total, 92 compounds identified by GC-MS were from the pericarps and leaves of C. migao, seven compounds out of which are closely related to the allelopathy of C. migao. Although both pericarp and leaf of C. migao had allelopathic effects on A. villosumt seedlings, but the most allelopathic parts (pericarp) would not accumulate in large quantity in the forest floor. It is feasible to construct the intercropping system of C. migao-A. villosumt by timely cleaning up fruit and leaf litter of C. migao and interplanting A. villosumt in the understorey.

Simulation of canopy rainfall interception of Platycladus orientalis forest and its mixed forest using the modified Gash model.

LI Yi-ran, MA Rui, ZHANG Yong-tao, CHENG Tian-tian, LI Ze-dong, NIU Yong

2019, 38(5):  1331-1338. 

Asbtract ( 345 )   PDF (686KB) ( 168 )  

The modified Gash model is commonly used to simulate the canopy interception process. We explored its applicability in a Platycladus orientalis pure forest and a mixed forest of P. orientalis andCotinus coggygria located in Badaling Forest Park of Beijing. Data from May to October in 2013 were collected and used to fit the modified Gash model. The sensitivity of the model parameters was analyzed. The results showed that the measured values of throughfall, stem flow and canopy interception in the P. orientalis pure forest were 395.2, 22.3 and 129.5 mmrespectively, and those measured values of the mixed forest were 414.6, 12.2 and 120.1 mm respectively. Based on the modified Gash model, the simulated values of throughfall, stem flow and canopy interception in the pure forest were 415.80, 18.04 and 113.09 mm respectively, with the relative errors being 5.2%, 19.0%, and 12.7% compared with the measured values. The simulated values of the mixed forest were 454.26, 10.27 and 82.40 mm, with the relative errors of 9.6%, 15.6% and 31.4%. The following indices, saturated canopy waterholding capacity (S), average rainfall intensity (R), average saturated canopy evaporation rate (E), canopy density (c), saturated trunk storage capacity (S_t) and stem flow coefficient (P_t) were used in the sensitivity analysis. The results of sensitivity analyses showed that, in the pure forest, when the parameters varied between -50% to -20%, the simulated canopy interception was the most sensitive to the parameter S, followed by c, R,E, S_t and P_t. When the parameters varied between -20% to 50%, the parameter S also was the most sensitive factor for the simulated canopy interception, followed by E,R,c, S_t and P_t. In the mixed forest, when the parameters varied between -50% to +50%, the simulated canopy interception was the most sensitive to the parameter S, followed by E, R, c, S_t  and P_t. According to results of accuracy analysis, we suggest that the modified Gash Model was more suitable for the P. orientalis pure forest than for the mixed forest of P. orientalis and C. coggygria. The parameter S was a primary factor affecting the accuracy of the model output.

Comprehensive evaluation of cold resistance of individual plants of different Acacia species.

HE Qin-fei, CAO Yan-yun, PENG Yu-hua, HUANG Zhi-ling, HAO Hai-kun, TAN Zhang-qiang

2019, 38(5):  1339-1345. 

Asbtract ( 393 )   PDF (782KB) ( 166 )  

Cold resistance of individual plants of three Acacia species \[Acacia mangium ×A. auriculiformis (Chiyun) (CY), A. mangium× A. auriculiformis (ZJ) and A. mangium (MZ)\] was evaluated by subjecting the cutting seedlings of eight individuals to different low temperatures (12, 9, 6, 3, 0 ℃, and 25 ℃ as the control). Six physiological indices (relative conductivity, malondialdehyde, soluble sugar, free proline, soluble protein, and superoxide dismutase content) were analyzed. Cold resistance ability of individual plants was evaluated by the membership function method. The results showed that relative conductivity, free proline, soluble protein and soluble sugar contents in the leaves increased under low temperature, which could be used as the reference indices for evaluating cold resistance of Acacia. Temperature threshold for cold injury of Acacia was 0-6 ℃ after low temperature stress. Results from the membership function analyses showed that ZJ1, ZJ4 and CY1 had the highest cold resistance, while MZ11 had the lowest cold resistance.

Effects of slope form on natural regeneration and growth of Calamus rhabdocladus.

LI Yan-bing, FAN Shao-hui, PENG Chao, CHEN Ben-xue, LIANG Chang-qiang, LIU Guang-lu

2019, 38(5):  1346-1351. 

Asbtract ( 365 )   PDF (607KB) ( 157 )  

To examine the effects of slope form on natural renewal of Calamus rhabdocladus in the lowland secondary rainforest, we investigated population size, growth characteristics (plant height, ground diameter, and leaf area), and mortality rate of Calamus rhabdocladus in Ganzaling, Hainan Province. The relationship between different slope forms (convex slope, gentle slope, and concave slope) and population renewal at different growth stages was analyzed by means of variance analysis, multiple comparison, and correlation analysis. The results showed that slope forms had significant effects on population size, plant height, basal diameter, leafarea, relative growth rate, and mortality of C. rhabdocladus (all P<0.05), but with no effect on the ratio of height to diameter (P>0.05). The population size, plant height, and leaf area of C. rhabdocladus were the highest on concave. The slope form was an important environmental factor affecting population size and growth of C. rhabdocladus by changing soil water, nutrient and light in Ganzaling of Hainan. The concave slope was relatively favorable to regeneration and growth of C. rhabdocladus. In the course of resource renewal and conservation of artificial cultivation of C. rhabdocladus, the concave slope should be given priority.

Population structure and companion community characteristics of the endangered species, Rhododendron changii.

YANG Yang, MA Li-hui, WANG Hai-yang

2019, 38(5):  1352-1362. 

Asbtract ( 391 )   PDF (965KB) ( 222 )  

Rhododendron changii is a threatened plant species. Here, we investigated its population structure, species composition of companion communities, vertical stratification and plant diameter class, and species diversity in tree and shrub layers. Furthermore, the relationships between R. changii population and species composition of tree and shrub layers in community and environmental factors were examined using redundancy analysis (RDA) and canonical correspondence analysis (CCA). The results showed that: (1) The diameter class pattern of R. changii was unimodal, indicating that the population renewability was limited in a discrete way and lack of seedlings. In addition, the sapling period was another peak of death, implying the population was continuing to decline. (2) There were four companion communities around the population, containing a total of 56 woody species belonging to 23 families and 40 genera. The dominant families were Fagaceae, Rosaceae, Aceraceae, and Ericaceae, with a large number of Fargesia spathacea in the understory. The diversity index of tree and shrub layers was relatively low with an underdeveloped herbaceous layer. The companion communities 1 and 2 belonged to shrubs with an average height of 1-1.5 m, the community 3 was an evergreen broadleaf-mossy dwarf forest with an average height of 3-4 m, and the community 4 was an evergreen deciduous mixed forest with an average height of 8-10 m. R. changii grew in the lower layer in all companion communities, while dominated in shrub communities compared to arbor one. There was a large proportion of small-diametric individuals of shade-tolerant species in the community, indicating increasing competition in the understory. (3) The results of the forward selection and Monte Carlo analysis showed that slope position exerted a significant impact on species composition of tree layer, while the canopy closeness and slope exposure controlled that of the shrub layer (P<0.01). Litter thickness and air humidity were two primary environmental factors affecting R. changii seedlings, while canopy coverage and slope exposure influenced the saplings and adults of R. changii. Besides, saplings and adult plants were also affected by the species density and bamboo coverage (P<0.01). In conclusion, it is important to decrease canopy cover, interfere with the growth of the other saplings and F. spathacea in forests and clean up litter layer, to relieve the endangered situation and maintain population development of R. changii.

Responses of mineral nutrients in brown rice of indica and japonica cultivars (Oryza sativa L.) to elevated atmospheric \[CO₂\]. 

JIANG Qian, ZHU Chun-wu, LIU Gang, XU Xi, CHEN Chen, ZHANG Ji-shuang, ZHU Jian-guo

2019, 38(5):  1363-1369. 

Asbtract ( 288 )   PDF (695KB) ( 248 )  

To estimate the effects of elevated \[CO₂\] on the mineral nutrition of brown rice as well as the differences of effect between indica and japonica cultivars (Oryza sativa L.), the concentrations and accumulations of Fe, Mn, Cu, Zn, Ni and Se in brown rice of indica IIY084 and japonica WYJ23 were investigated at a free-air CO₂ enrichment (FACE) experimental facility in eastern China during 2013 and 2014. The target \[CO₂\] of the FACE plots was 200 μmol·mol^-1 higher than the ambient. The results showed that there were significant CO₂ effects on grain and brown rice yields in both years. Average grain yield of two years increasedby 33.1% (IIY084) and 14.3% (WYJ23), and the average brown rice yield enhanced by 34.3% (IIY084) and 16.3% (WYJ23) respectively under elevated \[CO₂\]. The average brown rice Fe, Mn, Cu, Zn, Ni and Se concentrations of two years in IIY084 decreased by 10.4%, 13.4%, 15.5%, 11.7%, 25.7% and 3.2%, respectively, while the change trend of those in WYJ23 were inconsistent. Especially, there were negative CO₂ effects on Mn, Cu, Zn and Ni (P<0.05) concentrations in 2014. In addition, there were significant differences in Fe (P<0.1, 2014), Mn (P<0.01, 2013 and 2014), Cu (P<0.1, 2014), Zn (P<0.01, 2013 and 2014), Ni (P<0.01, 2014) and Se (P<0.05, 2013; P<0.01, 2014) concentrations in brown rice between the two cultivars. Fe, Mn, Cu, Zn, Ni and Se accumulations in both cultivars were affected by \[CO₂\] enrichment. Compared to the ambient, the average mineral nutrient accumulations of two years at elevated \[CO₂\] were increased by 2.1%-29.2% (IIY084) and 12.8%-19.3% (WYJ23), respectively. In short, concentrations of Fe, Mn, Cu, Zn, Ni and Se in the brown rice of II084 had greater reduction than that of WYJ23 under elevated \[CO₂\]. Taking into account the health of mankind who depend on rice, feeding on IIY084 may cause a greater risk of Fe, Mn, Cu, Zn, Ni and Se deficiency than WYJ23 under the global elevated \[CO₂\] scenario. In the future, more attentions should be paid on rice cultivars that can alleviate the nutrient deficiency due to the decline of mineral nutrition when screening and breeding of yield-increasing cultivars to ensure grain security.

Dry matter accumulation, transportation and their relationships with yield of japonica hybrid rice in northern China under different fertilization conditions.

FANG Min, SHI Wen-hua, JIANG Yi-hui, LIU Xiao-lin, LIU An-jin, WANG Xin, MIAO Wei

2019, 38(5):  1370-1375. 

Asbtract ( 415 )   PDF (439KB) ( 191 )  

To explore the reasons for the large biomass and strong stress resistance but no outstanding yield advantage of japonica hybrid rice, 140 hybrid combinations of japonica hybrid rice, which were cross-fertilized from 140 restorer lines and BT-type cytoplasmic male sterility (BT-CMS) line Liao-99A, were used to examine dry matter accumulation, transportation and their relationships with yield under two fertilization treatments: normal fertilization (including basic fertilizer, tillering fertilizer and spike fertilizer) and low fertilization (including basic fertilizer only). The results showed that lower seed setting rate and 1000-grain weight were the most important factors limiting the yield advantage of japonica hybrid rice. The yield of japonica hybrid rice was more dependent on dry matter accumulation after full heading stage. Under the low fertilization treatment, dry matter export percentage from stem and sheath increased and that from leaf decreased. Reducing the export percentage of dry matter accumulation in stem and increasing that in leaf were beneficial to decrease the yield discrepancy under different fertilizer treatments and promote the superiority of japonica hybrid rice in tolerating low-fertility. Our results could provide important insights in the selection of resistance breeding of japonica hybrid rice.

Effects of long-term mechanical compaction on preferential flow in oasis cropland.

YAN Jia-liang, ZHAO Wen-zhi

2019, 38(5):  1376-1383. 

Asbtract ( 309 )   PDF (1082KB) ( 308 )  

Long-term mechanical compaction could affect soil physical and hydraulic properties. These changes have further influence on the strength of soil preferential flow, but there is no consensus on such effect. To investigate the effects of long-term mechanical compaction on soil pre-ferential flow, we set three plots in each of the margin area (continuous compaction area, CC) and normal farming area (CK) in the Linze oasis croplands, and carried out a dye tracer experiment using the brilliant blue FCF solution. We measured soil bulk density, total soil porosity, and soil saturated hydraulic conductivity. Our results showed that long-term mechanical compaction had no effects on soil physical and hydraulic properties in the plow layer (0-20 cm), but had significant effects in the plow pan (20-60 cm) (P<0.05). Mechanical compaction increased soil bulk density by 10.8%, and decreased total soil porosity and soil saturated hydraulic conductivity separately by 11.9% and 32.3% at the 20-60 cm depth. Long-term mechanical compaction significantly affected the characteristics and strength of soil preferential flow. Lateral flow in continuous compaction area was significantly different from the macropore flow in normal farming area. The strength of soil preferential flow in continuous compaction area was also significantly greater than that in normal farming area (P<0.05), which was mainly related to the maximum infiltration depth (P<0.05). Our results indicated that long-term mechanical compaction significantly affected the soil physical and hydraulic properties in the plow pan and enhanced the strength of soil preferential flow.

Effects of biochar addition on soil microbial biomass C, N and enzyme activities in cucumber continuous cropping.

ZHANG Zhi-long, CHEN Xiao-min, QU Cheng-chuang, CHEN Can, ZHANG Jun, HUANG Chun-yan, LIU Yun-mei

2019, 38(5):  1384-1391. 

Asbtract ( 443 )   PDF (569KB) ( 221 )  

he objectives of this work were to clarify the effects of biochar addition on microbial biomass and enzyme activities in continuous cropping soil and to provide scientific basis for alleviating soil continuous cropping obstacles. There were six rates of biochar application (0, 5, 10, 20, 30, and 40 t·hm^-2, designated as CK, C₁, C₂, C₃, C₄ and C₅, respectively). Soil samples from 0 to 20 cm layer were collected in the third season of cucumber ripening to measure soil microbial biomass and enzyme activities. The results showed that microbial biomass C and N increased at first and then decreased with the increases of biochar addition rate. C₂ and C₃ treatments significantly increased microbial biomass C by 70.62% and 81.09% (P<0.01). Meanwhile, significant increases in microbial biomass N were observed in C₂ and C₃ treatments (P<0.01). Soil enzyme activity was increased first and then decreased with increasing biochar application rates. C₂, C₃ and C₄ treatments significantly increased the catalase activity. Meanwhile, C₄ treatment significantly increased the urease activity by 84.08%. The alkaline phosphatase activities in C₃, C₄ and C₅ treatments showed significant increases. Results from the cluster analysis revealed that the six treatments could be classified into four distinct groups (CK, C₁, C₂-C₃, and C₄-C₅) when the Eudidean distance was 1.01. Furthermore, the highest values of microbial biomass C and N, catalase, and urease and alkaline phosphatase activities were obtained when the application rates of biochar were 20, 20, and 30 t·hm^-2, respectively.

Modeling of organic nitrogen mineralization in paddy soils in Dongting Lake region of China.

LI Wen-jun, ZENG Xi-mei, PENG Bao-fa, YANG Ji-feng, ZHAO Di

2019, 38(5):  1392-1401. 

Asbtract ( 435 )   PDF (730KB) ( 186 )  

Soil organic nitrogen mineralization (SONM) is a critical N cycling process. Quantitative prediction of SONM is essential for assessing soil N supply capacity. In this study, four different mineralization models (i.e., effective accumulated temperature, hyperbolic, One-pool and Two-pool exponential models) were selected to fit SONM process in nine typical paddy soils in Dongting Lake region. The relationships between model parameters and soil organic nitrogen components were analyzed using correlation and path analysis. Results showed that SONM rate substantially varied with soil subtypes. The cumulative mineralized N measured throughout the whole incubation periods generally ranked as Fluvisols > Gleysols > Cambisols. Basing on the coefficients of determination (R²), root meansquare error estimations and model fitted parameter values, all  the four models could effectively simulate the SONM process, of which Twopool exponential model consistently had the best fitting effect, followed by hyperbolic, effective accumulated temperature and the One-pool exponential model. Pearson correlation analysis showed that model fitted SONM rate constants were insignificantly (P>0.05) correlated with soil organic nitrogen components due to their weak variability. On the contrary, all model parameters of characterizing SONM intensity or potential had significant positive correlations with amino acid N and ammonium N (r=0.755-0.950, P<0.05). Furthermore, amino acid N was the primary organic N component directly affecting soil mineralizable N capacity. Our results suggested that the Two-pool exponential model could simulate SONM process more effectively than others as it could reveal the mineralization processes of soil active and slow pools of mineralizable N simultaneously. Thus, Two-pool exponential model could improve the validity and accuracy of SONM prediction by assigning fixed values for the mineralization rate constants of soil active and slow mineralizable organic N pools.

Establishment of process rainfall indices for waterlogging damage in key growth stage of rice in cold region.

LV Jia-jia, WANG Liang-liang, SHI Lei, WANG Ming, LIAN Ping, ZHU Hai-xia, JIANG Li-xia, ZHAO Hui-ying

2019, 38(5):  1402-1409. 

Asbtract ( 394 )   PDF (671KB) ( 174 )  

The establishment of process rainfall indices for waterlogging damage to rice in cold region is important for coping with climate change, preventing and mitigating natural disasters, and ensuring production safety. Based on historical data of waterlogging damage and phenophase of japonica rice from 1961 to 2000, combined with daily precipitation data of 73 meteorological stations, we inverted rainy days and process rainfall of waterlogging at the key growth period of rice and established the process precipitation sequence of cold rice waterlogging samples, with japonica rice in Heilongjiang Province as the research object. The precipitation level index of waterlogging process of rice in cold regions was constructed by using K-S distribution fitting test and the lower limit value of confidence interval to determine the threshold value. The indices were verified with the reserved disaster samples. The results showed that under the condition of poor drainage of cropland, when rainy days were within 1-3, the lower limits of rainfall for rice with mild, moderate and severe waterlogging were 48, 89 and 136 mm at tillering stage, and 44, 87, 102 mm at heading stage, respectively. When rainy days were within 4-7, the lower limit values of rainfall were 68, 97 and 142 mm at tillering stage, and 66, 103, 127 mm at heading stage, respectively. The calculated results of the indices were well consistent with the historical waterlogging damage records. Our results can provide support for quantification of rice waterlogging damage in cold regions.

Effects of irrigation and nitrogen fertilization regulations on soil nitrogen supply potential in greenhouse.

WU Han-qing, LI Su-jie, LIU Yang-yi, ZHANG Xin-rui, ZHAO Qi-long, LI Meng-si, ZOU Hong-tao, DANG Xiu-li, ZHANG Yu-ling, YU Na

2019, 38(5):  1410-1418. 

Asbtract ( 437 )   PDF (578KB) ( 186 )  

Soil organic carbon (SOC), total nitrogen (TN), fixed ammonium (FA), microbial biomass nitrogen (SMBN) and organic nitrogen fractions are important indicators of soil nitrogen supply potential. A three-year tomato field experiment with mulchfilm drip irrigation was conducted to investigate the effects of lower irrigation limits (25, 35, and 45 kPa) and nitrogen fertilization levels (75, 300, and 525 kg·N·hm^-2) on greenhouse soil N supply potential (including SOC, TN, FA, SMBN and soil organic nitrogen fraction storage). The results showed that the main effects of irrigation and nitrogen fertilization on the storage of SOC and TN were statistically significant, but that was not the case for their interactive effects. The main and interactive effects of irrigation and nitrogen fertilization on the storage of greenhouse soil organic nitrogen fractions, SMBN and FA at 0-30 cm soil layer were significant in the fallow period. Under different treatments of irrigation and nitrogen fertilization regulations, the proportions of acidolysable organic nitrogen fractions in greenhouse soil during the fallow period followed the order: acidoly sable amino acid nitrogen (AAN) > acidolysable ammonium nitrogen (AN) > acidolysable unknown nitrogen (UN) > acidolysable amino sugar nitrogen (ASN). AAN was the major fraction of greenhouse soil organic nitrogen. AAN had a significant positive correlation with AN, ASN, acid hydrolyzed nitrogen (AHN), non-acidrolyzable nitrogen (NAN), SOC and TN. There was a significant positive correlation between FA and AAN. SMBN was positively correlated with ASN and AN, and negatively correlated with AAN. Therefore, AAN, SMBN and FA could be used as indicators for greenhouse soil nitrogen supply potential in a certain extent. Reasonable regulations of irrigation and nitrogen fertilization are conducive to improving greenhouse soil nitrogen supply potential.

Effects of longterm simulated nitrogen deposition on soil arthropods in a Pleioblastus amarus plantation in rainy area of western China.

LI Zeng-yan, QIU Xi-rong, CHEN Guan-tao, ZHENG Jun, LI Juan, TU Li-hua

2019, 38(5):  1419-1425. 

Asbtract ( 468 )   PDF (572KB) ( 180 )  

Soil fauna plays an important role in ecosystem nutrient cycling. Soil arthropods play a fundamental role in litter breaking process and in the formation of soil aggregates. We examined the effects of chronic N deposition on soil arthropod communities in a Pleioblastus amarus plantation in the rainy area of west China, with a field experiment involving monthly simulated N deposition using NH₄NO₃ since 2007. There were four levels of N addition: control (0 g N·m^-2·a^-1), low N (5 g N·m^-2·a^-1), medium N (15 g N·m^-2·a^-1) and high N (30 g N·m^-2·a^-1). After six and half years of treatment, litter of P. amarus and soil samples were collected in January 2014, October 2014 and January 2015. The results showed that 1852 individuals of soil arthropods were found, which could be classified into 3 phyla, 7 classes and 18 orders. The individuals and species number of soil arthropods increased with increasing N deposition levels in the litter layer, being significantly higher in the high N treatment than that in control. In the soil layer, the individuals and species number of soil arthropods decreased with increasing N deposition levels, although there was no significant difference among the different treatments. Simulated N deposition had no significant effects on the Shannon diversity, Pielou evenness, and Menhinick richness indices of soil arthropods in both litter layer and soil layer.

Responses of the invasive golden apple snails (Pomacea canaliculata) at different life-history stages to acidic stress.

JIN Shu-rui, LUO Du, ZHANG Hai-tao, MU Xi-dong, HU Yin-chang

2019, 38(5):  1426-1432. 

Asbtract ( 438 )   PDF (688KB) ( 195 )  

To examine the differences in responses of the invasive golden apple snails at various life-history stages to acidic stress, the survival behavior and lethal effect of Pomacea canaliculata with shell height of 5, 10, 15, 20, 25, 30, 40, 50, and 60 mm in the acidic environment were examined. At pH≥4, movement and spawning of P. canaliculata was normal within seven days, and its reactions to the acidic stress became stronger with the increases of acidity. The median lethal time (LT₅₀) at pH=2.0 was less than that at pH=3.0. The LT₅₀ was the largest in the 40 mm shell height group (22.95 h), while it was the smallest in the 60 mm shell height group (13.55 h). There were significant differences in mortality among different shell height groups (P<0.001) and among different time (P<0.001). The interaction between shell-height effect and timeeffect was significant (P<0.001). At pH=2.0, the mortality rates of P. canaliculata with shell height of 40 mm at 24 h and 30 h were 46.67%±11.50% and 53.33%±11.50%, respectively, being significantly lower than those in other groups. At pH=3, the mortality of P. canaliculata with shell height of 60 mm was 86.67%±11.50% at 24 h. The mortality (66.67%±11.50%) of P. canaliculata with shell height of 40 mm was lower than the other groups at 30 h. The mortality of P. canaliculata in the groups of 5, 10, 20 and 60 mm was 100%. Therefore, the variation of the snails’ acid resistance was parabolic shaped, with an increase following a decline along with the snail’s development. By illustrating the responses of the snails at various developmental stages to acidic stresses, our results would help explain their ecological adaptation mechanism and invasion strategy from the view of life-history.

The blocking effect of bubble curtain on Schizothorax oconnori.

FAN Wen-tong, LIU Yan, WANG Qian, SHI Xiao-tao, ZHAO Shou-jiang, LIU Guo-yong, LIN Chen-yu, XU Jia-wei, JIN Zhi-jun

2019, 38(5):  1433-1437. 

Asbtract ( 350 )   PDF (948KB) ( 179 )  

To investigate the blocking effect of bubble curtain on Schizothorax oconnori, three kinds of bubble curtain with different gas flows (60, 90 and 120 L·min^-1) were set up in the ringshaped water tank. Under the conditions of still water, the blocking effect of bubble curtain on S. oconnori in different periods and the spatial distribution of the fish were observed. Three kinds of bubble curtains had obvious blocking effect on the fish, but with no significant difference in blocking rate (P=0.130). The highest blocking rate reached 81.3% when the gas flow was at 60 L·min^-1. The fish had no obvious adaptability to the bubble curtain during the experiment. In addition, the fish preferred to stay near the bubble curtain at gas flows of 90 and 120 L·min^-1. Our results provide reference for the application of bubble trap technology in engineering.

Effects of polyethylene glycol-4000 on the electrophysiology of the intestinal epithelium of puffer fish (Takifugu obscurus).

ZHU Lin, LAI Qi-fang, GAO Peng-cheng, ZHANG Hai-ming, ZHOU Kai, YAO Zong-li

2019, 38(5):  1438-1443. 

Asbtract ( 283 )   PDF (580KB) ( 152 )  

To evaluate the effects of polyethylene glycol (PEG) on fish intestinal epithelium, we examined the electrophysiological responses of intestinal tissue from the puffer fish (Takifugu obscurus) using Ussing chambers. We measured the open circuit voltage, short circuit current (Isc), variation of shortcircuit current (?Isc), conductance （G）, and transepithelial potential （TEP）of the intestinal epithelium. The results showed that the residual concentration of PEG-4000 in the intestine within 6 h was 1.83 g·L^-1, which was significantly higher than that in the control (P<0.05). The residual rate was 184%. The intestine epithelial Isc of puffer fish in PEG group was 69.20 μA·cm^-2, which was significantly lower than that in the control (117.23 μA cm^-2) (P<0.05). The ?Isc of the PEG group was significantly lower than that of the control, being only 68.57% of that in the control. The average conductance of the PEG group was around 24.97mS·cm^-2, which was significantly lower than that of the control (36.22 mS·cm^-2). These results indicated that PEG-4000 was not permeable and had a high residual rate in the intestinal tract of puffer fish, which hindered ion channels and reduced the active flow of ions across the epithelium. Our results provide evidence that Ussing chamber is a valuable tool inassessing the effects of pollutants such as PEG on electrophysiological changes and ion transportation in the intestinal tract of fish.

Spatio-temporal evolution of water areas and croplands in the three provinces of Northeast China based on remote sensing data.

XUE Bing, XIAO Xiao, LI Jing-zhong, XIE Xiao, LU Cheng-peng

2019, 38(5):  1444-1452. 

Asbtract ( 403 )   PDF (4215KB) ( 173 )  

Water area and cropland are important resources for food production, the temporal and spatial changes of which maintain the sustainable development of regional agriculture. The three northeastern provinces in China are typical areas where human activities have exerted significant impacts on land cover change. It is of great significance to analyze the changes of water areas and croplands and their driving mechanisms from the perspective of humanenvironment coupling system. Through the land use classification data obtained from remote sensing interpretation in the three provinces in 2000, 2005, 2010, and 2015, the spatial and temporal evolution pattern of water areas and croplands were quantitatively expressed using spatial analysis and visualization methods. The results showed that water areas had changed from “slight reduction slight increase-sharp decrease” during the 15 years, with an average annual reduction of 213.48 km². The main reason was that the beaches, lakes, and other waters were converted into croplands. The water areas in the middle and upper reaches of the Songhua River and the Dongliao River watershed had been significantly reduced. The cropland areas had continued to increase due to deforestation and land reclamation, with a rate of 707.94 km²·a^-1. The area of reduced croplands turned into waters was less than that of water areas transferred to croplands. Our results provide scientific support for formulating agricultural resource management policies and implementing agricultural sustainable development planning programs in the three northeastern provinces of China.

Spatial-temporal changes of fraction of absorbed photosynthetically active radiation in Qinling-Daba Mountains from 2006 to 2015.

ZHANG Jin-cheng, ZHOU Wen-zuo

2019, 38(5):  1453-1463. 

Asbtract ( 394 )   PDF (8588KB) ( 185 )  

Fraction of absorbed photosynthetically active radiation (FPAR), the part of photosynthetically active radiation that is absorbed by vegetation, is one of the important parameters in terrestrial ecosystem simulating models. The purpose of this study was to clarify spatial-temporal changes of the FPAR in Qinling-Daba Mountains where is on the important north-south climate transitional zone in China. Based on the MODIS remote sensing data and climate datasets from 2006 to 2015, a linear regression analysis was used to examine spatial-temporal changes of FPAR at pixel scale in Qinling-Daba Mountains. A correlation analysis was conducted to analyze the relationship between vegetation FPAR and climate factors. The results showed that there was spatial difference in FPAR distribution in the Qinling-Daba Mountains, with high FPAR values in the center and southeast and lower values in the northwest and northeast of study area. They decreased with altitude, with obvious vertical zonality along mountains. From 2006 to 2015, the FPAR increased in the central region and decreased in the surrounding area. The areas with significantly increased FPAR values were mainly distributed in the basins of Jialing River and Danjiang River and the downstream of Hanjiang River. The FPAR values slightly decreased in parts of the Gannan Plateau and the Western Sichuan Plateau. During last decade, the FPAR of vegetation, on the whole, appeared a significantly increasing trend with a rate of 4.8%·10 a^-1 (P<0.05) and the most outstanding vegetation was crop (P<0.05). Among the four seasons, the FPAR significantly increased in winter (P<0.05). Annually, the correlation between vegetation FPAR and climate factors showed that vegetation FPAR was more correlated with mean annual temperature than that with mean annual precipitation on all vegetation types. However, the correlations differed among vegetation types. Coniferous forest and broad-leaved forest FPAR had higher correlations with mean annual temperature than other types, while grasslands and croplands were influenced much more by mean annual precipitation than by mean annual temperature.

Spatial and temporal variations of vegetation net primary productivity and its responses to climate change in Shandong Province from 2000 to 2015.

LIU Yu-hong, ZHANG Jun, ZHANG Chun-hua, XIAO Bei, LIU Lu, CAO Yu

2019, 38(5):  1464-1471. 

Asbtract ( 572 )   PDF (4654KB) ( 224 )  

Net primary productivity (NPP) of vegetation is an important indicator for the ecological functions and carbon cycling in terrestrial ecosystems. Based on MODIS MOD17A3 NPP and meteorological data over the past 16 years (from 2000 to 2015), the spatial and temporal variations of vegetation NPP in Shandong Province, as well as its responses to climate change, were estimated using the methods of correlation, regression, and spatial analysis. The results showed that vegetation NPP increased with fluctuations from 2000 to 2015, with mean annual value between 501.29 and 583.55 g C·m^-2·a^-1. Vegetation NPP increased at a rate of 2.05 g C·m^-2·a^-1 during the study period. There were substantial spatial variations in vegetation NPP, with high values in the south and east and low values in the north and west of the province. The vegetation NPP values in most areas of Shandong Province ranged from 200 to 400 g C·m^-2·a^-1, especially in the central and west parts. In areas with 44.5% of provincial total area, the mean vegetation NPP showed a slight increase for the period of 2000-2015, mainly occurring in the central, west and southwest regions. There were significantly positive correlations between vegetation NPP and temperature and precipitation. The latter was the dominant climatic factor driving the changes of vegetation NPP.

Spatial and temporal variation of rural human settlements in China based on provincial data.

LI Chen, ZHAO Rui, TANG Qing-yuan

2019, 38(5):  1472-1481. 

Asbtract ( 431 )   PDF (2660KB) ( 323 )  

Improving the rural human settlement environment is important for rural revitalization and building a welloff society in an allround way. Scientific evaluation of the construction of rural human settlement environment can provide decision-making basis for its optimization in China. Here, the coefficient of variation, Gini coefficient, Theil index, and convergence/divergence method were used to analyze the spatial-temporal variation of rural human settlement environment in China’s 30 provinces and three economic zones from 2006 to 2015. Results showed that China’s rural human settlement (RHS) score increased by 6.26%. The spatial pattern of “East, Middle, West” descending steps in the rural human settlement environment remained unchanged. The overall difference of human settlement environment in the rural areas tended to shrink, and the coefficient of variation, Gini coefficient and Theil index decreased by 5.32%, 6.50% and 10.59% respectively. The rural human settlement tended to be improved for China’s provinces mainly due to the improvement of rural living conditions, but with partial deterioration of the situation. The primary constraint factor of rural human settlement was basic public services, followed by environmental quality, and economic and social factors.

Urban landscape classification system under influences of atmospheric environment: A case study in Beijing.

LUAN Qing-zu, LI Bo, ZHANG Xin-shi

2019, 38(5):  1482-1490. 

Asbtract ( 365 )   PDF (5479KB) ( 148 )  

Scientific landscape classification system is a precondition requirement in research on atmospheric environment impacts of urban landscape pattern. However, there is no universal landscape classification system, especially lacking a landscape classification system under influences of atmospheric environment. After reviewing theories in landscape classification and methods in surface classification in meteorology, we proposed a landscape classification system oriented for the influence of atmospheric environment according to the nature of urban landscape and the characteristics of physical composition, which is a three-layer system consisting of landscape class, landscape sub-class and landscape type, using land use types and urban land surface parameters as classification criteria. Then, a case study was carried out in Beijing where urban expanding has significant influence on atmospheric environment. We analyzed potential impacts of urban landscape pattern on regional atmosphere through the landscape classification map produced by 3S technology. The results showed that landscape affected by human activities was in relatively high level among the first landscape classes. In second landscape sub-classes, woodland contributed the largest part (54.73%), while cities and towns contributed 15.09%. Among third landscape types, C7 was the matrix of cities and towns, and C3, C2 and C6 held percent less than 0.1% respectively, which implied that landscape with high surface roughness was still rare and helpful for atmospheric ventilation. The proposed classification system could reflect actual features of all kinds of landscape classes that produced impacts on atmospheric environment, which was helpful for understanding the effects of urban landscape on atmospheric environment and providing suggestions for urban planning and atmospheric management.

Spatiotemporal analysis of urban expansion in Xi’an from 1984 to 2016.

GE Yuan-yuan, HAN Lei, ZHAO Yong-hua, AO Yong, Ding Juan, ZHU Ying-ying, LIU Bing

2019, 38(5):  1491-1499. 

Asbtract ( 594 )   PDF (3647KB) ( 372 )  

Based on the Landsat TM/OLI remote sensing images and social statistical data of Xi’an in 1984, 1996, 2006 and 2016, the construction land information in the main urban area of Xi’an City was extracted through the ArcGIS 10.5. The spatiotemporal expansion characteristics of Xi’an City were analyzed using expansion intensity, fractal dimension, and elasticity coefficient. The driving forces and the urban sprawl trend of Xi’an were also studied. The results showed that the construction land increased by 478.62 km² from 1984 to 2016, being 3.27 times larger than that in 1984. The average annual expansion intensity was 6.88% with a growth rate of 14.50 km²·a^-1. The Barycenter of Xi’an City moved toward the northwest by 1.53 km. There were two types of urban expansion pattern including filling and expansion. The urban spatial expansion was unbalance. The city was expanded from center areas (Lianhu district, Xincheng district, Beilin district) to periphery suburb (Baqiao district, Yanta district, Weiyang district and Chang’an district). In general, the coordination relationship between the urban expansion and population growth was weak, with faster urban expansion than the population growth. Under the scenarios of the restriction of land space planning and the delimitation of urban boundary line, the core construction of Xi’an City should focus on protecting the historical culture. The development of population, environment, and economy should be coordinated and population distribution should be rationally planned, with the aim to build a unique national modern central city.

Effects of continuous application of organic fertilizer on the distribution of organic carbon in soil profile and its relationship with heavy metals.

WANG Yi-wen, XU Hao, RU Shu-hua, SU De-chun

2019, 38(5):  1500-1507. 

Asbtract ( 464 )   PDF (680KB) ( 168 )  

A field positioning experiment was conducted to examine the distribution of organic carbon and easily oxidized organic carbon, and their correlation with the concentrations of heavy metals in soil profile after four years continuous application of three different kinds of organic fertilizers. The results showed that after applying organic fertilizers, organic carbon and easily oxidized carbon mainly accumulated in the 0-15 cm soil layer, and their concentrations decreased with increasing soil depth. When high amount of chicken manure was applied, organic carbon could migrate to the 15-30 cm soil layer, and easily oxidized organic carbon could migrate to the 60-90 cm soil layer. Organic carbon didn’t significantly migrate when pig manure and sludge were applied, while easily oxidized organic carbon migrated to the 60-90 cm soil layer under high amount application of pig manure and sludge. The proportion of oxidized organic carbon to total organic carbon was much higher in the treatments of pig and sludge manure application as compared to chicken manure. There was a significant positive correlation between the distribution of organic carbon and easily oxidized organic carbon and Cu, Zn and Cd in the soil profile after application of different organic fertilizers.

Diffusion fluxes of heavy metals at the sediment-water interface during summer and winter from Aha Reservoir, Guiyang.

XIAO Xiong, LONG Jian, ZHANG Run-yu, CHEN Jing-an, ZOU Yin-hong, WU Qiu-sheng, WU Jin-nan

2019, 38(5):  1508-1519. 

Asbtract ( 451 )   PDF (900KB) ( 243 )  

Distribution characteristics and interfacial diffusion fluxes of seven heavy metals (Co, Ni, Cu, Zn, As, Cr, and Pb) were examined in the overlying water and sediment porewater from four sampling sites from Aha Reservoir in summer and winter, to understand the pollution status of dissolved heavy metals in the water body. Results showed that the average concentrations of dissolved heavy metals in the overlying water from Aha reservoir were lower than the standard of Grade I of Environmental Quality Standard for Surface Water (GB 3838-2002) and the Sanitary Standard for Drinking Water (GB 5749-2006) in China. Concentrations of As, Co and Cr in the bottom water increased during the anoxic period in summer, and the vertical changes of all heavy metals during the mixed season in winter were not significant. The mean concentrations of heavy metals in pore water were significantly higher than that in overlying water. There were significant positive correlations among Co, Ni and As, indicating their migration and transformation processes being affected by the iron-manganese cycle in Aha Reservoir. Concentrations of Cu, Zn and Pb had a positive correlation with the same pollution source. Results from the analysis of the diffusion fluxes of heavy metals at the sediment-water interface (SWI) showed that Zn remained negative diffusion, which indicated that sediment had a good adsorption effect on Zn. Co, Ni, As and Pb showed positive values at the SWI. The concentration of As reached 2.07 μg·cm^-2·a^-1 in summer, which may impose a greater release risk on the overlying water. Our results demonstrated that the pollution control of heavy metals had achieved remarkable results in the past decade in Aha Reservoir.

Characteristics of plant community in different types of coal mining subsidence in Bin-hang mining area.

DU Hua-dong, SONG Shi-jie, ZHANG Yong, ZHANG Yi-yang

2019, 38(5):  1520-1527. 

Asbtract ( 346 )   PDF (1007KB) ( 161 )  

Subsidence is one of the most serious forms of coal mining process on environment, which directly and indirectly affects plant species distribution and community structure. In this study, we investigated the characteristics of plant community in different types of coal mining subsidence in Bin-hang mining area to understand the responses of plant community to coal mining subsidence and underlying mechanisms. The results showed that families in Bin-hang mining area were mainly Compositae, Gramineae, and Legumes, the main plant growth forms were perennial herb, and the water ecological type was dominated by meso-erophytes. Disturbance of mining subsidence increased proportions of annual grass, perennial herbs and meso-erophytes, decreased the proportion of mesophytes, but had no effect on the proportion of shrubs and trees. The disturbance of surface crevasse in the tableland area did not cause significant change in plant community structure, but the number of species, coverage, biomass, species density and biodiversity index of plant community were significantly lower in stepped subsidence area and surface crevasse area at ravine edge. According to the damage of plant communities, the subsidences in Bin-hang mining area could be divided into three types: slightly damaged area, including surface crevasse in tableland area; medium damage area, including stepped subsidence area in tableland area and surface crevasse area at ravine edge; strong damage area, including stepped subsidence area at ravine edge.

Root characteristics and their resistance to shear strength at the initial stage of highway slope greening.

ZHANG Xiao-hang, YANG Jian-ying, ZHAO Hui-en, ZHU Li-juan, ZHANG Sen

2019, 38(5):  1528-1537. 

Asbtract ( 279 )   PDF (776KB) ( 238 )  

Plant roots could enhance the shear strength of soil. To understand the root characteristics and their impacts on shear strength at the initial stage of highway slope greening, the mixed grassshrub samples were prepared by spraying seeds. Seven kinds of grassshrub combinations were artificially simulated in the slope greening. The insitu shear test was carried out three months after plant growth. Plant roots were excavated, with root characteristics such as root diameter, root length density, total surface area, total volume, number of root tips, number of branches, root density and inclination angle being measured. The effects of root characteristics on the shear strength of soil were analyzed by grey correlation method. The results showed that there were differences of root characteristics in various grass-shrub combinations with the changes of soil depth. At the initial stage of greening, fine roots of 0-2 mm accounted for 96%-99% of the whole root system. The horizontal roots, lateral roots and vertical roots constituted 7%-16%, 44%-57% and 33%-47% of the total root system, respectively. The roots of different grassshrub combinations increased the shear strength of soil by 6-17 kPa, and the shear strength of the different ratios of shrubs and grasses was in the order of 1∶1 > 1∶4 > 1∶5 > 3∶1. The results of grey correlation analysis showed that the effects of root characteristics on shear strength were as follows: number of lateral roots > number of horizontal roots > depth of root distribution > root density > root length density above shear plane > root length density > number of fine roots (0-2 mm) > root length density below shear plane > total surface area> total volume > number of root tips > number of vertical roots> number of branches > number of roots (2-10 mm). Our results provide a basis for evaluating the stability of the slope at the initial stage of highway slope greening and guiding vegetation restoration of the slope.

Advances in research on the abnormal structure of tree-rings.

LI Cai-juan, CHEN Tuo, WANG Bo, XU Guo-bao, ZHANG Xuan-wen, WU Guo-ju

2019, 38(5):  1538-1550. 

Asbtract ( 412 )   PDF (4217KB) ( 271 )  

As an important indicator reflecting climatic changes, tree-rings have been widely used in the research of chronology, paleoclimatology, and paleoecology. Annual tree rings are considered as a consequence of the cambial activity and cell differentiation which are significantly associated with environmental variables. Under particularly adverse conditions, the cambial division and growth would be limited or inactive, no xylem or incomplete lignification or damaged cells may be produced in parts of the stem, resulting in abnormal structure of tree-rings. The position of the abnormal structure within tree ring is a time marker for their formation during abrupt extreme events. Such structures include false rings, frost rings, missing rings, light rings, radical crack, fire scars, reaction wood, and traumatic resin duct. These abnormal structures provide a promising approach to better understand growth-climate relations and the physiological processes underlying them. Therefore, they can be used as a climate multi proxy to reconstruct the history of past climatic extremes and to predict future forest dynamics in a changing climate. We summarized the knowledge of some of the most prominent abnormal types of tree-rings, their characteristics and possible causes, and discussed the application in some extreme climatic events or natural disturbances, highlighting the potential of analyzing the features of these special tree rings to reconstruct climatic change history.

Ecological compensation for mineral resources exploitation: A review.

LI Si-jia, WANG Jin-man, ZHANG Zhao-tong

2019, 38(5):  1551-1559. 

Asbtract ( 392 )   PDF (700KB) ( 252 )  

The large-scale exploitation of mineral resources deteriorates the environment of the mining area, with negative consequences on the healthy and sustainable development of the national economy. Improving the ecological compensation mechanism in the mining area is of great significance for governance, recovery and correction of natural resource destruction and environmental pollution, which is also the key to ensure sustainable development of the mining area. Here, we systematically reviewed the development history, the carrier and mode, and the standard and pattern of ecological compensation. Current researches still has some shortcomings in the theoretical research of ecological compensation. The research of ecological compensation theory is lagging behind empirical practice exploration. The research of ecological compensation standard of mineral resources in China lacks quantitative analysis. The study of quasimarket ecological compensation pattern needs to be promoted. For future study, more attention should be paid to the theory of ecological compensation, the quantitative research of ecosystem compensation standard, and the quasimarket ecological compensation pattern, with the aim to provide new guidance for ecological compensation and environmental remediation in mineral resources development area.

Effects of simulated N deposition on Q₁₀ of soil respiration in Chinese terrestrial ecosystems.

XU Li, YANG Yan-ru, ZHANG Jun-hui, FENG Yue

2019, 38(5):  1560-1569. 

Asbtract ( 448 )   PDF (746KB) ( 178 )  

Understanding the effects of simulated N deposition on temperature sensitivity of soil respiration (Q₁₀) can reduce the uncertainty in the assessment of soil carbon budget under global change scenarios. In this study, 60 literatures on the effects of simulated N deposition on Q₁₀ in China’s terrestrial ecosystems were investigated by meta analysis. The results showed that the effects of simulated N deposition on Q₁₀ were not significant (0.49%). Nitrogen deposition had negative effects on Q₁₀ in the plateau climate zone (16.32%) and positive effects on that in marsh (38.19%). The effect size was related to the dosage of simulated N deposition. When simulated N deposition dosage was less than 50 kg·hm^-2·a^-1, Q₁₀increased by 2.59%; when the dosage was 50-150 kg·hm^-2·a^-1 and greater than 150 kg·hm^-2·a^-1, Q₁₀ decreased by 4.33% and 1.61%, respectively. The deposited nitrate nitrogen significantly increased Q₁₀ (34.33%), while urea application significantly decreased Q₁₀ (8.11%). Moreover, simulated N deposition with a duration over 15 months significantly reduced Q₁₀ (19.24%). The alteration of Q₁₀ by simulated N deposition may be due to the alteration of the metabolism of roots and soil microbes.  

Oxygen stable isotopic analysis on water use strategy of Caragana microphylla in different ages.

FU Qing-yun, LIU Ting-xi, DUAN Li-min, WANG Guan-li, CAO Wen-mei, HUANG Tian-yu

2019, 38(5):  1570-1579. 

Asbtract ( 402 )   PDF (3106KB) ( 206 )  

Caragana microphyllais a typical sand-fixing species in Horqin sandy land. Using oxygen stable isotope technique, the relationships of δ¹⁸O of soil water, precipitation and xylem water were compared among 3-, 5- and 9-year-old C. microphylla individuals in the C. microphylla community during growing season. Water source of C. microphyllas with different tree ages was quantified using multiple linear mixing model. The water source of C. microphylla was analyzed according to the seasonal pattern of soil moisture and root distribution. By evaluating the adaptability of three aged C. microphylla individuals to regional water conditions, water competition of different aged individuals was analyzed to assess community stability. The results showed that root distribution determined the range of soil water use and water use strategy of different aged C. microphylla individuals, and soil water distribution also affected the main water sources of C. microphylla individuals. During the growing season, water in 30-80 cm soil layer was the main water source of three years old C. microphylla. The water in 30-100 cm soil layer was the main water source of five years old C. microphylla, with a larger contribution rate from 80-100 cm soil layer. For nine years old C. microphylla, 0-30 and 100-160 cm soil layers was the main water source. There was no strong water competition among different aged C. microphylla individuals, suggesting the community is stable.

Segmentation algorithm of annual ring image based on U-Net convolution network.

NING Xiao, ZHAO Peng

2019, 38(5):  1580-1588. 

Asbtract ( 602 )   PDF (4169KB) ( 331 )  

Dendrochronological research uses tree-age and annual-ring width to estimate environmental changes and tree growth. Thus, it is important to accurately extract the characteristics such as the early wood, late wood, and bark parts in the annual-ring images for further analysis. It is difficult to obtain the desired effect using traditional image segmentation algorithm due to the existence of defects such as fuzzy interface between the early and late woods, knots and pseudo-annual rings during growth and there are burrs and noise spots on the image of the annual ring disc during the cutting and collecting process. Here, we proposed a novel approach to perform annualring image semantic segmentation based on convolutional neural network. Firstly, 100 annual-ring images were marked as late wood, bark and other parts. Data enhancement was implemented- through image rotation, perspective, and deformation to generate 20000 image data, from which 16000 images were randomly selected as training data sets and 4000 images were used as test dataset. Secondly, according to the characteristics of image dataset, an annual-ring disc image segmentation network was developed based on U-Net convolutional network using the Tensorflow framework. Then, the training dataset was sent into the network, the training parameters were optimized, and the annual-ring image segmentation network was iteratively trained until the evaluation index and the loss function no longer change. Finally, the test dataset was segmented using the trained model and the segmentation indicators were evaluated. Experimental results showed that the constructed model can effectively avoid the defects mentioned above, and completely separate the late wood and bark parts of the annual-ring images. The proposed approach was tested with dataset consisting of 4000 tree ring images, the corresponding accuracy of mean pixels and the mean intersection over union achieved 96.51% and 82.30%, respectively. Thisapproach based on U-Net convolutional network is a more efficient algorithm for annual-ring image segmentation, with stronger generalization ability and robustness.

Evaluation of the accuracy of phenology extraction methods for natural vegetation based on remote sensing.

ZHANG Xiao-xuan, CUI Yao-ping, LIU Su-jie, LI Nan, FU Yi-ming

2019, 38(5):  1589-1599. 

Asbtract ( 627 )   PDF (2922KB) ( 370 )  

Analyzing vegetation phenology is the key step for the accuracy evaluation of extraction methods using remote sensing. There is no consensus about the advantages and disadvantages of different methods. It is necessary to comprehensively evaluate the accuracy of various extraction methods. In this study, 18 combining methods for vegetation phenology remote sensing extraction and observation data from 23 ground phenology stations were used to evaluate the accuracy in extracting three key vegetation phenophases: Start Of the growing Season (SOS), End Of the growing Season (EOS) and Length Of the growing Season (LOS). The results showed that SG_{Sa 0.1} (the combining Savitzky-Golay filter and Seasonal Amplitude method with a threshold of 0.1) had the optimal recognition effect. For single phenophase, the optimal combination for SOS, EOS and LOS was SG_{Sa 0.1}, SG_{Sa 0.3} and DL_{Sa 0.1}, respectively. The minimum deviation between the optimal extraction results and the groundbased observation phenology data were more than five days, indicating the accuracy of extraction phenology using remote sensing data with 8-day temporal resolution. The deviation highlighted the importance of choosing a suitable extraction combination. In addition, remote sensing phenology and groundbased phenology cannot completely match. Therefore, the multiple evaluation indices used in this study, especially the deviation consistency can effectively select the optimal vegetation phenology remote sensing extraction combination for various phenophases.

The prospects of development of the Three-North Afforestation Program (TNAP): On the basis of the results of the 40-year construction general assessment of the TNAP.

ZHU Jiao-Jun, ZHENG Xiao

2019, 38(5):  1600-1610. 

Asbtract ( 859 )   PDF (1260KB) ( 412 )  

The Three-North Afforestation Program (TNAP, also known as the Three North Protective Forest Program or the Green Great Wall) in China, the largest ecological project all over the world, was initiated in 1978 and will be fulfilled in 2050. The TNAP is an important landmark project for the construction of Ecological Civilization. During the past 40-years (1978-2018), TNAP has made remarkable achievements and accumulated valuable experiences, which makes it an exemplary record of global ecological management. However, some inevitable problems appeared synchronously. To scientifically and accurately understand the comprehensive situation and promote highquality development of the TNAP in the future, the National Forestry and Grassland Administration (formerly the National Forestry Administration, which is the Administration Agency of TNAP) commissioned the Chinese Academy of Sciences as a third-party evaluation agency to carry out a comprehensive and systematic assessment for the 40-year construction of TNAP. The assessment results would provide important evidence for the construction of Beautiful ChinaEcological Civilization, and offer the experiences and examples for the construction of global projects for ecological security. In this paper, we gave a brief introduction to the assessment, including history, achievements, impacts, and the problems of the 40-year construction of TNAP. On the basis of this assessment, we proposed some prospects for the future construction and development of TNAP.