Changes in sediment discharge in a sediment-rich region of the Yellow River from 1955 to 2010： implications for further soil erosion control

The well-documented decrease in the discharge of sediment into the Yellow River has attracted considerable attention in recent years. The present study analyzed the spatial and temporal variation of sediment yield based on data from 46 hydrological stations in the sediment-rich region of the Yellow River from 1955 to 2010. The results showed that since 1970 sediment yield in the region has clearly decreased at different rates in the 45 sub-areas controlled by hydrological stations. The decrease in sediment yield was closely related to the intensity and extent of soil erosion control measures and rainstorms that occurred in different periods and sub-areas. The average sediment delivery modulus(SDM) in the study area decreased from 7,767.4 t/(km2?a) in 1951–1969 to 980.5 t/(km2?a) in 2000–2010. Our study suggested that 65.5% of the study area with the SDM below 1,000 t/(km2?a) is still necessary to control soil deterioration caused by erosion, and soil erosion control measures should be further strengthened in the areas with the SDM above 1,000 t/(km2?a).     

Vertical root distribution and root cohesion of typical tree species on the Loess Plateau,China

Black locust(Robinia pseudoacacia L.) and Chinese pine(Pinus tabulaeformis Carr.) are two woody plants that are widely planted on the Loess Plateau for controlling soil erosion and land desertification. In this study, we conducted an excavation experiment in 2008 to investigate the overall vertical root distribution characteristics of black locust and Chinese pine. We also performed triaxial compression tests to evaluate the root cohesion(additional soil cohesion increased by roots) of black locust. Two types of root distribution, namely, vertical root(VR) and horizontal root(HR), were used as samples and tested under four soil water content(SWC) conditions(12.7%, 15.0%, 18.0% and 20.0%, respectively). Results showed that the root lengths of the two species were mainly concentrated in the root diameter of 5–20 mm. A comparison of root distribution between the two species indicated that the root length of black locust was significantly greater than that of Chinese pine in nearly all root diameters, although the black locust used in the comparison was 10 years younger than the Chinese pine. Root biomass was also significantly greater in black locust than in Chinese pine, particularly in the root diameters of 3–5 and 5–10 mm. These two species were both found to be deep-rooted. The triaxial compression tests showed that root cohesion was greater in the VR samples than in the HR samples. SWC was negatively related to both soil shear strength and root cohesion. These results could provide useful information on the architectural characteristics of woody root system and expand the knowledge on shallow slope stabilization and soil erosion control by plant roots on the Loess Plateau.     

Interactive effects of soil temperature and moisture on soil N mineralization in a Stipa krylovii grassland in Inner Mongolia,China

Determining soil N mineralization response to soil temperature and moisture changes is challenging in the field due to complicated effects from other factors. In the laboratory, N mineralization is highly dependent on temperature, moisture and sample size. In this study, a laboratory incubation experiment was carefully designed and conducted under controlled conditions to examine the effects of soil temperature and moisture on soil N mineralization using soil samples obtained from the Stipa krylovii grassland in Inner Mongolia, China. Five temperature(i.e. 9°C, 14°C, 22°C, 30°C and 40°C) and five moisture levels(i.e. 20%, 40%, 60%, 80% and 100% WHC, where WHC is the soil water holding capacity) were included in a full-factorial design. During the 71-day incubation period, microbial biomass carbon(MBC), ammonium nitrogen(NH4 +-N) and nitrate nitrogen(NO3--N) were measured approximately every 18 days; soil basal respiration for qCO2 index was measured once every 2 days(once a week near the end of the incubation period). The results showed that the mineral N production and net N mineralization rates were positively correlated with temperature; the strongest correlation was observed for temperatures between 30°C and 40°C. The relationships between moisture levels and both the mineral N production and net N mineralization rates were quadratic. The interaction between soil temperature and moisture was significant on N mineralization, i.e. increasing temperatures(moisture) enhanced the sensitivity of N mineralization to moisture(temperature). Our results also showed a positive correlation between the net nitrification rate and temperature, while the correlation between the NH4 +-N content and temperature was insignificant. The net nitrification rate was negatively correlated with high NH4 +-N contents at 80%–100% WHC, suggesting an active denitrification in moist conditions. Moreover, qCO2 index was positively correlated with temperature, especially at 80% WHC. With a low net nitrification rate and high soil basal respiration rate, it was likely that the denitrification concealed the microbial gross mineralization activity; therefore, active soil N mineralization occurred in 60%–80% WHC conditions.     

Radial profile of sap flow velocity in mature Xinjiang poplar（Populus alba L. var. pyramidalis） in Northwest China

Estimation of the transpiration rate for a tree is generally based on sap flow measurements within the hydro-active stem xylem. In this study, radial variation of sap flow velocity(Js) was investigated at five depths of the xylem(1, 2, 3, 5 and 8 cm under the cambium) in three mature Xinjiang poplar(Populus alba L. var. pyramidalis) trees grown at the Gansu Minqin National Studies Station for Desert Steppe Ecosystem from May to October 2011. Thermal dissipation probes of various lengths manufactured according to the Granier's design were installed into each tree for simultaneous observation of the radial patterns of Js through the xylem. The radial patterns were found to fit the four-parameter GaussAmp equation. The peak Js was about 27.02±0.95 kg/(dm2?d) at approximately 3 to 5 cm deep from the cambium of the three trees,and the lowest Js appeared at 1 cm deep in most of the time. Approximately 50% of the total sap flow in Xinjiang poplar occurred within one-third of the xylem from its outer radius, whereas 90% of the total sap flow occurred within two-fifth of the xylem. In addition, the innermost point of the xylem(at 8-cm depth), which appeared as the penultimate sap flow in most cases during the study period, was hydro-active with Js,8 of 7.55±3.83 kg/(dm2?d). The radial pattern of Js was found to be steeper in midday than in other time of the day, and steeper diurnal fluctuations were recorded in June, July and August(the mid-growing season). Maximum differences between the lowest Js(Js,1 or Js,8) and the highest Js(Js,3 or Js,5) from May through October were 12.41, 17.35, 16.30, 18.52, 12.60 and 16.04 g/(cm2?h), respectively. The time-dependent changes of Js along the radial profile(except at 1-cm depth) were strongly related to the reference evapotranspiration(ET0). Due to significant radial variability of Js, the mean daily sap flow at the whole-tree level could be over-estimated by up to 29.69% when only a single probe at depth of 2 cm was used. However, the accuracy of the estimation of sap flow in Xinjiang poplar could be significantly improved using a correction coefficient of 0.885.     

Impact of land use chanse on water resource allocation in the middle reaches of the Heihe River Basin in northwestern China

In recent decades, China has been experiencing rapid economic development, population growth and urbanization. These processes have stressed the shortages of water resources in China, especially in the arid re- gions of northwestern China. In order to sustain the expanding cropland, people increased groundwater exploitation in these regions. The purpose of this study was to quantitatively analyze the changes in land use and water re- sources, and their relationship in the middle reaches of the Heihe River Basin, a typical inland river basin in northwest China. The data of land use change were interpreted using aerial photographs(1965) and Landsat TM images(1986 and 2007). The data of irrigation water volume in the irrigation districts were spatialized in the middle reaches of the Heihe River Basin. The spatial variation of the groundwater depth was interpolated using the geo- statistical method. The results showed that the cultivated cropland area along oasis fringe increased by 15.38% and 43.60% during the periods 1965–1986 and 1986–2007, respectively. Surface water amount for irrigation had almost doubled from 1956 to 2010. The decrease of grassland area mainly occurred at the alluvial fan in front of the Qilian Mountains, with 36.47% during 1965–1986 and 38.56% during 1986–2007, respectively. The groundwater depth in front of the mountain constantly increased from 1986 to 2007. We found that the overuse of surface water and overexploitation of groundwater had direct consequences on the natural environments. We suggests that the efficiency of surface water resources use among different irrigation districts needs to be improved, which will sig- nificantly ease the conflicts between increasing water demand for irrigation and a shortage of water resources in the middle reaches of the Heihe River Basin.     

Localized salt accumulation： the main reason for cotton root length decrease during advanced growth stages under drip irrigation with mulch film in a saline soil

High salinity in soil can prevent root growth of most plants. To investigate soil salinity dynamics under drip irrigation with mulch film(DI) and its effects on cotton root length, we conducted field experiments in saline soil based on a monolith method using flooding irrigation with mulch film(FI) as a control at the Korla Experimental Station of the Xinjiang Academy of Agricultural Sciences, China in 2009 and 2010. The results showed that the total root length decreased 120 days after sowing(DAS) under DI, and was mainly centered in the 0–30 cm soil layer and at distances of 30–70 cm from the drip-lines. There was almost complete overlap in the area of root length decline and salt accumulation. In the soil depth of 0–30 cm and at distances of 30–70 cm from the drip-lines at 110 to 160 DAS in 2009 and 171 DAS in 2010, the electrical conductivity(EC) in all soil samples was at least 3 mS/cm and in some cases exceeded 5 mS/cm under DI treatment. However, EC barely exceeded 3 mS/cm and no reduc- tion in root length was observed under FI treatment. Correlation analysis of soil EC and root length density indicated that the root length declined when the soil EC exceeded 2.8 mS/cm. The main reason for the decrease of root length in cotton under DI was localized accumulation of salinity.     

Influence of vegetation parameters on runoff and sediment characteristics in patterned Artemisia capillaris plots

Vegetation patterns are important in the regulation of earth surface hydrological processes in arid and semi-arid areas. Laboratory-simulated rainfall experiments were used at the State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Yangling, northwestern China, to quantify the effects of Artemisia capillaris patterns on runoff and soil loss. The quantitative relationships between runoff/sediment yield and vegeta- tion parameters were also thoroughly analyzed using the path analysis method for identifying the reduction mechanism of vegetation on soil erosion. A simulated rainfall intensity of 90 mm/h was applied on a control plot without vegetation(C0) and on the other three different vegetation distribution patterns: a checkerboard pattern(CP), a banded pattern perpendicular to the slope direction(BP), and a single long strip parallel to the slope direction(LP). Each patterned plot received two sets of experiments, i.e. intact plants and roots only, respectively. All treatments had three replicates. The results showed that all the three other different patterns(CP, BP and LP) of A. capillaris could effectively reduce the runoff and sediment yield. Compared with C0, the other three intact plant plots had a 12%–25% less runoff and 58%–92% less sediment. Roots contributed more to sediment reduction(46%–70%), whereas shoots contributed more to runoff reduction(57%–81%). BP and CP exhibited preferable controlling effects on soil erosion compared with LP. Path analysis indicated that root length density and plant number were key pa- rameters influencing runoff rate, while root surface area density and root weight density were central indicators affecting sediment rate. The results indicated that an appropriate increase of sowing density has practical signifi- cance in conserving soil and water.     

Dry/wet climate zoning and delimitation of arid areas of Northwest China based on a data-driven fashion

The division of arid areas is important in water and land resources management, planning and for a long-term agricultural, economic and social planning. Northwest China(NW) dominates the main arid areas in China. There is thus a need to adopt adequate concepts relative to the scope of arid areas of NW China and identify its climate types and characteristics. In this study, we analyzed climatic data over the last 30 years(1981–2010) from 191 stations in three provinces and three autonomous regions of NW China. The factor-cluster analysis tech- nique(FC), an objective and automated method was employed to classify the dry/wet climate zones. The traditional methods with predefined thresholds were adopted for providing a comparison with FC. The results showed that the wet/dry climate zones by FC were mainly distributed along mountains, rivers and desert borders. Climate-division boundaries relied heavily on the major terrain features surrounding the grouped stations. It also showed that the climate was dry in the plain sandy areas but relatively wet in the high mountain areas. FC method can reflect the climate characteristics more fully in NW China with varied and complicated topography, and outperform the tradi- tional climate classifications. Arid areas of NW China were defined as four climate types, including five resultant classes in FC classifications. The Qinling and Da Hinggan Mountains were two important boundaries, besides main administrative boundaries. The results also indicated that there are some differences between two traditional clas- sifications. The precipitation moved and fluctuated to an extent, which confirmed that climate change played an important role in the dry/wet climate zoning, and the boundaries of dry/wet climate zones might change and migrate with time. This paper is expected to provide a more in-depth understanding on the climate characteristics in arid areas of NW China, and then contribute to formulate reasonable water and land management planning and agri- cultural production programs.     

Arbuscular mycorrhizal fungal colonization of GlycyrrhJza glabra roots enhances plant biomass,phosphorus uptake and concentration of root secondary metabolites

Arbuscular mycorrhizal(AM)fungi penetrate the cortical cells of the roots of vascular plants,and are widely distributed in soil.The formation of these symbiotic bodies accelerates the absorption and utilization of mineral elements,enhances plant resistance to stress,boosts the growth of plants,and increases the survival rate of transplanted seedlings.We studied the effects of various arbuscular mycorrhizae fungi on the growth and development of licorice(Glycyrrhiza glabra).Several species of AM,such as Glomus mosseae,Glomus intraradices,and a mixture of fungi(G.mosseae,G.intraradices,G.cladoideum,G.microagregatum,G.caledonium and G.etunicatum)were used in our study.Licorice growth rates were determined by measuring the colonization rate of the plants by the fungi,plant dry biomass,phosphorus concentration and concentration of secondary metabolites.We established two cloned strains of licorice,clone 3(C3)and clone 6(C6)to exclude the effect of genotypic variations.Our results showed that the AM fungi could in fact increase the leaf and root biomass,as well as the phosphorus concentration in each clone.Furthermore,AM fungi significantly increased the yield of certain secondary metabolites in clone 3.Our study clearly demonstrated that AM fungi play an important role in the enhancement of growth and development of licorice plants.There was also a significant improvement in the secondary metabolite content and yield of medicinal compounds from the roots.     

Detection and estimation of Citrus Tristeza Virus infection rates based on Elisa Assays of packing house fruit samples

Enzyme-linked immunosorbent assay (ELISA) proved to be a sensitive detector for citrus tristeza virus (CTV) in orange fruits (Citrus sinensis (L.) Osbeck). Samples of five fruits were taken from 350-kg packing house containers and tested by ELISA to predict the infection rate of CTV in two infected orange groves. The predicted infection rates, 1% and 11%, were in reasonable agreement with the observed rates of 1% (15/1400) and 16% (324/2053), respectively. The 360 test samples from reputedly uninfected groves all tested negative. These results suggest that the ELISA procedure may provide a general method of detecting viral or other systemic pathogenic infections using the fruit as the test material in place of tree tissue. Fruit samples can be collected routinely at the packing house to reduce test costs.     

Sensitive detection of two plant viruses by enzyme-amplified elisa

Enzyme-amplified ELISA (enzyme-linked immunosorbent assay) increased the sensitivity of detection of citrus tristeza virus and papaya ringspot virus in plant sap by 25- and 125-fold, respectively, compared with direct double antibody sandwich ELISA. The advantages of the new substrate system for the detection of low concentrations of viruses in plants are discussed.     

The distribution of passionfruit ringspot virus in its main host plants in Ivory Coast

A field survey and testing of leaf samples have given an impression of the distribution of passionfruit ringspot virus in twoAdenia and twoPassiflora spp. in Ivory Coast. The data suggest thatAdenia spp. are the original host plants of the virus. Introduction to Ivory Coast of the virus withP. edulis seems unlikely. Since theAdenia spp. prefer forest and shrub vegetations and aphid flights are shorter in the dryer savannah areas of the North, the cultivatedP. edulis has chances to remain healthy over a prolonged period of growth, which is excluded in the South of the country.     

Arthropod fauna and main insect pests of plane trees in Israel

Fifty-four insect and four mite species are included in a list of the entomofauna of plane trees in Israel. Only two species are monophagous:Phyllonorycter platani (Stgr.) (Lepidoptera: Gracillariidae) andEdwardsiana iranicola Zachv. (Heteroptera: Cicadellidae). Four species are noxious:P. platani, the main insect pest of the plane trees in Israel;Zeuzera pyrina L. (Lepidoptera: Cossidae);Kalotermes flavicollis F. (Isoptera: Kalotermitidae); andE. iranicola. Of much lesser importance areTargionia vitis Sign. (Homoptera: Diaspididae),Heliothrips haemorrhoidalis Bché. andRetithrips syriacus May. (Thysanoptera: Thripidae). About half of the listed species are natural enemies and many are parasites ofP. platani. Details are given on the noxious species, together with recommendations for prevention and control.     

Alien scale insects (Hemiptera Coccoidea) in European and Mediterranean countries: the fate of new and old introductions

This contribution focuses on recent interceptions and introductions of alien scale insects and their current distribution in European and Mediterranean countries. Data and collections were gathered in markets, nurseries, and botanical gardens, mostly in Italy, either indoors or outdoors. New or recent records of the following alien species are presented: Exallomochlus hispidus (Morrison); Ferrisia virgata (Cockerell) (Pseudococcidae); Coccus viridis (Green); Milviscutulus mangiferae (Green) (Coccidae); Aonidiella orientalis (Newstead); Aspidiotus destructor Signoret; Aulacaspis tubercularis Newstead; Fiorinia fioriniae Targioni Tozzetti; Lepidosaphes pinnaeformis (Bouché); Pseudaulacaspis brimblecombei Williams (Diaspididae). New data and pest status of Phoenicococcus marlatti Cockerell (Phoenicococcidae) and Trabutina mannipara (Hemprich & Ehrenberg) (Pseudococcidae) are also reported. The possible repeated introductions of the latter from North Africa to south Italy by trans-Mediterranean winds, is hypothesized.     

Development of conventional and real-time PCR protocols for specific and sensitive detection of Colletotrichum capsici in chilli (Capsicum annuum L.)

Anthracnose, caused by Colletotrichum capsici, is a major disease of chilli (Capsicum annuum L.) affecting both fruit and seed quality. The pathogen is both internally and externally seedborne. However, a rapid and sensitive method for detection of this pathogen in seeds is currently limited. In this study, a polymerase chain reaction (PCR) method based on sequence characterized amplified region (SCAR) marker was developed for specific and sensitive detection of C. capsici in chilli seeds and fruits. The developed SCAR primers were highly specific to C. capsici and resulted in the amplification of an expected 250-bp fragment from genomic DNA of all seven of the C. capsici isolates tested. No amplification occurred when the SCAR primers were tested with genomic DNA from three other fungal isolates and four other Colletotrichum species. The SCAR primers successfully amplified similar sized fragments from DNA derived from C. capsici-infected chilli fruits. The molecular detection sensitivity of C. capsici was 1 pg of purified C. capsici DNA template and 25 ng of DNA from C. capsici-infected chilli fruits. A real-time PCR assay was also developed using SYBR Green chemistry for detection of C. capsici in chilli fruits and seeds. The standard curve obtained showed a linear correlation between copy number of the cloned target DNA sequence of C. capsici and cycle threshold (Ct) values, with R² of 0.98. These PCR-based assays may be highly useful in detection of this important pathogen in chilli seeds and fruits in plant quarantine laboratories.     

Braconidae (Hymenoptera) associated with forest and ornamental trees and shrubs in Israel

Data are presented on the occurrence of Braconidae (Hymenoptera parasitica) parasitizing insects associated with forest and ornamental trees and shrubs in Israel. Fifty-five genera of plants are listed, the richest in braconid fauna being tamarisk (9 species); acacia, pistachio and poplar (8 species each); carob and oak (7 species each). Of the 95 species of insect hosts mentioned, 53 are Lepidoptera, mostly Gelechiidae (7 species), Pyralidae (6 species), Noctuidae (5 species), Gracillariidae, Tortricidae, Geometridae, Lymantriidae and Lycaenidae (3 species each); 44 are Coleoptera, mostly Cerambycidae (13 species), Scolytidae (12 species), and Bostrichidae (9 species); three are Diptera. Of the 92 species of braconids listed, of which only 65 have been fully named, 56 develop in Lepidoptera, mostly Noctuidae (15 species), Gelechiidae (11 species) and Pyralidae (9 species); 33 species develop in Coleoptera, mostly Cerambycidae (12 species, Bostrichidae (10 species) and Scolytidae (5 species); and three species develop in Diptera. Thirty-eight species are new to the fauna of Israel; at least three of them are new to science,viz., Gnaptodon, Gildoria andDendrosotinus titubatus Papp.     

First record of the red gum lerp psyllid,Glycaspis brimblecombei Moore (Hemiptera Psyllidae), in Tunisia

During a survey carried out in August 2013 along all coastal areas of north-eastern Tunisia (governorships of Bizerte, Ariana, Tunis, Ben Arous, Nabeul, Sousse), eucalyptus trees were found to be highly infested by the invasive pest Glycaspis brimblecombei Moore, 1964, also known as red gum lerp psyllid. This insect, native to the Australian region and secondarily dispersed also in the Americas, Mauritius, Madagascar and South Africa, very recently started to invade the Mediterranean region and in almost 5 years has spread to the Iberian Peninsula, Italy, Greece and Morocco. Its presence in Tunisia (which is recorded here for the first time) most probably dates back to summer 2012, since typical necrotic spots caused by the lerp of the psyllid had already been noted on leaves during spring 2013. No presence of its main parasitoid – Psyllaephagus bliteus Riek – nor of any other natural enemy, was noted up to now during our survey in Tunisia.     

Plant ferredoxin-like protein enhances resistance to bacterial soft rot disease through PAMP-triggered immunity in Arabidopsis thaliana

The protection of plants against bacterial disease is one of the important issues that need to be studied in agricultural applications. The application of a transgene, such as a gene that encodes plant ferredoxin-like protein (PFLP), to generate resistant plants is one possible strategy. Our previous reports have demonstrated that transgenic plants that express extracellular PFLP (ESF plants) are more resistant to bacterial pathogens. This protein intensifies the hypersensitive response (HR) in plants when they are infiltrated by a pathogen-associated molecular pattern (PAMP), harpin (HrpZ), from Pseudomonas syringae. In addition, this intensified HR is associated with the expression of membrane-bound NADPH oxidase. Thus, we attempted to determine the involvement of PFLP in intensifying PAMP-triggered immunity (PTI) to enhance disease resistance. First, we showed that transgenic Arabidopsis plants with the pflp gene were resistant to bacterial soft rot caused by Pectobacterium carotovorum subsp. carotovorum (Pcc). Then, the fliC gene which encoded flagellin from Pcc was cloned and expressed. The FliC protein was used in the functional study with PFLP in Arabidopsis Col-0 plants. The reactive oxygen species (ROS) generation and HR ratio were induced by the treatment with both PFLP and FliC together, but they were not induced by treatment with PFLP or FliC alone. Similar results were confirmed in ESF plants, where FliC elicited rapid ROS accumulation and callose deposition. Moreover, we demonstrated that the PFLP-intensified ROS generation and HR were related to Ca²⁺ influx and activation of NADPH oxidase. We concluded that the PFLP-intensified disease resistance is associated with the intensification of PAMP-triggered immunity.     

Control of phytophthora leaf blight of taro (Colocasia esculenta) by fungicides and roguing

Six fungicides were evaluated under laboratory and field conditions for control of Phytophthora leaf blight of taro,Coloeasia esculenta, incited byPhytophthora colocasiae. Inin vitro tests Deraosan 65W was the most effective in inhibiting the mycelial growth of the test pathogen followed by Difolatan 80W, Fytolan (copper oxychloride), Apron 35F, Topsin-M 50W and Dithane Z-78 75W. Excellent control was obtained with Demosan 65W and Difolatan 80W, good control with Apron 35F, fair control with Fytolan, and poor control with Topsin-M 50W and Dithane Z-78 75W. Results ofin vivo tests were correlated with those of thein vitro tests. Roguing of infected leaves did not eradicate the pathogen but can only delay epiphytotics.