Seasonal changes in the water-use strategies of three herbaceous species in a native desert steppe of Ningxia,China

Frequent periods of drought conditions are known to limit plant performance,primary production,and ecosystem stability in arid and semi-arid desert steppe environments.Plants often avoid competition by shifting their water use seasonally,which affects the water-use patterns of dominant species as well as the composition and structure of plant communities.However,the water-use strategies of dominant herbaceous species,which grow under natural field conditions in the desert steppe region of Ningxia Hui Autonomous Region,China,are poorly known.Here,we explored the possible sources of water uptake and water-use efficiency(WUE)of three dominant herbaceous plant species(Stipa breviflora,Agropyron mongolicum,and Glycyrrhiza uralensis)in a native desert steppe in the semi-arid area of Ningxia through an analysis of multiple parameters,including(1)the stable isotopic oxygen and hydrogen(δ18O andδ2H)compositions of precipitation,soil water,and stem water,(2)the carbon isotope(13C)composition of leaves,and(3)the soil water contents,based on field sampling across varying water conditions from June to September,2017.Frequent small precipitation events replenished shallow soil water,whereas large events only percolated down to the deep soil layers.Changes in soil water availability affected the water-use patterns of plants.Generally,during light precipitation periods,the deep root system of G.uralensis accessed deeper(>80 cm)soil water,whereas S.breviflora and A.mongolicum,which only have shallow roots,primarily absorbed water from the shallow and middle soil layers.As precipitation increased,all three plant species primarily obtained water from the shallow soil layers.Variation in soil water uptake between the dry and wet seasons enabled plants to make better use of existing satoil water.In addition,theδ13C values of G.uralensis and S.breviflora were higher than those of A.mongolicum.Theδ13C values of the three plant species were significantly negatively correlated with soil water content.Therefore,G.uralensis and S.breviflora maintained a higher WUE through their conservative and water-saving strategies across the entire growing season.In contrast,A.mongolicum,with a relatively low WUE in the wet season but a high WUE in the dry season,exhibited a more flexible water-use strategy.The different water-use strategies of these dominant plant species demonstrated the mechanisms by which plant communities can respond to drought.     

短花针茅荒漠草原斑块尺度物种多样性及其共存格局

阐明斑块尺度上物种共存格局,对于深入认识荒漠草原破碎化草地生物多样性的维持机理具有重要意义。按斑块的土壤生境退化程度,选取短花针茅荒漠草原3类典型群落斑块为研究对象,对比分析不同斑块的物种构成、多样性及物种间的共存关系格局。结果表明：① 斑块A属单优种短花针茅（Stipa breviflora）群落;斑块B为短花针茅+草木樨状黄耆（Astragalus melilotoides）群落;斑块C为苦豆子（Sophora alopecuroides）+老瓜头（Cynanchum komarovii）+猪毛蒿（Artemisia scoparia）群落。② 群落结构中斑块A和斑块B多样性相近,均高于无短花针茅生长的斑块C。③ 基于零模型的分析结果显示,物种共存格局的复杂性和强度为：斑块A>斑块B>斑块C,且下降趋势明显,斑块A存在的16组显著物种对中有4组为显著竞争关系,而斑块C中的物种对减少到7组,且仅存在猪毛蒿与苦豆子组显著竞争物种对。结论：表明未沙化的土壤生境斑块是荒漠草原破碎化草地生物多样性维持的一个重要前提,土壤生境的退化显著降低了斑块内部群落组织的复杂性和物种间相互作用的强度,不利于群落的自我维持。     

Biocrust-induced partitioning of soil water between grass and shrub in a desert steppe of Northwest China

Maintaining the stability of exotic sand-binding shrub has become a large challenge in arid and semi-arid grassland ecosystems in northern China. We investigated two kinds of shrublands with different BSCs (biological soil crusts) cover in desert steppe in Northwest China to characterize the water sources of shrub (Caragana intermedia Kuang et H. C. Fu) and grass (Artemisia scoparia Waldst. et Kit.) by stable ¹⁸O isotopic. Our results showed that both shrublands were subject to persistent soil water deficiency from 2012 to 2017, the minimum soil depth with CV (coefficient of variation) <15% and SWC (soil water content) <6% was 1.4 m in shrubland with open areas lacking obvious BSC cover, and 0.8 m in shrubland covered by mature BSCs. For C. intermedia, a considerable proportion of water sources pointed to the surface soil. Water from BSCs contributed to averages 22.9% and 17.6% of the total for C. intermedia and A. scoparia, respectively. C. intermedia might use more water from BSCs in rainy season than dry season, in contrast to A. scoparia. The relationship between shrub (or grass) and soil water by δ¹⁸O shown significant differences in months, which partly verified the potential trends and relations covered by the high variability of the water source at seasonal scale. More fine roots at 0-5 cm soil layer could be found in the surface soil layer covered by BSCs (8000 cm/m³) than without BSCs (3200 cm/m³), which ensured the possibility of using the surface soil water by C. intermedia. The result implies that even under serious soil water deficiency, C. intermedia can use the surface soil water, leading to the coexistence between C. intermedia and A. scoparia. Different with the result from BSCs in desert areas, the natural withdrawal of artificial C. intermedia from desert steppe will be a long-term process, and the highly competitive relationship between shrubs and grasses also determines that its habitat will be maintained in serious drought state for a long time.     

Snow resisting capacity of Caragana microphylla and Achnatherum splendens in a typical steppe region of Inner Mongolia,China

Snow resisting capacity of vegetation is important for secondary distribution of water resources in seasonal snow areas of grassland because it affects the regeneration,growth and nutrient circulation of vegetation in grassland.This study investigated vegetation characteristics(canopy height,canopy length and crown width)of Caragana microphylla Lam.(shrub)and Achnatherum splendens(Trin.)Nevski.(herb),and snow morphologies(snow depth,snow width and snow braid length)in a typical steppe region of Inner Mongolia,China in 2017.And the influence of vegetation characteristic on snow resisting capacity(the indices of bottom area of snow and snow volume reflect snow resisting capacity)was analyzed.The results showed that snow morphology depends on vegetation characteristics of shrub and herb.The canopy height was found to have the greatest influence on snow depth and the crown width had the greatest influence on snow width.The canopy length was found to have little influence on morphological parameters of snow.When the windward areas of C.microphylla and A.splendens were within the ranges of 0.0-0.5 m2 and 0.0-8.0 m2,respectively,the variation of snow cover was large;however,beyond these areas,the variation of snow cover became gradually stable.The potential area of snow retardation for a single plant was 1.5-2.5 m2 and the amount of snow resistance was 0.15-0.20 m3.The bottom area of snow and snow volume(i.e.,snow resisting capacity)of clumped C.microphylla and A.splendens was found to be 4 and 25 times that of individual plant,respectively.The results could provide a theoretical basis both for the estimation of snow cover and the establishment of a plant-based technical system for the control of windblown snow in the typical steppe region of Inner Mongolia.     

Responses of Amygdalus pedunculata Pall. in the sandy and loamy soils to water stress

Amygdalus pedunculata Pall. is a major species that is widely planted in afforested soils with different textures in the transitional zone between Mu Us Desert and Loess Plateau, China. However, the responses of A. pedunculata to increasing intensity of water stress in different textural soils are not clear. Here, we conducted a soil column experiment to evaluate the effects of different textures (sandy and loamy) on water consumption, water use efficiency (WUE), biomass accumulation and ecological adaptability of A. pedunculata under increasing water stress, i.e., 90% (±5%) FC (field capacity), 75% (±5%) FC, 60% (±5%) FC, 45% (±5%) FC and 30% (±5%) FC in 2018. A. pedunculata grown in the sandy soil with the lowest (30% FC) and highest (90% FC) water contents had respectively 21.3%-37.0% and 4.4%-20.4% less transpiration than those with other water treatments (45%-75% FC). In contrast, A. pedunculata transpiration in the loamy soil decreased with decreasing water content. The magnitude of decrease in transpiration increased with increasing level of water deficit (45% and 30% FC). Mean daily and cumulative transpirations of the plant were significantly lower in the sandy soil than in the loamy soil under good water condition (90% FC), but the reverse was noted under water deficit treatments (45% and 30% FC). Plant height, stem diameter and total biomass initially increased with decreasing water content from 90% to 75% FC and then declined under severe water deficit conditions (45% and 30% FC) in the sandy soil. However, these plant parameters decreased with decreasing water content in the loamy soil. WUE in the sandy soil was 7.8%-12.3% higher than that in the loamy soil, which initially increased with decreasing water content from 90% to 75% FC and then declined under water deficit conditions (45% and 30% FC). The study showed that plant transpiration, biomass production and WUE responded differentially to increasing intensity of water stress in the sandy and loamy soils. The contrasting responses of A. pedunculata to water stress in different textural soils can guide future revegetation programs in the northern region of Chinese Loess Plateau by considering plant adaptability to varying soil and water conditions.     

几种无公害技术对褐梗天牛的防治效果

褐梗天牛Arhopalus rusticus（L.）是松柏类等林木的重要害虫,近年来在山东泰安、威海等地发生严重。本文利用引诱剂诱杀、饵木诱杀和释放管氏肿腿蜂Sclerodermus guani Xiao et Wu与花绒寄甲Dastarcus helophoroides Fairmaire等无公害技术对褐梗天牛进行了室内外防治研究。Ⅱ号引诱剂诱捕效果最好,30 d平均诱捕量为69头。饵木诱杀每个样木平均诱捕量为63头。管氏肿腿蜂防治褐梗天牛幼虫的室内效果最高达71.00%,不同蜂虫比之间的防治效果差异不显著;林间释放管氏肿腿蜂对直径为10～15 cm被害木中的天牛幼虫的寄生率最高,为8.43%。利用花绒寄甲防治效果较好,室内当花绒寄甲成虫和天牛幼虫量为5:1时的寄生率最高,为80.02%;林间每株树释放20头花绒寄甲成虫的寄生率最高,达58.80%。结果表明,这几种防治技术都对褐梗天牛有良好的防治效果,可在防治中综合应用。     

Changes in the relationship between species richness and belowground biomass among grassland types and along environmental gradients in Xinjiang,Northwest China

The association between biodiversity and belowground biomass (BGB) remains a central debate in ecology. In this study, we compared the variations in species richness (SR) and BGB as well as their interaction in the top (0-20 cm), middle (20-50 cm) and deep (50-100 cm) soil depths among 8 grassland types (lowland meadow, temperate desert, temperate desert steppe, temperate steppe desert, temperate steppe, temperate meadow steppe, mountain meadow and alpine steppe) and along environmental gradients (elevation, energy condition (annual mean temperature (AMT) and potential evapotranspiration (PET)), and mean annual precipitation (MAP)) based on a 2011-2013 survey of 379 sites in Xinjiang, Northwest China. The SR and BGB varied among the grassland types. The alpine steppe had a medium level of SR but the highest BGB in the top soil depth, whereas the lowland meadow had the lowest SR but the highest BGB in the middle and deep soil depths. The SR and BGB in the different soil depths were tightly associated with elevation, MAP and energy condition; however, the particular forms of trends in SR and BGB depended on environmental factors and soil depths. The relationship between SR and BGB was unimodal in the top soil depth, but SR was positively related with BGB in the middle soil depth. Although elevation, MAP, energy condition and SR had significant effects on BGB, the variations in BGB in the top soil depth were mostly determined by elevation, and those in the middle and deep soil depths were mainly affected by energy condition. These findings highlight the importance of environmental factors in the regulations of SR and BGB as well as their interaction in the grasslands in Xinjiang.     

Succession of soil bacterial and fungal communities of Caragana korshinskii plantation in a typical agro-pastoral ecotone in northern China over a 50-a period

Bacterial and fungal communities play critical roles in reestablishing vegetation structure, function and biodiversity in ecosystem restoration in arid and semi-arid areas. However, the long-term successional changes in bacterial and fungal communities that occur with artificial vegetation development are not fully understood. In this study, we investigated the successional changes in bacterial and fungal communities in Caragana korshinskii Kom. plantation over a period of 50 a (6, 12, 18, 40 and 50 a) and their relationships with key soil environmental factors in a typical agro-pastoral ecotone, northern China. The results showed that bacterial and fungal diversities (α- and β-diversity) were significantly affected by plantation age; moreover, the change in fungal community was more evident than that in bacterial community. Soil samples from 12 a plantation had the highest (P<0.05) bacterial and fungal α-diversity (i.e., abundance-based coverage estimator (ACE) and Chao1 index) at 0-10 cm depth compared with other samples. However, soil samples from plantation at the late recovery stage (40-50 a) had the highest α-diversity at 10-20 cm depth. Soil bacterial community was not significantly affected by plantation age at the genus level; but, soil fungal community was significantly affected at the genus level. Overall, Mortierella and Chaetomium were the dominant genera at natural recovery stage (0 a); Inocybe was the dominant genus at the early recovery stage (6-12 a); Inocybe and Mortierella were the dominant genera at the mid-recovery stage (12-40 a); And Mortierella, Cladosporium and Humicola were the dominant genera at the late recovery stage (40-50 a). Redundancy analysis (RDA) showed that β-glucosidase activity, total nitrogen and soil organic carbon were closely associated with bacterial community composition, while alkaline phosphatase, urease activity and total nitrogen were associated with fungal community composition, indicating that changes in enzyme activity and soil nutrients were the most important determinants of dominant genera. Furthermore, pathogenic microorganisms (Cladosporium and Humicola) were dominant in soils from 40-50 a plantation, which may affect plant growth, resulting in the decline of C. korshinskii plantation. Overall, the findings of this study improve the understanding of ecological patterns of bacterial and fungal communities in artificial vegetation and provide an important scientific basis for comprehensive ecological restoration management in arid and semi-arid areas.     

浑善达克沙地不同植被下的土壤水分状况

浑善达克沙地的中东段阳坡近裸的流动风沙土 0 - 1 0cm土层整个生长季内平均含水量较低、波动也比较大 ,而在 1 0cm以下则基本稳定在 3%左右 ,尤其是深层。丘间低地草本群落下的土壤湿度随深度增加变化较大 ,2 0cm以上土层含量较高 ,40 - 5 0cm土层的含水量最低 ,波动也剧烈 ,90cm以下达裸沙含水量水平。阴坡灌丛下 ,最低土壤含水量出现在 70 -90cm土层 ,深层土壤含水量长期稳定在 1 .5 %左右。这说明植物的生长使根层土壤含水量下降 ,而且不同植物利用水的土层及利用土壤水的量不同。这可能是引起流动风沙土向固定风沙土转变过程中地表植被演替及决定地区顶级群落的主要原因。在干旱半干旱地区 ,植被影响着降水在土层中的分布及地表的蒸散条件 ,使土壤有效水向浅层分配。而降水在土壤不同深度的分配及入渗深度 ,决定着地表植被的生活型 ,从而影响地表植被的演替方向及顶级类型。需水量较大的灌丛在沙丘阴坡能形成稳定的群落 ,是由于沙丘为植物避免干旱胁迫 ,延长在干旱季节的生存时间创造了条件 ,因此 ,沙丘是沙地的重要环境资源 ,尤其是高大沙丘 ,在这类地区的防风固沙中具有重要的作用。     

Stable isotope analysis of water sources for Tamarix laxa in the mega-dunes of the Badain Jaran Desert,China

The complex interactions in desert ecosystems between functional types and environmental conditions could be reflected by plant water use patterns. However, the mechanisms underlying the water use patterns as well as the water sources of Tamarix laxa in the mega-dunes of the Badain Jaran Desert, China, remain unclear. This study investigated the water sources and water use patterns of T. laxa using the stable oxygen isotope method. The δ¹⁸O values of xylem water, soil water in different layers (0-200 cm), rainwater, snow water, lake water, atmospheric water vapor, condensate water, and groundwater were measured. The sources of water used by T. laxa were determined using the IsoSource model. The results indicate that T. laxa mainly relies on soil water. At the beginning of the growing season (in May), the species is primarily dependent on water from the middle soil layer (60-120 cm) and deep soil layer (120-200 cm). However, it mainly absorbs water from the shallow soil layer (0-60 cm) as the rainy season commences. In September, water use of T. laxa reverts to the deep soil layer (120-200 cm). The water use patterns of T. laxa are closely linked with heavy precipitation events and soil water content. These findings reveal the drought resistance mechanisms of T. laxa and are of significance for screening species for ecological restoration.     

六种蚜虫对多异瓢虫生长发育和繁殖的影响

多异瓢虫是新疆地区的优势捕食性天敌,可取食蚜虫、粉蚧、木虱等多种害虫。开展多异瓢虫的大规模扩繁对于推进害虫的绿色防控具有重要意义,选择适合多异瓢虫生长发育和繁殖的食物,是保证其人工扩繁的重要基础。本研究通过室内比较饲喂6种蚜虫（麦长管蚜、棉黑蚜、棉蚜、玉米蚜、豌豆蚜、桃蚜）后多异瓢虫的生命参数,筛选适合用于其人工扩繁的活体饲料。结果表明：多异瓢虫取食6种蚜虫显著影响幼虫的发育历期、存活率、成虫寿命、繁殖力以及世代历期。其中,多异瓢虫幼虫取食麦长管蚜（7.70d）和玉米蚜（7.67d）的发育历期明显短于取食其他4种蚜虫的;取食麦长管蚜发育成的雌、雄成虫均较重（雌11.02mg、雄8.54mg）;取食棉黑蚜时蛹期（3.80d）和卵期（2.52d）均较短;多异瓢虫取食麦长管蚜（20.02d）、棉黑蚜（21.14d）、棉蚜（20.07d）和玉米蚜（20.37d）的世代历期均较短;多异瓢虫幼虫取食麦长管蚜（96.33%）、棉黑蚜（96.50%）和棉蚜（90.67%）的存活率均明显高于取食其他3种蚜虫的。同时,多异瓢虫雌、雄成虫分别在取食棉黑蚜（44.67d）和麦长管蚜（59.13d）时寿命最长。在繁殖力方面,多异瓢虫成虫取食麦长管蚜（3.53d）和棉蚜（3.68d）时产卵前期均较短;取食棉黑蚜（1044.02粒）和棉蚜（1084.45粒）时单雌产卵量较高。综合来看,在6种蚜虫中,麦长管蚜、棉黑蚜和棉蚜均相对适合多异瓢虫的生长发育和繁殖,是饲养与人工扩繁多异瓢虫较为理想的活体饲料。     

宁夏不同地区农田土壤矿质氮的空间变异特征

在宁夏灌区和旱区共计选定肥力水平不同的30块农田,分别采集了0~120 cm深土壤剖面样品和小麦植株样品,测定了土壤铵、硝态氮含量和小麦地上部含氮量,分析了土壤矿质氮的空间变异性及其与小麦吸氮量的关系。结果表明,在0~120 cm深土壤剖面中,NH4-N、NO3-N和矿质氮含量及其累积量,灌区土壤显著高于旱区土壤,测点之间存在极显著差异,变异系数相当高。但在土层间不论灌区还是旱区变化不明显,在剖面上下分布比较均匀。矿质氮含量在土层间存在着正相关。在0~120 cm深土壤剖面中,矿质氮累积量在灌淤土、黑垆土、黄绵土和灰钙土间差异较大,平均分别为370.0、155.1、117.5和61.0 kg/hm2。其累积量与小麦籽粒产量、生物学产量、地上部总吸氮量之间呈极显著正相关,表明土壤较深层次的矿质氮对作物吸氮量也具有重要贡献。     

Responses in gross primary production of Stipa krylovii and Allium polyrhizum to a temporal rainfall in a temperate grassland of Inner Mongolia,China

In the arid and semi-arid areas of China, rainfall and drought affect the growth and photosynthetic activities of plants. Gross primary productivity (GPP) is one of the most important indices that measure the photosynthetic ability of plants. This paper focused on the GPP of two representative grassland species (Stipa krylovii Roshev. and Allium polyrhizum Turcz. ex Regel) to demonstrate the effect of a temporal rainfall on the two species. Our research was conducted in a temperate grassland in New Barag Right Banner, Hulun Buir City, Inner Mongolia Autonomous Region of China, in a dry year 2015. We measured net ecosystem productivity (NEP) and ecosystem respiration flux (ER) using a transparent chamber system and monitored the photosynthetically active radiation (PAR), air and soil temperature and humidity simultaneously. Based on the measured values of NEP and ER, we calculated the GPP of the two species before and after the rainfall. The saturated GPP per aboveground biomass (GPP_AGB) of A. polyrhizum remarkably increased from 0.033 (±0.018) to 0.185 (±0.055) μmol CO₂/(gdw?s) by 5.6-fold and that of S. krylovii decreased from 0.068 (±0.021) to 0.034 (±0.011) μmol CO₂/(gdw?s) by 0.5-fold on the 1^st and 2^nd d after a 9.1 mm rainfall event compared to the values before the rainfall at low temperatures below 35°C. However, on the 1^st and 2^nd d after the rainfall, both of the saturated GPP_AGB values of S. krylovii and A. polyrhizum were significantly lower at high temperatures above 35°C (0.018 (±0.007) and 0.110 (±0.061) μmol CO₂/(gdw?s), respectively) than at low temperatures below 35°C (0.034 (±0.011) and 0.185 (±0.055) μmol CO₂/(gdw?s), respectively). The results showed that the GPP responses to the temporal rainfall differed between S. krylovii and A. polyrhizum and strongly negative influenced by temperature. The temporal rainfall seems to be more effective on the GPP of A. polyrhizum than S. krylovii. These differences might be related to the different physiological and structural features, the coexistence of the species and their species-specific survival strategies.     

Influence of groundwater depth on species composition and community structure in the transition zone of Cele oasis

The paper analyzes the hypothesis that the distribution of dominant plant species and characteristics of plant communities are related to groundwater depth. The results showed that variations of groundwater depth impacted distributions and characteristics of dominant plant communities. However, besides groundwater depth, the community composition and species diversity were also influenced by physiognomy of the habitat. Based on the similarity coefficient, the differences between dominant plant communities were significant at different groundwater depths. Compared with other results relating to desert vegetation and groundwater depth, variations of community distribution were similar at the large spatial scale. However, in this extremely arid region, there were significant differences in community type and community succession when compared with other arid regions, especially in relationship to deep groundwater depth. With groundwater depth from deep to shallow, communities transformed with the sequence of Alhagi communities, Tamarix spp. communities, Populus communities, Phragmites communities, and Sophora communities. At groundwater depth of less than 6.0 m, the community type and composition changed, and the species diversity increased. Among these dominant species, Tamarix exhibited the biggest efficiency in resource utilization according to niche breadth, which means it possessed the best adaptability to environmental conditions at the oasis margins.     

Effects of native and invasive Prosopis species on topsoil physiochemical properties in an arid riparian forest of Hormozgan Province,Iran

Biological invasions can alter soil properties within the range of their introduced, leading to impacts on ecosystem services, ecosystem functions, and biodiversity. To better understand the impacts of biological invasions on soil, we compared topsoil physiochemical properties at sites with invasive alien tree species (Prosopis juliflora), native tree species (Prosopis cineraria, Acacia tortilis, and Acacia ehrenbergiana), and mixed tree species in Hormozgan Province of Iran in May 2018. In this study, we collected 40 soil samples at a depth of 10 cm under single tree species, including P. juliflora, P. cineraria, A. tortilis, and A. ehrenbergiana, as well as under mixed tree species. The results showed that organic matter, moisture, potassium, calcium, nitrogen, and magnesium in topsoil at sites with A. tortilis and A. ehrenbergiana growing in combination with P. cineraria were higher than that at sites where P. juliflora was present (P<0.05). Sodium at sites with A. tortilis and A. ehrenbergiana growing in combination with P. cineraria and P. juliflora was lower as compared to that at sites with just A. tortilis and A. ehrenbergiana. Electrical conductivity was lower at sites with A. tortilis and A. ehrenbergiana growing in combination with P. cineraria, and it was higher at sites with mixed Acacia and P. juliflora trees. Based on the generally more positive effect of native Acacia and P. cineraria on topsoil physiochemical properties as compared to the P. julifora, afforestation with native tree species is preferable for soil restoration. In addition, due to the negative effects of P. julifora on soil properties, P. julifora spread should be better managed.     

防风根腐病拮抗真菌的筛选鉴定及生防作用研究

从防风根际土壤中筛选得到1株对根腐病具有良好防治效果的拮抗菌株MR-47,基于形态学、ITS序列分析方法对菌株MR-47进行鉴定,确定该菌株为桃色顶孢霉Acremonium persicinum（GenBank No. OK287149.1）。通过对峙培养、显微镜观察,探究了菌株MR-47对木贼镰刀菌Fusarium equiseti的抑菌机理;基于盆栽试验,明确菌株MR-47的定殖能力及防病促生效果。结果表明,菌株MR-47对木贼镰刀菌抑菌率达69.26%,病原菌菌丝出现缢缩、膨大、扭曲、畸形等现象;对尖孢镰刀菌、腐皮镰刀菌等多种病原真菌表现出了良好的广谱抑菌活性;在土壤中定殖35 d内,最大定殖量为8.38×10⁶ CFU/g,最低为5.57×10⁶ CFU/g;MR-47对防风根腐病防效达75.05%。因此,桃色顶孢霉MR-47在防风根腐病的病害管理方面具有较好的开发价值及应用潜力。     

核盘菌菌核围微生物群落分析及其对盾壳霉重寄生的影响

重寄生真菌盾壳霉(Coniothyrium minitans)是核盘菌的一种生防菌,它通过寄生核盘菌菌核,减少初侵染来源,从而达到防病效果.但在田间自然土壤中,核盘菌菌核围微生物对盾壳霉寄生菌核的影响还不清楚.本研究对核盘菌菌核围微生物进行了分离鉴定,并评估了菌核围细菌对盾壳霉重寄生的影响.结果 表明,不同取样时间和不...     

Spatio-temporal variations of soil water content and salinity around individual Tamarix ramosissima in a semi-arid saline region of the upper Yellow River,Northwest China

Ecological restoration by Tamarix plants on semi-arid saline lands affects the accumulation, distribution patterns and related mechanisms of soil water content and salinity. In this study, spatio-temporal variations of soil water content and salinity around natural individual Tamarix ramosissima Ledeb. were invetigated in a semi-arid saline region of the upper Yellow River, Northwest China. Specifically, soil water content, electrical conductivity(EC_e), sodium adsorption ratio(SAR_e), and salt ions(including Na~+, K~+, Ca~(2+), Mg~(2+) and SO_4~(2–)) were measured at different soil depths and at different distances from the trunk of T. ramosissima in May, July, and September 2016. The soil water content at the 20–80 cm depth was significantly lower in July and September than in May, indicating that T. ramosissima plants absorb a large amount of water through the roots during the growing period, leading to the decreasing of soil water content in the deep soil layer. At the 0–20 cm depth, there was a salt island effect around individual T. ramosissima, and the EC_e differed significantly inside and outside the canopy of T. ramosissima in May and July. Salt bioaccumulation and stemflow were two major contributing factors to this difference. The SAR_e at the 0–20 cm depth was significantly different inside and outside the canopy of T. ramosissima in the three sampling months. The values of SAR_e at the 60–80 cm depth in May and July were significantly higher than those at the 0–60 cm depth and higher than that at the corresponding depth in September. The distribution of Na~+ in the soil was similar to that of the SAR_e, while the concentrations of K~+, Ca~(2+), and Mg~(2+) showed significant differences among the sampling months and soil depths. Both season and soil depth had highly significant effects on soil water content, EC_e and SAR_e, whereas distance from the trunk of T. ramosissima only significantly affected EC_e. Based on these results, we recommend co-planting of shallow-rooted salt-tolerant species near the Tamarix plants and avoiding planting herbaceous plants inside the canopy of T. ramosissima for afforestation in this semi-arid saline region. The results of this study may provide a reference for appropriate restoration in the semi-arid saline regions of the upper Yellow River.     

植株结构对不同虫态蠋蝽搜索和捕食斜纹夜蛾幼虫行为的影响

本研究旨在探明植株结构复杂性如何影响活动性较弱的捕食性昆虫对植株上防卫性较强的猎物的搜索和捕食行为.以蠋蝽Arna chinensis及其猎物斜纹夜蛾Spodoptera litura幼虫为捕食者-猎物模式,设置盆栽大豆Glycine max植株结构复杂性2个处理:1株/盆,2株/盆,接4头斜纹夜蛾4龄幼虫:在某一盆植...     

微润带埋深对温室番茄生长和土壤水分动态的影响

为探明微润灌溉对番茄生长和土壤水分的影响,设置了3种不同埋深和2种不同工作压力,研究了微润带埋设深度和压力对番茄生长、产量及水分利用效率的影响。结果表明:定植后94天,微润带压力水头为180cm、埋深为15 cm时的番茄株高分别比埋深10 cm和20 cm的处理增加9.17%和7.55%;此时番茄气孔导度最小,光合速率和水分利用效率最大,分别比埋深为10 cm和20 cm的处理增产3.24%和7.45%;不同埋深土壤含水率垂直分布随时间的变化存在差异,15 cm埋深时的土壤含水率最大。微润带埋深是影响土壤水分时空变化的主要因素;压力对土壤含水量时间变化影响不显著。