Phenotypic plasticity of Artemisia ordosica seedlings in response to different levels of calcium carbonate in soil

Plant phenotypic plasticity is a common feature that is crucial for explaining interspecific competition, dynamics and biological evolution of plant communities. In this study, we tested the effects of soil CaCO_3(calcium carbonate) on the phenotypic plasticity of a psammophyte, Artemisia ordosica, an important plant species on sandy lands in arid and semi-arid areas of China, by performing pot experiments under different CaCO_3 contents with a two-factor randomized block design and two orthogonal designs. We analyzed the growth responses(including plant height, root length, shoot-leaf biomass and root biomass) of A. ordosica seedlings to different soil CaCO_3 contents. The results revealed that, with a greater soil CaCO_3 content, A. ordosica seedlings gradually grew more slowly, with their relative growth rates of plant height, root length, shoot-leaf biomass and root biomass all decreasing significantly. Root N/P ratios showed significant negative correlations with the relative growth rates of plant height, shoot-leaf biomass and root length of A. ordosica seedlings; however, the relative growth rate of root length increased significantly with the root P concentration increased, showing a positive correlation. These results demonstrate that soil CaCO_3 reduces the local P availability in soil, which produces a non-adaptive phenotypic plasticity to A. ordosica seedlings. This study should prove useful for planning and promoting the restoration of damaged/degraded vegetation in arid and semi-arid areas of China.

Storage of biomass and net primary productivity in desert shrubland of Artemisia ordosica on Ordos Plateau of Inner Mongolia, China

Biomass and net primary productivity （NPP） are two important parameters in determining ecosystem carbon pool and carbon sequestration. The biomass storage and NPP in desert shrubland of Artemisia ordosica on Ordos Plateau were investigated with method of harvesting standard size shrub in the growing season （June-October） of 2006. Results indicated that above- and belowground biomass of the same size shrubs showed no significant variation in the growing season （p〉0.1）, but annual biomass varied significantly （p〈 0.01）. In the A. ordosica community, shrub biomass storage was 699.76-1246.40 g.m^-2 and annual aboveground NPP was 224.09 g-m^-2·a^-1. Moreover, shrub biomass and NPP were closely related with shrub dimensions （cover and height） and could be well predicted by shrub volume using power regression.

Damage characteristics of three boring pests in Artemisia ordosica

The population density and distribution of the three major boring pests, Holcocerus artemisiae, Sphenoptera sp. and Adosopius sp. were studied in their host plant Artemisia ordosica. Results show that the larvae ofH. artemisiae mainly bore the rhizome ofA. ordosica, but also the larvae of Sphenoptera sp. and Adosopius sp. bore the rhizome of A. ordosica. The adults of Sphenoptera sp. and Adosopius sp. feed on the leaves of A. ordosica as a nutritional supplement. The distribution of the larvae of three pests in their host plant is completely different. H. artemisiae and Sphenoptera sp. are distributed in the whole A. ordosica plant. The newly hatched larvae first feed on the phloem and xylem of stem and then burrow to the roots before the winter of the same year. However, ,4dosopius sp. is distributed mainly in the roots. The newly hatched larvae move from the phloem to the xylem, and gradually damage the lower part of the trunk. The larvae of the three pests sometimes coexist in a single A. ordosica plant. However, the probability of the coexistence of the three pests is very small. The highest probability of coexistence of two pests was observed in Sphenoptera sp. and H. artemisiae, while the probability of coexistence of Sphenoptera sp. and Adosopius sp. as well as H. artemisiae and Adosopius sp. was smaller. The reasons for coexistence or its avoidance are not only related to the amount of food provided nor the volume of larval living space in a single A. ordosica plant, but also related to the development characteristics of different kinds of larvae and interspecific competition.

Effects of N:P ratio of Artemisia ordosica on growth influenced by soil calcium carbonate

Soil calcium carbonate(CaCO_3) has a strong solid phosphorus effect, and high content of CaCO_3 can significantly reduce the effectiveness of soil phosphorus. To reveal the limiting effect of soil CaCO_3 on the growth of plants on sand land and its mechanism of plant physiology, we performed pot experiments with a two-factor randomized block design and a three-factor orthogonal design for different soil CaCO_3 content treatments using Artemisia ordosica seedlings. In the experiments, we surveyed plant height, aboveground biomass, root length and root weight and analyzed N, P concentrations and RNA content of the seedlings, and discussed the relationships between relative growth rate(RGR) of the seedlings and N:P ratio as well as RNA. Results show that, the RGRs of plant height and above-ground biomass of the seedlings decreased significantly with the increase of soil CaCO_3 content, and those for root length and root weight decreased. The RGRs of plant height and above-ground biomass of the seedlings were significantly negatively correlated with leaf N:P ratios, but significantly positively correlated with leaf RNA content and leaf P concentrations. It can be seen that soil CaCO_3 is a stress factor for the growth of A. ordosica seedlings, and the growth response of the seedlings under the influence of soil CaCO_3 is in line with the Growth Rate Hypothesis.

Effects of soil nitrogen:phosphorus ratio on growth rate of Artemisia ordosica seedlings

To address how the ratios of nitrogen and phosphorus (N:P ratios) in soil affect plant growth, we performed a two-factor (soil available N:P ratios and plant density) randomized block pot experiment to examine the relationships between soil N:P ratios, and the N:P ratios and growth rate of Artemisia ordosica seedlings. Under moderate water stress and adequate nutrient status, both soil N:P and plant density influenced the N:P ratios and growth rates of A. ordosica. With the increase of soil N:P ratios, the growth rates of A. ordosica seedlings decreased significantly. With the increase of soil N:P ratios, N:P ratios in A. ordosica seedlings increased significantly. While the nitrogen concentrations in the plant increased slightly, the phosphorus concentrations significantly decreased. With the increase of plant density, the shoot N:P ratios and growth rates significantly decreased, which resulted from soil N:P ratios. Thus, soil N:P ratios influenced the N:P ratios in A. ordosica seedlings, and hence, influenced its growth. Our results suggest that, under adequate nutrient environment, soil N:P ratios can be a limiting factor for plant growth.

Effects of surface cracks on the rhizospheric microhabitat of Artemisia ordosica in subsidence area caused by coal mining

The effects of surface cracks caused by underground coal mining on microhabitat in the rhizosphere of Artem＆ia ordosias were studied based on field investigation and sample analysis. The results show that the amounts of microorganisms, enzyme activity and water content in soil vary with the biomass ofA. ordosias, and that the account exhibits in an order of large A. ordosias〉medium A. ordosias〉small A. ordosias. Surface cracks apparently decrease microbial quantities and enzymatic ac- tivities, and change the composition and structure of microbial community in the rhizosphere of A. ordosias. Surface cracks reduce water content and electrical conductivity, enhance the R/S （ratio of root and soil） of water content, electrical conductivity and pH value, and raise the content of Na and Pb in rhizosphere soil ofA. ordosicas, It can be concluded that the disturbance of underground coal mining on the microhabitat in the rhizosphere ofA. ordosica is obvious in the early days.

Diurnal and seasonal dynamics of soil respiration in desert shrubland of Artemisia Ordosica on Ordos Plateau of Inner Mongolia, China

The diurnal and seasonal dynamics of soil respiration in the A. ordosica shrubland on Ordos Plateau were investigated in the growing season （May-October） of 2006 and their environmental driving factors were also analyzed, Results indicated that diurnal dynamics of soil respiration rate and its temperature dependence showed some discrepancy in two different growth stages （the vegetative growth stage and the reproductive growth stage）. During the vegetative growth stage, the diurnal variation of soil respiration was slight and not correlated with the daily temperature change, but during the reproductive growth stage, the daily respiration variation was relatively large and significantly correlated with the diurnal variation of air and soil temperature. In the growing season, the peak value of soil respiration occurred at July and August because of the better soil water-heat conditions and their optimal deployment in this period. In the shrubland ecosystem, precipitation was the switch of soil respiration pulses and can greatly increase soil respiration rates after soil rewetting. Moreover, the soil respiration rates in the growing season and the air temperature and soil surface water content were closely correlated （p〈0.05） each other. The stepwise regression model indicated that the variation of soil surface moisture accounted for 41.9% of the variation in soil respiration （p〈0.05）.

Biological soil crust distribution in Artemisia ordosica communities along a grazing pressure gradient in Mu Us Sandy Land, Northern China

This study investigated the distribution pattern of biological soil crust （BSC） in Artemisia ordosica communities in Mu Us Sandy Land. Three experimental sites were selected according to grazing pressure gradient. In each experimental site, the total vegetation cover, A. ordosica cover, BSC cover, litter-fall cover, BSC degree of fragmentation, BSC thickness and soil properties were investigated in both fixed and semi-fixed sand dunes and simultaneously analyzed in the laboratory. The results showed that at the same grazing pressure, BSC cover and composition were significantly affected by the fixation degree of sand dunes. In addition, BSC cover in the fixed sand dunes was 83.74% on average, whereas it is proportionally dominated by 28% mosses, 21% lichens, and 51% algae. Meanwhile, BSC cover in the semi-fixed sand dunes was 23.54% on average, which is proportionally domi- nated by 6.3% mosses, 2.5% lichens, and 91.2% algae. Fine sand, organic matter, and total nitrogen （N） contents in the fixed sand dunes were all significantly higher than those in the semi-fixed sand dunes. Litter-fall cover de- creased along the grazing pressure gradient, whereas BSC fragmentation degree increased. Fine sand content decreased along with the increase of grazing pressure, whereas medium sand content increased in both fixed and semi-fixed dunes. The organic matter and total N contents in the no grazing site were significantly higher than those in light and normal grazing sites. However, there were no significant differences between the light and normal grazing sites. In addition, there were also no significant differences in BSC thickness between the light and normal grazing sites in the fixed sand dunes. However, a significant decrease was observed in both BSC cover and thick- ness in the normal grazing site. The BSC in the semi-fixed dunes was more sensitive to disturbance.

Isolation and Identification of Capillarin from Artemisia Ordosica Kraschen

Capillarin was isolated from Artemisia Ordosica Kraschen and characterized by IR, 1H-NMR, 13C-NMR, 1H-1HCOSY, HMQC, HMBC and EIMS, and its crystal structure was determined by single-crystal X-ray diffraction analysis with the following data: triclinic, space group P1, Z = 2, a = 7.226(6), b = 7.297(6), c = 11.042(8) ?, α = 74.695(12), β = 78.479(12), γ = 62.063(10)°, V = 494.2(6) ?3, Mr = 198.21, Dc = 1.332 g/cm3, F(000) = 208, μ = 0.089 mm-1, S = 1.023, (?/σ)max = 0.000, the final R = 0.0408 and wR = 0.1110. The largest peak and deepest hole on the final difference Fourier map are 0.219 and –0.161 e/?3, respectively. The bond lengths and bond angles of the molecule are also given.

Wind-proof and sand-fixing effects of Artemisia ordosica with different coverages in the Mu Us Sandy Land,northern China

Wind erosion is a key global environmental problem and has many adverse effects.The Mu Us Sandy Land of northern China is characterized by an arid climate,where vegetation patches and bare sand patches are usually distributed mosaically,and aeolian activities occur frequently.Vegetation plays a significant role in controlling wind erosion.Artemisia ordosica is the most dominant native plant species in the Mu Us Sandy Land.It is urgent to study the wind-proof and sand-fixing effects of Artemisia ordosica in the Mu Us Sandy Land.This study analyzed the wind-proof and sand-fixing effects of Artemisia ordosica based on the field data of wind regimes,aeolian sediment transport,and surface change of Artemisia ordosica plots with four coverages(denoted as site A,site B,site C,and site D)in the Mu Us Sandy Land during the period from 1 June 2018 to 29 June 2019.The coverages of Artemisia ordosica at site A,site B,site C,and site D were 2%,16%,29%,and 69%,respectively.The annual average wind speeds at 2.0 m height above the ground for site A,site B,site C,and site D were 3.47,2.77,2.21,and 1.97 m/s,respectively.The annual drift potentials were 193.80,69.72,15.05,and 6.73 VU at site A,site B,site C,and site D,respectively.The total horizontal aeolian sediment fluxes during the period from 2-3 June 2018 to 6 June 2019 at site A,site B,site C,and site D were 4633.61,896.80,10.54,and 6.14 kg/m,respectively.Site A had the largest surface changes,and the surface changes at site B were significantly weaker than those at site A,whereas the surface changes at site C and site D were minimal.The results indicated that Artemisia ordosica significantly reduced the wind speed,drift potential,aeolian sediment transport,and surface changes.The higher the coverage of Artemisia ordosica is,the more obvious the effects of wind-proof and sand-fixing.Wind erosion would be effectively controlled in the Mu Us Sandy Land if the coverage of Artemisia ordosica is greater than 29%.These results provide a scientific basis for evaluating the ecosystem service function of Artemisia ordosica and the vegetation protection and construction projects in the Mu Us Sandy Land.

Ethno-medicinal study of Artemisia ordosica Krasch.(traditional Chinese/Mongolian medicine) extracts for treatment of allergic rhinitis and nasosinusitis

OBJECTIVE To evaluate the in vivo anti-inflammatory and allergic rhinitis(AR)alleviating effect as well as in vitro antimicrobial activities of Artemisia ordosica Krasch.(AOK)extracts to verify its ethno-medicinal claims.METHODS Crude extracts(methanol/95%-ethanol/ethyl acetate)of AOK root/stem/leaf and fractions(petroleum ether/ethyl acetate/n-butanol/aqueous)of AOK root extractwere prepared.Xylene-induced ear swelling model in mouse and ovalbumin(OVA)-induced AR model in guinea pig were established.Ear swelling degrees of mice were measured.The numbers of rubbing movement and sneezes of guinea pigs were counted to evaluate the symptoms of AR.The serum levels of histamine,INF-γ,IL-2/4/10,and VCAM-1 were measured by ELISA assay.The histological changes of nasal mucosa were investigated by light microscope after H&E staining.Antimicrobial activities of AOK extracts were also tested.LC-MS/MS analysis was performed to characterize the constituents of active extract and molecular docking was conducted to predict the biological mechanism.RESULTS In ear-swelling model,extract(100.00 mg·kg^-1)from the ethyl acetate layer of 95%ethanol(100.00 mg·kg^-1)showed better swelling inhibition in mice than positive control(dexamethasone,191.91 mg·kg^-1).In AR model,extract from the ethyl acetate layer of 95%ethanol significantly alleviated the AR symp⁃toms in guinea pigs,decreased the serum levels of histamine,INF-γ,IL-2/4/10,and VCAM-1,and reduced the infiltration of eosinophil in nasal mucosa.For Staphylococcus aureus,the ethyl acetate extract of AOK stem showed the highest inhibi⁃tion(MIC=1.25 g·L^-1),for Escherichia coli,n-butanol layer of 95%ethanol extract of AOK root showed the highest inhibi⁃tion(MIC=15.00 g·L^-1),for Candida glabrata,95%-ethanol extract of AOK stem showed the best inhibition(MIC=0.064 g·L^-1),while ethyl acetate and n-butanol layers showed similar inhibition on MRSA(MIC=7.50 g·L-1).LC-MS/MS characteriza⁃tion showed that dicaffeoylquinic acids account for more than 30%of ethyl acetate layer of AOK extract.Dicaffeoylquinic acids bind with histamine-1 receptor with high affinities and interesting modes.CONCLUSION Extracts from AOK had interesting anti-inflammatory activity in mice,alleviating effect against OVA-induced AR in guinea pigs,and antimicrobial activities in vitro,which support the ethno-medicinal use of it.The main constituents in ethyl acetate layer of AOK root extract are dicaffeoylquinic acids and could bind with histamine-1 receptor well.These findings highlighted the impor⁃tance of natural product chemistry study of AOK.

Relationships between Artemisia ordosica communities and environmental factors following sand-dune stabilization in the Mu Us desert,northwest China

Artemisia ordosica is an excellent sand-fixing shrub for sand stabilization in northwestern China. Sand dune stabilization, a critically important process, leads changes in abiotic factors, such as soil structure and nutrient contents. However, the effects of factors on an A. ordosica community following sand stabilization remain unclear. In this study, we used canonical correspondence analysis （CCA） to examine the relationships between A. ordosica communities and environmental factors at three habitats： semi-fixed dune （SF）, fixed dune with low-cov- erage biological soil crust （F）, and fixed dune with high- coverage biological soil crust （FC） in Mu Us desert. The mean height and coverage of plants increased with sand stabilization, while species diversity and richness increased initially and then reduced significantly. Correlation analysis and CCA revealed that slope, soil organic carbon, and nutrient contents, proportion of fine soil particles, soil moisture, and thickness of biological soil crust were all highly correlated with vegetation characteristics. These environmental factors could explain 40.42 % of the vege- tation-environment relationships at the three habitats. The distribution of plant species was positively related to soil moisture in the SF dune. Soil moisture, soil nutrient, and fine-particle contents mainly affected plants distribution in the F dune. In the FC dune, distribution of plant species was positively and negatively correlated with the thickness of biological soil crust and soil moisture at a depth 0-20 cm, respectively. The dominance value of typical steppe species increased significantly following sand-dune stabilization and relations between species and samples in CCA ordination bi-plots showed that perennial grasses could invade the A. ordosica community on FC, indicating A. ordosica communities had a tendency to change into typical steppe vegetation with the further fixation. We conclude that the significant differentiation not only occurred in community characteristics, but also in the relationships between vegetation and environmental factors among the three stages of dune fixation. So, restoration of degraded dune ecosystems should be based on habitat conditions and ecological needs.

Electroantennogram responses of Adosomus sp. to volatile components from Artemisia ordosica

Adosomus sp. eats the leaves and oviposits on the stems ofArtemisia ordosica Krasch. Based on an analytical PTI-GC/MS method, 21 volatile organic compounds （VOCs） from the leaves ofA. ordosica were identified. The major operating equipment consisted of a DB-5 column （30 m × 0.32 mm × 0.25 μm） and a flame ionization detector （FID）. The amounts of the components from VOCs were determined by a peak area normalization method and 17 VOC components were identified by PTI-GC/MS. The elec- troantennogram （EAG） responses ofAdosomus sp. to 17 of the VOCs were tested. The results show that seven compounds, i.e., oci- mene, myrcene, R-（＋）-α-pinene, caryophyllene, S-（＋）-2-canene, humulene and （＋）limonene elicited strong EAG responses by female Adosomus sp., with myrcene and ocimene eliciting the strongest responses. It is interesting to note that male Adosomus sp. presented different EAG responses from females to those compounds. Four volatile compounds： β-pinene, myrcene, trans-ocimene and longipinene elicited strong EAG responses to males with myrcene eliciting the strongest response.

Artemordins A-S, Cadinane-Type Sesquiterpenoid Dimers from Artemisia ordosica and Their Antihepatoma Activities

Nineteen new cadinane-involving sesquiterpenoid dimers,artemordins A-S(1-—19),together with 13 known SDs(20-32)were isolated from Artemisia ordosica.Their structures and absolute configurations were established by comprehensive spectral analyses,X-ray single crystal diffraction,theoretical ECD,and NMR calculations.Chemically,artemordins A-F(1—6)were the first examples of two cadinane units constructed by unprecedented C-3−C-15′or C-3−C-13′single bond with an oxido-rearranged 6/5/6/6 fused ring system;artemordins G-K(7-11)were biogenetically connected by[4+2]cycloaddition reaction and artemordins G-J(7-10)possessed a novel 5/6/6/6/6/6/5-heptacyclic fused ring system.Artemordins L-S(12-19)were formed by esterification,which involved three different types of sesquiterpenoids.Antihepatoma assay suggested that the most active compounds,artemordins B and H(2 and 8),exhibited inhibitory activities on three hepatoma cell lines with IC50 values of 26.9 and 25.1μmol/L(HepG2),29.5 and 18.3μmol/L(Huh7),19.7 and 15.7μmol/L(SK-Hep-1).

毛乌素沙地油蒿(Artemisia ordosica)根围AM真菌的时空分布研究

【目的】阐明荒漠地区AM真菌生态作用及其与沙生植物的互作关系,为AM真菌资源的合理利用及荒漠环境的恢复提供理论依据。【方法】在毛乌素沙地东北缘的中国科学院植物研究所鄂尔多斯沙地草地生态站设立样地,于2007年4,8和10月,采集油蒿（Artemisia ordosica）根围0-10,10-20,20-30,30-40和40-50 cm土层土样,分离其丛枝菌根（Arbuscular mycorrhiza,AM）真菌并测定相关土壤因子,系统研究油蒿根围AM真菌的时空分布。【结果】AM真菌在油蒿根系的总定殖率（86.9%）和丛枝定殖率（24.8%）均较高,说明二者间有良好的共生性;油蒿根围AM真菌孢子密度和定殖率随季节和土壤深度的变化而具有明显的时空性差异,并与土壤微环境显著相关。油蒿根围0-40 cm土层的菌丝定殖率和泡囊定殖率均较高且无显著变化,丛枝定殖率以30-40 cm土层较大。AM真菌孢子密度、土壤养分及土壤酶活性最大值均出现在0-20 cm土层,并随土壤深度增加而递减。AM真菌孢子密度、土壤速效磷含量、速效氮含量及土壤酶活性均随时间积累而增加,于10月份达到最大值。AM真菌孢子密度与土壤速效磷含量及磷酸酶活性呈显著正相关,丛枝定殖率与有机质含量、速效氮含量及土壤脲酶、酸性磷酸酶、碱性磷酸酶的活性均呈显著负相关,仅与pH显著正相关。【结论】AM真菌对提高寄主植物抵御外界干扰的能力维护荒漠土壤生态系统结构的完整性和功能稳定性具有重要意义。

油蒿(Artemisia ordosica)抗旱生理生化特性研究初报

测定了宁夏沙坡头地区固沙植物油蒿体内活性氧自由基的变化、膜伤害的程度、抗氧化保护酶系统以及光合特性与叶绿素含量的变化 ,对油蒿适应干旱胁迫的机理进行了分析。结果表明 ,灌溉地油蒿的MDA、·O-2 、H2 O2 、脯氨酸的含量以及CAT、SOD的活性低于固定沙丘的油蒿 ,而植物体内蛋白质的含量、POD的活性高于固定沙丘的油蒿。固定沙丘油蒿中的Chla、Chlb含量和H2 O→PCIP电子传递速率低于灌溉地油蒿。因此 。

油蒿(Artemisia ordosica)的化感作用研究

通过对鄂尔多斯高原毛乌素沙地油蒿(Artemisiaordosica)化感作用研究,发现油蒿茎叶的水浸提液对几种受体植物种子的萌发率、幼苗长和根长生长均有不同程度的抑制作用,随水浸提液浓度的增加抑制作用逐步增加;用油蒿茎叶水浸提液进行盆栽试验,受体植物的出苗率、苗高、根长和干物重也受到抑制,苗的形态也与对照有较明显的差异;在不同有机溶剂的水浸提液的萃取液中,乙酸乙酯萃取液对受体植物种子的萌发率、幼苗长和根长均有显著的抑制作用,形态差异明显;进一步对乙酸乙酯萃取液不同组分的生物试验表明,在洗脱出的3个组分中,其中的一个组分对受体植物种子萌发具有显著的抑制作用。经化学定性反应鉴定,此组分主要为黄酮类化合物。由此表明,油蒿具有一定的化感作用。

油蒿(Artemisia ordosica)对半干旱区沙地生境的适应及其生态作用

我国温带半干旱区沙地生境的主要特征是干旱少雨、沙源丰富和大风频繁 ,这种特定条件进化出我国特有的优良固沙植物———油蒿 .在长期的进化过程中 ,油蒿形成了独特的形态结构、生理特征和繁殖习性 ,能够很好地适应沙地环境 .油蒿群落不仅能够防风固沙 ,影响沙地生态系统的水分运移与分配 ,还能促进土壤的发育 .因此 ,油蒿在适应沙地生境的同时对沙地产生巨大的影响和改造作用 .油蒿群落对沙地生境的不断改造 ,推动了植物群落的演替 ,最终使流动沙丘转变为丰茂的植被 .

荒漠油蒿(Artemisia ordosica)根围AM真菌分布与土壤酶活性

于2007年10月在油蒿(Artemisia ordosica)集中分布区选取4个典型样地,分别从0～10cm、10～20cm、20～30cm、30～40cm和40～50cm土层采集根围土样,分离其丛枝菌根(arbuscular mycorrhiza,AM)真菌并测定了3种土壤酶活性。结果表明,在各样地0～50cm土层中油蒿根系AM真菌菌丝定殖率均很高,有典型的泡囊与丛枝结构。菌丝定殖率与泡囊定殖率呈显著正相关,但菌丝、泡囊和丛枝定殖率与AM真菌孢子密度和土壤酶活性之间都无相关性;孢子密度在不同样地及采样深度间差异明显,与土壤有机质、速效磷和速效氮含量都呈一定正相关关系。孢子密度与脲酶和酸性磷酸酶活性有显著或极显著相关关系,与碱性磷酸酶活性之间的相关性受到土壤pH的显著影响。孢子密度的峰值出现在0～10cm表层土,并随土壤剖面深度增加而降低。土壤酶活性在土壤垂直剖面显示与孢子密度同样的规律。不同样地间AM真菌分布及油蒿根系定殖率的差异表明,油蒿与AM真菌之间有良好共生性,对维护荒漠生态环境系统结构的完整性具有重要意义。

沙蒿(Artemisia ordosica)水浸提液对4种伴生草本植物的化感作用

以生长在我国荒漠和半荒漠地区的特有植物沙蒿为供体植物,沙米、虫实、草木樨状黄芪、狗尾草为受体植物,研究了沙蒿根、茎、叶、种子水浸提液对受体植物种子发芽、幼苗生长以及根对NH+4和K+吸收的化感效应的差异,为沙区植被恢复中伴生杂草种类的选择提供理论依据。结果表明:沙蒿水浸提液对4种受体植物种子发芽和幼苗生长均具有显著的化感效应,沙米、虫实、草木樨状黄芪表现为抑制作用,狗尾草表现为促进作用。不同部位沙蒿浸提液的化感作用不同,根浸提液对沙米、虫实、狗尾草的化感效应最强,茎浸提液对草木樨状黄芪的抑制最强。不同植物种及植物的不同发育时期对化感作用的敏感性也不同,在4种受体植物中,沙米受抑制最强,其次为虫实、草木樨状黄芪,且随浸提液浓度增加而显著增强,而狗尾草具有一定的耐受力,表现为促进作用。沙蒿浸提液对受体植物根长的影响最强,其次是种子发芽、苗高和幼苗干质量。浸提液显著降低沙米、虫实、草木樨状黄芪根对NH+4和K+的吸收,增加狗尾草根对NH+4和K+的吸收。研究结果表明雨水淋溶是沙蒿向环境中释放化感物质的途径之一,化感作用在增强沙蒿生存竞争力,扩大种群过程中起着不容忽视的作用,可能是沙蒿单优势种群落形成的原因之一。