Study on the variation in and selection of Fraxinus mandshurica provenances and families in northeast China

Fraxinus mandshurica Rupr.is one of the main afforestation species in northeast China,and there is great demand for improved F.mandshurica varieties.The results of an investigation into and analysis of the growth traits of F.mandshurica provenances and families showed that there were significant differences in different periods.However,variations in growth traits decreased year by year.There was a significant negative correlation between tree heights of the provenances and sunshine hours in their areas of origin.The provenances of Xinglong,Hailin and Wuchang were selected based on the volume of 18-year-old trees.The average genetic gain from the selection of fast-growing provenances was 19.4%.Ten superior fast-growing families were selected.The average volume of the selected families was22.6%,higher than that of all families.The correlation coefficient between heights at 6-year-old and at 18a was 0.838for provenances,and between heights at 4-year-old and at 18-year-old was 0.303 for families.These results indicate that early selection for height in provenances or families could be performed at 6 years or 4 years,respectively.Early selection for DBH and volume in families could start at 8 years.

Genetic variation and division of Pinus sylvestris provenances by ISSR markers

Inter Simple Sequence Repeat （ISSR） was used to detect genetic variation among nine provenances, including 135 individuals. A total of 108 loci were amplified using 10 random primers. The differentiation of the percentage of polymorphic bands （PPB） among different provenances was evident, ranging from 27% to 54%. of which Honghuaerji provenance had the highest PPB and Kalunshan provenance had the lowest PPB. Shannon＇s Information index （1） at species level was 0.1581 and Nei＇s gene diversity （h） was 0.2393. Coefficient of gene differentiation （Gsr） calculated by Popgene was 0.3965, these results indicated that majority of genetic variation （60.35%） was found within provenances. According to dendrogram among pinus sylvestriv provenances, nine provenances were divided into two provenance areas. namely Daxing＇an and Xiaoxing＇an Mountains provenance area and Hulunbeier provenance area.

Quantitative Genetic Variation in Gum Arabic (Acacia senegal (L) Willd) Provenances

Twelve (12) Acacia senegal provenances were evaluated at the Rubber Research Institute of Nigeria, Gum Arabic Sub-Station Gashua, Yobe state. Gum yield and some morphological data were collect in three years to estimate mean effects, genetic variability, heritability and genetic advance in Acacia senegal provenances. The analysis of variance revealed highly significant difference for all traits. Genetic component analysis showed that both genotypic coefficient of variation (GCV) and phenotypic coefficient of variation (PVC) were high for all the traits except bark thickness. PCV was higher in proportion than GCV with respect to all the traits. Gum yield gave the highest relative difference (RD) over other traits. Heritability estimates were high for bark thickness (77.36) and stem diameter (61.75). Expected genetic advance was high in number of tree incision (1.29), stem diameter (1.54) and yield in kg/ha (22.31). This study indicated that there was sufficient genetic variability in Acacia senegal provenances that could be used as a base for improvement of yield and other component attributes of this species through direct selection and hybridization.

Genetic variation and selection of introduced provenances of Siberian Pine(Pinus sibirica) in frigid regions of the Greater Xing'an Range,Northeast China

Siberian Pine （Pinus sibirica） is an ecologically and eco-nomically important species in pristine forests throughout northern Rus-sia. Four provenances of P. sibirica were introduced from Mongolia and Russia to the Greater Xing’an Range （the Daxing’anling）, northeast China in 1993. The aim of this research was to study genetic variation and selection of the introduced four Pinus sibirica provenances. Heights （H）, basal diameters （BD）, survival rates （SR） and crown lengths （CL） of different families were measured as primary outcomes in different growth years. Results of data analyses demonstrated high coefficients of phenotypic variation （PCV） and heritability （H2） for H, BD and CL at 18 years after introduction. PCV and H2 increased with age. Correlations of＆amp;nbsp;growth traits between any two growth years were all significantly positive, but the correlation coefficient was smaller when the growth year interval was larger. Correlations between H and the original environment factors decreased gradually, indicating that with long-term subsistence in the new environment, the influence of the source environment declined. Colligation of multiple traits to estimate provenances showed that Novosibirsk, Tomsk, and Altai Mountains had higher survival rates and biomass, and proved more suitable for introduction and plantation in the Greater Xing’an Range in China.

Germination and early seedling growth of Pinus densata Mast.provenances

We studied seed germination and early seedling growth of Pinus densata to explore the range of variability within the species and to inform afforestation practices. Phenotypes were evaluated at a forest tree nursery under conditions that support Pinus yunnanensis, one of the presumed parental species of P. densata. Seeds were col- lected from 20 open-pollinated trees within each of eight autochthonous populations representing the natural distri- bution of P. densata in China to assess variation in ger- mination traits and early seedling growth, and to examine the relationships among these traits. Results showed that seeds from all populations germinated and seedlings established successfully. There were significant differences among populations in 13 of 14 traits evaluated. Seed germination and early seedling growth were strongly related to seed size and seed weight. Bigger seeds germi- nated earlier and faster than small seeds, and seedling size was positively correlated with seed size. Some germination traits were strongly and significantly correlated with cli- matic variables associated with the provenance of the studied populations. Based on these observations, we conclude there were large, significant, and biologically important differences among P. densata populations in seed germination and seedling growth traits. The observed variability probably reflects a high degree of adaptive dif- ferentiation among populations that is likely to be relevant for future afforestation.

Seasonal variation of microelement contents in leaves of Cyclocarea paliurus among the provenances

Cyclocarya paliurus as a multiple function plant can accumulate biologically important microelement elements.To reveal the variation of selected microelement concentrations in leaves of C.paliurus provenances during the growing season,12 C.paliurus provenances in the field trial were sampled five times at approximately 1-month intervals.The method of inductively coupled plasma optical emission spectrometer（ICP-OES） was employed to determinate average concentrations of Fe,Mn,Zn,Cu and Se in leaves of 12 C.paliurus provenances.The results show that on average,the concentrations of five microelement in the leaves follows an order of Fe Mn Zn Cu Se.Variance analysis shows that there are significant differences in Fe,Mn and Zn concentrations among the twelve provenances（p0.05）,while there is no significant difference between Cu and Se concentrations.A significant difference was also observed in the concentrations of five microelements at the different sampling times（p0.001）,but the mean concentrations for each microelement showed different temporal dynamic patterns.Meanwhile,a significant correlation between concentrations of Se and other measured microelements was detected in the leaves of C.paliurus,except for Mn.Obtained results not only demonstrated that leaves of C.paliurus exhibited higher levels of microelements（Fe,Mn,Cu,Zn and Se）,but also provided a basis for breeding strategies of superior provenances with rich content of microelements,and choosing optimum harvesting time for food industry in future.

Variations in bark thickness and sapwood density of Calophyllum inophyllum provenances in Australia and in Sri Lanka

Sapwood density and bark thickness of Calophyllum inophyllum L. （a multipurpose durable timber species） were studied in various locations in Northern Australia and in Sri Lanka. Measurements were taken non-destructively by using core sampling and bark gauge. From each provenance, 4–15 mature trees having girth at breast height over bark （GBHOB） at 100–150 cm were selected on the basis of the population size. Significant （p0.05） hemispheric and provenance variations in bark thickness were found. Variations in the bark thickness are influenced by environmental variables. Variations in sapwood density were less pronounced compared to that of bark thickness. Variations in sapwood density are likely to be governed by genotypic variations.

Differentiation of Seed Germination and Early Seedling Growth in Ten Provenances of Eucalyptus Microtheca

An investigation of seed germination and early seedling growth of Eucalyptus microtheca was based onseed collection from 10 widely,separated provenanes in Australia. Genetic variation of seed germination and carly seedling growth was observed among a series of provcnances whose natural habitats range from different climatic condition Inthe ten provenances, both the model of seed relative germination percentage and the model of seed total germination percentage fitted Logistic regression [y=a/(1+exp(-cx+b))]. In comparison with provenanccs from four high temperature (meanannual maximum temperature >30.0 ℃: mean annual minimum temperature > 17.0 ℃) areas, six low temperature (meanannual maximum temperature <30℃, mean annual minimum temperature <17.0 ℃) areas showed the thst genninationrate and the high total germination percentage, For each provenance we have 45 seedlings equally divided into three watering levels (100%, 50%. and 25% of field capacity), and studies on relationship between early seedling growth and climaticfactors of the natural habitat of provenance. In control treatment. height growth of the seedling has beeb associated with intrinsically the driest quarter precipitation in the seed collection areas of provenance. In all the treatments, length growth ofthe biggest Ieaf of the seedling was related to mean annual maximum temperature and mean annual minimum temperaturein origin of provenance. In contrast, basal diameter growth of the seedling was related to mean annual minimum temperature of the seed collection areas in water stress treatment. From an ecological viewpint, the fast germination rate and thehigh total germination perecntage of the seed and rapid early grouth of the seedling appear to bc favourable adaptations tothe climatic conditions prevailing in the natural habitat of provenance.

Variations in seed size and seed mass related to tree growth over 5 years for 23 provenances of Quercus acutissima from across China

The origin of a seed strongly impacts its traits, and both origin and seed traits influence seed germination and seedling development. However, in many instances, this effect on the seedling does not persist into adulthood, and little is known about how seed traits and original environment affect seedling/tree growth over time. In this study, seed size, seed mass, seedling/tree growth and origins were collected and determined for 23 provenances of Quercus acutissima from across China. Origin variables correlated well with seed size and seed mass. In stepwise multiple regressions, a longitudinal aridity index explained 49.2-68.7% of the total variation in seed size and mass, while only seed width was correlated with seedling/tree height (H) and diameter at the ground (D) from seed traits and origins. The total variance in H and D explained by the models decreased over time, for example, the R 2 value of the models for H declined from 0.477 in the first year to 0.224 in the fourth year; no models was significant in the fifth year. These results indicate that seed size, regulated by the longitudinal aridity index strongly impacted seedling and tree growth, but the strength of the influence decreased over time, and disappeared after 4?years.

Performance and genetic diversity of 23 provenances of northern red oak(Quercus rubra L.)after 25 years of growth in South Korea

Growth traits and genetic diversity of 23 provenances of Quercus rubra introduced from North America were analyzed in a provenance trial established with a randomized block design in Hwaseong,Gyeonggi,South Korea in 1993.Growth variables and survival at age 25 were compared with results from early stages.Height,DBH,volume and stem straightness of Q.rubra was better than those of the domestic oak(Quercus accutissima).Growth of the Dunham Island provenance from New York was the best among the 23 provenances that of the Eagle River provenance from Wisconsin was poorest.Survival rate at age25 was on average 52%.The longitude of seed origin and growth of provenance were consistently significantly negatively correlated at all ages.Growth of coastal provenances was superior to that of the inland provenances,which were separated by the Appalachian Mountains.Genetic diversity and genetic distance among the provenances were evaluated using micro satellite markers.The allelic frequencies showed high polymorphism in 10 microsatellite loci,and 292 alleles were found.Of 10 loci,two were commonly found in the 23 provenances.The mean allelic diversity and heterozygosity observed among the provenances were similar to those from the native populations of Q.rubra in North America.Nei’s genetic distance among the 23 was estimated and showed that a clear trend between geographic and genetic distances,indicating that some provenances have high genetic diversity with superior growth performance.

Variations in shoot and root growth of three provenances of Faidherbia albida in clay and sand soil

The variation in shoot and root seedling growth traits was compared among three Faidherbia albida （Del）. A. Chev. provenances originating from Kenya （Taveta）, Malawi （Bolero） and Ghana （Bolgatanga）; representing east, south and west Africa, respectively. Bulked seeds from three provenances were grown in two soil types （clay and sand） at the World Agroforestry Centre nursery, Nairobi. Seedlings grown in clay soil had high shoot growth and shoot to root ratios but shorter root length, lower number of nodules and specific root length compared to seedlings in sand soil. Shoot to root ratios reduced with time and this was more pronounced in sand soil. Overall, the Bolero and Taveta provenances had higher growth than the Bolgatanga provenance. This was probably because plants grown in nutrient-rich clay soil invest more in shoot growth as compared to root growth. Longer root growth in sand soil shows a better adaptive mechanism that increases competitive ability and survival in nutrient-poor systems. Variations observed among the seedling variables such us shoot and root growth could be used for early selection for reforestation and agroforestry in predominantly clay and sand soil areas.

Genetic variation and superior provenances selection for wood properties of Larix olgensis at four trials

Larix olgensis,one of the most important timber species in northeastern China,is used for paper making and construction.In this study,10 wood properties(wood density,fiber length,fiber width,fiber length-to width ratio,hemicellulose content,cellulose content,holocellulose content,lignin content,ash content,and carbon content)of 10 provenances of L.olgensis planted at sites of CuoHai(CH),JiaGeDaQi(JGDQ),LiangShui(LS),and Mao'erShan(MES)were analyzed.The results of ANOVA showed that almost traits differed significantly among locations and provenances,with a significant interaction effect.Each trait also differed significant among provenances within sites.The phenotypic and genetic coefficient of variation(PCV and GCV)and provenance heritability(H 2)for wood properties ranged from 1.122 to 27.365%,from 0.564%to 21.113%and from 0.332 to 0.996,respectively.A correlation analysis showed that wood density was significantly negatively correlated with cellulose content and holocellulose content at sites CH,JGDQ,and LS,but were significantly positively correlated at site MES.Wood density was significantly negatively correlated with lignin content at CH and JGDQ,but not at LS and MES.Fiber width(FW)was negatively correlated with the ratio of fiber length(FL)to width across sites,and FW and FL/W were all positively correlated with FL.Lignin content was significantly positively correlated with hemicellulose content at site JGDQ and significantly negatively correlated with cellulose content and with holocellulose content at site MES.Interestingly,carbon content was positively correlated with cellulose content and holocellulose content at CH,but negatively correlated with these two traits at site MES.In a correlation analysis of wood properties with geographic,soil and climatic characteristics at the four sites,wood properties were mainly correlated with latitude and altitude of the site and affected by the average annual precipitation and temperature simultaneously.To select superior pulpwood provenances and high carbon storage provenances,we selected the two best provenances with excellent wood properties for each location based on a multi-trait comprehensive evaluation,which can be used as the preferred materials for the establishment of large-scale plantations in specific locations.

Early performance of Pinus radiata provenances in the earthquakeravaged dry river valley area of Sichuan, southwest China

A provenance experiment involving five native provenances and an Australian landrace of Pinus radiata （D. Don） was established over three sites in the dry river valley area of Sichuan, southwest China in 2004 in order to select the most suitable provenance for environmental planting on the dry, steep and degraded slopes to reduce soil erosion. Although with much lower soil moisture supply and mean minimum temperatures in winter compared to P. radiata provenance trials estab- lished elsewhere in the world, these sites are within the working limits of the species defined by previous climate modelling and matching. Be- cause of the difficult site conditions and severe natural disturbances after the experiment was established, mortality was high across the three sites in comparison to provenance trials in other countries.

Assessment of Water Provenances in Koxkar Glacier Region at the South Slope of Mt. Tianshan,China

Various water samples were collected for electrical conductivity (EC) and δ^18O analysis,and the proportion and contribution of atmospheric precipitation,glacier ice and shallow groundwater to discharge in the Koxkar glacier basin at the south slope of the Tianshan Mountains were studied.The results show that glacial ice-water recharge was dominant,accounting for 72.11% of the annual runoff.It also had a significant positive correlation with temperature during the warm season (from May to September).However,glacier ice ablation replenishment still existed when the temperature in the cold season was below the critical temperature of 0 ℃.This could be that the heat generated by the friction between the ice body and the ice bed during the subglacial ice sliding process led ice to melt,what's more,the stored water in the geometric passages inside and below the glacier could slowly release.Groundwater recharge accounted for 16.38% of the total runoff.The supplement was small and its variation range was relatively small in the cold season.But in the warm season,the amount of groundwater recharge increased and changed drastically.It might be that the seasonal frozen soil in the basin was widely developed and was affected by temperature changes.Atmospheric precipitation replenishment only accounted for 11.51%.The daily precipitation recharge river water had a significant response to regional precipitation,but there was hysteresis in time,and there was still precipitation recharge runoff even in the absence of precipitation.

Characteristic Features of Lapis Lazuli from Different Provenances, Revised by μXRF, ESEM, PGAA and PIXE

The objective of this study is to find out, to what extent the geochemical characteristics of lapis lazuli can be utilized in respect to its provenance. A wide range of variables is taken into consideration depending on the quantity of samples analysed from a specific geological region and the methods applied. In order to provide evidence, a multi-technique analytical approach using μXRF, ESEM, PGAA and PIXE is applied to samples from the most famous deposits of lapis lazuli. Special elements determined as fingerprints are compared in relation to the forming conditions obvious in textural features. The results and statistical output allow a differentiation that enables an optimized local classification of the blue stone. An absolute requirement for all geo-tracing performed on blue colored cultural objects of unknown provenance is awareness of the limits of analysis. The possible sources of lapis lazuli are tested by analysing the blue pigment used as paint on murals and ink on manuscripts from the Silk Road.

New insights into multiple provenances evolution of the Jurassic from heavy minerals characteristics in southern Junggar Basin, NW China

The method of random forest was used to classify the heavy mineral assemblages of 2 418 Jurassic samples in the southern Junggar Basin, and determine the distribution of the heavy mineral assemblages from the same provenance systems. Based on the analysis of heavy minerals assemblages, ZTR index, sedimentary characteristics, U-Pb zircon ages, whole-rock geochemical and paleocurrent direction analysis, the study reveals that five important provenances were providing sediments to the southern Junggar Basin in the Jurassic period: The North Tianshan(NTS), Central Tianshan(CTS), Bogda Mountains, Zhayier Mountains and Kalamaili Mountains. During the Early Jurassic, NTS-CTS, Kalamaili Mountains and Zhayier Mountains are primary provenances, Bogda Mountains started to uplift and supply clastic materials in the Middle Jurassic. There are three sedimentary area in the Jurassic of southern Junggar Basin: the western part, the central part and the eastern part. In the western part, the clastic materials of the Early Jurassic was mainly from NTS blocks and Zhayier Mountains, and the sediments were dominantly derived from the Zhayier Mountains during the Middle–Late Jurassic. In the central part, the main provenance of the Early Jurassic switched from NTS to CTS. In the Xishanyao Formation, the main source went back to NTS again. The NTS was the primary provenance during the sedimentary periods of Toutunhe Formation and Qigu Formation. In the eastern part, the contribution of CTS and Kalamaili Mountains were considered as major provenances in the Early Jurassic-Xishanyao Formation, small proportion of sediments were from NTS. The Bogda mountains uplifted and started to provide sediments to the Junggar Basin in the sedimentary period of Xishanyao Formation, and became the major source during the Toutunhe Formation period, with small amount of sediments from CTS. The provenance from CTS was hindered during the sedimentary period of Qigu Formation owing to the uplifting of the Bogda mountains, and the sediments were mainly from the Bogda mountains and NTS.

Geochemistry and depositional environment of fuchsite quartzites from Sargur Group,western Dharwar Craton,India

Meso-Neoarchean fuchsite quartzites are present in different stratigraphic positions of Dharwar Craton including the oldest(~3.3 Ga)Sargur Group of western Dharwar Craton.The present study deals with the petro-graphic and geochemical characteristics of the fuchsite quartzites from the Ghattihosahalli belt to evaluate their genesis,depositional setting and the enigma involved in the ancient sedimentation history.Their major mineral assemblages include quartz,fuchsite,and feldspars along with accessory kyanite and rutile.The geochemical com-positions are characterized by high SiO_(2),Al_(2)O_(3),low MgO,CaO,strongly enriched Cr(1326–6899 ppm),Ba(1165–3653 ppm),Sr(46–210 ppm),V(107–868 ppm)and Zn(11–158 ppm)contents compared to the upper continental crust(UCC).The UCC normalized rare earth element(REE)patterns are characterized by depleted light REE[(La/Sm)UCC=0.33–0.95]compared to heavy REE[(Gd/Yb)_(UCC)=0.42–1.65]with conspicuous positive Eu-anomalies(Eu/Eu^(*)=1.35–18.27)characteristic of hydrothermal solutions evidenced through the interlayered barites.The overall major and trace element systematics reflect a combined mafic-felsic provenance and suggest their deposition at a passive continental margin environ-ment.The comprehensivefield,petrographic,and geo-chemical studies indicate that these quartzites are infiltrated by Cr-richfluids released during high-grade metamorphism of associated ultramafic rocks.The Sargur and the subse-quent Dharwar orogeny amalgamated diverse lithounits from different tectonic settings,possibly leading to the release of Cr-richfluids and the formation of fuchsite quartzite during or after the orogeny.Thesefindings sug-gest a pre-existing stable crust prior to the Sargur Group and the link between orogenic events and various mineral deposits in the Dharwar Craton.

An integrated north–south paleo-Dadu-Anning River: New insights from bulk major and trace element analyses of the Xigeda Formation

The Xianshuihe-Anninghe fault extends SE–S and constitutes the southeastern margin of the Tibetan Plateau.However,the Dadu River which is associated with the fault does not flow following the path,but makes a 90ºturn within a distance of 1 km at Shimian,heading east,and joins the Yangtze River,finally flowing into the East China Sea.Adjacent to the abrupt turn,a low and wide pass near the Daqiao reservoir at Mianning separates the N–S course of the Dadu River from the headwater of the Anning River which then flows south into the Yunnan Province along the Anninghe fault.Therefore,many previous studies assumed southward flow of the paleo-Dadu River from the Shimian to the Anning River.However,evidences for the capture of the integrated N–S paleo-Dadu-Anning River,its timing,and causes are still insufficient.This study explored the paleo-drainage pattern of the Dadu and Anning Rivers based on bulk mineral and geochemical analyses of the large quantities of fluvial/lacustrine sediments along the trunk of the Dadu and Anning Rivers.Similar with sands in the modern Dadu River,the Xigeda sediments also exhibit a granitoid affinity with the bulk major mineral compositions of quartz(>50%),anorthite(about 10%),orthoclase(about 5%),muscovite(about 5%),and clinochlore(about 4%).Correspondingly,bulk major elements show high SiO_(2),with all samples>60%,and some of them>70%,low TiO_(2)(≤0.75%),P_(2)O_(5)(≤0.55%),FeO*(≤5%),and relatively high CaO(1.02%–8.51%),Na_(2)O(1.60%–2.52%),and K_(2)O(2.17%–2.71%),with a uniform REE patterns.Therefore,synthesizing all these results indicate that these lacustrine sediments have similar material sources,which are mainly derived from its course in the Songpan-Ganzi flysch block,implying that the paleo-Dadu originally flowed southward into the Anning River and provided materials to the Xigeda ancient lake.The rearrangement of the paleo-Dadu River appears to be closely related to the locally focused uplift driven by strong activities of the XianshuiheXiaojiang fault system.

Provenance of Conglomerate and Sandstone from Early Permian Shoushangou Formation in Xi Ujimqin,Inner Mongolia:Implications for Understanding Paleo-Asian Ocean Subduction

During the Late Carboniferous to Early Permian,a rift was formed by post-collisional extension after ocean closure or an island arc-related basin formed by Paleo-Asian Ocean(PAO)subduction in the Xi Ujimqin area.Nevertheless,the closure time of the PAO is still under debate.Thus,to identify the origin of the PAO,the geochemistry and U-Pb age of zircons were analyzed for the extra-large deep marine,polymict clastic boulders and sandstones in the Shoushangou Formation within the basin.The analyses revealed magmatic activity and tectonic evolution.The conglomerates include megaclasts of granite(298.8±9.1 Ma)and granodiorite porphyry(297.1±3.1 Ma),which were deposited by muddy debris flow.Results of this study demonstrated that the boulders of granitoids have the geochemistry of typical I-type granite,characterized by low Zr+Nb+Ce+Y and low Ga/Al values.The granitoid boulders were formed in island arc setting,indicating the presence of arc magmatism in the area that is composed of the Late Carboniferous to Early Permian subduction-related granitoid in southern Xi Ujimqin.Multiple diagrams for determining sedimentary provenance using major and trace elements indicate that Shoushangou sediments originated from continental island arc-related felsic rocks.Detrital zircon U-Pb age cluster of 330–280 Ma was obtained,indicating input from granite,ophiolite,Xilin Gol complex,and Carboniferous sources to the south.The basin was geographically developed behind the arc during the Early Permian period because the outcropped intrusive rocks in the Late Carboniferous to Early Permian form a volcanic arc.The comprehensive analyses of source areas suggest that Shoushangou sediments developed in a backarc basin in response to the northward subduction of the PAO.The backarc basin and intrusive rocks,in addition to previously published Late Carboniferous to Early Permian magmatic rocks of arc unit in Xilin Gol,confirm the presence of an Early Permian trencharc-basin system in the region,represented by the Baolidao arc and Xi Ujimqin backarc basin.This study highlights the importance and potential of combined geochemical and geochronological studies of conglomerates and sandstone for reconstructing the geodynamic setting of a basin.

Detecting APT-Exploited Processes through Semantic Fusion and Interaction Prediction

Considering the stealthiness and persistence of Advanced Persistent Threats(APTs),system audit logs are leveraged in recent studies to construct system entity interaction provenance graphs to unveil threats in a host.Rule-based provenance graph APT detection approaches require elaborate rules and cannot detect unknown attacks,and existing learning-based approaches are limited by the lack of available APT attack samples or generally only perform graph-level anomaly detection,which requires lots of manual efforts to locate attack entities.This paper proposes an APT-exploited process detection approach called ThreatSniffer,which constructs the benign provenance graph from attack-free audit logs,fits normal system entity interactions and then detects APT-exploited processes by predicting the rationality of entity interactions.Firstly,ThreatSniffer understands system entities in terms of their file paths,interaction sequences,and the number distribution of interaction types and uses the multi-head self-attention mechanism to fuse these semantics.Then,based on the insight that APT-exploited processes interact with system entities they should not invoke,ThreatSniffer performs negative sampling on the benign provenance graph to generate non-existent edges,thus characterizing irrational entity interactions without requiring APT attack samples.At last,it employs a heterogeneous graph neural network as the interaction prediction model to aggregate the contextual information of entity interactions,and locate processes exploited by attackers,thereby achieving fine-grained APT detection.Evaluation results demonstrate that anomaly-based detection enables ThreatSniffer to identify all attack activities.Compared to the node-level APT detection method APT-KGL,ThreatSniffer achieves a 6.1%precision improvement because of its comprehensive understanding of entity semantics.