Limited research on the hydrological impacts of invasive weeds hampers sustainable forest management and ecosystem restoration in biological invasive scenarios. This study assumed that alien weed invasion could affect surface runoff and sediment formation, with the extent of invasion determining its impact on soil and water conservation. To test this hypothesis, three Eucalyptus benthamii Maiden & Cambage plantations in Central Yunnan, Southwest China, infested with Agerina adenophora (Spreng.) R. M. King & H. Rob., were selected as the experimental sites. Runoff and sediment were monitored on slopes with varying invasion levels -severe invasion (SI), light invasion (LI), no invasion (NI) with litter coverage, and bare surface (BS) -over a year. The results showed that the cumulative runoff on the NI slopes (1.24 mm) and SI slopes (2.65 mm) was significantly lower ( p < 0.05) than that on the LI slopes (15.40 mm) and BS slopes (13.10 mm); similarly, the cumulative sediment on the NI slopes (3.3 x 10(-3) Mg/ha) and SI slopes (2.4 x 10(-3) Mg/ha) was significantly lower ( p < 0.05) than that on the LI slopes (0.11 Mg/ha) and BS slopes (0.14 x 10(-3) Mg/ha). Therefore, in areas of light invasion, weed -invaded slope forests are prone to serious soil and water loss, emphasizing the need for prevention; however, in severely degraded forests, maintaining heavily invasive weed populations is beneficial for soil and water conservation. This study provides a scientific foundation for ecologically restoring degraded forests impacted by exotic weed invasion.

Background: The hydrological effects of invasive plant control in forestland have not been well studied in the past, and numerous scientific mysteries remain unsolved. The long-term suspension of the unsolved issues will unavoidably influence the sound growth and sustainable management of forest ecosystems. This study investigates the hydrological effects of controlling invasive weeds in forestland. The research aims to understand the impact of invasive weed control on soil and water loss. Methods: Conducted in Eucalyptus benthamii Maiden & Cambage plantations in Central Yunnan, SW China, which are invaded by alien weed Ageratina adenophora (Spreng.) R. M. King & H. Rob., four surface cover treatments were applied to study runoff and sediment yielding properties. The four surface cover treatments were weed harvesting and litter elimination (WH&LE), weed harvesting and litter retention (WH&LR), litter burning and weed renewal (LB&WR), and weed retention and litter retention (WR&LR). Essentially, WH&LE and LB&WR served as integrated management approaches for invasive weeds and litter, WH&LR was an independent weed control measure, and WR&LR served as a research control. Results: Runoff was significantly higher in the LB&WR plots (3.03 mm) compared to the WR&LR plots (1.48 mm) (p < 0.05). The WH&LE plots had higher runoff (2.39 mm) than the WR&LR plots (not statistically significant), while the WH&LR plots had less runoff (1.08 mm) than the WR&LR plots (not significant). Sediment yield was lower in the WH&LR plots (0.50 t/km2) than in the WR&LR plots (0.52 t/km2) (not significant), but significantly higher in the WH&LE plots (2.10 t/km2) and LB&WR plots (1.57 t/km2) than in the WR&LR plots (p < 0.05). Conclusions: Managing invasive weeds independently reduces the risk of soil and water loss, but combined management with litter can exacerbate the issue. Invasive weed control and litter management should be performed separately in slope plantations. This study provides a scientific basis for soil and water conservation, restoration and rehabilitation of plantation ecosystems.

为探索紫茎泽兰对桉树的生态影响,采用盆栽实验法,测定了紫茎泽兰叶片干粉末添加(添加量:20g/盆、40g/盆、80g/盆,添加比例:单盆基质重量的0.5％、1％、2％)对直杆桉Eucalyptus maidenii盆栽苗生长及生理生态指标的化感作用.结果表明:(1)对桉树生长指标均显示促进作用,其中,对受体株高的促进强度20g/盆＞40g/盆＞80g/盆,对地径和叶片数量的促进强度40g/盆＞20g/盆＞80g/盆,对叶面积的促进强度40g/盆＞80g/盆＞20 g/盆.(2)对桉树生理生态指标的影响为:叶绿素总量和可溶性糖含量,均被抑制,且抑制强度20g/盆＞40g/盆＞80g/盆;丙二醛含量,20 g/盆时被抑制,80g/盆、40g/盆时则被促进;游离脯氨酸含量,20g/盆时被促进,80g/盆、40g/盆则被抑制.(3)对桉树生长指标的综合影响为促进作用,促进强度40g/盆＞20g/盆＞80g/盆,综合化感效应指数(SEI)介于0.214～0.343;对桉树生理生态指标的综合影响为抑制作用,抑制强度40g/盆＞20g/盆＞80g/盆,SEI值介于-0.084～-0.174.可见添加不同质量的紫茎泽兰叶片干粉末可对桉树盆栽幼苗的生长和生理生态指标产生不同性质和不同程度的影响.

To research the influence of Ageratina adenophora on germination and seedling growth of Eucalyptus, the effect of Ageratina adenophora allelopathy on E. globulus , E. maideni, and Eucalyptus smithii were determined by using 3 different mixed matrix of Ageratina adenophora and humus (1︰10, 1︰20, and 1︰30) based on greenhouse experiment method, and the results showed: 1) their effects on E. globulus were promoting effect, and the synthesized effect index ( SEI) increased from 0. 150 to 0. 296 with the increase of Ageratina adenophora mate-rial; 2) they had both promoting effect and inhibiting effect on E. maideni, the 1︰10 matrix showed inhibition effect with the SEI of -0. 148 , the 1︰20 matrix only showed slight boost with the SEI of 0. 000 25 , the 1︰30 matrix showed a certain promoting effect with the SEI of 0. 174; 3 ) they also had promoting effect and inhibiting effect on E. smithii, 1 ︰10 and 1 ︰20 matrix showed significantly inhibitory effect with the SEI ranged from-0. 898 to -0. 863 , 1︰30 matrix showed promoting effect with the SEI of 0. 279 . This study showed that the dif-ferent degrees of Ageratina aenophora material could have different effects on germination and seedling growth of Eucalyptus spp. .

Aim Much of what is known about invasion biology is based on research conducted in North America and Europe, leading to limitations and potential biases in our knowledge. We address these limitations by conducting a systematic review to assess the literature on ecological studies of two major tropical and subtropical invasive plant species, Ageratina adenophora and Chromolaena odorata. Our goals were to: (1) collect the literature on the invasion biology of these species by broadly searching five databases (one international and four regional); (2) determine limitations to the international literature available in the ISI Web of Science (WOS); (3) quantitatively summarize the scope of the invasion literature on the two species; and (4) propose future studies based on what we found.Location Global.Methods Using specific search terms, we searched the literature for A. adenophora and C. odorata in the ISI WOS, Chinese National Knowledge Infrastructure (CNKI), Indian Journals, Nepal Journals Online and African Journals Online (AJOL). We extracted information on journal titles, publication years, study area locations, habitats investigated and study focus.Results We found 101 papers for A. adenophora and 61 papers for C. odorata, published from 1987 to 2015. A high percentage of the studies were conducted in China, western and southern Africa, and India. Studies from WOS most frequently focused on the mechanism of invasion, while studies from CNKI and AJOL focused on the impacts of the invader.Main conclusions Web of Science is not sufficient for generalizing about the invasion biology literature, particularly if the goal is a comprehensive assessment that includes areas other than North America, Hawaii, Europe, Australia, South Africa and New Zealand. In future systematic reviews, other databases should be used if possible, including those in languages other than English. For future research, several research areas should be studied more thoroughly for A. adenophora and C. odorata invasions, including possible multiple factors responsible for invasion, and impacts of co-occurring invasive species.

The spatial-temporal succession of regional vegetation in Xishuangbanna, China from 1976 to 2010 was studied based on RS technology. The results showed the area fluctuation of main vegetation types in the study area during the research period. There was no great change in the total area of main vegetation, with the fluctuation area ranging from 12,579.84 to 14,698.75km2, averaging 13,664.48km2 annually, and with the fluctuation ratio between −7.94% and 7.57%. The area of natural vegetation (tropical rainforest, tropical seasonal moist forest, tropical seasonal rainforest, and tropical mountainous evergreen broad-1eaved forests) increased at first and gradually decreased afterwards, and the ratio of its distribution area to the total area of main vegetation was featured with an annual decrease, especially in 2005 and 2010. Both the distribution area and ratio of artificial vegetation (Rubber plantation) to the total area of main vegetation were characterized with the tendency of a gradual increase, especially in 2005 and 2010. Thus, the establishment of artificial vegetation (Rubber plantation) not only led to the decrease in natural vegetation (3641.16km2) but also covered 343.66km2 of lands for other uses. The results also showed the distribution succession of main vegetation types in the study area during the research period. In the later research period (after 1999), compared with the early research period (before 1999), the distribution range of natural vegetation was characterized with a certain decrease in the following aspects as at different altitudes (<600m, 600–800m, 800–1000m, 1000–1200m, 1200–1400m, and >1400m), and on different slopes (0–5°, 5–8°, 8–15°, 15–25°, 25–35°, and >35°). By contrast, the artificial vegetation was just the opposite whose distribution range was characterized with a tendency of a rapid growth at different altitudes, and on different slopes. It indicated that the establishment of artificial vegetation had broken the original ecological pattern in Xishuangbanna, which would bring direct threats to the regional ecological security and environment healthy development, thus countermeasures were urgent to be taken in order to prevent it from worsening.

On the basis of drought disaster occurred frequently in Southwest China in recent years,water suitability of regional vegetation was discussed.An important scientific issue concerned with the seasonal drought disaster was analyzed.The issue was whether could ecological water demand of Eucalyptus plantation and Hevea plantation be adapted to regional precipitation condition,or whether could ecological water demand of Eucalyptus plantation and Hevea plantation break the balance of supply and demand of regional ecological water use,and even lead to regional drought disaster.Research status and development trends in water suitability of regional vegetation were analyzed.It was pointed out that no great progress and no symbolic achievement was gotten in research related to water suitability of vegetation that based on the calculation of ecological water demand of vegetation.As for research on ecological water demand of vegetation,the basis for assessment of water suitability of vegetation,there are some problems left.Water suitability of typical vegetation in Yunnan Province and relationship between ecological water demand of regional vegetation and regional drought disaster should be investigated.

Understanding the leaf N, P concentrations and nutrient resorption of plants growing in phosphorus–enriched soil (PES) can provide new data for ecostoichiometric research and ecological model building. In this study, 117 green leaves and 53 senesced leaves of dominant plants in PES in the Dianchi Lake watershed, SW China, were sampled. Plants in PES had high fresh leaf P (4.60mg/g), senesced leaf P (2.70mg/g), and low fresh leaf N: P (4.41), senesced leaf N: P (3.21). P resorption efficiency (PRE) (25.09%) was significantly lower than N resorption efficiency (NRE) (52.68%). Forbs had the highest P content in fresh (5.35mg/g) and senesced leaf (3.25mg/g) among plants forms. Although NRE was varied among plant forms, the difference in PRE was not significant. In conclusion, PES has a tremendous impact on the patterns of leaf N, P and nutrient resorption of different plant forms, those results were different from general results.

Laboratory biological simulation experiment was conducted to investigate growth disturbance of high, moderate, low concentration of aqueous extracts (i.e. the original extracts with a solid liquid ratio of 1:40 g mL-1 and its 5 times diluents and 25 times diluents) from several crops straw (residue) on Ageratina adenophora, a worldwide notorious invasive weed. The results showed: (a) aqueous extracts from several crops straw (residue) brought about different impacts on the single index for germination and growth of A. adenophora, e.g., high concentration of aqueous extracts from Brassica oleracea waste leaves showed a strong inhibition against the germination rate (GR) and germination index (GI) of A. adenophora, while high concentration of aqueous extracts from Vicia cracca straw showed a strong inhibition against radicle length (RL) and hypocotyl length (HL) of A. adenophora; (b) high concentration of aqueous extracts from B. oleracea waste leaves and high, moderate and low concentration of aqueous extracts from Oryza sativa straw and Triticum aestivum straw showed rather strong synthetic effects (inhibition) on GR and GI of A. adenophora, which could be chosen for the control over the seeds germination of A. adenophora; (c) high and moderate concentrations of aqueous extracts from V. cracca straw, high concentration of aqueous extracts from B. campestris waste leaves, and moderate and low concentrations of aqueous extracts from O. sativa straw and T. aestivum straw showed rather strong synthetic effects (inhibition) on RL and HL of A. adenophora, which could be selected as ideal materials for the control over the seedlings growth of A. adenophora; and (d) high concentrations of aqueous extracts from V. cracca straw, B. oleracea waste leaves and B. campestris waste leaves, and high, moderate and low concentrations of aqueous extracts from O. sativa straw and T. aestivum straw showed rather strong synthetic effects (inhibition) on GR, GI, RL and HL of A. adenophora, which could be selected as ideal materials for the control over the seeds germination and seedlings growth of A. adenophora. Thus, this study would provide a theoretic guidance and technical support for the resources utilization of crops straw (residue) and the prevention and control over invasive weeds as well. (C) 2013 Elsevier B.V. All rights reserved.

Eucalyptus tree–Ageratina adenophora compound system is considered as a new invasion in Yunnan, southwest China in recent years. In this paper, the impacts of A. adenophora invasion on the soil physical and chemical properties of Eucalyptus plantation were investigated, based on the exploration of its causes, the assessment of its risk and the prediction of its succession. The results showed that the invasion had a different impact on eight different physical–chemical indexes of soil in Eucalyptus plantation, characterized with a certain complexity. Its impact on soil water was featured with seasonal difference, namely, during the rainy season, the soil water concentration decreased significantly, while, in the dry season, the soil water concentration increased significantly (excluding the severely invasive sample on shadowy slope). Meanwhile, its impact on soil organic matters (SOM), soil nitrogen (TN, AN), soil phosphorus (TP, AP) and soil potassium (TK, AK) was related to seasons, exposure and invasive degrees of A. adenophora, but there was no unified rule for them, which should be studied further. It is expected to provide a theoretical basis for the sustainable operation and scientific management of Eucalyptus plantation under the condition of A. adenophora invasion for sustainable agro-forest ecosystems.

In Eucalyptus globulus plantation spatial variation of biological indexes( density,height, and biomass) of invasive Ageratina adenophora population was investigated and analyzed. The results showed:(1) A. adenophora plants were affected by E. globulus plantation and part of them died. From the edge to the depth position of E. globulus plantation,density of survived A. adenophora plants decreased gradually while density of dead A. adenophora plants increased gradually.(2) Height of A. adenophora plants declined for being affected by E. globulus plantation. Height of A. adenophora(Height of the higher,the secondary and the shorter plant) was smaller with A. adenophora spreading to the depth position of E. globulus plantation.(3) Biomass of A. adenophora plant fluctuated for being affected by E. globulus plantation. From the edge to the depth position of E. globulus plantation, biomass of survived A. adenophora plant decreased gradually,while biomass of dead A. adenophora plant firstly decreased gradually and then increased slowly. This study showed that E. globulus planta-tion might have some barrier effect on diffusion of invasive A. adenophora population,which would have important enlightenment significance for prevention and control of A. adenophora,and development and utilization of plant resources from Eucalyptusspp.

Recently, the frequent seasonal drought in Southwest China has brought considerable concerns and continuous heated arguments on the "water pump" viewpoint (i.e., the water demand from Hevea spp. and Eucalyptus spp. can be treated as a water pump) once again. However, such viewpoint just focused on water consumption from vegetation transpiration and its ecoenvironment impacts, which had not considered other attributes of vegetation, namely, water saving and drought resistance, and hydrological regulation (water conservation) into consideration. Thus, in this paper, the synthesized attributes of regional vegetation water use had been mainly discussed. The results showed that the study on such aspects as the characters of water consumption from vegetation transpiration, the potential of water saving and drought resistance, and the effects of hydrological regulation in Southwest China lagged far behind, let alone the report on synthesized attributes of water utilization with the organic combination of the three aspects above or the paralleled analysis. Accordingly, in this paper, the study on the synthesized attributes of water use by regional vegetation in Southwest China was suggested, and the objectives of such a special study were clarified, targeting the following aspects: (i) characters of water consumption from transpiration of regional typical artificial vegetation; (ii) potential of water saving and drought resistance of regional typical artificial vegetation; (iii) effects of hydrological regulation of regional typical artificial vegetation; (iv) synthesized attributes of water use by regional typical artificial vegetation. It is expected to provide a new idea for the scientific assessment on the regional vegetation ecoenvironment effects and theoretical guidance for the regional vegetation reconstruction and ecological restoration.

The remote sense (RS) technology was adopted to explore the vegetation succession from 1976 to 2014 in Yao’an County, Yunnan Province, Southwest China. The results showed: (i) the changes in the distribution range of major vegetation types in the study area. In the 6 statistic years after 1976, in the study area, the distribution range of the secondary vegetation shrank greatly in 4 different subareas (northeast, southeast, northwest and northwest subarea), at 4 different altitudes (1500–1800m, 1800–2100m, 2100–2400m and 2400–2700m), on 4 different gradients (0–8°, 8–15°, 15–25°, 25–35°) and on 4 different aspects but the flat land (sunny slope, semi-sunny slope, semi-shadowy slope, and shadowy slope); by contrast, in the study area, the distribution range of artificial vegetation expanded greatly in all the subareas, at 2 different altitudes (1800–2100m and 2100–2400m), on 3 different gradients (0–8°, 8–15°, 15–25°), and on the 4 different aspects but the flat land. (ii) The increase and decrease in distribution area of major vegetation types in the study area. During the research period, the total area of major vegetation fluctuated between 1471.92 and 1196.94km2, averaging 1255.52km2 annually, with the fluctuation rate between −4.67% and 17.24%. In the second statistic year (1989), the total area of major vegetation decreased sharply, and then remained relatively stable afterward. During the research period, the distribution area of the secondary vegetation decreased sharply in the 6 statistic years after 1976, in contrast to the sharp increase in the distribution area of artificial vegetation in such 6 years. During the research period, the total area of major vegetation decreased by 258.73km2 in total, among which the total area of the secondary vegetation decreased by 342.52km2 in contrast to the increase in artificial vegetation by 83.78km2 in total. Thus, it indicated that the secondary vegetation in the study area had been damaged seriously, and the construction of artificial vegetation lagged behind, so there was a potential danger in ecological safety, which should be concerned and precautioned.

Eucalyptus trees and Ageratina adenophora complex system, a new ecological phenomenon that is worthy of attention, was proposed firstly in this paper, and some scientific problems were summarized from the new phenomenon. Causes of the new phenomenon were analyzed tentatively from the perspective of ecology. It was pointed out that ecological degradation of Eucalyptus plantation and strong invasiveness of A. adenophora are two apparent reasons for formation of Eucalyptus trees and A. adenophora complex system. Basic view of the authors on causes of the new phenomenon was put forward that resistance unbalance between chemical defensive potential of Eucalyptus trees and chemical invasive potential of A. adenophora might be the fundamental reason for formation of Eucalyptus trees and A. adenophora complex system, based on the two apparent reasons respectively connected with allelopathic effects of Eucalyptus trees and A. adenophora as dominant species of the complex system. Some proofs from studies on chemical components and biological activities of Eucalyptus species and A. adenophora have proved the basic view of the authors. It was discussed that formation of the complex system would influence some environmental elements such as soil environment, hydrology environment, and biology environment. It was proposed that three key scientific issues, namely chemical mechanism of formation of the complex system, ecological effects of formation of the complex system, and succession trends and impact factors of the complex system should be mainly studied as special researches to probe ecological relationship of exotic species because of absence study on the complex system and objective requirements of production practice in future. It was emphasized that the proposed researches might be of guidance significance to scientific management and sustainable operation of Eucalyptus plantation under the condition of biological invasion.

To determine the cause of the severe drought that hit five provinces (autonomous regions, municipalities) of Southwest China in 2010, the ecological water demand (EWD) of regional vegetation was explored. The key scientific question was whether the plantation of Eucalyptus and Hevea trees in this area could have led to the breaking of the regional EWD balance, thereby causing a regional drought. Therefore, major research progress and trends related to EWD of vegetation, such as characterization of vegetation water consumption from transpiration and eco-hydrological effects, were explored. Theories, methods, and practices regarding EWD of vegetation, and the correlation between regional vegetation types and droughts were evaluated. Finally, suggestions were made for specific scientific research on temporal and spatial evolution of typical artificial vegetation in Southwest China and on the relationship between EWD from regional vegetation and droughts. Thus, future research should include the following three aspects: (i) historical evolution and distribution pattern of regional artificial vegetation; (ii) water consumption from transpiration, water saving for drought prevention, and water and soil conservation of regional artificial vegetation; and (iii) the relationship between EWD of regional artificial vegetation and regional droughts. The proposed research focus is expected to provide a scientific basis for identifying the causes of regional droughts and the reasonable allocation of water resources. In addition, it will be of great importance in guiding restoration and reconstruction of regional artificial vegetation.

The formation causes of sparse vegetation under Acacia mearnsii plantation were studied from the perspective of plant allelopathy. The interference effects of water extract with different concentrations(1, 5, 10, 15 times) from Acacia mearnsii leaves on seed germination and seedling growth of four receptor plants was assayed through indoor biological simulation experiments, the four receptor plants are Ageratina adenophora, Trifolium repens, Eucalyptus robusta and Eucalyptus camaldulensis, respectively. The results show that different concentrations( 1, 5, 10, 15 times) of water extract from Acacia mearnsii leaves all had inhibitory effects on seed germination and seedling growth of the four receptor plants, the synthesized effect index(S EI) ranged from-0.246 to-0.002; there existed an obvious regularity of inhibitory effects to Ageratina adenophora and Trifolium repens, and the inhibitory effect reduced with the increase of water extract dilution ratio, the S EI of inhibitory effect on Ageratina adenophora treated with 1 times was-0.246; however, there was no regularity in inhibitory effect on Eucalyptus robusta and Eucalyptus camaldulensis, the inhibitory effects of 1 times and 10 times were more obvious than the other two groups, the S EI of inhibitory effect on Eucalyptus robusta treated with 5 times was-0.002. The possible cause of sparse vegetation under Acacia mearnsii plantation is allelopathy of Acacia mearnsii hydrotrope.

The ultimate goal of ecological sensitivity analysis,ecological analysis of the regional environmental,scientific planning,protection of sensitive areas of good study area within the rational development of the weak sensitivity of the area.Yuxi City,the sensitivity of habitats and soil erosion sensitivity analysis to evaluate the ecological service functions,provided a basis for decision making and reference for better protection of Yuxi biodiversity.The results showed that the the Yuxi City habitat extremely sensitive area of 65 061.78 hm2,accounting for 4.34% of the land area of the city,mainly the three lakes of water and Yuanjiang River Valley in southern part of the valley region;plant species diversity in Yuxi City,Yunnan Province of plant diversity had an important role to protect the species diversity of Yuxi City,the first to protect the good and diverse natural ecosystems.

Ageratina adenophora is a worldwide weed which leads to serious harm in Southwest China.It has been an urgent demand to be controlled.Previous studies have shown that chemical compositions from Eucalyputs spp.have various biological activities and broad application prospects.To explore the effects of five important chemical compositions from Eucalyptus spp.on seed germination and seeding growth of A.adenophora,the effects of five main chemical compositions from Eucalyputs spp.as 1,8-Cineole,α-Pinene,α-Terpineol,Limonene and Borneo on germination and growth of A.adenophora were studied by using indoor biological simulation experiment in this study.The results showed that seed germination and seeding growth of A.adenophora were inhibited comprehensively by the five chemical compositions at 10,50,100 mg/L concentration,and the synthetical allelopathic effect index ranged from-0.04 to-0.96.Among those,the inhibitory effects of α-Terpineol solution at different concentration were the most significant,which led receptor seeds to extremely low germination rate,seedling radicles and hypocotyls to cease growing and even die.Absolute value of comprehensive index of α-Terpineol reached over 0.95.The inhibitory actions of 1,8-Cineole,α-Pinene and Borneol on seed germination and seedling growth of A.adenophora enhanced with the concentration increased.The inhibitory effects of Limonene were weak at 50 mg/L concentration and strong at 10 mg/L and 100 mg/L concentration.The results above indicated that the five chemical compositions from Eucalyptus spp.inhibited seed germination and seeding growth of A.adenophora.The studies are expected to provide a new solution to prevention and control of A.adenophora and also a new development approach of plant-derived pesticides.

Eucalyptus trees and Ageratina adenophora complex system, a new ecological phenomenon that is worthy of attention, was proposed firstly in this paper, and some scientific problems were summarized from the new phenomenon. Causes of the new phenomenon were analyzed tentatively from the perspective of ecology. It was pointed out that ecological degradation of Eucalyptus plantation and strong invasiveness of A. adenophora are two apparent reasons for formation of Eucalyptus trees and A. adenophora complex system. Basic view of the authors on causes of the new phenomenon was put forward that resistance unbalance between chemical defensive potential of Eucalyptus trees and chemical invasive potential of A. adenophora might be the fundamental reason for formation of Eucalyptus trees and A. adenophora complex system, based on the two apparent reasons respectively connected with allelopathic effects of Eucalyptus trees and A. adenophora as dominant species of the complex system. Some proofs from studies on chemical components and biological activities of Eucalyptus species and A. adenophora have proved the basic view of the authors. It was discussed that formation of the complex system would influence some environmental elements such as soil environment, hydrology environment, and biology environment. It was proposed that three key scientific issues, namely chemical mechanism of formation of the complex system, ecological effects of formation of the complex system, and succession trends and impact factors of the complex system should be mainly studied as special researches to probe ecological relationship of exotic species because of absence study on the complex system and objective requirements of production practice in future. It was emphasized that the proposed researches might be of guidance significance to scientific management and sustainable operation of Eucalyptus plantation under the condition of biological invasion.