31 research outputs found
Comparative Analysis of Growth Types and Reproductive Characteristics of <I>Mikania micrantha</I>
No full textSwidden agriculture and sloping land conversion in China's Dulong Valley: impact and adaptation.
No full textRelationship Between Allelopathic Effects and Functional Traits of Different Allelopathic Potential Rice Accessions at Different Growth Stages
No full textIn this study, effects of temperature, light and their interactions on allelopathic effects and the functional traits specific leaf area (SLA) and stem mass fraction (SMF) of different allelopathic potential rice accessions at different growth stages were analyzed. The main results were as follows: Allelopathic responses to temperature and light varied with different allelopathic potential rice accessions at different growth stages. With the rise of temperature and the extension of photoperiod, allelopathic effect increased firstly and then decreased at 2–3 leaf stage, but increased constantly at the 4–5 and 7–8 leaf stages in strong allelopathic rice accessions [O. longistaminata, F1 (O. longistaminata × RD23), F2 (RL159 and RL169)]. Temperature had significant impact on allelopathic effect without considering light factors, but light showed little effect on rice allelopathy at the same temperature conditions. The greatest allelopathic effect was attained with moderate temperature and long photoperiod at 2–3 leaf stage in strong allelopathic rice accessions, but all the rice accessions showed weak allelopathic effects at the low temperature condition (15 °C/10 °C), and the influence of different factors on allelopathy followed a general trend as temperature > leaf stage > light, indicating that among the multiple factors impacting rice allelopathy, temperature was the main factor. Allelopathic characteristics of F1 and F2 to various temperature and light were similar to O. longistaminata, showing that allelopathic genes from wild rice can be expressed in its descendants. Temperature and light also had significant effects on SLA and SMF, and rice allelopathy was closely correlative to SLA in strong allelopathic rice accessions at the 4–5 and 7–8 leaf stages, but there was no correlation between rice allelopathy and SMF at different growth stages. These results suggested that rice adjust the relationship between allelopathy and SLA and adapt to the varied environments, and that high temperature and long photoperiod can enhance rice allelopathic activity
Predicting the potential distribution of the invasive weed Mikania micrantha and its biological control agent Puccinia spegazzinii under climate change scenarios in China
No full textResearch on the potential distribution of invasive plants and their biological control agents under climate change is critical for informing strategies in invasive species management. The rust fungus Puccinia spegazzinii shows significant potential as a biological control agent for the invasive weed Mikania micrantha. The MaxEnt (Maximum Entropy) model was used to simulate the distribution of M. micrantha and P. spegazzinii under current and future climate scenarios. The models achieved excellent prediction performance, with M. micrantha and P. spegazzinii having area under the curve values of 0.921 and 0.978 respectively, and true skill statistics values of 0.886 and 0.902 respectively. Precipitation is the primary factor influencing the distributions of M. micrantha, while P. spegazzinii is determined by both temperature and precipitation. The suitable areas for the two species are concentrated in southern China, with M. micrantha exhibiting broader adaptability compared to P. spegazzinii. Under future climate scenarios, the suitable areas for M. micrantha in China will expand northward, with a maximum projected growth rate of 84.6 % in the 2070 s, whereas P. spegazzinii exhibits a contracting trend (with a projected reduction of 40.8 % in the 2050 s). Under the current climate scenario, the overlapping suitable areas between the two species account for 25.2 % of the total suitable area for M. micrantha and 100 % of that for P. spegazzinii and both remain relatively stable under future climate scenarios. This work can provide guidance for the application of biological control, and serves as a valuable reference for developing early warning and management response strategies for invasive species in China
Effects of Various Nitrogen Regimes on the Ability of Rapeseed (Brassica napus L.) to Suppress Littleseed Canarygrass (Phalaris minor Retz.)
No full textUsing crops to control invasive weeds is an important approach for the long-term management of invasive species in agroecosystems. Nitrogen application can improve the yield and quality of crops, but may shift interactions of invasive weeds and crops, potentially affecting grass control ability. To explore the yield of a crop and its control efficacy of invasive weed under different nitrogen conditions, we studied the competitive effects of the high-value crop rapeseed (Brassica napus L.) on growth and photosynthetic characteristics of invasive species littleseed canarygrass in the field experiments. The results showed that the rapeseed yield and its control efficacy on littleseed canarygrass were significantly affected (p < 0.05) under different N regimes, and the control efficacy of littleseed canarygrass by rapeseed increased first and then decreased with the increase of basal nitrogen rates, while increasing topdressing N rates increased control efficacy of littleseed canarygrass by rapeseed. In fact, yield and weed control efficacy of rapeseed was most ideal when both basal and topdressing N was 90 kg·ha−1. We also found that N significantly impacted the competitive ability of rapeseed toward littleseed canarygrass, and rapeseed had the highest competitive ability when both basal and topdressing N was 90 kg·ha−1. With the increase of basal nitrogen rates, competitive balance index (CB) of rapeseed increased initially but decreased beyond an optimal level. CB continually increased with increasing topdressing N rates. Our research also showed level and period of N application had a significant effect (p < 0.01) on the photosynthetic rate (Pn) and chlorophyll content (Chl) of both rapeseed and littleseed canarygrass. Under the same N application regime, the Pn and Chl of littleseed canarygrass were higher than that of rapeseed in December, while the Pn and Chl of rapeseed was higher than that of littleseed canarygrass in February. Our study indicated that photosynthetic characteristics of rapeseed and littleseed canarygrass in different growth stages differ in their sensitivity to N regimes, creating a dynamic competitive relationship. Together, our results demonstrated that optimal application of fertilizer N could help rapeseed produce higher yields and greater weed control efficacy, suggesting that future modeling or experimental studies on utilizing crops to control invasive weeds should carefully consider both timing and placement of N
Weed biological control in the Greater Mekong Subregion: status and opportunities for the future
No full textTwenty biological control agents targeting nine weed species have been introduced into the six countries of the Greater Mekong Subregion. Thirteen of these agents have established and another nine have arrived unintentionally. These agents are having some impact on their target weeds. However, another 38 weeds occurring in the region have been targeted for biological control elsewhere presenting a tremendous opportunity to expand weed biological control in the region and reduce the dependency on herbicides while increasing productivity. Highly effective biological control agents are available for introduction and could assist with the management of the region's most important weeds, such as water lettuce, salvinia, Siam weed and mikania. There is also scope to increase the capacity and training in biological control to develop effective weed control and management
Weed biological control in the Greater Mekong Subregion: status and opportunities for the future.
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Suppression of the invasive plant mile-a-minute (Mikania micrantha) by local crop sweet potato (Ipomoea batatas) by means of higher growth rate and competition for soil nutrients
No full textBackground: Competitive crops may provide potent management tools against invasive plants. To elucidate the competitive mechanisms between a sweet potato crop (Ipomoea batatas) and an invasive plant mile-a-minute (Mikania micrantha) field experiments were carried out in Longchuan County of Yunnan Province Southwest China utilizing a de Wit replacement series. The trial incorporated seven ratios of sweet potato and mile-a-minute plants in 25 m2 plots. Results: In monoculture the total biomass biomass of adventitious root leafstalk length and leaf area of sweet potato were all higher than those of mile-a-minute and in mixed culture the plant height branch leaf stem node adventitious root flowering and biomass of mile-a-minute were suppressed significantly (P<0.05). The relative yield (RY) of mile-a-minute and sweet potato was less than 1.0 in mixed culture indicating that intraspecific competition was less than interspecific competition. The competitive balance index of sweet potato demonstrated a higher competitive ability than mile-a-minute. Except pH other soil nutrient contents of initial soil (CK) were significantly higher than those of seven treatments. The concentrations of soil organic matter total N total K available N available P available K exchange Ca exchange Mg available Mn and available B were significantly greater (P<0.05) in mile-a-minute monoculture soil than in sweet potato monoculture soil and were reduced by the competition of sweet potato in the mixture. Conclusions: Evidently sweet potato has a competitive advantage in terms of plant growth characteristics and greater absorption of soil nutrients. Thus planting sweet potato is a promising technique for reducing infestations of mile-a-minute providing weed management benefits and economic returns from harvest of sweet potatoes. Nomenclature: sweet potato Ipomoea batatas (L.) Lam. mile-a-minute Mikania micrantha H.B.K
Suppression of reproductive characteristics of the invasive plant Mikania micrantha by sweet potato competition
No full textBackground: As a means of biologically controlling Mikania micrantha H.B.K. in Yunnan, China, the influence of sweet potato [Ipomoea batatas (L.) Lam.] on its reproductive characteristics was studied. The trial utilized a de Wit replacement series incorporating six ratios of sweet potato and M. micrantha plants in 25 m2 plots over two years. Results: Budding of M. micrantha occurred at the end of September; flowering and fruiting occurred from October to February. Flowering phenology of M. micrantha was delayed (P<0.05), duration of flowering and fruiting was reduced (P<0.05) and duration of bud formation was increased (P<0.05) with increasing proportions of sweet potato. Reproductive allocation, reproductive investment and reproductive index of M. micrantha were significantly reduced (P<0.05) with increasing sweet potato densities. Apidae bees, and Calliphoridae or Syrphidae flies were the most abundant visitors to M. micrantha flowers. Overall flower visits decreased (P<0.05) as sweet potato increased. Thus the mechanism by which sweet potato suppressed sexual reproduction in M. micrantha was essentially two-fold: causing a delay in flowering phenology and reducing pollinator visits. The number, biomass, length, set rate, germination rate, and 1000-grain dry weight of M. micrantha seeds were suppressed (P<0.05) by sweet potato competition. With proportional increases in sweet potato, sexual and asexual seedling populations of M. micrantha were significantly reduced (P<0.05). The mortality of both seedling types increased (P<0.05) with proportional increases in sweet potato. Conclusions: These results suggest that sweet potato significantly suppresses the reproductive ability of the invasive species M. micrantha, and is a promising alternative to traditional biological control and other methods of control. Planting sweet potato in conjunction with other control methods could provide a comprehensive strategy for managing M. micrantha. The scenario of controlling M. micrantha by utilizing a crop with a similar growth form may provide a useful model for similar management strategies in other systems
