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Background: An ecological approach for managing biological invasions in agroecosystems is the selection of alternative crop species to manage the infestation of invasive alien plants through competition. In the current study, plant growth, photosynthesis, and competitive ability of the crop Helianthus tuberosus L. (Jerusalem artichoke) and the invasive alien plant Ageratina adenophora (Spreng.) R. M. King and H. Rob were compared under varying shade levels by utilizing a de Wit replacement series method. We hypothesized that H. tuberosus had higher competitive ability than A. adenophora even under shaded conditions. Results: The results showed the main stem, leafstalk length, leaf area, underground biomass, and aboveground biomass of A. adenophora were significantly lower compared to H. tuberosus in monoculture although A. adenophora had a greater number of branches that were longer on average. Under full sunlight, the total shoot length (stem + branch length), main stem length and branch length of A. adenophora were significantly suppressed (P < 0.05) by increasing proportions of H. tuberosus, and the same morphological variables of H. tuberosus were significantly higher with decreasing proportions of H. tuberosus. With increasing shade rates and plant ratios, the plant height, branch, leaf, and biomass of both plants were significantly suppressed, but to a greater degree in the case of A. adenophora. The net photosynthetic rate (Pn) of H. tuberosus and A. adenophora increased gradually from July to September, then decreased in October. The Pn of H. tuberosus was consistently higher than that of A. adenophora. Although the Pn for both species was significantly reduced with increasing shade rates and plant ratios, A. adenophora experienced greater inhibition than H. tuberosus. The relative yield (RY) of A. adenophora was significantly less than 1.0 (P < 0.05) in mixed culture under all shade levels, indicating that the intraspecific competition was less than interspecific competition. The RY of H. tuberosus was significantly less than 1.0 under 40-60% shade and greater than 1.0 (P < 0.05) under 0-20% shade in mixed culture, respectively, showing that intraspecific competition was higher than interspecific competition under low shade, but the converse was true under high shade. The relative yield total (RYT) of A. adenophora and H. tuberosus was less than 1.0 in mixed culture, indicating that there was competition between the two plants. The fact that the competitive balance (CB) index of H. tuberosus was greater than zero demonstrated a higher competitive ability than A. adenophora even at the highest shade level (60%). Conclusions: Our results suggest that H. tuberosus is a promising replacement control candidate for managing infestations of A. adenophora, and could be widely used in various habitats where A. adenophora invades. [ABSTRACT FROM AUTHOR]

Background: Xishuangbanna of Yunnan Province, southwest of China belongs to a global biodiversity and cultural hotspot. Agrobiodiversity plays an essential role in local livelihoods and traditional culture in the region. However, preliminary studies suggest that diversity of crop plants and livestock species is declining. We hypothesized that agrobiodiversity and traditional means of preserving agrobiodiversity are threatened because of changes in government policy in favor of commercial plantations, land use change and changes in traditional agricultural practices. We investigated whether or not agrobiodiversity was declining, the specific causes, and signs of active biodiversity conservation practices in ethnic minority communities of Xishuangbanna which could form the basis for extensive in situ conservation programmes. Methods: A series of field studies to document trends in agrobiodiversity were conducted in different ethnic minority communities in Menghai County, Mengla County and Jinghong City of Xishuangbanna of Yunnan Province, southwest of China between July 2015 and February 2016. Data was obtained through the use of semi-structured questionnaires, field observation and participatory rural appraisal (PRA) tools. A total of 360 ethnic households provided information on current status, functions, characteristics, changes, and threatened factors of farming crop and livestock resources. Some measures for in situ conservation of agricultural biological resources were also researched using PRA methods. Results: Two hundred twenty-six crop varieties belonging to 31 families, 71 genera and 101 species were identified in Xishuangbanna, which included 83 vegetable crops, 77 food crops, 24 spice crops, 22 fruit crops, 13 cash crops, 6 oil crops, and 1 cloth crop, respectively. There were 15 livestock varieties, belonging to 6 major species: cattle, pigs, goats, chickens, ducks, and geese. Different crop and livestock resources had their own characteristics, functions and threatened factors. Since 2002, agroecosystem, crop diversity and livestock diversity have declined greatly over the Xishuangbanna region as a whole under implementation of the Sloping Land Conversion Program (SLCP). Swidden agriculture was completely eliminated under this program and gradually replaced by large land areas devoted to rubber, tea and banana plantations. Villager numbers engaging in farming production and population of crops and livestock were greatly decreased, particularly in terms of production of local traditional varieties. However, some in situ conservation measures such as seeds preservation, planting of traditional crops and raising livestock have played an important role in local agrobiodiversity conservation. Conclusion: Abundant agricultural resources and agrobiodiversity are critical to the local livelihood and maintenance of traditional culture in Xishuangbanna. However, agrobiodiversity and related traditional culture have been greatly impacted by implementation of the SLCP since 2002. Therefore, in future conservation of agrobiodiversity, incorporating some sustainable protection measures based in local communities such as convening seed exchange fairs, conserving traditional varieties in permanent plots, making a visual documentary of indigenous cultivation, and providing traditional agricultural products to tourists should be carefully considered and adopted. [ABSTRACT FROM AUTHOR]

Background: 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 2 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. [ABSTRACT FROM AUTHOR]

Background: There are a variety of ways of increasing crop diversity to increase agricultural sustainability and in turn having a positive influence on nearby natural ecosystems. 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. This study also shows the potential value of replacement control methods which may apply to other crop-weed systems or invaded natural ecosystems. [ABSTRACT FROM AUTHOR]