Studies On Alien Invasive Weeds In Lishui And Their Occurrence In Fields Of Vegetable Crops

Alien species invasion is a global problem, alien species make its pitch via invasion, intentional introduction and unintentional inrtoduction, alien invansive species damages local biodiversity, entironment and leads to economic loss. In recent years, people pay more attention to their living environment, so alien species invasion gets hot in recent years. Many kinds of medias regard this as highlight. Few universities and research institutes launch on the studies on alien species invasion. According to some document, there are 108 alien invansive weeds in china, belonging to 23 families and 76 genus. In order to know how many invansive species in Lishui, what are their biological character like and what effects will be about the vegetable production, detailed investigation was conducted.(l)There are 50 alien invasive weeds in Lishui by immobility investigation and eyeballing investigaton, these weeds blong to 22 families. There are 13 species of composite weeds, ranking first; amaranthaceae, 5 species, ranking second; euphorbiaceae, 4 species; cruciferae and solanaceae, 3 species every; onagraceae, gramineae, scrophulariaceae and umbelliferae, 2 species every, cyperaceae, oxalidaceae, pontederiaceae, phytolaccaceae, caryophyllaceae, convolvulaceae, chenopodiaceae geraniaceae, malvaceae, basellaceae, nyctaginaceae and urticaceae, 1 species every. In these alien weeds, Aster subulatus, Bidens frondose, Bidens pilosa, Conyza canadensis, Conyza sumatrensis, Erigeron canadensis, Erigeron annum, Ageratum conyzoides, Alternanthera philoxeroides, Alternanthera retroflexus, Veronica persica, Cyperus rotundus, Oxalis corymbosa, Eichhornia crassipes, Stellaria apetala, Ipomoea purpurea and Chenopodium ambrosioids are often found in the crop fields and of heavy damage to the crops, Anredera cordifolia Geranium caroliniamum Pharbitis nil Phytolacca americana Veronica polita Avena fatua Eleusine indica and Euphorbia hetioscopia are of medium damage to the crops, Galinsoga parviflora, Alternanthera pungens, Amaranthus viridis, Euphorbia hirta, Ricinus communis, Nasturtium officinale, Coronopus didymus, Physalis pubescens, Solanum aculeatissimum, Datura stramonium, Denthera steraptera, Oenothera laciniata, Daucus carota, Hibiscus trionum, Peperomia pellucida, Mirabilis jalapa, Pilea microphylla and Amaranthus spinosusare seldem found in the fields and of slight damage to the crops. Solidago canadensis, Denthera steraptera and Oenothera laciniata are only of small population. Oenothera laciniata is a newly-found weed in Zhejiang Province, and has not reported in China mainland.(2) Five species of weeds are selected for biological character investigation and for occuranceinvestigation in vegetable fields. The five weeds are Ageratum conyzoides, Anredera cordifolia Steenis, Soliva anthemfolia, Geranium caroliniamum and Oenothera laciniata. Studies show that the seedling period of Ageratum conyzoides is as long as 61 days, the growth of little grass are not trim, so it is hard for farmers to prevent them from damaging. June and July are two growth peaks of Ageratum conyzoides. From August Ageratum conyzoides enters procreation growth period, its branches are not uniform and it may lead seed maturation untidy. Soil depth is of great effects on Anredera cordifolia seeding. If the soil coverage is narrow or the beads are exposed on the air, in a way, the beads keep relevant germination ability. Only the coverage is deep enough the beads would lose their ability. Cut the bead into pieces will affect their germination, but not so great. Branches with leaves or without leaves are both of definite livability, branches with leaves are of higher livability than those without leaves. Air temperature is of great effects on the growth of Soliva anthemfolia, under lower temperature Soliva anthemfolia grows slowly. In Lishui, the average branch number is 9.1, the average leaf number reaches 33.3, Soliva anthemfolia has two seedling peaks, one is in May, the other is in December, the later means under lower temperature seedlings...