淹灌和间歇灌溉对晚稻田杂草群落多样性的影响

为探明节水灌溉对稻田杂草群落组成及物种多样性的影响,运用群落生态学方法,开展了淹灌与间歇灌溉2种灌溉模式下水稻不同生育阶段稻田杂草群落动态变化研究。结果表明:间歇灌溉和淹灌稻田杂草种类分别有10科13属14种、10科11属11种;间歇灌溉稻田各生育期杂草密度平均降低27.8%;优势杂草种类虽与淹灌基本一致,但阔叶类杂草矮慈姑重要值降低9.76%,单子叶杂草浮萍重要值降低65.38%;间歇灌溉稻田以旱生杂草生长为主,总体各生育期旱生杂草群落密度增加277.51%,水生杂草群落密度降低81.44%,而淹灌稻田以水生杂草为主;间歇灌溉稻田Margalef物种丰富度指数、Shannon-Wienner多样性指数、Simpson优势度指数和Pielou均匀度指数,平均提高27.01%、14.31%、9.09%和3.48%,乳熟期差异尤为显著。间歇灌溉提高了稻田杂草多样性,有效地抑制了优势种杂草生长,有利于改善稻田生态保护。该研究可为节水灌溉稻田杂草控制及多样性保护提供科学依据。

Effect of flooding irrigation and intermittent irrigation patterns on weed community diversity in late rice fields

Abstract: Water-saving irrigation technique for rice is an essential agricultural practice to save water and increase crop yields. Weeds are important components of paddy fields, and play an important role in maintaining the ecological sustainability of rice-based ecosystems. In order to reveal the effects of water-saving irrigation on weed community composition and species diversity of rice fields, this study investigated weed community dynamics in rice field during different growth periods of rice. A field experiment was conducted in 2014 at Jiangxi Central Irrigation Experiment Station during the whole growth period of late rice, with two different irrigation levels (flooding irrigation and intermittent irrigation) and three repeats for each treatment. Using the methods of community ecology, three quadrates with an area of 1 m2 were set in each sampling plot to investigate weed species, plants, coverage in every quadrate. Weed density, dominant weed specie, importance value, weed community number and diversity were analyzed. The diversity of weeds was measured using 4 frequently-used indexes: Margalef species richness index, Simpson dominance index, Shannon-Wienner diversity index and Pielou eveness index. The results showed that 14 and 11 species of weeds were found in the rice fields with intermittent irrigation and flooding irrigation, respectively. Cyperus iria, Lindernia antipoda and C.difformis, which occurred in intermittent irrigation fields, did not grow in the rice fields with flooding irrigation. Weed density was suppressed in the intermittent irrigation fields compared to flooding irrigation rice fields. Intermittent irrigation reduced the weed density in all growth periods by 1.2%-53.2%, and by 27.8% on average, which inhibited weeds growth effectively and helped to control the infestation of weeds. However, intermittent irrigation had the same dominant weed species with the flooding irrigation in rice field. Dominant weed species in the experiment were Sagittaria pygmaea, Leptochloa chinensis, Lemna minor and Astragalus sinicus with the importance value being 0.39, 0.20, 0.17, and 0.09 respectively. With intermittent irrigation, the importance value of Sagittaria pygmaea classified as Broad-leaved weeds was reduced by 9.76%, and that of Lemna minor classified as monocotyledonous weeds was reduced by 65.38%. Our experiment showed that intermittent irrigation decreased the proportion of dominant weeds of Sagittaria pygmaea, Lemna minor in the community, avoided severely dominant weed such as Lemna minor outbreaking, and then made the distribution of weed community much more balanced. In addition, xerophytic weeds with high density dominated in the rice field with intermittent irrigation pattern, while aquatic weeds were dominant weeds in fields with flooding irrigation. Intermittent irrigation increased the density of drought weeds by 277.51% and reduced the density of aquatic weeds community from 344.81 down to 63.98 plants per m2 by 81.44% decline on average during the rice growth period. In the intermittent irrigation pattern, Margalef index, Simpson index, Shannon-Wienner index, and Pielou index were all higher than that in the flooding irrigation, increasing by 27.01%, 14.31%, 9.09% and 3.48% respectively. Moreover, weed community structure indexes were significant different during the milky stage between the 2 irrigation patterns. Weed diversity indexes were increased obviously in intermittent irrigation fields, which were beneficial to improve paddy ecological conservation. This study provided valuble data support for setting watering-saving irrigation system considering controlling the harm of dominant weeds and protecting weeds diversity. It was noted that this study included the experimental datum of one year in late rice field. Further studies about the effect of flooding irrigation and intermittent irrigation patterns on weed diversity without herbicides in a longer period should be considered.