小花山桃草季节生长动态及入侵特性

2001年在郑州黄河沿岸对外来植物小花山桃草(Gaura parviflora)的生物学特性、地上生物量动态进行了研究。结果表明：①小花山桃草各构件的变化特征为：茎高、叶数和花序数在6月25日都达到生长高峰，随后茎高、花序数继续增长，叶数迅速降低。②小花山桃草每株花序数为10．9枝。每个花序产134．23朵小花，产126．75粒种子，结实率为94．43％，不育率为5．57％。③小花山桃草单株地上生物量、叶生物量、茎生物量在6月25日达到最大，花序生物量在7月20日达到最大。在生长初期，小花山桃草占样方内所有植物生物量的78％，7月20日达100％。④小花山桃草入侵可能与植株高大、幼苗期短、生长快以及具有较强的传播和繁殖能力有关。

Study on the seasonal growing dynamics and invasive characteris-tics of Gaura parviflora

Invasion by exotic species is one of the main threats to the conservation of biodiversity. Once an invasive species becomes firmly established, its control can often be difficult and eradication is usually impossible. In addition, the impact on natural communities and ecosystem processes can be very serious. As international trade increases, the number of both accidental and intentional exotic introductions is likely to increase. To limit the impact that exotic species have on natural and man-made communities, we need to understand the major mechanisms that allow exotic plant to become invasive. Gaura parviflora is an exotic plant from the prairie of North America and can grow better in arid and low nutrient areas. Gaura parviflora is threatening the conservation of biodiversity on the banks of the Yellow River in Henan province of China. A studying regarding the biological characteristics, aboveground biomass dynamics, and invasive characteristics of Gaura parviflora is presented. The specific characteristics of every component are: the height of the stem, number of leaves and number of anthotaxies all get to the maximal numbers for individual plant in June 25, subsequently, the height of the stem and the number of anthotaxies continue to increase, but the number of leaves decrease rapidly. The growing model of the height of the stem is single kurtosis as those of number of leaves and number of anthotaxies. The number of anthotaxies of individual Gaura parviflora is 10.9 branches. Every anthotaxy produces an average of 134.23 flowerets and 126.75 seeds. Every plant produces an average of 1381.58 seeds and the seed setting rate is 94.43%. Every anthotaxy produces an average of 7.06 sterile seeds and the sterility rate is 5.57%. The average aboveground biomass of individual Gaura parviflora plant, biomass of leaves and biomass of stem all peak for individual plant on June 25. The biomass of anthotaxy peaks on July 20, their growing models are all single kurtosis. During the seedling stage, the ratio of stem and leaf are 66.67% and 33.33% respectively. In May 5,when the photosynthesis gets to the floruit, the ratio of leaf is 58.67%.At the last phase of flowering, the ratio of stem and leaf are 95.32% and 2.21% respectively, and the ratio of anthotaxy is 5.39%. The primary reasons of Gaura parviflora being able to successfully invade appear to be because of a bigger plant body size, shorter time seedling stage and more rapid growth. Individual plant can get to 169.67 cm and is higher than other native grasses. The shorter seedling stage is from March 20 to May 5,furthermore, the growing floruit is in late June, but other native grasses are still at the seedling stage at this time. So Gaura parviflora has a stronger ability to compete. The other reasons of Gaura parviflora invasion are the ability of stronger dispersion and reproduction. Firstly, its flowering stage is 3 months, May 5 to August 15,which can provide enough time to find appropriate weather condition and environment condition for pollination and seed dispersal. Secondly, the ability to produce copious seeds and a higher seed setting rate and a lower sterility rate may contribute Gaura parviflora to invade new habitat.