Effects Of Water Gradient On Soil Weed Seed Bank

This study adopted the combination of field investigation and indoor training as well as ecology research, using setting different water conditions (200,400,600 and 700 mm) in indoor artificial rainfed agriculture area on the seed bank of soil weed, to understand the history and present situation of soil weed, to master the fluctuation of weed seed bank, to explore the community composition and distribution of soil weed seed bank. The main purpose of the study is to predict the condition of farmland weed, to provide some accurate information for effective control of weed. On the other hand, revealing the reduction rules of weed community and providing reliable theoretical basis for overall management of weed are also important aims. We picked a piece of farmland every 200m along a north-south mountain road at Huoshizhai in Xiji country in southern of NingXia. In September 2014 and March 2015, we made a field sampling and indoor germination experiment respectively. And we investigated the aboveground vegetation and researched the characteristics of aboveground vegetation on farming area of rain and weed seed bank, and the effects of different rainfall on soil physics and chemical properties in late June, July and early August 2015. The results showed that:1). The basic features of soil seed bank:the weeds in the study area were recorded 32 species, belonging to 14 families,27 genera. There are many species of Compositae and Gramineae. And the total biomass on the ground is the biggest; the main ecological communities are GaliumaparineL., ChenopodiumbotrysLinn.,SonchusbrachyotusDC. Elsholtziaciliataland.. Galiumaparine (up to 1002 strains/ square meters), SonchusbrachyotusDC (928 strains/square meters), Chenopodiumvulvaria(900 plants/ square meters) have the highest density. Life form annual weeds and perennial weeds accounted for the proportion of 50%.2) The basic characteristics of vegetation on the ground of research area:According to the statistics,there are 29 species in research area of the soil weed seed bank.These belong to 24 genera of 16 families. The quantity of Gramineous plants is the most.The quantity of Chenopodiaceae plants and Compositaein plant are fewer; and higher than 5-10cm soil layer the density of soil seed bank of 0-5cm. The occurrence frequency of annual herbaceous plants in surface 0-5cm and 5-10cm soil was higher than that of perennial herbs. The main dominant species of weed soil seed bank are ChenopodiumAcuminatum, Setariaviridis, Artemisia Annua, ash Glaucum, arrow leaf bindweed, CephalanoplosSegetum.3) The similar performance of soil seed bank and vegetation:The coupling relation between the density of soil seed bank and the number of ground vegetation apparently varies with different moisture. With the increase of rainfall, Jacccard similar coefficient and Sorenson similarity coefficient show an increasing trend. The Pearson correlation coefficient between weed density of soil seed bank and the number plants on the ground in field weed exists a remarkable association on a level of 0.5. There are significant differences between Weed density of soil seed bank and the number of trees planted on the ground in order of magnitude. At the same time, the species reserves and the number of species density level of field weeds soil seed bank is much higher than that of the corresponding field vegetation.4) In fourwater conditions,the soil seed bank density is different from 600mm,400mm,700mm, 200mm, with the record of 4650/m2,3685/m2, particle particleparticle of 2592/m2,907/m2.The soil seed density is not high in both water deficiency and water sufficient conditions.The common species is the highest quantities in thetest of 600mm. And the Jacccard similarity coefficient and Sorenson similarity coefficient is relatively high;0-5cm Water is 600mm processing a total maximum,The moisture in the test of 700mm is the lowest.But the soil pHand soil moisture are on the contrary.With the increase of moisture,thesoilsalinity is decreasing.Thesoil pH and the soil moisture content is increasing with the increase of the moisture.The soil total nitrogen and the soil organic matter are the highest in the test of 400mm water treatment indicating the contents of the organic matter in the soil directly affects the total nitrogen; the soil total phosphorus content is the highest in the test of 600mm.The soil total salt of 5-10cm soil in 200mm moisture content is the highest,and the soil pH and soil water content is the highestin the test of 700mm water treatment,which indicated that the soil salinity is decreasing with the moisture increased. While the soil pH and the soil water content are the opposite; soil organic matter and soil total phosphorus are the highest, in the test of 600mm water processing content.Thesoil total nitrogen is the highest in the test of 400mm. The results show that the water influencesthe soil pH, total salt, total nitrogen, total phosphorus and other properties by influencing the soil moisture.5)The soil pH, total salt, total nitrogen, total phosphorus and other physicochemical properties are affected by the soil moisture through water.The main factors which influence the composition and the distribution of soil weed seed bank are soil moisture, organic matter, total nitrogen and total salt; the soil seed bank and soil physicochemical properties were significant is related to the physicochemical properties influencing the varies of weed community; The soil weed seed in 0-5mm and 5-10cm of the soil have the relativity of 0.002 with the soil physical and chemical properties of CCA axis and 1 axis 2,which is significantly related to physical and chemical properties of soil weed seed bank.The soil physicochemical propertiesinfluence the varieties of the. weed community as the soil environmental factors of soil; the cumulative contribution rate of 0-5cm is higher than 5-10cm soil layer, which is said the soil depth influences the speciesrelationship accumulation contribution rate.