Effect Of Simulated Rainfall On Phenotypic Plasticity Of Nitraria Tansutorum Bobr

The previous study suggested that climate change would increase the rainfall in the aridregion in Northwest China. The purpose of this study was to examine the adaptive strategiesand changes of the typical vegetation (Nitraria tangutorum Bobr and Nitrariasphaerocarpa Maxim) in the arid region due to increasing rainfall in the future. We hadestablished three open-simulated rainfall platforms in Dengkou,Minqin and Dunhuang.Basedon the average annual rainfall of three research regions, four water gradients (increasing water25%,50%,75%and100%, respectively) and one control plothad been set up. Each gradienthas4replicates,Total20plots in each research region. Artificial rainfall was made by using thefull light spray equipment in growing season(from May to September). This article is mainlybased on experimental data of the Inner Mongolia Dengkou County.The simulation rainfall wasoperated per15days from10May to10September in2008. In2009, the simulation rainfallinterval was adjusted to30days,the total of rainfall did not change. This paper mainlystudies:spatial and temporal dynamic characteristics of the soil moisture increased rainfall;different rainfall treatment on the old branches phenotypic plasticity; rainfall impact on theefficiency of stem support.. The main results are as follows:(1) Surface soil moisture is a plus amplitude (5%-8%) in the first days after the rainfall,increase with time, the surface moisture gradually reduce, the moisture of7days (the seventhday of the moisture is2%-4%) are significantly higher than the day before rainfall (less than1%).the50%plus and more than50%plot can influence the moisture of30cm and50cm,andthe more rainfall,the more obvious change.25%plot can only effect the moisture of surface.The same time, two small natural rainfall event (0.1mm and1.4mm, respectively) during theexperiment, have limited impact can only affect the surface water content and short time.according Artificial rainfall experiment, above7.5mm rainfall has a significant impact, andcan be maintained more than7days. In addition, not only the same year, pre-rainfall will impact the lower soil moisture (30cm and50cm depths),but last year rainfall has effectmoisture on this year.(25%plots excluded). It is performance that the moisture of the daybefore rainfall in May in50%and above rainfall plots (1.3%-2.1%) was significantly greaterthan on control plots (0.9%). In addition,100%rainfall have a greater kinetic energy, and rapidinfiltration to30cm depths.(2) Rainfall can change the phenotypic plasticity of Nitraria sphaerocarpa Maxim. Forshape of stem and leaf: rainfall promoted the stem growth, thickening, and shoot groth hasleggy tendency, stem wood density has a downward trend. the stem length and H/D offlowering shoot in100%plots has a significant difference with control plots(p<0.05). the stemlength and base diameter of vegetative shoot in75%and100%plots has a significant differentwith control plots(p<0.05). Rainfall can promote the growth of leaves, expressed as the rainfall,the leaf length, width, area, perimeter, l/w are has a increasing trend overall. Significantincrease in leaf shape index of100%of plots, plots, leaf length increased by40%, leaf widthincreased by30%,50%increase in area, perimeter increased by30%. In addition, the specificleaf area (SLA) of rainfall plots was significantly higher than control plots (p <0.05). for thebiomass, vegetative shoots and flowering shoots biomass are quite different. With the increaseof the water, the biomass of flowering shoots branches has no obvious trend, but the vegetativeshoot biomass has a clear increasing trend. The L/S (leaf dry weight/dry weight of stem) offlowering shoot has no obvious trend, while the L/S of vegetative shoot showed a significantincreasing trend. In terms of shoot moisture, regardless of flowering or vegetative shoots, leafmoisture (＞60%) were significantly higher than the stem moisture (＜50%). The intercept offlowering stem moisture lower than the the moisture of vegetative stems.(3) In the same rainfall gradient, with the thickening of the stem (or stem dry weight), theleaf area the twig supported also increased. At the same time as the moisture increased theefficiency of the stem an increasing trend, the leaf area/stem weight in rainfall plots wassignificantly higher than the control plots (p <0.05), it is that the support ability per stem increase. It further confirmed that a certain cross-sectional area (or stem weight) of the stemcan support more leaf area, when the ambient pressure decreases.