Impact Of Artificially Simulated Precipitation Patterns Change On The Growth Of Reaumuria Soongarica Seedlings In Hexi Corridor Of China

Morphological traits,growth rate and response patterns of plants are the responses to the external environment.There are lots of differences in each precipitation pattern.Studying the impact of different precipitation patterns on plant morphological characteristics,growth rate,and response patterns is critical for comprehending the distribution of plant life,and may help to predict the risk of species extinction and to conserve biodiversity,and to improve regional sustainable development capabilities in the face of environmental change.Reaumuria soongarica is the main dominant species and founder species of plant communities in arid and semi-arid areas of northwest China.In this study,R.soongarica seedlings were used as the research objects.R.soongarica seedlings were treated by artificially simulating changes in precipitation(30% reduction and 30% increase)and its frequency(50% reduction).We analyzed the changes of eight indexes,including plant height,above-ground biomass,below-ground biomass,total biomass,the root/shoot ratio,the root/height ratio,the above-ground radial density and the below-ground radial density of R.soongarica seedlings,with analysis of variance(ANOVA),Least-significant difference(LSD),Spearman's rank correlation coefficient,logarithm ratio response(LRR)andpower function fittingmethods.The impacts of morphological traits,growth rate and response patterns of R.soongarica seedlings were discussed in different precipitation patterns.The results are listed below.1.The increase in precipitation amount could promote the plant height,aboveground biomass,and total biomass of seedlings noticeably,which increased by 71.93%,71.95% and 70.59% at the end of the experiment(October 2018,same as following),respectively.The plant height and the biomass of seedlings were more affected by precipitation amount than by precipitation frequency.No interaction was found between precipitation amount and precipitation frequency on the growth of seedlings(P > 0.05).The root/height ratio was negatively correlated with precipitation and the difference between treatments was significant.Precipitation amount decreased by 30%,the root/height ratio increased by 74.80%.When characterizing the relationship between precipitation and plant morphology,the root/height ratio was more stable than the root/shoot ratio.The trend of the above-ground radial density was W+ treatment > W-treatment first,then W-treatment > W+ treatment,which were an increase of 39.73%(October 2017)and a decrease of 16.02%.The below-ground radial density was positively correlated with precipitation amount.When precipitation amount increased,the below-groundradial density increased and the root system became relatively thicker and shorter,increasing by 93.12%.A specific set of morphological and physiological characteristics would only produce a higher growth rate within the limited interference size or available resources.R.soongarica seedlings mainly adapted to the way of resource supply by adjusting plant height,root length,thickness and biomass.2.There was significant and different impact on the growth rate and response pattern of the same index in each precipitation pattern.Compared with group controls(WF and WF-),Plant height,above-ground biomass,total biomass and below-ground radial density change rate were positively correlated with precipitation,while the root/shoot ratio and root/height ratio change rate were negatively correlated with precipitation.When the precipitation amount was same and the precipitation frequency decreased,the plant height,the above-ground biomass,total biomass and below-ground radial density change rate increased;above-ground radial density was only monotonically positively correlated with time,but not with precipitation treatment.The response of R.soongarica seedlings to the environment was real-time(no delayed response was found during the growth period,there was no response during the dormant period).Direct response in different directions might occur.Dampning response and accelerated response often occured in the seedling stage.Sometimes in the early and later stages in experiments,the direction of response effects might be opposite.3.There was a significant and different impact on the growth rate and response pattern of different indexes of R.soongarica seedlings with same precipitation pattern.When precipitation increased,the above-ground biomass,total biomass,plant height and below-ground radial density of R.soongarica seedlings changed greatly,while when the precipitation amount decreased,the root/height ratio,the root/shoot ratio,below-ground biomass and aboveground radial density changed at a faster rate.The response direction of R.soongarica seedlings often changed during the experiment,and there were different types of response patterns in the same precipitation pattern.4.The impact on the relative growth rate of same index to plant height of R.soongarica seedlings was significant different with each precipitation pattern.All R.soongarica seedlings did not respond most positively to increased precipitation amount.Relative to the growth rate of plant height,above-ground biomass,below-ground biomass,total biomass,above-ground radial density and below-ground radial density were the smallest when precipitation increased,and the largest when precipitation decreased.In contrast,the plants treated with reduced precipitation amount were the best,while the plants treated with increased precipitation amount were the lowest.5.The impact on the relative growth rate of different indexes to plant height of R.soongarica seedlings was significant different in each precipitation pattern.The growth rate of above-ground and below-ground biomass relative to plant height was the most positive in each treatment.The growth rate of below-ground biomass was higher than that of above-ground biomass,and the growth rate of below-ground radial density was higher than that of above-ground.