| Helan Mountain is an important climate and vegetation boundary in western China.Natural conditions such as drought and little rainfall have led to the slow growth of most of the vegetation at the foot of the Helan Mountain and the formation of patchy A.mongolica and other shrub communities.It limits the full play of forest ecological service function and low ecological benefit.The relationship between vegetation and shrubs and water is inseparable.Through the processes of canopy interception,trunk interception,litter layer,soil layer water holding and surface runoff,vegetation and shrubs redistribute and adjust atmospheric precipitation,and play a unique ecological role hydrological function.In this study,the A.mongolica bushes distributed in patches in the low mountain area at the eastern foot of Helan Mountain were selected as the research object,and the rainfall redistribution of A.mongolica bushes and the collection of through rain and light rain with different rain harvesting techniques were carried out.The effects of rain harvesting technology on the physiological growth of A.mongolica bushes and its eco-hydrological process,the optimal rain harvesting method and water retention effect of A.mongolica bushes shrubs were discussed,and the regulation mechanism of different water content on A.mongolica bushes community growth was revealed.From the perspectives of restoration ecology and eco-hydrology,the optimal water requirements for the growth of A.mongolica bushes communities in arid and semi-arid areas were determined,which provided technical support for the development of a self-sustaining vegetation restoration model in the low mountain area of Helan Mountain.The results of the study are as follows:(1)The average penetration rate,stem flow rate and canopy interception rate of A.mongolica shrubs were 69.91%,10.40%and 19.69%,respectively;The theoretical critical rainfalls for through-rain and stem flow are 0.7 mm and 0.8 mm,respectively,and the water-holding capacity of the canopy is about 0.4 mm,indicating that rainfall below 1.9 mm basically does not contribute to the replenishment of soil water;A.mongolica shrubs had spatial heterogeneity for penetration rain,and "rain" appeared on the ground at the edge of the canopy.In the middle,there is a "dry area",and the collection rate of trunk and stem flow is extremely high,which is conducive to the accumulation of water in the soil in the root zone;rainfall and rainfall duration are positively correlated with through rainfall,trunk and stem flow,and canopy interception.(2)It is negatively correlated with rainfall intensity.There was a significant negative correlation between through rain and canopy area(P<0.05),a significant positive correlation between trunk flow and trunk dip angle(P<0.05),and a significant positive correlation between canopy interception and canopy thickness and canopy area(P<0.05),with no significant correlation with meteorological factors.(3)The effects of different rain harvesting measures on soil moisture were the greatest in covering litter and micro-topography with film and micro-topography with film mulching.The average soil moisture content was 11.91%and 10.64%,respectively.The impact is small;there are certain differences in the impact of different rain harvesting measures on soil nutrients,and the soil nutrient content with rain harvesting measures is relatively high.(4)Through the analysis of the growth of A.mongolica shoots under different rainwater harvesting treatments,May-June is the fastest growing period of Mongolian almond shoots.There was no significant difference,and the growth of small crowns was faster between different crowns of A.mongolica shoot growth.The analysis of leaf area showed that the leaf area of small-crown and middle-crown A.mongolica varied greatly among different rain harvesting treatments,while the leaf area of large-crown A.mongolica changed little,but there was no significant change.Chlorophyll content of the whole A.mongolica was analyzed.The chlorophyll content of control treatment of A.mongolica with small crown width was the highest,and the chlorophyll content of cover litter treatment was the lowest,and there was a significant difference between cover litter and the other three treatments(P<0.05).There was a significant difference between micro-topography with film mulching treatment and control,cover litter,and covering litter and micro-topography with film(P<0.05);it was found that there was no significant difference in chlorophyll content among the treatments of large-crowned A.mongolica.In summary,this study conducted a systematic study on the main ecological and hydrological processes of A.mongolica shrubs based on rainfall in the low mountain area of Helan Mountain.And the treatment of light rain harvesting measures is more conducive to the reconstruction of the ecological system and the sustainable development of vegetation restoration in this area. |
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