Effects Of Different Vegetation Restoration Patterns On Understory Plant Diversity In Rocky Coastal Shelter Forest

Due to natural disasters,human’s interferences and other reasons,the physiological functions of coastal shelter forest decline,forest productivity and soil fertility decline during the construction and development process,which leads to the reduction of plant diversity of shelter forest and seriously affects the effective play of its ecological protection function.Therefore,this article takes the rocky coastal protection forest in Shandong Province as the research object,and explores the impact of different vegetation restoration models on the diversity of understory plants and their relationship with understory environmental factors.It explores the vegetation restoration models which is suitable for the ecological restoration construction of rocky coastal protection forest,providing scientific and technological support for the construction of coastal protection forest system engineering.This study selected six vegetation restoration models,namely Quercus acutissima pure forest model(I),Quercus acutissima black pine mixed forest model(II),Robinia pseudoacacia black pine mixed forest model(III),Black pine pure forest model(IV),Chestnut pure forest model(V),and Chestnut black pine mixed forest model(VI),for the rocky coastal protection forest in Huangdao District,Qingdao City,to investigate their vegetation,soil,and microclimate indicators,Research and explore the relationship between understory plant diversity and its influencing factors in rocky coastal protective forests,and the research results are as follows(1)There are significant differences between vegetation growth and species numbers among different restoration models,with the chestnut pure forest model(V)and the oak pure forest model(I)having the highest average diameter at breast height and average tree height;The overall canopy structure of the mixed forest model is better than that of the pure forest model;Through a sample survey,there are a total of 38 species of understory plants in the study area,with a maximum of 18 species in the pure chestnut forest model(V).The mixed forest model of black pine and black locust(III)has at least 7 species;The number and coverage of understory plants are the highest in the mixed forest model of Chinese chestnut and black pine(VI),and the pure forest model of Chinese chestnut(V),respectively.The aboveground biomass of understory plants is the highest in the Quercus acutissima pure forest model(I).(2)The impact of different restoration models on soil physical and chemical properties vary.The soil bulk density of each vegetation restoration mode ranges from 1.24 to 1.87 g/cm~3,and the soil p H value ranges from 4.81 to 5.65.The maximum values were obtained in the pure chestnut forest mode(V)and the mixed chestnut black pine forest mode(VI),respectively.Rich plant species have a significant effect on improving soil texture,optimizing soil p H,and enhancing water conservation capacity.The rocky coastal mountains have thin soil layers and poor soil nutrients.The content of soil nutrientin the study area is at a relatively low level.The overall nutrient content is higher in the pure black pine forest model(IV),chestnut pure forest model(V),and chestnut black pine mixed forest model(VI)than in other vegetation restoration models.The above three models have their own advantages and disadvantages in terms of soil organic matter,soil total nitrogen,soil total phosphorus,and soil available phosphorus content,but the overall difference is not significant;In terms of soil available potassium content,the chestnut black pine mixed forest model(VI)and the locust black pine mixed forest model(III)are higher than other vegetation restoration models.The soil nutrient content of the mixed forest model of black locust and black pine(III)is generally at the lowest level.(3)There are certain differences in the microclimate within the forest under different restoration model.The air temperature and humidity are the highest in the pure chestnut forest mode(V)and the mixed chestnut black pine forest mode(VI),respectively,and the daily dynamic changes are also minimal.Rich plant species play an important role in maintaining the temperature and humidity within the forest.The light intensity in the forest is shown as follows:pure chestnut forest model(V)>mixed chestnut black pine forest model(VI)>pure black pine forest model(IV)>mixed oak black pine forest model(II)>pure oak forest model(I)>mixed locust black pine forest model(III).(4)There are significant differences in understory plant diversity among different restoration modes,with the overall Shannon wiener index and Marglaf index ranging from1.048 to 1.830 and 8.301 to 27.088,respectively.At the herbaceous floor,the species diversity of mixed forest model(Ⅵ)of Chinese chestnut and black pine is the highest;For shrub layer plants,the species diversity of pure forest model of Pinus thunbergii(Ⅳ)and pure forest model of Chinese chestnut(V)is at the highest level.The mixed forest model of black pine and black locust(III)has relatively poor understory shrub and herb diversity.(5)The relationship between understory plant diversity and forest environmental factors was found to be closely related through RDA redundancy analysis and Monte Carlo substitution test.Air humidity and soil available phosphorus have significant effects on species diversity in shrub layer;Light,air humidity,soil available phosphorus and soil moisture content in the forest significantly affected the species diversity of the herb layer.Comprehensive analysis shows that light,air humidity,soil phosphorus,and soil moisture content within the forest are the main factors affecting understory plant diversity.Overall,in terms of increasing plant diversity under coastal protective forests,the three models of pure chestnut forest(V),mixed chestnut black pine forest(VI),and pure black pine forest(IV)have the best effects;The mixed forest model of Quercus acutissima and Pinus nigra(II)also showed a significant increase in understory plant diversity compared to the pure forest model of Quercus acutissima(I),while the mixed forest model of Robinia pseudoacacia and Pinus nigra(III)showed relatively poor understory plant diversity.