| Fire is an important ecological factor in ecosystem.Changes in plant diversity and soil nutrient content in burned forestland have been hot topics in ecological research.The study on species composition,species diversity,soil physicochemical properties of soil and their interrelationships after burned forestland,to reveal the change pattern of scrub-grass community vegetation and soil after fire,and the mutual feedback mechanism,to guide the vegetation and soil soil restoration has important guiding significance.In order to reveal the changes of undergrowth shrubs and herbs community structure and diversity after fire of mixed Pinus thunbergii-Quercus acutissima forests understory plant community and exploring the relationship between communities species distribution and diversity index and soil factors in Jiaodong Hilly Area,Taking medium fire,low fire and unburned forest in Weihai burned forestland as research object.The testing combines of field investigation and indoor analysis was used to study the species composition,species diversity,soil physicochemical properties and the characteristics of nutrient eco-stoichiometry in three types of scrub-grass community,and the Canonical Correspondence Analysis(CCA)and Redundancy Analysis(RDA),revealing the differences in soil structure and spatial distribution characteristics of forest land under different fire intensities and the key soil factors that affect the species diversity of scrub-grass community in different fire sites.The results show that:(1)In the study area,there are 54 species,47 genus and 26 families of plants.Herbaceous plants are theconstructive species of shrub communities in the area.There are two trends in the composition of the three woodland species: On the one hand,the species composition is concentrated in large families such as Compositae,Leguminosae and Gramineae.On the other hand,it is dispersed to small families and regional single-sepcies families.These two trends reflect the characteristics of less large families and more small families.The total importance values of the three families show an increasing trend with the increase of fired intensity.Medium fire intensity forestland and unburned forestland are the most important for Compositae.Low fire intensity is the most important for Leguminosae.The dominant species in the three areas woody plants are shrubs.The dominant species in the Medium fire intensity and unburned forestland herbs are annual herbs,and the moderate fires are perennial herbs.(2)The effects of fire intensity on species diversity in shrub layer and herb layer are different.Richness,diversity and evenness index of all forestlands presented as herb layer > shrub layer in scrub-grass community.The richness,diversity and evenness index of shrub layer rose first and then decreased with the increase of fire intensity,reaching the maximum value in the Low fire intensity,it is the key transitional point of shrub community characteristic change.The herb layer Patrick,Shannon-wiener and Simpson index gradually decreased,and the Margalef index first decreased and then slightly increased,reaching the maximum value in the unburned forestland,and the evenness index showed no significant difference among the woodlands.The morista-horn index between unburned and fire intensity forestland was the smallest in shrub layer,herbaceous layer and shrub layer,with the highest ?-diversity,and different composition of undergrowth species.Low and medium fire intensity forestland have higher heterogeneity at shrub level,while unburned forestland and Low fire intensity forestland have higher heterogeneity at herb level.(3)Fire changes the distribution of soil physical properties.Low fire intensity forestland has the least bulk density,the best soil aeration status,and the best soil water holding performance in the 0-40 cm soil.These are beneficial to free soil,improve soil aeration and water holding capacity.Unburned forestland has the highest soil moisture content in the 0-40 cm soil.Medium fire can reduce soil moisture content,increase soil compactness and reduce soil aeration.Fire can change the vertical distribution of soil structure.The influence of fire disturbance on soil bulk density is mainly concentrated in 20-40 cm,and the improvement of ventilation status is mainly concentrated in 0-20 cm.Medium fire is helpful to improve the water holding capacity of the soil surface,and low fire is helpful to improve the water holding capacity of the lower soil layer.(4)Fire changes the distribution of soil nutrients.Soil organic carbon,total phosphorus,and available phosphorus contents gradually decreased with the increase of fire intensity in the 0-40 cm soil.Total nitrogen,total kalium,and available kalium contents increased first and then decreased with the increase of fire intensity in the 0-40 cm soil.Low fire intensity forestland has a significant effect on the increase of total kalium contents.Medium fire significantly reduced soil organic carbon,total nitrogen,total phosphorus,total kalium,available phosphorus,and available kalium.The vertical distribution of soil nutrients in three types of forest land has different performances.(5)Medium fire and Low fire intensity forestland understory shrubs and herbs community communities can be roughly divided into three groups.The shrub layer and herbaceous layer plants under unburned forest scattered without forming a community.There are similarities and differences in the factors affecting the species diversity of forest communities with different fire intensities.The main positive factors of moderate burning on plant diversity were Carbon Nitrogen Ratio(C/N),and the main negative factors were Total Phosphorus(TP)and Total Potassium(TK).The forward factor is Phosphorus Nitrogen Ratio(N/P)and the reverse factor is pH.The species diversity of unburned forest land is affected by a variety of soil factors.On the whole,TK and TP are the common influencing factors of plant diversity in the burned forestland,and P is the common limiting element of plant diversity in the burned forestland. |
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