Study On Herbage Diversity And Biomass Under Different Density Larix Principis Rupprechtii Forest

In order to explore the effects of stand density on herbage diversity and biomass(herbage and litter)under Larix principis rupprechtii forest,Taking the Larix principis rupprechtii forest and undergrowth herbs in Guandi mountain as the research object,The species diversity and biomass of herbaceous plants under seven different stand densities(240 plants/hm2,330 plants/hm2,450 plants/hm2,675 plants/hm2,970plants/hm2,1190 plants/hm2 and 1370 plants/hm2)of Larix principis rupprechtii were studied by field investigation and total harvest method.The species composition,diversity index and biomass(herbage and litter)characteristic value of undergrowth herbage were investigated,and the basic characteristics,herbage diversity index change trend and biomass(herbage and litter)change law of undergrowth herbage under different stand densities were analyzed.The main conclusions are as follows.(1)A total of 49 species of herbaceous plants were recorded in this study area,belonging to 43 genera of 26 families.There are more herbaceous species in Compositae,Leguminosae,Ranunculaceae and Liliaceae,among which Oriental strawberry,Carex tenuifolia and chrysanthemum are the main dominant species.With the increase of stand density,the number of herbaceous families,genera and species increased first and then decreased,and the herbaceous coverage decreased as a whole.When the stand density is 970 plants/hm2,the number of herbaceous plants is more,and the species composition is more abundant.When the stand density is 240~675 plants/hm2,the height and coverage of herbaceous plants are larger.(2)The richness index(S),diversity index(H),evenness index(J)and dominance index(D)of herbaceous plants increased first and then decreased with the increase of stand density.When the stand density was 970 plants/hm2,the herb diversity index was higher.(3)With the increase of stand density,the total biomass of herbage decreased,and the thickness and biomass of undecomposed layer and decomposed layer of litter increased first and then decreased.The thickness and biomass of litter decomposition layer are always larger than that of non decomposition layer.The herb biomass was the best at low stand density(240~675 plants/hm2).When stand density was 970plants/hm2,the litter in the undecomposed layer and decomposed layer was thicker,and the litter biomass was more.(4)Stand density was negatively correlated with herb biomass and coverage(P<0.05),and positively correlated with Shannon-Wiener diversity index(H),Pielou evenness index(J)and Simpson dominance index(D)(P<0.05).Shannon-Wiener diversity index(H)was positively correlated with Patrick richness index(S),Pielou evenness index(J),Simpson dominance index(D)and undecomposed layer thickness of litter(P<0.05),and negatively correlated with herb biomass and herb coverage(P<0.01).Pielou evenness index(J)was significantly positively correlated with Simpson dominance index(D),Patrick richness index(S)and undecomposed layer thickness of litter(P<0.05),and significantly negatively correlated with herb layer coverage and herb biomass(P<0.01).Simpson dominance index(D)was positively correlated with Patrick richness index(S)and the thickness of undecomposed layer of litter(P<0.05),and negatively correlated with Herbage Biomass and herbage coverage(P<0.05).There was a significant positive correlation between herbaceous biomass and herbaceous coverage(P<0.01),a significant negative correlation between herbaceous biomass and coverage and the thickness of undecomposed litter layer(P<0.05),and a significant positive correlation between the thickness of undecomposed litter layer and the biomass of decomposed litter layer(P<0.05),The biomass of undecomposed layer was significantly positively correlated with the thickness and biomass of decomposed layer(P<0.01),and the thickness of decomposed layer was significantly positively correlated with the biomass(P<0.05).