The Digital Image Charateristics Of The Common Phytolith In Surface Soils Of Forest, Steppe And Forest-steppe Ecotone In Northeast China

Phytolith is an important palaeo-environmental index widely used in recent years.Due to a number of common morphotypes in surface soil from different communities,it has a profound importance to quantitatively discribe and distinguish these common phytolith for the consistance of the classifying system and the elevation of the precision of palaeo-environmental reconstruction.In this paper,16 sampling sites in Northeast China(NE China)from forest,forest-steppe ecotone to steppe were selected and common phytolith(elongate psilate and rectangle)from surface soil and corresponding plant communities was collected to quantitatively distinguish these common phytolith in different communities using the computer-assistance image proccessing procedure.For the phytoliths in the surface soil,we collected 180 elongate psilate and 155 rectangle phytoliths.For the phytoliths in plant communities,we collected 168 elongate psilate and 98 rectangle phytoliths.MATLAB as a software was used to measure the 6 textrue characteristics and 7 invariant moments for each of these phtoliths,and the differences of common morphotypes in surface soils from different communities were revealed by variance analysis and discriminate analsis.Additionally,11 sampling sites were selected in Northeast China(NE China)with different climate conditions,and the elongate psilate phytolith in a single species,Phragmites communis,was collceted and their texture characteristics and invariant moments were measured.The results indicated that:(1)The texture characteristics of elongate psilate in surface soil present significant differences from forest,forest-steppe ecotone and steppe in NE China.The entropy and contrast ratio of the elongate psilate in forest are significantly lower than other two communities,but there are no significant differences about the invariant moments in these areas.The correct rate in discriminate analysis using texture characteritics and invariant moments for the elongate psilate in surface soil among three communities is 70.7%.Likewise the correct rate is 52.3% using only invariant moments,70.1% using only texture characteristics and 69.5% using stepwise discrinate analysis.As for rectangle phytolith,there are many invariant moments signifantly different among these three communities,but there are no significant differents about the texture characteristics.The correct rates of the rectangle phytoliths in surface soil from three communities in discriminate analysis using invariant moments and texture characteristics is 87.6%.Likewise the correct rate is 59.2% using only invariant moments,81.6% using only texture characteristics and 80.6% using stepwise discrinate analysis.(2)The texture characteristics and invariant moments of the common phytoliths from different plant communites were measured.The results indicated that the texture characteristics of the elongate psilate in the three communities are significantly different,just like the texture characteristics of the rectangle phytolith.Additionaly,the elongate psilate and rectangle phytoliths in forest community is roupher than in other two communities.However,the invariant moments of the two morphotypes from the three communities are not significantly different.(3)For each of the three areas,the texture characteristics are significantly different from plant community to surface soil.In forest,the elongate psilate in surface soil is smoother than in plant community,but it is contrast in other two areas.As for rectangle phytolith,the phytolith in community is significantly smoother than in surface soil in each of the three area,which reflected the influences of soil condition on phytolih taphonomy characterisrics.(4)The texure characteristics and invariant moments of the elongate psilate in a single species,phragmites communis,from different sampling sites in NE China were measured.The results indicated that these different sampling sites are effectively classified using cluster analysis,which reflected the differences in the combination of water and heat.The variance analysis indicated that the invariant moments of the elongate psilate are not significantly different,but the texture characteristics are significantly different among three areas.