| Cupressus funebris was the main local coniferous tree species in the hilly area of central Sichuan,which spread all over the basin and the low hilly area around the basin.It had a strong ability of drought resistance and barren resistance.C.funebris forest was beneficial to soil and water conservation,and also had remarkable significance to forest ecological environment.There were many functions of fine roots.On the one hand,fine root was the key organ for forest to obtain and transport nutrients and water.On the other hand,it showed a high degree of morphological plasticity in different soil environments,and its morphological characteristics had an important impact on the function of forest ecosystem.Although the importance of the morphological characteristics of fine roots had been recognized,the response mechanism of fine root morphology in different soil environments still needed to be explored.The purpose of this paper was to study the morphological plasticity and seasonal variation of fine roots of C.funebris under different soil conditions.In this paper,four sites（Chongqing,Deyang,Suining and Mianyang）representing the hilly area of Sichuan Basin were selected as the research objects.The complete fine roots were obtained by soil column method in January 2019（representing winter）,April 2019（representing spring）,July 2019（representing summer）and October2019（representing autumn）respectively.In this study,the diameter,specific root length,specific surface area and tissue density of 1-5 grade fine roots of C.funebris were measured.At the same time,the soil physical and chemical properties of each C.funebris stand were measured.The results were as follows:（1）Root order,site and season had significant effect on the diameter of fine root（P<0.01）.Fine root diameter of C.funebris showed a trend of increasing gradually with the increase of grade 1 to grade 5.The variation range（minimum to maximum）of fine root diameter of 1-5 grade fine roots were 0.42～0.61 mm、0.51～0.75 mm、0.60～1.21 mm、0.80～1.39 mm、1.36～1.94 mm,respectively.At the same time,Fine root diameter of C.funebris was obviously different in different sites,and it was mainly manifested in the 1-2grade of fine root.The change rule of fine root diameter was Chongqing>Suining>Mianyang>Deyang.From the perspective of seasonal change,generally speaking,the rule of seasonal change of fine root diameter of 1-5 grade of C.funebris was winter>spring>summer>autumn.（2）Root order,site and season had significant effect on the specific root length（P<0.01）.Specific root length of fine roots of C.funebris decreased with the increase of grade 1 to grade 5,and the variation range（minimum to maximum）of specific root length of 1-5 grade fine roots were 11.57～24.90 m·g-1、7.43～17.57 m·g-1、3.15～12.65 m·g-1、2.14～5.11 m·g-1、0.64～1.83 m·g-1,respectively.At the same time,specific root length of fine roots of C.funebris was significantly different in different sites,and it was mainly manifested in the 1-3 grade of fine root.The change rule of specific root length of fine root was Deyang>Mianyang>Chongqing>Suining.From the perspective of seasonal change,generally speaking,the rule of seasonal change of specific root length of 1-5 grade fine roots of C.funebris was autumn>summer>spring>winter.（3）Root order,site and season had significant effect on the specific surface area of fine roots（P<0.01）.Specific surface area of fine roots of C.funebris decreased with the increase of grade 1 to grade 5,and the variation range（minimum to maximum）of specific surface area of 1-5 grade fine roots were 199.48～375.83 cm2·g-1、155.86～281.68 cm2·g-1、86.91～238.66 cm2·g-1、75.59～171.66 cm2·g-1、36.67～106.94 cm2·g-1,respectively.At the same time,the specific surface area of the fine root of C.funebris was obviously different in different sites,and it was mainly on the 1-3 grade of fine root;the change rule of specific surface area of fine root was Deyang>Mianyang>Chongqing>Suining.From the perspective of seasonal change,generally speaking,the rule of seasonal change of specific root length of 1-5 grade fine roots of C.funebris was autumn>summer>spring>winter.（4）Root order,site and season had significant effect on the density of fine root tissue（P<0.01）.Tissue density of fine root of C.funebris increased gradually with the increase of grade 1 to grade 5,and the variation range（minimum to maximum）of fine root tissue density of C.funebris was 0.20～0.34 g·cm-3、0.21～0.36 g·cm-3、0.26～0.40 g·cm-3、0.30～0.44 g·cm-3、0.34～0.50 g·cm-3,respectively.At the same time,fine root tissue density of C.funebris was obviously different in different sites,and it was mainly manifested in the 1-2 grade of fine root.The change rule of fine root tissue density was Suining>Chongqing>Mianyang>Deyang.From the perspective of seasonal change,generally speaking,the rule of seasonal change of tissue density of 1-5 grade fine root of C.funebris was winter>spring>summer>autumn.（5）Pearson correlation analysis showed that there was a close correlation between the morphological characteristics of fine roots of C.funebris.This correlation could be divided into the following six points.Firstly,specific root length was remarkably positive correlated with specific surface area（P<0.01）.Secondly,the negative correlation between specific surface area and fine root diameter reached a significant level（P<0.01）.Thirdly,The positive correlation between fine root diameter and fine root tissue density reached a significant level（P<0.01）.Fourthly,fine root tissue density was remarkably positive correlated with specific root length（P<0.01）.Fifthly,The negative correlation between specific root length and fine root diameter reached a significant level（P<0.01）.Sixthly,The negative correlation between fine root tissue density and specific surface area reached a significant level（P<0.01）.（6）There were significant geographical and seasonal differences in physical and chemical properties of soil in four sites（P<0.05）.RDA analysis showed that:on the one hand,there was a positive correlation between specific root length of fine root and soil total nitrogen and soil alkali hydrolyzed nitrogen.It could also be seen that there was a positive correlation between specific root length of fine root and soil total phosphorus and soil available phosphorus.After that,specific root length of fine root was positively correlated with soil organic carbon and soil porosity.However,specific root length of fine root was negatively correlated with soil moisture and soil bulk density.Interestingly,the relationship between specific surface area of fine roots and the physical and chemical properties of soil was consistent with specific root length of fine roots.On the other hand,there was a negative correlation between fine root diameter and soil total nitrogen and soil alkali hydrolyzed nitrogen.It could also be seen that there was a negative correlation between fine root diameter and soil total phosphorus and soil available phosphorus.After that,Fine root diameter was negatively correlated with soil organic carbon and soil porosity.However,Fine root diameter was positively correlated with soil moisture and soil bulk density.Interestingly,the relationship between fine root diameter and the physical and chemical properties of soil was consistent with fine root tissue density.It could also be seen that the relationship between soil temperature and morphological characteristics of each fine root of C.funebris was not remarkable.In the end,further analysis showed that the effects of soil total nitrogen,alkali hydrolyzed nitrogen,soil water and available phosphorus on fine root morphology were significant（P<0.05）;the effects of soil total phosphorus,organic carbon and soil temperature on fine root morphology were not significant（P>0.05）.In summary,the final conclusion of this study was that soil nitrogen and soil water content were the main factors affecting the morphological characteristics of fine roots of C.funebris. |
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