The Affect Of Fine Root Morphological Characteristics,Biomass And Carbon And Nitrogen Content In Pinus Massoniana With The Crop Tree Management

Pinus massoniana is an important tree species of protective and timber forest in southern China.In recent years,plantations have been greatly developed in China,but accompanied by problems such as soil degradation,biodiversity reducing,ecological function decline,etc.The crop tree management regime emphasizes the forest ability of natural resilience,that is different from the conventional forest management measures.As the crop tree management is used,the forest soil nutrient environment changes,and the above-ground part of the crop tree grows more rapidly.Fine roots are key tach to link trees and soil space for energy transfer and dry material distribution as an important organ to absorb water and nutrients.The growth status of aboveground parts can be explained by the variations by the indicators of the root order.In this study,Pinus massoniana located in Sichuan,Huaying,was selected as research object.In 2015,crop tree management was carried out and crop tree indensity was 150 trees per hectare.After three years,fine root of crop tree and non-crop tree were collected by the sector method with the angel is 15 degrees.Then we used Fitter's river branch method and divided fine root into 1-5 root order,to analysis the discrepancy of fine roots morphological characteristics and biomass.Incording to the refer-ence to the functional modules of fine root,we devided fine root into low-level root(1-3)and high-level root(4 ? 5)to explore the difference of carbon and nitrogen contents.The results were as follows:(1)Fine root morphological characteristics.The fine roots diameters of Pinus massoniana increased with the root orders in the crop tree management regime,and the differences between root orders were significant.The specific root length(SRL),root length density(RLD)and specific surface area(SRA)decreased with the root orders.There was no significant difference of the root orders diameters between the crop trees and non-crop trees,but the SRL,RLD and SRA of the crop trees were larger than those of the non-crop trees;On the horizontal distribution,1-5 order roots varied slight by the increasing distance from trunk base.The SRL,RLD and SRA of the crop and non-crop trees increased significantly from the distance of 0-0.5m to 1-1.5m,butthere was no significantly difference of the crop trees between the distance at 1-1.5m and 1.5-2m,while those indexes of the non-crop trees manifested as 1.5-2m<1-1.5m.The result was caused by the larger growth space of the crop trees that absorb water and nutrients more strongly.The study on the fine root morphological characteristics of different soil layers manifested that the SRL,RLD and SRA of masson pines fine roots decreased with the soil layers depth,while the diameters varied slight.(2)Fine root biomass.The fine root biomass of masson pines in the crop tree management regime was increased with the root order,and the fine root biomass of the crop trees was significantly larger than that of the non-crop trees.In the horizontal direction,the fine root biomass of the crop trees and the non-crop trees increased with the horizontal distance from 0-0.5m to 1-1.5m.Those indexes of the non-crop trees at the distance of 1-1.5m and 1.5-2m was significantly different while the crop trees were not.This result indicated that the fine roots of the crop trees distributed further at the trees bases to make the growth of the aboveground parts more advantageous than the non-crop trees.The crop and non-crop trees fine root biomass of 1-5 order root in0-10 cm soil layer was higher than 10-20 cm,and the differences of 1-3 order root were more significant,indicating that the soil surface layer of the crop trees distributed more fine roots.(3)As for C and N content,fine root carbon content varied slight in horizontal distance,and the C content of 1-3 order roots had no significant difference with 4-5order roots.The fine root C content of the crop trees was significantly higher than that of the non-crop trees,and varied significantly on the vertical distribution.The fine root C content of the 0-10 cm soil layer was significantly higher than that of 10-20 cm.The fine root N content of smaller order roots was significantly higher than that of higher order roots.The fine root N content of the crop trees was significantly higher than that of the non-crop trees.The N content of different soil layers showed obvious vertical distribution characteristics.The N content of topsoil was higher than that of deeper soil.The crop tree management regime changed the distribution pattern of soil resources and the morphological characteristics and biomass of fine root showed heterogeneous changes.Meanwhile,the C and N contents of fine roots also respondedto changes in soil environment quickly.In a word,the crop tree management can affect the growth and development of root obviously by increase the efficiency of absorb the water and nutrient,of which is better on the ground.It is significant to cultivate large diameter timber.At the same time,it's also enhance the function of carbon sequestration.There is an important practical and strategic significance for"carbon sequestration" and "increasing foreign exchange" in forest.