The Root Biomass And Spatial Distribution Of Pinus Massoniana In Different Communities

Masson pine（Pinus massoniana）is the main tree species of timber productionforest and industrial material forest. Masson pine has important position on forestryconstruction for its widespread, well-adapted and fast growing features. The study onbiomass and spatial heterogeneity of Masson pine’s root system could deepen theunderstanding of spatial distribution pattern and responding to spatial heterogeneity ofsoil nutrient in root system of Masson pine forest, and the study also has great valueand significance to the choices of forest management measure and energy flow andmaterial cycle of forest ecological system.This research focus on the biomass and spatial heterogeneity of root system indifferent ages and different densities of Masson pine forests by digging all roots layerby layer and soil auger method. On the base of every tree measuring, average sampletrees were chosen and investigated on their biomass and spatial heterogeneity of rootsystem by digging all roots layer by layer, biomass and spatial heterogeneity of rootsystem in forest land line spacing were investigated by soil auger method. Biomass ofroot system, soil physicochemical properties and other factors were analyzed by Exceland SPSS. The results show that:(1) Total biomass of each organ of average sample trees was affected by densityand age of forest obviously. Total biomass became smaller with higher density andbecame bigger with older forest. The order of biomass in each organ of averagesample trees, except young forests, could be listed as follows: trunk> brunch> root> bark> leaf. The trunk took up the main part of total biomass with more than58.97%. Comparing with radicels and rootlets, big roots and medium roots hasweaker absorption function, their respective ratio of total biomass were4.8%-17.67% and5.95%-17.92%and the maximum all appeared in young forest. Biomass ofradicels and rootlets changed obviously in different community types, their biomassof total biomass was4.99%-34.31%.(2) Total biomass of average sample trees mainly found in the soil that about0-0.5meter around the root pole in different community types and the proportion wasmore than62.09%. Thick roots mainly found in the soil from0to0.5meter and tookpart of65.30%-83.88%, hardly to find in the range that1.5m more away from rootpole. The horizontal distribution of biomass in big roots showed that it was mainlyfound in the the soil from0to0.5meter with a ratio more than49.72%and wouldreduce with the increasing of distance from root pole. The horizontal distribution ofbiomass in medium roots would increase at first and then decrease with the increasingof distance from root pole. The maximum appeared in the range wich was1.0-1.5maway from root pole with a ratio about26.50%-33.13%. The horizontal distribution ofbiomass in radicels and rootlets was largely effected by density and age of forest, itwould increase at first and then decrease with the increasing of distance from rootpole except low density forest stand, the maximum appeared in the range wich was1.0-1.5m away from root pole except young forest which took30.97%-56.82%parts.(3) The change rules of total biomass of average sample trees in verticaldirection of artificial forest were much the same that it tend to decrease with theincreasing of soil depth. The root system of masson pine was mainly found in the soilfrom0-30cm which hold more than87.80%. The biomass of thick roots mainly foundin the soil from0-20cm which hold more than78.59%. The biomass of big rootsmainly found in the soil from10-20cm. The biomass of medium roots mainly foundin the soil from0-30cm which hold more than76.40%. The biomass of radicels androotlets mainly found in the soil from0-30cm, more than78.25%of them were here.(4) The general trend of distribution of total biomass in artificial forest linespacing was that total biomass would decrease with the deepen of soil depth, the totalbiomass of radicels, rootlets and medium roots was mainly found in the soil from0-30cm which took part of92.63%. The distribution of biomass in rootlets wasaffected little by density but huge by age of forest. Both the total biomass and the biomass of roots in different diameter classes, their vertical distribution in foreststanding line spacing were affected by soil depth obviously, the soil from0-30cm holdmore than90%biomass. The distribution of root system in different soil depth offorest standing line spacing had distinct difference, the diversity of radicels androotlets in different soil depth had reached the significant level.(5) The correlation between vertical distribution of biomass of root system andsoil depth in artificial forest standing line spacing had reached very significant leveland occurred with some regularity that it would decrease with the increasing of soildepth. The distribution of rootlets had a very significant negative correlation with thechanges of soil bulk density, but a very significant positive correlation with organicmatter, available K and available nitrogen. The distribution of radicels only had verysignificant correlation with available K with the different soil depth. Differentdiameter classes of roots had different levels of sensitivities to the change of soil andother microenvironment. Roots became more sensitive with lower diameter classes.