Research On The Carbon Density And Carbon Balance Of Larix Gmelinii Forest

Larix gmelinii is one of the vegetations which distribute widely in the highlatitudes of northern hemisphere. Quantifying the forest soil respiration （RS） componentsis vital to accurately evaluate the carbon sequestration of forest ecosystems. In thisresearch work, the biomass of arbor layer was measured based on the forest inventorydata and using allometric equation, the biomass of understory vegetation and the litteraccumulation were evaluated with the harvest method, the annual accumulation of litterwas determined with the collect method. We calculated the carbon density in thevegetation, litter and soil layer, respectively and researched the carbon distributionpattern in Great Hing’ an Mountains. At the same time, we determined soil respirationand CO₂emission flux based on the trenching-plot approach and quantified the carbonsink ability of different age group for Larix gmelinii forests. The results are as follow.1. Larix gmelinii from young forest to mature forest, the biomass of arbor layer andunderstory vegetation was98.63to249.46t·hm^-2, and2.10to6.01t·hm^-2, respectively, andthe total biomass of the vegetation layer was104.64to254.56t·hm^-2. The biomass of arborlayer increased with the increase of forest age, from young forest to mature forest. Whilethe biomass of understory vegetation presented “U” curve, which peaked in the youngforest and had a minimum value in the middle forest, and the vegetation layer biomassincreased.2. The biomass of organic detritus from young forest to mature forest was from15.17to48.46t·hm^-2, the litter accumulation was the most important component （67.46to90.86%）of organic detritus. The biomass of coarse woody debris （CWD） was1.39to13.43t·hm^-2.The biomass of organic detritus and litter accumulation all increased with forest age, whilethe biomass of CWD peaked in the middle aged forest.3. The litter accumulation for different aged Larix gmelinii forests, changed from0.81to1.37t·hm^-2. Highest annual litter accumulation was found in the mature forest, the orderwas mature forest＞young forest＞near mature forest＞middle forest. The litteraccumulation presented “U” curve. The fallen leaves were the mainly component of annuallitter accumulation （53.11to74.12%）.4. The net primary production （NEP） increased with forest age, the average was from8.81to10.81t·hm^-2·a^-1for the four aged forest. Of which, the NEP was72.97to90.88%,3.93to12.66%, and4.82to17.49%in the arbor layer, shrubby layer and herbaceous vegetation, respectively. The lowest of NEP was found in the lichen and mass layers.5. The carbon content order in the individual tree of Larix gmelinii forests was leaf＞branch＞trunk＞skin＞root. The carbon content order was shrubby layer＞herbaceouslayer＞litter layer. The carbon content in the aboveground was large than in theunderground in the three layers. The carbon content in the un-decomposed layer was largerthan in the composed layer. The carbon content in the leaf, skin and coarse root allincreased with forest age. The soil carbon content decreased with soil layer.6. The soil temperature in the top soil and5cm depth soil had an obviours correlationrelationship with the soil respiration（R²＞0.7068）. The soil temperature and airtemperature has a significant linear correlation relationship with the determined value（R²＞0.7068）.7. The carbon density in the four aged forest ecosystem was211.16,389.08,330.77, and435.2t·hm^-2, respectively. The carbon storage was60.91-74.82%,21.60-33.36%,2.34-5.91%,0.19-0.89%,0.05-0.35%and0-0.01%in the soil, arbor layer, detritus, shrubby,herbaceous layer, moss and lichen layer, respectively. The carbon density in the arbor layer,vegetation and detritus all increased with forest age, the order was mature forest＞middleforest＞near mature forest＞young forest.8. Annual carbon fixation of Larix gmelinii forests ecosystem from young forest tomature forest was4.02-4.85t·hm^-2·a^-1. Of which, the vegetation net increase was3.43to4.82t·hm^-2·a^-1and the litter return was0.38to0.59t·hm^-2·a^-1. Annual carbon emission was2.12to3.24t·hm^-2·a^-1. With the increase of forest age, the Annual carbon fixation of forestecosystem and the vegetation net increase all decreased. The litter return kept “U” shape.9. The result of ecosystem carbon balance estimation was: from young forest to matureforest, Larix gmelinii forests are all sink for air CO2, the net carbon sink was2.56,2.23,0.92,0.9t·hm^-2·a^-1. Thus, there was a significant difference between different age forest’secosystem carbon sink ability.