林龄对侧柏人工林碳储量以及细根形态和生物量的影响

Effects of stand ages on carbon storage,fine root morphology and biomass in Platycladus orientalis plantation

以徐州侧柏人工林为研究对象,运用生物量转化方程及土壤调查数据分析了3种林龄下(40、48和55 a)生态系统碳储量的变化及其机制。结果表明:(1)乔木层碳储量在系统碳储量中所占比例随林龄增加呈上升趋势,土壤层碳储量比例呈下降趋势,灌草层和枯落物层碳储量随林龄增加无明显变化。整个系统的碳储量随着林龄增加而增加,其中55年生侧柏人工林生态系统碳储量为109.55 t/hm2,分别是40和48年生的1.22倍和1.09倍,而这种差异主要是由乔木层和土壤层碳储量差异引起。(2)细根生物量方面,细根中低级根(1～3级根)生物量在不同林龄林分中无显著差异,高级根(4、5级根)和总生物量随林龄的增大而明显减少。细根形态方面,与40 a的相比,在表层土壤中,48年生林5级根的直径显著降低,5级根的根长和1级根的比根长显著提高;55年生林4级根的直径和根长以及1级根的比根长显著提高。在亚表层土壤,48年生林3级根的直径和4级根的根长显著增加,1级和2级根的比根长显著降低;55年生林3～5级根的直径和5级根的根长显著提高,3级根的根长以及1级和5级根的比根长显著降低。(3)3级根的直径与土壤层碳储量显著负相关,5级根与生态系统总碳储量显著正相关。2级和3级根的比根长与土壤层碳储量显著正相关,而3级根的比根长与乔木层碳储量、枯落物层碳储量和生态系统总碳储量显著负相关。4级和5级根的生物量与枯落物层碳储量显著正相关,与土壤层碳储量极显著负相关;细根总生物量与乔木层碳储量和总碳储量极显著负相关,与灌木层和草本层碳储量显著负相关。因此,细根形态和生物量的变化可能是导致生态系统碳储量变化的因素之一。

The research focused on Xuzhou Platycladus orientalis plantation,to study the changes on carbon storage of the ecosystem and related mechanism in different stand ages（40,48 and 55-yr-old） by applying biomass transformative equation and soil survey data.The results were as follows：（1） The percentage of carbon storage in tree layer rised with the increase of stand age.On contrast,the proportion of soil carbon storage was decreased.The carbon storage of the shrub,herb and floormass had no changes with the increase of stand age,while the whole ecosystem carbon storage rised with growing stand age.The total carbon storage of 55-yr-old stand was 109.55 t / hm2,respectively 1.22 times and 1.09 times as much as that of 40-yr-old stand and 48-yr-old stand.Yet,this difference was mainly caused by the different carbon storage of tree layer and soil layer.（2） Fine root biomass indicated that the 1st-3rd root order biomass was found non-significantly changed.Although the 4th-5th root order and total biomass significantly decreased with stand age.Fine root morphology showed： compared with 40-yr-old stand,in the surface soil layer,the diameter of 5th root order significantly decreased,while the root length of 5th root order and specific root length of 1st root order significantly increased in the 48-yr-old stand.The diameter and root length of 4th root order,and the specific root length of 1st root order significantly increased in the 55-yr-old stand.In the subsurface soil layer,the diameter of 3rd root order and the root length of 4th root order significantly increased,but the specific root length of 1st and 2nd root order significantly decreased in the 48-yr-old stand.The diameter of 3rd-5th root order and the length of 5th root order significantly increased,although the length of 3rd root order and the specific root length of 1st and 5th root order significantly reduced in the 55-yr-old stand.（3） The relationship between the diameter of 3rd root order and soil carbon storage was significant negatively correlated,but the diameter of 5th root order positively correlated with total ecosystem carbon storage.The specific root length of 2nd and 3rd root order significant positively correlated with soil carbon storage,while the specific root length of 3rd root order significant negatively correlated with tree layer carbon storage and litter layer carbon storage and ecosystem carbon storage.The biomass of 4th and 5th root order with litter layer carbon storage significant positively correlated,and with soil carbon storage in very significant negative correlation.Total fine root biomass significantly positive correlated with tree layer carbon storage and total carbon storage,and positively correlated with shrub layer carbon storage and herb layer carbon storage.As the results,the changes of fine root morphology and biomass may be one of the factors that cause the changes of ecosystem carbon storage.