Seasonal dynamics of soil microbial biomass C and N of Keteleeria fortunei var. cyclolepis forests with different ages

Soil microbial biomass is an important indicator to measure the dynamic changes of soil carbon pool.It is of great signifi cance to understand the dynamics of soil microbial biomass in plantation for rational management and cultivation of plantation.In order to explore the temporal dynamics and infl uencing factors of soil microbial biomass of Keteleeria fortunei var.cyclolepis at diff erent stand ages,the plantation of diff erent ages(young forest,5 years;middle-aged forest,22 years;mature forest,40 years)at the Guangxi Daguishan forest station of China were studied to examine the seasonal variation of their microbial biomass carbon(MBC)and microbial biomass nitrogen(MBN)by chloroform fumigation extraction method.It was found that among the forests of diff erent age,MBC and MBN diff ered signifi cantly in the 0–10 cm soil layer,and MBN diff ered signifi cantly in the 10–20 cm soil layer,but there was no signifi cant diff erence in MBC for the 10–20 cm soil layer or in either MBC or MBN for the 20–40 cm soil layer.With increasing maturity of the forest,MBC gradually decreased in the 0–10 cm soil layer and increased fi rstly and then decreased in the 10–20 cm and 20–40 cm soil layers,and MBN increased fi rstly and then decreased in all three soil layers.As the soil depth increased,both MBC and MBN gradually decreased for all three forests.The MBC and MBN basically had the same seasonal variation in all three soil layers of all three forests,i.e.,high in the summer and low in the winter.Correlation analysis showed that MBC was signifi cantly positively correlated with soil organic matter,total nitrogen,and soil moisture,whereas MBN was signifi cantly positively correlated with soil total nitrogen.It showed that soil moisture content was the main factor determining the variation of soil microbial biomass by Redundancy analysis.The results showed that the soil properties changed continuously as the young forest grew into the middle-aged forest,which increased soil microbial biomass and enriched the soil nutrients.However,the soil microbial biomass declined as the middle-age forest continued to grow,and the soil nutrients were reduced in the mature forest.

江南油杉优树子代苗期生长性状遗传变异研究

以10个种源地的82个家系江南油杉(Keteleeria fortunei var.cyclolepis)初选优树子代为研究对象,进行苗期试验。初步选择出江南油杉优良种源及家系。结果表明:参试的江南油杉家系/种源的千粒质量、苗高和地径生长量达到极显著水平。1年生江南油杉家系苗高、地径的遗传力分别为0.9495、0.9135;种源苗高、地径的遗传力分别为0.9727、0.9730。相关分析表明,江南油杉苗高、地径与千粒质量呈极显著正相关。根据苗高、地径的标准化值,初步选出FZ、LY为优良种源,所选出优良种源苗高、地径生长性状均值与种源总体平均值比较,苗高、地径分别提高12.54%、15.05%;最优种源与种源总体平均值比较,苗高、地径分别提高11.36%、27.18%;初步选出LY4、FZ6、LL5、LL10、FZ5、WM8、TE2、FN4、TE9、FZ2、WM9、TL6、BB5、FZ7、FZ9、JX1、LY2、TE3等18个优良家系,其苗高、地径生长性状均值与CK平均值比较,苗高、地径分别提高2403%、2282%;最优家系与CK平均值比较,苗高、地径分别提高60.28%、21.84%。

江南油杉幼苗生长及其物候特征

通过对江南油杉(Keteleeria cyclolepis)幼苗叶物候的观测和生长指标的测量分析,结果发现,江南油杉幼苗1年分春梢和秋梢2次发育,苗高和地茎分别在春梢和秋梢期出现2次快速生长期。苗高快速生长期出现在9—11月和3—5月,地茎快速生长期出现在8—10月和2—5月,地茎的2次快速生长期均比苗高快速生长期提前1个月。江南油杉苗期叶物候分为芽初露期、膨大期、初展期、展叶期4个时期,春梢从芽露期到展叶盛期总共经历57d,秋梢比春梢经历时间少3天。