木麻黄凋落物现存量的数量特征及影响因素

Quantitative characteristics and impact factors of litter accumulation for Casuarina equisetifolia

以海南岛木麻黄海防林为研究对象,设置71个临时样地,采用典型抽样法对木麻黄林分结构及凋落物现存量进行调查与分析,探究木麻黄凋落物数量特征及其影响因素。结果表明:平均胸径、胸高断面积、密度、郁闭度、草本盖度和土壤pH值是影响木麻黄海防林凋落物现存量的6个因子,其中凋落物现存量与平均胸径、胸高断面积和郁闭度呈极显著正相关,与草本盖度呈极显著负相关,与密度呈正相关,与土壤pH值呈负相关;半分解凋落物质量的影响因素及相关性与凋落物现存量相一致,但还与土壤pH值呈显著负相关。海南岛干湿不同气候区的凋落物现存量无显著差异。另外,这6个影响因子因对凋落物现存量的影响方式和影响程度的不同可划分为直接和间接影响因子,主要和非主要影响因子,其中平均胸径、胸高断面积和密度为直接影响因子,郁闭度、草本盖度和土壤p H值为间接影响因子;胸高断面积和草本盖度是主要影响因子,其中草本盖度则是凋落物现存量的重要指示因子。木麻黄海防林凋落物现存量较大,平均2.735 kg·m^-2,最大值为10.090 kg·m^-2;凋落物平均厚度为3.629 cm,最大厚度为8.000 cm;半分解凋落物质量占凋落物现存量的72.249%。大量的凋落物现存量既是木麻黄重要的养分库来源,也是影响林下植物更新的障碍因子之一。

Forest litter accumulation and decomposition contribute to the nutrient pool and are critical ecological processes in the ecosystem.The Casuarina equisetifolia L.coastal protection forest(CCPF)in Hainan Island was the focus of this study,and a total of 71 temporary sample plots were set up to investigate and analyze the stand structure and litter accumulation in CCPF by means of typical survey sampling,in order to explore the amount and impact factors of litter accumulation on C.equisetifolia.The results showed that six factors affect litter accumulation of CCPF,including the average diameter at breast height(DBH),basal area,density,canopy density,herb coverage,and pH value;litter accumulation was significantly positively correlated with the average DBH,basal area,and canopy density(P<0.01),highly negatively correlated with herb coverage(P<0.01),positively correlated with density,and negatively correlated with pH value.The impact factors and related properties of semi-decomposed litter mass were consistent with those of litter accumulation,but they were negatively correlated with pH value(P<0.05).There was no significant difference in litter accumulation in different semiarid and wet climate regions of Hainan Island(P>0.05).In addition,the six impact factors can be divided into direct and indirect factors,and into main and non-main factors according to their different impact modes and degrees on the litter accumulation.Among them,average DBH,basal area,and density were considered direct impact factors,whereas canopy density,herb coverage,and pH value were indirect impact factors.The basal area and herb coverage were the main impact factors,among which herb coverage was an important indicator of litter accumulation.The level of litter accumulation of CCPF was high,with an average of 2.735 kg·m^-2 and a maximum value of 10.090 kg·m^-2.The average litter thickness was 3.629 cm,and the maximum thickness was 8 cm.In litter accumulation,the semi-decomposed litter mass accounted for 72.249%.Therefore,a large amount of litter accumulation is not only an important nutrient source for C.equisetifolia,but also one of the barriers to the regeneration of undergrowth plants.