长白山北坡主要森林群落凋落物现存量月动态

以长白山北坡4种主要森林群落类型为研究对象,于2006年群落生长季节(5-10月)每月初采用直接收获法对森林凋落物现存量进行连续定位调查研究。结果表明:各群落内凋落物现存量大小依次为阔叶红松林(6.43 t/hm²)>白桦林(6.02 t/hm²)>云冷杉林(5.51 t/hm²)>山杨林(5.50 t/hm²);凋落叶和枝现存量占现存凋落物总量的比例最大,达50%以上,其次为半分解物(>35%),花果皮等所占比例较少,各占总量的10%和5%以下。凋落物现存量月动态阔叶红松林、白桦林和山杨林呈双峰型变化,峰值出现在5月和7月;云冷杉林则呈单峰型变化,峰值仅出现在7月。位于相近海拔高度的阔叶红松林、白桦林和山杨林,凋落物各组分现存量月动态变化趋势相似,其中白桦林和山杨林变化趋势基本相同,凋落枝、皮及半分解物现存量5月和7月较高,凋落叶则呈现下降趋势,而阔叶红松林凋落叶和枝现存量5月和7月较高,而位于较高海拔的云冷杉林,则与前者呈现不同变化趋势,8月前波动较大,从5月开始明显上升,7月达到峰值,8月后曲线渐趋平缓或略有下降。进一步对阔叶红松林和云冷杉林内凋落叶现存量月动态进行比较得出,阔叶红松林7月份凋落叶现存量高不完全取决于红松叶现存量,主要由色木槭、紫椴和水曲柳等阔叶树种叶凋落物现存量变化决定,而云冷杉林则取决于红松和云冷落叶的凋落物的量。

Seasonal dynamics of litter accumulation in major forest communities on the northern slope of Changbai Mountain, Northeast China

Litter is an important component of the nutrient cycle in forest ecosystems and a key link of substance and energy flows. The changes of nutrient and energy in different forest communities can be detected by examining the dynamics of litter accumulation. To study litter accumulation and its seasonal dynamics in four major forest communities on the northern slope of Changbai Mountain (Broad-leaved Korean Pine forest (BlKP), Asian white birch forest (AwB), David poplar forest (DP), and Spruce-fir forest (Sf)), we harvested litter accumulated on forest floor at the beginning of each month from May to October in the growing season of 2006. The results showed the total litter accumulated in the four communities was significantly different (P<0.05) and the ranking from high to low was BlKP (6.43t/hm²), AwB (6.02t/hm²), Sf(5.51t/hm²), and DP(5.50t/hm²) .Among the four communities, undecomposed leaves and twigs accounted for more than 50% of the total litter , partially-decomposed litter for more than 35%, and flowers, fruits and barks for less than 10% and 5%, respectively. The seasonal dynamics of litter accumulation showed two peaks in BlKP, AwB and DP in May and July, and one in Sf in July. The seasonal dynamics of litter components in BlKP, AwB and DP at similar altitudes were comparable In particular, the seasonal trends of the litter components in AwB and DP were identical, high twig, bark and partially-decomposed litter in May and July, but a steady decline of leaf litter during growing season. In the BlKP, however, leaf and twig litters were high in May and July. The Sf at high altitudes had different litter dynamics from other three forest communities, starting to increase in May, reaching the peak in July, and showing a gradual decrease after August. The comparison of monthly leaf litter accumulation between BlKP and Sf suggested that the peak leaf litter of BlKP in July was largely determined by broad-leaved species including Acer mono Maxim, Tilia amurensis Rupr, and Fraxinus mandshurica, instead of Pinus koraiensis, whereas the peak value of Sf depended on conifer species such as Pinus koraiensis,Abies,Picea and Larix.