杉木枯死枝、叶有在树上宿存多年的特性。江西分宜大岗山地区一立地指数14,林龄13a,保留密度2600株·hm-2的1代林,树上宿存枯死枝、叶总量达4108.0kg·hm-2,相当枯枝落叶层生物量的35.4%。树上宿存枯死枝、叶在冠层的分解速度,与置于枯枝落叶层的分解速度的测定结果表明,后者比前者快得多。说明在杉木林生长急需养分的速生期和杆材期,将树上宿存枯死枝、叶适时地打落于地表,使其在枯枝落叶层分解,与挂在冠层上的分解相比,对林木营养作用不同,前者比后者能及时、更多地提供养分。树上宿存枯死枝、叶在林冠下部由低到高呈4层分布。鉴于各层死亡时间不同,经受的分解时间和雨水淋溶的强度也相异,其在树冠上的分解速度是分层测定的,上下层差异较大。在枯枝落叶层的分解速度也分层测定,上下层的差异较小。在枯枝落叶层分解时,本实验1年间枝的各层分解量之和是树冠上分解时的近2.3倍,叶为5.4倍。在枯枝落叶层分解时,1年间各层枝、叶,营养元素归还量之和是树冠上分解时的3.5倍。速生、杆材期,适时地将树上宿存枯死枝、叶打落于地表,对连栽杉木林长期生产力的保持更是有积极作用。
The dead branches and leaves can hang on living trees for as long as ten years or so in Chinese fir plantation.The biomass of dead branches and leaves on living trees is 4108.0 kg·hm-2 in a first rotation stand of Chinese fir plantation with 14 site index and 13 years old, located in Dagang mountain area, Fenyi of Jiangxi. It is equal to 35.4% of the litter biomass of the stand.Determinations show the decay rates of dead branches and leaves taken from the canopy to the floor in the litter environment are far fast to the decay rates in the canopy.Therefore it is important for improving nutrient supply during the quick-growing phase and pole phase of Chinese fir plantation to take dead branches and leaves from the canopy to the floor to let them decay in the litter environment. There are four layers of dead branches and leaves distributing from 3.5 m to 8.0 m above the floor in the canopy. Because the dead time, the decay duration and suffered leaching intensity of one layer are different from another,so the decay rate of every layer in the canopy environment was determined separately.There are relatively distinct differences between decay rates of upper layers and decay rates of lower layers in the canopy environment. The decay rate of every layer in litter environment was determined also separately. There are a little differences between decay rates of upper layers and decay rates of lower layers in the litter environment.The decay mass of dead branches and leaves taken from the canopy to the floor in the litter environment is 2.3 times as much as that in the canopy.The total mass of nutrient return from the decaied branches and leaves in the litter environment is 3.5 times as much as that in the canopy.So taking dead branches and leaves on living trees from the canopy to the floor in good time during the quick growing phase and pole phase is one of effective measures to keep the productivity of Chinese fir plantation for long time.
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