油松人工林重度火烧后凋落物分解及水文效应

Litter Decomposition and Hydrological Effects in Pinus tabulaeformis Plantation After Severe Burning

以北京市重度火烧迹地油松人工林为对象,基于原位采样法和室内浸泡法于2020年7—12月在对照样地和火烧样地采集凋落物样品并测定分析其现存量、持水量、有效拦蓄量等指标,探究林火干扰下凋落物的分解及水文效应,为更好促进森林水源涵养功能以及水土保持功能提供依据。结果表明:(1)油松人工林半分解和完全分解层凋落物平均现存量分别为16.18(叶占比>80%),31.88 t/hm^(2),平均厚度分别为2.77,2.79 cm;与对照相比,火烧后半分解层凋落物厚度及现存量分别降低39.35%,53.77%。(2)油松人工林半分解层凋落物平均自然含水率(41.94%)略高于完全分解层(36.07%),平均最大持水率为201.88%,其在7—9月低于完全分解层,10—12月则反之;半分解层凋落物平均最大持水量和有效拦蓄量分别为35.80,19.85 t/hm^(2),在8—12月均显著(P<0.05)低于完全分解层(69.28,46.64 t/hm^(2))。与对照样地相比,火烧后半分解层凋落物自然含水率降低32.19%,最大持水率和最大持水量分别降低13.36%,60.05%,有效拦蓄量降低了62.47%。(3)在24 h浸水过程中,7—9月对照样地半分解层凋落物持水量、吸水速率小于完全分解层,10—12月则反之;火烧后,半分解层凋落物持水量、吸水速率较对照样地半分解层凋落物减少。综上,油松人工林凋落物(半分解层)分解表现为先快后慢,火烧后其分解加速;凋落物持水性能及持水过程主要呈现完全分解层>半分解层,未火烧>重度火烧,即凋落物水文效应受分解阶段和火烧干扰影响。

The Pinus tabulaeformis plantation of severely burned areas in Beijing was taken as the research object,based on in situ sampling method and indoor immersion method,litter samples were collected in control plot and burned plot from July 2020 to December 2020 and their standing crops,water holding capacity and effective retention were measured and analyzed to explore the decomposition and hydrological effects of litter under the interference of forest fire.It could provide a basis for giving better exerting the function of forest water conservation and soil and water conservation.The results showed that:(1)The average standing crop of litter in semi-decomposed layer and decomposed layer of Pinus tabulaeformis plantation were 16.18 t/hm^(2)(leaves proportion>80%)and 31.88 t/hm^(2),the average thickness were 2.77,2.79 cm,respectively.Compared with the control plot,the litter thickness and standing crop of the semi-decomposed layer after fire were decreased by 39.35%and 53.77%respectively.(2)The average natural moisture content of litter in semi-decomposed layer(41.94%)was slightly higher than that in decomposed layer(36.07%)in Pinus tabulaeformis plantation,and the average maximum water holding capacity was 201.88%,which was lower than that of decomposed layer from July to September,and vice versa from October to December.The average maximum water holding capacity and effective retention in semi-decomposed layer were 35.80,19.85 t/hm^(2),which were significantly(P<0.05)lower than those of decomposed layer from August to December(69.28,46.64 t/hm^(2)).Compared with the control plot,the natural moisture content,maximum water holding rate,maximum water holding capacity and the effective retention of litter in semi-decomposed layer after fire were decreased by 32.19%,13.36%,60.05%and 62.47%respectively.(3)In the 24-hour immersion process,the litter water holding capacity and water absorption rate in semi-decomposed layer were lower than those of decomposed layer from July to September,and vice versa from October to December.The water holding capacity and water absorption rate of litter after fire in semi-decomposed layer were lower than those in control plot.In conclusion,the decomposition of litter(semi-decomposed layer)in Pinus tabulaeformis plantation was first fast and then slow,and the decomposition was accelerated after burning.The indexes of water holding capacity and water holding processes of litter mainly showed that decomposed layer was higher than semi-decomposed layer,and non-burned was higher than severe burned,that is,the hydrological effects of litter was affected by the decomposition stage and burning.