滨海沙地不同人工林凋落物现存量及其持水特性

为了研究滨海沙地沿海防护林凋落物水源涵养功能,采用野外调查和室内浸泡相结合,对滨海沙地4种典型人工林(木麻黄林、湿地松林、尾巨桉林和纹荚相思林)不同分解阶段的凋落物现存量、持水率、持水量和吸水速率进行研究。结果表明:相同林龄的4种人工林凋落物现存量表现为木麻黄林(19.12 t/hm~2)湿地松林(17.51 t/hm~2)尾巨桉林(10.90 t/hm~2)纹荚相思林(10.13 t/hm~2),半分解层凋落物储量占比高于未分解层;4种人工林最大持水率在140.55%～206.47%,为尾巨桉林纹荚相思林木麻黄林湿地松林,最大持水量在20.75～30.85 t/hm~2,为木麻黄林湿地松林尾巨桉林纹荚相思林,4种人工林凋落物最大持水率和最大持水量均为半分解层大于未分解层,不同分解阶段凋落物持水率和持水量与浸水时间呈对数关系;4种人工林不同分解阶段凋落物平均吸水速率在前0.25 h内差异较大,未分解层中尾巨桉林最大为2.05 mm/h,半分解层中湿地松林最大为4.32 mm/h,不同分解阶段凋落物吸水速率与浸水时间均存在幂函数关系;凋落物有效拦蓄深为木麻黄林(2.45 mm)湿地松林(2.04 mm)尾巨桉林(1.87 mm)纹荚相思林(1.72 mm)。综合来看,木麻黄林凋落物的持水能力最强,湿地松林次之,之后是尾巨桉林和纹荚相思林,说明从凋落物水源涵养能力来看,木麻黄林和湿地松林更利于滨海沙地的水源涵养。

Water-holding Capacity and Accumulation Amount of Litters in Different Plantations in Coastal Sandy Area

In order to study the water conservation capacity of the litter in coastal shelterbelt forest on coastal sandy land, the litter accumulation amount, water-holding rate, water-holding capacity and water-absorption rate of different decomposition stages were investigated in four typical plantations with same age (Casuarina equisetifolia forest, Pinus elliottii forest, Eucalyptus urophylla×Eucalyptus grandis forest and Acacia culacocarpa forest) of coastal sandy area by the methods of field survey and laboratory soaking extraction. The results showed that the litter accumulation amount of the four plantations decreased in the order of C. equisetifolia forest (19.12 t/hm²) > P. elliottii forest (17.51 t/hm²) > E. urophylla×E. grandis forest (10.90 t/hm²) > A. culacocarpa forest (10.13 t/hm²), and the percentage of litter accumulation amount in semi-decomposed layer was higher than that in un-decomposed litter. The maximum water-holding rate of the four plantations was 140.55%~206.47%, which followed the order of E. urophylla×E. grandis forest > A. culacocarpa forest > C. equisetifolia forest > P. elliottii forest. The maximum water-holding capacity was 20.75~30.85 t/hm², which was sorted as C. equisetifolia forest > P. elliottii forest > E. urophylla×E. grandis forest > A. culacocarpa forest. The maximum water-holding rate and maximum water-holding capacity of litter in the four plantations were both greater in semi-decomposed litter layer than those in un-decomposed litter layer, and the water-holding rate and water-holding capacity of litter also changed logarithmically with immersing time at different decomposition stages. The average water-absorption rate at different decomposition stages varied greatly in the first 0.25 hours among the four plantations, in the un-decomposed layer, the water-absorption rate of E. urophylla×E. grandis forest was the maximum (2.05 mm/h), and in the semi-decomposed litter layer, the maximum value (4.32 mm/h) was found in P. elliottii forest. The litter water-absorption rate presented a power function with immersing time at the different decomposition stages. The effective interception depth of litter was in the order of C. equisetifolia forest (2.45 mm) > P. elliottii forest (2.04 mm) > E. urophylla×E. grandis forest (1.87 mm) > A. culacocarpa forest (1.72 mm). On the whole, the litter of C. equisetifolia forest had the strongest water-holding capacity, followed by P. elliottii forest, E. urophylla×E. grandis forest and A. culacocarpa forest, indicating that C. equisetifolia forest and P. elliottii forest were more conducive to water conservation in coastal sandy area.