南亚热带不同类型人工林的水土保持效应

Soil and water conservation effects of different plantations in southern subtropical area of China

为了探讨不同类型植被恢复过程中的水土保持效应,本文基于设在鹤山森林生态系统国家野外科学观测与研究站的9个地表径流场6年水文监测,研究了不同植被类型恢复过程中的水土流失特征。结果表明:幼龄人工林地表径流系数大小为:尾叶桉林(EU1)<10物种混交林(M1)<厚荚相思林(AC)<30物种混交林(M2)<红椎(CH),成熟人工林地表径流系数:荷木林(SS)<窿缘桉(EU)<马占相思(AM)<马尾松林(PM),成熟林6年平均径流量较幼龄林减少64.2%。幼龄人工林年平均推移质排序为AC<M1<M2<EU1<CH,成熟人工林年平均推移质:SS<AM<EU,幼龄人工林(3~7年林龄)中年均推移质量是成熟人工林(24~28年林龄)的7.14倍。混交林在短期和长期的减流效果都要好于纯林;桉林在减少地表径流方面短期和长期均有较好的效果,但在减少推移质方面效果不理想。幼龄期红锥林的减少径流和推移质的效果较差,成熟林中松林的减少径流效果较差。总的来看,幼龄人工林径流系数和推移质呈逐年降低趋势并趋于平缓,到2011年已经接近成熟林水平,而成熟林径流系数和推移质多年来均处于一个稳定较低水平;因此,保护森林应首要减少人为干扰,森林在一段时期自然恢复后,均可在水土保持方面发挥重要作用。

[Background]Soil and water conservation is one of the major ecological functions of plantations,which may be affected by plant species composition and age of the plantations.There are 69 million ha plantations in China,which is composed of tens of thousands of plant species including both native and exotic species.These plantations have played important role in soil and water conservation.A study at Heshan National Field Research and Observation Station of Forest Ecosystem was conducted.[Methods]Five kinds of young plantations and four mature plantations were selected,and runoff fields were built under all plantations in order to have the long,term data.Runoff was monitored by automatic level logger placed in every plot.Bed load sediment data was collected at the end of each year.Characteristics of runoff and bed load sediment of each plantation were analyzed with ANOVA.[Results]Mature plantations functioned better than young plantations in terms of runoff reduction,the former reduced runoff by 64.2%compared to young ones in six years(2008-2013).The annual mean runoff of young plantations was 159.4 mm,with the order of EU1(Eucalyptus urophylla)<M1(Eucalyptus urophylla)<AC(Acacia crassicarpa)<M2(30 species mixed forest)<CH(Castanopsis hystrix).Monthly mean runoff was 13.29 mm within the range of 9.22 to 16.59 mm.The annual mean runoff of mature plantations was 57.1 mm,with the order of EU(Eucalyptus urophylla)<AM(Acacia mangium)<SS(Schima superba)<PM(Pinus massoniana).Monthly mean runoff was 4.34 mm within the range of 3.22 to 6.04 mm.On the study of soil erosion,the average bed load sediment of young plantations(3-7 years)was 7.14 times of mature plantations(24-28 years).Bed load sediment varied with plantation type in the order of AC<M1<M2<EU1<CH for young plantations and in the order of SS<AM<EU for mature plantations.In 2010,the bed load sediment amount of all plantations except CH began to reach a steady low level,while in 2012 all plantations were at a steady low level.[Conclusions]Soil and water erosion from different plantations show a significant downward trend through young plantation stage.Eucalyptus spp.is a better candidate for water conservation both in young and mature plantations,but Castanopsis hystrix and Eucalyptus spp.do not act well in reducing bed load sediment in young plantations.Pinus massoniana’s bed load sediment is significantly higher than other forest types of mature ones,though the differences of quantity in runoff among different forest types are not big in the long,term restoration.In both young and mature forests,the mixed forests are better than monoculture forests in water and soil conservation.