集约经营雷竹林土壤有机质的时空变化

Temporal and spatial variation of soil organic matters in Phyllostachys praecox stands with intensive cultivation management

雷竹Phyllostachys praecox林强度集约经营是大量施用肥料和冬季地表覆盖增温,使竹笋早出高产,给竹农带来丰厚的经济收入的管理栽培技术。在雷竹主产区浙江临安三口镇,采集种植时间分别为1,5,10,15a的雷竹林土壤以及水田土壤（该区雷竹林主要是在这些水田上改制发展的）作为雷竹林的起始土壤（0a）,各4次重复,旨在分析雷竹林土壤有机质随雷竹种植时间和土壤剖面深度空间的变化情况,为雷竹林土壤的可持续利用提供一些依据。结果表明：雷竹林土壤有机质质量分数随种植时间先略微下降,再稳步上升。0,1,5,10和15 a的0-10cm表层土壤有机质质量分数分别为30.96,25.55,26.35,33.07和79.24g·kg^-1。10 a的雷竹林土壤有机质已超过起始土壤,15a雷竹林土壤有机质已达到起始土壤的2.5倍,证明强度集约经营导致了雷竹林表层土壤有机质快速累积。雷竹林土壤有机质在土壤剖面空间的变化呈随深度加深而递减的规律,以10 a为例,表层（0-10cm）,亚表层（10-20 cm）和底层（20-40 cm）的土壤有机质质量分数分别为33.07,27.64,13.73 g·kg^-1,表层土壤的有机质分别是亚表层和底层的1.2和2.4倍,其他年限的也都有相同的趋势。不同年限雷竹林土壤剖面底层的有机质质量分数都表现为最初没有明显下降,随种植时间的增长略增的趋势,变动幅度很小,相对平稳。可见强度集约经营措施主要对表层（0-10 cm）和亚表层（10-20 cm）即生产雷竹笋的主要土层有显著的作用。还讨论了土壤有机质快速积累对土壤肥力和环境质量的可能影响。

Phyllostachys praecox is a favourite bamboo species with higher economic value for its bamboo shoot as a delicious vegetable.The practice of intensive management by over fertilizing of complex fertilizer（16∶16∶16,2.25 t·hm^-2）and urea（1.125 t·hm^-2）per year plus heavier winter mulching（40 t·hm^-2 of rice straw and 55 t·hm^-2 of grounded bamboo leaves）every two years starting at 5 years for the higher yield of bamboo shoot and earlier marketing at the Chinese Spring Festival season to gain better price and incomes in Southeast China,especially in Zhejiang Province.The objective of this study is to analyse the temporal and spatial variation of soil organic matters（SOM）in Phyllostachys praecox stands during last 15 years with very intensive cultivation management in Lin＇an.Total of 20 soil profiles were sampled in main cultivation region of Sankou Town,choosing 1,5,10,15 and 0 years（paddy fields nearby as the beginning soil Phyllostachys praecox stands as a check）plantation of bamboo stands and each by 4 replications.Results indicated that with the increase of plantation year,SOM dropped a little in the beginning（1 year）,and then rose up steadily.SOM content in surface layer of 0-10 cm were gradually increased from 1,to 5 years,then 10 and 15 years,and were 30.96,25.55,26.35,33.07 and 79.24 g·kg^-1 respectively.Very high SOM content in 10 years and 15 years soils were resulted from over fertilization and heavy winter mulching of biomass.SOM spatial distribution in soil profiles showed that it was decreased with the soil depth increase in the layers of surface（0-10 cm）and subsurface（10-20 cm）,but not in the bottom layer（20-40 cm）,it neither dropped at 1 years clearly and nor increased later on,showed a relative steady situation.It indicated that intensive cultivation management had vigorously effect on SOM content in 0-10 cm surface and 10-20 cm subsurface layers where the bamboo shoot produced,but could not affect the deep layer of soil.The effect of high content of SOM in Phyllostachys praecox stands on soil quality and its sustainable use,the significance of carbon sequestration of such high SOM accumulation by this intensive management practices were also discussed.