【作者】 甘卓亭；

【导师】 刘文兆；

【作者基本信息】 中国科学院研究生院（教育部水土保持与生态环境研究中心） ， 生态学， 2007， 博士

【摘要】 根系是苹果树吸收水分和养分的重要器官,土壤条件影响苹果根系的空间分布,同时苹果根系的空间分布状况也是其利用土壤水分养分资源能力大小的反映。黄土塬和黄土梁作为渭北旱塬区果园建设的主要土地类型,其土壤水分循环过程有别,果园根系分布格局和蒸散耗水特征不同。果园中所实施的不同的耕作方式既改变了果园的土壤养分条件,也影响了果园的水分平衡状况,需要结合区域环境特点选择合适的耕作方式。本研究以渭北旱塬塬地和梁坡地不同生命周期苹果园为对象,就不同立地条件下苹果根系分布格局、果园土壤水分特征和蒸散耗水规律开展研究,并对果园耕作方式的保墒效应进行了初步评估。取得了如下主要研究结论:(1)幼龄期、初果期和盛果期梁坡果园根系取样发生率大于同期塬面果园,而衰老期塬面和梁坡果园差异不大。塬面果园细根发生率大小顺序为幼龄期<初果期<盛果期<衰老期,梁坡果园为幼龄期<初果期<衰老期<盛果期。幼龄果园细根生物量随深度递减;大龄果园细根生物量垂直分布呈单峰型,梁坡果园峰值点位置较对应塬面果园下移。比根长随深度和树龄增加而减小,塬面和梁坡幼龄果园的比根长差异不大,大龄果园的比根长梁坡大于塬面。大龄果园根长密度垂直分布呈单峰型,梁坡果园峰值点位置较对应塬面果园下移,梁坡果园根长密度大于对应塬面果园。(2)幼龄期塬面果园深层土壤水分显著高于同期梁坡果园;初果期塬面果园有干层发育,而同期梁坡果园干层发育不明显;盛果期梁坡果园土壤干层的发育程度强于同期塬面果园;衰老期塬面果园干层发育强度小于梁坡果园。土壤含水量与根系生物量和根长密度呈负相关。就塬面果园而言,幼龄果园的土壤水分条件较好;各龄果园间水分变动有土层差异,深层土壤水分随树龄增大而降低,衰老期果园1～3 m土壤水分有恢复趋势。就梁坡果园而言,随树龄增大果园土壤水分逐渐降低,幼龄和初果期果园土壤水分显著高于盛果期和衰老期果园。(3)果园生草加剧了果园土壤水分的消耗;生草和覆草方式有阶段性保墒作用;耕作方式对土壤水分的影响随深度递减。(4)果园日均蒸散耗水的周年变化具有年际相似性;塬面果园间种三叶草其日均蒸散周年变化整体呈单峰型,5~6月份为高峰期。梁坡果园日均蒸散前期上升,后期为多峰下降。塬面和梁坡果园蒸散耗水超过降水补给,土壤水分处于负平衡。更多还原

【Abstract】 Fine root of apple is an important organ for absorbing water and nutrition from soil, thus the distribution pattern of fine root reflects the ability of apple trees extracting resources from soil. Tableland and upper slope are main land types for apple orchard in the Weibei rainfed tableland of the Loess Plateau. They are of different characteristics of soil water cycle. Apple orchards in different land types have different distribution patterns of fine root and evapotranspiration characteristics. Meanwhile, different tillage methods not only change the nutrition environment of apple orchard, but also influence their water recycle. Thus, it should be applied according to the region environment.The distribution pattern of apple fine root, soil water dynamics and characteristics of evapotranspiration were studied based on different aged apple trees on tableland and upper slope of the Weibei reinfed tableland of the Loess Plateau. The moisture conservation of different tillage methods was also evaluated. The detailed results are as following:(1) Sampling incidences of apple fine root during young stage, initial fruiting stage and full fruiting period on upper slope orchard were greater than those on tableland. But there were few differences of those for senescence phase between upper slope and tableland orchards. Sampling incidences of apple fine root on tableland orchard ranked in the descending order of young stage, initial fruiting stage, full fruiting period and senescence phase, those on upper slope ranked in descending order of young stage, initial fruiting stage, senescence phase and full fruiting period.Fine root biomass decreased along with the soil depth increasing. The vertical distribution of fine root biomass under elder apple trees could be described by a single peak type. And its peak point position of upper slope orchard deeper than that of tableland orchard. Specific root length (SRL) reduced along with the soil depth and tree age increasing. There were few differences for SRL of young orchard between tableland and upper slope. SRL of young orchard on upper slope was greater than that on tableland. The vertical distribution of root length density (RLD) under elder apple trees could also be described by a single peak type. And its peak point position of upper slope orchard deeper than that of tableland orchard. RLD of young orchard on upper slope was greater than that on tableland.(2) Soil moisture in deep soil layer under tableland young orchard was greater than that under upper slope orchard significantly. The dried layer was developed under initial fruiting stage of tableland orchard, but it could not find under initial fruiting stage of upper slope orchard. The level of dried layer’s development under upper orchard during the full fruiting period was greater than that under tableland orchard in the same period, as well as orchard during the senescence phase. There was a negative correlation between fine root biomass and RLD.For tableland orchard, the soil moisture under the young orchard was well. Soil moisture under different aged trees is different in each soil layer. And it in deep soil layer decreased along with the tree’s age increasing. Soil moisture during 1-3 m soil layer has a tendency of recovery. For upper orchard, soil moisture reduced as the trees age rising. Soil moisture under young and initial fruiting orchard was significantly greater than that under full fruiting period and senescence phase orchard.(3) Orchard green covering aggravated the consumption of soil moisture. But Orchard green covering and Mulching Straw on Orchard could conserve soil moisture in certain period. The influence of tillage methods for soil moisture increased along with the soil depth rising.(4) There was a similar inter-annual tendency for daily evapotranspiration. The annual variation of daily evapotranspiration of tableland orchard interplant trifolium changed as a single peak curve. It was peaked in March and June. The daily evapotranspiration of upper slope increased in the previous period of each year, but decreased as a multi-peak curve in the later period. The water consumption by evapotranspiration was more than the supply of precipitation, thus the soil moisture was of negative balance.更多还原