Distribution Pattern Of Fine Roots And Soil Moisture Characteristics Of Apple Orchard In Weibei Rainfed Tableland Of The Loess Plateau

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.