Studies On Root Morphology And Soil Water Status Response To Different Mowed Height Of Pasture

Aiming to solve the competition between pasture growing and soil moisture of forest land in semi-arid area,this research choose the Poapratensis L.,Trifoliumrepens and Viciavillosa Roth mowed controled 3cm,6cm,9cm height and without mowed(CK), respectively.Observation and analysis of mowed height relationship with root morphology by the indoor and field data,which determined to proper mowed height of different pasture and evaluationed mowed measuers,which has a direct impact on root uptake water and soil water use in root zone. The test in order to explore new ways of root regulation and to reduce water consumption intensity of pasture.The main conclusions of this study were as follows:(1) Indoor tests proved that mowed measure can reduce root depth, root length and root surface area. The lower mowed height, the smaller values of root depth, root length and root surface area. Field tests showed that the maximum root depth order was Poapratensis L. < Viciavillosa Roth < Trifoliumrepens. The indoor root depth value less than the field value in the circumstances of equal height of pasture, the indoor root depth values was accounting for 48.7% of Trifoliumrepens in field. In contrast with the Trifoliumrepens, the root depth in field values was shallow than indoor of Poapratensis L. and Viciavillosa Roth.(2) The lower mowed height, the larger root length density of Poapratensis L. in field. The root length density in field is larger than indoor values under equal height of Poapratensis L.. The root length density is larger on 6 cm mowed height than other heights of Trifoliumrepens. However, the root length density is smaller on 6 cm mowed height than other mowed heights of Viciavillosa Roth and of which has united variation in field and indoor. The average root diameter in field less than indoor values of Poapratensis L. and Viciavillosa Roth that by contrast with the Trifoliumrepens. Difference root diameter between field and indoor, there was no significant difference in different mowed height of indoor Trifoliumrepens. However, the higher mowed height, the more obvious differences in field root diameter of Trifoliumrepens(P<0.01).(3) Distribution ratio differences in root length, root surface area and root length density of different root diameter levels. The highest root diameter proportion in range of ≤0.5 mm of root length of three pasture. The root surface area increases with mowing days and become thicken of root diameter, the root surface area shows increased first and then decreased like"parabolic" type with root diameter become thicken, the highest peak in 0.2-0.5 mm interval of root diameter. Root length density differences between different root diameter interval of pasture, the highest peak in 0-0.2 mm root diameter interval of Poapratensis L. root length density, the highest peak in 0.2-0.5 mm root diameter interval of Viciavillosa Roth root length density. The root length density was significant difference in field and indoor of Trifoliumrepens, the highest peak in 0-0.2 mm root diameter interval of field Trifoliumrepens, the highest peak in 0.2-0.5 mm root diameter interval of indoor Trifoliumrepens.(4) The root distribution above 40 cm soil layers of Poapratensis L., root length density of mowing 3 cm, 6 cm, 9 cm height and CK in 0-40 cm soil depth was 2.17 m/m3(under 3 cm mowed height), 3.52 m/m3(under 6 cm mowed height), 2.80 m/m3(under 9 cm mowed height), 3.83 m/m3(CK), respectively and the average soil moisture was 13.06%(under 3 cm mowed height), 12.61%(under 6 cm mowed height), 11.98%(under 9 cm mowed height), 11.56%(CK), respectively. The root distribution above 70 cm soil layers and roots concentrated distributed in 0-40 cm soil depth of Trifoliumrepens. The root length density in 40 cm soil depth order was 6 cm> 3 cm> 9 cm> CK and soil moisture order was 3 cm >9 cm>6 cm> CK of Trifoliumrepens. Root uptake water in the 0-60 cm soil layers of Viciavillosa Roth, the root length density order was 3 cm>6 cm>9 cm>CK and the average soil moisture order was 6 cm>9 cm>3 cm>CK. Entire observation soil layer, average soil moisture was 13.18% of Poapratensis L., average soil moisture was 10.09% of Trifoliumrepens and average soil moisture was 11.98% of Viciavillosa Roth.(4) The largest evapotranspiration in July and the smallest evapotranspiration in October of entire trial period. There was differences within each mowed height in season. The lower mowed height, the less evapotranspiration of Poapratensis L., the cumulative evapotranspiration was 230.29 mm(under 3 cm mowed height), 239.29 mm(under 6 cm mowed height), 248.47 mm(under 9 cm mowed height), respectively. Mowed treatments cumulative evapotranspiration was less compared with CK. The lower mowed height, the less evapotranspiration of Trifoliumrepens. The cumulative evapotranspiration order was 6 cm <3 cm <9 cm <CK of Viciavillosa Roth. In short, mowed can be reduced soil water consumption compared with no mowed pasture, the soil water consumption order was Trifoliumrepens> Viciavillosa Roth > Poapratensis L. of three test pasture.(5) In summary, the proposed control is 3 cm height of Poapratensis L. and 6 cm height of Viciavillosa Roth understory planting, there is not recommended as a grass understory choice of Trifoliumrepens in semi-arid region.