Study On Root Distribution Characteristics And Response To The Competition Of Avena Sativa L. And Vicia Villosa Roth In Mixed Grassland In Alpine Region

Root distribution pattern reflects the environmental condition and competition abilityof the plant. In the same environment conditions, different root morphology reflects thedifferent ecological strategy when it faces competition. In the growth process, in order toadapt to the environment changes, root shape showed a considerable plasticity, which is astrategy can overcome the disadvantage of unable move, and make the organs that intakeresources close contact with the resources that sustain the life. When the habitats change,the root system will produce the form, physiological to maintain its functional behavior.In the northern slope of Qilian Mountains, the pasture growth season was short andthe cold season was long, so it affected the solid carbon ability and limited the growth anddevelopment of the roots, which restrict the efficiency of using soil resource and againstgrow and flourish of the grass. Artificial grass root is sensitive to root morphologyplasticity and the response of the inter-specific relationship, the plant need to overcomethe environment condition of low temperature by adjusting the root morphology plasticity.The combination of the grasses with shallow root type and the legume forages root withstraight root type can improve soil resources use efficiency and forage plant yield bycollocating the soil root distribution and adjusting the root length and the transform ofinter-specific relationship well, and changing the morphology of top root and lateral rootto adapt the heterogeneous habitat. Signs in this, A field experiment was conducted in theupper reaches of Shiyang river in Sunan country of Gansu province in2010（latitude37°58′26〞N，longitude101°47′34〞E）. It was carried out to analyze the distribution ofannual pasture between Avena sativa L. and Vicia villosa Roth.The results showed that:（1） The RLD in mixed grassland was bigger than mono-culture, there was alsosignificantly difference among four types of mixed grassland, the RLD distributedbetween4.34cm/cm³and cm/cm³, the smallest RLD was found in Ⅰ group, and thebiggest RLD was found in Ⅳ group. With the increasing of Avena sativa L. density, theroot length density of annual pasture increased gradually, that is, it showed a phenomenonof high Avena sativa L. density and low RLD.（2） There was significantly difference in space distribution, Avena sativa L wasdistributed mainly in25cm soil layer and Vicia villosa Roth was distributed mainly in 15cm soil layer, the lateral roots of Avena sativa L. and Vicia villosa Roth were found indifferent soil layer, the difference that was showed in the vertical distribution graduallychanged the root structure and morphology, so the inhibition of top roots wereelongationed and the lateral roots were enhanced.（3） The root morphology was different in the mixed grassland, among four minedtreatments, the root length density of top root of Avena sativa L. was between1.4%and2.8%, the growth of top root clearly got controlling, but the root distribution tend to movedown to the soil floor. And the root length density of lateral root was between97.2%and98.6%, the mixed grassland promoted the growth of lateral root compared with theCK₁（96.5%）, in addition, the root length density of lateral root in lower layers of the soilwas bigger than CK₁.（4） Vicia villosa, as a population of tap root systems, its root length density of toproot and lateral root is depended on the conversion of root’s function in mixed grassland inalpine region. In four different treatments, the proportion of Vicia villosa’s root lengthdensity of top root ranges from14.3%to18.6.Compared with CK₂, its growth of top rootare restrained while the proportion of lateral root is more than80%, which means itslateral root are promoted.（5） The intra-specific competition and inter-specific competition of the two speciescan transform in different degree spatial and temporal scales. The results showed that RYy,RYmand RYT of each seeding group was less-than1from seeding stage to mature stage,the degree of inter-specific competition was stronger than intra-specific, Avena sativa L.and Vicia villosa Roth showed obvious hostile relations, however, the competitiveadvantage of two species has significant difference.（6） From seeding stage to tillering stage, the RCCyof group B and group E wasbigger than1, RCCmwas less-than1and the AG was bigger than0, so the competitivepower of Avena sativa L. was stronger than Vicia villosa Roth, Avena sativa L. gainadvantage in the competition by increasing the root length and advancing the nutrientabsorption abilit_y, the competitive power of other groups can’t be judged. From jointingstage to seeding stage, the RCC_yof group A, C and D was less-than1, RCCmwas biggerthan1and the AG was bigger than0, so the competitive power of Vicia villosa Roth wasstronger than Avena sativa L., which was caused by increasing the number of Avena sativa L. root, so the advantage in the competition gradually declined.