Research Of Afforestation Seedling' Water Consumption In The Upper Minjing River

Due to the uncoordinated relationship problem between vegetation and water resources,the experiment used different methods to analyze water consumption rules under different soil moisture gradients and drought coercion condition.The aim was supplying basic theory of saving water for forestation.The objects were the main afforestation trees species in the arid river valley area Minjiang River upstream,such as Pinus tabulaeformis Carr,Pinus radiate,Cupressus chengiana S.Y.Hu,Ulmus pumila and Platycladus orientalis.By man-made controlling soil moisture content,the experiment studied single tree water consumption diurnalvariation and month changing rules from March to September,as well as nursery stock's growth and biomass accumulation situation.The main obtained results were as follows:1) single nursery stock's water consumption rules under different soil moisture content conditionWater consumption diurnalvariation taken on three kinds curves: unimodal,the split-blip and the irregular.In initial period of plant growth,the curve is generally unimodal;in intermediate stage,the curve is commonly split-blip;in telophase,the curve is generally irregular.The relation between water consumption and soil moisture content appeared three kinds:just correlation,inverse correlation and not obvious.The water consumption rules is that Cupressus chengiana S.Y.Hu increased along with ascending soil moisture content;Pinus tabulaeformis Carr and Platycladus orientalis were relative higher under low soil water content condition,Ulmus pumila varied not obvious.The month change rules of water consumption divided into three kinds. The first kind,most trees species appeared maximum value in intermediate growth stage.The second kind,minority trees species appeared two peak values.When SWC were 5%and 15%,Ulmus pumila's water consumption peaks appeared in May and July,and in July it consumed most water.The third kind,water consumption changed gently like Platycladus orientalis under SWC 35%processing.The diurnalvariation curve of net photosynthesizes speed also divided into three kinds:the split-blip,unimodal and irregular.The relations between net photosynthesizes speed and moisture content gradient was not very obvious because of environmental effect,but still can be found some rules.Under the high soil moisture content condition,net photosynthesizes speed appeared maximum value at 8:00 early morning.Under SWC 15%and SWC 25% processing conditions,maximum value appeared at 12:00.Under the low soil moisture content condition,net photosynthesizes speed appeared irregular.The water use factor was regular under various moisture contents gradient. All trees species reached maximum value at 12:00.The moisture content use factor has direct ratio with net photosynthesizes speed and reverse ratio with the water consumption.But maybe caused by environment,Pinus tabulaeformis Carr taken on high net photosynthesizes speed and low moisture content use factor.2) Water consumption physiological rules of various tree species under arid coercion conditionThe water consumption decreased along with increased coercion.In the coercion initial stage,the falling range of water consumption is much bigger; in the coercion anaphase,it is less.At different coercion extent,water consumption diurnalvariation was the unimodal curve and also had invariable curve apex types.In each phase,Pinus radiate and Platycladus orientalis had all more water consumption,but Ulmus pumila indicated relative less.Under the arid coercion,leaf blade water content of the stronger drought resistance trees species descended slower than the weaker drought resistance. In the different times,the leaf blade relative water content of Pinus radiate and Platycladus orientalis descended more and Pinus tabulaeformis Carr descended less.Ulmus pumila had higher own leaf blade moisture content.The change results of each physiological target under coercion:As to MDA,Pinus tabulaeformis Carr and Platycladus orientalis contented more; Cupressus chengiana S.Y.Hu contented the lowest.From the soluble protein content change,Ulmus pumila indicated higher arid resistance ability, Cupressus chengiana S.Y.Hu indicated lower.As to dissolubility sugar,Pinus tabulaeformis Carr and Ulmus pumila contented more than Pinus radiate and Cupressus chengiana S.Y.Hu;Cupressus chengiana S.Y.Hu contented the least. As to prolineon,Pinus tabulaeformis Carr accumulated the most,next was Pinus radiate,Ulmus pumila and Platycladus orientalis.Cupressus chengiana S.Y.Hu was the lowest.As to dissolubility protein content,Pinus radiate and Platycladus orientalis changed least and Cupressus chengiana S.Y.Hu changed most.3) The relations of the biomass and soil moisture contentCupressus chengiana S.Y.Hu accumulated more biomass at the higher soil moisture content,but Pinus tabulaeformis Carr,Pinus radiate,Ulmus pumila and Platycladus orientalis accumulated more biomass at the lower soil moisture content.According to root cap,Pinus radiate accumulated biomass mainly in the root.Pinus tabulaeformis Carr and Platycladus orientalis accumulated mainly in the stem and leaf.Ulmus pumila assigned evenly.In the high moisture content gradient,Cupressus chengiana S.Y.Hu accumulated biomass in the branch and leaf;in low moisture content gradient,it accumulated in root.