【作者】 董雯怡；

【导师】 李吉跃；

【作者基本信息】 北京林业大学 ， 森林培育， 2011， 博士

【摘要】 以毛白杨(Populus tomentosa Carr.)S86号为材料分别于北京林业大学和河北威县进行盆栽和大田试验,对水分和肥料进行控制,研究不同土壤水分、不同肥料与施肥水平耦合对毛白杨生长发育、光合特性、植株酶活性、养分含量等生理指标的影响,实现节水、省肥、提高水肥利用率、提高产量的目的。研究结果表明：(1)对毛白杨生长影响最大的是土壤水分,其中土壤水分对苗高、整株叶面积和生物量的影响居于首位,且有显著的正效应；其次是氮肥和磷肥,影响小于土壤水分。不同水氮磷耦合下,生物量与各生长指标呈正相关,其中和整株叶面积相关性最大,其次为苗高,最低的是地径,但各生长指标相关性均达到显著水平。据此可以通过各个生长指标来预测盆栽毛白杨苗期生物量的生长情况。在本试验条件下,土壤水分和氮肥对毛白杨生物量影响有明显的交互作用,而土壤水分和磷肥、氮肥和磷肥交互关系未达到显著。对水氮进行田间耦合试验表明,水氮耦合处理下毛白杨苗木各部位干重大小为茎>根>叶,茎干重约占总生物量的59.48%,根干重占总生物量的22.13%,叶干重约占总生物量的18.38%。低水条件下,低氮能促进毛白杨生物量的累积,中氮和高氮均使生物量下降；中水条件下,中氮处理较利于毛白杨生长,生物量达到最大；高水条件下,中氮处理能获得较大的生物量。不施氮和低氮条件下,水分增加不利于生物量积累,此时水分胁迫对生物量积累有一定促进作用；但在中氮和高氮条件下,水分增加促进生长,水分供应越充足,获得的生物量越大。(2)毛白杨苗木叶片净光合速率(Pn)对环境条件中的水肥变化较敏感,7月到9月,毛白杨苗木Pn逐渐升高,其峰值出现9月。不同月份蒸腾速率(Tr)的变化规律与Pn有所不同,叶片Tr在苗木生长的过程中呈先升高后降低的趋势,8月达到峰值。毛白杨苗木Pn与气孔导度(Gs)、Tr和胞间CO2浓度(Ci)呈极显著正相关,与叶片水分利用效率(WUE)和气孔限制值(Ls)呈极显著负相关。WUE与Pn、Gs、Ci、Tr均呈极显著负相关,而与Ls呈极显著正相关。不同水肥处理下,导致毛白杨苗木光合速率变化的主导因素是气孔限制因素,同时也存在由于叶片营养和水分失衡导致的叶片自身光合能力下降等非气孔限制因素。低水条件下,增施氮肥不利于Pn的升高,高氮条件下,Pn值最低；中水条件下,施用氮肥对Pn的增加有一定促进作用,氮肥施用过多,Pn值同样下降,低氮下Pn最高;高水条件下,高氮水平下Pn值高于中低氮水平,不施氮肥处理Pn值最低。无论将氮固定在何种水平下Pn随土壤水分的变化趋势一致,随着土壤水分的增加而增加,分别在高水下达到最大值。当氮肥固定在一定水平时,光补偿点(LCP)随着土壤水分水平的升高而成下降趋势,表明苗木在弱光下光合能力越来越弱,不能很好的利用弱光。当土壤水分固定在一定水平时,LCP在低氮和中氮下较高,表明这些处理光合能力较强,低氮和中氮处理较利于毛白杨苗木弱光下的光合作用。(3)水肥互作效应对水分利用效率和养分吸收有显著的影响,水肥耦合存在一定的阈值。各时期毛白杨苗木的瞬时水分利用效率呈先降低后增高的趋势,9月>7月>8月。6-10月,毛白杨叶片全N量呈现降-升-降的总体趋势,叶片含P、K量呈升-降-升的趋势。低水条件下,增施氮肥能提供植株的养分吸收能力；中高水条件下,氮肥的施入对植株养分吸收也有促进作用,但是氮肥施入量过大,会抑制养分的吸收。土壤水分与植株吸收养分密切相关,充足的土壤供水能显著提高植株养分吸收能力。中低水条件下,低氮处理毛白杨苗木叶片WUE较大,随着氮肥水平的增大,WUE降低,水分胁迫下,施入较多的氮肥会降低苗木叶片WUE；而土壤水分较充足时,不施氮处理叶片WUE最高。另一方面,水分对叶片WUE影响较大,其中,低氮条件下,中水WUE较高；中高氮条件下,水分越充足,WUE越高,高水时达到最大。(4)盆栽条件下,构建多目标决策模型,对目标函数应用计算机寻求最优解可得,当各因素水平编码值分别为：X](土壤水分)=1.27,X2(氮肥)=1.33,X3(磷肥)=0.56时,即相当于水分为田间持水量的73.9%,施氮量为4.48 g·plant-1,施磷量为1.67 g·plant-1时各响应变量能达到最优。田间条件下,综合水氮处理对毛白杨生长、生理特征、经济效益、水分利用率和肥料吸收量的综合评价可看出,W3N2处理即土壤含水量控制在田间持水量的70-75%,施氮肥为300kg·hm-2处理在毛白杨苗期田间管理中综合评价最好,有利于毛白杨生长,同时能获得较高的经济利润,而W1N0处理在生产中应该被淘汰。更多还原

【Abstract】 With Clone S86 of Chinese white poplar (Populus tomentosa Carr.) as test materials, we conducted a pot experiment in a gas-permeable greenhouse in a nursery of Beijing Forestry University and a field experiment in the experimental base in Wei County, Hebei Province, China. The specific objectives of this study were to quantify the coupling effects of soil water and fertilizer application on the physiological indexes inducing growth parameters, photosynthetic characteristics, enzymatic activity and nutrient contents of P. tomentosa seedlings, and to achieve the result of economizing water, saving fertilizer and increasing yield. By means of research, main conclusions are elicited as follows:(1) Soil relative water content (W) had the biggest impact on the growth of P. tomentosa seedlings. All the W, nitrogen application (N) and phosphorus application (P) treatments had obvious positive effects on height growth, leaf area and biomass yield with the size sequence of W>N>P. Correlations among the growth parameters of P. tomentosa seedlings subjected to different combinations of W, N and P treatments showed that biomass yield was positively correlated with the other growth parameters and the correlation coefficient of BY and LA was the highest, next was height growth and finally was basal diameter. A significant positive correlation between leaf area and height growth or basal diameter was also found. Therefore, the biomass yield of P. tomentosa seedlings can be predicted with the values of growth parameters.There were significantly positive interaction effects of W×N on biomass yield of P. tomentosa seedlings, whereas the interaction effects of W×P and N×P were not significant. The field experiment of interactions between W and N indicted that stem had the heaviest dry matter, next was root and last was leaf, where the proportion of dry weight of stem, root and leaf in total biomass yield were 59.48%, 22.13% and 18.38%, respectively. At lower W levels, there was a higher growth and production with the lower levels of N but not with medium or higher levels. At medium W levels, the highest biomass yield could be obtained at medium N levels. At higher W levels, there was a higher growth and production at medium levels of N. Meanwhile, biomass yield of seedlings was decreased with W increasing at lower N or non-N levels and certain water deficit could improve plant growth. At medium or higher levels of N, biomass yield of seedlings was significantly increased with W increasing and the higher W levels, the greater biomass yield.(2) Net photosynthetic rate (Pn) in the leaves of P. tomentosa seedlings was sensitive to different combinations of W, N and P treatments. A progressive increase in Pn of the seedlings was found from July to September and the peak value found in September. Differing from Pn, the variation trend of transpiration rate (Tr) first increased and then dropped with time and the peak value of Tr was obtained in August. There was an obviously positive correlation between Pn and stomatal conductance (Gs),Tr or intercellular CO2 concentration (Ci) but highly negative correlation between Pn and water use efficiency (WUE) or stomatal limitation (Ls). And, there was an obviously negative correlation between WUE and Pn, Gs, Tr or Ci but highly positive correlation between WUE and Ls. Our results show that the inhibition of photosynthesis under different soil water and fertilizer treatments was mainly attributed to the stomatal factors and also due to nonstomatal factors, that is, the suppression of chloroplast capacity to fix CO2 caused by the imbalances of nutrient and water contents in leaves.At lower W levels, the value of Pn was decreased with the increase of N levels and the lowest Pn was found at the highest N levels. At medium W levels, the highest value of Pn was obtained at medium N levels and over-N applications also decreased Pn. At higher W levels, there was a higher Pn at higher N levels than medium or lower N levels and the value was lowest at non-N level. Pn kept increasing with the increase of W levels under the N at any fixed level and there was the highest values of the three parameters at the higher levels of W. When N at a fixed level, light compensate point (LCP) signifying the photosynthetic capacity in low light decreased with W increasing, whereas the value of LCP was higher at medium or lower N levels.(3) The coupling effects of soil water and fertilizer applications on WUE and nutrient contents were significant and had certain threshold. WUE in the leaves of P. tomentosa seedlings initially dropped and then improved with time and the peak value of WUE was obtained in September. From June to October, the variation trend of leaf N content was a down-up-down sequence and leaf P and K contents were up-down-up.Specifically, increasing N application could improve the nutrient absorption capacity of seedlings subjected to lower levels of W. At medium and higher W levels, plant nutrient content was initially improved with an increase of N application but actually decreased under excessively high levels of N fertilizer, suggesting that soil water was closely related to the nutrient content and sufficient water supply can significantly improved the nutrient absorption capacity. As for WUE, at medium and lower W levels, the value of WUE in the leaves of P. tomentosa seedlings was higher with the lower levels of N. And, the value of WUE of seedlings subjected to non-N level was highest when soil water was sufficient. In contrast, there was a higher WUE with the higher levels of W at higher or lower N levels.(4) In the pot experiment, a multiple target decision model synthesizing relevant parameters was established to obtain the optimized combination. We concluded that the recommended combination of W, N and P for growers was W=78.1% of the field capacity, N=4.48 g plant-1, and P=1.67 g plant-1 (i.e. coded values of W, N and P factors were 1.55,1.33 and 0.56, respectively).In the field experiment, we conducted a comprehensive evaluation on plant growth, physiological characters, water use efficiency, fertilizer absorption amount and economic benefits of Populus tomentosa seedlings grown in field coupling affected by W and N. The results showed that W3N2 treatment (i.e. W=70%～75%, N=300 kg hm-2) was the best combination whereas W1N0 treatment should be eliminated in the field management.All these recommendations should help to achieve maximum growth potential of P.tomentosa seedlings, obtain high water and fertilizer use efficiencies and reduce the risk of nitrate pollution of groundwater in arid and semi-arid regions.更多还原