Studies On Growth Promotion And Relevant Mechanism Of Different Cultivation Measures On Poplar Clone107(Populus×euramericana Cv.’Neva’)

At present, Chinese poplar cultivation area is the largest in the world. Owing to thecharacteristics of high-quality, fast-growing and high yield, the poplar(Populus×euramericana cv.‘Neva’) has been planted largely in Shandong province. However,there is such problem of lacking scientific and effective management measures in practicalproduction, which results in the degradation of forest soil and the decrease of forestproductivity. To solve the problem as above, system research on poplar was carried outincluding key techniques of co-applied with manure, root pruning, irrigation and plastic filmmulching. The main results were as follows:1. Co-applied with chicken manure: In comparison to the N100treatment (100%ofnitrogen was provided by urea), the M30N70treatment (30%and70%of nitrogen wasprovided by chicken manure and urea, respectively) could significantly increase soil enzymeactivity, microbial biomass C and microbial biomass N contents. With the increase in theproportion of chicken manure, the total organic carbon content in rhizosphere soil increasedconsistently, while the active organic carbon content had a trend of first up then down. TheM30N70treatment also obviously decreased the pH value, enhanced the contents of availablenutrients and humic acid carbon, as well as the ratio of humic acid to fulvic acid. Co-appliedwith chicken manure was beneficial to root growth, which evidently improved the rootactivity, total absorption area and active absorption area. In addition, the total length, surfacearea, volume and tips number of root system in M30N70treatment were distinctly higher thanthe other treatment, and the nitrogen use efficiency was61.38%, achieving the maximumamong all the treatments. As a result, chicken manure co-applied with inorganic fertilizer,especially the M30N70treatment, had the best effect on poplar seedlings.2. Root pruning: The study was conducted to determine the effects of different rootpruning methods on three-year-old, four-year-old and five-year-old poplar. The results showed that the8-2treatment (eight times of DBH and two sides) significantly improved the growthrates of DBH, height and volume, with the maximal increase. The second was either10-2(tentimes of DBH and two sides) or10-4(ten times of DBH and four sides) treatment. But the6-2(six times of DBH and two sides) and6-4(six times of DBH and four sides) were obviouslyreduced compared to the CK treatment, especially the6-4treatment.With8-2root pruning method, the study was carried out to determine the effects ofcontinuous and intermittent root pruning on rhizosphere soil characteristics and growth ofpoplar. The results indicated that all root pruning treatment could significantly enhance notonly the root activity and the root exudates content, but also the contents of IAA, GA and ZTin root system, however, the ABA content was obviously decreased. Every root pruningtreatment also significantly increased the microbial population and enzyme activities in therhizosphere soil. What is more, they had evident promotion effects on poplar growth. Indifferent root pruning treatments, the T35treatment (root pruning on three-year-old poplar inthe third and fifth years) played the most significant role in improving the ecologicalenvironment and growth of poplar.3. Water-saving irrigation: The BI treatment (border irrigation) significantly weakenedthe water deep seepage in comparison with the FI treatment (flooding irrigation). With theincrease of soil depth, the root biomass decreased layer by layer and most of the rootsconcentrated in the0-40cm soil layer. Compared to the FI treatment, BI treatment couldreduce the root biomass by8.28%in the0-20cm soil layer, while increase by35.87%in the20-80cm soil layer, furthermore, the total root biomass increased by5.52%in0-80cm soillayer. At the same time, the nitrate nitrogen content increased markedly in0-40cm soil layer,but reduced significantly in60-100cm soil layer. In the80-100cm soil layer, the nitratenitrogen content was decreased by21.84%,20.24%and19.53%at7days,14days and29days after irrigation, respectively. Additionally, the BI treatment had the same promotioneffect as the FI treatment on the poplar growth rates of DBH, height and volume.4. Plastic film mulching: The WM treatment (white plastic mulching) had the betterwarming effect than the BM treatment (black plastic mulching), while had no significantdifference on soil water content. In the0-20cm layer, the WM and BM treatmentssignificantly increased the soil total porosity, capillary porosity and non-capillary porosity, however, the soil bulk density was visibly decreased. Plastic film mulching could significantlyincrease the contents of alkaline hydrolysis N, microbial biomass C and active microbialbiomass. The activity of catalase enzyme, invertase enzyme and polyphonic oxidase enzymewas also obviously improved, but the pH value, the contents of organic matter, total nitrogenand available P, as well as the urease enzyme activity were significantly decreased. With theincrease of soil depth, the effects of plastic film mulching on soil physio-chemical propertiesand biological characteristics become smaller and smaller. Besides, two plastic film mulchingmethods could significantly improve the poplar growth rates of DBH, height and volume.Moreover, the WM treatment could significantly increase the growth rates of DBH, height andvolume by10.95%,9.26%and8.77%compared with the BM treatment, respectively. Inconclusion, two different plastic film mulching treatments significantly ameliorated the soilphsio-chemical properties and improved the growth of poplar; however, the WM treatmentwas obviously better than the BM treatment.