Study Of The Introduction And Cultivation Techniques Of The North American Oaks

The performances of 12 oak species and 38 provenances and families(including 5 seed sources of Quercus coccinea, 6 families of Q. rubra, 10provenances and families of Q. phellos, 4 seed sources of Q.nigra, 2 seed sources ofQ. falcate, 4 seed sources of Q. velutina, 2 seed sources of Q. macrocarpa, and 5mixed seed sources of Q. stellala, Q. alba, Q. robu, Q. nuttallii, Q. palustrisrespectively) introduced from North America have been investigated in JiangsuProvince, China, from 1998 to 2006. Test characters included the seed size and weight,germination percentage, seedling height and main stem diameter, seasonal growthrhythm and phonological phase in seedling phase and the survival rate, height, basaland breast stem diameter, crown diameter, leaves color variance in sapling phase atdifferent test sites. Moreover, under greenhouse conditions, 2-year-old sapling ofQ. nuttallii and Q. falcate were subjected to a flooding stress and subsequent growthand physiological responses were evaluated. The vegetative propagating methods bycutting and grafting in four exotic oaks were tried. The result indicated that:(1) The characters of seeds and seedlings were significantly different among oakspecies and provenances of each species. Seed size: Q. macrocarpa, Q. nuttallii, Q.rubra, Q. robur, and Q. alba were the biggest ones, Q. coccinea, Q. velutina and Q.palustris were middle types and Q. phellos, Q. nigra, Q. falcate, and Q. stellata werethe least. Germination time: Q. stellata (LA source) and Q. velutina (IA and MOsource) were the earliest, and the secondary species were Q. macrocarpa (IL source),Q. falcate (AR source) and Q.velutina (ON source) and all of the Q. nigraprovenances were the latest to germinate. Germination percentage: The germinationrate of Q. velutina (MO source) seeds was the highest, and Q. nigra (TX source) andQ. macrocarpa (MT source) were the least. 1-year-old seedling growth (height andmain stem diameter): The seedling growth condition of Q. nuttallii, Q. phellos and Q.robur were the best and Q. velutina, Q. rubra, Q. cocciea, Q. palustris and Q. albawere the worst, while the condition of Q. falcat, Q. nigra, Q. macrocarpa and Q.stellata was the middling.(2) The annual height growth rhythm of 8 exotic oaks seedlings growing incontainer was observed. Our results showed that the shoot growth flush had only oncein Q. velutina, Q. rubra, Q. cocciea and Q. macrocarpa, 3 or 4 times in O. falcat andQ. stellata, 4 or 5 times in Q. phellos and Q. nigra. Their growth period of one seasonwas classified into three types including short, middle and long period type. The monthly growth of seedling height in Q. falcat, Q phello and Q. nigra can be fittedwith "S" curves and simulated by Logistic Equations. Q. rubra and Q. coccieashooted twice in the sapling phase and the flush was episodic. Q. phellos sapling hadover four or five times shooting and the flush was continuous. According to dusteranalysis of sequential sample, the monthly height growth rhythm was divided into 3growth phases of fast (from16 Apr to 30 Apr), slow (from 1 May to 15 July) and stop(from 15 July to 30 Sep) in Q. rubra and Q. cocciea, and fast prophase (from 16 Aprto 30 Apr), fast (from 1 May to 31 Aug) and slow (in Sep) in Q. phellos. Thephonological phase: leaves expansion Of Q. phellos was earlier than that of Q. coccieaand Q. rubra was the latest in spring. Leaves colors of Q. cocciea changed earlier thanothers and Q. phellos was the latest in autumn. Leaves of Q. rubra fell earher thanthat of Q. phellos and Q. cocciea.(3) 2-year-old saplings of Q. nuttallii and Q. falcat can tolerant water stress for75d. In 20cm deep-drown treatment, Q.falcat saplings began to die after 49d and only30% survived after 75d, while Q. nuttallii was still alive. Under these two conditions,sapling height growth, mass, net photosynthetic rate and leaf stomatal conductancewere significantly reduced in Q. falcat and indistinctive in Q. nuttallii. The roots vigorand the activity of the ADH in roots declined in Q. falcat by two treatments. The rootsvigor was indistinctive by water saturation treatment and significantly reduced by20cm deep-drown in Q. nuttallii, however, the activity of the ADH in root increaseddramatically in later stage by 20cm deep-drown, wich suggested that theself-adjusting ability of Q. nuttallii in response to water stress was strong.Comprehensive analysis proved that flooding tolerance ability of Q. nuttall (about 75d)was stronger than that of Q. falcat (about 20d).(4) Within all the exotic oaks, the growth and survival rate of Q. nuttallii, Q. nigraand Q. phellos were the most. In Southern Jiangsu hill sites, the average annual growthof 3 -year-old tree of Q. nuttallii was 1.24m(high) and 2.85cm(collar diameter), that of6-year-old tree of Q. nigra was 0.96-1.20 m(H) and 1.36-1.55cm(C.D) and that of8-year-old tree of Q. phellos was 0.75-0.91m(H) and 1.17-1.62cm (C.D). The growthrate was approaching or exceeding that of native oak tree Q. acutissima (ck1) and overtexceeding that of Q. variabilis(ck2), Q. chenii(ck3) and Q. glauca (ck4). Q. falcat wassecondly and the growth rate exceeded ck2, ck3 and ck4. Q. macrocarpa, Q. coccieaand Q. alba had the slowest growth rate and less survival. In fall, the leaves of 7 oakspecies including Q. coccinea, O. rubra, O. falcate, Q. palustris, Q. alba, Q.nuttalliiand Q. nigra changed into red color and leaves of Q. pkellos grew yellow or orange.The leaves of native oaks changed into filemot color and the landscape value was low. (5) Based on growth, adaptability and ornamental characteristics, O. nuttallii, Q.nigra and Q. phellos were selected for timber and landscape trees because of their fastgrowth rate, and Q. falcate, Q. coccinea, Q. rubra and Q. palustris were selected forlandscape trees because of their excellent red leaves in the autumn. Introduction ofNorth American oaks in Jiangsu area should be focused in Q. nuttalli, Q. nigra, Q.falcata and Q. phellos that are distributed in subtropics of Southeast Unite States withthe similar climate.(6) Different provenances and families of each oak species also had significantvariation of growth and adaptability. There were preferable potential for choosingseed source. According to the synthetic index value, 2 elite provenances No.9818 andNo.9817 were selected from 9 provenances and families of Q. phellos. The averageheight and collar diameter of 8- year-old tree increased 10.6% and 13.9% respectivelycompared with the mean value of trees in northern Jiangsu hill site. The growth rate ofQ. phellos (height and diameter) was significantly different from 1 age to 8 age trees.(7) The cutting rooting rate of Q. phellos, Q. nuttalli, and Q. nigra branch tips of1-year-old sapling were 70%, 52.0% and 22.0% respective with the optimal treatment,but no rooting from Q. phellos branch of 6-year-old sapling. The rooting ability of Q.phellos was better than that of Q. nuttallii and Q. nigra. Rooting rate of the cuttingstreated with ABT₆ was higher than that of NAA +V_B2 and NAA. The field graftingsurvival rate of Q. nuttallii, Q. nigra and Q. coccinea were 47.5%-61.2%. 47.5% and13.3%-15.0% respectively with rootstock of Q. acutissima after 2 month, but thesurvival rate declined in the end of one season. The bench grafting in spring wasbetter than budding in autumn.(8) Main technologies for raising oak seedlings in the nursery: Maintain acornsmoisture level to keep seed vigor; Store acorns at 2-5℃and stratification for breakingseeds dormancy; Seed soaked in warm water (40℃) for 24h and treated with GA₃ for5h before sowing for increased germination speed. Planting acorn deep (2-3cm) andsidelong lying for the radicle and embryo better emerged; Undrecutting roots toincreased lateral roots of seedling; Transplanting seedlings in early spring or lateautumn.