Seedling raising techniques of 2-year-old container seedlings of Minnan and Zhengnan

Seedling raising techniques of 2-year-old container seedlings of Minnan and Zhengnan

In order to increase the species of Lauraceae in Anhui Province, protect and increase forest plant germplasm resources, enhance biodiversity and promote sustainable forest development, we purchased Minnan and Zhengnan seeds from Fujian from 2013 to 2015. the experimental study on introduction and domestication was carried out in the nursery of Chawan Forest Industry Mining Farm in Qimen County, and the 2-year-old container seedlings of Minnan and Zhengnan were successfully planted in Yilin Mountain Farm.

1 the natural conditions of the introduction site

Qimen County is located at 117 °37 °25 "E & M 29 °51 °47" N; the geomorphology is mountainous and hilly, with an elevation of 160 °220 m, and the terrain is relatively flat; the climate belongs to subtropical monsoon climate, with an annual average temperature of 15.7 ℃, an extreme maximum temperature of 41.5 ℃ in July, an extreme minimum temperature of-13.2 ℃ in January, an annual average relative humidity of 81%, an annual average daily sunshine hours of 1 809.7 h, a frost-free period of 239 days, and an average annual precipitation of 1 790.3 mm. The soil is mainly yellow soil and yellow brown soil developed from phyllite and granite. The content of organic matter is moderately high and the pH value is 5.5-6.5.

2 introduction and test methods of tree species

2.1 introduction of tree species

Minnan (P.bournei) and Zhengnan (P.zhennan) belong to valuable tree species of Lauraceae, which are valuable materials for construction, furniture and craftsmanship.

2.1.1 Minnan

Minnan, a large evergreen tree plant of Lauraceae and Phoebe, is endemic to China and is a national Ⅱ key wild plant [1]. It is distributed in the evergreen broad-leaved forest of Zhejiang, Fujian, Jiangxi, Guangdong, Guangxi, Hunan, Hubei, Guizhou and other provinces. It has been listed in the list of rare and Endangered plants in China and the Red Book of rare plants in China [2]. With its fragrant and durable wood and beautiful texture, it is a good material for fine architecture, furniture, craft carving and shipbuilding.

Minnan seed 1 kg was purchased from Qingyuan Forest Farm in Zhejiang Province on February 26th, 2015. The seeds have been peeled and purified before they are purchased. The weight of one thousand seeds is 305 g, which belongs to medium seeds, and the purity is 95%.

2.1.2 Zhen Nan

Zhen Nan, a large evergreen tree plant of Lauraceae and Phoebe, is a national Ⅱ key wild plant. It is distributed in broad-leaved forests in hills below 800m above sea level in Hubei, Jiangxi, Zhejiang, Guizhou and other provinces. It is often mixed with Castanopsis tibetana, C.fargesii, C.sclerophylla, Choerospondias axillaris, Machilus thunbergii and so on. Its wood texture crisscross, smooth and beautiful, easy to process, for high-quality furniture, construction, flooring, interior decoration, carving, precision instruments, plywood panels and shipbuilding and other materials.

Zhen Nan seed 1 kg, February 26, 2015 Qingyuan Forest Farm, Zhejiang Province. The seeds have been peeled and purified before they are purchased. The weight of one thousand seeds is 278 g, which belongs to medium seeds, and the purity is 96%.

The seeds of Minnan and Zhengnan were stored and germinated with wet sand after being bought back. Before sowing, the river sand was screened by sieve. After picking up the larger stones, the seeds were disinfected with 50% carbendazim wettable powder and sown.

2.2 Test method

2.2.1 Seedling experiment

The experimental site is in the nursery of Chawan Forest Industry Mining and breeding Field in Qimen County. The nursery is leeward to the sun, the soil is loose, the thickness is medium, the character of fertilizer and water conservation is general, and the drainage and irrigation is good. The first crop is the medium sandy soil dryland where Liquidambar formosana seedlings are cultivated. In the nursery, 500 kg of organic fertilizer, 50 kg of compound fertilizer and 40 kg of hydrated lime were applied per 667m2. After leveling the plow and rake, the seedbed was made according to 120 cm in width and 30 cm in height.

Each tree species is divided into 3 plots: 20 grains per row, 30 grains per row and 40 grains per row, with an area of 1 m2 per row repeated three times, each with 5 rows of sowing, the first 5 rows covered with 1.5 cm thick metasequoia leaves, the second 5 rows covered with 2 cm thick wet soil, the third 5 rows covered with perlite and vermiculite (1 ∶ 1) matrix (hereinafter referred to as "matrix"), the fourth 5 rows covered with Metasequoia glyptostroboides leaves, and the fifth 5 rows covered with wet soil. and so on. Sowing and mulching was completed on March 26, 2015, and 24% ethoxyflurane (fruit EC) herbicide was sprayed on the seedling bed on March 30 to control weeds in the nursery at seedling stage.

At the seedling stage, weeding, fertilization, irrigation and pest control were carried out according to the seedling management measures of broad-leaved trees such as Liquidambar formosana. Minnan and Zhengnan are tropical evergreen broad-leaved tree species. 1-year-old and 2-year-old seedlings are cultivated in Qimen County, and their seedlings may have the problem of overwintering frost injury. In order to reduce the cold wind directly invading the leaves and tender shoots of seedlings, in mid-October, we used double-layer "two-needle" sunshade net around the nursery to cover and protect the experimental seedlings.

2.2.2 observation of seedling growth index

In order to grasp the law of seedling phenology and growth and development, the phenology of seedling germination, leaf spreading and shoot drawing were observed and recorded after seed germination. 30 healthy seedlings were randomly selected as fixed standard plants in each plot. On the 30th (or 31st) of each month, the tapping (leaf spreading) and seedling height were measured with steel tape measure, and the ground diameter was measured with Vernier caliper, and the observed data were collated and analyzed.

3 test results

3.1 seed germination rate and seedling preservation rate

The seed coat of Minnan and Zhengnan is dense, and the wet sand storage treatment can break their dormancy very well. The emergence stage of the two kinds of nanmu is basically from seed germination to seedling bud emergence. The seed germination rate is affected by the seed size of the mother tree, the time of seed harvest, the methods of treatment, storage and sowing, the thickness of mulch, the weather and temperature after sowing, the environment of the small area of the nursery and artificial management measures. As can be seen from Table 1, under the conditions of suitable temperature, soil moisture and proper management after sowing, the germination rate and seedling preservation rate of Minnan and Zhengnan seed nursery can be maintained at a high level, which are 87.2%, 85% and 75.8%, 73.2%, respectively.

The results showed that the mulch of Metasequoia glyptostroboides leaves, wet soil and substrate had no significant effect on seed germination, but hindered the emergence of mulch from seedlings. After Rain Water, the leaves and wet soil of Metasequoia glyptostroboides become solid, affecting the buds to drill out of the ground, and at the same time, it is easy to absorb a lot of heat, which is easy to cause sunburn of seedlings at noon. Therefore, Minnan and Zhengnan are covered with substrate after sowing, and the effect is the best.

Table 1 Statistics of seed germination rate and seedling preservation rate of Minnan and Zhengnan

3.2 Phenology at seedling stage

After the seeds of Minnan and Zhengnan were sown, the seeds began to be unearthed on April 18, and the emergence peak was from April 25 to May 21, during which 85% of the seeds germinated, and the emergence on May 28 basically ended. It can be seen that the emergence period of Minnan and Zhengnan seeds is basically the same as that of Yunnan Nan seed sown in Shuanghekou nursery in Qimen County in early March 2013 [3].

The height growth of Minnan and Zhengnan seedlings began when the seedlings were unearthed and lasted until late October. After late October, the temperature gradually decreased, the height growth of the aboveground part stopped, the stem gradually completed Lignification, and entered the dormant period, and the growth of underground roots could be postponed to the end of December [3].

3.3 Seedling growth

3.3.1 height growth

The height growth process of one-year-old seedlings of Minnan and Zhengnan can be divided into three periods: the early growth period before the end of May, the fast-growing period from June to September, and the seedling hardening period in October. The height growth index of seedlings in each period is shown in Table 2.

Table 2 Statistics of average height growth of one-year-old seedlings of Minnan and Zhengnan in different periods

It can be seen from Table 2 that the height growth of one-year-old seedlings of Minnan and Zhengnan is slow, in which the annual height growth of Minnan is 17.7 cm, and the height growth in the initial growth stage, fast-growing period and seedling hardening period accounts for 23.7%, 57.1% and 19.2% of the total annual growth, respectively. On the other hand, the height growth of Zhen Nan is slower than that of Minnan, and the annual height growth is 17.2 cm, which is 97.2% of the total growth of Minnan. The height growth in the initial growth stage, fast-growing period and seedling hardening period accounts for 22.7%, 59.3% and 18.0% of the total annual growth, respectively. The slow growth of seedling height may be related to the low temperature in summer, the large temperature difference between day and night, the former stubble of seedling nursery is Liquidambar formosana, poor soil fertility and other factors, which need to be further studied.

3.3.2 diameter growth

The basal diameter growth process of one-year-old seedlings of Minnan and Zhengnan can also be divided into three stages: the initial stage, the rapid growth stage and the late growth stage (the diameter growth is postponed to the end of November). The annual basal diameter growth is 0.29 cm. The growth index of seedling diameter in each period is shown in Table 3.

During the whole growing period, the growth of ground diameter of one-year-old seedlings of Minnan and Zhengnan was relatively small, which was not only related to the site of seedling nursery and air temperature, but also closely related to the growth of seedling height.

Table 3 Statistics of average diameter growth of Minnan and Zhengnan seedlings in different periods in one year

3.4 Cold resistance of seedlings

Before and after the arrival of Frosts Descent from October to November, Minnan and Zhengnan were characterized by the fact that the seedlings in the bare land were vulnerable to cold wave attack and frost injury. the degree of freezing injury is related to the location of nursery site, soil fertility, seedling water and fertilizer management and whether to take anti-freezing measures before and after Frosts Descent. It can be seen from Table 4 that the one-year-old seedlings of Minnan and Zhengnan covered with "two-needle" double-layer sunshade net, a small number of upper leaves of seedlings and a small amount of unlignified young stems suffered frost injury to varying degrees in the experimental site (9 m2). The number of frozen leaves accounted for 3.5% of the total number of plants, of which the number of young stems accounted for 27.8% and 31.6% of the total number of frozen leaves. It can be seen that under the premise of taking protective measures, 1-year-old seedlings of Minnan and Zhengnan can survive the winter safely.

4 summary and discussion

Table 4 Frost injury statistics of leaves and tender stems of one-year seedlings of Minnan and Zhengnan

Minnan and Zhengnan are precious evergreen tree species in the middle subtropics, with excellent materials and a wide range of uses, and have great potential for development. In order to alleviate the contradiction between greening, beautification and wood supply and shortage of precious tree species in China, experimental studies on introduction, domestication, seedling cultivation and afforestation of six kinds of nanmu, such as Nan, Minnan, Zhennan and Zinan, have been carried out in Qimen County in recent years.

The main results are as follows: (1) under the premise of suitable seed treatment and storage conditions, good soil site, temperature and humidity and good management at seedling stage, the germination rate and seedling preservation rate of Minnan and Zhengnan seed field can reach a higher level. Therefore, Qimen can introduce and cultivate 1-year-old seedlings such as Minnan and Zhengnan, and plant them in the woodland after thinning of Cunninghamia lanceolata.

(2) Minnan and Zhengnan began to sprout 60 days after sowing, the emergence peak was from late April to May 21, the emergence basically ended in late May, and entered the high growth period after June. In the seedling emergence period, fine management should be strengthened.

From seedling emergence to the end of May is the early stage of height growth of Minnan and Zhengnan, the fast-growing period from June to September, and the hardening period of seedlings in October. The annual height growth of Minnan was 17.7 cm, and that of Zhengnan was 17.2 cm. The diameter growth of 1-year-old seedlings of Minnan and Zhengnan was also divided into early growth stage, fast-growing stage and late growth stage, and the annual ground diameter growth was 0.29 cm. The slow growth of seedling height and ground diameter may be related to low temperature in summer, large temperature difference between day and night, thin soil layer, poor ability of soil water and fertilizer conservation and intensive management at seedling stage. It is very important to strengthen the early management of the nursery, increase the application of organic fertilizer, promote the early height and diameter growth of seedlings, and ensure the Lignification of seedlings in the right period.

(3) before the arrival of Frosts Descent, the one-year-old seedlings of Minnan and Zhengnan should be protected by covering double-layer sunshade net, which can effectively reduce the freezing injury of seedlings and ensure their safe overwintering.

(4) in the middle and later stage of the fast-growing period of one-year-old seedlings of Minnan and Zhennan, spraying potash fertilizer and special antifreeze for seedlings were adopted to exercise the cold tolerance of the seedlings, promote the Lignification process, improve their cold resistance and anti-freezing ability, and ensure that the seedlings survive the winter more safely. it remains to be further studied.