| Sterculia lychnophora Hance, of the Sterculia Linn genus, Sterculiaceae family, is a tall deciduous tree living in sub-tropical forest ecosystems in East and Southeast Asia. In Vietnam, S. lychnophora is mainly distributed in natural second-growth forests from the North-central to the Southeast of the country, including highland areas. It is an endangered plant. S. lychnophora plays a very important role in forest ecosystems. Simultaneously. We performed a nationwide survey of S. lychnophora distribution, measured phenology and comparative analysis of S. Lychnophora population. We then took representative S. lychnophora populations in natural evergreen broad-leaved and semi-deciduous Southeastern forests, described their stand characteristics, measured its population characteristics, and found the main ecological environmental factors affecting S. lychnophora seedlings and saplings. We then tested these characters in nursery conditions, and found optimal growth conditions and tolerance ranges for seedlings. The main conclusions are as follows.(1) S. lychnophora population is mainly distributed in the sub-tropical evergreen broad-leaved forest, sub-tropical native secondary evergreen broad-leaved forest, and natural secondary moist semi-deciduous broad-leaved forest of natural parks and nature reserves, and a little forest farms which are scattered in North Central, South Central, Southeast, Highland and Southwest regions. In 2014, nationwide S. lychnophora stand area was about 26.000,0 hm2. S. lychnophora stand distribution in these five regions is uneven. The southeastern region area of S. lychnophora stand has the majority of trees with 15.190.1 hm2 (58.8%), and they are mainly distributed at Dongnai Natural and Culture Reserve and Cattien National Park. The area of S. lychnophora stands in different three forest dominance levels are variable. The area of S. lychnophora high forest dominance level (D3) is 5959.7 hm2 (23.1%); the area of medium forest dominance level (D2) is 10908.8 hm2 (42.26%) and area of low forest dominance level (Di) is 8943.2 hm2 (34.5%). The quality of S. lychnophora forest stands in Vietnam are not high. In recent years, S. lychnophora populations are facing a crisis due to negative human interference, such as cutting mother trees for fruit, and taking immature fruit which is common in Highlands and South Central regions are particularly serious. (2) The phenological period of S. lychnophora in different regional have a differences. In the South Central region most phenological phase starts very early, and in North and South Central flowering, fruiting, its fruit ripening and falling of S. lychnophora are 30-40 days earlier than the other regions. Germination period of S. lychnophora is shorter, starting on July 5th to 19th on average. Leaf expansion period annually starts from July 10th to August 20th, and approximately continue to June 10th next year. Leaf discoloration period annually begins on May 10th-25th on average, and continue 27.6 days. Defoliation begins on June 10th-25th annually, and continue 17.2 days. Flowering period is very short which is about 9.2 days on average and begins on April 8th to 29th. Fruiting period starts on April 10th-30th annually, and continue about 45.5 days. Every June 5th to 15th. S. lychnophora fruit begins to drop, and continue about 13.6 days. (3) Research on species diversity characteristics of different forest dominance levels, the results shows that:In the study area, species composition of different S. lychnophora dominance secondary forest is relatively abundant, over a total of nine plots 39 families,83 genus and 130 kinds were found; the endemic, rare and endangered species have a total of 16 species; five endemic species are from Dongnai region; common main associations have 4 types; S. lychnophora is one of the rare and endangered plants in Vietnam. S. lychnophora in the forest stands are a dominant species and also a constructive species, their the important value changes in the range of 15.41%-36.81%. Diversity indices of S. lychnophora in the different forest stands which performed D2 is greater than D1 and D3. The regeneration layer of tree species in different S. lychnophora forest stands dominance has a total of 31 families,62 genus and 77 kinds. Importance value of S. lychnophora sapling is the highest. The average value of species diversity indices expressed as D3> D2> D1 in observed forest stands.(4) Research on diameter distribution of trees in different S. lychnophora forest stand dominance levels, the results shows that:Diameter distribution of trees in three S. lychnophora forest stand dominance levels are obvious differences, and they are mainly unimodal and approximate decreasing distribution. In D3 forest stand, the number of trees diameter class basically is close to a unimodal distribution curve. In D2 and D1 forest stands the diameter distribution is a typical distribution of anti-approximate "J" distribution. Forest stand density decreasing order is from D2, D3 to D1 forest stand and diameter distribution range D3 is greater than D1 and D2 forest stands.(5) In different forest stand dominance levels, diameter of S. lychnophora was the best on D3, was greater than D2 and D1 stand, and is the dominant species. The diameter distribution curve of S. lychnophora presents a slowly decreasing distribution. Its diameter distribution presented an inverted "J" type.(6) In different forest dominance, spatial distribution pattern of S. lychnophora seedlings and saplings was an aggregated distribution pattern. Statistically random deviation of the F test showed:Iwao's (results meet the a> 0 and ??1) and Taylor's of regression models (results meet the a> 1 and b?1) so spatial distribution pattern of S. lychnophora seedlings and saplings was an aggregated distribution. This implies mild competition, but its less competitive. That has not reached the extent of making populations self-thinning to uniform distribution or random distribution, which meant species in populations were stably coexisting.(7) The effect of forest dominance levels to different S. lychnophora regeneration saplings phases was remarkable. Appearance frequency (Ey) of S. lychnophora sapling the first phase in low forest dominance level (D1) was greater than medium forest dominance level (D2) and high forest dominance level (D3); Ey of the second phase in D1 is less than D3, but and had no significant difference; Ey of the third phase in D1 is less than D2 and D3. Ey of the first phase S. lychnophora sampling in forest the first canopy density level (Ca1) is less than the second (Ca2) and fourth (Ca4), but more than forest the third canopy density level (Ca3); Ey of the second and third phases in Ca1 is greater than Ca2 and Ca3, but less than Ca4. Ey of S. lychnophora sapling was related to the biological and ecological characteristics. S. lychnophora sapling growth phases requires different light intensity. In regeneration saplings phase S. lychnophora could be fundamentally adapted to high canopy density of forest stand and are shade-tolerant.(8) The gaps characteristics in the different forest dominance levels had remarkable effect to characteristical of S. lychnophora regeneration saplings phases. The survival amount of S. lychnophora populations in the Di was less than D2 and D3. Mortality rate of S. lychnophora sapling from the first phase (SL1) to SL2c phase in D1 and D2 forest stands was higher than the D3 and its rate increased faster. When age of S. lychnophora phase reached SL3 the mortality rate was slow and stable. Then it continued to grow and later turned into the dominant tree layer. Spatial distribution pattern of S. lychnophora saplings belongs to an aggregated distribution. Spatial distribution of all populations in the D1 and D2 forest stands conformed to an aggregated distribution type, but distribution pattern of S. lychnophora saplings in D3 forest stand began to appear uniform type of tendency. Circumstances of S. lychnophora saplings under forest gaps in different forest dominance levels were not identical. Along with the increasing area of gaps, the density of S. lychnophora regeneration saplings changed accordingly. When the area of gaps range from 401 to 500 m2, most of the saplings grew best, and with increasing area the density of saplings reached a peak and then began to decrease. Although S. lychnophora saplings are shade-tolerant species and require a lower light intensity, but too small an area of gaps and too week light intensity also are not conducive for sapling development.(9) The characteristics of herbaceous and shrubs also have an effect on density of S. lychnophora saplings. Large shrub cover is not conducive to survival of S. lychnophora saplings. The density of saplings under shrub cover from the first level to fifth level in the forest dominance levels monotonically decreased?, the average density distribution was D1>D3>D2. The number of S. lychnophora trees and different shrub height levels had a significant positive correlation, and shrub cover and height levels with saplings density were also significantly correlated. Increasing shrub height and gradually declining cover level were favorable conditions for S. lychnophora survival. On the contrary it would be adverse for sapling survival and resulted in reduced density of saplings. In the herb cover lower levels (such as Un, Sol, Sp level) density of SL levels was higher, and an increase in herb cover led to a decreased sapling density. Sapling density showed a negative correlation with herb and shrub cover, that is the number of 5. lychnophora was less in forest stands have a herb and shrub cover were a higher.(10) Appearance frequency in three phases of S. lychnophora saplings'natural regeneration was related with forest dominance levels, surface soil moisture, pH value, total nitrogen, total phosphorus and total potassium. This relationship could be simulated by Logit Gauss models. Different height of S. lychnophora required different surface soil moisture, pH value, total nitrogen, total phosphorus and total potassium. The optimum of SL1 surface soil moisture, pH value, total nitrogen, total phosphorus and total potassium were 68.2%,4.6,2.351g · kg-1,0.292 g·kg-1 and 13.088 g·kg-1 respectively. And optimum of SL2 surface soil were: moisture was 72.8%; pH value was 5.1; total nitrogen element was 3.023 g · kg-1; total phosphorus element was 0.338 g · kg-1 and total potassium was 15.104 g · kg-1. The optimum of SL3 surface soil moisture, pH value, total nitrogen, total phosphorus and total potassium were 73.3%,5.5,3.347 g · kg-1,0.380 g · kg-1 and 15.581 g · kg-1 respectively. Along with growing age of saplings, the demands of surface soil moisture, pH value, total nitrogen, total phosphorus and total potassium gradually increased. Changes in forest types status will affect changes of forest ecological factors, and thereby affect occurrence and development process of different saplings phases.S. lychnophora saplings regeneration in D3 was better than D2 or D1, and most of the frequency of occurrence of saplings remained in the D3> D2> D1. Forest high dominance or high stability had more suitable environment for S. lychnophora saplings.(11) Diameter classes of S. Lychnophora mother trees had a great impact on the seed germination rate. Mother trees with diameter of 50-60 cm could provide best quality seed and its germination was very fast and relatively uniform.2 days to 5 days after seeding most of the seeds began to germinate, seedling grew healthy and with blue roots. Average germination rate of S. lychnophora seeds stored at 0 ? in the refrigerator were higher than at-5 ? or at room temperature. As storage time extended, S. lychnophora seeds germination rate and its vigor gradually decreased. If the seeds germination rate were controlled at 50%or more, the storage time at-5 ? in the refrigerator or under normal temperature, could not exceed 180 days. If it was under 0 ? in refrigerator, the storage time could not exceed 300 days. At different temperatures, average seed germination rate reached 80.17%after 30 days of storage, and decrease to only 25.75%after 360 days of storage.(12) Shading intensity on growth indicators and viability of S. lychnophora seedlings had an extremely significant effect.6 month old S. lychnophora seedlings need shade and shade trees. If shading intensity could be controlled between 50%and 75%, growing diameter, height and biomass could be promoted and high quality seedlings could be provided. Too much shade was bad to S. lychnophora seedling growth and development.(13) NPK fertilizer concentration from 0%to 6%levels on S. lychnophora seedlings had a significant effect. S. lychnophora seedlings 6 months old need NPK fertilizer. Optimum of NPK fertilizer for diameter of S. lychnophora seedling 6 months old growth is 3.38%, optimum of NPK fertilizer for height growth is 3.23%. NPK fertilizer concentration for S. lychnophora seedlings normal development is 2%-4%, and NPK fertilizer concentration 3.2%-3.4%is the most favorable for seedling growth and development. NPK fertilizer high concentration (5%-6%) was not conducive to seedling growth and harm for seedlings, due to cost increases associated with higher fertilizer application as well as soil and water pollution.(14) Under the treatment phosphate fertilizer (P) concentration of 0%to 6%S. lychnophora seedling diameter and height growth had a different effect. S. lychnophora seedlings need lower phosphate fertilizer concentrations, grow well at processed phosphate fertilizer 1%-3%, grow weakly at 4%-6%and grow the best in processed 2%. Optimum of phosphate fertilizer for diameter growth was 2.6%and tree height was 3.3%. In nursery need control concentration content of phosphate from 2.4%to 3.3%was the most reasonable. When concentration of phosphate fertilizer was too high seedling growth was weak and sometime even easily died, and destroy the water and soil environment, increase production costs.(15) S. lychnophora seedlings 6 months old require high content of manure (Fen), manure conducive to diameter, height of seedlings growth and improved biomass. Manure content controlled from 12.4% to 15.4% is most appropriate, optimum of manure content for diameter growth was 15.4%, and for tree height was14.5%. Manure can effectively improve the material of breeding, mainly in the increased porosity of the soil, increased water storage capacity, improve nutritional components, increase soil fertility, etc. Manure can reduce the pollution of land and water resources. Especially note, when using old alluvial soil and forest podzolic soil types for seeding one needs to use reasonable amounts of manure.(16) Combine two kinds of Manure and NPK fertilizer with growth index of S. lychnophora seedlings 6 months old has a significant impact. Combine manure content from 15%-20% with NPK concentration from 1%to 3% will promote S. lychnophora seedlings the normal development. Among them, combine 20%of manure and 2%of NPK fertilizer to promote seedling development well, diameter of seedling in combine 20% of manure and 2.21% of NPK fertilizer was at best growth, and 20%of manure and 2.69% of NPK fertilizer to promote height of seedling growth was at the most.(17) The components of container matrix have a significant effect on the growth of S. lychnophora seedlings. Generally used 4 soil types were Yellow brown, Brown-red soil, Old alluvial soil and forest Podzolic soil as container matrix component. When container matrix using forest podzolic soil and Old alluvial soil need note that improve soil physical and chemical properties, by increased organic manure and NPK fertilizer to improve the fertility and nutrients of soil. When using Yellow red and Brown-red soil as a container nursery substrate needs to actively improve the porosity of the soil, improving its minerals and humus content, by applying manure and coconut powder peel can effectively improve soil viscous.(18) The size of container with diameter and height growth indicators of S. lychnophora seedlings had a significant impact. Along with size of the container becomes large, growth index of seedlings gradually increased. For a short period (6 months to 12 months) seedlings raising required container size 15 cm×18 cm (L3) was the most appropriate. For a long period (1.5 to 2 years) seedling raising need container size 18 cm × 22 cm (L4) was the most appropriate. |
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