| Located in the tropical northern rim of species differentiation, preserving the rich tropical rainforest species, Hainan Island is of great significance to China and the whole Southeast Asian flora. Tropical forests have rich species and complex ecological systems. The ravine system in the rainforest is formed to be a natural ecological system with unique diversity and azonality flora by long term erosion by rivers and waters, which is a typical special microhabitat and ideal place to study the species differentiation and diversity formation mechanism. Over the years, much attention has been paid to the shrubs and woods with ignorance to the epiphytes inside the forests.As the biggest epiphytic fern in the tropical rainforest, the bird’s nest fern(Asplenium nidus L.) Aspleniaceae plays important role in biodiverstity maintaining mechanism and attracted more attention around. With understanding and market demand for value of the bird’s nest fern as medicinal, vegetable and ornamental use, the collecting for wild ferns by people has threatened the survival of the forest as well as the fern. It is highly urgent to strengthen some study to enhance the preservation and conservation to the forest as well as the ferns. We took bird’s nest fern as the study object to emulate its habitat characteristics in the rainforest ravines, including the characteristics of the ecological environment, niche and host trees. Then we made analysis of the nutritious value as well as the value as vegetable. We further explore the suitable growing conditions by cultivation. These provided a more comprehensive understanding of the bird’s nest fern in the tropical rain forest in the position, function, growth characteristics, which also provided new theory and knowledge for tropical rainforest community ecology, canopy epiphyte ecology, ecology and resource of bird’s nest fern. We set up two plots in Bawangling Nature Reserve and Limushan Nature Reserve separately to make survey to the habitat at site, to make the nutritional ananlysis of the young leaves in the lab and to make experiments in the field and greehouse to find favorable growing conditions for extensive field plantation. Main results and conclusions are as follows.(1) The relationship between plants and conditions is one of the most essential characters of plant communities. The land form of a hilly area usually consists of various micro-landform units. The heterogeneous habitats created by spatial arrangement of those units may support richer species and more communities. Landforms are assumed to be one of the most principal and determinant factors affecting the vegetation pattern within a climatic region. In humid hilly regions, the habitats are influenced by water erosion, which varies in frequency and extent. We took Limushan and Bawangling natural reserves to set up two plots which were rich in epiphytic bird’s nest fern. According to the micro-landform theory, we classified the plots according to seven types of micro-landform units:(i) crest slope (CS);(ii) upper sideslope (US); (iii) head hollow(HH);(iv) lower sideslope (LS);(v) foot slope (FS);(vi) flood terrace(FT); and (vii) river bed (RB).Then we made analysis of survey data of epiphytic bird’s nest fern ravines in the rainforest by floristic geography, comparing the two plots of species similarity, as well as slope species characteristics in up and down slopes, and correlation of species richness with micro-landforms, the two plots distinction with contact. The results show that, the Bawangling and Limushan epiphytic bird’s nest fern-as the terrain, landforms, vegetation, species with higher similarities, including the relatively rich because of the epiphytic species of bird’s nest fern and other special valley environment special habitats independent from human disturbance, light, heat, water, temperature, humidity, soil contour heterogeneous habitat conditions interactions together form the variety in this region of the mid-to-low elevation valley rainforest ecosystem, formed a strange rainforest epiphytic bird’s nest fern main distribution is more concentrated. The characteristics of the terrain is the ups and downs of the terrain, larger changes, mainly the river, it was decided the bird’s nest fern reproductive manner closely related to water. Investigation of the distribution of the two through the bird’s nest fern valley rain forest, we can see the bird’s nest fern preferences600-750m altitude area of large trees in the ravine rain epiphytic species-rich, perennial high temperature and humidity’habitat generally similar.(2) Plant communities are classified and ordinated based on community characteristics. The amount of niche breadth and niche overlap can be good indicators of the structure and stability of the community. To understand the function and characteristics of the epiphytic bird’s nest fern in tropical rainforests, we surveyed communities with bird’s next ferns at two sites within Hainan Province in2011. Two-Way Indicator Species Analysis (TWINSPAN) and Detrended Correspondence Analysis (DCA) revealed14distinct plant communities in one hundred10m×10m quadrats, indicating that the communities were highly diverse. Bird’s nest fern has the greatest niche breadth, followed by Ervatamia officinalis Tsiang, Bischofia polycarpa and Wrightia pubescens, indicating that these species are important generalists in these communities The niche overlap of the bird’s nest fern community was found to be relatively small, indicating that the community is stable.(3) To make a survey to host trees of the bird’s nest fern in the Bawangling and Limushan ravine with rich valley rainforest species, we investigated the Bird’s Nest of fern epiphytes host tree species, height, diameter at breast height, number, combined with the growth characteristics of the bird’s nest fern, epiphytic height, leaf number, length, etc. and epiphytic index measured. The results showed that the bird’s nest fern has a certain degree of host specificity as for host tree species, diameter at breast height and height requirements. The bird’s nest fern like high temperature, high humidity, low light habitats, also like to grow at an altitude of600-750m ravine, in particular, tend to grow in the valley side of the ravine. Bird’s nest fern is not very specific to selection of the host tree, the valley humid habitats outside depends largely on a combination of factors of the host species, including the diameter at breast height, tree height, crown, bark texture, and so on. It can be said that the bird’s nest fern like tall trees, crown.smooth bark and tree fissures or wrinkles. The bird’s nest fern mainly distribute in trunk area of the tree which is in the central position of the canopy in the community, within5-10m range of hight showing aggregation distribution preference.(4) Conventional soil analysis method was adopted and quantitative and qualitative analysis were made to suspended soil from bird’s nest fern. The results showed that organic matter content is about66.84%, pH4.4, similar or above to the other indicators of the forest floor soil. Some of the indicators were even superior to the soils on the ground. Suspended soils is formed by bird’s nest fern absorbing litters from tropical rainforest specialization to soils rich in organic matter, and promoting the role of the maintenance and evolution of tropical rain forest biodiversity the rainforest matter and energy cycle.(5) In order to find the suitable media formula for the domesticated bird’s nest fern better growth in fields, some mix of media were tried to see the adapatability from epiphytic to field. The results showed that the bird’s nest fern prefers growing in the combination of cultivations as that mix of peatcoco coils,volcanic rock and sand. This could make a healthy and rapid growth of the bird’s nest fern with a favorable leaf quality.The results of present study indicated that, the tropical ravine of Hainan Island with the high temperature, high humidity, rain, shaded environment is the habitat characteristics of the bird’s nest fern. In the same geographical unit, the most important environmental factor which determines the distribution pattern of bird’s nest fern is water or moisture. The bird’s nest fern has no strict specificity to the species of epiphytic host tree, while it has preferences to the height, thickness and width of the hosts with no specificity to the barks of the hosts. The bird’s nest fern has a broad niche which indicates it employs a favorable living condition within the population of the sampled forest. The suspended soil in its roots is rich in organic and inorganic nutrient which can provide not only habitat asylum for other organisms but also nutrients for itself. One of the favorable artificial cultivation substrate for bird’s nest fern is the mixture of coco coils, volcanic rock, river sand and peat soil. Commensalism and asylum other biological is the characteristic of epiphytic bird’s nest fern in the tropical rain forest communities and other species. The epiphytic fern depends on such a rain forest ecosystem with complex structure. So it is of great need to conserve and enrich the biological diversity of the rainforest. The forest ecosystem also relies on the epiphytes of this type, therefore we must protect the nest fern as well as the tropical rainforest related. The results of this study enriches the theory of plant ecology, forest canopy community ecology, conservation biology, providing advice and reference for rational protection of the tropical forests, utilization and protection of bird’s best fern resources in Hainan island. |
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