Habitat-Building Function Of Nest Ferns In Hainan Tropical Rainforest National Park

In the forest ecosystem of the old tropical area,the nest ferns composed of Asplenium nidus and its related species rely on the rosette-like leaf structure to collect canopy litter,and form canopy humus with the decay of their own old tissues.Canopy humus has strong water conservation ability,which not only meets the needs of nest ferns,but also provides a very important surface-like environment for many organisms that are difficult to adapt to canopy exposure and drought,and becomes an indispensable shelter for them in the canopy.Hainan Tropical Rainforest National Park is the most well-preserved continental island tropical rainforest in China.It is helpful for us to fully understand the current situation of nest fern resources in the park,the characteristics of the constructed habitats,and the interaction between the constructed habitats and the canopy biological groups.It is helpful for us to have a deeper understanding of the interaction between canopy biota in tropical areas,as well as the formation and maintenance mechanism of tropical forest ecosystem diversity,and provide scientific basis for biodiversity protection in Hainan Tropical Rainforest National Park.Under the above background,this study evenly laid sample trees and quadrats in the tropical rainforest national park to investigate the basic situation of nest fern resources and explore the effects of various environmental and biological factors on the growth of nest ferns.The dynamic temperature and humidity changes between different parts of nest ferns and the environment were monitored by temperature and humidity meter to understand the buffering capacity of different parts of nest ferns to environmental changes.By means of statistical records,the animal and plant groups that interact with nest ferns and their interaction modes were investigated.The main conclusions are as follows :(1)Nest ferns are mainly distributed in the range of 600 m-850 m above sea level,and tend to grow on the southwest slope of the mid-mountain mountains.In addition,there are also a large number of nest ferns in tropical karst limestone areas and valley rainforests.Nest ferns are mostly epiphytic on trees with smooth bark,and the most common host is Heptapleurum heptaphyllum.The size of nest ferns is proportional to the size of host trees.Nest ferns distributed in low latitudes have larger plant size.(2)According to the different structures and functions,the habitats constructed by nest ferns can be divided into four areas,namely the upper litter area,leaf area,lower humus area and lower infiltration area.From the perspective of temperature and humidity control ability,nest ferns have stronger buffering ability to high temperature than low temperature.The lower humus area has a strong temperature and humidity buffering capacity,and the daily temperature change range is very gentle.It can play a strong cooling effect when the environment is at high temperature at noon,and still maintain saturated humidity within 5days without rainfall.(3)A total of 32 families,59 genera and 78 species of canopy plants were recorded to interact with nest ferns.The largest number of species was Orchidaceae,followed by Polypodiaceae and Araceae.The most common interaction between canopy plants and nest ferns is through.Usually,climbing plants such as Hoya ovalifolia and Aeschynanthus moningeriae pass through the base of nest ferns and take root in humus.Climbing plants can absorb nutrients and water in humus,and nest ferns can rely on the entanglement of these climbing plants to stabilize in the canopy and prevent themselves from being blown off by typhoons.The interaction mode with the second probability of occurrence is lower epiphytic,usually epiphytic plants such as Haplopteris elongata and Davallia divaricata.The leaves of these epiphytic plants are usually drooping to avoid competition with nest ferns for sunlight.At the same time,their densely scaled rhizomes surround the lower part of nest ferns and obtain water from them.(4)A total of 10 classes,32 orders and 94 families of nest fern interaction animals were observed in the study.53 % of the interaction animals lived in the lower humus,25 %in the leaves,and 22 % in the upper litter.Among these interactions,41 % were carnivorous,37 % were saprophagous,17 % were omnivorous,and only 5 % were phytophagous.Arachnida is the group with the highest frequency of occurrence,and there is niche differentiation in different parts of nest ferns.The leaves and litter areas are mostly Araneae,while the humus areas are mostly Opiliones.There is a relatively fixed interaction mechanism between predatory animals and nest ferns.Nest ferns provide habitats for Arachnida and protect nest ferns from phytophagous animals as a reward.In addition,there are a large number of earthworms,horses and other saprophagous animals in the humus of nest ferns.These groups are highly dependent on the humus of nest ferns to survive in the canopy,and also play a role in assisting the decomposition of litter.This paper demonstrates that nest ferns have become ’umbrella species’ with great protection value in the context of global change by constructing special habitats and shelters.It is suggested to strengthen the research on the evolution history and ecological functions of different types of epiphytic vascular plants,and to explore the biodiversity conservation strategies of tropical and subtropical forest ecosystems in the context of global change.