Plant Diversity on the North of East Lake Luoyan Scenic Area in Wuhan Municipality

Hao HE, Yongqi SONG, Li LIU, Huan DAI

Wuhan Institute of Design and Sciences, Wuhan 430205, China

Urban waterfront green space enjoys the characteristics of by both terrestrial ecosystem and aquatic ecosystem.Therefore,it is the most active area where most living beings exist, as well as the most sensitive and fragile area of urban natural ecosystem[1], so that urban waterfront green space always holds a leading role in urban natural green space. In the area, ecological functions of urban waterfront region is always restored and improved by rich plants[2]. Hence,it is necessary to well develop the scenic value and ecological value of urban waterfront regions by creating a scientific and rational artificial waterfront phytocoenosium where abundant plant varieties are grown[3].

Research Method

Selection of research area

East Lake Luoyan Scenic Area has an area of 10.3 km2, including 6.2 km2land areas and 4.1 km2water area.According to roads in the Scenic Area, the green spaces in the north area can be classified into green space A, green space B, green space C, green space D and green space E(Fig.1).

Research method

The research was conducted as per biocenology normal sampling method. Generally speaking, the area of sample plot of phytocoenosium is the least of 400 m2,or replaced by four plots with an area of 100 m2for each.However, with consideration of small area of forestlands and the scattered distribution in the Scenic Area, the re-search divided 14 sample plots, with every plot of 100 m2, for the convenience of comparisons with greenspace plots in the Scenic Area.Furthermore, the research classified plant species into arbor layer, shrub layer and herbaceous layer for the sake of measurements and statistics of different factors. Specifically, the plants with diameter at breast height over 4 cm and trunk height of 1.3 m is divided into arbor layer; the plant with trunk height of 1.3 m and diameter at breast height below 4 cm, and the trees with height over 1.5 m are divided into shrub layer,and ball-shaped or columnar shrubs are also incorporated into shrub layers[4]. Annual, biennial and perennial herbaceous plants are classified into herbaceous layer. The statistic work was then conducted on shrubs and arbors in sample plots and two small sample plots with an area of 1×1 m2each was surveyed as per diagonal for herbaceous plants.

Five greenbelts were classified and the most typical region was selected in accordance with specifics of the greenbelts. Subsequently, stable and well-developed phytocoenosium was taken as research objects[5]and 1-2 sample plots were chosen from every research region, totaling 14 sample plots.Besides,some factors should be measured, including plant variety, the number of plant clumps, growth vigor,and vertical hierarchy. Finally, the research data were analyzed with Margalef, Simpson, Shannon-Weine and Pielou indices.

Table 1 The constitutions of plant variety in waterfront greenspace in East Lake Luoyan Scenic Area

Table 2 The dominant plant family in waterfront greenspace in East Lake Luoyan Scenic Area

Table 3 Statistics of family and genus of plants

Results and Analysis

The constituents of plants in north of East Lake Luoyan Scenic Area

Of 14 sample plots, there are 62 species in 56 genera in the families of 38, including arbors of 32 species of 28 genera in 21 families, representing 51.6%,shrubs of 22 species of 21 genera in 16 families, representing 35.5%and herbaceous plants of 8 species of 8 genera in 5 families, repsenting 12.9% (Table 1). In the Scenic Area,plants are cultivated as per artificial cultivation, covering 2/3 plants are grown by people and wild plants only take account of 1/3,because of uncivilized behaviors of tourists, such as treading, which significantly advances loss of wild plants. Therefore, it is key to accelerate researching, surveying and protection on wild plants in order to improve variety of wild plants.

According to surveys of the five greenbelts,arbor layer was dominated by Taxodium ascendens, Magnolia grandiflora and Cinnamomum camphora, shrub layer dominated by Rhododendron simsii, Ligustrum sinense and Loropetalum chinense and herbaceous layer by Ophiopogon japonicas, Zoysia matrella and Cynodon dactylon. It can be concluded from analysis on plant constituents in the Scenic Area that ornamental plant holds a high proportion.There are four dominant families,including Rosaceae(7 species), Oleaceae (5 species),Gramineae (5 species)and Pinaceae(5 species), which represent 10.5% of total number of plant family, 32.1% of total number of genus, and 35.5% of total species. Besides, few families with two or fewer species and the single family total 40 species of 38 genera in 34 families, which accounts for 64.5% of total number of species,67.9% of total number of genera and 89.5%of total number of family (Table 2).

Plant species in the Scenic Area contains world’s largest plant families,including Gramineae, Rosaceae,Oleaceae, Pinaceae, as well as fewer plant family and single family (Table 3). For example, Rosaceae includes 7 species as green ornamental plants,occupying 11.29% of plant species.In accordance to survey results of plant family and genus,the genus with over 7 species was just one among the surveyed plants, the genus with 3-6 species totaled 11; the genus with a species was as high as 25,representing 50% of total number of genus and 45.16%of total species.These indicated that the genus with fewer species or one species dominate in the Scenic Area.

The distribution frequency of plants in the Scenic Area

Statistical work and analysis were conducted on plants with distribution frequency over 20% in the Scenic Area.

At first, it is Cinnamomum camphora that holds the highest frequency of 64.3% among arbor layer, followed by gingko, weeping willow, pond cypress,and metasequoia of 42.9%.It is notable that there were 14 plants only appeared once in measuring plants,which accounted for 43.8%of plants in arbor layer.

Furthermore, the distribution frequency of plants in shrub layer was always lower, of which the highest was just 35.7% of Fraxinus hupehensis(Table 5). In addition, the shrubs only appearing just once in different sample plots totaled 11, which represented 50% of all shrubs. What’s more, the variety of shrub is few (22) in every sample plot compared with arbors, of which the rare plant rose was found,but Euonymus japonicas, Amygdalus persica, Nandina domestica, and Lonicera maackii were unavailable.

Finally, Cynodondactylon (Linn.)Pers. appeared the most frequently of 64.3% in herbaceous layer, and there were three herbaceous plants only appeared once in the survey, representing 37.5%.

Table 4 The major plant frequency of waterfront green spaces of the Scenic Area

Table 5 Margalef’s indices of plants in waterfront green spaces in the Scenic Area

Table 6 Plant diversity of waterfront regions in the Scenic Area

Comparisons of plant diversity in different areas

Plant diversity Margalef’s index reflects richness of plant varieties in a plant community.The higher the index,the higher the richness[6]. As shown in Fig.2, plants in arbor layer performed the richest and plants in herbaceous layer the lowest. Furthermore, arbor layer and shrub layer showed different in the five green spaces, because the objective of creating landscape and plant arrangements are volatile. Additionally, herbaceous layer was not discussed in the research, because the variety of herbaceous plants is limited in the research area.

It can be concluded from the survey results that the distribution of arbor and shrub in the Scenic Area was lower than 14, and arbor variety was far more than that of shrub, as well as Margalef’s index.

Of the five green spaces, arbor variety reached the most of 14 species in the arbor layer, and the least of 10 species. As for Margalef’s index, the highest reached 3.11 and the lowest 2.00. Besides, the richness of arbor layer tended to be volatile upon green spaces (Fig.2), and Margalef’s index in the layer was lower. Comparatively speaking, plant species in shrub layer reached the most of 10, and the least of 5,whose Margalef’s index achieved the highest of 2.96 and the lowest of1.33. Therefore, Margalef’s index of shrub layer keeps higher, with mean value of 1.96,but the index maintained lower than that of arbor layer. In conclusion, Margalef’s index of the Scenic Area is to be improved.

Considering from the type of green spaces, green spaces A and B,in entrance road of the Scenic Area,is situated between east second ringroad and east third ring-road of Wuhan and targets creating urban forest landscape. It is a road section with herbaceous plants as groundcover, supplemented by herbaceous plants. Hence,Margalef’s index of shrub layer maintained lower in the green spaces.Meanwhile, green space A is grown with metasequoia and pond cypress by people,performing ecological function of urban waterfront green spaces.

Margalef’s indices of green spaces C and D proved both higher than those of green spaces A and B,because many tourists have rest in both of green spaces C and D.Specifically, green spaces C and D make use of arbors, shrubs and herbaceous plants in order to create an urban waterfront park characterized by rich landscape stratification, good visual effects and virtuous ecological cycle.

In terms of green space E, the eastern part borders on lands, where lots of rare animals are fed. It is the smallest open waterfront viewing zone, where shrubs and covers are dominated by ornamental plants.What’s more,plant species are abundant compared with other green spaces. Additionally, waterborne platform and recreation square are constructed to present a multi-layered green space oriented by viewing landscapes and characterized by seasonal changes.

Plant diversity index and evenness index Simpson index (D) and Shannon-Weine index (H) reflect the degree of species diversity in a green space and evenness degree in distribution. The higher the indices, the higher the diversity degree, which is also suitable for evaluating health and stability of plant community in the green space[7]. Besides, the higher indices suggests that adaptability and adjustment capacities of the area is good[8]. Margalef’s index (R) incorporates the number of plant species in a green space, namely, the richness of the species and Pielou’s evenness index (J) indicates plant evenness in a green space, which is used to assess distribution evenness of different species. The higher the index, the more evenly the species distributed[9].In the research, richness and evenness of plants were measured by Simpson index, Shannon-Wiener index and Pielou’s evenness index in the Scenic Area(Table 6).

According to the research results,there were 32 arbor species in the Scenic Area, and Simpson index and Shannon-Wiener index of arbor layer were both higher than those of shrub layer and herbaceous layer, and Pielou’s evenness index also kept high, because waterfront green spaces are just suitable for introducing and growing arbors in large scales and arbors are less affected by human activities. Furthermore, there were 22 shrub species, and the Simpson index and Shannon-Wiener index were only second to arbor layer, because fewer shrub species were grown and far from wide application. Herbaceous plants totaled 8 species, and Simpson index and Shannon-Wiener index were far lower than those of arbor layer and shrub layer, but the Pielou’s evenness index achieved the highest,because extensive lawns are extensive here, composed of Cynodon dactylon and Zoysia matrella.

Shannon-Wiener index would better reflect diversity of grass species for it is free from effects of green space area. According to the survey results(Table 6), Shannon-Wiener indices of arbor and shrub layers were 0.691 and 0.602 respectively, which suggested that although the index of arbor layer kept a little higher, it is not so significant compared with Margalef’s index;Simpson indices of arbor and shrub layers were 0.199 and 0.195,which indicated that the evenness degrees of arbors and shrubs are generally in consistent in the waterfront green spaces.In general, plant diversity maintains higher.

Discussions

East Lake Luoyan Scenic Area is an urban green space by artificial modification,a representative of urban natural eco-park in Central China. In the green space, plant diversity is decreasing upon human activities, and plant community structure would be also affected by artificial pruning. It is surveyed that arbors in the Scenic Area are grown as border trees, including Cinnamomum camphora,Metasequoia glyptostroboides, and Taxodium ascendens, and arbors with large crowns should be planted individually, such as gingko, weeping willow,sycamore and southern magnolia.The Scenic Area almost contains most afforestation tree species in Wuhan,including metasequoia, pond cypress and weeping willow. However, with abundant plant species and high plant diversity index, the Scenic Area still falls behind compared with some Nature Ecological Parks,because arbors,shrubs and grasses are not well grouped and plants are grown exclusively upon species.

According to survey results, the proportions of arbors and shrubs are to be improved, for the former’s proportion is lower, which is contrary to ecological rules of natural community. In practice, the Scenic Area should increase plants from the perspective of structures in different green spaces,especially for shrubs on basis of plant diversity in order to build a stable and diversified eco-environment.

The survey showed that plant richness, evenness, and diversity in the five green spaces were arbor layer＞shrub layer ＞herbaceous layer.Specifically, richness index of arbor layer in green space D reached the highest of 3.11, and the lowest of herbaceous layer in green space D of 0.31. Besides, shrub layer showed insignificant differences in terms of richness and evenness among the five green spaces.

The Scenic Area takes advantages in geography, climate and ecoenvironment, which is conductive to creating a rich and diversified plant-oriented landscape and plays a key role in plant richness, plant diversity and evenness. Nevertheless, because of artificial planting in large scale, the ecosystem tends to be fragile. Therefore, some suggestions are proposed in order to build a more stable urbanwaterfront green spaces and create a richer urban green landscapes.

Firstly, it is necessary to properly increase aquatic plant species and number and introduce new species to beautify lake shoreline landscapes under the principles of abiding by natural ecological rules and adjusting measures to local conditions. Currently,aquatic plants, such as lotus, Thalia dealbata, calamus, cattail, lotus and Iris wilsonii are much common in Wuhan, and it is recommended to grow Vetiveria zizanioides, Cyperus alternifolius, Canna indica, Acorus calamus and Thalia dealbata collectively to enhance treatment effects on water[10],of which canna dominates,supplemented by vetiver grass, Cyperus alternifolius, calamus and Thalia dealbata,purifying water and beautifying environment simultaneously.

Secondly, due to few type of herbaceous plants in green spaces, it is recommended to increase wild plants, such as Viola philippica, Oxalis triangu laris, and Duchesnea indica to create beautiful ground covers.

Thirdly,it is crucial to increase application range of shrubs by enhancing shrub type and number and constructing artificial eco-community based on simulation of natural community, in accordance with ecological niche differentiation of natural community.Therefore, it becomes necessary for constructing a stable and rich artificial eco-community to select plant species to local conditions,as well as plant demands on sunshine and water.

Fourthly, it is suggested that border trees in cities should be the ones with diameter at breast height over 10 cm, underbranch height over or equal to 210 cm. What’s more, the wellshaped trees and the trees with fewer willow catkins are also indispensible.

Finally, flowering plants or colorleafed plants should be increased in terms of the type and planting range in order to beautify urban environment and improve artificial eco-community.Currently, the proportion of shrubs keeps higher nationwide in plant community. In Wuhan, however, with green shrubs widely distributed, colorleafed or flowering shrubs are fewer and plant landscape looks too simple and tedious.

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