CHAPTER VII
ECOLOGICAL CHARACTERISTICS OF THE ELM POPULATIONS IN THE GREAT GREEN VALLEY NATURE RESERVE

7.1 The Great Green Valley Nature Reserve

Daqinggou or the Great Green valley, a rare surviving eco-system, is located in the South-eastern Korqin Sandy Lands. It was declared a National Nature Reserve in the mid eighties. It consists of long stretched valleys, covered by dense woodlands with abundant water supply, contrasting sharply with the surrounding dune landscape almost without vegetation.

Geographically it is located between 122°13' and 122°15' E and from 42°45' to 42°48' N, 24 km southwest of Ganqika Township, Kezuohou Banner. It borders with Zhangwu County, Liaoning Province.

There are two valleys in the protected area: the Great Green valley is 20 km long, 40 to 50 m deep, on average 250 m wide and the average slope of the valley flanks is about 36°; Xiaoqinggou or the Little Green valley is 10 km long, on average 50 to 70 m deep, 200–300 m wide, and its flank slope is about 28°. The rivers in the two valleys intersect and flow into the Liu River (an affluent of the Liao River). The rivers are 2 to 4 m wide and not more than 1 m deep. The elevation above sea level of the upper valley is 225–253 m.

In the Valley, 709 plant species have been identified, about 30 percent of the total species number in Inner Mongolia, including some rare broadleaf tree species such as Fraxinus mandshurica and Phellodendron amurense. There are plants belonging to three different flora: Huabei, Inner Mongolia and Changbai.

The Daqinggou plant community is a very special eco-system, with high humidity at the valley bottom decreasing sharply when going up out of the Valley.

7.2 Niches, distribution patterns and species associations of the elm populations in the Great Green Valley

Three species of elm are represented: Ulmus pumila, U. macrocarpa, and U. japonica (U. propinqua). U. pumila occurs mainly on sandy land out of the Valley and it is the main tree species of the Elm open woodlands. U. macrocarpa is distributed along the upper slopes of the Valley, being the most prominent species of woody plants here. U. japonica exists mainly on the bottom and lower slopes of the Valley, and is a dominant species in the humid Fraxinus mandshurica community. A detailed description of the three species is given in chapter 1.5.

7.2.1 Elm Niches

Comparison of niche width

Zheng Yuanrun (1995)¹⁷ studied the niche width of plant communities in Daqinggou, using the methodology of Simpson. The following sequence ranks the species according to their niche-width, from widest to narrowest. The numbers refer to a relative comparison of the niche-width.:

Rhamnus parvifolia (4.188) >Acer mono (3.947) > Crataegus pinnatifida (3.931) >U. macrocarpa (3.634) > Lespedeza bicolor (3.509) >Securinega suffruticosa (3.184) > Quercus mongolica (3.129) >Prunus armeniaca (2.988) >Spiraea pubescens (2.961) >Acer ginnala (2.864) >Lonicera maackii (2.404) > Fraxinus mandshurica (2.051) > Malus baccata (2) = Phellodendron amurense (2) > Lonicera japonica (1. 976) > Acanthopanax sessiliflorus (1.96) > Celtis bungeana (1. 939) > Salix koreensis (1.8) > Ampelopsis aconitifolia (1) = U. japonica (1) =Celastrus articulatus (1).

Using the methodology based on the Shannon-Wienner index, the ranking is as follows:

Rhamnus parvifolia (1.5152) > Crataegus pinnatifida (1. 4636) > Acer mono (1.3793) > U. macrocarpa (1.3349) > Lespedeza bicolor (1.3195) > Quercus mongolica (1.2736) > Securinega suffruticosa (1.2694) > Spiraea pubescens (1.1774) > Prunus armeniaca (1.0967) > Acer ginnala (1.0733) > Lonicera maackii (0.963) > Fraxinus mandshurica (0.8599) > Malus baccata (0.6931) = Phellodendron amurense (0.6931) > Lonicera japonica (0.6869) > Acanthopanax sessiliflorus (0.6829) > Celtis bungeana (0.6775) > Salix koreensis (0.6365) > Ampelopsis aconitifolia (0) = U. japonica (0) = Celastrus articulatus (0).

It is obvious that the niche-width of U. macrocarpa is much wider than that of U. japonica in all tree communities in the Great Green valley. U. macrocarpa is distributed from mesic to xeric environments, occupying a wide range of living conditions. The niche of U. japonica is narrow and specialized and suggests that the habitat of U. japonica is mesic or a transition from hygric to mesic.

Niche overlap

From the point of species competition, the more niche overlap, the more severe and intense the competition among species.

The niche overlap coefficients for U. macrocarpa in the Great Green Valley are as follows with: Quercus monogolica (0.88) = Acer mono (0.88) > Prunus armeniaca (0.85) > Securinega suffruticosa (0.84) > Crataegus pinnatifida (0.78) > Lespedeza bicolor (0.75) > Spiraea pubescens (0.72) > Rhamnus parvifolia (0.62) > Celtis bungeana (0.54) > Celastrus articulatus (0.15) = Phellodendron amurense (0.15) = Acanthopanax sessiliflorus (0.15) = Acer ginnala (0.15) > Lonicera maackii (0.13) > Fraxinus mandshurica (0.09) > Lonicera japonica (0) = U. japonica (0) = Salix koreensis (0) = Malus baccata (0) = Ampelopsis aconitifolia

The order of niche overlap for the U. japonica community are: Salix koreensis (0.67) > Fraxinus mandshurica (0.64) > Malus baccata (0.5) > Lonicera japonica (0.44) > Acer ginnala (0.38) > Lonicera maackii (0.34) > Quercus monogolica (0.02) > Rhamnus parvifolia (0) = Celtis bungeana (0) = Securinega suffruticosa (0) = Spiraea pubescens (0) = Crataegus pinnatifida (0) = Prunus armeniaca (0) = Acer mono (0) = Celastrus articulatus (0) = Lespedeza bicolor (0) = Phellodendron amurense (0) = Ulmus macrocarpa (0) = Acanthopanax sessiliflorus (0) = Ampelopsis aconitifolia (0)

7.2.2. Pattern and dynamics of the elm populations

Population distribution pattern

The distribution pattern of plant population shows the location of plants in the population. Zheng Yuanrun studied the distribution patterns of the woody plant population in the Great Green Valley. The results show that distribution patterns of U. macrocarpa and U. pumila, were respectively clustered and random; the pattern of U. propinqua is random or clustered. The environment where U. pumila grows is harsh with low soil water contents and lack of soil nutrients, resulting in the random distribution of this species (Table 7.2.2.1).

Table 7.2.2.1: Distribution-patterns of populations in different communities

Legend to Table 1:
C: clustered distribution;
P: random distribution;

The communities are indicated by a lower-case letter, meaning:
a: Lonicera maackii-Fraxinus mandshurica community;
b: Sanicula chinensis + Glycine soja-Acanthopanax sessiliflorus-Fraxinus mandshurica community;
c: Carex spp.-Lonicera japonica U. japonica + Salix koreensis community;
d: Carex spp.-Lonicera maackii-U. japonica Salix koreensis community;
e: Carex spp.-Lonicera maackii-U. japonica + Fraxinus mandshurica community;
f: Carex spp.-Lespedeza bicolor - Quercus mongolica + Acer mono community;
g: Carex spp. + Artemisia sacrorum-Crataegus pinnatifida + Lespedeza bicolor - Quercus mongolica community;
h: Carex spp.-Crataegus pinnatifida-U. pumila+Celtis bungeana community;
i: Arundinella hirta-Crataegus pinnatifida-U. macrocarpa community;
j: Carex spp.-Crataegus pinnatifida-U. macrocarpa community;
k: Carex spp.-Prunus armeniaca-U. macrocarpa community;
l: Artemisia sacrorum-Lespedeza bicolor, U. macrocarpa + Q. mongolica community;
m: Artemisia sacrorum + Leymus chinensis-Crataegus pinnatifida-U. macrocarpa community;
n: Carex spp. + Cleistogenes squarrosa-Crataegus pinnatifida-U. macrocarpacommunity.

Dynamics of the population distribution pattern

Zheng Yuanrun studied also the dynamics of population distribution pattern in the Great Green Valley.

U. japonica population patterns (seedling-sapling-small tree-middle sized tree-big tree) varies from clustered to random distribution pattern in the Lonicera maackii-Fraxinus mandshurica community: seedlings, saplings and little trees show a clustered distribution, while middle and big sized trees tend to have a random distribution.

In the case of Ulmus macrocarpa, the spatial distribution, in the Carex spp. + Cleistogenes squarrosa-Crataegus pinnatifida-Ulmus macrocarpa community, was clustered for seedlings, saplings, small and mid-sized trees, and random for big tree.

7.2.3. Species associations between elms and other plants in the Great Green Valley

Species association is a mutual relation of spatial distribution among different species. Zheng Yuanrun determined the species association among 31 species of trees and shrubs in the deciduous hardwood land in the Great Green Valley.

These tendencies become important at the time of planning to recreate parts of natural eco-systems.

Association tendency for U. japonica

There is a positive association tendency between U. japonica on the one hand and Padus racemosa, Acer ginnala, Phellodendron amurense, Fraxinus mandshurica, Salix koreensis, Malus baccata, Acanthopanax sessiliflorus, Lonicera maackii. These species have the same way of adapting to the habitat and they prefer a humid habitat.

The association tendency is negative between U. japonica and U. macrocarpa, Quercus monogolia, Acer mono, Prunus armeniaca, Crataegus pinnatifida and Rhamnus parvifolia that prefer a dry habitat.

Association tendency for U. pumila

The association tendency for U. pumila was positive with Padus racemosa, Acer ginnala, Phellodendron amurense, Fraxinus mandshurica, Salix koreensis, Malus baccata and Lonicera maackii.

The tendency is negative with U. macrocarpa, Rhamnus parvifolia.

Association tendency for U. macrocarpa

The association tendency is positive with Quercus monogolica, Acer mono, Prunus armeniaca, Crataegus pinnatifida, Spiraea pubescens and Rhamnus parvifolia

The tendency is negative with Padus racemosa, Acer ginnala, Ulmus japonica, Phellodendron amurense, Fraxinus mandshurica, Ulmus pumila, Salix koreensis, Malus baccata, Acanthopanax sessiliflorus and Lonicera maackii.