Published online November 7, 2023
Journal of Ecology and Environment (2023) 47:16
1Department of Biological Sciences, Kongju National University, Gongju 32588, Republic of Korea
2Garden Promotion Department, Korea Arboreta and Gardens Institute, Sejong 30129, Republic of Korea
3Ecological Observation Team, National Institute of Ecology, Seocheon 33657, Republic of Korea
Correspondence to:Young-Han You
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Background: Inner Mongolia, desertification is happening due to climate change and land use alterations. In order to evaluate desert restoration effectiveness, this study compares number of species and species diversity in restored (with planted trees), unrestored area, and the reference ecosystem (Ref-E, typical steppe and woody steppe).
Results: The Ref-E had the most plant species (64 taxa), while the unrestored area had the fewest (5 taxa). Among restored areas (restored in 2012, 2008, 2005), older restoration sites had more species (18–42). Similarly, species richness (3.93–0.41) and diversity (1.99–0.40) were highest in the Ref-E and lowest in unrestored areas, with older restored sites having higher values.
Conclusions: More plant species and diversity in older restoration areas suggest progress toward ecosystem stabilization, approaching the Ref-E. Therefore, tree planting in Inner Mongolia’s Hulunbuir semi-arid desert is a successful restoration effort.
Keywords: desert plant, plantation, restoration, steppe, vascular plant
In 1994, the United Nations launched the Convention to Combat Desertification (UNCCD) through the agreement of many countries around the world, and UNCCD is the only legally binding international agreement linking environment and development for sustainable land management (United Nations General Assembly 1994). The areas referred to in the definition of desertification can be collectively referred to as dryland, and UNCCD refers to a dryland as an area where the ratio of potential evaporation to annual precipitation is in the range of 5 to 65% (Mcsweeney 2019).
According to the Intergovernmental Panel on Climate Change (IPCC), since 3 billion people live in drylands, which account for 46.2% of the entire world’s land area (Mirzabaev et al. 2019), about 9.2% of the drylands were expanded by desertification due to indiscreet use of lands by humans during 1980s–2000s, and the desertification affected about 500 million people in 2015 (Mirzabaev et al. 2019). The unsustainable management of lands caused devastation and eventually led to dust storms and eolian dust, which are directly linked to human death (Goldewijk et al. 2017; Montanarella et al. 2018).
The territory of China comprises about 20% forest, about 27% deserts, and about 42% steppes, which occupy the largest area (Xue et al. 2017). The dry lands, of which the area is 332 million km2 accounting for 34.6% of the total area of China, may be desertified. Although some forests increased by almost 20%, many habitats are continuously threatened, and it is said that nearly 90% of steppes have experienced desertification (UNCCD 2019; Wu et al. 2015).
However, in addition to recent changes in precipitation patterns due to climate change, the land is severely damaged due to the conversion of land use from grasslands to farmlands or from woodland steppe to farms, and rapid increases in the number of livestock (Jun Li et al. 2007). Consequently, the area of grasslands is rapidly decreasing (Akiyama and Kawamura 2007) and desertification is progressing due to land degradation (Kang et al. 2007).
Hulunbuir, which has the steppes of the largest area among the steppes in Inner Mongolia, has experienced reduction in the area ratio of steppes as steppes were devastated and changed into sandy dunes after converting forests into farms (Akiyama and Kawamura 2007; Kim et al. 2021). Since the area ratio of desertification has been increasing to 18.48% in the 2020s, it is predicted that Hulunbuir will become a desert in 40–50 years (XinShi et al. 2009).
The desertification of land is known to be the main culprit that secondarily causes sandstorms and eolian dust, and as damage to neighboring countries due to eolian dust has been increasing, the problem of desertification was recognized as an international environmental problem (Goldewijk et al. 2017; Mcsweeney 2019). In recent years, many sand movements have been observed in Hulunbuir, and the Chinese government is making great efforts to restore this region, which was steppes in the past, from desertification (XinShi et al. 2009). To prevent desertification, the Chinese government, in cooperation with Working Group 2 of the Korea-China-Japan Yellow Sand Joint Research Group, is conducting a monitoring survey at a restoration site where trees were planted in the Ganzuer Hulunbuir, Inner Mongolia (Ministry of Environment 2020).
By understanding the changes in flora caused by planting trees on damaged grasslands, the restoration effect can be known through the number of plant species. Therefore, we sought to investigate changes in the flora of damaged areas due to annual tree planting in the Hulunbuir, Inner Mongolia. Therefore, this study aims to assess the effects and extent of restoration by comparing and analyzing the plant species in restored and unrecovered vegetation areas, as well as in the reference ecosystems (Ref-Es), where woody plants have been introduced in the semi-arid desertified regions in Hulunbuir, Inner Mongolia.
This study site is a site to be jointly investigated by the WG (II) of the South Korea-China-Japan Yellow Dust Joint Research Group and is called Ganzhuer. This site is Xīnbā’ěrhǔ Zuǒ Qí among the 14 administrative districts in Hūlúnbèi’ěr Shì, in the northeastern area of Inner Mongolia Autonomous Region, and is located at N 48°04′13″–48°27′11″, E 119°18′37″–118°17′18″ (Fig. 1). In this site, forestry and livestock farming in steppes have been prosperous from the past and there are diverse ecosystems such as temperate monsoon coniferous forests and steppes. The topography here is sandy dunes thrist form the shape of honeycombs with fixed, semi-fixed, semi-floating, and floating sandy dunes that were already desertified or restored (Angerer et al. 2008).
The climate here belongs to the northern temperate climate, and the annual average precipitation is about 130–330 mm (275 mm) and has been increasing every year since 2014 but has been functioning greatly and not even with large yearly variations. In particular, the annual average rainfall in summer (June–August) is about 74–207 mm, accounting for 59% of the annual rainfall. The rainfall is highly concentrated on the growing season (May–September) at 116–282 mm (83%), and the annual average rainfall in other seasons is about 17–48 mm (17%). The relative humidity is 62%–72% (68%), and the annual potential evapotranspiration is 1,400–1,900 mm, which is considerably higher compared to the precipitation. The annual average temperature is –0.4°C to 0.58°C (0.3°C), the minimum temperature is –42° and the maximum temperature is 39°. Climate data used from the China Meteorological Observation Network (http://data.cma.cn/, 2023) measured by the National Meteorological Observatory of Inner Mongolia.
In this study site, restoration projects were carried out in devastated and desertified steppes from 2005 to 2012. Since the topography was in its original state, the vegetation was restored in most cases using seed sowing and tree planting methods. In order to investigate the flora of the regions restored from desertification, the regions restored in 2005 (R-2005yr), 2008 (R-2008yr), and 2012 (R-2012yr), the desertified sandy dune regions, which were not restored (NR), were selected as investigation sites, and the typical steppe area, which is about 80 km in a straight line from the investigation site, and the woody (
The trees selected for vegetation restoration were
In order to identify the distribution of all vascular plants appearing in the investigation target site in of Hulunbuir, the regions R-2005yr, R-2008yr, R-2012yr, the NR and Ref-E investigated while walking around the regions in late summer and early fall. Plant species were identified referring to the Flora of China (2020), the Color Atlas of plants of northern China’s grasslands (Gu and Wang 2009; Li 2012), the Colored Atlas Book of Chinese Desert Plants (Lu 2012) and the Korean Pictorial Book of Plants (Lee 2003). The scientific names were adopted, and the taxa were arranged according to the Flora of China, and the arrangements below the genus were organized in alphabetical order. The Korean names were given according to the Flora of Korea editorial committee (2007) of those taxa that had no Korean name because they are not distributed in Korea were newly made considering Chinese names, scientific names, and the taxonomic features of the plants.
The research sites for plant species analysis consisted of a total of three restoration areas, one unrecovered area, and one combined site representing the Ref-Es of steppe grassland and woody steppe. In each study area, changes in taxa that appeared over a five-year period from 2014 to 2018 were confirmed and differences in the average number of species were compared. Normal distribution was tested using the Shapiro–Wilk test, and due to the lack of normal distribution (
The richness index (RI) was calculated by measuring the number of species per square meter (1 m2) and applying it to the formula RI = (S – 1) / ln (N) (Margalef 1958), where S represents the total number of species within the community, and N denotes the total number of individuals present within the community. The Diversity Index (H’) was calculated by substituting it into the formula H’ = –∑ (Pn lnPn) (Shannon and Weaver 1949), where Pn represents the proportion of the nth species within the community, calculated by dividing the number of individuals in each taxonomic group by the total number of individuals. The analysis of species diversity involved determining the total number of species and individuals occurring in each research site (R-2005yr, R-2008yr, R-2012, NR, and Ref-E) to assess the richness and diversity of species distribution.
A total of 105 taxa comprising 34 families, 87 genera, 98 species and 7 varieties were identified. Among them, only 1 taxon was a gymnosperm, and the remaining 104 taxa were angiosperms comprising 78 dicotyledonous plants and 26 mono-cotyledonous plants corresponding to 75% and 25%, respectively. No Pteridophyta were found (Table 1). As for the ratios of distribution by family, the ratio of distribution of Asteraceae was the highest at 17% (18 species) followed by Poaceae at 12% (12 species), Chenopodiaceae and Fabaceae at 8% (8 species), and 16 families including Pinaceae, Ulmaceae, and Brassicaceae at the lowest ratio of distribution with 1 species each (Fig. 3).
Among the species growing in the study sites, the species with the highest frequency of appearance was
A total of 5 families, 10 genera, and 11 taxa were identified (Table 1). The ratio of the Fabaceae was the highest among the entire taxa, and the ratio of Orobanchaceae and that of Gramineae were the lowest with one species each (Table S1). Those species whose distribution has been continuously identified for 5 years are four species in total including
A total of 18 taxa comprising 9 families, 17 genera, 17 species and 1 variety was identified (Table 1). Among the entire taxa, the ratios of Fabaceae and Gramineae were the highest, and the ratios of Pinaceae, Ulmaceae, Borraginaceae, and Orobanchaceae were the lowest with one species each (Table S1). The species of which the distribution was continuously identified for 5 years are 7 species in total:
A total of 38 taxa comprising 17 families, 33 genera, 36 species, and 2 varieties was identified (Table 1). Among the entire taxa, the ratio of the Asteracese was the highest, followed by Gramineae and Fabaceae, in order of precedence. This is similar to the plant distribution ratios in the entire Hulunbuir. Species of which the growth was identified during the investigation in every year are a total of 12 species;
The average number of plant species during the entire investigation period was 25, and during the five years of investigation, the plant diversity decreased during the period of investigation in 2016 and increased thereafter (Fig. 4).
A total of 42 taxa comprising 15 families, 34 genera, 41 species, and 1 variety was identified (Table 1). Among the entire taxa, the ratio of the Asteracese was quite high at 24% followed by Gramineae and Chenopodiaceae, in order of precedence. Whereas only
The average number of plant species during the entire investigation period was 23, and during the investigation period, plant diversity was the highest in 2015, and rapidly decreased thereafter so that it was the lowest in 2016 (Fig. 4).
A total of 64 taxa comprising 26 families, 55 genera, 59 species, and 5 variety was identified (Table 1). Among the entire taxa, the ratio of the Asteracese was the highest and the ratios of other families were about equal. The taxa of which the growth was identified during every investigation were 26 species such as
During the entire investigation period, the average number of plant species was 41, and plant diversity was the highest in 2015 and the lowest in 2017. The Ref-Es were sandy dune areas, where
The Richness Index (RI) was highest in Ref-E at 3.93, followed by R-2005yr (1.49), R-2008yr (1.16), R-2012yr (0.70), and NR (0.41) (Fig. 5). The Shannon–Wiener diversity index (H’) was highest in Ref-E at 1.99, followed by R-2005yr (1.62), R-2008yr (0.99), R-2012yr (0.81), and NR (0.40) (Fig. 5). Both species richness and diversity indices were highest in the Ref-E, and they increased with longer restoration years (Fig. 5).
As a result of the investigation of flora in Hulunbuir, China, 105 taxa comprising a total of 34 families, 87 genera, 98 species and 7 varieties were identified (Table 1). In previous studies, the plant species identified as growing in the Sandy Land in Inner Mongolia were a total of 428 taxa comprising 48 families, 177 genera, 378 species, and 50 varieties, and among them, 39 families, 122 genera and 213 species were distributed in the desert, and 46 families, 174 genera, and 370 species were distributed in the temperate steppe areas (Wang et al. 2007). The difference between the number of plants at the research site and previous studies is believed to be due to differences in time and space (area, region, etc.). However, it is unfortunate that the flora survey in this study was conducted only in specific seasons, not all seasons. Nevertheless, the results of this study are meaningful in that they provide basic data for determining the number of plant species over time after planting trees in damaged grasslands.
The finding that the ratios of Asteracese, Gramineae, Chenopodiaceae, and Fabaceae were the highest among the entire plant taxa is identical to the announcement that a total of four plant families were dominant in the sandy areas in Inner Mongolia (Wang et al. 2007), As for genera, whereas Artemisia, Corispermum, Oxytropis, and Astragalus were dominant in the sandy areas in Inner Mongolia (Wang et al. 2007). The dominant genera in our research sites were Artemisia, Potentilla, Chenopodium, and Allium, and only Artemisia was consistent with the existing literature. In the arid-steppes of northern China, plants of the genera Stipa, Aster, and Artemisia are known to be major species and generalist with wide habitat (Tang et al. 2020). All the genera mentioned above appeared in our survey site, and among them, Artemisia was observed to be widely distributed.
Those species that had wide distribution arreas in the Ganzhuer sandy dune area so that they were identified in all study sites were a total of five species comprising
In the dry-temperate steppes in the north of China, plants in the genera Stipa, Aster, and Artemisia are known to be major species (Tang et al. 2020). Therefore, some of the species in the study sites correspond to the relevant genera, and it could be observed that the plants in the three genera are widely distributed in the surrounding areas not desertified other the investigation target areas in this study. Considering the characteristics of pioneer species, in the deserts,
Pioneer species refer indigenous species in the initial transition period that come and grow in areas where most plants can hardly grow and live while overcoming unfavorable conditions for growth in terms of nutrients, dryness, wetness, and light (Barbour et al. 2015). Among the major indigenous species that naturally occur and grow like pioneer tree species in the Ganzhuer desertified area,
The fact that the same distributed species as those in Korea exist in Hulunbuir, China found through the investigation of the flora in China is phytogeographically very important. Among the entire 105 taxa, 64 taxa accounting for 61% are identical to species distributed in Korea (Table S1). Although Hulunbuir is 1,580 km away from the South Korea in a straight line, and there is no desert ecosystem per se in South Korea, the same species may be investigated according to the characteristics and distributed areas and the results may be used as basic data for plant classification and ecology.
In the flora of Hulunbuir, 13 species, which are
Five species of plants that can be used as food sources for animals were identified as
There was a trend of increasing plant diversity with the passage of restoration years on an annual basis. However, the plant diversity in all restoration sites experienced a sharp decline in 2016, followed by a gradual recovery and increase (Fig. 4). In the case of the reference sites, the diversity was the lowest in 2017. Plant species with low distribution ratios in individual areas could not be found at all as of 2016 or rediscovered a few years later in many cases. In general, it can be estimated that there were negative factors in the growth environments, such as the death of most of trees and shrubs between 2016 and 2017 by only looking at the surrounding plant conditions. By investigation target area, the plant diversity of the areas that were restored more than 10 years earlier was more two times higher than areas that were restored 6 to 7 years earlier, and it seems that the outcomes of restoration will appear such as increased in the appearance of major native species of Hulunbuir.
Investigations of flora should be conducted in all seasons except for winter, when most plants wither to death for faithful data to be secured (Lee et al. 2016). In the study sites in Hulunbuir, Inner Mongolia too, investigations should be conducted in other seasons too by promoting smooth cooperation of the Chinese side, and it will greatly contribute to improving the reliability of data on changes in the plant diversity of the areas restored, hereafter.
When species diversity is low, it indicates short-term effects of vegetation restoration, while high diversity suggests long-term effects (Yeochon Association for Ecological Research 2005). High diversity implies the influx of plant species through mechanisms like seed dispersal, leading to an increase in species composition. This increase in species composition can be confirmed through species richness indices. In our study, a comparison of the entire annual restoration sites revealed that sites with longer restoration periods had higher species richness and diversity indices (Fig. 5). This trend aligns with the findings of a study on nearby desertified areas in Hulunbuir (Lv et al. 2008).
However, it’s essential to understand that species richness measures how rich the number of species is within a cluster. In our case, restoration sites had more than twice the richness compared to unrecovered sites but lower than the Ref-Es. Additionally, higher diversity indices indicate ecosystem stabilization, as clusters with higher values suggest maturity. These indices can be used as a measure of cluster structure and functional capacity (Yeochon Association for Ecological Research 2005). Therefore, while the vegetation cover in our annual restoration sites showed some signs of recovery, the restoration site with the lowest diversity index (R-2012yr) suggests that the ecosystem’s structure and function have not fully recovered to late-stage or pre-restoration levels. This indicates the need for long-term planning and management.
Comparing species richness and diversity indices among the restoration sites, it can be concluded that the vegetation cover in the 2005 and 2008 restoration sites is like or exceeds that of similar or Ref-Es, confirming the effectiveness of vegetation restoration. However, cluster analysis reveals significant differences in species richness, diversity, and evenness, indicating a need for further internal growth within the ecosystem. R-2012yr appears to have only partially recovered in terms of vegetation cover, with indices significantly lower than those of similar grassland ecosystems. This suggests that the ecosystem’s structure and function are still in the early stages of restoration, highlighting the need for long-term planning and management.
To prevent desertification, trees were planted in the semiarid desert, and the restoration effects of these areas were assessed. A comparison of plant species and diversity among the restored areas, unrecovered areas, and Ref-Es was conducted. The results showed that as time passed since restoration, the number of plant species, species richness, and species diversity indices increased among the restored areas. Conversely, the most recently restored areas had lower values. The increase in plant species and species diversity indices in older restoration areas indicates progress towards ecosystem stabilization, approaching the Ref-E. Therefore, the planting of trees in the semiarid desert of Inner Mongolia’s Hulunbeir is considered a successful restoration effort to combat desertification. This suggests that the ecosystem’s structure and function are still in the early stages of restoration, highlighting the need for long-term planning and management.
Supplementary information accompanies this paper at https://doi.org/10.5141/jee.23.058.
Table S1 The list of plants in study sites, Ganzhuer of Hulunbuir, Inner Mongolia.jee-47-16-supple.pdf
Ref-E: Reference ecosystem
UNCCD: United Nations launched the Convention to Combat Desertification
IPCC: Intergovernmental Panel on Climate Change
NR: Not restored
KEJ collected, analyzed, and visualized the data, wrote the original draft, and reviewed the finished version. LSH planned the article, collected, and analyzed the data and wrote the original draft. JSB collected, and created the manuscript and reviewed the finished version. YYH planned and supervised the article, conceived the paper, conducted experiments, collected, and analyzed data, visualized the data, and reviewed the completed version and received research funding.
This work was supported by Korea Environmental Industry & Technology Institute (KEITI) through Wetland Ecosystem Value Evaluation and Carbon Absorption Value Promotion Technology Development Project, funded by Korea Ministry of Environment (MOE) (2022003630003). This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2018R1D1A1B07050269).
The authors declare that they have no competing interests.