The increase in ecosystem services values of the sand dune succession in northeastern China.

Ecosystem services values play a vital role in evaluating the economic benefits of ecosystems and for drawing up the vegetation restoration policy. The change of ecosystem services values in sand dune succession, especially in China, is little reported. This study was conducted in the Wulanaodu region, southeastern of the Horqin Sandy Land, one of the largest sandy lands in China. Here, we used quantitative methods including marketing value method, the alternative market method, the carbon tax method, the industrial oxygen method, the opportunity cost method, the water balance method, and the shadow engineering method. We evaluated ecosystem services values in fixed sand dunes, semi-fixed sand dunes, and mobile sand dunes. These sand dunes constitute a sand dune succession. The results showed that ecosystem services values in mobile sand dunes, semi-fixed sand dunes, and fixed sand dunes were 6206.58 CNY·hm-2·a-1, 9986.28 CNY·hm-2·a-1, and 31466.56 CNY·hm-2·a-1 separately. The ecosystem services values in fixed sand dunes were five times to these in mobile sand dunes. It suggests that ecosystem services values increase along with the sand dune succession. Moreover, in fixed sand dunes, the main categories contributing to ecosystem services values were gas regulation (17748.11 CNY·hm-2·a-1), and soil formation and retention (6461.80 CNY·hm-2·a-1). Meanwhile, gas regulation (3696.61 CNY·hm-2·a-1), and soil formation and retention (3124.74 CNY·hm-2·a-1) were also the main categories contributing to ecosystem services values in semi-fixed sand dunes. The main categories contributing to ecosystem services values were gas regulation (2760.10 CNY·hm-2·a-1) and water regulation (2278.00 CNY·hm-2·a-1) in mobile sand dunes. This study provides evidence that an increase in ecosystem services values in sandy lands is consistent with the aim of the combat of desertification.

Introduction

Desertification, defined as a kind of land degradation occurred in arid, semi-arid and sub-humid arid areas, was confirmed in 1992 (Le Houérou, 1996). Desertification widely appears in one of the three of the land area in the world and influences the lives of 1.5 billion people (Rossi et al., 2015). China, the country with most people, is also suffered from desertification in the area of 2.61 million km2 (Feng et al., 2016).

Desertification, caused by various factors including climate changes and human activities, leads to the degradation in arid and semi-arid areas (Jiang et al., 2002). To prevent degradation in sandy lands, a series of measures have adopted since the 1950s in China. After decades of combating desertification, some mobile sand dunes were fixed and changed into semi-fixed and fixed sand dunes. The mobile sand dunes, semi-fixed sand dunes, and fixed sand dunes constitute a sand dune succession. The difference in these types of sand dunes includes the species diversity, vegetation dynamic, soil seed bank, soil moisture, and soil physical and chemical characteristics. For instance, species diversity, and richness gradually increase along with the sand dune succession (Zhang et al., 2005a). Moreover, the sand dune succession affects the distribution of microbial species (Poosakkannu et al., 2017). However, it is not well known that changes in ecosystem services values in the sand dune succession.

Calculating ecosystem services values is a method to evaluate ecosystems in a comparable way (Costanza et al., 1997). The ecosystem services values are mainly reported in forests, farmlands, and wetlands (Guo et al., 2001; Barbier et al., 2011; Sutcliffe et al., 2015). Recently, the ecosystem services values in sandy lands have received increasing attention, especially in coastal sand dunes. For example, the values of ecosystem services and their improvement are estimated with system dynamical models in coastal sand dunes in South Korea (You et al., 2018). Meanwhile, ecosystem services values in touristic infrastructure are measured using the cost of hotel rooms in coastal sand dunes in Mexico (Mendoza-González et al., 2018). Besides, ecosystem services values in stages in coastal sand dune succession are monetized and compared in Belgium (Van der Biest et al., 2017). However, it is little reported the change of ecosystem services values along the inland sand dune succession.

Although the long-term investigation on a located sand dune is little in reality, the sand dune succession could be observed with the space-for-time substitution method (Miao et al., 2018). According to this method, mobile sand dunes, semi-fixed sand dunes, and fixed sand dunes exsiting simultaneously, could be considered as a sand dune succession. In order to explore the changes in ecosystem services values in sand dune succession, typical communities should be selected, as plant communities found in mobile sand dunes, semi-fixed sand dunes and fixed sand dunes are different from each other. In the Horqin Sandy Land, one of the largest sandy lands in China, mobile sand dunes, semi-fixed sand dunes, and fixed sand dunes distribute widely. In mobile sand dunes, Caragana microphylla Lam. is commonly used to prevent the movement of sand dunes. In semi-fixed sand dunes, Artemisia halodendron is a dominant species. It declines along with the fixing of the sand dunes. In fixed sand dunes, sparse elm woodland is the climax community and original vegetation. Thus, we selected C. microphylla community, A. halodendron community, and sparse elm woodland as typical communities representing mobile sand dunes, semi-fixed sand dunes, and fixed sand dunes separately.

Sand dune succession goes along with an increase in plant community stability, higher soil quality, and more abundant biodiversity. Thus, we hypothesized that ecosystem services values increased along with the sand dune succession, i.e., the change from mobile sand dunes to semi-fixed sand dunes and fixed sand dunes. This study aims to test our hypothesis mentioned above and to reveal changes in ecosystem services in sand dune succession. This study could help us know the ecosystem services values of vegetation types in sandy lands exactly and make a decision to decide which vegetation type should be prior protected.

Methods

Study area

The study area is located in the Wulanaodu region, southeastern of the Horqin Sandy Land (42°29′–43°06′N, 119°39′–120 °02′E, 480 m) (Fig. 1). The region is a temperate continental semi-arid monsoon climate with the mean annual temperature of 6.3 °C. The average daily temperatures of the coldest month (January) and the warmest month (July) are -14 °C and 23 °C. The average annual precipitation is 340mm, 70% of which concentrates from June to August. The main wind direction is the northwesterly wind from March to May, followed by the southwesterly wind from June to September (Tang et al., 2014). The primary soil types are prodic arenosols and humic nitosols. Typical plants are C. microphylla, Setaria viridis, Bassia dasyphylla, Chenopodium glaucum, Chenopodium aristatum, Lespedeza daurica, Pennisetum centrasiaticum (Zhang et al., 2016a).

Fig. 1

The location of study area (cited from Zhang et al., (2016a)).

The estimation of ecosystem services values

In this study region, C. microphylla is a typical species in mobile sand dunes, as it is widely planted to fix the movement of sand dunes. Along with fixing of sand dunes, A. halodendron becomes a dominant species, especially in semi-fixed sand dunes. Then, A. halodendron declines along with the process of sand dune succession. In the last stage of the sand dune succession, i.e., fixed sand dunes, the sparse elm woodland come to be the climax community. Therefore, we selected C. microphylla community, A. halodendron community, and sparse elm woodland as typical communities representing mobile sand dunes, semi-fixed sand dunes, and fixed sand dunes separately.

The ecosystem services values in this study include five categories, including biodiversity protection, soil formation and retention, nutrient cycling, gas regulation, and water regulation.

Biodiversity protection

Net primary productivity (NPP) is an essential indicator of biodiversity protection. Here, we measured biodiversity protection following previous studies (He et al., 2005; Wen et al., 2013). We used the marketing value method to measure the value of biodiversity protection (Chaikumbung et al., 2016; Saarikoski et al., 2015).where is the value of biodiversity protection (CNY·hm−2·a−1); is the mass value of organic matter per ton of carbon (CNY·t−1 C).

We calculated the NPP following formulations in Li's study (Li, 2006).where is the biomass increment (g·cm−2); or is the biomass corresponding to the time or ; is the litter amount fromto (t·hm−2·a−1); : is the animal feed intake fromto ; is the time interval between investigations (a−1); is the maximum biomass of A. halodendron (g·cm−2); is the minimum biomass of A. halodendron.

The and represent in sparse elm woodland, C. microphylla community and A. halodendron community.

Soil formation and retention

Plant communities play critical roles in reducing soil loss and wind erosion, and in protecting soil fertility (Ouyang et al., 1999; Sutton et al., 2016). In this study, we evaluated ecosystem services values of soil retention considering soil fertility protection and soil erosion reduction. We calculated the value of the soil formation and retention following the equation.where is the value of soil formation and retention (CNY·hm−2·a−1); is the value of soil fertility protection (CNY·hm−2·a−1); is the value of soil erosion reduction (CNY·hm−2·a−1); is the soil retention (t·a−1); is the potential soil erosion in the test site (t·a−1); is the actual soil erosion in the test site (t·a−1); is the soil erosion modulus without forest (t·hm−2·a−1); is the soil erosion modulus after covering vegetation (t·hm−2·a−1); is the test area (hm2); is the contents of total N in soil (%); is the contents of available P in soil (%); is the contents of available K in soil (%); is the soil fertility gain per ton mass loss (CNY·t−1); is the test ground layer thickness (cm); is the soil bulk density (g·cm−3); is the biggest benefit from sand per hectare (CNY·hm−2·a−1).

Nutrient cycling

Nutrients in ecosystems work as a carrier for storing chemical energy and a material basis for life-sustaining activities (Shi et al., 2007; Tolessa et al., 2017). We calculated the number of nutrients stored in sand dunes ecosystems according to the alternative market method, which could estimate the economic value created by the sand dunes ecosystems in nutrient cycling (Escobedo et al., 2015). The formulation was below.where is the value of nutrient cycling (CNY·hm−2·a−1); is the contents of total N in soil (%); is the contents of available P in soil (%); is the contents of available K in soil (%); is the net primary productivity of the vegetation (t·hm−2·a−1); is the soil fertility gain per ton mass loss (CNY·t−1).

Gas regulation

The vegetation regulates the atmosphere mainly through the exchange of CO2 and O2 with the atmosphere through photosynthesis and respiration (Xu et al., 2013; Chaikumbung et al., 2016). We calculated the value of the adjustment of atmospheric balance using the opportunity cost method, the carbon tax method and industrial oxygen method. The formulation is below.where is the value of gas regulation (CNY·hm−2·a−1); is the value of carbon storage (CNY·hm−2·a−1); is the value of releasing oxygen (CNY·hm−2·a−1); is the annual CO2 fixed amount (t·hm−2·a−1); is the carbon sequestration coefficient; is the carbon fixation cost (CNY·t−1); is the annual O2 release (t·hm−2·a−1); is the oxygen release coefficient; is the oxygen release cost (CNY·t−1).

Water regulation

The provision of water is one of the most critical categories of ecosystem services that directly link growing human populations to ecosystems (Sajedipour et al., 2017). We calculated values of water regulation with the water balance method and shadow engineering method. The formulation was below (Xu et al., 2015).where is the water regulation value (CNY·hm−2·a−1); is the water source (mm·a−1); is the runoff coefficient (%); is the annual average rainfall (mm·a−1); is the water storage cost (CNY·m−3).

Some data were collected from previous studies to calculate ecosystem services values with the equations mentioned above (Table1).

Table 1

The variables and values to calculate ecosystem service values.

Vegetation	Variables	Values	Units	References
Sparse elm woodland	ΔB	213	g·cm−2	Zhang (2004)
	C_P	0.95	mg·kg−1	Zhang (2004)
	C_N	0.1	mg·kg−1	Zhang (2004)
	C_K	206.25	mg·kg−1	Zhang (2004)
	NPP_se	11.06	t·hm−2·a−1	Li (2006)
	ρ	1.44	g·cm−3	Jiang et al., (2008)
	ε_1	31.25	t·hm−2·a−1	Zhang et al., (2016b)
	ε_2	88.04	t·hm−2·a−1	Zhang et al., (2002)
C. microphylla	ΔB	416	g·cm−2	Jiang et al., (2008)
	C_P	3.81	mg·kg−1	Zhang et al., (2005b)
	C_N	0.043	mg·kg−1	Zhang et al., (2005b)
	C_K	40.67	mg·kg−1	Zhang et al., (2005b)
	NPP_cm	1.72	t·hm−2·a−1	Jiang et al., (2008)
	ρ	1.54	g·cm−3	Cao et al., (2004)
	ε_1	75.2	t·hm−2·a−1	Zhang et al., (2016b)
	ε_2	88.04	t·hm−2·a−1	Zhang et al., (2002)
A. halodendron	ΔB	49.75	g·cm−2	Yin et al., (2006)
	C_P	0.005	mg·kg−1	Zhang et al., (2005b)
	C_N	0.007	mg·kg−1	Zhang et al., (2005b)
	NPP_ah	2.30	t·hm−2·a−1	Yuan (2017)
	ρ	1.51	g·cm−3	Jiang et al., (2008)
	ε_1	25	t·hm−2·a−1	Zhang et al., (2016b)
	ε_2	88.04	t·hm−2·a−1	Zhang et al., (2002)

Results

Ecosystem services values in sand dunes

The ecosystem services values in mobile sand dunes, semi-fixed sand dunes, and fixed sand dunes were 6206.58 CNY·hm−2·a−1, 9986.28 CNY·hm−2·a−1, and 31466.56 CNY·hm−2·a−1. The values were the highest in fixed sand dunes and were the lowest in mobile sand dunes. More importantly, the ecosystem services value in fixed sand dunes was five times to that in mobile sand dunes (Fig. 2).

Fig. 2

The ecosystem service values increase along with the sand dune succession.

Categories of ecosystem services values

The value of biodiversity protection was 608.88 CNY·hm−2·a−1 in mobile sand dunes and increased to 815.47 CNY·hm−2·a−1 and 3915.24 CNY·hm−2·a−1 in the semi-fixed sand dunes and fixed sand dunes. The value of gas regulation was 2760.10 CNY·hm−2·a−1 in mobile sand dunes and increased to 3696.61 CNY·hm−2·a−1 and 17748.11 CNY·hm−2·a−1 in the semi-fixed sand dunes and fixed sand dunes. The value of nutrient cycling was 37.46 CNY·hm−2·a−1 in mobile sand dunes and increased to 71.46 CNY·hm−2·a−1 and 1063.41 CNY·hm−2·a−1 in the semi-fixed sand dunes and fixed sand dunes. The value of soil formation and retention was 522.16 CNY·hm−2·a−1 in mobile sand dunes and increased to 3124.74 CNY·hm−2·a−1 and 6461.80 CNY·hm−2·a−1 in the semi-fixed sand dunes and fixed sand dunes. The value of water regulation was 2760.10 CNY·hm−2·a−1 in three types of sand dunes (Table 2).

Table 2

The categories of ecosystem services in sand dunes (CNY·hm−2·a−1).

Categories	Mobile sand dunes	Semi-fixed sand dunes	Fixed sand dunes
Biodiversity protection	608.88	815.47	3915.24
Gas regulation	2760.10	3696.61	17748.11
Nutrient cycling	37.46	71.46	1063.41
Soil formation and retention	522.16	3124.74	6461.80
Water regulation	2278.00	2278.00	2278.00

Contributions to ecosystem services

In the mobile sand dunes, the ascending order of proportions in contributing ecosystem services was nutrient cycling (0.60%), soil formation and retention (8.41%), biodiversity protection (9.81%), water source conservation (36.70%), and gas regulation (44.47%). Meanwhile, in semi-fixed sand dunes, the ascending order of proportions in contributing ecosystem services was nutrient cycling (0.71%), soil formation and retention (8.17%), biodiversity protection (22.81%), water source conservation (31.29%), and gas regulation (37.02%). In fixed sand dunes, the ascending order of proportions in contributing ecosystem services was nutrient cycling (3.38%), water regulation (7.24%), biodiversity protection (12.44%), soil formation and retention (20.54%), and gas regulation (56.40%) (Fig. 3).

Fig. 3

The percentage of the proportion contributing to ecosystem services in sand dunes. MSD: mobile sand dunes, SFSD: semi-fixed sand dunes; FSD: fixed sand dunes.

Discussion

This result obtained in this work showed that ecosystem services values were the highest in fixed sand dunes and were the lowest in mobile sand dunes, indicating the ecosystem services values increased along with the sand dune succession. In this study region, the two categories, i.e., gas regulation, and soil formation and retention, contributed most of the ecosystem services values in fixed and semi-fixed sand dunes (76.94% and 68.31%). Meanwhile, the two categories, i.e., gas regulation, and water regulation contributed most of the ecosystem services values in mobile sand dunes (81.17%). The performance in aspects of gas regulation and soil formation and retention was better in fixed sand dunes (Li et al., 2004; Zhang et al., 2015). That might explain why the ecosystem services values are higher in fixed sand dunes.

The ecosystem services values in the Horqin Sandy Land are reported in a previous study. Yuan et al. (2018) reported ecosystem services value in the sparse elm woodlands in the Horqin Sandy Land was 5941.34 CNY·hm−2·a−1, which is much lower than this study. In this study, ecosystem services value was 31466.56 CNY·hm−2·a−1 in sparse elm woodlands. The reasons might be due to the values of O2 regulation and water regulation are not considered in Yuan's study. The lack of values of O2 regulation and water regulation might partly explain the difference in ecosystem services values in the sparse elm woodlands.

The ecosystem services values in deserts are also reported. For example, Taylor et al. (2017) evaluated the ecosystem services values in the Chihuahuan desert and found the ecosystem services value was 3907.71 CNY·hm−2·a−1 (1USD = 7.75CNY). Besides, Richardson (2005) reported the ecosystem services value was 331.43 CNY·hm−2·a−1 (1USD = 7.75CNY) in California desert in the USA. It seems that ecological services values in deserts are lower than that in this study. It might be partly explained by lower vegetation cover and poor soil in deserts (Hu et al., 2015b; Yue et al., 2016).

The ecosystem services values in coastal sand dunes are also reported. For instance, Brenner et al. (2010) studied the ecosystem services values of Catalan coastal sand dunes in Spain and claimed the ecosystem services values were 807.13 CNY·hm−2·a−1 (1USD = 7.75CNY). In Brenner's study, the ecosystem services values consisted of disturbance regulation, aesthetic values, recreation and cultural and spiritual values. You et al. (2018) reported the ecosystem services value was 232.35 CNY·hm−2·a−1 (1USD = 7.75CNY) in Shinduri coastal sand dunes in South Korea (You et al., 2018). In You's study, tourism infrastructure, thinning, coastal sand dune restoration, afforestation, and weeding constituted ecosystem services values. It seems that cultural values such as recreation and tourism are more considered in coastal sand dunes (Katz-Gerro and Orenstein, 2015). However, tourism and recreation are little considered in sand dunes in arid and semi-arid areas.

It is widely reported the ecosystem services values in forests and grasslands (Xie et al., 2010; Wen et al., 2013; Wang et al., 2006; Li et al., 2010; Costanza et al., 2014). According to these studies, ecosystem services values in sand dunes are relatively lower than that in forests and grasslands. It might be due to three reasons. Firstly, the forests and grasslands ecosystems have higher biomass, higher net primary productivity, and better ecosystem services functions occur in forests and grasslands (Wang et al., 2013; Cong et al., 2017). Secondly, soil bulk density, soil water capacity, and soil acidity are the most important factors (Duan et al., 2008). Compared with that in forests and grasslands, the lower vegetation coverage and poor soil cause lower ecosystem services values in sand dunes. Thirdly, land use patterns led by human beings have changed the supply of ecosystem services (Lawler et al., 2014). Human's behaviors tend to transform sand dunes ecosystems with less human benefits into forests and grasslands ecosystems that have greater benefits for humans to gain high economic returns and meet maximum available markets (Sawut et al., 2013).

This results reported the values of carbon storages in mobile, semi-fixed and fixed sand dunes were 1983.08 CNY·hm−2·a−1, 2655.94 CNY·hm−2·a−1, 12751.67 CNY·hm−2·a−1, claiming sand dunes were a vital source of carbon stocks. It is known that the global terrestrial system stores more than 80% of carbon and most of the carbon stored in forests and grasslands ecosystems (Sun et al., 2006). Recently, some studies claim that sand dunes are a potential carbon sink (Hu et al., 2015a; Gao et al., 2017). This result supported the evidence that sand dunes play a vital role in carbon stocks. Moreover, as the capacity of carbon sequestration is larger in fixed sand dunes, it suggests that fixed sand dunes are more critical for carbon stocks than mobile and semi-fixed sand dunes.

Conclusion

Here, ecological services values in sand dunes along the sand dune succession in the Horqin Sandy Land were evaluated and compared. The results showed that the ecosystem services values of mobile, semi-fixed, and fixed sand dunes were 6206.58 CNY·hm−2·a−1, 9986.28 CNY·hm−2·a−1, and 31466.56 CNY·hm−2·a−1 respectively. The two categories, i.e., gas regulation, and soil formation and retention were the main categories contributing to ecosystem services values in fixed and semi-fixed sand dunes. Their contributions were 76.94 % and 68.31% of ecosystem services values in fixed sand dunes and semi-fixed sand dunes. Meanwhile, gas regulation and water regulation were the main categories contributing to ecosystem services values in mobile sand dunes and they accounted for 81.17% of the ecosystem services values.

First of all, these results support our hypothesis that ecosystem services values increased along with the sand dune succession. The benefits of sand dune succession are mainly related to keeping biodiversity and promoting plant restoration. These findings enlarge the benefits of sand dune succession and provide evidence that the increase in ecosystem services values is consistent with the combat of desertification. Moreover, compared with A. halodendron community and C. microphylla community, the ecosystem services values are relatively high in sparse elm woodlands It suggests that sparse elm woodland should be under the priority protection for providing ecosystem services values.

Declarations

Author contribution statement

Jiawei Yang: Conceived and designed the experiments; Performed the experiments; Analyzed and interpreted the data; Contributed reagents, materials, analysis tools or data; Wrote the paper.

Yi Tang: Conceived and designed the experiments; Analyzed and interpreted the data; Contributed reagents, materials, analysis tools or data; Wrote the paper.

Funding statement

This work was supported by the National Natural Science Foundation of China (31870709).

Competing interest statement

The authors declare no conflict of interest.

Additional information

No additional information is available for this paper.