The balance of ecological and economic benefits of sea-buckthorn

Abstract

Sea-buckthorn, with high economic value, is one of the important tree species for windbreak, sand fixation and conservation of water and soil. Based on this, an equilibrium analysis method for ecological and economic benefits of sea-buckthorn was proposed. After analyzing the ecological function and economic value of sea-buckthorn, based on the system theory, the utilization benefit equilibrium model of sea-buckthorn was constructed from economy and ecology two dimensions. The equilibrium of sea-buckthorn utilization benefit in an evolutionary cycle was divided into low-level symbiosis, coordinated development, limit development and regeneration development four stages. In order to comprehensively reflect the overall situation of sea-buckthorn utilization benefits, an index system including two major systems of social economy and ecological environment was designed, and 12 indicators in the ecological function and economic value analysis results of sea-buckthorn were selected to judge the interaction balance between economic benefits and ecological benefits. Taking Liaoning Province as the research object, the comprehensive economic and ecological benefits of sea-buckthorn utilization between 2004 and 2017 shows that during this period, the growth rate of ecological benefits was slower than that of economic benefits and had fluctuations. From the evolution curve of the equilibrium of utilization benefits, the sea-buckthorn in Liaoning Province is in the coordinated development stage, but the coupling degree has been increasing in recent years, indicating that the utilization benefits of sea-buckthorn in Liaoning Province may enter the limit development stage. According to the research results, this method can effectively analyze the balance of ecological and economic benefits of sea-buckthorn, which is conducive to the maximum value of sea-buckthorn.

Keywords

System theory liaoning province index system weight entropy weight method

1 Introduction

Sea-buckthorn is a shrub or small tree that is highly adaptable to harsh environments such as high temperature, low temperature, drought, infertile land, saline-alkali land, and dust storm [4]. It is a deciduous shrub or small tree plant, belonging to Elaeanaeeae, Hippophae. There are five species of sea-buckthorn in China. There are four subspecies belonging to sea-buckthorn specie: Chinese sea-buckthorn, Yunnan sea-buckthorn, Central Asian sea-buckthorn and Mongolian sea-buckthorn. Chinese sea-buckthorn subspecies is the most widely distributed in China, mainly distributed in the northwest, north and northeastern provinces. The sea-buckthorn in Liaoning Province is mainly Chinese sea-buckthorn. In recent years, Liaoning Province has introduced varieties of sea-buckthorn from Russia and Mongolia, and also developed high-yielding varieties through systematic breeding methods. According to relevant survey [13], the total area of sea-buckthorn forest in China is about 8.7 million hectares, of which natural forests account for about 70%, and plantations account for about 30%. The area of sea-buckthorn forests in Shanxi, Shaanxi and Gansu province account for about 2/3 of the whole country. The sea-buckthorn in Liaoning Province is mainly distributed in the northwestern part. Among them, Jianping County has a large area of sea-buckthorn forest. With the development of research on the comprehensive exploit and utilization of sea-buckthorn, higher requirements have been put forward for the varieties. The economic varieties, grazing varieties, eco-economic varieties and ornamental varieties have been gradually developed.

For a long time, the afforestation work only focused on the construction of arbor forest and neglected the development of shrub forest including sea-buckthorn. With the destruction of human beings, in the arid cold area where the annual precipitation is below 350 mm, soil and gully land erosion occurred in many places [2]. The soil fertility in these areas decreased significantly, regressive successions and simplification occurred in the vegetation community, and the exposed area of soft rock increased rapidly. Sea-buckthorn has its own unique ecological advantages to restore vegetation in these places with special difficulty [20 , 26–28]: It can tolerate –50°C severe cold and 60°C high temperature on the ground; it can grow in dry areas with annual precipitation of 200 mm, and can also tolerate seasonal water accumulation; it has no strict requirements on the soil. It may grow in the alkaline soil with pH value of 9.5 and the salinized soil with salt content of 1.1%; the root of sea-buckthorn is developed, the lateral root may reach more than 10 meters, and the depth may reach 4 meters. The root has a nodule, which can fix the free nitrogen in the air, to help it grow rapidly. Its strong roots can conserve water and soil. For the above reasons, sea-buckthorn is one of the important tree species for windbreak, sand fixation and conservation of water and soil, and its ecological benefits have received increasing attention. At the same time, it is also important to comprehensively exploit the sea-buckthorn fruits and improve the economic benefits of sea-buckthorn forest.

The rapid economic development has achieved great economic profit, meanwhile, the ecological deterioration and the sharpening of contradictions between people and the environment have in turn restricted the sustainable development of the economy. Making a coordination between the economic benefits and ecological benefits of sea-buckthorn utilization has become the focus of people. Based on this, an equilibrium analysis method of ecological and economic benefits of sea-buckthorn was proposed to provide reference for structural adjustment and sustainable use of sea-buckthorn.

2 Material and methods

2.1 Sea-buckthorn and its nutrient analysis

The roots, stems, and leaves of sea-buckthorn, as well as fruits, contain a variety of biologically active substances, more than 200 of which have been detected [14]. These substances include a variety of amino acids, proteins, vitamins, fatty acids, alkaloids, flavonoids, and trace elements, which are essential for the human and their health but cannot be synthesized by human. The main nutrients in sea-buckthorn fruits are: (1) Vitamins: Sea-buckthorn fruit is rich in vitamin C. The vitamin C content in its fresh fruit is 580–800 mg/100 g, which is about 20 times that of hawthorn, 6 times that of orange, and 80 times that of tomato. It is also rich in vitamin E, vitamin A, and vitamin B. The carotenoid content in its fruit is about 4.5 mg/100 g. (2) Protein and amino acid: the protein content in sea-buckthorn fruit, fruit juice, seeds juice is 2.89%, 0.9% to 1.2%, 24.38%, respectively. Its flesh, fruit juice and seeds contain 7-8 kinds of essential amino acids. (3) Flavonoids: flavonoids such as quercetin, isorhamnetin, kaempferol, catechin, baicalin are mainly distributed in the leaves of sea-buckthorn. (4) Fatty acids and oils: sea-buckthorn fruit and seeds are rich in fatty acids, including myristic acid, lauric acid, palmitic acid, palmitoleic acid, stearic acid, oleic acid, linoleic acid, linoleic acid, and arachidonic acid. (5) Organic acids: The total acid content in sea-buckthorn fruit is about 3.86% to 4.52%, mainly including malic acid, citric acid, oxalic acid, succinic acid, gallic acid, and chlorogenic acid. (6) Trace elements: elements detected from sea-buckthorn juice or oil are potassium, calcium, sodium, magnesium, copper, zinc, iron, manganese, selenium, phosphorus, nitrogen and other macro or trace elements. (7) Sea-buckthorn leaves and fruits also contain a variety of triterpenoids, sterols, organisms, sugar and volatile components.

2.2 Ecological function of sea-buckthorn

2.2.1 Strong ability to conserve water and maintain soil

Intercept of rainfall, the sea-buckthorn is leafy, with a wide crown and strong rain carrying capacity. It can be used as the first line of defense to maintain soil and water in areas with serious soil erosion. The Sea-buckthorn Research Center of the Ministry of Water Resources in Inner Mongolia has observed the natural rainfall and artificial simulated rainfall in the small watershed of Jungar Banner in Inner Mongolia. The results show that the rain carrying capacity of sea-buckthorn of 6 to 8 years in the mountain is 9.5–13 mm, accounting for 21% to 27% of the amount of one rainfall.

The water conservation of sea-buckthorn litter, the sea-buckthorn forest falls into a layer of branches and leaves every autumn, and gradually accumulates a layer of sponge-like litter. It directly carries the rainwater that flows down the crown and the branches, avoiding the erosion of raindrops on the ground [21]. At the same time, the litter can absorb a considerable amount of rainwater, effectively control the generation of runoff, filter and disperse of the formed runoff, which avoid or reduce the erosion of runoff. According to the survey, when the thick of litter is 1 cm per square meter in sea-buckthorn forest, the soil erosion can be reduced from 168.4 g in bare land to 72.6 g. When the thick is 2 cm, the soil erosion is only 5.5 g. It can be seen that the litter has a great reinforcing effect on soil erosion resistance.

Strong ability of soil reinforcement, sea-buckthorn is a shallow-root tree, and its lateral roots have a strong ability to sprout. The root is densely layered from 0 to 40 cm under the topsoil. The adult roots and their lengths account for 73% and 54% of the total profile, respectively. The corrosion resistance of the topsoil is increased by the intensive roots of sea-buckthorn. The vertical and horizontal extension of the main and lateral roots increase the cohesive force and viscous force between the soil layers, which plays a role in preventing gravity erosion and reducing soil erosion [8]. For example, in Liangcheng, Inner Mongolia, the average runoff in sea-buckthorn forest reduced by 25.4% compared with the grassland, and it was 35.7% lower than that of the wasteland. The sediment yield of sea-buckthorn forest was 80% lower than that of the grassland, and 92% less than the wasteland.

2.2.2 The obvious effect of improving soil

The sea-buckthorn crown intercepts rainfall. Surface litter and grassland store water. Roots of sea-buckthorn promote the infiltration of precipitation into the ground. These increase the organic matter in soil, form agglomerate structure and improve the water retention capacity of soil. Sea-buckthorn roots die in the soil and form organic matter under the effect of microorganisms, which plays an important role in improving the physical and chemical properties of the soil [12]. It can be measured that in the 5-year-old sea-buckthorn forest, the soil capacity and water permeability of the 0–40 cm soil layer are 2.3 times that of the barren hill soil, the soil organic matter is increased by 41.8%, the soil moisture content is increased by 61.9%, and the porosity is increased by 9.1%.

Sea-buckthorn is a non-legume woody nitrogen-fixing tree species. The root is infested by Rhizobia to form nodules. Nitrogen fixation is the main source of nitrogen for nutrition and improving soil. Therefore, the number of nodules in the roots and the activity of Rhizobia are important indicators for judging the nitrogen-fixing ability of sea-buckthorn. Nitrogen is an essential element for plant growth and is also the major component of proteins and nucleic acids, so it is called a life element [1]. Therefore, sea-buckthorn is a pioneer tree species that improves the poor soils and erosion areas. According to the data in the foreign, every 667 m² sea-buckthorn forest can fix 12 kg nitrogen, which is equivalent to 12.5 kg of urea. According to the practical measurement, the weight of fresh root nodules of three, five, and nine years are 25 g, 38 g, and 42 g, respectively. The nitrogen fixation amount of each plant was 7.45, 11.324 and 12.56 mg, respectively. The soil nutrient content of the sea-buckthorn forest planted on the soft rock is higher than that of the control wasteland. It can be seen that sea-buckthorn has a significant effect on the improvement of soil fertility.

2.2.3 Improve the microclimate in the biosphere

Because the presence of sea-buckthorn forest changes the characteristics of the forest surface, microclimate with small temperature variation, high humidity and low wind speed is formed. According to tests, the temperature difference between day and night in sea-buckthorn forest is 2°C lower than that of open space. The ground temperature difference in sea-buckthorn forest is 17.7°C lower than that of open space. Its relative humidity is 0.9% higher than that of open space, and its wind speed is reduced by 18% compared with open space. It can be seen that the microclimate benefits of sea-buckthorn forest are considerable.

2.3 The unique economic value of sea-buckthorn

The sea-buckthorn fruit is sweet and sour, containing a variety of vitamins required by the human body [19]. It contains an average of 453.9 mg vitamin C per 100 g fruit, 200 mg vitamin E and 100 mg vitamin A per 100 g seed. Sea-buckthorn also contains more than 20 kinds of amino acids and trace elements essential for life, mainly including palmitic acid, oleic acid and linoleic acid. The fruit has stable property and can be made into a variety of beverages and foods such as various tablets or extracts, jams, preserves, juices, sherbet, and vinegar.

Sea-buckthorn has high medicinal value [18], which can improve digestion, promote metabolism and enhance vitality, so it is called anti-aging fruit. Its fruit is warm, sour, sputum, which can be used to treat colds, coughs, asthma, wind, malaria, belching and leakage. Its seeds can be used as laxatives, and the average oil content in the seeds is 7.8% to 11.9%. The sea-buckthorn oil extracted from its seeds, peels and pulp contains a variety of life-active substances, which can resist radiation and release fatigue. Anti-cancer substances can be extracted from its bark, and its leaves and shoots can be used as feed. Tannin can also be extracted from its bark. Figure 1 shows sea-buckthorn fruit, branches and leaves.

Fig.1

Sea-buckthorn fruit and its branches and leaves.

Sea-buckthorn has three main practical values. First, it can be used as a fuel. With luxuriant branches and leaves, large firewood production, fast combustion and strong firepower, sea-buckthorn has become the main fuel in arid, semi-arid and energy deficient areas. Second, it can be used as a feed. The feed value of the sea-buckthorn branches can be compared with the king of the feed grass, alfalfa. It is rich in nutrition and has good palatability, which is suitable for rapid fattening and increased yield of livestock. Third, it can be used as fertilizer. Sea-buckthorn is a non-legume nitrogen-fixing plant with strong fertility and soil improving effect. In addition, its wood is solid and its texture is fine, which can be used for furniture, farm tools and various handicrafts.

2.4 Analysis of sea-buckthorn ecological and economic benefits

The benefits of sea-buckthorn utilization are the general term for various useful results obtained by sea-buckthorn utilization activities [7], which is a composite system consisting of economic benefit and ecological benefit. The basic idea of system theory is to treat the object of research and treatment as a whole system, and to study the relationship between the whole system and the elements of the whole system from the whole, so as to grasp the whole system and achieve the optimal goal. In this composite benefit system, the economic benefit and ecological benefit of sea-buckthorn are closely related, and the balanced coordination of the two plays a role in promoting the sustainable development of the economic society and ecological environment [10]. From the perspective of system theory, it is considered that the sea-buckthorn utilization benefits system is a natural socio-economic complex system, which is a multi-dimensional equilibrium [17]. From the two dimensions of economy and ecology, using the equilibrium relationship model to analyze the sea-buckthorn utilization benefits, which enables to judge the interaction degree between economic benefit and ecological benefit.

2.4.1 Equilibrium relationship model of sea-buckthorn utilization benefit

Equilibrium is the phenomenon in which two (or more) systems or forms of motion interact with each other through various interactions [23]. Equilibrium degree is the degree to which a system or motion interacts with each other. In the equilibrium analysis, equilibrium is a quantitative data reflecting the interaction and coordinated development of the economic benefits system and ecological benefits system [3]. Assuming that x_i (i = 1, 2, ⋯ , n) is the n indicators of the economic benefit system for land use, and y_j (j = 1, 2, ⋯ , m) is the m indicators of the ecological benefit system for land use. Comprehensive development level of the economic benefit system and the ecological benefit system for sea-buckthorn utilization can be expressed as: $Q_{1} = \sum_{i = 1}^{n} a_{i} x_{i}, i = 1, 2, \dots, n$ (1) $Q_{2} = \sum_{j = 1}^{m} b_{j} y_{j}, j = 1, 2, \dots, m$ (2)

Where Q₁ indicates the comprehensive development level of sea-buckthorn economic benefit system, Q₂ indicates the comprehensive development level of sea-buckthorn ecological benefit system, x_i and y_j are the elements of two systems, a_i and b_j are the weights of each element. According to the balanced relationship between economic benefit and ecological benefit of sea-buckthorn utilization, they can be considered as a composite system composed of two dominant factors. Referring to general system theory, the evolution equation of this composite system can be expressed as: ${\begin{matrix} A = \frac{{dQ}_{1}}{dt} = f_{1} (Q_{1}, Q_{2}) \\ B = \frac{{dQ}_{2}}{dt} = f_{2} (Q_{1}, Q_{2}) \end{matrix}$ (3)

Where f₁ is the economic degree evolution of seabuckthorn; f₂ is the evolution degree of seabuckthorn ecological benefit. t is the year. A and B are the evolution state of the sea-buckthorn economic benefit subsystem and ecological benefit subsystem under the influence of themselves and the outside. A and B interact with each other. Any change in Q₁ or Q₂ will result in a change in A and B. Conversely, any change in A and B will result in a change in Q₁, Q₂ and the whole system. In conclusion, the change of any element depends on all the other elements, and the system behaves as a whole [15].

Under the joint influence of themselves and the outside world, the evolution speed of the economic benefit subsystem and the ecological benefit subsystem can be expressed as: $\begin{matrix} V_{A} = \frac{dA}{dt} \\ V_{B} = \frac{dB}{dt} \\ V = f (V_{A}, V_{B}) \end{matrix}$ (4)

Where V_A and V_B are the evolution speed of the economic benefit subsystem and the ecological benefit subsystem. V is the evolution speed of the whole system, regarded as a function of V_A and V_B. When the economic benefit subsystem is coordinated with the ecological benefit subsystem, the whole system is also in coordinated development. Therefore, taking V_A and V_B as control variables, the equilibrium relationship between the whole system and the economic and ecological benefit subsystems can be obtained through the analysis of the change of V.

Since the change of V is caused by V_A and V_B, V can be analyzed in a two-dimensional plane (V_A, V_B). Taking V_A and V_B as control variables to establish a coordinate system, the change trajectory of V is an ellipse in the coordinate system, because ecological benefit does not change as rapidly as economic benefit [11]. The angle between V and V_B is equalization α, which can be expressed as: $tan α = \frac{V_{A}}{V_{B}}$ (5) $α = arctan \frac{V_{A}}{V_{B}}$ (6)

According to the change of α, the evolution state of the whole system in a cycle can be determined, and the equilibrium of the coordinated development of sea-buckthorn economic and ecological benefits is shown in Table 1. Obviously, in an evolutionary cycle, the whole system will experience four stages: low-level symbiosis (I), coordinated development (II), extreme development (III), and regeneration development (IV) [22].

Table 1

Distinguishing the equilibrium relation between ecological benefit and economic benefit of sea-buckthorn

αvalue	Coupling Phase (and Equilibrium Relation)
–90°< α<0°	Low-level symbiotic stage: During this period, the intensity of land use is small, the capacity of ecological environment is large, and the social and economic benefits and ecological environmental benefits are not obvious.
0°< α<90°	The stage of coordinated development: the social and economic benefits and ecological and environmental benefits of land use are obvious. When α= 0 degree, the upper land use efficiency is most coordinated. When alpha approached 0 or 90 degrees, the land use efficiency was not well coordinated.
90°< α<180°	Limit development stage: Due to the destruction and deterioration of the ecological environment, the social and economic benefits of land use are limited and begin to decline from the limit. The contradiction between them becomes more and more prominent, which eventually leads to the disintegration of the system.
–180°< α< –90°	The stage of regeneration development: because the social and economic benefits of land use and the ecological and environmental benefits are in a bad state, the old system is disintegrated and the new system comes into being.

2.4.2 Indicator system and weights determination

In order to fully reflect the overall situation and the characteristics of sea-buckthorn utilization benefits, two major systems including socio-economic and ecological environment were designed based on the definition of sea-buckthorn utilization benefits, the analysis of inter-system relationships and related literature. According to the consultation of relevant experts, 12 system indicators were finally determined to establish an indicator system [9]. The weight of each indicator was determined by the entropy method. The results are shown in Table 2.

Table 2
Comprehensive evaluation index system and weight of sea-buckthorn utilization benefit

Index system Specific indicators Weight

Social and Economic Benefits Leaf yield per plant 0.0640

Accumulation per hectare 0.0781

Sea-buckthorn fruit per mu output value 0.0873

Total output value of sea-buckthorn fruit 0.0807

Per capita share of sea-buckthorn fruit output value 0.0852

Cost ratio of sea-buckthorn output value 0.0705

Eco-environmental Benefits Interception precipitation 0.0894

Impoundment 0.0911

Soil consolidation capacity 0.0841

Windbreak performance 0.0872

Exhaust gas absorption 0.0916

Improve the soil 0.0908

Index system	Specific indicators	Weight
Social and Economic Benefits	Leaf yield per plant	0.0640
	Accumulation per hectare	0.0781
	Sea-buckthorn fruit per mu output value	0.0873
	Total output value of sea-buckthorn fruit	0.0807
	Per capita share of sea-buckthorn fruit output value	0.0852
	Cost ratio of sea-buckthorn output value	0.0705
Eco-environmental Benefits	Interception precipitation	0.0894
	Impoundment	0.0911
	Soil consolidation capacity	0.0841
	Windbreak performance	0.0872
	Exhaust gas absorption	0.0916
	Improve the soil	0.0908

In order to eliminate the impact caused by the disunity of indicators dimension or indicators measurement level, the indicator data needs to be treated with non-dimensional process. Therefore, the positive and negative indicators of economic and ecological benefit are standardized as follows: $x_{ij}^{'} = {\begin{matrix} \frac{(x_{ij} - m_{i})}{(M_{i} - m_{i})} \\ \frac{(M_{i} - x_{ij})}{(M_{i} - m_{i})} \end{matrix}$ (7)

3 Results

According to the balanced relationship model of seabuckthorn utilization benefit constructed in this paper, the comprehensive value of economic benefit and ecological benefit of seabuckthorn utilization in Liaoning province from 2004 to 2017 is analyzed, and the data is processed by MATLAB software, the results are shown in Fig. 2. In the figure, the comprehensive benefit of seabuckthorn is represented by numerical value. The higher the numerical value is, the higher the comprehensive benefit of seabuckthorn is. The lower the numerical value is, the lower the comprehensive benefit of seabuckthorn is.

Fig.2

Evolution curve of sea-buckthorn utilization benefit in Liaoning province from 2004 to 2017.

It can be seen from Fig. 2 that the economic benefit of sea-buckthorn utilization in Liaoning Province in 2004–2017 showed a sustained and rapid upward trend, and its comprehensive value increased from 0.018 in 2004 to 0.9819 in 2017, with an increase of 0.9638 and an average annual growth rate of 23.06%. In 2007–2017, the comprehensive value of economic benefit increased significantly, and social economic benefit witnessed an obvious growth [6, 16]. The upward trend of the development of sea-buckthorn utilization economic benefit is basically consistent with the actual development of social economy. This is not only due to the strong support of the national macro-policy, but also strongly influenced by the internal driving force of social economic development in the remote urban area.

Using the comprehensive value curve of the economic benefit and the ecological benefit of the sea-buckthorn in Fig. 2 through the Eviews 6.0 tool, the evolution equation of the utilization benefit of the sea-buckthorn in Liaoning province was obtained. $\begin{matrix} A = 0.0001257 t^{3} + 0.0015911 t + 0.0236272, \\ R^{2} = 0.9970 \end{matrix}$ (8)

$\begin{matrix} B = 20.1831001 t^{0.0113858} - 20.0993012, \\ R^{2} = 0.7867 \end{matrix}$ (9)

Getting derivative with respect to t from Equation (3), the above two equations can be used to calculate the evolution rate equation of sea-buckthorn utilization benefit in Liaoning Province from 2004 to 2017: $\begin{matrix} V_{A} = \frac{dA}{dt} = 0.0003771 t^{2} \\ + 0.0031822 t + 0.0236272 \end{matrix}$ (10) $V_{B} = \frac{dB}{dt} = 0.22980074 t^{- 0.9886142}$ (11)

From Equations (10), (11) and (5), (6), the development speed and equilibrium of sea-buckthorn utilization benefits in Liaoning Province from 2004 to 2017 were calculated, as shown in Table 3.

Table 3

Development speed and equilibrium degree of sea-buckthorn utilization benefit in Liaoning Province during 2004–2017

Year / year	Economic performance	Ecological benefit	tan α	Equilibrium degree
2004	0.0272	0.0198	0.1183	6.75°
2005	0.0315	0.0158	0.272	15.22°
2006	0.0366	0.0776	0.4715	25.24°
2007	0.0424	0.0584	0.7263	35.99°
2008	0.0490	0.0468	1.0461	46.29°
2009	0.0563	0.0391	1.4402	55.23°
2010	0.0644	0.0336	1.9181	62.47°
2011	0.0732	0.0294	2.4893	68.11°
2012	0.0828	0.0262	3.1632	72.46°
2013	0.0932	0.0236	3.9490	75.79°
2014	0.1043	0.0215	4.8563	78.36°
2015	0.1161	0.0197	5.8944	80.37°
2016	0.1287	0.0182	7.0726	81.95°
2017	0.1421	0.0169	8.4002	83.21°

From Table 3, during the 14 years from 2004 to 2017, the equilibrium of utilization benefits of sea-buckthorn in Liaoning Province was generally in a coordinated development state, which can be roughly divided into two stages, respectively.

The first stage: from 2004 to 2008, the equilibrium of sea-buckthorn utilization benefit in Liaoning Province increased from 6.75° to 46.29°, and the comprehensive economic benefit value (V_A) maintained an upward trend, while the comprehensive value of ecological benefit (V_B) was in fluctuation and showed a decreasing trend in general. Study shows that when the equilibrium α is at 45°, the sea-buckthorn utilization benefits are most coordinated. During the study, the coupling degree reached 46.29° in 2008, close to 45°, indicating that during this economic development period, the development speed between economic benefit and ecological benefit gradually evolved from low-level coordination to relative coordination [5 , 30]. The economic subsystem had a weaker reaction to the ecological subsystem and made less damage to the ecology. The whole sea-buckthorn utilization benefit system is in a good coordinated development state. The possible reason is that in 2004, Liaoning Province completed the work of transforming county into urban district, and the area of sea-buckthorn forest in these regions had been expanded, and the economic potential had been gradually released. Since then, this province has initiated the construction of landscape garden cities, which had led to a significant decline in the main pollutants such as industrial wastewater and waste gas in the remote urban area, and the comprehensive value of ecological benefit was in a stable state during the study period.

The second stage: from 2009 to 2017, the development rate of economic benefit (V_A) is always higher than that of ecological benefit (V_B). The equilibrium of sea-buckthorn utilization benefits has increased continually, from 55.23° to 83.21°. Although the equilibrium of sea-buckthorn utilization benefits is generally in the range of coordinated development, since 2015, the equilibrium had exceeded 80° and was increasing continually [31]. The reason is that after the adjustment of the first stage, the social economy development of Liaoning Province had made great progress, and the government had intensified the construction of sea-buckthorn forest in six remote urban areas, which had accelerated the pace of coordinated development of sea-buckthorn forest in the central and urban areas. The construction of sea-buckthorn forest infrastructure promotes the improvement of the economic benefit of sea-buckthorn utilization. However, under the double pressure of population growth and industry agglomeration, the resources carrying capacity of sea-buckthorn had declined. The structure and intensity of sea-buckthorn utilization in the remote urban areas exceeded the intensity of environmental management and ecological protection, and the disadvantages of the ecological benefit lag were gradually emerging, leading to an increase in equilibrium. The utilization benefit of sea-buckthorn tended to be in a state of less coordination.

4 Discussion

This paper takes Liaoning Province as an example to compare and analyze the equilibrium of sea-buckthorn utilization benefits in this province from 2004 to 2017. Although the equilibrium between the economic and ecological benefits of sea-buckthorn utilization in this province has been in a coordinated development for 14 years, it cannot be ignored that the equilibrium was in rapid increased these years, and in the future sea-buckthorn utilization benefits may enter the limit development stage. In the research period, except in 2006 and 2007, the development speed of ecological benefits of sea-buckthorn in Liaoning Province was higher than that of economic benefits, the other years were behind the development speed of economic benefits [24, 25]. Especially after 2006, the development speed of ecological benefits has declined significantly. It is indicating that the economic potential was released, the resource carrying capacity of sea-buckthorn declined, and the economic subsystem had shown a stressing effect on the ecological subsystem. Therefore, under the premise of changing the traditional sea-buckthorn utilization mode and ensuring steady economic growth, the sustainable use of sea-buckthorn resources must be promoted in accordance with the construction requirements of resource-conserving and environmentally friendly, otherwise the lagging ecological environment construction will hinder and restrict the development of the social economy, and will eventually lead to the deterioration of the overall equilibrium system.

With the active start of ecological construction, soil and water conservation, windbreak and sand fixation projects in the northwestern part of China, sea-buckthorn, as an excellent tree species for soil and water conservation, windbreak and sand fixation, has met its time for development. At the same time, the optimal construction and comprehensive utilization of sea-buckthorn resources must also have strong technical support, which provides opportunities such as resources, environment and market for the innovative and comprehensive research on sea-buckthorn. In the “National Plan for the Development of Sea-buckthorn from 1996 to 2000”, the Sea-buckthorn Development Management Center of the Ministry of Water Resources proposed that the main purpose of developing sea-buckthorn in China is to use the ecological benefit of sea-buckthorn to promote environmental management, and to develop its economic and social benefits. The ecological benefit of sea-buckthorn should be put on the first place in the comprehensive development, and the utilization of its fruits should keep up with its ecological benefit. From the scientific perspectives, there is still a lot of research work to be done on the comprehensive development of sea-buckthorn, which can be summarized into the following four aspects.

4.1 Establish an effective sea-buckthorn development and protection mechanism

In order to protect the sea-buckthorn, the relevant supporting system must keep up and an effective sea-buckthorn development and protection system is necessary to ensure the coordinated development of sea-buckthorn economy and ecological protection. The institution-making department should clarify the responsible people for the development and protection of sea-buckthorn, refine the management functions of the local forestry management department, and strengthen the authority and details of the government in the regulation of sea-buckthorn. At the same time, it is necessary to strengthen the legislative work of sea-buckthorn protection. At present, there is a lack of corresponding legal provisions on the protection of sea-buckthorn all over the China. Government functional departments often face situations that there is no special law to refer to. It is necessary to establish ecology-dominant legislative principles rather than pursue short-term interests at the expense of long-term environmental ecology. Improving the legal system and protecting forests according to the law must be promoted to ensure the coordination of sea-buckthorn economic development and ecological protection.

4.2 Change the development and protection thought of sea-buckthorn

At present, the developing mode of sea-buckthorn in China mainly focuses on the development, and is supplemented by protection. The sea-buckthorn economy under this guidance developed rapidly in the short term, but the price is huge. The excessive cutting has caused a large amount of soil erosion and the significant decline of forest coverage, and this need to be improved. In the future development, people must adhere to the mode of combining economy with ecological environment, and carry out forestry economic development in a scientific and rational way.

4.3 Strengthen the construction of sea-buckthorn protection team

The protection of sea-buckthorn ecological environment requires not only the system, but also the cooperation of personnel. A professional and thorough sea-buckthorn protection staff is the basis of the environmental protection work. In terms of personnel selection and work arrangement, relevant policy and treatment are essential, and this will encourage college graduates to dedicate themselves in the forefront of work, put their professional expertise into and practice, and constantly improve their business level and ability.

4.4 Comprehensive utilization of sea-buckthorn

People should strengthen the extraction and quality assurance of sea-buckthorn juice, oil, yellow pigment, and focus on its application in medicine and health care products, food and cosmetics industries. Sea-buckthorn has become the first tree choice for windbreak, sand fixation and conservation of water and soil because of its special tolerance of drought, cold, salt, alkali, and sand. The ecological benefits of sea-buckthorn forest in extremely harsh environment have been approved. Sea-buckthorn has attracted much attention for its rich nutrients and more than 100 kinds of biological active substances that are beneficial to human health. Sea-buckthorn juice with unique flavor, oil with unique curative effect, and its yellow pigment, has become the hottest ingredients in medicine, food and cosmetics industries. The potential economic benefits of sea-buckthorn forest will be tapped.

5 Conclusions

Sea-buckthorn has attracted much attention for its rich nutrients and more than 100 kinds of biologically active substances that are beneficial to human health. Sea-buckthorn juice with unique flavor, sea buckthorn oil with unique curative effect, and its yellow pigment have become the hottest ingredients in the medicine, food and cosmetics industries. At the same time, sea-buckthorn is one of the important pioneer tree species to conserve water and soil, and prevent desertification. It is the nemesis of soft rock, which is called earth cancer. Its unique biological characteristics and economic value have gradually become the focus of investment and development. Based on the systematic vision, an equilibrium model of sea-buckthorn utilization benefits was constructed to analyze the equilibrium relationship between sea-buckthorn ecological and economic benefits. To develop sea-buckthorn economy, the protection of sea-buckthorn ecological balance must be taken into account at the same time. The development of sea-buckthorn economy is guaranteed by ecological protection, and the economy is promoted by the development of sea-buckthorn ecology. Although this method can effectively analyze the balance of economic value and ecological value of sea-buckthorn and get reliable results, it only takes Liaoning province as the research object, which has certain one sidedness. Therefore, it will expand the research scope and strive to further improve the application scope of this method.

Footnotes

Acknowledgments

This work is supported by National Natural Science Youth Foundation: the Regulation Mechanism of hydraulic structure and PIP Gene expression on Water diversion Resistance of Poplar leaves. Project number, 31400527.

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