Variation patterns of ecosystem types in the SNP
In 2015, the SNP was dominated by grassland, desert, water body and wetland ecosystems with areas of 6.90 × 104 km2, 4.34 × 104 km2, and 1.04 × 104 km2, respectively, which accounted for 56.2%, 35.2%, and 8.4% of the national park’s total area (Fig. 2).
Area (left) and proportion (right) of different ecosystem types in various sub-parks of the SNP.
The YRSP was dominated by grassland and desert ecosystems, accounting for 48.0% and 43.2% of its area. The grassland ecosystem was predominantly distributed in the southeast, whereas the desert ecosystem was predominantly distributed in the northwest. There were also numerous lakes and wetlands, which accounted for approximately 8.8% of its area, and 76.7% of the water body and wetland ecosystems in the SNP (Fig. 2).
The HRSP was dominated by grassland ecosystem, which accounted for approximately 72.5% of its area, followed by desert ecosystem, constituting approximately 17.8%. There were also plateau lakes (represented by Zhaling Lake and Eling Lake) and wetlands, which accounted for approximately 17.3% of the water body and wetland ecosystems in the SNP.
The grassland ecosystem in the LRSP comprised 88.1% of the park’s area. The desert, water body and wetland ecosystems constituted less than 10%. In addition, a small number of forest ecosystem distributed in the southern part of the LRSP, accounted for approximately 63.8% of the forest in the SNP.
Spatial distribution of ecosystem types in 2015 and ecosystem changes of the SNP from 2000 to 2015 were shown in Fig. 3. In general, ecosystem patterns changed not obvious during this period, which was mainly occurred in desert, water body and wetland ecosystems. Area of water body and wetland ecosystem increased by 416.68 km2, while desert area decreased by 356.75 km2. In spatial, ecosystem types changed mainly occurred in the YRSP and HRSP (Fig. 3).
Spatial distribution of ecosystem types in 2015 of the SNP (left) and ecosystem changes from 2000 to 2015 (right). Map created in ArcMap 10.4 (Environmental Systems Resource Institute, ArcMap 10.4 ESRI, Redlands, California, USA).
Spatial and temporal variations of ecosystem services in the SNP
Water regulation
The annual average amount of water regulation in the SNP was approximately 6.54 billion m3/yr during the period of 2000 to 2015. Water regulation capacity was approximately 0.068 million m3/km2 during this period. It was higher in the southeast and lower in the northwest (Fig. 4). The annual average amount of water regulation in the YRSP was the highest (3.33 billion m3/yr), followed by the HRSP (2.12 billion m3/yr), and the lowest in the LRSP (1.09 billion m3/yr). Water regulation capacity of the HRSP was the highest (0.12 million m3/km2), followed by the LRSP (0.08 million m3/yr), and the lowest in the YRSP (0.05 million m3/km2) (Fig. 4).
Spatial distribution of water regulation service in the SNP (left upper) and its changes from 2000 to 2015 (left bottom), annual average amount of water regulation and its capacity in the different sub-parks (the bars means water regulation amount and the diamonds means water regulation capacity) (right upper) and interannual variation of water regulation capacity (right bottom). Map created in ArcMap 10.4 (Environmental Systems Resource Institute, ArcMap 10.4 ESRI, Redlands, California, USA).
The annual amount of water regulation in the SNP exhibited a decreasing trend of −0.056 billion m3/yr, featuring fluctuations during the period of 2000 to 2015. The changing trend of water regulation capacity was approximately −617 m3/km2 during this period (Fig. 4). In particular, variation trend for water regulation amount increased approximately 1.33 million m3/yr in the HRSP. However, it decreased by −40.74 million m3/yr and −16.09 million m3/yr in the YRSP and the LRSP, respectively. Approximately 84.5% of the SNP exhibited an increasing trend of annual water regulation amount, and only 14.6% of the region exhibited a decrease. For the three different sub-parks, the regions with increased water regulation amount all exceeded 80% in each sub-park’s area. However, due to the small increased magnitude, annual amount of water regulation in the entire region still exhibited a decreasing trend.
Soil conservation
The annual average amount of soil conservation in the SNP was 0.15 billion t/yr, and 13.50 t/hectare/yr per unit area from 2000 to 2015. The soil conservation capacity was higher in the central part and low in the northwest. The annual average amount of soil conservation in the YRSP was the highest (0.10 billion t/yr), followed by the LRSP (0.03 billion t/yr), and the lowest in the HRSP (0.02 billion t/yr). Soil conservation capacity of the LRSP was the highest (26.4 t/hectare/yr), followed by the YRSP (12.3 t/hectare/yr), and the lowest in the HRSP (9.2 t/hectare/yr) (Fig. 5).
Spatial distribution of soil conservation service in the SNP (left upper) and its changes from 2000 to 2015 (left bottom), annual average amount of soil conservation and its capacity in the different sub-parks (the bars means soil conservation amount and the diamonds means soil conservation capacity) (right upper) and interannual variation of soil conservation capacity (right bottom). Map created in ArcMap 10.4 (Environmental Systems Resource Institute, ArcMap 10.4 ESRI, Redlands, California, USA).
The annual amount of soil conservation in the SNP exhibited an increasing trend of 9.87 million t/yr, featuring fluctuations during the period of 2000 to 2015. The trend of soil conservation per unit area was approximately 0.88 t/hectare/yr (Fig. 5). In particular, it increased in the three sub-parks. The increasing was greatest in the YRSP (approximately 5.70 million t/yr), followed by the LRSP (3.31 million t/yr), and smallest in the HRSP (0.86 million t/yr). For the soil conservation capacity, it was increasing largest in the LRSP by approximately 2.52 t/hectare/yr. The trends in the YRSP and the HRSP were comparable by 0.69 t/hectare/yr and 0.50 t/hectare/yr, respectively. The amount of soil conservation exhibited a rising trend in more than 95% of the entire region. Specifically, it exhibited a rising trend in 94.4% of the YRSP, as well as 98.6% and 99.5%, respectively, in the HRSP and the LRSP.
Sand fixation
The annual average amount of sand fixation in the SNP was 0.48 billion t/yr, and 42.6 t/hectare/yr per unit area from 2000 to 2015. The sand fixation capacity was higher in the west and lower in the east. The annual average amount of sand fixation in the YRSP was the highest (0.43 billion t/yr), followed by the LRSP (0.04 billion t/yr), and the lowest in the HRSP (0.01 billion t/yr). Sand fixation capacity of the YRSP was the highest (53.1 t/hectare/yr), followed by the LRSP (27.0 t/hectare/yr), and the lowest in the HRSP (4.1 t/hectare/yr) (Fig. 6).
Spatial distribution of sand fixation service in the SNP (left upper) and its changes from 2000 to 2015 (left bottom), annual average amount of sand fixation and its capacity in the different sub-parks (the bars means sand fixation amount and the diamonds means sand fixation capacity) (right upper) and interannual variation of sand fixation capacity (right bottom). Map created in ArcMap 10.4 (Environmental Systems Resource Institute, ArcMap 10.4 ESRI, Redlands, California, USA).
During the period 2000–2015, amount of sand fixation in the SNP exhibited a decreasing trend with fluctuations, and the annual variation trend was approximately −3.56 million t/yr. The variation trend of sand fixation per unit area was approximately −0.32 t/hectare/yr (Fig. 6). Sand fixation capacity in both the YRSP and the HRSP decreased by −0.36 t/hectare/yr. There was a relatively small change in the LRSP. The regions with relatively large-amplitude declines were primarily concentrated in the western part of the YRSP and east of the HRSP. Approximately 39.3% of the SNP exhibited an increasing trend of annual sand fixation amount, and approximately 56.0% of the region exhibited a decrease.
Comprehensive evaluation of ecosystem services
Area proportion of the generally important region for water regulation service comprised 74.6% of the SNP, predominantly distributed in the north-western part of the park. In particular, it was the highest in the YRSP, constituting 74% of its area, 16% in the HRSP, and 10% in the LRSP. The important region for water regulation service comprised 10.1% of the SNP, predominantly distributed in the central part of this park. In particular, it was the largest (45%) in the LRSP, followed by 36% in the YRSP, and18% in the HRSP. The extremely important region for water regulation service comprised 15.3%, predominantly distributed in the central and southern parts of the YRSP, central part of the HRSP, and northern and southern parts of the LRSP. In particular, it was the largest (52%) in the YRSP, followed by the HRSP (34%), and 14% in the LRSP (Fig. 7). From 2000 to 2015, the annual amount of water regulation in the extremely important regions declined considerably by approximately −69.69 million m/yr, whereas there were increasing trends in both the generally important and important regions.
Significance classification of ecosystem water regulation, soil conservation, sand fixation services in the SNP (left) and area proportion of the different sub-parks (right). Map created in ArcMap 10.4 (Environmental Systems Resource Institute, ArcMap 10.4 ESRI, Redlands, California, USA).
The generally important region for soil conservation service comprised 73.5% of the SNP, predominantly distributed in the northwest part of the park. In particular, it was the highest in the YRSP, constituting 75% of its area, 17% in the HRSP, and it was the lowest in the LRSP by 8%. The important region for soil conservation service comprised 12.8% of the SNP, predominantly distributed in the central part of the region. In particular, it was the largest in the YRSP, constituting 69% of its area, 16% in the HRSP, and 15% in the LRSP. The extremely important region for soil conservation service comprised 13.7%, predominantly distributed in the middle eastern part of the YRSP and southern part of the LRSP. In particular, it was the largest (67%) in the YRSP, followed by the LRSP (26%), and 8% in the HRSP (Fig. 7). The soil conservation amount in the extremely important regions demonstrably increased by approximately 5.67 million t/yr. It was also increased in both the generally important and important regions.
The generally important region for sand fixation service comprised 53.0% of the SNP, predominantly distributed in the HRSP, southern part of the LRSP and north central part of the YRSP. In particular, it was the highest in the YRSP, constituting 55% of its area, 29% in the HRSP, and 16% in the LRSP. The important region for sand fixation service comprised 24.6% of the SNP, predominantly distributed in southern part of the YRSP and northern part of the LRSP. In particular, it was the largest in the YRSP, constituting 87% of its area, and 13% in the LRSP. The extremely important region for sand fixation service comprised 22.4%, predominantly distributed in central and western regions of the YRSP. In particular, it was the largest (99%) in the YRSP, followed by the LRSP (1%) (Fig. 7). The average variation of sand fixation amount in the extremely important region exhibited a declining of −3.55 million t/yr. The trend declined slightly in the generally important region and increased in the important region.
The extremely important region for ecosystem services comprised 51.4% of the SNP. In which, it were 15.3%, 13.7% and 22.4% for the YRSP, the HRSP and the LRSP, respectively. Among the extremely important regions, the highest water regulation capacity was in the HRSP (0.36 million m3/km2), the highest soil conservation capacity was in the LRSP (68.4 t/hectare/yr), the highest sand fixation capacity was in the YRSP (95.1 t/hectare/yr) (Fig. 8).
Spatial distribution of the extremely important region for ecosystem services in the SNP (left) and area proportion of the different sub-parks (right). Map created in ArcMap 10.4 (Environmental Systems Resource Institute, ArcMap 10.4 ESRI, Redlands, California, USA).
From the sub-park perspective, the extremely important regions accounted for 32.9% of the HRSP, of which extremely important regions of water regulation service was the highest (26.0%). It is evident that the core ecosystem service of the HRSP during the study period was water regulation, which was primarily provided by wetland and grassland ecosystems. The extremely important region accounted for 45.6% of the LRSP, of which soil conservation service was the highest (29.9%). The core ecosystem service of the LRSP was soil conservation, which was primarily provided by forest and grassland ecosystems. The extremely important regions accounted for 54.1% of the YRSP, of which sand fixation service was the highest (30.5%). Finally, the core ecosystem service of the YRSP was sand fixation, which was primarily provided by desert and grassland ecosystems. Therefore, the SNP formed a spatial pattern of ecosystem services with water regulation as core in the eastern part, soil conservation as core in the central part and sand fixation as core in the western part (Fig. 8).
Source: Ecology - nature.com
