The increasing exploitation of natural resources has led to an excessive depletion of resources and has changed the environment [1
]. This unfolding ecological crisis can directly affect landscape pattern changes [2
]. The rapid transformation in land use from land development directly affects landscape patterns [3
]. The interaction between land use change and landscape pattern change is a focus of environmental change research because of the rapid land transformation [5
]. The landscape pattern and its changes reflect the combined influence of natural and human systems [6
Wetland ecosystems have experienced the most rapid decline among different ecosystems in the world [8
]. Agricultural expansion has caused half of the world’s wetlands to be lost over the past century, and population growth had put additional pressure on wetlands [9
]. Wetland loss and degradation has affected the well-being of many local communities [11
]. However, effective restoration is often hindered by limited information on the historical process of landscape change. Therefore, key features of the spatial and temporal variations of landscape patterns among marshlands, paddy fields, and dry farmlands are still uncertain.
Landscape ecology deals with the patterning of ecosystems in space [14
]. Landscape patterns indicate the actual spatial composition of landscape elements. Landscape pattern change is the most intuitive reflection of land use changes [15
]. In the early 1950s, descriptive research on landscape patterns was carried out by Forman, and quantitative research in the field began in the 1970s [16
]. Landscape stability is an important part of landscape ecology research, considered as a landscape that has been stable (the tendency of a perturbed system to return toward an undisturbed state) and which will not undergo tremendous structural changes in the short term [18
]. This also means the natural processes that contribute to the functions and sustainability will not be disrupted. However, when analyzing landscape stability, it is difficult to make a quantitative analysis of landscape stability only considering landscape heterogeneity, diversity, and landscape pattern. As such, it was assessed quantitatively in this study. The landscape pattern index (LPI) is commonly used in landscape pattern research. The LPI is a quantitative index that can condense landscape pattern information and reflect landscape structural compositions and spatial allocation. Several landscape pattern indices have been developed to evaluate landscape stability, and principal component analysis is often used to construct a model that can accurately reflect landscape stability. The spatial arrangement of a landscape also has a decisive influence on landscape stability in space [20
The conflicts between wetland conservation and cropland development are increasingly prominent, but less attention has been paid to the relationships between marshlands, paddy fields, and dry farmlands. It is useful to investigate the spatial and temporal dynamics of these landscape classes, especially over recent years. Further, the influence of landscape dynamics on landscape stability needs to be determined. Remote sensing and geographic information system technologies are often used to analyze land use changes. We aimed to analyze the transformation of marshlands into paddy fields or dry farmlands, or the relationships between paddy fields and dry farmlands along a time series in our study. The Xingkai Lake area, Northeast China, acted as the case study area. The area has typical natural marshlands and a history of reclamation to support a nationally important grain commodity base.
This study is focused on the landscape pattern changes experienced in the Xingkai lake area over the past thirty years. Land use changes around Xiangkai Lake in 1982, 1995, 2000, 2005, 2010, and 2015 were quantified by remote sensing data analysis. The spatiotemporal variations of landscape pattern at class and landscape levels were revealed by landscape pattern indices in Fragstats software. Based on the landscape pattern indices, we analyzed landscape stability using principal components analysis. Our findings are applicable for the effective planning and management of land resources.
The study presented the changes in landscape pattern over different time periods in the Xingkai Lake area. The time period with the largest land use conversion was found. The study revealed that landscape fragmentation was further aggravated until 2015. Human disturbances are the important reason for landscape fragmentation [29
]. The building of artificial canals for paddy field cultivation and the increase in canal densities has led to a decrease of plant community diversity in the wetlands of the Sanjiang Plain. The natural and seminatural areas have been gradually replaced by artificial and semiartificial areas [6
]. These human activities have influenced the water circulation and the landscape pattern. Reclamation has put great pressure on marshlands in the Xingkai Lake area. This mirrors human disturbance to peatlands, where approximately 15% globally and over 50% of peatlands in Europe have been drained for agricultural use [31
In our study, landscape pattern indices were selected from the literature and combined with our own understanding of landscape patterns. This means that there was some subjectivity in the selected process. Our selection might not necessarily show the complete relationship between landscape type stability and landscape pattern indices. We used principal component analysis to evaluate landscape type stability based on landscape pattern indices. Notably, landscape pattern indices focus on calculating the geometric relationship between patch types, but do not involve the measurement of biomass or species diversity within patches. Therefore, the results cannot fully reflect the characteristics of landscape stability. There are two main considerations in this paper, as follows. Landscape pattern indices can be used to quantitatively reflect the spatial distribution characteristics of the landscape, and on this basis, principal component analysis could be used to reveal the landscape type stability. However, the spatial scale is very important for landscape stability analysis [17
]. Further research should be undertaken to improve the accuracy of ecosystem stability classification criteria or construct a new ecosystem stability index system. In other words, a more innovative approach should be proposed for studying ecosystem stability and the landscape pattern indices influencing it.
The landscape pattern was obviously fragmented in our study over the past thirty years. It was characterized by a sharp increase of NP and decrease of IJI. Our results provide support for studying landscape pattern changes at a class level. Therefore, it was a remarkable increase in scale from the previous study [32
]. Marshlands were more dispersed and had poor patch connectivity, and marshland stability declined. These findings are consistent with the conclusions of other related studies [28
Compared to the loss of abundant resources, the loss and degradation of limited resources has an even stronger impact on human well-being [13
]. To protect natural wetland ecosystems and landscape stability, ecological compensation pilot studies have been launched since 2014 in China [35
]. The scope of compensation mainly includes internationally important wetlands or national natural reserves and their surrounding areas along the migration routes of waterfowl (Ministry of Finance, Ministry of Agriculture (2014) 9). Xingkai Lake National Natural Reserve is the first ecological compensation pilot in China and the largest waterfowl migration stopover in Northeast Asia. The numbers of wild ducks and goose occupied 70%–90% of the total number of water birds, and the ecological compensation ranged from 19.78 × 103
to 27.91 × 103
yuan per hectare [36
]. The willingness to protect natural ecosystems should be improved with the increasing public recognition of nonmarket service values [37
]. Wetlands in the Xingkai Lake area and other areas may not be restored to their original state by depending only on restoration programs [36
]. Human interventions related to biodiversity have great impacts on wetland ecosystems. Preventing or reversing these influences should be the main direction for restoration efforts. China proposes to establish a natural protected area system, which would be mainly composed of national parks. The first national park on earth was established in 1872. In 2016, China’s first national park, Sanjiangyuan National Park, marked the first step for this country.