Abstract
Agricultural reclamation has been the major threat to land use changes in the Sanjiang Plain, Northeast China, over the past decades. However, spatial and temporal dynamics of land use and landscape, especially in the recent years, are not well known. In this study, land use and landscape pattern changes from 1982 to 2015 were analyzed using remote sensing data by splitting the period into five periods. The results indicated that the largest reduction of forestland area was 648.70 km2 during 1995–2000, and the relative change was −1.84%. The converted area of forestlands to dry farmlands in this period was about 90% of the total reduced forestland area. Marshland areas decreased remarkably by 63.29% and paddy fields increased by 1.78 times from 1982 to 2015. Paddy fields experienced large conversion into dry farmlands during 2005–2010 (1788.57 km2), followed by a reverse conversion from 1995 to 2000 (2379.60 km2). The difference of relative change revealed development speed of paddy field was faster than that of dry farmlands among the five periods. Landscape pattern was analyzed using class- and landscape-level metrics. The landscape diversity index and number of patches increased, which showed that the degrees of the forestland, marshland, and cropland landscape fragmentation were aggravated. Our study provides the effective means of land use dynamic monitoring and evaluation at the landscape level for the existing forestlands and marshlands protection.
Highlights
Forests, wetlands, and oceans are known as the three major ecosystems in the Earth
We analyzed land use and landscape pattern changes based on remote sensing data
The precipitation was reduced at an annual average of 1.50 mm/a in the Naoli River catchment from 1956 to 2004 [22]
Summary
Wetlands, and oceans are known as the three major ecosystems in the Earth. Wetlands are the important components of the terrestrial ecosystems, providing significant ecosystem services as climate regulation, flood storage, water supply, and biodiversity conservation [1]. Climate change leads to increases in the frequency and magnitude of floods and droughts [2], augmenting the vulnerability of wetland ecosystems. Recent policy frameworks are being well developed, but wetland degradation is still widespread [4]. Wetlands worldwide have the fastest loss rates among any ecosystems [5]. Precisely complete wetland loss data cannot be available because of the different definitions and techniques employed by the various assessments. 50% of wetlands in Forests 2018, 9, 637; doi:10.3390/f9100637 www.mdpi.com/journal/forests
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