关于我国耕地保护问题的思考

社会经济的发展对耕地保护造成了较强烈的冲击 ,为了提出更有效的耕地保护措施 ,本文首先分析了社会经济发展、农业生产、生态建设等新形势对耕地保护造成的压力 ,认为经济发展、人口增长、资金短缺是制约耕地保护的因素 ,在此基础上 ,提出完善耕地保护政策的思路。

Multi-scales Analysis of Driving Forces on Land Use/Cover Change in China:Taking Farmland Returning to Forest or Grassland as a Case

Increasing populations are causing an increase in food demands, and the area of cultivated land expands every year. Inappropriate land transition from ecology to production results in the constant decline of the ecological security level and influences the regional sustainable development. Adjusting unreasonable land use mode and reconstructing natural land cover are important ways to maintain and improve the ecological environment. Also reclaiming farmland as areas for forests and grasslands (FRFG) is another way. Successful implementation of FRFG in China is the result of comprehensive effect of the multi-scales driving forces. This paper analyses the driving forces of FRFG in China on a national (country) –regional (province) – local (county) – household (farmer) level scale, and the results are: driving forces at the national scale include ecological and food security and the western development of China; at the regional scale, ecological and economic benefits become the main factors to influence the dimension of FRFG under the same policy. The driving forces can be divided into 6 types: industrial structure adjustment, water source protection, flood prevention, the Three-Gorge Project protection, reduction of the amount of sediment flowing into the Yellow River and wind erosion desertification prevention. The driving forces at the local scale can be divided into 12 types with developing leading industries, increasing farmers’ income and improving agricultural production conditions as the main types; at the household scale, the nationalpolicy meeting farmers’ demands and the optimization of individual interests are all driving forces.

Observations on forest restoration in Jilin, China

This paper reviews various forestry practices in Jilin Province, China. The authors emphasize the rich natural diversity of Jilin and the need to focus research efforts on understanding the potential of native species to meet the needs of land-management agencies involved in forest resource exploitation and ecological restoration. The native species of China hold great potential, and deserve more research attention, for meeting these needs. The introduction and testing of exotic species should be dbne only under rigorous scientific testing and after comparison with native species prior to operational introduction into forestry in order to avoid unwanted ecological consequences, including potential problems with alien invasives and pest introductions. The authors also emphasize the need to maintain viable （e.g., genetically diverse and reproductively fit） natural populations of native species in order to protect China＇s valuable natural diversity and maintain the potential of native species to function as future seed sources for local forest and ecological restoration activities.

China's Sloping Land Conversion Program at the Beginning of 21st Century and Its Habitat Suitability in Typical Region of Loess Plateau

自1999年我国开始试行以"退耕还林"工程为主的生态退耕以来,到目前已历时十年。特别是进入21世纪,工程实施强度较大,因此从国家尺度上进行宏观生态退耕格局的分析对于评估生态退耕政策和确定未来政策导向具有重要意义。本研究以TM遥感监测的土地利用变化数据库为基础分析2000-2005年生态退耕的时空格局。在此基础上,以黄土高原典型地区陕西中北部为研究区,采用生态位适宜度评价模型探讨了生态退耕工程实施的合理性。研究结果表明:(1)2000-2005年间,生态退耕主要集中在中国中部地区,尤其是在黄河和长江的中上游地区,生态退耕面积与建设占用面积基本持平。在各生态类型区中,黄土高原土壤侵蚀区生态退耕面积最大,达到了1162.50km^2,主要用于还林;(2)整体看来,研究区内生态退耕的空间格局是合理的,即适宜性越差的耕地退耕比例越大。从退耕区域的适宜性水平来看,有77.35%的地区属于勉强适宜区,其中退为林地的面积为603.32km^2,退为草地的面积为528.94km^2。整个研究区内前者大于后者。然而,退耕地中仍有19.38%属于中度适宜区,原因可能来自于退耕指标分配等管理因素,另外,当地农民外出务工从而将中等适宜度的耕地退耕。结果表明,当前仍有大面积不适宜和勉强适宜的耕地存在,在未来工程实施过程区应该首先考虑该类地区。

Spatial-temporal Changes in Ecological Risk of Land Use before and after Grain-for-Green Policy in Zhengning County, Gansu Province

The Grain-for-Green Policy aims to convert cropland to grassland and forest across western China, and evaluating ecological risk is essential to its implementation. Because few recent studies have focused on eco-risk changes of land use in the areas affected by significant policies, this paper took Zhengning County in Gansu Province as our focal area, and studied spatial-temporal changes in ecological risk before and after policy implementation. Based on indices of landscape fragmentation and ecosystem service value, an ecological risk assessment method using ArcGIS and Fragstats was done. The regional gravity center model and land spatial distribution model were also used to enrich the quantitative description of divisional eco-risk and its spatial-temporal variation in the county. Results showed that the implementation of the policy has contributed to an overall reduction in ecological risk in Zhengning County, with a divisional degree order reduction following the pattern： eastern Zhengning 〉 western Zhengning 〉 central Zhengning. The gravity center for eco-risk shifted 4288 m southwest from 1995 to 2010 due to landscape fragmentation. The study implies that greater attention should be paid to forest and grassland restoration in eastern Zhengning, cropland protection in central Zhengning, and soil and water conservation in western Zhengning.

Responses of Ecosystems to Ecological Compensation in a Key Ecological Function Area of the Loess Plateau

Evaluation of the ecological effects of eco-compensation policies helps analyze policy rationality and feasibility and provides scientific and practical bases for perfecting eco-compensation systems. Taking the key ecological function area of the Loess Plateau, China as a case study, we have evaluated ecosystem responses to the Grain-for-Green Project that commenced in 1999. Six indicators were selected to assess changes in ecosystem structure, quality and function. The results showed that implementation of the Grain-for-Green Project has reduced sloping cropland by 1571 km2 and increased ecological land by 1337 km2. The increase in ecological land alters ecosystem structures across the study area and the decline in sloping cropland reduces farming activity interference; both of these are conducive to the restoration of natural vegetation. From 2000 to 2010, the vegetation cover of grassland, desert and forest ecosystems increased 10.89%, 8.34% and 4.24% respectively and average NPP rose 51%, with an average annual growth rate of around 5%. This indicates that eco-compensation has promoted the improvement of ecosystem quality. Total biomass of ecosystems increased two times on average from 2000 to 2010, meaning that the carbon sequestration capacity of ecosystems also increased. The reduction in the area of water loss and soil erosion and the increase in retained runoff by forests indicate an improvement in ecosystem function and services on the Loess Plateau.

Synergic Relationship between the Grain for Green Program and the Agricultural Eco-economic System in Ansai County based on the VAR model

Understanding the synergic relationship between the Grain for Green Program(GGP)and the agricultural eco-economic system is important for designing an optimized agricultural eco-economic system and developing a highly efficient structure of an agricultural industry chain and a resource chain.This study used Ansai County time series data from 1995 to 2014,applied vector autoregressive(VAR)models and used tools such as Granger causality,impulse response analysis and variance decomposition,to explore the synergy between the GGP and the agricultural eco-economic system.The results revealed a synergic and reciprocal relationship between the GGP and the agroeconomic system.The contribution of the GGP to the agroecosystem reached 34%,which was significantly higher than either its largest contribution to the agroeconomic system(20.8%)or its peak contribution to the agrosocial system(26.7%).The agroeconomic system had the most prominent influence on the GGP,with a year-round stable contribution of up to 55.3%.These results were consistent with reality.However,the impact of the GGP on the agricultural eco-economic system was weaker than the effect of the agricultural eco-economic system on the GGP.The lag of variable stationarity after the shock was relatively short,indicating that optimal coupling had not formed between the GGP and the agricultural eco-economic system.On the basis of enhancing the ecological functions,we should construct the agricultural industry-resource chain such that it focuses on promoting the effective utilization of resources in the region.In addition,the development of a carbon sink industry can be used to manifest the ecological values of ecological functions.

Review of Conversion of Farmland to Forests Project:Ranking First in Investment in the World

The Conversion of Farmland to Forests Project (CFF) is one of the six great forest ecological Projects inChina and one of the ten great forest ecological Projects in the world, ranking the third in overall scale and the first ininvestment. CFF was officially initiated in 2002, covering 1897 counties (county-level cities and districts) in 25provinces (autonomous regions or municipalities) of China. The whole investment is more than 40 billion US$ duringabout 20 years (from 1999 to 2017), aiming to form better ecology system in fragile ecology regions and effectivelycontrol the soil and water erosion of the Yangtze and the Yellow River and sandstorm of the Three-north Regions inChina. The experimental Project of CFF began in 1999, including Sichuan, Shanxi and Gansu province, and the scopeof CFF was widened later. About 1.16 million ha of farmlands were converted to forestlands, and one million ha ofplantation in mountains and wasted lands were completed in 3 years, involving 20 provinces (autonomous regions andmunicipalities), 400 counties, 27 thousand villages, 5.7 thousand towns, 4.1 million farm families and 16 millionfarmers.