Selection of tree species by principal component analysis for abandoned farmland in southeastern Horqin Sandy Land,China

With changes in global climate and land use,the area of desertified farmland in southeastern Horqin Sandy Land(HSL)has increased in recent years,and farmlands are being abandoned.These abandoned farmlands(AFs)nega-tively impact the local ecology.Therefore,the aim of the present study was to select suitable trees and shrubs for those AFs to prevent and control the desertification tendency.In this study,three AFs were fenced for 2 years,then 37 arbor and shrub species or varieties of 21 families were planted in the fenced AFs and grown for 10 years.The ecological adaptability of the species was evaluated and ranked using a principal component analysis.The results showed that the biodiversity of the AFs significantly improved after 2 years of fencing;the Shannon-Wiener index and species rich-ness of perennial grasses and forbs were 1.45 and 3.6 times higher,respectively,than for the unfenced AF.Among all species planted in fenced AFs,nine tree species had posi-tive comprehensive F(CF)values;Pinus sylvestris(Russian Shira steppe provenance),Populus alba‘Berolinensis’and Gleditsia triacanthos had CF greater than 1,and the first(PC1),second(PC2)and third(PC3)principal component values(F_(1),F_(2),F_(3))were all positive.Among the shrubs,only Lespedeza bicolor and Rosa xanthina f.normalis had CF greater than 0.All these results suggest that fencing improves biodiversity and that planting trees and shrubs that have higher CF values on the basis of fencing is an effective way to green and beautify AFs in HSL.

Abandoned land identification in karst mountain area based on time series SAR characteristics at geo-parcels scale

Mapping abandoned land is very important for accurate agricultural management.However,in karst mountainous areas,continuous high-resolution optical images are difficult to obtain in rainy weather,and the land is fragmented,which poses a great challenge for remote sensing monitoring of agriculture activities.In this study,a new method for identifying abandoned land is proposed:firstly,a few Google Earth images are used to transform arable land into accurate vectorized geo-parcels;secondly,a time-series data set was constructed using Sentinel-1A Alpha parameters for 2020 on each farmland geoparcel;thirdly,the semi-variation function(SVF)was used to analyze the spatial-temporal characteristics,then identify abandoned land.The results show:(1)On the basis of accurate spatial information and boundary of farmland land,the SAR time-series dataset reflects the structure and time-series response.abandoned land with an accuracy of 80.25%.The problem of remote sensing monitoring in rainy regions and complex surface areas is well-resolved.(2)The spatial heterogeneity of abandoned land is more obvious than that of cultivated land within geoparcels.The step size for significant changes in the SVF of abandoned land is shorter than that of cultivated land.(3)The SVF time sequence curve presented a strong peak feature when farmland was abandoned.This reveals that the internal spatial structure of abandoned land is more disordered and complex.It showed that time-series variations of spatial structure within cultivated land have broader applications in remote sensing monitoring of agriculture in complex imaging environments.

Spatial pattern and mechanisms of farmland abandonment in Agricultural and Pastoral Areas of Qingzang Plateau

With the rapid development of social economy and urban−rural integration,the phenomenon of farmland aban-donment worldwide has proved to be one of the main trends of land use and land cover change(LUCC),and profoundly affected the rural landscape and regional ecological environment.Restricted by the natural environ-ment,economic development and backward agricultural technology,the phenomenon of farmland abandonment is also common in the Qingzang Plateau(QP).Therefore,this paper adopted the spatial autocorrelation method to analyze the spatial pattern of abandonment in the agricultural and pastoral areas of the Qingzang Plateau(APA−QP)in 2017,and the geographically weighted regression(GWR)model to explore the effects of geograph-ical resources,socio-economic development and location conditions on farmland abandonment.This study found that:1)From 2015 to 2017,the abandoned farmland area in the APA−QP was approximately 18.23×10^(4)ha,with an overall abandonment rate of 15.18%.On the whole,it showed the distribution characteristics of“strong in the south and weak in the north,strong in the east and weak in the west”.2)There were positive spatial correlation between both abandoned area and abandonment rate in the APA−QP,showing“concave”and“convex”patterns,respectively,mainly concentrated in the Huang−shui Valley and the Southeast Tibet;while in the western and northern regions,the degree of abandonment was relatively low.3)Farmland abandonment in the APA−QP was mainly driven by the geographical environment changes and farmers’decision−making on farmland utilization.There was significant spatial heterogeneity on farmland abandonment associated with the impact of geographical resources,socio−economics and location conditions.The geographical resource factors had a positive impact on the abandonment,and were strongly constrained by natural geographic conditions such as altitude and slope.The farmland resources in the Qingzang Plateau are limited,but are of strategic significance for the sustainable development of agriculture in the whole Qingzang Plateau.In order to realize the rational distribution of agricul-ture and animal husbandry and the sustainable utilization of farmland resources in the plateau region,land use strategies should be implemented according to regional differences and regional advantages in order to ensure the ecological environment security of Qingzang Plateau.

A dwarf bamboo(Pleioblastus chino) and winter browsing by Japanese hare(Lepus brachyurus) combine to limit establishment of transplanted native tree seedlings in an abandoned agricultural field

Natural forest recovery on abandoned farmland is hindered by a variety of factors and active restoration plays an important role when quick afforestation is desired. We investigated seedling survival of four transplanted native tree species （Quercus myrsinifolia, Quercus serrata, Aphananthe aspera, and Rhus sylvestris） by experimentally manipulating the vegetation cover, which was mainly dominated by dwarf bamboo （Pleioblastus chino）, and herbivore access to the planting sites on farmland that had been abandoned for 15 years at the start of the study. Few transplanted seedlings of any species survived under intact vegetation cover, irrespective of herbivore presence. In gaps in the vegetation cover, winter browsing by Japanese hare （Lepus brachyurus） damaged all species. However, lower browsing frequency and higher resprouting ability after grazing of the seedlings enabled both Quercus species to survive better than the other species. These results indicate that dwarf bamboo and the hare jointly limit the establishment of native trees in old fields. If active afforestation by transplanting seedlings at sites dominated by dwarf bamboo is planned, a combination of vegetation removal, selection of suitable species, and temporary seedling protection will be most effective.

An Empirical Study of Farmers' Perception and Behavior on Farmland Abandonment in Yunnan Province

In this study,using the PRA method,we conduct a questionnaire survey on 525 farmers in 10 typical villages in Yunnan Province,and study the farmers' farmland abandonment behavior as well as their perception. Studies have shown that there are some common problems for the villages in the inner suburbs and the villages in the outer suburbs such as small scale of rural land,dispersed plots and land fragmentation,and the scale and fragmentation problems are more prominent in the villages in the inner suburbs while the dispersed plot problems are more obvious in the villages in the outer suburbs; the levels of farmland abandonment vary in different sample villages,the farmland abandonment is more prevalent in the villages in the outer suburbs,the abandonment behavior involves more farmers,and farmers tend to abandon small plots of farmland; the proportion of the abandoned farmland perceived by the farmers in the villages in the inner and outer suburbs( especially in the inner suburbs) is significantly lower than the actual proportion,and farmers' perception greatly deviates from the actual reality; some farmers have wrong perception of farmland abandonment behavior,and even if there are farmers with correct perception,they also abandon farmland.

Intraregional Agricultural Characteristics Critical in Explaining Farmland Abandonment:Evidence from Chugoku and Shikoku Region of Japan

Since the 1980 s,Japan has witnessed an unprecedented decline in agriculture chiefly due to farmers’aging,depopulation,and unfavorable socio-economic conditions.This development has resulted in an increase of farmland abandonment(FLA)across the country.However,it remains unclear as to how and to what extent FLA is influenced by intraregional agricultural characteristics.As such,this article discusses the issue of FLA by taking a closer look at the Chugoku and Shikoku region,as it has experienced the highest FLA rates in Japan in recent years.For this analysis,a total of 25 indicators retrieved from the census of agriculture and forestry at the former municipalities scale were selected to describe intraregional agricultural characteristics.We employed principal component analysis(PCA)to evaluate agricultural characteristics,while multiple linear regressions(MLR)was applied to explore their correlations with FLA and spatial variations.First,there are strong intraregional differences in the agricultural characteristics across the Chugoku and Shikoku region,with eight different principle components(PCs)describing their characteristics.Second,variables measuring agricultural characteristics explain nearly 52.8%of the variation in FLA in our sample.The sales orientation and scale of agriculture have the strongest negative correlation to FLA in the region,while the status of agricultural succession displays the strongest positive correlation to FLA.Third,in areas where agriculture is more stable and easier to maintain,FLA is more strongly influenced by changes in agricultural characteristics than by geographical variations.We argue that localized approaches and policies for future management need to take intraregional differences in agricultural characteristics and FLA into account.Our findings help to explain spatial variations in agricultural characteristics and FLA in regional contexts,suggesting the need for better-informed farmland use policies to mitigate further abandonment.

Regional disparity in the changes of agricultural land use intensity in China during 1980-2002

Based on the cost-benefit data （1980-2002） of farm products and China Agriculture Yearbooks, this paper studies the regional disparity in the changes of the agricultural land use in China during the period 1980-2002 from three aspects such as the degree of intensity, the sown area and the abandoned farmland. The results show that： （1） The degree of intensity of land use in the westena region during 1980-2000 has a strong uptrend, but in the eastern and central regions the degree of intensity descends obviously and has shown a continuous downtrend since 1997. （2） The total sown area shrinks notably in the eastern region, while it enlarges constantly in the western region. （3） The sown area in the eastern, central and western regions has gone through a similar cyclic process： down （1980-1985）-up （1985-1991）-down （1991-1994）-up （1994-1999）-down （1999-2002）. However, there are obvious differences in amplitude variation and tendency among them. The sown area has shrunk in the eastern region and expanded in the central and western regions especially before 1999. （4） The most cases of abandoned farmland are reported in the central region, the second in the eastern region and the least in the western region. The abandonment phenomena chiefly occurred during 1992-1995 in the eastern region, and during 1998-2002 in the central region.

Removal of competitive native species combined with tree planting can accelerate the initial afforestation process: an experiment in an old field in Japan invaded by dwarf bamboo and kudzu

Restoring natural forests after field abandon- ment is a land management objective that fosters the re- covery of forest biodiversity. We performed seeding and transplanting of native tree species 40 years after the abandonment of an arable field that became dominated by a dwarf bamboo （Pleioblastus chino （Franch. et Sav.） Makino） and by kudzu （Pueraria lobata （Willd.） Ohwi）. By permutation tests, the removal of competing vegetation （gap creation） significantly increased the survival of three seeded species of Fagaceae and of eight transplanted spe- cies. In contrast, intact vegetation prevented most indi- viduals of all species from surviving for 1 year after planting. The lack of natural recruitment of Fagaceae in the nonseeded subplots indicated that seed limitation was a cause of the slow afforestation. Although litter accumula- tion in gaps at the time of seeding slightly increased sur- vival for late-germinating Quercus myrsinifolia Blume andCastanopsis sieboldii （Makino） Hatus. ex T. Yamaz. et Mashiba, the effect was not consistent among plots and was not statistically significant. Our results suggest that for successful afforestation using native trees in abandoned fields, it will be necessary to remove competitive native species to avoid severe limitations on microsite availability and that simultaneous tree establishment by seeding or transplanting should be implemented to accelerate the establishment of native tree species.

人口流动视角下的耕地利用行为及其影响因素研究

Due to rapid socio-economic development and urban-rural integration,the rural population is increasingly moving away from the primary industry,leading to a noticeable transformation of rural farmland use.This paper analyzed the changes in farmland use and the mechanisms in 213 villages of Longxi county,China in 2020,using multiple linear regression models,based on the aforementioned situation.Analysis revealed main findings:(1)Male and young and middle-aged emigration levels are concentrated in areas with higher and lower values,the emigration of talent is more evenly distributed.Overall,male emigration rates were high in all directions and low in the central area,whereas the young and middle-aged emigration rates exhibited a pattern of high loss in the north and south extremes,and low loss in the central area.The emigration of talent demonstrated a pattern of low losses to the east and high losses to the west of the G30 national highway.(2)Primary farmland use behavior was self-cultivation,then abandonment and finally transfer,with over 60%of the total area in 179 villages used for self-cultivation compared to less than 5%in 164 villages allocated for transfer,while less than 30%of the area in 179 villages was abandoned.(3)Significant differences were observed in the factors that influenced various farmland use behaviors,emigration of male,young and middle-aged and talent were the common influencing factors observed among all three types of farmland uses.The loss of males,young and middle-aged had a significant association with reduced self-cultivation while the emigration of talent led to an increase in self-cultivation use.Increased emigration of all three population constituencies significantly increased farmland transfer and abandonment.The conclusions carry significant theoretical and practical implications for enhancing the coordination of rural human-land relationships and improvement of the understanding of the relationship between population migration and farmland use.

Global understanding of farmland abandonment： A review and prospects

Since the 1950s, noteworthy farmland abandonment has been occurring in many developed countries and some developing countries. This global land use phenomenon has fundamentally altered extensive rural landscapes. A review of global farmland abandonment under the headings of ＂land use change - driving mechanisms - impacts and consequences - policy responses＂ found the following： （1） Farmland abandonment has occurred primarily in developed countries in Europe and North America, but the extent of abandonment has varied significantly. （2） Changing socio-economic factors were the primary driving forces for the farmland abandonment. And land marginalization was the fundamental cause, which was due to the drastic increase of farming opportunity cost, while the direct factor for abandonment was the shrink of agricultural labor forces. （3） Whether to abandon, to what extent and its spatial distributions were finally dependent on integrated effect from the physical conditions, laborer attributes, farming and regional socio-economic conditions at the village, household and parcel scales. With the exception of Eastern Europe, farmland abandonment was more likely to occur in mountainous and hilly areas, due to their unfavorable farming conditions. （4） A study of farmland abandonment should focus on its ecological and environmental effects, while which is more positive or more negative are still in dispute. （5） Increasing agricultural subsidies will be conductive to slowing the rate of farmland abandonment, but this is not the only measure that needs to be implemented. Due to China＇s rapid urbanization, there is a high probability that the rate of abandonment will increase in the near future. However, very little research has focused on this rapid land-use trend in China, and, as a result, there is an inadequate understanding of the dynamic mechanisms and consequences of this phenomenon. This paper concludes by suggesting some future directions for further research in China. These directions include monitoring regional and national abandonment dynamics, analyzing trends, assessing the risks and socio-economic effects of farmland abandonment, and informing policy making.

Interactions among dwarf bamboo, litter and consumption by small vertebrates place multiple constraints on the establishment of native tree seedlings in a Japanese agricultural landscape

Aims Faunal assemblage alterations due to anthropogenic impacts have changed herbivore-vegetation relationships in various ecosystems,but the influences of small vertebrates on revegetation processes remain unclear.In a peri-urban agricultural landscape in eastern Japan that lacks large ungulates but supports small generalist herbivores,fewer native seedlings have become established in thickets dominated by native dwarf bamboo,Pleioblastus chino(Franch.et Sav.)Makino.The mechanisms limiting tree seedling establishment are unknown.Our aim here was to evaluate the influence of interactions among the dwarf bamboo,its litter cover and small vertebrate herbivores on the micro-site conditions governing the establishment of native tree seedlings from different successional stages in an old field in temperate Japan.Methods First,seedling emergence and survival of seeded Pinus densiflora Siebold et Zucc.,Celtis sinensis Pers.,Aphananthe aspera(Thunb.)Planch.,Quercus serrata Murray,Quercus myrsinifolia Blume and Castanopsis sieboldii(Makino)Hatus.ex T.Yamaz.et Mashiba were observed in a factorial design that accounted for the presence or absence of dwarf bamboo and its litter cover,as well as the exclu-sion or access of small vertebrate fauna,in 2009 and 2010.To identify small vertebrate herbivores that reduced the emergence or survival of tree seedlings in the first experiment,reseeding experi-ments using P.densiflora,C.sinensis,A.aspera and Q.myrsinifolia were conducted by video trapping in 2011 and video and still-cam-era trapping in 2012.Important Findings The abiotic conditions under the dwarf bamboo were lethal to early-to mid-successional P.densiflora,C.sinensis,A.aspera and Q.serrata but led to better survival-although spindly growth-of late-succes-sional Q.myrsinifolia and C.sieboldii.The main consumers and the plants they found palatable differed between the bamboo thickets and the intervening gaps.Predation by mice appeared to have severely limited the emergence of all species,particularly in the bamboo thick-ets but occasionally in the gaps,whereas litter cover slightly mitigated this limitation.However,bamboo litter cover reduced the emergence of P.densiflora in the gaps.Chinese bamboo partridge(Bambusicola thoracicus Temminck),an introduced game bird,selectively and severely fed on the cotyledons-and probably seeds-of A.aspera and moderately preyed upon those of P.densiflora in the gaps.Apparent consumption of seedlings in the gaps by the Japanese hare(Lepus brachyurus Temminck)suppressed the growth of all species but apparently did not severely affect emergence and survival.Thus,the net balance of positive and negative interactions at the bamboo thicket scale(i.e.the presence of dominant dwarf bamboo cover or intervening gaps and the herbivore behaviours in these two environments)and at the microsite level(i.e.litter cover)shapes the early establishment patterns of native tree seedlings,and this balance differs among tree seedling species.