The tropical-subtropical evergreen forest transition in East Asia:An exploration

The transition from tropical to subtropical(warm temperate)evergreen forests is more clearly apparent in East Asia,fromNepal to the western Pacific coast,than elsewhere in the tropics.We review the nature of this transition and hypothesize the physical,ultimately climatic,factors thatmay maintain it,with a special focus on how the increasing instability and warming of climates will affect these forests.A primary climatic mediator of the transition is proposed,thereby offering a testable hypothesis for the climateeforest transition relationship.What is known of this transition is summarized in context of the primary climatic mediators of elevational zonation of forest formations in equatorial Asia to the tree line,in the Himalaya at the India-Indo-Burma northern tropical margin,and as both elevational and latitudinal zonation in southern China.Consequent secondary edaphic and other physical changes are described for the Himalaya,and hypothesized for southern China.The forest ecotones are seen to be primarily defined by tree floristic change,on which account changes in structure and physiognomy are determined.The montane tropical-subtropical transition in the Himalaya is narrowand observed to correlate with an as yet ill-defined frost line.A distinct tropical-subtropical transition forest is recognized in the southwest Chinamountains.There is a total change in canopy species at the Himalayan ecotone,but subcanopy tropical species persist along an elevational decline of c.400 m.The latitudinal transition in South China is analogous,but here the tropical subcanopy component extends north over ten degrees latitude,albeit in decline.The tropical-subtropical transition is uniquely clear in East Asia because here alone a tropical wet summer-dry winter monsoon extends to 35
north latitude,encompassing the subtropical evergreen forest,whereas subtropical evergreen forests elsewhere exist under drier temperate summer climate regimes.

Lost in transition： Forest transition and natural forest loss in tropical China

The term forest transition refers to a change in forest cover over a given area from a period of net forest area loss to a period of net gain. Whether transitioning from deforestation to reforestation can lead to improved ecosystem services, depends on the quality and characteristics of the newly established forest cover. Using publicly available data, we examine forest transition in two regions of tropical China: Hainan Island and Xishuangbanna. We found that the overall increase of forest cover in both areas during the1980 s was due to an increase in plantation forests rather than to increases in the area covered by natural forest. We also found a time lag between the increase in overall forest cover and an increase in natural forest. On Hainan Island, natural forest continued to decline beyond the point in time when overall forest cover had started to increase, and only began to recover ten years after the turning point in 1978. In Xishuangbanna, where the transition point occurred ten years later, the decline of natural forest cover is still going on. These divergent trends underlying forest transition are concealed by the continued practice to apply the term "forest" broadly, without distinguishing between natural forests and planted forests.Due to the use of undiscriminating terminology, the loss of natural forest may go unnoticed, increasing the risk of plantation forests displacing natural forests in the course of forest transition. Our findings are important for programs related to forest management and ecosystem services improvement, including reforestation and Payments for Ecosystem Services programs.

Spatial Differentiation Characteristics and Driving Forces of Forest Transition:A Case Study of Zunyi City,Guizhou

Spatial differentiation in forest transition was measured in terms of space transition and function transition using the exploratory spatial data analysis method（ESDA） and data from 2004—2014 for Zunyi city,Guizhou province,China.The validity of factors affecting forest transition was analyzed by constructing radial basis function neural networks（RBFNN） based on the data processing system（DPS）.Our results will provide references for scientific understanding of the potential mechanism underlying forest transition in mountainous areas.We found that Global Moran＇s I of space transition and function transition of forest land was 0.0336 and 0.2323,respectively.This suggests a significant positive correlation in spatial distribution of space transition and function transition of forest land,and significant spatial aggregation.The Global Moran＇s I of function transition was higher than that of space transition,and the spatial aggregation characteristics of function transition were more significant than for space transition.The Global Moran＇s I at each time period tended to increase,and the spatial aggregation degree of the function transition and space transition was further enhanced.Hot and cold spots of space transition of forest land stably evolved,suggesting a minor spatial difference in forest land among different administrative units at the county level.The number of hot spots at the county level in function transition increased.Hot spots were intensively distributed at the western edge and continuously distributed in the northeast.The space transition and function transition of forest land were both greatly influenced by urbanization rate and second and third industries.The development of urbanization and industrialization was the main factor driving forest transition,suggesting a positive role of economic growth on forest transition in mountainous areas.The development of urbanization and industrialization is an effective approach to forest transition in mountainous areas.

Forest Transition and Its Driving Forces in the Qian-Gui Karst Mountainous Areas

This study investigates the spatial differences and the factors influencing those differences as they affect forest transitions in the Qian-Gui Karst Mountain areas to provide references for policy makers,and ideas for ecological environmental protection strategies and adaptive management strategies for forest restoration projects in mountain areas.Forest transition characteristics are determined in relationship to spatial and functional transitions.SPSS and a geographical detector are used to analyze the forces driving forest transitions in terms of natural environmental and socio-economic factors.The results were as follows:(1)The area of forestland in the Qian-Gui Karst Mountain areas increased by 673.5 km^2 during 1990-2015,and a U-shaped curve generally describes the tendency of this change.More precisely,forest land area decreased initially and increased later,with the turning point occurring in the year 2000.This suggests that the Qian-Gui Karst Mountain areas are being maintained at a later stage of forest transition,and this means they are experiencing a net increase in forest land area.The average annual rainfall and temperature,distance to the nearest river and nearest rural residential area,amplitude of topographical relief,and slope contributed the most to forest spatial transitions.(2)During the study period,the tendency for forest coverage to change varied considerably in different parts of the study area,and the greatest increase occurred in the area of very high forest coverage,an area of 154173.71 km^2.The ranking of other forest coverages tended to decrease during the past 25 years.The vegetation ecosystem,in general,is being maintained in the process of restoration,and changes in the ranking of forest coverage were high in the northern part of the study area and low in the southern part.Forest spatial transitions were affected by the interaction between natural environmental and socio-economic factors,and the average annual temperature and rainfall,elevation,and lighting intensity at night were the most important factors that governed forest functional transitions.An examination of the direction in which spatial and functional transitions are moving in the forest area indicates that ecological construction,rather than spatial expansion of the forest area,should be used in the future to improve forest quality.

Farming-Biodiversity Segregation or Integration? Revisiting Land Sparing versus Land Sharing Debate

Land Sparing (LSP) was proposed to spatially segregate biodiversity and production in order to maximize both, while Land Sharing (LSH) defenders posit that farming and nature integration is preferable, through eco-agriculture and low-input systems. Based on a multidisciplinary review on historical land-use data, ecological aspects, agricultural production potential, economic and food security topics, we summarize LSP/LSH major findings and caveats. Although LSH still has to address some issues, LSP relies on a series of assumptions that are not supported by data, particularly regarding the positive effects of intensification on agriculture expansion. Furthermore, we developed conceptual models to theoretically predict the responses of biodiversity and ecosystems services in dynamic landscapes with different natural habitat proportions and different intensification levels on the farmed areas. Agriculture intensification may expand farmland reducing habitat area fostering population declines at the “natural” patches (via habitat reduction and decreasing species intra patch flux through the matrix), as well as at the farm site by direct effect of intensification (heterogeneity reduction and pesticide use), leading to a species extinction and ecosystems services loss. This multiple negative effect of agriculture intensification is worsening in regions where habitat proportion is below 30%, such as in many tropical biodiversity hotspots, making LSH a much safer strategy for conservation and food security.