This paper examines the spatial characteristics of farmer/household behaviors in regional rice cropping systems(RCS), and the results provide necessary information for developing strategies that will maintain regional...This paper examines the spatial characteristics of farmer/household behaviors in regional rice cropping systems(RCS), and the results provide necessary information for developing strategies that will maintain regional food security. Through field study and statistical analysis based on 402 households questionnaires finished in 2014-2015 in the Poyang Lake Region(PLR) of China, we arrived at two main conclusions. First, single-and double cropping rice were found across the study area, but showed a general distribution trend, with double cropping rice in the southeast part(especially in Jinxian county) and single cropping rice in the northwest(particularly in De’an county). Second, the household decisions concerning RCS varied in different parts of the PLR, but double cropping was the dominant type, with about 63.57% of the respondent households in the PLR cultivating double cropping rice. However, the multiple-cropping index of paddy rice was only 1.55. About 3% of interviewed households had altered their RCS during this period. Based on these findings, the local governments should guide farmers’ paddy field cultivation behaviors by increasing the comparative efficiency of rice production, promoting appropriate scale operations and land conversion, as well as optimizing rice growing conditions to improve the multiple cropping index and enhance food provision. Finally, land-use efficiency and more sustainable use of land resources should be improved.展开更多
Forests are the main components of terrestrial ecosystems and play an important role in the protection and construction of the national ecological security barrier. For a long time, China’s large-scale afforestation ...Forests are the main components of terrestrial ecosystems and play an important role in the protection and construction of the national ecological security barrier. For a long time, China’s large-scale afforestation had been practiced in areas with rainfall higher than the 400 mm threshold, but the issue of afforestation in high altitudes on the Tibetan Plateau remains elusive in both practical experience and theoretical exploration. It is worth thinking further about what principles should be followed in the selection of tree species and suitable altitudes for afforestation in high-altitude areas, as well as what experiences and lessons of previous afforestation efforts should be applied in high-altitude areas. As per the law of vegetation zonal distribution, this paper argues that afforestation at high altitudes should comply with the principle of vegetation zonal distribution and the low temperature limitation,and points out that afforestation is feasible only within the forest distribution area and below the altitudes of climate timberlines. Furthermore, we demonstrate the potential spatial areas of afforestation, and determine the local tree species that may be used for afforestation based on the existing problems of afforestation in eastern Tibet. In summary, afforestation in high-altitude areas of the eastern Tibetan Plateau must comply with the law of zonal vegetation distribution, focus on the upper limit of altitude and the selection of suitable tree species, and adopt only suitable native tree species.展开更多
Leaf longevity is an important adaptive strategy that allows plants to maximize photosynthetic carbon gain.Due to the difficulty of identifying overwintering bud scars and distinguishing the age sequence of twigs,leaf...Leaf longevity is an important adaptive strategy that allows plants to maximize photosynthetic carbon gain.Due to the difficulty of identifying overwintering bud scars and distinguishing the age sequence of twigs,leaf longevity is rarely studied in Cupressaceae species,which further limits our understanding of the leaf economic spectrum (LES) for these populations.Here,we investigated the leaf longevity,as well as mass-based leaf nitrogen concentration (N;),of Juniperus saltuaria at different canopy heights for both subalpine and alpine timberline forests in the Sergymla Mountains,southeastern Tibet.We found that the mean leaf longevity was 4.2±1.2 years,and overall it did not differ significantly between different elevations.Along the vertical profiles of juniper canopies,the leaf longevity did not reflect a linear trend.With increasing leaf longevity,N;showed declining trends.We further analyzed the relationship between leaf longevity and the corresponding length of green twigs,and found that the length of green twigs could only explain 1%-3%of the variation in leaf longevity,indicating that the length of green twigs is a poor predictor for the variation in leaf longevity.In summary,for the J.saltuaria species in timberline or nearby subalpine forests,the effects of elevation and canopy depths on leaf longevity are minor,and the leaf trait analysis is in accordance with the prediction of LES.展开更多
基金The Strategic Priority Research Program of the Chinese Academy of Sciences(XDA23100202)International Partnership Program of Chinese Academy of Sciences(131A11KYSB20170117)+1 种基金Consultation and Evaluation Project of the Academic Divisions of the Chinese Academy of Sciences(2017ZWH018A-042)Special Project of Lancang-Mekong River Cooperation of the Ministry of Science and Technology of the People’s Republic of China "Agricultural Resources and Environmental Survey with Information Platform Construction in Lancang-Mekong River Basin"
文摘This paper examines the spatial characteristics of farmer/household behaviors in regional rice cropping systems(RCS), and the results provide necessary information for developing strategies that will maintain regional food security. Through field study and statistical analysis based on 402 households questionnaires finished in 2014-2015 in the Poyang Lake Region(PLR) of China, we arrived at two main conclusions. First, single-and double cropping rice were found across the study area, but showed a general distribution trend, with double cropping rice in the southeast part(especially in Jinxian county) and single cropping rice in the northwest(particularly in De’an county). Second, the household decisions concerning RCS varied in different parts of the PLR, but double cropping was the dominant type, with about 63.57% of the respondent households in the PLR cultivating double cropping rice. However, the multiple-cropping index of paddy rice was only 1.55. About 3% of interviewed households had altered their RCS during this period. Based on these findings, the local governments should guide farmers’ paddy field cultivation behaviors by increasing the comparative efficiency of rice production, promoting appropriate scale operations and land conversion, as well as optimizing rice growing conditions to improve the multiple cropping index and enhance food provision. Finally, land-use efficiency and more sustainable use of land resources should be improved.
基金The National Natural Science Foundation of China and ICIMOD Joint Research Project (41661144045)。
文摘Forests are the main components of terrestrial ecosystems and play an important role in the protection and construction of the national ecological security barrier. For a long time, China’s large-scale afforestation had been practiced in areas with rainfall higher than the 400 mm threshold, but the issue of afforestation in high altitudes on the Tibetan Plateau remains elusive in both practical experience and theoretical exploration. It is worth thinking further about what principles should be followed in the selection of tree species and suitable altitudes for afforestation in high-altitude areas, as well as what experiences and lessons of previous afforestation efforts should be applied in high-altitude areas. As per the law of vegetation zonal distribution, this paper argues that afforestation at high altitudes should comply with the principle of vegetation zonal distribution and the low temperature limitation,and points out that afforestation is feasible only within the forest distribution area and below the altitudes of climate timberlines. Furthermore, we demonstrate the potential spatial areas of afforestation, and determine the local tree species that may be used for afforestation based on the existing problems of afforestation in eastern Tibet. In summary, afforestation in high-altitude areas of the eastern Tibetan Plateau must comply with the law of zonal vegetation distribution, focus on the upper limit of altitude and the selection of suitable tree species, and adopt only suitable native tree species.
基金The Key Scientific and Technological Research Projects in Tibet Autonomous Region (XZ202101ZY0005G)The Second Tibetan Plateau Scientific Expedition and Research (STEP) Program (2019QZKK0301-1)。
文摘Leaf longevity is an important adaptive strategy that allows plants to maximize photosynthetic carbon gain.Due to the difficulty of identifying overwintering bud scars and distinguishing the age sequence of twigs,leaf longevity is rarely studied in Cupressaceae species,which further limits our understanding of the leaf economic spectrum (LES) for these populations.Here,we investigated the leaf longevity,as well as mass-based leaf nitrogen concentration (N;),of Juniperus saltuaria at different canopy heights for both subalpine and alpine timberline forests in the Sergymla Mountains,southeastern Tibet.We found that the mean leaf longevity was 4.2±1.2 years,and overall it did not differ significantly between different elevations.Along the vertical profiles of juniper canopies,the leaf longevity did not reflect a linear trend.With increasing leaf longevity,N;showed declining trends.We further analyzed the relationship between leaf longevity and the corresponding length of green twigs,and found that the length of green twigs could only explain 1%-3%of the variation in leaf longevity,indicating that the length of green twigs is a poor predictor for the variation in leaf longevity.In summary,for the J.saltuaria species in timberline or nearby subalpine forests,the effects of elevation and canopy depths on leaf longevity are minor,and the leaf trait analysis is in accordance with the prediction of LES.
