成都平原林盘的固碳特征及其效益估算——以郫县为例

【目的】林盘是成都平原十分重要的生态系统以及农户赖以生存的生产生活空间,但是当前林盘各种生态系统服务的定量评估还十分欠缺,本文将科学揭示林盘的固碳释氧功能和价值。【方法】本文通过小型无人机与地面植物调查,利用材积-生物量模型和平均生产力法估算乔木与竹林的固碳释氧物质量,并采用造林成本法和工业制氧法测算其价值量。【结果】林盘内维管束植物合计106科254属310种,包括乔木81种和竹类11种,不同规模林盘的物种种类和数量具有一定差异性;小、中、大型林盘平均碳储量约为6.36、21.91和43.72 t/个,固碳能力约为0.26、0.81和1.56 t/a.个,固碳释氧价值量分别为456.05、1438.32和2762.63元/a.个;【结论】总体上看,郫县林盘2015年碳储量约为75594.36 t,固碳能力约为2885.74 t/a,固碳释氧的价值量约为509.73×10~4元/a,其中固定CO2247.17×10~4元/a,释放O2262.56×10~4元/a。

都市区生态产品价值实现多元化途径

生态产品是生态系统向人类提供的各种有形产品和无形服务的总称。生态产品的利用与人类福祉水平紧密相关。由于生态产品的多样性、复杂性和外部性特征,其价值形成及实现过程未能得到充分认识,既影响生态产品的价值实现,也难以保障生态产品的可持续供给。因此,生态产品价值实现机制是生态系统服务领域的重要科学问题。以成都市为例,通过对不同类型生态产品供给区域开展调查,采用半结构式访谈和案例分析方法,分析生态产品价值实现过程中的经验,以及面临的问题。结果表明生态农业、生态旅游和生态补偿是都市区生态产品价值实现的主要方式。其中生态农业起步较早,但发展较慢。生态旅游发展态势良好,并与生态农业相互融合。而生态补偿在流域治理和保护中有所突破,但在促进生态价值转化方面作用不足。建议充分发挥都市区区位优势,针对生态产品供需和转化的薄弱环节,逐步建立市场主导的多元化价值实现机制。

Changes in cultivated land patterns and driving forces in the Three Gorges Reservoir area, China, from 1992 to 2015

Changes of cultivated land patterns caused by major water conservation projects are rarely reported. We selected the Three Gorges Reservoir area in China to study the change in area and landscape pattern of the cultivated land in the head,central, and tail areas of the reservoir that took place between 1992 and 2015;we then studied the spatial distribution of the cultivated land in the three parts of the reservoir;finally, we studied the driving forces behind the changes in the cultivated land. The results derived are as follows.(1) During the construction of the Three Gorges Project(TGP, 1992–2015), the area of cultivated land around the reservoir decreased by30.23 million ha. This reduction occurred in phases:the most severe change in cultivated land occurred during the later stage of the project(2002–2010);only 0.62 million ha of cultivated land did not change between 1992 and 2015.(2) Spatial pattern analysis showed that the cultivated land in the three parts of the reservoir changed from a northern distribution to a southern distribution;thus, the area of cultivated land in the north decreased over the time period. The area of cultivated land in the head and tail areas decreased by varying degrees, while it increased in the central area over the 23 years, indicating that the change in cultivated land showed regional differences.(3) The TGP, the policy of reverting farmland to forest,and urbanization were the main driving factors for the change of cultivated land, but there were differences in their impacts at different stages.(4) According to the patch dynamics of the land cover change, the degree of change gradually intensified during the early and later stages of the project and then stabilized during the operational period. Our research provides scientific support for the protection of cultivated land resources and food security in the reservoir area and for the coordination of social and economic development, which is of great significance to sustainable development in the reservoir area.

Spatial patterns of farmland abandonment and its impact factors in the central Three Gorges Reservoir Area

The severe farmland abandonment phenomena in China have tremendously decreased the farmland usage efficiency and caused a series of profound ecological and social outcomes. The complexity of farmland abandonment necessitates a systematic research on its patterns and impact factors to underpin the dynamics of problem as well as potential solutions. This paper took Wanzhou district in the central part of Three Gorges Reservoir Area as an example to study the spatial distribution patterns of abandoned farmland at three scales, i.e., town, village, and plot, and analyzed the influence from labor transfer and farmland circulation. We conducted a survey on the distribution patterns of abandoned farmland via questionnaires at town and village scales, together with the modeling and interpretation of high-resolution aerial images taken by unmanned aerial vehicles at plot scale. Our research discloses a strong relationship between the distribution of abandoned farmland and the distance from population center at different scales. At eithertown or village scale, the abandonment proportion was recognized the highest in mid-distance areas and lowest in close-distance areas, and the per capita area of abandoned farmland increased with the distance to downtown or township. At plot scale, abandonment proportion presented exponential growth with the distance to village center, whereas the abandoned farmland was mainly distributed in the areas with distance above 500 m from the village center. Moreover, we noticed that labor transfer and farmland circulation are two important factors that influence farmland abandonment. Labor's outbound transfer distance has a positive linkage with the possibility of farmland abandonment. Finally, it is recommended that development and adoption of corresponding policies on local urbanization and farmland circulation will facilitate to alleviate farmland abandonment.

Microclimate regulation efficiency of the rural homegarden agroforestry system in the Western Sichuan Plain,China

Traditional rural homegarden agroforestry systems(referred to as homegarden) in the Western Sichuan Plain of China are often referred to as "Linpan" in Chinese. These homegardens are usually composed of farm houses, trees, bamboos, and small patches of land for flowers, fruits and vegetables. Over the Western Sichuan Plain’s area of approximately 18,800 km^2, there were more than 200,000 homegardens, accommodating 72.5% of the region’s rural population. As a unique local, cultural, and ecological resource, homegardens continuously support peasant households with provisioning, regulation, and landscape ecosystem services. This study combined low height remote sensing used unmanned aerial vehicle(UAV) photography, field investigation, and instrument monitoring. We try to identify the composition and structural characteristics of homegardens, as well as climatic regulation effects of the different types of homegardens. Temperature data were collected both for summer(June to August 2016) and winter(December 2016 to February 2017). The result shows that:(1) the average area of homegardens was 0.67 ha(sizes ranging from 0.16 ha to 1.24 ha), and with vegetation coverage 43.5%-76.9%(including 310 plant species).(2)In comparision with outside the homegardens, the average temperature inside the homegardens was significantly lower in summer(approximately 0.31 ℃-0.90 ℃). Although, the lowest summer temperature was differentiatee in between 13:30-16:00. Especially, the thermal effects of the home gardens were ranged from 2.00℃-2.65℃ at high temperatures(≥30℃).(3) The cooling effect of homegardens were positively correlated(p<0.05) with tree area(X_1), vegetation coverage(X_2), tree coverage(X_3), tree species(X_4), and tree biomassper unit area(X_5), and the contribution rate was represented by X_3>X_4>X_5>X_2>X_1.(4)This study indicates the major role of homegardens for climate regulation and energy efficiency, providing suggestions for homegarden transformation and construction planning for new rural communities.

Impacts of future climate change(2030-2059)on debris flow hazard:A case study in the Upper Minjiang River basin,China

An increase in extreme precipitation events due to future climate change will have a decisive influence on the formation of debris flows in earthquake-stricken areas. This paper aimed to describe the possible impacts of future climate change on debris flow hazards in the Upper Minjiang River basin in Northwest Sichuan of China, which was severely affected by the 2008 Wenchuan earthquake. The study area was divided into 1285 catchments, which were used as the basic assessment units for debris flow hazards. Based on the current understanding of the causes of debris flows, a binary logistic regression model was used to screen key factors based on local geologic, geomorphologic, soil,vegetation, and meteorological and climatic conditions. We used the weighted summation method to obtain a composite index for debris flow hazards, based on two weight allocation methods: Relative Degree Analysis and rough set theory. Our results showed that the assessment model using the rough set theory resulted in better accuracy. According to the bias corrected and downscaled daily climate model data, future annual precipitation(2030-2059) in the study area are expected to decrease, with an increasing number of heavy rainfall events. Under future climate change, areas with a high-level of debris flow hazard will be even more dangerous, and 5.9% more of the study area was categorized as having a high-level hazard. Future climate change will cause an increase in debris flow hazard levels for 128 catchments, accounting for 10.5% of the total area. In the coming few decades, attention should be paid not only to traditional areas with high-level of debris flow hazards, but also to those areas with an increased hazard level to improve their resilience to debris flow disasters.

Impact of climatic factors on vegetation dynamics in the upper Yangtze River basin in China

It is necessary to understand vegetation dynamics and their climatic controls for sustainable ecosystem management.This study examines the vegetation dynamics and the effect of climate change on vegetation growth in the pristine conditions of 58 woodland National Nature Reserves(NNRs)located in the upper Yangtze River basin(UYRB)in China which are little influenced by human activities.Changes in the normalized difference vegetation index(NDVI),precipitation,and temperature in the selected NNRs were observed and analyzed for the period between 1999 and 2015.The relationship between time-lag effect of climate and changes in the NDVI were assessed using Pearson correlations.The results showed three major trends.1)The NDVI increased during the study period;this indicates an increase in the amount of green vegetation,especially due to the warmer climate during the growing season.The NDVIs in March and September were significantly affected by the temperature of the previous months.Spring temperatures increased significantly(P<0.05)and there was a delay between climatic factors and their effect on vegetation,which depended on the previous season.In particular,the spring temperature had a delayed effect on the NDVI in summer.2)The way in which vegetation responds to climatic factors varied significantly across the seasons.Temperature had a greater effect on the NDVI in spring and summer and the effect was greater at higher altitudes.A similar trend was observed for precipitation,except for altitudes of 1000–2000 m.3)Temperature had a greater effect on the NDVI in spring and autumn at higher altitudes.The same trend was observed for precipitation in summer.These findings suggest that the vegetation found in NNRs in the upper reaches of the Yangtze River was in good condition between 1999 and 2015 and that the growth and development of vegetation in the region has not been adversely affected by climate change.This demonstrates the effectiveness of nature reserves in protecting regional ecology and minimizing anthropogenic effects.

Assessing the impacts of climate change and anthropogenic activities on vegetation in southwest China

The topography and geomorphology of southwest China are complex,and the intensity of human activities not balanced.The impact of climate change and anthropogenic activities on vegetation shows temporal and spatial differences.Therefore,we used normalized difference vegetation index(NDVI)to analyze the impact of climate change and anthropogenic activities on vegetation in four provinces and municipality in the southwest China from 2000 to 2015.The results showed that(1)NDVI increased 0.004–0.005/yr during this period.About 57.74%–69.09%of the area with significant changes was found to be primarily affected by anthropogenic activities during all four seasons and the growing season,while 6.05%–10.74%and 5.09%–9.77%of the area was affected by temperature and precipitation,respectively.(2)The impact of temperature and precipitation changes were spatially heterogeneous.Temperature had a positive impact during spring and summer in the northwestern region.Furthermore,NDVI was positively affected in the southwestern and eastern regions,while the western region was negatively affected by precipitation.Summer temperatures and precipitation had the greatest impact throughout the year.(3)Returning farmland to forests and improving agricultural management demonstrated positive impacts of anthropogenic activities on the vegetation,while areas with significant negative impacts due to anthropogenic activities were located near the provincial capitals of the four provinces and municipality.This study can provide a scientific basis for accurately identifying key ecological protection areas in Southwest China.

Cropland physical disturbance intensity： plot-scale measurement and its application for soil erosion reduction in mountainous areas

Various kinds of human disturbances on cropland are the main reasons for soil erosion and land degradation.Farming practices in mountainous areas vary greatly among cropland plots because of the heterogeneity of biophysical conditions and differences in farmers'management behavior.The main purpose of this paper is to develop a composite index of cropland physical disturbance intensity(CLDI)to reflect the plot-scale discrepancy of potential soil erosion in mountainous areas.The study was based on both plot survey and household interview data,collected from six typical catchments in mountainous areas of southwestern China.Four kinds of physical disturbance practices and two kinds of conservation practices during one crop rotation period were synthesized to develop the CLDI index.The rough set theory was referenced to avoid subjectivity during weight allocation.The results show that conventional tillage,deep fertilization,and manual weeding are the main causes of cropland soil erosion,whereas manure application in combination with seasonal fallow reduces soil erosion.Different crop types as well as cropland location factors determine the spatial pattern of CLDI.Crop rotation modes with major crops of tobacco and maize resulted in a maximal CLDI,and cropland plots with a distance radius of 150 meters away from households received the most intensive physical disturbance.These results are critical to help better protect rural environments in mountainous areas.Based on the results,methods to reduce cropland soil erosion are suggested.

Study on rain-runoff process in the peripheral mountainous area of the Sichuan Basin

Studies on rain-runoff process in the peripheral mountainous area of the Sichuan Basin, which is regarded as a key ecological shelter, will contribute to flood control and environmental protection for the Upper Yang-tze River Basin. In two typical catchments-the Fujiang River Catchment and the Wujiang River Catchment, rainfall simulations have been conducted to study the rain-runoff processes of yellow soil and limestone soil in three types of land use-forestland, farmland and grassland. Results showed that (1) within the same rainfall process, overland flow occurs first on farmland, then on grassland, and finally on forestland; (2) soil surface coverage has a great impact on the occurrence and amount of overland flow. The runoff amount can increase 2-4 times after the coverage is removed;(3) the infiltration before the occurrence of overland flow will decrease because of higher gravel contents of soil, but it takes no effect on infiltration once overland flow becomes stable; (4) the runoff coefficient of the limestone soil forestland is greater than that of the yellow soil forest land, but less than that of the farmland; (5) three empirical infiltration models, including Horton' model, Kostiakov' model, and modified Kostiakov' model, were compared by using the observed results under rainfall simulation. The results showed that the Kostiakov' model performed better than both the Horton' model and modified Kostiakov model. According to the results of this research, the Kostiakov's model can be used to simulate rainfall infiltration when water erosion is modeled in the peripheral mountainous area of the Sichuan Basin.

Agricultural opportunity costs assessment based on planting suitability:a case study in a mountain county in southwest China

Payment for ecosystem services(PES) has become an increasingly popular means of ecosystem conservation. Opportunity cost is an important factor to increase the investment efficiency of PES projects.However, the distribution of opportunity cost is usually unclear in mountainous regions due to the obvious environment changes. In this study, we developed a framework to assess the distribution of agricultural opportunity costs in mountainous regions and applied this method to Baoxing County, a typical mountainous county in Sichuan Province of southwest China. Planting suitability of 17 crops was assessed based on agricultural statistics and natural conditions data within a GIS environment.Agricultural opportunity cost was quantified with a weighted summation of farmers' willingness to cultivate and each crop's opportunity cost. Finally,specific agricultural opportunity cost was obtained according to the spatial areas of the protection programs and land use status. The results showed that agricultural opportunity costs of PES in Baoxing County were estimated to be more than $30 million,with a mean of 400.85 $/ha. Agricultural opportunity costs in mountainous regions displayed some obvious spatial variation and areas with lower agricultural opportunity costs could be selected as priority areas for PES. Our findings revealed that the planting suitability evaluation can make agricultural opportunity costs mapping more reasonable. It will be helpful for the PES programs implementation in mountainous regions.

Modelling spatial variation in the treatment costs of nonpoint source pollution in mountainous regions of southwest China

Non-point source(NPS) pollution is considered to be one of the main threats of the aquatic environment. Mountainous regions are particularly important water sources for urban areas. The various driving factors of NPS pollution such as terrain, precipitation, and vegetation type in mountainous regions show clear spatial heterogeneity. Consequently, the management systems required for NPS pollution in mountainous regions are complex. In this study, we developed a framework to estimate and map the treatment costs for NPS pollution in mountainous regions and applied this method in Baoxing County, a typical mountainous county in Sichuan Province of southwest China. The export levels of total nitrogen(TN) and total phosphorus(TP) in Baoxing County were estimated using the water purification model in InVEST(Itegrated Valuation of Ecosystem Services and Tradeoffs) tool. NPS pollutant treatment costs were calculated based on the level of pollutants exports, water yield, water quality targets, and treatment costs of NPS pollutants per unit mass. The results show that at the watershed level the amounts of TN and TP exported in Baoxing County were below threshold limits. However, at the sub-watershed level, TN and TP excesses of 291.64 and 2.96 tons per year were found, respectively, with mean TN and TP treatment costs of 6.58 US$/hm^2 and 0.35 US$/hm^2. Appraising pollution treatment cost intuitively reflects the overall expenditure in NPS pollution reduction from an economic perspective. This study provides a foundation for the implementation of Payment for Ecosystem Service(PES) and the prevention and control of NPS pollution.

An Assessment of Changes in Bioclimatic Types in Sichuan Province, 1961-2010

Assessing the impact of climate change is important for ecosystem conservation and plant recovery, especially in climate sensitive regions.Various studies suggested that the K?ppen classification is an effective method to depict climate change. However, these studies were restricted to large scales or of limited accuracy due to uncertainties in climate model projections. In addition, the impact of elevation on the shift of climate zones, as compared with other factors, is less emphasized. To address these issues we compiled the K?ppen Climate Classification(period 1961-2010) for the study area,Sichuan Province, China. The spatial resolution was selected as 1 km × 1 km. Sichuan Province may be characterized by 3 main climate classes and 10 subtypes. The east-west gradient of the climatic regimes in Sichuan is represented by the main climate classes, warm temperate climates(C), snow climates(D) and polar climates(E), at which the most abundant class is C. The most abundant subtype is snow climate with dry winter and cool summer(Dwc).Shifts in K?ppen climate classes reflect the observed trend of increasing temperature. Finally, the elevation showed an obvious impact on the distribution and the change of climate classes in Sichuan Province. Theshift of areas covered by K?ppen climate classes increases with elevation.

Planning conservation corridors in mountain areas based on integrated conservation planning models: A case study for a giant panda in the Qionglai Mountains

With the accelerated urbanization,human activities pose serious threats to species because of fragmentation.Planning conservation corridors between habitats could improve species mobility in order to address the human disturbance.However,there are a limited number of studies that focus on assessing the effect of human activities on species movement in mountain areas as well as how to integrate different conservation models relating to conservation corridors identification.In our study,we modified the resistance model and took land use data as input parameters to quantify the impacts of human activities in mountain areas.Meanwhile,different conservation planning models,including Circuit model and Least Cost Path(LCP)algorithm,were integrated.Moreover,our approach was applied to identify giant panda corridors in Miarro nature reserve,Caopo nature reserve,and Wolong nature reserve.The results suggested that the impacts of human activities were limited in valley regions due to topography by resistance model.Secondly,Circuit model demonstrated that the conservation corridors for giant panda could not be identified between the Miarro and the Caopo nature reserves.Additionally,more detailed corridors between habitats were planned by the LCP algorithm.Furthermore,we also identified bottlenecks for migration in each corridor,indicating that human activities’interference was the primary cause.Our approach not only could connect habitats for conservation in mountain areas but also found out that the corridor could not be identified between habitats.

Influence of nitrogen wet deposition on nitrogen output in a typical watershed in the Three Gorges Reservoir Area

In order to explore the influence of wet nitrogen(N)deposition on N output in watersheds,this study selected a typical small watershed(Chenjiagou,CJG)in the Three Gorges Reservoir(TGR)area based on one-year observation of rainfallrunoff N forms.Characteristics and sources of N output were clarified by chemical statistics and isotopic abundance,and the contribution of N deposition to the N output was quantified by the output coefficient method.The N flux of wet deposition was estimated at 18.53 kg N ha^(-1) yr^(-1),and originated mostly from agricultural activities.Watershed N was significantly accumulated from upper to lower reaches due to frequent human activities.Seasonal changes of riverine N were strongly affected by chemical fertilizer,with the highest concentration in spring and the lowest in winter.Nitrate was mainly derived from chemical fertilizer,accounting for 38.83% of all sources.N concentration in processes of different rainfall events had a hysteresis effect corresponding to the flow rate.Three rainfall events greatly changed DTN(Dissolved total N)outputs:rainstorm caused 91.26 kg DTN output,which was 11 times that of moderate rain(8.46 kg)and 4 times that of heavy rain(20.80 kg).N deposition contributed 19.89% of riverine N output in the watershed.The results can provide theoretical support for the control of N pollution in the TGR area.

三峡库区规模化顺坡沟垄果园氮、磷输出过程及流失负荷

通过对三峡库区顺坡垄沟构型的规模化柑橘园集水区次降雨过程径流氮、磷进行动态监测,分析典型降雨事件氮和磷流失负荷,并探讨了规模化柑橘种植对土壤氮磷流失及入库河流水环境的影响.结果表明:①顺坡沟垄柑橘园集水区径流氮和磷年流失负荷分别为13.43 kg·(hm^2·a)^-1和1.26 kg·(hm^2·a)^-1,春季施肥及强降雨冲刷是集水区污染物高负荷的主要原因;②集水区全年总氮(TN)和总磷(TP)的EMC为8.49 mg·L^-1和0.87 mg·L^-1,超过发生水体富营养化含量标准;③春季施肥后的2场典型降雨中,长历时暴雨径流硝态氮(NN)和溶解态磷(DP)负荷为4.94 kg·hm^-2和0.28 kg·hm^-2,分别占TN和TP流失负荷的92.90%和64.69%;短历时大雨径流NN和DP负荷为0.52 kg·hm^-2和0.05 kg·hm^-2,分别占TN和TP的65.92%和74.88%,溶解态氮和磷是顺坡沟垄坡面果园径流氮和磷流失的主要途径;④集水区氮磷流失表现出显著的"初始冲刷效应",初期20%的地表径流流失了58.0%的TN,57.0%的DN,58.5%的NN,79.0%的AN,62.0%的TP,63.5%的DP和60.0%的PP,控制初期地表径流对降低入库径流养分具有重要作用.

ZnO-TiO_(2)异质微米马达系统的光控重构变形行为

主要研究了ZnO-TiO_(2)异质微米马达系统的近红外光诱导对流原位定点构建方法和紫外光控重构变形行为。在近红外光诱导对流作用下,分散的TiO_(2)微米粒子于红外光斑中的ZnO微米针处原位聚集形成ZnO-TiO_(2)异质微米马达系统。当施加紫外斜光时,无规自驱动的ZnO微米针因其受光面发生光腐蚀反应释放离子产物(Zn^(2+))而产生基于电解质扩散泳的正趋光定向运动,TiO_(2)微米粒子因其受光面发生光催化H_(2)O_(2)分解反应释放出分子产物(O_(2))而产生基于非电解质扩散泳的负趋光性定向运动。因此,通过动态调节控制入射光的方向,可以实时控制强正趋光性ZnO微米马达的运动方向和运动轨迹,从而对弱负趋光性TiO_(2)集群进行复杂切割(如直线、圆形和多次切割),实现对分裂子群的大小、形态和数量以及整个系统重构变形的复杂操控。本研究将为微米马达集群的形态控制和智能多功能微米马达集群系统的构建提供新策略,推动其在动态微图案化和微纳米组装加工方面的应用。