利用BEPS模型估算城区植被净初级生产力的时空变化

为了定量评估北京奥运绿化工程改善生态环境的效果,在北京城区各主要公园绿地林木普查和叶面积指数观测及气象观测数据的基础上,修正模型参数建立适用的BEPS模型,利用年降水量相差不大的2004和2009年TM遥感数据估算北京城区植被NPP空间分布。结果表明,北京奥运绿化工程取得了显著效果,2004年与2009年相比,北京城区植被年NPP总量由2.71×1011g C·a-1增长到3.05×1011g C·a-1,年NPP均值由83.18g C·m-2a-1上升到93.39g C·m-2a-1;年NPP在0~100g C·m-2a-1范围的面积比例由53.61%下降到42.72%,而在100~200g C·m-2a-1范围的面积比例由20.98%上升到33.49%。城区各大公园林地的年NPP数值较高,植树造林是补偿因城市扩展导致NPP损失的最重要途径。     

新疆气候变化下植被净初级生产力格局分析

针对新疆独特的气候-植被特征,利用遥感技术对植被光合作用解析,应用有关模型参数修正,构建适用干旱区的光能利用率模型NPP-GPEM;模拟估算新疆20年陆地生态系统1 km像元的年净第一性生产力,并进行其时空格局变化分析。结果表明:模拟结果检验较好地反映了新疆NPP空间分布和变化特征,明显体现出研究区生态系统碳吸收的空间异质性特征;表明干旱区植被生理特征的光能利用模型较合理,为干旱区生态系统研究和陆地生态系统碳循环研究提供了借鉴。     

21世纪以来呼伦贝尔市植被净初级生产力时空变化特征分析

植被净初级生产力(NPP)体现植被在自然条件下的生产能力,是全球变化领域的热点内容。文中以呼伦贝尔市为研究区,利用遥感生产力模型(CASA模型)获取研究区2000、2005、2010和2015年四期NPP数据,分别从NPP空间分布特征、特征值变化、NPP变化的空间格局和不同植被类型NPP变化等方面分析近15年来呼伦贝尔市NPP的时空变化特点。结果表明:(1)呼伦贝尔市NPP空间分布呈现出明显的地带规律性,从西往东有明显的增加趋势;(2)呼伦贝尔市NPP取值范围主要集中在200-400g C/(m2·a),年均NPP为340.7g C/(m2·a),NPP取值>600g C/(m2·a)的面积虽然占比较小但有明显的增加趋势;(3)在2000-2015年期间,呼伦贝尔市NPP呈现出先略微下降后逐渐增加的趋势,西部草地区域呈现出持续下降趋势,而其他区域略有波动但整体增加趋势;(4)从不同植被类型NPP变化结果来看,在2000-2015年期间,旱地与水田呈现出逐渐增加趋势,天然草地呈现出逐渐减少趋势,其它植被类型的NPP变化虽有波动但总体呈现增加趋势。     

石羊河流域植被净初级生产力时空变化及驱动因素

利用CASA模型（Carnegie-Ames-Stanford Approach）模拟石羊河流域2000—2020年植被净初级生产力（NPP）,分析流域NPP的时空变化特征、稳定性和未来变化趋势,并从气候因素、地形因素和人类活动因素3个方面探讨对NPP的变化影响。结果表明：（1）2000—2020年石羊河流域植被NPP多年平均值为291.01 g C·m-2·a-1,呈不显著增加趋势,空间分布呈南高北低的分布格局。（2）2000年以来植被NPP呈增加趋势的区域占总面积的86.4%,其中极显著增加和显著增加的区域分别占6.7%和10.1%。（3）NPP变化在中等波动以上（变异系数Cv≥0.25）的区域所占比例为50.4%。（4）从未来变化趋势看,石羊河流域植被NPP恢复的持续性较弱,呈增加并反持续的地区所占比例达到57.1%。（5）流域的植被NPP变化与气温、降水均成正相关,对气温的响应更为敏感。NPP随海拔高度和坡度增加呈现增大后减小趋势,近年来流域实施的一系列人工造林、退耕还林还草等措施对植被NPP的增加具有明显促进作用。     

基于CASA模型的三江源地区植被净初级生产力遥感估算研究

以改进后的CASA模型为基础,利用MODIS数据、气象数据和植被类型数据,估算了2010年三江源地区植被净初级生产力(NPP)。结果表明:三江源地区NPP的总值为52.146×1012gC·a-1,平均值为146.66g C·m-2·a-1,呈现由东南向西北逐渐递减的空间分布趋势,并随着海拔和坡度的增高,NPP先升高后降低。     

黄河源地区植被净初级生产力对气候变化的响应

基于黄河源区1959—2008年月平均气温、最高气温、最低气温、相对湿度、降水量、风速和日照百分率等气候要素资料,应用修订的Thornthwaite Memorial模型计算了50 a植被净初级生产力(NPP),分析其年际和年代际变化特征及其对气候变化的响应。结果表明:1959—2008年间,研究区年NPP变化呈显著上升趋势,NPP变化曲线线性拟合倾向率在95.502～190.72 kg/(hm2.10a)之间,20世纪90年代后NPP较高。20世纪70年代表现为"冷干型"气候特征,NPP距平百分率偏少1.1%～2.1%;2001—2008年均为"暖湿型"气候特征,NPP距平百分率偏多2.1%～4.5%。影响黄河源区NPP变化的主要气候因子是降水量、最大蒸散量和平均最低气温。"暖湿型"气候对植被净生产力增加最有利,黄河源区NPP可增加5.5%～8.5%。而"冷干型"气候造成植被净生产力下降5%～9%。若2050年在"暖湿型"气候情景下,黄河源区未来NPP较多年平均值增加7%～17%。     

气候变化对渭河流域自然植被净初级生产力的影响研究(Ⅱ)——渭河流域自然植被净初级生产力的研究

利用渭河流域及其周边地区52个气象站1959～2010年的逐日气象资料,采用周广胜-张新时模型、Penman-Monteith模型、气候倾向率、相关分析和Spline插值等方法,分析了近52年湿润指数的时空变化特征及其对NPP(自然植被净第一性生产力)的影响,并对未来不同的气候变化情景下NPP对气候变化的可能响应进行预估。结果表明:NPP高值区位于秦岭山区、关中部分地区、子午岭、六盘山和华山地区,总体呈下降趋势(P>0.1),仅个别站点微弱上升;NPP与降水、相对湿度和湿润指数成正相关(P<0.001),与潜在蒸散量、日照时数和气温负相关,温度对于NPP累积起到的作用有限,降水是主要制约因素;不同的气候情景对NPP的模拟表明,温度和降水同时上升的情况下NPP增幅15%以上,仅温度升高而降水不变NPP增加10%左右,温度上升而降水下降导致NPP不升反降,仅个别地区出现小幅上升。     

植被净第一性生产力模型研究进展

建立符合实际情况的植被净第一性生产力模型，可以为研究土地承载力和制定人口、环境、资源协调发展战略和规划提供科学依据。详细了植被净第一性生产力模型的国内外研究进展，并对现有的自然植被和作物生产力模型进行了简要评价，比较其优劣，指出了今后的发展方向；建立植被叶面积指数与生物生产力区域遥感动态模型；在全球变化背景下，研究生物生产力的变化趋势尤为重要；对于作物生长模型应组建模型进行所需的各类数据库。     

黑河中游净初级生产力的人类占用时空分异北大核心CSCD

净初级生产力的人类占用（HANPP）是评估人类通过土地利用活动对生态系统影响的重要手段。采用遥感影像数据和社会经济统计数据,通过Thornthwaite Memorial模型、改进的CASA模型和全局空间自相关等方法,对黑河中游HANPP时空分异规律进行了研究。结果显示：（1）2001—2013年,在粮食产量逐年递增的情况下,黑河中游HANPP有明显的波动,与降水量的年际波动直接相关;HANPP率一直维持在较高的水平（38%～71%）;（2）HANPP空间格局变化显著,从民乐、山丹的南部较高的地区转移到了张掖市区的远郊和山丹中部,HANPP的空间格局直接受制于实际净初级生产力的空间格局;（3）HANPP存在一定的空间正自相关关系,2001—2013年HANPP整体相关性几乎没有变化。该研究对作为生态脆弱区的黑河中游在未来权衡经济发展和生态保护具有借鉴意义。     

近42 a黄河源区生长季植被净初级生产力变化及其对气象因子的敏感性分析

利用1971—2012年黄河源区5个气象站逐日气象数据,应用修定的Thornthwaite Memorial模型计算了区域内各站植被生长季（4—10月）NPP,分析了NPP的时空变化特征,同时,探讨了黄河源区NPP对各气象因子的敏感性及各气象要素对源区NPP变化的贡献程度。结果表明：42 a来黄河源区NPP在生长季平均以125.1 kg·hm^-2·a^-1·10a^-1呈逐年上升趋势,期间存在10 a主周期变化和5 a～6 a的次周期变化;源区NPP多年来在空间变化中存在明显的地域差异,具有由南向北、自东到西NPP依次减小的分布特征;黄河源区NPP对最高气温、日照和降水量的敏感性最强,而对风速、相对湿度和最低气温的敏感性相对较弱;气象因子对源区NPP的总和贡献西北部大于东南部,这与NPP多年相对变化的地域分布特点是相一致的。     

Spatiotemporal variation in vegetation net primary productivity and its relationship with meteorological factors in the Tarim River Basin of China from 2001 to 2020 based on the Google Earth Engine

Vegetation growth status is an important indicator of ecological security. The Tarim River Basin is located in the inland arid region of Northwest China and has a highly fragile ecological environment. Assessing the vegetation net primary productivity (NPP) of the Tarim River Basin can provide insights into the vegetation growth variations in the region. Therefore, based on the Google Earth Engine (GEE) cloud platform, we studied the spatiotemporal variation of vegetation NPP in the Tarim River Basin (except for the eastern Gobi and Kumutag deserts) from 2001 to 2020 and analyzed the correlations between vegetation NPP and meteorological factors (air temperature and precipitation) using the Sen slope estimation method, coefficient of variation, and rescaled range analysis method. In terms of temporal characteristics, vegetation NPP in the Tarim River Basin showed an overall fluctuating upward trend from 2001 to 2020, with the smallest value of 118.99 g C/(m²?a) in 2001 and the largest value of 155.07 g C/(m²?a) in 2017. Regarding the spatial characteristics, vegetation NPP in the Tarim River Basin showed a downward trend from northwest to southeast along the outer edge of the study area. The annual average value of vegetation NPP was 133.35 g C/(m²?a), and the area with annual average vegetation NPP values greater than 100.00 g C/(m²?a) was 82,638.75 km², accounting for 57.76% of the basin. The future trend of vegetation NPP was dominated by anti-continuity characteristic; the percentage of the area with anti-continuity characteristic was 63.57%. The area with a significant positive correlation between vegetation NPP and air temperature accounted for 53.74% of the regions that passed the significance test, while the area with a significant positive correlation between vegetation NPP and precipitation occupied 98.68% of the regions that passed the significance test. Hence, the effect of precipitation on vegetation NPP was greater than that of air temperature. The results of this study improve the understanding on the spatiotemporal variation of vegetation NPP in the Tarim River Basin and the impact of meteorological factors on vegetation NPP.     

Estimation of spatial and temporal changes in net primary production based on Carnegie Ames Stanford Approach (CASA) model in semi-arid rangelands of SemiromCounty,Iran

Net primary production (NPP) is an indicator of rangeland ecosystem function. This research assessed the potential of the Carnegie Ames Stanford Approach (CASA) model for estimating NPP and its spatial and temporal changes in semi-arid rangelands of Semirom County, Iran. Using CASA model, we estimated the NPP values based on monthly climate data and the normalized difference vegetation index (NDVI) obtained from the MODIS sensor. Regression analysis was then applied to compare the estimated production data with observed production data. The spatial and temporal changes in NPP and light utilization efficiency (LUE) were investigated in different rangeland vegetation types. The standardized precipitation index (SPI) was also calculated at different time scales and the correlation of SPI with NPP changes was determined. The results indicated that the estimated NPP values varied from 0.00 to 74.48 g C/(m²?a). The observed and estimated NPP values had different correlations, depending on rangeland conditions and vegetation types. The highest and lowest correlations were respectively observed in Astragalus spp.-Agropyronspp. rangeland (R²=0.75) with good condition and Gundeliaspp.-Cousiniaspp. rangeland (R²=0.36) with poor and very poor conditions. The maximum and minimum LUE values were found in Astragalus spp.-Agropyronspp. rangeland (0.117 g C/MJ) with good condition and annual grasses-annual forbs rangeland (0.010 g C/MJ), respectively. According to the correlations between SPI and NPP changes, the effects of drought periods on NPP depended on vegetation types and rangeland conditions. Annual plants had the highest drought sensitivity while shrubs exhibited the lowest drought sensitivity. The positive effects of wet periods on NPP were less evident in degraded areas where the destructive effects of drought were more prominent. Therefore, determining vegetation types and rangeland conditions is essential in NPP estimation. The findings of this study confirmed the potential of the CASA for estimating rangeland production. Therefore, the model output maps can be used to evaluate, monitor and optimize rangeland management in semi-arid rangelands of Iran where MODIS NPP products are not available.     

基于CASA模型的吉林西部植被净初级生产力及植被碳汇量估测

将MODIS数据,气象数据与植被数据相结合,利用CASA模型与土壤微生物呼吸模型,计算2001-2010年吉林西部的陆地植被净初级生产力(NPP)和土壤微生物呼吸RH,在此基础上估算了净生态系统生产力(NEP),分析NEP变化规律和原因,估测吉林西部植被碳汇量,结果表明:研究区NPP呈自西向东逐渐增加的趋势;碳源主要分布在通榆、镇赉和大安土地盐碱化比较严重的地区,其植被碳汇量为-160-0gC·m-2·a-1;前郭、扶余、松原、长岭以及白城和镇赉的两个水田灌区的NEP为150-300gC·m-2·a-1,起到碳汇的作用;10年间吉林西部NEP总体上呈波动上升趋势,2010年碳汇能力较2001年增加了47.10gC·m-2·a-1。     

近10年甘南牧区草地净初级生产力变化研究

以改进的CASA模型为基础,结合MODIS NDVI数据、气象资料,估算了甘南牧区草地2000、2005、2008年牧草生长旺季7月净初级生产力,并分析了其时空动态.结果显示:(1)甘南牧区草地净初级生产力(NPP)的空间分布基本格局是西南偏西和东北两区域最低,然后由西南-东北方向为轴心逐渐向内陆中心部分递增,该分布规...     

2000-2010年内蒙古防沙带草地NPP的变化特征

利用CASA模型计算得到2000-2010年净初级生产力(NPP)及2000年与2010年30 m分辨率的土地利用/覆被数据,探讨近年来内蒙古防沙带草地NPP的变化特征及其与自然因素之间的关系.结果表明:①2000-2010年,研究区草地转为建设用地成为草地流失的主要因素,而荒漠成为草地增加的主要来源,水体与耕地成为草地增加的第二来源.②内蒙古防沙带草地NPP表现为“整体改善,局部退化”的态势.NPP明显增加区主要为海拔低于500 m的东部科尔沁地区与东南部的宁城县、建平县等区域.NPP降低区西至固阳县东至正蓝旗呈带状分布.③从模型的回归结果看,影响草地NPP降低因素的重要性排序为:高程(DEM)＞降水量＞气温＞草地初始质量.草地NPP增加与降低面积在海拔1000m与1300m左右时达到峰值,而这两个海拔高度又恰好是人类活动活跃区,说明草地NPP受人类活动的影响也非常明显.降雨量对草地NPP有明显的正面影响,而气温则表现为负面影响.     

Estimation of net primary productivity and its driving factors in the Ili River Valley,China

Net primary productivity(NPP), as an important variable and ecological indicator in grassland ecosystems, can reflect environmental change and the carbon budget level. The Ili River Valley is a wetland nestled in the hinterland of the Eurasian continent, which responds sensitively to the global climate change. Understanding carbon budget and their responses to climate change in the ecosystem of Ili River Valley has a significant effect on the adaptability of future climate change and sustainable development. In this study, we calculated the NPP and analyzed its spatio-temporal pattern of the Ili River Valley during the period 2000–2014 using the normalized difference vegetation index(NDVI) and an improved Carnegie-Ames-Stanford(CASA) model. Results indicate that validation showed a good performance of CASA over the study region, with an overall coefficient of determination(R2) of 0.65 and root mean square error(RMSE) of 20.86 g C/(m~2·a). Temporally, annual NPP of the Ili River Valley was 599.19 g C/(m~2·a) and showed a decreasing trend from 2000 to 2014, with an annual decrease rate of –3.51 g C/(m~2·a). However, the spatial variation was not consistent, in which 55.69% of the areas showed a decreasing tendency, 12.60% of the areas remained relatively stable and 31.71% appeared an increasing tendency. In addition, the decreasing trends in NPP were not continuous throughout the 15-year period, which was likely being caused by a shift in climate conditions. Precipitation was found to be the dominant climatic factor that controlled the inter-annual variability in NPP. Furthermore, the correlations between NPP and climate factors differed along the vertical zonal. In the medium-high altitudes of the Ili River Valley, the NPP was positively correlated to precipitation and negatively correlated to temperature and net radiation. In the low-altitude valley and high-altitude mountain areas, the NPP showed a negative correlation with precipitation and a weakly positive correlation with temperature and net radiation. The results suggested that the vegetation of the Ili River Valley degraded in recent years, and there was a more complex mechanism of local hydrothermal redistribution that controlled the growth of vegetation in this valley ecosystem.     

Effects of grazing on net primary productivity,evapotranspiration and water use efficiency in the grasslands of Xinjiang,China

Grazing is a main human activity in the grasslands of Xinjiang, China. It is vital to identify the effects of grazing on the sustainable utilization of local grasslands. However, the effects of grazing on net primary productivity(NPP), evapotranspiration(ET) and water use efficiency(WUE) in this region remain unclear. Using the spatial Biome-BGC grazing model, we explored the effects of grazing on NPP, ET and WUE across the different regions and grassland types in Xinjiang during 1979–2012. NPP, ET and WUE under the grazed scenario were generally lower than those under the ungrazed scenario, and the differences showed increasing trends over time. The decreases in NPP, ET and WUE varied significantly among the regions and grassland types. NPP decreased as follows: among the regions, Northern Xinjiang(16.60 g C/(m~2·a)), Tianshan Mountains(15.94 g C/(m~2·a)) and Southern Xinjiang(-3.54 g C/(m~2·a)); and among the grassland types, typical grasslands(25.70 g C/(m~2·a)), swamp meadows(25.26 g C/(m~2·a)), mid-mountain meadows(23.39 g C/(m~2·a)), alpine meadows(6.33 g C/(m~2·a)), desert grasslands(5.82 g C/(m~2·a)) and saline meadows(2.90 g C/(m~2·a)). ET decreased as follows: among the regions, Tianshan Mountains(28.95 mm/a), Northern Xinjiang(8.11 mm/a) and Southern Xinjiang(7.57 mm/a); and among the grassland types, mid-mountain meadows(29.30 mm/a), swamp meadows(25.07 mm/a), typical grasslands(24.56 mm/a), alpine meadows(20.69 mm/a), desert grasslands(11.06 mm/a) and saline meadows(3.44 mm/a). WUE decreased as follows: among the regions, Northern Xinjiang(0.053 g C/kg H_2O), Tianshan Mountains(0.034 g C/kg H_2O) and Southern Xinjiang(0.012 g C/kg H_2O); and among the grassland types, typical grasslands(0.0609 g C/kg H_2O), swamp meadows(0.0548 g C/kg H_2O), mid-mountain meadows(0.0501 g C/kg H_2O), desert grasslands(0.0172 g C/kg H_2O), alpine meadows(0.0121 g C/kg H_2O) and saline meadows(0.0067 g C/kg H_2O). In general, the decreases in NPP and WUE were more significant in the regions with relatively high levels of vegetation growth because of the high grazing intensity in these regions. The decreases in ET were significant in mountainous areas due to the terrain and high grazing intensity.     

Temporal and spatial variations of net primary productivity and its response to groundwater of a typical oasis in the Tarim Basin,China

Net primary productivity (NPP) of the vegetation in an oasis can reflect the productivity capacity of a plant community under natural environmental conditions. Owing to the extreme arid climate conditions and scarce precipitation in the arid oasis regions, groundwater plays a key role in restricting the development of the vegetation. The Qira Oasis is located on the southern margin of the Taklimakan Desert (Tarim Basin, China) that is one of the most vulnerable regions regarding vegetation growth and water scarcity in the world. Based on remote sensing images of the Qira Oasis and daily meteorological data measured by the ground stations during the period 2006-2019, this study analyzed the temporal and spatial patterns of NPP in the oasis as well as its relation with the variation of groundwater depth using a modified Carnegie Ames Stanford Approach (CASA) model. At the spatial scale, NPP of the vegetation decreased from the interior of the Qira Oasis to the margin; at the temporal scale, NPP of the vegetation in the oasis fluctuated significantly (ranging from 29.80 to 50.07 g C/(m²•month)) but generally showed an increasing trend, with the average increase rate of 0.07 g C/(m²•month). The regions with decreasing NPP occupied 64% of the total area of the oasis. During the study period, NPP of both farmland and grassland showed an increasing trend, while that of forest showed a decreasing trend. The depth of groundwater was deep in the south of the oasis and shallow in the north, showing a gradual increasing trend from south to north. Groundwater, as one of the key factors in the surface change and evolution of the arid oasis, determines the succession direction of the vegetation in the Qira Oasis. With the increase of groundwater depth, grassland coverage and vegetation NPP decreased. During the period 2008-2015, with the recovery of groundwater level, NPP values of all types of vegetation with different coverages increased. This study will provide a scientific basis for the rational utilization and sustainable management of groundwater resources in the oasis.