不同放牧率对羊草+苔草低地草甸草地再生和净初级生产力的影响

在羊草 苔草低地草甸,通过小区围栏放牧,定量研究了不同放牧率对低地草甸牧草再生性能和地上净初级生产力的影响.结果表明:在不同放牧率下各再生期间的再生草量存在着明显的季节性差异,其最大值出现在5～6月份,为136.6 g/m2.适宜的放牧率有利于增加草地的再生草量,各放牧小区的相对生长速率均大于对照小区的相对生长速率,放牧率较低的P2小区相对生长速率最大.各放牧小区地上净初级生产力均小于对照小区地上净初级生产力,即不存在超补偿性生长现象.     

中亚草地NPP时空动态及其驱动因素研究

基于CASA模型和Miami模型计算中亚五国（哈萨克斯坦、塔吉克斯坦、吉尔吉斯斯坦、土库曼斯坦和乌兹别克斯坦）的草地净初级生产力（NPP）,旨在探究2001—2019年中亚草地NPP的时空动态及其驱动因素。结果表明：2001—2019年中亚地区草地的实际净初级生产力（ANPP）均值为118.9 g C·m-2·a-1;在空间尺度上,平原地区的草地ANPP随纬度增加而呈现由南到北逐渐增加的趋势,从平原到山地草地ANPP随海拔升高呈现明显的增加趋势;在时间尺度上,ANPP总体呈现不显著的增长趋势,近60%区域的草地ANPP未来的变化趋势将与过去相反,但不显著;在中亚草地ANPP增加的区域,人类活动占主导地位;在中亚草地ANPP降低的区域,气候变化是主要驱动力;中亚草地的ANPP与降水呈现显著正相关的区域达到67.8%,温度与中亚草地ANPP的变化关系不显著,降水是影响中亚草地ANPP变化的主要气候因子。     

干旱对我国西北地区生态系统净初级生产力的影响

根据西北地区139个气象观测站1980-2009年降水及温度资料,基于Z指数干旱指标,研究西北地区干旱时空特征;利用Miami模型估算该地区生态系统净初级生产力,分析干旱对净初级生产力的影响。结果表明:西北地区30年来,西部干旱有所降低,东部则出现加重趋势。生态系统净初级生产力年变化不规则,平均为524.5543g/(m2.a);空间特征明显,自东南向西北递减,新疆西北部又有所增加。该地区净初级生产力与Z指数线性相关极显著,随着干旱的发生,净初级生产力出现下降。出现轻旱及中旱的地区,净初级生产力较低;相对湿润的地区净初级生产力较高。     

甘肃气候生产力格局及演变

为揭示甘肃气候生产力的区域响应特征,利用甘肃省分布比较均匀的64站50a(1957-2006年)实测气象资料,研究该区域气候生产力格局和时空演变.结果表明:甘肃气候生产力对气候响应的空间一致性程度低,形成河西走廊、中北部区、甘南陇南山区次区域一致空间格局;中北部区是甘肃响应最敏感的地方,河西走廊次之,甘南陇南山区最低;...     

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.     

黄河上游重要水源补给区参考作物蒸散量变化特征分析

利用甘南牧区4个气象观测站1971-2010年的地面气象观测资料,运用Penman-Monteith公式计算得出牧区四站逐月ET0值.通过统计分析、相关分析、小波及Mann-Kendall法等方法对甘南牧区ET0的变化特征进行了分析,并就高原上气象因子与ET0的相关性做了进一步研究.结果发现甘南牧区各县ET0年际变化呈逐年上升趋势,上升趋势达8.8～ 19.5mm/10a;1985年以前有明显的准10 a周期,2000年到2010年间出现了准5 a周期;在90年代以后的20年中上升更快,并于1996年以后出现了突增.牧区ET0夏季最大,并且逐年上升最快;冬季最小,逐年上升最慢.牧区ET0的空间分布不均匀除了与当地高原特殊地形地貌复杂性有关外,还与影响参考作物蒸散量的主要气象因子的不同有关.     

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。     

青海气候变化趋势及对植被生产力影响的研究

应用青海省南部三江源区、东北祁连山地及环青海湖区气象站1961-2004年气温、降水和所在地区植被地上净初级生产力资料,分析和模拟了44年来有关气候变化特征以及植被生产力与气温、降水、地理坐标参数间的关系,模拟估算了假设未来气候温暖化情景下青海植被生产力变化的可能。结果表明:44年来青海各地气温均在升高,青海北部比南部增温明显;年降水量变化平稳,但北部比南部有所增加;土壤实际蒸发散表现出明显的升高趋势;青海南部植被地上净初级生产力(NPP)逐年降低,青海东北地区相对平稳。模拟计算表明,由于青藏高原植被的生长主要受温度条件的限制,在未来气候增暖,降水不变或增加的趋势下,植被地上NPP均有所增加。     

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。     

基于牧场生产力的内蒙古典型草原载畜率研究

基于长期放牧控制实验平台,研究了内蒙古典型草原群落在两种降水年型(平水年和丰水年)和两种地形系统(平地和坡地)条件下的初级生产力和次级生产力对不同载畜率(0、1.5、3.0、4.5、6.0、7.5、9.0羊单位/hm2)的响应.结果表明:随着载畜率的增加,地上现存生物量逐渐降低.两种降水年型不同地形条件下,载畜率为3.0和4.5羊单位/hm2处理均获得较高的地上净初级生产力,平均比对照区增加了30.87％,而重度放牧(SR =7.5、9.0羊单位/hm2)处理则降低了13.53％.羊公顷增重随载畜率的增加逐渐升高,载畜率为3.0和4.5羊单位/hm2处理的平均只羊增重均高于其他处理.综合分析初级和次级生产力的变化趋势可知,本试验条件下内蒙古典型草原牧场的最适载畜率为3.0 ～4.5羊单位/hm2.     

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.     

我国荒漠植被生产力动态及其与水热因子的关系

为了探讨近30 a来我国干旱区荒漠植被的净初级生产力(NPP)及其与水热因子相关性随时间的变化,运用CASA(Carnegie Ames Stanford approach)模型估算我国荒漠植被1982—2015年生长季的NPP,并运用线性回归和GIS空间分析方法分析了NPP的时空变化特征,利用滑动相关系数分析了荒漠植被NPP与水热因子的关系。结果表明：① 单位面积NPP均值为42 g·m^-2·a^-1,NPP整体水平较低。空间上呈西北部、东部边缘较高,中部、南部和中东部较低的分布特征。② 荒漠植被NPP年均总量为5.783×1013g·a^-1。从荒漠植被NPP的年际变化来看,1982—2015年中国荒漠植被NPP总量以1.64×1012g·(10a)^-1的线性速率（P=0.054）上升,荒漠植被生长状况总体上不断改善,但总量趋势呈现阶段性变化,1982—1993年荒漠植被NPP总量呈极显著增长态势（1.25×1012 g·a^-1,P<0.01）; 1993—2006年NPP总量呈极显著降低态势（-6.42×1011 g·a^-1,P<0.01）; 2006—2015年NPP总量缓慢增长（1.70×1011 g·a^-1,P>0.05）。从空间变化来看,47.65%的荒漠植被NPP呈增加态势,主要分布在阿拉善高原、天山北麓、塔里木盆地西部边缘、柴达木盆地的东南边缘、阿尔金山南麓和昆仑山脉。③ 从荒漠植被NPP与各气候因子之间的相关关系随时间的变化来看,NPP与气温的滑动相关系数随时间的变化保持为负相关,与降水、干燥度的滑动相关系数保持为正相关,与太阳总辐射的滑动相关系数随时间变化并未表现出显著的变化趋势。总体上,荒漠植被与水热因子的相关关系在研究时段均有进一步减弱的态势,即荒漠植被NPP对气候因子的变化愈来愈不敏感。     

基于改进光能利用率模型呼伦贝尔植被净初级生产力时空格局

呼伦贝尔作为全球气候变化的敏感区域,分析其植被生产力时空格局具有重要科学意义。简化光能利用率模型的水分胁迫系数,基于E0S/MODIS卫星遥感资料,研究呼伦贝尔地区植被净初级生产力(NPP)时空格局。结果表明:1)研究区内大兴安岭林区单位面积NPP为高值区,呼伦贝尔草原西部NPP为低值区,林草交错区和农牧交错区NPP介于林区和草原区之间;2)2000年-2008年4类土地覆被类型单位面积NPP为下降趋势;3)呼伦贝尔西部草原、呼伦贝尔林草交错区单位面积NPP主要受降水量的影响,而大兴安岭林区和岭东农牧交错区主要受生长季气温的影响。     

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.     

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.     

Desertification dynamic and the relative roles of climate change and human activities in desertification in the Heihe River Basin based on NPP

Relative roles of climate change and human activities in desertification are the hotspot of research on desertification dynamic and its driving mechanism.To overcome the shortcomings of existing studies,this paper selected net primary productivity(NPP) as an indicator to analyze desertification dynamic and its impact factors.In addition,the change trends of actual NPP,potential NPP and HNPP(human appropriation of NPP,the difference between potential NPP and actual NPP) were used to analyze the desertification dynamic and calculate the relative roles of climate change,human activities and a combination of the two factors in desertification.In this study,the Moderate Resolution Imaging Spectroradiometer(MODIS)-Normalised Difference Vegetation Index(NDVI) and meteorological data were utilized to drive the Carnegie-Ames-Stanford Approach(CASA) model to calculate the actual NPP from 2001 to 2010 in the Heihe River Basin.Potential NPP was estimated using the Thornthwaite Memorial model.Results showed that 61% of the whole basin area underwent land degradation,of which 90.5% was caused by human activities,8.6% by climate change,and 0.9% by a combination of the two factors.On the contrary,1.5% of desertification reversion area was caused by human activities and 90.7% by climate change,the rest 7.8% by a combination of the two factors.Moreover,it was demonstrated that 95.9% of the total actual NPP decrease was induced by human activities,while 69.3% of the total actual NPP increase was caused by climate change.The results revealed that climate change dominated desertification reversion,while human activities dominated desertification expansion.Moreover,the relative roles of both climate change and human activities in desertification possessed great spatial heterogeneity.Additionally,ecological protection policies should be enhanced in the Heihe River Basin to prevent desertification expansion under the condition of climate change.     

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。     

黄土高原地区NPP的自然影响因素分析

以SPOT NDVI和多种自然地理要素数据为基础,利用改进光能利用率计量模型,探究影响净第一性生产力（NPP ）变化的自然因素差异及各地貌类型区NPP变化的主导影响因素。结果表明：①1998—2010年黄土高原地区NPP物质量平均值为9．884～50．790 gC·m－2·a－1,明显低于全国平均水平342 gC·m－2·a－1。②影响NPP变化的自然因素差异显著。台塬区保水性好,水土流失强度较低,NPP物质量增加显著,风蚀地貌区NPP水平低,降幅明显;干湿条件是影响NPP变化的重要自然要素,半湿润区NPP增幅量较大;坡度对NPP变化的影响显著,陡坡区林、草植被覆盖度增加,NPP增幅明显;微观尺度上水热空间分布与海拔高度相关,研究区海拔200～1000 m范围NPP增幅显著,海拔高于1000 m的区域NPP呈下降趋势。③影响NPP空间分布格局差异的主导因素为水热条件,但决定黄土粱卯地貌类型区的NPP物质量水平正相关的主导因素为高程因子,0．01置信水平下相关系数为0．52;太阳辐射对NPP物质量表现为显著负相关关系,尤其对气候干旱区域表现突出。     

Simulating the vegetation-producing process in small watersheds in the Loess Plateau of China

Small watersheds are the basic composition unit of the Loess Plateau in China. An accurate estimation of vegetation net primary productivity (NPP) is of great significance for eco-benefit evaluation in small watershed management in this region. Here we describe the development and testing of a vegetation-producing process model (VPP) of a small watershed in the Loess Plateau. The model couples three modules: radiation adjustment; soil hydrological processes; and vegetation carbon assimilation. Model validation indicates that the VPP model can be used to estimate the NPP of small watersheds in the region. With the VPP model, we estimated the spatial NPP distributions in the Yangou watershed for 2007. The results show that in the Yangou watershed the NPP is relatively low, averaging 168 g C/(m 2 ·a). Trees and shrubs have a higher NPP than crops and grasses. The NPP is larger on the partly shaded and shaded slopes than on the partly sunny and sunny slopes. The NPP on the slopes increases gradually on 0-20° slopes and decreases slightly on slopes steeper than 20°. Our simulation indicates that the vegetation type is the most important factor in determining the NPP distribution in small watersheds in the Loess Plateau.     

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.