黄土高原主要树种树干液流研究进展

为了明晰黄土高原主要树种树干液流的动态特征,该文通过对已发表相关文献搜集与整理(19篇涉及11个树种),采用meta分析手段归纳黄土高原主要树种树干液流动态、耗水规律及其影响因素。研究发现:(1)该区主要树种树干液流存在明显的昼夜变化规律;(2)太阳辐射、水汽压亏缺、土壤含水率是影响树干液流的主要环境因素;(3)树干液流测量手段、树木生长阶段以及测量时的天气条件会给树木蒸腾耗水估算带来不确定性;(4)11个树种的蒸腾耗水量大小的顺序为:针叶树种(侧柏、油松)乡土阔叶树种(白榆、辽东栎、旱柳、柠条、河北杨、小叶杨、山杏)外来阔叶树种(刺槐、苹果)。本研究为黄土高原地区造林树种的合理选择及树种耗水评价提供参考。     

Evaluation of CLIGEN for storm generation on the semiarid Loess Plateau in China

The Stochastic generation of storm patterns is often necessary for driving process-based hydrological and ecological models. CLIGEN is the only weather generator being able to generate internal storm patterns. Its goodness needs to be evaluated for its proper application. This paper aims to find the advantages and limitations of CLIGEN on semiarid areas and provide references for custom-built weather generators for the Loess Plateau. The daily rainfall time series (1957–2002) and breakpoint rainfall data (more than 20 years) on six stations on the Loess Plateau were used to estimate input parameters for CLIGEN and to compare with CLIGEN-generated 50 years of storm data. Precipitation occurrence (wet day and dry day sequence) is well-simulated without significant difference across months and sites. Errors of monthly average number of wet days range from − 0.67 to 1.08 days, standard deviations range from − 1.19 to 0.76 days, and the distributions of continuous number of wet and dry days on the semiarid Loess Plateau are adequately simulated. Daily rainfall amount is not simulated as well as precipitation occurrence. The relative errors of average daily rainfall range from − 12.93% to 8.64% and those of standard deviations range from − 21.35% to 27.46%. During the rain seasons (May–September), among 30 month–location combinations, all the Mann–Whitney tests for the means passed, 47% for squared ranks tests rejected the null hypothesis of equality of standard deviations, and 73% for K–S test suggested that the generated and measured distributions of daily rainfall were different at 0.01 level of significance Three variables to describe internal storm patterns in CLIGEN are storm duration, relative peak intensity, and time to peak. Storm duration was not well-reproduced because none of squared ranks tests and K–S test passed at the significance level of 0.01. The frequency of short duration storms (< 300 min) was over-predicted while frequency of long duration storms (400–1200 min) was significantly under-predicted. The distribution of maximum 5 min rainfall intensity (ip₅) was well-simulated for four sites out of the six because all tests passed. However, generated maximum ip₅ for all six sites are around 190 mm/h, which are much larger than the measured (70 to 150 mm/h). Ip₃₀ is simulated better than ip₅, suggesting that CLIGEN can reliably generate rainfall erosivity. Time to peak was well-simulated because all the tests passed with P values significantly greater than the significance level of P = 0.01. Improvement for CLIGEN has to be made in terms of the daily rainfall simulation in rainfall-concentrated seasons and storm pattern generation in order to generate reliable rainfall time series on the Loess plateau.     

黄土高原主要水土保持树种的蒸腾特性

采用精度为0.001 g的精密电子天平和露点水势仪对山杨、刺槐、油松和侧柏的叶片保水力、蒸腾速率日变化及叶水势日变化进行测定。结果表明：自然条件下,4树种叶片保水力从小到大依次为山杨、刺槐、油松、侧柏,其叶片分别经过19、41、49和77 h达自然风干状态;各树种日平均蒸腾速率由大到小的顺序为山杨（0.616 mmol/（m^2·s））〉刺槐（0.605 mmol/（m^2·s））〉油松（0.318 mmol/（m^2·s））〉侧柏（0.270 mmol/（m^2·s））,日最大蒸腾速率的排序为山杨（1.196 mmol/（m^2·s））〉刺槐（1.190 mmol/（m^2·s））〉油松（0.723 mmol/（m^2·s））〉侧柏（0.704 mmol/（m^2·s））;4个树种叶水势以清晨最高,中午最低,傍晚又有所恢复,日变化呈波浪形,日变幅以刺槐最大,其次为山杨和侧柏,油松最小;4个树种叶水势与蒸腾速率之间的关系呈负相关,可用对数曲线来拟合;各树种单位叶面积（cm2）的日（以12 h计）蒸腾耗水量由大到小为：山杨（0.48 mm）〉刺槐（0.47 mm）〉油松（0.25 mm）〉侧柏（0.21 mm）。     

晋西黄土丘陵沟壑区油松刺槐混交林蒸腾耗水

 为了研究黄土丘陵沟壑区主要造林树种和林分蒸腾耗水规律,以位于山西省吉县蔡家川流域内密度为2 450株/hm2的16a油松刺槐混交林为对象,在2008年7—10月,应用热扩散探针技术(TDP)对油松和刺槐4个径阶共17株样木进行蒸腾液流野外实地定位连续观测,同时对环境因子进行同步连续动态观测。结果表明:典型晴天条件下,油松和刺槐树干液流速率在液流启动时间、达到峰值时间、开始快速下降时间和峰值波动范围上有较为显著的差异;2树种不同径阶单木日均蒸腾量的大小排序为油松12 cm>10 cm>6 cm>8 cm,刺槐12 cm>8 cm>6cm,呈现出日蒸腾量随胸径增加而增加的趋势;太阳辐射和水汽压差是影响油松和刺槐树木冠层蒸腾的主要因子;2008年7—10月油松刺槐混交林月蒸腾耗水量分别为30.8、24.1、26.3和18.4mm,总蒸腾量小于同期降雨量。     

黄土丘陵区人工林地土壤肥力质量

以黄土高原北部的陕西省吴起县为例,通过对不同灌木类型和不同生长年限的乔木林地土壤样品的分析测试与数理统计,研究黄土丘陵沟壑区不同人工林植被对土壤肥力质量的影响。结果表明：1）土壤碱解N和速效K,柠条林地是沙棘林地的2倍以上,二者之间达到极显著差异水平;柠条对土壤肥力的提高效果要优于沙棘,仅从对土壤性质的改善来看,建议选择种植柠条。2）乔木林地,从幼年林地到成年林地,土壤全N、碱解N、有机质和阳离子交换量不断增加,土壤速效K、全P和速效P略有增加,土壤有机质和养分的表聚性加强。3）总体上,乔木林地0～100cm土层土壤碱解N、速效K、有机质、阳离子交换量、全N、全P、全K均高于灌木林地,表明乔木林地对土壤的培肥效果优于灌木林地。     

黄土高原地区西气东输工程沿线水土流失敏感性评价

西气东输管道的建设将直接破坏施工区范围内的地表植被,导致区域生态环境的恶化和水土流失的进一步加剧,加剧的水土流失反过来会对西气东输管道的安全运行形成较大的威胁,甚至在某些严重地区,由于崩塌、滑坡和泥石流的发生,可能会直接破坏管道,影响其安全运行.如何控制管道工程沿线地区的水土流失,加强区域友好环境的构建,不仅对于提高区域生态系统的功能具有重要意义,而且对于管道工程的安全运行具有重要的实际价值.本文在系统分析影响区域水土流失敏感性因子的基础上,在GIS的支持下,选取土壤、植被类型、坡度和坡向作为评价指标,采用图层权重-叠加模型和模糊分级模型,以专家经验打分法对各指标进行赋值,评价了黄土高原地区西气东输管道工程沿线10 km范围内水土流失的敏感性.根据研究结果将该区分为弱敏感、较敏感、敏感和高度敏感4类地区,并评价了水土流失敏感性的空间特征及其主要原因.在此基础上,从区域生态系统和管道工程的安全角度探讨了生态恢复和友好环境构建的基本措施.     

陕北黄土丘陵沟壑区土地利用景观格局动态变化特征分析

以位于典型黄土丘陵沟壑区的延安赵庄村为例,选取多样性、优势度、均匀度、破碎度和偏离度等主要指标,对村庄尺度上的土地利用景观格局动态变化进行分析研究。结果表明：1）研究期间,研究区景观斑块数与景观斑块密度增加,而平均斑块面积减少;2）研究区2个时期的景观异质性差异显著,景观指数变化表现为：优势度指数与偏离度指数减小,多样性指数、均匀度指数和破碎度指数都有不同程度的增大;3）6年来,随着退耕还林（草）政策的实施,研究区土地利用景观格局有了较大变化,生态环境整体状况趋于改善,农民收入有所增加,产业结构趋向合理,其中,工副业比例增大与种植业、养殖业、果菜比例减小是研究期间农民收入构成的主要变化特点,农民收入以工副业、果菜为主。     

黄土高原植被水分利用效率对气候和植被指数的敏感性研究

生态系统水分利用效率(water use efficiency,WUE)连接了碳循环和水循环,是碳水耦合的重要参数。全面深入理解WUE的时空分布及其影响因素对预测陆地表面-大气相互作用和陆地生态系统的动态变化至关重要。该文基于大尺度遥感归一化植被指数(normalization difference vegetation index,NDVI)以及温度和降水栅格数据,采用中分辨率成像光谱仪的总初级生产力和蒸散产品计算2000—2014年黄土高原生态系统WUE,运用岭回归探究黄土高原WUE对温度、降水和NDVI的敏感性。结果表明:1)沿西北-东南随降水量的增加,黄土高原多年均WUE逐渐降低,且黄土高原西南部高海拔地区WUE最低;同时,WUE的年际变化明显,以2011年为转折点,2012—2014年WUE明显高于其他年份。2)WUE对温度的敏感性在整个黄土高原呈现正值,WUE对降水和NDVI的敏感性存在阈值效应,即小于500mm降水量,WUE随降水和NDVI的增加而升高,超过550mm降水量,WUE则随降水和NDVI增加而降低。3)草地和灌丛WUE与NDVI正相关,森林WUE与NDVI负相关;灌丛WUE对温度和降水的敏感度明显高于森林和草地。     

黄土高原侧柏、臭椿光合、蒸腾作用比较研究

对黄土高原半干旱区侧柏和臭椿的光合、蒸腾特性进行了系统的研究,并对光合速率、蒸腾速率、气孔导度、水分利用率和胞间CO₂浓度进行了分析,结果表明:臭椿的日蒸腾速率、日光合速率、水分利用效率和气孔导度均高于侧柏;臭椿和侧柏的胞间CO₂浓度都随着光合速率的变化而变化,光合速率高则胞间CO₂浓度较低,反之则较高,侧柏和臭椿在长期适应环境的过程中产生了不同的生理生态对策.     

从黄土高原植被指数数据中获取森林覆盖率信息

 由于存在既包含农作物又包含森林植被的混合像元,以年平均归一化植被指数(NDVI)作为反映森林覆盖率的指标有很大的局限性。在黄土高原,森林植被的季节变化与农作物的季节变化有很大差异,基于这种差异,以不同月份NDVI的不同组合和考虑某种权系数后计算出来的加权平均NDVI与森林覆盖率相联系,筛选对于森林覆盖率有较好反映的NDVI指标。结果表明:6、10月2月森林覆盖率与NDVI的决定系数最高,故以6、10月平均NDVI(INDVI,6+10)作为反映森林覆盖率的指标;全年森林覆盖率与INDVI,6+10之间的决定系数为0.5384,比全年森林覆盖率与全年平均NDVI之间的决定系数0.4432提高21.48%;以各月的决定系数作为权系数求得的NDVI加权平均值(INDVI,w)与全年森林覆盖率之间的决定系数为0.5144,比森林覆盖率与年平均NDVI(INDVI,m)之间的决定系数0.4432提高16.07%,因此,推荐全年各月加权平均NDVI(INDVI,w)或6、10月平均NDVI(INDVI,6+10)作为反映黄土高原森林覆盖率的遥感植被指标。     

中国黄土高原丘陵沟壑区退耕地植被分布的影响因子研究

A study was conducted in the forest-steppe region of the Loess Plateau to provide insight into the factors affecting the process of vegetation establishment, and to provide recommendations for the selection of indigenous species in order to speed up the succession process and to allow the establishment of vegetation more resistant to soil erosion. Four distinctive vegetation types were identified, and their distribution was affected not only by the time since abandonment but also by other environmental factors, mainly soil water and total P in the upper soil layers. One of the vegetation types, dominated by Artemisia scoparia, formed the early successional stage after abandonment while the other three types formed later successional stages with their distribution determined by the soil water content and total P. It can be concluded that the selection of appropriate species for introduction to accelerate succession should be determined by the local conditions and especially the total P concentration and soil water content.     

Effects of grazing on soil physical properties and soil erodibility in semiarid grassland of the Northern Loess Plateau (China)

Grazing animals provide a livelihood for farmers, but they may also produce adverse environmental effects. We investigated whether grazing leads to deterioration of soil physical properties that subsequently increases topsoil erodibility. We sampled three sites (an ungrazed grassland, a continuously grazed grassland, and a track trampled by stock) on the northern Loess Plateau of China. The bulk density, water content, proportion of stable aggregates, infiltration rate, and resistance to scouring were determined for each soil sample. The results showed that the track had the highest soil bulk density and the lowest soil water content, proportion of stable aggregates, infiltration rate, and ability to resist scouring. The ungrazed plots had the best results for these parameters, in terms of reduced erosion. Soil bulk density and the proportion of stable aggregates differed significantly with depth beneath the track. However, the effect of depth on water content, infiltration rate, and the soil resistance to scouring was not significant at any sampling site. The ability of the soil to resist scouring was negatively correlated with the soil's bulk density and positively correlated with the soil's water content, infiltration rate, and proportion of stable aggregates. Thus, soil physical properties played an important role in determining soil erodibility. Grazing and trampling by livestock therefore appear to cause deterioration of soil physical properties and to increase soil erodibility.     

黄土高原小杂粮作物生产态势与地域分异

分不同地区和作物,对黄土高原小杂粮生产情况进行了系统研究,表明小杂粮在黄土高原旱作农区粮食生产中居重要地位。山西省小杂粮播种面积最大,甘肃省次之,宁夏回族自治区播种面积虽不及陕西省,但所占粮食播种面积的比重却较高。在不同小杂粮作物中,以马铃薯分布面积最大,谷子次之,其后依次是荞麦、绿豆,其他作物则分布相对较少。同时对小杂粮分布最为集中的黄土高原水土流失区主要小杂粮作物区域分布进行了研究,将该区分为3个区,10个亚区,评述了各区主要小杂粮生产和分布特点,为合理开发小杂粮资源提供决策依据。     

多源土地利用/覆被产品在黄土高原应用和精度评估

为准确掌握黄土高原土地利用/覆被的时空格局,基于6种不同来源的土地利用/覆盖数据产品,MCD12Q1,ESA-CCI-LC,GlobeLand30,GLASS,CAS-LUCC和ChinaCover,开展了黄土高原地区退耕还林(草)实施以来土地利用/地表覆被时空格局和转类特征的研究,对不同来源数据产品的精度进行了验证分析。结果表明：(1)分类特征和变化趋势上,MCD12Q1和GLASS产品与其他产品的差异最大,其次为ESA-CCI-LC产品,GlobeLand30,CAS-LUCC和ChinaCover产品的差异相对较小。(2)除MCD12Q1产品外,不同来源土地利用/覆被产品各类型面积随时间变化趋势基本一致。(3)空间转类上,GLASS产品与其他产品的差异最大,解译类型明显错误;其次为MCD12Q1产品,转林类和转草类也存在明显错误,退耕还林(草)特征表现不明显;ESA-CCI-LC和GlobeLand30在黄土丘陵沟壑区退耕还林(草)的转类特征表现不足;CAS-LUCC和ChinaCover退耕还林(草)特征明显。(4)抽样精度上,GlobeLand30,CAS-LUCC,Chin...     

辽东栎不同方位边材液流季节动态及其对蒸腾耗水测算的影响

利用Granier树干液流测定系统,对黄土高原半干旱区天然辽东栎树干不同方位的边材液流动态进行了长期监测,并同步监测环境因子(空气温度、湿度、太阳辐射等),分析了不同方位液流通量密度的相互关系、对液流通量和蒸腾耗水量测算的影响以及与环境因子的关系。结果显示,辽东栎东、西、南、北4个方位测得的液流通量密度存在显著差异,并显著相关。辽东栎生长季内(5-10月)单株日蒸腾耗水量分别与日总太阳辐射和日均白天空气水气压亏缺进行指数饱和曲线拟合,拟合效果较好。采用2个方位和1个方位树干液流通量密度测算的整株蒸腾耗水量与采用4个方位的测算值分别相差约18%和30%,说明不同方位之间的液流差异可能成为蒸腾耗水测算的重要误差来源。     

黄土高原不同气候区降水时空变化特征

充分认识黄土高原不同气候区降水时空分布特征,对于揭示该区域水土保持及自然环境变化的驱动因素至关重要.以黄土高原73个气象站点、1961-2014年的降水日值数据为基础,通过变差系数、集中度与集中期、Mann-Kendall检验和Kriging空间插值等研究方法,探讨黄土高原全区和4个气候分区的降水时空变化特征.结果显示:近50年间,黄土高原及各个气候区的年际降水量均呈波动下降趋势,年内降水均集中于夏秋季节,且存在集中度逐渐升高和集中期逐渐推后的现象.空间上降水由东南半湿润区向西北干旱区呈阶梯状递减,变差系数恰与之相反;集中度表现为由南向北递增,集中期则受地形影响显著,体现为平原和谷地地区早于高原和山地地区.因地理位置和季风强度的差异,各气候区年降水量及其波动幅度和集中性差异较大.该研究旨在揭示黄土高原降水的时空分布规律,为合理利用配置水资源、规划部署水土保持工作等,提供一定的参考.     

黄土丘陵区刺槐人工林土壤养分特征及演变

为了探明黄土丘陵沟壑区人工林土壤养分状况及其演变规律,应用时空互代的方法,以刺槐林为代表,对该区不同利用年限的人工林土壤养分特征及其时空变化等进行了系统研究。结果表明,黄土丘陵区人工林土壤肥力处于低水平;人工林表层土壤养分中有机质和速效磷的空间变异性较大;坡度、坡向、坡位等环境因子对土壤养分有一定的影响。随利用年限的增加,人工林土壤全氮,有机质、碱解氮、速效钾含量及土壤养分指数均增加,与利用年限有极显著的相关性,其变化趋势符合y=axb模型。全氮,有机质和碱解氮随利用年限的增加量不显著,而速效钾每经过10年就有显著增加,全磷和速效磷含量则保持相对衡定的水平。黄土丘陵区人工林地土壤有机质、全氮、碱解氮、速效钾及养分指数年增长率分别约为0.20g.kg、0.01g.kg、0.69mg.kg、2.27mg.kg和0.04。该区人工林地土壤有机质、全氮、碱解氮及养分指数约需50年、速效钾约需30年可达到中上等养分水平。     

Temporal change in land use and its relationship to slope degree and soil type in a small catchment on the Loess Plateau of China

We sought to detect the temporal change (1958–1999) in land use patterns and its relationship to physical landscape parameters in a small catchment in the semi-arid hilly area of the Chinese Loess Plateau. Degree of slope and soil type were selected as stable discriminating parameters that might constrain land use. With the help of GIS and canonical correspondence analysis, the relationship between rural land use distribution or transformation and the selected physical parameters was examined. The land use had undergone a general shift from farmland to woodland or grassland. Canonical correspondence analyses (CCA) indicated that a relationship between land use and the selected physical parameters was evident, farmland coincided with favorable conditions of fertile soil and gentle slope, while grassland and woodland were associated with conditions of poorer soil and steep slope. In the more favorable conditions the main land use change process was the intensification of farming, while in the less favourable conditions it was the abandonment of farmland. A thorough understanding of the relationship between land use temporal or spatial patterns and landscape physical parameters in the Loess Plateau of China, like degree of slope and soil type, will enhance our capability to predict landscape dynamics and lead to more sound and effective land use management strategies.     

The effect of environmental variables on soil characteristics at different scales in the transition zone of the Loess Plateau in China

As a result of human disturbance and topographic variability, land use mosaics are characteristic of the transition zone of the Loess Plateau in Shaanxi Province, China. Soils are particularly sensitive to change when land degradation processes are dominant. An understanding of the influences of environmental variables is required to inform land management and agricultural production. In this study the relationships between land type, topography and soil properties were analysed for Hengshan County at two different scales using detrended canonical correspondence analysis. The results show that variations in soil properties are strongly influenced by topography, land use and vegetation. Slope, elevation and aspect are also of importance at the county and small catchment scales of analysis. Though land use type proved to be of lesser importance than topographic factors, ANOVA analysis showed that there were significant differences in soil organic matter (SOM), total nitrogen (TN), total phosphorus (TP), available nitrogen, available potassium and clay %. Areas under vegetables had significantly higher SOM and TN content at the catchment scale. The results will enhance our ability to predict spatial and temporal changes in soils. In addition, it is shown that soil fertility could be improved by land reform and management in the hilly‐gully area.