荒漠植被红砂（Reaumurta soongorica）水热响应的年轮学研究

 红砂是黄土高原荒漠植被带主要建群植物种之一，在植被恢复重建和生态建设中具有重要意义。本文以皋兰县40 a天然植被封育区为例，运用树木年轮学方法，对不同坡向红砂与当地水热条件变化的时空响应及分布格局进行了研究。研究结果表明，红砂具有明显的年轮特征，可以进行树木年轮方面的研究。虽然不同坡向水分条件和植被状况有很大差异，但红砂径向生长对区域水热变化具有非常一致的响应模式：同生长季降水呈正相关关系，尤以7月降水量最为显著；同生长季气温呈负相关关系，以6月最为显著。根据不同坡向红砂年龄分布格局分析结果，并考虑到水土流失的防治效果，黄土高原西部荒漠植被带的封育期限不宜少于10 a。     

黄土高原西部植物耗水实验研究

针对兰州地区8种常见植物的盆栽试验,比较了其耗水量的变化特征,结果表明：在充分供水条件下,8种植物在试验期间内都能正常生长,植物耗水量从大到小排序为：柽柳＞柠条＞芨芨草＞侧柏＞甘蒙锦鸡儿＞紫穗槐＞红砂＞珍珠;在集雨条件下,植物耗水排序为：芨芨草＞珍珠＞柠条、侧柏、甘蒙锦鸡儿、＞红砂、紫穗槐＞柽柳,但柽柳和紫穗槐在集雨条件下生长出现干枝,生长不好。在雨养条件下,除红砂、甘蒙锦鸡儿、珍珠受到干旱胁迫不明显外,其余植物不同程度上有枯叶出现。紫穗槐死亡,柽柳接近死亡,其他植物耗水排序为：珍珠、芨芨草＞侧柏、甘蒙锦鸡儿、柠条＞红砂。     

黄土丘陵沟壑区乔灌草植物空间优化配置——以甘肃省定西地区为例

黄土丘陵沟壑区水土流失的影响因素有气候、植被、土壤、地形等,而乔灌草植物在空间上的不合理配置是造成该区水土流失严重的主要原因之一。本文选择研究区内限制植物生长与分布的4个关键环境因子 (高程、坡度、坡向和降雨量),利用多属性决策分析(MCDA)的方法,探讨乔灌草植物在空间上的优化配置,将整个研究区划分为5类乔灌草植物空间优化配置主模式和18类乔灌草植物空间优化配置子模式;同时,应用GIS聚类分析与统计分析方法,对所划分的乔灌草植物空间优化配置模式进行空间布局分析。结果显示:农民赖以生存的经济林/农林复合配置模式和农田/庭院经济配置模式是研究区的主要配置模式,占配置模式总面积的76.02％。     

皋兰老虎台红砂种群在不同坡向的空间格局及关联性

种群的空间格局是研究植物种群相互作用及种群与环境关系的重要方法。红砂（Reaumuria soongarica）是黄土高原半干旱区的主要物种,通过野外的群落调查,运用空间点格局分析法中的Ripley K函数,分析甘肃皋兰老虎台荒漠植被不同坡向红砂种群的空间分布格局与种内关联。结果显示：红砂种群为增长型种群,其在不同坡向的分布具有显著差异;南坡及西南坡坡向上,红砂种群Ⅰ、Ⅱ级个体在小尺度上呈显著聚集分布,随着龄级及空间尺度的增加,红砂种群聚集强度逐渐减弱,最后趋于随机分布。西坡、西北坡坡向上生长大量的蓍状亚菊（Ajania achilloides）和短花针茅（Stipa breviflora）等对红砂的生长造成抑制并加剧种间竞争,各级红砂种群的分布格局均以随机分布为主。不同坡向上,红砂种群Ⅰ、Ⅱ龄级个体之间在小尺度内表现为负关联,随着尺度增加关联度降低,Ⅲ、Ⅳ龄级与Ⅰ、Ⅱ龄级个体之间呈显著的负关联,而Ⅲ、Ⅳ龄级之间没有明显关联性,表明龄级相近的个体在空间分布上是相互独立的。综上所述,在黄土高原半干旱区,影响红砂种群分布的主要因素除了其自身的生物、生态学特性外,微生境的影响也十分重要。     

红砂根系构型对干旱的生态适应

 对西北干旱、半干旱区不同生境条件下红砂（Reaumuria soongorica）根系构型参数进行了分析,以探讨红砂根系构型对干旱的生态适应性。结果表明:①不同生境条件下红砂根系的拓扑指数均较小,根系分支模式接近叉状分支模式,但在干旱的河西走廊风沙区和戈壁区红砂根系拓扑指数均逐渐增加,表明干旱有使红砂根系分支向鱼尾分支模式发展。②干旱的河西走廊风沙区和戈壁区红砂根系分形维数均较小,分别为1.1778、1.1169,分形特征不是很明显;而半干旱的黄土丘陵沟壑区分形维数较大,根系具有很好的分形特征。③干旱的河西走廊红砂根系总分支率均比半干旱的黄土丘陵沟壑区要小,表明在半干旱的黄土丘陵沟壑区红砂根系分支能力相对较强,随着干旱的增加其分支能力有所减弱。④不同生境条件下红砂根系的连接长度都较大,但不同生境却表现出明显差异,其中干旱风沙区根系平均连接长度最长。红砂为适应干旱的环境通过减少根系次级分支和根系的重叠、增加根系连接长度,使其根系的分支模式向鱼尾分支模式发展以降低根系内部对营养物质的竞争,提高根系对营养物质的吸收效率,保证植物有效的营养空间,从而在资源贫瘠的环境中吸收足够的水分和营养来保证其正常生理需求。     

新疆阜康绿洲荒漠过渡带植物群落物种多样性特征

分别采用重要值、盖度、多度计算多样性指数、均匀度指数、丰富度指数、优势度指数，对新疆阜康荒漠地区植物群落的物种多样性进行了研究。结果表明：1)各类型群落的物种多样性水平表现为红柳、红砂、梭梭这三个群落较高，肉叶雾冰藜群落、叉毛蓬群落、盐爪爪群落、囊果碱蓬群落和雾冰藜群落居中，无叶假木贼群落和碱蓬群落较低；2)研究区总体群落物种多样性水平较低，随着群落演替其物种多样性水平呈现低—高—较高的变化趋势；3)对荒漠植被，以重要值或盖度为指标计测多样性指数较为可行。     

Microcoring and dendrometer-detected intra-annual wood formation of Populus euphratica in the Ejina Oasis,northwestern China

Seasonal stem radial growth and wood formation of trees have become research hotspots because of their significance for dendroclimatological and dendroecological studies. However, until recently, these studies concentrated on coniferous tree species in high-altitude and high-latitude regions, while detailed information on arid-zone riparian forests is scarce. The main focus of this study is to monitor the intra-annual dynamics of radial growth and tree ring formation in a deciduous species, Populus euphratica. In 2013, we combined the dendrometer and microcoring methods to study this species in the riparian forest of the Ejina Oasis, in arid northwestern China. Vessel enlargement began in early May, and the maximum rate of cell production occurred in early June. The cell division then ceased from early to mid-July. The dendrometer method failed to reliably detect the date of growth initiation and cessation, but succeeded to detect the time of maximum growth rate just like the microcoring method did. We found that weekly stem radial increment data described xylem growth more accurately than daily datasets. Based on correlation analysis among climatic and hydrologic variables, and weekly stem radial increment, weekly ring width increase dataset, the depth to groundwater was the main factor that limited tree ring growth. From a practical perspective, such studies of intra-annual wood formation can provide empirical guidance for seasonal water allocations within a river basin.     

三种荒漠灌木根系的构形特征与叶性因子对干旱生境的适应性比较

以古尔班通古特沙漠南缘原始荒漠的三种建群灌木多枝柽柳、梭梭和琵琶柴为研究对象,采用挖掘法调查其根系构性特征及其与土壤水分的关系,同时测定其比叶面积(SLA),比叶重（LMA）,单位重量叶氮含量(Nmass)及单位面积叶氮含量(Narea)。结果表明,三种荒漠灌木的根系分属不同的功能型,多枝柽柳是深根潜水性植物,琵琶柴是浅根性植物,而梭梭介于两者之间。而且,三种荒漠灌木随着根系分布的由深到浅,即随着土壤水分亏缺的加剧,在叶性因子方面做了一定的适应性调整。这些事实表明,在水分为主要限制因子的干旱生境中,根系构型特征在很大程度上决定了灌木的叶性策略。同时研究表明,荒漠灌木在抗旱和生长之间存在相对平衡的关系。     

黄土丘陵区坡面柠条(Caragana korshinskii)林地草本植物分布特征

人工植被恢复会显著影响林下草本的分布及多样性,而人工植被恢复耦合坡面微地形变化对草本群落分布及其多样性响应尚缺乏系统的认识.以位于半干旱黄土丘陵区的甘肃定西龙滩小流域为研究区,系统调查和监测了不同坡向上、中和下坡位人工柠条(Caragana korshinskii)林地草本群落组成、生物量与柠条生长状况、凋落物量及土壤...     

内蒙古高原东南部森林-草原交错带的地形-气候-植被格局和植被恢复对策

探讨内蒙古高原东南缘森林-草原交错带地形-气候-植被格局,表明植被分布受气候和地形综合影响,在区域尺度上,随降水量减少阔叶林逐步由桦林向栎林、山杨林转变,针叶林更为接近森林旱极;在局地尺度上,阔叶林多分布在蒸发微弱、土壤容重较小的陡阴坡,草原分布在对应的阳坡上,非地带性榆树疏林分布在毛管作用微弱、蒸发小的沙地上。交错带植被建设应在降水量允许范围内优先考虑针叶树;其次要考虑坡向、坡位对土壤水分条件的影响,森林应尽量栽植在坡度10°~40°的阴坡;在区域和局地尺度上都应注意造林密度以及乔灌草结合,沙地不宜栽植密林。     

黄土高原气象干旱和农业干旱特征及其相互关系研究

选择标准化降水指数（SPI）和植被状态指数（VCI）分别作为评价黄土高原气象干旱和农业干旱的指标,使用干旱频率和Sen斜率分析了黄土高原地区干旱的分布特征与变化趋势,并探讨了气象干旱与农业干旱的相关性。结果表明：① 黄土高原西部干旱频率总体上高于东部。气象干旱和农业干旱变化趋势在空间上表现有所不同,黄土高原西部、北部气象干旱呈不显著减缓趋势,东部和南部呈不显著加重趋势,但绝大部分地区的农业干旱呈减缓趋势,尤其是400 mm等降水量一线两侧区域。② 季节上,黄土高原夏季和秋季气象干旱频率较高,春季和冬季气象干旱频率相对较低。黄土高原农业干旱频率春季最高,夏季其次,VCI对农业干旱实时监测的适用性更强。③ 不同季节,农业干旱滞后气象干旱的时间长短不同,冬季滞后约2个月,春季滞后约1个月,夏季和秋季滞后少于1个月。黄土高原一熟制种植区的SPI-12值与VCI值具有较好的正相关性。研究结果可以为黄土高原的干旱监测和预警、干旱区划以及干旱灾害风险评估提供科学依据。     

兰州市南北两山水热条件对侧柏根系分布的影响

根系是植物与外界环境进行物质和能量交换的主要场所之一,其分布特征反映了植物对环境的利用程度和适应性。试验采用土钻法研究了兰州地区的主要造林树种——侧柏的根系分布特性。结果表明：不同立地条件对侧柏根系分布特征有显著影响。阴坡根系分布比阳坡深,根系生长量比阳坡大,灌溉区根系分布比无灌溉区深;在无灌溉条件下向阳立地的根系集中分布在20～30 cm土层,向阴立地的根系集中分布在10～30 cm土层;在灌溉条件下向阳立地的根系集中分布在10～40 cm土层,向阴立地的根系集中分布在20～50 cm土层;向阳立地根系生长以Φ<1 mm为主,占所有根量的61.5％。向阴立地根系生长主要以Φ≥3 mm为主,占所有根量的68.5％。     

陕西黄土高原人工林土壤干层及形成原因

1 Introduction Abroad, a lot of research on soil water removal, seeping and evaporation has been done (Ole, 1998; Rapp, 2000). A seeping model of soil water was suggested (Yuin, 1998) and it was known that water removal is very slow in the unsaturated zon…     

Spatial and temporal variability of soil properties under Caragana microphylla shrubs in the northwestern Shanxi Loess Plateau, China

Shrub-induced spatial and temporal heterogeneity of soil properties is common in arid and semiarid ecosystems, and it facilitates the development of plant species diversity. We selected 5-, 10-, 20-, 30-, and 40-year-old Caragana microphylla shrubs in the Shanxi Loess Plateau to evaluate the spatial and temporal heterogeneity of soil properties under and outside the shrub canopy. In addition, the presence of adventitious plant species was investigated to assess the development of herbaceous species diversity. Soil samples were collected from two depths (0-5 cm and 5-10 cm). The establishment and development of shrubs promoted temporal variation, improved soil texture, enhanced soil organic matter (SOM), total nitrogen (TN), and cation exchange capacity (CEC), and decreased pH, bulk density (BD), and soil water content (SWC). The results further confirmed that SOM, TN, and CEC were significantly higher at the center than at the outside of the shrub canopies (P < 0.05) and were higher at the 0-5 cm depth than at the 5-10 cm depth. Moreover, the differences in SOM, TN, and CEC from the center to the outside of shrub canopies were greater under 30- and 40-year-old shrubs than under 10- and 5-year-old shrubs. Furthermore, the spatiotemporal heterogeneity of the soil properties facilitated the development of herbaceous species diversity.     

红砂育苗的土壤水分管理初步研究

分布于60~300 mm降水量区域的超旱生半灌木红砂,是该区域的建群种,也是人工辅助植被恢复的主要树种,探索其幼苗成活与土壤含水量之间的关系,对人工辅助恢复植被十分重要。以不同苗龄的红砂容器苗和直播实生幼苗为调查对象,研究了红砂幼苗成活数量与土壤含水量之间的相关性。结果表明：10 cm土层中的体积含水量在20~25 d内持续达20%~30%时,其成活率达到70%左右;25 d以后,含水量在10%时就能维持其生命,苗龄30~40 d后幼苗成活率趋于稳定。     

黄土丘陵区坡面尺度上不同植被格局下植物群落和土壤性质研究

通过对黄土丘陵沟壑区陕西延安羊圈沟小流域坡面上退耕还林还草后形成的林地(单一种植刺槐人工林)、草地(单一的撂荒草地)、草地-林地-草地(上坡位和下坡位撂荒草地,中坡位种植刺槐人工林)及林地-草地-林地(上坡位和下坡位种植刺槐人工林,中坡位为撂荒草地)四种不同的植被格局下植物物种多样性及土壤理化性质变化的研究,旨在揭示植被恢复过程中,坡面上植被不同的空间配置模式对植物物种的组成及土壤环境变化的影响.研究发现,4种植被格局下植物物种的多样性以单一的撂荒草地坡面最高,人工林的种植一定程度上影响了林下植物物种多样性的恢复,但整个灌木和草本的群落结构4种植被格局之间均未达到极不相似水平.土壤有机碳及总氮含量均以坡面上草地-林地-草地的空间配置格局最高且有机碳存在显著差异,而撂荒草地则在土壤水分的保持及改善土壤pH值上优于其他3种植被格局.     

Rock-magnetic proxies of climate change in the loess-palaeosol sequences of the western Loess Plateau of China

Results of the first detailed study of the climate proxy record in the loess-palaeosol sequence at Xining-one of the few palaeoclimate sites in the currently arid western Loess Plateau of China-illustrate the importance of making many types of rock-magnetic measurements other than susceptibility. A multiparameter approach yielded confirmation that here, as elsewhere in the Loess Plateau, the susceptibility enhancement in palaeosols was caused primarily by ultrafine magnetite and maghaemite. Nevertheless, magnetic enhancement was caused not exclusively by changes in relative grain size, but also by variations in concentration and mineralogy of the magnetic fraction.
The effects of concentration variations were removed through normalization of susceptibility and anhysteretic remanence with saturation magnetization and saturation remanence, respectively. the resulting signal was ascribed more confidently to variation in magnetic grain size, which in turn was interpreted as a better proxy of pedogenesis than simple susceptibility. Variations in magnetic mineralogy were also determined to constrain interpretations further. the data were then used to discuss climate history at Xining. Finally, results from Xining were compared with other western sites and contrasted with eastern sites.
In summary: (1) data is presented from a new Loess Plateau site which also appears to yield a global climate signal; (2) a demonstration is made of a more rock-magnetically robust way to separate concentration, composition and grain-size controls on susceptibility and other magnetic parameters; and (3) models are provided for inter-regional comparisons of palaeoclimate proxy records.     

Evapotranspiration of a Populuseuphratica Oliv. forest and its controlling factors in the lowerHeihe RiverBasin, Northwest China

Evapotranspiration (ET) within an ecosystem is crucial for the water-limited environment that currently lacks adequate quantification in the arid region of Northwest China, mainly covered by phreatophytes, such as the Populus euphratica Oliv. tree and the Tamarix ramosissima Ledeb. shrub species. Accordingly, ET was measured for an entire year using eddy covariance (EC) in P. euphratica stands in the lower Heihe River Basin, Northwest China. During the growing season, the total ET was 850 mm, with a mean of 4.0 mm/d, which is obviously more than that observed at tree-level and standlevel scales, which was likely due to the different level of soil evaporation induced by irrigation via water conveyance. Factors associated with ET fall into either environmental or plant eco-physiological categories. Environmental factors account for at least 79% variation of ET, and the linear relationship between ET and the groundwater table (GWT) revealed the potential water use of P. euphratica forests under the non-water stress condition with the GWT less than 3 m deep. Plant eco-physiological parameters, specifically the leaf area index (LAI), have direct impact on the seasonal pattern of ET, which provides a valuable reference to the wide-area estimates of ET for riparian forests by using LAI. In conclusion, P.euphratica forests have high water use after water conveyance, which may be the result of long-term adapting to local climates and limited water availability.     

黑河流域干旱生态系统红砂荒漠空间斑块结构及其生态适应策略（英文）

In many arid ecosystems,vegetation frequently occurs in high-cover patches interspersed in a matrix of low plant cover.However,theoretical explanations for shrub patch pattern dynamics along climate gradients remain unclear on a large scale.This context aimed to assess the variance of the Reaumuria soongorica patch structure along the precipitation gradient and the factors that affect patch structure formation in the middle and lower Heihe River Basin(HRB).Field investigations on vegetation patterns and heterogeneity in soil properties were conducted during 2014 and 2015.The results showed that patch height,size and plant-to-patch distance were smaller in high precipitation habitats than in low precipitation sites.Climate,soil and vegetation explained 82.5% of the variance in patch structure.Spatially,R.soongorica shifted from a clumped to a random pattern on the landscape towards the MAP gradient,and heterogeneity in the surface soil properties(the ratio of biological soil crust(BSC) to bare gravels(BG)) determined the R.soongorica population distribution pattern in the middle and lower HRB.A conceptual model,which integrated water availability and plant facilitation and competition effects,was revealed that R.soongorica changed from a flexible water use strategy in high precipitation regions to a consistent water use strategy in low precipitation areas.Our study provides a comprehensive quantification of the variance in shrub patch structure along a precipitation gradient and may improve our understanding of vegetation pattern dynamics in the Gobi Desert under future climate change.     

陕北黄土高原人工林下土壤干化原因与防治

黄土高原的退耕还林是一项史无前例的宏伟工程,成功实施该项工程对恢复该区严重恶化了的生态环境和减少黄河下游水患具重大现实意义。当前植树造林面临的需要解决的重要问题是土壤干化。土壤干化导致人工林生长不良,甚至干枯死亡,查明土壤干化原因对在植树造林工作中采取合理对策有重要作用。野外调查和资料分析显示,陕北黄土高原土壤干化原因有两个方面:一是自然原因;二是人为原因。自然原因包括该区本来降水量较少,近50 a来降水减少和气温升高3个方面。人为原因包括植被破坏,人工林密度过大,在不适于森林发育的地带进行了造林和没有遵循植被演替规律进行了造林4个方面。根据黄土高原已经发生了变化的自然条件,本文建议在陕西延安以南至关中盆地南缘的落叶阔叶林带应采取植被的自然恢复或人工草灌和稀疏的植树相结合的措施恢复森林植被,在延安至长城之间的森林草原带应以人工发展优良草灌为主,配合大间距的植树恢复森林草原植被,在长城以北以种草为主。为提高乔木成活率和确保人工林正常生长,继续采取建造鱼鳞坑等集雨工程措施是很必要的。