塔里木河中游洪水漫溢区荒漠河岸林实生苗更新

以塔里木河中游荒漠河岸林为研究对象,2008年6月至2009年8月,对洪水漫溢区河漫滩裸地、林下及林隙三种生境植物一年生实生苗进行了调查。结果表明：实生苗更新主要依赖洪水漫溢,在非漫溢区没有发现实生苗存在;洪水降低了漫溢区的土壤盐度,更重要的是其提供了宝贵的水分条件,在时间和水量上都有效地满足了胡杨等植物种子萌发和幼株生长的水分需求;河漫滩是河岸林种子实生苗产生的基地,洪水漫溢后的河漫滩种子实生苗密度显著大于其余两生境内实生苗密度,同时该生境内物种多样性也显著高于林下和林隙生境;光照决定着漫溢区实生苗能否成林,光照不同的空间样点上,实生苗发生数量和个体生长均存在显著差异,光照强的河漫滩,实生苗发生数量较多且幼苗能保持较高的生长活力和较多的生物量积累。     

The effects of riparian restoration following saltcedar (Tamarix spp.) biocontrol on habitat and herpetofauna along a desert stream

Amphibians and reptiles (herpetofauna) have been linked to specific microhabitat characteristics, microclimates, and water resources in riparian forests. Our objective was to relate variation in herpetofauna abundance to changes in habitat caused by a beetle used for Tamarix biocontrol (Diorhabda carinulata; Coleoptera: Chrysomelidae) and riparian restoration. During 2013 and 2014, we measured vegetation and monitored herpetofauna via trapping and visual encounter surveys (VES) at locations affected by biocontrol along the Virgin River in the Mojave Desert of the southwestern United States. Twenty‐one sites were divided into four riparian stand types based on density and percent cover of dominant trees (Tamarix, Prosopis, Populus, and Salix) and presence or absence of restoration. Restoration activities consisted of mechanically removing non‐native trees, transplanting native trees, and restoring hydrologic flows. Restored sites had three times more total lizard and eight times more yellow‐backed spiny lizard (Sceloporus uniformis) captures than other stand types. Woodhouse's toad (Anaxyrus woodhousii) captures were greatest in unrestored and restored Tam‐Pop/Sal sites. Results from VES indicated that herpetofauna abundance was greatest in the restored Tam‐Pop/Sal site compared with the adjacent unrestored Tam‐Pop/Sal site. Tam sites were characterized by having high Tamarix cover, percent canopy cover, and shade. Restored Tam‐Pop/Sal sites were most similar in habitat to Tam‐Pop/Sal sites. Two species of herpetofauna (spiny lizard and toad) were found to prefer habitat components characteristic of restored Tam‐Pop/Sal sites. Restored sites likely supported higher abundances of these species because restoration activities reduced canopy cover, increased native tree density, and restored surface water.     

神农架地区珍稀植物沿河岸带的分布格局及其保护意义

在神农架香溪河流域从源头到河口的不同海拔高度沿河岸带共设置 4 0个与河流方向平行的10 0m× 10m的样带 ,进行了植物群落学调查研究 .结果表明 ,沿河岸带分布有珍稀植物 14种 ,占神农架地区珍稀植物总数的 4 2 .4 % .这些珍稀物种主要分布在海拔 12 0 0～ 180 0m山地常绿阔叶落叶阔叶混交林带 ,珍稀植物种类的物种丰富度在中等海拔高度上最大 .珍稀植物的种类可划分为低海拔、中等海拔和高海拔 3组 .针对珍稀植物的分布特点 ,明确指出应重视河岸带在生物多样性、尤其是珍稀物种保护方面的重要作用 .     

Nutrient and water addition effects on day- and night-time conductance and transpiration in a C3 desert annual

Recent research has shown that many C₃ plant species have significant stomatal opening and transpire water at night even in desert habitats. Day-time stomatal regulation is expected to maximize carbon gain and prevent runaway cavitation, but little is known about the effect of soil resource availability on night-time stomatal conductance (g) and transpiration (E). Water (low and high) and nutrients (low and high) were applied factorially during the growing season to naturally occurring seedlings of the annual Helianthus anomalus. Plant height and biomass were greatest in the treatment where both water and nutrients were added, confirming resource limitations in this habitat. Plants from all treatments showed significant night-time g (~0.07 mol m⁻² s⁻¹) and E (~1.5 mol m⁻² s⁻¹). In July, water and nutrient additions had few effects on day- or night-time gas exchange. In August, however, plants in the nutrient addition treatments had lower day-time photosynthesis, g and E, paralleled by lower night-time g and E. Lower predawn water potentials and higher integrated photosynthetic water-use efficiency suggests that the nutrient addition indirectly induced a mild water stress. Thus, soil resources can affect night-time g and E in a manner parallel to day-time, although additional factors may also be involved.     

山东省部分水岸带土壤重金属含量及污染评价

为了解山东省水岸带土壤重金属的含量特征和污染状况,于2010年9月—10月采集了39个水岸带土壤样品,分析了土壤中Cr、Co、Ni、Cu、Zn、Cd、Pb和Hg的含量以及土壤的pH值、粒度和有机质,采用单因子指数法、综合指数法和潜在生态危害指数法对水岸带土壤重金属污染进行了评价,并利用相关分析和聚类分析对其来源进行了初步的解析。结果表明：水岸带土壤的pH值为5.67—8.66,主要呈碱性;有机质的平均含量为9.39 g/kg,土壤粒度主要以砂粒和粉粒为主,其平均体积百分比分别为50.33%和38.48%,平均粒径为89.69 μm;Cr、Co、Ni、Cu、Zn、Cd、Pb和Hg的平均含量为53.03 mg/kg、10.33 mg/kg、24.96 mg/kg、18.38 mg/kg、56.13 mg/kg、0.142 mg/kg、22.48 mg/kg和0.020 mg/kg。各水岸带土壤重金属的含量均符合《土壤环境质量标准》（GB15618-1995）二级标准。以山东省土壤元素背景值为评价标准,水岸带土壤重金属总体表现为轻度污染和轻微生态风险,其中Cd和Hg是主要的污染因子,其对潜在生态危害指数的平均贡献率分别为46.8% 和33.6%。洙赵新河、廖河、门楼水库和东平湖水岸带土壤重金属污染及潜在生态危害明显高于其他水源地。源解析的结果表明：水岸带土壤重金属的含量受自然源和人为源的双重影响,人为源主要包括地表径流、工业废气、垃圾和交通运输等。     

Nutrient cycling and productivity in a desert saline lake: observations from a dry,low-productivity year

Seasonal variability of nutrients and productivity were examined in Pyramid Lake, a hyposaline, N-deficient, terminal desert lake, during a dry period. River inflow and N-fixation during 1990 were minimal allowing internal nutrient cycling to be more closely studied. Nutrient cycling was strongly affected by seasonal thermal stratification that was typical for a warm monomictic lake. Concentrations of nitrate, phosphate, and silicate in surface waters were highest during winter mixing and decreased rapidly in the spring due to a diatom bloom. Maximum average chlorophyll concentration in surface waters was 2.7 ± 1.2 µg 1^–1 and occurred in April while surface nutrients were being depleted. In contrast to chlorophyll, maximum particulate carbon in surface waters occurred in July–August when areal productivity was highest (367–398 mg C m^–2 day^–1). Concurrent with spring nutrient depletion in surface waters was increasing N-deficiency in the plankton. After the spring bloom dissipated in May, particulate matter (POM) became increasingly N-deficient reaching maximum elemental C : N of > 18 during summer-fall. Profiles of the C : N ratio of POM were nearly constant with depth for individual sampling dates suggesting that the residence time of POM in the water column was short (< 1 month). While surface waters were nutrient depleted during summer stratification, nutrient concentrations of bottom waters progressively increased, presumably through the oxidation of POM sinking to the bottom (103 m). Converting the rate of oxygen depletion in bottom waters to carbon equivalents of POM suggests that 42 % of mean annual phytoplankton production in overlying waters during 1990 was mineralized in bottom waters.     

水淹干扰对水库水滨带植物群落稳定性与种间关系的影响

受城市化与人类活动等因素影响而退化的水滨带植被的恢复与重建是近年来生态环境的热点问题。植物群落的种间关系直接影响植被的演替与恢复。以南水北调中线一期工程通水前的丹江口水库原有水滨带植被为研究对象,对年均多于9个月（海拔142 m以下）、6-9个月（海拔142-147 m）、3-6个月（海拔147-151 m）和少于3个月（海拔151-157 m）的4种不同强度水淹干扰的水滨带植物群落的稳定性和种间关系进行分析,探讨不同水淹干扰强度对水库水滨带植物群落稳定性及种间关系的影响。采用M.Godron稳定性测定法对植物群落稳定性进行分析,通过方差比率（VR）、χ²检验、联结系数（AC）以及Spearman秩相关检验对不同水淹干扰强度下的植物群落优势种进行种间关联分析。结果表明：（1）水库水滨带植物群落稳定性从高到低依次为水淹时长3-6个月、水淹时长6-9个月、水淹时长少于3个月和水淹时长多于9个月。中度水淹干扰下的植物群落稳定性要好于重度和轻度水淹干扰的植物群落;（2）不同水淹干扰强度下水滨带植物群落总体性关联表现为显著正相关。随着水淹时间增加,群落中正联结种对占总对数的比例呈下降趋势,负联结种对比例呈增加趋势,正负联结比值降低,群落内种间联结强度逐渐降低,说明水淹干扰强度增加会导致水滨带植物群落种群间相互依存关系减弱或竞争关系加剧。在此基础上,探讨不同水淹干扰强度下物种的空间分布和生态习性,并提出针对不同水淹干扰强度的水滨带植被恢复的物种选择建议。     

黄河中下游过渡区河岸植物多样性与土壤因子的关系

【目的】河岸带物种多样性与土壤因子的关系对维持河岸带生态系统的稳定性十分重要,为揭示黄河中下游河岸带物种多样性与土壤因子的关系,进一步为黄河中下游过渡区河岸生态恢复、保护和高质量发展提供一定的参考与理论指导。【方法】采用样方调查法、试验分析法、CCA排序法等方法,以河南黄河中下游过渡区对植物分布和物种多样性与土壤因子的关系进行研究。【结果】结果表明：（1）黄河中下游过渡区河岸土壤含水量、有机质、速效钾及有效磷均属于中等变异程度,全氮变异系数为强变异性,土壤养分空间分布总体呈现中度不均匀的特征。（2）黄河中下游过渡区河岸植物优势度指数（D）与土壤全氮具有显著负相关关系（P＜0.05）;土壤pH值、速效钾和有效磷对物种丰富度指数（S）的影响不明显;均匀度指数（E）、香农-威纳指数（H）与6个土壤因子之间均没有达到显著水平。（3）红蓼、头状穗莎草、长芒稗、糠稷、醴肠群落的分布受土壤含水量的影响较大;青蒿、酸枣、毛白杨等的分布主要受全氮的影响较大,在全氮含量较高的区域分布较多;葎草和反枝苋受速效钾影响较大;而狗牙根、苍耳、芦苇、狗尾草、春蓼、绿豆等群落受土壤因子的影响较小。     

Effects of low water supplementation and nutrient addition on the aboveground biomass production of annual plants in a Chilean coastal desert site

Summary The effects of low water supplementation and nutrients on the aboveground biomass production of annual plants was tested in the field by mimicking small rainfall events of 5mm per month and by adding fertilizers to experimental quadrats. Field measurements were made during an extremely dry year, so the potential additional effects of rainfall probably had no important effect on plant responses. Biomass of non-native species was higher in irrigated than in non-irrigated quadrats. No significant responses to irrigation treatments were detected in native species. This lack of response may be due to higher thresholds of watering being required for either germination and/or growth. Because of the low water inputs, fertilizer additions did not promote any biomass response in either native or non-native species. Responses of non-native species to low and frequent pulses of water, which is characteristic of this arid system, may be important for the persistence of these species in this environment.This is a contribution of the Program of Arid zone Studies of Universidad de La Serena     

塔里木荒漠河岸林灰胡杨群落最小面积确定与研究方法比较

荒漠河岸林是塔里木极端干旱区唯一的森林群落类型,群落结构组成简单。我们采用种-面积曲线、群落系数-面积曲线与重要值-面积曲线3种方法对塔里木河上游荒漠河岸林灰胡杨（Populus pruinosa Schrenk）群落最小面积进行研究。结果显示,4种饱和种-面积曲线的拟合效果差异明显,S=aA/（1+bA）和S=a（1-e^-bA）模型拟合的相关系数较高（P < 0.01）,拟合效果优于其它2种模型。当取样面积为100 m²时,可包括群落60%~80%的物种数,取样面积为200 m²时,则可包括群落90%的物种数。群落系数-面积曲线与重要值-面积曲线2种方法确定的群落最小面积均为400 m²,二者克服了种-面积曲线仅关注物种出现与否和饱和种的估算问题,拟合结果更符合实际情况,更适用于塔里木荒漠河岸林最小取样面积的确定。本研究结果表明荒漠河岸林包括60%、80%、90%群落物种的临界抽样面积分别为100 m²、200 m²和400 m ²,可以满足不同研究精度的要求;塔里木河上游荒漠河岸林灰胡杨群落学调查的最适取样面积是400 m²。     

Nitrate depletion in the riparian zone and stream channel of a small headwater catchment

A mass balance procedure was used to determine rates of nitrate depletion in the riparian zone and stream channel of a small New Zealand headwater stream. In all 12 surveys the majority of nitrate loss (56–100%) occurred in riparian organic soils, despite these soils occupying only 12% of the stream's border. This disproportionate role of the organic soils in depleting nitrate was due to two factors. Firstly, they were located at the base of hollows and consequently a disproportionately high percentage (37–81%) of the groundwater flowed through them in its passage to the stream. Secondly, they were anoxic and high in both denitrifying enzyme concentration and available carbon. Direct estimates ofin situ denitrification rate for organic soils near the upslope edge (338 mg N m^–2 h^–1) were much higher than average values estimated for the organic soils as a whole (0.3–2.1 mg N m^–2 h^–1) and suggested that areas of these soils were limited in their denitrification activity by the supply of nitrate. The capacity of these soils to regulate nitrate flux was therefore under-utilized. The majority of stream channel nitrate depletion was apparently due to plant uptake, with estimates of thein situ denitrification rate of stream sediments being less than 15% of the stream channel nitrate depletion rate estimated by mass balance.This study has shown that catchment hydrology can interact in a variety of ways with the biological processes responsible for nitrate depletion in riparian and stream ecosystems thereby having a strong influence on nitrate flux. This reinforces the view that those seeking to understand the functioning of these ecosystems need to consider hydrological phenomena.     

Nitrogen and phosphorus economy of the riparian shrub <Emphasis Type="Italic">Salix gracilistyla</Emphasis> in western Japan

Salix gracilistyla is one of the dominant plants in the riparian vegetation of the upper-middle reaches of rivers in western Japan. This species colonizes mainly sandy habitats, where soil nutrient levels are low, but shows high potential for production. We hypothesized that S.␣gracilistyla uses nutrients conservatively within stands, showing a high resorption efficiency during leaf senescence. To test this hypothesis, we examined seasonal changes in nitrogen (N) and phosphorus (P) concentrations in aboveground organs of S. gracilistyla stands on a fluvial bar in the Ohtagawa River, western Japan. The concentrations in leaves decreased from April to May as leaves expanded. Thereafter, the concentrations showed little fluctuation until September. They declined considerably in autumn, possibly owing to nutrient resorption. We converted the nutrient concentrations in each organ to nutrient amounts per stand area on the basis of the biomass of each organ. The resorption efficiency of N and P in leaves during senescence were estimated to be 44 and 46%, respectively. Annual net increments of N and P in aboveground organs, calculated by adding the amounts in inflorescences and leaf litter to the annual increments in perennial organs, were estimated to be 9.9 g and 0.83 g m⁻² year⁻¹, respectively. The amounts released in leaf litter were 6.7 g N and 0.44 g P m⁻². These values are comparable to or larger than those of other deciduous trees. We conclude that S. gracilistyla stands acquire large amounts of nutrients and release a large proportion in leaf litter.     

Denitrification and patterns of electron donors and acceptors in eight riparian zones with contrasting hydrogeology

A better understanding of nitrate removal mechanisms is important for managing the water quality function of stream riparian zones. We examined the linkages between hydrologic flow paths, patterns of electron donors and acceptors and the importance of denitrification as a nitrate removal mechanism in eight riparian zones on glacial till and outwash landscapes in southern Ontario, Canada. Nitrate-N concentrations in shallow groundwater from adjacent cropland declined from levels that were often 10–30 mg L^–1 near the field-riparian edge to < 1 mg L^–1 in the riparian zones throughout the year. Chloride data suggest that dilution cannot account for most of this nitrate decline. Despite contrasting hydrogeologic settings, these riparian zones displayed a well-organized pattern of electron donors and acceptors that resulted from the transport of oxic nitrate-rich groundwater to portions of the riparian zones where low DO concentrations and an increase in DOC concentrations were encountered. The natural abundances of d15N and in situ acetylene injection to piezometers indicate that denitrification is the primary mechanism of nitrate removal in all of the riparian zones. Our data indicate that effective nitrate removal by denitrification occurs in riparian zones with hydric soils as well as in non-hydric riparian zones and that a shallow water table is not always necessary for efficient nitrate removal by denitrification. The location of hot spots of denitrification within riparian areas can be explained by the influence of key landscape variables such as slope, sediment texture and depth of confining layers on hydrologic pathways that link supplies of electron donors and acceptors.     

Changes in avian species composition following surface mining and reclamation along a riparian forest corridor in southern Indiana

Data on the response of bird communities to surface mining and habitat modification are limited, with virtually no data examining the effects of mining on bird communities in and along riparian forest corridors. Bird community composition was examined using line transects from 1994 to 2000 at eight sites within and along a riparian forest corridor in southwestern Indiana that was impacted by an adjacent surface mining operation. Three habitats were sampled: closed canopy, riparian forest with no open water; fragmented canopy, riparian forest with flood plain oxbows; and reclaimed mined land with constructed ponds. Despite shifts in species composition, overall bird species richness, measured as the mean number of bird species recorded/transect route, did not differ among habitats and remained unchanged across years. More species were recorded solely on mined land than in either closed forest or forested oxbow habitats. Mined land provided stopover habitat for shorebirds and waterfowl not recorded in other habitats, and supported an assemblage of grassland-associated bird species weakly represented in the area prior to mining. A variety of wood warblers and other migrants were recorded in the forest corridor throughout the survey period, suggesting that, although surface mining reduced the width of the forest corridor, the corridor was still important habitat for movement of forest-dependent birds and non-resident bird species in migration. We suggest that surface mining and reclamation practices can be implemented near riparian forest and still provide for a diverse assemblage of bird species. These data indicate that even narrow (0.4 km wide) riparian corridors are potentially valuable in a landscape context as stopover habitats and routes of dispersal and movement of forest-dependent and migratory bird species.     

Visual cue learning and odometry in guiding the search behavior of desert ants, Melophorus bagoti, in artificial channels

Terrestrial panoramic cues, path integration and search behavior are the main navigational strategies used by ants to locate food and find their way back to the nest. Searching becomes important when the other navigational cues are either not available or cannot provide sufficient information to pinpoint the goal. When searching in one-dimensional channels Melophorus bagoti ants exhibit a systematic drift in the starting-point-to-goal direction as they turn back and forth, sometimes past the goal location ( Narendra et al., 2008). Here we show that this drift in channels is not a stereotypical part of the search behavior in these ants. It rather depends on the conditions of training. In experiments in which the nest entrance is located not at the end but at the side of the channel, forward drift is not always part of the nest search. Experiments on food searches showed that with the food source at the end of the channel, ants performed a linear drift in the starting-point-to-food direction. With food at the side of the channel, they showed a less pronounced drift toward the food source. In this constrained environment, especially with the goal at the end of the channel, ants seem to learn a routine such as ‘run along the channel’, and mix this routine with their usual strategy of turning back and forth in search.     

咸水滴灌下塔克拉玛干沙漠腹地人工绿地土壤水分三维时空动态

通过对咸水滴灌下塔克拉玛干沙漠腹地人工绿地的土壤水分进行实时监测,研究了4—7月各灌水周期内土壤水平0～60 cm和垂直0～120 cm空间距离范围内的水分三维时空变化.结果表明: 咸水滴灌下绿地土壤水分表现出周期性的动态规律,且在忽略降雨时,这种规律随时间变化未表现出明显差异;非降雨与降雨条件下的土壤水分时空变化差异显著.土壤含水量在4月偏高,7月偏低,在有明显降雨的6月最高;土壤水分在不同时间尺度上的变化特征不同,但整体随月变化(4—7月)呈下降趋势,随日变化(1~15 d)呈幂函数递减规律,且在周期内先后经历3个不同变化阶段.土壤水分在水平空间距离上呈一元线性递减,在垂直空间上近似表现为双峰曲线,且在20 cm土层处有一个显著峰值;土壤水分空间分布特征取决于土壤自身的物理性质.     

Short-term patterns in water and nitrogen acquisition by two desert shrubs following a simulated summer rain

A field experiment was conducted at the Jornada Long-Term Ecological Research (LTER) site in the Chihuahuan Desert of New Mexico to compare the rapidity with which the shrubs Larrea tridentata and Prosopis glandulosa utilized water, CO² and nitrogen (N) following a simulated summer rainfall event. Selected plants growing in a roughly 50-m² area were assigned to treatment and control groups. Treatment plants received the equivalent of 3 cm of rain, while no supplemental water was added to the control plants. Xylem water potential (_x) and net assimilation rate (A_net) were evaluated one day before and one and three days after watering. To monitor short-term N uptake, soils around each plant were labeled with eight equally distant patches of enriched ¹⁵N before watering. Each tracer patch contained 20 ml of 20 mM ¹⁵ NH₄ ¹⁵NO³ (99 atom%) solution applied to the soil at 20 cm from the center of the plant at soil depths of 10 and 20 cm. Nitrogen uptake, measured as leaf ¹⁵N, was evaluated at smaller time intervals and for a longer period than those used for _x and A^net. Both A^net and ^x exhibited a significant recovery in watered vs. control Larrea plants within 3 days after the imposition of treatment, but no such recovery was observed in Prosopis in that period. Larrea also exhibited a greater capacity for N uptake following the rain. Leaf ¹⁵N was five-fold greater in watered compared to unwatered Larrea plants within 2 days after watering, while foliar ¹⁵N was not significantly different between the watered and unwatered Prosopis plants during the same period. Lack of a significant change in root ¹⁵ NO^{– 3} uptake kinetics of Larrea, even three days after watering, indicated that the response of Larrea to a wetting pulse may have been due to a greater capacity to produce new roots. The differential ability of these potential competitors in rapidly acquiring pulses of improved soil resources following individual summer rainfall events may have significant implications for the dynamic nature of resource use in desert ecosystems.