Germination in tamaulipan thornscrub of north-eastern Mexico

In semi-arid environments plants should be selected to germinate at times most suitable for seedling establishment. Germinability, rate of germination and temperature preference for germination (12 or 28°C constant) were analysed with respect to growth form (grass, forb, woody), longevity and seed size. Short-lived species showed preferential germination at either high or low temperature, whereas long-lived species tended to be indifferent to season. Germinability was >20% for 28 spp., 17 species were <10% and 21 species did not germinate under any circumstances. Growth form or life-span did not influence germination. Woody species germinated rapidly. Germinability and germination rate were positively associated.     

Comparison of soil bacterial communities associated with actinorhizal, non-actinorhizal plants and the interspaces in the sclerophyllous matorral from Central Chile in two different seasons

The spatial heterogeneity of resources in desert and semi-arid shrubland appears to be important in determining higher soil bacteria abundance around plants than in soil without plant cover. Thus, these bacterial communities could be important contributors to nutrient cycling in arid ecosystems. Bacterial diversity from Chilean sclerophyllous matorral was determined by Terminal Restriction Fragment Length Polymorphism (T-RFLP). Soil samples associated with the actinorhizal plant Colletia hystrix, non-actinorhizal plants and interspace soil without plant cover, were collected in May and October. The non-actinorhizal and interspace soil differed significantly in their potassium content in May and pH in October. The T-RFLP analysis revealed differences in the bacterial community structure from the different habitats. The soil bacterial communities associated with plants were the most similar, whereas the interspace soil community differed in both sampling times. The factors that best explained the groupings were potassium and pH. The greatest diversity was observed in the interspace soil. The Microbial Community Analysis showed a significant proportion of T-RFs identified as Firmicutes and Proteobacteria. Likewise, spatial and temporal differences were observed in the main groups' abundance. The dominance of Firmicutes suggests that the sclerophyllous matorral could be a different ecosystem to other arid and semi-arid soils with respect to the bacterial community structure.     

不同温度和沙埋深度对砂生槐种子萌发及幼苗生长的影响

在沙地环境中,沙埋是影响植物种子萌发和幼苗存活的一个重要因素。砂生槐是西藏特有的沙生植物,主要分布在雅鲁藏布江中游地区及拉萨河、年楚河等主要支流宽谷区。对砂生槐幼苗进行了控制沙埋试验,研究了不同温度和沙埋深度对砂生槐种子萌发特性的影响。结果表明,温度和沙埋深度显著影响砂生槐种子的萌发率和出苗率。在15～30 ℃的温度范围内,随着温度的升高,种子萌发率显著下降,15 ℃时,其种子萌发率达到最高值;砂生槐种子能在深度≤10 cm的沙埋中萌发,≤8 cm的沙埋中出苗,在此范围内,随着沙埋深度的增加,砂生槐种子的萌发率和出苗率逐渐降低。沙埋深度在植株高度的33％时,砂生槐幼苗能够存活,且总生物量大于未沙埋幼苗;当沙埋深度增至植株高度的66％时,砂生槐幼苗存活率降至43％,生长受到抑制;而当沙埋深度增至植株高度的100％和133％时,没有砂生槐幼苗存活。可见砂生槐植株在适应沙埋环境方面主要采用调整生物量分配模式的生态对策。     

沙埋对河西走廊4种旱生植物种子萌发和幼苗生长的影响

测定了驼蹄瓣(Zygophyllum fabago)、骆驼蒿(Peganum nigellastrum)、唐古特白刺(Nitraria tangutorum)和黒果枸杞(Lycium ruthenicum)等4种旱生植物种子重量、形状、萌发及活性,试验了沙埋深度(0、1、2、3、4、5 cm)对种子萌发、幼苗出土和生长的影响。结果表明:4种植物的种子扩散时为中度休眠;种子活性与重量、形状之间为显著负相关关系(p<0.05);种子初次萌发率与重量之间为不显著负相关关系;大而不规则种子有较低的活性,小种子扩散时有较高萌发率。随沙埋深度的增加,4种植物种子出苗率下降,首次出苗时间推迟,茎高、绝对株高和根长呈现先上升后下降的趋势,地下和地上生物量比值呈先上升后下降或随埋深增加而下降。幼苗出土和生长的最佳沙埋深度是:驼蹄瓣1~3 cm,骆驼蒿0~1 cm,唐古特白刺0~2 cm,黑果枸杞1~2 cm。在植被恢复过程中应考虑破除种子休眠的方法以及浅层沙埋等条件,以提高出苗率、增大幼苗定植率。     

水分和沙埋对4种沙生植物种子萌发和出苗的影响

通过室内试验研究了土壤水分和沙埋深度对4种沙生植物种子萌发和出苗的影响。结果表明:草本雾冰藜（Bassia dasyphylla）种子萌发和幼苗出土喜好水分,水分含量越高,种子发芽率越高;半灌木黑沙蒿（Artemisia ordosica）、灌木沙冬青（Ammopiptanthus mongolicus）和沙棘（Hippophae rhamnoides）种子在含水量为15%~20%的土壤中发芽率高,干旱或水分含量过高会导致种子发芽率降低。沙埋深度显著影响种子的萌发和出苗,雾冰藜种子在无沙埋时发芽率最高,黑沙蒿适宜沙埋深度为0.5 cm,沙冬青和沙棘适宜沙埋深度1.0 cm。     

喀斯特土壤厚度和水分变化对两种菊科草本种子及果实的物候、可塑性和子代种子萌发率的影响（英文）

缺水的浅层土壤是植物在脆弱喀斯特地区生长和繁殖的关键限制因素。一年生草本植物是适应喀斯特地区严苛生境的先驱,但其繁殖策略对短缺水资源和有限土壤资源的双重限制响应尚不明确。因此,在这项研究中,我们通过评估果序和种子的数量、生物量和后代种子的发芽率,研究了两种一年生的菊科草本苍耳（Xanthium sibiricum）和三叶鬼针草（Bidens pilosa）在恶劣的喀斯特土壤环境中,种子和果实物候的可塑性和后代种子萌发率。苍耳和三叶鬼针草在完整的双向随机区组设计中,设置了三种土壤深度和三种水分梯度下生长。主要研究结果如下：（1）随着土壤厚度或（和）水分的降低,苍耳的子代数量（种子和果实）和生物量显著减少（P<0.05）,三叶鬼针草在水分降低时增加果序和种子的生物量。（2）苍耳的亲本经历了资源减少后,种子数量和种子生物量没有相关性,而三叶鬼针草中种子数量和种子生物量之间存在显着的正相关（P<0.05）。（3）三种水分处理条件下,苍耳种子的萌发率没有随土壤厚度的减少而变化。对照条件下,随着土壤厚度的减小,三叶鬼针草的种子萌发率显著降低（P<0.05）。结果表明,苍耳倾向于通...     

Distribution and density of maguey plants in the arid Zacatecas Plateau, Mexico

The distribution and density of Agave salmiana ssp. crassispina within the state of Zacatecas, Mexico in the period from May 2001 to October 2002 is reported here for the first time. A field sampling was conducted based on a stratified random design. The resulting sample size was 154 plots, which were distributed randomly in three strata: high, medium, and low density. In each plot the following parameters were determined; latitude, longitude and number of agave plants that were classified into the following stages: juvenile; pre-reproductive; reproductive; and mature. The spatial data analysed using GIS showed that Agave salmiana ssp. crassispina is distributed over approximately 59,905 ha. Out of this total area, about 1142 ha were classified as high density, 51,529 ha as medium density, and 7234 ha as low density. The estimated density of agave plants in high-density strata was an average of 3125 individuals per hectare in comparison with 788 and 652 individuals per hectare for medium, and low density, respectively. It is recommended to protect the areas with higher density and to establish plantations in those with low density, but with the necessary conditions for the development and sustainability of this specie.     

准噶尔无叶豆土壤种子库特征及其对种子萌发的影响

 准噶尔无叶豆(Eremosparton songoricum (Litv.) Vass.)是中亚荒漠特有种,中国的单属种植物类群,稀有种,仅片段化分布在古尔班通古特沙漠风蚀坡地及流动-半流动沙丘上。按照不同微地形条件,于2008年9月、2009年的4月及6月分别对两个自然种群8种微地形条件(A种群为积沙灌丛下、积沙平缓处、风蚀灌丛下和风蚀平缓处4种; B种群为沙丘上部、中部、下部及底部4种)进行土壤种子库取样,并统计萌发季节的自然种群萌发率,同时对比室内萌发率,以研究土壤种子库的时空分布特征及其对种子萌发的影响。结果表明,从9月至次年4月和6月,种群种子库密度逐渐减少。自然状态下沙埋深度0—6 cm的种子能够萌发,主要萌发季节(4月)A种群有42%~73.56%的种子、B种群有63.33%~72.73%的种子分布在沙土6 cm以下的深度,为“无效种子”。A种群积沙灌丛下种子库密度值最大,但萌发季节的自然种群萌发率为0; B种群的沙丘下部种子库密度较大,但自然种群萌发率仅为4.8%±0.8%。不同微地形条件下沙粒打磨作用(去除种子硬实)和水分条件的差异,是微地形间种子萌发率差异的主要原因。本研究从土壤种子库角度解析自然种群有性更新困难的原因,为该稀有物种的保育提供理论依据。     

Spatial distribution of nitrate health risk associated with groundwater use as drinking water in Merida,Mexico

Water containing nitrate levels above 45 mg/l is not recommended for human consumption and its prolonged intake is associated with various health conditions. In Merida city, Mexico, the only source for water supply is a karstic aquifer, but the absence of sewerage and drainage networks makes it highly vulnerable to anthropogenic contamination. In this work, the concentration and spatial distribution of nitrate in the Merida's karstic aquifer were assessed by statistical and geostatistical techniques. The sources of nitrate contamination were tracked by making statistical correlations between nitrate concentrations and key ions; the potential risk to human health was also estimated by using the Hazard Index (HI). A total of 177 groundwater samples were collected from the four water supply systems serving Merida, during 2012 and 2013. Nitrate concentrations from collected samples varied between 15.51 and 70.61 mg/l, with maximum and minimum concentrations per sampling point ranging from 47.47 to 70.61 mg/l and from 15.51 to 17.32 mg/l, respectively. Significant positive correlations (P < 0.05) between nitrates and chlorides, sulphates and potassium were found, which may indicate potential contamination from domestic wastewater and agricultural activities. The spatial distribution of nitrate concentrations in the aquifer revealed an increase in nitrates following a trajectory South–North West, towards central and northwestern zones within Merida Metropolitan Area. From the health risk analysis, it was found that infants exposed at current nitrate levels are at a higher risk (HI_MAX = 1.40) than adults (HR < 1.0) and therefore, there is a clear need for implementing effective strategies to protect groundwater quality and to better manage and control nitrate pollution sources.     

Identifying and Preventing Biopiracy in Australia: patent landscapes and legal geographies for plants with Indigenous Australian uses

There are legal and moral imperatives to protect biological resources and the ‘traditional knowledge’ associated with them. These imperatives derive from complex legal geographies: international law (such as the Convention on Biological Diversity and the Nagoya Protocol), State and federal laws, Indigenous customary law, codes of ethics and research protocols. This paper reports on a ‘patent landscape’ analysis of patents that refer to Australian plant species for which there is Indigenous Australian knowledge. We have identified several patents of potential new biopiracy concern. The paper highlights the way in which actors can gain private property monopolies over biological resources and associated traditional knowledge, even though there are overlapping sovereign rights and Indigenous rights claims. Regulatory gaps need to be closed nationally to fully govern the diverse human–plant bio-geographies in Australia. Further, Indigenous laws and governance have largely been ignored by these actors. We suggest that the introduction of ‘disclosure of origin’ requirements in patent applications, sui generis Indigenous knowledge protections, the development of biocultural protocols, and a more nationally consistent system for ‘access and benefit-sharing’ are required to ensure more ‘fair and equitable’ use of plants and Indigenous knowledge in/from Australia, and to ensure the recognition of Indigenous rights to knowledge.     

Formation and failure of volcanic debris dams in the Chakachatna River valley associated with eruptions of the Spurr volcanic complex, Alaska

The formation of lahars and a debris avalanche during Holocene eruptions of the Spurr volcanic complex in south-central Alaska have led to the development of volcanic debris dams in the Chakachatna River valley. Debris dams composed of lahar and debris-avalanche deposits formed at least five times in the last 8000–10,000 years and most recently during eruptions of Crater Peak vent in 1953 and 1992. Water impounded by a large debris avalanche of early Holocene (?) age may have destabilized an upstream glacier-dammed lake causing a catastrophic flood on the Chakachatna River. A large alluvial fan just downstream of the debris-avalanche deposit is strewn with boulders and blocks and is probably the deposit generated by this flood. Application of a physically based dam-break model yields estimates of peak discharge (Q_p) attained during failure of the debris-avalanche dam in the range 10⁴<Q_p<10⁶ m³ s⁻¹ for plausible breach erosion rates of 10–100 m h⁻¹. Smaller, short-lived, lahar dams that formed during historical eruptions in 1953, and 1992, impounded smaller lakes in the upper Chakachatna River valley and peak flows attained during failure of these volcanic debris dams were in the range 10³<Q_p<10⁴ m³ s⁻¹ for plausible breach erosion rates.Volcanic debris dams have formed at other volcanoes in the Cook Inlet region, Aleutian arc, and Wrangell Mountains but apparently did not fail rapidly or result in large or catastrophic outflows. Steep valley topography and frequent eruptions at volcanoes in this region make for significant hazards associated with the formation and failure of volcanic debris dams.     

巴丹吉林沙漠高大沙山沉积物粒度特征及其与植被、地貌关系

沙丘形成演变是风-沉积物-其他地理因子相互反馈作用的一个动态系统过程,粒度可以揭示其中包含的部分环境信息并被广泛应用于风沙地貌研究。本文分析了巴丹吉林沙漠伊和吉格德湖高大沙山区沉积物粒度特征及其与植被、地貌形态的关系。结果表明:迎风坡中上部及中部剖面各层沉积物主粒径均一,分别为中沙、细沙;迎风坡中下部及底部剖面细沙、中沙及粗沙等不同主粒径层交替,粒配复杂,其成因与粗沙粒保护作用、风向季节变化及地质时期气候变迁等因素有关;背风坡表层沉积物以细沙为主,趋向底部粗沙、中沙及极细砂增多,说明不同粒径对风及重力作用的响应存在差异;粒度参数散点图可以区分不同部位样品,趋向迎风坡底部剖面,沙粒分选性变差,正偏、负偏及近对称沙层交替,说明风力分选作用在不同部位差异明显及存在其他外力作用;沙层粒配影响植被多样性,迎风坡中上部中沙含量高,背风坡表层中部偏上极细沙及大于2.65 Φ细沙含量突然增加,是植被影响粒配的反映;迎风坡沉积环境的差异,说明随地质时期气候变迁,沙山形成可能经历了两个重要阶段,一是早期风力和水动力交替影响、具有风成与非风成环境交替特征的基底形成时期,二是以风力作用为主的现代沙山形成时期。     

京藏高速青海东部地区汛期路面水膜厚度变化特征及预报模型构建

利用2018—2020年汛期（5—9月）京藏高速青海省公路沿线交通自动监测站逐小时气象观测资料,研究路面水膜厚度变化特征,构建水膜厚度与气象因子的预报模型。结果表明：（1） 京藏高速公路高庙桥站和汉庄村站逐小时路面水膜厚度主要分布均在0.0~0.2 mm之间,频率分别为66.0%和63.0%,大于0.5 mm以上的路面水膜厚度频率均较小（10.0%）,2站均属于强变异性地区。（2） 采用相对阈值法统计分析,发现2站路面水膜厚度在0.1 mm以内的比例分别为33.8%和36.3%,路面水膜厚度在0.1~0.6 mm之间的比例分别为59.2%和56.0%,路面水膜厚度大于0.7 mm以上即易发生水滑,引起车辆失稳、失控等危险的比例分别为7.0%和7.6%。（3） 路面水膜厚度日变化和月变化特征明显。高庙桥站和汉庄村站水膜厚度的月变化均呈弱双峰性,2站的月变化趋势不完全一致。高庙桥站的日变化峰值出现在02:00—06:00,低谷出现在14:00—16:00,汉庄村站日变化峰值出现在06:00,低谷出现在16:00。（4） 随着降水强度的增加,平均水膜厚度均遵循幂函数关系迅速增加;在降水强度0.00~1.75 mm·h^-1之间时,平均水膜厚度增加趋势明显,降水强度大于1.76 mm·h^-1平均水膜厚度变化有增有减。（5） 采用多元回归统计方法建立依据气象因子和不同降水强度下分别构建的水膜厚度模型具有较好的使用价值,可在实际业务工作中推广应用。（6） 不同降水强度下构建的水膜厚度模型计算值明显高于季天剑模型和罗京模型,本文模型与罗京模型变化趋势较为一致,水膜厚度随降雨强度增加增长趋势明显,季天剑模型水膜厚度计算值随降雨强度增加增长趋势缓慢。研究成果可应用于高原环境雨天车速管理和路面交通安全管理,能够为公路设计人员或运营管理人员提供辅助决策的依据。     

Inflow and lake controls on short-term mass accumulation and sedimentary particle size in a High Arctic lake: implications for interpreting varved lacustrine sedimentary records

Sedimentary processes were monitored in a varved lake in the Canadian High Arctic through three melt seasons and revealed that seasonal sediment deposition rates were highly dependent on short-lived inflow events driven by high suspended sediment concentrations that varied with runoff intensity. Our results illustrate that in accordance with the suspended sediment discharge into the lake, the rate of sediment accumulation changed over short distances down-lake, in a given year. This result indicates that there is a rate and accumulation dependence on short-lived, intense inflow conditions. In addition, there was strong evidence for substantial decoupling between deposition rate and mean grain size of sedimentary deposits. These results have important implications for paleoclimate interpretation of annually laminated sedimentary records from dynamic lake environments and suggest that grain size measures may not be representative proxies of inflow competence. Grain size indices based on a measure of the coarser fraction, rather than the bulk sediment, may be more appropriate to use as a link between contemporary runoff processes and sedimentary characteristics.     

Seasonal dynamics of N:P ratio stoichiometry and Ca fraction for four dominant plants in the Alxa Desert

Desert plants take on unique physiologically adaptive mechanisms in response to an adverse environment. In this study, we determined the concentrations of leaf nitrogen(N), phosphorus(P), and calcium(Ca) fraction for dominant species of Artemisia ordosica, A. frigida, Calligonum mongolicum, and Oxytropis aciphylla in the Alxa Desert and discussed seasonal changes of their leaf N:P ratio and Ca fraction. The results showed that, from May to September, the N:P ratios of A. ordosica and C. mongolicum gradually and significantly increased, while those of A. frigida, and O. aciphylla had an increase trend that was not significant; the physiologically active Ca of A. ordosica and A. frigida increased significantly,while that of C. mongolicum and O. aciphylla decreased significantly. The physiologically inert calcium of C. mongolicum increased extremely significantly, while that of others was not significant. There was a significantly positive correlation between the N:P ratio and physiologically active Ca for A. ordosica, and the N:P ratio was significantly and negatively correlated with physiologically active Ca for O. aciphylla. These findings revealed that the physiological regulation mechanism was different for the plants either in earlier stage or later stage of plant-community succession.     

Wetland changes in Jianghan Plain and simulation with GIS

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新疆天山山区近40年春季气候变化特征与平原区的比较

利用新疆1959～1998年的春季温度降水资料,分析了天山山区近40年来春季气候变化的基本特征,并与南疆、北疆进行了比较。所得的主要结果如下：(1)天山山区在春季温度的冷暖变化阶段上1981年前与北疆的相似,1981年后与南疆相似。(2)天山山区在春季降水量干湿变化阶段上与北疆的相似性强于南疆。(3)春季温度空间分布的同步变化性以北疆为最好,南疆最差。天山山区居中,而春季温度空间分布的反向变化性,以南疆为最大,北疆最小．天山山区居中。春季降水空间分布的同步变化性北疆较好,天山山区和南疆较差。而春季降水空问分布的反向变化性。以天山山区为最大。北疆最小,南疆居中。(4)三大区域的春季温度均表现为20世纪60与90年代偏高,70和80年代偏低。天山山区与北疆从60年代到90年代,春季降水均表现出了持续的增加的趋势。南疆春季降水除60年代外,不断增多。90年代是新疆三大区域春季降水最多的年代。(5)北疆和南疆近40年的春季最低温度存在着显著的增温趋势。增温率北疆大于南疆。