毛乌素沙地油蒿与杨柴异速生长模式及个体大小的种内竞争调节

通过对油蒿与杨柴种群在不同密度下个体大小与异速生长变化模式的比较研究,初步得出以下结论:①油蒿种群的个体平均大小、高径比平均值及静态异速生长指数均未随着密度的增加而发生明显的变化,其静态异速生长曲线都符合"简单的"异速生长类型。②杨柴种群的个体平均大小随着密度的增加则不断减小,且其自疏指数小于-3/2,这主要是由于种群在高密度时冠层未达到密接的缘故,而且可以将种群内个体的总植冠投影面积和是否达到最大值作为判断冠层密接的标准。③杨柴种群的高径比平均值及静态异速生长指数随着密度的增加也未发生明显变化,其静态异速生长曲线也符合"简单的"异速生长类型,表明杨柴的异速生长特性并未随着光竞争强度的增加而发生变化,这可能是因为杨柴能通过根状茎繁殖产生新枝来寻找更合适的生境从而避免了光竞争。     

Monitoring periodically national land use changes and analyzing their spatiotemporal patterns in China during 2015–2020

Journal of Geographical Sciences - High-resolution mapping and monitoring of national land use/cover changes contribute significantly to the knowledge of the interaction between human activities...     

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Surface modifications of comet‐exposed aerogel from the Stardust cometary collector

Abstract– Keystones removed from the Stardust cometary collector show varying degrees of visible fluorescence when exposed to UV light, with the brightest fluorescence associated with the space‐exposed surface. We investigated the spatial characteristics of this phenomenon further by using fluorescence microscopy, confocal Raman microscopy, and synchrotron Fourier transform infrared (FTIR) spectromicroscopy. Twenty‐four keystones, extracted from the Stardust cometary collector, were analyzed. Fluorescence measurements show two distributions with different excitation characteristics, indicating the presence of at least two distinct fluorophores. The first distribution is confined to within about 10 μm of the space‐exposed surface, whereas the second distribution is much broader with a maximum that is typically about 30–50 μm below the surface. Confocal Raman measurements did not reveal any changes associated with the surface; however, only features associated with aliphatic hydrocarbons were strong enough to be observed. FTIR measurements, on the other hand, show two distinct distributions at the space‐exposed surface: (1) a narrow, surface‐confined distribution originating from ?O₃SiH groups and (2) a broader, sub‐surface distribution originating from ?O₂SiH₂ groups. These functional groups were not observed in keystones extracted from the cometary flight spare or from the Stardust interstellar collector, indicating that they may result at least partially from cometary exposure. The presence of O₃SiH and O₂SiH₂ groups at the comet‐exposed surface suggests that the enhanced surface fluorescence is caused by defects in the O‐Si‐O network and not by organic contamination.     

Ground water radon anomalies in Bodrum Peninsula

Bodrum Peninsula is located between Hellenic Trench in the west and Gökova Fault Zone in the east which is affected by hundreds of earthquakes every year. Because of its active environment is allowed to monitor tracers/precursors continuously to analyse natural processes. This study focused on the determination of ground water radon (²²²Rn) concentrations in the Bodrum Peninsula in terms of seismic activities. Radon levels of ten ground water wells were measured periodically throughout the peninsula and these wells were divided into two groups according to the number of earthquakes they are exposed. Radon variations in second group stations are fairly significant as a result of high number of earthquakes. In these stations, radon continuously increased before the seismic storm and then decreased step by step. The results indicated that radon variations in ground waters of Bodrum Peninsula can be a good indicator for seismic storms instead of one specific event.     

Tracer hydrology of the data-scarce and heterogeneous Central American Isthmus

Numerous socio-economic activities depend on the seasonal rainfall and groundwater recharge cycle across the Central American Isthmus. Population growth and unregulated land use changes resulted in extensive surface water pollution and a large dependency on groundwater resources. This work combines stable isotope variations in rainfall, surface water, and groundwater of Costa Rica, Nicaragua, El Salvador, and Honduras to develop a regionalized rainfall isoscape, isotopic lapse rates, spatial–temporal isotopic variations, and air mass back trajectories determining potential mean recharge elevations, moisture circulation patterns, and surface water–groundwater interactions. Intra-seasonal rainfall modes resulted in two isotopically depleted incursions (W-shaped isotopic pattern) during the wet season and two enriched pulses during the mid-summer drought and the months of the strongest trade winds. Notable isotopic sub-cloud fractionation and near-surface secondary evaporation were identified as common denominators within the Central American Dry Corridor. Groundwater and surface water isotope ratios depicted the strong orographic separation into the Caribbean and Pacific domains, mainly induced by the governing moisture transport from the Caribbean Sea, complex rainfall producing systems across the N-S mountain range, and the subsequent mixing with local evapotranspiration, and, to a lesser degree, the eastern Pacific Ocean fluxes. Groundwater recharge was characterized by (a) depleted recharge in highland areas (72.3%), (b) rapid recharge via preferential flow paths (13.1%), and enriched recharge due to near-surface secondary fractionation (14.6%). Median recharge elevation ranged from 1,104 to 1,979 m a.s.l. These results are intended to enhance forest conservation practices, inform water protection regulations, and facilitate water security and sustainability planning in the Central American Isthmus.     

Effect of succession gaps on the understory water‐holding capacity in an over‐mature alpine forest at the upper reaches of the Yangtze River

The water‐holding capacity (WHC) of the understory in the headwater regions of major rivers plays an important role in both the capacity of the forest water reservoir and water quality and quantity in the butted rivers. Although forest gaps could regulate water‐holding patterns in the understory by redistributing coarse woody debris (CWD), fine woody debris (FWD), non‐woody debris (NWD) and understory vegetation, little information is available on the effects of forest gaps on understory WHC. Therefore, we investigated the WHCs of CWD, FWD, NWD, herbaceous vegetation, mosses, epiphytes (including fern and lichen growing on the surface of logs) and soils from the gap centre to the adjacent closed canopy in an alpine forest at the upper reaches of the Yangtze River. The total WHC of the alpine forest understory components was approximately 300 mm. Soil layer had the largest contribution to the total understory WHC (90%), and among the aboveground components, CWD and mosses contributed 5% and 4% to the aboveground WHC, respectively. With the exception of that of the herbaceous layer, the WHC of the forest floor increased from the gap centre to the closed canopy. Although mosses had the lowest biomass allocation on the alpine forest floor, the water‐holding ratio (k) of mosses reached 485%. In conclusion, biomass is the parameter that most strongly and positively correlated with the WHC of the alpine forest understory, and forest gap formation decreases the understory WHC of alpine forest resulting from a decrease in organic soils, CWDs and mosses. Copyright © 2015 John Wiley & Sons, Ltd. Highlights

• The effects of gaps on the understory WHC were examined in an alpine forest.
• Gaps decreased the understory WHC by decreasing the amounts of the larger WHC components.
• The contribution of CWD and mosses to the aboveground WHC was large.
• The WHC of dead debris was higher than that of the vegetation.

     

泰安地震台水管仪观测资料检验分析

分析泰安地震台DSQ水管倾斜仪2009-2011年运行现状,与“九五”数据进行对比检验,结果表明：观测资料的一般性质量评估均满足形变观测规范要求;各主波潮汐参数稳定,M2波潮汐因子均方差及观测资料噪声水平M1满足形变规范要求,最高精度达0.0015;年变形态一致性较好,标定干扰影响较大.     

基于PSInSAR技术的地面沉降监测研究——以北京怀柔区为例

怀柔应急水源地是北京第一个建成的特大型应急备用水源地,经过数年的开采后,应急水源地水位大幅度下降,地下水漏斗面积不断扩大。PSInSAR技术在监测地面沉降方面具有很大的优势,本文利用PSInSAR技术和2003年—2009年间28幅Enviast卫星的ASAR影像监测怀柔应急水源地地区地面沉降情况,试验结果表明该地区平均沉降量为8mm/a。通过该地区地面沉降状况和地下水漏斗发展趋势之间的对比,发现地面沉降范围和地下水漏斗有较大的空间一致性,平面分布趋势整体上由南西—北东向北西—南东转变。