内蒙古羊草草原呼吸的影响因素分析和区分

利用静态暗箱-气相色谱法在植物生长旺季测算了内蒙古锡林河流域羊草草原的土壤微生物呼吸、土壤呼吸和生态系统呼吸。地温和水分是植物生长旺季呼吸最重要的影响因素。地温在水分条件适宜的情况下可以解释CO₂通量的部分变化(R² = 0.376~0.655)。土壤水分含量也可以解释土壤呼吸和生态系统呼吸的部分变化(R² = 0.314~0.583),但基本不能解释土壤微生物呼吸的变化(R² = 0.063)。即使在较高温度下,较低的土壤水分含量(≤ 5%) 也会显著的抑制CO₂排放。长期干旱后降雨使CO₂通量在高温下迅速增大。基于5 cm地温和0~10 cm土壤水分含量的双变量模型可以解释CO₂通量约70%的变化。观测期间,土壤呼吸占生态系统呼吸的比例介于47.3%~72.4%之间,平均为59.4%;根呼吸占土壤呼吸的比例介于11.7%~51.7%之间,平均为20.5%。由于植物体去除引起的土壤水分含量上升可能使我们对土壤呼吸占生态系统呼吸比例的估计略微偏高,根呼吸占土壤呼吸的比例略微偏低。     

玛纳斯河流域人工绿洲扩张对社会经济和生态环境的影响分析

 利用2007—2009年的实地调查资料,结合1958—2006年的5期遥感影像解译数据,从干旱区内陆河流域典型绿洲的演变进程出发,分析了新中国成立以来近60 a玛纳斯河流域人工绿洲快速扩张的影响,强调了保持绿洲适宜规模的重要性,并从可持续发展的角度探讨了绿洲今后发展的方向。主要结论为:①近60 a玛纳斯河流域耕地和绿洲分别以107.756 km2·a-1和122.401 km2·a-1的速度迅速增长,二者扩张的方向基本一致;②绿洲的快速扩张对社会经济产生一定推动作用的同时,也带来了一系列的环境问题。如地表水利用率超过90%,地下水过度开采并以0.5~1 m·a-1的速度下降,水质污染增加,防护林大量死亡,森林破坏严重,草地从1958年到2006年减少4 316.39 km2,土地荒漠化威胁严重等;③从可持续发展的角度看,控制绿洲规模,适度开采地下水,转变产业结构,建立生态补偿机制等是今后本区发展的关键。     

Influencing factors and partitioning of respiration in a Leymus chinensis steppe in Xilin River Basin, Inner Mongolia, China

Based on the static opaque chamber method, the respiration rates of soil microbial respiration, soil respiration, and ecosystem respiration were measured through continuous in-situ experiments during rapid growth season in semiarid Leymus chinensis steppe in the Xilin River Basin of Inner Mongolia, China. Soil temperature and moisture were the main factor affecting respiration rates. Soil temperature can explain most CO2 efflux variations (R2=0.376–0.655) excluding data of low soil water conditions. Soil moisture can also effectively explain most of the variations of soil and ecosystem respiration (R2=0.314–0.583), but it can not explain much of the variation of microbial respiration (R2=0.063). Low soil water content (≤5%) inhibited CO2 efflux though the soil temperature was high. Rewetting the soil after a long drought resulted in substantial increases in CO2 flux at high temperature. Bivariable models based on soil temperature at 5 cm depth and soil moisture at 0–10 cm depth can explain about 70% of the variations of CO2 effluxes. The contribution of soil respiration to ecosystem respiration averaged 59.4%, ranging from 47.3% to 72.4%; the contribution of root respiration to soil respiration averaged 20.5%, ranging from 11.7% to 51.7%. The contribution of soil to ecosystem respiration was a little overestimated and root to soil respiration little underestimated because of the increased soil water content that occurred as a result of plant removal.     

放牧对内蒙古羊草群落土壤呼吸的影响

采用静态暗箱法,比较测定了放牧对内蒙古锡林河流域羊草群落土壤呼吸的影响以及水热等相关环境因子与土壤呼吸的关系。结果表明:放牧没有改变羊草群落土壤呼吸的季节性变化特征,但降低了土壤呼吸速率的年幅度;生长季放牧样地土壤呼吸速率显著低于封育样地,非生长季两样地土壤呼吸强度均处于较低水平,而且出现负通量的现象,放牧使羊草群落土壤呼吸年总量下降了约33.95％;从全年来看,无论是围栏还是放牧样地,封育样地和放牧样地土壤呼吸与温度因子均显著正相关(p<0.01,n=15),其中与10cm处地温相关性最好,但放牧降低了土壤呼吸对温度变化的敏感性;生长季水分影响作用高于温度,围栏封育样地0~10cm土壤含水量的变化可以解释土壤呼吸变异的87.4％,放牧样地10~20cm和20~30cm土壤含水量的变化共同可以解释土壤呼吸变异的74.9％。     

锡林河流域羊草草原暗栗钙土矿质氮动态变化

通过野外采样,分析了内蒙古锡林河流域三个不同放牧强度羊草草原0～30cm表层土壤中矿质氮（NH₄⁺-N+NO₃^--N）的浓度特征,研究了它们在生长季期间的含量变化情况。结果表明:羊草草原暗栗钙土中矿质氮主要以NH₄⁺-N形式存在,矿质氮含量仅占土壤全氮的0.20%～0.92%;土壤矿质氮含量随草地放牧强度升高而降低,围封禁牧多年的羊草样地矿质氮含量高于轮牧地和自由放牧地;生长季期间0～10cm、10～20cm和20～30cm各层次土壤NH₄⁺-N和NO₃^--N含量随土壤温度、水分和植物生长吸收的变化而波动明显,不同深度土壤矿质氮的季节变化趋势基本一致,表层0～10cm土壤矿质氮含量波动幅度最大:在4月和7、8月份,NO₃^--N和NH₄⁺-N浓度分别出现峰值;NH₄⁺-N和NO₃^--N含量随采样深度增加而降低,各采样点0～30cm土壤中NH₄⁺-N含量均高于NO₃^--N。     

新疆和田河流域柽柳沙堆的生物地貌发育过程(英文)

Tamarix nabkha is one of the most widespread nabkhas,distributing in the arid region of China.Based on the observations outdoors and the simulation experiments in laboratories,analysis in this paper refers to the biological geomorphologic features and growth process of Tamarix nabkhas in the middle and lower reaches of the Hotan River,Xin- jiang.And the results indicate that the ecological type of Tamarix in the study area is a kind of Tugaic soil habitat based on the deep soil of the Populus Diversifolia f...     

On the presence of <Emphasis Type="Italic">Stephanodiscus niagarae</Emphasis> Ehrenberg in central Mexico

Stephanodiscus niagarae is frequently reported from late Pleistocene (>10,000 yr BP) sediments in central Mexico, with lower abundances through the Holocene. Its presence in Holocene and modern environments in central Mexico was not well documented until our study, where we report on three populations of S. niagarae, one middle Holocene population with particularly high abundance from the Upper Lerma Basin, and two modern sites, Valle de Bravo and Santa Elena. The three sites are located in the same geographical area, in the State of Mexico. The fossil material dates to ca. 6600–4900 yr BP, with S. niagarae reaching up to 90% of the diatom counts. Stephanodiscus niagarae is present in association with Fragilaria pinnata, F. brevistriata, and Aulacoseira granulata. In Valle de Bravo (ca. 30 m deep) S. niagarae is present in very low numbers in water column and surface sediments samples (<1%); the diatom assemblage is dominated by Fragilaria crotonensis in association with A. granulata, A. granulata var. curvata and Cyclotella ocellata. In Santa Elena, a shallow, intermittent irrigation channel, S. niagarae is the second most abundant alga; the diatom assemblage is dominated by S. niagarae in association with A. granulata, A. granulata var. curvata and F. crotonensis. Both modern sites show a trend to eutrophy and these diatom assemblages are taken as indicative of this trend. It is suggested researchers should be cautions when the presence of S. niagarae in sedimentary records is taken as indicative of deep waters conditions, as the present data show that this species can thrive in rather shallow environments in Mexico.     

油松树轮记录的1776年以来贺兰山地区气温变化

Tree-ring standardized chronologies are developed by 78 cores collected from the eastern and western Helan Mountain. Statistical analysis shows that both the STD and RES chronologies correlate negatively with the temperature of different periods of early half year, especially with January to August mean （JA） temperature, which means that JA temperature is one of the predominant limiting factors of tree growth in the Helan Mountain. Based on this analysis, we reconstructed JA temperature, and the explained variance is 43.3% （F=21.422, p〈0.001 ）. The comparatively high temperature periods in the reconstruction were： 1805-1818 1828-1857, 1899-1907, 1919-1931 and 1968-1995; and the comparatively low temperatu re periods happened in 1858-1872, 1883-1895 and 1935-1953. Ten-year moving average curve shows three slow uplifting trends： 1766-1853, 1862-1931 and 1944-1995. Each temperature increase was followed by a sudden temperature decrease about 10 years, that is to say, the JA temperature in the Helan Mountain is characterized by slow increase and sudden decrease. The 70- and 10.77-year periodicities detected in the temperature series correspond to the Gleissberg （80-year） and Schwabe （11-year） periodicities of solar activity respectively, the 2.11-2.62 years cycles are considered to be influenced by QBO （Quasi-Biennial-Oscillation） and the local environmental change.     

Late Holocene palaeoenvironmental evolution of the Roman harbour of <Emphasis Type="Italic">Portus</Emphasis>, Italy

We present a Holocene record of climate and environmental change in central New York (USA) inferred using lithologic and stable isotope data from two sediment cores recovered in Cayuga Lake. The record was divided into three intervals: (1) early Holocene (~11.6–8.8 ka), (2) Hypsithermal (~8.8–4.4 ka), and (3) Neoglacial (~4.4 ka to present). The early Holocene began abruptly, with rising lake level and relatively deep water. Between ~10.8 and 9.2 ka, cool and dry conditions prevailed at a time of maximum solar insolation. This anomaly has been referred to as the “post-Younger Dryas climate interval” and lasted ~1,600 years, the approximate length of one “Bond cycle.” The Hypsithermal was the warmest, wettest and most biologically productive interval of the Holocene in central New York. The Hypsithermal was characterized by centennial to multi-centennial-scale variability. The 8.2 ka event is one such variation. The Neoglacial was an interval of generally cooler and dryer conditions, falling lake levels, and several prominent climate anomalies. At approximately 2.4 ka, δ¹³C of bulk organic matter increased abruptly by 5‰ as lake level declined, and the lake flora was dominated by Chara sp. during the coldest interval of the Neoglacial. Numerous sediment variables display increased variability ~2.0 ka, which continues today. Archaeological data from the literature suggest that Native American populations may have been large enough to impact land cover by about 2.4 ka and we hypothesize that the “Anthropocene” began at about that time in central New York. We also found paleolimnological evidence for the Medieval Warm Period (~1.4–0.5 ka), which was warmer and wetter than today, and for the Little Ice Age (~500–150 years ago), a period with temperatures colder than today.     

<Emphasis Type="Italic">Bosmina</Emphasis> remains in lake sediment as indicators of zooplankton community composition

We measured Bosmina spp. mucro and antennule lengths in surface sediment samples from Wisconsin lakes to test whether such measures could be used to reconstruct zooplankton community composition and size structure in paleolimnological studies. Our data set included 58 lakes of various depths, water chemistry, trophic state, macrophyte cover, and zooplankton community composition. We used non-metric multidimensional scaling ordination (NMS) and simple correlation analysis to assess whether mucro and antennule measurements reflect the zooplankton community size structure. Bosmina mucro length (r = 0.727, p < 0.05) and antennule length (r = 0.360, p < 0.05) correlated with the NMS axis, which essentially represents zooplankton community size structure. Bosmina mucro length correlated positively with the abundance of the large-bodied zooplankter Epischura lacustris (r = 0.364, p < 0.01), as well as Diacyclops thomasi (r = 0.256, p < 0.05), and Leptodiaptomus minutus (r = 0.578, p ≤ 0.001), but correlated negatively with the abundance of the small-bodied zooplankter Tropocyclops prasinus (r = −0.385, p < 0.01). Bosmina antennule length correlated positively with the abundance of L. minutus (r = 0.344, p < 0.01) and negatively with T. prasinus (r = −0.258, p < 0.05). This broad, spatial scale assessment supports the use of Bosmina mucro and antennule lengths as a proxy for zooplankton community size structure. Mucro length is a stronger indicator of zooplankton community size structure as seen in its strong correlation with the NMS axis 1 and the significant correlations with abundance of predatory copepods.