Species richness,diversity and density of understory vegetation along disturbance gradients in the Himalayan conifer forest

We investigated whether species richness, diversity and density of understory herbaceous plants differed along logging(gap) and grazing(primarily by cattle) disturbance gradients, and sought to identify drivers of richness, diversity and density of understory vegetation of logged sites. A factorial experiment was conducted in the mixed conifer forest of Gidakom in Western Bhutan. Levels of the logging treatment included small(0.15 – 0.24 ha), medium(0.25 – 0.35 ha) and large(0.36 – 1.31 ha) gaps. The grazing treatment included grazed(primarily by cattle) and ungrazed(where herbivores were excluded by a fence) plots nested within each gap. Data were collected from 12 gaps(4 replicates at each level of logging) using the point intercept method. Shannon Weaver Diversity and Margalef's indices were used to estimate species diversity and describe species richness, respectively. Soil samples were analyzed for pH and nutrients. The interaction effect of logging and grazing was significant(p≤0.001) only on species diversity. Relative to ungrazed areas, species diversity was significantly higher(0.01≤p≤0.05) in medium grazed gaps. Under grazed conditions, soil P was negatively correlated with gap size and species diversity. While species diversity was positivelycorrelated(0.01≤p≤0.05) with soil N in grazed plots species richness was positively correlated(0.001≤p≤0.01) with soil N in ungrazed plots. Relative density of Yushania microphylla and Carex nubigena were higher under ungrazed conditions. Our study suggests that the combined effect of cattle grazing and logging results in higher species diversity of understory vegetation in medium and grazed gaps in mixed conifer forests of Bhutan,whereas increase or decrease in relative density of major species is determined primarily by the independent effects of grazing and logging. From management perspective, forest managers must refrain from creating large gaps to avoid loss of nutrients(mainly P and N), which may eventually affect tree regeneration. Managers intending to maintain understory vegetation diversity must consider the combined effects of grazing and logging, ensuring low to moderate grazing pressure.     

折射法和高密度电法在古滑坡勘探中的应用

古滑坡体地球物理调查方法技术的选择对勘探效果至关重要。以吉林省通化市拟建集安-通化高速公路滑坡体为例,采用折射波法和高密度电法,利用二维反演技术进行数据处理。结合地质信息,确定了滑坡体的形态及厚度变化,厚度最大约20 m,滑坡性质为堆积层滑坡。研究结果表明折射波法和高密度电法进行古滑坡勘探,效果较好。     

东北地区风能资源空间分布特征与模拟

利用东北地区104个气象站1991~2010年观测资料和70个测风塔2009年6月~2010年5月测风资料,进行了风能资源空间分布特征分析,并利用中尺度模式WRF进行风能资源空间模拟,以研究观测站点稀少地区的风能资源分布特征。研究结果表明:1东北地区气象站和测风塔揭示的大风区域主要分布在平原和丘陵的高海拔地带。2中尺度模式WRF能够较好地模拟东北区域风速分布的气候特征,模拟结果既反映出平原大面积的大风区域,也可反映出山区因地形起伏造成的风速空间分布差异。3对风能资源参数模拟结果进行海拔高度订正,可以进一步提高模式计算结果的准确性和可靠性。4松嫩平原、辽河平原、三江平原70 m高度年平均风功率密度在300~500 W/m2之间,属于风能资源可利用区或较丰富区;在辽宁省西部、吉林省中部和黑龙江省中部丘陵以及东北地区东南部的呈东北-西南走向的中高山区的70 m年平均风功率密度可达300 W/m2以上,局部地方可达500 W/m2以上,风能资源丰富。     

福建三明马尾松树轮宽度对气候变化的响应

运用树木年代学的基本原理和方法,研究三明地区马尾松(Pinus massiniana)径向生长对气候要素的响应。结果表明:夏季温度限制着马尾松的径向生长,年轮宽度与上一年和当年7—8月平均气温均呈显著负相关(P0.01);马尾松的径向生长受到降水和湿度的影响较大,与上一年1—3月降水量和2—3月平均相对湿度显著负相关(P0.01),与当年6—11月平均降水量和7—8月相对湿度显著正相关(P0.01);同时宽度年表与上一年2—3月太阳日照时数显著正相关(P0.01);另外,宽度年表与6—11月PDSI显著正相关(P0.05),生长季的干旱胁迫抑制了马尾松的生长。研究说明本地区限制马尾松树木生长的因素较多,1年中不同时期限制马尾松径向生长的气候因子不同。     

Response to climate change of different tree species and NDVI variation since 1923 in the middle arid region of Ningxia, China

The normalized difference vegetation index （NDVI） is used extensively to describe vegetation cover and ecological environ- ment change. The purpose of this study was to contrast the response of different tree species growing in the same habitat to climate change and retrieve past NDVI using tree-ring width data from tree cores collected from the transitional zone of Pinus tabulaeformis and Picea crassifolia in the Luoshan Mountains in the middle arid region of Ningxia. Correlation analysis indi- cated that radial growth ofP tabulaeJbrmis is more sensitive to precipitation and temperature change than that ofP crassifolia. Natural factors such as water availability and heat at this elevation are more suited to the growth ofP crassifolia, and are more advantageous to its renewal and succession. P. crassifolia is probably the better of the two species for protecting the forest ecosystem and conserving water in the Luoshan desertification area. Ring width of P. crassifolia correlates significantly with average NDVI for April-May （r =0.641, p 〈0.01）, and both of them are influenced positively by precipitation in April-May. The reconstructed NDVI for 1923-2007 shows the relatively low vegetation cover occurred in the 1920s-1930s, the 1960s-1970s, and the early 21 st century. The reconstructed NDVI better reflected the drought climate in the study area.     

毫米波云雷达功率谱密度数据的检验和 在弱降水滴谱反演中的应用研究

本文首先利用数值模拟的方法,分析了利用毫米波云雷达功率谱密度反演雨滴谱时,降水粒子米散射效应、空气湍流、空气上升速度等对雨滴谱和液态水含量等参数反演的影响;建立了功率谱密度处理及其直接反演雨滴谱、液态水含量、降水强度和空气上升速度的方法;并利用2012年7月在云南腾冲观测的二次弱降水数据,采用毫米波雷达和Ku波段微降水雷达观测的回波强度、径向速度垂直廓线以及780 m高度上的功率谱密度对比的方法,以及毫米波云雷达观测的780 m高度上功率谱密度、回波强度与地面雨滴谱计算得到的这些量的对比方法,分析了毫米波雷达数据的可靠性;并将780 m高度上毫米波雷达反演的雨滴谱与地面雨滴谱数据进行了对比,分析了毫米波雷达反演的雨滴谱的准确性;分析了毫米波雷达回波强度偏弱的原因,讨论了该高度以下降水对毫米波雷达衰减的影响。结果表明:空气湍流对弱降水微物理参数反演影响不大,而空气上升速度和米散射效应均对反演结果有一定影响;毫米波雷达观测到的径向速度和功率谱密度与微降水雷达比较一致,回波强度的垂直廓线的形状与微降水雷达也比较一致,但毫米波雷达观测的回波强度偏弱;与雨滴谱计算值相比,毫米波雷达观测的低层的回波强度也偏弱,天线上的积水是造成毫米波雷达回波强度变弱的主要原因。毫米波雷达观测的低层的功率谱密度与地面雨滴谱观测的数据形状比较一致,但有一定的位移。毫米波雷达反演的雨滴谱与地面观测的谱型和粒子大小也比较一致。这些结果初步验证了毫米波雷达观测的功率谱密度及其反演方法的可靠性。     

华北地区香河站对流层NO_2的MAX-DOAS光谱仪观测及变化特征分析

利用中国科学院大气物理研究所香河大气探测综合试验站2010年3月至2012年2月(2年)的多轴差分吸收光谱仪(MAX-DOAS)观测数据和32 m高塔常规气象资料,反演了华北地区香河站对流层NO2柱浓度,分析了该区域NO2柱浓度的季节变化特征。研究表明:可见光455~485 nm、紫外330~370 nm都可以作为MAX-DOAS工作波段很好地反演NO2;香河地区NO2柱浓度夏季最低,几乎保持在2×1016 cm–2以下,春、秋季次之,在3×1016 cm–2上下小范围浮动,冬季最高,可达4.5×1016 cm–2;月平均最低值出现在7月,最高值出现在11月。NO2柱浓度与风速、风向密切相关:来自东边唐山方向的风,风速越大时NO2浓度越高,因为唐山是NO2的高值区之一;其它方向风速越大,浓度越低。春、夏两季NO2柱浓度日变化趋势比较平缓,秋、冬两季日变化明显,秋季正午偏高,冬季早晚偏高。     

西北太平洋海域风浪、涌浪、混合浪波浪能资源特征

用ECMWF的ERA-40海浪再分析资料,应用波浪能流密度计算方法,对西北太平洋海域的风浪能、涌浪能、混合浪能展开研究。结果表明:(1)波浪能流密度呈现出显著季节性差异。混合浪能流密度表现为冬高夏低;春、夏、秋季的涌浪能流密度明显大于风浪能流密度,冬季相反;(2)混合浪能流密度的大值区主要分布于阿留申群岛附近海域,高值中心可达60 kW/m以上;近海的大值区主要分布于琉球群岛—巴士海峡—传统的南海大风区一带,年平均值在4 kW/m以上,南海北部可达12 kW/m以上;(3)黄渤海的涌浪和混合浪能流密度峰值出现在8—9月,波谷出现在6月。风浪能流密度峰值出现在11月—次年3月,波谷出现在6—8月,均呈现双峰型月变化特征。东海、南海北部、南海中南部海域能流密度的月变化特征相似,都为双峰型,12月—次年4月的能流密度整体较高,波峰出现在12月,波谷出现在5—7月;(4)2 kW/m以上混合浪能流密度出现的频率较高,近海低于大洋;(5)0.5 m以上有效波高出现的频率都非常高,中国近海稍低于大洋;(6)涌浪能流密度的稳定性明显好于风浪能流密度;大洋的能流密度稳定性明显强于近岸。1月份能流密度的稳定性最好,4月和7月次之,10月的稳定性最差。     

重力异常的视密度反演推断扬子与华北块体在南黄海地区的地质界线

通过对南黄海及周边船载测量重力数据、现代卫星测高重力数据、陆地测量重力数据以及地球重力模型等多来源重力数据进行整理和融合,对南黄海地区布格重力异常特征进行了分析。利用基于切割法和插值迭代法的大深度位场向下延拓技术的视密度反演法对南黄海布格重力进行处理和解释,结合山东和朝鲜半岛的地质信息,推断了扬子块体和中朝块体在南黄海海域的界限。中朝和扬子块体在海上的分界位置为千里岩北缘断裂,向NE延伸到125°E后,折向NNW向并在36°N附近再次转为NE向进入朝鲜半岛并经过洪城南侧继续以NE向延伸。扬子的北缘为苏鲁造山带,穿过黄海与京畿造山带相接,苏鲁超高压变质带对应洪城杂岩。     

Thermodynamic properties of snow cover on sea ice during the austral summer in Prydz Bay,East Antarctica

The thermodynamic properties of snow cover on sea ice play a key role in the ice-ocean-atmosphere system and have been a focus of recent scientific research. In this study, we investigated the thermodynamic properties of snow cover on sea ice in the Nella Fjord, Prydz Bay, East Antarctica(69°20′S, 76°07′E), near the Chinese Antarctic Zhongshan Station. Our observations were carried out during the 29th Chinese National Antarctic Research Expedition. We found that the vertical temperature profile of snow cover changed considerably in response to changes in air temperature and solar radiation during the summer. Associated with the changes in the temperature profile were fluctuations in the temperature gradient within the upper 10 cm of the snow cover. Results of previous research have shown that the thermal conductivity of snow is strongly correlated with snow density. To calculate the thermal conductivity in this study, we measured densities in three snow pits. The calculated thermal conductivity ranged from 0.258–0.569 W?m-1?K-1. We present these datasets to show how involved parameters changed, and to contribute to a better understanding of melting processes in the snow cover on sea ice.