Impact of Grazing Exclusion on the Surface Heat Balance in North Tibet

The grazing exclusion program used by the Tibetan government to protect the ecological environment has changed the vegetation and impacted the surface heat balance in North Tibet. However, little information is available to describe the in?uences of the current grazing exclusion program on local surface heat balance. This study uses the records of fenced grassland patch locations to identify the impact of grazing exclusion on surface heat balance in North Tibet. The records of fenced grassland patch locations, including the longitude, latitude, and elevation of the vertices of each fenced patch (polygon shapes), were provided by the agriculture and animal husbandry bureaus of the counties where the patches were located. ArcGIS 10.2 was used to create polygon shapes based on patch location records. Based on satellite data and the surface heat balance system determined by the model, values for changes in land surface temperature (LST), albedo and evapotranspiration (ET) induced by grazing exclusion were obtained. All of these can influence surface heat balance and alter the fluctuation of LST in the northern Tibetan Plateau. The LST trends for day and night showed an asymmetric diurnal variation, with a larger magnitude of warming in the day than cooling at night. The maximum decrease in absorbed shortwave of LST (-0.5 - -0.4 ℃ per decade) occurred in the central region, while the minimum decrease (-0.2 - -0.1 ℃ per decade) occurred in the eastern region. The decreased latent heat lead to the LST increased maximum (>1 ℃ per decade) occurred in the central region, The eastern region increased at a rate of 0.2-0.5 ℃ per decade, while the minimum increase (0-0.1 ℃ per decade) occurred in the northwestern region.     

氨氮急性攻毒对水产经济动物棘胸蛙(Paa spinosa)蝌蚪死亡率、排氨率、耗氧率及窒息点的影响

以体长(1.932±0.204)cm、体质量(1.386±0.055)g的棘胸蛙蝌蚪为实验动物,在水温(24±0.2)℃、DO(7.30±0.01)mg/L、pH 7.30±0.01条件下,采用静水停食法开展了氨氮对蝌蚪的急性攻毒实验,并以此为基础,测定了不同氨氮质量浓度胁迫下棘胸蛙蝌蚪的排氨率、耗氧率、氧氮比及窒息点。结果表明:(1)蝌蚪对氨氮急性攻毒具明显的运动避毒行为,濒死个体的背部皮肤和肝脏均具明显的色变症状;(2)氨氮对蝌蚪的急性致死率具明显的剂量—时间效应,24h、48h、72h、96h LC50依次为177.5、151.7、148.6和146.8mg/L,毒性时段蓄积程度系数呈持续下降趋势,24—48h、48—72h、72—96h的时段MAC值分别为84.04%、10.1%和5.86%;(3)蝌蚪夜均、昼均、日均及时段排氨率随氨氮质量浓度增加均呈阶梯式下降趋势,其中时段排氨率与对照组均无显著差异的为9.80mg/L实验组,夜均、昼均、日均及时段排氨率与对照组均无显著差异的仅为2.45mg/L实验组(P0.05);(4)氨氮对蝌蚪呼吸耗氧具低毒兴奋效应,其夜均、昼均和日均耗氧率随氨氮质量浓度增加均呈先升后降趋势,峰值氨氮质量浓度范围均为4.90—7.35mg/L(P0.05),与对照组均无显著差异的仅为14.70mg/L实验组(P0.05),窒息点含氧量随氨氮质量浓度增加呈先降后升趋势,谷底出现于4.90mg/L实验组(P0.05),与对照组无显著差异的仅为9.80mg/L实验组(P0.05);(5)实验期间,蝌蚪氧氮比(O:N)波动于18.87—25.34之间,昼均和日均氧氮比(O:N)随氨氮质量浓度增加均依次呈"上升—稳定—下降—再稳定"之趋势,两者的峰值氨氮质量浓度范围分别为4.90—14.70mg/L和4.90—9.80mg/L,夜均氧氮比(O:N)呈先升后降趋势,峰值出现于7.35mg/L实验组(P0.05)。     

Effects of Enclosure on Plant and Soil Nutrients in Different Types of Alpine Grassland

Enclosure is one of the most widely used management tools for degraded alpine grassland on the northern Tibetan Plateau, but the responses of different types of grassland to enclosure may vary, and research on these responses can provide a scientific basis for improving ecological conservation. This study took one site for each of three grassland types (alpine meadow, alpine steppe and alpine desert) on the northern Tibetan Plateau as examples, and explored the effects of enclosure on plant and soil nutrients by comparing differences in plant community biomass, leaf-soil nutrient content and their stoichiometry between samples from inside and outside the fence. The results showed that enclosure can significantly increase all aboveground biomass in these three grassland types, but it only increased the 10-20 cm underground biomass in the alpine desert. Enclosure also significantly increased the leaf nutrient content of the dominant plants and contents of total nitrogen (N), total potassium (K), and organic carbon (C) in 10-20 cm soil in alpine desert, thus changing the stoichiometry between C, N and P (phosphorus). However, enclosure significantly increased only the N content of dominant plant leaves in alpine steppe, while other nutrients and stoichiometries of both plant leaves and soil did not show significant differences in alpine meadow and alpine steppe. These results suggested that enclosure has differential effects on these three types of alpine grasslands on the northern Tibetan Plateau, and the alpine desert showed the most active ecological conservation in the responses of its soil and plant nutrients.     

虾夷扇贝天然苗种筛选装置的研究与应用

随着贝类底播增养殖产业的迅猛发展,为保证底播贝苗的成活率,养殖企业对天然苗种更加重视。天然苗种采用中间育成方法,需要对苗种进行筛选作业,但目前筛选作业仍以人工作业为主,存在作业效率低、劳动强度大等问题。作者通过对大连地区虾夷扇贝(Patinopecten yessoensis)天然苗种筛选作业调研的基础上,设计了满足生产实际需求的扇贝苗种筛选装置,可实现3种规格贝苗的筛选作业。试验分2阶段进行,第1阶段对影响筛选准确性的因素进行正交分析于验证,确定了最佳工艺参数;第2阶段在大连旅顺进行的生产性对比试验得出,机械筛选的平均准确率为91.33%,误差率低于10%,且5组筛选结果无显著性差异(P0.05);同时机械筛选的平均作业效率为80g/(人/min),约为人工筛选作业效率的8倍。由此说明扇贝苗种筛选装置具有较高的准确性、稳定性和高效性,具有推广应用价值。     

钢管脐带缆扭转平衡设计

钢管脐带缆包含多种螺旋缠绕的功能单元，其在外力载荷下会发生相对运动，而且钢管的刚度较大对扭转平衡有重要影响，因此，相对于普通电缆，钢管脐带缆在扭转平衡设计时更加困难。根据扭转平衡理论公式，采用控制变量法，以第二层铠装钢丝的绞合角度为变量进行扭转平衡设计。首先建立脐带缆缆芯有限元模型，对其施加拉伸载荷，结果显示缆芯出现了扭转，这证明不能将脐带缆缆芯视为一实心圆柱。其次建立不同绞合角度的脐带缆有限元模型，设置各功能单元的材料属性和摩擦系数，分析模型在拉伸载荷下的扭转角度，并将相同拉伸载荷下的扭转角度拟合为直线，从而得到钢管脐带缆在扭转平衡状态时的最优绞合角度。最后，采用试验方法对实物钢管脐带缆进行扭转平衡测试，测试结果显示在拉伸载荷下脐带缆单位长度扭转角度十分微小，这表明缆是扭转平衡的。因此验证了使用的有限元方法在钢管脐带缆扭转平衡设计中的有效性。     

HHT-EEMD用于IGS站高程时间序列分析

利用经验模态分解（EMD）和整体经验模态分解（EEMD）方法，将BJFS站2000~2015年高程时间序列进行分解，发现其不仅存在1 a、0.5 a、0.25 a、2个月、1个月以及长周期等周期项，还存在以往方法很难探测出来的近似2 a周期信号。与EMD分解结果对比，整体经验模态分解可以明显减弱模式混叠现象。对各分量进行Hilbert 变换（HHT），得到时间-频率-能量的Hilbert 频谱图。结果表明，年周期和2 a周期变化是高程运动的主要贡献项。利用小波变换方法对比验证EEMD的分解结果表明，与小波分析相比，EEMD重构信号与高程序列差异的RMS更小，证明了HHT-EEMD方法在数据资料分析过程中的有效性。对环境负载及GRACE负载造成的测站位移进行功率谱分析得出，环境负载确实会造成IGS站高程时间序列的1 a、0.5 a以及季节性运动，GRACE负载还验证了2 a信号的存在。     

基于旅游开发影响的五台山植被景观特征分析

以往旅游对植被影响的评价成果较多,但是旅游影响下植被景观与地理因子之间的关系报道较少。本文利用多种数量生态学方法探讨了五台山旅游开发与植被景观之间的生态关系。结果表明：① 旅游开发影响下五台山植被景观可分为单优乔木区、草本区、差级乔草区、中级乔草区、中级灌草区、良级灌草区、良级乔灌草区、优级乔灌草区、以及寺庙区、商业区或居民区9种类型。② 在除趋势对应分析中,第一轴与所有因子的相关性都较大,第二轴与旅游干扰度和海拔呈显著的负相关性。各植被景观类型的空间分布在一定程度上取决于关键性指标的空间格局。③ 除趋势典范对应分析方法能够大大提高植被景观特征与地理因子间的相关性,并将其直观地表达于排序图中。在植被景观特征与地理因子的关系上,第一轴上的相关系数是0.858_DCCA>0.828_DCA,第二轴上的相关系数是0.583_DCCA>0.501_DCA,这说明除趋势典范对应分析方法更优。     

临震前地壳变形不动点现象与机制研究

在综合分析国内外地形变前兆研究现状的基础上,结合汶川8.0级地震前GPS、应变、重力等研究结果,提出临震前震源区域可能出现变形不动点现象。地壳变形过程中的不动点现象是临震前区域应力场进入临界状态的重要标志,是地震潜在危险区域划定的重要依据。借助不动点理论,给出汶川地震前变形不动点集合的演化,结合大区域地震活动空区与远场显著形变异常分布,探讨变形不动点现象发生的动力学背景,验证了汶川地震前地壳变形的不动点现象是大区域应力场有序运动的结果。