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971.
日本鲭(Scomber japonicus)是西北太平洋重要的鱼类资源之一,科学预测日本鲭的资源丰度有利于其资源的合理开发和利用。本研究依据日本渔业机构提供的1987–2012年日本鲭太平洋群体的资源量数据,结合产卵场和渔场的海洋环境数据以及气候因子,使用广义加性模型对影响日本鲭太平洋群体的海洋环境和气候因子进行分析,筛选出有显著影响的因子并建立该群体的资源量预测模型。结果表明,与该群体资源量有显著关系的影响因子有:北极涛动指数、太平洋年代际振荡指数、渔场海表面高度、渔场海表面盐度和渔场海表面温度。基于赤池信息准则筛选出的4个资源量预测模型分析表明,包含北极涛动指数、渔场海表面高度和渔场海表面温度的模型有较好的预测效果,该模型的验证结果也通过了t检验(P<0.05),可用于日本鲭太平洋群体资源量的预测。 相似文献
972.
本文以中国市域单元为研究对象,利用1990-2010年人口普查数据,采用探索性空间数据分析的方法,分析了过去20 年间中国市级人口增长率的空间分布特征和多变量的空间依赖关系。使用空间计量模型和空间滤波后的经典线性回归模型分别探究了经济、气候、地形、社会文化等因素对中国市级人口增长率的影响。模型对比结果显示,经过空间滤波后的经典线性回归模型能够更好的模拟中国市级人口增长率的变化。在该模型中,经济因素是影响中国城市人口增长率的主要因素,例如代表城市经济发展水平的城市夜光指数密度。气候因素对人口增长率也有着不可忽视的作用,如七月热指数随着等级的提升对人口增长率有着越来越强的负向影响。研究结果表明:人口的区域增长模式是多要素综合作用的结果,在相关建模研究和政策制定中需要重点考虑经济发展水平和气候条件因素对人口增长趋势的不同影响。 相似文献
973.
974.
珊瑚藻是珊瑚礁生态系统中重要的功能性群体。2010年通过水肺潜水分析了三亚珊瑚礁区的珊瑚藻种类组成和丰度, 以及群落空间特征与环境因子的关系。共鉴定出3科10属25种珊瑚藻, 其中珊瑚藻科占优势地位。三亚珊瑚礁区的珊瑚藻优势种分别为叉节藻Amphiroa ephedraea、拟中叶藻Mesophyllum simulans、串胞新角石藻Neogoniolithon fosliei、中叶藻M. mesomorphum、圆锥呼叶藻Pneophyllum conicum、孔石藻Porolithon onkodes和布氏水石藻Hydrolithon boergesenii。基于多元统计的分析结果, 将调查采样站位分为近岸型和离岸型2个主要集群, 其中近岸型的珊瑚藻种类以浊度、沉积速率(0~63μm)和悬浮物耐受种类为主, 离岸型则以光依赖-沉积物敏感种类为主。以珊瑚藻种类组成和丰度为基础的群落相似性分析结果表明, 其空间变异处于显著性水平。生物与非生物变量的相关分析结果表明, 最佳两变量组合(浊度和盐度)显著影响三亚珊瑚礁区2种类型调查站位中的珊瑚藻集合。在同一个研究站位, 因受干扰程度不同, 深水处的珊瑚藻的覆盖率比浅水处高。分析结果表明, 在三亚独特的珊瑚礁区中, 自然或人为的物理干扰因素都对调节珊瑚藻群落结构非常重要。 相似文献
975.
Improved knowledge on overland flow (OF) generation and its dynamics (i.e. spatial and temporal variations) is essential to understand catchment hydrology, a prerequisite for better water resources and soil management. In this study, our main objective was to quantify the dynamics of OF during rainfall events and to assess its main factors of control. The research study was undertaken in an agricultural 23‐ha catchment of a communal pasture in KwaZulu‐Natal (South Africa) experiencing Mediterranean climate and with variations of soil, topography and vegetation conditions. The dynamics of OF was evaluated during three rainfall seasons (2007 to 2010) by using 1 × 1‐m² microplots (n = 15) located at five landscape positions. At each location, a microplot was equipped with an automatic tipping bucket linked to a logger to estimate the delay between the start of the rain and the start of OF [i.e. the time to runoff initiation (TRI)]. Multivariate analysis was applied to the total OF and TRI data and the information on selected environmental factors (rainfall characteristics; soil type; soil clay content, Clay; proportion of the soil surface covered by vegetation, Cov; proportion of the soil surface covered by crusting, Crust; mean slope gradient, S; soil bulk density, ρb; soil water tension at different depths, SWT). The average OF rate over the 3‐year study period varied 2.3‐fold across the catchment (from 15% footslope to 35% backslope), whereas the average TRI varied by a 10.6‐fold factor (between 0.6 min at bottomland and 6.4 min at footslope). TRI temporal variations correlated the most with event duration (r = 0.8) and cumulative amount of rainfall since the onset of the rainy season (r = ?0.47), whereas TRI spatial variations were controlled the most by Crust (?0.97 < r < ?0.77). Ultimately, TRI spatial variations were modelled and mapped in an attempt to model OF dynamics over the entire microcatchment. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
976.
977.
Seasonal Variation and Meteorological Control of CO2 Flux in a Hilly Plantation in the Mountain Areas of North China 下载免费PDF全文
HUANG Hui ZHANG Jinsong MENG Ping FU Yuling ZHENG Ning GAO Jun 《Acta Meteorologica Sinica》2011,25(2):238-248
The carbon cycle of terrestrial ecosystems is an important scientific issue in global climate change re-
search. Plantation forest plays an important role in terrestrial carbon budget in China. In this study,
eddy covariance flux data measured at Xiaolangdi forest ecosystem research station (XLD) in 2007 and
2008 are used to analyze the seasonal variation and meteorological control of CO2 flux in a 30-yr-old mixed
plantation. The plantation forest mainly consists of Quercus variabilis, Platycladus orientalis, and Robinia
pseudoacacia. The results show that the seasonal variations of net ecosystem exchange of CO2 (NEE),
gross primary production (GPP), and ecosystem respiration (Re) display single-peak curves. The maximum
of carbon sequestration appears during May and June each year. The relative contribution of carbon re-
lease from ecosystem respiration to GPP varied slightly between 2007 and 2008. The relationship between
NEE and photosynthetic active radiation (Qp) accords with the rectangular hyperbola model on diurnal
scale, and shows a good linear correlation on monthly scale. The ecosystem photosynthetic parameters:
the maximum photosynthetic rate (Pmax), the ecosystem photosynthetic photonyield (α), and the daytime
ecosystem respiration (Rd) exhibit seasonal variations. Pmax reaches the maximum in August each year,
with small interannual di?erence. The interannual differences of α and Rd are obvious, which is attributed
to the changes of meteorological factors, such as solar radiation, vapor pressure deficit (D), precipitation,
etc. Parameters Re, GPP, and NEP (net ecosystem production) have obvious exponential relations with
temperature on monthly scale. There is a hysteresis in the response of GPP and NEP to temperature, i.e.,
the carbon sequestration is not the maximum when the temperature reaches the peak value. The Q10 values
were 1.37 and 1.45 in 2007 and 2008, respectively. On monthly scale, Re, GPP, and NEE increase as D
increases, but rise slowly and even decrease when D is higher than 1.5 kPa. 相似文献
978.
Fatemeh Amini‐Yekta Mohammad Reza Shokri Abdolvahab Maghsoudlou Hassan Rajabi‐Maham 《Marine Ecology》2019,40(3)
Variations in environmental factors can alter the species distribution pattern in intertidal rocky shores. The Persian Gulf (PG) and the Gulf of Oman (GO) vary substantially with respect to environmental and oceanographic conditions. The abundance and biodiversity of intertidal rocky gastropods in five locations across the northern PG and the GO were compared, and the environmental variables underlying the distribution pattern of these organisms were investigated. A total of 67 gastropod species were identified. The largest average density (294 ind./m2) and diversity (N = 43) for gastropods occurred in the Hotel Lipar station (LIP) located in Chabahar Bay in the GO. Clypeomorus bifasciata (107.43 ind./m2) followed by Cerithium caeruleum (94.67 ind./m2) were the most abundant species. Planaxis sulcatus and Siphonaria spp. occurred in all locations during both sampling occasions. Species richness and abundance of gastropods showed significant differences between LIP and remaining locations. A significant difference was found in assemblage structure across locations. In general, the species richness and density in the locations at GO were significantly larger than those locations in the PG, suggesting that the harsh environmental condition in the PG might be the forcing factor for this diminish. Distinct grouping was observed in both assemblage structure and species composition between locations in the PG and the GO. The spatial and temporal distribution patterns of gastropods assemblages were significantly correlated with variation in salinity and substrate rugosity. 相似文献
979.
青藏高原西部、南部和东北部边界地区天然水的水化学性质及其成因 总被引:1,自引:1,他引:1
特殊的地理和人文环境致使青藏高原天然水拥有独特的水化学性质并保存着较完整的原生状态,但随着人类活动强度的持续增大,可能导致当地水环境及水化学性质发生改变。通过对青藏高原存在人类活动的西部、南部和东北部边界地区进行水样采集、分析与测定,并探讨了当地天然水水化学性质的区域差异及其成因规律。结果表明:青藏高原不同边界地区天然水的物理性质、水化学性质和成因均存在差异,这些差异主要是地理环境、地质条件等综合作用的结果;水样pH的平均值为7.75,总溶解固体(TDS)的均值为171 mg/L,总硬度(TH)的均值为168 mg/L,总体来看水质较好,大部分能够满足国家和世界卫生组织(WHO)生活饮用水卫生标准,适宜饮用;水样中Ca 2+和Mg 2+为主要阳离子,HCO3 -和SO4 2-为主要的阴离子,主要由碳酸盐的风化和蒸发岩的溶解共同控制且碳酸盐岩风化的过程更为强烈;各边界地区天然水中的生物源物质均远低于国家和WHO标准,表明目前这些地区受人类活动的影响仍较小。 相似文献
980.
CH4 is a kind of important greenhouse gases in atmosphere. The current atmospheric concentration of CH4 is about 1.7ppmv and is increasing at almost 2% per year. The sources of CH4 include paddies, wetland and tundra, insects, the digestive tracts of ruminants, coal mining, biomass burning, and the leakage of natural gas. The total input to the atmosphere lies in the range 300- 550Tg per year. CH4 from paddy fields is about 10% - 20% of total source of atmospheric CH4 (DING, 1997). … 相似文献