Differences in seasonality and temperature dependency of stand transpiration and canopy conductance between Japanese cypress (Hinoki) and Japanese cedar (Sugi) in a plantation          下载免费PDF全文

Takami Saito  Tomo'omi Kumagai  Makiko Tateishi  Nakako Kobayashi  Kyoichi Otsuki  Thomas W. Giambelluca 《水文研究》2017,31(10):1952-1965

In this paper, we present an investigation of interspecies differences in transpiration of the 2 most common plantation forest tree species in Japan, both in the family Cupressaceae with different northern limits of native distribution, Japanese cypress (Hinoki; Chamaecyparis obtusa Sieb. et Zucc.) and Japanese cedar (Sugi; Cryptomeria japonica D. Don). The stem sap flow rate was measured in 2 nearby stands of similar leaf area index in a 42‐year‐old plantation. Single‐tree and stand‐scale transpiration rates (E_tre and E_sta, respectively) were observed during an ideal autumn environment. At the stand scale, mean sap flux density of Hinoki was greater than that of Sugi, whereas total sapwood area per ground area was smaller in Hinoki than Sugi. Because the 2 variables had counterbalancing effects on transpiration, E_sta of Hinoki was similar to (94% of) that of Sugi. This offset was also found between the mean E_tre of the 2 species. E_sta was similar between the stands from May to October, whereas E_sta of Sugi was notably greater than that of Hinoki from February to April. During these 3 months, the difference in cumulative E_sta was 21.7 mm, which accounted for 79% of the difference in annual E_sta between Hinoki and Sugi (192 and 219 mm/year, respectively). We found that canopy conductance (G_c) and its sensitivity to the mean vapour pressure deficit during daylight hours in Sugi were particularly high in early spring, whereas those in Hinoki shifted gradually throughout the growing season. This difference was related to the optimal temperature of G_c in Sugi, which was approximately 10 °C lower than that in Hinoki. Our results suggest that plantations of water‐conserving species such as Hinoki produce timber slowly but yield water resources generously. Moreover, for plantations of trees sensitive to high temperature, such as Sugi, managers should be concerned about possible future decline caused by anticipated global warming.  相似文献   

The first record of Cuon alpinus (Pallas, 1811) from Poland and the possible impact of other large canids on the evolution of the species     

Adrian Marciszak  Aleksandra Kropczyk  Grzegorz Lipecki 《第四纪科学杂志》2021,36(6):1101-1121

The presence of Cuon alpinus in Poland is documented here for the first time. Between 650 and 450 ka, Lycaon lycaonoides dominated the open lands, while Cuon alpinus priscus tended to prefer forests, mountains and highlands. Canis mosbachensis coexisted in all these environments. Between 480 and 430 ka, there was a drastic reduction in the number and range of L. lycaonoides. The balance between canids was disturbed and a critical point in the lycaon–wolf relationship was passed. Probably between 450 and 400 ka, the lycaon was too rare to be a real competitor and a limiting factor for the wolf. It was also at this time that the lycaon disappeared completely. With disappearance of the lycaon from Eurasia, there was a slow increase in the body size of the wolf. Between 400 and 300 ka, the dhole and the wolf were still close in body size, but the wolf was slowly increasing in size. Between 300 and 250 ka, the wolf became the dominant dog species and took a niche occupied until then by the lycaon. Because of competition, C. alpinus decreased in body size and adapted to hunting and living in forest, mountain and highland environments.  相似文献   

Why do certain species dominate? What we can learn from a rare case of Microdictyon dominance on a Caribbean reef     

Claire L. A. Dell  Guilherme O. Longo  Carrie Manfrino  Deron E. Burkepile 《Marine Ecology》2020,41(5):e12613

Many Caribbean reefs have shifted from coral dominance to macroalgal dominance, often by brown algae such as Dictyota and Lobophora. However, the north side of Cayman Brac in the Cayman Islands is dominated seasonally by the green macroalga Microdictyon (percent cover of Microdictyon is 4% in the winter and ~40% of the reef in the summer), although it is absent from the south side of the island and the remainder of the country. Indeed, Microdictyon is rare in much of the Caribbean, so this situation on Cayman Brac provides an opportunity to investigate the conditions that facilitate its distribution and dominance. The impact of herbivory, competition, nutrient input and other abiotic conditions were examined as factors that could influence the distribution and dominance of Microdictyon. While herbivory or nutrient input are frequently found to be key drivers of benthic community composition on coral reefs, here consumption of Microdictyon by herbivores was low, and thus, the alga was not subject to strong top-down control by herbivory. So, in this case, neither herbivore abundance nor feeding preference appeared to influence the distribution of Microdictyon. Nutrient input was also similar to both sides of the island suggesting nutrients played little role in differential distribution. But, in a controlled transplant experiment where Microdictyon was protected from herbivory and competition, it experienced almost complete mortality (93.3%) when transplanted to the south side, compared to only 11.8% mortality on the north. The south side was exposed to the strongest wave action 92% of the days in our study and was on average a slight, but significant 0.2°C warmer. Thus, these data suggest physical forcing (i.e. wave exposure) is the most likely factor dictating Microdictyon distribution. Conversely, a combination of reduced herbivory and increased competitive strength may explain the seasonal dominance of Microdictyon on the north side of Cayman Brac. Microdictyon was a competitive inferior to the other common algae in winter but increased in competitive strength to equal other species in summer. These results add to the literature on Microdictyon and on the forces impacting benthic community structure of coral reefs.  相似文献   

不同状态浒苔对东海原甲藻生长的影响     

林锟  杨雪  谭丽菊  王江涛 《海洋学报》2020,42(8):69-75

近年来富营养化等海洋污染现象日益加重，我国近海每年都会暴发浒苔绿潮和微藻赤潮现象。本文在实验室模拟条件下，研究了不同状态不同含量的浒苔（Ulva prolifera），即浒苔新鲜藻体、浒苔培养液和浒苔干粉末与东海原甲藻（Prorocentrum donghaiense）共培养时产生的竞争抑制作用。结果表明，浒苔新鲜藻体、浒苔培养液和浒苔干粉末在初始质量含量大于1 g/L的条件下都会对东海原甲藻产生抑制作用，浒苔干粉末的抑制强度远远超过浒苔培养滤液和浒苔新鲜藻体。在二者共培养时，出现了“低促高抑”的现象，即浒苔含量较低时会促进东海原甲藻的生长，而高含量的浒苔则抑制东海原甲藻的生长，且抑制作用随浒苔含量的升高而增大。浒苔对东海原甲藻的这种抑制作用，一方面可能来自于营养物质的竞争和消耗，另一方面可能来自于浒苔释放的化感物质对东海原甲藻产生的影响。利用浒苔对东海原甲藻的抑制作用，可为东海原甲藻赤潮的生物防治提供一种思路与方法。  相似文献   

中国三大航空公司市场竞争格局及演化研究     

杜德林  王姣娥  王祎 《地理科学进展》2020,39(3):367-376

国航、东航和南航三大国有航空公司在中国航空运输市场具有举足轻重的作用,其市场竞争格局一直是经济学、管理学以及地理学的重要研究议题。论文基于航班时刻表数据,采用市场占有率和市场重叠率等方法,对比分析了2005年和2015年三大航空公司在国内和国际的市场竞争格局及演化特征。研究发现：2005—2015年三大航空公司的市场规模快速扩大,在国内的新增通航机场主要选择中部和西部地区,尤其黑龙江、内蒙古和贵州等是三者新增的主要市场竞争地;三大航空公司在国内市场竞争具有明显的省际差异,分别在各自运营基地具有较大优势,在国内航空运输集中的航段主要表现为两两竞争的格局;国际市场竞争主要集中在东亚和东南亚地区,尤其在日本和韩国市场的竞争激烈。  相似文献   

中国高铁-民航竞争网络的空间演化模式及影响因素   总被引：2，自引：2，他引：0  

王姣娥  景悦  杨浩然 《地理科学》2020,40(5):675-684

随着中国高速铁路与民用航空的快速发展,两者运营网络的空间竞争范围越来越大。从个人出行视角出发,同时拥有高铁与民航直达列车/航班的城市对为出行提供了选择机会,定义为高铁-民航竞争网络。以2007-2015年高铁-民航竞争网络的所有城市对为切入点,尝试刻画其演化过程与模式、网络结构与距离分布规律,并最终总结网络演化的影响因素。研究结论为：① 中国高铁-民航竞争网络在空间上呈现出由东向西、由北向南的扩张趋势,规模不断扩大。② 高铁-民航竞争网络具有向北京、上海等少数城市集聚的特征。③ 高铁-民航竞争网络城市对的距离范围主要分布在800~1 500 km,但运营的列车/航班频率竞争关系的临界值为1 000~1 100 km。④ 高铁-民航竞争网络在空间上遵循核心-核心、核心-边缘自上至下的拓展规律,并主要受城市规模、行政职能等级以及地理空间约束等因素的影响。  相似文献   

2019年探矿工程十大新闻          下载免费PDF全文

本刊编辑部 《探矿工程》2020,47(1):1-4

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Flow Cross K-function: a bivariate flow analytical method     

Ran Tao  Jean-Claude Thill 《International journal of geographical information science》2019,33(10):2055-2071

Spatial flow data represent meaningful interaction activities between pairs of corresponding locations, such as daily commuting, animal migration, and merchandise shipping. Despite recent advances in flow data analytics, there is a lack of literature on detecting bivariate or multivariate spatial flow patterns. In this paper we introduce a new spatial statistical method called Flow Cross K-function, which combines the Cross K-function that detects marked point patterns and the Flow K-function that detects univariate flow clustering patterns. Flow Cross K-function specifically assesses spatial dependence of two types of flow events, in other words, whether one type of flows is spatially associated with the other, and if so, whether this is according to a clustering or dispersion trend. Both a global version and a local version of Flow Cross K-function are developed. The former measures the overall bivariate flow patterns in the study area, while the latter can identify anomalies at local scales that may not follow the global trend. We test our method with carefully designed synthetic data that simulate the extreme situations. We exemplify the usefulness of this method with an empirical study that examines the distributions of taxi trip flows in New York City.  相似文献   

科技地缘政治：从现实到理论——关于地理学加强科技地缘政治研究的思考     

段德忠  杜德斌 《地理科学》2023,43(1):20-30

世界在科技全球化、科技变革和大国科技博弈进程中正步入科技地缘政治时代。全球科技竞合是科技地缘政治时代的主旋律,也是大国博弈的主导形式。文章首先从全球科技竞合现实出发,明确了中国在科技地缘政治时代修正或重构国家科技地缘战略的重要性,认为应对国际国内形势变化,保障国家科技安全,中国需要加强科技地缘政治研究。其次,从时代变迁和地缘政治理论演进的视角阐释了科技地缘政治研究亟需建构新的理论体系和分析范式的原因。在此基础上,系统梳理了地理学、政治学和科技管理领域关于科技地缘政治研究的主要进展和存在的问题,认为：地理学领域的科技地缘政治探索虽详尽地揭示了全球科技竞合的时空特征,但并未从全球科技竞合的表象透视国家科技权力争夺的本质;政治学领域的科技地缘政治探索虽详细追溯了科技进步与地缘政治理论思潮演进和地缘政治格局演变的关系,但其剥离空间的抽象思维无法解释国家围绕一定地理空间进行博弈的现实;科技管理学领域的科技地缘政治探索虽进行了系统的全球科技体系演化与治理的研究,但其研究的立足点忽视了大国科技竞合的本质。鉴于此,提出了未来中国地理学在科技地缘政治研究的主要努力方向。  相似文献   

基于投影加权Voronoi图的GIS空间竞争分析模型研究   总被引：5，自引：1，他引：4  

朱渭宁  马劲松  黄杏元  徐寿成 《测绘学报》2004,33(2):146-150

提出加权Voronoi图的一种新形式--投影加权Voronoi图,由此形成平面剖分中的空隙(竞争三角形)可用于GIS空间竞争分析模型.进而分析不同的剖分模型以及竞争三角形的特性和分布.最后提出这种空间分析方法的应用领域.  相似文献