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31.
Urban green spaces provide manifold environmental benefits and promote human well‐being. Unfortunately, these services are largely undervalued, and the potential of urban areas themselves to mitigate future climate change has received little attention. In this study, we quantified and mapped city‐wide aboveground carbon storage of urban green spaces in China's capital, Beijing, using field survey data of diameter at breast height (DBH) and tree height from 326 field survey plots, combined with satellite‐derived vegetation index at a fine resolution of 6 m. We estimated the total amount of carbon stored in the urban green spaces to be 956.3 Gg (1 Gg = 109 g) in 2014. There existed great spatial heterogeneity in vegetation carbon density varying from 0 to 68.1 Mg C ha‐1, with an average density of 7.8 Mg C ha?1. As expected, carbon density tended to decrease with urban development intensity (UDI). Likely being affected by vegetation cover proportion and configuration of green space patches, large differences were presented between the 95th and 5th quantile carbon density for each UDI bin, showing great potential for carbon sequestration. However, the interquartile range of carbon density narrowed drastically when UDI reached 60%, signifying a threshold for greatly reduced carbon sequestration potentials for higher UDI. These findings suggested that urban green spaces have great potential to make contribution to mitigating against future climate change if we plan and design urban green spaces following the trajectory of high carbon density, but we should be aware that such potential will be very limited when the urban development reaches certain intensity threshold. 相似文献
32.
The loss of biotic integrity in ecosystems due to human pressure has been receiving much attention from the scientific community.
The primary aim of this study is to understand how the increasing human pressure on natural forests in the Azorean archipelago
(North Atlantic) is affecting their epigean arthropod communities and which biological parameters it affects most. An expert
team did fieldwork covering most of the natural forests (mainly inside nature reserves) of the archipelago using standardized
pitfall trapping. To build a multimetric index we tested a number of taxonomic and ecological parameters that can potentially
be influenced by disturbance. Sixteen of these were found to be significantly influenced by disturbance in forests. We retained
seven metrics due to both, desirable scalability properties and relatively low correlation between them. These included the
percentages of endemic and predator species richness and also predator abundance, which are inversely related to disturbance;
and the percentages of native and saprophagous species richness and introduced and herbivore abundance, which are positively
related to disturbance. All seven metrics were combined in an Index of Biotic Integrity (IBI) value. We then proceeded to
understand which potential disturbance factors are influencing the biotic integrity of communities and how such influence
is felt. Five disturbance factors were found to influence the IBI, although in different ways: the size and fragmentation
of reserves, the distance of sites to the reserve borders, the invasion by alien plants and the density of human paths at
the sites. Given that only percentages of taxonomical or ecological characteristics were chosen as metrics, we tested and
found the scalability of the IBI to be possible, allowing the comparison of sites with different collecting effort or even
the comparison of reserves with different areas and numbers of collecting sites in each. Finally, we propose a novel graphical
representation for multimetric indices like the IBI, one which allows retaining much of the information that is usually lost
in multimetric indices. 相似文献
33.
Reliable information about soil conservation capacities of different natural ecosystems is an important reference for the design of targeted erosion and sediment control strategies. The objective of this paper is to quantify the soil conservation capacities of different natural ecosystems that can represent different climatic zones. The 137Cs technique has been used to estimate soil redistribution rates in different natural ecosystems over the past 40 years in Wolong Nature Reserve. The reserve, transiting from the Chengdu plain to the Qinghai-Tibet plateau, maintains rich ecosystems from subtropical to frigid.The net soil erosion rates of 5 selected ecosystems that represent a warm coniferous-broadleaf-mixed forest, a cold-resistant deciduous taiga forest, a cold-resistant shrub, an evergreen cold-resistant taiga servation capacities are reversed in order. The reference inventories for 137Cs in different ecosystems velop effective erosion and sediment strategies in areas with similar climates should consider natural ecosystem types. 相似文献
34.
Infrared heater arrays for warming ecosystem field plots 总被引:2,自引:0,他引:2
BRUCE A. KIMBALL MATTHEW M. CONLEY SHIPING WANG† XINGWU LIN† CAIYUN LUO† JACK MORGAN‡ DAVID SMITH‡ 《Global Change Biology》2008,14(2):309-320
There is a need for methodology to warm open‐field plots in order to study the likely effects of global warming on ecosystems in the future. Herein, we describe the development of arrays of more powerful and efficient infrared heaters with ceramic heating elements. By tilting the heaters at 45° from horizontal and combining six of them in a hexagonal array, good uniformity of warming was achieved across 3‐m‐diameter plots. Moreover, there do not appear to be obstacles (other than financial) to scaling to larger plots. The efficiency [ηh (%); thermal radiation out per electrical energy in] of these heaters was higher than that of the heaters used in most previous infrared heater experiments and can be described by: ηh= 10 + 25exp(? 0.17 u), where u is wind speed at 2 m height (m s? 1). Graphs are presented to estimate operating costs from degrees of warming, two types of plant canopy, and site windiness. Four such arrays were deployed over plots of grass at Haibei, Qinghai, China and another at Cheyenne, Wyoming, USA, along with corresponding reference plots with dummy heaters. Proportional integral derivative systems with infrared thermometers to sense canopy temperatures of the heated and reference plots were used to control the heater outputs. Over month‐long periods at both sites, about 75% of canopy temperature observations were within 0.5 °C of the set‐point temperature differences between heated and reference plots. Electrical power consumption per 3‐m‐diameter plot averaged 58 and 80 kW h day? 1 for Haibei and Cheyenne, respectively. However, the desired temperature differences were set lower at Haibei (1.2 °C daytime, 1.7 °C night) than Cheyenne (1.5 °C daytime, 3.0 °C night), and Cheyenne is a windier site. Thus, we conclude that these hexagonal arrays of ceramic infrared heaters can be a successful temperature free‐air‐controlled enhancement (T‐FACE) system for warming ecosystem field plots. 相似文献
35.
新疆两盐湖可培养极端嗜盐菌组成及功能多样性研究 总被引:1,自引:0,他引:1
【目的】通过分析不同成盐类型盐湖中的极端嗜盐菌群落组成差异,探究可培养极端嗜盐菌的功能特性。【方法】采集新疆硫酸盐型盐湖七角井和碳酸盐型盐湖南湖的土壤样品,通过平板稀释涂布法分离极端嗜盐菌,经过形态学观察、特征分析获取代表菌株,通过耐盐性测定和16S rRNA基因序列测序等对代表菌株进行鉴定,并对极端嗜盐菌的蛋白酶、淀粉酶、纤维素酶和酯酶活性进行筛选,同时检测苯酚降解能力。【结果】本研究共获得1 679株极端嗜盐菌,代表菌株45株,隶属于5门14个属,古菌数量(70.58%)明显多于细菌,最优盐浓度生长范围为18.4%–20.0%。在属水平上,盐湖中优势类群为古菌的Haloterrigena属(32.94%)和Natrialba属(26.03%),以及细菌的Aquisalimonas属(9.85%)和Aliifodinibius属(8.10%)。两盐湖中,盐度较低的南湖物种丰富度高于七角井盐湖,古菌物种组成相似,均以Haloterrigena属为主;细菌群落组成有差异,南湖以Aquisalimonas属为主,而七角井以Aliifodinibius属为主。功能筛选表明,盐湖中80%的嗜盐... 相似文献
36.
A major aim of synthetic biology is to program novel cellular behavior using engineered gene circuits. Early endeavors focused on building simple circuits that fulfill simple functions, such as logic gates, bistable toggle switches, and oscillators. These gene circuits have primarily focused on single-cell behaviors since they operate intracellularly. Thus, they are often susceptible to cell-cell variations due to stochastic gene expression. Cell-cell communication offers an efficient strategy to coordinate cellular behavior at the population level. To this end, we review recent advances in engineering cell-cell communication to achieve reliable population dynamics, spanning from communication within single species to multispecies, from one-way sender-receiver communication to two-way communication in synthetic microbial ecosystems. These engineered systems serve as well-defined model systems to better understand design principles of their naturally occurring counterparts and to facilitate novel biotechnology applications. 相似文献
37.
S. J. Ormerod 《Journal of Applied Ecology》2003,40(2):204-213
38.
Commentary: Carbon Metabolism of the Terrestrial Biosphere: A Multitechnique Approach for Improved Understanding 总被引:2,自引:0,他引:2
J. G. Canadell H. A. Mooney D. D. Baldocchi J. A. Berry J. R. Ehleringer C. B. Field S. T. Gower D. Y. Hollinger J. E. Hunt R. B. Jackson S. W. Running G. R. Shaver W. Steffen S. E. Trumbore R. Valentini B. Y. Bond 《Ecosystems》2000,3(2):115-130
Understanding terrestrial carbon metabolism is critical because terrestrial ecosystems play a major role in the global carbon
cycle. Furthermore, humans have severely disrupted the carbon cycle in ways that will alter the climate system and directly
affect terrestrial metabolism. Changes in terrestrial metabolism may well be as important an indicator of global change as
the changing temperature signal. Improving our understanding of the carbon cycle at various spatial and temporal scales will
require the integration of multiple, complementary and independent methods that are used by different research communities.
Tools such as air sampling networks, inverse numerical methods, and satellite data (top-down approaches) allow us to study
the strength and location of the global- and continental-scale carbon sources and sinks. Bottom-up studies provide estimates
of carbon fluxes at finer spatial scales and examine the mechanisms that control fluxes at the ecosystem, landscape, and regional
scales. Bottom-up approaches include comparative and process studies (for example, ecosystem manipulative experiments) that
provide the necessary mechanistic information to develop and validate terrestrial biospheric models. An iteration and reiteration
of top-down and bottom-up approaches will be necessary to help constrain measurements at various scales. We propose a major
international effort to coordinate and lead research programs of global scope of the carbon cycle.
Received 7 May 1999; accepted 28 September 1999. 相似文献
39.
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