University of Peradeniya

About: University of Peradeniya is a education organization based out in Kandy, Sri Lanka. It is known for research contribution in the topics: Population & Poison control. The organization has 5970 authors who have published 7388 publications receiving 197002 citations.

Plant diversity increases with the strength of negative density dependence at the global scale.

Abstract: Theory predicts that higher biodiversity in the tropics is maintained by specialized interactions among plants and their natural enemies that result in conspecific negative density dependence (CNDD). By using more than 3000 species and nearly 2.4 million trees across 24 forest plots worldwide, we show that global patterns in tree species diversity reflect not only stronger CNDD at tropical versus temperate latitudes but also a latitudinal shift in the relationship between CNDD and species abundance. CNDD was stronger for rare species at tropical versus temperate latitudes, potentially causing the persistence of greater numbers of rare species in the tropics. Our study reveals fundamental differences in the nature of local-scale biotic interactions that contribute to the maintenance of species diversity across temperate and tropical communities.

Global mortality from firearms, 1990-2016

Abstract: Importance Understanding global variation in firearm mortality rates could guide prevention policies and interventions. Objective To estimate mortality due to firearm injury deaths from 1990 to 2016 in 195 countries and territories. Design, Setting, and Participants This study used deidentified aggregated data including 13 812 location-years of vital registration data to generate estimates of levels and rates of death by age-sex-year-location. The proportion of suicides in which a firearm was the lethal means was combined with an estimate of per capita gun ownership in a revised proxy measure used to evaluate the relationship between availability or access to firearms and firearm injury deaths. Exposures Firearm ownership and access. Main Outcomes and Measures Cause-specific deaths by age, sex, location, and year. Results Worldwide, it was estimated that 251 000 (95% uncertainty interval [UI], 195 000-276 000) people died from firearm injuries in 2016, with 6 countries (Brazil, United States, Mexico, Colombia, Venezuela, and Guatemala) accounting for 50.5% (95% UI, 42.2%-54.8%) of those deaths. In 1990, there were an estimated 209 000 (95% UI, 172 000 to 235 000) deaths from firearm injuries. Globally, the majority of firearm injury deaths in 2016 were homicides (64.0% [95% UI, 54.2%-68.0%]; absolute value, 161 000 deaths [95% UI, 107 000-182 000]); additionally, 27% were firearm suicide deaths (67 500 [95% UI, 55 400-84 100]) and 9% were unintentional firearm deaths (23 000 [95% UI, 18 200-24 800]). From 1990 to 2016, there was no significant decrease in the estimated global age-standardized firearm homicide rate (−0.2% [95% UI, −0.8% to 0.2%]). Firearm suicide rates decreased globally at an annualized rate of 1.6% (95% UI, 1.1-2.0), but in 124 of 195 countries and territories included in this study, these levels were either constant or significant increases were estimated. There was an annualized decrease of 0.9% (95% UI, 0.5%-1.3%) in the global rate of age-standardized firearm deaths from 1990 to 2016. Aggregate firearm injury deaths in 2016 were highest among persons aged 20 to 24 years (for men, an estimated 34 700 deaths [95% UI, 24 900-39 700] and for women, an estimated 3580 deaths [95% UI, 2810-4210]). Estimates of the number of firearms by country were associated with higher rates of firearm suicide ( P R2 = 0.21) and homicide ( P R2 = 0.35). Conclusions and Relevance This study estimated between 195 000 and 276 000 firearm injury deaths globally in 2016, the majority of which were firearm homicides. Despite an overall decrease in rates of firearm injury death since 1990, there was variation among countries and across demographic subgroups.

Thermal limits of leaf metabolism across biomes.

Abstract: High-temperature tolerance in plants is important in a warming world, with extreme heat waves predicted to increase in frequency and duration, potentially leading to lethal heating of leaves. Global patterns of high-temperature tolerance are documented in animals, but generally not in plants, limiting our ability to assess risks associated with climate warming. To assess whether there are global patterns in high-temperature tolerance of leaf metabolism, we quantified Tcrit (high temperature where minimal chlorophyll a fluorescence rises rapidly and thus photosystem II is disrupted) and Tmax (temperature where leaf respiration in darkness is maximal, beyond which respiratory function rapidly declines) in upper canopy leaves of 218 plant species spanning seven biomes. Mean site-based Tcrit values ranged from 41.5 °C in the Alaskan arctic to 50.8 °C in lowland tropical rainforests of Peruvian Amazon. For Tmax, the equivalent values were 51.0 and 60.6 °C in the Arctic and Amazon, respectively. Tcrit and Tmax followed similar biogeographic patterns, increasing linearly (˜8 °C) from polar to equatorial regions. Such increases in high-temperature tolerance are much less than expected based on the 20 °C span in high-temperature extremes across the globe. Moreover, with only modest high-temperature tolerance despite high summer temperature extremes, species in mid-latitude (~20–50°) regions have the narrowest thermal safety margins in upper canopy leaves; these regions are at the greatest risk of damage due to extreme heat-wave events, especially under conditions when leaf temperatures are further elevated by a lack of transpirational cooling. Using predicted heat-wave events for 2050 and accounting for possible thermal acclimation of Tcrit and Tmax, we also found that these safety margins could shrink in a warmer world, as rising temperatures are likely to exceed thermal tolerance limits. Thus, increasing numbers of species in many biomes may be at risk as heat-wave events become more severe with climate change.

The Imperata grasslands of tropical Asia: area, distribution, and typology

Abstract: The rehabilitation or intensified use of Imperata grasslands will require a much better understanding of their area, distribution, and characteristics We generated estimates of the area of Imperata grasslands in tropical Asia, and suggested a typology of Imperata grasslands that may be useful to define the pathways toward appropriate land use intensification We conclude that the area of Imperata grasslands in Asia is about 35 million ha This about 4% of the total land area The countries with the largest area of Imperata grasslands are Indonesia (85 million ha) and India (80 million ha) Those with the largest proportion of their surface area covered with Imperata are Sri Lanka (23%), the Philippines (17%), and Vietnam (9%) Laos, Thailand, Myanmar, and Bangladesh evidently all have similar proportions of their land area infested with Imperata (about 3 to 4%) Malaysia (< 1%), Cambodia (1%), and the southern part of China (2%) have but a minor proportion of their total land area in Imperata The species was found widely distributed on the full range of soil orders It occupied both fertile (eg some of the Inceptisols and Andisols) and infertile soils (Ultisols and Oxisols) across a wide range of climates and elevations Imperata lands fall into four mapping scale-related categories: Mega-grasslands, itmacro-grasslands, meso-grasslands, and micro-grasslands The mega-grasslands are often referred to as ‘sheet Imperata’ They are the large contiguous areas of Imperata that would appear on small-scale maps of say 1:1,000,000 We propose that this basic typology be supplemented with a number of additional components that have a key influence on intensification pathways: land quality, market access, and the source of power for tillage The typology was applied in a case study of Indonesian villages in the vicinity of Imperata grasslands We propose an international initiative to map and derive a more complete and uniform picture of the area of the Imperata grasslands This should include selected studies to understand conditions at the local level These are critical to build the appreciation of change agents for the indigenous systems of resource exploitation, and how they relate to local needs, values and constraints

Soil Lead Bioavailability and in Situ Remediation of Lead-Contaminated Soils: A Review

Abstract: The environmental risk from soil lead (Pb) is related to its bioavailability. Soil Pb bioavailability depends on the solubility of Pb solid phases and other site-specific soil chemistry, suggesting that in situ stabilization of soil Pb can be accomplished by changing soil Pb chemistry. This paper presents a review of soil Pb bioavailability and an evaluation of in situ stabilization methods that can be used to reduce Pb bioavailability. A promising in situ approach involves the amendment of Pb-contaminated soil with phosphorus (P) in various forms or P with other amendments. Two general categories of P are insoluble forms, such as phosphate rock or synthetic apatites, and soluble forms typically present in commercially available fertilizer products or phosphoric acid. Numerous indirect assessment techniques show marked reductions in soil Pb biovailability upon addition of P and other amendments to Pb-contaminated soils. The techniques include physiologically based extraction tests, plant uptake of Pb, and other soil Pb extraction methods. More directly, animal feeding studies also show reductions in soil Pb biovailability. In situ stabilization of soil Pb using P and other soil amendments is an emerging technology integrating soil chemistry, agricultural practices, and engineering that is gaining public and regulatory acceptance. © 2004 American Institute of Chemical Engineers Environ Prog, 23: 78–93, 2004