Alien plant species coexist over time with native ones in Chilean Mediterranean grasslands

Aims Alien species are commonly considered as harmful weeds capable of decreasing native biodiversity and threatening ecosystems. Despite this assumption, little is known about the long-term patterns of the native–alien relationships associated with human disturbed managed landscapes. This study aims to elucidate the community dynamics associated with a successional gradient in Chilean Mediterranean grasslands, considering both native and alien species.Methods Species richness (natives and aliens separately) and life-form (annuals and perennials) were recorded in four Chilean post-agricultural grazed grasslands each covering a broad successional gradient (from 1 to 40 years since crop abandonment). A detrended correspondence analysis (DCA), mixed model effects analyses and correlation tests were conducted to assess how this temporal gradient influenced natives and aliens through community dynamics.Important findings Our results show different life-form patterns between natives and aliens over time. Aliens were mainly represented by annuals (especially ruderals and weeds), which were established at the beginning of succession. Annual aliens also predominated at mid-successional stages, but in old grasslands native species were slightly more representative than alien ones within the community. In the late successional states, positive or no correlations at all between alien and native species richness suggested the absence of competition between both species groups, as a result of different strategies in occupation of the space. Community dynamics over time constitute a net gain in biodiversity, increasing natives and maintaining a general alien pool, allowing the coexistence of both. Biotic interactions including facilitation and/or tolerance processes might be occurring in Chilean post-agricultural grasslands, a fact that contradicts the accepted idea of the alien species as contenders.     

Carbon dioxide exchange and biomass productivity of the herbaceous layer of a managed tropical humid savanna ecosystem in western Kenya

Aims Humid savannas, as a result of high precipitation amounts, are highly productive. They are also hotspots for land use change and potential sources of carbon dioxide (CO₂) due to the large soil carbon (C) stocks. Understanding how ecosystem CO₂ exchange is influenced by changes arising from agricultural land use is vital in future management of these ecosystems and in responding to the ongoing shifts in management and climate. The aim of this study was to identify how ecosystem CO₂ exchange and biomass productivity of the herbaceous layer of a humid savanna in Kenya respond to current management practices.Methods We used flux chambers to quantify CO₂ fluxes, while monthly harvests were undertaken to determine biomass development of the herbaceous layer of three sites that were (i) fenced to exclude livestock grazing, (ii) subjected to grazing by livestock and (iii) abandoned after being cultivated for maize production and also open to grazing by livestock.Important findings The peak aboveground biomass ranged between 380 and 1449g m ?2 and biomass production was significantly (P < 0.05) lower in the grazed and abandoned plots. The maximum gross primary production (GPP) and net ecosystem CO₂ exchange (NEE) ranged between 21.8±1.3 to 32.5±2.7 and ?9.6±0.7 to^-17.9±4.8 μmol m ?2 s^-1, respectively. Seasonal NEE fluctuations ranged between 10 and 21 μmol m ?2 s^-1, while spatial (among sites) differences ranged between 2 and 10 μmol m ?2 s^-1. Ecosystem respiration (R eco) fluctuated between 5 and 10 μmol m ?2 s^-1 during the growing season. R eco was, however, not significantly different among the sites. Unlike in other similar ecosystems where ecosystem respiration is determined by the ambient temperature, we did not find any relationship between R eco and temperature in this savanna. Instead, soil moisture accounted for 38–88% of the spatial and seasonal fluctuations in ecosystem CO₂ fluxes and aboveground biomass production. Management influenced the maximum GPP and NEE rates through modification of soil moisture, plant species composition and aboveground biomass. We concluded that soil moisture is the key determinant of ecosystem CO₂ exchange and productivity in this tropical savanna. Management, however, significantly modifies C fluxes and productivity through its influence on soil moisture, plant species composition and aboveground green biomass and should be taken into consideration in future similar studies.     

Cattle change plant reproductive phenology,promoting community changes in a post-fire Nothofagus forest in northern Patagonia,Argentina

Aims Variations in rates and length of flowering and fruiting not only affect the reproduction of a given plant species but also the behavior and reproduction of associated taxa. Flowering and fruiting variations may be influenced by herbivory, especially by large mammals. The aim of this study was to determine the effects of cattle browsing on the reproductive phenology of understory species in a subalpine post-fire Nothofagus forest in Patagonia.Methods The effects of herbivory on plant reproductive phenology were studied in a set of experimental exclosures (fenced plots) installed since 2001 in a post-fire N. pumilio forest, located in Nahuel Huapi National Park (NHNP), Argentina. We monitored the beginning and duration of each reproductive phenological stage: floral bud, open flower, immature fruit and mature fruit. We also counted the number of flowers, fruits, seeds and viable seeds of the dominant plants to assess whether browsing modifies temporal patterns of the flowering and fruiting periods.Important findings Cattle reduced the total number of species flowering and fruiting and changed the reproductive phenology of some species. We found that palatable species seem to be negatively affected by browsing in terms of reduced fitness due to changes in flowering and fruiting periods. In contrast, cattle benefitted the reproduction of non-palatable species and could promote the invasion of shade-intolerant exotic forbs such as Cirsium vulgare. The effects of livestock reported in this study are important to understanding how browsing could alter native species establishment and possibly alter successional trajectories during recolonization after fire.     

Livestock Protection Dogs for Deterring Deer From Cattle and Feed

Abstract: Disease transmission between wildlife and livestock is a worldwide issue. Society needs better methods to prevent interspecies transmission to reduce disease risks. Producers have successfully used livestock protection dogs (LPDs) for thousands of years to reduce predation. We theorized that LPDs raised and bonded with cattle could be used to also reduce risk of bovine tuberculosis (Myobacterium bovis; TB) transmission between white-tailed deer (Odocoileus virginianus) and cattle by minimizing contact between the 2 species and use of cattle feed by deer. We evaluated 4 LPDs over 5 months, utilizing 2 data collection methods (direct observation and motion-activated video) on deer farms that supported higher densities than wild populations. Dogs were highly effective in preventing deer from using concentrated cattle feed (hay bales), likely the greatest risk factor of TB transmission on farms. Dogs also prevented deer from approaching cattle in core areas of pastures (near hay bales) and were very effective throughout pastures. Our research supports the theory that LPDs, specifically trained to remain with cattle, may be a practical tool to minimize potential for livestock to contract TB from infected deer in small-scale cattle operations. Where disease is present in deer, it may be possible to reduce the potential for disease transmission by employing LPDs.     

Linkage disequilibrium and the genetic distance in livestock populations: the impact of inbreeding

Genome-wide linkage disequilibrium (LD) is subject to intensive investigation in human and livestock populations since it can potentially reveal aspects of a population history, permit to date them and help in fine-gene mapping. The most commonly used measure of LD between multiallelic loci is the coefficient D''. Data based on D'' were recently published in humans, livestock and model animals. However, the properties of this coefficient are not well understood. Its sampling distribution and variance has received recent attention, but its expected behaviour with respect to genetic or physical distance remains unknown. Using stochastic simulations of populations having a finite size, we show that D'' fits an exponential function having two parameters of simple biological interpretation: the residual value (rs) towards which D'' tends as the genetic distance increases and the distance R at which this value is reached. Properties of this model are evaluated as a function of the inbreeding coefficient (F). It was found that R and rs increase when F increases. The proposed model offers opportunities to better understand the patterns and the origins of LD in different populations and along different chromosomes.     

Spatial and temporal dynamics of methane emissions from agricultural sources in China

Agricultural activities contribute significantly to the global methane budget. Agricultural sources of methane are influenced by land‐use change, including changes in agricultural area, livestock keeping and agricultural management practices. A spatially explicit inventory of methane emissions from agriculture is made for China taking the interconnections between the different agricultural sources into account. The influence of land‐use change on methane emissions is studied by linking a dynamic land‐use change model with emission calculations. The land‐use change model calculates changes in rice area and livestock numbers for a base‐line scenario. Emissions are calculated for 1991 based on land‐use statistics and for 2010 based on simulated changes in land‐use patterns. Emissions from enteric fermentation and manure management are based on emission factors, while emissions from rice paddies involve the calculation of total organic carbon added to rice paddy soils and assume that a constant fraction is emitted as methane. Spatial patterns of emissions are presented for the different sources. For the land‐use scenario considered it is expected that total methane emissions from agricultural sources in China increase by 11% while the relative contribution of rice fields to the emission decreases. Emissions from manure management are expected to become more important. These results indicate that agencies should anticipate changes in source strengths as a consequence of land‐use changes when proposing mitigation strategies and future national greenhouse gas budgets.     

Fate of Escherichia coli O145 present naturally in bovine slurry applied to vegetables before harvest,after washing and simulated wholesale and retail distribution

Aims

To determine the fate of Escherichia coli on vegetables that were processed through commercial wash treatments and stored under simulated retail conditions at 4°C or wholesale at fluctuating ambient temperatures (0–25°C, dependent on season).

Methods and Results

Bovine slurry that was naturally contaminated with E. coli O145 was applied without dilution or diluted 1:10 using borehole water to growing potatoes, leeks or carrots. Manure was applied 1 week prior to harvest to simulate a near‐harvest contamination event by manure deposition or an application of contaminated water to simulate a flooding event or irrigation from a contaminated water source. At harvest, crops were contaminated at up to 2 log cfu g^?1. Washing transferred E. coli into the water of a flotation tank used for potato washing and did not completely remove all traces of contamination from the crop. Manure‐contaminated potatoes were observed to contain 0·72 cfu E. coli O145 g^?1 after processing and retail storage. Manure‐contaminated leeks harboured 0·73–1·55 cfu E. coli O145 g^?1 after washing and storage. There was no cross‐contamination when leeks were spray washed. Washing in an abrasive drum resulted in less than perfect decontamination for manure‐contaminated carrots. There were five post‐distribution isolations from carrots irrigated with contaminated water 24 h prior to harvest.

Conclusions

Standard commercial washing and distribution conditions may be insufficient to reliably control human pathogenic E. coli on fresh produce.

Significance and Impact

Previous speculation that the cause of a UK foodborne disease outbreak was soil from imperfectly cleaned vegetables is plausible.     

Identification of human–carnivore conflict hotspots to prioritize mitigation efforts

Human–carnivore conflict is a primary driver of carnivore declines worldwide and resolving these conflicts is a conservation priority. However, resources to mitigate conflicts are limited and should be focused on areas of highest priority. We conducted 820 semistructured interviews with community members living within Kenya's Maasai Mara ecosystem. A multiscale analysis was used to determine the influence of husbandry and environmental factors on livestock depredation inside livestock enclosures (bomas). Areas with a high proportion of closed habitat and protected areas had the highest risk of depredation. Depredation was most likely to occur at weak bomas and at households where there were fewer dogs. We used the results to identify potential conflict hotspots by mapping the probability of livestock depredation across the landscape. 21.4% of the landscape was classified as high risk, and within these areas, 53.4% of the households that were interviewed had weak bomas. Synthesis and applications. With limited resources available to mitigate human–carnivore conflicts, it is imperative that areas are identified where livestock is most at risk of depredation. Focusing mitigation measures on high‐risk areas may reduce conflict and lead to a decrease in retaliatory killings of predators.     

Could we live with reintroduced large carnivores in the UK?

1. Literature on the wolf Canis lupus, brown bear Ursus arctos and lynx Lynx lynx is reviewed to determine if sufficient semi‐natural habitat exists in the UK for a viable population of any of these species and to assess the potential risks to human safety, livestock and economically valuable wildlife. Public attitudes to the recovery and reintroduction of some other mammals are also briefly reviewed. 2. The large home range sizes and low population densities of large carnivores mean that the Scottish Highlands is the only UK region with the potential to support a viable population. Human population density is also lower in the Highlands and the density of wild ungulate prey higher than in many parts of Europe where large carnivores survive. 3. Attacks on people have been recorded in Europe for healthy bears and for rabid bears and wolves but there are no reports of attacks by lynx. Bears are more carnivorous in the north of their range than in the south and although wild mammals seldom appear to be important prey serious predation of livestock can occur. Livestock predation is also reported for the wolf and the lynx but they appear to prefer wild prey if available. However, mass kills of up to 100 or more sheep are occasionally recorded for wolves. 4. Attitudes to reintroductions and carnivores generally tend to be favourable amongst the general public, but negative amongst those most likely to be adversely affected. Fears for human safety and significant livestock predation with bears and wolves, respectively, suggest that reintroduction of these species is unlikely to be acceptable in the foreseeable future. Reintroduction of the lynx may be feasible but habitat suitability and potential impact on vulnerable native wildlife need to be assessed. Socio‐economic and legal issues also need to be addressed before such a reintroduction is considered.     

高寒草地生态经济系统价值流、畜群结构、最优控制管理及可持续发展

高寒草地是中国西部青藏高原地区重要的生态系统,该系统直接和该地区少数民族的民生相联系。由于长期过度放牧,该系统已经开始严重退化,而单纯的保护将会与当地畜牧业发展发生冲突。为了能深入地认识高寒草地牧业生态经济系统存在的经济规律,本砑究以甘南合作藏族自治州畜牧业经济为对象,首先从生态经济学角度以货币为计量标度,定量分析了一个以草地牧业为主的高寒牧区生态经济复合系统中单位面积上能流过程和价值流过程,解释该生态经济系统的耦合关系。然后利用线性规划方法,对该系统中的关键问题,即畜群结构进行优化分析并提出优化方案。最后利用最优控制方法,对放牧及刈割强度进行分析,提出合理的放牧强度模式,使高寒草地的经济效益与生态效益达到最佳平衡。利用这3种方法建立起高寒草地生态经济复合系统的可持续发展监督和管理模式,用价值流分析明确系统的价值走向和倍增效应,用线性规划使畜牧业的种内和品种结构达到最优化并使其经济效益最大,利用最优控制方法使畜牧业生产和草地保护有机结合,形成既保护高寒生态系统又改良并发展当地畜牧业的可持续发展模式。