On the role of small mammals in mediating climatically driven vegetation change

Biotic and abiotic processes jointly influence natural systems, yet opportunities to integrate studies of both processes are uncommon. For two decades we have excluded different subsets of the small mammal community from a series of plots near a grassland-desert ecotone in the northern Chihuahuan Desert. These studies spanned a period of historically high winter rainfall, allowing us to distinguish the effects of climate and small mammals on the composition and patch structure of vegetation. Removal of only kangaroo rats ( Dipodomys ) or of all small mammals led to increased cover of large herbaceous vegetation. The size of vegetative patches increased in all plots but this increase was three times greater where all rodents were removed. Thus, the activity of small mammals that forage under and near shrub canopies appear to significantly inhibit the expansion of existing vegetative patches, and may have a stronger influence on habitat structure than previously recognized.     

A multi-site experiment to test biocontrol effects of wildflower strips in different French climate zones

Sowing of wildflower strips has been integrated in agri-environment schemes of several European countries. Their beneficial effects on natural enemies of pest insects are well documented but (1) the desired spill-over into crop fields has not always been demonstrated, and (2) the need to adapt sown mixtures to regional climatic differences has been rarely addressed.We set up a multi-site experiment in different French climatic regions to compare effects of a wildflower strip with a grass mixture and spontaneous vegetation. The design included five regions, three to five fields per region and the three strip treatments being repeated in each field. We tested strip treatment effects on vegetation (plant species richness, plant and flower cover) and on natural enemies (hoverflies, ladybirds, aphid predation). In a subset, we further analysed the spill-over into winter wheat fields including natural enemies and pest insects (cereal aphids, leaf beetles).The wildflower strip mixture developed well in all regions and increased plant species richness and flower cover compared with grass strips and spontaneous vegetation. We found a corresponding higher hoverfly abundance and aphid predation in wildflower strips that were consistent in all regions, whereas ladybird abundance was not affected. A significantly higher hoverfly abundance, aphid predation and aphid parasitism in wheat fields close to wildflower strips indicated a spill-over. No corresponding margin treatment effects were observed for aphid and leaf beetle abundance in the field. A multivariate analysis comparing the influence of climate and vegetation parameters showed that floral cover better explained variation in natural enemy abundance and predation than climate. Our results demonstrated that similar mixtures of native plants can be used over large climatic gradients to improve biocontrol. Further research is needed to improve spill-over into crop fields and to obtain consistently strong effects in different climate zones.     

Life after establishment: factors structuring the success of a mountain invader away from disturbed roadsides

Climate change and increased anthropogenic activity may both alter the current ranges of non-native plant species in mountainous areas, and could result in increased success of such species at higher elevations in the future. However, the course that management should take is often unclear due to a lack of information about the dynamics of how successful mountain invaders spread away from roadsides. The goals of this study were to determine if patterns of growth of a successful mountain invader, Linaria dalmatica (L.) Mill., (as measured by species cover) were: (1) similar to those of establishment (as measured by probability of occurrence), and (2) structured by the extant plant community. Study sites were established throughout the current elevation range of L. dalmatica in the Greater Yellowstone Ecosystem, and cover of the species was measured along with several vegetative community characteristics. Elevation influenced probability of occurrence (i.e., chance of establishment) for L. dalmatica, but not cover (which represents growth after establishment). L. dalmatica cover was negatively associated with several vegetative community characteristics which did not appear to be influenced by the presence of L. dalmatica. These results suggest that L. dalmatica establishment may be limited by climate, but that spread of established populations away from roadsides is most influenced by properties of the vegetative community. They further suggest that the resident vegetative communities structure the abundance of this invader, and that to limit spread of this species in mountainous areas, disturbance to the existing vegetative communities should be minimized.     

A continent under stress: interactions, feedbacks and risks associated with impact of modified land cover on Australia's climate

Global climate change is the major and most urgent global environmental issue. Australia is already experiencing climate change as evidenced by higher temperatures and more frequent and severe droughts. These impacts are compounded by increasing land use pressures on natural resources and native ecosystems. This paper provides a synthesis of the interactions, feedbacks and risks of natural climate variability, climate change and land use/land cover change (LUCC) impacting on the Australian continent and how they vary regionally. We review evidence of climate change and underlying processes resulting from interactions between global warming caused by increased concentration of atmospheric greenhouse gases and modification of the land surface. The consequences of ignoring the effect of LUCC on current and future droughts in Australia could have catastrophic consequences for the nation's environment, economy and communities. We highlight the need for more integrated, long-term and adaptive policies and regional natural resource management strategies that restore the beneficial feedbacks between native vegetation cover and local-regional climate, to help ameliorate the impact of global warming.     

The effects of arbuscular mycorrhizal fungal inoculation at a roadside prairie restoration site

Arbuscular mycorrhizal fungi (AMF) may play an important role in ecological succession, but few studies have documented the effectiveness of mycorrhizal inoculation at restoration/reclamation sites. At a roadside prairie restoration in Shakopee, Minnesota, we compared AMF root colonization and resulting vegetative cover among four inoculation treatments. After 15 mo of growth, we found that AMF colonization was high in all treatments but was significantly higher in treatments that received AMF inoculum propagated from a local prairie site or commercially available inoculum than the uninoculated control. For the prairie inoculum, this increase in colonization occurred whether the inoculum was applied with seeds in furrows or broadcast with seeds on the soil surface. However, increased colonization did not discernibly affect the restored vegetation; neither total vegetative cover nor the proportion "desired" prairie vegetation differed among inoculation treatments. By the end of the third growing season (27 mo after planting) there were no longer differences in AMF colonization among the inoculation treatments nor were there differences in vegetative cover. It is likely that natural recolonization of the plots by remnant AMF populations at the site limited the duration of the inoculation effect. This natural recolonization, in combination with relatively high soil phosphorus levels, likely rendered inoculation unnecessary. In contrast to previous published studies of AMF inoculation in landscape restorations, this study shows that AMF inoculation may not be warranted under some circumstances.     

Genetic mapping of the chromosome of the cyanobacterium, Anabaena variabilis. Proximity of the structural genes for nitrogenase and ribulose-bisphosphate carboxylase

A cosmid library of DNA from the chromosome of the nitrogen-fixing cyanobacterium, Anabaena variabilis, has been organized into about 40 linkage groups on the basis of cosmid-cosmid hybridization. Nitrogenase and ribulose-bisphosphate carboxylase are protein complexes that are, respectively, active in heterocysts and absent from vegetative cells, and active in vegetative cells and absent from heterocysts. The structural genes for the proteins of these two complexes are found to be in close proximity within one of the linkage groups. Other genes have also been tentatively localized on the basis of heterologous hybridization. Possible methods for linking the defined linkage groups are discussed.     

Long-term Impacts of Contrasting Management of Large Ungulates in the Arctic Tundra-Forest Ecotone: Ecosystem Structure and Climate Feedback

The arctic forest-tundra ecotone (FTE) represents a major transition zone between contrasting ecosystems, which can be strongly affected by climatic and biotic factors. Expected northward expansion and encroachment on arctic tundra in response to climate warming may be counteracted by natural and anthropogenic processes such as defoliating insect outbreaks and grazing/browsing regimes. Such natural and anthropogenic changes in land cover can substantially affect FTE dynamics, alter ground albedo (index of the amount of solar energy reflected back into the atmosphere) and provide important feedbacks into the climate system. We took advantage of a naturally occurring contrast between reindeer grazing regimes in a border region between northern Finland and Norway which was recently defoliated by an outbreak of the geometrid moth. We examined ecosystem-wide contrasts between potentially year-round (but mainly summer) grazed (YRG) regions in Finland and mainly winter grazed (WG) regions in Norway. We also used a remotely sensed vegetation index and albedo to quantify effects on local energy balance and potential climate feedbacks. Although differences in soil characteristics and ground vegetation cover were small, we found dramatic differences in the tree layer component of the ecosystem. Regeneration of mountain birch stands appears to have been severely hampered in the YRG regime, by limiting regeneration from basal shoots and reestablishment of individual trees from saplings. This has led to a more open forest structure and a significant 5% increase in spring albedo in the summer grazed compared to the winter grazed regions. This supports recent suggestions that ecosystem processes in the Arctic can significantly influence the climate system, and that such processes must be taken into account when developing climate change scenarios and adaptation strategies.     

Spatial–Temporal Dynamics in Barrier Island Upland Vegetation: The Overlooked Coastal Landscape

Barrier islands provide the first line of defense against storms for millions of people living in coastal areas. Upland vegetation (that is, grassland, shrubland, and maritime forest) has received little attention, even though this land surface is most strongly affected by development pressures. We use remote-sensing analysis to assess state change on seven undeveloped Virginia barrier islands over 27 years (1984–2011) that are free from direct human influence. Our analysis highlights the spatial–temporally dynamic nature of barrier island upland land area and vegetation, with rapidly changing ecosystem states. Over the time period, upland vegetation was dramatically reduced by 29% whereas woody vegetation cover increased 40% across all islands. Although conversions between sand, grassland, and woody vegetation were variable within each island, three major patterns of vegetative land-cover change were apparent: overall loss of vegetative cover, frequent transitions between grass and woody cover, and gain in woody cover. These patterns are valuable for understanding natural evolution of barrier islands in response to sea-level rise. Evaluation of temporal dynamics in barrier upland is needed to characterize underlying processes including island resilience or chronic stress, and is a prerequisite to sustainable coastal management- and resilience-based planning, especially when implementing ecosystem-based solutions.     

Varying responses in mean surface air temperature from land use/cover change in different seasons over northern China

Research on the impacts of land use change on climate change has become a foremost topic in the field of global climate change research. Although many researchers have studied the impacts of LUCC, data related to these impacts on the Chinese climate system remain sparse because of the diversity of China’s regional changes in land use, especially related to agricultural changes. Therefore, additional studies are needed that address regional LUCC in combination with climate modeling. Two simulations with current land use/cover patterns and potential natural vegetation cover were used to investigate the impact of LUCC on surface air temperature in northern China. Simulations of 11 years of climate in northern China (1 January 1990–31 December 2000) were carried out using Regional Environment Integrated Modeling System 2.0 (RIEMS2.0). The results showed that: (1) When potential natural vegetation cover types were changed to current vegetation cover types, mean summer surface air temperature decreased in the central northeastern area, eastern Gansu Province and Ningxia Hui Autonomous Region, but increased in Shanxi, Henan and Anhui provinces. Also, surface air temperature changed significantly on a local scale in the central northeastern area, central Henan Province and eastern Gansu Province (P < 0.05). In winter, major portions of the study area exhibited non-significant decreases in mean surface air temperature. (2) In summer, a temperate forests removal simulation in northern China behaved more like a tropical forests removal simulation. In winter, removal of the temperate forests in northern China behaved more like a boreal forests removal simulation. In model grids where forest were converted to cropland, the net radiation absorbed has less influence on surface air temperature at lower vs. higher latitudes. Further, latent heat flux has a stronger influence on surface air temperature at lower latitudes.     

我国三北地区植被变化的动因分析

地表植被变化是气候变化、人类活动等多种因素共同作的结果。然而,以往的研究要么集中在与气候变化有关的气象因素,要么集中在与人类活动有关的人为因素,鲜有基于长期数据监测下对自然与社会因素之间相互作用的定量评估。因此,气候变化和人为因素对地表植被变化的相互作用并不明确,各个因素对植被变化影响的量化贡献仍然不确定。为了评价生态修复项目对荒漠化防治的效果、以及在土地荒漠化防治中自然与社会因素对我国植被变化的影响、及其复杂的相互作用机理,该研究应用卫星遥感影像资料,通过面板数据混合回归模型大数据分析方法,计算了1983年至2012年气候变化和人类活动对我国北方地区植被变化的贡献率。结果表明,气候变化和人类活动对NDVI变化均有重要作用,其中人类活动对植被覆盖度变化的影响占58.2%—90.4%、气候变化占9.6%—41.8%;不同地区表现出不同的地理分异特征,并存在时滞效应。由此可见,荒漠化防治必须充分考虑不同因素的综合作用和地域特征,才能取得事半功倍的效果。研究结果较好地体现了卫星遥感影像资料在大尺度(省域尺度)下与社会经济统计指标的融合,为进一步中尺度(县域尺度)研究提供了方法借鉴。     

论边坡的生态恢复

对裸露边坡采用植被防护的方式日益引起全球重视,但边坡植被恢复是一项比较复杂的工程,本文阐述了边坡植被的功能,生态恢复的原理,植物品种的筛选,边坡生态恢复的方法及应用,边坡生态恢复的发展方向。     

Natural Hazards in a Changing World: A Case for Ecosystem-Based Management

Communities worldwide are increasingly affected by natural hazards such as floods, droughts, wildfires and storm-waves. However, the causes of these increases remain underexplored, often attributed to climate changes or changes in the patterns of human exposure. This paper aims to quantify the effect of climate change, as well as land cover change, on a suite of natural hazards. Changes to four natural hazards (floods, droughts, wildfires and storm-waves) were investigated through scenario-based models using land cover and climate change drivers as inputs. Findings showed that human-induced land cover changes are likely to increase natural hazards, in some cases quite substantially. Of the drivers explored, the uncontrolled spread of invasive alien trees was estimated to halve the monthly flows experienced during extremely dry periods, and also to double fire intensities. Changes to plantation forestry management shifted the 1∶100 year flood event to a 1∶80 year return period in the most extreme scenario. Severe 1∶100 year storm-waves were estimated to occur on an annual basis with only modest human-induced coastal hardening, predominantly from removal of coastal foredunes and infrastructure development. This study suggests that through appropriate land use management (e.g. clearing invasive alien trees, re-vegetating clear-felled forests, and restoring coastal foredunes), it would be possible to reduce the impacts of natural hazards to a large degree. It also highlights the value of intact and well-managed landscapes and their role in reducing the probabilities and impacts of extreme climate events.     

Climate change alters plant biogeography in Mediterranean prairies along the West Coast,USA

Projected changes in climate are expected to have widespread effects on plant community composition and diversity in coming decades. However, multisite, multifactor climate manipulation studies that have examined whether observed responses are regionally consistent and whether multiple climate perturbations are interdependent are rare. Using such an experiment, we quantified how warming and increased precipitation intensity affect the relative dominance of plant functional groups and diversity across a broad climate gradient of Mediterranean prairies. We implemented a fully factorial climate manipulation of warming (+2.5–3.0 °C) and increased wet‐season precipitation (+20%) at three sites across a 520‐km latitudinal gradient in the Pacific Northwest, USA. After seeding with a nearly identical mix of native species at all sites, we measured plant community composition (i.e., cover, richness, and diversity), temperature, and soil moisture for 3 years. Warming and the resultant drying of soils altered plant community composition, decreased native diversity, and increased total cover, with warmed northern communities becoming more similar to communities further south. In particular, after two full years of warming, annual cover increased and forb cover decreased at all sites mirroring the natural biogeographic pattern. This suggests that the extant climate gradient of increasing heat and drought severity is responsible for a large part of the observed biogeographic pattern of increasing annual invasion in US West Coast prairies as one moves further south. Additional precipitation during the rainy season did little to relieve drought stress and had minimal effects on plant community composition. Our results suggest that the projected increase in drought severity (i.e., hotter, drier summers) in Pacific Northwest prairies may lead to increased invasion by annuals and a loss of forbs, similar to what has been observed in central and southern California, resulting in novel species assemblages and shifts in functional composition, which in turn may alter ecosystem functions.     

Soil chemistry and mineral problems in farm livestock. A review

A review is made of the influence of soil chemistry and soil characteristics on the occurrence of mineral problems in farm livestock, with major emphasis on ruminants maintained on pastures and forages. The review is developed in two sections: (1) a general discussion of factors affecting transfer of elements through the soil—plant—animal complex, with some reference to techniques employed in assessing problems of animal health; (2) a more detailed review of certain mineral deficiency and toxicity conditions in livestock caused by specific elements for which a relationship with soil properties has been clearly demonstrated on an international basis. This includes phosphorus, calcium, magnesium, copper, molybdenum, cobalt, selenium, iodine and fluorine. The relationships are, in general, quite complex and affected not only by geology and soil chemistry but by climate, intensity of the agricultural systems, nature of the vegetative cover and characteristics and management of the grazing animal.     

Vegetation cover—another dominant factor in determining global water resources in forested regions

Forested catchments provide critically important water resources. Due to dramatic global forest change over the past decades, the importance of including forest or vegetation change in the assessment of water resources under climate change has been highly recognized by Intergovernmental Panel on Climate Change (IPCC); however, this importance has not yet been examined quantitatively across the globe. Here, we used four remote sensing‐based indices to represent changes in vegetation cover in forest‐dominated regions, and then applied them to widely used models: the Fuh model and the Choudhury‐Yang model to assess relative contributions of vegetation and climate change to annual runoff variations from 2000 to 2011 in forested landscape (forest coverage >30%) across the globe. Our simulations show that the global average variation in annual runoff due to change in vegetation cover is 30.7% ± 22.5% with the rest attributed to climate change. Large annual runoff variation in response to vegetation change is found in tropical and boreal forests due to greater forest losses. Our simulations also demonstrate both offsetting and additive effects of vegetation cover and climate in determining water resource change. We conclude that vegetation cover change must be included in any global models for assessing global water resource change under climate change in forest‐dominant areas.     

Tipping points in tropical tree cover: linking theory to data

It has recently been found that the frequency distribution of remotely sensed tree cover in the tropics has three distinct modes, which seem to correspond to forest, savanna, and treeless states. This pattern has been suggested to imply that these states represent alternative attractors, and that the response of these systems to climate change would be characterized by critical transitions and hysteresis. Here, we show how this inference is contingent upon mechanisms at play. We present a simple dynamical model that can generate three alternative tree cover states (forest, savanna, and a treeless state), based on known mechanisms, and use this model to simulate patterns of tree cover under different scenarios. We use these synthetic data to show that the hysteresis inferred from remotely sensed tree cover patterns will be inflated by spatial heterogeneity of environmental conditions. On the other hand, we show that the hysteresis inferred from satellite data may actually underestimate real hysteresis in response to climate change if there exists a positive feedback between regional tree cover and precipitation. Our results also indicate that such positive feedback between vegetation and climate should cause direct shifts between forest and a treeless state (rather than through an intermediate savanna state) to become more likely. Finally, we show how directionality of historical change in conditions may bias the observed relationship between tree cover and environmental conditions.     

遥感探测土地植被覆盖指数的准确度评估

GIS数据的准确度一直是GIS应用的考虑事项。用虚例和实例揭示了土地植被覆盖指数的准确度与图像分类的准确度之间的复杂关系,并进一步用数学方式进行了解释。土地植被覆盖指数的准确度取决于图像分类准确度,但与分类总准确度没有直接关系。用户和产家准确度比总准确度对土地植被覆盖指数的准确度具有更直接的控制,所以在图像分类报告中不应被忽略为了保证土地植被覆盖指数的准确度,某土地类型的用户和产家准确度应该尽可能一致,同时要使得这两个准确度数值越高越好。     

Differences in pattern of a DNA protein complex isolated from vegetative cells and spores of Bacillus subtilis.

Summary A DNA protein complex has been isolated from vegetative cells and spores of Bacillus subtilis. Properties of the DNA protein complex prepared from vegetative cells were studied and SDS gel electrophoresis was employed to compare the different DNase-untreated and-treated DNA protein complexes. It is concluded that proteins are associated with the DNA and differences in protein pattern in polyacrylamide gels indicates the involvement of DNA-binding proteins in the regulation of spore formation.     

Possibilities and limitations of seed production of Catharanthus roseus (L.) G. Don under Polish climatic conditions

The studies were carried out at Radzików, Central Poland in the years 1982–1991, using a progeny of an Indian population. It was proved that Catharanthus roseus may be grown in Poland under field conditions as an annual crop, using plants previously raised in glass or plastic houses. However, the culture of C. roseus in the greenhouse resulted in a higher yield of herb and particularly in a better setting of fruits and seeds than under field conditions. The yield of seeds obtained under cover was several times higher than in the field. Growing of plants under cover may be justified, as greenhouses usually are not utilised in the summertime. Consequent mass selection conducted during successive seasons has lead to obtaining the lines better adapted to the conditions of a cool climate and hence more productive. Improvement of generative traits, resulting from selection, was more pronounced than improvement of the vegetative indices. The ‘yellow silique’ has been recognised as an optimal stage for harvest, as at this stage siliques could be easily separated from the stems, whereas the risk of seed shedding was still minimal. Germinability of seeds obtained from siliques harvested at this stage was high and uniform.     

Adaptation of <Emphasis Type="Italic">Pteridium aquilinum</Emphasis> (L.) Kuhn in Siberia

The study has revealed some specific ecological and biological characteristics of bracken that facilitate not only its adaptation to temperate climate, but also dominance in the herbaceous cover, and advancement into new areas within its range. It has been shown that the ecological optimum of bracken is oceanic climate and in Siberia the fern occurs at the northern limits of its range.