Life Cycle Impacts and Benefits of Wood along the Value Chain: The Case of Switzerland

Sustainable use of wood may contribute to coping with energy and material resource challenges. The goal of this study is to increase knowledge of the environmental effects of wood use by analyzing the complete value chain of all wooden goods produced or consumed in Switzerland. We start from a material flow analysis of current wood use in Switzerland. Environmental impacts related to the material flows are evaluated using life cycle assessment–based environmental indicators. Regarding climate change, we find an overall average benefit of 0.5 tonnes carbon dioxide equivalent per cubic meter of wood used. High environmental benefits are often achieved when replacing conventional heat production and energy‐consuming materials in construction and furniture. The environmental performance of wood is, however, highly dependent on its use and environmental indicators. To exploit the mitigation potential of wood, we recommend to (1) apply its use where there are high substitution benefits like the replacement of fossil fuels for energy or energy‐intensive building materials, (2) take appropriate measures to minimize negative effects like particulate matter emissions, and (3) keep a systems perspective to weigh effects like substitution and cascading against each other in a comprehensive manner. The results can provide guidance for further in‐depth studies and prospective analyses of wood‐use scenarios.     

Urban Stormwater Runoff: A New Class of Environmental Flow Problem

Environmental flow assessment frameworks have begun to consider changes to flow regimes resulting from land-use change. Urban stormwater runoff, which degrades streams through altered volume, pattern and quality of flow, presents a problem that challenges dominant approaches to stormwater and water resource management, and to environmental flow assessment. We used evidence of ecological response to different stormwater drainage systems to develop methods for input to environmental flow assessment. We identified the nature of hydrologic change resulting from conventional urban stormwater runoff, and the mechanisms by which such hydrologic change is prevented in streams where ecological condition has been protected. We also quantified the increase in total volume resulting from urban stormwater runoff, by comparing annual streamflow volumes from undeveloped catchments with the volumes that would run off impervious surfaces under the same rainfall regimes. In catchments with as little as 5–10% total imperviousness, conventional stormwater drainage, associated with poor in-stream ecological condition, reduces contributions to baseflows and increases the frequency and magnitude of storm flows, but in similarly impervious catchments in which streams retain good ecological condition, informal drainage to forested hillslopes, without a direct piped discharge to the stream, results in little such hydrologic change. In urbanized catchments, dispersed urban stormwater retention measures can potentially protect urban stream ecosystems by mimicking the hydrologic effects of informal drainage, if sufficient water is harvested and kept out of the stream, and if discharged water is treated to a suitable quality. Urban stormwater is a new class of environmental flow problem: one that requires reduction of a large excess volume of water to maintain riverine ecological integrity. It is the best type of problem, because solving it provides an opportunity to solve other problems such as the provision of water for human use.     

Organic amendment additions to rangelands: A meta‐analysis of multiple ecosystem outcomes

Interest in land application of organic amendments—such as biosolids, composts, and manures—is growing due to their potential to increase soil carbon and help mitigate climate change, as well as to support soil health and regenerative agriculture. While organic amendments are predominantly applied to croplands, their application is increasingly proposed on relatively arid rangelands that do not typically receive fertilizers or other inputs, creating unique concerns for outcomes such as native plant diversity and water quality. To maximize environmental benefits and minimize potential harms, we must understand how soil, water, and plant communities respond to particular amendments and site conditions. We conducted a global meta‐analysis of 92 studies in which organic amendments had been added to arid, semiarid, or Mediterranean rangelands. We found that organic amendments, on average, provide some environmental benefits (increased soil carbon, soil water holding capacity, aboveground net primary productivity, and plant tissue nitrogen; decreased runoff quantity), as well as some environmental harms (increased concentrations of soil lead, runoff nitrate, and runoff phosphorus; increased soil CO₂ emissions). Published data were inadequate to fully assess impacts to native plant communities. In our models, adding higher amounts of amendment benefitted four outcomes and harmed two outcomes, whereas adding amendments with higher nitrogen concentrations benefitted two outcomes and harmed four outcomes. This suggests that trade‐offs among outcomes are inevitable; however, applying low‐N amendments was consistent with both maximizing benefits and minimizing harms. Short study time frames (median 1–2 years), limited geographic scope, and, for some outcomes, few published studies limit longer‐term inferences from these models. Nevertheless, they provide a starting point to develop site‐specific amendment application strategies aimed toward realizing the potential of this practice to contribute to climate change mitigation while minimizing negative impacts on other environmental goals.     

Review of distribution of nitrogen and phosphorus in riparian zones of Chinese inland water bodies

This review tries to explain the effects of river infiltration and the interaction between groundwater and surface water on nitrogen (N) and phosphorus (P) distribution in riparian zones. On the basis of previous studies, this review summarized the distribution characteristics of N and P of 7 different riparian zones in China, compared the water quality of water bodies adjoining these riparian zones, proposed the distribution regularity of N and P in diverse riparian zones. The concentrations of N and P in the riparian zones with better water quality have increasing trend from riverside to upland. And those rivers with poorer water quality have decreasing trend. If the infiltrated concentration of runoff pollutant is more than river pollutant infiltration, the upland soil may obtain higher contaminants. On the contrary, if the concentration of river infiltration is more than that of the runoff, the riverside soil will show higher concentration. Similarly, if those two effects are equivalent, the concentration of N and P in the riparian zone will be low on riverside and upland, and somewhere in the middle will be higher than elsewhere. Clean rivers and polluted rivers taken with different quantity of contaminants will infiltrate diverse concentrations of N and P. It is expected that this review can provide a new theoretical basis for revealing the environmental effects of riparian zones and managing, protecting and restoring the riparian ecosystems.     

Responses of Woody Plants To Human-Induced Environmental Stresses: Issues,Problems, and Strategies for Alleviating Stress

Forest ecosystems are enormously important to mankind.They not only supply wood,foods,medicines,waxes,oils,gums,resins and tannins,but they also regulate climate, hydrology,mineral cycling,soil erosion,and cleansing of air and water.A variety of natural and human-induced environmental stresses have both beneficial and harmful effects on forest ecosystems.However,human-induced stresses are much more harmful than naturally induced disturbances.Human-induced stresses,which often are catastrophic although avoidable,include defor estation,fire,pollution,flooding,and soil compaction.Such stresses variously injure woody plants,impede vegetative and reproductive growth,and induce mortality,largely by causing physiological dysfunction in plants.Human-induced environmental stresses have led to decimation of forest ecosystems,loss of biodiversity,forest declines,and potential global warming. Short-rotation plantations,especially in the tropics,are increasing rapidly,largely to produce wood quickly.Plantations also stabilize soil,prevent water runoff,provide shelter from wind and heat,and relieve pressure for exploiting natural forests.However,plantations alone are unlikely to satisfy society 's growing needs for the products and services that can be provided by woody plant ecosystems.Hence,several multiple concurrent strategies are urgently needed to lessen the many destructive effects of human-induced environmental stresses on woody plants.These include not only the expansion of plantations but also of agroferestry systems and forest reserves as well as the development of innovative silvicultural techniques with a focus on the preservation of natural forests.Conserving sustainability of natural forests will require a land ethic as prelude to understanding the functioning of forest ecosystems,ecological and physiological impacts of disturbances on ecosystems,and the processes involved in recovery of disturbed ecosystems. Many of the harmful effects of pollution,fire,flooding,and soil compaction can be abated by judicious planning to create and perpetuate the critical components of forest stand structure and species composition.Strategies for continuous production of the products and services that can be supplied by woody plants will need to be reinforced by expanded long-term research and close cooperation among forest biologists,social scientists,economists,and regulatory government agencies.     

不同耕作和覆盖方式对紫色丘陵区坡耕地水土及养分流失的影响

采用随机区组试验,研究了四川紫色丘陵区坡耕地不同耕作和覆盖方式对玉米生育期中水土及养分流失的影响。结果表明:秸秆覆盖对减少水土流失和增加玉米产量的效果均优于地膜覆盖。秸秆覆盖能显著减少地表径流(73.9%—86.2%),但增加了壤中流(15.4%—156.4%);使径流总量降低32.5%—66.6%,并极显著降低土壤侵蚀总量达96.4%—98.1%。地膜覆盖虽能在一定程度上减少壤中流和径流总深,但差异未达到显著水平。土壤N平均损失量达37.4kg/hm2,其中70.1%经由壤中流流失。秸秆覆盖虽然增加了一定的壤中流N损失,但能减少N流失总量达12.8%—65.1%。土壤P素损失量相对较小,仅为9.32kg/hm2,并主要随侵蚀泥沙迁移,占流失总量的92.1%。土壤K损失量达183.3kg/hm2,其流失载体也主要是侵蚀泥沙,占96.5%。因此,两种覆盖方式均能显著控制土壤P和K的损失。无论是秸秆还是地膜覆盖,与顺坡垄作相比,横坡垄作均能减少地表径流、地下径流、土壤侵蚀量及氮、磷、钾素总流失量,同时还能提高玉米产量。从简便、增产和防治面源污染的角度考虑,紫色土区坡耕地最适宜的种植方式为平作+秸秆覆盖。     

基于随机森林模型的茹河流域水沙变化及其影响因素研究

水沙关系不协调已成为制约黄河高质量发展的关键问题,揭示径流量与输沙量变化的主要影响因素,对适应生态经济发展条件下的水土流失治理工作具有指导意义。以茹河流域为研究对象,采用M-K检验和Pettitt检验分析茹河流域1989—2019年水沙变化趋势,运用双累积曲线法定量研究了降雨和人类活动对茹河流域径流量、输沙量变化的贡献率,通过随机森林回归分析探索了影响水沙变化的主控因子。结果表明：(1)茹河流域径流量和输沙量峰值对应情况良好,但在2012年之后径流量和输沙量呈现出明显分异,径流量逐渐增加,输沙量平稳减小。(2)茹河流域径流量突变点为1996年和2003年,输沙量突变点为1996年和2004年,影响期的两个阶段中,人类活动对径流量的贡献率分别为95.95%和77.52%,对输沙量的贡献率分别为78.31%和77.91%。(3)显著影响径流量的因子为农作物播种面积、耕地面积、草地面积和人口密度,显著影响输沙量的因子为植被覆盖度、水利环境投资占比、人口密度和工业总产值。(4)农作物播种面积和耕地面积的变化对径流量的影响均呈显著正相关,草地面积和人口密度对径流量响应关系为显著负相关;植被覆盖度...     

Potential for Plant-Based Remediation of Pesticide-Contaminated Soil and Water using Nontarget Plants such as Trees,Shrubs, and Grasses

Appropriate environmental management of pesticides includes their proper application, use of filter strips and riparian buffers to contain pesticides in runoff from fields, prompt cleanup of spills, and treatment processes for wastewater associated with manufacturing and equipment usage. Plants have beneficial effects in the management of pesticide-contaminated soil and water, including direct metabolism of many pesticides, stimulation of microbial activity in the root zone, extraction of contaminated water, and reduction of infiltrating contaminated water. In this work, we review the literature on nontarget plants that can grow in pesticide-contaminated soil and water, and the fate of pesticides in filter strips, riparian buffers, and vegetated remediation environments. Past research indicates that there are significant differences in the tolerance of plants to pesticides present in soil and water, and that some plants are more effective than others in the remediation of pesticide-contaminated soil and water. Thus, there is value in the identification of tolerant plants and favorable plant-based remediation technologies for management of pesticides and contaminated sites.     

A Protocol for Conducting Rainfall Simulation to Study Soil Runoff

Rainfall is a driving force for the transport of environmental contaminants from agricultural soils to surficial water bodies via surface runoff. The objective of this study was to characterize the effects of antecedent soil moisture content on the fate and transport of surface applied commercial urea, a common form of nitrogen (N) fertilizer, following a rainfall event that occurs within 24 hr after fertilizer application. Although urea is assumed to be readily hydrolyzed to ammonium and therefore not often available for transport, recent studies suggest that urea can be transported from agricultural soils to coastal waters where it is implicated in harmful algal blooms. A rainfall simulator was used to apply a consistent rate of uniform rainfall across packed soil boxes that had been prewetted to different soil moisture contents. By controlling rainfall and soil physical characteristics, the effects of antecedent soil moisture on urea loss were isolated. Wetter soils exhibited shorter time from rainfall initiation to runoff initiation, greater total volume of runoff, higher urea concentrations in runoff, and greater mass loadings of urea in runoff. These results also demonstrate the importance of controlling for antecedent soil moisture content in studies designed to isolate other variables, such as soil physical or chemical characteristics, slope, soil cover, management, or rainfall characteristics. Because rainfall simulators are designed to deliver raindrops of similar size and velocity as natural rainfall, studies conducted under a standardized protocol can yield valuable data that, in turn, can be used to develop models for predicting the fate and transport of pollutants in runoff.     

基于环境容量的汶川地震重建规划区环境适宜性评价

基于对四川汶川地震中受灾严重的51个县1271个乡镇的水环境容量估算,对不同地域的环境适宜性进行评价,旨在为震区恢复重建的人口、经济布局提供一定科学依据。水环境容量选择COD和NH3-N两个指标进行评价,首先利用降雨量、径流系数和径流深等参数评价单元的径流量,再根据水环境质量标准、水体自然背景值等参数估算环境容量;进而在水环境污染胁迫程度计算的基础上,进行了环境适宜性评价。结果显示：水环境容量区域性差异明显,北部三省交界区域的乡镇容量较高、东南部四川盆地边缘和内部区域的乡镇容量较高、西部的山区乡镇环境容量低;西南部污染胁迫程度较低,环境适宜性较高;西部自然保护区胁迫程度较大,环境适宜性较低;成都平原附近县域胁迫较大,环境适宜性较低;环境适宜性区域性明显,但也呈现出一定的分散性。     

干旱半干旱区坡面覆被格局的水土流失效应研究进展

植被恢复与建设是控制水土流失的重要措施.在干旱半干旱地区,植被在空间上的分布呈现离散特征,在坡面上形成的裸地-植被镶嵌和植被条带分布等覆被格局对水土流失过程具有重要影响.覆被格局与水土流失关系研究是景观生态学格局与过程研究的重要内容.从植被斑块、坡面覆被格局对水土流失的影响与耦合覆被格局与水土流失的手段和方法三个方面对国内外相关研究进行总结分析.从中发现,植被类型、层次结构和形态特征是植被斑块尺度上影响径流泥沙的关键因素;不同覆被类型的产流产沙特征与覆被格局的准确描述是研究覆被格局水土流失效应的重要基础;坡面覆被格局对水土流失的影响关键在于其改变了径流泥沙运移和汇集的连续性,应重点关注径流泥沙源汇区的连通性和空间分布在水土流失中的作用;以坡面的精确覆被制图为基础,建立基于水土流失过程的覆被格局指数和耦合格局信息的径流与侵蚀模型是定量研究覆被格局影响的有效手段.今后应加强以下研究:以动态系统的观点研究覆被格局的变化对水土流失的影响,系统理解覆被格局与水土流失之间的相互联系与反馈机制,探讨两者间动态关系随尺度变化的规律性并发展尺度上推方法;构建过程意义明确且简单实用的格局指数,将覆被格局与水土流失过程有机联系起来;发展覆被格局的动态信息与产流产沙过程相结合的水文模型,加强对格局与径流泥沙反馈系统的耦合,建立真正意义上的覆被格局-水土流失过程耦合模型.     

基于生态需水保障的农业生态补偿标准

面向流域农业需水和生态需水间的矛盾问题和协调发展的要求,提出了基于生态需水保障的农业生态补偿标准计算方法。其中考虑农业用水定额计算基于生态需水保障的农业用水短缺,引入水分生产函数模型建立保障生态需水量产生的农业用水短缺与产量损失间的关系,根据不同季节作物产量响应系数的变化,定量确定具有时间和等级差异性的农业生态补偿标准。以保障黄河口生态需水引起的山东引黄灌区农业损失补偿标准分析为实例,计算了冬小麦和夏玉米种植户不同等级的生态补偿标准。结论认为,农业生态补偿标准需根据不同的来水过程及生态需水等级确定,面积稳定和保障功能显著的粮食作物应作为补偿标准计算的依据。     

Discharge and the response of biofilms to metal exposure in Mediterranean rivers

The expected response of fluvial biofilms to the environment and metal pollution prevailing under different discharge conditions was investigated. The relationship between inter-annual hydrological variability and metal concentration in water and sediments was explored in Mediterranean rivers (Catalonia, NE Spain) affected by low but chronic metal pollution, using monitoring data provided by the Catalan Water Agency (ACA). During the period investigated (2000–2006), metal pollution was characterized by low water concentrations and high concentrations in sediments. The most consistent pattern was observed for sediment cadmium (Cd) concentrations, showing a positive relationship with annual discharge, reaching values of environmental concern (above ecotoxicological benchmarks). A different pattern was observed for Cu, Zn, and As increasing with flow in some sites and decreasing in others. While Cd seems to proceed from diffuse sources being washed by surface runoff, Zn, Pb, and As may proceed from either diffuse or point-sources in the different river sites investigated. The relevance of diffuse metal pollution in the area of study indicates that polluted landfills runoff might be an important source of metals causing repetitive pulses of high metal concentration in the receiving water courses. The experimental results presented demonstrate that metal effects in fluvial biofilms may be accumulative, increasing the toxicity after repetitive pulse exposures. Since draughts and extreme rain events are expected to increase at higher latitudes due to global change, the sources of metal pollution, its final concentration and potential effects on the fluvial ecosystem may also change following the patterns expected for human-impacted Mediterranean rivers.     

Effects of flooding on wood and bark anatomy of four species in a mangrove forest community

Variation in the wood and bark anatomy of the dominant species of a mangrove forest community in Mexico was evaluated in relation to some environmental factors, and their physiological adaptations to salinity and flooding period are discussed. The forest is characterized by three zones according to the presence of dominant tree species and flooding periodicity. Vessel arrangement and wood and bark ray height are strongly associated with flooding zones where trees are growing. Variance analyses revealed significant differences among zones for these anatomical characteristics. Soil texture and water salinity were the most useful parameters for the prediction of values of anatomical characteristics. More abundant vessels in radial multiples in a shorter flooding period suggest a functional advantage of multiple vessel groups. Taller wood and bark rays in response to prolonged flooding period can be attributed to anoxic conditions. Among zones, significant differences in the vulnerability index of the species were detected, but not with respect to relative conductivity. Significant differences among zones exist for wood and bark characteristics involved in vertical and horizontal water transport, photosynthates and gas exchange.     

Spatial and temporal scales relevant for conservation of dead-wood associated species: current status and perspectives

Dead wood is a key substrate for forest biodiversity, hosting a rich and often threatened biodiversity of wood-living species. However, the relationship between the occurrence of dead wood and associated species is modified by several environmental factors. Here we review the present state of knowledge on how dead wood on different spatial and temporal scales affects saproxylic biodiversity. We searched for peer-reviewed studies on saproxylic species that compared dead wood distribution on at least two spatial or temporal scales. We scanned close to 300 articles, of which 34 fit our criteria. 20 studies were directed towards the current amount of dead wood at different scale levels and how this relates to the abundance or occurrence of saproxylic species, embracing scales from 10 m to 10 km. 14 studies compared time-lagged effects of dead wood, covering time-lags from 25 years to more than 200 years. The reviewed articles focused mainly on European forest and addressed invertebrates (mostly beetles), alone or in combination with fungi (27 articles), fungi (six articles), or lichens (one article). Although the significance of dead wood for forest biodiversity is firmly established, the reviewed studies show that we still have limited knowledge of the relationship between saproxylic biodiversity and spatial and temporal scales. Based on the reviewed studies, we conclude that there is large variation in response to spatial and temporal dead wood patterns between different taxa and sub-groups. Still, several of the reviewed papers indicate that time-lagged effects deserve more attention, especially on a landscape scale and for specialized or red-listed species. Further work is required before firm management recommendations can be suggested.     

Potential environmental impacts associated with the proposed abstraction of water from the Okavango River in Namibia

The Namibian Department of Water Affairs has in the past faced considerable pressure to relieve the water shortages caused by recent droughts. One of the options considered in 1996, following poor runoff during the 1994/95 and 1995/96 seasons, was a proposal to abstract some 17Mm³ of water per year from the Okavango River at Rundu, and transfer this via a 260km long pipeline to the head of the Eastern National Water Carrier at the town of Grootfontein. Part of the overall evaluation of this scheme included an assessment of the potential environmental impacts that could arise. An initial environmental evaluation was conducted from a point approximately 40 kilometres upstream of Rundu in Namibia, to the distal end of the Okavango Delta at Maun in Botswana.

Hydrological studies showed that the proposed abstraction represented a reduction of approximately 0.32% in the mean annual flow of the Okavango River at Rundu. The abstraction represents 0.17% of the mean annual flow at Mukwe, downstream of the Cuito River confluence. The adverse effects of the proposed water abstraction scheme would be extremely small along the Okavango River in Namibia, whilst outflows from the lower end of the Okavango Delta to the Thamalakane River would be reduced by some 1.44Mm³/year (11%). Additional studies showed that these effects could be reduced by some 10–13% if abstraction was confined to the falling limb of the hydrograph.

Hydrological simulations have shown that the maximum likely loss of inundated area in the Okavango Delta would total approximately 7km² out of some 8 000km². This potential loss in inundated area would be concentrated in the lower reaches of the seasonal swamps and seasonally inundated grasslands, specifically in the lower reaches of the Boro, Gomoti, Santantadibe and Thaoge channels. However, these effects would most likely be expressed as a shoreline effect, with the loss in area spread out over the shoreline and periphery of islands and would not be restricted to a single specific area. This anticipated loss in inundated area is unlikely to have measurable impacts on environmental components.

Overall, the study found no 'fatal flaws' which would prevent the water abstraction scheme from proceeding and the anticipated effects on the Okavango system are more likely to be seen in the Okavango Delta, rather than along the Okavango River. The anticipated ecological implications of the scheme were small in spatial extent and are unlikely to be perceptible against the natural year-to-year variability in inundation of the Okavango Delta or outflows to the Thamalakane River. However, the public perceptions of the proposed water transfer project were strongly negative and appeared to be at least in part due to the very low water levels in the Okavango River and Okavango Delta during the past three years and during the study period. These low water levels were amongst the lowest on record and it is likely that the public would attribute any adverse effect recorded in the future to the abstraction scheme, whether this were true or not. These negative perceptions of the desirability and acceptability of the proposed scheme were strongly linked to potential adverse affects on the tourism industry along the Okavango River and in the Okavango Delta, with possible adverse economic effects on local residents.     

火干扰对森林土壤斥水性的影响研究进展

土壤斥水性是指水分不能或很难湿润土壤颗粒表面的现象,很多植被类型及气候带森林存在土壤斥水性。土壤斥水性受水分、温度、干湿交替、土壤质地、植被类型等生物和非生物因子的影响。而火干扰是森林生态系统土壤斥水性的重要影响因子,使森林土壤斥水性增强,渗透率降低,地表截留体减少,从而增加地表径流和土壤侵蚀。就火干扰对土壤斥水性的发生机理及其对水文过程的影响进行了较为全面的总结和讨论,并指出目前存在的问题和未来的研究重点。森林火灾后火烧迹地地表径流和土壤侵蚀显著增加,定量预测火灾后土壤斥水性对径流与侵蚀的影响比较困难,因此,基于不同尺度和自然降雨的火灾后斥水性对地表径流和土壤侵蚀的实验及长期定位观测是今后的研究方向与重点。     

Additive impacts of experimental climate change increase risk to an ectotherm at the Arctic's edge

Globally, Arctic and Subarctic regions have experienced the greatest temperature increases during the last 30 years. These extreme changes have amplified threats to the freshwater ecosystems that dominate the landscape in many areas by altering water budgets. Several studies in temperate environments have examined the adaptive capacity of organisms to enhance our understanding of the potential repercussions of warming and associated accelerated drying for freshwater ecosystems. However, few experiments have examined these impacts in Arctic or Subarctic freshwater ecosystems, where the climate is changing most rapidly. To evaluate the capacity of a widespread ectotherm to anticipated environmental changes, we conducted a mesocosm experiment with wood frogs (Rana sylvatica) in the Canadian Subarctic. Three warming treatments were fully crossed with three drying treatments to simulate a range of predicted changes in wetland environments. We predicted wetland warming and drying would act synergistically, with water temperature partially compensating for some of the negative effects of accelerated drying. Across all drying regimes, a 1 °C increase in water temperature increased the odds of survival by 1.79, and tadpoles in 52‐day and 64‐day hydroperiod mesocosms were 4.1–4.3 times more likely to survive to metamorphosis than tadpoles in 45‐day mesocosms. For individuals who survived to metamorphosis, there was only a weak negative effect of temperature on size. As expected, increased temperatures accelerated tadpole growth through day 30 of the experiment. Our results reveal that one of the dominant herbivores in Subarctic wetlands, wood frog tadpoles, are capable of increasing their developmental rates in response to increased temperature and accelerated drying, but only in an additive manner. The strong negative effects of drying on survival, combined with lack of compensation between these two environmental drivers, suggest changes in the aquatic environment that are expected in this ecosystem will reduce mean fitness of populations across the landscape.     

Modeling biogeochemical impacts of bioenergy buffers with perennial grasses for a row‐crop field in Illinois

Current research on the environmental sustainability of bioenergy has largely focused on the potential of bioenergy crops to sequester carbon and mitigate greenhouse gas emissions and possible impacts on water quality and quantity. A key assumption in these studies is that bioenergy crops will be grown in a manner similar to current agricultural crops such as corn and hence would affect the environment similarly. In this study, we investigate an alternative cropping system where bioenergy crops are grown in buffer strips adjacent to current agricultural crops such that nutrients present in runoff and leachate from the traditional row‐crops are reused by the bioenergy crops (switchgrass, miscanthus and native prairie grasses) in the buffer strips, thus providing environmental services and meeting economic needs of farmers. The process‐based biogeochemical model Denitrification‐Decomposition (DNDC) was used to simulate crop yield, nitrous oxide production and nitrate concentrations in leachate for a typical agricultural field in Illinois. Model parameters have been developed for the first time for miscanthus and switchgrass in DNDC. Results from model simulations indicated that growing bioenergy crops in buffer strips mitigated nutrient runoff, reduced nitrate concentrations in leachate by 60–70% and resulted in a reduction of 50–90% in nitrous oxide emissions compared with traditional cropping systems. While all the bioenergy crop buffers had significant positive environmental benefits, switchgrass performed the best with respect to minimizing nutrient runoff and nitrous oxide emissions, while miscanthus had the highest yield. Overall, our model results indicated that the bioenergy crops grown in these buffer strips achieved yields that are comparable to those obtained for traditional agricultural systems while simultaneously providing environmental services and could be used to design sustainable agricultural landscapes.     

基于AnnAGNPS模型的三峡库区秭归县非点源污染输出评价

非点源(NPS)污染已成为全球关注的环境问题。由于NPS特点、实验手段和监测数据的局限,其研究多采用数学模型进行时间和空间模拟。模型模拟提供了一种成本低效率高的手段来评定区域非点源污染。选择连续农业非点源污染AnnAGNPS(Annualized AGricultural Non-Point Source)模型,构建该模型数据库,模拟秭归县黑沟、兰陵溪、杉木溪等3条典型流域和县域径流、泥沙和营养物质的输出。结果表明：AnnAGNPS模型对3条典型流域的径流模拟能力高于对泥沙和养分的模拟,径流模拟误差均在可接受范围之内,说明模型中采用的径流预测(SCS曲线)法对研究区的地理气候条件是适用的;对3条典型流域泥沙输出模拟误差较高,对氮磷等养分输出模拟的误差最高,通过调整RUSLE和HUSLE等子模型的输入参数来减小泥沙模拟误差;对小型降雨径流事件,模型泥沙、养分模拟误差有偏大趋势,对较大降雨径流事件,模型泥沙和养分模拟误差有偏小趋势;2006年秭归县县域模型模拟的地表径流量为363 mm,泥沙输出为19.6 t/hm2,总氮输出为122 kg/hm2,总磷输出为28 kg/hm2,有机碳输出为581 kg/hm2,模拟结果与相关文献研究和政府统计数据较为相符;AnnAGNPS模型对NPS污染物输出模拟具有一定的不确定性,但作为一个较好的高级农业流域管理工具,该模型可以在三峡库区地理气候条件下使用。