Prioritize Management Efforts Research Articles

Spatial prioritization for widespread invasive species control: Trade-offs between current impact and future spread.

Spatially explicit prioritization of invasive species control is a complex issue, requiring consideration of trade-offs between immediate and future benefits. This study aimed to prioritize management efforts to account for current and future threats from widespread invasions and examine the strength of the trade-off between these different management goals. As a case study, we identified spatially explicit management priorities for the widespread invasion of introduced willow into riparian and wetland habitats across a 102,145-km2 region in eastern Australia. In addition to targeting places where willow threatens biodiversity now, a second set of management goals was to limit reinfestation and further spread that could occur via two different mechanisms (downstream and by wind). A model of likely willow distribution across the region was combined with spatial data for biodiversity (native vegetation, threatened species and communities), ecological conditions, management costs, and two potential dispersal layers. We used systematic conservation planning software (Zonation) to prioritize where willow management should be focussed across more than 100,000 catchments for a range of different scenarios that reflected different weights between management goals. For willow invasion, we found that we could prioritize willow management to reduce the future threat of dispersal downstream with little reduction in the protection of biodiversity. However, accounting for future threats from wind dispersal resulted in a stronger trade-off with protection of threatened biodiversity. The strongest trade-off was observed when both dispersal mechanisms were considered together. This study shows that considering current and future goals together offers the potential to substantially improve conservation outcomes for invasive species management. Our approach also informs land managers about the relative trade-offs among different management goals under different control scenarios, helping to make management decisions more transparent. This approach can be used for other widespread invasive species to help improve invasive species management decisions.

Paired acoustic recordings and point count surveys reveal Clark's nutcracker and whitebark pine associations across Glacier National Park.

Global declines in tree populations have led to dramatic shifts in forest ecosystem composition, biodiversity, and functioning. These changes have consequences for both forest plant and wildlife communities, particularly when declining species are involved in coevolved mutualisms. Whitebark pine (Pinus albicaulis) is a declining keystone species in western North American high-elevation ecosystems and an obligate mutualist of Clark's nutcracker (Nucifraga columbiana), an avian seed predator and disperser. By leveraging traditional point count surveys and passive acoustic monitoring, we investigated how stand characteristics of whitebark pine in a protected area (Glacier National Park, Montana, USA) influenced occupancy and vocal activity patterns in Clark's nutcracker. Using Bayesian spatial occupancy models and generalized linear mixed models, we found that habitat use of Clark's nutcracker was primarily supported by greater cone density and increasing diameter of live whitebark pine. Additionally, we demonstrated the value of performing parallel analyses with traditional point count surveys and passive acoustic monitoring to provide multiple lines of evidence for relationships between Clark's nutcracker and whitebark pine forest characteristics. Our findings allow managers to gauge the whitebark pine conditions important for retaining high nutcracker visitation and prioritize management efforts in whitebark pine ecosystems with low nutcracker visitation.

The influence of extreme water levels on coastal wetland extent across the Laurentian Great Lakes

Laurentian Great Lakes coastal wetlands (GLCW) are ecological hotspots and their integrity depends upon dynamic hydrologic regimes of the Great Lakes. GLCW naturally adjust to changes in hydrologic regimes via migration, but Great Lakes water levels may be shifting faster than wetlands can manage: 2000–2015 marked an extended low water level period and was followed by record highs in 2017–2020. Our objective was to quantify how Great Lakes water levels impact GLCW linear extent (from the shoreline to open water). We calculated wetland extent and migration from 2011 to 2019 using data from 1538 vegetation transects at 342 sites across the U.S. shoreline of the Great Lakes. Mediated multiple linear regression with Bayesian hierarchical modeling investigated the relationship between water levels and wetland extent. We employed Bayesian hierarchical modeling because (1) the dataset was spatially nested, with sampling points within wetlands within Great Lakes and (2) Bayesian statistics offer flexibility for environmental modeling, such as the inclusion of mediation in models, where we can assess both direct influences of Great Lake water levels on wetland extent and indirect (i.e., mediated) influences of water levels via the presence of vegetation zones on thus wetland extent. Results showed that, overall, there was a landward migration from 2011 to 2019 (although 38 % of wetlands had lakeward migration of the wetland-upland border). Wetland length and inundation length decreased with increased water levels, as mediated by the presence of certain vegetation zones. This decrease in wetland extent is of concern because it likely relates to a decrease in wetland function and habitat. A better understanding of how GLCW migrate with shifts in water levels enables decision makers to better predict where Great Lakes coastal wetlands are at risk of being lost and thus where to prioritize management efforts.

An approach to assess data-less small-scale fisheries: examples from Congo rivers

Small-scale fisheries (SSF) account for much of the global fish catch, but data to assess them often do not exist, impeding assessments of their historical dynamics and status. Here, we propose an approach to assess 'data-less' SSF using local knowledge to produce data, life history theory to describe their historical multispecies dynamics, and length-based reference points to evaluate stock status. We demonstrate use of this approach in three data-less SSFs of the Congo Basin. Fishers' recalls of past fishing events indicated fish catch declined by 65–80% over the last half-century. Declines in and depletion of many historically important species reduced the diversity of exploited species, making the species composition of the catch more homogenous in recent years. Length-at-catch of 11 of the 12 most important species were below their respective lengths-at-maturity and optimal lengths (obtained from Fishbase) in recent years, indicating overfishing. The most overfished species were large-bodied and found in the Congo mainstem. These results show the approach can suitably assess data-less SSF. Fishers' knowledge produced data at a fraction of the cost and effort of collecting fisheries landings data. Historical and current data on fish catch, length-at-catch, and species diversity can inform management and restoration efforts to curb shifting baselines of these fisheries. Classification of stock status allows prioritizing management efforts. The approach is easy to apply and generates intuitive results, having potential to complement the toolkits of researchers and managers working in SSF and engage stakeholders in decision-making processes.

Prioritizing pollinators over pests: wild bees are more important than beetle damage for watermelon yield.

Insect pests and pollinators can interact directly and indirectly to affect crop production; however, impacts of these interactions on marketable yield are little known. Thus, the evaluation of interactions between pests and pollinators are needed to best prioritize management efforts. Over 2 years, we evaluated the impact of pollinator visitation and/or beetle (<i>Acalymma vittatum</i>) infestation on fruit set and yield in seedless watermelon production. In 2020, we tested the main effect of pollinator visitation: two or eight honeybee visits, two wild bee visits, hand pollinated and open pollinated. In 2021, we crossed wild and managed pollinator visitation (two or four honeybee visits, two or four wild bee visits, hand pollinated and open pollinated) with varying beetle infestation levels (0, 3, 6 and 9 beetles/plant). In both years, wild bees contributed significantly to high fruit yields, and exclusive visitation from wild bees increased yield by a factor of 1.5-3 compared to honeybees. In 2021, pollination was the only significant factor for fruit set and marketable yield even when compared to the varying beetle infestation levels. These data advocate for a reprioritization of management, to conserve and protect wild bee pollination, which could be more critical than avoiding pest damage for ensuring high yields.

Comparing Methods of Defining Priority Areas for Greater Sage-Grouse

Wildlife managers delineate priority areas for species to define critical habitat and to prioritize management efforts. Each method used to identify priority areas involves data that can be unavailable or expensive to obtain. Therefore, it is of interest to compare spatial efficiency between methods used for defining priority areas. We compared priority areas created using different methods and data types. We used resource selection function (RSF) models to predict areas of high use and generated a map depicting ≥ 90% predicted use in three seasons; it was 1,143 km2, encompassed 91% of nests, 68% of summer locations, and 71% of winter locations. We compared the RSF priority area to priority areas developed using two alternative methods: (1) modified conservation buffer, and (2) utilization distribution (UD) models. The modified conservation buffer method was used by South Dakota Game, Fish and Parks in 2014 to delineate a priority area by buffering active lek sites by 6.4 km, including connectivity corridors defined via expert opinion, and known high use areas. The priority area generated by the modified conservation buffer method was 3,977 km2, encompassed 95% of nest locations, 92% of spring/summer locations, and 99% of winter locations. Lastly, we developed a priority area using combined UDs from radio-tracking data gathered during spring/summer, and winter and included a lek buffer encompassing 90% of known nest-sites. This priority area was 3,498 km2, encompassed 99% of nests, 98% of spring/summer locations, and 97% of winter locations. The priority area generated by RSF models was the smallest and encompassed the least number of nests and spring/summer and winter locations but was considered the most spatially efficient; it had the most nests, spring/summer locations, and winter locations per 100 km2. The UD and modified conservation buffer methods created priority areas that were similar in size and spatial efficiency. The modified conservation buffer method encompassed &amp;gt;90% of known sage-grouse locations and nests, indicating that in the absence of detailed movement data and more sophisticated modeling, the method can be sufficient in developing an adequate priority area.

Exploring the influence of weeds on cranberry yield and quality

AbstractThe influence of weeds on cranberry yield and quality is not well known and cannot be extrapolated from other cropping systems given the unique nature of both cranberry production and the weed species spectrum. The work presented here addresses this need with four common weed species across multiple production seasons and systems in Wisconsin, Massachusetts, and New Jersey: Carolina redroot, earth loosestrife, bristly dewberry, and polytrichum moss. The objectives were to use these representative species to quantify the impact of weed density, groundcover, and biomass on several cranberry yield components and related interactions with other cranberry pests, and to determine whether these relationships were consistent enough across seasons to be reliably used in weed management decision-making. The relationships between Carolina redroot and bristly dewberry growth measures and marketable cranberry yield were highly significant (P ≤ 0.001 in 12 of 13 regressions) and consistent across growing seasons, but not significant for similar regressions with earth loosestrife. In particular, the strong relationship between Carolina redroot and bristly dewberry visual groundcover observations and cranberry yield suggests a simple way for growers and crop scouts to reliably estimate yield loss. The relationship between polytrichum moss biomass and cranberry yield was also significant in both years, but not consistent between years. Weed competition also affected cranberry quality, in that Carolina redroot density was strongly related to the percentage of insect-damaged fruit and bristly dewberry growth reduced cranberry color development. On a practical level, this information can be used to educate growers, consultants, agrichemical registrants, and regulators about the impacts of weeds on cranberry yield and quality, and to economically prioritize management efforts based on the weed species and extent of infestation.

Pedogenic Threshold in Acidity Explains Context-Dependent Tree Species Effects on Soil Carbon

Despite the general agreement that maximizing carbon storage and its persistence in forest soils are top priorities in the context of climate change mitigation, our knowledge on how to steer soil organic carbon (SOC) through forest management remains limited. For some soils, tree species selection based on litter quality has been shown a powerful measure to boost SOC stocks and stability, whereas on other locations similar efforts result in insignificant or even opposite effects. A better understanding of which mechanisms underpin such context-dependency is needed in order to focus and prioritize management efforts for carbon sequestration. Here we discuss the key role of acid buffering mechanisms in belowground ecosystem functioning and how threshold behavior in soil pH mediates tree species effects on carbon cycling. For most forests around the world, the threshold between the exchange buffer and the aluminum buffer around a pH-H2O of 4.5 is of particular relevance. When a shift between these buffer domains occurs, it triggers changes in multiple compartments in the soil, ultimately altering the way carbon is incorporated and transformed. Moreover, the impact of such a shift can be amplified by feedback loops between tree species, soil biota and cation exchange capacity (CEC). Hence, taking into account non-linearities related to acidity will allow more accurate predictions on the size and direction of the effect of litter quality changes on the way soil organic carbon is stored in forest soils. Consequently, this will allow developing more efficient, context-explicit management strategies to optimize SOC stocks and their stability.

Innovation capabilities for sustainability: a comparison between Green and Gray companies

PurposeThis paper aims to identify and compare the arrangements of innovation capabilities and their correlation with the socio-environmental responsibility of two groups: companies with less socio-environmental concern (Group Gray) and companies with greater socio-environmental concern (Group Green).Design/methodology/approachDescriptive and quantitative research with 1,322 Brazilian manufacturing companies was conducted. We analyzed (1) the actual arrangement of capabilities and (2) the ideal arrangement of capabilities with the greatest impact on innovation.FindingsResults suggest that there is a difference in the arrangement of capabilities between the two groups. Also, there is a difference between the capabilities that effectively receive the companies' attention and the capabilities that should be valued and developed. Green companies must focus their efforts on Transaction capability, followed respectively by Management, Development and Operation capabilities. Gray companies must focus on Development capability, followed by Management, Transaction and Operation capabilities.Originality/valueBy identifying the ideal capability arrangement, this research provides important information that can guide managers in planning internal strategies for investments, prioritizing management efforts and rearranging capabilities to boost innovation for sustainability.

Visualizing riparian ecotone fragmentation in urbanizing watersheds: A case study of upper Hickory Creek, north‐Central Texas

AbstractMany pollution sources and heavy runoff often plague urbanizing watersheds. Riparian ecotones can filter pollutants and attenuate runoff; however, changing land cover tends to diminish this buffering capacity. Visualizing riparian ecotone fragmentation at the watershed scale can help prioritize management efforts. A geographic information systems approach was developed to illustrate land cover and soil properties affecting buffering potential along riparian corridors. An application to the Hickory Creek watershed in north‐central Texas shows significant riparian ecotone fragmentation, suggesting high‐priority areas for preservation and restoration.

What and where? Predicting invasion hotspots in the Arctic marine realm.

The risk of aquatic invasions in the Arctic is expected to increase with climate warming, greater shipping activity and resource exploitation in the region. Planktonic and benthic marine aquatic invasive species (AIS) with the greatest potential for invasion and impact in the Canadian Arctic were identified and the 23 riskiest species were modelled to predict their potential spatial distributions at pan‐Arctic and global scales. Modelling was conducted under present environmental conditions and two intermediate future (2050 and 2100) global warming scenarios. Invasion hotspots—regions of the Arctic where habitat is predicted to be suitable for a high number of potential AIS—were located in Hudson Bay, Northern Grand Banks/Labrador, Chukchi/Eastern Bering seas and Barents/White seas, suggesting that these regions could be more vulnerable to invasions. Globally, both benthic and planktonic organisms showed a future poleward shift in suitable habitat. At a pan‐Arctic scale, all organisms showed suitable habitat gains under future conditions. However, at the global scale, habitat loss was predicted in more tropical regions for some taxa, particularly most planktonic species. Results from the present study can help prioritize management efforts in the face of climate change in the Arctic marine ecosystem. Moreover, this particular approach provides information to identify present and future high‐risk areas for AIS in response to global warming.

Spatiotemporal Trend Analysis of PM2.5 Concentration in China, 1999–2016

China is experiencing severe PM 2 . 5 (fine particles with a diameter of 2.5 μ g or smaller) pollution problem. Little is known, however, about how the increasing concentration trend is spatially distributed, nor whether there are some areas that experience a stable or decreasing concentration trend. Managers and policymakers require such information to make strategic decisions and monitor progress towards management objectives. Here, we present a pixel-based linear trend analysis of annual PM 2 . 5 concentration variation in China during the period 1999–2016, and our results provide guidance about where to prioritize management efforts and affirm the importance of controlling coal energy consumption. We show that 87.9% of the whole China area had an increasing trend. The drastic increasing trends of PM 2 . 5 concentration during the last 18 years in the Beijing–Tianjin–Hebei region, Shandong province, and the Three Northeastern Provinces are discussed. Furthermore, by exploring regional PM 2 . 5 pollution, we find that Tarim Basin endures a high PM 2 . 5 concentration, and this should have some relationship with oil exploration. The relationship between PM 2 . 5 pollution and energy consumption is also discussed. Not only energy structure reconstruction should be repeatedly emphasized, the amount of coal burned should be strictly controlled.

Genetic diversity, admixture, and hatchery influence in Brook Trout (Salvelinus fontinalis) throughout western New York State.

Although Brook Trout are distributed across most of eastern North America, population numbers have declined in many regions due to habitat loss, climate change, and competition with non‐native species. In New York State, Brook Trout habitat has been substantially reduced, with many areas showing complete extirpation of Brook Trout populations, predominantly in the western portion of the state. Small, fragmented populations are at risk of genetic diversity loss, inbreeding depression, and reduced fitness, leading to a greater potential for local extirpation. Genetic monitoring is a practical tool that can facilitate further conservation‐decision making regarding small populations. In this study, we used 12 microsatellite loci to examine 3,436 sampled Brook Trout, representing 75 sites from the Allegheny, Erie/Niagara, Genesee, Oswego, Lake Ontario, and Susquehanna drainage basins throughout western New York State. Three Brook Trout hatchery strains were also genetically characterized to evaluate the degree of hatchery introgression between wild populations and hatchery strains stocked in the region. Overall, estimates of genetic diversity varied widely: Allelic richness ranged from 2.23 to 7.485, and expected heterozygosity ranged from 0.402 to 0.766. As observed for Brook Trout in other regions, we found a high degree of genetic differentiation among populations, with all comparisons except one showing significant F ST values. Hatchery introgression was found to be minimal, with estimates ranging from 1.96% to 3.10% of wild individuals exhibiting membership proportions to a hatchery strain cluster exceeding 10% (q ≥ 0.10). Results from this investigation can be used to prioritize management efforts for Brook Trout in western New York State and act as a baseline to monitor future population trends.

Phenotypic variations alter the ecological impact of invasive alien species: Lessons from Parthenium hysterophorus

Invasive plant species constantly adjust their behavior with ecological shifts by virtue of phenotypic plasticity and/or local adaptations. Changes in the phenotype of an invasive species may also trigger variations in its community level impacts, which is an acceptable, yet unexplored aspect of invasion biology. Our study attempts to fill important knowledge gaps on the basic behavior and ecological interactions of invasive species. Parthenium hysterophorus, a widely distributed invasive alien species of tropical and sub-tropical regions, was evaluated for variations in its morpho-functional traits and ecological performance at a common spatial and temporal scale. Field surveys were conducted in Chandigarh, India, in five sites identified as invaded with P. hysterophorus. Individuals of P. hysterophorus randomly sampled from these sites, showed from trait analyses that the population is differentiated into two morphotypes, PA and PB. Morphotype PB exhibits traits comparable to the shrub life-form in terms of woody stem (with higher stem circumference [+32.26%], stem specific density [+128.57%], twig dry matter content [+25.15%]); profuse branching (+46.38%); larger canopy (+91.16%); and better reproductive output (+190.29%) compared to PA. PA, on the other hand, reflected herbaceous characteristics with greater leaf area (+67.58%) and higher content of chlorophyll (+21.92%) compared to PB. Based on these morphotypes, the plots were divided into three invasion categories: areas invaded by PA [IPA], areas invaded by PB [IPB] and uninvaded areas [UI]. Ecological indices and soil chemical properties were compared across IPA, IPB and UI. Shannon's index (p < 0.001), evenness index (p = 0.008), and richness index (p < 0.001) were significantly lower in IPB compared to IPA. UI areas were found to have higher soil pH, phenolics, organic matter, and concentrations of N, P and K, compared to IPA and IPB, but lower Ca and Mg. Results suggest that phenotypic variations within population of P. hysterophorus regulate its ecological impact on associated vegetation. Conservation managers would benefit from studying its invasion patterns and identifying the morphotype with higher ecological impact to prioritize management efforts. Monitoring these behavioral and ecological patterns in P. hysterophorus over the long-term may also help in anticipating challenges to preventive measures.

A spatially explicit analysis of Paysandisia archon attack on the endemic Mediterranean dwarf palm

Autochthonous plant species are heavily threatened by the increasing spread of invasive insects. The spatial distribution of invasive species’ hosts is likely to play a pivotal role in the establishment and further expansion of the invading species; more specifically, distance and density dependent (DDD) processes linked to plant spatial arrangement are crucial in determining susceptibility to attack, but they have usually been overlooked in invasive research. We take a spatially explicit approach to evaluate potential DDD processes in the interaction between Paysandisia archon, a tropical lepidopteran recently introduced in Spain, and the endemic Mediterranean dwarf palm (Chamaerops humilis) in Mallorca (Balearic Islands). Specifically, we used spatial marked point pattern analyses, which allowed testing whether DDD processes affect attack probability and intensity on three dwarf palm populations corresponding to three different invasion phases (i.e., infestation core, early expansion, and expansion front). Our approach also allowed evaluation of whether and how intrinsic palm traits (size, sex) alter the proneness to P. archon attack over a range of spatial scales. The occurrence and nature of DDD effects on C. humilis performance varied largely among localities. At the infestation core, our analyses revealed positive density dependence, i.e., reduced damage at high densities or proximity to conspecific neighbors. By contrast, the early expansion locality showed negative density dependence of C. humilis performance, whereas at the expansion front, there was no evidence of DDD effects. Larger palms were consistently more prone to P. archon attack than small ones up to scales of 50 m. We found no evidence that palm sex altered the probability of attack by P. archon. Our results highlight the importance of spatially explicit analyses for assessing invasive events and point to the need of early interventions and prioritizing management efforts on larger palms in order to guarantee the conservation of autochthonous dwarf palm populations.

Vulnerability of spawning aggregations of a coastal marine fish to a small-scale fishery

For marine fishes that form spawning aggregations, vulnerability to aggregation fishing is influenced by interactions between the spatio-temporal patterns of spawning and aspects of the fishery that determine fishing effort, catch, and catch rate in relation to spawning. We investigated the spatio-temporal dynamics of spawning and fishing for the barred sand bass, Paralabrax nebulifer, in Punta Abreojos, Mexico from 2010 to 2012 as a means to assess its vulnerability to aggregation fishing by the local commercial fishery. Monthly, spatial patterns in gonadal development in collected females indicated that adults formed spawning aggregations at two sites in Punta Abreojos during July and August. Monthly patterns in the spatial distribution of fishing matched the spawning behavior of P. nebulifer, with effort and catch concentrated at spawning aggregation sites during those months. However, fishing effort, catch, and catch-per-unit effort did not increase during the spawning season, and fishing activities associated with the spawning season comprised only a small percentage of the total annual effort (22%) and catch (17%). Therefore, while the population of P. nebulifer at Punta Abreojos should be vulnerable to aggregation fishing due to the spatio-temporal dynamics of its spawning aggregations, vulnerability is greatly reduced, because fishing activities are not disproportionately focused on spawning aggregations and fishing methods are not optimized to maximize harvest from the aggregations. Differences between our results and previous studies on aggregation fisheries for P. nebulifer in California, USA, reinforce the importance of assessing factors influencing vulnerability to aggregation fishing at regional scales for prioritizing management efforts.

Drivers of Change and Sustainability in Linked Social–Ecological Systems: An Analysis in the Volta River Basin of Ghana, West Africa

ABSTRACTUnderstanding the nature and relative importance of various drivers of change is crucial for sustainable management of natural resources and in prioritizing management efforts, allocating limited resources, and understanding cumulative effects. For this article, we employed structured an expert judgments approach to identify, characterize, and assess the relative importance of the key biophysical and socioeconomic drivers of change within the Volta River Basin, West Africa. Precipitation variability, water availability, land use change, drought events, and population growth were perceived as most important, while biodiversity loss, social conflicts, pest and disease occurrence, urbanization, and pollution were viewed as less critical. A majority of these drivers were characterized as “slow” acting processes as compared to rapidly changing drivers. Intra- and interexpert groups agreement were found to be significant and convergent, indicating the reliability of the results. The implications of these results for sustainable water resources management and agricultural production are discussed.

Local Environmental Context Conditions the Impact of Russian Olive in a Heterogeneous Riparian Ecosystem

Local abiotic and biotic conditions can alter the strength of exotic species impacts. To better understand the effects of exotic species on invaded ecosystems and to prioritize management efforts, it is important that exotic species impacts are put in local environmental context. We studied how differences in plant community composition, photosynthetically active radiation (PAR), and available soil N associated with Russian olive presence are conditioned by local environmental variation within a western U.S. riparian ecosystem. In four sites along the South Fork of the Republican River in Colorado, we established 200 pairs of plots (underneath and apart from Russian olive) to measure the effects of invasion across the ecosystem. We used a series of a priori mixed models to identify environmental variables that altered the effects of Russian olive. For all response variables, models that included the interaction of environmental characteristics, such as presence/absence of an existing cottonwood canopy, with the presence/absence of Russian olive canopy were stronger candidate models than those that just included Russian olive canopy presence as a factor. Compared with reference plots outside of Russian olive canopy, plots underneath Russian olive had higher relative exotic cover (exotic/total cover), lower perennial C4 grass cover, and higher perennial forb cover. These effects were reduced, however, in the presence of a cottonwood canopy. As expected, Russian olive was associated with reduced PAR and increased N, but these effects were reduced under cottonwood canopy. Our results demonstrate that local abiotic and biotic environmental factors condition the effects of Russian olive within a heterogeneous riparian ecosystem and suggest that management efforts should be focused in open areas where Russian olive impacts are strongest.

Is biotic resistance to invaders dependent upon local environmental conditions or primary productivity? A meta-analysis

Biotic resistance is an important component to limiting the spread of invasive plants into native communities. However, under certain conditions native plants may also facilitate invasion, a process identified as biotic assistance. Identifying the conditions that associate with resistance and assistance is needed to better understand the factors driving species invasion.Substantial theory and empirical work suggests net effects of neighbors may be dependent upon habitat productivity and environmental conditions. How that applies to the interaction among the resident community and the invaders is largely untested. Here we compiled data from 23 articles, which had experimentally determined the strength of biotic resistance and/or assistance. We then combined these data with remote-sensing estimates of productivity, precipitation and temperature at each study site. Using standard meta-analytical techniques we determined the overall effect resident communities had on the emergence, growth, reproduction and survival of non-native invaders. Further, we tested whether the interaction between resident communities and invasive species was influenced by primary productivity, temperature and precipitation.Across all sites, we found broad support for biotic resistance, while evidence for biotic assistance was rare. However, we found the relative magnitude of biotic resistance on invaders increased with temperature or precipitation; a pattern consistent with the stress gradient hypothesis. In contrast we found no evidence that the strength of biotic resistance varied as a function of primary productivity. Further evaluation of the relationship between productivity and environmental conditions on the direction and strength of the effect of resident species on invaders may help predict invasion establishment and success. Understanding or predicting the susceptibility of communities to invasion may help prioritize management efforts.

Water Quality Indices as Tools for Decision Making and Management

Water Quality Indices (WQIs) are composite indicators of water quality that pool together otherwise complex water quality data into an aggregate value that can be quickly and easily communicated to its intended audience. These indices have been used to provide comparisons of water quality status for different locations and at different times, which is helpful in prioritizing management efforts and funds. These WQIs can also be used as tools to predict potentially harmful conditions. They are also potentially valuable in assessing and communicating overall impacts of existing, planned, or proposed water quality interventions and management decisions. This manuscript presents a primarily literature-based look at WQI potentials with regard to their use as tools for decision making and management. Illustrations using monitoring data are also presented to provide additional information and comparisons to literature-based determinations. Of the existing WQIs, objective index formulations offer more flexible options for application allowing incorporation of varying determinant sets to capture location-specific conditions and changing water quality concerns. Incorporation of expert opinion at some level is important for the acceptability of WQIs as tools in water resources management. The use of the indices on a continuous basis provides long-term data which is helpful for decision making and management.