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1. Ecological restoration is a global priority that holds great potential for benefiting natural ecosystems, but restoration outcomes are notoriously unpredictable. Resolving this unpredictability represents a major, but critical challenge to the science of restoration ecology. 2. In an effort to move restoration ecology toward a more predictive science, we consider the key issue of variability. Typically, restoration outcomes vary relative to goals (i.e. reference or desired future conditions) and with respect to the outcomes of other restoration efforts. The field of restoration ecology has largely considered only this first type of variation, often focusing on an oversimplified success vs. failure dichotomy. The causes of variation, particularly among restoration efforts, remain poorly understood for most systems. 3. Variation associated with restoration outcomes is a consequence of how, where and when restoration is conducted; variation is also influenced by how the outcome of restoration is measured. We propose that variation should decrease with the number of factors constraining restoration and increase with the specificity of the goal. When factors (e.g. harsh environmental conditions, limited species reintroductions) preclude most species, little variation will exist among restorations, particularly when goals are associated with metrics such as physical structure, where species may be broadly interchangeable. Conversely, when few constraints to species membership exist, substantial variation may result and this will be most pronounced when restoration is assessed by metrics such as taxonomic composition. 4. Synthesis and applications. The variability we observe during restoration results from both restoration context (how, where and when restoration is conducted) and how we evaluate restoration outcomes. To advance the predictive capacity of restoration, we outline a research agenda that considers metrics of restoration outcomes, the drivers of variation among existing restoration efforts, experiments to quantify and understand variation in restoration outcomes, and the development of models to organise, interpret and forecast restoration outcomes.

Aim Efforts to evaluate the impact of non-native plants on ecosystems rarely consider the role of such plants in sustaining local food webs of arthropods, or whether the effect is similar across arthropod feeding guilds and life stages. We assess this response by comparing arthropod herbivores on native plants (species with evolutionary histories within local food webs) and non-native plants (species without such histories). We further compare the impact of non-native plants that are congeners of local native species with those of non-natives with no close local relatives. Location Suburban landscapes, Mid-Atlantic United States (Delaware, Pennsylvania). Methods We manipulated the composition of the first trophic level by planting four large common gardens of 50 woody plant species replicated in time and space. After an establishment year, we sampled herbivorous arthropods supported by each plant species and classified them by herbivore species, feeding guild and life stage. Results We found that (1) native plants support larger and more diverse herbivore communities, (2) arthropods with chewing mouthparts and immature herbivores were more sensitive to plant origin than arthropods with piercing-sucking mouthparts and adult herbivores, (3) arthropods laid more eggs on native plants, (4) internal feeders were rare on all non-native plants and (5) the reduction in herbivore populations on non-native plants was smaller, but still significant, if species had a close native relative. Main conclusions Novel ecosystems comprised of plant species with no evolutionary history with local members of higher trophic levels may reduce the diversity and complexity of local food webs. Given the rate at which novel ecosystems are replacing coevolved plant communities worldwide, this result has global implications for the conservation of biodiversity. Using more native plants within human-dominated landscapes may help maintain the integrity of arthropod communities, as well as the populations of animals that consume arthropods.

Declines in species diversity resulting from anthropogenic alterations of the environment heighten the need to develop management strategies that conserve species and ecosystem services. This study examined how native plant species and their diversity influence the abundance and richness of beneficial arthropods, a functionally important group that provides ecosystem services such as pollination and natural pest suppression. Beneficial arthropods were sampled in replicated study plots containing native perennials planted in one-, two-, and seven-species mixtures. We found plant diversity had a positive impact on arthropod richness but not on arthropod abundance. An analysis of arthropod community composition revealed that each flower species attracted a different assemblage of beneficial arthropods. In addition, the full seven-species mixture also attracted a distinct arthropod community compared to single-species monocultures. Using a multivariate approach, we determined whether arthropod assemblages in two- and seven-species plots were additive and could be predicted based on assemblages from their component single-species plots. On average, assemblages in diverse plots were nonadditive when compared to assemblages predicted using single-species plots. Arthropod assemblages in two-species plots most closely resembled those of only one of the flower species in the mixture. However, the arthropod assemblages in seven-species plots, although statistically deviating from the expectation of an additive model, more closely resembled predicted communities compared to the assemblages found in two-species plots, suggesting that variability in arthropod community composition decreased as planting diversity increased. Our study demonstrates that careful selection of plants in managed landscapes can augment beneficial arthropod richness and support a more predictable arthropod community, suggesting that planning and design efforts could shape arthropod assemblages in natural as well as managed landscapes to meet targeted conservation or management goals.

The central premise of this paper is that extensive modifications of land use and hydrology, coupled with intensive management of watersheds in the Midwestern United States over the past century, have increased the predictability of hydrologic responses, allowing for the use of simpler, minimum‐calibration models. In these engineered watersheds, extensive tile‐and‐ditch networks have increased the effective drainage density and have created bypass flow hydrologic systems that generate “flashy” and “predictable” hydrographs. We propose a simple, threshold‐based model, the Threshold‐Exceedance‐Lagrangian Model (TELM), for predicting event hydrographs. TELM was evaluated by comparing predicted hydrographs with those measured over a 4 year period at the outlet of a mesoscale watershed (Cedar Creek, approximately 700 km2) in northeastern Indiana. Application of the Soil‐Land Inference Model (SoLIM) indicated that, despite structural heterogeneities (e.g., spatial variability in soil taxonomic mapping units), about 80% of the area of the watershed could be assigned a single value of available soil water storage, which was the primary soil parameter that defined hydrograph response. Hydrograph recession curves for multiple events were described well using an exponential function, with the mean arrival time (t(r)) estimated on the basis of the contributing drainage area (A) and the mean occurrence time (t(h)) of the event hyetograph. Also, functional responses (event hydrographs) at the subwatershed scale could be grouped into just two categories on the basis of only spatial variability in rainfall patterns. TELM, with no parameter calibration, matched the observed hydrographs as well as the widely used SWAT model predictions with calibration. Advantages and limitations of the proposed modeling approach were identified, and needed improvements were discussed.

Trees in urban ecosystems are valued for shade and cooling effects, reduction of CO₂ emissions and pollution, and aesthetics. However, in arid and semi-arid regions, urban trees must be maintained through supplemental irrigation, in competition with other water needs. Currently, a comprehensive understanding of the factors which influence water use of urban tree species is lacking. In order to study the drivers of whole tree water use of two common species in the Los Angeles Basin urban forest, four sites in Los Angeles and Orange County were instrumented with sap flow and meteorological sensors. These sites allowed comparisons of the water use of a native riparian (Platanus racemosa Nutt.; California sycamore) and non-native (Pinus canariensis C. Sm.; Canary Island pine) Mediterranean species, as well as the spatial variability in water use under different environmental and management conditions. We found higher rates of sapflux (J O ) in native California sycamore as compared to non-native Canary Island pine. Within each species, we found considerable site-to-site variability in the magnitude and seasonality of J O . For Canary Island pine, the majority of inter-site variability derived from differences in water availability: response to vapor pressure deficit was similar during a period without water limitations. In contrast, California sycamore did not appear to experience water limitation at any site; however, there was considerable spatial variability in water use, potentially linked to differences in nutrient availability. Whole tree transpiration (E) was similar for the two species when water was not limiting, but Canary Island pine was able to withstand unirrigated conditions with a very low E. These results add to the currently small pool of data on urban tree water use and ecophysiology, and contribute to establishing a more quantitative understanding of urban tree function.

The widespread conversion of natural habitats to agricultural land has created a need to integrate intensively managed landscapes into conservation management priorities. However, there are no clearly defined methods for assessing the conservation value of managed landscapes at the local scale. We used remotely sensed landscape heterogeneity as a rapid practical tool for the assessment of local biodiversity value within a predominantly agricultural landscape in Canterbury, New Zealand. Bird diversity was highly significantly correlated with landscape heterogeneity, distance from rivers and the Christchurch central business district, altitude and average annual household income, indicating that remotely sensed landscape heterogeneity is a good predictor of local biodiversity patterns. We discuss the advantages and limitations of using geographic information systems to determine local areas of high conservation value.[PUBLICATION ABSTRACT]

Ecological traps and other cases of apparently maladaptive habitat selection cast doubt on the relevance of density as an indicator of habitat quality. Nevertheless, the prevalence of these phenomena remains poorly known, and density may still reflect habitat quality in most systems. We examined the relationship between density and two other parameters of habitat quality in an open-nesting passerine species: the Ovenbird (Seiurus aurocapilla). We hypothesized that the average individual bird makes a good decision when selecting its breeding territory and that territory spacing reflects site productivity or predation risk. Therefore, we predicted that density would be positively correlated with productivity (number of young fledged per unit area). Because individual performance is sensitive to events partly determined by chance, such as nest predation, we further predicted density would be weakly correlated or uncorrelated with the proportion of territories fledging young. We collected data in 23 study sites (25 ha each), 16 of which were located in untreated mature northern hardwood forest and seven in stands partially harvested (treated) 1-7 years prior to the survey. Density explained most of the variability in productivity ( R²= 0.73), and there was no apparent decoupling between density and productivity in treated plots. In contrast, there was no significant relationship between density and the proportion of territories fledging greater-than-or-equal1 young over the entire breeding season. These results suggest that density reflects habitat quality at the plot scale in this study system. To our knowledge this is one of the few studies testing the value of territory density as an indicator of habitat quality in an open-nesting bird species on the basis of a relatively large number of sizeable study plots.

Community management of natural resources is well supported by many field experiences as an effective way to improve people's well-being while maintaining their natural resource base. The approach has been reasonably achieved within community groups and the community as a whole. Nonetheless, there are fewer experiences at multi-community or regional levels (landscape). In this article we describe a participatory action research project that led to a successful multicommunity regional management plan. Using the Community Capitals Framework to help community members see their region as a system with assets and the managed landscape approach to focus on key decision points, the process led to an inclusive and successful planning process with high potential for implementation. We highlight the lessons learned from this experience and identify potential limitations to its use.

1. Recruitment, i.e. the influx of new breeding individuals into a population, is an important demographic parameter, especially in species with a short life span. Few studies have measured this parameter in solitary-breeding animal populations even though it may yield critical information on habitat suitability and functional connectivity. 2. Using a before-after, control-impact pairs (BACIP) experimental design, we measured: (i) the return rate and apparent survival rate of individually marked territorial males of a neotropical migrant bird species, the Ovenbird Seiurus aurocapilla Linnaeus and (ii) the age-specific recruitment rate. Study plots (n = 10) were paired: one was treated through single-tree selection harvesting (30-40% basal area removal) and the other acted as a control. We hypothesized that experienced males would out-compete inexperienced ones and tend to avoid settling in lower-quality, treated stands. 3. In the first year post-harvest, the mean density of territorial males was significantly lower in treated plots (-41%) than in controls and the difference remained relatively stable thereafter. This lower density mainly reflected a lower recruitment rate compared to controls (17·9 vs. 49·0% of males present), itself driven by a lower recruitment rate of experienced males (2·8 vs. 22·8%). Return rate was similar between controls and treated plots in the first year post-harvest (59 vs. 55%, respectively) but it decreased in treated plots during the second (-15·8% relative to controls) and third (-12·7%) year post-harvest. The trend was even stronger when considering only experienced males. The treatment was followed by a major expansion in mean territory size in treated plots (+49% relative to controls, 3rd year post-treatment). 4. Neither apparent survival rate nor recruitment rate varied as predicted. There was a strong year effect but no treatment effect on apparent survival rate, whereas male recruitment patterns were both year- and age-specific. Three years post-harvest, recruitment rate was sufficient to fill most territory vacancies in treated plots, due mainly to first-time breeders. 5. To our knowledge, this is the first study documenting the effects of experimental habitat alteration on recruitment rate in a songbird species using a BACI design. The response of this male subpopulation highlights the influence of recruitment on the density of open populations of solitary-nesting birds and age-specific patterns in the response of individuals to habitat alterations.