Context
To understand, even improve, the land of shrinking nature and spreading urbanization, a science applicable from remote natural areas to cities is needed.
Objective
Today’s scientific ...principles of urban ecology are articulated and compared with ecology based primarily on natural ecosystems; we either robustly merge the trajectories or watch them diverge.
Methods
A literature review emphasizes that the field of ecology emerged from late 19th century and early 20th century research mostly in semi-natural environments, whereas urban ecology mainly developed from studying plants, habitat types, and ecosystem nutrient flows in late 20th century city environments.
Results
Ninety urban ecology principles are identified and succinctly stated. Underlying the principles, 18 distinctive types of urban attributes are recognized in four major groups: land uses; built objects; permeating anthropogenic flows; human decisions/activities. The attributes or objects studied in “natural area” ecology and urban ecology differ sharply, as do the primary objects present in late 19th century and late 20th century cities. None of the 90 basic principles would have emerged from research on natural areas, and all are readily usable for improving urban and urbanizing areas.
Conclusion
Incorporating urban ecology science into ecology’s body of principles and theory now should catapult the field of ecology to the next level, and noticeably increase its usefulness for society.
Experimental evidence for limitation of net primary productivity (NPP) by nitrogen (N) or phosphorus (P) in lowland tropical forests is rare, and the results from the few existing studies have been ...inconclusive. To directly test if N or P limit NPP in a lowland tropical wet forest in Costa Rica, we conducted a full factorial fertilization experiment (4 treatments × 6 replicates in 30 × 30 m plots). We focused on the influence of tree size and taxa on nutrient limitation, because in these forests a wide variety of tree functional traits related to nutrient acquisition and use are likely to regulate biogeochemical processes. After 2.7 years, a higher percentage of trees per plot increased basal area (BA) with P additions (66.45% ± 3.28% without P vs. 76.88% ± 3.28% with P), but there were no other community-level responses to N or P additions on BA increase, litterfall productivity, or root growth. Phosphorus additions resulted in doubled stem growth rates in small trees (5-10 cm diameter at breast height (dbh);
P
≤ 0.01) but had no effect on intermediate (10-30 cm dbh) or large trees (>30 cm dbh). Phosphorus additions also increased the percentage of seedling survival from 59% to 78% (
P
< 0.01), as well as the percentage of seedlings that grew (
P
= 0.03), and increased leaf number (
P
= 0.02). Trees from
Pentaclethra macroloba
, the most abundant species, did not increase growth rates with fertilization (
P
= 0.40). In contrast, the most abundant palms (
Socratea exorrhiza
) had more than two times higher stem growth rates with P additions (
P
= 0.01). Our experiment reiterates that P availability is a significant driver of plant processes in these systems, but highlights the importance of considering different aspects of the plant community when making predictions concerning nutrient limitation. We postulate that in diverse, lowland tropical forests "heterogeneous nutrient limitation" occurs, not only driven by variability in nutrient responses among taxa, but also among size classes and potential functional groups. Heterogeneous responses to nutrient additions could lead to changes in forest structure or even diversity in the long term, affecting rates of NPP and thus carbon cycling.
We tested whether and how functional composition changes with succession in dry deciduous and wet evergreen forests of Mexico. We hypothesized that compositional changes during succession in dry ...forest were mainly determined by increasing water availability leading to community functional changes from conservative to acquisitive strategies, and in wet forest by decreasing light availability leading to changes from acquisitive to conservative strategies. Research was carried out in 15 dry secondary forest plots (5-63 years after abandonment) and 17 wet secondary forest plots (<1-25 years after abandonment). Community-level functional traits were represented by community-weighted means based on 11 functional traits measured on 132 species. Successional changes in functional composition are more marked in dry forest than in wet forest and largely characterized by different traits. During dry forest succession, conservative traits related to drought tolerance and drought avoidance decreased, as predicted. Unexpectedly acquisitive leaf traits also decreased, whereas seed size and dependence on biotic dispersal increased. In wet forest succession, functional composition changed from acquisitive to conservative leaf traits, suggesting light availability as the main driver of changes. Distinct suites of traits shape functional composition changes in dry and wet forest succession, responding to different environmental filters.
1. The idea that biotic interactions, including herbivory, predation and competition are more intense at lower latitudes is widely accepted and underpins several dominant theories on the latitudinal ...gradient in biodiversity. Current theory also predicts that the intense biotic interactions at low latitudes will select plants for greater defence against herbivores. We reviewed the literature to provide an assessment of the evidence for and against the hypothesis that herbivory is more intense at lower latitudes, and that plants from low latitudes are better defended than are plants from high latitudes. 2. Only 37% of the 38 latitudinal comparisons of herbivory showed higher herbivory at lower latitudes, and the average effect size in a meta-analysis was not significantly different from zero. Thus, the available data do not support the idea that herbivory is generally more intense in the tropics. 3. Only nine of 56 comparisons found higher chemical defences at lower latitudes, and a meta-analysis showed that overall, chemical defences were significantly higher in plants from higher latitudes. This result is counter to the predictions of much of the literature. 4. A meta-analysis showed no significant effect of latitude on physical defence. 5. A review of the literature on feeding trials and common garden experiments showed that herbivores tend to prefer tissue from high latitudes. This trend could stem from differences in overall defence that were not captured by the metrics used in the literature, but could also result from differences in nutritional quality. 6. The empirical data do not support the widespread view that herbivory is generally more intense at lower latitudes, or that plants from low latitudes are generally better defended than are plants from higher latitudes. These results are counter to the prevailing thought on this topic, and suggest that this field may be ripe for the development of new theory.
1. Ecogeomorphic feedbacks between mineral sediment deposition and above‐ground plant growth are thought to have dominated the evolution of many coastal ecosystems and landforms. However, ...land‐use‐related reductions in sediment delivery rates to estuaries world‐wide suggest that these above‐ground feedbacks may not apply in some of the world’s most vulnerable coastal landscapes. 2. To understand the relationships between sea level rise and marsh survival, we measured root and shoot growth over experimentally manipulated elevations in a rapidly submerging, sediment deficient marsh. 3. Root growth was highest at a distinct optimum elevation in both Schoenoplectus americanus and Spartina patens. S. americanus shoot growth was highest at an optimum elevation, but S. patens shoot growth increased with elevation throughout the intertidal zone. 4. For marsh elevations that are higher than optimum (expected at low sea level rise rates), we propose that an acceleration in the rate of sea level rise will lead to enhanced root growth, organic accretion and wetland stability. For suboptimum marsh elevations (expected at rapid sea level rise rates and/or low sediment supply), increases in the water level will lead to reduced root growth and a decrease in the rate of elevation gain. 5. More than 80% of the marshland in our study area has an elevation below the optimum for root growth, suggesting that this previously unknown feedback could explain observations of rapid marsh deterioration in the region. 6. Synthesis. Below‐ground responses of marshes to sea level rise are more broadly applicable than above‐ground feedbacks because they are consistent among different species and do not depend on the availability of mineral sediment.
Ecology Letters (2010) 13: 838-848 Despite the increasing importance of functional traits for the study of plant ecology, we do not know how variation in a given trait changes across ecological ...scales, which prevents us from assessing potential scale-dependent aspects of trait variation. To address this deficiency, we partitioned the variance in two key functional traits (leaf mass area and leaf dry matter content) across six nested ecological scales (site, plot, species, tree, strata and leaf) in lowland tropical rainforests. In both traits, the plot level shows virtually no variance despite high species turnover among plots and the size of within-species variation (leaf + strata + tree) is comparable with that of species level variation. The lack of variance at the plot level brings substantial support to the idea that trait-based environmental filtering plays a central role in plant community assembly. These results and the finding that the amount of within-species variation is comparable with interspecific variation support a shift of focus from species-based to trait-based ecology.
In this article Lila Athanasiadou and Goda Klumbytė engage in a conversation with Antoinette Rouvroy to revisit Guattari's "Three Ecologies" and discuss their dynamics in and for the digital age. ...While a lot of the discourses on algorithms and digital future invoke catastrophic imaginaries of totalizing control, this conversation works with a propositional format, teasing out affirmative politics by pointing to spaces of potentiality within the environmental, the social and the mental realm. Starting from the environmental ecology and thinking of data as a waste, Rouvroy discusses planetary exhaustion as the result of the depletion of natural resources, forced labour practices and the assumption that data hold the answers to the problems posed by global capital. Proposing a space for material experimentation, she speculates on the potential of emerging subjectivities that remain irreducible to data flows. Within social ecology, Rouvroy advocates for the urgency to center digital policy as the space in which the new forms of institutions emerge in order to reorient the power of computation towards the commons. Lastly, within the mental ecology, Rouvroy reconceptualizes the legal subject as a performance that operates within the proliferation of asignifying data signs, reimagining a "we" beyond the gathering of reductions.
Unruly hills Karlsson, Bengt G
2011., 20110515, 2011, 2011-05-23, 20110101
eBook, Book
The questions that inspired this study are central to contemporary research within environmental anthropology, political ecology, and environmental history: How does the introduction of a modern, ...capitalist, resource regime affect the livelihood of indigenous peoples? Can sustainable resource management be achieved in a situation of radical commodification> of land and other aspects of nature? Focusing on conflicts relating to forest management, mining, and land rights, the author offers an insightful account of present-day challenges for indigenous people to accommodate aspirations for ethnic sovereignty and development.
Animal migrations are costly and are often characterized by high predation risk for individuals. Three of the most oft‐assumed mechanisms for reducing risk for migrants are swamping predators with ...high densities, specific timing of migrations and increased body size. Assessing the relative importance of these mechanisms in reducing predation risk particularly for migrants is generally lacking due to the difficulties in tracking the fate of individuals and population‐level characteristics simultaneously. We used acoustic telemetry to track migration behaviour and survival of juvenile sockeye salmon (Oncorhynchus nerka) smolts released over a wide range of conspecific outmigration densities in a river associated with poor survival. The landscape was indeed high risk; smolt survival was poor (˜68%) over 13·5 km of river examined even though migration was rapid (generally <48 h). Our results demonstrate that smolts largely employ swamping of predators to reduce predation risk. Increased densities of co‐migrant conspecifics dramatically improved survival of smolts. The strong propensity for nocturnal migration resulted in smolts pausing downstream movements until the next nightfall, greatly increasing relative migration durations for smolts that could not traverse the study area in a single night. Smolt size did not appear to impact predation risk, potentially due to unique characteristics of the system or our inability to tag the entire size range of outmigrants. Movement behaviours were important in traversing this high‐risk landscape and provide rare evidence for swamping to effectively reduce individual predation risk.
1. Functional traits have been extensively used to describe, group and rank species according to their functions. There is now growing evidence that intraspecific functional variability, as well as ...interspecific variability, can have significant effects on community dynamics and ecosystem functioning. A core hypothesis for the use of functional traits expressed as species means, that their intraspecific variability is negligible compared with their interspecific variability, has however been too rarely tested empirically. We then addressed four questions: Is intraspecific functional variability across species ranges negligible compared with interspecific variability? Are the major resource economics trade‐off and functional strategies robust to individual trait variability? Are species rankings or ordination robust across species ranges once considering intraspecific variability? Can species be discriminated by their leaf traits? 2. Using an environmentally stratified sampling design within an alpine catchment, we collected five functional traits for 13 common plant species with contrasting life histories and traits. Several populations from a range of environmental conditions were then sampled for each species across their ranges. 3. With an original combination of single‐trait and multi‐trait analyses, we highlighted a non‐negligible contribution of intraspecific variability to overall functional trait variability (∼30%). Although not affecting general and well‐known functional trade‐offs and strategies, intraspecific functional variability had the potential to alter species ordination and produced a functional continuum rather than a clear‐cut species classification. 4. Deciding whether intraspecific functional variability can be considered as negligible - species being represented by mean trait values -, or not - species being represented by multivariate trait distributions -, is an essential question for multiple ecological issues. However, this decision cannot be generic, but will depend on the studied system and selected traits and species, as well as on study objectives.
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