Evidence for competition and facilitation trade-offs: effects of Sitka alder density on pine regeneration and soil productivity

2006 ◽  
Vol 36 (5) ◽  
pp. 1286-1298 ◽  
Author(s):  
Suzanne W Simard ◽  
Steven R Radosevich ◽  
Donald L Sachs ◽  
Shannon M Hagerman
Keyword(s):  
Resource Availability ◽  
Pinus Contorta ◽  
Soil Productivity ◽  
Deciduous Species ◽  
Competitive Effects ◽  
Trade Offs ◽  
Alnus Viridis ◽  
Pine Regeneration ◽  
Over Time

We suggest that the net outcome of interactions between regenerating conifers and early seral deciduous species depends on trade-offs between competition and facilitation over time. Vegetation management treatments that dramatically reduce competitive effects of deciduous species may constrain the ability of conifers to optimize resource trade-offs (e.g., increased growth response to light at the expense of increased drought mortality), potentially affecting long-term productivity. In a 15-year study in southern interior British Columbia, we investigated whether lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) survival, growth, and resource availability differed among manipulated stand compositions, from pure pine stands to mixtures with native N2-fixing Sitka alder (Alnus viridis subsp. sinuata (Regel) Á. Löve & D. Löve) or herbs. We found that pine growth increases were sustained only in pure stands, where alder and herbs were completely removed, corresponding with short-term increases in light, soil and air temperature, and soil nitrate. However, this came at a significant cost to survival (through loss of protection from browsing, desiccation, and sun scald), as well as dramatic depletions in soil nitrogen mineralization over the longer term. Our results support a competition–facilitation trade-off hypothesis, suggesting that treatment-imposed shifts in resource availability over time could negatively affect forest productivity.

Comparing lodgepole pine growth and disease occurrence at six Long-Term Soil Productivity (LTSP) sites in British Columbia, Canada

2016 ◽  
Vol 46 (4) ◽  
pp. 595-599 ◽  
Author(s):  
Anya M. Reid ◽  
William K. Chapman ◽  
Cindy E. Prescott
Keyword(s):  
British Columbia ◽  
Tree Growth ◽  
Pinus Contorta ◽  
Lodgepole Pine ◽  
Forest Health ◽  
Soil Productivity ◽  
Growth Data ◽  
Disease Occurrence ◽  
Disease Attack

Recently, the assumption that stands with fast growth will have minor losses to insect and disease attack has been challenged. Although tree growth and health are both critical for long-term forest productivity, standardized forest-health data are rarely collected in conjunction with tree-growth data. Using six Long-Term Soil Productivity (LTSP) installations in British Columbia, Canada, we explore the relationships between lodgepole pine (Pinus contorta Douglas ex Loudon) growth and disease occurrence. Treatment plots and random groups of 100 trees that had larger trees generally had more disease. These findings suggest that we can no longer assume that fast-growing plantations will be free of disease, which has implications for predicting future timber supply.

scholarly journals Delayed Impact of Fair Machine Learning

2019 ◽  
Author(s):  
Lydia T. Liu ◽  
Sarah Dean ◽  
Esther Rolf ◽  
Max Simchowitz ◽  
Moritz Hardt
Keyword(s):  
Machine Learning ◽  
Well Being ◽  
Temporal Modeling ◽  
Common Criteria ◽  
Feedback Model ◽  
Trade Offs ◽  
One Step ◽  
New Challenges ◽  
Over Time

Static classification has been the predominant focus of the study of fairness in machine learning. While most models do not consider how decisions change populations over time, it is conventional wisdom that fairness criteria promote the long-term well-being of groups they aim to protect. This work studies the interaction of static fairness criteria with temporal indicators of well-being. We show a simple one-step feedback model in which common criteria do not generally promote improvement over time, and may in fact cause harm. Our results highlight the importance of temporal modeling in the evaluation of fairness criteria, suggesting a range of new challenges and trade-offs.

Connecting Crop Nutrient Use Efficiency to Future Soil Productivity

2018 ◽  
Vol 102 (4) ◽  
pp. 8-10
Author(s):  
Fernando García ◽  
Andrés Grasso ◽  
María González Sanjuan ◽  
Adrián Correndo ◽  
Fernando Salvagiotti
Keyword(s):  
Nutrient Management ◽  
Nutrient Use Efficiency ◽  
Management Strategies ◽  
Crop Productivity ◽  
Soil Productivity ◽  
Nutrient Use ◽  
Grain Crop ◽  
Wide Scale ◽  
Use Efficiency

Trends over the past 25 years indicate that Argentina’s growth in its grain crop productivity has largely been supported by the depletion of the extensive fertility of its Pampean soils. Long-term research provides insight into sustainable nutrient management strategies ready for wide-scale adoption.

Enhancing community welfare through improved water quality: a case for applying staggered pollution charges in the river Musi sub-basin of Andhra Pradesh, India

Water Policy ◽  
2005 ◽  
Vol 7 (5) ◽  
pp. 469-483
Author(s):  
Tishya Chatterjee
Keyword(s):  
Andhra Pradesh ◽  
Relevant Literature ◽  
Pollution Prevention ◽  
Economic Benefits ◽  
Environmental Damage ◽  
Marginal Costs ◽  
Community Acceptance ◽  
Level Data ◽  
Over Time

In conditions of severe water-pollution and dormant community acceptance of accumulating environmental damage, the regulator's role goes beyond pollution prevention and more towards remediation and solutions based on the community's long-term expectations of economic benefits from clean water. This paper suggests a method to enable these benefits to become perceptible progressively, through participatory clean-up operations, supported by staggered pollution charges. It analyses the relevant literature on pollution prevention and applies a cost-based “willingness to pay” model, using primary basin-level data of total marginal costs. It develops a replicable demand-side approach imposing charge-standard targets over time in urban-industrial basins of developing countries.

The Short-Term and Long-Term Impacts of Sarbanes-Oxley Act on Composition and Characteristics of Corporate Board of Directors

2015 ◽  
Vol 5 (4) ◽  
Author(s):  
Halil Kaya ◽  
Gaurango Banerjee
Keyword(s):  
Board Composition ◽  
Corporate Boards ◽  
Corporate Accountability ◽  
Corporate Board ◽  
Short Term ◽  
Dual Roles ◽  
Board Characteristics ◽  
Sarbanes Oxley ◽  
Over Time

The paper examines the Sarbanes-Oxley (2002) Acts immediate impact on board composition and characteristics as well as possible reversals in its impact over time. Effects on directors age and tenure are analyzed over the 2001-06 sample period. Female participation in corporate boards is also studied in the pre-SOX and post-SOX periods. The dual roles of directors in being a member of the board as well as serving as either CEO, CFO, Chairman, Co-Chair, Founder, or Lead Director of their respective companies is also examined. We observe a short-term impact of SOX on board compositions due to changes seen in board characteristics between 2001 (pre-SOX), and 2003-05 short-term period (post-SOX). Also, we observe a reversal of board characteristics in 2006 to pre-SOX levels implying that the effects of SOX on board composition were short-lived, and needs to be monitored over time to ensure adherence to corporate accountability guidelines over the long-term.

Decision Processes and Value Endogeneity

2018 ◽  
Author(s):  
James G. March
Keyword(s):  
Decision Processes ◽  
Hard Problem ◽  
Trade Offs ◽  
Definition Of ◽  
Over Time ◽  
What Matters

Humans use reasons to shape and justify choices. In the process, trade-offs seem essential and often inevitable. But trade-offs involve comparisons, which are problematic both across values and especially over time. Reducing disparate values to a common metric (especially if that metric is money) is often problematic and unsatisfactory. Critically, it is not that values just shape choices, but that choices themselves shape values. This endogeneity of values makes an unconditional normative endorsement of modern decision-theoretic rationality unwise. This is a hard problem and there is no escaping the definition of good values, that is, those that make humans better. This removes the wall between economics and philosophy. If we are to adopt and enact this perspective, then greater discourse and debate on what matters and not just what counts will be useful and even indispensable.

scholarly journals Predictors of historical change in drug treatment coverage among people who inject drugs in 90 large metropolitan areas in the USA, 1993–2007

2020 ◽  
Vol 15 (1) ◽  
Author(s):  
Barbara Tempalski ◽  
Leslie D. Williams ◽  
Brooke S. West ◽  
Hannah L. F. Cooper ◽  
Stephanie Beane ◽  
...  
Keyword(s):  
Public Health ◽  
Drug Treatment ◽  
Resource Availability ◽  
People Who Inject Drugs ◽  
Census Data ◽  
Poverty Rate ◽  
Community Action ◽  
Historical Change ◽  
Treatment Coverage ◽  
Over Time

Abstract Background Adequate access to effective treatment and medication assisted therapies for opioid dependence has led to improved antiretroviral therapy adherence and decreases in morbidity among people who inject drugs (PWID), and can also address a broad range of social and public health problems. However, even with the success of syringe service programs and opioid substitution programs in European countries (and others) the US remains historically low in terms of coverage and access with regard to these programs. This manuscript investigates predictors of historical change in drug treatment coverage for PWID in 90 US metropolitan statistical areas (MSAs) during 1993–2007, a period in which, overall coverage did not change. Methods Drug treatment coverage was measured as the number of PWID in drug treatment, as calculated by treatment entry and census data, divided by numbers of PWID in each MSA. Variables suggested by the Theory of Community Action (i.e., need, resource availability, institutional opposition, organized support, and service symbiosis) were analyzed using mixed-effects multivariate models within dependent variables lagged in time to study predictors of later change in coverage. Results Mean coverage was low in 1993 (6.7%; SD 3.7), and did not increase by 2007 (6.4%; SD 4.5). Multivariate results indicate that increases in baseline unemployment rate (β = 0.312; pseudo-p < 0.0002) predict significantly higher treatment coverage; baseline poverty rate (β = − 0.486; pseudo-p < 0.0001), and baseline size of public health and social work workforce (β = 0.425; pseudo-p < 0.0001) were predictors of later mean coverage levels, and baseline HIV prevalence among PWID predicted variation in treatment coverage trajectories over time (baseline HIV * Time: β = 0.039; pseudo-p < 0.001). Finally, increases in black/white poverty disparity from baseline predicted significantly higher treatment coverage in MSAs (β = 1.269; pseudo-p < 0.0001). Conclusions While harm reduction programs have historically been contested and difficult to implement in many US communities, and despite efforts to increase treatment coverage for PWID, coverage has not increased. Contrary to our hypothesis, epidemiologic need, seems not to be associated with change in treatment coverage over time. Resource availability and institutional opposition are important predictors of change over time in coverage. These findings suggest that new ways have to be found to increase drug treatment coverage in spite of economic changes and belt-tightening policy changes that will make this difficult.

Sign in / Sign up

Export Citation Format

Share Document