Allison Aldous

Resource management in a changing and uncertain climate

Climate change is altering ecological systems throughout the world. Managing these systems in a way that ignores climate change will likely fail to meet management objectives. The uncertainty in projected climate-change impacts is one of the greatest challenges facing managers attempting to address global change. In order to select successful management strategies, managers need to understand the uncertainty inherent in projected climate impacts and how these uncertainties affect the outcomes of management activities. Perhaps the most important tool for managing ecological systems in the face of climate change is active adaptive management, in which systems are closely monitored and management strategies are altered to address expected and ongoing changes. Here, we discuss the uncertainty inherent in different types of data on potential climate impacts and explore climate projections and potential management responses at three sites in North America. The Central Valley of California, the headwaters of the...

Droughts, floods and freshwater ecosystems: evaluating climate change impacts and developing adaptation strategies

Climate change is expected to have significant impacts on hydrologic regimes and freshwater ecosystems, and yet few basins have adequate numerical models to guide the development of freshwater climate adaptation strategies. Such strategies can build on existing freshwater conservation activities, and incorporate predicted climate change impacts. We illustrate this concept with three case studies. In the Upper Klamath Basin of the western USA, a shift in land management practices would buffer this landscape from a declining snowpack. In the Murray–Darling Basin of south-eastern Australia, identifying the requirements of flood-dependent natural values would better inform the delivery of environmental water in response to reduced runoff and less water. In the Savannah Basin of the south-eastern USA, dam managers are considering technological and engineering upgrades in response to more severe floods and droughts, which would also improve the implementation of recommended environmental flows. Even though the three case studies are in different landscapes, they all contain significant freshwater biodiversity values. These values are threatened by water allocation problems that will be exacerbated by climate change, and yet all provide opportunities for the development of effective climate adaptation strategies.

FORMS AND ACCUMULATION OF SOIL P IN NATURAL AND RECENTLY RESTORED PEATLANDS—UPPER KLAMATH LAKE, OREGON, USA

Forms, amounts, and accumulation of soil phosphorus (P) were measured in natural and recently restored marshes surrounding Upper Klamath Lake located in south-central Oregon, USA to determine rates of P accumulation in natural marshes and to assess changes in P pools caused by long-term drainage in recently restored marshes. Soil cores were collected from three natural marshes and radiometrically dated to determine recent (137Cs-based) and long-term (210Pb-based) rates of peat accretion and P accumulation. A second set of soil cores collected from the three natural marshes and from three recently restored marshes was analyzed using a modification of the Hedley procedure to determine the forms and amounts of soil P. Total P in the recently restored marshes (222 to 311 μg cm−3) was 2–3 times greater than in the natural marshes (103 to 117 μg cm−3), primarily due to greater bulk density caused by soil subsidence, a consequence of long-term marsh drainage. Occluded Fe- and Al-bound Pi, calcium-bound Pi and residual P were 4 times, 22 times, and 5 times greater, respectively, in the recently restored marshes. More than 67% of the P pool in the both the natural and recently restored marshes was present in recalcitrant forms (humic-acid Po and residual P) that provide long-term P storage in peat. Phosphorus accumulation in the natural marshes averaged 0.45 g m−2 yr−1 (137Cs) and 0.40 g m−2 yr−1 (210Pb), providing a benchmark for optimizing P sequestration in the recently restored marshes. Effective P sequestration in the recently restored marshes, however, will depend on re-establishing equilibrium between the P-enriched soils and the P concentration of floodwaters and a hydrologic regime similar to the natural marshes.

Soil phosphorus release from a restoration wetland, Upper Klamath Lake, Oregon

Many wetland restoration projects are initiated with phosphorus (P) retention as a primary objective. While undisturbed wetlands often are net sinks for P and other nutrients, there is evidence that newly flooded restoration wetlands on former agricultural land initially release P to surface waters. The objectives of this study were to: 1) measure P release from soils to overlying surface waters that would occur when re-flooding agricultural fields to restore a lake fringe wetland connected to Upper Klamath Lake, Oregon; and 2) identify management strategies to abate nutrient release from soils during restoration to minimize P loading to Upper Klamath Lake. We simulated the process of re-flooding soils using mesocosms in a laboratory experiment. The soils were flooded with lake water, and the water was replenished on a weekly basis. The net P flux from soils to surface water was estimated by measuring differences in P concentrations between water that had been in the mesocosms and the lake water used for replenishment. After the flooding experiment, we measured the concentrations of four forms of soil P using a modification of the Hedley procedure, to examine relationships between soil P chemistry and P release. The majority of P was released in the first two days of the experiment, and all detectable P was released by the end of the second month. We estimated that 1–9 g P/m2 were released from the soils to the water column over the course of the experiment, which amounted to 1%–16% of total soil P. Scaling up to the entire wetland, this totals approximately 64 tons P released over 3,000 ha. We did not find any statistically significant relationships between any of the four forms of soil P and the amount of P released in the flooding experiment. Even though we demonstrate here that P is released while undertaking wetland restoration projects on former agricultural land, it is likely to be a temporary process, and once the wetland begins to resume more natural hydrological and biogeochemical functions and vegetation structure, it will re-start the process of soil accretion and P sequestration.

Groundwater‐dependent ecosystems in Oregon: an assessment of their distribution and associated threats

Effective protection and management of groundwater-dependent ecosystems (GDEs) are hindered by inadequate information on their locations and the condition of associated groundwater supplies. We addressed this knowledge gap by developing a methodology that uses existing datasets to locate GDEs (including groundwater-dependent springs, lakes, rivers, wetlands, and species) and assess threats to groundwater quantity and quality. Here we report on the application of this method across the US state of Oregon. Nearly 40% of watersheds in Oregon contain two or more types of GDEs – termed “GDE clusters” – indicating the widespread importance of groundwater to ecosystems. Documented problems may underestimate the threat to ecosystems from altered groundwater supply or quality. Although documented occurrences of water-table declines are limited, high densities of permitted wells (for irrigation or other commercial purposes) pose a threat to groundwater availability in 18% of GDE clusters. Furthermore, although only...

Hydro-ecology of groundwater-dependent ecosystems: applying basic science to groundwater management

Abstract Effective policies to protect groundwater-dependent ecosystems require robust methods to determine the environmental flows and levels required to support species and processes. Frameworks to support groundwater management must incorporate the relationships between hydrology and species and ecological processes. These hydro-ecological relationships can be used to develop quantitative, measurable thresholds that are sensitive to changes in groundwater quantity. Here we provide a case study from a group of fens in central Oregon, USA, that are used for cattle watering, but also support numerous sensitive species. We developed quantitative relationships between the position of the water table and wetland indicator plant species and the process of peat development, to propose groundwater withdrawal thresholds. A maximum depth to water table of –0.9 to –34.8 cm for fen plants and –16.6 to –32.2 cm for peat accretion can be tolerated in these wetlands. Defining hydro-ecological relationships as thresholds can support management decisions. Editor D. Koutsoyiannis; Guest editor M. Acreman Citation Aldous, A.R. and Bach, L.B., 2014. Hydro-ecology of groundwater-dependent ecosystems: applying basic science to groundwater management. Hydrological Sciences Journal, 59 (3–4), 530–544.