Lydia P. Olander

Regulation of soil phosphatase and chitinase activity by N and P availability.

Soil microorganisms and plants produce enzymes thatmineralize organically bound nutrients. When nutrientavailability is low, the biota may be able to increase production ofthese enzymes to enhance the supply of inorganicnitrogen (N) and phosphorus (P). Regulation of enzyme productionmay be a point where N and P cyclesinteract. We measured acid phosphatase and chitinase(N-acetyl ß-D-glucosaminide) activity in soilacross a chronosequence in Hawaii where N and Pavailability varies substantially among sites and longterm fertilizer plots had been maintained for over 4years.Phosphatase activity was high at all sites. Chitinaseactivity decreased significantly as age and Navailability increased across the chronosequence.Phosphorus addition suppressed phosphatase activity atall sites, while N addition increased phosphataseactivity at the young, N-limited site. In contrast,N addition repressed chitinase activity only at the Nlimited young site, and P additions had no effect onchitinase activity. These results suggest that theregulatory relationship between nutrient supply andnutrient mineralization are asymmetric for N and P,and that the differences could help to explaindifferences observed in patterns of N and Pavailability.

Nitrogen and Nature

Abstract Anthropogenic changes to the global N cycle are important in part because added N alters the composition, productivity, and other properties of many natural ecosystems substantially. Why does added N have such a large impact? Why is N in short supply in so many natural ecosystems? Processes that slow the cycling of N relative to other elements and processes that control ecosystem-level inputs and outputs of N could cause N supply to limit the dynamics of ecosystems. We discuss stoichiometric differences between terrestrial plants and other organisms, the abundance of protein-precipitating plant defenses, and the nature of the C–N bond in soil organic matter as factors that can slow N cycling. For inputs, the energetic costs of N fixation and their consequences, the supply of nutrients other than N, and preferential grazing on N-fixers all could constrain the abundance and/or activity of biological N-fixers. Together these processes drive and sustain N limitation in many natural terrestrial ecosystems.

Reference scenarios for deforestation and forest degradation in support of REDD: a review of data and methods

Global climate policy initiatives are now being proposed to compensate tropical forest nations for reducing carbon emissions from deforestation and forest degradation (REDD). These proposals have the potential to include developing countries more actively in international greenhouse gas mitigation and to address a substantial share of the worlds emissions which come from tropical deforestation. For such a policy to be viable it must have a credible benchmark against which emissions reduction can be calculated. This benchmark, sometimes termed a baseline or reference emissions scenario, can be based directly on historical emissions or can use historical emissions as input for business as usual projections. Here, we review existing data and methods that could be used to measure historical deforestation and forest degradation reference scenarios including FAO (Food and Agricultural Organization of the United Nations) national statistics and various remote sensing sources. The freely available and corrected global Landsat imagery for 1990, 2000 and soon to come for 2005 may be the best primary data source for most developing countries with other coarser resolution high frequency or radar data as a valuable complement for addressing problems with cloud cover and for distinguishing larger scale degradation. While sampling of imagery has been effectively useful for pan-tropical and continental estimates of deforestation, wall-to-wall (or full coverage) allows more detailed assessments for measuring national-level reference emissions. It is possible to measure historical deforestation with sufficient certainty for determining reference emissions, but there must be continued calls at the international level for making high-resolution imagery available, and for financial and technical assistance to help countries determine credible reference scenarios. The data available for past years may not be sufficient for assessing all forms of forest degradation, but new data sources will have greater potential in 2007 and after. This paper focuses only on the methods for measuring changes in forest area, but this information must be coupled with estimates of change in forest carbon stocks in order to quantify emissions from deforestation and forest degradation.

Biological and Geochemical Sinks for Phosphorus in Soil from a Wet Tropical Forest

In many tropical and volcanic soils, phosphorus (P) availability is strongly influenced by geochemical sorption, which binds P to soil minerals. The aim of this study was to determine whether biological demand or soil sorption strength was the primary control over phosphate availability and retention in a wet tropical soil with high sorption capacity and low P availability. We added 32PO4 to soil from the upper two horizons and assessed the ability of soil microbes to immobilize the added phosphate in the presence of strong sorption. We added phosphate at two concentrations, one representing background turnover that adds low concentrations of P to the soil solution, and the other representing nutrient pulses that can add fairly high fluxes of P to the soil solution. Sorption and microbial immobilization were rapid for both concentrations, consuming most added P within 30 min. Thus, little P remained in the soil solution or extractable pools, which are considered more available to plants. Although soil sorption strength was almost identical for the two horizons, immobilization of tracer P was approximately three times greater in the upper horizon, where most microbial activity was located. This result suggests that microbial demand controlled how P was partitioned into biological versus geochemical sinks. Further evidence for microbial control is suggested by the movement of tracer P from the sorbed pool into the microbial pool when demand was stimulated by the addition of carbon (C). We also explored how increased nitrogen (N) and P availability changed P dynamics in this nutrient poor soil. In contrast to the unfertilized soil, long-term N and P fertilization substantially reduced biological control over inorganic P. P fertilization saturated the soils, overwhelming biological P demand, whereas N fertilization appeared to increase available P through reduced P sorption. Where biological demand for P is high and P becomes available in the soil solution, microbes may play an important role in controlling P partitioning into biological versus geochemical sinks even in soils that have high sorption capacity.

Get the science right when paying for nature's services

Few projects adequately address design and evaluation Payments for Ecosystem Services (PES) mechanisms leverage economic and social incentives to shape how people influence natural processes and achieve conservation and sustainability goals. Beneficiaries of natures goods and services pay owners or stewards of ecosystems that produce those services, with payments contingent on service provision (1, 2). Integrating scientific knowledge and methods into PES is critical (3, 4). Yet many projects are based on weak scientific foundations, and effectiveness is rarely evaluated with the rigor necessary for scaling up and understanding the importance of these approaches as policy instruments and conservation tools (2, 5, 6). Part of the problem is the lack of simple, yet rigorous, scientific principles and guidelines to accommodate PES design and guide research and analyses that foster evaluations of effectiveness (4). As scientists and practitioners from government, nongovernment, academic, and finance institutions, we propose a set of such guidelines and principles.

Reducing greenhouse gas emissions and adapting agricultural management for climate change in developing countries: providing the basis for action

Agriculture in developing countries has attracted increasing attention in international negotiations within the United Nations Framework Convention on Climate Change for both adaptation to climate change and greenhouse gas mitigation. However, there is limited understanding about potential complementarity between management practices that promote adaptation and mitigation, and limited basis to account for greenhouse gas emission reductions in this sector. The good news is that the global research community could provide the support needed to address these issues through further research linking adaptation and mitigation. In addition, a small shift in strategy by the Intergovernmental Panel on Climate Change (IPCC) and ongoing assistance from agricultural organizations could produce a framework to move the research and development from concept to reality. In turn, significant progress is possible in the near term providing the basis for UNFCCC negotiations to move beyond discussion to action for the agricultural sector in developing countries.

Institutions and Policies to Protect Rural Livelihoods in REDD+ Regimes

While there is growing interest among researchers and practitioners concerning the risks that emerging REDD regimes pose to rural livelihoods, there has been little scholarly analysis of specific policies that could be applied to guard against these risks. We argue that for REDD regimes to avoid negative impacts on local populations, social safeguard policies will need to overcome the significant barriers posed by ambiguous property rights and weak governance and create five institutional conditions: (1) local community support for project-level activities, (2) citizen participation in reforms affecting property rights and land use, (3) transparency of forest carbon revenue flows, (4) citizen access to grievance mechanisms, and (5) opportunities for adaptive management through evaluation. We identify and discuss various policies that could be applied to produce these conditions. We argue that positively engaging rural populations in REDD may be integral to the effectiveness of programs in reducing deforestation and degradation, and enhancing forest carbon stores. Future research should aim to identify the causal mechanisms (policies and institutions) responsible for positive socioeconomic and ecological impacts in REDD, while testing key theories that link participation to conservation and development outcomes.

Surface Soil Changes Following Selective Logging in an Eastern Amazon Forest

Abstract In the Brazilian Amazon, selective logging is second only to forest conversion in its extent. Conversion to pasture or agriculture tends to reduce soil nutrients and site productivity over time unless fertilizers are added. Logging removes nutrients in bole wood, enough that repeated logging could deplete essential nutrients over time. After a single logging event, nutrient losses are likely to be too small to observe in the large soil nutrient pools, but disturbances associated with logging also alter soil properties. Selective logging, particularly reduced-impact logging, results in consistent patterns of disturbance that may be associated with particular changes in soil properties. Soil bulk density, pH, carbon (C), nitrogen (N), phosphorus (P), calcium (Ca), magnesium (Mg), potassium (K), iron (Fe), aluminum (Al), δ13C, δ15N, and P fractionations were measured on the soils of four different types of logging-related disturbances: roads, decks, skids, and treefall gaps. Litter biomass and perce...

Advancing agricultural greenhouse gas quantification

Better information on greenhouse gas (GHG) emissions and mitigation potential in the agricultural sector is necessary to manage these emissions and identify responses that are consistent with the food security and economic development priorities of countries. Critical activity data (what crops or livestock are managed in what way) are poor or lacking for many agricultural systems, especially in developing countries. In addition, the currently available methods for quantifying emissions and mitigation are often too expensive or complex or not sufficiently user friendly for widespread use.The purpose of this focus issue is to capture the state of the art in quantifying greenhouse gases from agricultural systems, with the goal of better understanding our current capabilities and near-term potential for improvement, with particular attention to quantification issues relevant to smallholders in developing countries. This work is timely in light of international discussions and negotiations around how agriculture should be included in efforts to reduce and adapt to climate change impacts, and considering that significant climate financing to developing countries in post-2012 agreements may be linked to their increased ability to identify and report GHG emissions (Murphy et al 2010, CCAFS 2011, FAO 2011).

Chapter Three – Greenhouse Gas Mitigation with Agricultural Land Management Activities in the United States—A Side-by-Side Comparison of Biophysical Potential

Abstract Responsible for 6% of U.S. greenhouse gas (GHG) production, agricultural land use has significant potential to reduce these emissions and capture additional carbon in the soil. Many different activities have been proposed for such mitigation, but assessments of the biophysical potential have been limited and have not provided direct comparison among the many options. We present an in-depth review of the scientific literature, with a side-by-side comparison of net biophysical GHG mitigation potential for 42 different agricultural land management activities in the United States, many of which are likely applicable in other regions. Twenty of these activities are likely to be beneficial for GHG mitigation and have sufficient research to support this conclusion. Limited research leads to uncertainty for 15 other activities that may have positive mitigation potential, and the remaining activities have small or negative GHG mitigation potential or life-cycle GHG concerns. While we have sufficient information to move forward in implementing a number of activities, there are some high-priority research needs that will help clarify problematic uncertainties.