Marcia S. DeLonge

Seasonal evapotranspiration patterns in mangrove forests

Diurnal and seasonal controls on water vapor fluxes were investigated in a subtropical mangrove forest in Everglades National Park, Florida. Energy partitioning between sensible and latent heat fluxes was highly variable during the 2004–2005 study period. During the dry season, the mangrove forest behaved akin to a semiarid ecosystem as most of the available energy was partitioned into sensible heat, which gave Bowen ratio values exceeding 1.0 and minimum latent heat fluxes of 5 MJ d−1. In contrast, during the wet season the mangrove forest acted as a well-watered, broadleaved deciduous forest, with Bowen ratio values of 0.25 and latent heat fluxes reaching 18 MJ d−1. During the dry season, high salinity levels (> 30 parts per thousand, ppt) caused evapotranspiration to decline and correspondingly resulted in reduced canopy conductance. From multiple linear regression, daily average canopy conductance to water vapor declined with increasing salinity, vapor pressure deficit, and daily sums of solar irradiance but increased with air temperature and friction velocity. Using these relationships, appropriately modified Penman-Monteith and Priestley-Taylor models reliably reproduced seasonal trends in daily evapotranspiration. Such numerical models, using site-specific parameters, are crucial for constructing seasonal water budgets, constraining hydrological models, and driving regional climate models over mangrove forests.

Networking our science to characterize the state, vulnerabilities, and management opportunities of soil organic matter

Soil organic matter (SOM) supports the Earths ability to sustain terrestrial ecosystems, provide food and fiber, and retains the largest pool of actively cycling carbon. Over 75% of the soil organic carbon (SOC) in the top meter of soil is directly affected by human land use. Large land areas have lost SOC as a result of land use practices, yet there are compensatory opportunities to enhance productivity and SOC storage in degraded lands through improved management practices. Large areas with and without intentional management are also being subjected to rapid changes in climate, making many SOC stocks vulnerable to losses by decomposition or disturbance. In order to quantify potential SOC losses or sequestration at field, regional, and global scales, measurements for detecting changes in SOC are needed. Such measurements and soil-management best practices should be based on well established and emerging scientific understanding of processes of C stabilization and destabilization over various timescales, soil types, and spatial scales. As newly engaged members of the International Soil Carbon Network, we have identified gaps in data, modeling, and communication that underscore the need for an open, shared network to frame and guide the study of SOM and SOC and their management for sustained production and climate regulation.

Triggering a positive research and policy feedback cycle to support a transition to agroecology and sustainable food systems

ABSTRACT An ecologically sustainable and socially equitable food system, one that restores ecosystem services, enhances human welfare, and promotes community-based economic development, is urgently needed. Applied agroecological research and the development of regional and community food systems are key means through which pressing ecological and social externalities may be mitigated. However, progress in both of these areas has been limited, particularly in the USA, with constraints in each likely holding the other back. In this article, we first review and explore how public investment in agroecology research and development has been limited in the USA. We then discuss how agricultural research funds could be shifted to better support the development of more resilient and equitable food systems. Finally, we explore a broader set of structural obstacles to food system change and identify key policies that could work jointly to strengthen a positive feedback cycle of research, policy, education and practice. Such a feedback cycle could work to accelerate a transition to ecological farming and food system norms that enhance natural resources sustainability, equity and resilience.