Northern hemisphere evergreen forests assimilate a significant fraction of global atmospheric CO2 but monitoring large-scale changes in gross primary production (GPP) in these systems is challenging. Recent advances in remote sensing allow the detection of solar-induced chlorophyll fluorescence (SIF) emission from vegetation, which has been empirically linked to GPP at large spatial scales. This is particularly important in evergreen forests, where traditional remote-sensing techniques and terrestrial biosphere models fail to reproduce the seasonality of GPP. Here, we examined the mechanistic relationship between SIF retrieved from a canopy spectrometer system and GPP at a winter-dormant conifer forest, which has little seasonal variation in canopy structure, needle chlorophyll content, and absorbed light. Both SIF and GPP track each other in a consistent, dynamic fashion in response to environmental conditions. SIF and GPP are well correlated (R2 = 0.62–0.92) with an invariant slope over hourly to weekly timescales. Large seasonal variations in SIF yield capture changes in photoprotective pigments and photosystem II operating efficiency associated with winter acclimation, highlighting its unique ability to precisely track the seasonality of photosynthesis. Our results underscore the potential of new satellite-based SIF products (TROPOMI, OCO-2) as proxies for the timing and magnitude of GPP in evergreen forests at an unprecedented spatiotemporal resolution.

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Abstract. Photosynthesis by terrestrial plants represents the majority of CO2 uptake on Earth, yet it is difficult to measure directly from space. Estimation of gross primary production (GPP) from remote sensing indices represents a primary source of uncertainty, in particular for observing seasonal variations in evergreen forests. Recent vegetation remote sensing techniques have highlighted spectral regions sensitive to dynamic changes in leaf/needle carotenoid composition, showing promise for tracking seasonal changes in photosynthesis of evergreen forests. However, these have mostly been investigated with intermittent field campaigns or with narrow-band spectrometers in these ecosystems. To investigate this potential, we continuously measured vegetation reflectance (400–900 nm) using a canopy spectrometer system, PhotoSpec, mounted on top of an eddy-covariance flux tower in a subalpine evergreen forest at Niwot Ridge, Colorado, USA. We analyzed driving spectral components in the measured canopy reflectance using both statistical and process-based approaches. The decomposed spectral components co-varied with carotenoid content and GPP, supporting the interpretation of the photochemical reflectance index (PRI) and the chlorophyll/carotenoid index (CCI). Although the entire 400–900 nm range showed additional spectral changes near the red edge, it did not provide significant improvements in GPP predictions. We found little seasonal variation in both normalized difference vegetation index (NDVI) and the near-infrared vegetation index (NIRv) in this ecosystem. In addition, we quantitatively determined needle-scale chlorophyll-to-carotenoid ratios as well as anthocyanin contents using full-spectrum inversions, both of which were tightly correlated with seasonal GPP changes. Reconstructing GPP from vegetation reflectance using partial least-squares regression (PLSR) explained approximately 87 % of the variability in observed GPP. Our results linked the seasonal variation in reflectance to the pool size of photoprotective pigments, highlighting all spectral locations within 400–900 nm associated with GPP seasonality in evergreen forests.

SUMMARY: A three-dimensional, non-linear, baroclinic model is described and tested for the first time to study the residual circulation and the thermohaline distribution of the Ría de Vigo (NW Spain) at short time scales and under different wind stress regimes. Two markedly different realistic scenarios were chosen: northerly upwelling-favourable winds and southerly downwelling-favourable winds. The numerical experiments carried out indicate that the hydrodynamic regime of the Ría de Vigo is mostly a consequence of wind events. As could be expected, moderately strong North winds reinforce the normal (positive) Ría circulation, while winds blowing from the South, when sufficiently strong, reverse the typical circulation pattern and reduce the characteristic outgoing velocities and the flushing time inside the Ría. The temperature and salinity fields generated by the model in both situations were compared with observations and found to be in qualitatively good agreement, supporting the 3D velocity field distribution.

IntroductionUNFPA recently developed a composite indicator to assess sexual and reproductive health (SRH)-related laws as part of the Sustainable Development Goals monitoring framework (Indicator 5.6.2). However, there is still little understanding of how best to ensure a supportive SRH-related legal framework can improve SRH outcomes. This research draws on country case studies (Colombia, Malawi, Uruguay, Zambia) to provide more generalizable lessons on the processes by which these laws are translated into practice and their impact on lived realities.MethodsPeer-reviewed and gray literature on laws and policies related to maternity care, contraception, sexuality education, HIV and HPV was reviewed. Key informant interviews were carried out with 8–16 people in each country, including representatives of government, civil society and academia to understand factors affecting implementation of relevant laws and policies. Findings were thematically analyzed by country and contextualized within each country's score on Indicator 5.6.2 and relevant SRH outcome data.FindingsAcross these countries, some common organizational steps help move from laws on paper to impacting people's lives including budget allocation, development of technical guidance, health worker training, population awareness creation and demand generation. It is also important to address sociocultural challenges such as entrenched inequalities, conservative cultural and religious beliefs and the potential existence of customary law. Challenges can be encountered across all these steps and can vary based on the area of SRH: implementation of laws to reduce maternal mortality is generally less controversial than laws around abortion, often making the latter harder to implement. Local specificities in structures, systems and cultures bring opportunities and challenges, highlighting the need for tailored actions.DiscussionA legal framework supportive to SRH is critical, particularly in the face of backlash against sexual and reproductive rights, but alone it is insufficient. Understanding that a generic pathway exists for moving laws into practice is a critical starting point for exploring the specificities of each national context as a way of identifying entry points for action. These findings can be used to inform advocacy and monitoring to help ensure that the potential benefits of supportive SRH-related laws can be realized in these four countries and around the world.