Ideas and perspectives: strengthening the biogeosciences in environmental research networks

Many scientific approaches are improving our understanding and management of the rapidly changing environment. Long-term environmental research networks are one approach to advancing local, regional, and global environmental science and education. A remarkable number and wide variety of environmental research networks operate around the world today. These are diverse in funding, infrastructure, motivating questions, scientific strengths, and the sciences that birthed and maintained the networks. Some networks have individual sites that were selected because they had produced invaluable long-term data, while other networks have new sites selected to span ecological gradients. However, all long-term environmental networks share two challenges. Networks must keep pace with scientific advances and interact with both the scientific community and society at large. If networks fall short of successfully addressing these challenges, they risk becoming irrelevant. The objective of this paper is to assert that the biogeosciences offer environmental research networks a number of opportunities to expand scientific impact and public engagement. We explore some of these opportunities with four networks: the International Long Term Ecological Research programs (ILTERs), the Critical Zone Observatories (CZOs), the Earth and Ecological Observatory networks (EONs), and the FLUXNET program of eddy flux sites. While these networks were founded and grown by interdisciplinary scientists, the preponderance of expertise and funding have gravitated activities of ILTERs and EONs toward ecology and biology, CZOs toward the Earth sciences and geology, and FLUXNET toward ecophysiology and micrometeorology. Our point is not to homogenize networks, nor to diminish disciplinary science. Rather, we argue that by more fully incorporating the integration of biology and geology in long-term environmental research networks, scientists can better leverage network assets, keep pace with the ever-changing science of the environment, and engage with larger scientific and public audiences

Beyond arctic and alpine: the influence of winter climate on temperate ecosystems

Winter climate is expected to change under future climate scenarios, yet the majority of winter ecology research is focused in cold-climate ecosystems. In many temperate systems, it is unclear how winter climate relates to biotic responses during the growing season. The objective of this study was to examine how winter weather relates to plant and animal communities in a variety of terrestrial ecosystems ranging from warm deserts to alpine tundra. Specifically, we examined the association between winter weather and plant phenology, plant species richness, consumer abundance, and consumer richness in 11 terrestrial ecosystems associated with the U.S. Long-Term Ecological Research (LTER) Network. To varying degrees, winter precipitation and temperature were correlated with all biotic response variables. Bud break was tightly aligned with end of winter temperatures. For half the sites, winter weather was a better predictor of plant species richness than growing season weather. Warmer winters were correlated with lower consumer abundances in both temperate and alpine systems. Our findings suggest winter weather may have a strong influence on biotic activity during the growing season and should be considered in future studies investigating the effects of climate change on both alpine and temperate systems.This is the publisher’s final pdf. The published article is copyrighted by the Ecological Society of America and can be found at: http://esajournals.onlinelibrary.wiley.com/hub/journal/10.1002/%28ISSN%291939-9170/Keywords: ecosystem stability, temperate ecosystem, US LTER Network, global change, critical climate periods, winterKeywords: ecosystem stability, temperate ecosystem, US LTER Network, global change, critical climate periods, winte

Disentangling species and functional group richness effects on soil N cycling in a grassland ecosystem

Species richness (SR) and functional group richness (FGR) are often confounded in both observational and experimental field studies of biodiversity and ecosystem function. This precludes discernment of their separate influences on ecosystem processes, including nitrogen (N) cycling, and how those influences might be moderated by global change factors. In a 17-year field study of grassland species, we used two full factorial experiments to independently vary SR (1 or 4 species, with FGR=1) and FGR (1-4 groups, with SR=4) to assess SR and FGR effects on ecosystem N cycling and its response to elevated carbon dioxide (CO2) and N addition. We hypothesized that increased plant diversity (either SR or FGR) and elevated CO2 would enhance plant N pools because of greater plant N uptake, but decrease soil N cycling rates because of greater soil carbon inputs and microbial N immobilization. In partial support of these hypotheses, increasing SR or FGR (holding the other constant) enhanced total plant N pools and decreased soil nitrate pools, largely through higher root biomass, and increasing FGR strongly reduced mineralization rates, because of lower root N concentrations. In contrast, increasing SR (holding FGR constant and despite increasing total plant C and N pools) did not alter root N concentrations or net N mineralization rates. Elevated CO2 had minimal effects on plant and soil N metrics and their responses to plant diversity, whereas enriched N increased plant and soil N pools, but not soil N fluxes. These results show that functional diversity had additional effects on both plant N pools and rates of soil N cycling that were independent of those of species richness

Long-term nitrogen addition does not increase soil carbon storage or cycling across eight temperate forest and grassland sites on a sandy outwash plain

Experimental nitrogen (N) deposition generally inhibits decomposition and promotes carbon (C) accumulation in soils, but with substantial variation among studies. Differences in ecosystem properties could help explain this variability: N could have distinct effects on decomposition and soil C due to differences in vegetation characteristics (that is, root C inputs and chemistry) that influence microbial biomass or soil properties like pH that can affect organic matter stabilization. We used a 12-year N addition experiment to determine effects of sustained N addition on soil C pool sizes and cycling across different grassland, conifer and deciduous forest sites in Minnesota, USA, while controlling for soil type and climate. We conducted a year-long soil incubation, and fit one- and two-pool decay models to respiration data to identify C pool sizes and decay rates. Contrary to previous studies, we found no consistent effects of N on soil C across sites: soil C stocks, microbial respiration, soil C decay rates and pool sizes all showed no general response to N in these sandy soils. Nevertheless, microbial biomass, microbial respiration, and the root biomass C pool responses to N addition were highly correlated, suggesting that soil C responses were ultimately driven by fine root biomass C responses to N addition, which in turn affected microbial biomass. However, the inconsistent directional responses to N among sites with similar vegetation cover highlight that N addition effects can be site-specific and raise caution for broad extrapolation of results from individual systems to global models

Reducing climate impacts of beef production: A synthesis of life cycle assessments across management systems and global regions.

The global demand for beef is rapidly increasing (FAO, 2019), raising concern about climate change impacts (Clark et al., 2020; Leip et al., 2015; Springmann et al., 2018). Beef and dairy contribute over 70% of livestock greenhouse gas emissions (GHG), which collectively contribute ~6.3 Gt CO2 -eq/year (Gerber et al., 2013; Herrero et al., 2016) and account for 14%-18% of human GHG emissions (Friedlingstein et al., 2019; Gerber et al., 2013). The utility of beef GHG mitigation strategies, such as land-based carbon (C) sequestration and increased production efficiency, are actively debated (Garnett et al., 2017). We compiled 292 local comparisons of "improved" versus "conventional" beef production systems across global regions, assessing net GHG emission data from Life Cycle Assessment (LCA) studies. Our results indicate that net beef GHG emissions could be reduced substantially via changes in management. Overall, a 46 % reduction in net GHG emissions per unit of beef was achieved at sites using carbon (C) sequestration management strategies on grazed lands, and an 8% reduction in net GHGs was achieved at sites using growth efficiency strategies. However, net-zero emissions were only achieved in 2% of studies. Among regions, studies from Brazil had the greatest improvement, with management strategies for C sequestration and efficiency reducing beef GHG emissions by 57%. In the United States, C sequestration strategies reduced beef GHG emissions by over 100% (net-zero emissions) in a few grazing systems, whereas efficiency strategies were not successful at reducing GHGs, possibly because of high baseline efficiency in the region. This meta-analysis offers insight into pathways to substantially reduce beef production's global GHG emissions. Nonetheless, even if these improved land-based and efficiency management strategies could be fully applied globally, the trajectory of growth in beef demand will likely more than offset GHG emissions reductions and lead to further warming unless there is also reduced beef consumption

Table_2_Silvopasture offers climate change mitigation and profit potential for farmers in the eastern United States.XLSX

Silvopasture—integrating trees, forage, and grazing livestock on the same piece of land—is increasingly popular, given its potential to store carbon (C) and improve farmers’ livelihoods. We examined the C and economic implications of adding different silvopastoral systems to existing pastures in historically forested areas of the eastern United States (U.S.). We assessed nine distinct systems, varying by species and product (timber, nuts, and fodder for livestock), for two market scenarios: one based on current demand and one that assumes increased demand for products from silvopasture systems. For each system, we assessed C storage (biomass) and economics (internal rates of return (IRR) with and without C payments). We find that silvopasture in the eastern U.S. could expand by 5.6–25.3 million hectares under base case and full adoption scenarios (equaling a 6% increase in the global footprint of silvopasture), and could capture up to 4.9 or 25.6 Tg CO2e yr.−1, respectively. Expansion of silvopasture in these scenarios would come largely from demand for fodder as a supplemental feed, as well as specialty timber products. Per ha mitigation potential varied widely (0.5–6.5 tCO2e ha−1 yr.−1), due to species differences in C accumulation rates. Economics differed too, with some systems offering short break-even timelines (e.g., 7–9 years for fodder systems), and others costing more up front but having greater long-term returns (e.g., Chestnut). Furthermore, while some systems are profitable without any price on C (e.g., fodder-based silvopasture offers 6–14% 10-year IRRs without a price on C), higher payments for C would likely be necessary to unleash broad investment in timber and nut-based silvopasture. Our analysis included planting, maintenance, and harvest costs and tree product revenue. Future work is needed to fully incorporate additional considerations, like loss of grazing use during establishment, shade-induced effects on forage production, and livestock productivity. Furthermore, specific economic, ecological, site- and operation-level considerations are critical to evaluate the appropriateness of silvopasture systems for a given setting. This analysis suggests that across the eastern U.S., silvopasture could offer both climate change mitigation and enhanced profitability for farmers, with notable differences in the system-specific magnitude of opportunity.</p

Table_1_Silvopasture offers climate change mitigation and profit potential for farmers in the eastern United States.docx

Silvopasture—integrating trees, forage, and grazing livestock on the same piece of land—is increasingly popular, given its potential to store carbon (C) and improve farmers’ livelihoods. We examined the C and economic implications of adding different silvopastoral systems to existing pastures in historically forested areas of the eastern United States (U.S.). We assessed nine distinct systems, varying by species and product (timber, nuts, and fodder for livestock), for two market scenarios: one based on current demand and one that assumes increased demand for products from silvopasture systems. For each system, we assessed C storage (biomass) and economics (internal rates of return (IRR) with and without C payments). We find that silvopasture in the eastern U.S. could expand by 5.6–25.3 million hectares under base case and full adoption scenarios (equaling a 6% increase in the global footprint of silvopasture), and could capture up to 4.9 or 25.6 Tg CO2e yr.−1, respectively. Expansion of silvopasture in these scenarios would come largely from demand for fodder as a supplemental feed, as well as specialty timber products. Per ha mitigation potential varied widely (0.5–6.5 tCO2e ha−1 yr.−1), due to species differences in C accumulation rates. Economics differed too, with some systems offering short break-even timelines (e.g., 7–9 years for fodder systems), and others costing more up front but having greater long-term returns (e.g., Chestnut). Furthermore, while some systems are profitable without any price on C (e.g., fodder-based silvopasture offers 6–14% 10-year IRRs without a price on C), higher payments for C would likely be necessary to unleash broad investment in timber and nut-based silvopasture. Our analysis included planting, maintenance, and harvest costs and tree product revenue. Future work is needed to fully incorporate additional considerations, like loss of grazing use during establishment, shade-induced effects on forage production, and livestock productivity. Furthermore, specific economic, ecological, site- and operation-level considerations are critical to evaluate the appropriateness of silvopasture systems for a given setting. This analysis suggests that across the eastern U.S., silvopasture could offer both climate change mitigation and enhanced profitability for farmers, with notable differences in the system-specific magnitude of opportunity.</p

Plant diversity maintains multiple soil functions in future environments

Biodiversity increases ecosystem functions underpinning a suite of services valued by society, including services provided by soils. To test whether, and how, future environments alter the relationship between biodiversity and multiple ecosystem functions, we measured grassland plant diversity effects on single soil functions and ecosystem multifunctionality, and compared relationships in four environments: ambient conditions, elevated atmospheric CO2, enriched N supply, and elevated CO2 and N in combination. Our results showed that plant diversity increased three out of four soil functions and, consequently, ecosystem multifunctionality. Remarkably, biodiversity-ecosystem function relationships were similarly significant under current and future environmental conditions, yet weaker with enriched N supply. Structural equation models revealed that plant diversity enhanced ecosystem multifunctionality by increasing plant community functional diversity, and the even provision of multiple functions. Conserving local plant diversity is therefore a robust strategy to maintain multiple valuable ecosystem services in both present and future environmental conditions

Beyond arctic and alpine : the influence of winter climate on temperate ecosystems

Winter climate is expected to change under future climate scenarios, yet the majority of winter ecology research is focused in cold-climate ecosystems. In many temperate systems, it is unclear how winter climate relates to biotic responses during the growing season. The objective of this study was to examine how winter weather relates to plant and animal communities in a variety of terrestrial ecosystems ranging from warm deserts to alpine tundra. Specifically, we examined the association between winter weather and plant phenology, plant species richness, consumer abundance, and consumer richness in 11 terrestrial ecosystems associated with the U.S. Long-Term Ecological Research (LTER) Network. To varying degrees, winter precipitation and temperature were correlated with all biotic response variables. Bud break was tightly aligned with end of winter temperatures. For half the sites, winter weather was a better predictor of plant species richness than growing season weather. Warmer winters were correlated with lower consumer abundances in both temperate and alpine systems. Our findings suggest winter weather may have a strong influence on biotic activity during the growing season and should be considered in future studies investigating the effects of climate change on both alpine and temperate systems

Beyond arctic and alpine: the influence of winter climate on temperate ecosystems

Winter climate is expected to change under future climate scenarios, yet the majority of winter ecology research is focused in cold-climate ecosystems. In many temperate systems, it is unclear how winter climate relates to biotic responses during the growing season. The objective of this study was to examine how winter weather relates to plant and animal communities in a variety of terrestrial ecosystems ranging from warm deserts to alpine tundra. Specifically, we examined the association between winter weather and plant phenology, plant species richness, consumer abundance, and consumer richness in 11 terrestrial ecosystems associated with the U.S. Long-Term Ecological Research (LTER) Network. To varying degrees, winter precipitation and temperature were correlated with all biotic response variables. Bud break was tightly aligned with end of winter temperatures. For half the sites, winter weather was a better predictor of plant species richness than growing season weather. Warmer winters were correlated with lower consumer abundances in both temperate and alpine systems. Our findings suggest winter weather may have a strong influence on biotic activity during the growing season and should be considered in future studies investigating the effects of climate change on both alpine and temperate systems