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Climatic variability and episodic Pinus ponderosa establishment along the forest-grassland ecotones of Colorado
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The primary objective of this study was the detection of possible climatic influences on the recent (i.e., past c. 40 years) establishment of ponderosa pine (Pinus ponderosa) at or near forest-grassland ecotones in the northern Front Range of Colorado. Germination dates were precisely determined for >500 juvenile ponderosa pine collected in six widely dispersed sample areas. All sites sampled were open areas lacking an overstory tree cover but located near seed sources. To evaluate the effects of recent climatic variation on recruitment and survival patterns, three types of climate data were used: (1) instrumental climate records from nearby local weather stations; (2) a multivariate index of El Nino/Southern Oscillation (ENSO); and (3) a regional, ponderosa pine tree-ring index sensitive to moisture variation. There is a strong association between episodic recruitment of ponderosa pine and years in which spring and fall moisture availability is high in the instrumental climate record. During the past 40 years, tree establishment was highly episodic and concentrated mainly in four years—1973, 1979, 1983, and 1990. These years are also associated with large-scale warming of sea-surface temperatures in the eastern tropical Pacific (i.e., El Nin ̃o events). These years of abundant seedling establishment also coincide with years of above average radial growth in mature ponderosa pine. Thus, at open sites suitable for the survival of shade-intolerant ponderosa pine, successful establishment of seedlings is highly episodic depending on local moisture availability related to broad-scale climatic variation. This study demonstrates the climatic sensitivity of ponderosa pine recruitment at low elevation sites along forest-grassland ecotones in the northern Colorado Front Range.
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CO2 emissions from land-use change affected more by nitrogen cycle, than by the choice of land-cover data
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The high uncertainty in land-based CO2 fluxes estimates is thought to be mainly due to uncertainty in not only quantifying historical changes among forests, croplands, and grassland, but also due to different processes included in calculation methods. Inclusion of a nitrogen (N) cycle in models is fairly recent and strongly affects carbon (C) fluxes. In this study, for the first time, we use a model with C and N dynamics with three distinct historical reconstructions of land-use and land-use change (LULUC) to quantify LULUC emissions and uncertainty that includes the integrated effects of not only climate and CO2 but also N. The modeled global average emissions including N dynamics for the 1980s, 1990s, and 2000–2005 were 1.8 ` 0.2, 1.7 ` 0.2, and 1.4 ` 0.2 GtC yr␣1, respectively, (mean and range across LULUC data sets). The emissions from tropics were 0.8 ` 0.2, 0.8 ` 0.2, and 0.7 ` 0.3 GtC yr␣1, and the non tropics were 1.1 ` 0.5, 0.9 ` 0.2, and 0.7 ` 0.1 GtC yr␣1. Compared to previous studies that did not include N dynamics, modeled net LULUC emissions were higher, particularly in the non tropics. In the model, N limitation reduces regrowth rates of vegetation in temperate areas resulting in higher net emissions. Our results indicate that exclusion of N dynamics leads to an underestimation of LULUC emissions by around 70% in the non tropics, 10% in the tropics, and 40% globally in the 1990s. The differences due to inclusion/exclusion of the N cycle of 0.1 GtC yr␣1 in the tro- pics, 0.6 GtC yr␣1 in the non tropics, and 0.7 GtC yr␣1 globally (mean across land-cover data sets) in the 1990s were greater than differences due to the land-cover data in the non tropics and globally (0.2 GtC yr␣1). While land-cover information is improving with satellite and inventory data, this study indicates the importance of accounting for different processes, in particular the N cycle.
Keywords: carbon cycle, carbon emissions, land-use change, model, nitrogen cycle
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DOI Nature-based Solutions Roadmap
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The purpose of the Department of the Interior Nature Based Solutions Roadmap is to provide Department of the Interior (DOI) staff with consistent and credible information about nature-based solutions, such as which strategies match certain conditions and goals, what co-benefits they are likely to provide, example projects, and additional resources for project planning, construction, and monitoring.
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DOI Nature-based Solutions Roadmap
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The purpose of the Department of the Interior Nature Based Solutions Roadmap is to provide Department of the Interior (DOI) staff with consistent and credible information about nature-based solutions, such as which strategies match certain conditions and goals, what co-benefits they are likely to provide, example projects, and additional resources for project planning, construction, and monitoring.
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Driftless Prairies: Native Ecosystems-The Interaction of Fire and Grass
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Understanding the biology and physiology of grass in management decisions
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Effects of grazing on grassland soil carbon: a global review
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Soils of grasslands represent a large potential reservoir for storing CO2, but this potential likely depends on how grasslands are managed for large mammal grazing. Previous studies found both strong positive and negative grazing effects on soil organic carbon (SOC) but explanations for this variation are poorly developed. Expanding on previous reviews, we performed a multifactorial meta-analysis of grazer effects on SOC density on 47 independent experimen- tal contrasts from 17 studies. We explicitly tested hypotheses that grazer effects would shift from negative to positive with decreasing precipitation, increasing fineness of soil texture, transition from dominant grass species with C3 to C4 photosynthesis, and decreasing grazing intensity, after controlling for study duration and sampling depth. The six variables of soil texture, precipitation, grass type, grazing intensity, study duration, and sampling depth explained 85% of a large variation (`150 g m␣2 yr␣1) in grazing effects, and the best model included significant interactions between precipitation and soil texture (P = 0.002), grass type, and grazing intensity (P = 0.012), and study duration and soil sampling depth (P = 0.020). Specifically, an increase in mean annual precipitation of 600 mm resulted in a 24% decrease in grazer effect size on finer textured soils, while on sandy soils the same increase in precipitation pro- duced a 22% increase in grazer effect on SOC. Increasing grazing intensity increased SOC by 6–7% on C4-dominated and C4–C3 mixed grasslands, but decreased SOC by an average 18% in C3-dominated grasslands. We discovered these patterns despite a lack of studies in natural, wildlife-dominated ecosystems, and tropical grasslands. Our results, which suggest a future focus on why C3 vs. C4-dominated grasslands differ so strongly in their response of SOC to grazing, show that grazer effects on SOC are highly context-specific and imply that grazers in different regions might be managed differently to help mitigate greenhouse gas emissions.
Keywords: carbon sequestration, grasslands, grazing, grazing intensity, precipitation, soil organic carbon, soil texture
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Evolution of Grasses and Grassland Ecosystems
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The evolution and subsequent ecological expansion of grasses (Poaceae) since the Late Cretaceous have resulted in the establishment of one of Earth’s dominant biomes, the temperate and tropical grasslands, at the expense of forests. In the past decades, several new approaches have been applied to the fossil record of grasses to elucidate the patterns and processes of this ecosystem transformation. The data indicate that the development of grassland ecosystems on most continents was a multistage process involving the Pale- ogene appearance of (C3 and C4) open-habitat grasses, the mid-late Cenozoic spread of C3 grass-dominated habitats, and, finally, the Late Neogene expansion of C4 grasses at tropical-subtropical latitudes. The evolution of herbivores adapted to grasslands did not necessarily coincide with the spread of open-habitat grasses. In addition, the timing of these evolutionary and ecological events varied between regions. Consequently, region-by-region investigations using both direct (plant fossils) and indirect (e.g., stable carbon isotopes, faunas) evidence are required for a full understanding of the tempo and mode of grass and grassland evolution.
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Evolutionary history and the effect of biodiversity on plant productivity
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Loss of biological diversity because of extinction is one of the most pronounced changes to the global environment. For several decades, researchers have tried to understand how changes in biodiversity might impact biomass production by examining how biomass correlates with a number of biodiversity metrics (especially the number of species and functional groups). This body of research has focused on species with the implicit assumption that they are independent entities. However, functional and ecological similarities are shaped by patterns of common ancestry, such that distantly related species might contribute more to production than close relatives, perhaps by increasing niche breadth. Here, we analyze 2 decades of experiments performed in grassland ecosystems throughout the world and examine whether the evolutionary relationships among the species comprising a community predict how biodiversity impacts plant biomass production. We show that the amount of phylogenetic diversity within communities explained significantly more variation in plant community biomass than other measures of diversity, such as the number of species or functional groups. Our results reveal how evolutionary history can provide critical information for understanding, predicting, and potentially ameliorating the effects of biodiversity loss and should serve as an impetus for new biodiversity experiments.
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Extreme contagion in global habitat clearance
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Habitat clearance remains the major cause of biodiversity loss, with consequences for ecosystem services and for people. In response to this, many global conservation schemes direct funds to regions with high rates of recent habitat destruction, though some also emphasize the conservation of remaining large tracts of intact habitat. If the pattern of habitat clearance is highly contagious, the latter approach will help prevent destructive processes gaining a foothold in areas of contiguous intact habitat. Here, we test the strength of spatial contagion in the pattern of habitat clearance. Using a global dataset of land-cover change at 50 50 km resolution, we discover that intact habitat areas in grid cells are refractory to clearance only when all neighbouring cells are also intact. The likelihood of loss increases dramatically as soon as habitat is cleared in just one neighbouring cell, and remains high thereafter. This effect is consistent for forests and grassland, across biogeographic realms and over centuries, constituting a coherent global pattern. Our results show that landscapes become vulnerable to wholesale clearance as soon as threatening processes begin to penetrate, so actions to prevent any incursions into large, intact blocks of natural habitat are key to their long-term persistence.
Keywords: habitat loss; global change biology; conservation; wilderness
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Framework for Conservation Action in the Great Plains Grasslands Biome
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A ‘Call to Action’ has emerged in the Great Plains to scale-up conservation on private lands and meet the sustainability targets that benefit both agriculture and wildlife. In 2020, a multi-state, areawide planning initiative produced the first biome-scale framework for grassland wildlife conservation on the region’s sustainable working rangelands. This initiative features an action-based framework for 2021-2025 focused on addressing the two most severe and large-scale threats to the Great Plains biome: woodland expansion and land use conversion.
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