Integrating precipitation, grazing, past effects and interactions in long-term vegetation change

Morris, Christo; Badik, Kevin J.; Morris, Lesley R.; Weltz, Mark A.

doi:10.1016/j.jaridenv.2015.08.005

Cited by 11 publications

(5 citation statements)

References 55 publications

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“…Even within a relatively small study area, differences due to environmental heterogeneity (associated with pasture) interacted with, and were more significant, than the effects of moderate grazing in general. Studies which do not explicitly include effects of past intense grazing, relevant to much of the Great Basin (Morris and Rowe 2014) and much of the western USA (Holechek 1981), or major environmental gradients such as low soil fertility (Harrison et al 2003) or weather (Vermeire et al 2008, Morris et al 2016), are likely to arrive at different conclusions regarding the effects of contemporary grazing on plant communities. Furthermore, documenting the nuanced differences between contemporary cattle grazing and past, less regulated practices may be critical for sustainably managing grazing in dryland systems to avoid potential negative effects from increases in invasive species (Williamson et al 2020) or greater soil erosion (Fick et al 2020).…”

Section: Discussionmentioning

confidence: 99%

Recovery of the herbaceous component of degraded sagebrush steppe is unimpeded by 75 years of moderate cattle grazing

et al. 2021

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Understanding the effects of contemporary cattle grazing on herbaceous perennial communities in big sagebrush steppe is important for managing for wildlife habitat, plant diversity, and productivity, yet potentially complicated by legacy impacts of historic, often higher intensity, livestock grazing. Here, we evaluate whether recovery of herbaceous communities in eastern Oregon, USA, after the cessation of intense spring sheep grazing (1935) was affected by moderate cattle grazing in paired plots with or without grazing over the past 75 yr (1936-2011). We tested for the effects of cattle grazing on herbaceous community recovery, as indicated by changes over time in plant density, and composition, as measured by Bray-Curtis dissimilarity. We also included current and prior to sampling year precipitation anomalies, to account for the weather effects, and a random term for pasture location of plot pairs to include potential subtle differences in abiotic environment and grazing management. We further tested whether time since cessation of intense sheep grazing and moderate cattle grazing were associated with convergence or divergence in community composition indicated by changes in evenness, richness, species relative abundance (rank order), and turnover or species appearance or disappearance. Total perennial herbaceous, forb, and grass density increased over time in sites grazed and ungrazed by cattle, though species varied in the direction of their response to contemporary cattle grazing. Community composition metrics indicated convergence over time including increasing evenness, decreasing Bray-Curtis dissimilarity, decreasing shifts in species relative abundance (rank order), and lower rates of species turnover (and gain and loss). Contemporary cattle grazing was not associated with convergence or divergence in composition. Precipitation anomalies for the current or prior water year were only occasionally significant in herbaceous density and community composition change models. Our results indicate similar long-term recovery trajectories occurred in sites with moderate cattle grazing or removal of all livestock following cessation of intense sheep grazing. Management planning and resource assessment focused on herbaceous perennial communities in sagebrush steppe should seek to separate the impacts of historic from contemporary livestock grazing practices.

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Section: Discussionmentioning

confidence: 99%

Recovery of the herbaceous component of degraded sagebrush steppe is unimpeded by 75 years of moderate cattle grazing

et al. 2021

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“…We test two modeling methods to determine which produces the most accurate results. Because the interaction of disturbance, interannual variation in climate, soils, and interacting effects is needed to fully understand the drivers of vegetation change (Morris et al 2016), we included soils and topographic data as spatial modifiers of future projections (Munson et al 2016b). Our 30-m projections of component cover are based on empirical spatiotemporally informed climate-biophysical relationships developed across 33 yr in the entire sagebrush biome.…”

Section: Introductionmentioning

confidence: 99%

Projected change in rangeland fractional component cover across the sagebrush biome under climate change through 2085

2021

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Climate change over the past century has altered vegetation community composition and species distributions across rangelands in the western United States. The scale and magnitude of climatic influences are unknown. While many studies have projected the effects of climate change using several modeling approaches, none has evaluated the impacts to fractional component cover at a 30-m resolution across the full sagebrush (Artemisia spp.) biome. We used fractional component cover data for rangeland functional groups and weather data from the 1985 to 2018 reference period in conjunction with soils and topography data to develop empirical models describing the spatiotemporal variation in component cover.To investigate the ramifications of future change across the western United States, we extended models based on historical relationships over the reference period to model landscape effects based on future weather conditions from two emission scenarios and three time periods (2020s, 2050s, and 2080s). We tested both generalized additive models (GAMs) and regression tree models, finding that the former led to superior spatial and statistical results. Our results indicate more xeric vegetation across most of the study area, with an increasing dominance of non-sagebrush shrubs, annual herbaceous cover, and bare ground over herbaceous and sagebrush cover in both the representative concentration pathway (RCP) 4.5 and 8.5 scenarios. In general, both scenarios yielded similar results, but RCP 8.5 tended to be more extreme, with greater change relative to the reference period. Results demonstrate that in cool sites some degree of warming to growing season maximum temperature or nongrowing season minimum temperature could be beneficial to sagebrush and shrub growth. However, warming nongrowing season maximum temperature was beneficial to shrub, but not to sagebrush growth. Our results inform rangeland managers of potential future vegetation composition, cover, and species distributions, which could improve prioritization of conservation and restoration efforts.

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“…Indeed, Rosén (1988) found strong below‐ground competition for water resources between individuals of J. communis , as well as between J. communis and other woody and non‐woody species. In particular, J. communis shrubs may be inhibited by the better ability of shallowly rooted herbaceous plants to capitalize on soil moisture in spring and summer (Morris et al, 2016) or by mechanical resistance of grassland root systems to its invasion (Abbate et al, 1994). Moreover, J. communis may remain relatively unaffected by poor soil nutrients as a consequence of its ability to obtain nitrogen and phosphorus from symbiosis with feather mosses (Houle & Babeux, 1994; DeLuca & Zackrisson, 2007), especially on the lateral branches.…”

Section: Discussionmentioning

confidence: 99%

Dynamics of dwarf shrubs in Mediterranean high‐mountain ecosystems

Toma

Carboni

Bazzichetto

et al. 2022

J Vegetation Science

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Question: Vegetation around the alpine-treeline ecotone faces changes in both climate and land use (i.e. grazing abandonment). Broad-scale shrub encroachment is considered an effect of these changes, but it remains unclear how this process is mediated by local-scale environmental heterogeneity. Our goal is to determine which local-scale environmental factors shape the spatial distribution and temporal trends of alpine dwarf shrub vegetation dominated by Juniperus communis in Mediterranean mountains. Location: Three sites in the Central Apennine Mountain Range (Italy): Mt. Terminillo, Mt. Duchessa and Mt. Ernici. Methods: Combining a set of environmental variables obtained at a fine scale (25-m resolution) from multi-year remote sensing imagery and field-collected vegetation data, we modelled the occurrence and cover of Juniperus communis-dominated dwarf shrubland, as well as its change over time, as a function of local climate, topography and land use, using linear and generalized mixed effects models. Results: Over a period of almost 60 years (1954-2012) shrubland occurrence increased by 12% and shrubland cover by 10% in our study sites. Its current distribution and change over time appear to be strongly shaped by the joint influences of fine-scale topography, above-ground biomass, land use and microclimate. Shrublands have been favoured locally in areas with harsher alpine environmental constraints and stronger resource limitations. Conclusions:Our study shows that in the Mediterranean high-mountain environment J. communis dwarf shrubland acts as a stress-tolerant pioneer vegetation, occurring in areas that are otherwise sparsely vegetated. Contrary to our expectations, at fine scales, warmer temperatures and the regional decline in grazing did not favour shrub encroachment. Despite increasing overall, J. communis shrubs have little competitive ability to successfully encroach grasslands, and remain restricted to less-productive areas. Our results confirm that fine-scale environmental heterogeneity can strongly influence shrub distribution and dynamics, thereby modulating future responses in evolving alpine ecosystems.

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Integrating precipitation, grazing, past effects and interactions in long-term vegetation change

Cited by 11 publications

References 55 publications

Recovery of the herbaceous component of degraded sagebrush steppe is unimpeded by 75 years of moderate cattle grazing

Recovery of the herbaceous component of degraded sagebrush steppe is unimpeded by 75 years of moderate cattle grazing

Projected change in rangeland fractional component cover across the sagebrush biome under climate change through 2085

Dynamics of dwarf shrubs in Mediterranean high‐mountain ecosystems

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