Soil C and N responses to woody plant expansion in a mesic grassland

McCarron, James K.; Knapp, Alan K.; Blair, John M.

doi:10.1023/a:1026255214393

Cited by 59 publications

(47 citation statements)

References 57 publications

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“…McCulley et al (2004) concluded that there was an increase in both soil respiration and ecosystem C and N storage after shrub expansion in subtropical savanna. However, McCarron et al (2003) measured a significant decrease in soil respiration and no change in C or N storage in tallgrass prairie. Hughes et al (2006) also measured no change in surface soil C and N pools, despite substantial changes in aboveground C and N. Jackson et al (2002) concluded that mesic systems with large soil C pools could serve as a C source after replacement of grasses with woody vegetation because of increased soil respiration.…”

Section: Discussionmentioning

confidence: 86%

“…Changes in ecosystem function after shrub expansion, especially with regards to C and N cycling, are often quite substantial (Vitousek et al 1987;McCarron et al 2003;McCulley et al 2004;Hughes et al 2006). Shrubs and other woody vegetation in grasslands act to reduce soil erosion, subsidize nutrient inputs by intercepting atmospheric inputs and serve as a nutrient reservoir, especially in sandy and/or low-nutrient soils (García-Moya and McKell 1970;Vitousek et al 1987;Joy and Young 2002).…”

Section: Introductionmentioning

confidence: 99%

“…Shrubs and other woody vegetation in grasslands act to reduce soil erosion, subsidize nutrient inputs by intercepting atmospheric inputs and serve as a nutrient reservoir, especially in sandy and/or low-nutrient soils (García-Moya and McKell 1970;Vitousek et al 1987;Joy and Young 2002). Furthermore, shrub expansion is often accompanied by substantial changes in annual net primary production (ANPP) and changes in tissue chemistry that affect both litter quality and quantity (McCarron et al 2003;McCulley et al 2004;Hughes et al 2006). For example, Briggs et al (2005) observed a consistent trend of increased leaf N concentration when shrubs replaced grasses, especially when expanding shrubs were N-fixers.…”

Section: Introductionmentioning

confidence: 99%

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Shifts in litterfall and dominant nitrogen sources after expansion of shrub thickets

Brantley

Young

2007

Oecologia

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Woody encroachment into herbaceous ecosystems is emerging as an important ecological response to global change. A primary concern is alterations in C and N cycling and associated variations across a variety of ecosystems. We quantified seasonal variation in litterfall and litter N concentration in Morella cerifera shrub thickets to assess changes in litterfall and associated N input after shrub expansion on an Atlantic coast barrier island. We also used the natural abundance of (15)N to estimate the proportion of litterfall N originating from symbiotic N fixation. Litterfall for shrub thickets ranged from 8,991 +/- 247 to 3,810 +/- 399 kg ha(-1) year(-1) and generally declined with increasing thicket age. Litterfall in three of the four thickets exceeded previous estimates of aboveground annual net primary production in adjacent grasslands by 300-400%. Leaf N concentration was also higher after shrub expansion and, coupled with low N resorption efficiency and high litterfall, resulted in a return of as much as 169 kg N ha(-1) year(-1) to the soil. We estimated that approximately 70% of N returned to the soil was from symbiotic N fixation resulting in an ecosystem input of between 37 and 118 kg ha(-1) year(-1) of atmospheric N depending on site. Considering the extensive cover of shrub thickets on Virginia barrier islands, N fixation by shrubs is likely the largest single source of N to the system. The shift from grassland to shrub thicket on barrier islands results in a substantial increase in litterfall and foliar N concentration that will likely have a major impact on the size and cycling of ecosystem C and N pools. Increasing C and N availability in these nutrient-poor soils is likely to permanently reduce cover of native grasses and alter community structure by favoring species with greater N requirements.

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Section: Discussionmentioning

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Shifts in litterfall and dominant nitrogen sources after expansion of shrub thickets

Brantley

Young

2007

Oecologia

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“…A shift in plant biomass from belowground to aboveground in areas of woody encroachment may cause short-term carbon sinks, though these are more vulnerable to fire and sequester less carbon as woody plants mature. In a complementary Konza Prairie study, annual soil CO 2 flux diminished by 16% as grasslands shifted to shrublands [50]. Juniperus virginiana L. or eastern red cedar is another invasive species found at site K4B that has been shown to alter ecosystem processes by increasing aboveground NPP, litter, and accrual of organic carbon in litter and soil, while decreasing soil respiration [51].…”

Section: Discussionmentioning

confidence: 99%

Comparing Surface and Mid-Tropospheric CO2 Concentrations from Central U.S. Grasslands

Cochran

Brunsell

Mechem

2013

Entropy

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Comparisons of eddy covariance (EC) tower measurements of CO 2 concentration with mid-tropospheric observations from the Atmospheric Infrared Sounder (AIRS) allow for evaluation of the rising global signal of this greenhouse gas in relation to surface carbon dynamics. Using an information theory approach combining relative entropy and wavelet multi-resolution analysis, this study has explored correlations and divergences between mid-tropospheric and surface CO 2 concentrations in grasslands of northeastern Kansas. Results show that surface CO 2 measurements at the Kansas Field Station (KFS) and the Konza Prairie Biological Stations 1B (KZU) and 4B (K4B) with different land-cover types correlate well with mid-tropospheric CO 2 in this region at the 512-day timescale between 2007 and 2010. Relative entropy further reveals that AIRS observations are indicative of surface CO 2 concentrations for all land-cover types on monthly (32-day) and longer timescales. AIRS observations are also similar to CO 2 concentrations at shorter timescales at sites KFS and K4B experiencing woody encroachment, though these results require further investigation. Differences in species composition and microclimate add to the variability of surface concentrations compared with mid-tropospheric observations.

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“…Typically encroachment is viewed negatively by land managers and considered a factor in ecosystem degradation [3,4]. Impacts include increased soil erosion, changes in wildfire occurrence and intensity, changes in vegetation composition, and shifts in local wildlife species [5,6]. To avoid such impacts land managers often seek to remove encroaching conifers and restore historic plant communities.…”

Section: Introductionmentioning

confidence: 99%

A War of Words: Do Conflict Metaphors Affect Beliefs about Managing “Unwanted” Plants?

Nay

Brunson

2013

Societies

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Woody plants have increased in density and extent in rangelands worldwide since the 1800s, and land managers increasingly remove woodland plants in hopes of restoring pre-settlement conditions and/or improved forage for grazing livestock. Because such efforts can be controversial, especially on publicly owned lands, managers often attempt to frame issues in ways they believe can improve public acceptance of proposed actions. Frequently these framing efforts employ conflict metaphors drawn from military or legal lexicons. We surveyed citizens in the Rocky Mountains region, USA, about their beliefs concerning tree-removal as a management strategy. Plants targeted for removal in the region include such iconic tree species as Douglas-fir and ponderosa pine as well as other less-valued species, such as Rocky Mountain juniper, that are common targets for removal nationwide. To test the influence of issue frame on acceptance, recipients were randomly assigned surveys in which the reason for conifer removal was described using one of three terms often employed by invasive biologists and land managers: "invasion", "expansion", and "encroachment". Framing in this instance had little effect on responses. We conclude the use of single-word frames by scientists and managers use to contextualize an issue may not resonate with the public.

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Soil C and N responses to woody plant expansion in a mesic grassland

Cited by 59 publications

References 57 publications

Shifts in litterfall and dominant nitrogen sources after expansion of shrub thickets

Shifts in litterfall and dominant nitrogen sources after expansion of shrub thickets

Comparing Surface and Mid-Tropospheric CO2 Concentrations from Central U.S. Grasslands

A War of Words: Do Conflict Metaphors Affect Beliefs about Managing “Unwanted” Plants?

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