Biogeochemical Cycling of Carbon and Nitrogen in Chaparral Dominated Ecosystems

Jenerette, G. Darrel; Park, Isaac; Andrews, Holly M.; Eberwein, J. R.

doi:10.1007/978-3-319-68303-4_6

Cited by 6 publications

(8 citation statements)

References 161 publications

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“…There have been excellent reviews of chaparral ecosystems (Parker et al, 2016; Underwood et al, 2018b), California grasslands (Eviner, 2016), and California sage scrub (Cleland et al, 2016). There have been two recent reviews for some topics considered here (Jenerette et al, 2018; Park and Jenerette, 2019). The extent and causes of VTC have been examined in numerous recent papers and are thus not a main focus of this review.…”

Section: An Introduction To Vegetation‐type Conversion (Vtc)mentioning

confidence: 99%

Vegetation‐type conversion of evergreen chaparral shrublands to savannahs dominated by exotic annual herbs: causes and consequences for ecosystem function

Pratt

2021

American J of Botany

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Woody, evergreen shrublands are the archetypal community in mediterranean‐type ecosystems, and these communities are profoundly changed when they undergo vegetation‐type conversion (VTC) to become annual, herb‐dominated communities. Recently, VTC has occurred throughout southern California chaparral shrublands, likely with changes in important ecosystem functions. The mechanisms that lead to VTC and subsequent changes to ecosystem processes are important to understand as they have regional and global implications for ecosystem services, climate change, land management, and policy. The main drivers of VTC are altered fire regimes, aridity, and anthropogenic disturbance. Some changes to ecosystem function are certain to occur with VTC, but their magnitudes are unclear, whereas other changes are unpredictable. I present two hypotheses: (1) VTC leads to warming that creates a positive feedback promoting additional VTC, and (2) altered nitrogen dynamics create negative feedbacks and promote an alternative stable state in which communities are dominated by herbs. The patterns described for California are mostly relevant to the other mediterranean‐type shrublands of the globe, which are biodiversity hotspots and threatened by VTC. This review examines the extent and causes of VTC, ecosystem effects, and future research priorities.

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Section: An Introduction To Vegetation‐type Conversion (Vtc)mentioning

confidence: 99%

Vegetation‐type conversion of evergreen chaparral shrublands to savannahs dominated by exotic annual herbs: causes and consequences for ecosystem function

Pratt

2021

American J of Botany

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“…Mediterranean-type shrublands and woodlands, already noted for their globally important biodiversity [83], are increasingly being recognized for their importance regionally and globally in carbon sequestration [4,29], net primary productivity [29,84,85], and water quantity and quality [86]. Carbon sequestration rates may be comparable to those estimated for temperate old-growth forests [4]. Vegetation biomass is an essential part of the landscape assessment process for these services and the ability of chaparral shrublands to deliver these services is not consistent across spatio-temporal gradients due to the environmental differences (e.g., slope, aspect, and elevation) and disturbance from fire.…”

Section: Discussionmentioning

confidence: 99%

“…One of these services, albeit not widely recognized compared to forest landscapes, is the contribution shrublands make to climate mitigation through carbon storage and sustained carbon sequestration. Studies show old-growth chaparral shrublands to be a significant sink for carbon and, consequently, an important component of the global carbon budget [4,5].…”

Section: Introductionmentioning

confidence: 99%

New Biomass Estimates for Chaparral-Dominated Southern California Landscapes

Schrader-Patton

Underwood

2021

Remote Sensing

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Chaparral shrublands are the dominant wildland vegetation type in Southern California and the most extensive ecosystem in the state. Disturbance by wildfire and climate change have created a dynamic landscape in which biomass mapping is key in tracking the ability of chaparral shrublands to sequester carbon. Despite this importance, most national and regional scale estimates do not account for shrubland biomass. Employing plot data from several sources, we built a random forest model to predict aboveground live biomass in Southern California using remote sensing data (Landsat Normalized Difference Vegetation Index (NDVI)) and a suite of geophysical variables. By substituting the NDVI and precipitation predictors for any given year, we were able to apply the model to each year from 2000 to 2019. Using a total of 980 field plots, our model had a k-fold cross-validation R2 of 0.51 and an RMSE of 3.9. Validation by vegetation type ranged from R2 = 0.17 (RMSE = 9.7) for Sierran mixed-conifer to R2 = 0.91 (RMSE = 2.3) for sagebrush. Our estimates showed an improvement in accuracy over two other biomass estimates that included shrublands, with an R2 = 0.82 (RMSE = 4.7) compared to R2 = 0.068 (RMSE = 6.7) for a global biomass estimate and R2 = 0.29 (RMSE = 5.9) for a regional biomass estimate. Given the importance of accurate biomass estimates for resource managers, we calculated the mean year 2010 shrubland biomasses for the four national forests that ranged from 3.5 kg/m2 (Los Padres) to 2.3 kg/m2 (Angeles and Cleveland). Finally, we compared our estimates to field-measured biomasses from the literature summarized by shrubland vegetation type and age class. Our model provides a transparent and repeatable method to generate biomass measurements in any year, thereby providing data to track biomass recovery after management actions or disturbances such as fire.

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“…Mediterranean-type shrublands and woodlands, already noted for their globally important biodiversity [81], are increasingly being recognized for their importance regionally and globally in carbon sequestration [4,29]; net primary productivity [29,82,83]; and water quantity and quality [84]. Carbon sequestration rates may be comparable to those estimated for temperate old-growth forests [4]. Vegetation biomass is an essential part of the landscape assessment process for these services and the ability of chaparral shrublands to deliver these services is not consistent across spatio-temporal gradients due to environmental differences (e.g., slope, aspect, elevation) and disturbance from fire.…”

Section: Discussionmentioning

confidence: 99%

“…Pinyon -juniper, Sierran mixed conifer, Jefferey Pine, and eastside pine CWHR types 3. Montane hardwood and coastal oak woodland, CWHR types 4. Based on three validation plots.…”

mentioning

confidence: 99%

New Biomass Estimates for Chaparral-Dominated Southern California Landscapes

Schrader-Patton¹,

Underwood²

2021

Preprint

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Chaparral shrublands are the dominant wildland vegetation type in southern California and the most extensive ecosystem in the state. Disturbance by wildfire and climate change have created a dynamic landscape in which biomass mapping is key in tracking the ability of chaparral shrub-lands to sequester carbon. Despite this importance, most national and regional scale estimates do not account for shrubland biomass. Employing plot data from several sources, we built a random forest model to predict above ground live biomass in southern California using remote sensing data (Landsat NDVI) and a suite of geophysical variables. By substituting the NDVI and precipi-tation predictors for any given year we were able to apply the model to each year from 2000-2019. Using a total of 980 field plots, our model had a k-fold cross validation R2 of 0.51 and a RMSE of 3.9. Validation by vegetation type ranged from R2 = 0.17 (RMSE=9.7) for Sierran mixed conifer to R2 = 0.91 (RMSE = 2.3) for sagebrush. Our estimates showed an improvement in accuracy over a two other biomass estimates that included shrublands, with an R2 = 0.82 (RMSE = 4.7) compared to R2 = 0.068 (RMSE = 6.7) for a global biomass estimate and R2 = 0.29 (RMSE = 5.9) for a regional biomass estimate. Given the importance of accurate biomass estimates for resource managers we calculated the mean year 2010 shrubland biomass for the four national forests which ranged from 3.5 kg/m2 (Los Padres) to 2.3 kg/m2 (Angeles and Cleveland). Finally, we compared our estimates to field-measured biomass from the literature summarized by shrubland vegetation type and age class. Our model provides a transparent and repeatable method to generate biomass measure-ments in any year, thereby providing data to track biomass recovery after management actions or disturbances such as fire.

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Biogeochemical Cycling of Carbon and Nitrogen in Chaparral Dominated Ecosystems

Cited by 6 publications

References 161 publications

Vegetation‐type conversion of evergreen chaparral shrublands to savannahs dominated by exotic annual herbs: causes and consequences for ecosystem function

Vegetation‐type conversion of evergreen chaparral shrublands to savannahs dominated by exotic annual herbs: causes and consequences for ecosystem function

New Biomass Estimates for Chaparral-Dominated Southern California Landscapes

New Biomass Estimates for Chaparral-Dominated Southern California Landscapes

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