Community and Ecosystem-level Changes in a Species-rich Tallgrass Prairie Restoration

Changes in the plant community and ecosystem properties that follow the conversion of agriculture to restored tallgrass prairies are poorly understood. Beginning in 1995, we established a species-rich, restored prairie chronosequence where -3 ha of agricultural land have been converted to tallgrass prairie each year. Our goals were to examine differences in ecosystem properties between these restored prairies and adjacent agricultural fields and to determine changes in, and potential interactions between, the plant community and ecosystem properties that occur over time in the restored prairies. During the summers of 2000-2002, we examined species cover, soil C and N, potential net C and N mineralization, litter mass, soil texture, and bulk density across the 6- to 8-year-old prairie chronosequence and adjacent agricultural fields in southern Minnesota. We also established experimentally fertilized, watered, and control plots in the prairie chronosequence to examine the degree of nitrogen limitation on aboveground and belowground net primary production (ANPP and BNPP). Large shifts in functional diversity occurred within three growing seasons. First-year prairies were dominated by annuals and biennials. By the second growing season, perennial native composites had become dominant, followed by a significant shift to warm-season C4 grasses in prairies ?3 yr old. Ecosystem properties that changed with the rise of C4 grasses included increased BNPP, litter mass, and C mineralization rates and decreased N mineralization rates. ANPP increased significantly with N fertilization but did not vary between young and old prairies with dramatically different plant community composition. Total soil C and N were not significantly different between prairie and agricultural soils in the depths examined (0-10, 10-20, 20-35, 35-50, 50-65 cm). We compared the results from our species-rich prairie restoration to published data on ecosystem function in other restored grasslands, such as Conservation Reserve Program (CRP) and old-field successional sites. Results suggest that rapid changes in functional diversity can have large impacts on ecosystem-level properties, causing community- and system-level dynamics in species-rich prairie restorations to converge with those from low-diversity managed grasslands

Late-Glacial and Holocene Climatic Effects on Fire and Vegetation Dynamics at the Prairie–Forest Ecotone in South-Central Minnesota

1. Treeline ecotones, such as the prairie–forest boundary, represent climatically sensitive regions where the relative abundance of vegetation types is controlled by complex interactions between climate and local factors. Responses of vegetation and fire to climate change may be tightly linked as a result of strong feedbacks among fuel production, vegetation structure and fire frequency/severity, but the importance of these feedbacks for controlling the stability of this ecotone is unclear. 2. In this study, we examined the prairie–forest ecotone in south-central Minnesota using two lake sediment cores to reconstruct independent records of climate, vegetation and fire over the past 12 500 years. Using pollen, charcoal, sediment magnetic analyses and LOI properties, we investigated whether fires were controlled directly by climate or indirectly by fuel production. 3. Sediment magnetic and LOI data suggest four broad climatic periods occurring c. 11 350–8250 BP (cool/humid), c. 8250–4250 BP (warm/dry), c. 4250–2450 BP (warm/humid), and c. 2450–0 BP (cool/humid), indicating that, since the mid-Holocene, climate has shifted towards wetter conditions favouring greater in-lake production and fuel production on the landscape. 4. The area surrounding both lakes was characterized by boreal forest c. 12 500–10 000 BP, changing to an Ulmus-Ostrya forest c. 10 000–9000 BP, changing to a community dominated by prairie (Poaceae-Ambrosia-Artemisia) and deciduous forest taxa c. 8000–4250 BP, and finally shifting to a Quercus-dominated woodland/savanna beginning c. 4250–3000 BP. 5. Charcoal influx increased from an average of 0.11–0.62 mm2 cm−2 year−1 during the early Holocene forest period (c. 11 350–8250 BP) to 1.71–3.36 mm2 cm−2 year−1 during the period of prairie expansion (c. 8250–4250 BP) and again increased to 4.18–4.90 mm2 cm−2 year−1 at the start of the woodland/savanna period (c. 4250 BP). 6. As a result of the influence of climate on community composition and fuel productivity, changes in fire severity may be the result and not the cause of shifts in vegetation

Late-Glacial and Holocene Climatic Effects on Fire and Vegetation Dynamics at the Prairie–Forest Ecotone in South-Central Minnesota

1. Treeline ecotones, such as the prairie–forest boundary, represent climatically sensitive regions where the relative abundance of vegetation types is controlled by complex interactions between climate and local factors. Responses of vegetation and fire to climate change may be tightly linked as a result of strong feedbacks among fuel production, vegetation structure and fire frequency/severity, but the importance of these feedbacks for controlling the stability of this ecotone is unclear. 2. In this study, we examined the prairie–forest ecotone in south-central Minnesota using two lake sediment cores to reconstruct independent records of climate, vegetation and fire over the past 12 500 years. Using pollen, charcoal, sediment magnetic analyses and LOI properties, we investigated whether fires were controlled directly by climate or indirectly by fuel production. 3. Sediment magnetic and LOI data suggest four broad climatic periods occurring c. 11 350–8250 BP (cool/humid), c. 8250–4250 BP (warm/dry), c. 4250–2450 BP (warm/humid), and c. 2450–0 BP (cool/humid), indicating that, since the mid-Holocene, climate has shifted towards wetter conditions favouring greater in-lake production and fuel production on the landscape. 4. The area surrounding both lakes was characterized by boreal forest c. 12 500–10 000 BP, changing to an Ulmus-Ostrya forest c. 10 000–9000 BP, changing to a community dominated by prairie (Poaceae-Ambrosia-Artemisia) and deciduous forest taxa c. 8000–4250 BP, and finally shifting to a Quercus-dominated woodland/savanna beginning c. 4250–3000 BP. 5. Charcoal influx increased from an average of 0.11–0.62 mm2 cm−2 year−1 during the early Holocene forest period (c. 11 350–8250 BP) to 1.71–3.36 mm2 cm−2 year−1 during the period of prairie expansion (c. 8250–4250 BP) and again increased to 4.18–4.90 mm2 cm−2 year−1 at the start of the woodland/savanna period (c. 4250 BP). 6. As a result of the influence of climate on community composition and fuel productivity, changes in fire severity may be the result and not the cause of shifts in vegetation

Appendix C. Mean annual water table depths from 1998 to 2002 used as a treatment in the seedling growth and seedling survival experiments.

Mean annual water table depths from 1998 to 2002 used as a treatment in the seedling growth and seedling survival experiments

Appendix E. Parameter estimates for the parametric seedling survival model.

Parameter estimates for the parametric seedling survival model

Appendix D. Seed rain influx on permafrost plateaus and in collapse scars by year.

Seed rain influx on permafrost plateaus and in collapse scars by year

Appendix A. The interface between frozen and unfrozen peat landforms in a boreal permafrost peatland landscape.

The interface between frozen and unfrozen peat landforms in a boreal permafrost peatland landscape

Appendix F. Treatment combinations for the parametric seedling survival functions rank ordered by the median time to death (months).

Treatment combinations for the parametric seedling survival functions rank ordered by the median time to death (months)