Germination and Seedling Establishment in California Annual Grassland

Bartolome, James W.

doi:10.2307/2259350

Cited by 142 publications

(119 citation statements)

References 7 publications

Supporting

Mentioning

105

Contrasting

Order By: Relevance

“…To estimate competition coefficients (a ii , a jj , a ij and a ji ), we grew species in pairwise competition in pots at an expected density of 70 plants (based on germination rates from pilot experiments). This density is comparable with the seeding density found in annual grasslands (2500 to 5500 plants m 22 [29,30]). Within these pots, we varied the numbers of individuals of the two species (10 : 60, 20 : 50, 30 : 40, 40 : 30, 50 : 20 and 60 : 10 individuals) to create six relative frequency ratios, and had two replicates per frequency ratio.…”

Section: (C) Experimental Designsupporting

confidence: 80%

Species coexistence: macroevolutionary relationships and the contingency of historical interactions

2016

View full text Add to dashboard Cite

Evolutionary biologists since Darwin have hypothesized that closely related species compete more intensely and are therefore less likely to coexist. However, recent theory posits that species diverge in two ways: either through the evolution of 'stabilizing differences' that promote coexistence by causing individuals to compete more strongly with conspecifics than individuals of other species, or through the evolution of 'fitness differences' that cause species to differ in competitive ability and lead to exclusion of the weaker competitor. We tested macroevolutionary patterns of divergence by competing pairs of annual plant species that differ in their phylogenetic relationships, and in whether they have historically occurred in the same region or different regions (sympatric versus allopatric occurrence). For sympatrically occurring species pairs, stabilizing differences rapidly increased with phylogenetic distance. However, fitness differences also increased with phylogenetic distance, resulting in coexistence outcomes that were unpredictable based on phylogenetic relationships. For allopatric species, stabilizing differences showed no trend with phylogenetic distance, whereas fitness differences increased, causing coexistence to become less likely among distant relatives. Our results illustrate the role of species' historical interactions in shaping how phylogenetic relationships structure competitive dynamics, and offer an explanation for the evolution of invasion potential of non-native species.

show abstract

Section: (C) Experimental Designsupporting

confidence: 80%

Species coexistence: macroevolutionary relationships and the contingency of historical interactions

2016

View full text Add to dashboard Cite

show abstract

“…We surveyed the plot-level community structure and corresponding environmental parameters during peak biomass in the following growing season. Plots were surveyed April 20 to May 2 in 2014, using percentage of cover estimates of each species because small-statured annuals can occur at densities up to 5,500 individuals per square meter (46); additional surveys were conducted later in the season to confirm the identities of late-flowering species. We surveyed the innermost 0.5 × 0.5 m 2 of each plot to account for any edge effects in our analyses.…”

Section: Methodsmentioning

confidence: 99%

Experimental dispersal reveals characteristic scales of biodiversity in a natural landscape

Germain

Strauss

Gilbert

2017

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

Ecological theory posits that dispersal among habitat patches links local communities and is a key "regional" process that maintains biological diversity. However, manipulations required to experimentally test regional processes are infeasible for most systems, and thus more work is needed to detect the scales at which regional processes manifest and their overall effect on diversity. In a Californian grassland, a hotspot for global biodiversity, we used a seed vacuum to increase dispersal at spatial scales varying from 1 m to 10 km while maintaining a realistic spatial structure of species pools and environmental conditions. We found that dispersal limitation has a profound influence on diversity; species richness increased with the spatial scale of seed mixing, doubling in plots that received seed from large (≥5 km) compared with small (≤5 m) scales. This increase in diversity corresponded to an increase in how well species distributions were explained by environmental conditions, from modest at small scales (R 2 = 0.34) to strong at large scales (R 2 = 0.52). Responses to the spatial scale of seed mixing were nonlinear, with no differences below 5 m or above 5 km. Nonlinearities were explained by homogeneity of environmental conditions below 5 m and by a lack of additional variation in the species pool above 5 km. Our approach of manipulating natural communities at different spatial scales reveals (i) nonlinear transitions in the importance of environmental sorting and dispersal, and (ii) the negative effects of dispersal limitation on local diversity, consistent with previous research suggesting that large numbers of species are headed toward regional extinction.The problem of pattern and scale is the central problem in ecology, unifying population biology and ecosystem science, and marrying basic and applied ecology. S. A. Levin (1992) T he processes that structure ecological populations, biodiversity, and ecosystem properties transition in importance across spatial scales (1, 2). As the spatial scale of observation increases, the range of environments sampled (1, 3) and the geographic distance separating localities (4) become increasingly important in shaping species distributions. As a consequence, the relative spatial scaling of different ecological processes is thought to underlie some of the most important patterns in ecology, such as species-area (5) and biodiversity-ecosystem function relationships (6). Because identifying the important scales is challenging, ecologists often compare ecological patterns among local and regional scales to simplify theoretical (7-9) and empirical research (10, 11). However, how closely local and regional delineations match up with the actual scaling of ecological processes is rarely known (2, 12). Quantifying the spatial scaling of these processes promises to enrich our understanding of the mechanisms that maintain diversity, yet remains elusive even in biodiversity hotspots that require this information for conservation decisions (13).A major challenge to testing how ...

show abstract

“…Grass seed germination normally occurs in the fall, 1 week after a major rain event with total precipitation of at least 15 mm (Bartolome, 1979;Chiariello, 1989). One such rain event occurred on 10 October for the 2000-2001 growing season, 1 month earlier as compared to 11 November for the second season.…”

Section: Weather Conditions and Canopy Structurementioning

confidence: 99%

“…Mediterranean grasslands, in contrast, are functional during the winter and early spring and are dead during the summer, as temperature is out phase with precipitation (Bartolome, 1979;Chiariello, 1989). Consequently, the length of its growing season depends on the timing of the beginning and end of the rainy season.…”

Section: Introductionmentioning

confidence: 99%

Seasonal variation in carbon dioxide exchange over a Mediterranean annual grassland in California

Baldocchi

2004

Agricultural and Forest Meteorology

538

350

View full text Add to dashboard Cite

Understanding how environmental variables affect the processes that regulate the carbon flux over grassland is critical for large-scale modeling research, since grasslands comprise almost one-third of the earth's natural vegetation. To address this issue, fluxes of CO 2 (F c , flux toward the surface is negative) were measured over a Mediterranean, annual grassland in California, USA for 2 years with the eddy covariance method.To interpret the biotic and abiotic factors that modulate F c over the course of a year we decomposed net ecosystem CO 2 exchange into its constituent components, ecosystem respiration (R eco ) and gross primary production (GPP). Daytime R eco was extrapolated from the relationship between temperature and nighttime F c under high turbulent conditions. Then, GPP was estimated by subtracting daytime values of F c from daytime estimates of R eco .Results show that most of carbon exchange, both photosynthesis and respiration, was limited to the wet season (typically from October to mid-May). Seasonal variations in GPP followed closely to changes in leaf area index, which in turn was governed by soil moisture, available sunlight and the timing of the last frost. In general, R eco was an exponential function of soil temperature, but with season-dependent values of Q 10 . The temperature-dependent respiration model failed immediately after rain events, when large pulses of R eco were observed. Respiration pulses were especially notable during the dry season when the grass was dead and were the consequence of quickly stimulated microbial activity.Integrated values of GPP, R eco , and net ecosystem exchange (NEE) were 867, 735, and −132 g C m −2 , respectively, for the 2000-2001 season, and 729, 758, and 29 g C m −2 for the 2001-2002 season. Thus, the grassland was a moderate carbon sink during the first season and a weak carbon source during the second season. In contrast to a well-accepted view that annual production of grass is linearly correlated to precipitation, the large difference in GPP between the two seasons were not caused by the annual precipitation. Instead, a shorter growing season, due to late start of the rainy season, was mainly responsible for the lower GPP in the second season. Furthermore, relatively higher R eco during the non-growing season occurred after a late spring rain. Thus, for this Mediterranean grassland, the timing of rain events had more impact than the total amount of precipitation on ecosystem GPP and NEE. This is because its growing season is in the cool and wet season when carbon uptake and respiration are usually limited by low temperature and sometimes frost, not by soil moisture.

show abstract

Germination and Seedling Establishment in California Annual Grassland

Cited by 142 publications

References 7 publications

Species coexistence: macroevolutionary relationships and the contingency of historical interactions

Species coexistence: macroevolutionary relationships and the contingency of historical interactions

Experimental dispersal reveals characteristic scales of biodiversity in a natural landscape

Seasonal variation in carbon dioxide exchange over a Mediterranean annual grassland in California

Contact Info

Product

Resources

About