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Abstract Global change has created less stable forest systems and given urgency to understanding limitations to the establishment of tree seedlings beyond current range boundaries. We quantified trends in 13 years of annual northern red oak (QURU) seedling survival data for 1733 marked individuals at a local species distribution boundary within the northern hardwood forest in New Hampshire, USA. Over the study period, the median distance of seedlings into the valley did not change, although there was a net gain of 89 plots (5 m2) occupied. For a subset of seedlings that were marked in their year of birth (N = 937), we examined relationships among terrain, vegetation community, and initial individual seedling traits, and evaluated their effects on time to seedling mortality using a parametric accelerated failure time model. The year of seedling germination had the largest effect on survival with increasing mortality rates for seedlings from more recent cohorts. Seedlings had longer survival times where oak seedling densities were lower, shrub cover was higher, and when the acorn remained attached. Additionally, survival time was increased in higher elevation plots, which were also located further into the valley. Interannual seedling survival (N = 1580) was strongly impacted by seedling condition in the previous year, particularly leaf number and amount of leaf damage. Most seedling deaths occurred over winter, and seedlings failed to break bud the following spring. Interannual variation in seasonal climate, particularly deep, heavy snowpack in 2019 followed by drought conditions in 2020, coincided with recent elevated mortality. Overall, the median survival time of 3–4 years and the rapid turnover of the oak seedling population currently limit ability for expansion, although the net gain of occupied plots and increase in survival at higher elevation plots with lower QURU densities present some mechanisms that could promote expansion if the current suboptimal understory conditions shift to favor QURU.
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Larrea Seedling Monitoring Study at the Sevilleta National Wildlife Refuge, New Mexico (1999-2018)
{"Abstract":["The germination rate of creosote (Larrea tridentata) on the\n Sevilleta appears to be very low. During the early years of the LTER\n project it was attempted to quantify such germination through the\n use of seedling plots which were monitored on a bi-annual basis\n (spring and fall). During the period from 1989 through 1992 there\n were no creosote seedling that germinated on the monitoring plots.\n In 1999 a rather sizeable population of small seedlings was observed\n in one quite localized area in the vicinity of Five Points. This\n rather large number of individuals in one very limited area raised\n several questions:1. When did this small community of individuals\n germinate- the supposition is that they had all germinated at the\n same time.2. What conditions existed in this particular location\n which allowed such prolific germination when there was no indication\n of virtually any other germination in this vicinty.3. The most\n immediate question was whether these seedlings would survive through\n the impending La Nina winter, spring and summer as many of the\n individuals did not appear to be very "healthy." To help\n answer these questions it was decided to begin a "small"\n monitoring project. All of the individuals in this small area that\n appeared to be of the same age were marked with posts, located with\n GPS, measured (height) and photographed. This initial survey\n included 78 individuals. The population was resurveyed in August,\n 2000 and it was discovered that: 1. Many individuals were missed in\n the initial survey; 2. Most of the individuals (72 of 78) had\n survived the intervening 9 months; and 3. The average individual\n growth during this period was 1.4 cm. It is planned that this\n population will continue to be monitored (probably on an annual\n basis) to track survival and growth rate of these individuals. "]}
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- Award ID(s):
- 1655499
- PAR ID:
- 10424117
- Publisher / Repository:
- Environmental Data Initiative
- Date Published:
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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{"Abstract":["Humans are creating significant global environmental change,\n including shifts in climate, increased nitrogen (N) deposition, and\n the facilitation of species invasions. A multi-factorial field\n experiment is being performed in an arid grassland within the\n Sevilleta National Wildlife Refuge (NWR) to simulate increased\n nighttime temperature, higher N deposition, and heightened El Niño\n frequency (which increases winter precipitation by an average of\n 50%). The purpose of the experiment is to better understand the\n potential effects of environmental change on grassland community\n composition and the growth of introduced creosote seeds and\n seedlings. The focus is on the response of three dominant species,\n all of which are near their range margins and thus may be\n particularly susceptible to environmental change. It is hypothesized\n that warmer summer temperatures and increased evaporation will favor\n growth of black grama (Bouteloua eriopoda), a desert grass, but that\n increased winter precipitation and/or available nitrogen will favor\n the growth of blue grama (Bouteloua gracilis), a shortgrass prairie\n species. Furthermore, it is thought that the growth and survival of\n introduced creosote (Larrea tridentata) seeds and seedlings will be\n promoted by heightened winter precipitation, N addition, and warmer\n nighttime temperatures. Treatment effects on limiting resources\n (soil moisture, nitrogen mineralization), species growth\n (photosynthetic rates, creosote shoot elongation), species\n abundance, and net primary production (NPP) are all being measured\n to determine the interactive effects of key global change drivers on\n arid grassland plant community dynamics. To measure above-ground NPP\n (i.e., the change in plant biomass, represented by stems, flowers,\n fruit and foliage, over time), the vegetation variables in this\n dataset, including species composition and the cover and height of\n individuals, are sampled twice yearly (spring and fall) at permanent\n 1m x 1m plots. The data from these plots is used to build\n regressions correlating biomass and volume via weights of select\n harvested species obtained in SEV157, "Net Primary Productivity\n (NPP) Weight Data." This biomass data is included in SEV205,\n "Warming-El Nino-Nitrogen Deposition Experiment (WENNDEx):\n Seasonal Biomass and Seasonal and Annual NPP.""]}more » « less
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