Seedling growth responses to light and mineral N form are predicted by species ecologies and can help explain tree diversity

Walters, Michael B.; Willis, John; Gottschalk, Kurt W.

doi:10.1139/cjfr-2013-0400

Cited by 16 publications

(17 citation statements)

References 54 publications

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“…Canopy trees affect both light and belowground resource availability and abiotic stress, and differences between canopy gaps and the closed canopy were reflected in patterns of seedling survival and growth. We focus here primarily on the effects of canopy cover type, as previous research on sugar maple suggest that the effects on growth of canopy openness as it ranges from understory to gap equal or exceed those of soil moisture or nutrient availability (Walters and Reich 1997, 2000, Walters et al 2014. A review of root competition in forests also found that for understory individuals, belowground competition with canopy trees is of secondary importance to light competition at all but the most xeric and nutrient poor sites (Coomes and Grubb 2000).…”

Section: Biotic Interactionsmentioning

confidence: 99%

“…Above-and belowground resource gradients may interact to affect seedling performance, and the effect depends on the species Grubb 2000, Ibáñez andMcCarthy-Neumann 2014). While there is evidence from a range of studies that sugar maple performance in the understory is primarily influenced by light availability (e.g., Walters and Reich 1997, Ricard et al 2003, Ibáñez and McCarthy-Neumann 2014, Walters et al 2014), belowground resources have been shown to matter in some cases (Walters and Reich 1997, 2000, Walters et al 2014, and we do not know the extent and direction of belowground effects on sugar maple survival or growth at our experimental sites.…”

Section: Other Potential Range-limiting Factorsmentioning

confidence: 99%

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Climate and competition affect growth and survival of transplanted sugar maple seedlings along a 1700‐km gradient

Putnam

Reich

2017

Ecological Monographs

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Plant species distributions, broadly shaped by climate, may also be constrained by other species. The degree to which biotic factors affect range limits is unclear, however, and few experimental studies have investigated both biotic and abiotic factors across and beyond a species’ range. We examined seedling survival and net growth for three years in contrasting canopy type (closed canopy vs. gap) and neighbor density (clipped vs. unclipped) environments for northern, central, and southern populations of sugar maple (Acer saccharum) representing a climate‐of‐origin gradient, experimentally planted from Arkansas, USA to Ontario, Canada at ten forested sites along a 1700‐km transect spanning beyond the species’ range. We hypothesized that each population's highest survival and growth would occur in its region of origin, with poorer performance in cooler or warmer areas. Refuting this hypothesis, seedlings of all three populations had greater growth and survival in sites increasingly warmer than their point of origin, although they did show poorer growth and survival at increasingly colder sites. We also hypothesized that maple survival and net growth near and beyond range margins are constrained primarily by cold temperature limitation in the north, where we expected neighbors to facilitate survival, and by competition in the south, where we expected to enhance survival and growth by reducing neighbor density. Results partially supported the hypothesis concerning biotic interactions: in canopy gaps, understory neighbors enhanced maple growth at the coolest sites but did not suppress growth as expected at the warmest sites. As the northern population grew and survived reasonably well beyond the northern range limit, and as all populations performed best at warmer sites, including beyond the southern range limit, there was tepid, if any, support for the hypothesis that climate regulated the northern limit and absolutely no support for the hypothesis that competition regulated the southern limit. Together, these three‐year findings with juvenile trees suggest that sugar maple range limits may instead be constrained by factors besides climate and competition, by those factors at another life stage, and/or by climate events such as heat waves, droughts, and cold snaps that occur at longer return intervals.

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Section: Biotic Interactionsmentioning

confidence: 99%

Section: Other Potential Range-limiting Factorsmentioning

confidence: 99%

Climate and competition affect growth and survival of transplanted sugar maple seedlings along a 1700‐km gradient

Putnam

Reich

2017

Ecological Monographs

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“…Even under favorable developmental conditions, newly germinated seedlings require multiple years to decades to complete the transition from seedling to sapling (Walters et al. ). Our experiment tracked seedlings for only 14 months, potentially truncating the development of species‐specific responses to substrate that may have developed over a longer time frame.…”

Section: Discussionmentioning

confidence: 99%

“…However, shade‐intolerant deciduous species have been shown to be more responsive to NO 3 − ‐N availability (Walters et al. ) and thus may not have fully responded to the increase in available N following sterilization. Such a process could account for the growth response of seedlings on sterilized balsam fir CWD, which supported the third shortest mean seedling height despite having the highest total [N] (NO 3 − ‐N + NH 4 + ‐N) concentrations.…”

Section: Discussionmentioning

confidence: 99%

“…While these findings could be taken as evidence that mineral soil and conifer CWD provide the optimal conditions for seedling survival, we urge caution against this broad generalization, as our experiment was not intended to evaluate the importance of substrate under natural stand dynamics. Even under favorable developmental conditions, newly germinated seedlings require multiple years to decades to complete the transition from seedling to sapling (Walters et al 2014). Our experiment tracked seedlings for only 14 months, potentially Note: Substrates with different letters were found to be significantly different in Tukey's honestly significant difference post hoc comparisons that were conducted at a = 0.05. ns, not significant.…”

Section: Survivalmentioning

confidence: 97%

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Nutrition and mycorrhizae affect interspecific patterns of seedling growth on coarse wood and mineral soil substrates

Willis

Walters

2018

Ecosphere

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Smaller‐seeded tree species often require mineral soil and coarse woody debris (CWD) to establish. Limited data suggest that species‐based variation in tree seedling–CWD relations exists; however, the generalizability of this pattern and its mechanistic basis remain unknown. We investigated interspecific substrate–seedling relations and the potential that differences in mycorrhizal status and substrate nutrition underlie these patterns with a potted plant experiment. Eight temperate tree species were grown in a lath shade house on six species of CWD and mineral soil that had either been sterilized with gamma irradiation or left untreated to separate the effects of mycorrhizae from substrate nutrition. We assessed the impact of substrate identity on height growth and investigated possible mechanisms via relating growth to substrate inorganic N concentration, seedling foliar N (%), and mycorrhizal colonization. Seedling height varied across substrates consistently among species (i.e., substrate effects were strong, but seedling species x substrate interactions were weak). Seedlings were generally tallest on mineral soil followed by Betula papyrifera and Thuja occidentalis CWD, and shortest on B. alleghaniensis or Acer saccharum CWD. Sterilization main effects on height were not significant; however, the response of species to sterilization varied, as Acer rubrum and T. occidentalis seedlings were significantly shorter on sterilized substrate. For all seedling species, growth correlated positively with substrate [N] and foliar N. Among the four species examined for mycorrhizae, root colonization density was highest on mineral soil and lowest on A. saccharum and B. alleghaniensis CWD). For these species, mean colonization density was more strongly associated with mean seedling height than substrate inorganic [N]. Beneficial mycorrhizal effects were suggested by positive height–mycorrhizal root density relationships for B. alleghaniensis, A. rubrum, and T. occidentalis. Collectively, for the group of northern hardwood tree species examined in this study, these results demonstrate that in a controlled environment, most species grow best on mineral soil, B. alleghaniensis and Picea glauca attained maximum growth on CWD, species‐specific growth responses occur on CWD, and that substrate nutrient availability and mycorrhizal fungi contribute to the variation observed in seedling growth response across substrates.

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Managing for diversity: harvest gap size drives complex light, vegetation, and deer herbivory impacts on tree seedlings

et al. 2016

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Abstract. Many managed northern hardwood forests are characterized by low-diversity tree regeneration. Small harvest gaps, competition from shrub-herb vegetation, and browsing by white-tailed deer (Odocoileus virginianus) contribute to this pattern, but we know little about how these factors interact. With a stand-scale experiment, we examined the effects of gap size (0-3234 m 2 ), vegetation (weeded:unweeded), and deer (fenced:unfenced) on seedling growth and survival for 18 tree species. With increasing gap size and light, shrub-herb vegetation density increased, while deer browsing on seedlings in unweeded plots decreased. Fenced:weeded seedlings of all species increased in height up to 35-45% light, with optimal growth in large-group selection and patch cut harvest gaps. Height growth rank order among tree species changed between gap sizes, but growth varied little in small, low-light gaps. Instead, a low-light survival (i.e., shade tolerance) vs. high-light growth tradeoff we observed is likely more important for species sorting of gap sizes. Shrub-herb vegetation decreased seedling survival and growth, especially in larger harvest gaps, shifting gap size optima to smaller gaps, but had little effect on growth/survival rank order among species. In contrast, deer had strong impacts on growth rank order, especially in larger gaps where species differences in growth potential were trumped by differences in deer browsing pressure responses. However, contrary to their consistently negative main effects, vegetation and deer had two positive interacting effects: dense shrub-herb vegetation in large gaps protected seedlings of faster-growing species from browsing and deer browsing of shrub-herb vegetation modestly increased light and growth of short, suppressed, browsing-avoided species. In summary, harvest gap size-mediated light availability, shrub-herb vegetation, and deer herbivory had strong interacting effects on tree seedling interspecific performance ranks and intraspecific optimal gap sizes. For management, a broad range of harvest gap sizes and rapid establishment of tree regeneration (naturally or planted) to minimize shrub-herb competition should increase tree diversity in forests with few deer. However, with deer browsing pressure, a more limited set of lesser-browsed species are likely to recruit successfully regardless of gap size, except in large patch cut gaps, where recruitment of faster-growing, shade-intolerant species is possible.

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Seedling growth responses to light and mineral N form are predicted by species ecologies and can help explain tree diversity

Cited by 16 publications

References 54 publications

Climate and competition affect growth and survival of transplanted sugar maple seedlings along a 1700‐km gradient

Climate and competition affect growth and survival of transplanted sugar maple seedlings along a 1700‐km gradient

Nutrition and mycorrhizae affect interspecific patterns of seedling growth on coarse wood and mineral soil substrates

Managing for diversity: harvest gap size drives complex light, vegetation, and deer herbivory impacts on tree seedlings

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