The biological and functional diversity of ectomycorrhizal ( To determine how fungal diversity and function are linked to elevation, we characterized fungal communities, edaphic variables, and eight extracellular enzyme activities along six elevation transects in Tierra del Fuego (Argentina and Chile). We also tested whether pairing Fungal community shifts across elevations were mediated primarily by soil Our results suggest that soil fungi in
- Award ID(s):
- 1636476
- NSF-PAR ID:
- 10083294
- Date Published:
- Journal Name:
- PeerJ
- Volume:
- 6
- ISSN:
- 2167-8359
- Page Range / eLocation ID:
- e5008
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Summary ECM ) associations remain largely unknown in South America. In Patagonia, theECM treeNothofagus pumilio forms monospecific forests along mountain slopes without confounding effects of vegetation on plant–fungi interactions.ITS 1rDNA Illumina sequences generated taxonomic biases related to sequence length.pH with the most species‐rich fungal families occurring mostly within a narrowpH range. By contrast, enzyme activities were minimally influenced by elevation but correlated with soil factors, especially total soil carbon. The activity of leucine aminopeptidase was positively correlated withECM fungal richness and abundance, and acid phosphatase was correlated with nonECM fungal abundance. Several fungal lineages were undetected when using exclusively paired or unpaired forwardITS 1 sequences, and these taxonomic biases need reconsideration for future studies.N. pumilio forests are functionally similar across elevations and that these diverse communities help to maintain nutrient mobilization across the elevation gradient. -
Tree mortality is a key process in forest dynamics. Despite decades of effort to understand this process, many uncertainties remain. South American broadleaf species are particularly under-represented in global studies on mortality and forest dynamics. We sampled monospecific broadleaf Nothofagus pumilio forests in northern Patagonia to predict tree mortality based on stem growth. Live or dead conditions in N. pumilio trees can be predicted with high accuracy using growth rate as an explanatory variable in logistic models. In Paso Córdova (CO), Argentina, where the models were calibrated, the probability of death was a strong negative function of radial growth, particularly during the six years prior to death. In addition, negative growth trends during 30 to 45 years prior to death increased the accuracy of the models. The CO site was affected by an extreme drought during the summer 1978–1979, triggering negative trends in radial growth of many trees. Individuals showing below-average and persistent negative trends in radial growth are more likely to die than those showing high growth rates and positive growth trends in recent decades, indicating the key role of droughts in inducing mortality. The models calibrated at the CO site showed high verification skill by accurately predicting tree mortality at two independent sites 76 and 141 km away. Models based on relative growth rates showed the highest and most balanced accuracy for both live and dead individuals. Thus, the death of individuals across different N. pumilio sites was largely determined by the growth rate relative to the total size of the individuals. Our findings highlight episodic severe drought as a triggering mechanism for growth decline and eventual death for N. pumilio, similar to results found previously for several other species around the globe. In the coming decades, many forests globally will be exposed to more frequent and/or severe episodes of reduced warm-season soil moisture. Tree-ring studies such as this one can aid prediction of future changes in forest productivity, mortality, and composition.more » « less
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Abstract Disturbances can interrupt feedbacks that maintain stable plant community structure and create windows of opportunity for vegetation to shift to alternative states. Boreal forests are dominated by tree species that overlap considerably in environmental niche, but there are few tests of what conditions initiate and sustain different forest states. Here, we examine patterns of post‐fire growth and density of tree seedlings in early succession and use structural equation models to estimate relative effects of environmental and pre‐fire conditions, fire characteristics, and biotic interactions. We surveyed tree seedling recruits for 13 yr across a broad range of environmental and fire conditions (
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Summary Successive droughts have resulted in extensive tree mortality in the southwestern United States. Recovery of these areas is dependent on the survival and recruitment of young trees. For trees that rely on ectomycorrhizal fungi (
EMF ) for survival and growth, changes in soil fungal communities following tree mortality could negatively affect seedling establishment.We used tree‐focused and stand‐scale measurements to examine the impact of pinyon pine mortality on the performance of surviving juvenile trees and the potential for mutualism limitation of seedling establishment via altered
EMF communities.Mature pinyon mortality did not affect the survival of juvenile pinyons, but increased their growth. At both tree and stand scales, high pinyon mortality had no effect on the abundance of
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Abstract Questions What are the primary biotic and abiotic factors driving composition and abundance of naturally regenerated tree seedlings across forest landscapes of Maine? Do seedling species richness (
SR ) and density (SD ) decrease with improved growing conditions (climate and soil), but increase with increased diversity of overstorey composition and structure? Does partial harvesting disproportionately favour relative dominance of shade‐intolerant hardwoods (PIHD ) over shade‐tolerant softwoods (PTSD )?Location Forest landscapes across the diverse eco‐regions and forest types of Maine,
USA .Methods This study used
USDA Forest Service Forest Inventory Analysis permanent plots (n = 10 842), measured every 5 yr since 1999. The best models for each response variable (SR ,SD ,PIHD andPTSD ) were developed based onAIC and biological interpretability, while considering 35 potential explanatory variables incorporating climate, soil, site productivity, overstorey structure and composition, and past harvesting.Results Mean annual temperature was the most important abiotic factor, whereas overstorey tree size diversity was the most important biotic factor for
SR andSD . Both mean annual temperature and overstorey tree size diversity had a curvilinear relationship withSR andSD . Average overstorey shade tolerance and percentage tolerant softwood basal area in the overstorey were the top predictor variables ofPIHD andPTSD , respectively. Partial harvesting favouredPIHD but notPTSD .Conclusions This is one of the first studies to comprehensively evaluate a number of factors influencing naturally established tree seedlings at a broad landscape scale in the Northern Forest region of the eastern
USA and Canada. Despite limitations associated with relatively small plot size, large seedling size class and lack of direct measurements of light, water and nutrients, this study documents the influence of these factors amid high variability associated with patterns of natural regeneration. The curvilinear relationship between mean annual temperature withSR andSD supports the argument that species richness and abundance usually have unimodal relationships with productivity indicators, whereas the curvilinear relationship between overstorey tree size diversity andSR andSD suggest that moderate overstorey diversity incorporates multiple species as well as higher seedling individuals.