ORCID Profile
0000-0001-7822-3560
Current Organisation
Harvard Forest, Harvard University
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Publisher: American Association for the Advancement of Science (AAAS)
Date: 25-05-2018
Abstract: Chisholm and Fung claim that our method of estimating conspecific negative density dependence (CNDD) in recruitment is systematically biased, and present an alternative method that shows no latitudinal pattern in CNDD. We demonstrate that their approach produces strongly biased estimates of CNDD, explaining why they do not detect a latitudinal pattern. We also address their methodological concerns using an alternative distance-weighted approach, which supports our original findings of a latitudinal gradient in CNDD and a latitudinal shift in the relationship between CNDD and species abundance.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 25-05-2018
Abstract: Hülsmann and Hartig suggest that ecological mechanisms other than specialized natural enemies or intraspecific competition contribute to our estimates of conspecific negative density dependence (CNDD). To address their concern, we show that our results are not the result of a methodological artifact and present a null-model analysis that demonstrates that our original findings—(i) stronger CNDD at tropical relative to temperate latitudes and (ii) a latitudinal shift in the relationship between CNDD and species abundance—persist even after controlling for other processes that might influence spatial relationships between adults and recruits.
Publisher: Elsevier BV
Date: 2021
Publisher: Wiley
Date: 23-11-2021
Abstract: Allometric equations for calculation of tree above‐ground biomass ( AGB ) form the basis for estimates of forest carbon storage and exchange with the atmosphere. While standard models exist to calculate forest biomass across the tropics, we lack a standardized tool for computing AGB across boreal and temperate regions that comprise the global extratropics. Here we present an integrated R package, allodb , containing systematically selected published allometric equations and proposed functions to compute AGB . The data component of the package is based on 701 woody species identified at 24 large Forest Global Earth Observatory (ForestGEO) forest dynamics plots representing a wide ersity of extratropical forests. A total of 570 parsed allometric equations to estimate in idual tree biomass were retrieved, checked and combined using a weighting function designed to ensure optimal equation selection over the full tree size range with smooth transitions across equations. The equation dataset can be customized with built‐in functions that subset the original dataset and add new equations. Although equations were curated based on a limited set of forest communities and number of species, this resource is appropriate for large portions of the global extratropics and can easily be expanded to cover novel forest types.
Publisher: Wiley
Date: 30-05-2019
Publisher: American Association for the Advancement of Science (AAAS)
Date: 30-06-2017
Abstract: Negative interaction among plant species is known as conspecific negative density dependence (CNDD). This ecological pattern is thought to maintain higher species ersity in the tropics. LaManna et al. tested this hypothesis by comparing how tree species ersity changes with the intensity of local biotic interactions in tropical and temperate latitudes (see the Perspective by Comita). Stronger local specialized biotic interactions seem to prevent erosion of bio ersity in tropical forests, not only by limiting populations of common species, but also by strongly stabilizing populations of rare species, which tend to show higher CNDD in the tropics. Science , this issue p. 1389 see also p. 1328
Publisher: Cold Spring Harbor Laboratory
Date: 21-05-2023
DOI: 10.1101/2023.05.18.541254
Abstract: The complex spatial structure and dynamics of ecological communities continue to defy explanation by simple principles despite decades of attention from ecologists and theoreticians. For ex le, the relationship between plant spatial distributions and species coexistence is often challenging to resolve in empirical settings. By analysing the spatial patterns of trees in 21 large forest plots we find a general and strong latitudinal gradient in the relationship between conspecific aggregation and abundance of tree species, with stronger negative abundance-dependency as latitude increases. To derive theoretical expectations for how interactions between multiple spatial pattern and processes can impact species coexistence, we incorporate the observed spatial patterns together with neighbourhood crowding competition into a mathematical model to estimate the local extinction risk of species. Strikingly, we find simple relationships that predict species local extinction risk from their demography and spatial distribution. Compared to a corresponding non-spatial analysis, accounting for spatial patterns reduces the 1000-year extinction risk on average by 52% when species invade from low abundances of 50 in iduals. Additionally, based on their current abundances, only 8% of the species had an extinction risk greater than 5%. Our approach opens up new avenues for integrating observed spatial patterns with multiple ecological processes into mathematical theory. Our results demonstrate that emerging spatial patterns can contribute substantially to coexistence in species-rich forests, emphasizing the need to understand the interacting multiple processes underpinning spatial patterns in greater detail than has previously been appreciated.
Publisher: Elsevier BV
Date: 03-2022
Publisher: Springer Science and Business Media LLC
Date: 25-05-2021
DOI: 10.1038/S41467-021-23236-3
Abstract: Arbuscular mycorrhizal (AM) and ectomycorrhizal (EcM) associations are critical for host-tree performance. However, how mycorrhizal associations correlate with the latitudinal tree beta- ersity remains untested. Using a global dataset of 45 forest plots representing 2,804,270 trees across 3840 species, we test how AM and EcM trees contribute to total beta- ersity and its components (turnover and nestedness) of all trees. We find AM rather than EcM trees predominantly contribute to decreasing total beta- ersity and turnover and increasing nestedness with increasing latitude, probably because wide distributions of EcM trees do not generate strong compositional differences among localities. Environmental variables, especially temperature and precipitation, are strongly correlated with beta- ersity patterns for both AM trees and all trees rather than EcM trees. Results support our hypotheses that latitudinal beta- ersity patterns and environmental effects on these patterns are highly dependent on mycorrhizal types. Our findings highlight the importance of AM-dominated forests for conserving global forest bio ersity.
Publisher: Wiley
Date: 08-05-2018
DOI: 10.1111/GEB.12747
Publisher: Torrey Botanical Society
Date: 23-11-2020
Publisher: Wiley
Date: 19-10-2020
DOI: 10.1002/ECM.1423
Location: United States of America
Location: United States of America
No related grants have been discovered for David Orwig.