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H. J. Andrews Experimental Forest site, station Andrews Watershed 1, study of plant cover of forest understory in units of percent on a yearly timescale

The EcoTrends project was established in 2004 by Dr. Debra Peters (Jornada Basin LTER, USDA-ARS Jornada Experimental Range) and Dr. Ariel Lugo (Luquillo LTER, USDA-FS Luquillo Experimental Forest) to support the collection and analysis of long-term ecological datasets. The project is a large synthesis effort focused on improving the accessibility and use of long-term data. At present, there are ~50 state and federally funded research sites that are participating and contributing to the EcoTrends project, including all 26 Long-Term Ecological Research (LTER) sites and sites funded by the USDA Agriculture Research Service (ARS), USDA Forest Service, US Department of Energy, US Geological Survey (USGS) and numerous universities. Data from the EcoTrends project are available through an exploratory web portal (http://www.ecotrends.info). This web portal enables the continuation of data compilation and accessibility by users through an interactive web application. Ongoing data compilation is updated through both manual and automatic processing as part of the LTER Provenance Aware Synthesis Tracking Architecture (PASTA). The web portal is a collaboration between the Jornada LTER and the LTER Network Office. The following dataset from H. J. Andrews Experimental Forest (AND) contains plant cover of forest understory measurements in percent units and were aggregated to a yearly timescale.

H. J. Andrews Experimental Forest site, station Andrews Watershed 1, study of plant species richness of forest understory in units of numberPer250SquareMeters on a yearly timescale

The EcoTrends project was established in 2004 by Dr. Debra Peters (Jornada Basin LTER, USDA-ARS Jornada Experimental Range) and Dr. Ariel Lugo (Luquillo LTER, USDA-FS Luquillo Experimental Forest) to support the collection and analysis of long-term ecological datasets. The project is a large synthesis effort focused on improving the accessibility and use of long-term data. At present, there are ~50 state and federally funded research sites that are participating and contributing to the EcoTrends project, including all 26 Long-Term Ecological Research (LTER) sites and sites funded by the USDA Agriculture Research Service (ARS), USDA Forest Service, US Department of Energy, US Geological Survey (USGS) and numerous universities. Data from the EcoTrends project are available through an exploratory web portal (http://www.ecotrends.info). This web portal enables the continuation of data compilation and accessibility by users through an interactive web application. Ongoing data compilation is updated through both manual and automatic processing as part of the LTER Provenance Aware Synthesis Tracking Architecture (PASTA). The web portal is a collaboration between the Jornada LTER and the LTER Network Office. The following dataset from H. J. Andrews Experimental Forest (AND) contains plant species richness of forest understory measurements in numberPer250SquareMeters units and were aggregated to a yearly timescale.

H. J. Andrews Experimental Forest site, station Andrews Watershed 3, study of plant cover of forest understory in units of percent on a yearly timescale

H. J. Andrews Experimental Forest site, station Andrews Watershed 3, study of plant species richness of forest understory in units of numberPer250SquareMeters on a yearly timescale

The EcoTrends project was established in 2004 by Dr. Debra Peters (Jornada Basin LTER, USDA-ARS Jornada Experimental Range) and Dr. Ariel Lugo (Luquillo LTER, USDA-FS Luquillo Experimental Forest) to support the collection and analysis of long-term ecological datasets. The project is a large synthesis effort focused on improving the accessibility and use of long-term data. At present, there are ~50 state and federally funded research sites that are participating and contributing to the EcoTrends project, including all 26 Long-Term Ecological Research (LTER) sites and sites funded by the USDA Agriculture Research Service (ARS), USDA Forest Service, US Department of Energy, US Geological Survey (USGS) and numerous universities. Data from the EcoTrends project are available through an exploratory web portal (http://www.ecotrends.info). This web portal enables the continuation of data compilation and accessibility by users through an interactive web application. Ongoing data compilation is updated through both manual and automatic processing as part of the LTER Provenance Aware Synthesis Tracking Architecture (PASTA). The web portal is a collaboration between the Jornada LTER and the LTER Network Office. The following dataset from H. J. Andrews Experimental Forest (AND) contains plant species richness of forest understory measurements in numberPer250SquareMeters units and were aggregated to a yearly timescale.

opencc-zeroSep 2020View details →

Canopy structure and forest understory conditions in a wet Amazonian forest – no change over the last 20 years

Climate change is altering forest dynamics in the tropics, with large potential impacts on forest structure and understory conditions. However, we found that canopy height distribution and openness remained stable over two decades in the western Amazon, and that gap creation rates would need to increase 300% before affecting equilibrium.

opencc-zeroDec 2020View details →

Divergent responses of forest dominant trees species to the manipulated canopy and understory nitrogen additions in terms of foliage stoichiometric, economic and hydraulic traits

Nitrogen (N) deposition effects on the stoichiometric balance and photosynthetic and hydraulic couplings in subtropical forests has drawn wide attentions. The previously adopted understory application of N fertilization is criticized because it might ignore foliar N retention for different species. This paper reports a fertilizing application from the canopy (CAN) and under the canopy (UAN) in a phosphorus (P) limited ecosystem. Foliage stoichiometric, photosynthetic and hydraulic traits of six dominant species were measured and analyzed. Both treatments equally enhanced foliage N and N/P, but not foliage P, who was highly species-specific depending on tree height, which implied enhanced P limitation. Decreased isotope abundance of 15N (δ15N) that approaching to the level in the urea fertilizer under CAN suggested the existence of canopy retention of N. Besides, N response sensitivity of N, P and δ15N that positively related to tree height (H) under CAN indicated different exposure to the added N, which promoted stoichiometric imbalance among species. The photosynthetic traits represented by net photosynthesis (An) increased under both treatments. A divergent foliar photosynthetic and hydraulic traits varations was identified by signifcant decreased stomatal conductance (gs) and An /gs for CAN treatments, which induced the elevated isotope abundance of 13C (δ13C). Correspondingly, foliage hydraulic traits that shifted to water use efficiency axis were identified only under CAN in principal component analysis. Overall, our results proved that the canopy obsorbtion and species heterogeneity should be considered regarding foliar safety vs efficiency trade-off in response to nitrogen additions in the future.

opencc-zeroJan 2021View details →

Remotely sensed forest understory density and nest predator occurrence interact to predict suitable breeding habitat and the occurrence of a resident boreal bird species

Habitat suitability models (HSM) based on remotely sensed data are useful tools in conservation work. However, they typically use species occurrence data rather than robust demographic variables, and their predictive power is rarely evaluated. These shortcomings can result in misleading guidance for conservation. Here, we develop and evaluate a HSM based on correlates of long term breeding success of an open nest building boreal forest bird, the Siberian jay. In our study site in northern Sweden, nest failure of this permanent resident species is driven mainly by visually hunting corvids that are associated with human settlements. Parents rely on understory nesting cover as protection against these predators. Accordingly, our HSM includes a light detection and ranging (LiDAR) based metric of understory density around the nest and the distance of the nest to the closest settlement to predict breeding success. It reveals that a high understory density 15-80 m around nests is associated with increased breeding success in territories close to settlements (<1.5 km). Farther away from human settlements breeding success is highest at nest sites with a more open understory providing a favourable warmer microclimate. We validated this HSM by comparing the predicted breeding success with landscape-wide census data on Siberian jay occurrence. The correlation between breeding success and occurrence was strong up to 40 km around the study site. However, the HSM appears to overestimate breeding success in regions with a milder climate, and therefore higher corvid numbers. Our findings suggest that maintaining patches of small diameter trees may provide a cost-effective way to restore the breeding habitat for Siberian jays up to 1.5 km from human settlements. This distance is expected to increase in the warmer, southern, and coastal range of the Siberian jay where the presence of other corvids is to a lesser extent restricted to settlements.

opencc-zeroDec 2016View details →

Data from: Herbivory and pollen limitation at the upper elevational range limit of two forest understory plants of eastern North America

Studies of species' range limits focus most often on abiotic factors, although the strength of biotic interactions might also vary along environmental gradients and have strong demographic effects. For example, pollinator abundance might decrease at range limits due to harsh environmental conditions, and reduced plant density can reduce attractiveness to pollinators and increase or decrease herbivory. We tested for variation in the strength of pollen limitation and herbivory by ungulates along a gradient leading to the upper elevational range limits of Trillium erectum (Melanthiaceae) and Erythronium americanum (Liliaceae) in Mont-Mégantic National Park, Québec, Canada. In T. erectum, pollen limitation was higher at the range limit, but seed set decreased only slightly with elevation and only in one of two years. In contrast, herbivory of T. erectum increased from <10% at low elevations to >60% at the upper elevational range limit. In E. americanum, we found no evidence of pollen limitation despite a significant decrease in seed set with elevation, and herbivory was low across the entire gradient. Overall, our results demonstrate the potential for relatively strong negative interactions (herbivory) and weak positive interactions (pollination) at plant range edges, although this was clearly species-specific. To the extent that these interactions have important demographic consequences – highly likely for herbivory on Trillium, based on previous studies – such interactions might play a role in determining plant species' range limits along putatively climatic gradients.

opencc-zeroDec 2014View details →

Data from: Plant-soil feedbacks shift from negative to positive with decreasing light in forest understory species

Net pairwise plant–soil feedbacks (PSF) may be an important factor structuring plant communities, yet the influence of abiotic context on PSF is not yet understood. Abiotic factors such as light availability can alter plant–soil interactions, potentially resulting in strong context dependence of PSF. Here, we present an experiment in which we measured whole-soil net pairwise feedbacks amongst six common forest understory species across a gradient of light availability. Light treatments were imposed throughout both phases (the conditioning phase and the response phase) of the feedback experiment. Across the plant community, PSF shifted from negative at high light availability to weakly positive under low light (P = 0.013). Differences in the biomass of plants during the conditioning phase did not fully explain light-imposed differences in feedbacks, indicating that reduced light availability qualitatively changes the nature of PSF rather than simply weakening feedbacks by reducing plant growth. Results indicate that abiotic context can fundamentally alter the role of PSF in structuring plant communities.

opencc-zeroDec 2013View details →

Data from: Experimental defaunation of terrestrial mammalian herbivores alters tropical rain forest understory diversity

It has been suggested that tropical defaunation may unleash community-wide cascading effects, leading to reductions in plant diversity. However, experimental evidence establishing cause–effect relationships thereof is poor. Through a 5 year exclosure experiment, we tested the hypothesis that mammalian defaunation affects tree seedling/sapling community dynamics leading to reductions in understorey plant diversity. We established plot triplets (n = 25) representing three defaunation contexts: terrestrial-mammal exclosure (TE), medium/large mammal exclosure (PE) and open access controls (C). Seedlings/saplings 30–100 cm tall were marked and identified within each of these plots and re-censused three times to record survival and recruitment. In the periods 2010–2011 and 2011–2013, survival was greater in PE than in C plots and recruitment was higher in TE plots than in C plots. Overall, seedling density increased by 61% in TE plots and 23% in PE plots, whereas it decreased by 5% in C plots. Common species highly consumed by mammals (e.g. Brosimum alicastrum and Ampelocera hottlei) increased in their abundance in TE plots. Rarefaction curves showed that species diversity decreased in TE plots from 2008 to 2013, whereas it remained similar for C plots. Given the prevalence of tropical defaunation, we posit this is an anthropogenic effect threatening the maintenance of tropical forest diversity.

opencc-zeroDec 2016View details →

Data from: Intraspecific variability and reaction norms of forest understory plant species traits

1.Trait-based models of ecological communities typically assume intraspecific variation in functional traits is not important, though such variation can change species trait rankings along gradients in resources and environmental conditions, and thus influence community structure and function. 2. We examined the degree of intraspecific relative to interspecific variation, and reaction norms of 11 functional traits for 57 forest understory plant species, including: intrinsic water-use efficiency (iWUE), Δ15N, 5 leaf traits, 2 stem traits and 2 root traits along gradients in light, nitrogen, moisture and understory cover. 3. Our results indicate that interspecific trait variation exceeded intraspecific variation by at least 50% for most, but not all traits. Intraspecific variation in Δ15N, iWUE, leaf nitrogen content and root traits was high (47-70%) compared with most leaf traits and stem traits (13-38%). 4. Δ15N varied primarily along gradients in abiotic conditions, while light and understory cover were relatively less important. iWUE was related primarily to light transmission, reflecting increases in photosynthesis relative to stomatal conductance. Leaf traits varied mainly as a function of light availability, with some reaction norms depending on understory cover. Plant height increased with understory cover, while stem specific density was related primarily to light. Resources, environmental conditions and understory cover did not contribute strongly to the observed variation in root traits. 5. Gradients in resources, environmental conditions and competition all appear to control intraspecific variability in most traits to some extent. However, our results suggest that species cross-over (i.e., trait rank reversals) along the gradients measured here are generally not a concern. 6. Intraspecific variability in understory plant species traits can be considerable. However, trait data collected under a narrow range of environmental conditions appears sufficient to establish species rankings and scale between community and ecosystem levels using trait-based models. Investigators may therefore focus on obtaining a sufficient sample size within a single set of conditions rather than characterizing trait variation across entire gradients in order to optimize sampling efforts.

opencc-zeroOct 2021View details →

Stoichiometric traits (N:P) of understory plants contribute to reductions in plant diversity following long-term nitrogen addition in subtropical forest

Nitrogen enrichment is pervasive in forest ecosystems, but its influence on understory plant communities and their stoichiometric characteristics is poorly understood. We hypothesize that when forest is enriched with nitrogen (N), the stoichiometric characteristics of plant species explains changes in understory plant diversity. A 13 year field experiment was conducted to explore the effects of N addition on foliar carbon (C): N: phosphorus (P) stoichiometry and understory plant species richness in a subtropical Chinese fir forest. Four levels of N addition were applied: 0, 6, 12, and 24 g m-2 yr-1. Individual plant species were categorized into resistant plants, intermediate resistant plants, and sensitive plants based on their response to nitrogen addition. Results showed that N addition significantly decreased the number of species, genera and families of herbaceous plants. Foliar N:P ratios were greater in sensitive plants than resistant or intermediate resistance plants, while intrinsic water use efficiency showed an opposite trend. However, no relationship was detected between soil available N and foliar N, and soil N:P and foliar N:P ratios. Our results indicated that long-term N addition decreased the diversity of understory plants in a subtropical forest. Through regulating water use efficiency with N addition, sensitive plants change their N:P stoichiometry and have a higher risk of mortality, while resistant plants maintain a stable N:P stoichiometry, which contributes to their survival. These findings suggest that plant N:P stoichiometry plays an important role in understory plant performance in response to environmental change of N.

opencc-zeroJan 2022View details →

Dry season intensity has equivocal effects on the nutritional condition of understory birds in a Neotropical forest

Rainfall regime, the amount and timing of annual precipitation, can influence the breeding phenology, individual fitness, and population dynamics of tropical birds. In Neotropical regions with rainfall seasonality (i.e., wet and dry seasons), the warm phase of the El Niño Southern Oscillation (ENSO) can exacerbate seasonal drought and negatively impact avian survival and reproduction. However, the mechanisms underlying associations between seasonal drought conditions and avian demography are largely unexplored. One hypothesis is that nutritional condition mediates demographic responses to seasonal drought– individuals in poor condition may be less capable of balancing their energy budgets and consequently suffer reduced survival, lower reproductive output, or both. We estimated nutritional condition (i.e., scaled mass index, percent hematocrit, plasma lipid metabolites) as a proxy of energy balance in understory forest birds with contrasting population-level responses to dry season length. This study took place across two dry seasons of differing intensity in central Panama– an El Niño dry season (2016, severe drought) and a more typical dry season (2017). Scaled mass index remained relatively constant throughout both dry seasons and across years for five common focal species and among four foraging guilds (22 additional species, 27 species total). Three of five focal species did exhibit reduced nutritional condition (i.e., lower hematocrit and/or higher β-hydroxybutyrate) during the El Niño dry season but not during the more typical dry season. However, foraging guilds did not show consistent nutritional responses to seasonal drought and we found little evidence of reduced nutritional condition at the guild level, suggesting that many Neotropical forest bird species are capable of tolerating seasonal drought.

opencc-zeroMar 2022View details →

Diversification and phylogenetic correlation of functional traits for co-occurring understory species in the Chinese boreal forest

Functional traits impact species interactions, community composition, and ecosystem functioning. However, few studies have focused on the diversification and phylogenetic correlation of multiple functional traits over geological time. We conducted phylogenetic comparative analysis for boreal forest understory species in northeast China to examine the diversification and phylogenetic correlation in several functional traits: leaf area (LA), leaf carbon content (LCC), leaf dry matter content (LDMC), leaf nitrogen content (LNC), plant height (PH), and specific leaf area (SLA). Phylogenetic signals showed that there were very low levels of phylogenetic niche conservatism (PNC) in understory leaf-related traits and plant height, suggesting divergence of functional traits for the co-occurring understory species. The disparity through time analyses (DTT) indicated that trait disparities mainly originated during recent divergence events and there were no differences in the observed trait disparities compared to that expected under Brownian motion. Furthermore, we found both positive and negative phylogenetic correlations among the measured functional traits. The very low levels of PNC suggests that these functional traits diverged among co-occurring understory species, and that those species are distantly phylogenetically related. The phylogenetic correlations among traits maybe caused by both positively and negatively correlated adaptions which correspond to resource acquisition strategies. This study provides evidence that divergence in functional traits may reflect understory adaptations to boreal conditions.

opencc-zeroMay 2022View details →

Interactions between local and global drivers determine long-term trends in boreal forest understory vegetation

Aim: Global change effects on forest ecosystems are increasingly claimed to be context dependent, indicated by interactions between global and local environmental drivers. Most examples of such context dependencies originate from temperate systems, while limited research comes from the boreal biome. Here we set out to test if interactions between climate warming, nitrogen deposition, land-use change resulting in increasing forest density and soil pH drive long-term changes of understory vegetation in boreal forests. Location: Sweden Time period: 1953-2012 Major taxa studied: Vascular plants Methods: We used long-term (50 years) National Forest Inventory data on forest understory vegetation in Sweden to model the combined effects of climate warming, nitrogen deposition, increase in forest density (tree basal area) and soil pH. Results: Our results identify increasing temperature, nitrogen deposition and denser, shadier forest conditions as main drivers of understory vegetation changes during this time period. More importantly, we found that these effects varied with local conditions, i.e. that the change towards a more nitrophilic understory vegetation was more pronounced at low than high soil pH. Forest density was an important modulator of nitrogen deposition and temperature increase, with effects generally decreasing with density. Decreased cover of ericaceous dwarf shrubs was driven by both forest density and nitrogen deposition, with a stronger effect at low than at high pH. Main conclusions: Our results highlight that to understand forest ecosystems´ response to global change, and to make adequate management decisions to mitigate the effects of global change, we need to understand how changes in local environmental factors (forest density and soil pH) interact with global-scale drivers (nitrogen deposition and climate warming). Neglecting such interactions will lead to incorrect estimations of effects. In our case, we would e.g. have underestimated the eutrophication effects on acid soils, which constitute a considerable part of the boreal biome. --

opencc-zeroNov 2022View details →

Understory plant removal counteracts tree thinning effect on soil respiration in a temperate forest

Elucidating the response mechanism of soil respiration (Rs) to silvicultural practices is pivotal to evaluating the effects of management practices on soil carbon cycling in planted forest ecosystems. However, as common management practices, how thinning, understory plant removal, and their interactions affect Rs and its autotrophic and heterotrophic components (Ra and Rh) remains unclear. Therefore, we investigated Rs, Ra and Rh by the trenching method from 2011 to 2015 in a Pinus tabuliformis plantation in northern China, subjecting to four treatments [intact control plots (CK), thinning (T), understory removal (UR), and thinning with understory removal (TUR)]. Mean annual Rs was significantly increased by thinning (by 15.3%), whereas decreased by UR (by 17.4%), compared with CK. These variations in Rs were mainly attributed to changes in Ra. The increments of Ra were caused by the enhanced growth of fine root biomass after thinning. However, UR led to lower Ra compared with CK (P < 0.05), indicating that understory growth is inadequate to compensate for the decreased respiring root biomass induced by understory removal. Rs was unchanged between TUR and the intact control plot due to the opposite effects of thinning and UR on the Ra. Changes in Rh exhibited no significant differences among the treatments, partly because of the stable microbial biomass carbon (MBC) and forest floor mass (litter and fine woody debris). No interaction effect between thinning and understory removal was detected on Rs, Ra and Rh. The lowest temperature sensitivity (Q10) value of Ra was found in CK. This study highlights the necessity of incorporating understory plant effects on soil CO2 efflux in assessing forest management practices on soil carbon cycling.