scholarly journals An experimental approach for crown to whole-canopy defoliation in forests

2021 ◽  
Author(s):  
Robert Fahey ◽  
Danielle Tanzer ◽  
Brandon Alveshere ◽  
Jeff W. Atkins ◽  
Christopher M. Gough ◽  
...  
Keyword(s):  
Large Scale ◽  
Ecosystem Structure ◽  
Variable Intensity ◽  
Area Index ◽  
Canopy Volume ◽  
Leaf Level ◽  
Leaf Surface Area ◽  
And Function ◽  
Forested Ecosystems ◽  
Ecosystem Structure And Function

Canopy defoliation is an important source of disturbance in forest ecosystems that has rarely been represented in large-scale manipulation experiments. Scalable crown to canopy level experimental defoliation is needed to disentangle effects of variable intensity, timing, and frequency on forest structure, function, and mortality. We present a novel pressure washing-based defoliation method that can be: implemented at the canopy-scale, throughout the canopy volume, targeted to individual leaves/trees, and completed within a timeframe of hours/days. Pressure washing proved successful at producing consistent leaf-level and whole-canopy defoliation with 10-20% reduction in leaf area index and consistent leaf surface area removal across branches and species. This method allows for stand-scale experimentation on defoliation disturbance in forested ecosystems and has the potential for broad application. Studies utilizing this standardized method could promote mechanistic understanding of defoliation effects on ecosystem structure and function and development of synthetic understanding across forest types, ecoregions, and defoliation sources.

scholarly journals Mortality in Forested Ecosystems: Suggested Conceptual Advances

Forests ◽  
2020 ◽  
Vol 11 (5) ◽  
pp. 572
Author(s):  
Mark E. Harmon ◽  
David M. Bell
Keyword(s):  
Forest Management ◽  
Large Scale ◽  
Tree Mortality ◽  
Structure And Function ◽  
Ecosystem Structure ◽  
General Process ◽  
A Chain ◽  
And Function ◽  
Forested Ecosystems ◽  
Ecosystem Structure And Function

Mortality of trees is an important ecological process altering forest structure and function as well as influencing forest management decisions. Recent observations suggest that the overall rate of tree mortality is increasing at local to global scales. While more data on mortality is needed to document these changes, key concepts are also needed to guide the collection, interpretation, and use of this information. Mortality can be considered as a general process that includes all forms of tree-related death ranging from parts of trees to large-scale disturbances. Viewing mortality as a continuum allows one to examine how the lifespan of trees and their parts (e.g., branches), as well as multiple disturbances, influence ecosystem structure and function. Statistically, mortality does not follow the law of large numbers because, regardless of the scale analyzed, consequential, infrequent episodes can occur. This causes mortality to occur in irregular pulses. While the causes of mortality are indeed complex, this stems from the fact many processes, each with its own set of controls, can lead to mortality. By analyzing and predicting mortality using a chain of events influenced by specific mechanisms, a clearer understanding of this process should develop, leading to a more science-based and less reactive forest management.

scholarly journals Interdependent Dynamics of LAI-Albedo across the Roofing Landscapes: Mongolian and Tibetan Plateaus

2018 ◽  
Vol 10 (7) ◽  
pp. 1159 ◽  
Author(s):  
Li Tian ◽  
Jiquan Chen ◽  
Changliang Shao
Keyword(s):  
Land Surface ◽  
Experimental Investigations ◽  
Ecosystem Structure ◽  
Mongolian Plateau ◽  
Area Index ◽  
Spatiotemporal Changes ◽  
Underlying Mechanisms ◽  
Logarithmic Relationship ◽  
And Function ◽  
Ecosystem Structure And Function

The Mongolian Plateau (MP) and Tibetan Plateau (TP) have experienced higher-than-global average warming in recent decades, resulting in many significant changes in ecosystem structure and function. Among them are the leaf area index (LAI) and albedo, which play a fundamental role in understanding many causes and consequences of land surface processes and climate. Here, we focused on the spatiotemporal changes of LAI, albedo, and their spatiotemporal relationships on the two roofing landscapes in Eurasia. Based on the MODIS products, we investigated the spatiotemporal changes of albedo(VIS, NIR and SHO) and LAI from 2000 through 2016. We found that there existed a general negative logarithmic relationship between LAI and three measures of albedo on both plateaus. No significant relationship was found for LAI-albedoNIR on the TP, due to more complex land surface canopy characteristics affected by the NIR reflection there. During 2000–2016, overall, annual mean LAI increased significantly by 119.40 × 103 km2 on the MP and by 28.35 × 103 km2 on the TP, while the decreased areas for annual mean albedoVIS were 585.59 × 103 km2 and 235.73 × 103 km2 on the MP and TP, respectively. More importantly, the LAI-albedo relationships varied substantially across the space and over time, with mismatches found in some parts of the landscapes. Substantial additional efforts with observational and/or experimental investigations are needed to explore the underlying mechanisms responsible for these relationships, including the influences of vegetation characteristics and disturbances.

scholarly journals Ecosystem-level effects of large-scale disturbance in kelp forests

2020 ◽  
Vol 656 ◽  
pp. 163-180 ◽  
Author(s):  
KM Norderhaug ◽  
K Filbee-Dexter ◽  
C Freitas ◽  
SR Birkely ◽  
L Christensen ◽  
...  
Keyword(s):  
Large Scale ◽  
Single Species ◽  
Structure And Function ◽  
Trophic Levels ◽  
Kelp Forests ◽  
Ecosystem Structure ◽  
Substantial Impact ◽  
Large Scale Disturbance ◽  
And Function ◽  
Ecosystem Structure And Function

Understanding the effects of ecological disturbances in coastal habitats is crucial and timely as these are anticipated to increase in intensity and frequency in the future due to increasing human pressure. In this study we used directed kelp trawling as a scientific tool to quantify the impacts of broad-scale disturbance on community structure and function. We tested the ecosystem-wide effects of this disturbance in a BACI design using two 15 km2 areas. The disturbance had a substantial impact on the kelp forests in this study, removing 2986 tons of kelp and causing a 26% loss of total kelp canopy at trawled stations. This loss created a 67% reduction of epiphytes, an 89% reduction of invertebrates and altered the fish populations living within these habitats. The effect of habitat loss on fish was variable and depended on how the different species used the habitat structure. Our results show that large-scale experimental disturbances on habitat-forming species have ecological consequences that extend beyond the decline of the single species to affect multiple trophic levels of the broader ecosystem. Our findings have relevance for understanding how increasing anthropogenic disturbances, including kelp trawling and increased storm frequency caused by climate change, may alter ecosystem structure and function.

scholarly journals Can we predict groundwater discharge from terrestrial ecosystems using eco-hydrological principals?

2011 ◽  
Vol 8 (4) ◽  
pp. 8231-8253 ◽  
Author(s):  
A. P. O'Grady ◽  
J. L. Carter ◽  
J. Bruce
Keyword(s):  
Groundwater Discharge ◽  
Terrestrial Ecosystems ◽  
Ecosystem Structure ◽  
Empirical Relationships ◽  
Data Set ◽  
Area Index ◽  
Climatic Regime ◽  
Groundwater Systems ◽  
And Function ◽  
Ecosystem Structure And Function

Abstract. There is increasing recognition of the role that groundwater plays in the maintenance of ecosystem structure and function. As a result, water resources planners need to develop an understanding of the water requirements for these ecosystems. However, their capacity to do this is constrained by a lack of empirical information on groundwater discharge from terrestrial systems. In this study we reviewed estimates of groundwater discharge from around Australia focussing particularly on terrestrial groundwater discharge. The review examined detailed water balance studies where discharge has been identified as a component of evapotranspiration and we have explored this data set for empirical relationships that could be used to aid in predicting groundwater discharge in data poor areas. In general, terrestrial groundwater systems discharging groundwater lie above the theoretical water limit line as defined by the Budyko framework. However, when climate wetness was recalculated to include groundwater discharge there was remarkable convergence of these sites along the water limit line. Similarly, the leaf area index of ecosystems with access to groundwater had higher LAI than those without access to groundwater, for a given climatic regime. However, when discharge was included in the calculation of climate wetness index there was again strong convergence between the two systems, providing support for ecological optimality frameworks that maximize LAI under given water availability regimes. The simplicity and utility of these simple ecohydrological insights potentially provide a valuable tool for predicting groundwater discharge from terrestrial ecosystems.

Analytical expressions of variability in ecosystem structure and function obtained from three-dimensional stochastic vegetation modelling

2013 ◽  
Vol 469 (2155) ◽  
pp. 20130003 ◽  
Author(s):  
Stephen P. Good ◽  
I. Rodriguez-Iturbe ◽  
K. K. Caylor
Keyword(s):  
Leaf Area ◽  
Three Dimensional ◽  
Landscape Scale ◽  
Mathematical Framework ◽  
Ecosystem Structure ◽  
Area Index ◽  
Vegetation Modelling ◽  
Analytic Expressions ◽  
Leaf Level ◽  
And Function

Whole ecosystem exchange of water, carbon and energy is predominately determined by complex leaf-level processes occurring at individual plants. Interaction between individuals results in a distribution of environmental conditions that drive a variety of nonlinear response functions such as transpiration and photosynthesis. The nonlinearity of biophysical processes requires higher-order statistical descriptions of micro-environment distributions in order to accurately determine the landscape-scale mean functional response. We present a mathematical framework for describing vegetation structure based on the density, dispersion, size distribution and allometry of individuals within a landscape. Using three-dimensional stochastic vegetation modelling, we develop analytic expressions of the second-order statistics of vegetation canopies, namely the mean and variance of leaf area density and leaf area index with height. These expressions also allow for the approximation of the distribution of beam penetration and sunfleck statistics through the canopy as a function of height. Finally, we demonstrate how landscape-scale fluxes are strongly affected by the variability in canopy micro-environments, and how stochastic vegetation modelling improves flux estimates relative to traditional homogeneous canopy models.

scholarly journals Quantifying the demographic vulnerabilities of dry woodlands to climate and competition using range-wide monitoring data

2020 ◽  
Author(s):  
Robert K. Shriver ◽  
Charles B. Yackulic ◽  
David M. Bell ◽  
John B. Bradford
Keyword(s):  
Tree Species ◽  
Large Scale ◽  
Pinus Edulis ◽  
Monitoring Data ◽  
Ecosystem Structure ◽  
Remotely Sensed Data ◽  
Climate Conditions ◽  
Drying Conditions ◽  
And Function ◽  
Ecosystem Structure And Function

AbstractClimate change is expected to alter the distribution and abundance of tree species, impacting ecosystem structure and function. Yet, anticipating where this will occur is often hampered by a lack of understanding of how demographic rates, most notably recruitment, vary in response to climate and competition across a species range. Using large-scale monitoring data on two dry woodland tree species (Pinus edulis and Juniperus osteosperma), we develop an approach to infer recruitment, survival, and growth of both species across their range. In doing so, we account for ecological and statistical dependencies inherent in large-scale monitoring data. We find that warming and drying conditions generally lead to declines in recruitment and survival, but there were some idiosyncrasy in the strength of responses across species. Climate conditions lead to vulnerable regions, such as Pinus edulis in N. Arizona, where both survival and recruitment are low. Our approach provides a path forward for leveraging emerging large-scale monitoring and remotely sensed data to anticipate the impacts of global change on species distributions.

scholarly journals The effects of modern war and military activities on biodiversity and the environment

2015 ◽  
Vol 23 (4) ◽  
pp. 443-460 ◽  
Author(s):  
Michael J. Lawrence ◽  
Holly L.J. Stemberger ◽  
Aaron J. Zolderdo ◽  
Daniel P. Struthers ◽  
Steven J. Cooke
Keyword(s):  
Military Training ◽  
Structure And Function ◽  
Aquatic Systems ◽  
Ecosystem Structure ◽  
Population Declines ◽  
Exclusion Zone ◽  
Negative Effects ◽  
And Function ◽  
Ecosystem Structure And Function ◽  
Modern War

War is an ever-present force that has the potential to alter the biosphere. Here we review the potential consequences of modern war and military activities on ecosystem structure and function. We focus on the effects of direct conflict, nuclear weapons, military training, and military produced contaminants. Overall, the aforementioned activities were found to have overwhelmingly negative effects on ecosystem structure and function. Dramatic habitat alteration, environmental pollution, and disturbance contributed to population declines and biodiversity losses arising from both acute and chronic effects in both terrestrial and aquatic systems. In some instances, even in the face of massive alterations to ecosystem structure, recovery was possible. Interestingly, military activity was beneficial under specific conditions, such as when an exclusion zone was generated that generally resulted in population increases and (or) population recovery; an observation noted in both terrestrial and aquatic systems. Additionally, military technological advances (e.g., GPS technology, drone technology, biotelemetry) have provided conservation scientists with novel tools for research. Because of the challenges associated with conducting research in areas with military activities (e.g., restricted access, hazardous conditions), information pertaining to military impacts on the environment are relatively scarce and are often studied years after military activities have ceased and with no knowledge of baseline conditions. Additional research would help to elucidate the environmental consequences (positive and negative) and thus reveal opportunities for mitigating negative effects while informing the development of optimal strategies for rehabilitation and recovery.

scholarly journals Experimental warming differentially affects vegetative and reproductive phenology of tundra plants

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Courtney G. Collins ◽  
Sarah C. Elmendorf ◽  
Robert D. Hollister ◽  
Greg H. R. Henry ◽  
Karin Clark ◽  
...  
Keyword(s):  
Growing Season ◽  
Plant Phenology ◽  
Reproductive Phenology ◽  
Ecosystem Structure ◽  
Experimental Warming ◽  
Growing Seasons ◽  
Tundra Ecosystem ◽  
Phenological Shifts ◽  
And Function ◽  
Ecosystem Structure And Function

AbstractRapid climate warming is altering Arctic and alpine tundra ecosystem structure and function, including shifts in plant phenology. While the advancement of green up and flowering are well-documented, it remains unclear whether all phenophases, particularly those later in the season, will shift in unison or respond divergently to warming. Here, we present the largest synthesis to our knowledge of experimental warming effects on tundra plant phenology from the International Tundra Experiment. We examine the effect of warming on a suite of season-wide plant phenophases. Results challenge the expectation that all phenophases will advance in unison to warming. Instead, we find that experimental warming caused: (1) larger phenological shifts in reproductive versus vegetative phenophases and (2) advanced reproductive phenophases and green up but delayed leaf senescence which translated to a lengthening of the growing season by approximately 3%. Patterns were consistent across sites, plant species and over time. The advancement of reproductive seasons and lengthening of growing seasons may have significant consequences for trophic interactions and ecosystem function across the tundra.

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