https://www.fs.fed.us/pnw/pubs/journals/pnw_2002_franklin001.pdf

Disturbances and structural development of natural forest ecosystems with silvicultural implications, using Douglas-fir forests as an example

Experimental evidence for positive interactions, or facilitation, among plants has increased markedly during the last 10 years. Experiments documenting facilitation have been conducted in many diverse ecological systems, which suggests that positive interactions may be fundamental processes in plant communities. Here, I review the evidence for facilitation, the mechanisms by which facilitation operates, and the effects facilitation has on community structure. Facilitative mechanisms may act simultaneously with resource competition or allelopathy, and the overall effect of one species on another may be the product of multiple, complex interactions. Positive interactions may also determine community spatial patterns, permit coexistence, enhance diversity and productivity, and drive community dynamics. Once viewed as anecdotal and idiosyncratic, facilitation is now contributing to a more complete understanding of community structure and dynamics.

Positive interactions among plants

https://www.fs.fed.us/pnw/pubs/journals/pnw_2010_kennedy002.pdf

Detecting trends in forest disturbance and recovery using yearly Landsat time series: 1. LandTrendr — Temporal segmentation algorithms

Publisher Summary This chapter reviews the evidence for the pattern of growth decline with age and discusses the evidence for the mechanisms that may be responsible. It begins with an overview of the proposed mechanisms. The chapter also presents a framework for understanding the changes in stand productivity with age, because many of the proposed mechanisms are linked and affect carbon allocation. The available information on the importance of various mechanisms behind growth decline, in the context of the stand carbon cycle is presented. The common patterns of a decline in stand leaf area and leaf photosynthetic capacity suggest a new model of carbon balance with stand development. In this model, photosynthesis and above-ground dry-matter production increase with canopy development. After the forest reaches a maximum leaf area, photosynthesis and dry-matter production decline as leaf area, photosynthetic capacity, and photosynthesis also decline. The model assumes that allocation to respiration and below ground to roots and symbionts is a constant fraction of assimilation over the life of a forest stand.

Age-Related Decline in Forest Productivity: Pattern and Process

Landscape structural characteristics, such as patch size, edge length, and configuration, are altered markedly when management regimes are imposed on primeval landscapes. The ecological consequences of clearcutting patterns were explored by using a model of the dispersed patch or checkerboard system currently practiced on federal forest lands in the western United States. Thresholds in landscape structure were observed on a gradient of percentages of landscape cutover. Probability of disturbance,e.g., wildfire and windthrow, and biotic components,e.g., species diversity and game populations, are highly sensitive to these structural changes. Altering the spatial configuration and size of clearcuts provides an opportunity to create alternative landscapes that differ significantly in their ecological characteristics. Both ecosystem and heterogeneous landscape perspectives are critical in resource management.

/pdf/creating-landscape-patterns-by-forest-cutting-ecological-2m5gmdc4mi.pdf

Creating landscape patterns by forest cutting: Ecological consequences and principles

Natural Vegetation of Oregon and Washington

Techniques in Bioproductivity and Photosynthesis

Highlight: Roots of plants express phenology significant to competitive relationships, as do aerial parts. The following developmental stages of root phenology are proposed: (1) germination, (2) initial root growth, (3) rapid extension of root-soil contact, (4) dormancy, and (5) death. Examples of root phenological development in seedlings of three grass species are given to demonstrate effects on competition.

/pdf/root-phenology-as-a-factor-of-competition-among-grass-2x4q6tau64.pdf

Root phenology as a factor of competition among grass seedlings.

Bear Attacks: Their Causes and Avoidance

The importance of morphological variation for evolutionary and phylogenetic stud- ies is well recognized. This paper concentrates on morphological differences within and among population samples of several species of grasses to interpret potential for further differentiation. Analysis of gross morphology, a traditional tool of systematics, is coupled with numerical taxonomy to identify kinds of morphological differentiation among populations of species of four steppe grasses: Bromus japonicus, B. tectorum, Poa secunda, Pseudoregneria spicata. Floral and vegetative vari- ation in Poa secunda is consistent with apomictic differentiation. Floral characteristics in this species were responsible for more phenotypic divergence between populations (71%) than within popu- lations (35%), while vegetative traits were responsible for 29% of total variance between populations and 65% within populations. Inbreeding in the two Bromus species is not associated with any notable morphological differentiation between populations. Bromus tectorum appears to retain mor- phological uniformity throughout the area sampled. Character states for Pseudoregneria spicata ex- hibit varying degrees of plasticity depending on the population. This comparative study, concerned with differences and similarities in amounts and kinds of variation of morphological traits, repre- sents a first attempt to assess how morphological variation can be examined to detect the potential for some kinds of speciational events.

Grant A. Harris

Papers

Natural Vegetation of Oregon and Washington

Techniques in Bioproductivity and Photosynthesis

Root phenology as a factor of competition among grass seedlings.

Bear Attacks: Their Causes and Avoidance

Variability within and among Populations of Four Grass Species