II. PROCEDURE .................................. 285 Study Areas ................................. 285 Vegetation Samples and Soil Data ..... ..... 286 Arrangement of Samples in Transects .... . 286 Evaluation of Transect Techniques . ..... . 288 Transect Tables ................... ....... 289 III. VEGETATION DESCRIPTION ...... ............. 291 Low Elevations on Diorite . ... ......... .. 291 Low Elevations on Gabbro ..... ........ 297 Low Elevations on Serpentine and the Two-Phase Ef fect .......... .............. . 299 Forest Vegetation of Higher Elevations on Diorite ......................... ....... 302 Vegetation of Higher Elevations on Serpentine . . 305

Vegetation of the Siskiyou Mountains, Oregon and California

An important aim of plant ecology is to identify leading dimensions of ecological variation among species and to understand the basis for them. Dimensions that can readily be measured would be especially useful, because they might offer a path towards improved worldwide synthesis across the thousands of field experiments and ecophysiological studies that use just a few species each. Four dimensions are reviewed here. The leaf mass per area-leaf lifespan (LMA-LL) dimension expresses slow turnover of plant parts (at high LMA and long LL), long nutrient residence times, and slow response to favorable growth conditions. The seed mass-seed output (SM-SO) dimension is an important predictor of dispersal to establishment opportunities (seed output) and of establishment success in the face of hazards (seed mass). The LMA-LL and SM-SO dimensions are each underpinned by a single, comprehensible tradeoff, and their consequences are fairly well understood. The leaf size-twig size (LS-TS) spectrum has obvious consequences for the texture of canopies, but the costs and benefits of large versus small leaf and twig size are poorly understood. The height dimension has universally been seen as ecologically important and included in ecological strategy schemes. Nevertheless, height includes several tradeoffs and adaptive elements, which ideally should be treated separately. Each of these four dimensions varies at the scales of climate zones and of site types within landscapes. This variation can be interpreted as adaptation to the physical environment. Each dimension also varies widely among coexisting species. Most likely this within-site variation arises because the ecological opportunities for each species depend strongly on which other species are present, in other words, because the set of species at a site is a stable mixture of strategies.

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Plant Ecological Strategies: Some Leading Dimensions of Variation Between Species

ing and summarizing knowledge about range dynamics without distorting it. The amount of detail lost in a particular description would depend on how many states and transitions were recognized. We are proposing the state-and-transition formulation because it is a practicable way to organize information for management, not because it follows from theoretical models about dynamics. In consequence, we consider management rather than theoretical criteria should be used in deciding what states to recognize in a given situation. As a general rule, one would distinguish 2 states only if the difference between them represented an important change in the land from the point of view of management. For example, variation due to seasonal phenology of the plants would not normally be subdivided into states, while important changes in the underlying botanical composition would be recognized. It follows that a given rangeland could be described in terms of a greater or lesser number of states and transitions, depending on the nature and objectives of management and on the state of existing knowledge. There would not be a single correct description. Under the state-and-transition formulation, knowledge about a given rangeland should be organized and expressed in the follow-

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Opportunistic management for rangelands not at equilibrium.

A leaf-height-seed (LHS) plant ecology strategy scheme is proposed. The axes would be specific leaf area SLA (light-capturing area deployed per dry mass allocated), height of the plant's canopy at maturity, and seed mass. All axes would be log-scaled. The strategy of a species would be described by its position in the volume formed by the three axes. The advantages of the LHS scheme can be understood by comparing it to Grime's CSR scheme, which has Competitors, Stress-tolerators and Ruderals at the corners of a triangle. The CSR triangle is widely cited as expressing important strategic variation between species. The C–S axis reflects variation in responsiveness to opportunities for rapid growth; in the LHS scheme, SLA reflects the same type of variation. The R axis reflects coping with disturbance; in the LHS scheme, height and seed mass reflect separate aspects of coping with disturbance. A plant ecology strategy scheme that permitted any species worldwide to be readily positioned within the scheme could bring substantial benefits for improved meta-analysis of experimental results, for placing detailed ecophysiology in context, and for coping with questions posed by global change. In the CSR triangle the axes are defined by reference to concepts, there is no simple protocol for positioning species beyond the reference datasets within the scheme, and consequently benefits of worldwide comparison have not materialized. LHS does permit any vascular land plant species to be positioned within the scheme, without time-consuming measurement of metabolic rates or of field performance relative to other species. The merits of the LHS scheme reside (it is argued) in this potential for worldwide comparison, more than in superior explanatory power within any particular vegetation region. The LHS scheme avoids also two other difficulties with the CSR scheme: (a) It does not prejudge that there are no viable strategies under high stress and high disturbance (the missing quadrant in the CSR triangle compared to a two-axis rectangle); (b) It separates out two distinct aspects of the response to disturbance, height at maturity expressing the amount of growth attempted between disturbances, and seed mass (inverse of seed output per unit reproductive effort) expressing the capacity to colonize growth opportunities at a distance. The advantage of LHS axes defined through a single readily-measured variable needs to be weighed against the disadvantage that single plant traits may not capture as much strategy variation as CSR's multi-trait axes. It is argued that the benefits of potential worldwide comparison do actually outweigh any decrease in the proportion of meaningful variation between species that is captured. Further, the LHS scheme opens the path to quantifying what proportion of variation in any other ecologically-relevant trait is correlated with the LHS axes. This quantification could help us to move forward from unprofitable debates of the past 30 years, where CSR opponents have emphasized patterns that were not accommodated within the scheme, while CSR proponents have emphasized patterns that the scheme did account for.

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A leaf-height-seed (LHS) plant ecology strategy scheme

Gradient analysis of vegetation

T ODAY there are many different bases for range condition classifications. Stockmen commonly associate the term “range condition” with favorableness of the season. In this sense, good range condition may mean simply that an area recently received good rains. However, professional range conservationists have long associated good range condition with something less fleeting than good seasonal growth. In the glossary of technical terms published by the Society of American Foresters (11)) range condition is defined as “The state of health or productivity of both soil and forage of a given range, in terms of what it could or should be under normal climate and best practicable management”. This article describes a system for determining range condition which considers climate, soil, and vegetation both present and potential. It includes a review of researches that provide a scientific foundation for the system, and shows how earlier qualitative applications have been replaced by quantitative ones. An actual example is used to demonstrate practical application of the system to range management.

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E.J. Dyksterhuis

Papers

Condition and Management of Range Land Based on Quantitative Ecology.