Measurements were taken in 15 communities along the elevation gradient from fir forest at high elevations, through pine forest, woodlands, and desert grassland, to deserts at low elevations in the Santa Catalina Mountains, Arizona, and in a Cercocarpus shrubland on limestone. Eight small-tree and shrub species of woodlands and deserts were subjected to dimension analysis by the Brookhaven system. Aboveground biomass decreased along the elevation gradient from 36-79 dry kg/m2 in fir and Douglas-fir forest to 0.26-0.43 kg/m 2 in the desert grassland and two desert samples. Net aboveground primary productivity similarly decreased from 1,050-1,150 g/m 2 • yr in mesic high-elevation forests to 92-140 g/m 2 • yr in desert grassland and deserts. Both biomass and production show a two-slope relation to elevation (and, probably, to precipitation), with a steeper decrease from the high-elevation forests to the mid-elevation woodlands, and a less steep decrease from dry woodlands through desert grassland into desert. The two groups of communities at higher vs. lower elevations also show different relations of leaf area index and chlorophyll to elevation and to productivity. The two groups may represent different adaptive patterns: surface-limiting, with low productivity in relation to precipitation but high production efficiency in relation to surface in the more arid lower elevations, vs. surface-abundant, with high productivity relative to precipitation based on high community surface area, but lower production efficiency in relation to this area, in the more humid higher elevations. Vascular plant species diversity shows no simple relation to productivity, but decreases from high-elevation fir forests to the pine forests, increases from these to the open woodlands, and decreases from dry woodlands through the desert grassland and mountain slope desert to the lower bajada (creosotebush) desert.

Vegetation of the southwest slope of the Santa Catalina Mountains of southeastern Arizona was sampled and transects prepared for 1,000—ft (305 m) elevation belts on granite and gneiss soils from the summit forests (2,440—2,750 m) to the base of the mountains (900 m). Transects also represented subalpine forests above 2,750 m in the Pinaleno Mts. and vegetation of the valley plain or bajada below the mountains, and samples were taken from volcanic soils below 900 m in the Tucson Mts. Principal community—types from high elevations to low are: subalpine forest (Picca engelmanni in the Pinaleno Mts. and Abies lasiocarpa), montane fir forest (Abies concolor, Pseudotsuga menziesii), pine forests (Pinus ponderosa, P. strobiformis), pine—oak forests (P. ponderosa, Quercus hypoleucoides), pine—oak woodlands (P. ponderosa, P. chihuahuana, Q. hypoleucoides, Q. arizonica), pygmy conifer—oak scrub (Pinus cembroides, Juniperus deppeana, Q. arizonica, Q. emoryi, Arctostaphylos pringlei, A. pungens, monocot shrubs), open oak woodland (Q. emoryi, Q. oblongifolia, Vauquelinia californica, monocot shrubs, and grasses), desert—grassland (Agave schottii, Haplopappus laricifolius, and grasses), Sonora desert of mountain slopes (north—slope shrub phase, and south—slope spinose—suffrutescent phase), upper bajada desert (Cercidium microphyllum, Franseria deltoidea), and lower bajada desert (Larrea tridentata). Forests of canyons and arroyos are also described. Relations of communities to elevation and topograhic moisture gradients are represented in a mosaic chart. Physiognomic relations of communities are represented in charts of growth—form coverage in relation to elevation and topographic moisture gradients. Growth—form diversity increases from high—elevation forests strongly dominated by evergreen—needleleaf trees to desert of lower mountain slopes in which pinnate leguminous trees, spinose shrubs, suffrutescent semi—shrubs, and stem—succulents share dominance. Among Raunkiaer life—forms hemicryptophyte species are most numerous at middle and higher elevations, phanerophyte species at lower elevations. In open oak woodlands and desert grasslands phanerophytes, hemicryptophytes, and suffrutescent chamaephytes each make up about one—third of the perennial flora. Desert floras of mountain slopes are characterized by predominance of suffrutescent chamaephytes over both phanerophytes and hemicryptophytes, and large numbers of therophyte species. Analysis in terms of geographic areas of species shows decreasing numbers of Rocky Mountain, Western, and Northern species from high—elevation forests downward, increasing numbers of Southwestern and Latin American species at lower elevations. Madrean species of the Mexican Plateau and Southwestern species predomonate in pine—oak forests and woodlands and pygmy conifer—oak scrub. Sonoran, Chichuahuan, and Latin American species predominate in the desert of lower mountain slopes, and widely distributed Southwestern species in the Larrea desert. Flora of the Catalina Mountains is rich and community s...

The saguaro (Cereus giganteus, Carnegiea gigantea) a giant cactus, is a conspicuous and important plant of the Sonoran Desert in southern Arizonaand northern Mexico (Sonora). Since the turn of the century it has been known to be failing to reproduce in certain environments (1). This failure has stimulated considerable research on various aspects of its biology (2). Decline in reproduction dates from the rapid growth of the cattle industry in the 1880's, an influence which has left a lasting imprint on parts of the Southwest. The aim of this article is to combine the knowledge of saguaro biology with the authors' population data from the Santa Catalina Mountains and adjacent ranges in a discussion of saguaro as a natural population in relation to environment and disturbance. The influence of climate, soils, overgrazing, and heavy rodent populations is considered in relation to saguaro survival (3). Biology and DistributionThe saguaro (Cereus giganteus, Carnegiea gigantea) is often more than 9 meters tall, with a trunk more than 40 centimeters in diameter in larger individuals. A member of an essentially subtropical group (the subfamily 4 OCTOBER 1963 The authors are ecologists in, respectively, the )n (1, 8). The department of botany, Connecticut College; the department of biology, 'Brooklyn College; and the eS it possible to department of zoology, University of Arizona. 15

Increasing rates of relative sea—level rise (RSL) have been linked to coastal wetland losses along the Gulf of Mexico and elsewhere. While such losses have yet to be reported for New England tidal marshes, rapidly rising RSL may still be affecting these systems. Studies of the Wequetequock—Pawcatuck tidal marshes over four decades have documented dramatic changes in vegetation that appear to be related primarily to differential rates of marsh accretion and sea—level rise. Other environmental factors such as sediment supply and anthropogenic modifications of the system may be involved as well. When initially studied in 1947—1948 the high marsh supported a Juncus gerardi—Spartina patens belting pattern typical of many New England salt marshes. On the most of the marsh complex the former Juncus belt has been replaced by forbs, primarily Triglochin maritima, while the former S. patens high marsh is now a complex of vegetation types–stunted Spartina alterniflora, Distichlis Spicata, forbs, and relic stands of S. patens. These changes are documented by vegetation sampling that closely followed the 1947—1948 methods and by peat core analysis. Marsh elevations were determined by leveling, and the mean surface elevation of areas where the vegetation has changed is significantly lower than that of areas still supporting the earlier pattern (4.6 vs. 13.9 cm above mean tide level). The differences in surface elevation reflect differences in accretion of marsh peat. Calculations based on sandy overwash layers deposited during historically recorded storms as well as on experimentally placed marker horizons of known age indicate that stable areas have been accreting at the rate of local sea—level rise, 2.0—2.5 mm/yr at least since 1938; changed areas have accreted at about one half that rate. Lower surface elevations result in greater frequency and duration of tidal flooding, and thus in increased peat saturation, salinity, and sulfide concentrations, and in decreased redox potential, as directly measured over the growing season at both changed and stable sites. It is proposed that these edaphic changes have combined to favor establishment of a wetter, more open vegetation type dominated by to distinctive communities–Stunted S. alterniflora and forbs. Changes documented on the Wequetequock—Pawcatuck system have been observed on the other Long Island Sound marshes and may serve as a model for the potential effects of seal—level rise on New England tidal salt marshes.

In 1980 the State of Connecticut began a tidal marsh restoration program targeting systems degraded by tidal restrictions and impoundments. Such marshes become dominated by common reed grass ( Phragmites australis ) and cattail ( Typha angustifolia and T. latifolia ), with little ecological connection to Long Island Sound. The management and scientific hypothesis was that returning tidal action, reconnecting marshes to Long Island Sound, would set these systems on a recovery trajectory. Specific restoration targets (i.e., predisturbance conditions or particular reference marshes) were considered unrealistic. However, it was expected that with time restored tides would return ecological functions and attributes characteristic of fully functioning tidal salt marshes. Here we report results of this program at nine separate sites within six marsh systems along 110 km of Long Island Sound shoreline, with restoration times of 5 to 21 years. Biotic parameters assessed include vegetation, macroinvertebrates, and use by fish and birds. Abiotic factors studied were soil salinity, elevation and tidal flooding, and soil water table depth. Sites fell into two categories of vegetation recovery: slow, ca. 0.5%, or fast, more than 5% of total area per year. Although total cover and frequency of salt marsh angiosperms was positively related to soil salinity, and reed grass stand parameters negatively so, fast versus slow recovery rates could not be attributed to salinity. Instead, rates appear to reflect differences in tidal flooding. Rapid recovery was characterized by lower elevations, greater hydroperiods, and higher soil water tables. Recovery of other biotic attributes and functions does not necessarily parallel those for vegetation. At the longest studied system (rapid vegetation recovery) the high marsh snail Melampus bidentatus took two decades to reach densities comparable with a nearby reference marsh, whereas the amphipod Orchestia grillus was well established on a slow-recovery marsh, reed grass dominated after 9 years. Typical fish species assemblages were found in restoration site creeks and ditches within 5 years. Gut contents of fish in ditches and on the high marsh suggest that use of restored marsh as foraging areas may require up to 15 years to reach equivalence with reference sites. Bird species that specialize in salt marshes require appropriate vegetation; on the oldest restoration site, breeding populations comparable with reference marshland had become established after 15 years. Use of restoration sites by birds considered marsh generalists was initially high and was still nearly twice that of reference areas even after 20 years. Herons, egrets, and migratory shorebirds used restoration areas extensively. These results support our prediction that returning tides will set degraded marshes on trajectories that can bring essentially full restoration of ecological functions. This can occur within two decades, although reduced tidal action can delay restoration of some functions. With this success, Connecticut...