Similar Tree Species Research Articles

Comparing the soil macro-fauna in two oak-wood forests: does community structure differ under similar ambient conditions?

Summary Taxa, specimen richness and biodiversity were compared in the forest floor of two old natural oak forests in the Mediterranean region in the Galil mountains and in the Golan Heights. The study sites, about 35 km (by air) apart, had similar tree species composition, similar climatic and micro-climatic conditions, but different soil physical texture. The fauna was extracted from samples of leaf litter and top soil. Decomposition parameters (organic matter, nitrogen, calcium, phosphorus) and climatic conditions (precipitation, air and forest floor temperature, leaf litter and top soil water content) were measured. The dynamics of taxa moving between the leaf litter and top soil, were determined. The two forests did not differ significantly in biodiversity, taxa and specimen richness, except for the taxa numbers in the soil phase. However the forest floor community composition differed. Thus, oligochaetes were more abundant in the Golan whereas diplopods, isopods and hymenoptera were more abundant in the Galil, and gastropods were found exclusively in the Galil. In both forests, no correlation was found between specimen richness and the decomposition parameters, though some groups (oligochaetes, arachnids and insects) were influenced by mineral levels. In both forests, climate affected the dynamics of taxal vertical movement. Moreover, in both forests, (leaf litter and top soil), specimen richness and biodiversity index were low during the dry season and high during the wet season. The influence of climatic changes on the taxa composition and vertical movement, were similar in the two forests. We conclude that in similar forest types under similar climatic conditions, the soil composition and texture do not directly affect biodiversity and fauna richness. The soil texture has a direct influence on the relative abundance of certain animal taxa.

Habitat patterns in forested landscapes: management practices and the uncertainty associated with natural disturbances

We present the results of a study to examine the effects of management actions and natural disturbances in influencing the evolution of habitat patterns on forested lands. TELSA, a spatially explicit vegetation succession model with the ability to apply user-defined management actions and stochastic wildfires calibrated to local conditions, was used to evaluate changes in several indicators of habitat condition. We assessed seral stage and patch size changes over multiple 200-year simulations under a constant rate of harvest within each of these analyses. In the absence of natural disturbances, old growth habitat and large patches of forest of similar age and tree species composition decreased unless special management practices were applied. Old-growth management area reserves and periodic ‘aggregated cutblock’ harvesting entries helped maintain forest seral stage distribution at the target level, and patch size characteristics similar to the patterns that would have occurred under historic natural disturbances. Adding wildfire to the management scenarios substantially reduced the amount of old-growth habitat in designated old-growth management area reserves, compromising the ability to maintain old-growth at target levels. A 50% increase in the area designated as old-growth management area reserves would be required to offset the loss of old growth due to wildfire. Although the amount of old-growth habitat was diminished by wildfire, the availability of large habitat patches greater than 250 ha increased. We discuss the need to consider the role of management and natural disturbances in landscape planning, and suggest that redundancy is essential to maintain those features vulnerable to stochastic disturbances. Landscape scenario modeling can facilitate the development of risk averse plans, and encourage the development of innovative approaches to achieving timber and non-timber objectives.

Tropical tree diversity, forest structure and the demography of a frugivorous rodent, the spiny rat (Proechimys semispinosus)

AbstractPopulations of the Central American spiny rat Proechimys semispinosus isolated on eight small islands in Panama were sampled monthly for 1 year to examine the relationships of demography to tree species composition and forest structure. Demography was characterized by calculating seven variables from the monthly census data. Tree species composition was determined by marking, measuring and identifying all trees ð 10 cm in diameter at breast height (dbh) on each island. Forest structure (tree stature, density and species richness) was quantified by measuring seven variables at each of the 470 sampling stations. Bivariate correlations were computed between spiny rat demography and tree species composition and forest structure. To examine whether islands with more similar tree species composition or forest structure supported P. semispinosus populations with more similar demography, dendrograms based on complete‐linkage cluster analysis were constructed. Spiny rat densities were correlated positively with the density of large‐fruited fig trees and non‐linearly to an index of forest age based on tree species composition. Spiny rat densities were not related to any structural variable. Dendrograms based on cluster analysis showed that spiny rat demography did not map onto forest structure, overall tree species composition or any group of selected tree species except figs Ficus spp. Thus, islands with more similar fig tree composition contained spiny rat populations with more similar demography. Tree species composition, which partly determines resource abundance, is apparently more important than forest structure in influencing spiny rat demography. Proechimys semispinosus has a temporally and spatially variable demography, and this flexible demography, in concert with an ability to use diverse resources, presumably promotes abundance and persistence in heterogeneous tropical forests and may contribute to the ubiquity of this rodent.

Comparisons of riparian vs. over stream trap location in the estimation of vertical litterfall inputs

Vertical inputs of allochthonous organic matter to streams can be estimated directly with traps; traps may be placed over the stream, in the riparian forest or at other locations in the catchment. In this study, we compared litter inputs estimated from traps located over the stream with those obtained from traps placed on the stream bank in two stretches (orders 2 and 3) of the Mera stream, with similar tree species composition and riparian forest structure. The amount of annual litter input measured with the traps on the stream was similar in the two stretches, 748 and 730 g m-2 yr-1, for orders 2 and 3, respectively. However, there appeared to be differences in the composition of litter; a lower percentage of leaves and a higher percentage of wood was found in the stretch of order 3 than in the stretch of order 2. In both sites, the mean input measured under the riparian forest was lower than the input recorded with the traps placed over the stream by approximately 10%. In relation to the traps located over the stream, the traps located on the bank overestimated the input from adjacent terrestrial tree species and, therefore, underestimated the input from riparian species.

Effects of overstory and understory vegetation on the understory light environment in mixed boreal forests

Abstract. The percentage of above‐canopy Photosynthetic Photon Flux Density (%PPFD) was measured at 0, 50 and 100 cm above the forest floor and above the main understory vegetation in stands of (1) pure Betula papyrifera (White birch), (2) pure Populus tremuloides (Trembling aspen), (3) mixed broad‐leaf‐conifer, (4) shade‐tolerant conifer and (5) pure Pinus banksiana (Jack pine) occurring on both clay and till soil types. %PPFD was measured instantaneously under overcast sky conditions (nine locations within each of 29 stands) and continuously for a full day under clear sky conditions (five locations within each of eight stands). The percentage cover of the understory layer was estimated at the same locations as light measurements.Mean %PPFD varied from 2% at the forest floor under Populus forests to 15% above the understory vegetation cover under Betula forests. Percent PPFD above the understory vegetation cover was significantly higher under shade intolerant tree species such as Populus, Betula and Pinus than under shade tolerant conifers. No significant differences were found in %PPFD above the understory vegetation cover under similar tree species between clay and till soil types. The coefficient of variation in %PPFD measured in the nine locations within each stand was significantly lower under deciduous dominated forests (mean of 19%) than under coniferous dominated forests (mean of 40%). %PPFD measured at the forest floor was positively correlated with %PPFD measured above the understory vegetation and negatively correlated with cumulative total percent cover of the understory vegetation (R2 = 0.852). The proportion of sunflecks above 250 and 500 mmol m–2 s–1 was much lower and %PPFD in shade much higher under Populus and Betula forests than under the other forests. Differences in the mean, variability and nature of the light environment found among forest and soil types are discussed in relation to their possible influences on tree succession.

Seedling survival and growth of four Shorea species in a Sri Lankan rainforest

ABSTRACTIn this study four species of the genus Shorea section Doom were investigated. All occur together as canopy trees in the Sinaraja rainforest of south-west Sri Lanka. Partitioning of the regeneration niche can be one explanation for the co-existence of ecologically similar canopy tree species within a forest. Seedlings were planted in plots located in five zones that represent a range of forest groundstorey microenvironments found adjacent to and across canopy openings of three sites – valley, midslope, ridgetop. Experiments were designed to monitor survíval and growth of planted seedlings for two years. At the end of two years percentage survival was calculated, height increment recorded and destructive samples taken to measure dry mass gain of root, stem and leaves. Comparisons were made of establishment and growth performance of seedlings planted in the different plots and sites. Results demonstrated clear differences in survival and growth among species. These differences appeared related to availability of soil moisture and groundstorey radiation regimes. Disturbance patterns that determine species co-existence are suggested.

The verification of the heat pulse velocity technique for estimating sap flow in Eucalyptusgrandis

The heat pulse velocity technique was verified on a diffuse porous hardwood, Eucalyptusgrandis Hill ex. Maiden, using the cut-tree method. The heat pulse velocity apparatus accurately reflected sap flow in the stems of 3-year-old trees and of a 16-year-old tree. Measured sap flow was found to be particularly sensitive to errors in the estimation of the wound size and probe separation. Four probes, each providing a point estimate of heat pulse velocity, were sufficient to estimate sap flow in young trees, but a minimum of eight was needed for trees larger than about 20 cm in diameter. For the successful field application of the heat pulse velocity technique on standing E. grandis trees, it is necessary to wait 5 days after implanting the probes to enable tyloses to form, which facilitates wound size measurement. This technique is recommended for the accurate and rapid measurement of water use by E. grandis and other similar plantation tree species.

Mechanical Site Preparation and Early Chemical Tending in White Spruce: 19-year Results

A white spruce outplanting trial, with about 480 trees, was established on a fertile mixedwood site in Ontario (47°N, 84°W) in 1967 to study the effects of two site preparation methods and early chemical tending on the development of the crop species and non-crop woody vegetation. Nineteen-year results are presented. Early chemical tending of white spruce resulted in a significant increase in growth on the drum-prepared block, but not on the blade-prepared block. On the drum-prepared block, mortality of white spruce outplants did not differ significantly between herbicide-treated and untreated plots. On the blade-prepared block, mortality was significantly greater with herbicide application than without it. Similar non-crop tree and shrub species were found on sites prepared with both sharkfin drums and angle-dozer blades. However, woody weeds were less abundant on the herbicide-treated plots than on the untreated plots. Key words: white spruce outplant performance; chemical weed control; 2.4-D and 2,4,5-T; mechanical site preparation; herbicide efficacy; silvicultural efficacy; early tending; sharkfin drum; angle-dozer blade.

The Effect of Host Specificity on the Interspecific Associations of Bark Lichens

Ten corticolous macrolichen species occurring in eleven upland forest stands in north central Oklahoma were tested for interspecific associations in the forest as a whole and on each of the two major oak species. Results in- dicate that association values for lichen pairs in the forest as a whole are gen- erally not useful since they are composites of the association values on the two tree species. The two tree species are not equally inhabited by all lichens; hence, associations between lichens vary--somtimes radically--from one tree to another. The fact that many bark-inhabiting lichen species tend to be host specific is by now well documented (e.g., Barkman, 1958; Hale, 1967; Adams & Risser, 1971). In attempting to delineate bark communities with the aid of Cole's (1949) index, a means of measuring the degree of association between two species, Hale (1955) found that host specificity presented a problem. As he pointed out, two cryptogams with high preference for the same tree species may appear highly positively associated, when in fact they are distributed independently of each other. Hale demonstrated that this effect of host specificity can be avoided by testing for cryptogamic associations on one tree species at a time, or on groups of similar tree species. This approach is more expensive in terms of computation time and may be impractical when more than a few tree species are involved. Hale, who was working with an unwieldy amount of data and seven major tree species, limited his analysis to a single pair of similar tree species. Our investigation was conducted in north central Oklahoma, where only two tree species comprise more than 90% of the total basal area in upland forests. With forests of such simple composition it is relatively easy to test for lichen associations on each of the important tree species. Measurements of association in the forest as a whole can be compared with measurements on each of the two major tree species, and, al- though causal relationships remain obscure, variations in associations from one host species to another can be detected.