In lowland tropical forests, natural disturbances such as treefall gaps are consid- ered fine-scale disturbances necessary for the regeneration of canopy species Denslow ; Popma and Bongers Increment in light levels at the for- est floor after gap formation may increase the probability of establishment of some pioneer trees Turner ; Davies However, gap partitioning among pioneer tree species arises directly from morphological and biochem- ical specialization to particular light gap environments, and in turn may result from a trade-off between seedling growth and survival Kitajima ; Dalling et al.
By contrast, in pine-oak-Liquidambar forests POLF under human disturbance, seedling species richness may decrease from 26 to four tree species, and density varies from 0.
- Publicación en libro "Restoration of Boreal and Temperate forests".
- Articles citing this article!
- Cited article:!
- Quark Model and High Energy Collisions!
- Key Concepts in Learning Disabilities?
- Markov Chains and Decision Processes for Engineers and Managers?
Climate is temperate sub-humid with summer rains. Site characteristics include a wide range of elevations 1,—2, m on relatively poor soils and steep slopes Table There is a different number of successional habitats at each study site, due to variations in area. In many of these habitats, a variable number of seedlings and saplings 25— of different species 4—25 were planted, with time reaching a total of 40 species, corresponding to 7, individuals Table Only 27 species used under greenhouse conditions had at least one replicated habitat under field conditions Table Black houses were used to create four shade treatments, i.
Seedlings of each species total of 3, individ- uals were randomly placed in black houses in order to have four replicates for each shade treatment except in the non-shaded treatment, where only three replicates were used.
Seedlings were homogeneously watered in order to avoid desiccation, and periodically rotated. Survival and relative growth rates were evaluated after one year. Description of the study sites. Initial number of seedlings of 54 native tree species within four ecological groups used in experiments conducted in eight different successional habitats and in greenhouse controlled conditions GH in the northern and central highlands of Chiapas, Mexico see Table This classification is useful to understand the effects of light variation associated with canopy cover along successional gradients in MPOF in Chiapas.
Since our design is evidently non- balanced, having unequal numbers of species, different seedling ages, and dif- ferent periods of evaluation, we present an exploratory analysis considering the overall response of the four groups of species, rather than individual species responses in each successional habitat or shade treatment.
Mean seedling survival, and relative growth rates of height and basal stem diameter were obtained for all individual species, and these data then combined for each of the four ecological groups. Greenhouse Survival Under field conditions, the survival of seedlings of the four ecological groups showed high variation among successional habitats Fig. By contrast, the mean sur- vival of seedlings under greenhouse conditions showed different trends. In general, after a year of evaluation, the survival of the four groups of species was higher with increasing shade density Fig.
Shade treatments under green- house conditions roughly represent mean values of canopy cover of each corresponding successional habitat.
N Number of species included within each group Oaks and the shade-tolerant broad-leaved seedlings grew more in the ESF, whereas the shade-intolerant broad-leaved seedlings did not show any trend; still, the variation within this group was less pronounced in the MSF Fig. Box plot for the relative growth rate of stem height RGRheight, cm cm—1 year—1 of tree seedlings of four ecological groups conifers, oaks, shade-intoler- ant broad-leaved trees, and shade-tolerant broad-leaved trees under field a and green- house b conditions.
Successional habitats and shade treatments as in Fig. Oaks and conifers showed an increase in basal diameter in the OA and SHR habitats, the latter being where conifers had their greatest increase in basal diameter Fig. Among the four ecological groups evaluated in the greenhouse, conifers presented the lowest diameter increases — probably because the seedlings were smaller than those of the other groups.
It is well known that seedlings of conifers grow less efficiently than those of angiosperms, at least during the initial stages of growth Bond Box plot for the relative growth rate of basal stem diameter RGRdiameter, cm cm—1 year—1 of tree seedlings of four ecological groups conifers, oaks, shade-intoler- ant broad-leaved trees, and shade-tolerant broad-leaved trees under field a and green- house b conditions.
However, due to the high intensity and fre- quency of human disturbances in the MPOF of Chiapas, natural recovery can be slow. The cumulative effect of this type of disturbance tends to favor the regeneration of some pioneer species such as pines, oaks, Alnus acuminata, Arbutus xalapensis, Buddleja cordata, and Prunus serotina, which showed good performance in open areas or shrublands.
Diurnal patterns of solar radiation, temperature, and relative humidity display more extreme variations in open pine forests than in closed- canopy old-growth oak forests. Restoration of native plant communities requires identifying those factors that favor or impede natural colonization by native tree species Denslow In the study region, successful colonization of native trees in early seral stages is limited not only by physical conditions such as light intensity and related temperature e.
Therefore, a viable strategy for MPOF recovery in Chiapas seems to be through the reintroduction of seedlings in appropriate successional habitats.
From a biological viewpoint, there could be two routes for forest restoration: 1 the suppression of disturbance in forested areas, which would promote natural regeneration, and 2 the establishment of enrichment planting in poor-species forested areas. Based on this and previous evidence, we consider feasible the reintroduction of pines and oaks, and some other shade-intoler- ant broad-leaved species in open and shrubland habitats, and of seedlings of shade-tolerant broad-leaved species in pinelands or other successional forests with intermediate light levels under the canopies.
As a consequence, only low numbers of naturally recruited seedlings of these species are observed in the remaining secondary forests, which may lead to their local extinction. Our classification of plant functional types sensu Denslow based on a combination of taxonomical and ecological traits will help us to understand the interaction between physical factors mostly light conditions and succes- sional gradients in MPOF in Chiapas.
Grouping of species is useful to identify which species show similar responses to specific environmental conditions. Duncan Golicher, Pedro F. Quintana-Ascen- cio, and Luis Galindo-Jaimes provided useful comments that improved the manuscript. References Augspurger CK Light requirements of neotropical tree seedlings: a comparative study of growth and survival. J Trop Ecol — Bond WJ The tortoise and the hare: ecology of angiosperm dominance and gym- nosperm persistence.
Introduction to the flora of Chiapas. Brudvig, M. Ecohydrological implications of restoring Midwestern bur oak savannas after woody encroachment. Ecological Restoration. Schulte, L. Asbjornsen , T. Unplowing the land: Restoring agroecosystem health and function through perennialization. Journal of Soil and Water Conservation. Karnitz, H. Composition and age structure of a degraded tallgrass oak savanna in central Iowa, USA.
Classic Canopy Citations | ICAN
Natural Areas Journal. Deep ground fires cause massive above- and below-ground biomass losses in tropical montane cloud forests in Oaxaca, Mexico. Journal of Tropical Ecology. Brudvig, C. Defining appropriate reference conditions for restoring ecologically rare oak savanna ecosystems in the Midwest, USA. Journal of Forestry. Belcher, B. Michon, A. Angelsen, M.
Cultivating in tropical forests?
- tales of the oak Manual.
- Ecological Studies;
- Dr. Heidi Asbjornsen | Natural Resource Ecology and Management;
- Ecology and Conservation of Neotropical Montane Oak Forests.
Driving forces in the rise and fall of forest garden systems. Economic Botany. Oak regeneration before and after restoration efforts in a tallgrass oak savanna. American Midland Naturalist. DOI: Vogt, P. Synergistic responses of oak, pine and shrub seedlings to edge environments and drought in a fragmented tropical highland oak forest; Oaxaca, Mexico. Ashton, D.
Vogt, S. Effects of habitat fragmentation on the buffering capacity of edge environments in a seasonally-dry tropical oak forest ecosystem in Oaxaca, Mexico. Agriculture, Ecosystems and Environment.
- Dr. Heidi Asbjornsen!
- Forest-Atmosphere Interactions.
- The 00s (Designers & Dragons, Volume 4);