Understanding causes of tree growth response to gap formation: D13C-values in tree rings reveal a predominant effect of light
Sleen, J.P. van der; Soliz-Gamboa, C.C. ; Helle, G. ; Pons, T.L. ; Anten, N.P.R. ; Zuidema, P.A. - \ 2014
Trees-Structure and Function 28 (2014)2. - ISSN 0931-1890 - p. 439 - 448.
water-use efficiency - carbon-isotope discrimination - tropical rain-forest - nutrient availability - microbial biomass - wood delta-c-13 - canopy gaps - size - photoinhibition - dynamics
Carbon isotope ratios in growth rings of a tropical tree species show that treefall gaps stimulate diameter growth mainly through changes in the availability of light and not water. The formation of treefall gaps in closed canopy forests usually entails considerable increases in light and nutrient availability for remaining trees, as well as altered plant water availability, and is considered to play a key role in tree demography. The effects of gaps on tree growth are highly variable and while usually stimulatory they may also include growth reductions. In most studies, the causes of changes in tree growth rates after gap formation remain unknown. We used changes in carbon isotope 13C discrimination (D13C) in annual growth rings to understand growth responses after gap formation of Peltogyne cf. heterophylla, in a moist forest of Northern Bolivia. We compared growth and D13C of the 7 years before and after gap formation. Forty-two trees of different sizes were studied, half of which grew close (\10 m) to single treefall gaps (gap trees), the other halfmore than 40 m away from gaps (controls). We found variable responses among gap trees in growth and D13C. Increased growth was mainly associated with decreased D13C, suggesting that the growth response was driven by increased light availability, possibly in combination with improved nutrient availability. Most trees showing zero or negative growth change after gap formation had increased D13C, suggesting that increased water stress did not play a role, but rather that light conditions had not changed much or nutrient availability was insufficient to support increased growth. Combining growth rates withD13Cproved to be a valuable tool to identify the causes of temporal variation in tree growth.
Influence of foliar phenology and shoot inclination on annual photosynthetic gain in individual beech saplings: A functional-structural modeling approach
Umeki, K. ; Kikuzawa, K. ; Sterck, F.J. - \ 2010
Forest Ecology and Management 259 (2010)11. - ISSN 0378-1127 - p. 2141 - 2150.
temperate deciduous forests - broad-leaved trees - light conditions - leaf development - fagus-crenata - woody-plants - canopy gaps - carbon gain - growth - architecture
We developed a functional-structural plant model for Fagus crenata saplings and calculated annual photosynthetic gains to determine the influences of foliar phenology and shoot inclination on the carbon economy of saplings. The model regenerated the three-dimensional shoot structure and spatial and temporal display of leaves; we calculated the hourly light interception of each leaf with a detailed light model that allowed us to estimate hourly leaf photosynthetic gain taking leaf age into account. To evaluate the importance of simultaneous foliar phenology and slanting shoots in beech saplings, we calculated the photosynthetic budgets for saplings with contrasting foliar phenologies and shoot inclinations. In our simulations, we distinguished between simultaneous and successive foliar phenologies, upright and slanting shoot inclinations, and environments with and without a vertical gradient in light intensity. Other model parameters (including photosynthesis vs. light curve, leaf size, and leaf shape) were obtained directly from live beech saplings. With no vertical gradient in light intensity, modeled saplings with simultaneous foliar phenology and slanting shoots (as in live beech) had larger annual photosynthetic gains than saplings with other combinations of traits. Hence, simultaneous foliar phenology and slanting shoots are efficient ways to display leaves in the shaded forest understory light regime where beech saplings thrive. In the presence of vertical light gradients, which can occur in canopy gaps, saplings with upright shoots had larger annual photosynthetic gains than counterparts with slanting shoots. Although mean daily photosynthetic gains of saplings with successive foliar phenology were elevated by exposing leaves to strong light when young and productive, the annual photosynthetic budget of these saplings was reduced (compared to saplings with simultaneous foliar phenology) by their relatively short leaf lifespan. Overall, our results suggest that slanting shoots with simultaneous foliar phenology are particularly successful in shaded environments, where beech often dominates, because they appear to maximize the annual carbon budget by avoiding self-shading and extending leaf lifespans.
Verjonging in douglasbos neigt weer naar douglas
Dekker, M. - \ 2009
Vakblad Natuur Bos Landschap 2009 (2009)1. - ISSN 1572-7610 - p. 18 - 22.
houtteelt - bossen - groei - gaten in het kroondak - natuurlijke verjonging - bosbedrijfsvoering - silviculture - forests - growth - canopy gaps - natural regeneration - forest management
Het Nederlandse bos is nog steeds voor het grootste deel gelijkjarig en weinig gemengd, zo blijkt uit metingen over de periode 2001-2005 van het Meetnet Functievervulling Bos. Bosbeleid en -beheer zijn er al decennialang op gericht om de voormalige plantagebossen op een natuurgerichte wijze om te vormen en te beheren. In het bos kom je dan ook veel natuurlijke verjonging tegen die opkomt op plaatsen waar flinke gaten in het kronendak zijn gemaakt. Verjonging die vaak mooi gemengd is. De natuur doet zijn werk na een initiële beheersmaatregel; doel bereikt dus? Uit metingen aan verjongingen in een douglasmonoculture blijkt dat in eerste instantie berk, lariks en douglasspar het goed doen, en dat grove den het van het begin af moeilijk heeft. Op langere termijn neigt deze verjonging echter weer naar douglas, tenzij flink en vaak ingegrepen wordt.
Soil and light effects on the sapling performance of a shade-tolerant tree species in a Mexican rain forest
Lopez, L. ; Martinez, M. ; Breugel, M. van; Sterck, F.J. - \ 2008
Journal of Tropical Ecology 24 (2008)6. - ISSN 0266-4674 - p. 629 - 637.
dipterocarp seedling growth - tree-seedlings - leaf traits - resource availability - canopy gaps - carbon gain - responses - herbivory - gradient - defense
Many studies conclude that light is the most important resource that determines plant performance of tree saplings in tropical rain forests, and implicitly suggest that soil resources are less important. To provide a quantitative test for soil versus light effects on sapling performance, we studied how saplings of the shade-tolerant tree species Brosimum alicastrum responded to contrasting levels of light availability and soil fertility in a Mexican tropical rain forest. Therefore saplings were selected from ten low-light exposure (crown position index
Above- and below-ground competition in high and low irradiance: tree seedling responses to a competing liana Byttneria grandifolia
Chen, J.Y. ; Bongers, F. ; Cao, K.F. ; Cai, Z.Q. - \ 2008
Journal of Tropical Ecology 24 (2008)5. - ISSN 0266-4674 - p. 517 - 524.
tropical wet forest - rain-forest - biomass allocation - liquidambar-styraciflua - plant competition - root biomass - canopy gaps - growth - regeneration - architecture
Abstract: In tropical forests, trees compete not only with other trees, but also with lianas, which may limit tree growth and regeneration. Liana effects may depend on the availability of above- and below-ground resources and differ between tree species. We conducted a shade house experiment to test the effect of light (4% and 35% full sun, using neutral-density screen) on the competitive interactions between seedlings of one liana (Byttneria grandifolia) and three tree species (two shade-tolerant trees, Litsea dilleniifolia and Pometia tomentosa, and one light-demanding tree, Bauhinia variegata) and to evaluate the contribution of both above- and below-ground competition. Trees were grown in four competition treatments with the liana: no competition, root competition, shoot competition and root and shoot competition. Light strongly affected leaf photosynthetic capacity (light-saturated photosynthetic rate, Pn), growth and most morphological traits of the tree species. Liana-induced competition resulted in reduced Pn, total leaf areas and relative growth rates (RGR) of the three tree species. The relative importance of above- and below-ground competition differed between the two light levels. In low light, RGR of the three tree species was reduced more strongly by shoot competition (23.1¿28.7% reduction) than by root competition (5.3¿26.4%). In high light, in contrast, root competition rather than shoot competition greatly reduced RGR. Liana competition affected most morphological traits (except for specific leaf area and leaf area ratio of Litsea and Pometia), and differentially altered patterns of biomass allocation in the tree seedlings. These findings suggest that competition from liana seedlings can greatly suppress growth in tree seedlings of both light-demanding and shade-tolerant species and those effects differ with competition type (below- and above-ground) and with irradiance
Growth patterns, competition and coexistence in gap-phase regeneration under close-to-nature silviculture
Dekker, M. - \ 2008
Wageningen University. Promotor(en): Frits Mohren, co-promotor(en): Jan den Ouden. - [S.l.] : S.n. - ISBN 9789085049746 - 169
houtteelt - verjonging - groei - natuurlijke verjonging - bosbedrijfsvoering - bossen - bosbouw - bosbeleid - gaten in het kroondak - europa - silviculture - regeneration - growth - natural regeneration - forest management - forests - forestry - forest policy - canopy gaps - europe
The dominant European forest policy objective is to create multifunctional, mixed-species and uneven-aged forests. This objective includes the nature‐oriented conversion of monospecific plantations. To reach this objective, close-to-nature silviculture is applied. This generally entails natural regeneration in canopy gaps. In the Netherlands, experience with gap-phase regeneration is limited, making it difficult to asses the effect of close-to-nature management on forest development. In this thesis, this problem is addressed by investigating species coexistence between the four dominant species that occur in naturally regenerated canopy gaps in Douglas fir forest in the Netherlands. These species are Silver birch (Betula pendula Roth.), Japanese larch (Larix kaempferi Carr.), Scots pine (Pinus sylvestris L.) and Douglas fir (Pseudotsuga menziesii Mirb. Franco).
During gap‐phase regeneration, saplings undergo self‐thinning. This affects species composition of the regeneration unit. Important factors in self‐thinning are species‐specific morphological growth patterns, emergent stand characteristics, the effect of stand characteristics on competitive relationships, and the effect of light availability on growth and mortality.
Growth patterns differed between species and resulted in differences in the achieved height per unit biomass. Differences in mass‐based heights subsequently caused a vertical stratification in the regeneration unit which, in turn, affected the interspecific competition for light. However, results demonstrated a competitive response rather than a competitive effect. Surrounding saplings formed a functionally equivalent neighborhood, and target individuals responded mainly to their position in the canopy.
Canopy position affected the radial growth of saplings. Mortality probabilities depended on radial growth, but did not differ between species despite a wide range in light demand. Scots pine did not show a relation between growth and mortality, even though it is highly responsive to light.
Under continued autogenic development, a low-density top stratum of Silver birch and Japanese larch will develop, overtopping a declining number of Scots pine and a large number of increasingly dominant Douglas fir. This implies that Scots pine will be outcompeted by the other species, and Douglas fir will gain dominance in the future. Forest conversion by natural regeneration will therefore not lead to the desired mixed-species composition, but stands will eventually revert back to Douglas fir forest. Maintaining a diverse forest thus means the need for interventions in the early developmental stage.
Rehabilitation of monotonous exotic coniferous plantations: A case study of spontaneous establishment of different tree species
Jonásová, M. ; Hees, A.F.M. van; Prach, K. - \ 2006
Ecological Engineering 28 (2006)2. - ISSN 0925-8574 - p. 141 - 148.
regeneration dynamics - forest regeneration - central sweden - sitka spruce - canopy gaps - transformation - recruitment - succession - britain - rodents
Conversion of plantations of exotic coniferous species, such as Norway spruce (Picea abies), Douglas fir (Pseudotsuga menziesii) and Sitka spruce (Picea sitchensis), into more natural woodland is intended in two national parks in the province of Drenthe, The Netherlands. For that purpose, artificial gaps in the plantations were made and natural regeneration of both indigenous and exotic species was investigated. A total of 87 sample plots were analysed, each 100 m2 in size, and located under canopy or in the gaps. The densities of naturally established seedlings and saplings of tree species were recorded. Norway spruce attained the highest regeneration among all species investigated, both in gaps and under canopy. However, as in the case of other exotics (except Japanese larch, Larix kaempferi), its abundance was higher under canopy than in gaps. Indigenous species generally regenerated better in gaps than under canopy, forming 28% of the total number of seedlings in gaps and only 3.8% under canopy. The most numerous indigenous species were rowan (Sorbus aucuparia) and silver birch (Betula pendula). Scots pine (Pinus sylvestris) and pedunculate oak (Quercus robur) were less common. The most important factors influencing the regeneration of indigenous species were: numbers of seed trees within a 50 m distance from the plot, the type of plot (gap or canopy), canopy cover and age and size of gaps. It was obvious that regeneration of indigenous species can be stimulated by suitable forestry management practices, such as thinning dense stands and creating gaps of various sizes. Mixed stands of Norway spruce and indigenous broadleaves represent a reasonable target resulting from the interventions.
Photosynthetic acclimation to light changes in tropical monsoon forest woody species differing in adult stature
Cai, Z.Q. ; Rijkers, A.J.M. ; Bongers, F.J.J.M. - \ 2005
Tree Physiology 25 (2005)8. - ISSN 0829-318X - p. 1023 - 1031.
central new-england - rain-forest - chlorophyll fluorescence - shade tolerance - photosystem-ii - french-guiana - maples acer - canopy gaps - tree-fall - photoinhibition
We studied morphological and physiological leaf and whole-plant features of seedlings of six late-successional woody species common in the Xishuangbanna lowland rain forest in southwest China. Study species differed in adult stature and shade tolerance and included the shrubs Lasianthus attenuatus Jack and Lasianthus hookeri C.B. Clarke ex Hook. f.; the sub-canopy species Barringtonia macrostachya (Jack) Kurz and Linociera insignis C.B. Clarke; the canopy tree Pometia tomentosa (Blume) Teijsm. & Binn.; and the emergent species Shorea chinensis (Wang Hsie) H. Zhu. After 1 year of growth in low light (4.5% full sun), seedlings were transferred to high light (24.5% full sun) to investigate acclimation responses of existing leaves to forest gap opening and to determine whether seedling capacity for acclimation is a limiting factor in its natural regeneration. Leaves of the shrub species are shade-adapted, as indicated by their lowphotosynthetic capacity, efficiency in using sunflecks, low stomatal density, low Chl a/b ratio and high spongy/palisade mesophyll ratio. The shrub species utilized sunflecks efficiently because they had a short photosynthetic induction time and low induction loss. In all species, transfer of seedlings to high light resulted in a substantial initial reduction in the dark-adapted quantum yield of photosystem II (variable chlorophyll fluorescence/ maximum chlorophyll fluorescence; Fv /Fm) at midday. Predawn Fv /Fm of the taller species did not change greatly, but predawn Fv /Fm of the shrub species decreased significantly without complete recovery within 25 days of transfer to high light, indicating chronic photoinhibition and damage to the previously shade-adapted leaves. Maximum net photosynthetic rate and dark respiration of the four taller species increased considerably after transfer to high light, but not in the shrub species. Similar trends were observed for the number of newly formed leaves and relative height growth rate. We conclude that the shrubs L. hookeri and L. attenuatus have limited potential for developmental and physiological acclimation to high light, which explains their absence from forest gaps. Compared with the shrub species, the taller tree species, which are more likely to experience high light during their life span, showed a greater potential for light acclimation. Physiological differences among the four tree species were not consistent with differences in adult stature. Keywords: chlorophyll fluorescence, leaf anatomy, light acclimation, photosynthesis, photosynthetic induction
Disentangling above- and below-ground competition between lianas and trees in a tropical forest
Schnitzer, S.A. ; Kuzee, M.E. ; Bongers, F.J.J.M. - \ 2005
Journal of Ecology 93 (2005)6. - ISSN 0022-0477 - p. 1115 - 1125.
host liquidambar-styraciflua - fine root biomass - rain-forest - canopy gaps - wet forest - species-diversity - amazonian forests - vine competition - eastern amazonia - seedling growth
1 Light is thought to be the most limiting resource in tropical forests, and thus aboveground competition is commonly accepted as the mechanism that structures these communities. In many tropical forests, trees compete not only with other trees, but also with lianas, which compete aggressively for below-ground resources and thus may limit tree growth and regeneration. 2 Using a replicated experiment, we tested the relative strengths of above- and belowground competition from lianas on tree saplings in a disturbed forest in Côte d¿Ivoire with a heterogeneous canopy and relatively high light penetration. We planted seedlings of three tree species and subjected them to below-ground competition with lianas (BGC), above- and below-ground competition with lianas (ABGC), or a liana-free control treatment. After 2 years, we harvested the saplings and compared the amount of above-ground biomass and its relative allocation among the three experimental treatments and different tree species. 3 Lianas competed intensely with saplings in this tropical forest, substantially limiting sapling growth. Saplings grown in the ABGC and BGC treatments had only 18.5% and 16.8% of the above-ground dry biomass of those grown in the liana-free control treatment. 4 Sapling biomass did not differ significantly among the ABGC and BGC treatments, suggesting that below-ground competition was the driving force behind liana vs. tree competition in this forest. Above-ground competition with lianas, however, did affect the allocation of biomass in saplings, resulting in shorter, thicker stems and a poorly developed crown. 5 Collectively, our findings suggest that below-ground competition with lianas plays a substantial role in limiting the growth of saplings in disturbed and secondary tropical forests, and above-ground effects may be due to a combination of above-ground competition and mechanical stress. 6 Disentangling above- and below-ground competition between lianas and trees is critical for a comprehensive understanding of the dynamics of naturally regenerating tropical forests, as well as formulating successful management plans for sustainable timber harvest. Key-words: above-ground, below-ground, competition, Côte d¿Ivoire, forest regeneration, lianas, trees, tropical forest
Gaten in het bosbeheer
Wijdeven, S.M.J. ; Willems, A.J.H. ; Groot Bruinderink, G.W.T.A. - \ 2004
Vakblad Natuur Bos Landschap 1 (2004)8. - ISSN 1572-7610 - p. 18 - 19.
bosbouw - bosbeheer - verjonging - natuurlijke verjonging - velling - kaalslag - geïntegreerde systemen - opstandskenmerken - opstandsstructuur - opstandsontwikkeling - bossen - botanische samenstelling - bosecologie - gaten in het kroondak - soortendiversiteit - biodiversiteit - bosopstanden - geïntegreerd bosbeheer - forestry - forest administration - regeneration - natural regeneration - felling - clear felling - integrated systems - stand characteristics - stand structure - stand development - forests - botanical composition - forest ecology - canopy gaps - species diversity - biodiversity - forest stands - integrated forest management
Pleidooi voor het toepassen van grotere gaten bij de natuurlijke verjonging van bosopstanden. In de huidige praktijk wordt geïntegreerd bosbeheer veelal ingevuld door kleinschalige ingrepen, afgestemd op het opstandsniveau. Weliswaar verhoogt dit op dit schaalniveau (de plek of de opstand) de variatie, maar het leidt tot een meer uniforme situatie op het niveau van terreindelen en de beheerseenheid. Grote verjongingsgaten hebben niet alleen een specifiek effect op de soortensamenstelling en structuur van de verjonging, maar zijn ook van belang voor andere soorten, zoals kruiden, korstmossen, reptielen, insecten, vogels en grote hoefdieren, en leveren daarmee een bijdrage aan vergroting van de biodiversiteit en de belevingswaarde
Leaf traits and herbivory rates of tropical tree species differing in successional status.
Poorter, L. ; Plassche, M. van de; Willems, S. ; Boot, R.G.A. - \ 2004
Plant Biology 6 (2004)6. - ISSN 1435-8603 - p. 746 - 754.
rain-forest trees - papua-new-guinea - life-span - chemical-composition - construction costs - light environment - canopy gaps - plant - growth - area
We evaluated leaf characteristics and herbivory intensities for saplings of fifteen tropical tree species differing in their successional position. Eight leaf traits were selected, related to the costs of leaf display (specific leaf area [SLA], water content), photosynthesis (N and P concentration per unit mass), and herbivory defence (lignin concentration, C:N ratio). We hypothesised that species traits are shaped by variation in abiotic and biotic (herbivory) selection pressures along the successional gradient. All leaf traits varied with the successional position of the species. The SLA, water content and nutrient concentration decreased, and lignin concentration increased with the successional position. Herbivory damage (defined as the percentage of damage found at one moment in time) varied from 0.9-8.5% among the species, but was not related to their successional position. Herbivory damage appeared to be a poor estimator of the herbivory rate experienced by species, due to the confounding effect of leaf lifespan. Herbivory rate (defined as percentage leaf area removal per unit time) declined with the successional position of the species. Herbivory rate was only positively correlated to water content, and negatively correlated to lignin concentration, suggesting that herbivores select leaves based upon their digestibility rather than upon their nutritive value. Surprisingly, most species traits change linearly with succession, while resource availability (light, nutrients) declines exponentially with succession.
Recruitment of lianas into logging gaps and the effects of pre-harvest climber cutting in a lowland forest in Cameroon
Schnitzer, S.A. ; Parren, M.P.E. ; Bongers, F.J.J.M. - \ 2004
Forest Ecology and Management 190 (2004)1. - ISSN 0378-1127 - p. 87 - 98.
species-diversity - tropical forest - canopy gaps - rain-forest - growth - impact - damage - regeneration - management - dominance
The abundance of lianas (woody vines) and the detrimental impact that they have on tropical rain forest trees is widely recognized. Lianas are particularly abundant in disturbed areas of the forest, such as logging gaps, and pre-harvest liana cutting has been widely recommended throughout the tropics to reduce the impact of lianas during and following tree harvest. The effectiveness of forest-wide liana cutting, however, is currently unresolved, particularly for reducing liana abundance in logging gaps. Furthermore, our understanding of the dynamics and rate of liana colonization in gaps is limited. We tested: (1) the speed at which lianas recruit into logging gaps and their dynamics afterwards; and (2) whether pre-harvest liana cutting actually reduces the abundance of lianas in post-harvest logging gaps. To test hypothesis 1, we compared liana recruitment in new, I and 6-year-old logging gaps. For hypothesis 2, we compared liana abundance and tree infestation by lianas in 1-year-old logging gaps in which all lianas had been cut 9 months prior to tree felling vs. 1-year old logging gaps in which lianas were not cut. Lianas recruited heavily into logging gaps within I year, mostly by means of stem sprouts, and many of these new stems were apparently able to persist for longer than 6 years. Lianas were significantly more abundant in the root/bole zone of gaps than in the canopy zone, mostly due to the vigorous regeneration of stem sprouts. Canopy openness was highest in gaps one year after logging, possibly due to the smothering effect of the lianas on developing trees. Although liana abundance increased significantly over the 6-year gap chronosequence, direct liana infestation of trees remained the same. Pre-logging liana cutting, however, significantly reduced the number of lianas and also the number of liana-infested trees in logging gaps. Consequently, liana cutting appears to be an effective method to reduce the abundance of lianas and thus minimize their detrimental effects on regenerating trees in logging gaps. (C) 2003 Elsevier B.V. All fights reserved.
The consequences of crown traits for the growth and survival of tree saplings in a Mexican lowland rain forest
Sterck, F.J. ; Martinez-Ramos, M. ; Dryer-Leal, G. ; Rodriguez-Velazquez, J. ; Poorter, L. - \ 2003
Functional Ecology 17 (2003)2. - ISSN 0269-8463 - p. 194 - 200.
rain-forest trees - understory plants - leaf dynamics - light capture - carbon gain - canopy gaps - architecture - compensation - morphology - seedlings
1. Many studies discuss the adaptive value of plant architecture, but few have actually measured architectural effects on plant growth and survival. In this study, sapling growth and survival are related to crown traits for two tree species, Trophis mexicana (Liebm.) Bur. and Pseudolmedia oxyphyllaria Donn. Sm., in the Los Tuxtlas lowland rainforest of Mexico. The traits investigated were crown width, crown depth, number of leaves, number of leaves per unit crown area (horizontal self-shading), and number of leaves per unit silhouette area (vertical self-shading). 2. Self-shading indices decreased with crown size, but were unaffected by the number of leaves per tree. Larger crowns thus had more diffuse foliage, with less self-shading. 3. The number of leaves had positive effects on growth and survival, while self-shading indices had no effect. This indicates that shaded leaves do not necessarily have negative carbon balances. 4. Negative effects of crown width on horizontal crown growth, and positive effects on vertical crown growth, suggest that saplings tend to grow towards a shape intermediate between the narrow and wide crown extremes. 5. Survival was positively correlated with crown width in Pseudolmedia, and with the number of leaves in Trophis. Apparently, dependence of survival on crown traits differed among species. 6. Crown traits affected plant growth and survival, but the hypothesis emerging from light-limited carbon acquisition was confounded by other factors, such as tree size and the inherent branching patterns. 7. Crown traits are good and rather simple predictors of future sapling growth and survival, and may help foresters to select potential crop trees
Lianas and logging in West Africa
Parren, M.P.E. - \ 2003
Wageningen University. Promotor(en): Frans Bongers; Frits Mohren. - Wageningen : Wageningen Universiteit - ISBN 9789058088710 - 168
klimplanten - houtkap - snijden - gaten in het kroondak - houtteelt - tropische bossen - bosbedrijfsvoering - bosecologie - west-afrika - climbing plants - logging - cutting - canopy gaps - silviculture - tropical forests - forest management - forest ecology - west africa
The role of lianas in relation to logging activities is analysed in a lowland moist forest in Cameroon. Lianas are an abundant, diverse, and conspicuous growth form in nearly all tropical forests. Lianas are mostly seen as a nuisance by foresters. Cutting of liana stems is an important operation in forest management practices. Pre-harvest liana cutting is aimed at a reduction of logging damage, an improved precision of felling, an enhancement of the development of the growing tree stock and a reduction of the regrowth capacity of lianas. Lianas were very abundant: on average nearly 5000 individuals per ha of which over 100 large ones (³ 5 cm dbh). Felling gap sizes, tree mortality and damage were not significantly affected by pre-harvest liana cutting. However, this intervention significantly reduced the number of lianas and also the number of liana-infested trees in logging gaps. Cut lianas were monitored and proved that certain species were extremely vulnerable while others hardly. To avoid problems related to the negative impacts that both liana cutting and fire can have on liana species, which are vulnerable to these interventions, it is recommended to apply this treatment only selectively. Spatially, treatments should be limited to zones where lianas are heavily interfering with trees to be felled. Treatments also should be species-specific, by limiting liana cutting to those species, which cause most of the damage.
Natuurlijke verjonging: van kleine naar grote gaten
Wijdeven, S.M.J. ; Berg, C.A. van den; Oosterbaan, A. - \ 2003
Vakblad Natuurbeheer 42 (2003)6. - ISSN 1388-4875 - p. 111 - 115.
bossen - bosbeheer - bosbedrijfsvoering - natuurlijke verjonging - verjongingsinventarisaties - bosinventarisaties - opstandsstructuur - opstandsontwikkeling - plantensuccessie - botanische samenstelling - bosecologie - gaten in het kroondak - soortendiversiteit - bosopstanden - forests - forest administration - forest management - natural regeneration - regeneration surveys - forest inventories - stand structure - stand development - plant succession - botanical composition - forest ecology - canopy gaps - species diversity - forest stands
Resultaten van een analyse van de natuurlijke verjonging in relatie tot de gatgrootte op 240 geïnventariseerde verjongingsplekken in naaldbossen op de hoge zandgronden. De grootte van de gaten varieerde van kleine gaten (1 maal de boomhoogte) tot vlakten van 0,5-6 ha (ontstaan na de stormen van de jaren zeventig). Onderzocht werden het stamtal van de verjonging, de aandelen van schaduwtolerante en lichteisende soorten, en de aantallen individuen per soort. Op de grote vlakten is gekeken naar de dichtheid en soortensamenstelling van de verjonging en de aanwezigheid van ruimtelijke patronen. Binnen grote gaten blijkt een grote variatie te zijn in dichtheid en in individuele en groepsgewijze mengingen van verschillende soorten