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Forest floor light conditions in a secondary tropical rain forest after artificial gap creation in northern Borneo
Abstract
Forest floor light conditions were monitored in a field experiment regarding alternative approaches to canopy gap creation. To establish gaps, three pioneer canopy treatments (canopy tree felling, girdling and untreated control) were combined with two sub-canopy treatments (slashing or untreated control). The canopy treatments were performed within sub-plot circles (radius 5 m) while the sub-canopy treatment was confined to the central parts (2.5 m radius). Pioneer canopy felling and girdling (stripping of the bark) treatments affected 31% (mean value) of the initial mean standing basal area (39 m2 ha−1). Relative photosynthetic photon flux densities (PPFDR) and canopy openness were measured (1.5 m above the forest floor) in the sub-plots before and immediately after treatment and at subsequent intervals of 6, 18 and 30 months. During the study period all treatments resulted in increased PPFDR and canopy openness compared to pre-treatment mean values (PPFDR: 1.8–2.3%, canopy openness: 8.8–10.7%). Felling selected pioneer canopy trees provided distinct but transient shade reduction; mean PPFDR values were 12.5% after 6 months and 8.5% 30 months after initial treatment, while canopy openness averaged 14.2 and 11.8% after 6 and 30 months, respectively. Girdling effects were less drastic but after 30 months forest floor openness and PPFDR averaged values similar to, or slightly higher than the felling treatment. Sub-canopy slashing resulted in 2.4–5.1% higher PPFDR and 2.0–2.4% higher canopy openness compared to the untreated control plots and this effect persisted throughout the study period.
... Therefore, the introduction of important ecological and commercial species to secondary forests by enrichment planting requires initial silvicultural treatments that increase the canopy openness and, consequently, light availability (named irradiance here) at the forest floor (Schwartz et al., 2015). The objective of this intervention is to reduce interspecific competition and increase the availability of resources, mainly irradiance, fundamental to the survival and growth of arboreal species regenerating naturally in the area, as well as those introduced artificially in enrichment plantations (Kuijk et al., 2014;Mesquita, 2000;Romell et al., 2009;Schwartz et al., 2015). ...
... Manipulation of the light environment in secondary forests can be achieved by different techniques, such as cutting lines (Peña-Claros et al., 2002), localized canopy gaps (Balderrama and Chazdon, 2005) and basal area reduction by the thinning of upper-canopy trees, named canopy tree refinement (Romell et al., 2009;Wiener, 2010). These silvicultural techniques have been successfully studied in tropical secondary forests, but few studies have investigated the application of these techniques over a wide range of levels, which comprise the poor understory light environment in intact forests, for intense interventions that cause a close to full-sun condition (Dupuy and Chazdon, 2008). ...
... The negative effects have been attributed to competition for light (Romell et al., 2008) and underground resources (Duclos et al., 2013). There is evidence indicating that understory slashing is an efficient silvicultural intervention for enhancing environmental light (Dupuy and Chazdon, 2006;Romell et al., 2009). Without light stimulation for aggressive pioneer trees, lianas and shrubs species and, consequently, understory regrowth, the effects of understory slashing can persist for at least 30 months in a Macaranga spp. ...
Silvicultural treatments can change the microclimate inside tropical secondary forests and thus enable the artificial regeneration of ecologically and economically important tree species. Increasing levels of canopy tree refinement (diameter at breast height, DBH > 5 cm) were applied and combined with understory slashing to investigate how these silvicultural treatments affect the microclimate of a Central Amazon secondary forest. The refinement treatment was performed in six levels of basal area reduction (0, 20, 40, 60, 80, and 100%) in rectangular plots (2318 m 2) and was equally divided in two subplots that did (understory slashed) or did not (control) receive the application of understory slashing. Canopy openness was estimated using hemispherical photography before treatment implementation and periodically over 26 months. Light transmittance, total daily irradiance, air temperature, air humidity and soil moisture were measured during two climatic seasons (Dry and Wet season) of the two years following the application of the treatments. Understory slashing doubled the canopy openness before the refinement and had an effective and persistent effect on canopy openness, light trans-mittance and total daily irradiance for the 26 months. Refinement increased canopy openness, light trans-mittance and total daily irradiance; however, after one year of treatment application, the effect was greater in understory slashed than in control subplots. In plots with higher basal area reduction (>60%), the understory slashed subplots total daily irradiance was 19% and 60% higher than control subplots after nine and 26 months, respectively. Refinement increased air temperature and reduced air humidity and soil moisture. The refinement of canopy trees and understory slashing change the microclimate (particularly light availability) in secondary forests and performed best when applied together. Silvicultural implications for sustainable secondary forest management and productive objectives are discussed.
... In Indonesia, reduced-impact logging (RIL) and line planting have been introduced to create sustainable forest management. The success of RIL in minimizing the effect of logging has been demonstrated, showing that it has less impact on the canopy than conventional logging [6][7][8]. In Indonesia, the line planting system, which involves selective logging using the RIL method, followed by the planting of Shorea species, has been tested for the establishment of sustainable forest management [9]. ...
... Our results were consistent with previous research that demonstrated a low level of CO in primary forest environments [3,11,20], largely due to multilayer canopies [6,16]. Logging these canopy trees significantly alters the light conditions on the forest floor. ...
... Our results were consistent with previous research that demonstrated a low level of CO in primary forest environments [3,11,20], largely due to multilayer canopies [6,16]. Logging these canopy trees Figure 5). ...
We monitored changes in light conditions at a primary forest and two managed forest sites (one with line planting) after reduced-impact logging in Central Kalimantan, Indonesia. We also assessed the effect of the light conditions on seedlings in the planting lines. Hemispherical photographs were taken over a period of 31 months in three 50 × 50-m quadrats at each site and in three 100-m transects along the planting lines. The location of each photo was categorized according to the corresponding type of disturbance, including skid trails, logging gaps, and planting lines. Following logging, the level of canopy openness (CO) increased at both managed forest sites and did not differ significantly between the two. However, CO was greater in skid trails and logging gaps than in planting lines. After 31 months, the mean level of CO at each managed site had decreased significantly due to the establishment of new seedlings. Correlations between changes in CO and the growth of planted seedlings suggested that growth was inhibited by the invasion of the new species. However, the level of CO along the planting lines was greater than that at other disturbed locations. A high level of CO promoted invasion by new species that colonized the space. Line planting may influence forest dynamics and maintain a high level of CO.
... The majority of studies on tropical understorey light environment focused on consequences of canopy gaps at different scales (Ferreira de Lima & Cunha de Moura 2006;Martinez-Ramos et al. 1989;Rijkers et al. 2000;Romell et al. 2009;Smith et al. 1992). But, a distinct categorisation into gap and canopy-shade leaves the complex architecture beneath the canopy and their dynamics aside (Grubb 1996;Popma et al. 1988). ...
... The results of Romell et al. (2009) demonstrated the influence of artificial gap creation on forest floor light conditions in Borneo and provided results in structural as well as temporal scales. In spite of quantifying the effects of an artificial treatment, this study focused on the consequences of forest structure and natural dynamics on understorey light fluctuations in a small scale approach. ...
... The coefficient of variation (cv, ratio of standard deviation to the mean) was calculated for PPFDt to assess the heterogeneity within this data set. Because of the reduction of diffuse assimilation by tree crowns and stand density (Rich et al. 1993;Romell et al. 2009), all measurements resulting in a PPFDr value > 0.8 were considered out of range and discarded. PPFDr is the quotient of the measurements inside the forest plots and the recordings in the clearance (above canopy PPFD). ...
The effect of small scale structural dynamics of forest stands and their canopies on spatiotemporal heterogeneity of the understorey light regime was assessed in this study. Forest structure and woody species composition in combination with canopy structure parameters and photosynthetic photon flux density (PPFD) were measured in three investigation plots. Sampling took place during two periods in 2004 and 2005 to check on inter-annual differences of canopy conditions and light availability. All plots differed considerably in species composition and high α-diversity was recorded. Forest structure and canopy openness differed between plots. No differences in leaf area estimations and photon flux density were found during the same sampling period. Inter-annual differences were identified for leaf area index and canopy openness, but not in conjunction. On the other hand, inter-annual differences in photon flux density were only identified in combination with significant canopy openness changes. Our study confirmed hemispherical photography and quantum sensor based PPFD measurement as a valid tool for rapid assessment approaches regarding canopy structure and their spatiotemporal heterogeneity and the effect on understorey PPFD fluctuations. The variability and heterogeneity of canopy structure may help to explain the impact on stand dynamics and the reduced importance of classic gaps in communities identified for some rainforests.
... Understanding the regeneration niche of dipterocarps and how they partition along axes associated with light as well as edaphic factors (Matsune et al. 2006;Romell et al. 2008;Dent and Burslem 2009;Romell et al. 2009) is not only important for site selection, but for determining their requirements post-planting. Although low light intensity is important during germination and early establishment, there is considerable variation between species survival and growth rates in response to tending, weeding and gap management, such as by girdling or thinning of fast growing pioneer species (Adjers et al. 1995;Matsune et al. 2006). ...
... Although low light intensity is important during germination and early establishment, there is considerable variation between species survival and growth rates in response to tending, weeding and gap management, such as by girdling or thinning of fast growing pioneer species (Adjers et al. 1995;Matsune et al. 2006). Research on the effects of gap creation and its shape has provided insight into the importance of light environment for regeneration of dipterocarp forest (Romell et al. 2008Romell et al. , 2009). Survival rates for planted dipterocarps in gap or line planting have been recorded ranging from 40 to 86%. ...
... Canopy openness appears to have clear effects on growth, with dipterocarp seedlings growing faster under wider gaps (Adjers et al. 1995;Otsamo 2000;Bebber et al. 2002;Romell et al. 2008). Interestingly, girdling of canopy trees led to increased relative height growth (Romell et al. 2008) despite having no effect on light availability (Romell et al. 2009), suggestive of the potential effects of below ground competition. In summary, once planted, dipterocarp seedlings are likely to require considerable tending to maintain optimal light environments for growth and survival, especially during restoration of completely degraded lands. ...
... Tending and site maintenance Understanding the regeneration niche of dipterocarps and how they partition along axes associated with light as well as edaphic factors (Matsune et al. 2006; Romell et al. 2008; Dent and Burslem 2009; Romell et al. 2009) is not only important for site selection, but for Biodivers Conserv (2010) 19:1137–1151 1145 determining their requirements post-planting. Although low light intensity is important during germination and early establishment, there is considerable variation between species survival and growth rates in response to tending, weeding and gap management, such as by girdling or thinning of fast growing pioneer species (Adjers et al. 1995; Matsune et al. 2006). ...
... Although low light intensity is important during germination and early establishment, there is considerable variation between species survival and growth rates in response to tending, weeding and gap management, such as by girdling or thinning of fast growing pioneer species (Adjers et al. 1995; Matsune et al. 2006). Research on the effects of gap creation and its shape has provided insight into the importance of light environment for regeneration of dipterocarp forest (Romell et al. 2008Romell et al. , 2009). Survival rates for planted dipterocarps in gap or line planting have been recorded ranging from 40 to 86%. ...
... Canopy openness appears to have clear effects on growth, with dipterocarp seedlings growing faster under wider gaps (Adjers et al. 1995; Otsamo 2000; Bebber et al. 2002; Romell et al. 2008). Interestingly, girdling of canopy trees led to increased relative height growth (Romell et al. 2008) despite having no effect on light availability (Romell et al. 2009), suggestive of the potential effects of below ground competition. In summary, once planted, dipterocarp seedlings are likely to require considerable tending to maintain optimal light environments for growth and survival, especially during restoration of completely degraded lands. ...
The lowland dipterocarp forests of Southeast Asia support a substantial proportion of the world’s biodiversity. They are of
considerable environmental and economic value at the local, regional and global scale, providing many goods and services to
a growing population. The forests of this region are among the fastest disappearing in the world and restoration is urgently
required. This paper provides a review of the ecological constraints to restoration of lowland dipterocarp forest in Southeast
Asia. It focuses on the production of planting stock, the significance of site-species matching and post-planting site maintenance.
It identifies gaps in our knowledge and highlights priority areas of research. Adopting a long-term view is essential for
restoring as well as conserving the dipterocarp forests of Southeast Asia. An immediate strategy for the conservation and
management of dwindling genetic resources of these important timber species is essential. This will provide the foundations
for sourcing seed and production of planting material for longer term restoration. The importance of species-site matching,
mycorrhizal fungi and post-planting maintenance for restoration are apparent. Financing is a major limiting factor to dipterocarp
forest restoration. Trading in carbon, private finance and environmental markets afford considerable opportunities for restoring
these forests providing their total value is recognised. Despite the wealth of ecological knowledge we already have for scientifically-informed
forest restoration, without the backing of governments and corporate stakeholders, forest restoration will not gain the urgently
required momentum.
KeywordsConservation-Restoration-Rehabilitation-Tropical rainforest-Dipterocarpaceae-Enrichment planting
... The majority of studies on tropical understorey light environment focused on consequences of canopy gaps at different scales (Ferreira de Lima & Cunha de Moura 2006; Martinez-Ramos et al. 1989; Rijkers et al. 2000; Romell et al. 2009; Smith et al. 1992). But, a distinct categorisation into gap and canopy-shade leaves the complex architecture beneath the canopy and their dynamics aside (Grubb 1996; Popma et al. 1988). ...
... The results of Romell et al. (2009) demonstrated the influence of artificial gap creation on forest floor light conditions in Borneo and provided results in structural as well as temporal scales. In spite of quantifying the effects of an artificial treatment, this study focused on the consequences of forest structure and natural dynamics on understorey light fluctuations in a small scale approach. ...
... The coefficient of variation (cv, ratio of standard deviation to the mean) was calculated for PPFDt to assess the heterogeneity within this data set. Because of the reduction of diffuse assimilation by tree crowns and stand density (Rich et al. 1993; Romell et al. 2009), all measurements resulting in a PPFDr value > 0.8 were considered out of range and discarded. PPFDr is the quotient of the measurements inside the forest plots and the recordings in the clearance (above canopy PPFD). ...
The effect of small scale structural dynamics of forest stands and their canopies on spatiotemporal heterogeneity of the understory light regime was assessed in this study. Forest structure and woody species composition in combination with canopy structure parameters and photosynthetic photon flux density (PPFD) were measured in three investigation plots. Sampling took place during two periods in 2004 and 2005 to check on inter-annual differences of canopy conditions and light availability. All plots differed considerably in species composition and high -diversity was recorded. Forest structure and canopy openness differed between plots. No differences in leaf area estimations and photon flux density were found during the same sampling period. Inter-annual differences were identified for leaf area index and canopy openness, but not in conjunction. On the other hand, inter-annual differences in photon flux density were only identified in combination with significant canopy openness changes. Our study confirmed hemispherical photography and quantum sensor based PPFD measurement as a valid tool for rapid assessment approaches regarding canopy structure and their spatiotemporal heterogeneity and the effect on understory PPFD fluctuations. The variability and heterogeneity of canopy structure may help to explain the impact on stand dynamics and the reduced importance of classic gaps in communities identified for some rainforests.
... Enrichment plantings are a suitable alternative for the conservation of the broad area of tropical secondary forests because increase the density of economically and ecologically valuable tree species (ITTO, 2002). Generally, silvicultural treatments are applied in the secondary forest before and after enrichment planting to manipulate the light conditions to the seedlings planted (Ådjers et al., 1995;Gustafsson et al., 2016;Romell et al., 2009;Peña-Claros et al., 2002). The light modifications under the forest canopy is achieved by different levels of canopy openness created by localized artificial gaps, cutting lines or thinning of canopy trees (Peña-Claros et al., 2002;Romell et al., 2009;Santos et al., 2020;Wiener, 2010). ...
... Generally, silvicultural treatments are applied in the secondary forest before and after enrichment planting to manipulate the light conditions to the seedlings planted (Ådjers et al., 1995;Gustafsson et al., 2016;Romell et al., 2009;Peña-Claros et al., 2002). The light modifications under the forest canopy is achieved by different levels of canopy openness created by localized artificial gaps, cutting lines or thinning of canopy trees (Peña-Claros et al., 2002;Romell et al., 2009;Santos et al., 2020;Wiener, 2010). The seedling growth response to light in enrichment planting is dependent on the species selected Li et al., 2017;Poorter et al., 2018). ...
Understanding light-induced plasticity of growth and its relationship with photosynthetic trait plasticity is central to the identification of the mechanisms associated with tropical tree seedling establishment in enrichment plantings. In a secondary forest submitted to silvicultural treatments-that manipulate light environment-and enriched with six tropical tree species we tested three main hypothesis. First, the growth of the six species are related to photosynthetic leaf traits; second, there is a relationship between the light-induced plasticity of growth and photosynthetic leaf traits and, finally, that growth plasticity is a subjacent mechanism of the growth-survival trade-off. Growth was analyzed as a biomass index that combines collar and height growth. Photosynthetic leaf traits were selected considering their significance in the photosynthetic process: light interception (specific leaf area, SLA), light absorption (chlorophyll a and b ratio, Chl a/b), light use (fluorescence parameters, F v /F m ; PI abs , PI total), biochemical limitations (light-saturated CO 2 assimilation, A sat) and diffusive limitations (stomatal conductance, g s). The plasticity was represented by the slope of the relationship between the canopy light transmittance and growth and the photosynthetic leaf traits. At the end of the first year after planting, growth was related to almost all photosynthetic leaf traits, and the strongest relationships (high slope and R 2) were observed with A sat , SLA and PI total. Light-induced growth plasticity varied three times between species. The interspecific growth plasticity was related to SLA and F v /F m plasticity, which varied 4.9 and 2.4 times between species, respectively. Seedling mortality in the shaded understory and the growth in a high light environment were associated with growth plasticity. Photosynthetic leaf traits effectively represent the growth response mechanisms to silvicultural treatments that manipulate the light environment in enrichment plantings, and the subjacent mechanism of growth plasticity has an intrinsic effect on the growth-survival trade-off.
... However, we assumed that ring-barking would be more favorable over time as the gradual death of the ring-barked trees can create larger canopy openings through unintended damage of residual trees compared to gap creation (cf. Romell et al. 2009) and edge-planting. The latter treatment has not been tested experimentally on planted tōtara, although natural tōtara regeneration often favors forest margins where forest floor irradiance is higher than in forest interior (Young & Mitchell 1994). ...
... The gradual removal of canopy trees by ring-barking did not have a significant effect on tōtara growth because only a portion of the treated trees died, and after 6 years dead trees remained standing with intact branches resulting in insignificant increases in light transmission. In other studies, it took a minimum of 6 months for ring-barked trees to die (Romell et al. 2009), which in some instances created larger gaps and higher light transmission than gaps created by selective felling. In the case of kānuka, further ring-barking may be necessary due to its stringy bark characteristics, which appears to have prevented some ring-barked trees from dying. ...
Low‐light environments in early‐successional forests that have established after abandonment of farming often restrict the establishment of later successional species resulting in an arrested succession. This 6‐year study tested the potential of different canopy manipulations to facilitate the establishment of a light‐demanding canopy tree species, tōtara (Podocarpus totara), within a regenerating kānuka (Kunzea robusta) stand. Results highlighted the effectiveness of artificial gaps over other methods (ring‐barking and edge planting) in accelerating the growth of planted tōtara. Seedlings under gaps grew consistently taller and faster over time indicative of an improved understorey light environment. Ring‐barking did not have a significant effect on tōtara growth because only a portion of the treated trees died, and after six years dead trees remained standing with intact branches resulting in insignificant increases in light transmission. At the forest edge sites, tōtara growth was highly variable. Although some seedlings grew as tall as in the gaps, others did not. Survival was also lower in the edge sites than in other treatments, which was likely due to enhanced herbivory from ungulates which impacted some plants at these sites. Gap creation is likely to be an important tool for restoring late‐successional canopy species in regenerating stands both through providing ideal sites for the growth of light‐demanding species such as tōtara and through natural establishment of other future canopy trees into the gaps.
... The solar radiation required for growth differs among tree species (Whitmore 1990). In and around gaps, many species respond to the change in light conditions according to their biological characteristics (Romell and Karlsson 2009). In particular, Macaranga spp., which are primary pioneer species (Slik et al. 2002, Slik andEichhorn 2003), may invade and compete with planted dipterocarp seedlings in gaps created by strip cutting. ...
... Mean CO in primary forest stands was very low ( 5 %), which is explained by the presence of high multilayer canopies (Silbernagel andMoeur 2001, Romell andKarlsson 2009). In the two logged-over forests, logging activities and strip cutting treatment induced major changes in light conditions. ...
... Several studies have examined tree growth responses after canopy reduction treatments in lowland mixed dipterocarp rainforest (Duclos et al., 2013;Romell et al., 2009;Rozendaal et al., 2006). The overall change in visible sky from 4.8% to 7.3% in our study might seem minor, but it is actually an increase in canopy openness of 34%. ...
... According to another study from a lowland dipterocarp forest in Sabah that was slightly more disturbed than ours (visible sky 8.8-10.7% before treatment) the level of openness returned to values equivalent to those before the treatment 18 months after the canopy reduction treatment (Romell et al., 2009). ...
Rainforest restoration is an important application in today's multipurpose management of secondary forest. However, our knowledge of tree species' traits and responses to treatment is insufficient for foresters to make good decisions for sustainable management. The aim of our study was to see whether it is possible to predict tree species' responses to increased light based on species' traits, and to relate these responses to a possible pioneer-climax continuum of life history traits, also among species with presumed climax properties. We examined 33 taxa (including 19 from the dipterocarp family) replicated 20 times and randomly planted in lines over a 3. ha area in the interior of Sabah, Borneo. Four years after establishment we performed a canopy reduction treatment to increase the light conditions up to levels present in tree gaps in the forest. We created a PLS (Partial Least Square Regressions) model with the two predicted variables HGR (height growth response) and Q3 HGR (the 75 percentile of a species' HGR, interpreted as the potential HGR). The model captured 47% of the variation for the predicted variables. We found significant tree species' responses in height growth to the increased light. High specific leaf area, strong early height growth, high foliar N content, high leaved stem length and large crown were linked to fast growth, while high wood density and high foliar K content were associated with slow growth. We also found a trade-off between growth response and survival among the species. We conclude that climax tree species have specific life history adaptations along a pioneer-climax continuum, which can be predicted from species' traits. The importance of easily observed or extracted traits such as initial growth rate, specific leaf area and wood density for predicting growth suggests the possibility of fast screening of species with unknown characteristics, which could be of great value in practical forest management.
... i.e. size 20 m × 20 m for observation at tree level, (r = 5 m) and inner circle (r = 2.5 m). collection used the modified of transects establishment by [2] as shown in Figure 1. ...
... Based on the test model fit (sequential analysis of variance) Equation (1) can be used as a basis for determining the vertical liberation treatment, because the model has a p-value (0.000) <5 %. Figure 3 describes the distribution of tree diameter wih the distance of competitor trees. The trees of the (x,y) coordinates under the curve be vertically reduced [2]. According to the research results the vertical reduction will be performed on trees with 5−9 cm dbh and located 1−2.5 m from the center of subplot, except for the trees located at > 2.5 m from the center of subplot. ...
... Thus, even if no clear signs of opening in the upper canopy are visible from imagery data, minor disturbances can be accounted for with detailed forest inventory. Although understory gaps have lower associated losses of biomass, they can promote changes in light quality and availability, which lead to effective and persistent effects on the natural regeneration, structure and species composition of tropical forests (dos Santos et al., 2020;Romell et al., 2009;355 Dupuy and Chazdon, 2008;Magnabosco Marra et al., 2014b). ...
Understanding mechanisms of tree mortality and geometric patterns of canopy gaps is relevant for robust estimates of carbon stocks and balance in tropical forests, and for assessing how they are responding to climate change. We combined monthly RGB images acquired from an unmanned aerial vehicle with field surveys to identify gaps in an 18-ha permanent plot in an old-growth Central Amazon forest over a period of 28 months. In addition to detecting, we measured the size and shape of gaps, and analyzed their temporal variation and correlation with rainfall. We further described associated modes of tree mortality or branch fall and quantified associated losses of biomass. Overall, the sensitivity of gap detection differed between field surveys and imagery data. In total, we detected 32 gaps either in the images and field, ranging in area from 9 m2 to 835 m2. Relatively small gaps (< 39 m2) associated with branch fall were the most frequent (11 gaps). Out of 18 gaps for which both field and imagery data were available, three could not be detected remotely. This result shows that a considerable fraction of tree mortality and branch-fall events (~ 17 %) affect only the lower canopy and the understory of the forest and thus, are likely neglected by assessments of top of the canopy. Regardless the detection method, the size distribution of gaps in our study region was better captured by a Weibull function. As confirmed by our detailed field surveys, we believe that this pattern was not biased by gaps possibly undetected from image data. Although not related to differences in gap size, the main modes of tree mortality partially explained associated losses of biomass. The rate of gap area formation expressed as the percent per month was positively correlated with the frequency of extreme rainfall events, which may be related to a higher frequency of storms propagating destructive wind gusts. Our results demonstrate the importance of combining field observations with remote sensing methods for monitoring gap dynamics in dense forests. The correlation between modes of tree mortality and gap geometry with associated losses of biomass provide evidence on the importance of small-scale events of tree mortality and branch fall as processes that contribute to landscape patterns of carbon balance and species diversity in Amazon forests. Regional assessments of the dynamics and geometry of canopy gaps formed from branch fall and individual tree-mortality (e.g., from few to hundreds of m2) up to catastrophic blowdowns associated with extreme rain and wind (e.g., from hundreds of m2 to thousands of ha) can reduce the uncertainty of landscape assessments of carbon balance, especially as the frequency and intensity of storms causing these events is likely to change with future Amazon climate.
... Early occupation of shade-intolerant seedlings in newly created gaps may play an important role in gap regeneration; however, very few studies have explored seedling regeneration processes during early years after gap formation (Brokaw 1985;Walters et al. 2014;Lu et al. 2015), possibly due to the difficulty to locate suitable gaps immediately after their formation. Moreover, the effects of within-gap position on seedling establishment are often investigated in tropical areas (Barton et al. 1989;Kennedy and Swaine 1992;Brown 1996;Dalling et al. 1998;Romell et al. 2009) other than in high northern latitudes where the light regimes in gaps are different (Coates 2000;Naaf and Wulf 2007;Willis et al. 2015). ...
Artificial gaps are widely created for forest management. However, the interactive effects of gap sizes and within-gap locations on seedling regeneration are rarely tested. Therefore, whether there are lower and upper size limits for artificial gaps remains controversial. Here, we aimed to test the hypothesis that the effects of within-gap positions on seedling regeneration are dependent on gap sizes. Newly germinated wild seedlings of shade-intolerant Quercus mongolica scattered in different positions within artificially created gaps of different sizes were surveyed to test our hypothesis. Large gaps promoted seedling growth more than medium and small gaps. The increase in Q. mongolica seedling growth in large gaps can be largely attributed to the dormancy breaking of the apical buds and increased net photosynthetic rates. More importantly, we showed that the effects of within-gap position were prominent only in medium gaps, i.e., the effect of within-gap position appears to be dependent on gap size. We show an integrative effect of gap size and within-gap location on seedling performance of shade-intolerant oaks, suggesting future studies should evaluate the influence of within-gap location in conjunction with the role of gap size. We therefore suggest that gap creation in silvicultural systems should highlight the lower and upper size limits of forest gaps, which will vary with the species and regions studied.
... In addition, light availability plays an important role in regenerating tropical tree seedlings (Agyeman 1994). Creating gaps by slashing the understory seems to be an efficient treatment for forest floor shade reduction in secondary tropical forests (Romell et al. 2009). Mauricio (1987) also reported that dipterocarp seedlings or stands with DBH values ranging from 5-20 cm will triple their growth when competing for secondary growth is cleared. ...
Wasli ME, Ambun DB, Kalu M, Sidi M, Nahrawi H, Elias H. 2020. Assessment on the growth performance of planted Dryobalanops beccarii at reforestation sites after implementation of selective girdling. Biodiversitas 21: 1880-1889. This study was conducted to evaluate the growth performance of planted Dryobalanops beccarii Dyer at reforestation sites after silvicultural practices in Gunung Apeng National Park (GANP), Sarawak. The assessed area was planted with D. beccarii in 2005 and undergo silvicultural treatment by understory clearing which implemented annually. Due to the suppressed growth rate of the planted trees, an additional silvicultural treatment, the selective girdling on selected pioneer species, was implemented once, in 2012. In this study, study plots with two treatments were established: T1: understory clearing only (control plot), and T2: additional selective girdling of existing pioneer species in addition to the understory clearing practice applied in T1. The growth performance of the planted D. beccarii in terms of DBH, height, survival and mean annual increments in diameter (MaiD) and height (MaiH) were assessed and monitored at the initial stage when the selective girdling treatment was applied and 4, 24, 36, 48, 60 and 72 months after girdling. Our findings showed that the survival rates of planted trees at 72 months under treatments T1 and T2 were 82.9% and 79.2%, respectively. The average tree DBH in T2 was significantly higher than that in T1, and the average tree DBH values for T1 and T2 were 7.5 cm and 9.4 cm, respectively. The average tree heights for T1 and T2 were 8.3 m and 9.2 m, respectively. In terms of the mean annual increments in height (MaiH) and diameter (MaiD), those in T2 were significantly higher than those in T1. Our findings indicated that T2 started to show better growth performance than T1 after a period of 36 months. In conclusion, the additional silvicultural treatment by selective girdling at the reforestation site had a long-term, progressive effect on the growth performance of the planted trees.
... Thus, it is widely recognized that the environmental heterogeneity induced by gap formation influences the regeneration and distribution of species, population dynamics, species diversity and succession (Gray et al. 2012;Forrester et al. 2014;Liu et al. 2014;Stan and Daniels 2014;Jing et al. 2015;Zenner et al. 2015;Guan et al. 2016). The features of micro-climate and seedling regeneration after the formation of gaps is well understood, including differences in micro-climate between the inside and outside of gaps, the influence of light on the regeneration of forests, and heterogeneities in the soil moisture and air humidity (Duan et al. 2008;Romell et al. 2009;Zhu et al. 2009;Li et al. 2012;Zenner et al. 2015). However, few researches have been reported on the influence of adverse meteorological conditions on seedlings within forest gaps. ...
In forest ecosystems, gap formation changes the allocation of abiotic resources and thus affects the survival and growth of understory plants. However, how tree seedling survival and growth respond to low-temperature events and the influencing mechanisms remain unclear. To clarify how low-temperature event limits the survival and growth of tree seedlings in the montane regions of eastern Liaoning Province, northeast China, we investigated temperature and light intensity within secondary forest gaps, and the survival and growth of Juglans mandshurica seedlings after a low-temperature event in the spring of 2014. Damage to seedlings due to low temperature significantly varied in different aspects. Seedlings in gaps on southeast-facing slopes were the most seriously damaged, followed by those in gaps on northeast-facing slopes. In contrast, seedlings in west-facing gaps and in control plots without slope aspect were not damaged. The freezing injury index for seedlings was negatively correlated with minimum temperature (r = − 0.608, P < 0.01), but it was positively correlated with light intensity (r = 0.818, P < 0.01). In addition, height and root collar diameter of damaged seedlings were significantly lower than those of the undamaged seedlings (P < 0.01) during the early growing season (April–July), but no significant difference were observed during the late growing season (July–October) (P > 0.05). The extent of seedling damage was directly related to slope aspect. Low temperature and high light intensity were found to be the dominant factors affecting extent of damage to seedlings on southeast- and northeast-facing slopes.
... Timber harvesting system by selective logging and selective planting significantly increase the canopy openness and light conditions of the opened forest compared to the primary forest. Canopy openness was found for each element, including skid trail, logging gaps, and strip cutting lines (Romell and Karlsson 2009;Inada et al. 2014). Gap area was positively correlated with the diameter of the fallen tree and the basal area of felled trees (Sapkota and Ode'n 2009;Arihafa and Mack 2013). ...
Selective logging caused the formation of forest gaps, which stimulate the growth of the pioneer tree species. This study aims to determine the characteristic of soil nutrients status and plant growth of Macaranga gigantea in the tropical rainforest gaps after selective logging in East Kalimantan, Indonesia. We established research plots 50mx50m in natural forest production, 1 until 10 years after selective logging. The measured data of each plot is the number of trees of M. gigantea, its stem diameter, and its height, and also the soil and leaf nutrient concentration. The results showed that the soil has a pH (H2O) of 5.3 ± 0.27, cation exchange capacity of 10.6 ± 2.98 meq. 100 g-1, base saturation of 27.7 ± 10.44%, while the concentration of nutrients carbon of 1. 04 ± 0.27%, nitrogen of 0.10± 0.02%, phosphorus of 6.35 ± 3.4%, potassium of 67.15± 30.1%, calcium of 1.7 ± 1.09% and magnesium of 0. 99 ± 0.8%. The highest stem diameter and height of M. gigantea (19.5 cm; 18.07 m) was obtained in plots of 8 years after selective logging and then declined, while the highest diameter increment and height increment obtained in plants located in a plot of 4 years after selective logging and decline until 10 years after selective logging. The concentration of nutrients accumulated in the leaves of M. gigantea was N with 1.51 ± 0.19%, P with 0.16 ± 0.01%, K with 1.37 ±0.28%, Ca with 1.78 ± 0, 43% and Mg with 1.53 ± 0.37%. The soil nutrients concentration of N, K, Ca and Mg correlated with plant growth of M. gigantea (p≤ 0.05), potassium concentration of soil positively correlated with a potassium concentration of leaves (p≤ 0.05), whereas magnesium concentration in the leaf correlated with plant growth (p≤ 0.05). We suspect that bases nutrient elements, potassium, calcium, and magnesium are nutrients absorbed in large quantities by M. gigantea and extremely important to its growth. © 2017, Society for Indonesian Biodiversity. All rights reserved.
... Litter and humus thickness on forest floor were measured with a ruler at five positions (the center and four at the corners) in each plot of 400 m 2 . Light conn dition was measured as photosynthetically active radii ation (PAR) using Meteon irradiance meter within each plot 400 m 2 at elevation 1m above the forest floor at sunny days (Pritchard and Comeau 2004; Albanesi et al., 2005) in 10–14 hours (Romell et al., 2009). In each subbplot, RI (relative irradiance) was measured as RI = PAR stand/PAR nearest open area × 100 (Molder et al., 2008). ...
... Germination and establishment were high where relative canopy openness and incident PAR were respectively 20.4 and 11.4%, limited to germination where they were 11.4 and 6.6%, and absent where they were 6.6 and 2.2%. Similarly, in secondary forest in Borneo, rates of survival and growth of seedlings of four dipterocarp species were lower in closed forest where relative incident PAR at 1.5-m height was 2.4% than in artificially created gaps where PAR was 11.4% (Romell et al. 2008(Romell et al. , 2009). In shade-house trials, 15 tropical shade-tolerant species were able to survive but not grow at levels of transmitted PAR as low as 0.8% (Bloor & Grubb 2003). ...
... Germination and establishment were high where relative canopy openness and incident PAR were respectively 20.4 and 11.4%, limited to germination where they were 11.4 and 6.6%, and absent where they were 6.6 and 2.2%. Similarly, in secondary forest in Borneo, rates of survival and growth of seedlings of four dipterocarp species were lower in closed forest where relative incident PAR at 1.5-m height was 2.4% than in artificially created gaps where PAR was 11.4% (Romell et al. 2008(Romell et al. , 2009). In shade-house trials, 15 tropical shade-tolerant species were able to survive but not grow at levels of transmitted PAR as low as 0.8% (Bloor & Grubb 2003). ...
... By creating large gaps, selective timber harvesting affects both forest structures (e.g., Pereira et al. 2002, Sist & Nguyen-T e 2002 and light conditions (Yamada et al. 2014). Selective logging of tall trees is likely to alleviate competition in the residual stand, primarily for light (Romell et al. 2009) and in a lesser extent for soil resources . Benefiting from enhanced light conditions in logged forests (Nicotra et al. 1999), developing trees are more likely to fork and expand their crown at the expense of height growth (Sterck & Bongers 2001). ...
By harvesting scattered large trees, selective logging increases light availability and thereby stimulates growth and crown expansion at early-life stage among remnant trees. We assessed the effects of logging on total and merchantable bole (i.e., lowest branch at crown base) heights on 952 tropical canopy trees in French Guiana. We observed reductions in both total (mean, −2.3 m) and bole (mean, −2.0 m) heights more than a decade after selective logging. Depending on local logging intensity, height reductions resulted in 2–13 percent decreases in aboveground tree biomass and 3–17 percent decreases in bole volume. These results highlight the adverse effects of logging at both tree and stand levels. This decrease in height is a further threat to future provision of key environmental services, such as timber production and carbon sequestration. L'abattage commercial de grands arbres en forêts tropicales crée des ouvertures dans la canopée. L'augmentation de lumière qui en résulte a pour effet de stimuler la croissance et l'expansion de la couronne des arbres sous-jacents. Dans cette étude, nous avons mesuré l'effet de l'intensité d'exploitation (i.e. biomasse perdue) sur la hauteur totale et du tronc (jusqu’à la base de la couronne) de 952 arbres de canopée en Guyane Française. Nous avons observés une réduction significative de la hauteur totale (moyenne : -2.3 m) et du tronc (moyenne : -2.0) plus d'une décennie après exploitation. En fonction de l'intensité d'exploitation, la réduction en hauteur observée induit une diminution de 2-13% de la biomasse épigée et 3-17% du volume du tronc. Ces résultats illustrent les conséquences néfastes de l'exploitation intensive à l’échelle de l'arbre et du peuplement. Une diminution de la hauteur des arbres en forêts tropicales exploitées est une menace supplémentaire sur la production future de services écosystemiques, tels que la production de bois ou la séquestration de carbone.
... Litter and humus thickness on forest floor were measured with a ruler at five positions (the center and four at the corners) in each plot of 400 m 2 . Light con dition was measured as photosynthetically active radi ation (PAR) using Meteon irradiance meter within each plot 400 m 2 at elevation 1m above the forest floor at sunny days (Pritchard and Comeau 2004;Albanesi et al., 2005) in 10-14 hours (Romell et al., 2009). In each sub plot, RI (relative irradiance) was measured as RI = PAR stand/PAR nearest open area × 100 (Molder et al., 2008). ...
... directly with quantum sensors or indirectly with hemispherical photographs) [Hardy et al., 2004]. These measurements are time consuming, thus not feasible for area wide acquisition and sometimes requiring frequent repetitions due to seasonality effects [Oshima et al., 1997;Romell et al., 2009]. Modern remote sensing techniques provide a time-and cost-efficient way of data acquisition, enabling wide-area analysis of locations otherwise very hard to reach for ground based inventories. ...
The amount of available sunlight in vegetated areas is an important factor influencing species composition, plant morphology and natural succession. It is therefore a significant parameter in forestry, ecology and other sciences dealing with biodiversity relevant studies. Research indicates a strong correlation between the quality and quantity of sunlight and the vegetation structure, both in horizontal and vertical direction. Due to the high complexity and variability of the canopy architecture, continuous area-wide data collection of light conditions in the understorey is needed for accurate modelling of light transmission. However, conventional ground based measurement methods are pointwise and time consuming, therefore not feasible for data acquisition of large areas. The ability of small-footprint airborne laser scanning (ALS) to penetrate small canopy gaps makes this remote sensing method especially suitable for vegetation studies. Geometric information of the vegetation structure can be derived directly from the 3D point cloud. This allows for modelling of the distribution of sunlight-absorbing or intercepting parts of the foliage, which consequently cast shadows on the surrounding understorey vegetation or the ground. Light transmission through the canopy can therefore be described in a very direct way by employing this 3D structural information. In this paper a methodology for modelling light conditions in forests using ALS data is proposed. The approach is based on a modified version of photogrammetric monoplotting. The parallel sun rays from variable sun positions act as projection rays being traced through the 3D point cloud (i.e. laser echoes) that represents the canopy. A defined size is assigned to each individual laser echo which casts a shadow of the respective size and shape. Shadowed areas are then derived by intersecting these projection rays with a digital terrain model and by rasterizing the projected point cloud. By employing ALS data from different acquisition times (leaf-on and leaf-off) the influence of vegetation phenology is explored. The derived shadow raster maps describe where a shadow is cast and how many intercepting parts of the canopy contribute to it. Consequently, these maps provide an excelent input for modelling the amount of available sunlight in vegetated areas, considering canopy gaps in arbitrary directions and also the seasonal variability of vegetation. The first results show that ALS is a time-and cost-efficient means for area-wide analysis of sunlight condition for forest floors, as well as for different understorey layers.
... Canopy openness is a strong predictor of seedling survival in early stages of ecosystem recovery (Comita et al., 2009). Other work has also shown that light availability is an important factor in models that predict sapling mortality (Kobe et al., 1995), canopy growth (Beaudet and Messier, 2002;Sonnentag et al., 2012), and regeneration (Comita et al., 2009;Romell et al., 2009), indicating a long term role in forest dynamics. Canopy structure provides much needed insight into forest ecosystem function, highlighting the importance of accurate quantification of forest canopy characteristics. ...
Accurate measurement of canopy structure is fundamental to the fields of ecological modeling and restoration. A large number of methods exist for estimating the structure of forest canopies, with widely varying costs and effectiveness. Hemispherical photography has been in use for several decades, and the rise of lower-cost consumer grade digital SLR cameras has expanded the availability of this technique. We examine two improvements to the hemispherical photography technique for estimating canopy closure: computer-based blue channel analysis and under-exposing images. Photographs taken in the field (without a filter) showed much lower variation in the blue channel than in red or green channel of the same images. We found a higher variance in canopy closure measurements due to over-exposure of images, while images with automatic light metering and under-exposed images remained consistent. We conclude that under- or normal exposure combined with blue channel analysis together minimize variability and maximize the precision of canopy closure estimates. Results from hemispherical photography were comparable to the widely used LAI-2200, supporting hemispherical photography as a viable, low-cost alternative.
... In each subplot, humus layer thickness was measured by ruler. Light conditions were estimated using LI-250A photometric sensor (Licor, Nebraska, USA) at 1.00 m above the ground (Pritchard et al. 2004; Albanesi et al. 2005) at 1000-1400 hours on a sunny day (Romell et al. 2009Table 1). ...
We studied the species diversity of the herb layer and ecological factors in harvest-created gaps in beech stands under a single-tree selection system in Northern Iran. To determine diversity, the number of beech seedlings, and other ecological factors, 16 gaps were selected and subplots of 5 m2 were positioned at the centre and at the cardinal points of each gap. Species richness and Simpson diversity index increased with increasing gap area as did numbers of seedlings. With increasing humus layer thickness, species richness declined but the Hill evenness index increased. Species richness increased with increasing light availability. There was no relationship between crown radii of beech trees and diversity indices. Correlations between environmental factors and numbers of individuals of some species in the herb layer were not significant except in a few cases. The results help explain the effects of man-made gaps on the dynamics of managed beech stands and this benefits evaluation of silvicultural operating plans.
... For example, research has demonstrated that matching species to appropriate soil type and light regimes enhances survival (Paoli et al. 2006; Shono et al. 2007; Russo et al. 2008). Careful tending of planted trees for several years after planting is necessary to reduce competition from faster growing pioneer species or lianas (Romell et al. 2009 ). Many of these principles have been long embedded in forest management guidelines, such as the Indonesian Selective Cutting and line Planting System for lowland forest (TPTJ) and forest management rules in Malaysia (www.forest.sabah.gov.my/ ...
The recent mass fruiting of forest trees in Borneo is an urgent wakeup call: existing policy instruments, financial mechanisms, and forestry infrastructure are inadequate to take full advantage of these infrequent opportunities for forest restoration and conservation. Tropical forest restoration can provide substantial benefits for biodiversity conservation, climate change mitigation, and poverty alleviation. Yet the unpredictability of the synchronized flowering and consequent mass fruiting of many forest trees in Borneo presents a distinctive set of challenges for forest restoration. Significant financing and a considerable coordinated effort are required to prepare for future mass fruiting events if we are to capitalize on opportunities for ecological restoration. The continued high rate of forest clearance in this region and the rarity of mass fruiting events suggest that there may be few remaining opportunities to prevent widespread species extinctions. In this article we propose a facilitatory policy framework for forest restoration in Borneo to stimulate action in advance of the next mass fruiting of forest trees.
... An One-Way ANOVA including the Student-Newman-Keuls multiple comparison procedure was used to check for significant differences in canopy openness and LAI between the plots. PPFD r is the quotient of the measurements inside the forest plots and the recordings in the clearance (above canopy PPFD) Because of the reduction of diffuse assimilation by tree crowns and stand density (Rich et al., 1993;Romell et al., 2009) all measurements resulting in a PPFD r value >0.8 were considered out of range and discarded. The data of the PPFD measurements failed to provide a normal distribution, therefore a non-parametric Kruskall-Wallis One-Way ANOVA on ranks was used to check for significant differences between the plots. ...
This study represents a small scale approach on forest structure and biomass in the Atlantic Rainforest in Brazil and provides information to an ecosystem in which there still is a lack of data in this regard.
The project was carried out in the National Park “Serra dos Orgãos” in the state of Rio de Janeiro, which is one of the largest remnants of continuous forest in this area. This forest is marked by a mosaic of forest types differing in tree composition and structure. Within this heterogeneous habitat the stand structure in three investigation plots was assessed to estimate the above-ground dry biomass (AGB) for all trees with a dbh 5 cm.
This study indicates the structural diversity of the Atlantic Rainforest. Trees with a dbh > 30 cm were represented by 6 % of all sampled individuals (18 out of 318 trees), but contributed 72 % of total estimated AGB. The results implicate that big trees in the Atlantic Rainforest may contribute more into total AGB as reported for other tropical rainforests. Small scale structural approaches like this study are able to form an initiating framework of more detailed results and help to improve estimates on biomass amounts and therefore on carbon storage capacity.
... Since the tree, at least in the short term, can continue to take up water and nutrients, girdling results in a less immediate disturbance of the abiotic conditions in the soil than clear-cutting, but the tree will eventually die. Girdling is not commonly used for thinning of forests, but can be used for creating gaps in the tree canopy (Romell et al., 2009) or to remove individual trees at a relatively low cost (Kiehn et al., 2006). Since girdling stops the transport of carbohydrates from the canopy to the roots it also selectively removes the supply of host-derived assimilates that EM fungi are dependent on. ...
The aim of this project was to investigate and clarify the feeding habits of fungivorous soil fauna, with the overall objective of improving our understanding of their functional roles in the ecosystem. Special focus was given to symbiotic ectomycorrhizal (EM) fungi, that, owing to their abundance and diversity, are considered to constitute an important food source for fungivorous soil fauna and
may be a factor regulating these faunal communities. Previous studies on soil animal feeding habits have been strongly dependent on the methodology used; therefore an
additional aim was to find the technique most suitable for studying fungivorous feeding. The results in this thesis confirm that it is necessary to combine a number of different methods in order to determine the feeding habits of fungivorous soil fauna. The total abundance of oribatid mites was significantly reduced in spruce forest stands that were girdled to restrict flow of photoassimilates to roots and ectomycorrhizal fungi, and Oppiella nova was the species that showed the most marked reduction in abundance, especially in spruce forest soils. This reduction in abundance could be explained by the results from a microcosm study, in which O. nova was clearly favoured by the presence of certain EM fungi and increased its abundance of both adults and juveniles in microcosms with the two EM species Suillus variegatus and Paxillus involutus. In the same study, Cognettia sphagnetorum was
suppressed by the presence of EM fungi, which partly explains why this species reach high populations after clear-cutting.
PCR in combination with washing of the body surface and dissection was a successful method for analysing diets of fungal feeding oribatid mites. This method will be considered for future analyses of field collected animals. We could also demonstrate that the isotopic composition of fungivorous animals should be interpreted with great care, when used as a method for studying fungivore feeding
habits. The range of values recorded from field collected Diptera larvae utilising a single food source was large enough to span across several trophic levels when these
were determined using fixed enrichment values from literature data. The δ¹⁵N of the animals was higher than that of the ingested fungal tissue, but similar to the δ¹⁵N
of the protein and amino acids of the food.
West Nusa Tenggara is well known as an eminent producer of cashew (Anacardium
occidentale L.) in Eastern Indonesia. However, Indonesia's cashew plantation faces several constraints in increasing productivity, mainly because of the pest attack. This study aimed to provide early information on protecting local cashew varieties belonging to the farmers due to termite attack in Sambik Elen Village, Bayan District, North Lombok Regency, West Nusa Tenggara Province. The broader termite attack was found in cashew plantation and damaged the trees through root and trunk. The termite attack observed in all plants (100%) with light and heavy intensity was 60% and 40%, respectively. Four dominant insects commonly affected cashew plants, namely Helopeltis spp., Bactrocera dorsalis, Sanurus indecora, and Sphaeniscus sexmaculata. The high economic losses of farmers caused by these harmful insects need to protect local varieties by Integrated Pest Management (IPM) and its replantation. Several superior cashew varieties released by the Ministry of Agriculture or superior local varieties approved by the Director-General of Estate Crops could be an alternative solution for the replanting cashew program in West Nusa Tenggara.
Keywords: superior local varieties, Anacardium occidentale, attack, termite, damage.
Tratamentos silviculturais são críticos para o adequado estabelecimento inicial de espécies arbóreas plantadas em sistemas silviculturais de enriquecimento de floresta
secundária. Entretanto, o nível ótimo de irradiância – obtido com intervenções silviculturais que promovem a abertura do dossel (e.g. refinamento) – depende das
espécies que serão introduzidas. Além dos tratamentos aplicados em árvores no dossel, tratamentos no sub-bosque (e.g. corte do sub-bosque) reduzem a competição entre a vegetação nativa e as espécies plantadas, podendo aprimorar os efeitos da abertura do dossel. A plasticidade fenotípica é crucial para a compreensão das respostas
interespecíficas à abertura do dossel durante os anos iniciais que seguem o plantio de enriquecimento. O objetivo geral neste estudo de doutoramento é compreender o estabelecimento inicial de seis espécies florestais sob gradiente de irradiância em sistema silvicultural de enriquecimento de floresta secundária. Para tanto, em março de 2017, um plantio de enriquecimento de floresta secundária foi estabelecido na Fazenda Experimental da Universidade Federal do Amazonas (FAEXP-UFAM). O experimento foi conduzido em um delineamento experimental fatorial com parcelas subdivididas (seis níveis de refinamento das árvores do dossel x dois tratamentos de corte do subbosque). Entre setembro e dezembro de 2016, foram aplicados seis níveis de redução de área basal via refinamento (0, 20, 40, 60, 80 e 100%) em parcelas principais de 2318 m2 replicadas em cinco blocos. Cada parcela principal foi dividida em duas subparcelas (com e sem corte do sub-bosque), onde foram plantadas seis espécies arbóreas comerciais (Cedrela fissilis, Tabebuia rosea, Swietenia macrophylla, Hymenaea courbaril, Carapa guianensis e Bertholletia excelsa). Tratamentos silviculturais afetaram o microclima, em especial a disponibilidade de irradiância, da floresta
secundária (Capítulo 1), e, consequentemente, o crescimento, sobrevivência e a susceptibilidade ao ataque de pragas das seis espécies (Capítulo 2). A variação no
crescimento das espécies teve boa relação com a plasticidade das características fotossintéticas foliares (morfológicas e fisiológicas) e, portanto, pode ajudar a nossa compreensão sobre os principais mecanismos responsáveis pelas respostas de crescimento de mudas de árvores tropicais a tratamentos silviculturais no enriquecimento de florestas secundárias (Capítulo 3).
Computer simulation models have seldom been applied for estimating the structural and biophysical variables of forest canopy. In this study, an approach for the estimation of leaf area index (LAI) using the information contained in hyperspectral, multi-angle images and the inversion of a computer simulation model are explored. For this purpose, L-systems combined with forest growth model ZELIG were applied to render 3-D forest architectural scenarios. The Radiosity-graphics combined model (RGM) was used to estimate forest LAI from the Compact High-Resolution Imaging Spectrometer/Project for On-Board Autonomy (CHRIS/PROBA) data. LAI inversion was performed using the look-up table (LUT) method. The estimated LAI was evaluated against in situ LAI measurement and compared against the LAI predictions from CHRIS data obtained using the Li-Strahler geometric-optical canopy reflectance model (GOMS). The results indicated that the proposed method can be used to estimate LAI and the accuracy of LAI estimation using the RGM (R² = 0.78, RMSE = 0.53) was slightly higher than that of the GOMS (R² = 0.68, RMSE = 0.66). The method used in this study can be efficient strategy to estimate LAI by RGM model inversion.
Matching species to suitable sites is important in reforestation. This study investigated the site conditions that support regeneration of Hopea odorata, a valuable timber species, in a secondary evergreen natural forest. Stand structure, light intensity at seedling level and soil condition were examined in three representative 50 × 50 m plots. The upper canopy was dominated by four dipterocarps: H. odorata, Shorea roxburghii, Anisoptera costata and Dipterocarpus alatus. The prevailing stand structure supported vigorous germination but not development of seedlings of all four species. Low light levels near the forest floor were the major constraint on seedling development of H. odorata. There was no regeneration when the mean per cent transmitted incident daily photosynthetic active radiation (PAR) was 2.2%; seedling germination but not development was supported when PAR was 6.6%; regeneration and development occurred when PAR was 11.4%. The soils were slightly acidic with low clay and high sand contents and low nutrient concentration, but this was apparently not a constraint on growth given adequate light conditions. The results suggest that the re-establishment of H. odorata on degraded sites using nurse crops should be possible provided that high levels of shading are avoided.
Tree species composition (diameter at breast height (dbh) ≥ 10 cm) was studied in primary, selectively logged and heavily burnt forests in East Kalimantan, Indonesia. The number of trees, tree species, and the Fishers's-α diversity index were determined for the first 15 years (burnt forest) and 25 years (selectively logged forest) after disturbance. Additionally the population structure of six common and typical Macaranga pioneer tree species was compared through time between selectively logged, burnt and primary forest. Both selectively logged and burnt forest showed a significant reduction in number of trees and tree species per surface area directly after disturbance. Fire especially affected dominant tree species, while for selective logging the opposite was observed. In selectively logged forest the number of trees, tree species and the Fishers's-α index reached pre-disturbance levels within c. 15 years. For burnt forest, only the number of trees recovered to pre-disturbance levels. The number of tree species stayed constant after disturbance, while the Fishers's-α index decreased. The six studied Macaranga pioneer tree species seedlings were present in all forest types. Their density seems to be unrelated to light levels in the forest understorey but strongly related to the number of mature parent trees. Their sapling densities were strongly related to light levels in the forest understorey. The studied Macaranga species formed an important part of both under- and over-storey in burnt forest 15 years after disturbance, while they were almost absent in the understorey and only moderately common in the overstorey of selectively logged forest.
The forest canopy is one of the chief determinants of the microhabitat within the forest. It affects plant growth and survival, hence determining the nature of the vegetation, and wildlife habitat. A plethora of different techniques have been devised to measure the canopy. Evaluation of the literature reveals confusion over what is actually being measured. This paper distinguishes two basic types of measurement: canopy cover is the area of the ground covered by a vertical projection of the canopy, while canopy closure is the proportion of the sky hemisphere obscured by vegetation when viewed from a single point. The principal techniques used to measure canopy cover, canopy closure, and a number of related measures are described and discussed. The advantages and limitations are outlined and some sampling guidelines are provided. The authors hope to clarify the nature of the measurements and to provide foresters with sufficient information to select techniques suitable for their needs.
Secondary forests now play a vital role in the conservation of tree species diversity in Southeast Asia because of the continuing fragmentation and decreasing extent of undisturbed forests in this region. To be able to determine the structural and compositional integrity of secondary forests, a ground based rapid assessment method was developed. For this purpose species from the genera Macaranga and Mallotus (Euphorbiaceae) were classified into early and late successional species based on morphological characters that were found to correlate with the light establishment preferences of these species. These characters were wood density (found to be significantly negatively correlated with light establishment preference), seed size (also significantly negatively correlated with light establishment preference), and leaf shape (the leaf length/width ratio was significantly negatively correlated with light establishment preference). Based on this species classification, number of pioneers and non-pioneers could be determined in 71 plots of 0.3 ha, covering 11 common forest disturbance types in Southeast Asia. Three main patterns were detected with this methodology: (1) pioneer and non-pioneer densities were significantly correlated with the forest disturbance level; (2) pioneer densities decreased with time since disturbance; (3) pioneer densities increased with repeated disturbance. A sample size test indicated that forest disturbance in general, and the differences between the major disturbance types could be significantly determined with a minimum of five plots of 0.3 ha. An interactive version of the developed forest disturbance methodology is available at http://www.nationaalherbarium.nl/MacMalBorneo/index.htm.
Identifying factors that influence variation in light availability within forested ecosystems represents an important component in our understanding of the complex determinants of tree seedling regeneration. We assessed the influence of forest structure and canopy tree architecture on spatial heterogeneity of understory light availability in three old-growth and three second-growth forests in lowland Costa Rica. Forest structure and understory light availability were measured within forest types using contiguous 10 × 10 m quadrats along three 130-160 m transects in each stand. Two 20 × 60 m plots in each forest type were sampled more intensively, including vertical profiles of light availability from 1 to 9 m height. Mean diffuse light transmittance increased from 2% at 1 m height to over 10% at 9 m height and did not differ significantly between forest types at any height. However, the relationships among height classes differed between forest types. Second-growth plots showed a negative spatial autocorrelation for light measurements separated by vertical distances over 4 m Differences in the vertical distribution of light and foliage suggest that old-growth and second-growth stands differ in vertical organization of the vegetation. The most pronounced structural differences between forest types were found in trees between 10 and 25 cm in diameter at breast height (dbh). In second-growth stands, trees in the 10-25 cm dbh size class were more abundant and differed in allometry. They were taller for a given stem diameter and had narrower crowns for a given height than old-growth trees. Within forest types, we did not find strong relationships between measures of forest structure and light availability, although the strength of these relationships differed between forest types. In both old- and second-growth forest, understory light availability at 0.75 m decreased with increased sapling and shrub density, but was not significantly influenced by local tree density or basal area. From 1-m to 9-m heights, tree density was a significant, but weak, predictor of light availability in old-growth plots. In second-growth plots, tree density showed little or no influence on light availability at heights below 9 m. Our findings challenge the view that, within a forest, canopy and subcanopy vegetation directly influence light transmittance near the forest floor. Instead, we argue that spatial patterning of the light environment occurs through complex interactions among canopy, subcanopy, and understory vegetation.
Factorial designs are among the most frequently employed for arranging treatments in forestry experiments. Yet researchers often fail either to recognize the factorial treatment structure or to take full advantage of the structure for interpreting treatment effects. The analysis of factorial experiments should focus on comparisons of means of research interest specified by the investigator. Reliance on default options of computing packages or routine application of multiple comparison procedures often fails to address research hypotheses directly. A two-step strategy for the analysis of factorial experiments entails a check for interaction followed by estimation of either main effects or simple effects. This strategy emphasizes sensible mean comparisons through estimation of contrasts and their standard errors. The strategy also applies to the analysis of factorial experiments in which unequal replication or empty cells complicate the analysis. We summarize a practical approach for use by forest scientists and applied statisticians consulting with such scientists so that they may analyze and interpret their experiments more effectively.
Study of forest dynamics commonly requires measurement of canopy gap size. Hemispherical photographs can be analysed to provide various measures whereby gaps can be ranked in order of size. For ten artificial gaps in a Bornean tropical rain forest these measures were better correlated with gap microclimate than gap area measured physically on the ground. All these measures are however relative. For detailed (e.g. ecophysiological) studies the greater detail provided by absolute measures of photosynthetically active radiation (PAR) are required. Long term PAR values can be computed from hemiphots so long as measurements in the open nearby are available. Correction for cloudy weather is essential. Computed and measured PAR are compared for the test gaps. Both have inherent limits which means that below c. 15% canopy openness, differences in PAR between gaps cannot be assessed accurately.
Tree species composition (diameter at breast height (dbh) 10 cm) was studied in primary, selectively logged and heavily burnt forests in East Kalimantan, Indonesia. The number of trees, tree species, and the Fishers's- diversity index were determined for the first 15 years (burnt forest) and 25 years (selectively logged forest) after disturbance. Additionally the population structure of six common and typical Macaranga pioneer tree species was compared through time between selectively logged, burnt and primary forest. Both selectively logged and burnt forest showed a significant reduction in number of trees and tree species per surface area directly after disturbance. Fire especially affected dominant tree species, while for selective logging the opposite was observed. In selectively logged forest the number of trees, tree species and the Fishers's- index reached pre-disturbance levels within c. 15 years. For burnt forest, only the number of trees recovered to pre-disturbance levels. The number of tree species stayed constant after disturbance, while the Fishers's- index decreased. The six studied Macaranga pioneer tree species seedlings were present in all forest types. Their density seems to be unrelated to light levels in the forest understorey but strongly related to the number of mature parent trees. Their sapling densities were strongly related to light levels in the forest understorey. The studied Macaranga species formed an important part of both under- and over-storey in burnt forest 15 years after disturbance, while they were almost absent in the understorey and only moderately common in the overstorey of selectively logged forest.
The conversion of tropical forests into pastures has increased dramatically in the last 20 years. Once these lands are abandoned it is not clear if they will recover to forest or if they will become permanent grasslands. Economic changes in Puerto Rico have led to the abandonment of agricultural lands over the last 60 years, providing an opportunity to assess the longer term patterns of forest recovery following human disturbance. This study focuses on the changes in vegetation in abandoned pastures ranging in age from 0 to 60 years or more in two replicate chronosequences. Species richness and density of woody species were very low during the first 10 years following abandonment and woody biomass did not increase substantially until approximately 15 years post-abandonment, Recovery in pastures is greatly delayed in comparison with forest recovery following other types of human and natural disturbance. The successional trajectory is quite different in comparison to those following natural disturbances in the nearby Luquillo Mountains. In particular, the initial colonizing species are not 'typical' pioneer species (e.g. Cecropia sp., Scheffleria morotononi), but a group of shrubs and treelets in the Rubiaceae, Melastomataceae, and Myrtaceae. The presence of grasses and the rapid colonization and growth of ferns and herbaceous species in the abandoned pastures appears to be a major factor inhibiting the establishment of secondary forest and imparts a selective barrier on the colonizing woody species.
The objective of this study was to relate patterns in forest structure, tree species diversity, and tree species composition to stem diameters and topography in unburned, once burned and twice burned lowland dipterocarp rain forests in East Kalimantan, Indonesia. To do this four unburned old growth forests were compared with three forests that burned once (1997/1998) and three forests that burned twice (1982/1983 and 1997/1998). Fire resulted in a strong reduction of climax tree density which was negatively related to tree diameter. However, a disproportionate reduction in small diameter understorey climax tree species occurred only after repeated fires. Climax tree species in both burned forest types were most common in swamps, river valleys and on lower slopes, while their density was much lower on places higher along hillsides. In unburned forest the opposite was observed, with climax tree density increasing steadily from swamp and river valleys to upper slopes and ridges. In contrast to climax trees, pioneer trees were abundant throughout the burned forest, with highest numbers on hill sides and ridges. Our results indicate that both diameter and topographic position of trees strongly affect their fire survival chances in tropical lowland forests.
Identifying factors that influence variation in light availability within forested ecosystems represents an important component in our understanding of the complex determinants of tree seedling regeneration. We assessed the influence of forest structure and canopy tree architecture on spatial heterogeneity of understory light availability in three old-growth and three second-growth forests in lowland Costa Rica. Forest structure and understory light availability were measured within forest types using contiguous 10 × 10 m quadrats along three 130–160 m transects in each stand. Two 20 × 60 m plots in each forest type were sampled more intensively, including vertical profiles of light availability from 1 to 9 m height. Mean diffuse light transmittance increased from 2% at 1 m height to over 10% at 9 m height and did not differ significantly between forest types at any height. However, the relationships among height classes differed between forest types. Second-growth plots showed a negative spatial autocorr...
In Sabah, Malaysia, logging operations leave substantial areas denuded of vegetation and topsoil. These sites are prone to erosion and slow to become reforested. Stands of pioneer trees established in these heavily disturbed sites may provide environmental conditions that foster recruitment of persistent forest species. Results of a field experiment indicate that recruitment of pioneer trees in recently logged sites is limited more by site conditions than by availability of seeds. In lightly disturbed areas, where the canopy is open and soils are uncompleted, seed addition does not increase the density of pioneer tree seedlings; resprouting vegetation coven such gaps within 3 mo following logging. On landings and skid trails, pioneer seedling densities increase initially following seed addition but by 12 mo after seeding, densities of pioneer seedlings are similar to those on unseeded areas. High seedling mortality in seed addition plots on skid trails and landings indicate that conditions on these compacted and nutrient poor sites during the first year after logging are unfavorable for the persistence of pioneer seedlings. On log landings, seedlings recruit adjacent to debris and bark fragments more frequently than expected by chance. Eighty percent of artificial seeds sown on landings and skid trails were washed away by overland water flow after three storms. The scattering of bark fragments and other small debris over denuded sites may assist seed capture and increase seedling survival temporarily, but many seedlings die within a year. Improving harvesting practices to minimize the area scraped and compacted by heavy machinery will be more effective management than attempting to rehabilitate these areas following logging. The broadcasting of seeds of pioneer trees onto landings and skid trails immediately after logging may be a reasonable management option for hastening tree cover in denuded areas, but only if it is combined with site preparations that improve conditions for the survival of pioneer tree seedlings.
Extensive tracts of tropical rain forest were burnt in Borneo during the El Nino drought of 1983. Severe droughts have occurred previously but without causing such extensive fires. This extensive burning is a result of forests becoming more fire-prone after disturbance by logging. Rates of tree mortality after drought and fire ranged from 38 to 94 percent in logged forests and from 19 to 71 percent in unlogged forests, while for saplings rates of mortality exceeded 80 percent in both forest types. Secondary succession after logging was truncated by fire with the result that the post-fire condition of a forest logged six years before fire was similar to that of a forest logged two years before fire. The impact of fire differs from other natural or man-made gap forming processes in that most pre-existing seedlings and saplings are killed by fire. This left the regrowth in burnt forest depauperate in species diversity and in regeneration of upper-canopy species. Logged and burnt forests suffered severe canopy loss and the ground cover was dominated by grasses (e.g., Imperata cylindrica) or woody creepers (e.g., Eupatorium odoratum). In burnt primary forest, however, canopy loss was less severe and there was a low density of grasses. The prospects for recovery of forest structure appear to be good in burnt primary forest although species composition may be permanently altered. In forests logged prior to the fire, however, prospects for recovery of forest structure are not good, especially if further burning occurs. The recovery of these forests depends heavily on the ability of the secondary tree species to shade out the vigorous grasses, the continued presence of which may herald the conversion of the forest to unproductive grassland as has occurred widely elsewhere in the tropics after over-intensive shifting cultivation.
The Malaysian state of Sabah occupies an area of 73 371 km2 which is about 10% of the island of Borneo. About 60% of the land area is forested and 48% is gazetted as Permanent Forest Reserve or State or National Parks. The largest agent of forest disturbance is the timber industry, which plays a leading role in the state economy. A statutory body, the Sabah Foundation, holds a 100-year timber concession of 973 000 ha (9730 km2) in the southeast of the state. Of this concession 9.7% has been reserved for conservation, including 43 800 ha (438 km2) of uninhabited, mostly lowland forest in an area called Danum Valley. Since 1986, this has been the site of a field centre and a collaborative research programme devoted to comparative study of primary forest ecology and the impacts of selective logging. The paper includes a summary account of the ecology of the Danum Valley Conservation Area.
Interspecific differences in tree performance due to variation in resource availability are expected to influence the structure and dynamics of tropical forest communities. Patterns of mortality and growth over 32 mo in 11 species of Macaranga were analyzed to investigate factors influencing tree spatial distributions and the dynamics of early successional communities. Tree performance was assessed in relation to variation in light levels, soil texture, and tree ontogeny. Rates of mortality and growth varied by over an order of magnitude among species. Species common in high-light microsites had higher mortality and growth rates. Higher low-light mortality for these species reflected lower shade tolerances, supporting the view that shade tolerance involves a trade-off between high-light growth and low-light mortality. Logistic and multiple regressions were used to test for independent effects of tree size and microenvironment on performance in the 11 species. Mortality and growth were significantly related to tree size in nine and eight species, respectively. Higher mortality and lower growth rates for juvenile trees were common. Despite positive correlations between light availability and tree size, mortality rates increased in three species, and growth rates decreased in four species at larger tree sizes. This pattern was particularly strong in smaller statured shade-intolerant species and may reflect changes in biomass allocation following reproductive onset. Declines in growth at larger tree sizes for only some species resulted in changes in species' performance rankings through succession. Low-light mortality rates were strongly correlated with species' distributions in the forest with respect to light levels, whereas biases in distributions with respect to soil texture were not supported by differential mortality. For all trees pooled and in several species, growth showed a threshold response to light levels, being light-limited in low light but not in high light. Across all light levels, soil texture significantly influenced growth in six species. Five species and all trees pooled had significantly lower growth on the more nutrient-poor and potentially drought-prone sandy soils. The dynamics of Macaranga-dominated early successional communities are strongly influenced by soil resource and light availability, coupled with species-specific ontogenetic trajectories of performance.
Gap formation is a critical process for plant establishment that may be absent or infrequent in second-growth forests, negatively influencing their ability to become diverse mature forest. I simulated treefall gaps within a 10-year-old secondary forest established on a clear-cut area, because cut areas may have a greater potential for economic exploitation than areas used for pastures and shifting cultivation. I explored the effects of varying degrees of canopy opening on the growth of plants already established as advanced regeneration. Five intensities of canopy opening were created: total removal (100%), 80–90%, 50–60%, 20–30% and a 0% control. Only trees >5cm DBH were cut. The established plant community was diverse, and comprised 37 families and 126 species and morpho-species, of which 72% had some use reported in the literature. I found that the canopy opening treatments resulted in very little disturbance to the established seedling and sapling community, with no significant increase in mortality, but had a strong positive effect on their growth. Light levels reaching the understory were increased from 1% of incident photosynthetic active radiation in control plots to 35% in 100% canopy opening plots. During the first year, differences in plant growth were not significant, but by the second year, differential plant growth associated with canopy opening became evident. Most seedlings (51%) grew approximately 25cm in height, and approximately one quarter grew more than 25cm. Only 2.6% of the seedlings decreased in height, and 12% did not grow at all. Fifty percent canopy removal resulted in an almost threefold increase in plant height compared to control plots (0.52±0.4m and 0.20±0.2m, respectively), and was not significantly different from 80 or 100% removal. This indicates that intermediate levels of canopy removal had positive effects and total removal was unnecessary to stimulate the best growth responses. I conclude that regeneration of diverse mature forest can be accelerated under some conditions by partial removal of secondary forest canopy.
Enrichment planting is a technique used to accelerate the natural recovery of species such as dipterocarps (non-pioneer species of the Dipterocarpaceae family), in situations where natural regeneration is insufficient for satisfactory regeneration in secondary tropical rain forests. Such planting can be done either in artificially created gaps or lines. The fundamental issues to address when creating artificial gaps are the effects of gap creation on seedling survival, height and biomass. The study presented here was performed in secondary forests of Northern Borneo dominated by pioneer species of the genus Macaranga established after selective logging and fire. In a randomized split plot block design, three methods of canopy treatment (selective felling, selective girdling and untreated control) were combined with two methods of sub-canopy treatment (slashing woody stems or untreated control) and seedlings from four dipterocarp species were used for under-planting. The survival rates and height of the seedlings were regularly recorded throughout a 30-month study period. Above ground biomass functions were constructed for each species using data from a selection of individuals which were destructively sampled after 30 months.
Variation in forest canopy structure influences both understory light avail- ability and its spatial distribution. Because light is a major environmental factor limiting growth and survival of many forest species, its distribution may affect stand-level regen- eration patterns. We examined spatial patterning in light availability and seedling regen- eration in old-growth, second-growth, and selectively logged stands of tropical moist forest in northeastern Costa Rica. Our objectives were to determine how the frequency distribution and spatial pattern of understory light ''microsites'' differ among tropical wet forests; whether patterns of seedling regeneration are linked to spatial patterning of light availability; and whether these relationships differ among old-growth, second-growth, and selectively logged forest stands. We used both sensor-based and hemispherical photograph-based meth- ods to measure light availability along three 130-160 m long transects in each of eight stands (three old-growth, three second-growth, and two selectively logged). Woody seedling abundance was assessed at 4 m 2 ,2 5 m 2, and full-stand scales (430 m2), and species richness was computed at the 25-m2 and full-stand levels. Data were analyzed using both conven- tional parametric approaches and spatial statistics. Mean light availability did not differ markedly among stand types, but variance and frequency distributions of light availability did. Second-growth stands had significantly higher unweighted canopy openness along solar tracks and a higher frequency of microsites at intermediate light levels. Old-growth stands had greater representation of both low- and high-light microsites, and greater overall vari- ance in light availability. Old-growth stands also had slightly higher abundance and species richness of woody seedlings. Light availability was significantly spatially autocorrelated in all stand types, but patch size (analogous to gap size) was twice as large in old-growth stands, based on sensor data. Seedling abundance was also spatially autocorrelated over greater distances in old-growth than in second-growth stands, often at similar spatial scales to light distribution. The selectively logged stands demonstrated spatial autocorrelation of light and seedling abundance over distances intermediate to the other two stand types. Despite the similarities in patterns of light and seedling distributions, relationships between woody seedling abundance, species richness, and the three light availability measures were not strong or consistently positive, regardless of whether standard regressions or partial Mantel tests were applied. Although seedling abundance is likely to be affected by a wide variety of factors, the similarities in the scales of spatial autocorrelation of light and seedling abundance suggest that current seedling abundance distributions may reflect past patterns of light distribution within the stands. Our results confirm the importance of examining spatial dependence of resource availability in studies of forest dynamics, but they also underscore the limitations of a single period of data collection. Long-term studies as well as experimental manipulations of resource availability are needed to establish causal re- lationships between resource availability and stand-level patterns of seedling regeneration.
Daily total photosynthetic photo flux density (PPFD) in the understorey, 200 m2 gap, and 400 m2 gap were 1-1%, 9%, and 20-35% respectively, of PPFD in the clearing. Daily total PPFD in the 400 m2 gap during the dry season was, on average, 2.4 times greater than in the 200 m2 gap, and 20-25 times those in the understorey. In the 200m2 gap daily total PPFD was 9 times greater than in the understorey during the dry season. In the clearing, PPFD was significantly different between seasons with 24% higher PPFD during the dry season. In the 400 m2 gap and understorey, PPFD was not significantly different between seasons. In the clearing, a high proportion of 10-min averages were greater than 500 mu mol m-2s-1; in the 400 m2 gap, a high proportion of 10-min averagegs were between 100 mu mol m-2s-1 and 500 mu mol m-2s-1; in the understorey over 70% of the 10-min averages were below 10 mu mol m-2s-1. The clearing exhibited the greatest diurnal variation in PPFD and the least day-to-day variation, whereas the understorey exhibited the least diurnal variation and the greatest day-to-day variation in PPFD.-from Authors
Using data from forest sites in Sarawak, East Malaysia, a demographic comparison is made of pioneer species in the genus Macaranga with understorey trees of the primary forest in the closely related genus Mallotus . In primary forest, saplings and trees of these genera arc uncommon and have low growth rates. For the six years following disturbance by logging, a Macaranga population was characterized by high rates of diameter growth and recruitment. Eleven years after disturbance, seedling and sapling abundance had declined sharply. In contrast, the Mallotus population was stable in size class distribution and increased slightly in total population size during the 11 years after logging. Growth rates of Mallotus trees increased after logging but were still much less than Macaranga trees.
A morphological comparison shows that most Macaranga species, in contrast with Mallotus species, have large hollow twigs that are occupied by ants and have larger, hairier, thicker, more toothed leaves with longer petioles, axillary inflorescences with more flowers, infructescences with more fruit, fruits that are smaller in size and smaller seeds.
1 Horizontal and vertical heterogeneity of resource availability, coupled with the specialized use of resources by tree species, results in complex patterns of tree species distributions in tropical rain forests. We studied the horizontal and vertical distributions of 4014 individuals in 11 species of early successional Macaranga (Euphorbiaceae) in tropical rain forest in Sarawak, Malaysia.2 The horizontal distribution of individual trees was assessed with respect to crown light levels, establishment microsites, and broader scale variation in soil textural properties. Vertical distribution was assessed using an allometric approach to estimate maximum tree height (Hmax) and the slope of the sapling height–diameter relationship.3 Average light levels intercepted and the proportion of individuals in each of five crown illumination classes varied significantly among the 11 species. Species ranged from extremely high-light demanding, to quite shade tolerant. Average light levels intercepted by trees generally increased through ontogeny, but the ranking of species did not change significantly.4 Fewer individuals of the more shade-tolerant species established on disturbed microsites, irrespective of light levels. Among the more high-light demanding species, the proportion of trees on different types of disturbed sites varied.5 Trees of seven species were significantly more common on clay-rich soils, two preferred sand-rich soils, and two were not strongly affected by soil texture.6 Hmax ranged from 5.5 to 31.3 m and was negatively correlated with shade tolerance among species, although among the more high-light demanding species there was a wide range of tree sizes. Among species, Hmax was negatively correlated with both the slope and y-intercept of the sapling height–diameter relationship, indicating that small-statured species (also more shade tolerant) had more slender saplings than larger statured species.7 Heterogeneity of resource availability leads to differences in horizontal and vertical tree distribution, which are important for the coexistence of 11 Macaranga species.
The photosynthetic induction response under constant and fluctuating light was examined in naturally occurring saplings (about 0.5–2 m in height) of three shade-tolerant tree species, Pourouma bicolor spp digitata, Dicorynia guianensis, and Vouacapoua americana, growing in bright gaps and in the shaded understorey in a Neotropical rain forest. Light availability to saplings was estimated by hemispherical photography. Photosynthetic induction was measured in the morning on leaves that had not yet experienced direct sunlight. In Dicorynia, the maximum net photosynthesis rate (A
max) was similar between forest environments (ca 4 µmol m–2 s–1), whereas for the two other species, it was twice as high in gaps (ca 7.5) as in the understorey (ca 4.5). However, the time required to reach 90% of A
max did not differ among species, and was short, 7–11 min. Biochemical induction was fast in leaves of Pourouma, as about 3 min were needed to reach 75% of maximum carboxylation capacity (V
cmax); the two other species needed 4–5 min. When induction continued after reaching 75% of V
cmax, stomatal conductance increased in Pourouma only (ca 80%), causing a further increase in its net photosynthesis rate. When fully induced leaves were shaded for 20 min, loss of induction was moderate in all species. However, gap saplings of Dicorynia had a rapid induction loss (ca 80%), which was mainly due to biochemical limitation as stomatal conductance decreased only slowly. When leaves were exposed to a series of lightflecks separated by short periods of low light, photosynthetic induction increased substantially and to a similar extent in all species. Although A
max was much lower in old than in young leaves as measured in Dicorynia and Vouacapoua, variables of the dynamic response of photosynthesis to a change in light tended to be similar between young and old leaves. Old leaves, therefore, might remain important for whole-plant carbon gain, especially in understorey environments. The three shade-tolerant species show that, particularly in low light, they are capable of efficient sunfleck utilization.
Photosynthetically active radiation, air temperature, humidity and wind speed were registered along a vertical profile within and above a steeply sloped lower tropical montane rain forest in southern Ecuador. The upper canopy layer accounted for the absorption of more than 90% of incident photosynthetic photon flux density (PPFD); on an average only 5.5% reached the forest floor. Forest floor PPFD was modelled for the whole plot using hemispherical images, analysed with the Software HemiView 2.1. Model performance could be enhanced considerably when taking the narrowed horizon and a PPFD-adjusted atmospheric extinction coefficient into account. However, the simulation revealed high temporal variability of light conditions at the forest floor; modelled PPFD transmission ranged from 5.5% to 10.5% on an average and so was higher than measured values. Daytime temperature and water vapour gradients within the forest were weak, and the understory stratum appeared not to be decoupled from the atmospheric conditions above the forest. Even if methodology was insufficient with respect to quantification of turbulent structures, the measured gradients and the low wind deceleration within the forest indicates an efficient turbulent mixing of the stand air volume during typical daytime conditions. The importance of regional wind characteristics became evident under the influence of exceptionally strong, persistent, and dry mountain winds resulting in steeper aero-dynamic gradients throughout the measured profile. Thus, compared to level sites, forest meteorology of sloped mountain forests must be considered of higher complexity, due to the topography-influenced light conditions and the impact of complex local wind and turbulence patterns on the mountainous landscape.
During selective logging of tropical rainforest in Malaysia, the topsoil is removed from log landings and skid trails by bulldozers. The exposed subsoil is compacted, nutrient-poor, low in organic matter, drought-prone and hot. Vegetation on log landings and skid trails recovers extremely slowly. Tree seedlings planted on these degraded areas perform much less well than those planted in adjacent manually disturbed areas. An experiment was set up to investigate whether soil factors reduced early tree growth. The treatments used were: digging to reduce soil compaction; fertilizing to replace lost nutrients; mulching to reduce soil temperatures and evaporation rates; replacement of topsoil. Two pioneer tree species (Macaranga hypoleuca and M. gigantea) and two dipterocarp species (Dryobalanops lanceolata and Shorea leprosula) were planted in treated plots. Fertilizing of seedlings resulted in a dramatic improvement in height, basal diameter and dry weight increments of all species 6 months after planting. Digging improved seedling growth slightly, but mulching had little effect. This suggests that nutrient deficiency is the most important factor limiting early tree growth on degraded soil. Topsoil replacement resulted in growth as good as that of fertilized seedlings. The topsoil plots also contained 35 times more volunteer plants than any other treatment. Pioneer tree seedlings grew significantly faster than dipterocarp seedlings.
Natural dipterocarp seedling stock is usually very scarce or totally absent from heavily logged dipterocarp forests which have been subjected to shifting cultivation. Instead, a dense cover of secondary forest of low commercial or ecological value prevails. These logged-over low-volume forests can either be converted into plantations or restocked by local, valuable timber. The aim of this study was to obtain information on appropriate silvicultural methods for restocking such secondary forests with dipterocarps, with particular emphasis on the most commonly applied line planting method.
A comprehensive stand level growth model for secondary forest in the Central Amazon is presented. The model has been established for a study site in the Tapajós region for secondary forest of an age up to ca. 35 years. The Bertalanffy–Chapman–Richards equation is applied in a state space approach: a set of differential equations is fitted by nonlinear least-squares to observed stand level growth data in top height, tree density and basal area. Other forest variables are derived by auxiliary relationships to the state variables. The observed growth patterns are first modeled, and then discussed. All fitted coefficients of the growth and increment functions are provided along with a growth table. This study counts with a usual data record for Central Amazonia and presents the first comprehensive growth model for secondary forests in the region. The results are basic data on forest growth and its patterns that are of utmost importance in many ecological contexts.
Daily photosynthetic photon flux density (PPFD) was monitored for 1 year in the understorey of a tropical wet forest along a transect extending from a treefall gap to the closed canopy at La Selva Biological Station, Costa Rica. Quantum sensors attached to data loggers were operated continuously. Hemispherical photographs were taken monthly above the sensors. An additional quantum sensor was used to monitor PPFD outside the canopy. Sensor measurements show large differences between gap and closed-canopy locations and high daily and seasonal variability at each sensor location, with notable increases in solar radiation in gap stations during September and April. The photographs demonstrate that seasonal variation in PPFD results primarily from shifts in the solar angle relative to canopy openings and secondarily from variation in PPFD levels outside the canopy (cloudiness). Photographs also demonstrate an overall decrease in PPFD with time, for the gap stations, owing to vegetation regrowth. Analyses reveal excellent agreement between sensor PPFD measurements and estimates from hemispherical photographs. Long-term monitoring of PPFD enables calibration of hemispherical photography to permit estimation of PPFD with a high degree of reliability.
Hemispherical canopy photographs are now widely used to estimate the proportion of above canopy PPFD (photosynthetic photon flux density) that is transmitted to the forest understorey. Some studies have obtained good results, while others have found that predictions are not always independent of forest type or condition, and that errors are sometimes large beneath very dense canopies. Lack of repeatability can make it difficult to compare sites, studies, or photographs taken at different times. In this study the method for calibrating predictions from photographs was tested in logged and undisturbed tropical broadleaf forest in Borneo, during both the wet and dry seasons. During the dry season a regional smoke ‘haze’ caused by widespread forest fires provided very uniform diffuse conditions and thus a unique test of the calibration. Total transmission (the ‘global transmission factor’, Tt) was modelled as the weighted average of direct and diffuse transmission, with the weighting on diffuse transmission (fd′) determined as the value which maximised the correlation between Tt and measured PPFD. fd′ is an indirect measure of fd, the actual proportion of above canopy PPFD that is diffuse. fd′ should increase with cloudiness or smoke haze. Accurate determination of fd′ is important for prediction of transmission over short time-scales, such as days or weeks. fd′ was modelled for each day and was correlated (r2 = 0.65) with daily shadow band measurements of the above canopy diffuse component during the wet season. During the dry season, fd′ initially decreased with the expected increase in sunshine hours, then the smoke haze halved above canopy PPFD and fd′ increased from less than 0.5 to 1.0, thus validating this method of calibration. After calibration, predictions of Tt from photographs in logged forest were repeatable, accurate (r2 > 0.96) and linear for sites with PPFDs ranging from less than 5% of above canopy PPFD to sites with more than 50% of above canopy PPFD. fd′ modelled from monthly or longer averages of transmission factors and PPFD was within 0.12 of fd. Results were more variable (r2 = 0.68) if calibration was based on data from undisturbed forest only. Overall accuracy and repeatability between sites were attributed to increased digitised image resolution, the use of a spot meter with a narrow field of view to set photograph exposure times, and other improvements in methodology.
Summarises recent information on the nature of gap-understorey environments, paying particular attention to the role of light amount and duration, soil nutrient availability and soil moisture and gap dynamics (focusing on gap-size frequency distributions and forest turnover rates). Patterns of growth and mortality are noted. Evidence is considered regarding habitat specialisation by tropical trees, reviewing data on the distribution of adult and juvenile trees, and on the relative performances of similar species along gap-understorey gradients. Discussion centres on life history attributes in a gap-understorey mosaic.-P.J.Jarvis
To examine rates of aboveground biomass accumulation (ABA) in global secondary forests following stand-clearing disturbances, we compiled aboveground biomass data from 283 known-age plots drawn from chronosequence and long-term studies. We focused on three likely influences on ABA for which data are readily available: climate, soil texture, and forest type. Growing-season degree-years (GSDY, stand age x growing-season length x growing-season temperature) generally predicted ABA better than stand age alone. Using regression analyses and slope homogeneity tests, we determined that broadleaf forest plots on sandy textured soils exhibited slower GSDY-adjusted ABA than those on nonsandy soils. On nonsandy soils, the GSDY-adjusted ABAs of tropical and nontropical plots were indistinguishable; tropical forest post-disturbance ABA was not particularly slow. Compared to broadleaf forests, needle-leaf forest, GSDY-adjusted ABA was less sensitive to soil texture and was intermediate in rate between sandy and nonsandy broadleaf forest ABA. Foliar nutrient concentration did not significantly influence the GSDY-adjusted ABA of a subset of the nonsandy broadleaf forests for which foliar nutrient data were available. At the global scale, differences in climate (represented by growing-season length and temperature) and moisture-holding capacity (represented by soil texture) are the principal independent factors influencing ABA in most post-disturbance secondary forests.
To examine rates of aboveground biomass accumulation (ABA) in global secondary forests following stand-clearing disturbances, we compiled aboveground biomass data from 283 known-age plots drawn from chronosequence and long-term studies. We focused on three likely influences on ABA for which data are readily available. climate, soil texture, and forest type. Growing-season degree-years (GSDY, stand age x growing-season length x growing-season temperature) generally predicted ABA better than stand age alone. Using regression analyses and slope homogeneity tests, we determined that broadleaf forest plots on sandy textured soils exhibited slower GSDY-adjusted ABA than those on nonsandy soils. On nonsandy soils, the GSDY-adjusted ABAs of tropical and nontropical plots were indistinguishable; tropical forest post-disturbance ABA was not particularly slow. Compared to broadleaf forests, needle-leaf forest, GSDY-adjusted ABA was less sensitive to soil texture and was intermediate in rate between sandy and nons
Leaf defences, leaf nutritional quality and leaf expansion rates may vary with resource availabilities to plants. Such variation could affect rates of leaf loss to herbivores, particularly along the steep resource gradients in disturbed forests. Intraspecific and interspecific variation in leaf damage and leaf expansion rates were measured on dipterocarp seedlings planted into secondary forests 1, 5 and 15 y after logging, and in adjacent primary forest of Sabah, Malaysia. Herbivory rates or amounts of leaf damage were compared across habitats and species for expanding, recently expanded, and mature leaves of Shorea leprosula and Dryobalanops lanceolata (Dipterocarpaceae). In all four habitats, leaves of the faster growing S. leprosula sustained higher rates and amounts of leaf-area loss than did the tougher leaves of slower growing D. lanceolata. Expanding leaves accumulated more leaf-area loss per week than did mature leaves. In all habitats and in both species, more than 25% of expanding leaves disappeared entirely. Rates of leaf-area loss per week differed among habitats for expanding leaves but not for mature leaves. In a relatively open, 1-y-old logged forest, faster leaf expansion reduced the time leaves spent in the most vulnerable stage; however, in S. leprosula a greater rate of leaf area loss countered the shorter expansion time. Thus, leaves accumulated similar total damages across habitats, and herbivory did not produce differences among habitats in seedling growth or mortality. High levels of resources may increase both leaf palatability and leaf expansion rates, with counteracting effects on herbivory. Journal Article
Thesis (doctoral)--University College of North Wales, 1972.
In the deeply shaded understorey of S.E. Asian rain forests the growth and survival of dipterocarp seedlings is limited by their ability to maintain a positive carbon balance. Photosynthesis during sunflecks is an important component of carbon gain in understorey plants. To test the sensitivity of photosynthesis and growth to variation in the pattern of dynamic irradiance, dipterocarp tree seedlings (Shorea leprosula and Hopea nervosa) were grown for 370 days under shaded forest light treatments of equal total daily photosynthetic photon flux density (~3.3 mol m-2 day-1), but characterised by either long flecks (LF) or short flecks (SF). Seedling growth was more than 4-fold greater under LF, compared with SF, in both species. Variation in the relative growth rates (RGR) and light saturated rates of photosynthesis (A
max) were strongly positively correlated with the mean duration of sunflecks. Variation in RGR was strongly correlated with greater unit leaf rate growth, indicating that photosynthetic carbon gain per unit leaf area was greater under LF. The accumulation of starch in leaves over the diurnal period was 117% greater in both species under LF, compared with SF. Greater carbon gain in seedlings under LF is likely to have resulted from the combination of (1) greater A
max (S. leprosula 35%, H. nervosa 40%), (2) more efficient dynamic photosynthesis, and (3) greater incident photosynthetic quantum yield, compared with seedlings receiving the SF irradiance treatment. The pattern of dynamic irradiance received by seedlings may significantly impact their growth and survival to a previously unrecognised extent, with important consequences for regeneration processes and hence forest structure and composition.
Irradiance is highly dynamic in many plant canopies. Photosynthesis during sunflecks provides 10-90% of daily carbon gain. The survivorship of tree seedlings in the deeply shaded understorey of tropical rain forests is limited by their ability to maintain a positive carbon balance. Dipterocarp seedlings from the SE Asian rain forest were used as a model system to test novel aspects of the physiological and ecological significance of sunflecks. First, understorey seedlings experienced leaf temperatures up to 38 degrees C in association with sunflecks. Under controlled environment conditions, the inhibition of carbon gain at 38 degrees C, compared with 28 degrees C, was significantly greater during a sequence of sunflecks (-59%), than under uniform irradiance (-40%), providing the same total photosynthetic photon flux density (PPFD). Second, the relative enhancement effects of elevated [CO2] were greater under sunflecks (growth +60%, carbon gain +89%), compared with uniform irradiance (growth +25%, carbon gain +59%), supplying the same daily PPFD. Third, seedling growth rates in the forest understorey were 4-fold greater under a dynamic irradiance treatment characterized by long flecks, compared with a regime of short flecks. Therefore, stresses associated with dynamic irradiance may constrain photosynthetic carbon gain. Additionally, seedling photosynthesis and growth may be more responsive to interactions with abiotic factors, including future changes in climate, than previously estimated. The sensitivity of seedling growth to varying patterns of dynamic irradiance, and the increased likelihood of species-specific responses through interactions with environmental factors, indicates the potential for sunflecks to influence regeneration processes, and hence forest structure and composition.
The soils of Sabah Western parts of Tawau and Lahad Datu. Land Resource Study 20, Land Resources Division
- P S Wright
- England
- J Wyatt-Smith
Wright, P.S., 1975. The soils of Sabah. Volume 3. Western parts of Tawau and Lahad Datu. Land Resource Study 20, Land Resources Division, Surrey, England. Wyatt-Smith, J., 1963. Manual of Malayan Silviculture for Inland Forest, 2nd ed. Malayan Forest Records No. 23, Kepong, Malaysia. Zar, J.H., 1999. Biostatistical Analysis, 4th ed. Prentice Hall, Upper Saddle River, NJ.
Key to the Macaranga and Mallotus species (Euphorbiaceae) of East Kalimantan
- J W F Slik
- Priyono
- P C Van Welzen
Slik, J.W.F., Priyono, van Welzen, P.C., 2000. Key to the
Macaranga and Mallotus species (Euphorbiaceae) of East
Kalimantan, Indonesia. Garden's Bulletin Singapore 52, 11-87.
The natural vegetation of Sabah and Natural Regeneration of Dipterocarps. Ph.D. Thesis. Department of Forestry and Wood Sciences Herbivory on planted dipterocarp seedlings in secondary logged forests and primary forests of Sabah, Malaysia
- J E D Fox
Fox, J.E.D., 1972. The natural vegetation of Sabah and Natural Regeneration of Dipterocarps. Ph.D. Thesis. Department of Forestry and Wood Sciences, University College of North Wales, Bangor, UK. Howlett, B.E., Davidsson, D.W., 2001. Herbivory on planted dipterocarp seedlings in secondary logged forests and primary forests of Sabah, Malaysia. Journal of Tropical Ecology 17, 285–302.
Use of hemispherical photographs in forest ecology, calculations of absolute amount of radiation beneath the canopy. O.F.I. Occasional Papers No. 44
- P L Mitchell
- T C Whitmore
Mitchell, P.L., Whitmore, T.C., 1993. Use of hemispherical
photographs in forest ecology, calculations of absolute
amount of radiation beneath the canopy. O.F.I. Occasional
Papers No. 44. Oxford Forestry Institute, Department of
Plant Sciences, University of Oxford, UK.
Assessing the need for transformation of response variables
- T E Sabin
- S G Stafford
Sabin, T.E., Stafford, S.G., 1990. Assessing the need for
transformation of response variables. Special Publication
20, College of Forestry, Oregon State University.
The effectiveness of current silvicultural practice in Sabah
- Chai
Chai, D.N.P., Udarbe, M.P., 1977. The effectiveness of current
silvicultural practice in Sabah. Malaysian Forester 40, 27-35.
- J H Zar
Zar, J.H., 1999. Biostatistical Analysis, 4th ed. Prentice Hall,
Upper Saddle River, NJ.
Winscanopy 2005a for hemispherical image analyses Available from
- Instruments Ré
- Inc
Ré gent Instruments Inc., 2005. Winscanopy 2005a for
hemispherical image analyses. Available from (1996–2008):
(March 15, 2008) http://www.regentinstruments.com.