Effects of nitrogen on the growth of jack pine competing with Canada blue-joint grass and large-leaved aster

Biomass, leaf area, canopy photosynthesis, photosynthetic nitrogen-use efficiency (PNUE), nitrogen-partitioning ratio (NPR: ratio of nitrogen taken up by jack pine relative to two different competitor species), and nitrogen uptake (NU) of jack pine (Pinus banksiana Lamb.) competing with large-leaved aster (Aster macrophyllus L.) and Canada blue-joint grass (Calamagrostis canadensis (Michx.) Beauv.) were examined at three nitrogen levels in a controlled-environment growth chamber. When grown with large-leaved aster, jack pine biomass, photosynthesis and PNUE (p<0.001) increased as nitrogen level increased. Jack pine biomass, photosynthesis and NPR (p<0.001) decreased as nitrogen level increased when grown with Canada blue-joint grass. At the lowest nitrogen supply level, jack pine photosynthesis decreased as competitor PNUE increased (r²=0.84, p<0.001). Jack pine photosynthesis decreased as NU of large-leaved aster (37.5 mg N l⁻¹: r²=0.75, p<0.001; 100 mg N l⁻¹: r²=0.86, p<0.001) and Canada blue-joint grass (37.5 mg N l⁻¹: r²=0.96, p<0.001; 100 mg N l⁻¹: r²=0.84, p<0.001) increased. NU and PNUE may play an important role in the outcome of interactions between jack pine seedlings and competing forest vegetation in newly planted stands.     

Crown architecture of understory and open-grown white pine (Pinus strobus L.) saplings

Crown architecture and growth allocation were studied in saplings of eastern white pine (Pinus strobus L.), a species classified as intermediate in shade tolerance. A comparison was made of 15 understory saplings and 15 open-grown saplings that were selected to have comparable heights (mean of 211 cm, range of 180-250 cm). Mean ages of understory and open-grown trees were 25 and 8 years, respectively. Understory trees had a lower degree of apical control, shorter crown length, and more horizontal branch angle, resulting in a broader crown shape than that of open-grown trees. Total leaf area was greater in open-grown saplings than in understory saplings, but the ratio of whole-crown silhouette (projected) leaf area to total leaf area was significantly greater in understory pine (0.154) than in open-grown pine (0.128), indicating that the crown and shoot structure of understory trees exposed a greater percentage of leaf area to direct overhead light. Current-year production of understory white pine was significantly less than that of open-grown white pine, but a higher percentage of current-year production was allocated to foliage in shoots of understory saplings. These modifications in crown structure and allocation between open-grown and understory white pine saplings are similar to those reported for more shade-tolerant fir (Abies) and spruce (Picea) species, but the modifications were generally smaller in white pine. As a result, white pine did not develop the flat-topped "umbrella" crown structure observed in understory fir and spruce, which approaches the idealized monolayer form that maximizes light interception. The overall change to a broader crown shape in understory white pine was qualitatively similar, but much more limited than the changes that occurred in fir and spruce. This may prevent white pine from persisting in understory shade as long as fir and spruce saplings.     

The impact of hemlock looper (Lambdina fiscellaria fiscellaria (Guen.)) on balsam fir and spruce in New Brunswick, Canada

In 1989, the first recorded outbreak of hemlock looper (Lambdina fiscellaria fiscellaria (Guen.)) occurred in New Brunswick, Canada. Data were collected from ten plots established in an area infested from 1992–1994, to assess impacts of hemlock looper. Ocular and branch sample assessments of current defoliation and ocular assessments of total defoliation (all age classes of foliage) were conducted for balsam fir (Abies balsamea [L.] Mill.), white spruce (Picea glauca [Moench] Voss), and black spruce (Picea mariana (Mill.) B.S.P.). Stand response was assessed and related to cumulative defoliation. Ocular assessments were found to accurately estimate defoliation, which was significantly related to tree mortality. Ninety-two percent of balsam fir trees that had cumulative defoliation >90% died. Mortality of balsam fir was significantly (p < 0.05) related to tree size, in both lightly and severely defoliated plots; trees with DBH <11 cm sustained 22–48% higher mortality than larger trees. Mortality of balsam fir, in terms of both percent stems/ha and m³/ha merchantable volume, increased exponentially in relation to three estimates of cumulative (summed) plot mean defoliation. The strongest relationships (r² = 0.75–0.79) were between mortality and the ocular defoliation assessment for 1990–1993 foliage. Tree mortality caused by the looper outbreak ranged from 4–14% stems/ha in lightly defoliated and from 32–100% in severely defoliated plots; merchantable volume killed was 3–14 m³/ha and 51–119 m³/ha, respectively. Relationships between mortality and defoliation were similar when defoliation was assessed for 1987–1993 and 1990–1993 foliage age classes.     

Irradiance in thinned Norway spruce (Picea abies) stands and the possibilities to prevent suckers of broadleaved trees

Both incoming shortwave radiation (R_g) and photosynthetically active radiation (PAR) in percentage of full daylight were measured at the same time by point and strip sampling in four plots (0.1 ha) of Picea abies (L.) Karst. The standard deviations (%) of R_g and PAR were, respectively, 11.1 and 9.8 at 64 points, 15.7 and 13.9 at 32 points, and 24.7 and 23.8 at 16 points per plot.

A period of at least 40 s per strip (30 m min⁻¹) gives a CV (coefficient of variation) of 30%. There is no significant difference between relative irradiance (RI) estimated by the point method (64 points) and by the strip method (8 strips). Curves of RI (R_g and PAR) and basal area (m² ha⁻¹), diameter sum (m ha⁻¹) and density (stems ha⁻¹) of fifteen trials with different thinning programmes are presented. Irradiance (R_g) in heavily thinned stands was 3–14% of irradiance on an open place. The irradiance, R_g, in extra-heavily thinned stands is 12–27%, and in unthinned stands, 1–3% that of an open place. The R_g curve lies above the PAR curve in all cases. Some practical implications of the study are presented. Heavy thinning of Norway spruce stands gives RI (R_g) values 10% at basal area of 25m² ha⁻¹ which is necessary to minimize development of suckers of broadleaved trees.     

Bud activity of decapitated, nursery-grown plants ofTriplochiton scleroxylon in Nigeria: effects of light, temperature and humidity

This study is a continuation of earlier work on apical dominance inTriplochiton scleroxylon K. Schum., aimed at the development of an early clonal selection test for branching habit and yield in tree improvement programmes. Decapitated plants of five to seven clones were treated with either: (i) two photon flux densities (photosynthetically active radiation at full or 10% sunlight, approximately 2000 and 200 μmol quanta m⁻²s⁻¹ measured at midday on a clear day); (ii) two temperatures (ambient 30°C or 40°C in a polythene tent); (iii) two humidities (ambient=40–70% relative humidity at 30°C or with humidification=95–100% relative humidity at 28°C). Bud activity, shoot length and numbers of leaves produced following decapitation were all increased by high photon flux density and high humidity. In contrast to similar studies under glasshouse conditions in Britain, dominance was not re-established following the initial period of sprouting. The sprouting phase was similar in Nigeria and Britain. Clonal differences in bud activity were similar under different treatments, although there were minor changes in ranking. Increasing the air temperatures from 30 to 40°C resulted in leaf areas of 165 cm² and 23 cm², respectively. Normal polarity of lateral shoot production following decapitation was completely inverted by high temperature.     

Relationships between growing-season soil water-deficit, mineralizable soil nitrogen and site index of coastal Douglas fir

Relationships between measures of soil water availability, available soil macronutrients and site index of coastal Douglas fir were examined in 53 stands. Growing-season water-deficit was able to explain the most variation in site index of all soil water-balance measures examined (R² = 0.42). Of all soil chemical properties examined, mineralizable N in the surface 30 cm of the mineral soil and in the forest floor accounted for the most variation in site index (R² = 0.54). Multiple regression of the natural log of mineralizable N, and growing-season water-deficit on site index gave an R² of 0.63. Use of mineralizable N as a measure of N availability is supported, and interactions between water-use efficiency and stand N status are suggested.     

Regeneration of timber trees in a logged tropical forest in North Bolivia

For sustainable forest management, it is important to know the response of timber species to the change in environment caused by logging. We performed a 2-year study on germination, survival and growth of four timber species, Cedrela odorata, Swietenia macrophylla, Hymenaea courbaril, and Cariniana micrantha, and one non-commercial species Tachigali vasquezii. We sowed seeds of these species in five microenvironments: log landing, gap-crown and gap-trunk, skidder trail and understory, in a tropical lowland moist rain forest in northern Bolivia. We related seed and seedling performance to light availability, soil compaction, and plant competition. Germination did not differ significantly between microenvironments but survival of germinated seeds for most species was significantly higher (P < 0.05) in the log landing (46–100%) than in the understory (0–7%). After 2 years, the tallest plants were always found in the log landing (119–190 cm) and the smallest in the understory (12–26 cm) caused by a higher relative height growth rate (RHGR) in the log landing (0.003–0.004 cm cm⁻¹ per day) compared to the understory (0.000–0.001 cm cm⁻¹ per day). During the first year RHGR was positively related to canopy openness for all species and negatively to the number of overtopping competitors for three species. During the second year also water infiltration explained observed variation to RHGR. These results show that abandoned log landings and logging gaps are suitable environments for the regeneration of timber species studied. This finding suggests that the removal of competitors in log landings and logging gaps combined with leaving seed trees near these microenvironments or sowing seeds, will improve regeneration of timber species in tropical forests.     

Above- and below-ground biomass and nutrient distribution of a paper birch and subalpine fir mixed-species stand in the Sub-Boreal Spruce zone of British Columbia

Stand structure, height and diameter growth, above- and below-ground biomass, and nutrient concentrations and content were determined for a 35-year-old fire-origin paper birch (Betula papyrifera) and subalpine fir (Abies lasiocarpa) mixed-species stand in the Sub-Boreal Spruce (SBS) zone of British Columbia. Paper birch, which formed the dominant overstory following the 1961 fire, had normal distributions of height and diameter classes. Subalpine fir, which dominated the understory, had the reverse J-shaped height and diameter distributions that are expected of a shade tolerant, climax species. Paper birch grew more than three times the height of subalpine fir. Growing in the summer shade of the birch, subalpine fir had slow but steady height growth during the first 10–15 years, after which height growth declined somewhat. Allometric equations, relating dry weight of foliage, branches, stemwood, stembark, roots, and total biomass to diameter at breast height (DBH), were developed to estimate above- and below-ground biomass. Total biomass of paper birch reached 83.2 t ha⁻¹, while subalpine fir biomass was 26.7 t ha⁻¹. Subalpine fir allocated more biomass to foliage and branches compared to paper birch. Foliage of paper birch had higher nutrient concentrations of N, P, K, Ca, and Mg than subalpine fir foliage. Branches and stembark of subalpine fir had higher P, and Ca concentrations than paper birch. Subalpine fir branches contained more of all examined nutrients than paper birch branches. This is a significant component in nutrient cycling of the mixed-species forest.     

The relationship between cavity-nesting birds and snags on clearcuts in western Oregon

Relationships between cavity-nesting birds (CNB) and density and characteristics of snags were investigated on 13 clearcuts in central coastal Oregon. Species richness and density of CNB were positively (P<0.05) related to snag density and were still increasing at the maximum snag density evaluated. Cavity-nesting birds selected (P<0.05) snags taller than 6.4 m and greater than 78–102 cm in diameter, and avoided (P<0.05) snags less than 28 cm in diameter. Snags of intermediate decay stages were used for nesting more (P<0.05) than snags of early and advanced stages of decay. Cavity-nesting birds selected snags with more (P<0.05) bark cover (greater than 11%) than the average cover found on available snags. Individual CNB species exhibited significantly different (P<0.05) selections for snag height, diameter, hardness and bark cover. To optimize density and richness of CNB, forest managers should provide ≥ 14 snags ha⁻¹ between 28 and 128 cm diameter at breast height (dbh), between 6.4 and 25 m tall, with at least 10% bark cover, and with a majority in hardness stages 3 and 4.     

Growth analysis on the competition–density effect in Chinese fir (Cunninghamia lanceolata) and Masson pine (Pinus massoniana) stands

The competition–density (C–D) effect for Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) and Masson pine (Pinus massoniana Lamb.) stands was analyzed using the reciprocal equation of the C–D effect, i.e. 1/w=Aρ+B, where w and ρ, respectively, represent mean stem volume and stand density. The C–D curve, which is given by the reciprocal equation on logarithmic coordinates, shifted upward with the progress of time. The coefficients A and B included in the reciprocal equation were calculated at each growth stage. The biological time τ defined as the integral of λ(t), the coefficient of growth in the general logistic growth curve, with respect to physical time t, tended to increase to an asymptote with increasing t. With increasing τ, the coefficient A, the reciprocal of which means the asymptote of yield (=wρ), increased abruptly up to a maximum value and then tended to decrease gradually to a constant level. On the other hand, the coefficient B, the reciprocal of which means the asymptote of mean stem volume, decreased exponentially and tended to close to zero with increasing τ. The λ(t) decreased with increasing stand age, whereas the final yield Y(t) defined as W(t) ρ, where W(t) is the asymptote of w in the general logistic growth curve, tended to increase gradually with increasing stand age.     

Physiological, morphological and allocational plasticity in understory deciduous trees: importance of plant size and light availability

In a 4-year study, we investigated changes in leaf physiology, crown morphology and whole-tree biomass allocation in seedlings and saplings of shade-tolerant sugar maple (Acer saccharum Marsh.) and intermediate shade-tolerant yellow birch (Betula alleghaniensis Britt.) growing in natural understory light (0.5 to 35% of full sunlight) or in understory light reduced by 50% with shade nets to simulate the effect of gap closure. Leaf physiological parameters were mainly influenced by the light gradient, whereas crown morphological and whole-tree allocational parameters were mainly influenced by tree size. No single physiological, morphological or allocational trait was identified that could explain the difference in shade tolerance between the species. Yellow birch had higher growth rates, biomass allocation to branches and leaf physiological plasticity and lower crown morphological plasticity in unmodified understory light than sugar maple. Sugar maple did not display significant physiological plasticity, but showed variation with tree size in both crown morphology and whole-tree biomass allocation. When sugar maple was small, a greater proportion of whole-tree biomass was allocated to roots. However, physiological differences between the species decreased with decreasing light and most morphological and allocational differences tended to disappear with increasing tree size, suggesting that many species differences in shade-tolerance are expressed mainly during the seedling stage. Understory trees of both species survived for 4 years under shade nets, possibly because of higher plasticity when small and the use of stored reserves when taller.     

Tree allometry, leaf size and adult tree size in old-growth forests of western Oregon

Relationships between tree height and crown dimensions and trunk diameter were determined for shade-tolerant species of old-growth forests of western Oregon. The study included both understory and overstory species, deciduous and evergreen angiosperms and evergreen conifers. A comparison of adult understory species with sapling overstory species of similar height showed greater crown width and trunk diameter in the former, whether the comparison is made among conifers or deciduous trees. Conifer saplings had wider crowns than deciduous saplings, but the crown widths of the two groups converged with increase in tree height. Conifer saplings had thicker trunks than deciduous saplings of similar crown width, possibly because of selection for resistance to stem bending under snow loads. The results suggest that understory species have morphologies that increase light interception and persistence in the understory, whereas overstory species allocate their biomass for efficient height growth, thereby attaining the high-light environment of the canopy. The greater crown widths and the additional strength requirements imposed by snow loads on conifer saplings result in less height growth per biomass increment in conifer saplings than in deciduous saplings. However, the convergence in crown width of the two groups at heights greater than 20 m, and the proportionately smaller effect of snow loads on large trees, may result in older conifers equalling or surpassing deciduous trees in biomass allocation to height growth.     

Influence of artificial gaps in tropical forest on survival, growth, and Phytolyma lata attack on Milicia excelsa

Milicia excelsa and M. regia are important timber species in moist tropical areas of Africa. They have not been successfully grown largely because of attacks by gall-forming psyllids in the genus Phytolyma. Our objectives were to evaluate the growth of planted Milicia seedlings and incidence of psyllid attack in small (4.2 m²), medium (18.5 m²) and large (>500 m²) artificial gaps in the Bobiri Forest Reserve in the Moist Semi-Deciduous Forest of Ghana. After 13 months, height and diameter growth of Milicia seedlings were significantly greater in the medium and large gaps than in the small gaps. Insect attacks occurred first and most severely in the large gaps, but spread to gaps of all sizes between the 11th and 13th months after planting. While gap size significantly affected the susceptibility of seedlings to psyllid attack, it is not the only factor important in determining susceptibility of Milicia excelsa under field conditions. We conclude that gap sizes in the range of 10–50 m², where irradiances are from 30–60% of full sunlight, in forests similar to those at the study site, seem to be most suitable for regeneration of Milicia.     

Performance of twelve selected Australian tree species on a saline site in southeast Queensland

The establishment and early growth of 12 species within the genera Eucalyptus, Casuarina, Melaleuca and Tipuana was tested on a saline site in southeast Queensland. Electrical conductivity (EC) in the top 50 cm of soil was measured using an electromagnetic induction method and calibrated against the EC of 1:5 soil:water suspensions. The site was then stratified into five salinity classes: 0.75–1.0, 1.0–1.25, 1.25–1.5, 1.5–1.75 and over 1.75 dSm⁻¹. Relationships were developed for predicting the survival and height production of 18-month-old trees. These regressions explained 15–88% of the variation in survival and 2–66% of the variation in height production. Tree species were grouped by determining the EC level where height production declined by 25% relative to that at 0.75 ds m⁻¹. Casuarina glauca, Melaleuca bracteata, Eucalyptus moluccana, Eucalyptus camaldulensis, Eucalyptus tericornis and Eucalyptus raveretiana were all highly salt tolerant (25% reductions over 1.5 dS m⁻¹). Casuarina cunninghamiana, Eucalyptus grandis, Eucalyptus melliodora and Eucalyptus robusta exhibited moderate salt tolerance (25% reductions between 1.0 and 1.5 dS m⁻¹). The responses to increased salinity of Tipuana tipu and Eucalyptus intermedia (25% reductions at less than 1.0 dS m⁻¹) suggest that these species are not suitable for revegetating similar saline sites.     

Effects of flow rate and chamber position on measurement of stem respiration rate with an open flow system in a Japanese red pine

The effects of air flow rate and chamber position on measuring stem respiration rate (R_stem) were examined using an open flow system on six Japanese red pine (Pinus densiflora Sieb. and Zucc) trees. R_stem was more closely correlated with stem temperature observed 2–6 h earlier than with current stem temperature. R_stem was not affected by the air flow rate passing through the stem chamber. Although there were no differences in stem temperatures between azimuth angles, there were significant differences in R_stem between azimuth angles (except for only one case) of each sample stem. The distance from below the bark to the stem centre varied at each azimuth in the samples, and was significantly positively correlated with R₀ (p < 0.01). The chamber type did not affect the measurement of stem respiration, because the mean R_stem of four azimuth angles measured with in a rectangular chamber was almost the same as R_stem measured with in a circular chamber. From these results, we suggest that a whole circumference estimate made by either:

(1) measuring stem respiration at each azimuth separately with a rectangular chamber, or

(2) measuring the total CO₂ efflux from the whole radial circumference with a circular chamber,

must be conducted for scaling-up chamber measurements to individual or stand level.

Relative importance of water and nutrients on the growth of coast Douglas fir in the Pacific Northwest

The Douglas-fir region in northwestern North America is characterized by abundant moisture supply during winter, extended dry periods during the growing-season and significant differences in water availability. Many soils have low fertility and native tree species respond to nitrogen fertilization, especially Pseudotsuga menziesii (Mirb.) Franco (coast Douglas fir). Although irrigation of commercial forests in this region is currently impractical, questions arising about the relative importance of water and nutrients were examined using long-term growth data from three studies.

At Pack Forest, fertilization within irrigation doubled growth rates, and no positie growth responses were measured from irrigation. Short-term (5 years) irrigation with sewage effluent containing many nutrients resulted in a six-fold increase in biomass production for poplar and three-fold for Douglas fir as compared to irrigation with equal volumes of river water.

Volume growth in 12- to 65-year-old stands in southwestern Oregon was increased by fertilization at about 70% of the location; annual gain averaged 2.73 m³ ha⁻¹ for 5–12 years. Response was not related to annual precipitation, which ranhed from 81 to 279 cm, nor other moisture-related variables. Absolute and relative volume response showed highest correlation with soil carbon: nitrogen ratio.

Compared with nutrition, moisture does not seem to be a major limiting factor for growth in the Douglas-fir region of the Pacific northwest.     

Tree regeneration responses to microsite characteristics following a severe tornado in the Georgia Piedmont, USA

For 3 years following a severe, November 1992 tornado, abundance and growth of tree regeneration in intact forest-floor and windthrow-pit microsites were studied in three mixed pine and hardwood stands in the Georgia Piedmont, USA. The research had two objectives: (1) determine if performance of tree regeneration differed between microsite types and between pre- and post-tornado cohorts on intact forest-floor microsites, and (2) determine if variation in light and soil water availability from the disturbance affected performance of eight species artificially seeded into intact forest-floor microsites. Near each of the 42 sample points (12–20 per site) spaced on 15 m grids, species and height of tree seedlings were recorded within a 1 m radius plot of intact forest floor and the nearest windthrow pit. Intact forest-floor microsites were dominated by two late-successional species, Acer rubrum (3.5 pre-tornado stems per m² and 1.8 post-tornado stems per m²) and Ostrya virginiana (2.6 post-tornado stems per m²), while windthrow pits were dominated by an early successional species, Liriodendron tulipifera (1.7 stems per m²). Although seedling survival did not vary significantly among species or microsite types, first-year height of seedlings in intact forest-floor microsites (24 cm) was significantly greater than those in windthrow-pit microsites (19 cm). Second-year height growth of new seedlings of Cornus florida in intact forest-floor microsites (52 cm) significantly exceeded that of many other combinations of species and microsite type. Species artificially-seeded into intact forest-floor microsites in 1994 and 1995 varied considerably in emergence (<1–24%), survival (<1–16%), and height (5–15 cm), and those with the heaviest seed survived best. From 1994 to 1995, average gap fraction, an index of light availability, decreased 17% from 0.23 to 0.19. Soil water content in 1995 under gap fractions of greater than 0.3 (21%) averaged significantly less than under gap fractions of either 0.1–0.3 (24%) or less than 0.1 (26%). Significant positive correlations were detected for relationships of emergence and survival of several species to soil water content. Overall rankings of seedling performance between microsites (intact forest floor>windthrow pits), between cohorts (pre-tornado>post-tornado origin), and among species (mid- to late->early-successional species) indicate that advanced regeneration and new seedlings of A. rubrum, O. virginiana, and C. florida will be long-term dominants of the understory because of their high abundance, initial growth responses, and shade tolerance.     

Interaction between moisture, nutrients and growth of white spruce in interior Alaska

Two thinning and fertilization studies, the first in 1969 and the second in 1971, were established to evaluate the question of nutrient limitation to tree growth and the consequences of stand manipulation of soil moisture supply. Fertilizer was applied yearly for the first 5 years in both studies; growth response has been measured through 1987. Results indicate that thinning is necessary to obtain a growth response to fertilizer applied at the rate of 111 kg nitrogen ha⁻¹. The response to fertilization after fertilization ended lasted for 4 years in plots thinned to 800 stems ha⁻¹, while a significant response continued for only 2 years in plots thinned to 1600 stems ha⁻¹.

A soil water-balance model was calibrated for the control and treatment plots of these two studies. Soil water-deficits were estimated and correlated with yearly average basal-area growth per tree. Results indicated that there is a correlation between seasonal soil-moisture deficit and growth during the years when soil moisture was measured for the unthinned control plots (r² = −0.787, P = 0.002) but not for the thinned and fertilized plots (r² = −0.652, P = 0.057).     

Canopy tree development and undergrowth bamboo dynamics in old-growth Abies–Betula forests in southwestern China: a 12-year study

Interactions between forest canopy characteristics and plants in the forest understory are important determinants of forest community structure and dynamics. In the highlands of southwestern, China the dwarf bamboo Bashania fangiana Yi is an understory dominant beneath a mixed canopy of the evergreen Abies faxoniana (Rheder & Wilson) and the deciduous Betula utilis (D. Don). The goal of this study was to better understand the role of bamboo dominance, canopy characteristics, and periodic bamboo dieback on forest development. To achieve this goal, we measured tree seedling, tree saplings, and trees, forest canopy characteristics, and bamboo cover in permanent forest (n = 4) and gap plots (n = 31) in a mixed A. faxoniana and B. utilis forest in Sichuan, China. Dwarf bamboos died off in 1983 in the gap plots, and in three of the four forest plots. Forest development was assessed for the period 1984–1996. The seedling bank in forest and gap plots increased after bamboo die-off. A. faxoniana seedlings increased more than B. utilis in forest plots; the opposite pattern characterized gap plots. The proportion of seedlings on raised micro-sites on the forest floor also changed and new seedling were more abundant on the forest floor. By 1996, bamboo seedling cover and biomass had recovered to ca. 45% or their pre-flowering values. Rates of bamboo seedling recovery were faster beneath canopy gaps and deciduous trees than beneath forest or evergreen trees. Tree mortality exceeded recruitment in plots with dense bamboo; the opposite pattern was found in the plot with little bamboo. The mortality rate for B. utilis trees (2.4% year⁻¹) was higher than that for A. faxoniana (0.8% year⁻¹) and forests with dense bamboos became more open over the census period. Tree mortality was size-dependent and intermediate sized trees had the lowest rates of mortality. Stand basal area increased mainly due to greater basal area gain than loss for A. faxoniana. Interactions between tree species life history, canopy type, and bamboo life-cycles create heterogeneous conditions that influence tree and bamboo regeneration and contribute to the coexistence of A. faxoniana and B. utilis in old-growth forests in southwestern China.