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1.
We re-visited a seven-stand boreal chronosequence west of Thompson, Manitoba, Canada, in which coarse woody debris (CWD) and
its instantaneous decomposition were measured in 2000. New CWD measurements were performed in 2007, and tree inventories updated
to provide mortality and snag failure data. These data were used to model CWD changes, compare methods of estimating decomposition,
and infer possible fragmentation rates. Measured CWD was between 9.7 (in both the 77- and 43-year-old stands) and 80.4 (in
the 18-year-old stand) Mg ha−1 in 2007. Spatial variability was high; at most stands CWD levels had not changed significantly from 2000 to 2007. Tree mortality
was a significant flux only in older stands, whereas snag fall rate varied by an order of magnitude, from 2.9% y−1 (0.2 Mg ha−1 y−1) in the 9-year-old stand to 9.8% y−1 (2.3 Mg ha−1 y−1) in the 12-year-old stand. A one-pool model based on these inputs underestimated actual 2000–2007 CWD decomposition in the
younger stands, suggesting that fragmentation could be an important part of the carbon flux exiting the CWD pool. We compared
three independent measures of annual decomposition (k): direct measurements of CWD respiration, rates based on the 7-year re-sampling effort described here, and rates inferred
from the chronosequence design itself. Mean k values arrived at via these techniques were 0.06 ± 0.03, 0.05 ± 0.04, and 0.05 ± 0.05 y−1, respectively. The four-pool model suggested that the transition rate between decay classes was 0.14–0.19 y−1; the model was most sensitive to initial CWD values. Although the computed k values implied a problem with chronosequence site selection for at least one site, the overall CWD trend was consistent with
a larger number of sites surveyed in the region. 相似文献
2.
Eun-Jae Lee Woo-Shin Lee Seung Hun Son Shin-Jae Rhim 《Landscape and Ecological Engineering》2011,7(1):137-143
We examined differences in bird communities in relation to characteristics of habitat structure in a pine forest, Samcheok,
South Korea. An unburned stand, a stand burned 7 years earlier and then naturally restored, and a stand where Japanese red
pine Pinus densiflora seedlings were planted after the fire were used for the survey. Habitat structure was dramatically changed by postfire silvicultural
practices. Number of stand trees, shrubs, seedlings, snags, and vegetation coverage were significantly different among study
stands. We made 1,421 detections of 46 bird species during 23 separate line transect surveys per stand between February 2007
and December 2008. The mean number of observed bird species and individuals, bird species diversity index (H′), and Simpson’s diversity index (D
s) were highest in the unburned stand and lowest in the pine seedling stand. There were more species and individuals of forest-dwelling
birds in the unburned stand than both burned stands. Canopy and cavity nesters, foliage searchers, bark gleaners, and timber
drillers were significantly higher in the unburned stand. In the pine seedling stand, densities of birds that prefer open
field and shrub cover were higher. Stand structure was simplified in the pine seedling stand by postfire practices. Because
of differences in habitat structure and bird communities, postfire practices in the burned stand should be re-evaluated. Also,
management strategies for pine forest after forest fires are needed based on results of long-term experiments. 相似文献
3.
Shun’ichi Makino Hideaki Goto Motohiro Hasegawa Kimiko Okabe Hiroshi Tanaka Takenari Inoue Isamu Okochi 《Ecological Research》2007,22(3):372-381
We studied the species richness and assemblages of longicorn beetles (Coleoptera, Cerambycidae, Disteniidae) in ten secondary
broad-leaved stands and eight plantation stands of Japanese cedar (Cryptomeria japonica) of various ages after clear-cutting or plantation in Ibaraki, central Japan. The species richness of longicorns, which were
collected with Malaise traps, was the highest in young stands, decreasing with the age of the stand for both broad-leaved
and conifer stands. A canonical correspondence analysis divided the 18 plots into three groups based on longicorn assemblages
and environmental variables. These three groups consisted of (1) very young (1–4 years old) stands after clear-cutting or
plantation; (2) 12- to over 100 year-old broad-leaved stands; (3) 7- to 76-year-old conifer stands. The species richness of
the longicorns was the highest in the young stands followed, in order of decreasing species richness, by broad-leaved stands
and conifer stands. Possible causes of the high species richness in young stands include large amounts of coarse wood debris
and flowers, which are resources for oviposition and nutrition for adults, respectively. The lower longicorn diversity in
conifer stands than in broad-leaved stands may be due to the lower diversity of trees available as host plants in the former.
Almost all species that occurred in conifer stands were also collected in young and/or broad-leaved stands, but the reverse
was not true, suggesting that conifer plantations cannot replace broad-leaved stands in terms of longicorn biodiversity. We
argue that an extensive conversion of broad-leaved forests into conifer plantations will lead to an impoverishment of the
longicorn fauna, which may result in the degradation of ecosystem functions possibly carried out by them. 相似文献
4.
Differential Snowpack Accumulation and Water Dynamics in Aspen and Conifer Communities: Implications for Water Yield and Ecosystem Function 总被引:2,自引:0,他引:2
Early succession aspen and late succession conifer forests have different architecture and physiology affecting hydrologic
transfer processes. An evaluation of water pools and fluxes was used to determine differences in the hydrologic dynamics between
stands of quaking aspen (Populus tremuloides) and associated stands of mixed conifer consisting of white fir (Abies concolor), Douglas-fir (Pseudotsuga menziesii), and Engelmann spruce (Picea engelmannii). In 2005 and 2006, measurements of snow water accumulation, snow ablation (melt), soil water content, snowpack sublimation,
and evapotranspiration (ET) were measured in adjacent aspen and conifer stands. Peak snow water equivalent (SWE) averaged
34–44% higher in aspen in 2005 (average snow fall) and 2006 (above average snow fall), respectively, whereas snow ablation
rates were greater in aspen stands (21 mm day−1) compared to conifer stands (11 mm day−1). When changes in soil water content (due to over-winter snowmelt) were combined with peak snow accumulation in 2006, aspen
had greater potential (42–83%) water yield for runoff and groundwater recharge. Snowpack sublimation during the ablation period
was not significantly different between meadow, aspen, and conifer sites and comprised less than 5% of the winter precipitation.
Extended conifer transpiration in spring and fall did not contribute to large differences in water yield (<28 mm y−1). Summertime ET rates were higher in aspen plots (3.6 mm day−1) than in conifer plots (2.7 mm day−1), and differences in net ET largely reflected soil column porosity. This study shows that the largest differences in annual
water yield between aspen and conifer stands result from differences in SWE and net summertime ET. Although SWE and accumulation
of water in soil was greater in aspen, it was partly offset by greater net annual ET losses in aspen. 相似文献
5.
Natural regeneration is the natural process by which plants replace themselves. It is a cost-effective way to re-establish vegetation, and it helps to preserve genetic identity and diversity. In this study, we investigated the natural regeneration of trees in three types of afforested stands in the Taihang Mountains, China, which were dominated by Robinia pseudoacacia (black locust), Quercus variabilis (Chinese cork oak) and Platycladus orientalis (Chinese arborvitae) respectively. A consistent pattern was found among the three types of stands, being that the density of seedlings was positively correlated with the overstory canopy cover and negatively correlated with the covers of shrub, herb and litter layers. While a positive correlation between the density of seedlings and stand age was found for the conifer stands, negative correlations were found for the two types of broadleaf stands. Correlations between the density of saplings and the stand attributes were not consistent among the three types of stands. The two types of broadleaf stands had higher densities of seedlings and saplings than the conifer stands. While the broadleaf stands had adequate recruits for regeneration, the conifer stands did not have enough recruits. Our findings suggest that the overstory canopy should be prevented from being disturbed, any reduction of the canopy cover will decrease the recruits and affect the regeneration. 相似文献
6.
Wildfire and clearcutting are two main disturbances in North American forests, but whether root systems may respond differently to such disturbances is unknown. Here, we studied how the dynamics of fine roots (<2 mm in diameter) varied with stand origins in a boreal forest in northern Ontario, Canada. Fine root biomass increased with stand age, but did not differ between stands originating from fire and clearcutting. By contrast, fine root production, mortality and turnover rates were lower in 3- and 11-year-old clearcut-origin than fire-origin stands, but did not differ in 29-year-old stands of different stand origins. The lower rates of production, mortality, and turnover rates in 3- and 11-year-old clearcut-origin than fire-origin stands are attributable to a lower density of shrubs and herbs and larger nutrient pools after clearcutting than fire. The similarities among 29-year-old stands indicate that the effects of stand origin on fine root processes tend to converge at this time scale. Our results illustrate that time scale is critical for assessing ecosystem responses to disturbances. 相似文献
7.
The Imprint of Land-use History: Patterns of Carbon and Nitrogen in Downed Woody Debris at the Harvard Forest 总被引:9,自引:1,他引:8
Few data sets have characterized carbon (C) and nitrogen (N) pools in woody debris at sites where other aspects of C and N
cycling are studied and histories of land use and disturbance are well documented. We quantified pools of mass, C, and N in
fine and coarse woody debris (CWD) in two contrasting stands: a 73-year-old red pine plantation on abandoned agricultural
land and a naturally regenerated deciduous forest that has experienced several disturbances in the past 150 years. Masses
of downed woody debris amounted to 40.0 Mg ha−1 in the coniferous stand and 26.9 Mg ha−1 in the deciduous forest (20.4 and 13.8 Mg C ha−1, respectively). Concentrations of N were higher and C:N ratios were lower in the deciduous forest compared to the coniferous.
Pools of N amounted to 146 kg N ha−1 in the coniferous stand and 155 kg N ha−1 in the deciduous forest; both are larger than previously published pools of N in woody debris of temperate forests. Woody
detritus buried in O horizons was minimal in these forests, contrary to previous findings in forests of New England. Differences
in the patterns of mass, C, and N in size and decay classes of woody debris were related to stand histories. In the naturally
regenerated deciduous forest, detritus was distributed across all size categories, and most CWD mass and N was present in
the most advanced decay stages. In the coniferous plantation, nearly all of the CWD mass was present in the smallest size
class (less than 25 cm diameter), and a recognizable cohort of decayed stems was evident from the stem-exclusion phase of
this even-aged stand. These results indicate that heterogeneities in site histories should be explicitly included when biogeochemical
process models are used to scale C and N stocks in woody debris to landscapes and regions.
Received 27 April 2001; accepted 4 January 2002. 相似文献
8.
Differences of Soil Microbial Biomass and Nitrogen Transformation under Two Forest Types in Central Germany 总被引:1,自引:0,他引:1
In order to observe the tree species effect on soil N status, soil microbial biomass C and N (Cmic, Nmic), potential N mineralization and potential nitrification (under laboratory incubation conditions, 22 °C) in different subhorizons
(LOf1, Of2, Oh and mineral soil at 0–10 cm depth) were determined at three forest sites in central Germany. At each site, two contrasting
stands (Beech, Norway spruce or Scots pine) were selected, where the initial soil conditions were similar. Three sampling
dates that represented different stages of tree growth were selected: growing season - August, dormant season - November,
after budbreak – April. In organic layers, Cmic-to-total C (Ct) ratios under beech and under conifer were 0.72–4.74% and 0.34–2.11%, respectively. Nmic-to-total N (Nt) ratios were 2.47–11.61% and 0.71–5.77%, respectively. Both concentrations of Cmic and Nmic were significantly affected by the stand type and sampling time. Potential N mineralization rates, ranging from 3.7 to 19.7 mg
N kg−1 d−1, showed no clear pattern in relation to stand type. However, potential nitrification rates were mostly significantly higher
under beech than under contrasting conifer. In mineral soils, concentrations of Cmic and Nmic showed a clear temporal pattern in the order: August>November>April. The average Nmic and Nmic-to-Nt were higher in soils from beech than conifer, while Cmic and Cmic-to-Ct ratios were similar between the two forest types. In organic layers, the highest values of Cmic-to-Nmic ratio and Cmic were found in November samples, especially under beech. By contrast, in mineral soils the highest value of Cmic-to-Nmic ratios were found in April samples, and at that time the Cmic concentrations were the lowest, especially under conifer. These results revealed the differences in microbial growth form
and survival strategy associated with different tree species and soil layers. 相似文献
9.
Neth Top Nobuya Mizoue Satoshi Ito Shigetaka Kai Toshio Nakao Sokhun Ty 《Biodiversity and Conservation》2009,18(3):717-738
This study examined differences in stand structure, tree species richness, and tree species diversity in relation to population
density in Kampong Thom Province, Cambodia. Tree data were obtained from a 1997 forest inventory involving 60 clusters (540
plots) systematically distributed over 30% of the provincial forest area. Spatially referenced population data were obtained
from the 1998 national population census. The average number of trees per cluster was 356/ha, the average basal area, 23 m2/ha, the average stand volume, 217 m3/ha, and the average aboveground biomass, 273 Mg/ha for all trees of DBH 10 cm and larger. The average species richness per
cluster was 37 species, while average species diversity was measured as 0.916 using Simpson’s index and 2.98 by Shannon’s
index. Significant negative correlations were generally found between population density surrounding clusters and tree density,
basal area, stand volume, aboveground biomass, and species richness and diversity for three examined diameter classes (DBH
of 10–30, ≥30, and ≥10 cm). As the distance from clusters for calculating population density increased, the correlation levels
increased up to 5 or 7 km, depending on the variables and diameter class, and then stayed relatively constant for stand structure
variables and decreased for species richness and diversity. The results indicate that evidence of disturbance was more pronounced
at higher population density up to around 5 to 7 km. We suggest that introduction of greater controls on human disturbance
should be a high priority for resource management and conservation in Kampong Thom Province and, presumably, Cambodia as a
whole. 相似文献
10.
Nam-Jin Noh Yowhan Son Sue-Kyoung Lee Kyung-Won Seo Su-Jin Heo Myong-Jong Yi Pil-Sun Park Rae-Hyun Kim Yeong-Mo Son Kyeong-Hak Lee 《中国科学:生命科学英文版》2010,53(7):822-830
The carbon (C) and nitrogen (N) storage capabilities of Pinus densiflora in six different stand ages (10, 27, 30, 32, 44, and 71 years old) were investigated in Korea. Thirty sample trees were destructively
harvested and 12 were excavated. Samples from the above and belowground tree components, coarse woody debris (CWD), forest
floor, and mineral soil (0–30 cm) were collected. Tree biomass was highest in the 71-year-old stand (202.8 t ha−1) and lowest in the 10-year-old stand (18.4 t ha−1). C and N storage in the mineral soil was higher in the 71-year-old stand than in the other stands, mainly due to higher
soil C and N concentrations. Consequently, the total ecosystem C and N storage (tree+forest floor+CWD+soil) was positively
correlated with stand age: increasing from a minimum in the 10 year old stand (18.8 t C ha−1 and 1.3 t N ha−1) to a maximum in the 71-year-old stand (201.4 t C ha−1 and 8.5 t N ha−1). The total ecosystem C storage showed a similar sigmoidal pattern to that of tree C storage as a function of the age-sequence,
while N storage in the CWD, forest floor and mineral soil showed no significant temporal trends. Our results provide important
insights that will increase our understanding of C and N storage in P. densiflora stands and our ability to predict changes according to stand age in the region. 相似文献
11.
Root Growth and Recovery in Temperate Broad-Leaved Forest Stands Differing in Tree Species Diversity
In contrast to studies on aboveground processes, the effect of species diversity on belowground productivity and fine-root
regrowth after disturbance is still poorly studied in forests. In 12 old-growth broad-leaved forest stands, we tested the
hypotheses that (i) the productivity and recovery rate (regrowth per standing biomass) of the fine-root system (root diameter < 2 mm)
increase with increasing tree species diversity, and that (ii) the seasonality of fine-root biomass and necromass is more
pronounced in pure than in tree species-rich stands as a consequence of non-synchronous root biomass peaks of the different
species. We investigated stands with 1, 3, and 5 dominant tree species growing under similar soil and climate conditions for
changes in fine-root biomass and necromass during a 12-month period and estimated fine-root productivity with two independent
approaches (ingrowth cores, sequential coring). According to the analysis of 360 ingrowth cores, fine-root growth into the
root-free soil increased with tree species diversity from 72 g m−2 y−1 in the monospecific plots to 166 g m−2 y−1 in the 5-species plots, indicating an enhanced recovery rate of the root system after soil disturbance with increasing species
diversity (0.26, 0.34, and 0.51 y−1 in 1-, 3-, and 5-species plots, respectively). Fine-root productivity as approximated by the sequential coring data also
indicated a roughly threefold increase from the monospecific to the 5-species stand. We found no indication of a more pronounced
seasonality of fine-root mass in species-poor as compared to species-rich stands. We conclude that species identification
on the fine root level, as conducted here, may open new perspectives on tree species effects on root system dynamics. Our
study produced first evidence in support of the hypothesis that the fine-root systems of more diverse forest stands are more
productive and recover more rapidly after soil disturbance than that of species-poor forests. 相似文献
12.
Influence of stand structure on carbon-13 of vegetation, soils, and canopy air within deciduous and evergreen forests in Utah, United States 总被引:15,自引:0,他引:15
Carbon isotope ratios (δ13C) were studied in evergreen and deciduous forest ecosystems in semi-arid Utah (Pinus contorta, Populus tremuloides, Acer negundo and Acer grandidentatum). Measurements were taken in four to five stands of each forest ecosystem differing in overstory leaf area index (LAI) during
two consecutive growing seasons. The δ13Cleaf (and carbon isotope discrimination) of understory vegetation in the evergreen stands (LAI 1.5–2.2) did not differ among canopies
with increasing LAI, whereas understory in the deciduous stands (LAI 1.5–4.5) exhibited strongly decreasing δ13Cleaf values (increasing carbon isotope discrimination) with increasing LAI. The δ13C values of needles and leaves at the top of the canopy were relatively constant over the entire LAI range, indicating no
change in intrinsic water-use efficiency with overstory LAI. In all canopies, δ13Cleaf decreased with decreasing height above the forest floor, primarily due to physiological changes affecting c
i/c
a (> 60%) and to a minor extent due to δ13C of canopy air (< 40%). This intra-canopy depletion of δ13Cleaf was lowest in the open stand (1‰) and greatest in the denser stands (4.5‰). Although overstory δ13Cleaf did not change with canopy LAI, δ13C of soil organic carbon increased with increasing LAI in Pinus contorta and Populus tremuloides ecosystems. In addition, δ13C of decomposing organic carbon became increasingly enriched over time (by 1.7–2.9‰) for all deciduous and evergreen dry temperate
forests. The δ13Ccanopy of CO2 in canopy air varied temporally and spatially in all forest stands. Vertical canopy gradients of δ13Ccanopy, and [CO2]canopy were larger in the deciduous Populus tremuloides than in the evergreen Pinu contorta stands of similar LAI. In a very wet and cool year, ecosystem discrimination (Δe) was similar for both deciduous Populus tremulodies (18.0 ± 0.7‰) and evergreen Pinus contorta (18.3 ± 0.9‰) stands. Gradients of δ13Ccanopy and [CO2]canopy were larger in denser Acer spp. stands than those in the open stand. However, 13C enrichment above and photosynthetic draw-down of [CO2]canopy below tropospheric baseline values were larger in the open than in the dense stands, due to the presence of a vigorous understory
vegetation. Seasonal patterns of the relationship δ13Ccanopy versus 1/[CO2]canopy were strongly influenced by precipitation and air temperature during the growing season. Estimates of Δe for Acer spp. did not show a significant effect of stand structure, and averaged 16.8 ± 0.5‰ in 1933 and 17.4 ± 0.7‰ in 1994. However,
Δe varied seasonally with small fluctuations for the open stand (2‰), but more pronounced changes for the dense stand (5‰).
Received: 15 April 1996 / Accepted: 19 October 1996 相似文献
13.
Floral composition and structural parameters of the herbaceous vegetation of four recovering tropical dry deciduous forest
stands protected for 2, 4, 6 and 10-year periods, on the Eastern Ghats of India, situated at Kandhamal district of Orissa,
India were investigated. More than 1 ha of recovering forest stands of each of the four stages was selected and fifteen sample
quadrats of 1 m × 1 m were randomly placed at each stand for vegetation analysis. Floristic analysis revealed highest number
of species (69) in 2-year recovering stand, which declined with increase in age. A total of 87 species, 71 genera and 32 families
were recorded in the forest stands. Total number of herbaceous species encountered in the stands was 44, 28, 30 and 24 in
2, 4, 6 and 10-year stands, respectively. Total individuals of all herb species were 114, 70, 88 and 68 plant m−2 in 2, 4, 6 and 10-year stands, respectively. Herbaceous stand basal areas were 7.84, 3.66, 4.77 and 5.23 cm2 m−2 in 2, 4, 6, and 10-year stands, respectively. Importance value index (IVI) revealed that Heteropogon contortus was predominant in 2 and 4-year stands, Andrographis paniculatus in 6-year stand and Elephantopus scaber in 10-year stand. Diversity-dominance curve revealed lognormal distribution in all the four stands. Simpson’s dominance index
(C) was highest in 2-year stand which decreased in other stands, while Shannon’s diversity index (H1) was almost the same in all the stands. Biomass of herbaceous vegetation was 83.2 g m−2 in 2 year, 62.2 g m−2 in 4 year, 58.0 g m−2 in 6 year and 64.0 g m−2 in 10-year stand. 相似文献
14.
Han Y. H. Chen Amber N. Brant Meelis Seedre Brian W. Brassard Anthony R. Taylor 《Ecosystems》2017,20(4):830-844
Litterfall is a fundamental process in the nutrient cycle of forest ecosystems and a major component of annual net primary production (NPP). Despite its importance for understanding ecosystem energetics and carbon accounting, the dynamics of litterfall production following disturbance and throughout succession remain poorly understood in boreal forest ecosystems. Using a replicated chronosequence spanning 209 years following fire and 33 years following logging in Ontario, Canada, we examined the dynamics of litterfall production associated with stand development, overstory composition type (broadleaf, mixedwood, and conifer), and disturbance origin. We found that total annual litterfall production increased with stand age following fire and logging, plateauing in post-fire stands approximately 98 years after fire. Neither total annual litterfall production nor any of its constituents differed between young fire- or logging-originated stands. Litterfall production was generally higher in broadleaf stands compared with mixedwood and conifer stands, but varied seasonally, with foliar litterfall highest in broadleaf stands in autumn, and epiphytic lichen litterfall highest in conifer stands in spring. Contrary to previous assumptions, we found that the contribution of litterfall production to net primary production increased with stand age, highlighting the need for modeling studies of net primary productivity to account for the effects of stand age on litterfall dynamics. 相似文献
15.
Biodiversity effects on ecosystem functioning in forests have only recently attracted increasing attention. The vast majority
of studies in forests have focused on above-ground responses to differences in tree species diversity, while systematic analyses
of the effects of biodiversity on root systems are virtually non-existent. By investigating the fine root systems in 12 temperate
deciduous forest stands in Central Europe, we tested the hypotheses that (1) stand fine root biomass increases with tree diversity,
and (2) ‘below-ground overyielding’ of species-rich stands in terms of fine root biomass is the consequence of spatial niche
segregation of the roots of different species. The selected stands represent a gradient in tree species diversity on similar
bedrock from almost pure beech forests to medium-diverse forests built by beech, ash, and lime, and highly-diverse stands
dominated by beech, ash, lime, maple, and hornbeam. We investigated fine root biomass and necromass at 24 profiles per stand
and analyzed species differences in fine root morphology by microscopic analysis. Fine root biomass ranged from 440 to 480 g m−2 in the species-poor to species-rich stands, with 63–77% being concentrated in the upper 20 cm of the soil. In contradiction
to our two hypotheses, the differences in tree species diversity affected neither stand fine root biomass nor vertical root
distribution patterns. Fine root morphology showed marked distinctions between species, but these root morphological differences
did not lead to significant differences in fine root surface area or root tip number on a stand area basis. Moreover, differences
in species composition of the stands did not alter fine root morphology of the species. We conclude that ‘below-ground overyielding’
in terms of fine root biomass does not occur in the species-rich stands, which is most likely caused by the absence of significant
spatial segregation of the root systems of these late-successional species. 相似文献
16.
Woody debris stocks in different secondary and primary forests in the subtropical Ailao Mountains, southwest China 总被引:3,自引:0,他引:3
Woody debris (WD), including coarse woody debris (CWD) and fine woody debris (FWD), is an essential structural and functional
component of many ecosystems, particularly in montane forests. CWD is considered to be the major part in forest WD and it
is primarily composed of logs, snags, stumps and large branches, while FWD mainly consists of small twigs. Attributes of dead
woody material may change in accordance with trends in stand dynamics. The primary forest (primary montane moist evergreen
broad-leaved forest) in Ailao Mountain National Nature Reserve (NNR) preserves the largest tract of natural vegetation in
China. The Alnus nepalensis (D. Don) association, Populus bonatii (Levl.) association and secondary Lithocarpus association represent the secondary and chronological types following human disturbance by fires and logging under different
intensity. The mass and composition of coarse woody debris (CWD, ≥10 cm in diameter) and fine woody debris (FWD, 2.5–10 cm
in diameter) were inventoried in a primary forest and its three secondary counterparts. Estimates of total mass of woody debris
across secondary types to primary forest ranged from 2.4 to 74.9 Mg ha−1. The lowest value was found in the A. nepalensis association and the highest values were in the primary forest of which logs are the considerable differences. The ratios
of CWD to FWD were low in the secondary types (about 1–4) but high in the primary forest (above 15). Our results suggested
that for the recovery of woody debris in the secondary forest, it might last longer than the age of the oldest successional
stage studied.
Yang Lipan and Ma Wenzhang contributed equally to this work. 相似文献
17.
Previous studies have indicated that recruitment of Abies sachalinensis, a representative conifer species of northern Japan, decreased following single-tree selection harvesting in stands with
dense dwarf bamboo understory. We tested the hypothesis that growth and survival of A. sachalinensis seedlings are reduced by canopy opening in that type of stand. A 0.75 ha study plot was examined, and all the seedlings (defined
as trees with height 0.5–2 m) were identified and their shoot extensions measured for three years after single-tree selection
harvesting (26% intensity in terms of basal area). The leader extensions of A. sachalinensis seedlings that experienced canopy opening were greatly improved. However, a negative effect on survival was also apparent;
nearly 40% of seedlings died at the sites that experienced canopy opening. These results were supported by generalized linear
models that examined variations of local harvesting intensity for individual seedlings. Despite the ability of A. sachalinensis to respond rapidly to exposure, some physiological stresses may have appeared, and presumably were amplified by co-occurring
dwarf bamboos. With regard to the low seedling density (156 stems ha−1), common in this type of stands, local harvesting intensity in the selection system should be reduced to maintain survival
of advanced regeneration, thus sustaining stand structure and composition. 相似文献
18.
The accumulation and decomposition of coarse woody debris (CWD) are processes that affect habitat, soil structure and organic
matter inputs, and energy and nutrient flows in forest ecosystems. Natural disturbances such as fires typically produce large
quantities of CWD as trees fall and break, whereas human disturbances such as timber harvesting remove much of the CWD. Our
objective was to compare the amount of CWD removed and left behind after clear-cutting to the amount consumed and left behind
after natural fires in Rocky Mountain lodgepole pine. The masses of fallen logs, dead-standing trees, stumps, and root crowns
more than 7.5 cm in diameter were estimated in clear-cut and intact lodgepole pine forests in Wyoming and compared to estimates
made in burned and unburned stands in Yellowstone National Park (YNP), where no timber harvesting has occurred. Estimates
of downed CWD consumed or converted to charcoal during an intense crown fire were also made in YNP. No significant differences
in biomass of downed CWD more than 7.5 cm in diameter were detected between burned stands and those following a single clear-cut.
However, the total mass of downed CWD plus the mass of snags that will become CWD was nearly twice as high in burned stands
than in clear-cuts. In YNP, approximately 8% of the downed CWD was consumed by fire and an additional 8% was converted to
charcoal, for an estimated loss of about 16%. In contrast, approximately four times more wood (70%) was removed by clear-cutting.
Considering all CWD more than 7.5 cm in diameter that was either still present in the stand or removed by harvesting, slash
treatment, or burning, clear-cut stands lost an average of 80 Mg ha−1 whereas stands that burned gained an average of 95 Mg ha−1. Some CWD remains as slash and stumps left behind after harvesting, but stands subjected to repeated harvesting will have
forest floor and surface soil characteristics that are beyond the historic range of variability of naturally developing stands.
Received 16 November 1999; Accepted 31 May 2000. 相似文献
19.
K. Lõhmus M. Truu J. Truu I. Ostonen E. Kaar A. Vares V. Uri S. Alama A. Kanal 《Plant and Soil》2006,283(1-2):1-10
Grey alder (Alnus incana) and black alder (Alnus glutinosa) stands on forest land, abandoned agricultural, and reclaimed oil-shale mining areas were investigated with the aim of analysing
the functional diversity and activity of microbial communities in the soil–root interface and in the bulk soil in relation
to fine-root parameters, alder species, and soil type. Biolog Ecoplates were used to determine community-level physiological
profiles (CLPP) of culturable bacteria in soil–root interface and bulk soil samples. CLPP were summarized as AWCD (average
well color development, OD 48 h−1) and by Shannon diversity index, which varied between 4.3 and 4.6 for soil–root interface. The soil–root interface/bulk soil
ratio of AWCD was estimated. Substrate-induced respiration (SIR) and basal respiration (BAS) of bulk soil samples were measured
and metabolic quotient (Q = BAS/SIR) was calculated. SIR and Q varied from 0.24 to 2.89 mg C g−1 and from 0.12 to 0.51, respectively. Short-root morphological studies were carried out by WinRHIZOTM Pro 2003b; mean specific root area (SRA) varied for grey alder and black alder from 69 to 103 and from 54 to 155 m2 kg−1, respectively. The greatest differences between AWCD values of culturable bacterial communities in soil–root interface and
bulk soil were found for the young alder stands on oil-shale mining spoil and on abandoned agricultural land. Soil–root interface/bulk
soil AWCD ratio, ratio for Shannon diversity indices, and SRA were positively correlated. Foliar assimilation efficiency (FOE)
was negatively correlated with soil–root interface/bulk soil AWCD ratio. The impact of soil and alder species on short-root
morphology was significant; short-root tip volume and mass were greater for black alder than grey alder. For the investigated
microbiological characteristics, no alder-species-related differences were revealed. 相似文献
20.
Byung Bae Park Ruth D. Yanai Timothy J. Fahey Scott W. Bailey Thomas G. Siccama James B. Shanley Natalie L. Cleavitt 《Ecosystems》2008,11(2):325-341
Losses of soil base cations due to acid rain have been implicated in declines of red spruce and sugar maple in the northeastern
USA. We studied fine root and aboveground biomass and production in five northern hardwood and three conifer stands differing
in soil Ca status at Sleepers River, VT; Hubbard Brook, NH; and Cone Pond, NH. Neither aboveground biomass and production
nor belowground biomass were related to soil Ca or Ca:Al ratios across this gradient. Hardwood stands had 37% higher aboveground
biomass (P = 0.03) and 44% higher leaf litter production (P < 0.01) than the conifer stands, on average. Fine root biomass (<2 mm in diameter) in the upper 35 cm of the soil, including
the forest floor, was very similar in hardwoods and conifers (5.92 and 5.93 Mg ha−1). The turnover coefficient (TC) of fine roots smaller than 1 mm ranged from 0.62 to 1.86 y−1 and increased significantly with soil exchangeable Ca (P = 0.03). As a result, calculated fine root production was clearly higher in sites with higher soil Ca (P = 0.02). Fine root production (biomass times turnover) ranged from 1.2 to 3.7 Mg ha−1 y−1 for hardwood stands and from 0.9 to 2.3 Mg ha−1 y−1 for conifer stands. The relationship we observed between soil Ca availability and root production suggests that cation depletion
might lead to reduced carbon allocation to roots in these ecosystems. 相似文献