共查询到20条相似文献,搜索用时 31 毫秒
1.
Pinus kesiya 《Acta Oecologica》2001,22(5-6)
Seasonal changes and vertical distribution of fine (< 2 mm diameter) and coarse (2-10 mm diameter) root mass of Pinus kesiya and fine root and rhizome mass of herbaceous species, and root production were studied in the 6-, 15- and 23-year old Pinus kesiya forest stands at Shillong, in the Meghalaya state of north-east India. Maximum fine and coarse root mass of P. kesiya, and fine root and rhizome mass of the ground vegetation were recorded during the rainy season. The contribution of the tree fine roots in 0-10 cm soil layer declined from 51% in the 6-year old stand to about 33% in the older stands. The major proportion (63-88%) of herbaceous fine root and rhizome mass was concentrated in this soil layer in all the three stands. The majority (36-57%) of tree coarse roots were present in the 10-20 cm layer in all the stands. The biomass and necromass values in the case of fine roots were more or less equal in a given stand, but the coarse roots had 5 to 9 times more live than the dead mass. The proportion of herbaceous fine root mass to the total fine root mass declined from 54% in the 6-year old stand to 30-32% in the 15- and 23-year old stands. The mean total fine root mass (pine + herbaceous species) decreased from 417 g m–2 in the 6-year old stand to 302 in 15-year and 322 g m–2 in the 23-year old stand. Annual fine root production showed a marked decrease from 1055 g m–2 in the 6-year old stand to 743 g m–2 in the 23-year old stand, but coarse root production increased from 169 g m–2 in the 6-year to 466 g m–2 in the 23-year old stand; the total root production thus remained approximately constant. 相似文献
2.
B. E. LAW O. J. SUN J. CAMPBELL S. VAN TUYL P. E. THORNTON† 《Global Change Biology》2003,9(4):510-524
Forest development following stand‐replacing disturbance influences a variety of ecosystem processes including carbon exchange with the atmosphere. On a series of ponderosa pine (Pinius ponderosa var. Laws.) stands ranging from 9 to> 300 years in central Oregon, USA, we used biological measurements to estimate carbon storage in vegetation and soil pools, net primary productivity (NPP) and net ecosystem productivity (NEP) to examine variation with stand age. Measurements were made on plots representing four age classes with three replications: initiation (I, 9–23 years), young (Y, 56–89 years), mature (M, 95–106 years), and old (O, 190–316 years) stands typical of the forest type in the region. Net ecosystem productivity was lowest in the I stands (?124 g C m?2 yr?1), moderate in Y stands (118 g C m?2 yr?1), highest in M stands (170 g C m?2 yr?1), and low in the O stands (35 g C m?2 yr?1). Net primary productivity followed similar trends, but did not decline as much in the O stands. The ratio of fine root to foliage carbon was highest in the I stands, which is likely necessary for establishment in the semiarid environment, where forests are subject to drought during the growing season (300–800 mm precipitation per year). Carbon storage in live mass was the highest in the O stands (mean 17.6 kg C m?2). Total ecosystem carbon storage and the fraction of ecosystem carbon in aboveground wood mass increased rapidly until 150–200 years, and did not decline in older stands. Forest inventory data on 950 ponderosa pine plots in Oregon show that the greatest proportion of plots exist in stands ~ 100 years old, indicating that a majority of stands are approaching maximum carbon storage and net carbon uptake. Our data suggests that NEP averages ~ 70 g C m?2 year?1 for ponderosa pine forests in Oregon. About 85% of the total carbon storage in biomass on the survey plots exists in stands greater than 100 years, which has implications for managing forests for carbon sequestration. To investigate variation in carbon storage and fluxes with disturbance, simulation with process models requires a dynamic parameterization for biomass allocation that depends on stand age, and should include a representation of competition between multiple plant functional types for space, water, and nutrients. 相似文献
3.
Heather D. Alexander Michelle C. Mack Scott Goetz Michael M. Loranty Pieter S. A. Beck Kamala Earl Sergey Zimov Sergey Davydov Catharine C. Thompson 《Ecosystems》2012,15(7):1065-1082
Increased fire activity within boreal forests could affect global terrestrial carbon (C) stocks by decreasing stand age or altering tree recruitment, leading to patterns of forest regrowth that differ from those of pre-fire stands. To improve our understanding of post-fire C accumulation patterns within boreal forests, we evaluated above- and belowground C pools within 17 Cajander larch (Larix cajanderi) stands of northeastern Siberia that varied in both years since fire and stand density. Early-successional stands (<20-year old) exhibited low larch recruitment, and consequently, low density, aboveground larch biomass, and aboveground net primary productivity (ANPPtree). Mid-successional stands (21- to 70-year old) were even-aged with considerable variability in stand density. High-density mid-successional stands had 21 times faster rates of ANPPtree than low-density stands (252 vs. 12?g?C?m?2?y?1) and 26 times more C in aboveground larch biomass (2,186 vs. 85?g?C?m?2). Density had little effect on total soil C pools. During late-succession (>70-year old), aboveground larch biomass, ANPPtree, and soil organic layer C pools increased with stand age. These stands were low density and multi-aged, containing both mature trees and new recruits. The rapid accumulation of aboveground larch biomass in high-density, mid-successional stands allowed them to obtain C stocks similar to those in much older low-density stands (~8,000?g?C?m?2). If fire frequency increases without altering stand density, landscape-level C storage could decline, but if larch density also increases, large aboveground C pools within high-density stands could compensate for a shorter successional cycle. 相似文献
4.
N. N. Koshurnikova 《Biology Bulletin》2007,34(5):532-536
The biological production of the moss layer was analyzed in dark coniferous stands in progressive succession in the southern taiga in West Siberia. The rate of organic matter production by mosses changed from 15–22.2 g/(m2 y) in 50–90-year-old fir forests to 51.6 g/(m2 y) in 170-year-old mixed Siberian pine-spruce-fir stands. In forest phytocenosis that were formed with species replacement (after cuttings with understory clearing), the annual moss production (net primary production) ranged from 2.8 to 20.6 g/(m2 y). The annual moss cover production amounted to 35–36% of the moss photosynthetic biomass irrespective of the type of native stand progressive succession and the stand age. 相似文献
5.
Carbon storage and fluxes in ponderosa pine forests at different developmental stages 总被引:12,自引:0,他引:12
B.E. Law P.E. Thornton † J. Irvine P.M. Anthoni‡ S. Van Tuyl 《Global Change Biology》2001,7(7):755-777
We compared carbon storage and fluxes in young and old ponderosa pine stands in Oregon, including plant and soil storage, net primary productivity, respiration fluxes, eddy flux estimates of net ecosystem exchange (NEE), and Biome‐BGC simulations of fluxes. The young forest (Y site) was previously an old‐growth ponderosa pine forest that had been clearcut in 1978, and the old forest (O site), which has never been logged, consists of two primary age classes (50 and 250 years old). Total ecosystem carbon content (vegetation, detritus and soil) of the O forest was about twice that of the Y site (21 vs. 10 kg C m?2 ground), and significantly more of the total is stored in living vegetation at the O site (61% vs. 15%). Ecosystem respiration (Re) was higher at the O site (1014 vs. 835 g C m?2 year?1), and it was largely from soils at both sites (77% of Re). The biological data show that above‐ground net primary productivity (ANPP), NPP and net ecosystem production (NEP) were greater at the O site than the Y site. Monte Carlo estimates of NEP show that the young site is a source of CO2 to the atmosphere, and is significantly lower than NEP(O) by c. 100 g C m?2 year?1. Eddy covariance measurements also show that the O site was a stronger sink for CO2 than the Y site. Across a 15‐km swath in the region, ANPP ranged from 76 g C m?2 year?1 at the Y site to 236 g C m?2 year?1 (overall mean 158 ± 14 g C m?2 year?1). The lowest ANPP values were for the youngest and oldest stands, but there was a large range of ANPP for mature stands. Carbon, water and nitrogen cycle simulations with the Biome‐BGC model suggest that disturbance type and frequency, time since disturbance, age‐dependent changes in below‐ground allocation, and increasing atmospheric concentration of CO2 all exert significant control on the net ecosystem exchange of carbon at the two sites. Model estimates of major carbon flux components agree with budget‐based observations to within ± 20%, with larger differences for NEP and for several storage terms. Simulations showed the period of regrowth required to replace carbon lost during and after a stand‐replacing fire (O) or a clearcut (Y) to be between 50 and 100 years. In both cases, simulations showed a shift from net carbon source to net sink (on an annual basis) 10–20 years after disturbance. These results suggest that the net ecosystem production of young stands may be low because heterotrophic respiration, particularly from soils, is higher than the NPP of the regrowth. The amount of carbon stored in long‐term pools (biomass and soils) in addition to short‐term fluxes has important implications for management of forests in the Pacific North‐west for carbon sequestration. 相似文献
6.
A sequential coring approach was used to measure root biomass and production over 1 year in four different communities within the Great Dismal Swamp. A second method, an implanted bag technique, was also used to measure root production, and values were generally lower using this technique. On all sites, fine roots were the most dynamic root component. Both biomass (1,887 g/m2) and production (354–989 g m 2 yr-1) were highest on the mixed hardwood site, the least flooded site, and second highest on the cedar site, the site with the longest duration of soil saturation (1,033 g/m2 and 274–366 g m-2 yr-1). The maple-gum (696 g/m2 and 59–91 g m-2 yr-1) and cypress (824 g/m2 and 68–308 g m-2 yr-1) sites had similarly low amounts of biomass and rates of production. Environmental parameters that influenced production include frequency and duration of flooding, and soil type. Peaks in belowground production were observed on the most productive sites (mixed hardwood and cedar) in summer and late fall-winter; the other two sites exhibited little seasonal variability. The least flooded stand appears to allocate a greater percentage of net primary production belowground than the more extensively flooded stands. The ratio of above- and belowground allocation appears to change in response to a flooding gradient. This has major implications for ecosystem functions as carbon allocation patterns determine the array of litter types generated (leaves vs. roots) which affect decomposition rates and nutrient availability. 相似文献
7.
Fiala K. etHerrera R. (1988): Living and dead belowground biomass and its distribution in some savanna communities in Cuba.—Folia Geobot. Phytotax., Praha, 23: 225–237.— The paper sums up the first results obtained from the study of belowground biomass estimated in natural and anthropic savanna communities in different regions of Cuba at the end of the 1984 rainy season. The percentage of living roots in total root biomass of natural savannas was lower (34–50%) than that in the anthropic savanna stands (68–74%). The total belowground biomass in three savanna stands ranged from 1,073 to 1,257 g. m?2. In the natural savanna stands 433 to 517 g. m?2 of living belowground biomass was found, which was less than in the anthropic savanna stand (745 g. m?2). In all the savanna stands studied, more than 80% of both the total and living belowground biomass were found in the upper 0–0.2 m soil layer. The share of the living biomass in the belowground plant organs varied from 71 to 79%. 相似文献
8.
We compared four types of 30‐year‐old forest stands growing on spoil of opencast oil shale mines in Estonia. The stand types were: (1) natural stands formed by spontaneous succession, and plantations of (2) Pinus sylvestris (Scots pine), (3) Betula pendula (silver birch), and (4) Alnus glutinosa (European black alder). In all stands we measured properties of the tree layer (species richness, stand density, and volume of growing stock), understory (density and species richness of shrubs and tree saplings), and ground vegetation (aboveground biomass, species richness, and species diversity). The tree layer was most diverse though sparse in the natural stands. Understory species richness per 100‐m2 plot was highest in the natural stand, but total stand richness was equal in the natural and alder stands, which were higher than the birch and pine stands. The understory sapling density was lower than 50 saplings/100 m2 in the plantations, while it varied between 50 and 180 saplings/100 m2 in the natural stands. Growing stock volume was the least in natural stands and greatest in birch stands. The aboveground biomass of ground vegetation was highest in alder stands and lowest in the pine stands. We can conclude that spontaneous succession promotes establishment of diverse vegetation. In plantations the establishment of diverse ground vegetation depends on planted tree species. 相似文献
9.
Modelling the limits on the response of net carbon exchange to fertilization in a south-eastern pine forest 总被引:5,自引:0,他引:5
C.-T. Lai G. Katul J. Butnor M. Siqueira D. Ellsworth C. Maier K. Johnsen S. Mckeand & R. Oren 《Plant, cell & environment》2002,25(9):1095-1120
Using a combination of model simulations and detailed measurements at a hierarchy of scales conducted at a sandhills forest site, the effect of fertilization on net ecosystem exchange (NEE) and its components in 6‐year‐old Pinus taeda stands was quantified. The detailed measurements, collected over a 20‐d period in September and October, included gas exchange and eddy covariance fluxes, sampled for a 10‐d period each at the fertilized stand and at the control stand. Respiration from the forest floor and above‐ground biomass was measured using chambers during the experiment. Fertilization doubled leaf area index (LAI) and increased leaf carboxylation capacity by 20%. However, this increase in total LAI translated into an increase of only 25% in modelled sunlit LAI and in canopy photosynthesis. It is shown that the same climatic and environmental conditions that enhance photosynthesis in the September and October periods also cause an increase in respiration The increases in respiration counterbalanced photosynthesis and resulted in negligible NEE differences between fertilized and control stands. The fact that total biomass of the fertilized stand exceeded 2·5 times that of the control, suggests that the counteracting effects cannot persist throughout the year. In fact, modelled annual carbon balance showed that gross primary productivity (GPP) increased by about 50% and that the largest enhancement in NEE occurred in the spring and autumn, during which cooler temperatures reduced respiration more than photosynthesis. The modelled difference in annual NEE between fertilized and control stands (approximately 200 1;g 2;C 3;m?2 y?1) suggest that the effect of fertilization was sufficiently large to transform the stand from a net terrestrial carbon source to a net sink. 相似文献
10.
Biomass and production of two stands with Quercus variabilis Bl. as the dominant species (stands 1 and 3) and one with Q. mongolica Fisch. as the dominant species (stand 2) were investigated in southern Korea. Stands 1 and 3 naturally occurred on sites with southerly aspects while stand 2 naturally occurred on northerly aspects; stand ages were similar for the three stands (36–38 years old). Total above- and belowground biomass including understory vegetation (Mg ha–1) was 108.4 for stand 1, 115.6 for stand 2, and 132.0 for stand 3, respectively. Understory vegetation constituted 17.4% of the total biomass in stand 1 but only 3.7–4.5% in stand 2 and stand 3. Roots constituted 20.1–24.6% of the biomass of the overstory vegetation. Although stand 3 showed the highest total biomass, net production was highest in stand 2 at 12.6 (Mg ha–1 year–1); net production levels for stands 1 and 3 were 11.7 and 11.1 (Mg ha–1 year–1), respectively. It appeared that the differences in site conditions related to aspect influenced the distribution of naturally regenerated oak species within a relatively small area and resulted in differences in biomass and production among the stands. 相似文献
11.
A. Montagnoli M. Terzaghi A. Di Iorio G. S. Scippa D. Chiatante 《Plant biosystems》2013,147(4):1012-1022
Abstract The aim of this study was to investigate the possible effects of coppice conversion to high forest on the beech fine-root systems. We compared the seasonal pattern of live and dead fine-root mass (d < 2 mm), production and turnover in three beech stands that differed in management practices. Tree density was higher in the 40-year-old coppice stand than in the stands that were converted from coppice to high forest in 1994 and 2004, respectively. We found that a reduction in tree density reduced the total fine-root biomass (Coppice stand, 353.8 g m?2; Conversion 1994 stand, 203.6 g m?2; Conversion 2004 stand, 176.2 g m?2) which continued to be characterised by a bimodal pattern with two major peaks, one in spring and one in early fall. Conversion to high forest may also affect the fine-root soil depth distribution. Both fine-root production and turnover rate were sensitive to management practices. They were lower in the Coppice stand (production 131.5 g m?2 year?1; turnover rate 0.41 year?1) than in the converted stands (1994 Conversion stand: production 232 g m?2 year?1, turnover rate 1.06 year?1; 2004 Conversion stand: production 164.2 g m?2 year?1, turnover rate 0.79 year?1). 相似文献
12.
Net primary productivity of two mangrove forest stands on the northwestern coast of Sri Lanka 总被引:2,自引:2,他引:0
Productivity studies were carried out from September, 1985 to August, 1987 in two mangrove stands, i.e. estuarine and island fringing, in Dutch bay, a lagoon situated on the northwestern coast of Sri Lanka. Net above-ground primary productivity was measured by monitoring litterfall and above-ground biomass increment. The average annual rate of litterfall in the estuarine and island-fringing mangrove stands are 588.14 g m–2 (approximately 6 t ha–1) and 407.33 g m–2 (approximately 4 t ha–1) respectively. The average annual rates of above ground woody growth are 614.74 g m–2 (approximately 6 t ha–1) in the estuarine stands and 286.8 g m–2 (approximately 3 t ha–1) in the island-fringing mangrove stands. Hence estuarine mangrove stands record a higher annual rate of above-ground net primary production (NPP; 1207.88 g m–2 or approximately 12 t ha–1) than the fringing mangrove stands (694.22 g m–2); approximately 7 t ha–1). The annual rate of NPP in the water front zones of the stands (1300.47 g m–2 in the estuarine stands and 874.56 g m–2 in the fringing stands) are greater than those in the back-mangrove zones (115.28 g m–2 in the estuarine stands and 513.88 g m–2 in the island-fringing stands). These variations may be attributed to the differences in tidal flushing and influence of freshwater in the two localities. 相似文献
13.
Reiner Zimmermann Ernst- Detlef Schulze‡ Christian Wirth† Ernst-Eckart Schulze† Kyle C. Mcdonald† Natascha N. Vygodskaya‡ Waldemar Ziegler 《Global Change Biology》2000,6(1):25-37
Tree transpiration was measured in 28, 67, 204 and 383‐y‐old uniform stands and in a multicohort stand (140–430 y) of Pinus sylvestris ssp. sibirica Lebed. in Central Siberia during August 1995. In addition transpiration of three codominant trees was monitored for two years in a 130‐y‐old stand. All stands established after fire. Leaf area index (LAI) ranged between 0.6 (28‐y‐old stand) and 1.6 for stands older than 67‐y. Stand xylem area at 1.3 m height increased from 4 cm2 m?2 (28‐y) to 11.5 cm2 m?2 (67‐y) and decreased again to 7 cm2 m?2 in old stands. Above‐ground living biomass increased from 1.5 kg dry weight m?2 (28‐y) to 14 kg dry weight m?2 (383‐y). Day‐to‐day variation of tree transpiration in summer was dependent on net radiation, vapour pressure deficit, and soil water stress. Tree‐to‐tree variation of xylem flux was small and increased with heterogeneity in canopy structure. Maximum rates of xylem flux density followed the course of net radiation from mid April when a constant level of maximum rates was reached until mid September when low temperatures and light strongly reduced flux density. Maximum sap flux density (60 g m?2 s?1) and canopy transpiration (1.5 mm d?1) were reached in the 67‐y stand. Average canopy transpiration of all age classes was 0.72 ± 0.3 mm d?1. Canopy transpiration (E) was not correlated with LAI but related to stand sapwood area SA (E = ? 0.02 + 1.15SA R2) which was determined by stand density and tree sapwood area. 相似文献
14.
Jeffrey M. Klopatek 《Plant and Soil》2007,294(1-2):157-167
Litterfall and fine root production were measured for three years as part of a carbon balance study of three forest stands
in the Pacific Northwest of the United States. A young second-growth Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] stand, a second-growth Douglas-fir with red alder (Alnus rubra Bong.) stand, and an old-growth (∼550 years) Douglas-fir stand were monitored for inputs of carbon and nitrogen into the
soil from litterfall and fine root production, as well as changes in soil C and N. Fine root production and soil nutrient
changes were measured through the use of soil ingrowth bags containing homogenized soil from the respective stands. Litterfall
biomass was greatest in the Douglas-fir-alder stand (527 g m−2 yr−1) that annually returned nearly three times the amount of N as the other stands. Mean residence time for forest floor material
was also shortest at this site averaging 4.6 years and 5.5 years for C an N, respectively. Fine root production in the upper
20 cm ranged from 584 g m−2 in the N rich Douglas-fir-alder stand to 836 g m−2 in the old-growth stand. Fine root production (down to one meter) was always greater than litterfall with a below:above ratio
ranging from 3.73 for the young Douglas-fir stand to 1.62 for the Douglas-fir-alder stand. The below:above N ratios for all
three stands closely approximate those for biomass. Soil changes in both C and N differed by site, but the soil C changes
in the old-growth stand mirrored those obtained in an ongoing CO2 flux study. Results from the soil ingrowth bags strongly suggest that this method provides a simple, but sufficient device
for measuring potential fine root biomass production as well as soil chemical changes. 相似文献
15.
Forest fire dramatically affects the carbon storage and underlying mechanisms that control the carbon balance of recovering ecosystems. In western North America where fire extent has increased in recent years, we measured carbon pools and fluxes in moderately and severely burned forest stands 2 years after a fire to determine the controls on net ecosystem productivity (NEP) and make comparisons with unburned stands in the same region. Total ecosystem carbon in soil and live and dead pools in the burned stands was on average 66% that of unburned stands (11.0 and 16.5 kg C m−2, respectively, P<0.01). Soil carbon accounted for 56% and 43% of the carbon pools in burned and unburned stands. NEP was significantly lower in severely burned compared with unburned stands (P<0.01) with an increasing trend from −125±44 g C m−2 yr−1 (±1 SD) in severely burned stands (stand replacing fire), to −38±96 and +50±47 g C m−2 yr−1 in moderately burned and unburned stands, respectively. Fire of moderate severity killed 82% of trees <20 cm in diameter (diameter at 1.3 m height, DBH); however, this size class only contributed 22% of prefire estimates of bole wood production. Larger trees (> 20 cm DBH) suffered only 34% mortality under moderate severity fire and contributed to 91% of postfire bole wood production. Growth rates of trees that survived the fire were comparable with their prefire rates. Net primary production NPP (g C m−2 yr−1, ±1 SD) of severely burned stands was 47% of unburned stands (167±76, 346±148, respectively, P<0.05), with forb and grass aboveground NPP accounting for 74% and 4% of total aboveground NPP, respectively. Based on continuous seasonal measurements of soil respiration in a severely burned stand, in areas kept free of ground vegetation, soil heterotrophic respiration accounted for 56% of total soil CO2 efflux, comparable with the values of 54% and 49% previously reported for two of the unburned forest stands. Estimates of total ecosystem heterotrophic respiration (Rh) were not significantly different between stand types 2 years after fire. The ratio NPP/Rh averaged 0.55, 0.85 and 1.21 in the severely burned, moderately burned and unburned stands, respectively. Annual soil CO2 efflux was linearly related to aboveground net primary productivity (ANPP) with an increase in soil CO2 efflux of 1.48 g C yr−1 for every 1 g increase in ANPP (P<0.01, r2= 0.76). There was no significant difference in this relationship between the recently burned and unburned stands. Contrary to expectations that the magnitude of NEP 2 years postfire would be principally driven by the sudden increase in detrital pools and increased rates of Rh, the data suggest NPP was more important in determining postfire NEP. 相似文献
16.
Summary Seasonal and total primary productivity was measured for a Carex meadow in southern Quebec, Canada. Forty-five one-meter2 plots were sampled for dry weight biomass, species composition, structure (species density, diversity, height) and soil parameters including macronutrient concentrations (Ca, K, Mg, Na, N, P), pH, organic matter, and water depth. Shoot net productivity and litter decomposition rates were computed for 20-day intervals May–September, inclusive. Relationships between all parameters were examined by principal components analysis.Dominant species included Carex lacustris, C. aquatilis, Calamagrostis canadensis, and Typha angustifolia. For a 130-day growth period, mean shoot net productivity was 6.3 g·m-2· da-1 and terminal standing crop 807 g·m-2. Terminal standing crop was very close to above ground biomass predicted by the Gorham equation based on thermal relations for Carex ecosystems and to total accumulated litter mass (779 g·m-2). Seasonal production showed a strong bimodal pattern with peak productivities in mid-June (15.3 g·m-2·da-1) and mid-July (4.3 g·m-2·da-1). Decomposition of the previous year's litter was 81% complete by late September.Soil fertility, fire incidence, and topographic position were the three most important gradients resolved by principal components analysis. The first component distinguished sediment-rich Typha angustifolia communities near open water from oligotrophic stands of Carex spp. on central areas of the meadow. Production levels correlated closely with extractable soil calcium (r=0.40**) and phosphorus levels (r=0.39**). Species diversity and stem density related inversely to productivity on this component. Fire incidence (component II) had a marked effect on species diversity due to surface scarification and removal of litter mass. Component III was a topographic gradient separating composition, and community structure.Magnesium and sodium levels decreased from upland to open water. Soil phosphorus increased markedly at water's edge related to mineral input by sedimentation. Pattern of N, P, K, and Ca coincided closely with total shoot production and litter mass levels suggesting closed biotic cycles of these elements.A model accounting for species diversity levels in Carex meadow was formulated based on the assumption that high productivity results in competitive species elimination. 相似文献
17.
Recovery of Aboveground Plant Biomass and Productivity After Fire in Mesic and Dry Black Spruce Forests of Interior Alaska 总被引:1,自引:0,他引:1
Michelle C. Mack Kathleen K. Treseder Kristen L. Manies Jennifer W. Harden Edward A. G. Schuur Jason G. Vogel James T. Randerson F. Stuart Chapin III 《Ecosystems》2008,11(2):209-225
Plant biomass accumulation and productivity are important determinants of ecosystem carbon (C) balance during post-fire succession.
In boreal black spruce (Picea mariana) forests near Delta Junction, Alaska, we quantified aboveground plant biomass and net primary productivity (ANPP) for 4 years
after a 1999 wildfire in a well-drained (dry) site, and also across a dry and a moderately well-drained (mesic) chronosequence
of sites that varied in time since fire (2 to ∼116 years). Four years after fire, total biomass at the 1999 burn site had
increased exponentially to 160 ± 21 g m−2 (mean ± 1SE) and vascular ANPP had recovered to 138 ± 32 g m−2 y−1, which was not different than that of a nearby unburned stand (160 ± 48 g m−2 y−1) that had similar pre-fire stand structure and understory composition. Production in the young site was dominated by re-sprouting
graminoids, whereas production in the unburned site was dominated by black spruce. On the dry and mesic chronosequences, total
biomass pools, including overstory and understory vascular and non-vascular plants, and lichens, increased logarithmically
(dry) or linearly (mesic) with increasing site age, reaching a maximum of 2469 ± 180 (dry) and 4008 ± 233 g m−2 (mesic) in mature stands. Biomass differences were primarily due to higher tree density in the mesic sites because mass per
tree was similar between sites. ANPP of vascular and non-vascular plants increased linearly over time in the mesic chronosequence
to 335 ± 68 g m−2 y−1 in the mature site, but in the dry chronosequence it peaked at 410 ± 43 g m−2 y−1 in a 15-year-old stand dominated by deciduous trees and shrubs. Key factors regulating biomass accumulation and production
in these ecosystems appear to be the abundance and composition of re-sprouting species early in succession, the abundance
of deciduous trees and shrubs in intermediate aged stands, and the density of black spruce across all stand ages. A better
understanding of the controls over these factors will help predict how changes in climate and fire regime will affect the
carbon balance of Interior Alaska.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
18.
CREIGHTON M. LITTON MICHAEL G. RYAN† DENNIS H. KNIGHT PETER D. STAHL‡ 《Global Change Biology》2003,9(5):680-696
The effects of fire on soil‐surface carbon dioxide (CO2) efflux, FS, and microbial biomass carbon, Cmic, were studied in a wildland setting by examining 13‐year‐old postfire stands of lodgepole pine differing in tree density (< 500 to > 500 000 trees ha?1) in Yellowstone National Park (YNP). In addition, young stands were compared to mature lodgepole pine stands (~110‐year‐old) in order to estimate ecosystem recovery 13 years after a stand replacing fire. Growing season FS increased with tree density in young stands (1.0 µmol CO2 m?2 s?1 in low‐density stands, 1.8 µmol CO2 m?2 s?1 in moderate‐density stands and 2.1 µmol CO2 m?2 s?1 in high‐density stands) and with stand age (2.7 µmol CO2 m?2 s?1 in mature stands). Microbial biomass carbon in young stands did not differ with tree density and ranged from 0.2 to 0.5 mg C g?1 dry soil over the growing season; Cmic was significantly greater in mature stands (0.5–0.8 mg C g?1 dry soil). Soil‐surface CO2 efflux in young stands was correlated with biotic variables (above‐ground, below‐ground and microbial biomass), but not with abiotic variables (litter and mineral soil C and N content, bulk density and soil texture). Microbial biomass carbon was correlated with below‐ground plant biomass and not with soil carbon and nitrogen, indicating that plant activity controls not only root respiration, but Cmic pools and overall FS rates as well. These findings support recent studies that have demonstrated the prevailing importance of plants in controlling rates of FS and suggest that decomposition of older, recalcitrant soil C pools in this ecosystem is relatively unimportant 13 years after a stand replacing fire. Our results also indicate that realistic predictions and modeling of terrestrial C cycling must account for the variability in tree density and stand age that exists across the landscape as a result of natural disturbances. 相似文献
19.
Earthworm Succession in Afforested Colliery Spoil Heaps in the Sokolov Region, Czech Republic 总被引:2,自引:0,他引:2
Václav Pil 《Restoration Ecology》2001,9(4):359-364
Earthworm communities were studied at six heap sites representing a chronosequence of Alnus glutinosa (black alder) stands (age 3–62 years) and compared with those on an unameliorated heap and in an alder stand (60 years old) on natural soil. Spoil heaps in the open‐cast coal mining area near Sokolov (northwestern Bohemia) were mainly reclaimed using afforestation. No earthworms were found on the virgin heap. Young plots were colonized by euryecious epigeic earthworms (i.e., those living above soil surface), but higher proportions of endogeic species (i.e., soil dwellers), did not appear until after more than 30 years of succession. The density and biomass of earthworms increased from the youngest stand (67 individuals/m2; 5 g/m2) to the older ones (e.g., 407 ind/m2; 13 g/m2 in the 23‐year‐old stand). However, both parameters were low in the oldest stand (35 ind/m2; 3 g/m2), but this may have been the result of extensive soil disturbance. Earthworm populations were often higher in reclaimed sites than in the control alder stand (150 ind/m2; 7 g/m2). However, the community structures were different, with the control being dominated by the litter‐feeding species, Dendrobaena vejdovskyi. 相似文献
20.
Summary The relative allocation of biomass within monospecific stands of Acaena magellanica that vary in level of wind and water stress differ greatly. Populations in January 1983 varied in leaf biomass from 192 to 2373 g wet wt m-2 (1105 to 10023 kJ m-2) Inflorescences were not produced at either of these extremes of leaf biomass. In two populations with intermediate levels of leaf biomass (597 and 640 g wet wt m-2, 3185 and 2664 kJ m-2), inflorescent biomass was 104 and 273 g wet wt m-2 (385 and 1127 kJ m-2). The relative allocation to sexual reproduction is thus not constant in A. magellanica. The levels of energy in the leaves and inflorescences did not differ greatly despite differences in proximate composition. 相似文献