Carbon bio‐sequestration within the phytoliths of economic bamboo species

The rates of carbon bio‐sequestration within silica phytoliths of the leaf litter of 10 economically important bamboo species indicates that (a) there is considerable variation in the content of carbon occluded within the phytoliths (PhytOC) of the leaves between different bamboo species, (b) this variation does not appear to be directly related to the quantity of silica in the plant but rather the efficiency of carbon encapsulation by the silica. The PhytOC content of the species under the experimental conditions ranged from 1.6% to 4% of the leaf silica weight. The potential phytolith carbon bio‐sequestration rates in the leaf‐litter component for the bamboos ranged up to 0.7 tonnes of carbon dioxide (CO₂) equivalents (t‐e‐CO₂) ha^?1 yr^?1 for these species. Assuming a median phytolith carbon bio‐sequestration yield of 0.36 t‐e‐CO₂ ha^?1 yr^?1, the global potential for bio‐sequestration via phytolith carbon (from bamboo and/or other similar grass crops) is estimated to be ～1.5 billion t‐e‐CO₂ yr^?1, equivalent to 11% of the current increase in atmospheric CO₂. The data indicate that the management of vegetation such as bamboo forests to maximize the production of PhytOC has the potential to result in considerable quantities of securely bio‐sequestered carbon.     

Radiocesium Distribution in Bamboo Shoots after the Fukushima Nuclear Accident

The distribution of radiocesium was examined in bamboo shoots, Phyllostachys pubescens, collected from 10 sites located some 41 to 1140 km from the Fukushima Daiichi nuclear power plant, Japan, in the Spring of 2012, 1 year after the Fukushima nuclear accident. Maximum activity concentrations for radiocesium ¹³⁴Cs and ¹³⁷Cs in the edible bamboo shoot parts, 41 km away from the Fukushima Daiichi plant, were in excess of 15.3 and 21.8 kBq/kg (dry weight basis; 1.34 and 1.92 kBq/kg, fresh weight), respectively. In the radiocesium-contaminated samples, the radiocesium activities were higher in the inner tip parts, including the upper edible parts and the apical culm sheath, than in the hardened culm sheath and underground basal parts. The radiocesium/potassium ratios also tended to be higher in the inner tip parts. The radiocesium activities increased with bamboo shoot length in another bamboo species, Phyllostachys bambusoides, suggesting that radiocesium accumulated in the inner tip parts during growth of the shoots.     

Biomass production by alders on four abandoned agricultural soils in Québec

The production of aboveground tissue of three alder species (Alnus crispa (Ait.) Pursh,A. rugosa (Du Roi) Spreng. andA. glutinosa (L) Gaertn.) on four sites ranged from 0.4 t ha^–1 yr^–1 to 4.0 t ha^–1 yr^–1 after four growing seasons. Large differences were observed among the four sites studied and among species. Soil nutrient levels affected the biomass production and foliar symptoms of P and Mg deficiency occurred withA. crispa andA. rugosa. Because of their poor aboveground biomass production (0.4–1.4 t ha^–1 yr^–1),A. crispa andA. rugosa should be used mainly as nurse trees. For its higher potential for biomass production (up to 4.0 t ha^–1 yr^–1), and its apparent higher ability to use P and Mg on deficient sites,A. glutinosa should be used preferably toA. crispa andA. rugosa for the production of biomass.     

Effects of removal of organic matter on the productivity of heathlands

Abstract. Effects of milling, mowing and sod cutting on productivity in a Deschampsia grass heath and a Molinia-Deschampsia grass heath were studied from 1977 to 1986. The sum of above-ground biomass, litter and accumulated humified matter (TOM) in both types was ca. 70 ton/ha and the primary productivity 3–5 ton ha^-1yr^-1. Mulching did not affect the annual production. Sod cutting reduced the productivity to 1–2 ton ha^-1yr^-1; on the Molinia-Deschampsia site this reduction lasted for at least a decade, while the Deschampsia heath started to recover from sod cutting soon and increased in productivity again. Annual mowing both with and without removal of hay reduced the production as well, particularly on the Molinia-Deschampsia heath. Lower production was either the result of phosphorus depletion - Molinia-Deschampsia site - or nitrogen depletion - Deschampsia site. In the mowing treatments there was also a depletion of carbohydrate reserves.     

Biomass and net production in a bambooPhyllostachys bambusoides stand

Biomass and net production were measured in aPhyllostachys bambusoides stand in Kyoto Prefecture, central Japan, which had carried out gregarious flowering in 1969 and has been recovering vegetatively. The culm density fluctuated around an average value of 12 040 ha⁻¹ during the research period (1985–91). Annual recruirment and mortality rates of culms were 1340 and 1133 ha⁻¹, respectively. The mean diameter at breast height increased from 7.28 cm in 1985 to 8.68 cm in 1991, and the biomass of culms increased from 71.3 to 111.6t ha⁻¹ over the same time period. Branch and leaf biomasses were almost constant, 10.0 and 9.4t ha⁻¹ on average, respectively. The leaf area index of the stand was 11.6 ha ha⁻¹, which is one of the largest values found in Japanese forests. The belowground biomass of 32.6t ha⁻¹ for rhizomes and 14.8t ha⁻¹ for fine roots resulted in the smaller ratio of aboveground parts to the root system (2.38) than those determined for forest stands. The amount of litterfall, excluding culms and large branches, was large (9.13t ha⁻¹ year⁻¹), corresponding to those measured in equatorial stands. The aboveground net production was 24.6t ha⁻¹ year⁻¹, larger than the average value reported for forest stands under similar weather conditions.     

Allocation of carbon in a mature eucalypt forest and some effects of soil phosphorus availability

Pools and annual fluxes of carbon (C) were estimated for a mature Eucalyptus pauciflora (snowgum) forest with and without phosphorus (P) fertilizer addition to determine the effect of soil P availability on allocation of C in the stand. Aboveground biomass was estimated from allometric equations relating stem and branch diameters of individual trees to their biomass. Biomass production was calculated from annual increments in tree diameters and measurements of litterfall. Maintenance and construction respiration were calculated for each component using equations given by Ryan (1991a). Total belowground C flux was estimated from measurements of annual soil CO₂ efflux less the C content of annual litterfall (assuming forest floor and soil C were at approximate steady state for the year that soil CO₂ efflux was measured). The total C content of the standing biomass of the unfertilized stand was 138 t ha^-1, with approximately 80% aboveground and 20% belowground. Forest floor C was 8.5 t ha^-1. Soil C content (0–1 m) was 369 t ha^-1 representing 70% of the total C pool in the ecosystem. Total gross annual C flux aboveground (biomass increment plus litterfall plus respiration) was 11.9 t ha^-1 and gross flux belowground (coarse root increment plus fine root production plus root respiration) was 5.1 t ha^-1. Total annual soil efflux was 7.1 t ha^-1, of which 2.5 t ha^-1 (35%) was contributed by litter decomposition.The short-term effect of changing the availability of P compared with C on allocation to aboveground versus belowground processes was estimated by comparing fertilized and unfertilized stands during the year after treatment. In the P-fertilized stand annual wood biomass increment increased by 30%, there was no evidence of change in canopy biomass, and belowground C allocation decreased by 19% relative to the unfertilized stand. Total annual C flux was 16.97 and 16.75 t ha^-1 yr^-1 and the ratio of below- to aboveground C allocation was 0.43 and 0.35 in the unfertilized and P-fertilized stands, respectively. Therefore, the major response of the forest stand to increased soil P availability appeared to be a shift in C allocation; with little change in total productivity. These results emphasise that both growth rate and allocation need to be estimated to predict changes in fluxes and storage of C in forests that may occur in response to disturbance or climate change.     

Effects of High Nutrient Supply on the Growth of Seven Bamboo Species

Over the last decade, bamboo has emerged as an interesting plant for the treatment of various polluted waters using plant-based wastewater treatment systems. In these systems, nitrogen and phosphorous concentrations in wastewater can exceed plant requirements and potentially limit plant growth. The effects of two nutrient rates on the growth of seven bamboo species were assessed in a one-year experiment: Dendrocalamus strictus, Thyrsostachys siamensis, Bambusa tuldoides, Gigantochloa wrayi, Bambusa oldhamii, Bambusa multiplex and Bambusa vulgaris. Nutrient rates were applied with a 20:20:20 NPK fertilizer as 2.6 and 13.2 t.ha.yr^?1NPK to three-year-old bamboo planted in 70 L containers. Morphological characters, photosynthetic responses, and NPK content in bamboo tissues were investigated. Under high-nutrient supply rate, the main trend observed was an increase of culm production but the culms’ diameters were reduced. For the seven species, the aboveground biomass yield tended to increase with high-nutrient rate. Increasing in nutrient rates also improved the photosynthetic activity which is consistent with the increase of nitrogen and phosphorus contents measured in plant tissues. All the bamboo species tested appears suitable for wastewater treatment purposes, but the species Bambusa oldhamii and Gigantochloa wrayi showed the higher biomass yield and nutrient removal.     

Carbon balance of a tropical savanna of northern Australia

Through estimations of above- and below-ground standing biomass, annual biomass increment, fine root production and turnover, litterfall, canopy respiration and total soil CO₂ efflux, a carbon balance on seasonal and yearly time-scales is developed for a Eucalypt open-forest savanna in northern Australia. This carbon balance is compared to estimates of carbon fluxes derived from eddy covariance measurements conducted at the same site. The total carbon (C) stock of the savanna was 204±53 ton C ha^–1, with approximately 84% below-ground and 16% above-ground. Soil organic carbon content (0–1 m) was 151±33 ton C ha^–1, accounting for about 74% of the total carbon content in the ecosystem. Vegetation biomass was 53±20 ton C ha^–1, 39% of which was found in the root component and 61% in above-ground components (trees, shrubs, grasses). Annual gross primary production was 20.8 ton C ha^–1, of which 27% occurred in above-ground components and 73% below-ground components. Net primary production was 11 ton C ha^–1 year^–1, of which 8.0 ton C ha^–1 (73%) was contributed by below-ground net primary production and 3.0 ton C ha^–1 (27%) by above-ground net primary production. Annual soil carbon efflux was 14.3 ton C ha^–1 year^–1. Approximately three-quarters of the carbon flux (above-ground, below-ground and total ecosystem) occur during the 5–6 months of the wet season. This savanna site is a carbon sink during the wet season, but becomes a weak source during the dry season. Annual net ecosystem production was 3.8 ton C ha^–1 year^–1.     

Relationship between C:N/C:O Stoichiometry and Ecosystem Services in Managed Production Systems

Land use and management intensity can influence provision of ecosystem services (ES). We argue that forest/agroforestry production systems are characterized by relatively higher C:O/C:N and ES value compared to arable production systems. Field investigations on C:N/C:O and 15 ES were determined in three diverse production systems: wheat monoculture (C_wheat), a combined food and energy system (CFE) and a beech forest in Denmark. The C:N/C:O ratios were 194.1/1.68, 94.1/1.57 and 59.5/1.45 for beech forest, CFE and C_wheat, respectively. The economic value of the non-marketed ES was also highest in beech forest (US$ 1089 ha^-1 yr^-1) followed by CFE (US$ 800 ha^-1 yr^-1) and C_wheat (US$ 339 ha^-1 yr^-1). The combined economic value was highest in the CFE (US$ 3143 ha^-1 yr^-1) as compared to the C_wheat (US$ 2767 ha^-1 yr^-1) and beech forest (US$ 2365 ha^-1 yr^-1). We argue that C:N/C:O can be used as a proxy of ES, particularly for the non-marketed ES, such as regulating, supporting and cultural services. These ES play a vital role in the sustainable production of food and energy. Therefore, they should be considered in decision making and developing appropriate policy responses for land use management.     

Structure and dynamics of a tropical dry forest in Ghana

Forest under low rainfall (averaging 745 mm yr^-1) on the Shai Hills in S.E. Ghana has redeveloped following cessation of farming in the 1890s. Forest stature is low, with a canopy at about 11 m, principally of three species, Diospyros abyssinica, D. mespiliformis and Millettia thonningii. Drypetes parvifolia and Vepris heterophylla are common understorey trees. Twelve species of woody liane were recorded. Species of thicket vegetation in the area were also present at low density. Most species are evergreen.Tree mortality averaged 2.3% yr^-1 and exceeded recruitment (1.5% yr^-1). Differences between species in mortality and recruitment were pronounced: canopy species showed a small decline in density; understorey species increased markedly and the thicket species declined. Seed production was very variable, but seedling establishment was very poor for all species. Seedling mortality was high (11% yr^-1) especially for small seedlings. These population trends probably represent the latter stages of succession of forest regrowth after farming about 100 years ago.Compared with tropical rain forest, Shai Hills forest has similar relative tree diameter growth (1–3.5% yr^-1), mortality and recruitment rates, and small-litter fall (5.52 t ha^-1 yr^-1).Shai Hills forest differs from rain forest by its short stature, relatively few (evergreen) tree species, poor regeneration from seed, high soil nutrient status and low rainfall. Similar forests have been reported in east Africa and in parts of New Guinea.Abbreviations dbh diameter at breast height (1.3 m) - gbh girth at breast height died May 1984     

Savanna fires and their impact on net ecosystem productivity in North Australia

Savannas comprise a large area of the global land surface and are subject to frequent disturbance through fire. The role of fire as one of the primary natural carbon cycling mechanisms is a key issue in considering global change feedbacks. The savannas of Northern Australia burn regularly and we aimed to determine their annual net ecosystem productivity (NEP) and the impact of fire on productivity. We established a long‐term eddy covariance flux tower at Howard Springs, Australia and present here 5 years of data from 2001 to 2005. Fire has direct impacts through emissions but also has indirect effects through the loss of productivity due to reduced functional leaf area index and the carbon costs of rebuilding the canopy. The impact of fire on the canopy latent energy exchange was evident for 40 days while the canopy was rebuilt; however, the carbon balance took approximately 70 days to recover. The annual fire free NEP at Howard Springs was estimated at −4.3 t C ha⁻¹ yr⁻¹ with a range of −3.5 to −5.1 t C ha⁻¹ yr⁻¹ across years. We calculated the average annual indirect fire effect as +0.7 t C ha⁻¹ yr⁻¹ using a neural network model approach and estimated average emissions of fine and coarse fuels as +1.6 t C ha⁻¹ yr^‐1. This allowed us to calculate a net biome production of −2.0 t C ha⁻¹ yr^‐1. We then partitioned this remaining sink and suggest that most of this can be accounted for by woody increment (1.2 t C ha⁻¹ yr^‐1) and shrub encroachment (0.5 t C ha⁻¹ yr^‐1). Given the consistent sink at this site, even under an almost annual fire regime, there may be management options to increase carbon sequestration by reducing fire frequency.     

Production of Carbon Occluded in Phytolith Is Season-Dependent in a Bamboo Forest in Subtropical China

Carbon (C) occluded in phytolith (PhytOC) is a stable form of C; when PhytOC is returned to the soil through litterfall it is stored in the soil which can be an effective way for long-term C sequestration. However, few estimates on the rate of PhytOC input to the soil are available. To better understand the seasonal dynamics of PhytOC production and the annual rate of stable C sequestration through PhytOC input, we quantified the monthly litterfall, phytolith and PhytOC return to the soil over a year in a typical Lei bamboo (Phyllostachys praecox) forest in subtropical China. The monthly litterfall ranged between 14.81 and 131.18 g m⁻², and the phytolith concentration in the monthly litterfall samples ranged between 47.21 and 101.68 g kg⁻¹ of litter mass, with the PhytOC concentration in the phytolith ranged between 29.4 and 44.9 g kg⁻¹ of phytolith, equivalent to 1.8–3.6 g kg⁻¹ of PhytOC in the litterfall (based on litterfall dry mass). The amount of phytolith input to the soil system was 292.21±69.12 (mean±SD) kg ha⁻¹ yr⁻¹, sequestering 41.45±9.32 kg CO₂−e ha⁻¹ yr⁻¹ of C in the studied Lei bamboo forest. This rate of C sequestration through the formation of PhytOC found in this study falls within the range of rates for other grass-type species reported in the literature. We conclude that return of C occluded in phytolith to the soil can be a substantial source of stable soil C and finding means to increase PhytOC storage in the soil should be able to play a significant role in mitigating the rapidly increasing atmospheric CO₂ concentration.     

Changes in ecosystem functioning after replacement of forest by Lantana shrubland in Kumaun Himalaya

Abstract. Lantana camara shrubland is compared with the adjacent Quercus leucotrichophora and Pinus roxburghii forests to understand changes occurring in net primary productivity and nutrient cycling, as a consequence of degradation of these forests. The total net primary productivity of Lantana camara shrubland was 17 t ha^-1 yr^-1, which is similar to the values reported for forests: 16 - 21 t ha^-1 yr^-1. Total nutrient content (N, P) in the soil in the L. camara shrubland: 2932 kg ha^-1 N and 111 kg ha^-1 P, was lower than that of the forest soils.     

Estimating above-ground biomass and production in mangrove communities of Biscayne National Park,Florida (U.S.A.)

Total above-ground production isusually estimated by a combination of allometry andlitter collection. However, in coastal sites that aretidally influenced, or in juvenile or dwarf forestswhere the crown bases of dominant individuals maybegin within a few decimeters of ground level,estimates of community leaf production that depend onlitter collection may not be feasible. Thus, in thispaper, we present 1) allometric equations that allowaccurate estimation of total above-ground biomass ofthree mangrove species (Rhizophora mangle, Laguncularia racemosa, and Avicennia germinans)in very small to medium size classes, and 2) analternative method of estimating total above-groundproduction that overcomes the limitations of littercollection. The method we employ to estimate mangroveproductivity is an adaptation for woody plantcommunities of a procedure introduced by Dai andWeigert (1996) for grasslands. It incorporates adetailed census of all individuals within fixedsampling plots, along with periodic observations ofmarked leaf cohorts. The method allows the comparisonof biomass allocation patterns among forests thatdiffer widely in physiognomy and physiographicsetting.The method was applied to a South Florida fringemangrove forest in the early stages of recovery fromHurricane Andrew (August 1992), and an adjacent dwarfforest which was not substantially damaged by thestorm. Total above-ground production in the fringeforest from July 1996 through June 1997 was about 3times higher than dwarf forest production,26.1 Mg·ha^-1·yr^-1 vs.8.1 Mg·ha^-1·yr^-1, respectively. Furthermore, when compared to the dwarf forest, fringeproduction rates were approximately eight, six, six,and two times as high as dwarf forest rates forproproots, branches, stems, and leaves, respectively. Calculations of leaf production were based on mean redmangrove leaf longevities that ranged from about 189days to 281 days, depending on cohort and site.Repeated measures analysis of variance indicated thatleaf life spans did not differ significantly betweendwarf and fringe forests, but did differ among leafcohorts.Based on reported values for similar mangrove forests,the method provided reasonable estimates ofabove-ground biomass and production, while furnishingrelevant auxiliary information on spatial and temporalvariation in leaf demographic patterns. Furthermore,the partitioning of annual production between woodytissues and leaves followed the reported trend in mostforest ecosystems.     

Production of brook charr and ouananiche in a large rapid,tributary of the Caniapiscau River,northern Quebec

Synopsis The age structures of brook charr (Salvelinus fontinalis) and ouananiche (Salmo salar) stocks inhabiting a large rapid the river Méo, tributary to the Caniapiscau River were used to compare population stability and production of these species in north central Quebec. The brook chart stock was stable whereas ouananiche showed considerable variation in year class strength. Stock estimates were not significantly different for the two species although the brook charr estimate was 1.5 that of the ouananiche. Production estimates differed by a greater margin because of different growth patterns. Brook chair production was estimated at 19.4 kg ha⁻¹ yr⁻¹. Above age 2+ it was 11.4 kg ha⁻¹ yr⁻¹ which compares with 4.8 kg ha⁻¹ yr⁻¹ for the same age groups of ouananiche.     

LITTER NUTRIENT CONTENT AND PRODUCTION IN THE GREAT DISMAL SWAMP

Litter production was studied in the Great Dismal Swamp, Virginia in four plant communities which differ primarily in species composition and flooding regime. Greatest leaf deposition occured in the more flooded communities, maple-gum (Acer-Nyssa) with 536 gm^-2 yr^-1 and cypress (Taxodium distichum (L.) Richard) with 528 gm^-2 yr^-1, followed by the cedar (Chamaecyparis thyoides (L.) BSP) and mixed hardwood (Quercus-Acer-Nyssa-Liquidambar) communities, with 506 gm^-2 yr^-1 and 455 gm^-2 yr^-1, respectively. Apparently periodic flooding promotes production. Peaks occurring in October and November corresponded to autumn leaf fall, while peaks in January and May were due to some leaf litter combined with a large amount of woody litter. Litter nutrient concentrations were higher, except for Ca, in the most abundant species (cypress and water gum) in the frequently flooded cypress community. Higher leaf fall rates and litter nutrient concentrations resulted in greater nutrient deposition in the cypress and maple-gum communities.     

Bio‐mitigation of carbon following afforestation of abandoned salinized farmland

As the global demand for food continues to increase, the displacement of food production by using agricultural land for carbon mitigation, via either carbon sequestration, bioenergy or biofuel is a concern. An alternative approach is to target abandoned salinized farmland for mitigation purposes. Australia, for example, has 17 million ha of farmland that is already or could become saline. At a representative, salinized, low rainfall (350 mm yr^?1) site at Wickepin, Western Australia, we demonstrate that afforestation can mitigate carbon emissions through either providing a feedstock for bioenergy or second generation biofuel production and produce salt‐tolerant fodder for livestock. A range of factors markedly affect this mitigation. These include hydrological conditions such as salinity, site factors such as slope position and soil properties and a range of silvicultural factors such as species, planting density and age of the planting. High density (2000 stems ha^?1) plantings of Eucalyptus occidentalis Endl. produced a mean total biomass of 4.6 t ha^?1 yr^?1 (8.5 t CO₂‐e ha^?1 yr^?1) averaged over 8 years. Atriplex nummularia Lindl. produced a mean total biomass of 3.8 t ha^?1 yr^?1 (6.9 t CO₂‐e ha^?1 yr^?1) averaged over 4 years and approximately 1.9 t ha^?1 yr^?1 of edible dry matter annually to 8 years of age. With differences in salt tolerance between E. occidentalis and A. nummularia, we propose an integrated approach to treating salinized sites that takes salinity gradients into account, replicates natural wetland ecosystems and produces both fodder and biomass. Continued mitigation is expected as the stands mature, assuming that growth is not affected by the accumulation of salt in the soil profile. Such carbon mitigation could potentially be applied to salinized farmland globally, and this could thus represent a major contribution to global carbon mitigation without competing with food production.     

Culm recruitment,dry matter dynamics and carbon flux in recently harvested and mature bamboo savannas in the Indian dry tropics

Culm recruitment, standing crop biomass, net production and carbon flux were estimated in mature (5 years after last harvest) and recently harvested bamboo (Dendrocalamus strictus (Roxb.) Nees) savanna sites in the dry tropics. During the 2 study years bamboo shoot recruitment was 1711–3182 and 1432–1510 shoots ha⁻¹ in harvested and mature sites, respectively. Corresponding shoot mortality was 66–93% and 62–69%, respectively. Total biomass was 34.9 t ha⁻¹ at the harvested site and 47.4 t ha⁻¹ at the mature site. Harvesting increased the relative contribution of belowground bamboo biomass. Annual litter input to soil was 2.7 and 5.9 t ha⁻¹ year⁻¹ at the harvested and mature sites, respectively. The bulk of the annual litterfall (78–88%) occurred in the cool dry season (November to February). The mean litter mass on the savanna floor ranged from 3.1 to 3.3 t ha⁻¹; at the harvested site wood litter contributed 70% of the litter mass and at the mature site leaves formed 77% of the litter mass. The mean total net production (TNP) for the two annual cycles was 15.8 t ha⁻¹ year⁻¹ at the harvested site and 19.3 t ha⁻¹ year⁻¹ at the mature site. Nearly half (46–57%) of the TNP was allocated to the belowground parts. Short lived components (leaves and fine roots) contributed about four-fifths of the net production of bamboo. Total carbon storage in the system was 64.4 t ha⁻¹ at the harvested site and 75.4 t ha⁻¹ at the mature site, of which 23–28% was distributed in vegetation, 2% in litter and 70–75% in soil. Annual net carbon deposition was 6.3 and 8.7 t ha⁻¹ year⁻¹ at harvested and mature sites, respectively.     

毛竹种群向常绿阔叶林扩张的细根策略

为了探讨毛竹(Phyllostachys pubescens)种群向常绿阔叶林扩张的根系策略, 该文采用根钻法和内生长法, 在江西大岗山选取毛竹林与阔叶林的交错区——竹阔界面(bamboo-broad-leaved forest interface), 并垂直于界面连续设置毛竹林、毛竹与阔叶树的混交林(以下简称为竹阔混交林)、常绿阔叶林3种样地, 比较分析其细根的空间分布格局、比根长、根长密度、生长速率和周转率等指标。结果表明: 毛竹林细根生物量(1201.60 g·m^-2) >竹阔混交林(601.18 g·m ^-2) >常绿阔叶林(204.88 g·m ^-2); 在毛竹与阔叶树竞争的混交林中, 毛竹细根分布趋向于上层土壤(与毛竹林细根相比), 且其比根长也显著增加, 平均增幅高达123.42%, 总根长密度比阔叶树大2.1倍; 同时, 毛竹细根生长速率和周转率均高于阔叶树。这些结果说明毛竹可通过广布、精准、灵活、快速等细根竞争策略, 提高资源获取能力, 实现种群扩张。     

Above- and belowground organic matter storage and production in a tropical pine plantation and a paired broadleaf secondary forest

The distribution of tree biomass and the allocation of organic matter production were measured in an 11-yr-old Pinus caribaea plantation and a paired broadleaf secondary forest growing under the same climatic conditions. The pine plantation had significantly more mass aboveground than the secondary forest (94.9 vs 35.6 t ha^-1 for biomass and 10.5 vs 5.0 t ha^{-1 for litter}), whereas the secondary forest had significantly more fine roots (⩽2 mm diameter) than the pine plantation (10.5 and 1.0 t ha^-1, respectively). Standing stock of dead fine roots was higher than aboveground litter in the secondary forest. In contrast, aboveground litter in pine was more than ten times higher than the dead root fraction. Both pine and secondary forests had similar total organic matter productions (19.2 and 19.4 t ha^-1 yr^-1, respectively) but structural allocation of that production was significantly different between the two forests; 44% of total production was allocated belowground in the secondary forest, whereas 94% was allocated aboveground in pine. The growth strategies represented by fast growth and large structural allocation aboveground, as for pine, and almost half the production allocated belowground, as for the secondary forest, illustrate equally successful, but contrasting growth strategies under the same climate, regardless of soil characteristics. The patterns of accumulation of organic matter in the soil profile indicated contrasting nutrient immobilization and mineralization sites and sources for soil organic matter formation.