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1.
In order to assess the possibility of root competition in agroforestry, the vertical distribution of fine roots (< 2 mm in
diameter) of five tree species in pure two-year-old stands was compared to that of mature maize.Cassia siamea, Eucalyptus tereticornis, Leucaena leucocephala andProsopis chilensis had a rooting pattern similar to that of maize, i.e. a slow decline in fine root mass from 0–100 cm soil depth.Eucalyptus camaldulensis had its roots evenly distributed down to 100 cm. On an average, the fine root biomass of the tree species was roughly twice
as that of the maize. We conclude that the studied tree species are likely to compete with maize and other crops with a similar
rooting pattern for nutrients and water. 相似文献
2.
Observations on the growth performance, rooting behaviour and distribution of fine roots of five tree species viz., Bauhinia purpurea, Grewia optiva, Eucalyptus tereticornis, Leucaena leucocephala and Ougeinia oojeinensis (Family: Papilionaceae) are being presented here. Roots were exposed at the time of planting, 6 months, 16 months, and 28 months after planting. Total root weight and root volume were highest in Eucalyptus tereticornis and lowest in Bauhinia purpurea. Major part of the root system confined within 90–120 cm soil depth in case of Bauhinia purpurea, Grewia optiva and Leucaena leucocephala but Eucalyptus tereticornis and Ougeinia oojeinensis strike their roots to deeper depths. Bauhinia purpurea had its roots evenly distributed down to 120 cm. In general, the vertical distribution of fine roots (< 2 mm in diameter) of the five species indicate that more the depth, fewer the number of roots. The observations on soil binding capacity, indicated that Ougeinia oojeinensis had the maximum and Eucalyptus tereticornis had the minimum binding value. Due to leaf shading and other litter fall significant increase of nutrient components in soils under the tree canopies has been observed. The study indicates that bulk of the roots of the five tree species are found near the surface, but observation on soil moisture and nutrient content does not indicate variation under the tree canopies and in open, hence there may not be root competition in initial years of plantation.Authorised for publication by the Institute as contribution No.3311/239/89. 相似文献
3.
Fine-root dynamics (diameter < 2.0 mm) were studied on-farm in associations of Coffea arabica with Eucalyptus deglupta or Terminalia ivorensis and in a pseudo-chronosequence of C. arabica-E. deglupta associations (two, three, four and five years old). Coffee plants were submitted to two fertilisation types. Cores were taken
in the 0–40 cm soil profile two years after out-planting and subsequently in the following year in depth layers 0–10 and 10–20
cm, during and at the end of the rainy season, and during the dry season. Fine root density of coffee and timber shade trees
was greater in the coffee fertilisation strip as compared to unfertilised areas close to the plants or in the inter-rows.
Coffee fine roots were more evenly distributed in the topsoil (0–20 cm) whereas tree fine roots were mostly found in the first
10 cm. Although the two tree species had approximately the same fine root length density, lower coffee / tree fine root length
density ratios in T. ivorensis suggest that this shade tree is potentially a stronger competitor with coffee than E. deglupta. Coffee and tree fine root length density for 0–10 cm measured during the rainy season increased progressively from two to
five-year-aged associations and coffee fine root length density increased relatively more than E. deglupta fine root length density in the four and five-year-aged plantations suggesting that contrary to expectations, coffee fine
roots were displacing tree fine roots. 相似文献
4.
Comparison of minirhizotron and soil core methods for quantifying root biomass in a temperate alley cropping system 总被引：1，自引：0，他引：1
A study was carried out in southern Indiana, USA with the objective of comparing soil core sampling and the minirhizotron
technique in quantifying fine root biomass and root distribution patterns in an alley cropping system with black walnut (Juglans nigra L.), northern red oak (Quercus rubra L.) and maize (Zea mays L.). Spatial variation in tree rooting pattern was investigated prior to planting maize. Tree fine root biomass was quantified
at distances of 0, 1.1, 2.3, 3.5, and 4.3 m where 0 m represents the tree row and 4.3 m represents the middle of the alley.
Root samples were collected to a depth of 90 cm using a hydraulic auger. Maize rooting pattern was determined 65 days after
planting to the same depth. Using plexiglass access tubes installed near the actual soil core locations and a minirhizotron
camera root images were recorded on a VHS tape. These images were later analyzed using a raster based GIS software (ERDAS-IMAGINE).
Regression analysis revealed significant relationships between root surface area measurements from minirhizotron observations
and fine root biomass data from soil coring for all species. Predicted fine root biomass data were also in close agreement
with actual fine root biomass for all species examined. Maize root biomass was slightly, but not significantly, underestimated
by the minirhizotron technique in the top 30 cm soil layer. No significant underestimation or overestimation of root biomass
in surface or deeper soil layers was observed for the tree species. The results indicate that minirhizotron can be used in
quantifying fine root biomass if site and species specific predictive models can be developed.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
5.
A major constrait to alley cropping is the competition of tree or shrub roots with those of companion food crops for available water and nutrients in the topsoil. Root distribution patterns of Acioa barteri, Alchornea cordifolia, Cassia siamea and Gmelina arborea grown on an acid Ultisol at Onne in the humid forest zone of southeastern Nigeria were examined to a depth of 120 cm and laterally to 200 cm from the tree trunk to study the suitability of the species for alley cropping. The four woody species have roots throughout the soil profile examined but differ in the concentration of roots both laterally and vertically. Alchornea cordifolia, Cassia siamea and Gmelina arborea, in spite of higher underground biomass production, most of their fine roots (<2 mm diameter) were in the top 20 cm of the soil. This soil layer had 73%, 76%, and 74% of the total Alchornea cordifolia, Cassia siamea, and Gmelina arborea fine roots in the profile examined, respectively. Such root systems would compete with food crops for nutrients and moisture in the surface soil. Alchornea cordifolia and Gmelina arborea have many large woody roots in the surface soil which will make any tillage operation or seedbed preparation difficult. Acioa barteri in contrast, has the desirable rooting system with fewer fine roots in the surface soil (49%), and roots that are concentrated close to tree trunk and decrease markedly away from the tree base. In addition, Acioa barteri roots penetrate deeper soil horizons and can result in more efficient nutrient cycling from these layers, and reduced competition with shallow-rooted food crops. The rooting distribution patterns of Acioa barteri indicated that the species is a promising alley shrub in acid soils of the humid forest ecology. Therefore, consideration of rooting characteristics of potential tree/shrub species is recommended for the development of agroforestry systems such as alley cropping.IITA Journal Paper No: 91:/JA/24. 相似文献
6.
The present study deals with root architecture of 6-year-old trees of 9 indigenous and 3 exotic species growing in arid climate of north-western India. Observations, made on excavated root systems (3 tree replicates of each species) showed large variation in horizontal and vertical spread of roots. In Morus alba, Melia azedarach and Populus deltoides, the roots were confined to 80 cm, while in Prosopis cineraria, Acacia nilotica and Eucalyptus tereticornis, roots penetrated more deeply to 233 cm. The number of total roots ranged from 103 in Acacia catechu to 1932 in Eucalyptus tereticornis, and 62 to 80% of the roots were less than 2 mm in diameter. The primary roots were more horizontal than the secondary roots. The total root biomass varied from 2.2 kg in Acacia catechu to 30.6 kg–1 tree in Populus deltoides, and top 30 cm soil contained 42 to 78% of the total biomass. The implications of the results are discussed in the context of the ecological niche of the species, and its usefulness in agroforestry systems. 相似文献
7.
Patterns of fine root biomass, production, and distribution were estimated for pure stands and mixtures of three-year-old loblolly pine (Pinus taeda L.) with red maple (Acer rubrum L.) or black locust (Robinia pseudoacacia L.) on the Virginia Piedmont to determine the role of fine roots in interference between pine and hardwood tree species. Estimates were based on amounts of live and dead fine roots separated from monthly core samples during the third growing season after planting. Live and dead fine root biomass and production varied by species, but mixtures of loblolly pine and black locust generally had greater fine root biomass and fine root production than pure stands or loblolly pine-red maple mixtures. Hardwood species had greater live fine root biomass per tree in mixtures with pine compared to pure stands. Greater live fine root biomass in pine-locust stands may be attributed to differential utilization of the soil volume by fine roots of these species. For all stands, approximately 50% of live five root biomass was located in the upper 10 cm of soil. 相似文献
8.
Biomass and production of fine and coarse roots of trees under agrisilvicultural practices in north-east India 总被引：1，自引：0，他引：1
An understanding of the rooting pattern of tree species used in agroforestry systems is essential for the development and management of systems involving them. Seasonal variation, depth wise and lateral distribution of biomass in roots of different diameter classes and their annual production were studied using sequential core sampling. The investigations were carried out in four tree species under tree only and tree+crop situations at ICAR Research Farm, Barapani (Meghalya), India. The tree species were mandarin (Citrus reticulata), alder (Alnus nepalensis), cherry (Prunus cerasoides) and albizia (Paraserianthes falcataria). The contribution of fine roots to the total root biomass ranged from 87% in albizia to 77% in mandarin. The bulk of the fine roots (38% to 47%) in the four tree species was concentrated in the upper 10 cm soil layer, but the coarse roots were concentrated in 10–20 cm soil depth in alder (46%) and albizia (51%) and at 0–10 cm in cherry (41%) and mandarin (48%). In all the four tree species, biomass of both fine- and coarse-roots followed a unimodal growth curve by showing a gradual increase from spring (pre-rainy) season to autumn (post rainy) season. Biomass to necromass ratio varied between 2 to 3 in the four tree species. The maximum (3.2) ratio was observed during spring and the minimum (2) in the rainy season. In alder and albizia, the fine roots were distributed only up to 1 m distance from the tree trunk but in the other two species they were found at a distance up to 1.5 m from the tree trunk. The annual fine root production varied from 3.6 Mg ha–1 to 6.2 Mg ha–1 and total production from 4.2 to 8.4 Mg ha–1 in albizia to mandarin, respectively. Cherry and mandarin had a large number of woody roots in the surface layers which pose physical hindrance during soil working and intercultural operations under agroforestry. But the high biomass of roots of these two species may be advantageous for sequential or spatially separated agroforestry systems. However, alder and albizia have the most desirable rooting characteristics for agroforestry systems.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
9.
Spatial distribution characteristics of fine roots of Populus euphratica in a desert riparian forest
The soil-plant system is a very important subsystem of the soil-plant-atmosphere continuum (SPAC). The water uptake by plant
roots is an important subject in the research on water transport in this SPAC and is also the most active study direction
in the fields of ecology, hydrology and environment. The study of the spatial distribution pattern of fine roots of plants
is the basis of constructing a water absorption model of plant roots. Our study on the spatial distribution pattern of fine
roots of Populus euphratica in a desert riparian forest shows that the density distribution of its root lengths can be expressed horizontally as a parabola.
The fine roots are concentrated within the range of 0–350 cm from the tree trunk and their amount accounts for 91.9% of the
total root mass within the space of 0–500 cm. In the vertical direction, the density distribution of the fine root lengths
shows a negative exponential relation with soil depth. The fine roots are concentrated in the 0–80 cm soil layer, accounting
for 96.8% of the total root mass in the 0–140 cm soil layer.
__________
Translated from Chinese Journal of Ecology, 2007, 26(1): 1–4 [译自: 生态学杂志] 相似文献
10.
The biomass and the spatial distribution of fine and small roots were studied in two Japanese black pine (Pinus thunbergii Parl.) stands growing on a sandy soil. More biomass of fine and small roots was found in the 17-year-old than in the 40-year-old
stand. There were 62 g m−2 of fine roots and 56 g m−2 of small roots in the older stand, which represented mean values of 608 g for fine and 552 g for small roots per tree, respectively.
In the younger stand, a total of 85 g m−2 of fine roots and 66 g m−2 of small roots were determined, representing a mean of 238 g for fine and 186 g for small roots per tree, respectively. Fine
and small root biomasses decreased linearly with a soil depth of 0–50 cm in the older stand. In the younger stand, the fine
and small roots developed only up to a depth of 30 cm. Horizontal distributions (with regard to distance from a tree) of both
root groups were homogeneous. A positive correlation in the amount of biomass of fine and small roots per m2 relative to tree size was found. Fine and small root biomasses increased consistently from April to July in both stands.
The results also indicated earlier growth activity of the fine roots than small roots at the beginning of the growing season.
The seasonal increases in fine and small root biomasses were slightly higher in the younger stand than the older stand. 相似文献
11.
Variability of fine root (diameter < 2 mm) distribution was investigated in four 55 to 56-year-old Maritime pine (Pinus pinaster) stands using a combination of trench wall observations and destructive sampling. Our objectives were to assess patterns
of fine root distribution, to estimate tree fine root biomass and to explore interactions with understorey vegetation in a
gradient of relevant site conditions. Results showed that root density decreased with soil depth in all stands, and variability
appeared to be highest in litter and subsoil layers especially where compacted soil layers occurred. Roots were clustered
in patches in the top 0–50 cm of the soil or were present as root channels at greater depths. Cluster number, cluster size
and number of root channels were comparable in all four stands. Overall fine root biomass at depths of 0–120 cm ranged from
2.7 to 7.2 Mg ha−1 and was highest for the two driest stands. The use of trench wall records made it possible to reduce the variability of these
estimates. Understorey species represented as much as 90% of the total number of fine roots in the upper layers, and the understorey
formed a considerable proportion of the total ecosystem biomass, suggesting that understorey species are likely competitors
for nutrients in this ecosystem. Further studies should focus on the interaction of the understorey and pine roots and the
ecological significance of clustered roots and nutrient distributions. 相似文献
12.
B. Vanlauwe F. K. Akinnifesi B. K. Tossah O. Lyasse N. Sanginga R. Merckx 《Agroforestry Systems》2002,54(1):1-12
Although crucial for assessing the functioning of alley cropping systems, quantitative information related to the hedgerow
tree root distribution remains scarce. Soil mapping and destructive soil sampling was used to assess the impact of soil profile
features on selected root characteristics of Senna siamea hedgerows, growing in alley cropping systems in three sites (Glidji, Amoutchou, and Sarakawa) representative for the derived
savanna of Togo, West Africa. While the soil profiles in Glidji and Sarakawa contained a clay accumulation horizon, the Amoutchou
profile was sandy up to 1 m. The number of small roots (diameter < 2 mm), quantified on a soil profile wall, decreased with
depth in all sites. For most soil depths, the abundance of small roots tended to be higher near the tree base, e.g., ranging
from 5.3 dm−2 in Amoutchou to 21.4 dm−2 in Glidji for the 0–20 cm layer, than in the middle of the alley, e.g., ranging from 3.1 dm−2 in Amoutchou to 13.8 dm−2 in Glidji for the 0–20 cm layer. Root length density (RLD) of the 0–10 cm and 10–20 cm layers was significantly higher in
Glidji than in Amoutchou (P < 0.05) and in Sarakawa (P = 0.08). Differences in RLD between sites were not significant for layers below 30 cm. For each layer, root weight densities
(RWD) were similar in all sites, e.g., ranging from 0.44 mg cm−3 in Amoutchou to 0.64 mg cm−3 in Glidji in the 0–10 cm layer, indicating that the roots in the Glidji topsoil had a smaller overall diameter than in Amoutchou.
In Amoutchou, the relative RLD was lower than in Glidji or Sarakawa for the top 40 cm of soil, while the inverse was observed
for the layers between 50 and 100 cm deep and this was related to the sandy soil profile in Amoutchou. Another consequence
of the sandy profile was the larger tap root diameter below 50 cm in Amoutchou compared to Sarakawa. For all sites, significant
(P < 0.001) linear regressions were observedbetween RLD's, RWD's, and the abundance of small roots, although the variation explained
by the regression equations was highest for the relationship between RLD and RWD. The potential of the hedgerows to recover
nutrients leached beyond the reach of food crops or the safety-net efficiency was evaluated for the tree sites.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
13.
Picea mongolica is an endemic but endangered species in China. The spruce forest is only found in sandy forest-steppe ecotones. In this study, we examined the initial response of the quantity and refilling process of fine roots in an artificial canopy gap with a diameter of 36 m in a P. mongolica forest. Under the canopy, the fine root length densities of trees, shrubs and herbs were 2,622, 864 and 3,086 m·m–2, respectively. The fine root biomass of trees, shrubs and herbs were 148, 62 and 65 g·m–2, respect... 相似文献
14.
Fine root distribution of pruned trees and associated crops in a parkland system in Burkina Faso 总被引：2，自引：0，他引：2
Besides aboveground interactions, pruning of trees may also modify their rooting pattern for which a better understanding is needed for the optimisation of agroforestry systems. Thus, variation in fine root (d 2 mm) distribution of pruned trees and crops were assessed during three cropping seasons by sampling soil layers at 10 cm intervals up to 50 cm and at four distances from tree trunk. Three crown pruning treatments (totally-pruning, half-pruning and no-pruning) were applied to karité (Vitellaria paradoxa) and néré (Parkia biglobosa). In 1999, 59% (0.477 cm cm–3) and 69% (0.447 cm cm–3) of fine roots for karité and néré respectively occurred in the upper 20 cm with a significant decrease in root length density with soil depth. However, in 2000, totally-pruned trees of néré and karité showed 32% (0.051 cm cm–3) and 34% (0.078 cm cm–3) of their density in the upper 20 cm whereas root distribution in 2001 was similar to that of 1999. Thus, pruning to reduce belowground competition for the benefit of associated crops can be recommended in the light of the temporary reduction of root density in crop rooting zone and consequently the increase in crop production.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
15.
Morphology and vertical distribution patterns of spruce and beech live fine roots (diameter ≤2 mm) were studied using a soil
core method in three comparable mature stands in the Solling: (1) pure beech, (2) pure spruce and (3) mixed spruce–beech.
This study was aimed at determining the effects of interspecific competition on fine root structure and spatial fine root
distribution of both species. A vertical stratification of beech and spruce fine root systems was found in the mixed stand
due to a shift in beech fine roots from upper to lower soil layers. Moreover, compared to pure beech, a significantly higher
specific root length (SRL, P<0.05) and specific surface area (SSA, P<0.05) were found for beech admixed with spruce (pure beech/mixed beech SRL 16.1–23.4 m g−1, SSA 286–367 cm2 g−1). Both indicate a flexible ‘foraging’ strategy of beech tending to increase soil exploitation and space sequestration efficiency
in soil layers less occupied by competitors. Spruce, in contrast, followed a more conservative strategy keeping the shallow
vertical rooting and the root morphology quite constant in both pure and mixed stands (pure spruce/mixed spruce SRL 9.6/7.7 m g−1, P>0.10; SSA 225/212 cm2 g−1, P>0.10). Symmetric competition belowground between mixed beech and spruce was observed since live fine roots of both species
were under-represented compared to pure stand. However, the higher space sequestration efficiency suggests a higher competitive
ability of beech belowground. 相似文献
16.
A considerable amount of data is available about above-ground biomass production and turnover in tropical agroforestry systems, but quantitative information concerning root turnover is lacking. Above- and below-ground biomass dynamics were studied during one year in an alley cropping system withGliricidia sepium and a sole cropping system, on aPlinthic Lixisol in the semi-deciduous rainforest zone of the Côte d'Ivoire. Field crops were maize and groundnut. Live root mass was higher in agroforestry than in sole cropping during most of the study period. This was partly due to increased crop and weed root development and partly to the presence of the hedgerow roots. Fine root production was higher in the alleys and lower under the hedgerows compared to the sole cropping plots. Considering the whole plot area, root production in agroforestry and sole cropping systems was approximatly similar with 1000–1100 kg ha–1 (dry matter with 45% C) in 0–50 cm depth; about 55% of this root production occured in the top 10 cm. Potential sources of error of the calculation method are discussed on the basis of the compartment flow model. Above-ground biomass production was 11.1 Mg ha–1 in sole cropping and 13.6 Mg ha–1 in alley cropping, of which 4.3 Mg ha–1 were hedgerow prunings. The input of hedgerow root biomass into the soil was limited by the low root mass ofGliricidia as compared to other tree species, and by the decrease of live root mass of hedgerows and associated perennial weeds during the cropping season, presumably as a result of frequent shoot pruning. 相似文献
17.
Exploring below ground complementarity in agroforestry using sap flow and root fractal techniques 总被引：2，自引：0，他引：2
C. K. Ong J. D. Deans J. Wilson J. Mutua A. A. H. Khan E. M. Lawson 《Agroforestry Systems》1998,44(1):89-106
Indices of shallow rootedness and fractal methods of root system study were combined with sapflow monitoring to determine
whether these ‘short-cut’ methods could be used to predict tree competition with crops and complementarity of below ground
resource use in an agroforestry trial in semi-arid Kenya. These methods were applied to Grevillea robusta Cunn., Gliricidia
sepium (Jacq.) Walp., Melia volkensii Gürke and Senna spectabilis syn. Cassia spectabilis aged two and four years which were
grown in simultaneous linear agroforestry plots with maize as the crop species. Indices of competition (shallow rootedness)
differed substantially according to tree age and did not accurately predict tree:crop competition in plots containing trees
aged four years. Predicted competition by trees on crops was improved by multiplying the sum of proximal diameters squared
for shallow roots by diameter at breast height2, thus taking tree size into account. Fractal methods for the quantification of total length of tree root systems worked well
with the permanent structural root system of trees but seriously underestimated the length of fine roots (less than 2 mm diameter).
Sap flow measurements of individual roots showed that as expected, deep tap roots provided most of the water used by the trees
during the dry season. Following rainfall, substantial water uptake by shallow lateral roots occurred more or less immediately,
suggesting that existing roots were functioning in the recently wetted soil and that there was no need for new fine roots
to be produced to enable water uptake following rainfall.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
18.
Roots of trees (Sesbania sesban) and crops (Zea mays) were quantified during two tree/crop cycles in a sequential tree — crop system at Chipata, Eastern Zambia. The experiment included one- and two-year fallows as well as fertilized and unfertilized controls. The roots of S. sesban represent a standing biomass in the soil of 3 Mg hat-1 in the top 1.5 m after two years, with 45–60% and 70–75% being in the top 25 and 50 cm respectively. S. sesban fallow improved early rooting and growth of the following maize crop. Increased soil infiltration was also observed in the two-year fallow treatment, as well as decreased bulk density and resistance to penetration in the soil. No differences between maize root parameters could be detected at tasselling, nor differences between nutrient status of the different treatments. Study results indicate that under the drought-prone conditions of Eastern Zambia, where improved soil physical conditions are important for early deep rooting of crops and access to water and nutrients, tree roots could play an important role in the fallow effect. Further studies are required to assess the relative importance of the improvement of soil chemical and physical properties.Submitted as ICRAF Journal Article # 95/28. 相似文献
19.
Variations of fine root diameter with root order in Manchurian ash and Dahurian larch plantations 总被引：1，自引：0，他引：1
Xiangrong Wang Zhengquan Wang Youzhi Han Jiacun Gu Dali Guo Li Mei 《Frontiers of Forestry in China》2007,2(1):34-39
Fine root lifespan and turnover play an important role in carbon allocation and nutrient cycling in forest ecosystems. Fine
roots are typically defined as less than 1 or 2 mm in diameter. However, when categorizing roots by this diameter size, the
position of an individual root on the complex lateral branching pattern has often been ignored, and our knowledge about relationships
between branching order and root function thus remains limited. More recently, studies on root survivals found that longevity
was remarkably different in the same branching level due to diameter variations. The objectives of this study were: (1) To
examine variations of fine root diameter from the first-to fifth-orders in Fraxinus mandshurica Rupr and Larix gmelinii Rupr roots; and (2) To reveal how the season, soil nutrient, and water availability affect root diameter in different branch
order in two species. This study was conducted at Maoershan Forest Research Station (45°21′–45°25′N, 127°30′–127°34′E) owned
by Northeast Forestry University in Harbin, northeast China. Both F. mandshurica and L. gmelinii were planted in 1986. In each plantation, fine roots of two species by sampling up to five fine root branch orders three
times during the 2003 growing season from two soil depths (i.e., 0–10 and 10–20 cm) were obtained. The results showed that
average diameters of fine roots were significantly different among the five branch orders. The first-order had the thinner
roots and the fifth order had the thickest roots, the diameter increasing regularly with the ascending branch orders in both
species. If the diameter of fine roots was defined as being smaller than 0.5 mm, the first three orders of F. mandshurica roots and the first two orders of L. gmelinii roots would be included in the fine root population. The diameter ranges of the fine roots from first-order to fifth-order
were 0.15–0.58, 0.18–0.70, 0.26–1.05, 0.36–1.43, and 0.71–2.96 mm for F. mandshurica, and 0.17–0.76, 0.23–1.02, 0.26–1.10, 0.38–1.77, and 0.84–2.80 mm for L. gmelinii. The average coefficient of variation in first-order roots was less than 10%, second-and third-order was 10–20%, and fourth-and
fifth-order was 20–30%. Thus, variation in root diameter also increased with the ascending root order. These results suggest
that “fine roots”, which are traditionally defined as an arbitrary diameter class (i.e., <2 mm in diameter) may be too large
a size class when compared with the finest roots. The finest roots have much shorter lifespan than larger diameter roots;
however, the larger roots are still considered a component of the fine root system. Differences in the lifespan between root
diameter and root order affect estimates of root turnover. Therefore, based on this study, it has been concluded that both
diameter and branch order should be considered in the estimation of root lifespan and turnover.
__________
Translated from Acta Phytoecologica Sinica, 2005, 29(6): 871–877 [译自: 植物生态学报] 相似文献
20.
In designing agroforestry systems, the combination of tree genotype (orspecies) and pasture species and the spatial arrangement
of trees are importantconsiderations. The spatial variation of fine root length density (FRLD) ofthree radiata pine (Pinus radiata D. Don) genotypes,referred to here as clone 3, clone 4 and seedlings, was studied in athree-year-old temperate silvopastoral
experiment. The genotypes were plantedwith three understorey types: ryegrass (Lolium perenne)mixed with clovers (Trifolium spp), lucerne(Medicago sativa), and control (bare ground). Also fineroot distribution of both tree and pasture species with soil depth and inrelation to
tree row (0.9 m north or south of and within the rippedtree row) was studied. Greater FRLD was found in clonal than in seedling
treesin the bare ground treatment but not in the two pasture treatments, and in the0–0.1 m but not in the 0.1–0.2 or 0.2–0.3m
soil layers. Clonal trees had a greater ability to develop a moreextensive root system, especially in the 0–0.1 m soil layer,but
that advantage disappeared when they were planted with pasture species sincecompetition from the pasture species was most
severe in the 0–10cm layer. The FRLD of lucerne was greater than that ofryegrass/clovers, consistent with the greater aboveground
biomass production oflucerne. Pasture species FRLD was greater on the south (wetter) than on thenorth side of the ripline
or in the ripline. The interception of prevailingsoutherly rain-bearing wind by tree crowns resulted in the south side beingwetter
than the north side. Results indicated that production and distributionof fine roots of both tree and pasture species responded
to changes in themicroclimate. We suggest that to optimize pasture/tree biomass productionplanting trees in the north-south
direction is better than in the east-westdirection at the studied site.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献