Aims
Functional traits play key role in plant resource-use strategy, but the intraspecific variation of root traits particularly of anatomy along large-scale environmental gradient has been poorly ...understood.
Methods
Here, we examined 16 morphological, anatomical, and chemical traits of leaves and absorptive roots (i.e., the first-order roots) for two wide-planted tree species,
Ginkgo biloba
and
Eucommia ulmoides
, sampled at five locations from subtropical, temperate, and cold-arid regions in China.
Results
Morphological traits in leaves tended to shift from conservative at resource-poor sites to acquisitive at resource-rich sites, showing lower leaf thickness and larger specific leaf area, while roots showed a reverse pattern. All anatomical traits in leaves and roots inclined to be more conservative in resource-poor sites. Leaves and roots generally showed negative relationships in analogous morphological traits, but positive in anatomical and chemical traits across both species. Intraspecific variation of leaf traits confirmed the existence of one-dimensional economics spectrum, whereas root traits displayed multidimensional variation, showing an independent dimension of cortex to stele size ratio.
Conclusions
Leaf and root traits in both species showed considerable intraspecific variations under changing environments, which improved whole-plant-level adaptions to climate and soil constraints, and exhibited different above- and belowground intraspecific economics spectra.
Despite extensive research on the seasonal dynamics of non-structural carbohydrate (NSC) and nitrogen (N) concentrations, the size and relative contributions of NSC and N pools across different tree ...organs are not well understood. We have measured the changes in NSC and N concentrations in leaves, branches, stems and all root branch orders at monthly intervals in control and girdled trees of larch (Larix gmelinii) and ash (Fraxinus mandshurica). The biomass of each plant compartment was also determined to calculate the size of the NSC and N pools. In both species, 13–37 % of the NSC and N pools were mobilized at the beginning of the growing season. Among the mobilized pools, stems and non-absorptive roots (branch orders 4–9) acted as the largest NSC sources in larch and ash, respectively, while branches served as the largest N source in both species. After stem girdling, 22 and 50 % of the root NSC stores in larch and ash, respectively, were mobilized to maintain root activities during the growing season. Tree mortality was observed 1 year after girdling, at which time there was still an abundant NSC pool in the roots. We conclude that (1) different storage organs differ in their contribution to new tissue growth at the beginning of the growing season and that those storage organs holding higher fractions of the NSC or N pool are not necessarily those which mobilize more NSC or N; (2) tree growth may not be limited by carbon (C) availability; (3) C storage in non-absorptive roots plays an important role in maintaining tree survival after the termination of photosynthate flow from aboveground sources.
Aims
Absorptive and transport roots (diameter ≤ 2 mm) are closely related to soil resource uptake for plant growth, carbon budget and nutrient cycling in forest ecosystems, but how and why the ...relative share of root biomass or root length for both root functional types changes with tree species is not well understood. Our aims were to examine the inter-specific variations of root biomass and length per unit area of absorptive and transport roots, and their relationships with stand structure and soil characteristics, root morphological and architectural traits.
Methods
We measured root biomass and length per unit area, diameter, specific root length (SRL), root tissue density (RTD), and branching ratio of the first five order roots, stand and soil characteristics in seven forests consisting of different tree species at a common site. The first order roots were classified as absorptive roots and the other orders as transport roots based on our earlier work.
Results
Biomass ratios of absorptive to transport roots varied from 1:5.56 to 1:1.12 among species, and length ratios ranged from 1:1.56 to 1:0.29. Root biomass was not influenced by root morphology or architecture, nor by stand or soil characteristics. Absorptive root length was significantly correlated with SRL, RTD, and branching ratio of the first to second order roots among species, whereas transport root length was significantly correlated with stem density.
Conclusions
The relative share of biomass and length for absorptive and transport roots differed among tree species, which may influence belowground carbon allocation and resource competition.
Protoxylem grouping (PG), a classification based on the number of protoxylem poles, is a crucial indicator related to other functional traits in fine roots, affecting growth and survival of ...individual root. However, within root system, less is known about the arrangement of PG. Moreover, the responses of PG to fertilization are still unclear. Here, we selected three common hardwood species in Northeast China,
Juglans mandshurica
,
Fraxinus mandshurica,
and
Phellodendron amurense
, conducted root pruning and nutrient addition. In this study, we analyzed the PG, morphology, and other anatomy traits of newly formed root branches. The results showed all root length, diameter, and stele, as well as hydraulic conductivity, were significantly positive related to the PG number, and the PG number generally decreased with ascending root developmental order; these patterns were independent of species and fertilization. Additionally, we also found the plasticity of PGs to environmental changes, in terms of the increased frequency of high PG roots after fertilization, significantly in
J. mandshurica
and
F. mandshurica
. Therefore, the heterogeneity, hierarchy, and plasticity of individual roots within root system may be widespread in woody plants, which is of great significance to deepen our understanding in root growth and development, as well as the belowground ecological process.
Key message
In the organic layer, absorptive fine roots of
Larix gmelinii
represent a significant proportion of the total fine-root biomass and can morphologically adjust during the growing season to ...optimize resource acquisition.
Larix gmelinii
is a foundational tree species in forests of northern China and Far-East Russia. A better understanding of the species’ belowground resource acquisition strategy is important for soil nutrient and carbon estimates. Here, we investigated seven traits of absorptive fine-roots at four depth levels, from the organic layer (organic, decomposed litter from dead plants) down to a soil depth of 30 cm in May, July and September of 2016. Biomass and functional traits of absorptive fine roots varied significantly, indicating the species ability to adjust its resource acquisition across the four depth layers. From the organic layer to deeper mineral soil layers, root diameter and tissue density increased, while specific root length decreased, in other words, roots become longer and thinner with increasing values of soil water and nutrient concentrations. At the same time, the average biomass and length of absorptive fine roots in the organic layer accounted for 14% and 16% of the total, respectively. With increasing soil depth, the averaged proportion of biomass and length density of absorptive fine roots to the total fine roots decreased significantly from almost 57 to 32%, and 80–62%, respectively. Finally, total soil nitrogen concentration showed the strongest link with absorptive fine-root traits, such as root diameter, specific root length, root standing biomass and length density. Our results indicate that absorptive fine roots in the organic layer play a crucial role in belowground resource acquisition and carbon cycle in a common and economical important species.
The collection of tree canopy samples in forest ecosystems has been challenging for researchers and managers during the past decades. Various methods, including pole pruner, tree climber, shooter, ...throw-line launcher, hydraulic lift (e.g., tower crane) and UAV (unmanned aerial vehicle)-based devices, have been used, however, they are limited by sampling height restrictions, safety hazards to a climber, low retrieving accuracy, high equipment costs, and transportation inconvenience. This study proposed a novel method for collecting tree canopy samples using a portable mini-drone. The mini-drone is operated to pull a traction line across the target branch, drag the retrieving rope to the selected cutting point of the branch, and carry the equipped wire saw or chain saw to cut the canopy sample off. Through on-site testing and field trials, this method was feasible for lower- and middle-canopy sampling (up to 30 meters tall) across most temperate broad-leaved and coniferous tree species. This technique would have great potential in plantation and old-growth forests. Adopting this low-cost mini-drone technique, researchers can collect tree canopy samples safely and efficiently, leading to improvements in relevant physiological and ecological studies focusing on functional traits of branches, leaves, and seeds.
We have limited understanding of architecture and morphology of fine root systems in large woody trees. This study investigated architecture, morphology, and biomass of different fine root branch ...orders of two temperate tree species from Northeastern China--Larix gmelinii Rupr and Fraxinus mandshurica Rupr --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). Branching ratio (R b) differed with the level of branching: R b values from the fifth to the second order of branching were approximately three in both species, but markedly higher for the first two orders of branching, reaching a value of 10.4 for L. gmelinii and 18.6 for F. mandshurica. Fine root diameter, length, SRL and root length density not only had systematic changes with root order, but also varied significantly with season and soil depth. Total biomass per order did not change systematically with branch order. Compared to the second, third and/or fourth order, the first order roots exhibited higher biomass throughout the growing season and soil depths, a pattern related to consistently higher R b values for the first two orders of branching than the other levels of branching. Moreover, the differences in architecture and morphology across order, season, and soil depth between the two species were consistent with the morphological disparity between gymnosperms and angiosperms reported previously. The results of this study suggest that root architecture and morphology, especially those of the first order roots, should be important for understanding the complexity and multi-functionality of tree fine roots with respect to root nutrient and water uptake, and fine root dynamics in forest ecosystems.
Background
The introduction of broadleaved tree species in monoculture larch plantations to establish mixed plantations is a feasible way to improve soil properties. However, our understanding of how ...mixed plantations of larch and broadleaved tree species affect soil properties, particularly microbial community structures and functions, remains limited. We compared three paired monoculture larch (
Larix gmelinii
) and mixed
L. gmelinii
–
Fraxinus mandshurica
(a dominant broadleaved species) plantations to investigate the effect of a larch–broadleaved tree species combination on the carbon (C) and nitrogen (N) content, abundance and composition of microbial communities, and enzyme activities associated with litter and soil.
Results
The bacterial abundance in the litter, soil N availability, pH and electronic conductivity were significantly higher in the mixed-species plantation in comparison with those of the monoculture plantation. However, in the litter of mixed-species plantation, the relative levels of Agaricomycetes fungi were lower than those of the monoculture plantation, indicating that soil fungal communities were affected more than bacterial communities. In contrast, soil in the mixed-species plantation showed increased exoglucanase and
N
-acetyl-β-glucosaminidase activities. However, the C and N levels, δ
13
C and δ
15
N values, and fungal abundance in litter and soil were not significantly different between the monoculture and mixed-species plantations.
Conclusions
Our findings suggest that fungal community compositions and enzyme activities are sensitive to the introduction of broadleaved tree species into larch plantations. Thus, these parameters can be used as important indicators to evaluate the effects of tree species selection on soil restoration.
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