Higher Fine Root Biomass Research Articles

Spatial Heterogeneity of Total and Labile Soil Organic Carbon Pools in Poplar Agroforestry Systems

Agroforestry systems are considered effective methods of carbon sequestration. In these systems, most of the carbon is stored in the soil, and the pattern of tree planting can influence the spatial distribution of organic matter input into the soil. However, limited information is available about the extent of this influence. In this study, the horizontal and vertical distributions of soil organic carbon (SOC) and labile fractions were investigated in four planting systems: a pure poplar (Populus deltoides cv. “35”) planting system, a wide-row (14 m spacing) poplar and wheat (Triticum aestivum L.) agroforestry system, a narrow-row (7 m spacing) poplar and wheat agroforestry system, and a pure wheat field. The results showed that although the poplar system had the highest vegetation biomass (147.50 t ha−1), the agroforestry systems overall had higher SOC contents than the pure poplar system and wheat fields. Especially in the wide-row agroforestry system, the SOC, readily oxidizable carbon, and dissolved organic carbon contents were, respectively, 25.3%, 42.4%, and 99.3% higher than those of the pure poplar system and 60.3%, 148.7%, and 6.3% higher than those of the wheat field in a 1 m soil profile, and it also had the highest fine root biomass. However, the microbial biomass carbon content was highest in the pure poplar system. The SOC of the three poplar planting systems was spatially heterogeneous, with the highest values occurring at 1.5 m in the narrow-row systems and within the tree rows in the wide-row system, similar to the distribution of fine root biomass. Additionally, we found that the larger the diameter at the breast height of the trees, the greater their positive effect on SOC at greater distances.

Persistent soil organic carbon deficits from converting primary forests to plantations and secondary forests in subtropical China

Soil organic carbon (SOC) plays a critical role in supporting key ecosystem functions and services for humanity. Despite the widespread conversion of primary forests to plantations and secondary forests, it remains uncertain how it affects the content and distribution of SOC. We evaluated SOC content, its components in two fractions, particulate organic carbon (a mean residence time shorter than decades) and mineral-associated organic carbon (a mean residence time of multiple decades to centuries), and the fine root characteristics (biomass, necromass, and C: N of dead fine roots) across Chinese fir plantations and secondary forests during stand development (5–41 years old) in subtropical China, employing primary forests as a reference. We found that SOC content differed significantly between forest types and soil depths, but not with stand age within plantations or secondary forests. In the topsoil (0–10 cm), the SOC content of primary and secondary forests was 47 % and 25 % higher than that of Chinese fir plantations, respectively. The SOC content in the subsoil (40–60 cm) was approximately 6 ± 1.7 mg C g−1 and did not change significantly with forest types or stand ages. The higher SOC contents in primary forests and secondary forests in topsoil resulted primarily from particulate organic carbon accumulation caused by higher fine root biomass and dead root C: N. The fraction of mineral-associated organic carbon to SOC increased with soil depth and was higher in Chinese fir plantations than in secondary forests, suggesting that more SOC is composed of mineral-associated organic carbon that was associated with a higher amount of fine root necromass. Contrary to our expectations, we found SOC content or its fractions did not increase with 40 years of plantation and secondary forest development. Our results reveal persistent SOC deficits from converting primary forests to plantations and secondary forests and highlight the urgent need to conserve the remaining primary forests and protect secondary forests and plantations from disturbances, allowing them to evolve towards older-aged primary forests.

Relationship between the vertical distribution of fine roots and residual soil nitrogen along a gradient of hardwood mixture in a conifer plantation

In forest ecosystems, understanding the relationship between the vertical distribution of fine roots and residual soil nitrogen is essential for clarifying the diversity-productivity-water purification relationship. Vertical distributions of fine-root biomass (FRB) and concentrations of nitrate-nitrogen (NO3 -N) in soil water were investigated in a conifer plantation with three thinning intensities (Control, Weak and Intensive), in which hardwood abundance and diversity were low, moderate and high, respectively. Intensive thinning led to the lowest NO3 -N concentration in soil water at all depths (0-100 cm) and highest FRB at shallow depths (0-50 cm). The NO3 -N concentration at a given depth was negatively correlated with total FRB from the surface to the depth at which NO3 -N concentration was measured, especially at shallow depths, indicating that more abundant fine roots led to lower levels of downward NO3 -N leaching. FRB contributed positively to nitrogen content of hardwood leaves. These findings demonstrate that a hardwood mixture in conifer plantations resulted in sufficient uptake of NO3 -N from soil by well developed fine-root systems, and translocation to canopy foliage. This study suggests that productivity and water purification can be achieved through a hardwood mixture in conifer plantations.

Soil carbon and nutrient stocks under Scots pine plantations in comparison to European beech forests: a paired-plot study across forests with different management history and precipitation regimes

BackgroundOrganic carbon stored in forest soils (SOC) represents an important element of the global C cycle. It is thought that the C storage capacity of the stable pool can be enhanced by increasing forest productivity, but empirical evidence in support of this assumption from forests differing in tree species and productivity, while stocking on similar substrate, is scarce.MethodsWe determined the stocks of SOC and macro-nutrients (nitrogen, phosphorus, calcium, potassium and magnesium) in nine paired European beech/Scots pine stands on similar Pleistocene sandy substrates across a precipitation gradient (560–820 mm∙yr− 1) in northern Germany and explored the influence of tree species, forest history, climate, and soil pH on SOC and nutrient pools.ResultsWhile the organic layer stored on average about 80% more C under pine than beech, the pools of SOC and total N in the total profile (organic layer plus mineral soil measured to 60 cm and extrapolated to 100 cm) were greater under pine by about 40% and 20%, respectively. This contrasts with a higher annual production of foliar litter and a much higher fine root biomass in beech stands, indicating that soil C sequestration is unrelated to the production of leaf litter and fine roots in these stands on Pleistocene sandy soils. The pools of available P and basic cations tended to be higher under beech. Neither precipitation nor temperature influenced the SOC pool, whereas tree species was a key driver. An extended data set (which included additional pine stands established more recently on former agricultural soil) revealed that, besides tree species identity, forest continuity is an important factor determining the SOC and nutrient pools of these stands.ConclusionWe conclude that tree species identity can exert a considerable influence on the stocks of SOC and macronutrients, which may be unrelated to productivity but closely linked to species-specific forest management histories, thus masking weaker climate and soil chemistry effects on pool sizes.

Response of density-related fine root production to soil and leaf traits in coniferous and broad-leaved plantations in the semiarid loess hilly region of China

Fine roots are the most active and functional component of root systems and play a significant role in the acquisition of soil resources. Density is an important structural factor in forest plantations but information on changes in fine roots along a density gradient is limited. In this study, plantations of black locust (Robinia pseudoacacia L.) and Chinese pine (Pinus tabuliformis Carr.) with four density classes were analyzed for the influence of soil and leaf traits on fine root growth. Fine root biomass increased with stand density. High fine root biomass was achieved through increases in the fine root production and turnover rate in the high-density black locust plantations and through an increase in fine root production in the pine plantations. In the high-density Chinese pine stand, there was a high fine root turnover which, coupled with high fine root production, contributed to a high fine root biomass. Overall, fine root production and turnover rate were closely related to soil volumetric water content in both kinds of plantations, while fine root biomass, especially the component of necromass, was related to soil nutrient status, which refers to phosphorous content in black locust plantations and nitrogen content in Chinese pine plantations. There was a close linkage between leaf area index and fine root dynamics in the black locust plantations but not in the pine plantations.

Fine root biomass and necromass dynamics of Chinese fir plantations and natural secondary forests in subtropical China

Fine roots play a critical role in terrestrial carbon and nutrient cycling. Despite this, quantitative evaluation of the fine root dynamics in plantations and natural secondary forests is lacking. This study examined the dynamics of fine root biomass and necromass of Chinese fir plantations and natural secondary forests (5–41 years old) and employed primary forests as a reference in subtropical China. In the top 60-cm soil depth, the sum of fine root biomass of Chinese fir plantations and natural secondary forests initially increased and then decreased with stand development, attaining a peak in the 27–31-year age class. The total fine root biomass of natural secondary forests was significantly higher than that of Chinese fir plantations across all age classes. The total fine root biomass of primary forests was similar to that in the 38–41-year-old natural secondary forests and Chinese fir plantations. The total fine root necromass was higher in Chinese fir plantations than in natural secondary forests across all ages except in the youngest age class. The necromass to biomass ratio was significantly higher in Chinese fir plantations. Most of the fine root biomass resided in the topsoil (0–10 cm) for all stand types and ages. The higher fine root biomass in the secondary natural forests than in the Chinese fir plantation was most apparent in the topsoil. Across all age classes, the fine root biomass was positively correlated with stand basal area, mean diameter at breast height, and shrub cover, whereas the fine root necromass and the necromass to biomass ratio tended to be more consistent across measured stand characteristics. Our results highlight profound influences of forest management on fine root biomass and necromass and suggest that the low fine root biomass of Chinese fir plantations may have a negative impact on carbon and nutrient cycling in the subtropical forests.

Mulched drip irrigation increases cotton yield and water use efficiency via improving fine root plasticity

The morphological characteristics of crop roots, especially the plasticity of fine roots, are directly related to the crop’s ability to obtain soil water. Mulched drip irrigation can effectively regulate soil water distribution to achieve high cotton yield with reduced water consumption. In the previous study, from the perspective of root-shoot coordination, we found that mulched drip irrigation reduced the growth redundancy of roots and improved the root productivity of cotton, thus achieving the goal of water-saving and increased yield. However, it is unclear if and how mulched drip irrigation enhances absorptive capacity of roots via regulating dry and wet soil areas and optimizing fine root morphology and distribution compared with traditional flood irrigation. To achieve this, the effects of fine root plasticity on the absorptive capacity of roots were studied in a two-year field experiment. Mulched drip irrigation (conventional drip irrigation and excessive drip irrigation) and traditional flood irrigation (reduced flood irrigation and conventional flood irrigation) were used, and soil water distribution and root distribution were determined. The results showed that compared with traditional flood irrigation, mulched drip irrigation significantly increased the soil water content (SWC) in the 0–60 cm soil layer and reduced the fluctuation amplitude of SWC at the flowering and boll stage of cotton. Mulched drip irrigation formed different dry and wet areas in the root zone, i.e., the SWC was higher in the shallow layer (0–40 cm) at 0–20 cm on both sides of the drip line, and most of the cotton roots were in the wet area. The higher SWC increased the distribution of fine roots in this area and shaped the shallow fine root system, which enhanced the cotton plant’s ability to absorb soil water. Statistical analysis showed that the higher fine root biomass in the 0–40 cm soil layer at the late full boll stage of cotton under mulched drip irrigation was beneficial to increase aboveground biomass, thus increasing total bolls and seed cotton yield. However, compared with the irrigation amount of field production (390 mm), an excessive amount of irrigation (600 mm) reduced the seed cotton yield of mulched drip irrigation, resulting in the decrease of irrigation water use efficiency (IWUE). Therefore, mulched drip irrigation optimizes the distribution of fine roots and enhances water uptake by effectively regulating the water–root relationship, and thus improves seed cotton yield and IWUE.

Soil factors determining the fine-root biomass in soil regeneration after a post-fire and soil reconstruction in reclaimed post-mining sites under different tree species

For this study, we analyzed the increase in fine root biomass under pine, birch, and larch (Pinus sylvestris, Betula pendula, and Larix decidua, respectively) plantings growing in regenerated (postfire sites) and reconstructed (reclaimed mine soils) forest ecosystems. The control sites were located in natural habitats on podzolic soils in managed forests of the Olkusz Forest District, Poland. The objective of the manuscript included determination of the chemical properties of soils that influence the biomass of fine roots of different tree species under the conditions of regenerated and reconstructed forest ecosystems. We found that there was no difference in the biomass of the fine roots of the studied species in the reconstructed forest system. The afforestation of forest ecosystems with birch may be particularly beneficial to environment because of its higher fine root biomass. Additionally, the fine root biomass increased with pH. Factors reducing the growth of fine root biomass were the availability of magnesium and the total soil carbon content. These results confirm the vulnerability of fine roots to site conditions and highlight the utility of fine root biomass evaluation when studying the dynamics and regeneration of soils.

Effect of earthworms on mycorrhization, root morphology and biomass of silver fir seedlings inoculated with black summer truffle (Tuber aestivum Vittad.)

Species of the genus Tuber have gained a lot of attention in recent decades due to their aromatic hypogenous fruitbodies, which can bring high prices on the market. The tendency in truffle production is to infect oak, hazel, beech, etc. in greenhouse conditions. We aimed to show whether silver fir (Abies alba Mill.) can be an appropriate host partner for commercial mycorrhization with truffles, and how earthworms in the inoculation substrate would affect the mycorrhization dynamics. Silver fir seedlings inoculated with Tuber. aestivum were analyzed for root system parameters and mycorrhization, how earthworms affect the bare root system, and if mycorrhization parameters change when earthworms are added to the inoculation substrate. Seedlings were analyzed 6 and 12 months after spore inoculation. Mycorrhization with or without earthworms revealed contrasting effects on fine root biomass and morphology of silver fir seedlings. Only a few of the assessed fine root parameters showed statistically significant response, namely higher fine root biomass and fine root tip density in inoculated seedlings without earthworms 6 months after inoculation, lower fine root tip density when earthworms were added, the specific root tip density increased in inoculated seedlings without earthworms 12 months after inoculation, and general negative effect of earthworm on branching density. Silver fir was confirmed as a suitable host partner for commercial mycorrhization with truffles, with 6% and 35% mycorrhization 6 months after inoculation and between 36% and 55% mycorrhization 12 months after inoculation. The effect of earthworms on mycorrhization of silver fir with Tuber aestivum was positive only after 6 months of mycorrhization, while this effect disappeared and turned insignificantly negative after 12 months due to the secondary effect of grazing on ectomycorrhizal root tips.

Frequent Fire Reduces the Magnitude of Positive Interactions Between an Invasive Grass and Soil Microbes in Temperate Forests

Fire activity is increasing in many regions. Although increased fire activity is expected to promote plant invasion, over longer time periods, frequent fire can shift the nutrient status of ecosystems, which may alter interactions between invasive plants and soil microbial decomposers. Here, we applied a fire treatment to plots embedded in deciduous forests under regimes of either fire exclusion or frequent fire and invaded by the most widespread invasive grass in the eastern USA (Microstegium vimineum) to determine how frequent fire affects plant–soil interactions while controlling for time after fire. We predicted that frequent fire would increase microbial nitrogen (N) limitation, leading to lower Microstegium productivity and reduced soil carbon (C) and N loss. We found that Microstegium leaf, root, and microbial biomass C/N ratios were significantly wider under frequent fire than fire exclusion. Consistent with these patterns, dissolved organic N concentration was 22% lower and the activity of an exoenzyme targeting N acquisition was 59% higher under frequent fire, indicating that frequent fire increased microbial N limitation. Higher surface soil C and N and fire-induced increases in particulate soil organic matter N suggest that frequent fire in these grass-invaded forests enhanced microbial N limitation through the accumulation of microbially resistant pyrogenic N. A structural equation model confirmed that these changes were interrelated and associated with 87% lower Microstegium aboveground biomass and 85% higher fine root biomass. These findings provide new insights into how frequent fire impacts plant–soil microbial interactions and thus may feedback to plant invasion over longer time periods.

Long-term (42 years) effect of thinning on soil CO2 emission in a mixed broadleaved-Korean pine (Pinus koraiensis) forest in Northeast China

Thinning is an important forest management practice that has great potential to influence regional soil carbon storage and dynamics. The present study measured soil respiration (RS, the efflux of CO2 emitted) and its two components (heterotrophic (RH) and autotrophic (RA) respiration) from soil 42 years after thinning in comparison to un-thinning (control). Autotrophic respiration was significantly greater in the thinning plot, approximately 44% higher compared to the control, while both Rs and RH were slightly, but not significantly, higher in the thinning plot. Higher fine root biomass might have contributed to the higher Ra in the thinning plot. Both Rs and RH showed clear soil temperature-dependent seasonal patterns, whereas Ra was less responsive to changes in temperature, especially within one specific season. The annual and season-specific temperature sensitivities of RS and RH were lower in the thinning plot, specifically during the mid-growing season. Furthermore, variations in the season-specific temperature sensitivity of Rs and RH were less intense in the thinning plot. We conclude that forest thinning can reduce the temperature sensitivity of RS and RH during the mid-growing season and increase soil CO2 emission in the long term.

Fine root biomass and its contribution to the mangrove communities in three saline zones of Sundarbans, Bangladesh

Globally, sea levels are rising due to climate change which would influence the salinity levels in mangroves. In the framework of this study, we focused on the influence of salinity and differences of forest structure on the fine root biomass (FRB) and carbon stocks in the Sundarbans mangrove forest, Bangladesh. Also, the relationships FRB to different stand structural parameters were investigated using the data obtained from 50 sample plots (100 sq. m each) in different salinity zones in Sundarbans. Four random soil samples (30 cm in length) were taken within study plots, which were further divided into 10 cm, 20 cm, and 30 cm to identify the most active soil layer for FRB stocks. Results suggest differences in forest structural parameters and diversity indices with salinity changes in different saline zones. The low and medium saline zone is dominated by Heriteira fomes, while Excoecaria agallocha dominates the high saline zone. The carbon stocks (Mg C ha−1) in Sundarbans show a significant decrease with increasing salinity in different saline zones, e.g. oligohaline (252 ± 60.2), mesohaline (199 ± 37.7), and polyhaline (171 ± 20.0) zone. FRB carbon (Mg C ha−1) allocation in different saline zones also followed a decreasing order, such as oligohaline (12.8), mesohaline (7.9), and polyhaline (7.3). Fine root biomass showed a decreasing trend with increasing soil depth, where the differences, however, were not significant (p > 0.05) among the soil layers. Our results provide evidence on FRB variations in Sundarbans, which has implications on the mangrove species conservation and management. The mature stands at different saline zones of Sundarbans mangrove forest, Bangladesh has a high fine root biomass, which is valuable for mangrove restoration and the studied species plantation in the shore line or coastal area which can help to decrease the erosion effects of tidal inundation.

Pinus sylvestris L. and Fagus sylvatica L. effects on soil and root properties and their interactions in a mixed forest on the Southwestern Pyrenees

Tree species alter soil properties, potentially modifying forest nutrients cycling. In the current management context in which mixed species forests are favoured over monocultures due to their biodiversity and productivity-related advantages, the assessment of species effects on soils, as well as their interactions with other species, gains increasing relevance. In this study, the effects of Scots pine (Pinus sylvestris L.) and European beech (Fagus sylvatica L.) on soil properties were evaluated. Fine roots were paid special attention, measuring their biomass, functional traits (specific root length, root tissue density) and vertical distribution in order to discern the direction of these species interaction, either complementary or competitive. The research was carried out in the Southwestern Pyrenees (northern Spain), in an originally Scots pine stand transformed nowadays into a mixed forest by European beech natural regeneration. Soil and root samples were taken close to pine trees surrounded by other pines in areas that remain similar to pine monospecific stands, and close to pine and beech trees surrounded by both species in mixed areas. A lower C/N ratio was found in the soil close to beech stems. This suggests better quality in mixed litter in comparison to pine litter, leading to higher decomposition rates. Higher fine root biomass was found in the mixed areas mainly due to beech fine roots great abundance, which correlated positively with microbial biomass. Fine roots functional traits such as specific root length and diameter did not vary depending on their proximity to different tree species, though Scots pine fine root biomass decreased sharply when close to beech trees. This reduction, together with the already more abundant fine root biomass of beech, with higher specific root length and root tissue density than pine, lead to a competitive interaction in which European beech tends to dominate the soil at all depths. In this case, no complementarity effect at belowground level, strong enough to allow Scots pines to cope with beech soil colonization, was found under natural conditions.

Contrasting Root System Structure and Belowground Interactions between Black Spruce (Picea mariana (Mill.) B.S.P) and Trembling Aspen (Populus tremuloides Michx) in Boreal Mixedwoods of Eastern Canada

This study explored the underground interactions between black spruce and trembling aspen in pure and mixed stands to understand how their soil resource use help these species coexist in the boreal mixedwoods of Western Quebec. We analyzed species-specific fine root foraging strategies (root biomass and root tissue density) along three soil layers (organic, top 0–15 cm, and bottom 15–30 cm mineral soil), using 180 soil cores. We collected cores in three sites, each containing three 20 × 50 m2 plots of pure spruce, pure aspen, and mixed spruce and aspen stands. Spruce had a shallow rooting, whereas aspen had a deep rooting in both types of stands. Compared to pure spruce stands, spruce had a lower fine root biomass (FRB) and a higher root tissue density (RTD) in the organic layer of mixed stands. Both patterns were indicative of spruce’s more intensive resource use strategy and competitive advantage over aspen in that layer. Aspen FRB in the organic soil did not differ significantly between pure and mixed stands, but increased in the mineral soil of mixed stands. Since we did not observe a significant difference in the nutrient content of the mineral soil layer between pure aspen and mixed stands, we concluded that aspen may experience competitive exclusion in the organic layer by spruce. Aspen exhibited an extensive nutrient uptake strategy in the organic layer of mixed stands: higher FRB and lower RTD than spruce. In mixed stands, the differences in aspen rooting patterns between the organic and mineral layers suggested the use of contrasting nutrient uptake strategies along the soil profile. We speculate that the stronger spatial separation of the roots of spruce and aspen in mixed stands likely contribute to a higher partitioning of their nutrient uptake along the soil profile. These results indicate the competitive exclusion of aspen by spruce in boreal mixedwoods, which likely occurs in the soil organic layer.

Vegetation type and plant diversity affected soil carbon accumulation in a postmining area in Shanxi Province, China

AbstractCoal mining causes severe land degradation, which poses a great damage to carbon (C) sequestration function of the original ecosystem. Vegetation restoration in postmining areas plays an important role in rebuilding soil C pool and improving soil quality. In this study, soil C sequestration and soil properties of different vegetation types were investigated along restoration chronosequences in a postmining area in the eastern Loess Plateau. The results showed that soil properties improved substantially through artificial restoration by planting Rhus typhina (exotic species) and Platycladus orientalis (indigenous species) and through natural restoration. Soil C stock (0–20 cm depth) increased significantly with restoration duration in all of the vegetation types and was positively correlated to plant diversity except in R. typhina. After 12–20 years from restoration, accumulation rates of soil C varied significantly with vegetation type, with the maximum in P. orientalis (0.60 Mg ha−1 yr−1) and the minimum in naturally restored grassland (0.21 Mg ha−1 year−1). The optimum performance of P. orientalis plantation could be attributed mainly to high plant diversity and associated high fine root biomass (1.72 Mg ha−1). A sharp decrease of plant diversity (39.0%) in R. typhina 12 years after restoration implied that soil C accumulation might not be sustainable in the long term. Our results suggest that P. orientalis as an indigenous species adaptable to harsh environment may facilitate the succession of a diverse ecosystem and promote soil C accumulation in degraded lands of postmining areas.

The Dynamics of Living and Dead Fine Roots of Forest Biomes Across the Northern Hemisphere

Research Highlights: A detailed picture of the seasonality in fine root biomass (FRB), necromass (FRN), and the biomass/necromass ratio (FRBN) throughout the whole year is crucial to uncover profound effects of long-term environmental changes on fine root dynamics. Materials and Methods: We used meta-analysis to characterize the variability of FRB, FRN and FRBN, and determined their relations with climatic (monthly versus annual), edaphic and geomorphic factors for tropical, temperate and boreal forest biomes across the Northern Hemisphere. Results: Boreal forests exhibited the highest FRB and FRN, while tropical forests yielded the lowest FRN, and thus the greatest FRBN. FRB and FRN significantly decreased with sampling depth, but increased with soil organic carbon content and elevation, while an opposite pattern was found for FRBN. Temperature and precipitation at different time scales (monthly versus annual) and latitude had varying influences on fine roots. High FRB and FRN were observed during dry season for tropical forests, but in the late growing season for temperate forests. The three forest biomes exhibited the high root activity (measured as FRBN) in June or July. Conclusions: It is crucial to realize the universal and specific responses of fine roots to multiple environmental factors when attempting to incorporate these parameters into fine root monthly dynamic models in forest ecosystems. The biome-specific fluctuation of fine roots contributes to identify the influence factors on fine root seasonal patterns throughout the whole year. Our analysis is expected to improve the understanding of the key role of fine roots at monthly level in modeling and predicting carbon budget of various forest biomes under future climate change.

How Low Can They Go? Plant-Parasitic Nematode Distribution in a Washington Vineyard

Summary Goals: To map the distribution of two plant-parasitic nematode species, the northern root-knot nematode Meloidogyne hapla and the dagger nematode Xiphinema spp., in a Washington State winegrape vineyard slated for replanting. These nematode species can reduce vineyard longevity and weaken or kill young vines. Knowing how these nematodes are spatially distributed in soil can improve implementation of management strategies. Key Findings: Northern root-knot nematode and dagger nematode had distinctly different distributions within the soil profile. Northern root-knot nematode was concentrated near the vine rows and drip-irrigation lines, in the upper 61 cm (24 inches) of the soil profile. This is reflective of its life strategy, in which association with fine roots and areas of moisture is essential. Dagger nematode was relatively evenly distributed at all distances from the vine row, and significant populations were found down to the deepest sampling depth of 122 cm (48 inches). This demonstrates that it can survive readily on hosts other than grape and can parasitize root types that are not parasitized by northern root-knot nematode. Impact and Significance: This work provides evidence for how and why nematode management practices may differ in their efficacy. Dagger nematodes were distributed throughout the sampled area and were found at depths that most fumigation efforts cannot reach. This increases the likelihood that dagger nematodes will recolonize treated areas, but this may take time as they move upward from deep in the soil. Root-knot nematodes may be more easily controlled via chemigation or fumigation, as their distribution corresponds to shallower areas with high fine root biomass wetted by drip irrigation.

Effects of heterogeneous distribution of soil resources on the growth of Chinese fir seedlings under warming

A three-factor experiment with air temperature manipulation, soil temperature manipulation and nutrients distribution pattern was conducted in Forest Ecosystem and Global Change Research Station of Fujian Normal University in Chenda, Sanming, Fujian Province. We examined the effects of heterogeneous distribution of soil resources and warming on underground and aboveground growth of Chinese fir (Cunninghamia lanceolata) seedlings, and whether warming could change the recognition of fine roots to the heterogeneous distribution of soil resources, to understand the response of Chinese fir seedlings to heterogeneous distribution of soil resources under the background of global warming. The results showed that the recognition degree of Chinese fir to the nutrients distribution pattern was mainly reflected by the absorbing root (0-1 mm diameter class) rather than by the 1-2 mm diameter class fine roots. There were no significant effects of warming on the ratio of fine root biomass between nutrient-poor and nutrient-rich patches, the coefficient of nutrients-avoidance and the coefficient of nutrients-preference of fine roots of young Chinese fir except for the single air warming. Chinese fir had higher fine root biomass (0-1 mm diameter class) and lower height in the heterogeneous soil resource environment. Air warming decreased the biomass of fine roots (both 0-1 and 0-2 mm diameter classes) and increased the height of trees. Soil warming decreased the fine root biomass of 1-2 mm diameter class and increased the height of trees and the length of lateral branches. There was no significant interactive effect of air warming, soil warming and heterogeneity of soil resource on aboveground and belowground growth of Chinese fir. The results demonstrated that the absorbing roots of Chinese fir seedlings could recognize the heterogeneous distribution of soil resources,which was not altered by warming.

Inconsistent responses of soil respiration and its components to thinning intensity in a Pinus tabuliformis plantation in northern China

Understanding the responses of soil respiration (Rs) to thinning is essential to evaluate the effects of management practices on carbon cycling in plantation forest ecosystems. However, how Rs and its components (autotrophic, Ra and heterotrophic respiration, Rh) vary with thinning intensity and the underlying mechanisms are not well understood. In the present study we monitored Rs, Ra and Rh over five growing seasons using a trenching method in a Pinus tabuliformis plantation subjected to four thinning treatments (no thinning, CK; light thinning, LT; moderate thinning, MT and heavy thinning, HT). On average, LT and MT significantly increased Rs by 13% and 17%, respectively, compared with the CK. These increments of Rs were ascribed to the enhanced Ra in LT and MT plots, because light and moderate thinning promoted root growth and productivity (higher fine root biomass). However, HT did not result in a further increase in Ra, suggesting that increases in the activity of remaining trees and understory plants did not compensate for the reduced photosynthesis and the amount of respiring tree roots by extensive tree-cut. In contrast to Ra, variation in Rh was unrelated to thinning, partly due to the stable forest floor mass (non-living organic materials such as litter and fine woody debris) and microbial biomass carbon content (MBC) between thinned and control plots. The temperature sensitivity (Q10) of Ra and Rh ranged from 1.40 to 3.07 and 2.34–3.42, respectively. The highest Q10 of Ra was observed in MT while that of Rh occurred in LT. Soil moisture was significantly correlated with Rh but a poor predictor for Ra. Our findings demonstrated that Ra and Rh responded to thinning intensity independently of each other. The intensity of management and plant-mediated biological processes are of particular importance in evaluating the impacts of forest management on C sequestration potential in plantation forests.

Fine root biomass and the associated C and nutrient pool under the alder (Alnus spp.) plantings on reclaimed technosols

In the study we have analysed the increment of fine-root biomass (FRBI) and the associated pool of carbon and nutrients (N, S, P, K, Ca, Mg, Na) under alder plantings (Alnus incana, A. glutinosa and A. viridis) growing on technosols developed from combustion wastes and extremely poor quaternary sands excavated by sand mining. The control sites were located in natural habitats in the Bieszczady Mountains within the natural range of the occurrence of the investigated alder species. The fine root biomass depended on the type and properties of the technosols substrate but did not differ between the alder species. The highest fine root biomass (>1000 g m−2) was found in the nutrient-poor sandy soils (SS) of a former sand pit, whereas technosols formed from combustion waste was <301 g m−2, and the lowest (below 264 g m−2) was in natural soils. The results indicate an important role of fine roots in the development of the carbon and nutrient pools in technosols. This is particularly important in the case of barren sandy soils where a deficit of nutrients is balanced by an efficient circulation and release of elements in the decomposition process of dead organic matter, largely connected to the fine roots biomass.