Fine Root Dry Weight Research Articles

Effects of stumping on fine root architecture, growth, and physiology of Hippophae rhamnoides.

Fine roots are vital to a plant's ability to absorb water and nutrients. Stumping is a practice that may encourage fine root growth and the rapid recovery of decaying Hippophae rhamnoides plants. However, the effect of stumping on the fine roots and physiological indices is still unknown. The differential indices between stumped forests and non-stumped forests must also be defined. We recorded the changes in the fine roots of structure H. rhamnoides one year after stumping. Using single factor analysis of variance and general linear models we comprehensively analyzed the number of root tips and the plant's growth and physiological indices in response to stumping. Partial least squares discriminant analysis (PLS-DA) was used to compare fine root growth and physiological indices with and without stumping in order to identify the differential indices. The proportion of root tips in the vertical layers at 30-40 cm and 40-50 cm and in the horizontal layers at 60-80 cm and 80-100 cm, increased after stumping by 1.85%, 2.60%, 1.96% and 4.32%, respectively. In the 0-50 cm soil layer, the fine root dry weight rose by 27.6% compared with the control, which was not significant. However, other indices were significantly different from the control. The proportions in the growth indices in the 30-40 cm and 40-50 cm layers increased after stumping. Stumping had a significant, negative effect on proline and malondialdehyde content, which dropped by 40.95% and 55.32%, respectively, indicating that the harms caused by these two chemicals was alleviated. Stumping had a significant positive effect on root activity and soluble sugar contents, which increased by 68.58% and 36.87%, respectively, and improved the growing ability of fine roots. PLS-DA revealed that malondialdehyde, soluble sugars, root density, and the number of root tips ranked from having the least to greatest effect on the classification of stumping and no-stumping. The process of stumping may promote fine roots growth in H. rhamnoides, and is favorable for their longitudinal development. The fine root growing indices of H. rhamnoides responded positively to this process. Stumping promotes root activity and the creation of soluble sugar to maintain the growth and development of fine roots. It also inhibits the negative effects of proline and malondialdehyde on fine roots. Our study showed that the differential physiological indices were more important for classification than the differential growing indices.

Spatial distribution and seasonal dynamics of fine roots of Castanea mollissima

To confirm the spatial distribution and seasonal dynamics of fine roots in the non-timber forest products breeding and cultivation practice base for Castanea mollissima (chestnut) of Beijing Forestry University in Qianxi, Hebei Province, the monthly dynamics and spatial distribution characteristics of fine root length density and dry weight density in a six-year-old chestnut plantation for the 0-20, 20-40, and 40-60 cm soil layers were studied using the soil coring method. Soil cores with a diameter of 8 cm were taken each month during the growing period (from April to October) about 50 and 100 cm away from the chestnut tree stem. Results showed that the fine root length density with a monthly average value of 1 274.9 m·m-3 had two growth peaks. Compared to the previous month, June and October both had significant difference (P < 0.05), which increased 203.0 m·m-3 and 524.6 m·m-3 separately. The fine root dry weight density had a monthly average value of 184.7 g·m-3 and two growing periods from April to June and from September to October. The fine root dry weight density in October was 39.5 g·m-3 higher compared to that in September (P < 0.05). The value of the fine root length density and dry weight density reached a maximum and changed with the seasons most noticeably in the vertical direction of the 20-40 cm soil layer (P < 0.05). Also, the fine root length density and dry weight density in the horizontal direction about 100 cm were greater than those about 50 cm (P < 0.05). This study indicated that spatial distribution and seasonal dynamics of fine roots likely resulted from spatial soil properties and the growth rule of C. mollissima.

Plastic Responses Mediated by Identity Recognition in Below-Ground Competition in Cycas micronesica K.D. Hill

We studied the ability of Cycas micronesica roots to recognize the identity of competitor roots using pot culture. Pairs of seedlings were grown in single pots for 10.5 months, and morphological traits of the focal plant were determined when the non-focal plant was a half-sibling, a close relative from a mother 170 m away, a distant relative from a habitat 40 km away, or a different species ( Cycas edentata) from Mindanao, Philippines. Most of the measured response traits exhibited similar trends and confirmed that C. micronesica plant roots were able to recognize the identity of competitors. For example, focal plants grown in pots with C. edentata competitors exhibited 66% increase in fine root dry weight, 54% increase in coralloid root dry weight, and 49% increase in total plant dry weight, compared to focal plants grown in competition with half-siblings. Our methods have shown that plot design in ex situ conservation and botanic garden settings would improve by positioning C. micronesica plants adjacent to non-relatives. Recruitment may improve within in situ conservation plots if managers distribute seeds away from the maternal parent so that emerging seedlings are not forced into immediate competition with half-siblings. These findings may be useful for designing more complex experiments to quantify the influence of these plastic root responses on plant nutrient status and physiology.

‘Abnormal vertical growth’: a disorder threatening the viability of the Australian macadamia industry

'Abnormal vertical growth' (AVG) was recognised in Australia as a dysfunction of macadamia (Macadamia spp.) in the mid-1990s. Affected trees displayed unusually erect branching, and poor flowering and yield. Since 2002, the commercial significance of AVG, its cause, and strategies to alleviate its affects, has been studied. The cause is still unknown, and AVG remains a serious threat to orchard viability. AVG affects both commercial and urban macadamia. It occurs predominantly in the warmer-drier production regions of Queensland and New South Wales. An estimated 100,000 orchard trees are affected, equating to an annual loss of $ 10.5 M. In orchards, AVG occurs as aggregations of affected trees, affected tree number can increase by 4.5% per year, and yield reduction can exceed 30%. The more upright cultivars 'HAES 344' and '741' are highly susceptible, while the more spreading cultivars 'A4', 'A16' and 'A268' show tolerance. Incidence is higher (p<0.05) in soils of high permeability and good drainage. No soil chemical anomaly has been found. Fine root dry weight of AVG trees (0-15 cm depth) was found lower (p<0.05) than non-AVG. Next generation sequencing has led to the discovery of a new Bacillus sp. and a bipartite Geminivirus, which may have a role in the disease. Trunk cinctures will increase (p<0.05) yield of moderately affected trees. Further research is needed to clarify whether a pathogen is the cause, the role of soil moisture in AVG, and develop a varietal solution.

Nine years of irrigation cause vegetation and fine root shifts in a water-limited pine forest.

Scots pines (Pinus sylvestris L.) in the inner-Alpine dry valleys of Switzerland have suffered from increased mortality during the past decades, which has been caused by longer and more frequent dry periods. In addition, a proceeding replacement of Scots pines by pubescent oaks (Quercus pubescens Willd.) has been observed. In 2003, an irrigation experiment was performed to track changes by reducing drought pressure on the natural pine forest. After nine years of irrigation, we observed major adaptations in the vegetation and shifts in Scots pine fine root abundance and structure. Irrigation permitted new plant species to assemble and promote canopy closure with a subsequent loss of herb and moss coverage. Fine root dry weight increased under irrigation and fine roots had a tendency to elongate. Structural composition of fine roots remained unaffected by irrigation, expressing preserved proportions of cellulose, lignin and phenolic substances. A shift to a more negative δ13C signal in the fine root C indicates an increased photosynthetic activity in irrigated pine trees. Using radiocarbon (14C) measurement, a reduced mean age of the fine roots in irrigated plots was revealed. The reason for this is either an increase in newly produced fine roots, supported by the increase in fine root biomass, or a reduced lifespan of fine roots which corresponds to an enhanced turnover rate. Overall, the responses belowground to irrigation are less conspicuous than the more rapid adaptations aboveground. Lagged and conservative adaptations of tree roots with decadal lifespans are challenging to detect, hence demanding for long-term surveys. Investigations concerning fine root turnover rate and degradation processes under a changing climate are crucial for a complete understanding of C cycling.

Sour orange fine root distribution after seventeen years of atmospheric CO2 enrichment

Long-term (more than 15 years) effects of elevated CO2 on belowground responses of trees have received limited attention in the literature. We report on a study in which sour orange trees (Citrus aurantium L.) grown in an Avondale loam in Phoenix, AZ, were exposed to ambient and elevated (ambient+300μmolmol−1) levels of atmospheric CO2 for 17 years. At study termination, soil cores were collected to determine how long-term CO2 enrichment affected horizontal (0.5, 1.0, 1.5, and 2.0m from each tree) and vertical (0–105cm in 15cm increments) standing crop fine root dry weight and length. Overall, elevated CO2 increased both root length (35.6%) and root dry weight (39.1%) densities. There was no effect of CO2 concentration on horizontal root distribution patterns. However, significant CO2 by depth interactions were noted for both root length and root dry weight densities with differences occurring only in the top two depths. Elevated CO2 increased fine root length density by 64.5 and 57.2% at the 0–15 and 15–30cm depths. Respective increases for root dry weight were 80.3 and 82.8%. These large responses occurred under water and nutrient supplies typical of orchard conditions and suggest that long-term citrus productivity can be enhanced under future levels of atmospheric CO2.

SOIL INJECTIONS OF CARBOHYDRATES IMPROVE FINE ROOT GROWTH OF ESTABLISHED URBAN TREES

Summary Four established mature tree species (Aesculus hippocastanum L., Betula pendula Roth., Primus avium L. and Quercus rohur L.) commonly planted in UK urban landscapes were subjected to soil injections of the carbohydrate sucrose at 25, 50 and 70g per litre of water. Fine root dry weight was recorded at month 5 following soil injections. Soil injections of sucrose significantly increased fine root dry weight compared to controls, however; growth responses were influenced by species and the con-centration of sucrose applied. Results indicate soil injections of sucrose ≥ 50g litre of water may be able to improve root growth of established mature trees. Such a response is desirable as root damage following con-struction is a frequent problem encountered by established trees growing in UK towns and cities.

Long-term effects of lime application on 15N availability to Sitka spruce seedlings growing in pots containing peat soils

The long-term effects of liming a peat soil on nitrogen availability to 3-year-old Picea sitchensis seedlings were assessed in greenhouse experiments. Seedlings were planted in pots containing either unlimed or limed peat soils that had been limed 28 years earlier. The plants were harvested in October 1993, April 1994 and July 1994 with these dates representing 100, 160 and 263 days after planting respectively. Concentration of extractable NO 3 – in the limed peat was higher than in the unlimed peat. Liming also resulted in increases in extractable organic N and total extractable N in the peat. On all harvesting occasions, percentage 15 N utilization and total N were reduced in plants grown on the limed peat. Decreased concentrations of N in the fine-root fractions were apparent for plants grown on the limed peat at the October and July harvests only. During the growing season, the above-ground parts of the plant were the dominant sinks for nitrogen. The needles and fine roots were the major fractions for the utilization of 15N particularly in April and July. The only effect of a limed peat on dry weight of plant fractions was a decrease in fine-root dry weight when plants were examined in October 1993. On all harvesting occasions, populations of mycorrhizae were decreased and roots were blackened for plants grown in the limed peat soil.

Input control of organic matter dynamics

The amount and quality of inputs into soil organic matter will be altered by both climate and landuse change. The increase in growth of plants caused by increasing CO 2 concentration implies not only potential increases in yields but also increases in plant residues. Simulation models using doubled CO 2 levels predict global net primary productivity (NPP) to increase by 16.3%, over half of which will occur in the tropics. For tropical ecosystems increases in NPP will be dominated by the effects of elevated CO 2, with water and nitrogen availability and temperature playing a less significant role. Phosphorus limitation may determine whether the potential for increased plant growth will be realized. The distribution of C3 and C4 species in the tropics could be affected by landuse change and estimates of yield increases will be dependent on their proportions. The allocation of photosynthate to the root will increase under elevated CO 2, resulting in increased fine root dry weight and root length. Root sink strength and the turnover of roots and associated symbionts are critical knowledge gaps. Carbon: nitrogen ratios in tissues will increase resulting in decreased decomposition rates. The concentration of secondary compounds will be affected more by nitrogen limitations than a direct CO 2 effect. Changes in lignin, tannin and polyphenol levels are more important in the decomposability of tropical litters than changes in the C : N ratios. Decomposition models will have to be altered to take into account changes in plant composition. The role of models in predicting the effects of management practice on long-term fertility is addressed.

Formation of cluster roots and mycorrhizal status of Comptonia peregrina and Myrica pensylvanica in Maine, USA

Extent of cluster (proteoid) root formation in the field was examined in relation to availability of P and successional status of the site in two actinorhizal, N2‐fixing shrubs. Comptonia peregrina (L.) Coult. and Myrica pensylvanica Loisel. In C. peregrina cluster roots were present at all 13 sites and comprised between 0.2 and 19% of total fine root dry weight. Cluster root formation was most extensive at recently disturbed sites and was negatively correlated with cover of associated woody species (r =−0.85), litter depth (r =−0.81) and available (extractable) soil P (r =−0.75). In M. pensylvanica cluster roots were present at all 11 sites and comprised between 6 and 20% of total fine root dry weight. On mineral soils (n = 6), extent of cluster root formation was negatively correlated (r =−0.86) with cover of associated woody species and with litter depth (r =−0.78; P= 0.07). Comptonia peregrina and M. pensylvanica lack functional mycorrhizae at these sites because only intracellular infections were found and these lacked arbuscules. None of 22 non‐N2‐fixing, dominant woody species associated with C. peregrina and M. pensylvanica formed cluster roots. Cluster roots probably allow C. peregrina and M. pensylvanica to obtain sufficient P from nutrient‐poor soils in the absence of functional mycorrhizae. Extensive cluster root formation on disturbed, early successional sites may aid these species in colonizing these sites because they have to form only one symbiosis (with Frankia) and not two (with Frankia and a mycorrhizal fungus).

Soil-plant water relations, root distribution and biomass partitioning inLupinus albusL. under drought conditions

Lupinus albus L. from different climatic origins responded to a 15 d period of water shortage during flowering by losing 50% of the total leaf canopy and gaining 55% in stem dry weight. Water deficits also led to a significant increase in the fine root length density and a slight increase in the fine root dry weight. The latter increase was especially pronounced in the deeper soil layers. Some marginal differences among genotypes were observed in the responses. Stomatal closure by midday was an early response to water deficit, giving rise to constant predawn leaf water potentials during the first week of water shortage in spite of a decrease of 60% in the available soil water. No osmotic regulation or adjustments of the cell wall properties were observed in any of the lupin lines. We explained the maintenance of seed production in water-stressed plants by their ability to accumulate assimilates in the shoot, which would be diverted to the pods during the seed filling stage.

Factors affecting formation of cluster roots in Myrica gale seedlings in water culture

The effect of nutrient deficiency, aeration, phosphorus supply, and nitrogen source on the formation of cluster (proteoid) roots was examined in Myrica gale seedlings growing in water culture. Only the omission of phosphorus resulted in the formation of significant numbers to cluster roots when plants were grown in a number of 1/4 strength Hoagland's solutions, each lacking one mineral nutrient. Aeration shortened the time required for cluster root formation and increased the percentage of plants forming cluster roots. The proportion of the root system comprised of cluster roots decreased as the phosphorus concentration in the solution increased and no cluster roots formed in solutions containing 8 mg P/L. Phosphorus supply also affected total plant biomass, proportion of biomass comprising nitrogen-fixing nodules, shoot:root ratio, phosphorus concentration in the leaves and phosphorus content of the plants. The plants showed luxury consumption of phosphorus and were able to produce large amounts of biomass utilizing only stored phosphorus. Nitrogen source also affected cluster root formation. Urea-fed plants produced cluster roots more quickly and devoted a substantially larger proportion of root growth to cluster roots than did nitrate-fed plants. The longest cluster root axes were produced in nitrate-fed plants supplied with no phosphorus and the shortest were in urea-fed plants at 4 mg P L−1. Four methods for expressing the extent of cluster root formation were examined and it was concluded that cluster roots as a proportion of total fine root dry weight is preferable in many cases. Formation of cluster roots in response to phosphorus deficiency coupled with previously demonstrated traits allows Myrica gale to adapt to a wide range of soil conditions.

Prescribed-fire effects on fine-root and tree mortality in old-growth ponderosa pine

Old-growth Pinusponderosa Dougl. stands were surveyed at Crater Lake National Park to investigate potential accelerated mortality of large pines due to prescribed burning. Mortality of P. ponderosa greater than 22 cm diameter at breast height was higher in burned areas (19.5%) than in unburned areas (6.6%), and early-season burns had over 30% mortality. Mortality was associated with fire severity, as measured by scorch height and ground char, season of burning, and tree vigor. Pines of high, moderate, and low vigor were subjected to a prescribed burn in June; half of the trees had debris raked from tree bases as an additional treatment. Lethal heat loads (&gt;60 °C) occurred in &gt;75% of samples at the soil surface and at 5 cm soil depth, with duration exceeding 5 h. Burning reduced fine-root dry weight 50–75% 1 and 5 months after burning; raking and burning reduced fine-root dry weight more than burning alone after 1 month and had similar effects to burning after 5 months. A low-vigor tree that had been raked and burned died by the beginning of the fourth dry season after burning. Present fuel loads may be too high to burn during spring if old-growth P. ponderosa are to be protected.