Pinus Taeda Seedlings Research Articles

Colonization of root endophytic fungus Serendipita indica improves drought tolerance of Pinus taeda seedlings by regulating metabolome and proteome.

Pinus taeda is an important forest tree species for plantations because of its rapid growth and high yield of oleoresins. Although P. taeda plantations distribute in warm and wet southern China, drought, sometime serious and long time, often occurs in the region. To explore drought tolerance of P. taeda and usage of beneficial microorganisms, P. taeda seedlings were planted in pots and were inoculated with root endophytic fungus Serendipita indica and finally were treated with drought stress for 53 d. Metabolome and proteome of their needles were analyzed. The results showed that S. indica inoculation of P. taeda seedlings under drought stress caused great changes in levels of some metabolites in their needles, especially some flavonoids and organic acids. Among them, the levels of eriocitrin, trans-aconitic acid, vitamin C, uric acid, alpha-ketoglutaric acid, vitamin A, stachydrine, coumalic acid, itaconic acid, calceolarioside B, 2-oxoglutaric acid, and citric acid were upregulated more than three times in inoculated seedlings under drought stress, compared to those of non-inoculated seedlings under drought stress. KEGG analysis showed that some pathways were enriched in inoculated seedlings under drought stress, such as flavonoid biosynthesis, ascorbate and aldarate metabolism, C5-branched dibasic acid metabolism. Proteome analysis revealed some specific differential proteins. Two proteins, namely, H9X056 and H9VDW5, only appeared in the needles of inoculated seedlings under drought stress. The protein H9VNE7 was upregulated more than 11.0 times as that of non-inoculated seedlings under drought stress. In addition, S. indica inoculation increased enrichment of water deficient-inducible proteins (such as LP3-1, LP3-2, LP3-3, and dehydrins) and those involved in ribosomal structures (such as A0A385JF23). Meanwhile, under drought stress, the inoculation caused great changes in biosynthesis and metabolism pathways, mainly including phenylpropanoid biosynthesis, cutin, suberine and wax biosynthesis, and 2-oxocarboxylic acid metabolism. In addition, there were positive relationships between accumulation of some metabolites and enrichment of proteins in P. taeda under drought stress. Altogether, our results showed great changes in metabolome and proteome in inoculated seedlings under drought stress and provided a guideline to further study functions of metabolites and proteins, especially those related to drought stress.

Targeted and untargeted metabolomics reveals deep analysis of drought stress responses in needles and roots of Pinus taeda seedlings.

Drought stress is one of major environmental stresses affecting plant growth and yield. Although Pinus taeda trees are planted in rainy southern China, local drought sometime occurs and can last several months, further affecting their growth and resin production. In this study, P. taeda seedlings were treated with long-term drought (42d), and then targeted and untargeted metabolomics analysis were carried out to evaluate drought tolerance of P. taeda. Targeted metabolomics analysis showed that levels of some sugars, phytohormones, and amino acids significantly increased in the roots and needles of water-stressed (WS) P. taeda seedlings, compared with well-watered (WW) pine seedlings. These metabolites included sucrose in pine roots, the phytohormones abscisic acid and sacylic acid in pine needles, the phytohormone gibberellin (GA4) and the two amino acids, glycine and asparagine, in WS pine roots. Compared with WW pine seedlings, the neurotransmitter acetylcholine significantly increased in needles of WS pine seedlings, but significantly reduced in their roots. The neurotransmitters L-glutamine and hydroxytyramine significantly increased in roots and needles of WS pine seedlings, respectively, compared with WW pine seedlings, but the neurotransmitter noradrenaline significantly reduced in needles of WS pine seedlings. Levels of some unsaturated fatty acids significantly reduced in roots or needles of WS pine seedlings, compared with WW pine seedlings, such as linoleic acid, oleic acid, myristelaidic acid, myristoleic acid in WS pine roots, and palmitelaidic acid, erucic acid, and alpha-linolenic acid in WS pine needles. However, three saturated fatty acids significantly increased in WS pine seedlings, i.e., dodecanoic acid in WS pine needles, tricosanoic acid and heptadecanoic acid in WS pine roots. Untargeted metabolomics analysis showed that levels of some metabolites increased in WS pine seedlings, especially sugars, long-chain lipids, flavonoids, and terpenoids. A few of specific metabolites increased greatly, such as androsin, piceatanol, and panaxatriol in roots and needles of WS pine seedlings. Comparing with WW pine seedlings, it was found that the most enriched pathways in WS pine needles included flavone and flavonol biosynthesis, ABC transporters, diterpenoid biosynthesis, plant hormone signal transduction, and flavonoid biosynthesis; in WS pine roots, the most enriched pathways included tryptophan metabolism, caffeine metabolism, sesquiterpenoid and triterpenoid biosynthesis, plant hormone signal transduction, biosynthesis of phenylalanine, tyrosine, and tryptophan. Under long-term drought stress, P. taeda seedlings showed their own metabolomics characteristics, and some new metabolites and biosynthesis pathways were found, providing a guideline for breeding drought-tolerant cultivars of P. taeda.

Dirt cheap: an experimental test of controls on resource exchange in an ectomycorrhizal symbiosis.

To distinguish among hypotheses on the importance of resource-exchange ratios in outcomes of mutualisms, we measured resource (carbon (C), nitrogen (N), and phosphorus (P)) transfers and their ratios, between Pinus taeda seedlings and two ectomycorrhizal (EM) fungal species, Rhizopogon roseolus and Pisolithus arhizus in a laboratory experiment. We evaluated how ambient light affected those resource fluxes and ratios over three time periods (10, 20, and 30 wk) and the consequences for plant and fungal biomass accrual, in environmental chambers. Our results suggest that light availability is an important factor driving absolute fluxes of N, P, and C, but not exchange ratios, although its effects vary among EM fungal species. Declines in N:C and P:C exchange ratios over time, as soil nutrient availability likely declined, were consistent with predictions of biological market models. Absolute transfer of P was an important predictor of both plant and fungal biomass, consistent with the excess resource-exchange hypothesis, and N transfer to plants was positively associated with fungal biomass. Altogether, light effects on resource fluxes indicated mixed support for various theoretical frameworks, while results on biomass accrual better supported the excess resource-exchange hypothesis, although among-species variability is in need of further characterization.

Invasive alien species in protected areas: the dynamics of Pinus taeda at Rio Canoas State Park – Brazil

Biological invasion is a growing problem, and species of the genus Pinus are known to be a problem in the forests of southern Brazil, including in conservation units. Here, we studied the ecology of Pinus taeda L. invasion in Rio Canoas State Park (PAERC) in regards to forest inventory, soil seed bank analysis, and seed rain assessment, in three distinct successional stages inside the park referred to as “Pinus invasion”, “Old Growth Vegetation”, and “Initial Vegetation”. The forest inventory of 33 (20 m × 20 m) plots found Pinus in two of the three evaluated environments. Seed rain was collected bimonthly using 33 (1 m × 1 m) seed traps for a period of 1 year. The major seed distribution periods were in April and June, confirming data found in the literature. The seed bank was analyzed in February (summer) and June (winter) of 2018. Samples were kept in a greenhouse for a period of 120 days each. Summer evaluation showed no emergence of Pinus taeda seedlings, but the winter evaluation (June) did show the emergence of seedlings. The results showed that the soil seed bank is not persistent. Accordingly, the Pinus invasion reported at PAERC requires a restoration program, as well as one that controls reinfestation.

Soil rehabilitation and growth of pine and eucalyptus in area degraded by coal mining

For rehabilitation of degraded soil by open-pit coal mining it is necessary to correct the acidity and nutrients contents and promote revegetation. We evaluated different rehabilitation methods of a degraded area by coal mining on constructed soil chemical and physical attributes, and on growth of pine and eucalypt. The experiment was established between 2001 and 2004 in southern Brazil using treatments with lime, palisade grass (Urochloa brizantha), and poultry litter. Seedlings of Pinus taeda and Eucalyptus saligna were planted in 2004. In 2010, soil samples were collected at 0-5 and 5-10 cm layers for chemical and physical analysis and height and diameter of the trees were measured. Poultry litter and palisade grass did not affect soil chemical attributes, but palisade grass reduced soil penetration resistance. Lime increased soil pH, calcium and magnesium contents and base saturation and decreased aluminum saturation, however, the difficulty of lime incorporation resulted in overliming in the soil surface layer, however, the difficulty of lime incorporation resulted in overliming in the soil surface layer, which decreased pine growth. The growth of eucalypt decreased with palisade grass and poultry litter but had impaired growth throughout the area due probably to the physical (low porosity) and chemical (low phosphorus) limitations. Therefore, in similar constructed soils the reforestation with Eucalyptus saligna cannot be indicated, while reforestation with Pinus taeda is viable with lower rates of lime.

PARTIÇÃO DA MATÉRIA SECA E DE CARBONO EM MUDAS DE <i>Pinus taeda </i> L. SUBMETIDAS À TIGMOMORFOGÊNESE

O presente trabalho objetivou quantificar os efeitos da tigmomorfogênese induzida por flexões caulinares na fase de rustificação de mudas de Pinus taeda L. sobre a partição da matéria seca e de carbono. Mudas de Pinus taeda com 22 cm de altura, produzidas em tubetes, foram submetidas a cinco intensidades de flexões caulinares (0, 5, 10, 20 e 40 flexões) realizadas diariamente, com o auxílio de um aparato mecânico, por 60 dias. Ao final, quantificou-se a área foliar e os incrementos na altura e no diâmetro do coleto. Posteriormente, determinaram-se os incrementos na massa de matéria seca de raízes e da parte aérea foram subdivididas em cinco componentes: raiz pivotante, raízes laterais, acículas, casca e lenho. Na matéria seca resultante, foi determinado o teor e conteúdo de carbono. O experimento seguiu o delineamento inteiramente ao acaso com quatro repetições. Os resultados foram submetidos à análise de regressão a 5% de probabilidade de erro. A tigmomorfogênese induzida por flexões caulinares resultou na redução do crescimento em altura, área foliar e matéria seca da parte aérea, mas, com até 20 flexões caulinares, promoveu o aumento da taxa de crescimento em diâmetro e matéria seca do sistema radicular. A alteração no crescimento primário e secundário foi resultante da redistribuição de carbono e do conteúdo de matéria seca no caule e no sistema radicular, principalmente em raízes laterais, através de redução de área foliar. Os resultados sugerem que em mudas perturbadas mecanicamenteo aumento em área foliar deixa de ser o dreno preferencial de carbono, predominando o crescimento de caule e sistema radicular.

Inoculation of Pinus taeda Seedlings with Plant Growth-promoting Rhizobacteria

The aim of this study was to evaluate the effect of Azospirillum brasilense , Bacillus subtilis and Pseudomonas fluorescens on the growth of Pinus taeda seedlings. Bacterial inoculants were applied in two different forms: at sowing and 20 days after emergence. At 30, 60 and 90 days after emergence, we evaluated plant height and root-colar diameter. At 180 days after emergence, we also measured shoot and root dry weight. Data were analyzed by analysis of variance and means were ranked by Duncan’s test. The most pronounced results were observed for root and shoot biomass when plants were inoculated with Bacillus subtilis and Pseudomonas fluorescens. Bacillus subtilis increased root and shoot biomass by 67.1% and 33.1%, respectively, when comparing values with those of non-inoculated plants. On the other hand, inoculation with Pseudomonas fluorescens decreased root biomass up to 31.42%. Inoculation with Azospirillum brasilense did not promote any difference in Pinus taeda seedling growth and may not be an efficient alternative for inoculation practices. According to these results, inoculation of Pinus taeda seedlings with Bacillus subtilis has great potential to improve plant growth regarding adaptation to field conditions.

LIFE AND FERTILITY TABLES OF Pineus boerneri ANNAND (HEMIPTERA: ADELGIDAE) ON Pinus spp. (PINACEAE)

Biological parameters of Pineus boerneri were evaluated in laboratory using seedlings of Pinus taeda and Pinus elliottii. The nymphs were observed along their development. The total life cycle was not significantly different on P. taeda and P. elliottii, being, respectively, 69 and 65 days. The same trend was observed for mean fecundity, being about 40 eggs/female on P. taeda and 53 on P. elliottii. However, when daily mean fecundity was considered, the difference was significant, being 1.3 eggs/female/day on P. taeda and 1.8 on P. elliottii. The nymphal mortality was greater on P. taeda (50%) than on P. elliottii (28%). These results reflected on life expectancy which was higher on P. elliottii for the nymphal stage, but for the adult stage there was no significant difference between both host plants. The intrinsic rate of natural increase and the finite rate of increase were similar, indicating that P. boerneri shows the same reproductive capacity on both hosts, despite the net reproductive rate being much greater on P. elliottii (23.8 eggs/female) than on P. taeda (15.4). The highest nymphal survival and reproductive rates on P. elliottii indicate that this host plant is more suitable for the development of P. boerneri.

Elevated [CO2] and growth temperature have a small positive effect on photosynthetic thermotolerance of Pinus taeda seedlings

Key message Growth temperature had little effect on the response of net photosynthesis to high temperatures (up to 47 °C). On the other hand, elevated [CO 2 ] increased net photosynthesis at high temperatures.

Water availability is the decisive factor for the growth of two tree species in the occurrence of consecutive heat waves

The frequency and intensity of heat waves are predicted to increase as a consequence of climate warming, yet no experimental evidence exists for the potential magnitude of these effects. Therefore, we investigated whether consecutive heat waves of different severities would have the same impact on tree growth as a constant increase in temperature with equivalent heat sum and considered (CO2) and available soil moisture as potential interacting factors. Seedlings of Quercus rubra and Pinus taeda were grown under ambient or elevated (CO2) (380/700μmol CO2mol−1) and three temperature treatments: ambient +3°C, moderate heat wave every second week (+6°C) or severe heat wave every fourth week (+12°C). All temperature treatments had the same average temperature (+3°C above ambient) across the five-month experimental growth period. Half the seedlings were watered to field capacity (50% (v/v) on average), the other half to 30%. Stem height and diameter were measured monthly. Biomass accumulation and partitioning were measured after five months. In ambient (CO2), seedlings of both species had significantly less biomass (up to 39%) when exposed to +12°C heat waves compared to a constant +3°C increase. These decreases were mitigated by elevated (CO2) in Quercus but not in Pinus. Despite having the lowest biomass, Quercus seedlings in the +12°C heat wave treatment grew taller (up to 17%) than all other Quercus seedlings. In contrast, Pinus seedlings in the +12°C heat wave treatment had consistently lower height and stem diameter compared with all other treatments within each soil water treatment. Soil water treatment had a greater effect than (CO2) on stem height, diameter and total biomass, with reduced growth under low soil water content compared with high soil water content (up to 55% smaller and up to 63% less biomass). We conclude that (a) heat waves produced more stress than the same amount of heat applied uniformly; (b) elevated (CO2) at least partially mitigated negative effects of heat waves; and (c) drought was a more severe stressor than heat waves.

Effects of predicted future and current atmospheric temperature and [CO2] and high and low soil moisture on gas exchange and growth of Pinus taeda seedlings at cool and warm sites in the species range

Predicted future changes in air temperature and atmospheric CO(2) concentration ([CO(2)]), coupled with altered precipitation, are expected to substantially affect tree growth. Effects on growth may vary considerably across a species range, as temperatures vary from sub-optimal to supra-optimal for growth. We performed an experiment simultaneously at two locations in the current range of loblolly pine, a cool site and a warm site, to examine the effect of future climate conditions on growth of loblolly pine seedlings in contrasting regions of the species range. At both sites 1-year-old loblolly pine seedlings were grown in current (local ambient temperature and [CO(2)]) and predicted future atmospheric conditions (ambient +2 °C temperature and 700 μmol mol(-1) [CO(2)]). Additionally, high and low soil moisture treatments were applied within each atmospheric treatment at each site by altering the amount of water provided to the seedlings. Averaged across water treatments, photosynthesis (A(net)) was 31% greater at the cool site and 34% greater at the warm site in elevated temperature and [CO(2)] compared with ambient temperature. Biomass accumulation was also stimulated by 38% at the cool site and by 24% at the warm site in that treatment. These results suggest that a temperature increase of 2 °C coupled with an increase in [CO(2)] (predicted future climate) will create conditions favorable for growth of this species. Reduced soil moisture decreased growth in both current and predicted atmospheric conditions. Biomass accumulation and A(net) were reduced by ∼39 and 17%, respectively, in the low water treatment. These results suggest that any benefit of future atmospheric conditions may be negated if soil moisture is reduced by altered precipitation patterns.

Sobrevivência e crescimento inicial de mudas de <i>Pinus taeda</i> L. com diferentes diâmetros do colo

Com o objetivo de avaliar a sobrevivência e o crescimento de mudas de Pinus taeda produzidas em recipientes e em raiz nua com diferentes diâmetros do colo (DC) inicial, foram estabelecidos dois experimentos em solo de drenagem deficiente localizados na província de Corrientes, Argentina. O delineamento experimental utilizado foi o de blocos completos ao acaso, com três repetições por tratamento, sendo cada unidade experimental composta por 64 plantas e bordadura perimetral dupla. Os tratamentos avaliados, no experimento 1, foram mudas de recipientes com DC de 1,6 mm; 2 mm; 3 mm e 4 mm, e no experimento 2, foram mudas de raiz nua com DC de 3 mm; 4 mm; 5 mm e 6 mm. Aos 4 anos de idade, as mudas de recipientes não apresentaram diferenças significativas em sobrevivência e crescimento; enquanto que nas mudas de raiz nua, a sobrevivência foi maior nos tratamentos de 4 e 5 mm não se encontrando diferença significativa em crescimento entre os tratamentos. Para os dois tipos de produção de mudas, o diâmetro do colo não teve influência significativa no crescimento a campo.

CRESCIMENTO JUVENIL DE Pinus taeda EM FUNÇÃO DO ESPAÇO VITAL DE CRESCIMENTO

Avaliou-se o desempenho de Pinus taeda L. aos quatro anos de idade, plantado em diferentes espaçamentos, simulando espaços vitais entre 1 m² e 16 m². O experimento foi implantado em 2002, com mudas de Pinus taeda L. produzidas com sementes de pomar clonal. O delineamento experimental foi de blocos ao acaso, com cinco repetições e nove tratamentos (espaçamentos 1,0 x 1,0; 2,0 x 1,0; 2,0 x 2,0; 3,0 x 2,5; 3,0 x 3,0; 3,0 x 3,5; 4,0 x 3,0; 4,0 x 3,5; 4,0 x 4,0 m), constituídos por 25 mudas e uma linha de bordadura. Não foram significantes as correlações entre espaço vital e altura, nem entre espaço vital e DAP. O diâmetro dos ramos, entretanto, está correlacionado com o espaço vital. Existe correlação entre altura e DAP e entre DAP e diâmetro de ramos. A altura das árvores variou entre 4,08 m e 4,60 m, e o DAP entre 5,65 cm e 7,69 cm. Não se detectou diferenças significantes no crescimento da altura e do DAP. O espaço vital afetou o crescimento dos ramos, cujos diâmetros variaram entre 11,45 mm e 19,01 mm. Quanto maior o espaço vital, maiores os diâmetros dos ramos.Palavras-chave: Espaçamento; diâmetro de ramos; desrama. AbstractGrowth of Pinus taeda at early age as function of the growing space. It was evaluated the growth of four years old Pinus taeda L. planted at nine different spacings (1.0 x 1.0; 2.0 x 1.0; 2.0 x 2.0; 3.0 x 2.5; 3.0 x 3.0; 3.0 x 3.5; 4.0 x 3.0; 4.0 x 3.5; 4.0 x 4.0 m), simulating vital spaces ranging from 1 m² to 16 m². The trial was established in 2002 with seedlings of Pinus taeda L. originated from a clonal seed orchard. It was used randomized blocks with five replications, each plot with 25 seedlings, excluding a border line. There were no significant correlation between growing space and height or between growing space and DBH. The diameter of branches was correlated with growing space. Positive correlations were obtained between height and DBH and between branch diameter and DBH. Tree height ranged from 4.08 m to 4.60 m and the DBH from 5.65 cm e 7.69 cm and there were no significant differences for both variables. The growing space affected branch growth. Larger growing spaces resulted in larger branch diameter. Branch diameters ranged from 11.45 mm to 19.01 mm.Keywords: Spacing; diameter of branches; pruning.

Araucaria Forest conservation: mechanisms providing resistance to invasion by exotic timber trees

Since only 12.6% of the Brazilian Araucaria Forest remains and timber tree monocultures are expanding, biological invasion is a potential threat to the conservation of natural forest remnants. Here, we test (1) the susceptibility of Araucaria Forest to invasion by Pinus taeda and Eucalyptus saligna, (2) the efficiency of different mechanisms controlling the early establishment of these two exotic timber tree species, and (3) the potential of the native timber tree Araucaria angustifolia to establish successfully in ecologically-managed monocultures of Araucaria, Pinus and Eucalyptus. In Araucaria Forest, more than a thousand Pinus seeds landed annually in a hectare; however, experimentally exposed seeds were 100% removed in only 6 days. Furthermore, all experimentally transplanted seedlings of Pinus taeda and Eucalyptus saligna died in less than a year in Araucaria Forest, but not in the monocultures. Correlative evidence suggests that this mortality was associated to plant community richness, plant abundance, and soil fertility. Araucaria angustifolia, in contrast, showed an establishment success in ecologically-managed tree monocultures as high as that exhibited in its natural habitat. The current resistance of Araucaria Forest to invasion by exotic timber trees is good news for the conservation of Araucaria Forest remnants and for its keystone species. The understanding of the mechanisms providing such resistance against invasion points towards management tools for minimizing future threats.

First report of the pitch canker fungus Fusarium circinatum affecting Pinus taeda seedlings in Uruguay

In recent years Pinus spp. plantations have become an important resource that is continuously increasing in Uruguay as well as in other countries. Fungal diseases in nurseries are common, and among them, Fusarium circinatum (the pitch canker fungus) was found associated with Pinus taeda seedling, representing the first record of this pathogen in Uruguay.

Rhizospheric streptomycetes as potential biocontrol agents of Fusarium and Armillaria pine rot and as PGPR for Pinus taeda

Pinus taeda is one of the main timber trees in Brazil, occupying 1.8 million ha with an annual productivity of 25–30 m3 ha−1. Another important species is Araucaria angustifolia, belonging to the fragile Rainforest biome, which for decades has been a major source of timber in Brazil. Some diseases that affect the roots and/or the stem of these trees and cause “damping-off” of the seedlings, with economic and environmental losses for the forest sector, are caused by the plant pathogenic fungi Fusarium sp. or Armillaria sp. This research project intended to isolate actinobacteria from the Araucaria rhizosphere, which present an antagonistic effect against these fungi. After the selection of the best pathogen inhibitors, morphologic characteristics, enzyme production, and their effect on the growth of Pinus taeda were studied. The actinobacteria were tested for their antagonistic capacity against Fusarium sp. in Petri plates with PDA as substrate. The inhibition zone was measured after 3, 5, 7, and 10 days. Of all the isolates tested, only two of them maintained inhibition zones up to 4 mm for 10 days. The inhibition of Armillaria sp. was tested in liquid medium and also in Petri dishes through the evaluation of the number of the fungal rhizomorphs in dual culture with the actinobacteria. It was found that all five isolates were able to inhibit the rhizomorph production, with the best performance of the isolate A43, which was capable of inhibiting both fungi, Fusarium and Armillaria. In a greenhouse experiment, the effect of five isolates on the growth of Pinus taeda seedlings was tested. Plant height, stem diameter, root and shoot dry matter were determined. The Streptomyces isolate A43 doubled plant growth. These results may lead to the development of new technologies in the identification of still unknown bacterial metabolites and new management techniques to control forest plant diseases.

Imperata cylindrica, an alien invasive grass, maintains control over nitrogen availability in an establishing pine forest

In a field experiment in Florida, USA, 15N-labeled Ammonium Sulfate was used to compare how Pinus taeda seedlings take up and use N in the presence of I. cylindrica and native vegetation using three treatments: 1) vegetation free 2) native competition, and 3) I. cylindrica competition. Imperata cylindrica competition led to smaller pine seedlings with significantly less N content in the pine foliage and roots than those in the native treatment. Competition from I. cylindrica for N contributed to the pine seedlings taking up a greater percentage of the applied fertilizer than the seedlings competing with native vegetation; however, because of their reduced growth they were less efficient in utilizing the fertilizer N. The belowground biomass of I. cylindrica on average was seven times higher than the native species. Despite its lower N concentration in foliage and roots, it retained significantly more N per hectare compared to the native vegetation. While the native species retained more N aboveground, I. cylindrica held significantly more belowground, thus invasion by this grass would lead to a shift of N pools from above to belowground. The fact that we were able to account for 81.5% of the applied fertilizer in the I. cylindrica treatment compared to 62.2% in the native treatment suggests that I. cylindrica tightly retains most of the available N on site making it a particularly good invader.

Cogongrass (Imperata cylindrica), an Alien Invasive Grass, Reduces Survival and Productivity of an Establishing Pine Forest

Abstract A 27-month-long study was conducted to compare the impacts of Imperata cylindrica (L.) (Beauv.) and native vegetation competition on the productivity of Pinus taeda (L.) seedlings. In March 2003, 1-year-old pine seedlings were planted in the following treatments: vegetation free (VF), native competition (NC), and I. cylindrica (IC) competition. At the end of the study, only 26% of the IC seedlings survived, half of what was observed in the NC treatment. The IC seedlings had significantly smaller root collar diameter than the NC seedlings (P < 0.0001) after the first growing season and by the end of the third growing season the height and stem volume index were significantly less as well (P < 0.0001). After one full growing season, the NC and IC pine seedlings had 21 and 11.5% of the total biomass of the VF seedlings, respectively. After three growing seasons, the IC pine seedling total biomass was 2.4% of that of the VF seedlings and 18% of that of the NC seedlings (P < 0.0001). The greatest difference was in the pine needle biomass with the IC pine needle biomass being only 11% of that of the NC. During the first growing season, the IC pine seedlings maintained the lowest levels of light-saturated net photosynthesis and stomatal conductance. These results may be explained by reduced amounts of foliar nitrogen and water stress that result from I. cylindrica competition. The pines in the IC treatment had the lowest total foliar surface area and the lowest specific leaf area, which may explain the reduced productivity. Evidence from this study suggests that I. cylindrica competition significantly reduces the productivity and growth of P. taeda seedlings compared with that from native vegetation.

Quantificação das perdas no desenvolvimento de <i>Pinus taeda </i>após o ataque de formigas cortadeiras.

Neste trabalho, o objetivo foi quantificar as perdas no desenvolvimento inicial em diâmetro, altura e índice de produtividade de mudas de Pinus taeda em plantios na Argentina, após o ataque de formigas cortadeiras. Os tratamentos foram: T1 = testemunha sem ataque; T2 = atacada por formigas; e T3 = desaciculamento artificial seqüencial. Avaliaram-se ainda três estágios de desenvolvimento das plantas em dois tipos de relevos distintos. Os resultados obtidos permitem concluir que existe redução significativa no desenvolvimento das plantas de Pinus taeda quando atacadas por formigas cortadeiras durante os primeiros 24 meses de idade. Nas plantas desaciculadas artificialmente, houve uma redução mais significativa em relação às desaciculadas por formigas, para todas as variáveis analisadas.

Soil DIC uptake and fixation in Pinus taeda seedlings and its C contribution to plant tissues and ectomycorrhizal fungi

Plants can acquire carbon from sources other than atmospheric carbon dioxide (CO(2)), including soil-dissolved inorganic carbon (DIC). Although the net flux of CO(2) is out of the root, soil DIC can be taken up by the root, transported within the plant, and fixed either photosynthetically or anaplerotically by plant tissues. We tested the ability of Pinus taeda L. seedlings exposed to (13)C-labeled soil DIC and two NH(4)(+) availability regimes to take up and fix soil DIC. We also measured the concentration and distribution of the fixed soil DIC within the plant and mycorrhizal tissues, and quantified the contribution of soil DIC to whole-plant carbon (C) gain. Seedlings exposed to labeled DIC were significantly enriched in (13)C compared with seedlings exposed to unlabeled DIC (6.7 versus -31.7 per thousand). Fixed soil DIC was almost evenly distributed between above- and belowground biomass (55 and 45%, respectively), but was unevenly distributed among tissues. Aboveground, stem tissue contained 65% of the fixed soil DIC but represented only 27% of the aboveground biomass, suggesting either corticular photosynthesis or preferential stem allocation. Belowground, soil DIC had the greatest effect (measured as (13)C enrichment) on the C pool of rapidly growing nonmycorrhizal roots. Soil DIC contributed approximately 0.8% to whole-plant C gain, and approximately 1.6% to belowground C gain. We observed a slight but nonsignificant increase in both relative C gain and the contribution of soil DIC to C gain in NH(4)(+)-fertilized seedlings. Increased NH(4)(+) availability significantly altered the distribution of fixed soil DIC among tissue types and increased the amount of fixed soil DIC in ectomycorrhizal roots by 130% compared with unfertilized seedlings. Increased NH(4)(+) availability did not increase fixation of soil DIC in nonmycorrhizal roots, suggesting that NH(4)(+) assimilation may be concentrated in ectomycorrhizal fungal tissues, reflecting greater anaplerotic demands. Soil DIC is likely to contribute only a small amount of C to forest trees, but it may be important in C fixation processes of specific tissues, such as newly formed stems and fine roots, and ectomycorrhizal roots assimilating NH(4)(+).