Artificial canopy gaps accelerate restoration within an exotic Pinus radiata plantation

We created small‐scale artificial canopy gaps to accelerate the growth of mature indigenous forest canopy species for restoration of an 18‐year‐old exotic Pinus radiata plantation forest, in the Marlborough Sounds, New Zealand. Small and large circular gaps were formed by felling. Seedlings of two indigenous forest canopy species, Podocarpus totara (Podocarpaceae) and Beilschmiedia tawa (Lauraceae), were planted within artificial gaps and undisturbed plantation canopy. Seedling height growth, mortality, and occurrence of animal browse were monitored at approximately 6‐month intervals over 17 months. Both P. totara and B. tawa differed significantly in height growth and in animal browse occurrence among artificial gap treatments. Growth of the light‐demanding P. totara was better under large canopy gaps, whereas growth of the shade‐tolerant B. tawa increased under gaps of any size but was most consistent under small gaps. For P. totara, any significant restoration benefit of gap formation on height growth was lost when browsed seedlings were taken into account. Animal browse significantly limited B. tawa height growth in large but not in small gaps. Small‐scale canopy gap creation is an effective method of modifying light transmission to the plantation understorey and accelerating seedling growth rates. Canopy gap size can be used to optimize understorey illumination according to species‐specific light requirements. The increased occurrence of animal browse in gaps requires consideration. Artificial canopy gaps within planted monocultures create structural heterogeneity that would otherwise take an extended period of time to develop. These results further support the role of plantations as indigenous forest restoration sites.     

Family 34 glycosyltransferase (GT34) genes and proteins in Pinus radiata (radiata pine) and Pinus taeda (loblolly pine)

Using a functional genomics approach, four candidate genes (PtGT34A, PtGT34B, PtGT34C and PtGT34D) were identified in Pinus taeda. These genes encode CAZy family GT34 glycosyltransferases that are involved in the synthesis of cell‐wall xyloglucans and heteromannans. The full‐length coding sequences of three orthologs (PrGT34A, B and C) were isolated from a xylem‐specific cDNA library from the closely related Pinus radiata. PrGT34B is the ortholog of XXT1 and XXT2, the two main xyloglucan (1→6)‐α‐xylosyltransferases in Arabidopsis thaliana. PrGT34C is the ortholog of XXT5 in A. thaliana, which is also involved in the xylosylation of xyloglucans. PrGT34A is an ortholog of a galactosyltransferase from fenugreek (Trigonella foenum‐graecum) that is involved in galactomannan synthesis. Truncated coding sequences of the genes were cloned into plasmid vectors and expressed in a Sf9 insect cell‐culture system. The heterologous proteins were purified, and in vitro assays showed that, when incubated with UDP‐xylose and cellotetraose, cellopentaose or cellohexaose, PrGT34B showed xylosyltransferase activity, and, when incubated with UDP‐galactose and the same cello‐oligosaccharides, PrGT34B showed some galactosyltransferase activity. The ratio of xylosyltransferase to galactosyltransferase activity was 434:1. Hydrolysis of the galactosyltransferase reaction products using galactosidases showed the linkages formed were α‐linkages. Analysis of the products of PrGT34B by MALDI‐TOF MS showed that up to three xylosyl residues were transferred from UDP‐xylose to cellohexaose. The heterologous proteins PrGT34A and PrGT34C showed no detectable enzymatic activity.     

岷江上游本地种油松和外来种辐射松造林对土壤磷的影响

通过测定岷江上游16年生本地种油松和外来种辐射松人工林下不同土壤层次中各形态磷素含量以及磷酸酶活力,阐述两种林分对土壤磷素含量及其分布的影响.结果表明,在各个土层中,两种林分下的土壤含水量、pH值、有机碳的含量以及微生物生物量磷均无显著差异.在0～20cm土层中,油松林与辐射松林土壤全磷、Al-P、Fe-P、Ca-P含量以及磷酸酶活力均无显著差异,而油松林土壤有效磷和有机磷显著高于辐射松林;在20～40cm土壤中,油松林土壤全磷、有效磷、有机磷、Al-P、Fe-P含量与辐射松林差异不显著,油松林土壤Ca-P含量、酸性磷酸酶和中性磷酸酶活力显著高于辐射松林;在40～60cm土壤中,油松林土壤除中性磷酸酶活力与辐射松林的差异不显著外,其余各形态磷素含量和酸性磷酸酶活力变化与20～40cm土壤中的一致.此外,随土壤深度的增加,两种人工林土壤各形态磷素含量、磷酸酶活力都呈降低的趋势.单从土壤磷的状况看,油松林土壤中磷素含量高于辐射松林.     

Ecological research in Australia: Identifying links versus gaps between hotspots of ecological research and biodiversity

Increasing anthropogenic impacts on biodiversity has been a cause for concern in Australia in recent years. Areas that hold high levels of endemic species and also face exceptional threats of destruction have been described as biodiversity hotspots. Ecological research focused on biodiversity hotspots will provide a better understanding of the flora and fauna of these regions and thus inform conservation strategies. Consequently, it is important to understand where biodiversity hotspots are located and how well they have been researched in the past. However, the choice of ecological research sites may be influenced by a variety of factors such as proximity to research institutions. This study utilized a geographic information system to investigate the spatial distribution of ecological research field sites in Australia and its territorial waters, the hotspots of the field sites around research institutions and the proximity of ecological research field sites from the main campus of the research institutions. Furthermore, these hotspots of ecological research were linked to biodiversity hotspots to identify the regions that were commonly depicted in the ecological literature and to identify others that may need more attention. We demonstrated that hotspots of ecological research were concentrated around research institutions, with a large number of field sites being located between 0 km and 500 km from the nearest institution, especially along the eastern coast. This study highlighted areas that have been the focus of much ecological research as well as areas that need more attention from ecologists to add new knowledge to Australian ecological science.     

Ecology of the corticolous lichens on Pinus radiata at five sites of increasing age near Linton,Victoria, Australia

Abstract Thirteen lichen species were studied on trunk segments of Pinus radiata D.Don between 1.0 and 1.5m above-ground from five plantings of known, different ages near Linton, Victoria. Significant frequency and size-class differences were found for most species between sites. These parameters generally increased up to 32 years, and then either declined or showed evidence of recolonization by small thallus size-classes in some species. Nevertheless, only relict populations for any species were present at 52 years. Most species had no aspect preferences; only three species had a significant majority of their thalli on the western trunk face. Site-species association frequency analyses clustered, as pairs, the 11 and 52, and 16 and 39 year old sites. These site patterns were correlated with a number of environmental factors as well as species abundance at the sites, but there is also a possible response by the community to bark shedding, seen after 32 years, with a return to earlier colonization states in the system. This cyclic pattern is similar to a competitive hierarchy succession, although due to accelerating chronic disturbance (bark shedding) the system may be subject to secondary succession and, ultimately, to severe degradation.     

Stable transformation and regeneration of transgenic plants of Pinus radiata D. Don

A biolistic particle delivery system was used to genetically transform embryogenic tissue of Pinus radiata. The introduced DNA contained a uidA reporter gene under the control of either the tandem CaMV 35S or the artificial Emu promoter, and the npt II selectable marker controlled by the CaMV 35S promoter. The average number of stable, geneticin-resistant lines recovered was 0.5 per 200 mg fresh weight bombarded tissue. Expression of the uidA reporter gene was detected histochemically and fluorimetrically in transformed embryogenic tissue and in derived mature somatic embryos and regenerated plants. The integration of uidA and npt II genes into the Pinus radiata genome was demonstrated using PCR amplification of the inserts and Southern hybridisation analysis. The expression of both genes in transformed tissue was confirmed by Northern hybridisation analysis. More than 150 transgenic Pinus radiata plants were produced from 20 independent transformation experiments with four different embryogenic clones. Received: 9 May 1997 / Revision received: 18 September 1997 / Accepted: 18 October 1997     

Photosynthesis and wood structure in Pinus radiata D. Don during dehydration and immediately after rewatering

Abstract. Experiments were carried out on Pinus radiata (D. Don) trees grown as cuttings from clonal parent stock. Some of these trees were about 0.4 m high while others were about 5 m high; all were grown in containers. The stem diameters at the tops and at the bottoms of the large trees, rates of photosynthesis, and needle water potentials were measured both when the trees were well watered and as they dehydrated after water was withheld. The water potentials of well-watered plants was highest in the small trees and lowest at the top of the large trees. When water was withheld, photosynthesis was in most cases unaffected by a small reduction in water potential, but the rate of photosynthesis fell as water potentials declined further. The stems of the large trees expanded at a constant rate when the trees were well watered and for part of the dehydration period, while subsequent stem shrinkage and the fall in photosynthesis both occurred at approximately the same time.
Water potentials increased little in the 24 h after rewatering, and significant rates of photosynthesis were not measured until 2 or 3 d later while renewed stem expansion was not measured until 2 d after rewatering.
Water deficits reduced the lumen diameter of newly matured stem tracheids, but increased the thickness of their walls. After 1 month of water potentials of about −2.4 MPa, tracheid lumen diameter and wall thickness were both much reduced, and this reduction continued in tracheids maturing shortly after rewatering.     

The response of photosynthetic model parameters to temperature and nitrogen concentration in Pinus radiata D. Don

Responses of photosynthesis (A) to intercellular CO₂ concentration (c_i) in 2-year-old Pinus radiata D. Don seedlings were measured at a range of temperatures in order to parametrize a biophysical model of leaf photosynthesis. Increasing leaf temperature from 8 to 30°C caused a 4-fold increase in V_cmax, the maximum rate of carboxylation (10.7–43.3 μol m^?2 s^?1 and a 3-fold increase in J_max, the maximum electron transport rate (20.5–60.2 μmol m ^?2 s^?1). The temperature optimum for J_max was lower than that for V_cmax, causing a decline in the ratio J_max:V_cmax from 2.0 to 1.4 as leaf temperature increased from 8 to 30°C. To determine the response of photosynthesis to leaf nitrogen concentration, additional measurements were made on seedlings grown under four nitrogen treatments. Foliar N concentrations varied between 0.36 and 1.27 mol kg^?1, and there were linear relationships between N concentration and both V_cmax and J_max. Measurements made throughout the crown of a plantation forest tree, where foliar N concentrations varied from 0.83 mol kg^?1 near the base to 1.54 mol kg^?1 near the leader, yielded similar relationships. These results will be useful in scaling carbon assimilation models from leaves to canopies.     

Evaluation of AFLP for genetic mapping in Pinus radiata D. Don

Efficient construction of reasonable density genetic linkage maps is an essential component of QTL detection programmes. The AFLP technique has been used to produce genetic linkage maps in a range of species. We have developed protocols to generate reproducible AFLP profiles in Pinus radiata and have evaluated the inheritance and informativeness of AFLP markers in this important timber species. The large genome size of P. radiata necessitated increased levels of selection at both the pre-amplification and selective amplification steps of the AFLP protocol to generate reproducible AFLP profiles. Once optimised ca. 41.3 scorable AFLP bands were resolvable through denaturing gels, of which 48.4% were polymorphic in a screen of eight unrelated trees. This level of polymorphism is ca. three times higher than with RAPD markers. The total number of bands and the number of polymorphismic bands per PCR were ca. halved when AFLPs were electrophoresed on non-denaturing gels and stained with ethidium bromide. Using the protocols developed, AFLP is an efficient method for generating the DNA markers required for genetic linkage map construction in P. radiata. This revised version was published online in June 2006 with corrections to the Cover Date.     

CCoAOMT suppression modifies lignin composition in Pinus radiata

A cDNA clone encoding the lignin‐related enzyme caffeoyl CoA 3‐O‐methyltransferase (CCoAOMT) was isolated from a Pinus radiata cDNA library derived from differentiating xylem. Suppression of PrCCoAOMT expression in P. radiata tracheary element cultures affected lignin content and composition, resulting in a lignin polymer containing p‐hydroxyphenyl (H), catechyl (C) and guaiacyl (G) units. Acetyl bromide‐soluble lignin assays revealed reductions in lignin content of up to 20% in PrCCoAOMT‐deficient transgenic lines. Pyrolysis‐GC/MS and 2D‐NMR studies demonstrated that these reductions were due to depletion of G‐type lignin. Correspondingly, the proportion of H‐type lignin in PrCCoAOMT‐deficient transgenic lines increased, resulting in up to a 10‐fold increase in the H/G ratio relative to untransformed controls. 2D‐NMR spectra revealed that PrCCoAOMT suppression resulted in formation of benzodioxanes in the lignin polymer. This suggested that phenylpropanoids with an ortho‐diphenyl structure such as caffeyl alcohol are involved in lignin polymerization. To test this hypothesis, synthetic lignins containing methyl caffeate or caffeyl alcohol were generated and analyzed by 2D‐NMR. Comparison of the 2D‐NMR spectra from PrCCoAOMT‐RNAi lines and synthetic lignins identified caffeyl alcohol as the new lignin constituent in PrCCoAOMT‐deficient lines. The incorporation of caffeyl alcohol into lignin created a polymer containing catechyl units, a lignin type that has not been previously identified in recombinant lignin studies. This finding is consistent with the theory that lignin polymerization is based on a radical coupling process that is determined solely by chemical processes.     

Application of QuickBird and aerial imagery to detect Pinus radiata in remnant vegetation

The invasion of Pinus radiata from long‐term established plantations is contributing to the degradation of fragmented and isolated remnants of native vegetation. Within the south‐east of South Australia, the 20 vegetation communities that occur within 500 m of a plantation edge are at risk, including nine state threatened communities. To plan effective mitigation strategies, the current extent and distribution of P. radiata needs to be ascertained. High spatial resolution, multispectral QuickBird imagery and aerial photography were used to classify P. radiata within eucalypt and acacia woodlands, melaleuca shrubland, modified pasture and an Eucalyptus globulus plantation. Unsupervised classification of aerial photography gave the best result showing reasonable conformity with the observed distribution of P. radiata at the site scale. However, the 9.4 ± 13.5 (SD) cover classified in the quadrats sampled for the accuracy assessment exceeded the 1.4 ± 2.4 (SD) P. radiata cover determined from an independent dataset. Only 30.1 ± 37.9% (SD) of trees within the quadrats and 9.40 ± 13.49% (SD) of their foliage cover were classified. Trees detected by partial classification of canopy were positively correlated with both tree height and canopy diameter. Overall, the low detection rates were attributed to insufficient spectral resolution. Using higher resolution imagery, together with an object‐based image analysis or combination of multispectral and airborne digital image classification, restricted to large emergent adult trees using LiDAR analysis, is likely to improve adult P. radiata detection accuracy.     

Alternative and cytochrome pathway respiration during shoot bud formation in cultured Pinus radiata cotyledons

Respiration rates for excised cotyledons of Pinus radiata cultured in the presence (shoot-forming) and absence (non-shoot-forming) of N⁶-benzyladenine (BA) over a 21-day period were measured using a Clark-type oxygen electrode. The capacities and activities of cytochrome and alternative pathways of respiration were determined from titrations with KCN (1-10 m M ) and salicylhydroxamic acid (2–20 m M ) individually and in combination. Respiration accounted for by alternative (AP) and cytochrome (CP) pathways varied with both culture treatment and age in culture. Rates of total respiration, CP respiration and AP activity rose concurrent with key developmental events of shoot bud formation. The greatest AP capacity was measured at day 3 in shoot-forming tissue. In contrast, for cotyledons cultured under non-shoot-forming conditions, no AP activity was observed after day 3 despite relatively constant AP capacity throughout the culture period. Although initial increases in cotyledon respiration during the culture period may be related to wounding and introduction to a tissue culture environment, later differences in respiratory patterns between shoot-forming and non-shoot-forming cotyledons appear to be associated with the cytokinin-induced developmental changes which give rise to shoot primordia in cultured radiata pine cotyledons.     

Inhibition of polyamine biosynthesis by dicyclohexylamine in cultured cotyledons of Pinus radiata

Biondi, S., Torrigiani, P., Sansovini, A. and Bagni, N. 1988. Inhibition of polyamine biosynthesis by dicyclohexylamine in cultured cotyledons of Pinus radiata. - Physiol. Plant. 72: 471–476.
The effect of 1 mAf dicyclohexylamine (DCHA) on the synthesis of spermidine and spermine was examined in excised cotyledons of radiata pine ( Pinus radiata D. Don) cultured under shoot-forming (with cytokinin) and non-shoot-forming (minus cytokinin) conditions by incubation with [¹⁴C]-putrescine. In control cotyledons incorporation into spermidine showed a peak at day 2 in the presence and at day 5 in the absence of N⁶-benzyldenine (BA). DCHA-treated cotyledons gave the same labeling pattern, both in the presence and absence of benzyladenine, with a much smaller peak at day 2. The incorporation into spermidine and spermine was insignificant at day 5 and later. The total radioactivity in the trichloroacetic acid supernatant indicated that precursor uptake was strongly reduced by the drug. In addition, the percentage label found in the benzene phase and combined in the 3 polyamines was lower in DCHA-treated cotyledons. Thus, treatment with DCHA not only inhibited the conversion from putrescine to spermidine and spermine, but also reduced its conversion to other benzene-extractable compounds. S-Adenosylmethionine decarboxylase (SAMDC, EC 4.1.1.50) activity, which furnishes the propylamine group to spermidine and spermine synthases (EC 2.5.1.16 and EC 2.5.1.-), was not significantly affected by DCHA and appeared to be independent of the spermidine and spermine synthase reactions, suggesting that spermine synthesis decreased as a result of substrate depletion. The correlation between morphological development and polyamine biosynthesis is discussed.     

Characteristics of single- and multi-copy microsatellites from Pinus radiata

 Dinucleotide microsatellites were isolated from Pinus radiata using both a standard genomic library and libraries enriched for microsatellites. Locus-specific primers were designed to amplify 43 unique microsatellites. Thirty two of these loci had interpretable PCR patterns, 11 of which were polymorphic in a screen of 19 P. radiata individuals; all 11 polymorphic loci contained at least 17 repeats in the sequenced plasmid. Six of the eleven primer pairs amplified multiple fragments per individual (3–8), suggesting that these loci were present in multiple copies in the genome. Genotyping a 48-tree P. radiata production population with seven of the most polymorphic microsatellites revealed an average of 17 bands per locus (the multi-copy microsatellites were treated as one locus). When tested on known pedigrees, both single and multi-copy microsatellites exhibited co-dominant inheritance and Mendelian segregation. Two loci had null alleles and one locus had a high frequency of non-parental alleles, suggesting a high mutation rate. Eight of these microsatellites, including five multi-copy loci, were placed on a partially constructed P. radiata genetic map. Four of the five multi-copy microsatellites had two or more sets of alleles that mapped to the same locus, and the fifth mapped to two unlinked loci. All seven tested primer pairs amplified PCR products from other species of hard pine, three amplified products from soft-pine species, and one amplified bands in other conifers. Received: 10 November 1997 / Accepted: 5 January 1998     

The origin and genetic diversity of Pinus radiata in Australia

Summary Despite the fact that forest trees are in early stages of domestication there has been little direct evaluation of either the origin of, or genetic diversity within the breeding material in tree improvement programs. Allozyme variation was used to compare the total genetic diversity in the breeding programs of P. radiata within Australia and the five wild populations in North America. The current breeding populations were very similar genetically and were essentially homogenous with only 1.8% of the variation among programs. The total genetic diversity in the species was 0.12, which is a low estimate compared to most conifers. Overall in the Australian material the genetic diversity was somewhat less. The comparison of allelic frequencies in the five native populations with the Australian material indicates that the Monterey and Año Nuevo populations were probably the major source of the original introductions and that a substantial portion of the genetic diversity in the two populations has been captured in current breeding programs. The three southern populations do not appear to be currently represented in the breeding programs. The implications for future breeding strategies are discussed.     

Mechanisms for changes in soil carbon storage with pasture to Pinus radiata land-use change

In this study, we simulated pasture to Pinus radiata land‐use change with the Generic Decomposition And Yield (G'DAY) ecosystem model to examine mechanisms responsible for the change in soil carbon (C) under pine. We parameterized the model for paired sites in New Zealand. Our simulations successfully reproduced empirical trends in ecosystem productivity and soil inorganic nitrogen (N), and modeled an increase in soil C and a small decline in soil N after 30 years under pine. We determined the mechanisms contributing to soil C change based on an established hypothesis that attributes increases in soil C storage to three main factors: increased ecosystem N inputs relative to outputs, increased C/N ratios in plant and soil, or a shift of N from plant to soil. The mechanisms we attributed to the simulated increase in soil C under pine were increased soil C inputs through tree litterfall, and an increase in the soil C/N ratio. In the first 7 years following pine establishment, a decline in soil C was simulated; this was matched by a decline in soil N. The simulated longer‐term increase in soil C with afforestation by pine contrasts with results from published field studies, which show either a decline or no change in soil C under pine. The discrepancy between measured and simulated changes in soil C was attributed to the G'DAY model overestimating the transfer of litter C into the mineral soil.     

An allele responsible for seedling death in Pinus radiata D. Don

 When inbred, most outcrossing species show high mortality, manifested at several life stages. The occurrence of homozygotes for deleterious or lethal alleles is believed to be responsible. Here, we report the identification of an allele responsible for the death of selfed Pinus radiata D. Don seedlings in their first month after germination. Among 291 S₁ seedlings of plus-tree 850.55, 76 died within 1 month of emergence. Their death appears to be caused by a single recessive lethal allele, SDPr (seedling death in Pinus radiata). SDPr is located in a linkage group with 28 RAPD markers, the closest of which is ai05800a. Of the 76 seedlings that died, megagametophytes of 73 could be genotyped. Of these, 71 had the null (no band) allele of ai05800a; only two had the band allele. Of the 190 surviving S₁ diploids that were genotyped, only two individuals were homozygous for the null allele of ai05800a. By two different methods, the map distance between SDPr and ai05800a was estimated to be between 1.0 and 2.7 cM respectively. The frequency of band and null alleles in the combined population of dead and surviving seedlings and in un-sown seeds shows no evidence of selection at this locus prior to germination. Received: 30 September 1997 / Accepted: 29 October 1997     

High resolution analysis of mating systems: inbreeding in natural populations of Pinus radiata

Pinus radiata has a history of population bottlenecks and is currently restricted to five relatively small populations, three in mainland California, and two on islands off the coast of Baja California. Using highly polymorphic microsatellite markers and a newly developed statistical approach, we were able to estimate individual inbreeding coefficients and can thus analyse the mating system with high resolution. We find a bimodal distribution of inbreeding coefficients: most individuals result from selfing whereas few (in the mainland populations) to a modest number (in the island populations) are likely selfed. In most other pine species and presumably in the ancestral P. radiata population, occurrence of mature selfed individuals would be impossible because of the high genetic load. We therefore conclude that inbreeding depression has been purged in P. radiata and that the mating system has changed as a consequence.     

Putrescine metabolism in excised cotyledons of Pinus radiata cultured in vitro

The metabolism of ¹⁴C-putrescine and the changes in the endogenous concentrations of putrescine, spermidine and spermine were studied when cotyledons of Pinus radiata D. Don were cultured under shoot-forming (SF, + N⁶-benzyladenine) and non-shoot-forming (NSF, - N⁶-benzyladenine) conditions. Differences in the total uptake of ¹⁴C-putrescine during a 2 h pulse feeding were not significant between the SF and NSF cotyledons except on day 3. The maximum uptake of label was on day 3 in the SF cotyledons, which released the highest amount of ¹⁴CO₂ as well. ¹⁴C from the labeled putrescine was incorporated mainly into γ-aminobutyric acid, aspartate and glutamate. High performance liquid chromatography of the endogenous polyamines indicated that spermidine was the most predominant polyamine in the cultured cotyledons of radiata pine. Spermine increased by about 60% in the SF and 25% in the NSF cotyledons between days 0 and 3 of culture.