Progressive accretion recorded in sedimentary rocks of the 3.28−3.23 Ga Fig Tree Group, Barberton Greenstone Belt

One of the major challenges in early Earth geology is the interpretation of the nature of the crust and tectonic processes due to the limited exposures of Archean rocks. This question is predominantly addressed by numerical modeling, structural geology, geochemical analyses, and petrological approaches. Here we report on the reconstruction of one of the oldest, well-preserved volcano-sedimentary sequences on Earth, the 3.28−3.22 Ga Fig Tree Group in the Barberton Greenstone Belt, South Africa, based on geochronology, provenance, and stratigraphy to provide new constraints on the nature of tectonic processes in the Archean. The Fig Tree basin was asymmetric and the onset of deposition varied across the greenstone belt. The Fig Tree Group is now preserved in east-west oriented bands of fault-bounded structural belts with those preserved in the southern parts of the greenstone belt showing an onset of deposition at 3.28 Ga, those in the center at 3.26 Ga, and those in the north at 3.24 Ga. Stratigraphically, the rocks display a general up-section trend from deeper to shallower-water deposition and/or from finer- to coarser-grained sedimentary rocks. Associated with this up-section stratigraphic trend, the sedimentary rocks show a change in provenance from more regionally similar to more locally variable, and an increase in felsic volcanic activity, especially toward the closure of Fig Tree deposition. The data is consistent with formation of the Fig Tree Group in a compressional tectonic setting by deposition in a foreland basin that experienced progressive accretion of crustal terranes onto a northward prograding fold-and-thrust belt.

Supplemental Material: Progressive accretion recorded in sedimentary rocks of the 3.28–3.23 Ga Fig Tree Group, Barberton Greenstone Belt

Supplemental File S1: Additional figures; Supplemental File S2: List of dated tuffs of the Fig Tree Group; Supplemental File S3: U-Pb geochronological data; Supplemental File S4: Mudstone geochemical data.

What We Know and What We Do Not Know about Dragon Trees?

This article is a broad review focused on dragon trees—one of the most famous groups of trees in the world, well known from ancient times. These tertiary relicts are severely endangered in most of the area where they grow. The characteristic features of the dragon tree group are described and the species belonging to this group are listed. This review gathers together current knowledge regarding the taxonomy, evolution, anatomy and morphology, physiology, and ontogeny of arborescent dragon tree species. Attention is also paid to the composition, harvesting, medicinal, and ethnobotanical use of the resin (dragons’ blood). An evaluation of population structure, distribution, ecology, threats, and nature conservation forms the final part of the review. In the conclusions we recommend further avenues of research that will be needed to effectively protect all dragon tree species.

Leaf Net Photosynthesis, Leaf Greenness, and Shoot Lignin Content of Nonbearing Pecan Trees at Two Nitrogen and Nickel Application Rates

In recent years, nickel (Ni) deficiency symptoms has been observed in commercial pecan [Carya illinoinensis (Wangenh.) K. Koch.] orchards in New Mexico. Nickel deficiency can cause a reduction in lignin formation, which could affect the risk for breakage on pecan tree shoots. Ni deficiency might furthermore disrupt ureide catabolism in pecan and, therefore, could negatively affect nitrogen (N) nutrition in the plant. The objective of this study was to identify the effects of Ni and N fertilizer applications, at two rates, on net photosynthesis (Pn), leaf greenness (SPAD), and branch lignin concentration in New Mexico’s nonbearing pecan trees. Sixty trees for year 2012 (Pawnee and Western cultivars) and 40 trees for year 2013 (Pawnee cultivar) were used at two New Mexico locations (Artesia and Las Cruces) to evaluate the effects of Ni and N on tree measures. Treatments were as follows: (1) High N plus Ni (+Ni); (2) Low N no Ni (−Ni); (3) High N −Ni; and (4) Low N +Ni. In 2012 and 2013, there was an increase in leaf greenness for each location and cultivar (tree group) through time (June to September). Photosynthesis measures in 2012 differed between tree group, time in the season, and N and Ni treatments. In 2013, Pn was influenced by tree group and time (P < 0.0001), but N and Ni interaction did not present a significant effect related to Ni benefits. Photosynthesis varied over time in 2012 and 2013, with an inconsistent pattern. In this study, Ni application at the high N rate had a negative effect on ‘Pawnee’ Pn early in the season at the Artesia site, but this application had a positive effect for ‘Western’ from Artesia at the low N level, also early in the season. Lignin content varied between tree groups only. The application of N and Ni did not affect lignin in pecan shoots. The results show an inconsistent pattern regarding the benefits of Ni on nonbearing pecan orchards for leaf greenness, Pn, and lignin content during the 2-year study. Future studies on Ni should focus on pecan trees exhibiting leaf Ni deficiency symptoms or on soils with less than 0.14 mg·kg−1 of DTPA extractable Ni, as well as the long-term effect of Ni on pecan growth and development to optimize the addition of Ni into an efficient fertilization program.

Sitka spruce in Estonia

An overview of introduction of Sitka spruce in Estonia. First reports of cultivation of Sitka spruce in Estonia come from 1879. In 1895, Peravalla forest area (now Järvselja) obtained a small amount of seed from Thüringen. Saplings from that seed were planted in the forest in 1904, but for 1928 all trees were perished. During the 20th century, seed of Sitka spruce from different provenance of the natural distribution area was repeatedly sown and seedlings grown in Järvselja and some other places in Estonia, but all the cultivation attempts failed sooner or later. There are no Sitka spruces remained from the pre-War period in the mainland part of Estonia. In 1984, a group of saplings from seed of 1978 was planted in Järvselja. These trees are 15 m mean height with 20.6 cm mean diameter now. In 1975, a small group of large Sitka spruces was found growing in a remote forest park of Suuremõisa Manor, island of Hiiumaa. These Sitka spruces were revisited by us in spring 2018, to measure the trees and determine their age by tree rings. Nine trees out of 13 bigger spruces were cored. Age of the trees exceeded nearly 120 years. The planting time coincides with work period of Karl Ahrens, the forest officer of Suuremõisa Manor at that time. In spring 2018, the mean diameter at breast height (DBH) of the tree group was 62 cm and mean height ca 36 m. The biggest tree had DBH 101 cm (with 37 m height) while the maximum height for the tree group was 38 m. The Suuremõisa group of Sitka spruces on 0.02 ha is remarkable by its dense stand. If to extrapolate to one hectare, the growing stock of the stand would exceed 3 thousand cubic meters. The vital group of Sitka spruces at Suuremõisa have proved that this foreign tree species can grow rather well in the western islands and coastal region of Estonia. Sitka spruce can grow faster than native Norway spruce in Estonia. Future decades will show the viability of Sitka spruce cultures in the mainland of Estonia.