Biological soil crusts in ecological restoration: emerging research and perspectives

Drylands encompass over 40% of terrestrial ecosystems and face significant anthropogenic degradation causing a loss of ecosystem integrity, services, and deterioration of social‐ecological systems. To combat this degradation, some dryland restoration efforts have focused on the use of biological soil crusts (biocrusts): complex communities of cyanobacteria, algae, lichens, bryophytes, and other organisms living in association with the top millimeters of soil. Biocrusts are common in many ecosystems and especially drylands. They perform a suite of ecosystem functions: stabilizing soil surfaces to prevent erosion, contributing carbon through photosynthesis, fixing nitrogen, and mediating the hydrological cycle in drylands. Biocrusts have emerged as a potential tool in restoration; developing methods to implement effective biocrust restoration has the potential to return many ecosystem functions and services. Although culture‐based approaches have allowed researchers to learn about the biology, physiology, and cultivation of biocrusts, transferring this knowledge to field implementation has been more challenging. A large amount of research has amassed to improve our understanding of biocrust restoration, leaving us at an opportune time to learn from one another and to join approaches for maximum efficacy. The articles in this special issue improve the state of our current knowledge in biocrust restoration, highlighting efforts to effectively restore biocrusts through a variety of different ecosystems, across scales and utilizing a variety of lab and field methods. This collective work provides a useful resource for the scientific community as well as land managers.     

A simple and sensitive assay for 1-aminocyclopropane-1-carboxylic acid

A simple, rapid, and sensitive method for the quantitative determination of 1-amino-cyclopropane-1-carboxylic acid (ACC), the immediate precursor of ethylene in plant tissues, is described. The assay is based on the liberation of ethylene from ACC with NaOCl in the presence of Hg²⁺; ethylene is assayed by gas chromatography. The yield is normally 80% and can be determined by internal standards. The method is quite specific and can detect as little as 5 pmol of ACC.     

The C termini of Arabidopsis cryptochromes mediate a constitutive light response

Cryptochrome blue light photoreceptors share sequence similarity to photolyases, flavoproteins that mediate light-dependent DNA repair. However, cryptochromes lack photolyase activity and are characterized by distinguishing C-terminal domains. Here we show that the signaling mechanism of Arabidopsis cryptochrome is mediated through the C terminus. On fusion with beta-glucuronidase (GUS), both the Arabidopsis CRY1 C-terminal domain (CCT1) and the CRY2 C-terminal domain (CCT2) mediate a constitutive light response. This constitutive photomorphogenic (COP) phenotype was not observed for mutants of cct1 corresponding to previously described cry1 alleles. We propose that the C-terminal domain of Arabidopsis cryptochrome is maintained in an inactive state in the dark. Irradiation with blue light relieves this repression, presumably through an intra- or intermolecular redox reaction mediated through the flavin bound to the N-terminal photolyase-like domain.     

StructureSelector: A web‐based software to select and visualize the optimal number of clusters using multiple methods

Inferences of population genetic structure are of great importance to the fields of ecology and evolutionary biology. The program structure has been widely used to infer population genetic structure. However, previous studies demonstrated that uneven sampling often leads to wrong inferences on hierarchical structure. The most widely used ΔK method tends to identify the uppermost hierarchy of population structure. Recently, four alternative statistics (medmedk , medmeak , maxmedk and maxmeak ) were proposed, which appear to be more accurate than the previously used methods for both even and uneven sampling data. However, the lack of easy‐to‐use software limits the use of these appealing new estimators. Here, we developed a web‐based user‐friendly software structureselector to calculate the four appealing alternative statistics together with the commonly used Ln Pr(X|K) and ΔK statistics. structureselector accepts the result files of structure , admixture or faststructure as input files. It reports the “best” K for each estimator, and the results are available as HTML or tab separated tables. The program can also generate graphical representations for specific K, which can be easily downloaded from the server. The software is freely available at http://lmme.qdio.ac.cn/StructureSelector/ .     

Differential responses of freshwater wetland soils to sulphate pollution

Sulphate (SO₄ ^2-)reduction rates are generally low in freshwaterwetlands and are regulated by the scarceavailability of the ion. Increasedconcentrations of this electron acceptor due tosulphur (S) pollution of groundwater andsurface water may, however, lead to highSO₄ ^2- reduction rates now regulatedby the availability of appropriate electrondonors. Due to variations in this availability,the response to S pollution (e.g. from surfacewater or groundwater) is expected to differbetween soils. This hypothesis was tested inlaboratory mesocosm experiments by comparingtwo wetland soil types with distinctlydifferent humus profiles: a Hydromoder and aRhizomull type. In the first type, expected tohave a higher availability of degradable soilorganic matter (SOM), SO₄ ^2-availability appeared to be rate limiting forSO₄ ^2- reduction. In the Rhizomullsoils, in contrast, the electron acceptor didnot limit SO₄ ^2- reduction rates athigher concentrations. These differences inresponse could not, however, be attributed todifferences in the various SOM fractions or inSOM densities. Eutrophication and free sulphideaccumulation, two major biogeochemical problemscaused by SO₄ ^2- pollution, occurredin both types. The absolute extent ofphosphorus mobilisation was determined by theconcentration of this element in the soil (C/Pratio), while the level of sulphideaccumulation was governed by the concentrationof dissolved iron in the pore water. It wastherefore concluded that neither the humusprofile nor the concentrations of different SOMfractions in the soils are reliable indicatorsfor the sensitivity of wetland types to Spollution.     

Five New Guaiane Sesquiterpenes from the Endophytic Fungus Xylaria sp. YM 311647 of Azadirachta indica

Five new guaiane sesquiterpenes, 1 – 5 , were isolated from the culture broth of the endophytic fungus Xylaria sp. YM 311647, isolated from Azadirachta indica A. Juss . The structures of these compounds were elucidated on the basis of spectroscopic analyses, and their inhibitory activities against five pathogenic fungi were evaluated. All guaiane sesquiterpenes showed moderate or weak antifungal activities in a broth microdilution assay.     

Growth hormone affects behaviour of wild brown trout Salmo trutta in territorial owner–intruder conflicts

The effects of growth hormone (GH) implants on aggression, and ability to win dyadic territorial conflicts were studied in brown trout Salmo trutta parr. Bovine GH or vehicle (C) was given to either the territory owner or the intruder in four treatment combinations: C and C, C and GH, GH and C, GH and GH (owner and intruder). GH‐treated intruders initiated significantly more conflicts compared to control intruders. Furthermore, GH treatment of either the owner or intruder tended to increase aggression of the intruder. This indicates that intruders have more scope for motivational increase, while the motivation of owners is already at a maximum. The GH treatment, however, did not affect the outcome of the conflict. It thus appears that growth enhancement increases intruder aggression without increasing the chance of winning the conflict, which may have implications for the effect of growth‐selected or growth‐enhanced farmed Atlantic salmon Salmo salar on wild populations.     

High frequency of plant regeneration from hypocotyl explants of Brassica carinata A. Br.

An efficient tissue culture system for high frequency of plant regeneration from hypocotyl explants of Brassica carinata was developed via manipulation of culture medium and selection of explants. Explants grown on medium containing combinations of 2 mg l^-1 BA and 0.01 mg l^-1 NAA or 4 mg l^-1 kinetin and 0.01 mg l^-1 2,4-D regenerated shoots at 100% frequency. High frequency shoot regeneration occurred only from explants originating from 6 to 7-day-old but not younger or older seedlings. Explants showed higher regeneration capacity at the distal end than the proximal end, and the upper segment was more regenerative than the lower segment of hypocotyl. Regenerants were rooted on half-strength growth regulator-free medium, acclimatized and developed into normal, fertile plants.Abbreviations BA benzyladenine - 2-4-D 2,4-dichlorophenoxyacetic acid - NAA naphthaleneacetic acid - MS Murashige & Skoog