Anthropogenic influence on 2018 summer persistent heavy and daily extreme rainfall in central western China

Anthropogenic forcing has reduced the probability of summer persistent heavy rainfall in central western China similar to 2018 by ~47%, but increased that of daily extremes by ~1.5 times, based on HadGEM3-GA6 ensembles

Short-term effects of experimental burning and thinning on soil respiration in an old-growth, mixed-conifer forest

To understand the roles of forest management practices in meeting the goals of forest sustainability and CO2 sequestration, we evaluated the effects of burning and thinning treatments on soil respiration and soil environments in an old-growth, mixed-conifer forest in California’s southern Sierra Nevada. Six experimental treatments with two levels of burning and three levels of thinning were implemented across three dominant patch types: closed canopy (CC), Ceanothus shrub (CECO), and open canopy (OC). We measured soil respiration rate (SRR), soil temperature (T10), moisture (Ms), and litter depth (LD), in the summers of 2000 and 2002. Soil total C and total N were measured in 2002. SRR was significantly different among the three patch types. In 2000, SRR was 0.75, 0.86, and 0.26 g CO2 m-2 hr-1 in CC, CECO, and OC, respectively. In 2002, SRR was 0.79, 0.97, and 0.44 g CO2 m-2 hr-1 in CC, CECO, and OC, respectively. The analysis of variance indicated that burning and thinning significantly affected soil respiration and soil environments. In particular, SRR significantly decreased in burned CECO patches but increased in unburned and thinned CECO. SRR in CC and OC did not significantly change. T10 and Ms increased, whereas LD and soil C decreased in treated patches. We also developed pre- and posttreatment exponential models to predict SRR using soil environmental variables. The effects of burning and thinning on soil CO2 efflux and soil environments imply that forest carbon pools would be reorganized with widespread application of these forest management practices.Keywords: Thinning, Soil moisture, Soil temperature, Prescribed burning, Mixed conifer, Soil respiratio

Biophysical controls on soil respiration in the dominant patch types of an old-growth, mixed-conifer forest

Little is known about biophysical controls on soil respiration in California’s Sierra Nevada oldgrowth, mixed-conifer forests. Using portable and automated soil respiration sampling units, we measured soil respiration rate (SRR) in three dominant patch types: closed canopy (CC), ceanothus-dominated patches (CECO), and open canopy (OC). SRR varied significantly among the patch types, ranging from 2.0 to 4.5 �μmol m�⁻² s�⁻¹ and from 0.9 to 2.9 �μmol m�⁻² s�⁻¹ during the 1999 and 2000 measuring periods, respectively, with the maximum in CECO and the minimum in OC. Multiple peaks of seasonal SRR were functions of soil temperature and moisture dynamics. The relationship between SRR and soil temperature switched from a positive to a negative correlation when soil moisture dropped from saturation to drought. Time lag, as a function of soil moisture, was included in an exponential model to assess the effects of soil moisture on SRR in this seasonal water-stressed ecosystem. The total soil C flux summed by an area-weighted average across all three patch types was 660 �± 163 g C m�⁻² from May to Oct. 2000. These results may be applicable to other water-stressed forests in the Mediterranean climate zone, and have implications for the conservation of soil carbon.Key Words: Soil CO₂ efflux, soil temperature, soil moisture, Sierra Nevada, California

Study on the structure-activity relationship of an antimicrobial peptide, Brevinin-2GUb, from the skin secretion of Hylarana guentheri

Antimicrobial peptides (AMPs) are considered potential alternatives to antibiotics due to their advantages in solving antibiotic resistance. Brevinin-2GUb, which was extracted from the skin secretion of Hylarana guentheri, is a peptide with modest antimicrobial activity. Several analogues were designed to explore the structure–activity relationship and enhance its activity. In general, the Rana box is not an indispensable motif for the bioactivity of Brevinin-2GUb, and the first to the 19th amino acids at the N-terminal end are active fragments, such that shortening the peptide while maintaining its bioactivity is a promising strategy for the optimisation of peptides. Keeping a complete hydrophobic face and increasing the net charges are key factors for antimicrobial activity. With the increase of cationic charges, α-helical proportion, and amphipathicity, the activity of t-Brevinin-2GUb-6K (tB2U-6K), in combatting bacteria, drastically improved, especially against Gram-negative bacteria, and the peptide attained the capacity to kill clinical isolates and fungi as well, which made it possible to address some aspects of antibiotic resistance. Thus, peptide tB2U-6K, with potent antimicrobial activity against antibiotic-resistant bacteria, the capacity to inhibit the growth of biofilm, and low toxicity against normal cells, is of value to be further developed into an antimicrobial agent

A coupled ground heat flux-surface energy balance model of evaporation using thermal remote sensing observations

One of the major undetermined problems in evaporation (ET) retrieval using thermal infrared remote sensing is the lack of a physically based ground heat flux (G) model and its integration within the surface energy balance (SEB) equation. Here, we present a novel approach based on coupling a thermal inertia (TI)-based mechanistic G model with an analytical surface energy balance model, Surface Temperature Initiated Closure (STIC, version STIC1.2). The coupled model is named STIC-TI. The model is driven by noon–night (13:30 and 01:30 local time) land surface temperature, surface albedo, and a vegetation index from MODIS Aqua in conjunction with a clear-sky net radiation sub-model and ancillary meteorological information. SEB flux estimates from STIC-TI were evaluated with respect to the in situ fluxes from eddy covariance measurements in diverse ecosystems of contrasting aridity in both the Northern Hemisphere and Southern Hemisphere. Sensitivity analysis revealed substantial sensitivity of STIC-TI-derived fluxes due to the land surface temperature uncertainty. An evaluation of noontime G (Gi) estimates showed 12 %–21 % error across six flux tower sites, and a comparison between STIC-TI versus empirical G models also revealed the substantially better performance of the former. While the instantaneous noontime net radiation (RNi) and latent heat flux (LEi) were overestimated (15 % and 25 %), sensible heat flux (Hi) was underestimated (22 %). Overestimation (underestimation) of LEi (Hi) was associated with the overestimation of net available energy (RNi−Gi) and use of unclosed surface energy balance flux measurements in LEi (Hi) validation. The mean percent deviations in Gi and Hi estimates were found to be strongly correlated with satellite day–night view angle difference in parabolic and linear pattern, and a relatively weak correlation was found between day–night view angle difference versus LEi deviation. Findings from this parameter-sparse coupled G–ET model can make a valuable contribution to mapping and monitoring the spatiotemporal variability of ecosystem water stress and evaporation using noon–night thermal infrared observations from future Earth observation satellite missions such as TRISHNA, LSTM, and SBG

Vegetation and ecological characteristics of mixed-conifer and Red Fir forests at the Teakettle Experimental Forest

Detailed analysis of mixed-conifer and red fir forests were made from extensive, large vegetation sampling, systematically conducted throughout the Teakettle Experimental Forest. Mixed conifer is characterized by distinct patch conditions of closed-canopy tree clusters, persistent gaps and shrub thickets. This heterogeneous spatial structure provides contrasting microclimate, habitat and resource conditions probably associated with the high diversity of understory plants, fungi, and invertebrates found in ongoing studies in the Teakettle Experiment. In contrast, red fir forests are more homogeneous with continuous high canopy cover, cooler, more consistent microclimate conditions and fewer plant species. In both forests, annual fluctuations in available soil moisture resulting from El Niño influences on snow pack depth may have a significant influence on tree establishment and understory diversity. In depth descriptions of Teakettle’s mixed conifer may provide a target of historic old-growth conditions for forest management

Vegetation and ecological characteristics of mixed-conifer and red fir forests at the Teakettle Experimental Forest

Detailed analysis of mixed-conifer and red fir forests were made from extensive, large vegetation sampling, systematically conducted throughout the Teakettle Experimental Forest. Mixed conifer is characterized by distinct patch conditions of closed-canopy tree clusters, persistent gaps and shrub thickets. This heterogeneous spatial structure provides contrasting microclimate, habitat and resource conditions probably associated with the high diversity of understory plants, fungi, and invertebrates found in ongoing studies in the Teakettle Experiment. In contrast, red fir forests are more homogeneous with continuous high canopy cover, cooler, more consistent microclimate conditions and fewer plant species. In both forests, annual fluctuations in available soil moisture resulting from El Niño influences on snow pack depth may have a significant influence on tree establishment and understory diversity. In depth descriptions of Teakettle’s mixed conifer may provide a target of historic old-growth conditions for forest management

Vegetation and ecological characteristics of mixed-conifer and Red Fir forests at the Teakettle Experimental Forest

Detailed analysis of mixed-conifer and red fir forests were made from extensive, large vegetation sampling, systematically conducted throughout the Teakettle Experimental Forest. Mixed conifer is characterized by distinct patch conditions of closed-canopy tree clusters, persistent gaps and shrub thickets. This heterogeneous spatial structure provides contrasting microclimate, habitat and resource conditions probably associated with the high diversity of understory plants, fungi, and invertebrates found in ongoing studies in the Teakettle Experiment. In contrast, red fir forests are more homogeneous with continuous high canopy cover, cooler, more consistent microclimate conditions and fewer plant species. In both forests, annual fluctuations in available soil moisture resulting from El Niño influences on snow pack depth may have a significant influence on tree establishment and understory diversity. In depth descriptions of Teakettle’s mixed conifer may provide a target of historic old-growth conditions for forest management.Retrieval Terms: ectomycorrhizae, fire history, flying squirrels (Glaucomys sabrinus), hydrology, hypogeous fungi, incense cedar (Calocedrus decurrens), invertebrates, Jeffrey pine (Pinus Jeffreyi), old growth, pathogens, plant association, red fir (Abies magnifica), Sierra Nevada, soil nutrients, songbirds, sugar pine (Pinus lambertiana), truffles, vegetation classification, white fir (Abies concolor)