Potential natural vegetation and NPP responses to future climates in the US Great Plains
ECOSPHERE
Authors: Klemm, Toni; Briske, David D.; Reeves, Matthew C.
Abstract
Asymmetric climate projections throughout the U.S. Great Plains may intensify the existing latitudinal temperature gradient and magnify the longitudinal precipitation gradient. These potential changes present a unique challenge to understanding the ecological consequences of future climates in the region. Here we investigate how climate change may affect the spatio-temporal patterns of potential natural vegetation types (PVT) and net primary production (NPP) throughout the 21st century with the global dynamic vegetation model MC2. Simulations were driven by projected climate variables from five global climate models under representative concentration pathway (RCP) 8.5. MC2 simulated C3 and C4 grassland, shrubland, forest, and woodland (shrubland + forest) PVTs, and total NPP for each PVT. The largest increases in woodland and grassland NPP occurred in the Northern Plains (17.5% and 4.7%), followed by the Central Plains (10.6% and 0.0%), while NPP in the Southern Plains remained unchanged compared to historic means (1981-2010). A shift from grassland to woodland in the Northern and Central Plains further affected regional NPP; regional woodland NPP increased 72% and 26% in the Northern and Central Plains, respectively, while regional grassland NPP decreased 18% and 12%, respectively. The most pronounced shift in PVT was associated with increasing, rather than decreasing, mean annual precipitation in the Northern Plains where grassland contracted in response to westward expansion of woodland. C3 grassland was gradually replaced by C4 grassland in the Northern Plains by 2080, and only a trace remained at centuries end. C3 grassland decreased to a trace amount ca. 2060 in the Central Plains, while C4 grassland increased slightly. The relative stability of PVTs in the Southern Plains suggests that species and functional trait diversity may buffer grassland responses to future climates by providing the capacity for species reordering. The asymmetric response of simulated vegetation and NPP to 21st century climate change suggests that the provision of ecosystem services-beef cattle production, carbon sequestration, and grassland bird habitat-will be modified in distinct ways along a latitudinal gradient throughout the Great Plains.
Enzyme-treated soy protein supplementation in low protein diet enhanced immune function of immune organs in on-growing grass carp
FISH & SHELLFISH IMMUNOLOGY
Authors: Song, Yan; Yan, Liang-Chao; Xiao, Wei-Wei; Feng, Lin; Jiang, Wei-Dan; Wu, Pei; Liu, Yang; Kuang, Sheng-Yao; Tang, Ling; Zhou, Xiao-Qiu
Abstract
A 56 days feeding trial was conducted to investigate the effects of enzyme-treated soy protein (ETSP) supplementation in low protein diets on immune function of immune organs (head kidney, spleen and skin) in on-growing grass carp. A total of 540 on-growing grass carp (initial average weight: 325.72 +/- 0.60 g) were fed six diets, which included a normal protein diet (28% crude protein) and five low protein diets (26% crude protein) supplemented with graded levels of ETSP (0.0, 0.8, 1.2, 1.6 and 2.0%). At the end of feeding period, a challenge test was performed by infection with Aeromonas hydrophila for two weeks. The results indicated that (1) reducing dietary protein content from 28 to 26% decreased antibacterial substances and aggravated inflammatory responses of above three immune organs; (2) under the condition of reducing protein level in diet, 0.8-1.2% ETSP supplementation reversed these above adverse effects on immune function of above three immune organs; (3) suitable ETSP supplementation-decreased inflammatory responses were partly associated with [I kappa B kinase beta (IKK beta)/inhibitor of kappa B alpha (I kappa B alpha)/nuclear factor kappa B (NF-kappa B) p65 and p52 or NF-kappa B p65] signaling and [target of rapamycin (TOR)/(S6K1, 4E-BP)] signaling in above three immune organs. (4) On the basis of C3 content (head kidney), C4 content (spleen) and skin hemorrhage and lesion, the optimal ETSP supplementation levels in low protein diets were estimated to be 1.48%, 1.61% and 1.03%, respectively. In summary, ETSP supplementation in low protein diets improved immune function of head kidney, spleen and skin in on-growing grass carp.