Plant Species Composition and Forage Production 14 Yr After Biosolids Application and Grazing Exclusion

This paper examines the effects of a single surface application of biosolids (at 20 dry Mg ha^{? 1}) on plant species composition, forage quality and quantity, and C stocks after 14 yr of rest in rangelands of the Central Interior of British Columbia. More than two times the aboveground biomass of grasses and the percent cover of plant litter were found in the biosolids treatment relative to the control, along with reductions in bare soil and microbiotic crust cover. Significantly greater plant uptake of all macronutrients (C, N, P, K, S, Ca, and Mg); most micronutrients (B, Cu, Mn, Mo, and Zn); and Al occurred in the biosolids treatment. P and Cu were the only two nutrients to be more concentrated in the biosolids-treated forage relative to the control forage, while N, Mg, and protein were more concentrated in the control forage. No significant difference in forage digestibility was found between biosolids and control treatments. Bluebunch wheatgrass, the late-seral native grass species, had significantly increased cover and aboveground biomass in the biosolids treatment relative to the control; however, between 2006 and 2016, non-native Kentucky bluegrass had reached > 25% cover in the biosolids plots, perhaps restricting the full recovery of bluebunch wheatgrass. Our findings indicate that biosolids application to ungrazed rangeland can increase long-term forage production and reduce bare soil. However, at our study site biosolids application also led to a long-term shift in the plant community composition away from the late-seral (i.e., bluebunch wheatgrass) trajectory, and the effects of this shift on rangeland health and productivity require further investigation.     

基于涡度相关法的中国草地生态系统碳通量研究进展

草地生态系统碳循环研究是全球碳循环研究的热点,涡度相关法使草地生态系统碳通量的长期和连续观测成为可能。本研究介绍了以涡度相关法为手段的中国草地生态系统碳通量的研究进展,重点阐述了中国草地生态系统碳通量在不同时间尺度上的变化特征,同时概括了不同的环境因子对草地生态系统碳通量控制机理方面的研究成果,并在此基础上对今后中国草地生态系统碳通量研究提出了建议。     

祁连山东段不同退化高寒草甸土壤有机碳密度研究

于2008年在祁连山东段天祝地区选取轻度、中度和重度3个不同退化程度的高寒草地,以土壤有机碳密度为研究对象,探讨高寒草地在不同退化程度干扰下土壤有机碳密度的变化特征。结果表明:随着高寒草地退化程度的加重,土壤含水量降低,容重和pH值增大;土壤有机质和全氮有相似的变化趋势,中度与轻度或重度退化草地土壤有机质和全氮差异显著(P<0.05);土壤有机碳密度在0-10 cm土层显著高于其他土层(P<0.05),并随着土层加深有显著的垂直变化趋势;不同退化程度草地在0-30 cm土层总土壤有机碳密度表现为中度>轻度>重度退化草地。     

The Effect of Levothyroxine Treatment on Resting Energy Expenditure of Hypothyroid Dogs

Thirty adult, client-owned dogs were diagnosed with hypothyroidism based on history, physical examination findings, hematologic and biochemical abnormalities, thyrotropin (TSH) response testing, endogenous canine thyrotropin (cTSH) concentration, or both, and total serum thryoxine concentration. All dogs received levothyroxine (L-thyroxine) at an initial dose of 22 μg/kg PO sid in either a tablet (13 dogs) or chewable form (17 dogs). Energy expenditure of each dog during apparent rest was estimated with an open-flow indirect calorimetry system by determining the rates of carbon dioxide production and oxygen consumption. Energy expenditure of apparent rest (EE) was lower in untreated hypothyroid dogs compared with reference values for EE. After treatment with L-thyroxine, EE of the hypothyroid dogs was significantly ( P < .05) higher than pretreatment values.     

黑河上游冰沟流域3种林地土壤有机碳分布特征与土壤特性的关系

研究了青海省祁连县黑河上游冰沟流域3种林地的土壤有机碳分布特征与土壤特性的关系,以期为黑河上游冰沟流域水源涵养研究提供科学依据。结果表明,3种林地0-60mm土层有机碳密度表现为针叶林森林灌丛阔叶林,针叶林有机碳密度为7.18kg·m-2,是森林灌丛、阔叶林的1.24和1.58倍,针叶林、森林灌丛、阔叶林0-10mm土层有机碳密度分别为13.22、9.49和8.62kg·m-2,是剖面有机碳密度均值的1.84、1.63和1.89倍。3种林地0-60mm土层自然含水量、团聚体、全氮均值表现为针叶林森林灌丛阔叶林,而容重、物理性沙粒、pH均值表现为针叶林森林灌丛阔叶林。3种林地土壤有机碳含量与自然含水量、团聚体、全氮之间呈显著的正相关关系(P0.05),与容重、物理性沙粒、pH之间呈显著的负相关关系。     

Flash electroretinography in standing horses using the DTL microfiber electrode

Purpose The goal of our study was the evaluation of a practical method for the recording of flash electroretinograms (ERGs) in sedated, standing horses with the DTL? microfiber electrode. Methods The horses were sedated intravenously with detomidine hydrochloride (0.015 mg/kg). The pupil was dilated and the auriculopalpebral nerve was blocked. The ERGs were recorded with the active electrode on the cornea (DTL?), the reference electrode near the lateral canthus, and the ground electrode over the occipital bone. The light intensities of the white strobe light were 0.03 cd·s/m² (scotopic) and 3 cd·s/m² (scotopic and photopic). Photopic and scotopic single flash and flicker responses to Ganzfeld stimulation were recorded. During the 20‐min dark adaptation period the retina was stimulated every 5 min with the 0.03 cd·s/m² single flash. Results The median b‐wave amplitudes and implicit times were 38 µV and 33 ms (photopic cone‐dominated response), 43 µV and 63 ms (5‐min dark adaptation), 72 µV and 89 ms (10 min), 147 µV and 103 ms (15 min), 188 µV and 109 ms (20 min, 0.03 cd·s/m², rod response), and 186 µV and 77 ms (20 min, 3 cd·s/m², maximal combined rod‐cone response). A steady increase in amplitude and implicit time was noted during dark adaptation. No oscillatory potentials could be isolated. Conclusions The use of detomidine hydrochloride sedation and the DTL? microfiber electrode allowed the recording of good quality ERGs. This protocol should permit the detection of functional problems in the retina without the risk involved with general anesthesia.     

紫色土丘陵坡地恢复过程中土壤微生物生物量碳与水溶性有机碳变化特征

为了研究湖南省衡阳市紫色土丘陵坡地恢复过程中土壤微生物生物量碳（SMBC）与水溶性有机碳（SWSOC）的变化特征。采用空间序列代替时间序列的方法,选用立地条件基本相似的草坡阶段（GT）、草灌阶段（MT）、灌丛阶段（FX）、灌乔阶段（FA）、乔木阶段（AR）和顶极阶段（TV）,通过调查取样和试验分析,对不同恢复阶段的0~10,10~20和20~40 cm土层土壤的SMBC、土壤微生物熵（SMQ）、SWSOC、水溶性有机碳与土壤有机碳的比值（SWSOC/SOC）、土壤基础呼吸（SBR）的变化规律以及他们与土壤理化性质的关系进行了研究。结果表明：SMBC和SBR随着土层深度的增加而减小,随着恢复的进行而增加;SMQ随着土层深度的增加和恢复进行而增加;在不同的恢复阶段,SWSOC均随着土层深度的增加而减小,在0~10 cm土层,SWSOC随着恢复的进行而增加,在10~20和20~40 cm土层,SWSOC随着恢复的进行先增后减;SWSOC/SOC随着土层深度的增加而增加,随着恢复的进行而减小;SMBC,SMQ,SWSOC,SBR均与土壤理化性质存在密切的相关性。研究表明,植被恢复有利于土壤质量的提高和土壤有机碳库的累积。     

不同地区取样点土壤中木质素降解优势菌株的筛选及生长特性比较

本试验旨在研究基于不同地区取样点土壤成分条件下,木质素降解菌的生长特性,并为筛选出降解农作物秸秆中木质素的优势菌奠定基础.通过对扬州、南京、临沂、潍坊和连云港地区5个取样点的土壤成分测定,并利用选择培养基和马铃薯葡萄糖琼脂(PDA)-RB亮蓝与PDA-Bavendamm平板显色反应鉴定不同土壤中木质素降解菌生长量及其木质素降解酶特性,依据各取样点菌株的生长特性最终选择优势菌株.结果表明,扬州取样点土壤中木质素降解菌密度[(5.67±0.58) 105g-1]极显著高于另外4个取样点(P＜0.01),所获得的木质素降解菌的产酶特性亦优于其他取样点.可知,5个取样点土壤中木质素降解菌密度存在明显差异,并与土壤中总有机碳含量呈强正相关(r=0.84,P＜0.01).     

放牧管理模式对高寒草甸生态系统有机碳、氮储量特征的影响

为探讨不同放牧管理模式高寒草甸生态系统有机碳、氮储量特征的变化,对青藏高原东缘禁牧(NG)、全生长季休牧(RG)、传统放牧(TG)和连续放牧(CG)4种放牧管理模式高寒草甸地上植被、地表凋落物、根系和土壤有机碳、氮储量进行测定和分析。结果表明,1)NG、RG和TG较CG显著提高了土壤、根系、植被和凋落物有机碳、氮储量。2)高寒草甸生态系统中,土壤有机碳储量所占比例最大(88.859%~98.242%),其次为根系(1.563%~8.742%),再次为植被(0.172%~1.430%),最小为凋落物(0.022%~0.969%);氮储量所占比例最大的是土壤(97.331%~99.633%),其次为根系(0.316%~2.071%),再次为植被(0.047%~0.442%),凋落物最小(0.003%~0.157%)。3)不同放牧管理模式土壤有机碳、氮储量具有明显的垂直分布特征,随土壤深度的增加土壤有机碳、氮储量明显降低。为期4年不同放牧模式仅对0~40 cm土层土壤有机碳、氮储量有影响。4)土壤有机碳、氮储量主要分布在0~40 cm土层,同时,放牧有使有机碳、氮向深层转移的趋势。5)NG、RG和TG显著提高了高寒草甸生态系统总有机碳、氮储量,而CG显著降低了总有机碳、氮储量,导致有机碳、氮的流失。禁牧和季节性休牧能有效增加青藏高原东缘高寒草甸生态系统有机碳、氮储量,实现碳、氮增汇的目的,是该区和类似区域草地放牧管理的重要模式。