长年耕作对北方旱作麦田土壤细菌群落结构及理化性质的影响

为探究旱作麦田长期耕作对不同土层细菌群落结构的影响及其与土壤理化性质的关系,于2016~2021年在山西农业大学闻喜旱地小麦试验示范基地开展长期定位试验,研究夏闲期免耕（NT）、深松（ST）和深翻（DP）这3种耕作方式对不同土层土壤理化性质,细菌群落α、β多样性,细菌门和属优势物种及差异物种的影响,并采用PICRUSt2预测其代谢功能.结果表明,旱作麦田连续5a深松和深翻较免耕显著提高了20~40 cm土层土壤含水量,显著降低了0~20 cm土层土壤有机碳含量;深松较深翻显著提高了0~20 cm土层土壤含水量、土壤有机碳、可溶性有机碳和可溶性有机氮含量.深松和深翻较免耕可提高0~40 cm土层土壤细菌群落的α多样性,且深松高于深翻.深松和深翻较免耕显著提高了0~20 cm土层中酸杆菌门、硝化螺旋菌门和20~40 cm土层中酸杆菌门、绿弯菌门、芽单胞菌门、Rokubacteria门、GAL15门和硝化螺旋菌门的相对丰度;显著提高了0~20 cm土层硝化螺旋菌属和20~40 cm土层Rubrobacter属和链霉菌属的相对丰度.深松较深翻显著提高了0~40 cm土层酸杆菌门、芽单胞菌门的相对丰度.冗余分析表明,0~20 cm土层的土壤有机碳、可溶性有机碳和可溶性有机氮含量对放线菌门和牙殖球菌属产生正向效应,且深松下0~40 cm土层的土壤含水量对酸杆菌门、绿弯菌门和芽单胞菌门产生正向效应.PICRUSt2预测结果表明,深松和深翻较免耕显著提高了20~40 cm土层细菌群落的氨基酸代谢和辅酶维生素代谢的相对丰度,但降低了脂质代谢的相对丰度;深松较深翻显著提高了0~40 cm土层细菌群落的氨基酸代谢和0~20 cm土层其他氨基酸代谢的相对丰度.总之,旱地麦田夏闲期深松或深翻均可提高土壤含水量、土壤细菌群落的α多样性及细菌群落的代谢能力,深松还可提高酸杆菌门和芽单胞菌门的相对丰度,并提高细菌群落的氨基酸代谢能力,从而提高了土壤可溶性有机碳、氮含量.     

周年轮作休耕对土壤AMF群落和团聚体稳定性的影响

为探究轮作休耕对丛枝菌根真菌（AMF）群落组成及土壤团聚体稳定性的影响,以坡耕地红壤为研究对象,采用Illumina MiSeq高通量测序和湿筛法分别测定AMF群落组成和团聚体,研究了苕子轮作玉米（V-C）、豌豆轮作玉米（P-C）、冬闲-玉米（F-C）和周年休耕（F-F）这4个处理下AMF群落组成及其与土壤养分和团聚体稳定性之间的关系.结果表明,F-F、V-C和P-C处理的>2 mm团聚体含量、R_0.25及MWD均显著高于F-C （P<0.05）,<0.25 mm团聚体含量均显著低于F-C （P<0.05）;F-F处理的ACE、Chao1和Shannon指数较F-C分别显著提高29.56%、35.78%和45.55%;球囊霉属（Glomus）为各处理AMF群落的优势属,盾巨孢囊霉属（Scutellospora）在各处理间差异显著（P<0.05）;PCoA分析发现,PC1和PC2分别累计解释了AMF群落组成差异的29.99%和22.40%;相关性分析表明,盾巨孢囊霉属与碱解氮（AN）和有机质（SOM）呈显著负相关（P<0.05）,与速效钾（AK）呈显著正相关（P<0.05）,球囊霉属与碱解氮呈显著正相关（P<0.05）;RDA分析表明,AMF多样性（Shannon指数）和盾巨孢囊霉属分别与>2 mm和2~1 mm团聚体含量显著正相关（P<0.05）.因此,周年休耕和苕子轮作玉米有利于提高土壤团聚体稳定性和改变AMF群落组成,研究结果为我国南方周年轮作系统提高土壤质量和推行合理轮作休耕模式提供理论依据和参考.     

Carbon accumulation in lowland bog soils of fallow lands in Murmansk oblast

The dynamics of organic carbon accumulation in lowland bog soils of Murmansk oblast were assessed by analyzing soil samples from fields formerly sown with perennial grasses but withdrawn from agricultural use three, six, and eight years ago. Within three years, the organic carbon content in the topsoil (0–20 cm) increased by 0.07%, compared to that in cultivated soil. In six-and eight-year-old fallows, the increase in the soil carbon content averaged 0.2 and 0.46%, respectively. Experimental data were used for verifying calculations of carbon turnover in lowland bog soils of fallows in Murmansk oblast by the RothC model.     

山坡农地水土流失防治技术若干进展与成效分析

本文分析了山坡农地水土流失的现状 ,着重介绍了 7种防治农田水土流失的技术措施 ,并详细分析了其研究进展与应用成效。     

Calculating Field‐Scale Evapotranspiration with Closed‐Chamber and Remote Sensing Methods

Currently, there is no agreed upon method for estimating evapotranspiration (ET) across large regions such as the state of New Mexico. Remote sensing methods have potential for providing a solution, but require validation. A comparison between field‐scale ET measurements using a portable chamber ET measurement device and modeled ET using the remote sensing Regional Evapotranspiration Estimation Model (REEM) was performed where the model had not been previously evaluated. Data were collected during the growing season of 2015 in three irrigated agricultural valleys of northern New Mexico in agricultural and nonagricultural settings. No statistically significant difference was observed in agricultural datasets between means of measured (M = 3.7 mm/day, SE = 0.31 mm/day) and modeled (M = 4.0 mm/day, SE = 0.01 mm/day) daily ET; t(17) = ?1.50, p = 0.15, α = 0.05. As there was no statistical difference observed between agricultural datasets, results support the use of REEM in irrigated agricultural areas of northern New Mexico. A statistically significant difference was observed in nonagricultural datasets between means of measured (M = 1.7 mm/day, SE = 0.22 mm/day) and modeled (M = 0.0 mm/day, SE = 0.00 mm/day) daily ET; t(9) = 1.79, p = 5.7 × 10^?6, α = 0.05. With additional calibrations and air temperature sensors placed outside of agricultural areas, REEM may be suitable for use in nonagricultural areas of northern New Mexico.     

Transboundary Issues in Wilderness Management

/ The management of lands adjacent to federally designated wilderness is increasingly seen to have the potential to negatively impact wilderness resources and management objectives. This paper first examines the numerous and often conflicting laws and regulations that influence how managers can mitigate transboundary issues. We then examine the various types of transboundary issues, and describe how they impact wilderness resources. Transboundary issues include recreational use, extractive activities, fire management, exotic species introductions, aircraft overflights and military operations, water diversion, urban encroachment, and transported pollutants. KEY WORDS: Adjacent lands; Buffer zones; Ecosystem management; Wilderness; Zones of influence     

Mapping legal authority for terrestrial conservation corridors along streams

Wildlife corridors aim to promote species’ persistence by connecting habitat patches across fragmented landscapes. Their implementation is limited by patterns of land ownership and complicated by differences in the jurisdictional and regulatory authorities under which lands are managed. Terrestrial corridor conservation requires coordination across jurisdictions and sectors subject to site-specific overlapping sources of legal authority. Mapping spatial patterns of legal authority concurrent with habitat condition can illustrate opportunities to build or leverage capacity for connectivity conservation. Streamside areas provide pragmatic opportunities to leverage existing policy mechanisms for riverine and terrestrial habitat connectivity across boundaries. Conservation planners and practitioners can make use of these opportunities by harmonizing actions for multiple conservation outcomes. We formulated an integrative, data-driven method for mapping multiple sources of legal authority weighted by capacity for coordinating terrestrial habitat conservation along streams. We generated a map of capacity to coordinate streamside corridor protections across a wildlife habitat gap to demonstrate this approach. We combined values representing coordination capacity and naturalness to generate an integrated legal-ecological resistance map for connectivity modeling. We then computed least-cost corridors across the integrated map, masking the terrestrial landscape to focus on streamside areas. Streamside least-cost corridors in the integrated, local-scale model diverged (∼25 km) from national-scale least-cost corridors based on naturalness. Spatial categories comparing legal- and naturalness-based resistance values by stream reach highlighted potential locations for building or leveraging existing capacity through spatial coordination of policy mechanisms or restoration actions. Agencies or nongovernmental organizations intending to restore or maintain habitat connectivity across fragmented landscapes can use this approach to inform spatial prioritization and build coordination capacity. Article impact statement: Combined mapping of legal authority and habitat condition reveals capacity to coordinate actions along streams for clean water and wildlife.     

Scale dependency of conservation outcomes in a forest-offsetting scheme

Offset schemes help avoid or revert habitat loss through protection of existing habitat (avoided deforestation), through the restoration of degraded areas (natural regrowth), or both. The spatial scale of an offset scheme may influence which of these 2 outcomes is favored and is an important aspect of the scheme's design. However, how spatial scale influences the trade-offs between the preservation of existing habitat and restoration of degraded areas is poorly understood. We used the largest forest offset scheme in the world, which is part of the Brazilian Forest Code, to explore how implementation at different spatial scales may affect the outcome in terms of the area of avoided deforestation and area of regrowth. We employed a numerical simulation of trade between buyers (i.e., those who need to offset past deforestation) and sellers (i.e., landowners with exceeding native vegetation) in the Brazilian Amazon to estimate potential avoided deforestation and regrowth at different spatial scales of implementation. Allowing offsets over large spatial scales led to an area of avoided deforestation 12 times greater than regrowth, whereas restricting offsets to small spatial scales led to an area of regrowth twice as large as avoided deforestation. The greatest total area (avoided deforestation and regrowth combined) was conserved when the spatial scale of the scheme was small, especially in locations that were highly deforested. To maximize conservation gains from avoided deforestation and regrowth, the design of the Brazilian forest-offset scheme should focus on restricting the spatial scale in which offsets occur. Such a strategy could help ensure conservation benefits are localized and promote the recovery of degraded areas in the most threatened forest landscapes.     

Estimating Evapotranspiration for Dryland Cropping Systems in the Semiarid Texas High Plains Using SWAT

The Soil and Water Assessment Tool (SWAT) is one of the most widely used watershed models for simulating hydrology in response to agricultural management practices. However, limited studies have been performed to evaluate the SWAT model's ability to estimate daily and monthly evapotranspiration (ET) in semiarid regions. ET values were simulated using ArcSWAT 2012 for a lysimeter field managed under dryland conditions at the USDA‐ARS Conservation and Production Research Laboratory at Bushland, Texas, and compared with measured lysimeter values from 2000 to 2010. Two scenarios were performed to compare SWAT's performance: (1) use of default plant leaf area index (LAI) values in the embedded plant database and (2) adjusted LAI values. Scenario 1 resulted in an “unsatisfactory” Nash‐Sutcliffe efficiency (NSE) of 0.42 and 0.38 for the calibration and validation periods, respectively. Scenario 2 resulted in a “satisfactory” NSE value for the calibration period while achieving a “good” NSE of 0.70 for the validation period. SWAT generally underestimated ET at both the daily and monthly levels. Overestimation during fallow years may be due to the limitations of the pothole function used to simulate furrow diking. Users should be aware of potential errors associated with using default LAI parameters. Inaccuracies in ET estimation may also stem from errors in the plant stress functions, particularly when evaluating water management practices for dryland watersheds.     

我国营养体产业发展及种植业结构调整

本文根据我国气候的基本特征,提出了发展营养体产业是高效利用我国土地资源和气候资源的有效途径的观点,比较了营养体产业和传统农业在光能利用和产量等方面的差别,指出了营养体产业和技术关键是科学利用Ｓ－型生长曲线。