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Columbian sharp-tailed grouse (Tympanuchus phasianellus columbianus) are endemic to grassland and shrub-steppe ecosystems of western North America, yet their distribution has contracted to <10% of their historical range. Primary threats to Columbian sharp-tailed grouse include loss of native habitat and conversion to agriculture, reductions in habitat once provided by the Conservation Reserve Program (CRP), wildfire, and drought conditions, yet population-level consequences of these threats and their spatio-temporal scales of effect are poorly understood. We evaluated multi-scale effects of land cover, weather, and fire histories on patterns of abundance and productivity for Columbian sharp-tailed grouse populations during 1995–2020 in Idaho, USA, using mixedeffects generalized regression and remotely sensed data. We demonstrated negative effects of fire, tree encroachment, and bare ground, positive effects of spring and summer precipitation and cover of shrubs and perennial forbs and grasses, and positive effects of CRP on grouse abundance that changed in magnitude with cover of perennials and shrubs near leks (i.e., strongest effects when average cover of shrubs and perennial forbs and grasses were less abundant). We also demonstrated per capita recruitment of Columbian sharp-tailed grouse is positively associated with late-summer greenness. Our results show that several suspected threats have measurable, population-level impacts to Columbian sharp-tailed grouse within Idaho. Moreover, our results suggest ongoing changes occurring within the core range of Columbian sharp-tailed grouse, including loss of CRP cover to tilled agriculture and changes to wildfire and precipitation dynamics are likely to have negative effects on populations.

Identifying how plant species diversity varies across environmental gradients remains a controversial topic in plant community ecology because of complex interactions among putative factors. This is especially true for grasslands where habitat loss has limited opportunities for systematic study across broad spatial scales. Here we overcome these limitations by examining restored plant community responses to a large-scale precipitation gradient under two common Conservation Reserve Program (CRP) restoration approaches. The two restoration strategies examined were CP2, which seeds a relatively low number of species, and CP25, which seeds a higher number of species. We sampled plant communities on 55 CRP fields distributed along a broad precipitation gradient (410–1,170 mm mean annual precipitation) spanning 650 km within the grassland biome of North America. Mean annual precipitation (MAP) was the most important predicator of plant species richness and had a positive, linear response across the gradient. To a lesser degree, restoration practices also played a role in determining community diversity. The linear increase in species richness across the precipitation gradient reflects the species pool increase from short to tallgrass prairie communities and explained most of the richness variation. These findings provide insight into the diversity constraints and fundamental drivers of change across a large-scale gradient representing a wide variety of grassland habitats. Across a broad environmental gradient, initial planting differences between restoration practices had lower effects on plant diversity than expected. This suggests that new strategies are needed to effectively establish diverse plant communities on large-scale restorations such as these.

Perennial grass mixtures established on Conservation Reserve Program (CRP) lands can be an important source of feedstock for bioenergy production. This study aimed to evaluate management practices for optimizing the quality of bioenergy feedstock and stand persistence of grass‐legume mixtures under diverse environments. A 5‐year field study (2008–2012) was conducted to assess the effects of two harvest timings (at anthesis vs after complete senescence) and three nitrogen (N) rates (0, 56, 112 kg N ha−1) on biomass chemical compositions (i.e., cell wall components, ash, volatiles, total carbon, and N contents) and the feedstock energy potential, examined by the theoretical ethanol yield (TEY) and the total TEY (i.e., the product of biomass yield and TEY, L ha−1), of cool‐season mixtures in Georgia and Missouri and a warm‐season mixture in Kansas. The canonical correlation analysis (CCA) was used to investigate the effect of vegetative species transitions on feedstock quality. Although environmental variations (mainly precipitation) greatly influenced the management effect on chemical compositions, the delayed harvest after senescence generally improved feedstock quality. In particular, the overall cell wall concentrations and TEY of the warm‐season mixtures increased by approximately 7%. Additional N supplies improved the total TEY of both mixtures by ~1.6–4.2 L ha−1 per 1.0 kg N ha−1 input but likely lowered the feedstock quality, particularly for the cool‐season mixture. The cell wall concentrations of cool‐season mixture reduced by approximately 3%–6%. The CCA results indicated that the increased legume compositions (under low N input) likely enhanced lignin but reduced ash concentrations. This field research demonstrated that with proper management, grass‐legume mixtures on CRP lands can provide high‐quality feedstock for bioenergy productions. Perennial grass‐legume mixtures have a great potential for improving ecosystem services in marginal lands (an ideal polyculture production system) and providing renewable feedstock for biofuel productions, simultaneously. We achieved these goals via the implementation of a sustainable and quality bioenergy feedstock supply by optimizing the harvest and nitrogen management practices. This study also used a sophisticated multivariate analysis (Canonical correlation analysis, CCA) to investigate the effect of vegetative species transitions on feedstock quality, considered as a powerful tool for predicting bioenergy yields via a cost‐effective assessment or scout technology (e.g., remote‐sensing techniques) in the future.

In the US, agriculture rapidly expanded beginning in the 1850s, influenced by homesteader policies and new technologies. With increased production also came widespread land-use/land-cover change. We analyze historical agricultural policies and associated land and water use trajectories with a focus on the Southern Great Plains (SGPs). Rapid changes in agriculture and reoccurring drought led to the infamous Dust Bowl, triggering new agricultural and land management policies, with lasting impacts on the landscape. To understand historical agricultural change, we use mixed methods, including archival literature and historical agricultural census data (1910 to 2017) from three counties in a tri-state (Oklahoma, New Mexico, Colorado) area of the SGPs. Our archival policy and agricultural census analysis illustrates 110 years of agricultural change, showing that agricultural policies and technological advances play an integral role in the development of agroecological systems, especially the Conservation Reserve Program (CRP), the Environmental Quality Incentives Program (EQIP), and the Livestock Forage Disaster Program (LFP). Further, while communities began with distinct agricultural practices, agricultural policy development resulted in increasing uniformity in crop and livestock practices. The results suggest that there are sustainability lessons to be learned by looking to the land and water trajectories and accompanying unintended consequences of the past.

A modern challenge for conservation biology is to assess the consequences of policies that adhere to assumptions of stationarity (e.g., historic norms) in an era of global environmental change. Such policies may result in unexpected and surprising levels of mitigation given future climate-change trajectories, especially as agriculture looks to protected areas to buffer against production losses during periods of environmental extremes. We assessed the potential impact of climate-change scenarios on the rates at which grasslands enrolled in the Conservation Reserve Program (CRP) are authorized for emergency harvesting (i.e., biomass removal) for agricultural use, which can occur when precipitation for the previous 4 months is below 40% of the normal or historical mean precipitation for that 4-month period. We developed and analyzed scenarios under the condition that policy will continue to operate under assumptions of stationarity, thereby authorizing emergency biomass harvesting solely as a function of precipitation departure from historic norms. Model projections showed the historical likelihood of authorizing emergency biomass harvesting in any given year in the northern Great Plains was 33-28% based on longterm weather records. Emergency biomass harvesting became the norm (>50% of years) in the scenario that reflected continued increases in emissions and a decrease in growing-season precipitation, and areas in the Great Plains with higher historical mean annual rainfall were disproportionately affected and were subject to a greater increase in emergency biomass removal. Emergency biomass harvesting decreased only in the scenario with rapid reductions in emissions. Our scenario-impact analysis indicated that biomass from lands enrolled in the CRP would be used primarily as a buffer for agriculture in an era of climatic change unless policy guidelines are adapted or climate-change projections significantly depart from the current consensus. Un reto moderno para la biología de la conservación es la evaluación de las consecuencias de las políticas que se adhieren a las suposiciones de inmovilidad (p. ej.: las normas históricas) en una era de cambio ambiental global Dichas políticas pueden resultar en niveles inesperados y sorprendentes de mitigación dadas las futuras trayectorias del cambio climático，especialmente cuando la agricultura se fija en las áreas protegidas para amortiguar las pérdidas de producción durante los periodos de extremos ambientales. Evaluamos el impacto potencial de los escenarios de cambio climático sobre las tasas a las que los pastizales enlistados en el Programa de Reservas para Conservación (CPR，en inglés) están autorizados para cosechas de uso agrícola por emergencia (es decir，extracción de biomasa)，lo que puede ocurrir cuando la precipitación de los cuatro meses previos está por debajo del 40% de la precipitación media normal o histórica para ese periodo de cuatro meses. Desarrollamos y analizamos escenarios bajo la condición que las políticas continuarán operando bajo suposiciones de inmovilidad, autorizando así la cosecha de biomasa solamente como función de la separación entre la precipitación y las normas históricas. Las proyecciones de los modelos mostraron que la probabilidad histórica de la autorización de cosechas de biomasa por emergencia en cualquier año dado en la parte norte de las Grandes Planicies fue de 33.28% con base en registros climáticos de largo plazo. La cosecha de biomasa por emergencia se convirtió en la norma (>50% de los años) en el escenario que reflejó incrementos continuos en las emisiones y una disminución en la precipitación durante las temporadas de crecimiento，y las áreas en las Grandes Planicies con una precipitación media anual más alta históricamente estuvieron afectadas desproporcionalmente y estuvieron sujetas a un incremento mayor en la extracción de biomasa por emergencia. La cosecha de biomasa por emergencia disminuyó solamente en el escenario con las reducciones rápidas en las emisiones. Nuestro análisis de impacto de escenarios indicó que la biomasa de los terrenos enlistados en el CRP se usaría principalmente como amortiguador para la agricultura en una era de cambio climático a menos que las pautas políticas se adapten o las proyecciones del cambio climático se separen significativamente del consenso actual. 保护生物学目前面临的ー个挑战是评估在全球环境变化的时代背景下，遵循稳定性假设（如历史常态)的 政策可能的结果。考虑到未来的气候变化轨迹，这样的政策可能导致出人意料的减排水平，特別是农业生产还依 靠保护地来缓冲极端环境出现时的生产损失。我们评估了气候变化情景对纳入《土地休耕保护计划，CRP) 的 草地被授权用于农业用途的紧急采收（即生物质移除) 比例的潜在影响，当前 4 个月的降水量低于正常或历史上 这四个月的平均降水量的40%时可以得到授权。我们发展并分析了当政策仍继续遵循稳定性假说时的情景，这 样对紧急生物质采收的授权仅依据降水量对历史常态的偏离。模型预测表明，根据长期的天气记录，在任意一年 北美大平原北部被授权进行紧急生物质采收的历史可能性是33.28%。在排放量持续增长、生长期降水量下降 的情景下，紧急生物质采收将成为常态(超过50%的年份)，北美大平原上历史平均年降雨量较高的地区会不成 比例地受到影响，紧急生物质采收大大增加。只有在快速减排的情景下，紧急生物质采收会減少。我们的情景影 响分析表明，在气候变化的时代，納入CRP计划土地的生物质将主要被用于农业生产的缓冲，除非政策准则能够 作出相应的调整，或气候变化预测显著偏离当前的共识。翻译: 胡怡& •审校:親辅文

Grassland ecosystems established under the conservation reserve program (CRP) in the Prairie Pothole Region (PPR) currently provide soil conservation and wildlife habitat services. We aimed to determine if these lands also sequester soil organic carbon (SOC), as compared with neighboring croplands across multiple farms in the North Dakota PPR. We sampled soil from small plots at 17 private farms in the central North Dakota PPR, where long-term (≥15 years) grasslands managed under the CRP were paired with neighboring annual croplands. Cores were collected to 100 cm and split into 0–10, 10–20, 20–30, 30–40, 40–70, and 70–100 cm soil depth layers. We hypothesized the effect of land use on soil organic carbon (SOC), root carbon (C), and bulk density would be greatest near the surface. For 0–10 and 10–20 cm layers, grasslands managed under the CRP were lower in bulk density and higher in SOC. From 0 to 70 cm, grasslands managed under the CRP were higher in root C. Average (±standard error) SOC for re-established grasslands and croplands was 25.39 (0.91) and 21.90 (1.02), respectively, for the 0–10 cm soil layer and 19.88 (0.86) and 18.31 (0.82), respectively, for the 10–20 soil layer. Compared to croplands, re-established grasslands sampled in the North Dakota PPR were 3–13 % lower in bulk density and 9–16 % higher in SOC from 0 to 20 cm, while root C was 2–6 times greater from 0 to 70 cm.

Changes in aboveground vegetation, roots, and soil characteristics were examined from a 12-yr chronosequence of formerly cultivated fields restored to native C4grasses through the Conservation Reserve Program (CRP). Following 6-8 yr in the CRP, the native grasses dominated vegetation composition, and the presence of forbs was negligible. Productivity of the restored grasslands did not exhibit any directional changes with the number of years in the CRP, and productivity was generally higher than native prairie in this region. Over time, the restored grasslands accumulated root biomass of decreasing quality as indicated by increasing root biomass and C:N ratio of roots along the 12-yr chronosequence. Root biomass, root C:N ratio, C storage in roots, and N storage in roots of restored grasslands approached that of native tallgrass prairie within the 12 yr of restoration. Establishment of the perennial vegetation also affected soil physical, chemical, and biological characteristics. Soil bulk density in the surface 10 cm decreased with time since restoration. Total C, microbial biomass C, and C mineralization rates increased as a function of time since restoration. The greatest change in total C occurred in the surface 5 cm, where total C was 26% greater in 12- vs. 2-yr restored grasslands. Extractable soil nitrate and soil N transformations (i.e., net N mineralization rates and net nitrification rates) declined over the restoration chronosequence, but these values were not representative of steady-state conditions due to the high variability in these measures among the native prairies. Although complete restoration of ecosystem structure and function was not the primary intention of the CRP, this study demonstrates that establishment of the matrix vegetation (i.e., native C4grasses) drives ecosystem processes in the trajectory of the original system. Moreover, restoration may hasten the recovery of soil C pools relative to formerly cultivated systems undergoing natural succession.

Soil C and N have long been recognized as important indicators of soil productivity. The current low levels of soil C and N of cropland soils have led to interest in sequestering C with reduced tillage cropping systems and the Conservation Reserve Program (CRP). Our objective was to assess agroecosystem effects on soil C and N pools in the Southern High Plains. The agroecosystems included three cotton (Gossypium hirsutum L.) cropping systems, CRP land, and native rangeland (NR). We sampled 0- to 5-, 5- to 10-, 10- to 15-, and 15- to 30-cm soil depths at 12 farm sites in five counties in West Texas. Total soil C and N, particulate organic matter (POM) C and N, natural abundance of carbon-13 isotope (delta13C) of POM and of whole soil, potentially mineralizable C and N, water-extractable carbon (WEC), and extractable ammonium (NH+4) and nitrate (NO-3) were determined. Total C and N in the 0- to 30-cm soil profile were 34 Mg C ha-1 and 2.5 Mg N ha-1 for NR, and 23 Mg C ha-1 and 1.9 Mg N ha-1 for cropland systems, respectively. Total soil C and N in CRP land were greater in cropland soils only in the 0- to 5-cm layer, and were 24 Mg C ha-1 and 2.1 Mg N ha-1 in 0 to 30 cm. Labile C and N pools were positively correlated with each other and with total soil C and N. Low soil test P may have limited C and N sequestration in CRP land and NR. Improved management practices are needed to sequester C and N in CRP and conservation-tillage cotton systems in the Southern High Plains.

The Conservation Reserve Program (CRP), established by the Food Security Act of 1985, offers annual rental payments to farm operators who voluntarily retire environmentally sensitive cropland under ten- to fifteen-year contracts. The CRP is notable for the size of both its budget and its environmental benefits. This paper measures the cost-effectiveness of the CRP's bidding mechanism. Currently, landowners submit bids that are ranked according to a score that comprises both an environmental benefits index (EBI), which includes erodibility and other environmental factors, as well as the landowner's proposed rental rate, subject to soil-specific maximums. Bids with the highest scores are accepted into the program after each sign-up period. By establishing maximum rental payments, the current scheme seeks to limit transfers to farmers, but it also inhibits farmers with reservation rents above maximum rents from submitting bids, even if their land would have high EBI scores.

Pulses of water availability characterize semiarid and arid ecosystems. Most precipitation events in these ecosystems are small (≤10 mm), but can stimulate carbon flux. The large proportion of carbon stored belowground and small carbon inputs create the potential for these small precipitation events to have large effects on carbon cycling. Land-use change can modify these effects through alteration of the biota and soil resources. The goal of our research was to determine how small precipitation events (2, 5, and 10 mm) affected the dynamics of soil carbon flux and water loss in previously cultivated Conservation Reserve Program (CRP) fields and undisturbed shortgrass steppe. Total carbon loss and duration of elevated carbon flux increased as event size increased in all field types. Time since cultivation increased in importance for carbon flux as event size increased. A comparison of water loss rates to carbon flux suggests that water is limiting to carbon flux for the smallest events, but is less limiting for events above 5 mm. We also describe how water availability interacts with temperature in controlling carbon flux rate. We conclude that small precipitation events have the potential for large short-term losses of carbon in the shortgrass steppe.