Rangeland scientists struggle with how long rangeland experiments must continue in order to detect treatment effects, particularly in semiarid ecosystems characterized by slow responses and high spatiotemporal variability. We compared changes in eight grass and three shrub categories to grazing systems (yearlong vs. seasonal rotation with equivalent long-term stocking rates), and covariates (precipitation and mesquite [Prosopis velutina] gradients) over 12 yr (1972-1984) and 34 yr (1972-2006) on the Santa Rita Experimental Range, Arizona. We used split-plot analysis of variance, with year as the split, to make these comparisons. Grazing systems did not influence plant dynamics as shown by the lack of grazing system by year effect on all response variables in either time period. The absence of a detectable grazing effect on vegetation changes may be due to overriding influences of grazing intensity, pasture size, precipitation variability, and few replicates. Also, more time may be needed to detect the small accumulating and potentially temporary effects from grazing systems. The grazing system main effects present at the beginning and throughout the study suggest that pastures assigned to each grazing system had different potentials to support vegetation. Nearly twice the number of response variables were related to the precipitation covariate than to mesquite cover, but only about half of all the relationships were consistent between time periods. The struggle to know how long to observe before detecting a grazing system effect was not resolved with the additional 22 yr of observation because we cannot definitively reject that either more time is needed to detect small but cumulative effects or that the two grazing systems are not different. Resumen Científicos en la ciencia de manejo de pastizales tienen dificultades al determinar la extensión de los proyectos sobre manejo de pastizales de forma que se puedan determinar los efectos debido a los tratamientos, especialmente en ecosistemas de zonas áridas que se caracterizan por una respuesta demasiado lenta y una alta variabilidad a nivel de espacio y tiempo. Se comparó los cambios de ocho gramíneas y tres arbustivas entre diferentes sistemas de pastoreo (continuo Vs. rotacional estacional, con cargas animales similares a largo plazo). Se utilizó la precipitación y el Mesquite (Prosopis velutina) como covariables sobre 12 añ os (1972-1984) y 34 añ os (1972-2006), en la estación experimental de Santa Rita, en Arizona. Se usó un análisis de varianza de parcelas-dividas utilizando los añ os como parcelas, para llevar a cabo estas comparaciones. Los sistemas de pastoreo no afectaron la dinámica de las plantas como pudo observarse por no haber efecto de añ o para todas las variables de respuesta en ninguno de los dos períodos. La falta detección de los efectos del pastoreo en los cambios de la vegetación se puede haber debido a los efectos de la intensidad de pastoreo, tamañ o de los potreros, variación en la precipitación y el resultado de pocas repeticiones. Además ...
Exotic annual grasses such as medusahead [Taeniatherum caput-medusae (L.) Nevski] and downy brome (Bromus tectorum L.) dominate millions of hectares of grasslands in the western United States. Applying picloram, aminopyralid, and other growth regulator herbicides at late growth stages reduces seed production of most exotic annual grasses. In this study, we applied aminopyralid to T. caput-medusae to determine how reducing seed production in the current growing season influenced cover in the subsequent growing season. At eight annual grassland sites, we applied aminopyralid at 55, 123, and 245 g ae ha −1 in spring just before T. caput-medusae heading. The two higher rates were also applied pre-emergence (PRE) in fall to allow comparisons with this previously tested timing. When applied in spring during the roughly 10-d period between the flag leaf and inflorescence first becoming visible, just 55 g ae ha −1 of aminopyralid greatly limited seed production and subsequently reduced T. caput-medusae cover to nearly zero. Fall aminopyralid applications were less effective against T. caput-medusae, even at a rate of 245 g ae ha −1 . The growing season of application, fall treatments, but not spring treatments, sometimes reduced cover of desirable winter annual forage grasses. The growing season after application, both spring and fall treatments tended to increase forage grasses, though spring treatments generally caused larger increases. Compared with other herbicide treatment options, preheading aminopyralid treatments are a relatively inexpensive, effective approach for controlling T. caput-medusae and increasing forage production.
Governance of global natural resources is increasingly hybrid, with complementary public and private sector initiatives layered on landscapes to improve environmental outcomes. The challenge of polycentric land use governance is alignment of goals across diverse governance mechanisms when agricultural producers, public agencies, and corporations have distinct motivations. This case study of soil carbon governance on California rangelands explores a new payment for ecosystem services (PES) initiative led by the food and agriculture industry, called the Ecosystem Services Market Consortium (ESMC). Applying hybrid governance theory to agricultural lands, we conduct an ex-ante policy evaluation of potential policy impact based on (i) alignment between corporate sustainability goals and ranchers' priorities and (ii) complementarity of the ESMC market with existing public and private policies enabling rangeland conservation. We found corporations developing the PES market to be motivated by carbon insetting, the objectives of which converge with ranchers' goals of preserving soils. Each policy offers distinct benefits and challenges, with synergies around climate change adaptation and soil health. As a new policy tool, carbon markets like the ESMC are positioned to meet demand for soil health financing, support resilience and ranch productivity, and improve ranchers' access to soil health data for adaptive management. Given carbon markets' outcome-based payment structure, we highlight the importance of complementary governance mechanisms that mitigate upfront risk with financial and technical support during the transition period, including Farm Bill cost-share programs and private sector financing tools. This policy evaluation highlights the challenges and opportunities surrounding rangelands soil carbon governance, particularly the trade-offs that ranchers, corporations, and society at large must consider for landscape-scale conservation programs.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.