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Background: Cotton bollworm, Helicoverpa armigera (Hübner), threatens many crops. Bacillus thuringiensis (Bt) cotton has been planted to control this severe pest in northern Xinjiang, China. In 2021 and 2022, we monitored the activity densities of H. armigera males using sex pheromone traps in Bt cotton and non-Bt maize fields. We assessed how much of the population variation of cotton bollworm in the fields within the Bt cotton planting area could be explained by (i) landscape composition [including the proportion of Bt cotton among total area of host crops (cotton, maize, wheat and vegetables)], (ii) landscape configuration (patch density - i.e. the number of patches within a given area) across 0.5-2.0 km scales, or (iii) the population density of the previous pest generation., Results: Cotton bollworm activity-density exhibited two distinct peaks annually (mid- to late May and mid-July each year), with the number of males caught during the second peak significantly and positively correlated with the first peak's numbers. The suppressive effect of the proportion of Bt cotton in the landscape on bollworms was more pronounced at larger scales, and patch density had a significant positive effect on bollworm activity density., Conclusions: These findings support (i) the promotion of Bt cotton in northwestern China has reduced and suppressed the occurrence of cotton bollworms at the landscape scale and (ii) the importance of controlling spring populations for effective summer outbreak management, and (iii) that cotton bollworm control should be coordinated at a large scale across multiple crop fields. © 2024 Society of Chemical Industry., (© 2024 Society of Chemical Industry.)

We provide a sufficient condition for sets of mobile sampling in terms of the surface density of the set. [ABSTRACT FROM AUTHOR]

Stratospheric mean residence time  and mean age on the tropopause ΓΩ are shown to measure physically distinct aspects of stratospheric transport. Both ΓΩ and  are mean transit times through the stratosphere of air that enters through tropopause region Ω i and exits through region Ω f, but they represent averages over different populations of fluid elements. The averaging for ΓΩ is based on the population of fluid elements exiting the stratosphere, while  is based on the population of Ω i → Ω f fluid elements residing in the stratosphere. Thus, ΓΩ is the mean age on exit, while is the expected mean residence time in the interior of the stratosphere. The physical basis for defining and robustly computing both timescales is the one-way stratosphere-to-troposphere flux of air labeled with the boundary-propagator Green function, . By re-expressing the boundary-value problem for in terms of first-order loss in a tropopause layer with a timescaleτ c in the limit τ c → 0, we show that both  and ΓΩ can be obtained as ratios of moments of  extrapolated to the tropopause. One obtains  = ΓΩ + 2Δ2/ΓΩ, where Δ quantifies the width of the transit-time distribution. Because the moments of  can be estimated from the mixing ratio of transient trace gases, it is in principle possible to estimate  from measurements of two independent transient tracers. The distinctness of  and ΓΩ is elucidated using idealized models.

We diagnose changes in the decadal‐mean ocean transport over the 21st century as simulated by the ACCESS‐1.3 model under RCP8.5 forcing. A matrix formulation of advection‐diffusion is used to quantify transport into the ocean interior and from the interior back to the surface. We compute the ocean volumes last ventilated at the surface, as well as the volumes next reexposed to the atmosphere, per unit area, and the distributions of water in transit between key ventilation regions. We find that for the 2090s circulation, Antarctic Bottom Water formation and Antarctic ventilation have collapsed but are compensated by increased mode water formation and ventilation at the poleward edge of the southern subtropical gyres. Reexposure of deep water back to the atmosphere in the Antarctic Southern Ocean is also reduced but compensated by enhanced reexposure in the subpolar Southern Ocean. Labrador Sea ventilation is suppressed, while there is increased ventilation in the eastern subpolar Atlantic. The 2090s surface‐to‐surface interbasin transport is much more sluggish than that of the 1990s, with 30–40% reduced volume flow rates. For transport from last ventilation in the subpolar North Atlantic to next ventilation in the tropical Eastern Pacific, the 2090s residence‐time distribution has a ∼40% longer mode with much more slowly decaying tails and correspondingly lagged path densities. The 2090s mean times since last ventilation, as well as the mean times to reexposure are older in the Antarctic Southern Ocean and elsewhere progressively with depth, by up to ∼1,000 years in the abyss.Plain Language Summary: The ocean's uptake and distribution of greenhouse gases, oxygen, and heat are determined by the time scales and pathways with which water is transported from the surface into the ocean interior, and from the interior back to the surface. Here we use highly efficient numerical methods to analyze climate model simulations of the global ocean circulation over the 21st century for a scenario with strong greenhouse gas emissions. We find that for the 2090s circulation, Antarctic deep‐water formation has nearly collapsed and the ocean volume that had last surface contact in the Southern Ocean has been roughly halved. To compensate, the volume that forms in subantarctic regions and provides nutrients to much of the world ocean nearly doubles. Less water is reexposed to the atmosphere in Antarctic seas while more is reexposed in adjacent waters to the north. Compared to the 1990s, the 2090s circulation is much more sluggish. Although the pathways from North Atlantic deep‐water formation to reexposure in the tropical eastern Pacific have similar geographic patterns, their most likely transport times are about 40% slower. For the ocean's deepest waters, the mean surface‐to‐surface transit times along the paths of the 2090s circulation are up to 2,000 years longer.Key Points: Transport time scales into and out of the abyssal ocean slow by nearly 1,000 years for the 2090s circulationThrottled Antarctic Bottom Water formation and high‐latitude reexposure are compensated by enhanced subpolar ventilation and reexposureThe residence time partitioned pathways of the 2090s have geographic patterns similar to the 1990s but are strongly lagged in residence time [ABSTRACT FROM AUTHOR]

We study the design of sampling trajectories for stable sampling and the reconstruction of bandlimited spatial fields using mobile sensors. The spectrum is assumed to be a symmetric convex set. As a performance metric we use the path density of the set of sampling trajectories that is defined as the total distance traveled by the moving sensors per unit spatial volume of the spatial region being monitored. Focusing first on parallel lines, we identify the set of parallel lines with minimal path density that contains a set of stable sampling for fields bandlimited to a known set. We then show that the problem becomes ill-posed when the optimization is performed over all trajectories by demonstrating a feasible trajectory set with arbitrarily low path density. However, the problem becomes well-posed if we explicitly specify the stability margins. We demonstrate this by obtaining a non-trivial lower bound on the path density of an arbitrary set of trajectories that contain a sampling set with explicitly specified stability bounds. [ABSTRACT FROM AUTHOR]