Recent berkeley_geography_oapdeposits items

Corn and the range: rethinking ranching, agriculture and the feedlot

Wed, 22 Apr 2026 00:00:00 +0000

Debates about modern beef production suffer from a major historical blind spot. For over a century, the feedlot relied on a closed nutrient loop to sustain soil fertility in the United States Corn Belt. Driven by industrial capitalist urbanization, a cattle-grain-beef complex shaped land use, tenure systems, management practices and environmental politics on the expanding frontier, sacrificing the tall-grass prairies and fracturing agrarian resistance to corporate concentration and the Union Stock Yards. Concentrated Animal Feeding Operations (CAFOs) emerged after 1950, breaking the nutrient cycle of the original feedlot and turning the relationship between ranching and agriculture into a dysfunctional one.

Mortality correlates with tree functional traits across a wood density gradient in the Central Amazon

Wed, 18 Mar 2026 00:00:00 +0000

Introduction: Understanding the mechanisms of tree mortality in tropical ecosystems remains challenging, in part due to the high diversity of tree species and the inherently stochastic nature of mortality. Plant functional traits offer a mechanistic link between plant physiology and performance, yet their ability to predict growth and mortality remains poorly understood. Given recent increases in tree mortality rates in the Amazon forest following extreme drought and wind events, we tested if lower wood density and acquisitive plant functional traits were associated with increased growth and mortality for common co-occurring trees in the Central Amazon. Methods: Seventeen trees of different species with similar sizes but a range in wood density (WD) and wood traits were felled, then assessed for 27 different individual functional parameters, including whole tree architecture, stem xylem anatomical and hydraulic traits and leaf traits. Traits of the individual trees were related...

Water availability modulates maximum canopy heights of low-elevation Amazonian second-growth forests

Tue, 17 Feb 2026 00:00:00 +0000

Tropical second-growth forests of the Amazon sequester large amounts of carbon and are important carbon sinks, contributing substantially to climate change mitigation, biodiversity conservation, and providing crucial ecosystem services. Deforestation due to selective logging and shifting cultivation is expanding second-growth forest areas in tropical forest regions, which if well managed, regenerate rapidly over time. Maximum forest canopy height is an important metric of biomass and carbon accumulation in second-growth forests and is strongly influenced by water availability. The water limitation hypothesis explains the positive influence of water availability on maximum tree heights and has been examined and demonstrated at a small-scale using field data, and at a global scale, with limited accuracy, using remote sensing data in tropical ecosystems. However, this hypothesis concerning maximum canopy height has not been much studied at regional and national scales for tropical...

Seasonal Dependence of Atmospheric Responses to Extratropical Forcing

Wed, 22 Oct 2025 00:00:00 +0000

Abstract Previous studies have shown that the extratropical-to-tropical teleconnection exhibits seasonal dependence, but the underlying mechanisms remain unclear. In this study, we use an idealized framework to explore the teleconnection and its underlying dynamics. We impose extratropical thermal warming in an aquaplanet model coupled to a mixed layered ocean under two idealized control climates: a perpetual winter-like climate and a perpetual summer-like climate. The extratropical-to-tropical teleconnection is more pronounced in the perpetual summer-like case, primarily due to differences in eddy momentum flux behavior. The unstable environment in the summer-like climate leads to vertically extended warming, which suppresses baroclinicity effectively and results in a subtropical eddy momentum flux convergence anomaly. This in turn drives adjustments in the Hadley cell. Moreover, the summer-like climatological Hadley cell is in a regime that responds effectively to anomalous...

The Seasonal Cycles of Tropical Sea Surface Temperature from Earth’s Axial Tilt and Orbital Eccentricity

Tue, 26 Aug 2025 00:00:00 +0000

Abstract: We explore the relative roles of Earth’s axial tilt (“tilt effect”) and orbital eccentricity (“distance effect”) in generating the seasonal cycle of tropical sea surface temperature (SST), decomposing the two contributions using simulations of an Earth system model varying the eccentricity and longitude of perihelion. Tropical SST seasonality is largely explained by the annual contribution from tilt, but with significant contributions from the semiannual contribution from tilt and annual contribution from distance, especially in regions where the tilt annual contribution is relatively small. Precessional changes to tropical SST seasonality are readily explained by the distance annual component whose amplitude increases linearly with eccentricity and whose phase changes linearly with the longitude of perihelion, while the tilt contributions remain essentially unchanged. As such, the annual cycle contribution from distance can become significant at high eccentricity...

Real-Time Partitioning of Diurnal Stem CO2 Efflux into Local Stem Respiration and Xylem Transport Processes

Tue, 26 Aug 2025 00:00:00 +0000

The apparent respiratory quotient (ARQ) of tree stems, defined as the ratio of net stem CO2 efflux (ES_CO2) to net stem O2 influx (ES_O2), offers insights into the balance between local respiratory CO2 production and CO2 transported via the xylem. Traditional static chamber methods for measuring ARQ can introduce artifacts and obscure natural diurnal variations. Here, we employed an open flow-through stem chamber with ambient air coupled with cavity ring-down spectrometry, which uses the molecular properties of CO2 and O2 molecules to continuously measure ES_CO2, ES_O2, and ARQ, at the base of a California cherry tree (Prunus ilicifolia) during the 2024 growing season. Measurements across three stem chambers over 3–11-day periods revealed strong correlations between ES_CO2 and ES_O2 and mean ARQ values ranging from 1.3 to 2.9, far exceeding previous reports. Two distinct diurnal ARQ patterns were observed: daytime suppression with nighttime recovery, and a morning peak followed...

Hyperspectral leaf reflectance of grasses varies with evolutionary lineage more than with site

Tue, 22 Jul 2025 00:00:00 +0000

Abstract To predict ecological responses at broad environmental scales, grass species are commonly grouped into two broad functional types based on photosynthetic pathway. However, closely related species may have distinctive anatomical and physiological attributes that influence ecological responses, beyond those related to photosynthetic pathway alone. Hyperspectral leaf reflectance can provide an integrated measure of covarying leaf traits that may result from phylogenetic trait conservatism and/or environmental conditions. Understanding whether spectra‐trait relationships are lineage specific or reflect environmental variation across sites is necessary for using hyperspectral reflectance to predict plant responses to environmental changes across spatial scales. We measured hyperspectral leaf reflectance (400–2400 nm) and 12 structural, biochemical, and physiological leaf traits from five grass‐dominated sites spanning the Great Plains of North America. We assessed if variation...

Arctic sea-ice loss drives a strong regional atmospheric response over the North Pacific and North Atlantic on decadal scales

Mon, 2 Jun 2025 00:00:00 +0000

Previous studies have suggested that Arctic sea-ice loss can have a profound influence on atmospheric circulation far away from the Arctic. However, there is little scientific consensus on the features of these remote responses, with the opposite impacts reported. Here we present a multi-model analysis of the decadal climate response to Arctic sea-ice loss using state-of-the-art energy conserving methodologies to isolate the impacts of sea-ice decline. We observe weakening of the Aleutian Low and development of a geopotential ridge in the North Pacific, associated with drier winter conditions over the southwest United States. Over the Atlantic, a negative NAO-like response drives wetter winter conditions across the western Mediterranean. These decadal-scale impacts substantially differ from reported centennial-scale responses to Arctic sea-ice loss simulated using non-energy conserving methodologies. Factors such as the timescale of the response and methodologies used to isolate...

What Causes the Hemispheric Difference in the Asymmetry of the Temperature Annual Cycle?

Mon, 2 Jun 2025 00:00:00 +0000

Previous studies have noted the asymmetry in the annual cycle of zonal mean surface air temperature, defined as the difference in the lengths of warming and cooling periods. Pronounced north-south hemispheric differences in this asymmetry, by up to 40 days, were attributed to the eccentricity of Earth's orbit. However, we propose that the dominant factor comes from the difference in the land-sea fraction between hemispheres, because the asymmetry is strongly influenced by the annually varying heat capacity and land-sea interactions. The oceanic temperature annual cycle generally features a longer cooling period than warming due to the seasonal variation in ocean mixed layer depth, and exhibits the opposite situation when there is seasonal sea ice. Land-sea interactions impact the zonal mean temperature annual cycle by resulting in an earlier winter trough of the downstream oceanic temperature and delaying the summer peak in west coasts.

Transformation of Unregulated Cannabis Cultivation Under Proposition 64

Wed, 12 Mar 2025 00:00:00 +0000

Transformation of Unregulated Cannabis Cultivation Under Proposition 64

No evidence of canopy-scale leaf thermoregulation to cool leaves below air temperature across a range of forest ecosystems

Fri, 14 Feb 2025 00:00:00 +0000

Understanding and predicting the relationship between leaf temperature (T_leaf) and air temperature (T_air) is essential for projecting responses to a warming climate, as studies suggest that many forests are near thermal thresholds for carbon uptake. Based on leaf measurements, the limited leaf homeothermy hypothesis argues that daytime T_leaf is maintained near photosynthetic temperature optima and below damaging temperature thresholds. Specifically, leaves should cool below T_air at higher temperatures (i.e., > ∼25-30°C) leading to slopes <1 in T_leaf/T_air relationships and substantial carbon uptake when leaves are cooler than air. This hypothesis implies that climate warming will be mitigated by a compensatory leaf cooling response. A key uncertainty is understanding whether such thermoregulatory behavior occurs in natural forest canopies. We present an unprecedented...

Coupled model intercomparison project phase 6 (CMIP6) high resolution model intercomparison project (HighResMIP) bias in extreme rainfall drives underestimation of amazonian precipitation

Thu, 16 Jan 2025 00:00:00 +0000

Extreme rainfall events drive the amount and spatial distribution of rainfall in the Amazon and are a key driver of forest dynamics across the basin. This study investigates how the 3-hourly predictions in the High Resolution Model Intercomparison Project (HighResMIP, a component of the recent Coupled Model Intercomparison Project, CMIP6) represent extreme rainfall events at annual, seasonal, and sub-daily time scales. TRMM 3B42 (Tropical Rainfall Measuring Mission) 3 h data were used as observations. Our results showed that eleven out of seventeen HighResMIP models showed the observed association between rainfall and number of extreme events at the annual and seasonal scales. Two models captured the spatial pattern of number of extreme events at the seasonal and annual scales better (higher correlation) than the other models. None of the models captured the sub-daily timing of extreme rainfall, though some reproduced daily totals. Our results suggest that higher model resolution...

A Later Onset of the Rainy Season in California