High Vcmax, Jmax and photosynthetic rates of Sonoran Desert species : using nitrogen and specific leaf area traits as predictors in biochemical models

Dryland ecosystems largely control the inter-annual variability of the global carbon cycle. Unfortunately, there is a paucity of data on key biochemical parameters, such as maximum carboxylation velocity (Vcmax25) and electron transport rate (Jmax25), from species in these ecosystems which limits our capacity to model photosynthesis across ecological scales. We studied six dominant C3 shrub and tree species from the Sonoran Desert with different leaf traits and phenological strategies. We characterized Vcmax25 and Jmax25 for each species and assessed which traits or trait combinations were the best predictors of these parameters for biochemical models of photosynthesis. All species had high values of Vcmax25 and Jmax25, mostly explained by high leaf nitrogen content (Narea) and high nitrogen allocation to photosynthetic enzymes comparable to those reported for herbs and crop species but higher than those of shrubs and other functional types in world databases. We found that the high values of Vcmax25 and Jmax25, by increasing rates of photosynthetic reactions, enhance photosynthetic water and nitrogen-use efficiencies and may favor carbon gain under typical conditions in drylands. Our findings improve the parameterization of photosynthesis models, and provide novel implications to common findings of high Narea in dryland species

Perspectivas del cultivo de la saya (Amoreuxia spp.) en el noroeste de México como nuevo producto agronómico.

In the past, the inhabitants of northwestern Mexico benefited from the saya plant (several species from the Amoreuxia genus), taking advantage of it for both food and medicinal purposes, and subsequently European colonizers utilized it as food, when faced with famine. Currently, some of these species have shown a decline in populations, so they are now considered to be in the NOM 059, 2010 risk category of the Ministry of the Environment and Natural Resources. Recent endeavors have provided knowledge concerning how to propagate this plant under agricultural conditions. In this work, cultivation of saya (A. palmatifida) crop was evaluated over two consecutive years, in order to compare productivity during the first year with plants obtained from direct germination of seeds under agricultural conditions, with those produced the second year from tuberous root regrowth. Greater plant productivity was found in the second year evaluation (p<0.0001), in terms of plant growth, seed production and weight of tuberous roots. In the future, it may be possible for some species from the Amoreuxia genus to have very positive social impact, if multiplication techniques for this species, as described in this work are applied, in order to rehabilitate this plant in grazing lands of northwestern Mexico and even to generate new plants.En el pasado los pobladores del noroeste de México se beneficiaron de la planta saya (varias especies del género Amoreuxia), aprovechándola tanto con fines alimenticios como medicinales, luego los colonizadores europeos la aprovecharon como alimento ante hambrunas. Actualmente algunas de estas especies presentan disminución en sus poblaciones, por lo cual han sido consideradas en categorías de riesgo de la NOM 059 de la Secretaría del Medio Ambiente y Recursos Naturales en el año 2010. Esfuerzos recientes han aportado conocimiento sobre formas de multiplicación de la planta bajo condiciones agrícolas. En este trabajo se evaluó el cultivo de saya (A. palmatifida) durante dos años consecutivos, para comparar la productividad del primer año de plantas obtenidas de germinación directa de semillas en condiciones agrícolas, con la productividad del segundo año a partir del rebrote las raíces tuberosas. Se encontró una mayor productividad de las plantas en el segundo año de evaluación (p < 0.0001), tanto en crecimiento de la planta, producción de semillas y peso de las raíces tuberosas. El futuro impacto social de algunas especies del género Amoreuxia puede ser muy positivo aplicando las técnicas de multiplicación de esta especie, descritas en este trabajo, para recuperar esta planta en los terrenos de agostadero del noroeste de México e incluso para generar nuevos cultivos

Global city densities: Re-examining urban scaling theory

Understanding scaling relations of social and environmental attributes of urban systems is necessary for effectively managing cities. Urban scaling theory (UST) has assumed that population density scales positively with city size. We present a new global analysis using a publicly available database of 933 cities from 38 countries. Our results showed that (18/38) 47% of countries analyzed supported increasing density scaling (pop ~ area) with exponents ~⅚ as UST predicts. In contrast, 17 of 38 countries (~45%) exhibited density scalings statistically indistinguishable from constant population densities across cities of varying sizes. These results were generally consistent in years spanning four decades from 1975 to 2015. Importantly, density varies by an order of magnitude between regions and countries and decreases in more developed economies. Our results (i) point to how economic and regional differences may affect the scaling of density with city size and (ii) show how understanding country- and region-specific strategies could inform effective management of urban systems for biodiversity, public health, conservation and resiliency from local to global scales.200 word statement of contribution: Urban Scaling Theory (UST) is a general scaling framework that makes quantitative predictions for how many urban attributes spanning physical, biological and social dimensions scale with city size; thus, UST has great implications in guiding future city developments. A major assumption of UST is that larger cities become denser. We evaluated this assumption using a publicly available global dataset of 933 cities in 38 countries. Our scaling analysis of population size and area of cities revealed that while many countries analyzed showed increasing densities with city size, about 45% of countries showed constant densities across cities. These results question a key assumption of UST. Our results suggest policies and management strategies for biodiversity conservation, public health and sustainability of urban systems may need to be tailored to national and regional scaling relations to be effective

Plant Traits Help Explain the Tight Relationship between Vegetation Indices and Gross Primary Production

Remotely-sensed Vegetation Indices (VIs) are often tightly correlated with terrestrial ecosystem CO2 uptake (Gross Primary Production or GPP). These correlations have been exploited to infer GPP at local to global scales and over half-hour to decadal periods, though the underlying mechanisms remain incompletely understood. We used satellite remote sensing and eddy covariance observations at 10 sites across a California climate gradient to explore the relationships between GPP, the Enhanced Vegetation Index (EVI), the Normalized Difference Vegetation Index (NDVI), and the Near InfraRed Vegetation (NIRv) index. EVI and NIRv were linearly correlated with GPP across both space and time, whereas the relationship between NDVI and GPP was less general. We explored these interactions using radiative transfer and GPP models forced with in-situ plant trait and soil reflectance observations. GPP ultimately reflects the product of Leaf Area Index (LAI) and leaf level CO2 uptake (Aleaf); a VI that is sensitive mainly to LAI will lack generality across ecosystems that differ in Aleaf. EVI and NIRv showed a strong, multiplicative sensitivity to LAI and Leaf Mass per Area (LMA). LMA was correlated with Aleaf, and EVI and NIRv consequently mimic GPP’s multiplicative sensitivity to LAI and Aleaf, as mediated by LMA. NDVI was most sensitive to LAI, and was relatively insensitive to leaf properties over realistic conditions; NDVI lacked EVI and NIRv’s sensitivity to both LAI and Aleaf. These findings carry implications for understanding the limitations of current VIs for predicting GPP, and also for devising strategies to improve predictions of GPP

High Vcmax, Jmax and photosynthetic rates of Sonoran Desert species : using nitrogen and specific leaf area traits as predictors in biochemical models

Dryland ecosystems largely control the inter-annual variability of the global carbon cycle. Unfortunately, there is a paucity of data on key biochemical parameters, such as maximum carboxylation velocity (Vcmax25) and electron transport rate (Jmax25), from species in these ecosystems which limits our capacity to model photosynthesis across ecological scales. We studied six dominant C3 shrub and tree species from the Sonoran Desert with different leaf traits and phenological strategies. We characterized Vcmax25 and Jmax25 for each species and assessed which traits or trait combinations were the best predictors of these parameters for biochemical models of photosynthesis. All species had high values of Vcmax25 and Jmax25, mostly explained by high leaf nitrogen content (Narea) and high nitrogen allocation to photosynthetic enzymes comparable to those reported for herbs and crop species but higher than those of shrubs and other functional types in world databases. We found that the high values of Vcmax25 and Jmax25, by increasing rates of photosynthetic reactions, enhance photosynthetic water and nitrogen-use efficiencies and may favor carbon gain under typical conditions in drylands. Our findings improve the parameterization of photosynthesis models, and provide novel implications to common findings of high Narea in dryland species

From Reductionism to Reintegration: Solving society's most pressing problems requires building bridges between data types across the life sciences.

Decades of reductionist approaches in biology have achieved spectacular progress, but the proliferation of subdisciplines, each with its own technical and social practices regarding data, impedes the growth of the multidisciplinary and interdisciplinary approaches now needed to address pressing societal challenges. Data integration is key to a reintegrated biology able to address global issues such as climate change, biodiversity loss, and sustainable ecosystem management. We identify major challenges to data integration and present a vision for a "Data as a Service"-oriented architecture to promote reuse of data for discovery. The proposed architecture includes standards development, new tools and services, and strategies for career-development and sustainability

Protección contra herbivoría en reforestación de terreno árido degradado, con palo verde(Parkinsonia microphylla Torr.)

ABSTRACT Rehabilitating degraded arid lands requires overcoming biotic and abiotic limitations. The objective of this study was to determine if low-cost protective shelters improve the survival and growth of palo verde (Parkinsonia microphylla) plants during the first year of reforestation at degraded sites in the Sonoran Desert. Protective shelters were built using pruning waste and plastic containers. For one year, 264 palo verde plants were subjected to differential protection treatments against herbivores: unprotected, and protected by branch shelters, polyethylene terephthalate (PET) shelters or both), and their survival and height were monitored. The survival of plants with the use of protective shelters was greater than that of unprotected plants (34.9-56.7 vs. 1.8%, x2 = 63.5; p < 0.0001); also, the heights of protected plants were greater. The use of shelters is an alternative for reforestation with palo verde in degraded lands in the Sonoran desert.RESUMEN Rehabilitar terrenos degradados áridos, demanda superar limitaciones bióticas y abióticas. El objetivo del estudio fue conocer si refugios protectores de bajo costo, mejoran la supervivencia y el crecimiento de plantas de palo verde (Parkinsonia microphyllá), durante el primer año de reforestación en sitios degradados del Desierto Sonorense. Se construyeron refugios protectores reutilizando desechos de poda y envases plásticos. Durante un año, 264 plantas de palo verde fueron sometidas a tratamientos diferenciales de protección contra herbívoros (sin protección, y con protección por refugios de ramas, PET o ambos), y se monitoreó su supervivencia y altura. La supervivencia de plantas con el uso de refugios protectores fue mayor que la de las plantas sin protección (34.9-56.7 vs. 1.8%, x2 = 63.5; p < 0.0001); también las alturas de las plantas protegidas fueron mayores. El uso de refugios es una alternativa para la reforestación con palo verde en terrenos degradados del desierto Sonorense

Table_1_Global city densities: Re-examining urban scaling theory.docx

Understanding scaling relations of social and environmental attributes of urban systems is necessary for effectively managing cities. Urban scaling theory (UST) has assumed that population density scales positively with city size. We present a new global analysis using a publicly available database of 933 cities from 38 countries. Our results showed that (18/38) 47% of countries analyzed supported increasing density scaling (pop ~ area) with exponents ~⅚ as UST predicts. In contrast, 17 of 38 countries (~45%) exhibited density scalings statistically indistinguishable from constant population densities across cities of varying sizes. These results were generally consistent in years spanning four decades from 1975 to 2015. Importantly, density varies by an order of magnitude between regions and countries and decreases in more developed economies. Our results (i) point to how economic and regional differences may affect the scaling of density with city size and (ii) show how understanding country- and region-specific strategies could inform effective management of urban systems for biodiversity, public health, conservation and resiliency from local to global scales.200 word statement of contribution: Urban Scaling Theory (UST) is a general scaling framework that makes quantitative predictions for how many urban attributes spanning physical, biological and social dimensions scale with city size; thus, UST has great implications in guiding future city developments. A major assumption of UST is that larger cities become denser. We evaluated this assumption using a publicly available global dataset of 933 cities in 38 countries. Our scaling analysis of population size and area of cities revealed that while many countries analyzed showed increasing densities with city size, about 45% of countries showed constant densities across cities. These results question a key assumption of UST. Our results suggest policies and management strategies for biodiversity conservation, public health and sustainability of urban systems may need to be tailored to national and regional scaling relations to be effective.</p

Table_2_Global city densities: Re-examining urban scaling theory.docx

Understanding scaling relations of social and environmental attributes of urban systems is necessary for effectively managing cities. Urban scaling theory (UST) has assumed that population density scales positively with city size. We present a new global analysis using a publicly available database of 933 cities from 38 countries. Our results showed that (18/38) 47% of countries analyzed supported increasing density scaling (pop ~ area) with exponents ~⅚ as UST predicts. In contrast, 17 of 38 countries (~45%) exhibited density scalings statistically indistinguishable from constant population densities across cities of varying sizes. These results were generally consistent in years spanning four decades from 1975 to 2015. Importantly, density varies by an order of magnitude between regions and countries and decreases in more developed economies. Our results (i) point to how economic and regional differences may affect the scaling of density with city size and (ii) show how understanding country- and region-specific strategies could inform effective management of urban systems for biodiversity, public health, conservation and resiliency from local to global scales.200 word statement of contribution: Urban Scaling Theory (UST) is a general scaling framework that makes quantitative predictions for how many urban attributes spanning physical, biological and social dimensions scale with city size; thus, UST has great implications in guiding future city developments. A major assumption of UST is that larger cities become denser. We evaluated this assumption using a publicly available global dataset of 933 cities in 38 countries. Our scaling analysis of population size and area of cities revealed that while many countries analyzed showed increasing densities with city size, about 45% of countries showed constant densities across cities. These results question a key assumption of UST. Our results suggest policies and management strategies for biodiversity conservation, public health and sustainability of urban systems may need to be tailored to national and regional scaling relations to be effective.</p