Rossella Guerrieri

University of Bologna | UNIBO · Department of Agri-Food Sciences and Technologies

Tropical forests take up more carbon (C) from the atmosphere per annum by photosynthesis than any other type of vegetation. Phosphorus (P) limitations to C uptake are paramount for tropical and subtropical forests around the globe. Yet the generality of photosynthesis-P relationships underlying these limitations are in question, and hence are not r...

The ability of forests to withstand, and recover from, acute drought stress is a critical uncertainty regarding the impacts of climate change on the terrestrial carbon (C) cycle, but it is unclear how drought responses scale from individual trees to whole forests. Here, we assembled a dataset of tree-ring chronologies co-located within the footprin...

Uncertainties surrounding tree carbon allocation to growth are a major limitation to projections of forest carbon sequestration and response to climate change. The prevalence and extent to which carbon assimilation (source) or cambial activity (sink) mediate wood production are fundamentally important and remain elusive. We quantified source-sink r...

Atmospheric nitrogen deposition is an important global change driver, potentially affecting forest health and productivity. In order to evaluate the potential effects on tree growth and above-ground biomass production in southern European conditions, a long-term manipulation experiment was carried out in a prealpine beech forest (Pian Cansiglio, BL...

This chapter aims at summarizing strengths and caveats on the suitability of stable carbon and oxygen isotopes in tree rings as recorders for fingerprints of environmental influences. First, environmental constraints limiting tree growth and shaping tree species distribution worldwide are discussed. Second, examples are presented for environmental...

Carbon isotope discrimination (Δ13C) in C3 woody plants is a key variable for the study of photosynthesis. Yet how Δ13C varies at decadal scales, and across regions, and how it is related to gross primary production (GPP), are still incompletely understood. Here we address these questions by implementing a new Δ13C modelling capability in the land‐...

Purpose of Review We provide an overview of the main processes occurring during the interactions between atmospheric nitrogen and forest canopies, by bringing together what we have learned in recent decades, identifying knowledge gaps, and how they can be addressed with future research thanks to new technologies and approaches. Recent Findings The...

Drought, a natural hydrometeorological phenomenon, has been more frequent and more widespread due to climate change. Water availability strongly regulates the coupling (or trade-off) between carbon uptake via photosynthesis and water loss through transpiration, known as water-use efficiency (WUE). Understanding the effects of drought on WUE across...

Forest regrowth following farmland (agriculture and pasture) abandonment has been positively associated with a number of processes including the regulation of hydrological cycling, the enhancement of soil functioning and an increase in forest productivity and carbon (C) sequestration. Although these changes in ecosystem functioning post‐farmland ab...

Increasing water‐use efficiency (WUE), the ratio of carbon gain to water loss, is a key mechanism that enhances carbon uptake by terrestrial vegetation under rising atmospheric CO2 (ca). Existing theory and empirical evidence suggest a proportional WUE increase in response to rising ca as plants maintain a relatively constant ratio between the leaf...

Rising atmospheric CO2 (ca) has been shown to increase forest carbon uptake. Yet, whether the ca-fertilization effect on forests is modulated by changes in sulphur (Sdep) and nitrogen (Ndep) deposition and how Ndep affects ecosystem N availability remains unclear. We explored spatial and temporal (over 30-years) changes in tree-ring δ¹³C-derived in...

Microbial activity plays a central role in nitrogen (N) cycling, with effects on forest productivity. Although N biotransformations, such as nitrification, are known to occur in the soil, here we investigate whether nitrifiers are present in tree canopies and actively process atmospheric N. This study was conducted in a Mediterranean holm oak ( Que...

Multiple lines of evidence suggest that plant water-use efficiency (WUE)—the ratio of carbon assimilation to water loss—has increased in recent decades. Although rising atmospheric CO2 has been proposed as the principal cause, the underlying physiological mechanisms are still being debated, and implications for the global water cycle remain uncerta...

Earth system models (ESMs) use photosynthetic capacity, indexed by the maximum Rubisco carboxylation rate (Vcmax), to simulate carbon assimilation and typically rely on empirical estimates, including an assumed dependence on leaf nitrogen determined from soil fertility. In contrast, new theory, based on biochemical coordination and co‐optimization...

Human societies depend on an Earth system that operates within a constrained range of nutrient availability, yet the recent trajectory of terrestrial nitrogen (N) availability is uncertain. Examining patterns of foliar N concentrations and isotope ratios (δ15N) from more than 43,000 samples acquired over 37 years, here we show that foliar N concent...

Precipitation regimes are changing in response to climate change, yet understanding of how forest ecosystems respond to extreme droughts and pluvials remains incomplete. As future precipitation extremes will likely fall outside the range of historical variability, precipitation manipulation experiments ( PME s) are critical to advancing knowledge a...

The increase in aridity, mainly by decreases in precipitation but also by higher temperatures, is likely the main threat to the diversity and survival of Mediterranean forests. Changes in land use, including the abandonment of extensive crop activities, mainly in mountains and remote areas, and the increases in human settlements and demand for more...

Rationale We evaluated the applicability of tree‐ring δ¹³C and δ¹⁸O values in bulk wood – instead of the more time and lab‐consuming α‐cellulose δ¹³C and δ¹⁸O values, to assess climate and physiological signals across multiple sites and for six tree species along a latitudinal gradient (35°97'N to 45°20'N) of the northeastern United States. Method...

One of the major challenges in ecology is to understand how ecosystems respond to changes in environmental conditions, and how taxonomic and functional diversity mediate these changes. In this study, we use a trait-spectra and individual-based model, to analyse variation in forest primary productivity along a 3.3 km elevation gradient in the Amazon...

Understanding relations among forest carbon (C) uptake and water use is critical for predicting forest-climate interactions. Although the basic properties of tree-water relations have long been known, our understanding of broader-scale patterns is limited by several factors including: 1) incomplete understanding of drivers of change in coupled C an...

Why do forest productivity and biomass decline with elevation? To address this question, research to date generally has focused on correlative approaches describing changes in woody growth and biomass with elevation. We present a novel, mechanistic approach to this question by quantifying the autotrophic carbon budget in 16 forest plots along a 330...

We examined whether variations in photosynthetic capacity are linked to variations in the environment and/or associated leaf traits for tropical moist forests ( TMF s) in the Andes/western Amazon regions of Peru. We compared photosynthetic capacity (maximal rate of carboxylation of Rubisco ( V cmax ), and the maximum rate of electron transport ( J...

Nitrogen (N) deposition and changing climate patterns in the northeastern USA can influence forest productivity through effects on plant nutrient relations and water use. This study evaluates the combined effects of N fertilization, climate and rising atmospheric CO2 on tree growth and ecophysiology in a temperate deciduous forest. Tree ring widths...

This study examines the role of tree canopies in processing atmospheric nitrogen (Ndep) for four forests in the UK subjected to different Ndep: Scots pine and beech stands under high Ndep (HN, 13-19 kg N ha−1 yr−1), compared to Scots pine and beech stands under low Ndep (LN, 9 kg N ha−1 yr−1). Changes of NO3-N and NH4-N concentrations in rainfall (...

Leaf dark respiration (Rdark ) is an important yet poorly quantified component of the global carbon cycle. Given this, we analyzed a new global database of Rdark and associated leaf traits. Data for 899 species were compiled from 100 sites (from the Arctic to the tropics). Several woody and nonwoody plant functional types (PFTs) were represented. M...

Water use efficiency (WUE), defined as the ratio of carbon assimilation (A) to water loss via transpiration, is the key physiological parameter that explicitly links water and carbon cycling in forest ecosystems. Most studies examining the influence of climatic factors on forest-WUE have focused on site-specific and water-limited ecosystems. Much l...

Background/Question/Methods Nitrogen (N) deposition and changing climate patterns in the northeastern U.S. can influence forest productivity through effects on plant nutrient relations and water use efficiency, defined as the ratio between CO2 assimilation (A) and water loss via transpiration. To assess this impact, we considered the unique manip...

Background/Question/Methods Water use efficiency (WUE), defined as the ratio of carbon assimilation (A) to water loss via transpiration, is the key physiological parameter that explicitly links water and carbon (C) cycling in forest ecosystems. Most studies examining the influence of climatic factors on forest-WUE have focused on water-limited Me...

Partially mycoheterotrophic (mixotrophic) plants gain carbon from both photosynthesis and their mycorrhizal fungi. This is considered an ancestral state in the evolution of full mycoheterotrophy, but little is known about this nutrition, and especially about the physiological balance between photosynthesis and fungal C gain. To investigate possible...

Background/Question/Methods As an integral part in carbon cycle, photosynthetic capacity has been increasingly incorporated in vegetation-climate models for predicting ecosystem productivity. To predict variations in photosynthetic capacity over large spatial and temporal scales, assumptions are made on the relationship between photosynthetic cap...

The objective of this study is to globally assess the effects of atmospheric nitrogen deposition and climate, associated with rising levels of atmospheric CO2, on the variability of carbon isotope discrimination (?13C), and intrinsic water-use efficiency (iWUE) of angiosperm and conifer tree species. Eighty-nine long-term isotope tree-ring chronolo...

This study aimed to evaluate the effects of long-term repeated aerial nitrogen (N) and sulphur (S) misting over tree canopies of a Sitka spruce plantation in Scotland. We combined δ13C and δ18O in tree rings to evaluate the changes in CO2 assimilation (A) and stomatal conductance (gs) and to assess their contribution to variations in the intrinsic...

In this study, we investigated the potential of the photochemical resistance index (PRI) to track photosynthetic activity under water stress conditions by measuring PRI, leaf fluorescence, the xanthophyll cycle and photosynthetic activity in different forest tree species subjected to progressive drought. The PRI declined with pre-dawn water potenti...

We investigated the effect of N deposition (Ndep) on intrinsic water-use efficiency (WUEi), the ratio of photosynthesis (A) to stomatal conductance (gs), for two Quercus cerris stands at different distances to an oil refinery in Southern Italy. We used delta13C in tree rings for assessing changes in WUEi; while the influence of climate and NOx emis...

Recent studies recognised nitrogen deposition (Ndep) as one of the main drivers of the terrestrial carbon sink, together with elevated atmospheric CO2. This is particularly true for N-limited temperate and boreal forests, where Ndep can act as a low-level but long-term input of fertiliser. The scientific debate has been mainly focused on the quanti...

Significant decrease in precipitation up to 15–20% has been observed in the Mediterranean area in the last two decades as a consequence of climate change. To simulate an analogous scenario, the precipitation regime was altered in replicated experimental plots in a Mediterranean macchia dominated by Arbutus unedo L. species. Two different levels of...

Due to climate change, drier summers have been observed over the last ten years in Mediterranean areas. Increasing drought levels may have a different weight in influencing the stomatal versus photosynthetic activity of forests, altering the water-use efficiency (i.e., WUE, the amount of carbon gain per water lost) and, consequently, the global car...

The importance that nitrogen (N) deposition has in driving the carbon (C) sequestration of forests has recently been investigated using both experimental and modeling approaches. Whether increased N deposition has positive or negative effects on such ecosystems depends on the status of the N and the duration of the deposition. By combining δ13C, δ1...

Pinus leucodermis Antoine (= Pinus heldreichii var. leucodermis) is a species of the Balkan flora which in Italy grows in a small area between the Regions of Basilicata and Calabria, in the Pollino National Park. A relict of the oro-Mediterranean Tertiary forests, it is found from the lower vegetation belt, where it is mixed with evergreen scleroph...

Increase of nitrogen depositions, as oxidized (NOx) and reduced (NHx) compounds, has important implications on ecosystem nitrogen cycle. NOx comes predominantly from fossil fuel combustion in car engines and industrial processes, while agricultural activities (cattle farming, fertilizations) are the main sources for NHx emissions. Such fertilisatio...

Tree-ring δ¹³C is widely employed in ecophysiological studies, because it represents an integrated proxy of the ratio between photosynthesis ( A ) and stomatal conductance ( g ), which expresses the intrinsic water use efficiency ( iWUE ), strongly affected by the environmental conditions experienced by the plant during its life span. Tr...