Predicting resprouting of Platanus × hispanica following branch pruning by means of machine learning.

Introduction: Resprouting is a crucial survival strategy following the loss of branches, being it by natural events or artificially by pruning. The resprouting prediction on a physiological basis is a highly complex approach. However, trained gardeners try to predict a tree's resprouting after pruning purely based on their empirical knowledge. In this study, we explore how far such predictions can also be made by machine learning. Methods: Table-topped annually pruned Platanus × hispanica trees at a nursery were LiDAR-scanned for two consecutive years. Topological structures for these trees were abstracted by cylinder fitting. Then, new shoots and trimmed branches were labelled on corresponding cylinders. Binary and multiclass classification models were tested for predicting the location and number of new sprouts. Results: The accuracy for predicting whether having or not new shoots on each cylinder reaches 90.8% with the LGBMClassifier, the balanced accuracy is 80.3%. The accuracy for predicting the exact numbers of new shoots with the GaussianNB model is 82.1%, but its balanced accuracy is reduced to 42.9%. Discussion: The results were validated with a separate dataset, proving the feasibility of resprouting prediction after pruning using this approach. Different tree species, tree forms, and other variables should be addressed in further research.

A multilayered urban tree dataset of point clouds, quantitative structure and graph models.

The significance of urban trees in promoting human health and well-being has been amplified by urbanization and the climate change effects. Simultaneously, advancements in remote sensing techniques have enhanced the opportunities for studying urban trees. The TreeML-Data has been compiled to support these efforts. It consists of labelled point clouds of 40 scanning projects of streets in Munich, 3,755 leaf-off (scans in winter) point clouds of individual trees, quantitative structure models (QSM), tree structure measurements, and tree graph structure models of these trees. The dataset offers valuable data for generating and evaluating models in various scientific disciplines, which include remote sensing, computer vision, machine learning, urban forestry, urban ecosystem, green architecture, and graph analysis. To ensure its quality, the tree structure measurements and QSM have been crosschecked. For instance, the tree diameter at breast height (DBH) in the sample dataset exhibits a deviation of approximately 1.5 cm (4.3%) when compared to manual measurements. In conclusion, the quality checks confirm its reliability for subsequent studies when compared to manual measurements.

A comparative analysis of urban forests for storm-water management.

Large-scale urban growth has modified the hydrological cycle of our cities, causing greater and faster runoff. Urban forests (UF), i.e. the stock of trees and shrubs, can substantially reduce runoff; still, how climate, tree functional types influence rainfall partitioning into uptake and runoff is mostly unknown. We analyzed 92 published studies to investigate: interception (I), transpiration (T), soil infiltration (IR) and the subsequent reduction in runoff. Trees showed the best runoff protection compared to other land uses. Within functional types, conifers provided better protection on an annual scale through higher I and T but broadleaved species provided better IR. Regarding tree traits, leaf area index (LAI) showed a positive influence for both I and T. For every unit of LAI increment, additional 5% rainfall partition through T (3%) and I (2%) can be predicted. Overall, runoff was significantly lower under mixed species stands. Increase of conifer stock to 30% in climate zones with significant winter precipitation and to 20% in areas of no dry season can reduce runoff to an additional 4%. The study presented an overview of UF potential to partition rainfall, which might help to select species and land uses in different climate zones for better storm-water management.

Accuracy, realism and general applicability of European forest models.

Forest models are instrumental for understanding and projecting the impact of climate change on forests. A considerable number of forest models have been developed in the last decades. However, few systematic and comprehensive model comparisons have been performed in Europe that combine an evaluation of modelled carbon and water fluxes and forest structure. We evaluate 13 widely used, state-of-the-art, stand-scale forest models against field measurements of forest structure and eddy-covariance data of carbon and water fluxes over multiple decades across an environmental gradient at nine typical European forest stands. We test the models' performance in three dimensions: accuracy of local predictions (agreement of modelled and observed annual data), realism of environmental responses (agreement of modelled and observed responses of daily gross primary productivity to temperature, radiation and vapour pressure deficit) and general applicability (proportion of European tree species covered). We find that multiple models are available that excel according to our three dimensions of model performance. For the accuracy of local predictions, variables related to forest structure have lower random and systematic errors than annual carbon and water flux variables. Moreover, the multi-model ensemble mean provided overall more realistic daily productivity responses to environmental drivers across all sites than any single individual model. The general applicability of the models is high, as almost all models are currently able to cover Europe's common tree species. We show that forest models complement each other in their response to environmental drivers and that there are several cases in which individual models outperform the model ensemble. Our framework provides a first step to capturing essential differences between forest models that go beyond the most commonly used accuracy of predictions. Overall, this study provides a point of reference for future model work aimed at predicting climate impacts and supporting climate mitigation and adaptation measures in forests.

Dynamics of initial carbon allocation after drought release in mature Norway spruce-Increased belowground allocation of current photoassimilates covers only half of the carbon used for fine-root growth.

After drought events, tree recovery depends on sufficient carbon (C) allocation to the sink organs. The present study aimed to elucidate dynamics of tree-level C sink activity and allocation of recent photoassimilates (Cnew ) and stored C in c. 70-year-old Norway spruce (Picea abies) trees during a 4-week period after drought release. We conducted a continuous, whole-tree 13 C labeling in parallel with controlled watering after 5 years of experimental summer drought. The fate of Cnew to growth and CO2 efflux was tracked along branches, stems, coarse- and fine roots, ectomycorrhizae and root exudates to soil CO2 efflux after drought release. Compared with control trees, drought recovering trees showed an overall 6% lower C sink activity and 19% less allocation of Cnew to aboveground sinks, indicating a low priority for aboveground sinks during recovery. In contrast, fine-root growth in recovering trees was seven times greater than that of controls. However, only half of the C used for new fine-root growth was comprised of Cnew while the other half was supplied by stored C. For drought recovery of mature spruce trees, in addition to Cnew , stored C appears to be critical for the regeneration of the fine-root system and the associated water uptake capacity.

Spatial and temporal changes of outdoor thermal stress: influence of urban land cover types.

Green infrastructure (GI) has emerged as a feasible strategy for promoting adaptive capacities of cities to climate change by alleviating urban heat island (UHI) and thus heat stress for humans. However, GI can also intensify the winter cold stress. To understand the extent of UHI within a city as well as the link between outdoor thermal stress both diurnally and seasonally, we carried out an empirical study in Würzburg, Germany from 2018 to 2020. At sub-urban sites, relative humidity and wind speed (WS) was considerably higher and air temperature (AT) lower compared to the inner city sites. Mean AT of inner city sites were higher by 1.3 °C during summer and 5 °C during winter compared to sub-urban sites. The magnitude followed the spatial land use patterns, in particular the amount of buildings. Consequently, out of 97 hot days (AT > 30 °C) in 3 years, 9 days above the extreme threshold of wet bulb globe temperature of 35 °C were recorded at a centre location compared to none at a sub-urban site. Extreme heat stress could be halved with 30-40% cover of greenspaces including grass lawns, green roofs, and green walls with little compromise in increasing winter cold stress.

Expression of additional transcription factors is of prognostic value for aggressive behavior of pituitary adenomas.

OBJECTIVE: According to the latest WHO classification of tumors of endocrine organs in 2017, plurihormonal adenomas are subclassified by their transcription factor (TF) expression. In the group of plurihormonal adenomas with unusual immunohistochemical combinations (PAWUC), the authors identified a large fraction of adenomas expressing TFs for gonadotroph adenoma (TFGA) cells in addition to other TFs. The aim of this study was to compare clinicopathological parameters of PAWUC with TFGA expression to gonadotroph adenomas that only express TFGA. METHODS: This retrospective single-center series comprises 73 patients with TFGA-positive pituitary adenomas (SF1, GATA3, estrogen receptor α): 22 PAWUC with TFGA (TFGA-plus group) and 51 with TFGA expression only (TFGA-only group). Patient characteristics, outcome parameters, rate of invasiveness (assessed by direct endoscopic inspection), and MIB1 and MGMT status were compared between groups. RESULTS: Patients in the TFGA-plus group were significantly younger than patients in the TFGA-only group (age 46 vs 56 years, respectively; p = 0.007). In the TFGA-only group, pituitary adenomas were significantly larger (diameter 25 vs 18.3 mm, p = 0.002). Intraoperatively, signs of invasiveness were significantly more common in the TFGA-plus group than in the TFGA-only group (50% vs 16%, p = 0.002). Gross-total resection was significantly lower in the nonfunctioning TFGA-plus group than in the TFGA-only group (44% vs 86%, p = 0.004). MIB1 and MGMT status showed no significant difference between groups. CONCLUSIONS: These data suggest a more aggressive behavior of TFGA-positive adenomas if an additional TF is expressed within the tumor cells. Shorter radiographic surveillance and earlier consideration for retreatment should be recommended in these adenoma types.

Influence of Corticosteroids and Antiepileptic Drugs on Visible 5-Aminolevulinic Acid Fluorescence in a Series of Initially Suspected Low-Grade Gliomas Including World Health Organization Grade II, III, and IV Gliomas.

OBJECTIVE: 5-aminolevulinic acid (5-ALA) has been increasingly used in recent years to identify anaplastic foci in primarily suspected low-grade gliomas (LGGs). However, 5-ALA fails to visualize a subgroup of focally anaplastic gliomas. Recently, 2 in vitro studies and 1 in vivo study assumed that antiepileptic drugs (AEDs) and dexamethasone have an influence on the 5-ALA metabolism/visible fluorescence in gliomas. The aim of this study was to analyze for the first time the influence of different AEDs and dexamethasone on visible 5-ALA fluorescence in a large cohort of suspected LGG. METHODS: We retrospectively analyzed adult patients with resection of radiologically suspected diffusely infiltrating LGG after 5-ALA administration at 2 specialized centers. Clinical data on the intraoperative 5-ALA fluorescence status, preoperative treatment with AED/dexamethasone, and the total daily dose in cases of levetiracetam and dexamethasone intake were noted. RESULTS: Altogether, 110 patients with suspected LGG were included. A significantly higher percentage of visible fluorescence was present in World Health Organization grade III/IV (73%) compared with World Health Organization grade II gliomas (11%; P < 0.001). In the multivariate analysis, we did not find an independent correlation between the visible fluorescence status and intake of dexamethasone/AED. Furthermore, the median daily dose of dexamethasone and levetiracetam did not differ significantly between fluorescing and nonfluorescing gliomas. CONCLUSIONS: In the largest series to date, we did not find a drug-related influence of either dexamethasone or different AED on visible 5-ALA fluorescence in suspected LGG. According to our preliminary data, preoperative treatment with these common drugs in neurosurgery can be performed safely before 5-ALA-assisted surgery of suspected LGG.

Tree species from two contrasting habitats for use in harsh urban environments respond differently to extreme drought.

The role of trees in city cooling has warranted much attention based on concerns over climate change and urban expansion. Simultaneously, there is an interest in introducing species from dry habitats to cope with the increasing risks of drought under climate change. The general understanding is that the evolutionary adaptation to respective resource supplies in species' habitats affects their environmental tolerance. The physical performances of six frequently planted species, originating from two contrasting habitats, were tested in a drought experiment. We (1) investigated if species from drier habitats are more drought tolerant than species that have evolved in Central European woodlands under a temperate climate regime and (2) discussed the effect of tolerance on the cooling potential of these trees. Native species from mesic habitats maintained only 48% of their controls sap flux and of these species, Tilia cordata had the worst performance with premature leaf senescence. Species from drier habitats had less reduction in sap flux (60%) but lower stem growth, possibly favouring (fine) root development into deeper soil layers, as observed when comparing linden species. Higher stem water exploitation and stronger regulation of water use at high evaporative demand were further reaction patterns that likely helped species from dry habitats maintain good physiological functions. Therefore, even under sustained drought, we expect them to have a higher cooling capacity. As a conclusion, they should be favoured for planting in extreme urban environments. Systematic screening and testing of promising species from target habitats is recommended to diversify the choice of species.

Vertical air temperature gradients under the shade of two contrasting urban tree species during different types of summer days.

Moderation of thermal energy balance through the canopies of urban trees is well known. However, a more functional and quantitative view of the heterogeneous urban environment and their influence on the below-canopy vertical air temperature gradients is largely missing. Throughout the summer 2016 we continuously measured air temperature at three different heights (at 1.5, 3 and 4.5m from the ground) under the canopies of two common but contrasting street tree species in respect of eco-physiology and morphology in Munich, Germany: Robinia pseudoacacia L. (ring porous) and Tilia cordata Mill. (diffuse porous). Along with air and surface temperature we also measured meteorological and edaphic variables and categorized summer time as cool, mild, summer and hot days. Global radiation, vapour pressure deficit and soil temperature increased as the days got warmer but precipitation, soil moisture and wind speed showed the reversed pattern. Overall, T. cordata trees with higher leaf area index and sap-wood area provided three times more transpiration than R. pseudoacacia. On an average air temperature gradient of outside to inside canopy dropped from 1.8°C to 1.3°C for T. cordata but from 1.5°C to only 0.5°C for R. pseudoacacia as the days got warmer. Vertical decline of air cooling effect was around 1°C from canopy to the near-ground (1.5m). Lower soil moisture but higher soil temperature suggested that cool air from the canopy mixed with a higher amount of sensible heat flux under the canopies of T. cordata compared to the R. pseudoacacia as the days got warmer. The study indicated a threshold for extreme hot days when grass surface evapotranspirational cooling will not be as effective and act like built surfaces rather deep shading from tree canopies will be important.

Urban climate modifies tree growth in Berlin.

Climate, e.g., air temperature and precipitation, differs strongly between urban and peripheral areas, which causes diverse life conditions for trees. In order to compare tree growth, we sampled in total 252 small-leaved lime trees (Tilia cordata Mill) in the city of Berlin along a gradient from the city center to the surroundings. By means of increment cores, we are able to trace back their growth for the last 50 to 100 years. A general growth trend can be shown by comparing recent basal area growth with estimates from extrapolating a growth function that had been fitted with growth data from earlier years. Estimating a linear model, we show that air temperature and precipitation significantly influence tree growth within the last 20 years. Under consideration of housing density, the results reveal that higher air temperature and less precipitation led to higher growth rates in high-dense areas, but not in low-dense areas. In addition, our data reveal a significantly higher variance of the ring width index in areas with medium housing density compared to low housing density, but no temporal trend. Transferring the results to forest stands, climate change is expected to lead to higher tree growth rates.

Climate change accelerates growth of urban trees in metropolises worldwide.

Despite the importance of urban trees, their growth reaction to climate change and to the urban heat island effect has not yet been investigated with an international scope. While we are well informed about forest growth under recent conditions, it is unclear if this knowledge can be simply transferred to urban environments. Based on tree ring analyses in ten metropolises worldwide, we show that, in general, urban trees have undergone accelerated growth since the 1960s. In addition, urban trees tend to grow more quickly than their counterparts in the rural surroundings. However, our analysis shows that climate change seems to enhance the growth of rural trees more than that of urban trees. The benefits of growing in an urban environment seem to outweigh known negative effects, however, accelerated growth may also mean more rapid ageing and shortened lifetime. Thus, city planners should adapt to the changed dynamics in order to secure the ecosystem services provided by urban trees.

Inter- and intraannual growth patterns of urban small-leaved lime (Tilia cordata mill.) at two public squares with contrasting microclimatic conditions.

The effects of urban conditions on tree growth have been investigated in an increasing number of studies over the last decades, emphasizing the harsh environment of cities. Urban trees often grow in highly paved, compacted sites with consequently less soil moisture, higher soil temperatures, and greater vapor pressure deficits. However, there is still a knowledge gap regarding the impact of harsh paved environments on urban tree growth during drought years on the growth patterns of urban trees. The present study investigated the structure and growth of the common urban tree species small-leaved lime (Tilia cordata) at a highly paved public square (CPS) compared with a contrasting more open, greener square (OGS). Continuously, measured high precision dendrometer data along with meteorological data of the extreme dry and warm summer 2015 as well as dendrochronological data of the sampled trees were investigated to analyze tree growth during a drought year. The results highlight different tree dimensions and growth patterns of the trees at both sites, influenced by tree age and distinct site conditions. While the trees at OGS grew up to 2.5 mm from July until mid of August, the trees at CPS had only 0.4-mm diameter increment. After the initial expansion at CPS, tree diameter contracted again during summer to the point of shrinkage (up to 0.8 mm) at the end of our investigation. Further drought year analysis confirmed the patterns of significant stem growth reductions in the consecutive two years following the drought. A correlation analysis revealed that transpiration, air temperature, and vapor pressure deficit were negatively correlated with the daily diameter growth, whereas precipitation had a strong positive effect. Due to high transpiration rates associated with anisohydric water use behavior, T. cordata was able to provide evaporative cooling even during drought. However, this anisohydric behavior resulted in substantial growth decline afterwards especially at paved sites like CPS. Our results suggest selection of tree species, such as those with isohydric water use behavior, which may achieve a better balance between growth, transpiration, and hence evaporative cooling.

Forest stand growth dynamics in Central Europe have accelerated since 1870.

Forest ecosystems have been exposed to climate change for more than 100 years, whereas the consequences on forest growth remain elusive. Based on the oldest existing experimental forest plots in Central Europe, we show that, currently, the dominant tree species Norway spruce and European beech exhibit significantly faster tree growth (+32 to 77%), stand volume growth (+10 to 30%) and standing stock accumulation (+6 to 7%) than in 1960. Stands still follow similar general allometric rules, but proceed more rapidly through usual trajectories. As forest stands develop faster, tree numbers are currently 17-20% lower than in past same-aged stands. Self-thinning lines remain constant, while growth rates increase indicating the stock of resources have not changed, while growth velocity and turnover have altered. Statistical analyses of the experimental plots, and application of an ecophysiological model, suggest that mainly the rise in temperature and extended growing seasons contribute to increased growth acceleration, particularly on fertile sites.

Combating the effects of climatic change on forests by mitigation strategies.

BACKGROUND: Forests occur across diverse biomes, each of which shows a specific composition of plant communities associated with the particular climate regimes. Predicted future climate change will have impacts on the vulnerability and productivity of forests; in some regions higher temperatures will extend the growing season and thus improve forest productivity, while changed annual precipitation patterns may show disadvantageous effects in areas, where water availability is restricted. While adaptation of forests to predicted future climate scenarios has been intensively studied, less attention was paid to mitigation strategies such as the introduction of tree species well adapted to changing environmental conditions. RESULTS: We simulated the development of managed forest ecosystems in Germany for the time period between 2000 and 2100 under different forest management regimes and climate change scenarios. The management regimes reflect different rotation periods, harvesting intensities and species selection for reforestations. The climate change scenarios were taken from the IPCC's Special Report on Emission Scenarios (SRES). We used the scenarios A1B (rapid and successful economic development) and B1 (high level of environmental and social consciousness combined with a globally coherent approach to a more sustainable development). Our results indicate that the effects of different climate change scenarios on the future productivity and species composition of German forests are minor compared to the effects of forest management. CONCLUSIONS: The inherent natural adaptive capacity of forest ecosystems to changing environmental conditions is limited by the long life time of trees. Planting of adapted species and forest management will reduce the impact of predicted future climate change on forests.

Simulating stand climate, phenology, and photosynthesis of a forest stand with a process-based growth model.

In the face of climate change and accompanying risks, forest management in Europe is becoming increasingly important. Model simulations can help to understand the reactions and feedbacks of a changing environment on tree growth. In order to simulate forest growth based on future climate change scenarios, we tested the basic processes underlying the growth model BALANCE, simulating stand climate (air temperature, photosynthetically active radiation (PAR) and precipitation), tree phenology, and photosynthesis. A mixed stand of 53- to 60-year-old Norway spruce (Picea abies) and European beech (Fagus sylvatica) in Southern Germany was used as a reference. The results show that BALANCE is able to realistically simulate air temperature gradients in a forest stand using air temperature measurements above the canopy and PAR regimes at different heights for single trees inside the canopy. Interception as a central variable for water balance of a forest stand was also estimated. Tree phenology, i.e. bud burst and leaf coloring, could be reproduced convincingly. Simulated photosynthesis rates were in accordance with measured values for beech both in the sun and the shade crown. For spruce, however, some discrepancies in the rates were obvious, probably due to changed environmental conditions after bud break. Overall, BALANCE has shown to respond to scenario simulations of a changing environment (e.g., climate change, change of forest stand structure).

Quantifying ozone uptake and its effects on the stand level of common beech (Fagus sylvatica L.) in Southern Germany.

Stand level O(3) fluxes were calculated using water balance calculations for 21 Common beech (Fagus sylvatica L.) stands and O(3) data from 20 monitoring stations in Southern Germany. For this intention, the daily loss of water by evapotranspiration per stand area was set against the daily O(3) uptake. During the last 30 years, O(3) uptake ranges between 0 and 187 mmol ha(-1) d(-1) per stand area. Cumulative O(3) uptake (CUO(3)), ranging between 0.1 and 0.7 mmol m(-2) yr(-1) per stand area, shows increasing trends since 1971 with considerably greater values at high altitudes. Effects in radial growth were used to derive an initial approximate critical threshold value for O(3) impacts on the vitality and growth of mature beech stands in Southern Germany. It is concluded that this concept of O(3) flux estimation in combination with dendroecological analyses offers both a site specific and regional applicable approach to derive new critical levels for O(3).