Trees最新文献

The objective of this study was to develop more accurate predictions of the diameter growth of Pinus yunnanensis and to analyze the impact of various factors on its diameter growth, providing valuable management recommendations for forest management. To this end, various machine learning methods were employed to construct individual tree diameter growth models for P. yunnanensis. The research was based on single-period survey data and core sample data from 11 permanent plots in Cangshan mountain, Dali, Yunnan Province. In addition, the impacts of tree size, competition, site quality, and climatic factors on the growth of P. yunnanensis diameters were considered. Four machine learning methods were employed to develop the models: Random Forest, XGBoost, Multilayer Perceptron, and Stacked Multilayer Perceptron (Stacked-MLP). The models were evaluated and compared using a k-fold strategy, based on the coefficient of determination, Root Mean Square Error, and Mean Absolute Error. The results of the fivefold cross-validation demonstrated that the Stacked-MLP model exhibited the highest performance, with an R2 of 0.8508, RMSE of 0.2907 cm², and MAE of 0.1928 cm². The feature importance methods from Random Forest, XGBoost, and SHAP analysis indicated that competition and tree size were the primary drivers of tree growth, while climate and site factors had a more limited impact in explaining variations in tree growth on a small, local scale.

Key message

Developed species-specific allometric equations using terrestrial laser scanning (TLS). Found significant species-specific differences in branch biomass allocation. Introduced a non-destructive method for estimating urban tree biomass.

Abstract

Urban trees contribute to climate change adaptation by providing multiple ecosystem services, including carbon sequestration. Yet accurate information about above-ground biomass, particularly branch biomass, is scarce. This study aimed to develop allometric models for estimating branch biomass for ten common European urban tree species using terrestrial laser scanning (TLS) and quantitative structure models (QSM) data. Conducted in Munich, the study analyzed 3,283 trees, using structural variables such as diameter at breast height (dbh), height, and crown diameter. The dbh of trees in the dataset reached up to 0.8 m, with mean above-ground biomass ranging from 550 to 1.496 kg C, and branch biomass from 32.2 to 164.5 kg C. The results confirmed that dbh was the strongest predictor of branch biomass (r = 0.69–0.9), and adding height improved model accuracy (R² = 0.69–0.93). Species-specific models revealed significant variations, with R. pseudoacacia showing the highest branch biomass when standardized by tree height, and P. nigra 'italica' the lowest. Conversely, when standardized by dbh, P. acerifolia showed the highest branch biomass and C. betulus the lowest. Comparisons with established forest tree models revealed that the developed allometric models tend to underestimate branch biomass for most species, with deviations ranging from 1 to 36%, reflecting unique growth forms and urban environmental conditions. The study highlights the need for species-specific allometric models to improve assessments of ecosystem services provided by urban trees.

Salix, known for its rapid growth, versatility, and distinctive properties, carries substantial economic value across various industries. Given its significant commercial importance, it is essential to identify a stable clones that can be introduced or reproduced in diverse agro-climatic zones. In this study, we utilized three distinct models, namely, AMMI, GGE, and MTSI, to evaluate the stability of Salix clones concerning key growth attributes, such as height, diameter, and volume index. The AMMI model's IPCA values ranged from 69.90% (plant height) to 81.10% (volume index), with the biplot indicating J799 superior performance across all growth variables. Utilizing AMMI 2 biplots, we observed that several clones, including J799, 131/25, J795, UHFS119, UHFS144, UHFS180/5, UHFS222, UHFS296, and UHFS340, performed similarly in all conditions. The GGE model highlighted Denali (environment 3) as more discriminative and representative for growth traits. Overall, the clones J799, 131/25, Kashmiri, and J795 demonstrated superior performance and stability across various growth features, as indicated by both GGE and MTSI functions. These findings provide valuable insights for selecting stable clones for commercial plantations in diverse geographical locations.

Key message

Tree rings of Chamaecyparis thyoides exhibit growth responses that are influenced by local hydrologic conditions through decadal timescales. That perspective can assist peatland natural resource managers in selection of hydrologic restoration targets that minimize chronic microbial oxidation and acute peat loss associated with fire.

Abstract

Temperate forested peatlands are valued for myriad ecosystem services including carbon storage and biodiversity which may be lost through anthropogenic disturbance of hydrologic regimes. Hydrologic alterations may be recorded in tree stem growth patterns and provide insights for management and restoration. In Chamaecyparis thyoides (Atlantic White Cedar, Juniper) swamps, stand drainage causes a shift from net soil carbon sink to source as microbial oxidation and catastrophic fire oxidize stored organic matter. Here, we analyze historic radial growth patterns in C. thyoides in order to characterize drainage history to guide hydrologic management for peat conservation and restoration. Basal area increment (BAI) estimates across a ~ 60-year chronology (1939–2003) were analyzed by flexible beta cluster analysis of 185 trees from 13 C. thyoides stands in the Great Dismal Swamp National Wildlife Refuge in Virginia and North Carolina, USA. Stands formed 3 groups, and growth rates among all groups were indicative of a drained hydrologic regime throughout the chronology compared to an undrained control stand. Regime shift analyses identified positive shifts for 2 stand groups in 1954 and for all 3 stand groups in 1963. Multiple response permutation procedures and partial mantel tests both identified two predictive growth variables including (1) visual observations of fluctuation in the water table and (2) proximity to a primary ditch. Growth rate was suppressed when weirs were installed in the mid-1980s; however, growth rebounded within ~ 2 years. The chronology ends when stands were struck by a major hurricane in 2003 and fires in 2008 and 2011 liberated 1.38 Tg of peat carbon. We conclude that dendroecology can detect hydrologic changes through time and can reduce risks of microbial oxidation and catastrophic fire in forested peatlands.

Key message

Incorporating height to crown base, competition index, climate variable, initial planting density, and thinning intensity into base crown width model significantly improved the performance of the crown width prediction of L. kaempferi at high altitudes in southern China.

Abstract

Crown width (CW) is significantly related to tree growth and the ability to predict crown width with high accuracy is essential. To develop a CW model for planted Japanese Larch (L. kaempferi) at high altitudes in southern China, a total of 3950 trees from 78 permanent sample plots with altitudes ranging from 1372 to 1932 m were measured. The best base model including only diameter at the breast height (DBH) was selected by using the evaluation statistics. Tree-level, stand-level, and climate variables were introduced into the basic model using reparameterization approach. Initial planting density and thinning intensity were introduced through dummy variable method. We developed a nonlinear mixed effects crown width (NLME-CW) model. The prediction performance of the NLME model was evaluated using the leave-one-out validation approach. The results show that power equation performed better than other base CW models. Using reparameterization approach, tree level variable of height to the crown height (HCB), competition variable of basal area of the trees larger than the subject tree (BAL) and the climate variable of spring degree-days below 0 ℃ (DD_0_sp) were finally included into the CW model. The developed NLME-CW model including initial planting density and thinning intensity showed good stability and applicability. Power variance equation was used to reduce the heteroscedasticity in the residuals. The six individual trees were randomly selected from each sample plot to estimate random parameters. CW increased with the increasing of DBH and decreasing of HCB, BAL and DD_0_sp. CW decreased with the increasing of planting density and increased with the increasing of thinning intensity. Considering timber production and management costs, we recommend moderate-intensity thinning as the optimal management strategy. The model is widely applicable to L. kaempferi plantations and holds significant practicality for predicting the CW of L. kaempferi in high-altitude areas of southern China.

Key message

Osmotically-driven radial transfer of water from xylem to phloem occurs during the day in the branches of hinoki cypress, even though branch diameter shrinks.

Abstract

The hydraulic coupling between xylem and phloem has been explicitly included in theoretical models of phloem transport; however, the predicted radial water transfer from xylem to phloem during the day has not yet been demonstrated experimentally. In a first experiment, we tested the hypothesis of a water transfer from xylem to the inner bark during the day, assuming that, if the transfer does not occur, phloem water would be isotopically enriched due to an influx of enriched water concomitant with sugar loading in the foliage. The inner bark water from branches of mature hinoki cypress was, however, only slightly enriched in ¹⁸O in the afternoon compared to sapwood water (δ¹⁸O of − 6.3 and − 6.6‰ respectively), but much less than foliage water (16.0‰ at noon and 18.9‰ in the afternoon). This suggests that the isotopically enriched leaf water concurrently loaded with sugars in the leaf phloem was mixed with the unenriched xylem water. In a second experiment, to confirm that water transfer from xylem to the inner bark during the day occurs in branches, deuterium-enriched water was sprinkled on the soil. Concomitant deuterium enrichment of xylem and inner bark water extracted from branches was observed during the day after labelling, earlier than in leaves, when branches were still shrinking. This provides experimental support for theoretical models of phloem transport that have predicted radial transfer of water from xylem to phloem along the path.

Forest management aims to improve the growing conditions of trees to ensure the sustainable utilization of forest resources. This study compares the effects of different forest management practices on tree growth, forest production, stand structure, and soil nutrient status. We selected a mixed oak forest in the western part of the Qinling Mountains range in China and implemented three forest management practices: target tree forest management (TTFM), structure-based forest management (SBFM), and secondary forest comprehensive silviculture (SFCS). As expected, all three management practices significantly reduce stand mortality rate compared to the unmanaged plots. And these three management practices mainly influenced biomass by affecting soil available potassium, basal area by adjusting tree species diversity, and stand mortality rate by varying spatial structure and tree size diversity. Stand structure and soil nutrient status explained 63.1% and 36.5% of the variation in tree growth and forest production, respectively. Spatial structure, tree size diversity, and tree species diversity explained 34.5%, 26.6%, and 26.6% of the variation in tree growth and forest production, respectively. The results show that managed plots, especially the SBFM, had a positive impact on tree growth and forest production compared with the unmanaged plots. Furthermore, compared to soil nutrient status, stand structure, especially spatial structure, plays a more significant role in tree growth and forest production.

Key message

This study in tropical dry forests reveals cambial activity varies by species and site, linked to rainfall patterns, impacting tree growth and highlighting importance of xylem and phloem development consideration.

Abstract

Ecological studies on cell division in the vascular cambium have emerged as a key need for understanding tree growth dynamics in tropical dry forests, as well as the effects of year-to-year variation in precipitation. To address this gap, we selected five representative tree species from the tropical dry forest to study dynamics in vascular cambium cell division. The study was conducted at three sites in Mexico with different rainfall regimes from May 2022 to May 2023. Monthly samples were collected, and anatomical features were recorded during cambial activity. The beginning and end of cambial activity were established, and differences between species and sites were analyzed. Linear and exponential models were tested to fit the data. The cambium remained active for six to nine months. Cell divisions toward the phloem maintained cambial activity until the dry season, and in 2023, cambial reactivation occurred with the formation of new phloem. The number of cells in the cambial region showed high monthly variation, with a rapid increase during the first months of the rainy season and a peak between July and November. Cell numbers gradually decreased toward the end of the dry season. Tree species showed low variation between sites. Site analysis supported the adjustment of different growth models and growth rates across sites. Cell divisions were faster at the site with the least precipitation and slower at the wetter site. This study highlights the importance of considering xylem and phloem formation when studying cambial activity, providing valuable insights into tropical dry forest ecology.

Key message

Visual inspection parameters for predicting the risk of urban trees falling match the actual internal condition of the stem, as well as the results of tomograms (SoT and ERT).

Abstract

Eliminating the risk of tree falls in urban areas is economically and technically unfeasible. Effective management requires reliable tools to guide interventions and maximize urban forest benefits. This study examined the relationship between visual analysis and the internal condition of Spathodea campanulata trunks, using sonic (SoT) and electrical resistance (ERT) tomograms. The trunk sections from 30 removed trees at UFV (Viçosa-MG) were analyzed. The cavities appeared in 26.7% of cases, cracks in 20%, and wood deterioration in 10%. Tomograms aligned with cutting results in 70% of cases, with sonic tomography being easier for cavity detection and electrical tomography more accurate for wood deterioration. It was not possible to define a visual analysis methodology with association with the problems evidenced in the section. Combining tomographic and visual inspections enhances tree fall risk assessments.

Key message

A multi-parameter-study of quantitative wood anatomy of oak reveals site-dependent climate-growth relations. Many of these are unstable, making climate reconstructions based on oak questionable. Winter temperatures may be an exception.

Abstract

In Europe, oak tree-ring chronologies spanning millennia offer considerable potential for dendroclimatology. However, site conditions might influence the climate-growth relationships, particularly for species such as lowland European oak (Quercus robur/petraea) that grow under a range of soil moisture conditions. The inclusion of sub-fossil or archaeological samples in chronologies often introduces uncertainty regarding the soil moisture regime in which the trees grew, potentially impacting the contained signal and the suitability of millennia-long oak chronologies as paleoclimate proxies. Here, we present a rare example of a multi-parameter study on the quantitative wood anatomy of oak. We analysed the climate-growth relationships of earlywood vessel sizes, earlywood width and latewood width in trees from five nearby stands situated on wet and dry soils in north-eastern Switzerland that experienced the same atmospheric conditions. We observed a large variety of climate-growth relationships. And we observed both signal plasticity (variability of climate growth relationships between site categories) and classical signal instability over time. In fact, the only stable relationships are between earlywood vessel sizes in trees on wet soils and winter/early spring temperatures. The relationship between late spring/early summer precipitation and latewood width on dry soils is probably stable as well but less reliable. In both cases, the correlation coefficient reaches values as high as r = 0.6. We suggest that signal instability needs to be explored with further and larger datasets before oak can be reliably used as a paleoclimate proxy.