No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Effects of thinning intensity on productivity and water use efficiency of Quercus robur L
Abstract
Thinning intensity is an important factor affecting forest structure and density and influencing tree growth.
The main objective of the study is to evaluate how the different intensity of thinning can influence, in the short and long term, the productivity and intrinsic water use efficiency (WUEi) of Quercus robur L., a widespread European species. Three thinning types of different intensity were applied in 14-year mixed plantation of Quercus robur L. growing with Alnus glutinosa (L) Gaertn., a N-fixing species, with an initial density of 625 trees/ha. A multidisciplinary approach was applied, coupling the tree-ring analyses with the measurements of stable isotopes of carbon and oxygen.
Findings highlighted how the different conditions of light and competition, determined by the type and intensity of thinning, triggered different responses of Q. robur species in terms of growth and WUEi.
Data suggested that the moderate selective thinning (31% reduction of total biomass) was not able to reduce the high competition for resources among individuals: this condition negatively influenced the trees growth. The presence of the N-fixing species, left after the thinning, was not able to counteract the negative effect of competition.
A negative effect on productivity was recorded with the geometric thinning (62% reduction of total biomass). Indeed, this treatment resulted in an increase of asymmetry of the canopy (0.90 vs 0.83, respectively in pre- and post-thinning period), due to the partial crown competition from one side and with a consequent limitation of the photosynthetic activity of the trees. Finally, the very high selective thinning (75% reduction of total biomass) resulted to be the most appropriate management practice, as it guarantees positive effects both in terms of growth and intrinsic water use efficiency. The post thinning conditions determined high photosynthesis rates, an increase of productivity and a limited water loss.
... Improvements in tree adaptability are mediated by shaping critical functional traits that can effectively contribute to resistance under comprehensive trait for evaluating vegetation responses to climate change, water use efficiency (WUE), the ratio of CO 2 assimilation to water loss, is a critical connection between carbon and water cycles in forest ecosystems (Niu et al 2011;Liu et al 2015;Tarin et al 2020;Cooley et al 2022). Forest management, through the optimization of tree WUE, directly determines the structure, function, productivity and stability of plantations (Lechuga et al 2017;Niccoli et al 2020). Understanding plant WUE and its crucial controlling processes in response to various forest management practices is helpful for projecting the relationships of carbon-water to climate change. ...
... Other reports have indicated that WUE decreases with thinning intensity (McDowell et al 2003). In contrast, other studies noted an increase in WUE because of intensive thinning (Fernandes et al 2016;Park et al 2018;Niccoli et al 2020). Given these contradictions, it is important to investigate the effect of understory removal and thinning on the WUE of trees. ...
... The response of WUE to thinning and understory removal has been related to tree physiological characteristics, which are driven by variations in temperature, humidity and irradiance (Saurer and Siegenthaler 1989;Sheng et al 2011;Su and Shangguan 2020;Niccoli et al 2020). The consensus view is that increased soil water availability following understory removal and thinning may result in differential enhancement of net photosynthetic rate (A n ) and stomatal conductance (g s ) in the remaining trees and thus variation in WUE (Skov et al 2004). ...
Understanding the relationship between forest management and water use efficiency (WUE) is important for evaluating forest adaptability to climate change. However, the effects of thinning and understory removal on WUE and its key controlling processes are not well understood, which limits our comprehension of the physiological mechanisms of various management practices. In this study, four forest management measures (no thinning: NT; understory removal: UR; light thinning: LT; and heavy thinning: HT) were carried out in Pinus massoniana plantations in a subtropical region of China. Photosynthetic capacity and needle stable carbon isotope composition (δ13C) were measured to assess instantaneous water use efficiency (WUEinst) and long-term water use efficiency (WUEi). Multiple regression models and structural equation modelling (SEM) identified the effects of soil properties and physiological performances on WUEinst and WUEi. The results show that WUEinst values among the four treatments were insignificant. However, compared with the NT stand (35.8 μmol·mol−1), WUEi values significantly increased to 41.7 μmol·mol−1 in the UR, 50.1 μmol·mol−1 in the LT and 46.6 μmol·mol−1 in HT treatments, largely explained by photosynthetic capacity and soil water content. Understory removal did not change physiological performance (needle water potential and photosynthetic capacity). Thinning increased the net photosynthetic rate (An) but not stomatal conductance (gs) or predawn needle water potential (ψpd), implying that the improvement in water use efficiency for thinned stands was largely driven by radiation interception than by soil water availability. In general, thinning may be an appropriate management measure to promote P. massoniana WUE to cope with seasonal droughts under future extreme climates.
... Indeed, tree density reduction has been considered to be a promising way in enhancing forest resilience to climate extremes as well as easing tree mortality and thus is viewed as a window of opportunity for forest climate-change adaptation (Bradford and Bell, 2017;Sterck et al., 2021). By alleviating resource limitation to the remaining trees, reductions in stand density can usually improve photosynthetic carbon assimilation and enhance tree growth (Sohn et al., 2016a;Niccoli et al., 2020). For example, significant growth release effect of thinning on tree radial growth has been identified in numerous studies using dendrochronological methods (McDowell et al., 2006;Andrews et al., 2020;Niccoli et al., 2020). ...
... By alleviating resource limitation to the remaining trees, reductions in stand density can usually improve photosynthetic carbon assimilation and enhance tree growth (Sohn et al., 2016a;Niccoli et al., 2020). For example, significant growth release effect of thinning on tree radial growth has been identified in numerous studies using dendrochronological methods (McDowell et al., 2006;Andrews et al., 2020;Niccoli et al., 2020). The current researches about stand density effects on tree performance have focused on quantifying patterns of changes in tree growth, health status and forest productivity in response to stand density change (Carnwath and Nelson, 2016;Tsamir et al., 2019;Blazier et al., 2021;Wang et al., 2021), while comprehensive ecophysiological studies combing investigations on patterns of tree growth response to changes in stand density and the underlying physiological mechanisms are scarce. ...
... Deng et al., 2020;Bradford et al., 2022). Evaluating the potential influence of stand density on water-related physiology and long-term patterns of tree growth performance provides a comprehensive framework for forest managements in water-limited environments particularly considering the increase in frequency and intensity of drought stresses under the influence of climate change (Bradford and Bell, 2017;Niccoli et al., 2020;Wang et al., 2022). ...
... Furthermore, in the early phase after planting, appropriate agronomical practices are needed to allow for a rapid tree growth. Thinning plays a significant role in the next stages, modifying the specific composition of the stand, the inter-and intraspecific competition among trees, and promoting growth and water use efficiency of the favoured trees (Niccoli et al. 2020). ...
... Tree-rings analysis is one of the most used techniques for detecting tree growth responses to environmental factors, as the coupled effects of site and climatic conditions can be assessed (Tardif et al. 2003), and it has been applied in studies on mixed forest plantations to these aims (Battipaglia et al. 2017, Niccoli et al. 2020, Mazza et al. 2021. Moreover, the positive effects of mixed-species composition, especially for resistance to climatic disturbances such as drought, can change under different growing conditions (e.g., nutrient-rich vs. nutrient-poor sites or wet vs. dry sites), suggesting the need to carefully consider specific site conditions (Pretzsch et al. 2013). ...
... In this regard, a dynamic successional process of colonization by spontaneous tree and shrubs species (e.g., Acer campestre L. and Cornus sanguinea L.) started only a few years ago (data not shown). According to many studies on the reforestation of degraded lands, we found a significant impact of thinning and species composition on planted trees (Ravagni et al. 2015, Battipaglia et al. 2017, Liu et al. 2018, Niccoli et al. 2020. The increasing coherence in synchronization since the last thinning among the tree-ring chronologies, as well as the increase in their correlation coefficients, points to similar thinning effects affecting the growth of pedunculate oak in the long period. ...
... Thinning and pruning are management measures implemented to effectively control the forest or shrub density for sustainable water use (Raz-Yaseef et al., 2010;Goodwin et al., 2018). The reduction of plant density by thinning results in lower root competition and rainwater interception and an increase in nutrient availability and water supply (Sohn et al., 2016;Coble et al.,2020;Niccoli et al., 2020). Reducing the leaf area of the canopy by pruning decreases the loss of transpiration, thus ensuring better plant growth under extreme drought conditions (Chen et al., 2016). ...
... Thus, the stem length, diameter, and biomass of the remaining branches increased after 25% and 75% of the branches were pruned. Alternatively, pruning branches can decrease the competition of community and the mutual shadowing of individual canopies, consequently improving the availability of light (Niccoli et al., 2020). Overall, thinning and pruning modified the structural characteristics of the C. korshinskii plantation, improving microclimatic conditions, such as soil water and light, and the general functionality of shrubs. ...
... Thinning and pruning improved the infiltration of soil water and its replenishment by controlling the stand densities and canopy leaf area of the plants (Niccoli et al., 2020). Hipps et al. (2014) and Ma et al. (2019) found that pruning the shrubs or trees reduced the canopy volume and significantly enhanced the SWS. ...
High‐density afforestation of single‐species causes soil desiccation and vegetation degradation, posing severe challenges for plant rehabilitation, survival and its sustainable soil water use in drought regions. We explored the eco–hydrological responses of density adjustment for a typical degraded Caragana korshinskii plantation on the Chinese Loess Plateau, using 2‐year field observations. The treatments included two thinning intensities [thinning one at an interval of one (T50) and two (T67) shrubs], three pruning intensities [pruning 25% (P25), 50% (P50), and 75% (P75) of branches], and a control treatment (CK). Results indicated that the total soil water storage (0–600 cm) in T50 and T67 was 14.1% and 17.0% higher than that in CK in 2020 (p < 0.05). Treatments T67 and P25 significantly affected the length, basal diameter, and biomass of stems compared with the CK. Moreover, canopy transpiration at the individual–scale in T67 was 43.5% and 37.6% higher in 2019 and 2020 than that in CK (p < 0.05). At the stand–scale, the canopy transpiration in T67 was reduced by 81.2% in 2019 and by 79.2% in 2020 compared with that in CK (p < 0.05), respectively. In 2020, the water use efficiency in T67 was 13.8% and 101.7% higher (p < 0.05) than that in CK and T50, respectively. These observations indicate that thinning the stand density by 67% (T67) promotes plant rejuvenation and improves highly efficient use of soil water for the excessively afforested C. korshinskii plantations on the Loess Plateau. Our findings will guide the rational management of overcrowded C. korshinskii plantations in similar dry regions.
... The results of this study showed that thinning increased the gap, improved resource availability, increased throughfall, and increased rainfall reaching the ground. Specifica lly, thinning reduced competition among individuals in afforested land, increased resource availability and growth space (Park et al., 2018;Niccoli et al., 2020), and thus promoted photosynthesis of trees (Gauthier and Jacobs, 2009) and late growth of trees (inhibited stem growth (plant height), and promoted lateral growth (crown width and DBH)) (Manrique-Alba et al., 2020). The greater the thinning intensity, the more favorable for the growth of trees. ...
... Therefore, it will change the meteorological conditions in the canopy, which control the evaporation of intercepted water (Grunicke et al., 2020). Meanwhile, the asymmetry of tree crown caused by thinning also had a significant impact on tree growth, because it helped trees adapt to light heterogeneity (Niccoli et al., 2020). After thinning, the crown loses symmetry, and the growth ability of the remaining trees reduces due to transverse compression, while in other directions, the width of trees will increase due to larger growth space. ...
... With the increase in thinning intensity and the death of residual roots, the remaining trees will absorb more nutrients and water resources by promoting the growth of roots (Olesinski et al., 2012;Krause et al., 2014;Lemay et al., 2018), what is more, improving the photosynthetic capacity of the remaining plants to increase tree growth and water use efficiency (Lagergren et al., 2008;Hawthorne et al., 2013;Giuggiola et al., 2013;Niccoli et al., 2020). Additionally, soil water content is strongly affected by rainfall infiltration and groundwater recharge (Wu et al., 2021). ...
Large‐scale planted afforestation worldwide has exacerbated soil desiccation and led to a serious shortage of water resources for forests sustainability in semiarid areas. Consequently, thinning is discussed as an important management approach to conserve water resources and to maintain plantation forestland sustainability. Here, we explored the effects of thinning intensity on semiarid forest production and soil water supply. Three artificial forests of Populus cathayana with an age of 15 yr were selected and thinned with different intensities [1/3 amount of trees removed (T1/3), 2/3 amount of trees removed (T2/3), and using no thinning (NT) as a control]. Results showed that thinning presented a significant impact on the above‐ground three‐dimensional structure of planted forests and increased forest gaps. Meanwhile, the rainfall redistribution pattern changed significantly. Thinning increased throughfall (T1/3, 43% ± 9%; T2/3, 79% ± 18%), reduced stemflow (T1/3, −44 ± 2%; T2/3, −71% ± 2%), and increased the soil water replenishment (T1/3, 34% ± 7%; T2/3, 64% ± 19%) of forest land. Meanwhile, the dead root channel caused by thinning effectively increased the water infiltration rate and groundwater replenishment, and effectively reduced soil water deficit (T1/3, 41% ± 33%; T2/3, 57% ± 33%). Through trade‐off analysis, we found that non‐thinning aboveground biomass yields were the highest, and T2/3 yields higher water yield, while T1/3 can maintain acceptable aboveground biomass while keeping better soil water. We conclude that thinning increased soil water supply, reduced soil water deficit and maintained forestland sustainability, and there are synergies of thinning on forest production and soil water supply through rainfall redistribution for maintaining the sustainability of semiarid plantation forestlands.
... Because thinning can increase both tree growths and water use (transpiration), its effects on WUE largely depend upon relative incremental rates of these two variables. In general, thinning increased WUE (Gavinet et al., 2019;Fernandes et al., 2016;Forrester et al., 2012), and these positive effects are even more pronounced in more heavily thinning treatments (Niccoli et al., 2020;Park et al., 2018;Wang et al., 2019aWang et al., , 2019b or under the drought conditions (Wang et al., 2019a(Wang et al., , 2019b. However, Dore et al (2012) showed that thinning effects on WUE are minor and short-lived in the ponderosa pine forest ecosystem. ...
... WUEi responses to thinning treatments are also assessed. The results include no significant responses (Martín-Benito et al., 2010;McDowell et al., 2006), positive responses (Niccoli et al., 2020;Park et al., 2018) and negative responses (Wang et al., 2019a(Wang et al., , 2019bD'Alessandro et al., 2006;McDowell et al., 2003). Based on these limited studies (about a dozen), the results on WUEi responses to thinning treatments are more variable and even contradictory as compared with the results on WUE. ...
Forest thinning can significantly affect hydrological processes. However, these effects largely vary with forest types, climate, thinning intensity, and hydrological variables of interest. Understanding these effects and their variations can significantly support thinning treatments' design and selection to ensure desired hydrological benefits. In this global-level review paper, we report the first comprehensive meta-analysis on the effects of thinning on major hydrological processes with an emphasis on rainfall partitioning, soil moisture and evapo-transpiration processes. The synthesized and reviewed studies encompass different biophysical conditions (climate and forest ecosystems), silvicultural systems, and time scales (from weeks to decades) across continents. The results showed a significant increase in net precipitation, soil moisture and tree-level water use after thinning (the effect sizes are 1.19, 1.14 and 1.56 relative to the value of the control, respectively), while decreases in stemflow and transpiration (the effect sizes of 0.42 and 0.6 relative to the value of the control, respectively). Thinning intensity of about 50% of the stand density is determined as the threshold at or over which hydrological processes are significantly affected. The duration of thinning effect can be set between 2.6 and 4.3 (throughfall) and 3.1-8.6 years (soil moisture and transpiration), asking for repeated thinning in order to effectively sustain these effects. These global averages can serve as benchmarks for assessment and comparisons, but the effects of thinning depend on local biophysical conditions and thinning treatments. The literature review on the rest of the studied hydrological variables suggests that thinning generally enhance runoff to increase water yield and groundwater recharge. Thinning can also have a positive or limited role in water use efficiency (WUE), but it mitigates the effects of drought through increasing WUE. Moderate adverse effects on water quality can be prevented by adequate forest managements to prevent soil degradation. Nevertheless, more researches at relatively less studied regions are needed to support a more robust analysis of these reviewed hydrological variables. The management implications of the synthesized and reviewed results are suggested and discussed within the context of climate change.
... Thinning changes the forest base area (de Oliveira et al., 2021), water use efficiency (Ma et al., 2020), photosynthesis rate (Niccoli et al., 2020;Chi et al., 2020), and soil quality (Romeo et al., 2020). Therefore, the life activities of soil microorganisms and plant root systems, are affected, which in turn influence the physical and chemical properties of the soil (Palta et al., 2024). ...
The effects of thinning were studied on stand growth and the physicochemical soil characteristics of typical plantations in the Yellow River flood plain in northern Shandong Province. Growth indices and soil physical and chemical indices were monitored and in 8-year-old plantations of Fraxinus chinensis, Salix matsudana, and Ulmus pumila in the Yellow River Delta. Data were collected at an initial stand density of 3 m × 3 m and 3 years after artificial thinning to a stand density of 3 m × 6 m. (1) Thinning promoted growth, and the effect on the U. pumila plantation was the greatest. The diameter at breast height, tree height and crown width increased by 41.28, 19.98, and 59.49%, respectively. (2) Thinning increased the soil moisture at the studied plantations, reduced the soil bulk density, and increased the soil porosity and the water holding capacity. The results differed among the plantations, with the greatest improvement occurring at the U. pumila plantation. (3) Thinning had a greater effect on inorganic than on organic soil nutrients according to forest type; the changes in nitrogen, phosphorus and potassium contents in different soil layers substantially varied with the species planted. Most variables significantly differed at the S. matsudana plantation, and the changes in different soil layers were inconsistent. (4) Thinning significantly increased the correlations between stand growth and soil physicochemical properties. Thinning positively affected forest growth and soil physicochemical properties, but the variation in each index across the different plantations was quite different. Thus, thinning could help promote the stable and sustainable development of forest plantations in the Yellow River Delta, and these results provide a reference for the rational management of plantations.
... Consequently, there is a surge of interest in innovative methods to replenish soil moisture, such as tree felling, agroforestry, and altering land use patterns 13,14 . Tree felling has emerged as a widely adopted strategy to combat soil water deficits and prevent drought-induced tree mortality 15,16 . Research by Cui 17 demonstrates that tree thinning can significantly enhance soil water infiltration rates and cumulative infiltration, effectively replenishing soil water storage in the short term. ...
A large-scale conversion of apple orchards into farmland has occurred in the tableland region of the Chinese Loess Plateau due to the aging of apple trees and the increase in pests and diseases. However, the impact of this conversion on soil desiccation recovery and soil nutrient transportation remains unclear, posing a new challenge for sustainable agricultural development in the region. The study employed the space-time substitution approach to select a long-standing orchard and croplands that has been growing maize for 1-, 3-, 5-, and 10-years post-orchard conversion as sampling sites, to investigate the effects of recovery durations of orchard-to-cropland conversion on deep soil water recharge and residual nitrate dynamics, as well as the key factors driving these changes. The results indicated that within 5 years, the conversion led to a rapid recharge of desiccated deep soil (6–9 m), followed by a stable and slow increase in subsequent years. The annual soil water recovery rate in the deep soil was as high as 5.90 mm m⁻¹ a⁻¹. While, the increased water input also caused rapid leaching and accumulation of nitrate in the deep soil, with its peak depth increasing significantly from 3.4 m to 7.0 m over time (R² = 0.92). Soil water was identified as the key factor influencing nitrate leaching, with a correlation coefficient of 0.48 (P < 0.05). In conclusion, orchard-to-cropland conversion effectively replenished the deep soil water in the short term but also accelerated soil nitrate leaching. Therefore, while large-scale conversion of orchards to farmland is undertaken, it is crucial to acknowledge the trade-off relationship involving the recharge of deep soil water and the subsequent increase in deep nitrogen leaching. The findings of this study hold significant implication for the management of water and nutrient resources after the conversion of orchards to farmland, highlighting the necessity to mitigate nitrogen leaching while soil water is being restored.
... The influence of origin and thinning on tree shape and the potential for valuable products in low coppice have been neglected in recent scientific research. Thinning affects coppice structure, density, tree growth [25], species composition, and stem development [26], as well as in-stand ecological factors such as light, heat, moisture, etc. Coppice development can only be regulated by tending measures (e.g., thinning, cleaning); thinning is also beneficial in the preparation of coppice for conversion [27,28]. Thinning, performed appropriately and in a timely manner, can significantly influence the development of coppices [28][29][30] not only in terms of tree diversity and quality but also tree health [26]. ...
Coppicing has been neglected in recent decades, leaving gaps in knowledge on silvicultural interventions, especially the long-term effects on coppices of Southeast Europe. The recent economic crisis, the sudden increase in energy prices, and the increased demand for assorted wood products have initiated higher interest in coppices in Croatia. Thus, our work aims to define the long-term effects of thinning in sessile oak (Quercus petraea (Matt.) Liebl.) and European beech (Fagus sylvatica L.) sub-mountainous thermophilic low coppices in the Croatian Dinarides. The experiment includes two localities with thinning and control plots. Thinning was performed in 2002, with 17.71% of wood volume removed in the European beech coppice and 26.09% in the sessile oak coppice. In 2020, 1276 trees were marked, measured (DBH, tree height, number of stems per stump), and assessed for vitality, origin, and six silvicultural features revealing tree quality. In 2022, trees were again measured (DBH, tree height) to gain data on tree growth. Conventional data analysis methods were used. The results show a statistically significant positive long-term effect of thinning on tree growth, stem, and crown features and support findings that thinning, by increasing growth and quality, is a necessary intervention in European beech and sessile oak low coppices. Thinning promoted the healthiest and best quality trees/stems, resulting in a more valuable range of wood products and the potential for higher income. It had a positive impact on tree growth regardless of the tree’s origin (seed or stump) and improved the growth and quality of trees among the supporting tree species. Short-term effects of thinning in trial plots suggested that thinning supported tree species diversity, but this effect diminished over time, showing no positive effect after twenty years. The study points to the need for more frequent thinning in coppices to support tree species diversity (i.e., to allow growth to less competitive tree species) but underlines the need for further research.
... al., 2023). Tree felling has emerged as a widely adopted strategy to combat soil water de cits and prevent drought-induced tree mortality (Manrique-Alba et al., 2020; Niccoli et al., 2020). Research by Cui et al. (2022) demonstrates that tree thinning can signi cantly enhance soil water in ltration rates and cumulative in ltration, effectively replenishing soil water storage in the short term. ...
A large-scale conversion of apple orchards into farmland has occurred in the tableland region of the Chinese Loess Plateau due to the aging of apple trees and the increase in pests and diseases. However, the impact of this conversion on soil desiccation recovery and soil nutrient transportation remains unclear, posing a new challenge for sustainable agricultural development in the region. This study aimed to investigate the effects of orchard-to-cropland conversion on deep soil water recharge and residual nitrate dynamics, as well as the key factors driving these changes. The results indicated that within 5 years, the conversion led to a rapid recharge of desiccated deep soil (6-9 m), followed by a stable and slow increase in subsequent years. The annual soil water recovery rate in the deep soil was as high as 5.90 mm·m ⁻¹ ·a ⁻¹ . While, the increased water input also caused rapid leaching and accumulation of nitrate in the deep soil, with its peak depth increasing significantly from 3.4 m to 7.0 m over time (R ² = 0.92). Soil water was identified as the key factor influencing nitrate leaching, with a correlation coefficient of 0.48 ( P <0.05). In conclusion, orchard-to-cropland conversion effectively replenished the deep soil water in the short term but also accelerated soil nitrate leaching. Therefore, while large-scale conversion of orchards to farmland is undertaken, it is crucial to acknowledge the trade-off relationship involving the recharge of deep soil water and the subsequent increase in deep nitrogen leaching. The findings of this study hold significant implication for the management of water and nutrient resources after the conversion of orchards to farmland, highlighting the necessity to mitigate nitrogen leaching while soil water is being restored.
... Silvicultural practices aimed at enhancing photosynthesis efficiency, such as thinning, fertilization, and genetic improvement, can further enhance forest performance and sustainability [5]. Thinning, which involves selectively removing certain trees, reduces competition for light, water, and nutrients among the remaining trees [104]. Fertilization is another key practice that improves photosynthesis efficiency by supplying essential nutrients that may be deficient in the soil [46]. ...
This systematic literature review explores the pivotal role of photosynthesis efficiency in guiding decision-making processes for forest design and redesign. Beginning with an examination of plant characteristics and their conjunction to forest biodiversity, the review highlights the intricate interplay between plant traits and the broader ecosystem. It emphasizes the importance of understanding how plant diversity influences photosynthetic processes and ecosystem productivity. Central to the review is an in-depth exploration of photosynthesis efficiency and its critical role in forest design and redesign strategies. Recognizing photosynthesis as the primary mechanism driving carbon assimilation and energy flow within forest ecosystems, the review underscores the significance of optimizing photosynthetic performance for sustainable forest management. It discusses how maximizing photosynthesis efficiency can enhance ecosystem productivity, carbon sequestration, and overall ecosystem health. Furthermore, the review thoroughly examines various methods for measuring photosynthesis efficiency, ranging from traditional gas exchange measurements to advanced remote sensing techniques and stable isotope analysis. Each method is evaluated for its strengths and limitations, providing valuable insights for researchers and practitioners alike. In conclusion, this systematic literature review underscores the imperative of prioritizing photosynthesis efficiency in decision-making processes for forest design and redesign. It advocates for an ecosystem-centric approach grounded in optimizing photosynthetic performance to enhance forest resilience, productivity, and sustainability in the face of ongoing environmental challenges .
... The influence of origin and thinning on tree shape and so potential for valuable products in low coppice has been neglected in recent scientific research. Thinning affects coppice structure, density and tree growth [25], species composition and stem development [26] as well as in-stand ecological factors such as light, heat, moisture, etc. Coppice development can only be regulated by tending measures (e.g., thinning, cleaning); thinning is also beneficial in preparation of coppice for conversion [27,28]. Thinning done appropriately and in a timely manner, can significantly influence the development of coppices [28][29][30] not only in terms of tree diversity and quality, but some studies also stress that it is important for tree health [26]. ...
Coppicing has been neglected in recent decades leaving gaps in knowledge on silvicultural interventions, especially the long-term effects on coppices of South-East Europe. Thus, our work aims to define the long-term effects of thinning in sessile oak (Quercus petraea (Matt.) Liebl.) and European beech (Fagus sylvatica L.) sub-mountainous thermophilic low coppices in the Croatian Dinarides. The experiment includes two localities with thinning plots and control plots. Thinning was done in 2002 with 17.71% of wood volume removed in the European beech coppice and 26.09% in the sessile oak coppice. 1276 trees were marked, measured (DBH, tree height, number of stems per stump) and assessed for vitality, origin and six silvicultural features revealing tree quality. Descriptive statistics for all variables, RMANOVA for DBH and height and for continuous variables mean+-+ standard deviation for categorical frequency and relative frequency variables were carried out. The results show a statistically significant positive long-term effect of thinning on tree growth, stem and crown features and support findings that thinning, by increasing growth and quality, is a necessary intervention in European beech and sessile oak low coppices. The recent economic crisis, the sudden increase in energy prices, and the increased demand for assorted wood products have initiated higher interest in coppices in Croatia.
... The consistency of trends between several TRW series was assessed using the Gleichlaufigkeit (GLK) index [61]. The results were considered valid when they satisfied the criterion of having a GLK value higher than 60 [62]. The dplR package in RStudio [63] was used for cross-dating tree rings: the program calculated TRW correlation coefficients between a given sample and residual samples from different trees. ...
In recent years, several drought events hit Poland, affecting its forests. In Opole, Poland, tons of Pinus sylvestris L. deadwood is removed every year due to drought. Understanding the physiological mechanisms underlying tree vulnerability to drought, and tree responses, is important to develop forest management strategies to face the ongoing climate change. This research provides comprehensive local-scale analyses of the sensitivity of healthy and declining trees to drought. We used dendrochronology and stable isotope analysis to compare five healthy and five declining trees. The analysis focused particularly on comparisons of basal area increment (BAI), δ¹³C, and intrinsic water-use efficiency (iWUE), as well as tree resistance, resilience, and recovery in response to drought events and sensitivity to selected meteorological parameters. We observed a significant reduction in BAI values in declining trees after 2000. Fifteen years later, the reduction was also visible in the iWUE values of these trees. Despite similar δ¹³C chronology patterns, declining trees showed higher δ¹³C correlations with meteorological parameters. We have shown that dendrochronology enables early detection of poor forest health conditions. Differences in iWUE chronologies occurring in recent years suggest that trees of both groups have chosen different adaptive strategies to cope with drought stress.
... At both the individual tree and stand levels, WUE is often determined by using the ratio of diameter increments at breast height (DBH) to transpiration [46]. Plantation management practices such as thinning and pruning can increase WUE by providing more light to the lower canopy and improving the efficiency of the remaining foliage [11,15,16,21,47,48]. Understanding WUE under the combined effects of thinning and pruning is crucial to comprehend and regulate the forest water cycle, as well as to optimize plantation management practices. ...
Water is a vital resource for tree growth, and changes in plantation and canopy structure can affect stand transpiration (Ec), consequently influencing water use efficiency (WUE). Populus tomentosa is a fast-growing and productive timber species in China. In recent years, thinning combined with pruning has become a widely used silvicultural practice for timber management. However, its effect on water utilization has been less well studied. To address this gap, we designed experiments with two thinning intensities and three pruning treatments. Thermal dissipation probes were employed to monitor tree sap flow density (Js), and estimated Ec and canopy conductance (gc). We established a relationship between the canopy transpiration per unit leaf area (EL) and gc and climatic factors. Finally, we compared basal area increment (BAI) and WUE among treatments under different rainfall conditions. The results indicated that: (1) The pattern of transpiration changes was consistent at both the individual tree and stand level. (2) The combined effect of T1 (thinning intensity of 833 trees per hectare) and pruning reduced Ec, decreasing the sensitivity of tree transpiration to the climate, with no discernible impact on EL and gc. Conversely, T2 (thinning intensity of 416 trees per hectare) and pruning increased EL and gc but had no effect on Ec, enhancing the sensitivity of tree transpiration to the climate. The sensitivity of gc to VPD suggested a flexible stomatal regulation of transpiration under different combined thinning and pruning treatments. (3) Under T1, only P2 (4 m pruning from ground) promoted WUE, while pruning effects significantly reduced WUE under T2. Overall, the WUE of T2P0 (thinning intensity of 416 trees per hectare combined with no pruning) was significantly higher than that of the other treatments, and that of T1P0 (thinning intensity of 833 trees per hectare combined with no pruning) was significantly lower than that of the other treatments. Additionally, significant differences in Ec and BAI were observed among treatments under different rainfall conditions, with the promotion effect of Ec on BAI being more pronounced in the dry season.
... The Gleichlaufigkeit (GLK) parameter was used to evaluate the consistency of trends between different TRW series (Eckstein and Bauch, 1969). Results were considered valid with a GLK greater than 60 (Niccoli et al., 2020). The dplR package in R-studio was used for cross-dating of tree rings: the program calculated TRW correlation coefficients between a given sample and residual samples from different trees. ...
Pinus sylvestris L. is the most common tree species growing in Poland. Trees of this species are considered to be resistant to difficult meteorological conditions; however, in the past decades, many of them have died and been cut down by foresters. The measurements of the annual tree ring width can provide information on how trees respond to drought events. This study aimed to investigate the potential differences between healthy and declining trees (identified as trees to be cut down by foresters). For this purpose, we collected samples of five trees from each group and analysed them using dendrochronological and quantitative wood anatomy approaches. We measured ring width index (RWI) chronologies for healthy and declining trees and compared them with climate data. Additionally, we compared some anatomical features of trees from both groups as cell wall thickness (CWT) and lumen area (LA). The conducted analyses showed significant differences between healthy and declining trees. In particular, declining trees were characterised by lower RWI, LA and CWT values, especially in the past 20 years, and showed greater sensitivity to changes in temperature and humidity than healthy trees.
... Correlations and multivariate analysis were performed on anatomical, isotopic and climatic data to visibly point out relationships among variables which allow us to see patterns of data and understand multiple factors at once, making clear comparisons. To assess the correlations between climatic and anatomical/isotopic data, the approach reported in Fritts (1976) for climate-growth relationships as used by Niccoli et al. (2020) was followed. More specifically, the climatic data of interest were divided by single or multiple months and were subjected to the linear Spearman's correlation analysis to highlight the climatic parameter that has mostly influenced the anatomical traits of V. vinifera. ...
In the Mediterranean region, prolonged droughts affect the growth and reproductive cycles of grapevine. Changes in the physiological processes of grapevine, consequent to variations in environmental factors or cultivation management, are recorded in wood anatomical and isotopic traits in grapevine stems. In this study, we measured the anatomical traits and stable carbon isotope content in the annual rings of Vitis vinifera L. subsp. vinifera ‘Falanghina’ in four vineyards located in southern Italy, characterised by different water availability. The aim was to investigate how wood anatomical traits respond to interannual climatic variations according to local conditions. Wood cores were taken from the stem of the grapevines and subjected to both microscopy and carbon stable isotope analyses to quantify functional wood anatomical traits, such as vessel size and frequency, and the intrinsic water-use efficiency of the grapevine. Wood traits were correlated with data on precipitation and temperature. The results showed that the plants at the four vineyards were characterised by differences in wood structure influencing the grapevine’s physiology under different conditions of water availability. Overall, the analyses showed that the grapevines at the wetter sites developed wood traits, e.g., wide vessels, which favour the efficiency of water flow, while at the drier sites, they developed plant traits, e.g., small vessels, which favour safety against embolism. However, the robustness of such main trends is trait-specific and is influenced by interannual climatic variability.
... (1916), Solomon (1995) Q. alba (white oak) Blatchley and Leng (1916), Solomon (1995) Q. coccinea (scarlet oak) Blatchley and Leng (1916), Solomon (1995) Q. falcata (Spanish oak) Solomon (1995) Acer negundo (box elder) Solomon (1995) Acer rubrum (red maple) Blatchley and Leng (1916), Dajoz (2005) (Figure 4). Oak species can be found in pure or mixed forests (Bernetti, 1995), pure or mixed plantations (e.g. for production of timber) (Ravagni et al., 2015;Niccoli et al., 2020), or as ornamental trees in cities and parks (Bonner and Karrfalt, 2008 Other confirmed host genera are also widespread in the EU territory ( Figure 5) There are no data on the flight ability of A. minutus. As a reference, adult males of the sweet potato weevil Cylas formicarius (a well-studied species belonging to the same beetle family, Brentidae, but smaller in size than A. minutus) can cover a mean distance of 53.6 m in a 23 h flight trial in laboratory conditions (Moriya and Hiroyoshi, 1998), and 55-64 m (Sugimoto et al., 1994) and 32-162 m (Miyatake et al., 1997) per day in field conditions. ...
... Figure 5). Oak species can be found in pure or mixed forests (Bernetti, 1995), pure or mixed plantations (e.g. for the production of valuable timber assortments; Ravagni et al., 2015;Niccoli et al., 2020), or as ornamental trees in cities and parks (Bonner and Karrfalt, 2008 (Table 1), especially Castanea, are also widespread in the EU territory ( Figure 6). ...
This document provides the conclusions of the pest survey card that was prepared in the context of the EFSA mandate on plant pest surveillance (M‐2020‐0114) at the request of the European Commission. The full pest survey card for Pseudopityophthorus minutissimus and P. pruinosus is published and available online in the EFSA Plant Pest Survey Cards Gallery at the following link and will be updated whenever new information becomes available: https://efsa.europa.eu/plants/planthealth/monitoring/surveillance/pseudopityophthorus-minutissimus-pruinosus
... In fact, the years with the lowest BAI, mostly occurring since 2007, were not associated with higher water use efficiency. Niccoli et al. (2020) showed that a high intensity thinning increased tree growth and iWUE in the temperate deciduous species Quercus robur, due to a reduction in competition intensity and an enhanced photosynthetic activity under non-water limited conditions. In contrast, increases in stomatal conductance far prevailed in water-limited environments over increases in assimilation rates when the inter-tree competition was reduced (Giuggiola et al., 2016). ...
The forests of south‐central Chile are facing a drying climate and a megadrought that started in 2010. This study addressed the physiological responses of five Nothofagus obliqua stands across the Mediterranean‐Temperate gradient (35.9°−40.3°S) using carbon isotope discrimination (Δ¹³ C) and intrinsic water use efficiency (iWUE) in tree rings during 1967–2017. Moreover, tree ring δ¹⁸O was evaluated in the northernmost site to better understand the effects of the megadrought in this drier location. These forests have become more efficient in their use of water. However, trees from the densest stand are discriminating more against ¹³C, probably due to reduced photosynthetic rates associated with increasing light competition. The strongest associations between climate and Δ¹³C were found in the northernmost stand, suggesting that warmer and drier conditions could have reduced ¹³C discrimination. Tree growth in this site has not decreased, and δ¹⁸O was negatively related to annual rainfall. However, a shift in this relationship was found since 2007, when both precipitation and δ¹⁸O decreased, while correlations between δ¹⁸O and growth increased. This implies that tree growth and δ¹⁸O are coupled in recent years, but precipitation is not the cause, suggesting that trees probably changed their water source to deeper and more depleted pools. Our research demonstrates that forests are not reducing their growth in central Chile, mainly due to a shift toward the use of deeper water sources. Despite a common climate trend across the gradient, there is a non‐uniform response of N. obliqua forests to climate drying, being their response site‐specific.
... Light thinning mainly removed suppressed trees below the general canopy level since thinning from below was adopted in our plots. Such an intensity may not be able to create enough gaps between crowns to improve the light condition of the remaining trees (Niccoli et al. 2020), thus leading to an insignificant thinning effect in light thinning plots. ...
An improved understanding of the effects of thinning and climate on tree growth is essential to adopting adaptive forest management strategies under climate change. In this study, we developed a climate-sensitive individual-tree growth model for Changbai larch (Larix olgensis) in northeast China by fusing tree-ring and permanent sample plot data. We assessed the impacts of tree age, competition, site condition, thinning, and climate on radial growth using the mixed-effects modeling approach. Results showed that the radial growth rate of Changbai larch decreased with increasing cambial age and competition intensity. Radial growth was negatively associated with summer water deficit and positively associated with spring growing degree-days. Radial growth also responded positively to mean annual precipitation of the previous year. In addition, a significant positive effect of thinning on radial growth was observed. The magnitude of thinning effects was affected by thinning intensity and time elapsed since the thinning. Hierarchical partitioning analysis showed that cambial age was the most important factor affecting growth (relative contribution 35.96%), followed by competition (31.42%), climate (19.24%), thinning (8.40%), and site condition (4.98%). Compared to unthinned plots, moderate- and high-intensity thinning significantly enhanced the radial growth under unfavorable climates, indicating that thinning has great potential to mitigate the negative effects of future climate. Disentangling different sources of variations in ring width will help advance our understanding of the factors driving radial growth and reduce the uncertainty in forest management decisions.
... Therefore, studies of species diversity of forests (Vacek et al., 2019) in river basins are relevant, especially in climate change conditions. A study of natural regeneration, productivity determination, pests, and diseases of common oak , Niccoli et al., 2020, Scots pine (Garmash, 2019;Conte et al., 2018;Sharma et al., 2020), common ash (Beyer et al., 2013;Davydenko et al., 2019), black alder (Buhaiov et al., 2019;Deptuła et al., 2020), silver birch (Tyschenko, 2018;Álvarez-López et al. 2020) was performed in many scientific papers. However, research on the determination of species diversity, distribution, and origin in the river basins of the Left-Bank Forest-Steppe of Ukraine has hardly been conducted (Tkach, 1999;Bondar et al., 2020). ...
Species diversity of forests in basins of the rivers Sula, Vorskla, Psel, and Seversky Donets and their tributaries (on the territory of Ukraine) are analyzed. The research aimed to identify forest species diversity in 109 watersheds of the rivers Sula, Vorskla, Psel, and Seversky Donets and determine the share of forests in the origin and composition of plantations in the river basins. To delineate the boundaries of 109 catchment areas of the Sula, Psel, Vorskla, and Seversky Donets rivers, the MapInfo Professional 12.5 and a vector map of Ukraine were used. After defining the boundaries of 109 river basins, a vector layer of forest stands (which are subordinated to the State Forest Resources Agency of Ukraine) was applied, and the distribution database of these rivers was formed. It was determined that 63 species of trees were identified in the study region, the most common of which are common oak and Scots pine. The distribution of several tree species on 109 river basins is analyzed. Thus, the most significant number of tributaries (50%) has concentrated from 11 to 20 species of trees, slightly less number of tributaries (24 and 22%) represented 1-10 and 21-30 species, and the smallest number of tributaries (6 and 2%) represented 31-40 and 41-50%, respectively. Mixed plantations dominate (61% of the total forest area) in the river basin; pure plantations are the rest (39%).
... The experimental design of the common garden in blocks and micro-blocks was made to minimize as much as possible the variation in environmental conditions among trees to improve the detection of genetic variations. However, in addition to the influence of genetic factors on WUE i , that of variations in the microenvironment, including those generated by differences in social status, cannot be excluded (McDowell et al., 2003;Niccoli et al., 2020). ...
ContextAs a widespread species, sessile oak (Quercus petraea) populations occupy a wide range of ecological conditions, with large gradients of soil water availability. Drought acclimation involves a plastic increase in water-use efficiency (WUE), a trait that is easily measured using the carbon isotope composition (δ13C). However, the question remains whether WUE is an adaptive trait that impacts the fitness of trees in natural environments.Objectives and Methods
To investigate whether WUE was a drought-adaptive trait, we studied a sample of 600 trees originating from 16 provenances, grown for 21 years in a common garden. Intrinsic WUE (WUEi), estimated from tree ring δ13C, was compared among and within populations for three climatically contrasted years. The adaptive character of WUEi was evaluated by relating population mean WUEi, as well as its plasticity to drought, to the pedoclimatic conditions of their provenance sites. The contribution of WUEi to tree and population fitness was finally assessed from the relationship between WUEi and tree radial growth (GI).ResultsSignificant differences in WUEi were found among populations but a much larger variability was observed within than among populations. The population WUEi of the juvenile oak trees growing in the relatively mesic conditions of the common garden showed no relationship with a modeled water deficit index for the provenance sites. However, a higher population WUEi plasticity to severe drought was related to a higher proportion of silt and carbon and a lower proportion of sand in the soil of the provenance sites. In response to severe drought, populations with a higher increase in WUEi showed a lower decrease in GI. Populations with lower GI reduction were from sites with higher vapor pressure deficit in May–July (VPD). For the wet year only, populations with a higher WUEi also had a higher GI.Conclusion
The correlations observed at the common garden site between (i) population means of WUEi plasticity to drought and soil texture of the provenance sites, and (ii) GI plasticity to drought and VPD, suggested a local adaptation of sessile oak.
... The use of BAI avoids detrending procedure [46] allowing to not lose information on low frequency variability. Then average of Cumulative Basal Area (CBA) was determined by summing the average BAI and propagating uncertainties [47,48]. To distinguish the measurements of the two studied tree species in each intercropping systems, hereafter we refer to intercropping and then P (for poplar) and the J (for walnut) after an underscore, e.g., PJ_P refers to P. alba sampled in the PJ intercropping and PJ_J refers to J. regia sampled in the PJ intercropping. ...
Species interactions in mixed plantations can influence tree growth, resources capture and soil fertility of the stands. A combined approach of tree-ring analyses and carbon stable isotope was used to check tree growth and water use efficiency of two species, Populus alba L. and Juglans regia L., intercropped with each other and with N-fixing or competitive production species. Furthermore, soil analyses were performed to understand how the different intercropping systems can influence soil characteristics, in particular soil carbon stock. Dendrochronological data showed that during the first years, the growth of principal species was favored by intercropping. This positive effect decreased in the following years in most of intercropped stands, due to light competition with the crown of companion species. Carbon isotope data showed that P. alba and J. regia had the highest intrinsic water use efficiency when growing with Elaeagnus umbellata Thunb, a shrubby species with a shallow root system that favors a non-competitive exploitation of soil water resources. Finally, the intercropping of the principal species with Corylus avellana L. promoted the highest soil C stock. Our findings confirmed the importance to consider the plantation dynamics and wood formation in the long-run and to apply appropriate thinning and pruning interventions to counteract interspecific competition.
... Il primo diradamento è stato realizzato a 14 anni di età, testando tre diverse modalità: i) geometrico, ii) selettivo di moderata intensità (preservando l'ontano), iii) selettivo di forte intensità, eliminando attorno alle candidate (70-80 ad ettaro) tutte le concorrenti comprese le piante di ontano nero (Niccoli et al. 2020). I migliori risultati, in termini di risposta incrementale, sono stati ottenuti con il diradamento selettivo di forte intensità, seguito dal diradamento geometrico e infine dal diradamento selettivo di moderata intensità che ha preservato l'ontano. ...
The paper describes the principal techniques and cultural models suitable for common walnut cultivation pointing out the high potentiality of this tree and the limitations of walnut cultivation.
... These results agree with previous studies suggesting that tree species' responses to climate are site-dependent and may be modulated by stand density (Moreno-Gutierrez et al., 2012;Camarero et al., 2013;Sanchez-Salguero et al., 2013). Zalloni et al. (2019) found that intraspecific facilitation effects decreased with increasing stand density in a Quercus ilex stands, while Niccoli et al. (2020) demonstrated that sparse stands, resulting from selective thinning, have higher productivity associated with increased photosynthetic rate and decreased water loss relative to low thinned stands. Moreover, several microclimatic parameters such as soil nutrient availability were shown to change with increased stand density (Barron-Gafford et al., 2003;Zhao et al., 2012;Liu et al., 2013;Bolat, 2014), impacting tree growth at site level (Granda et al., 2017). ...
This study investigated the impacts of environmental (e.g., climate and CO2 level) and ecological (e.g., stand density) factors on the long-term growth and physiology of ponderosa pine (Pinus ponderosa) in a semi-arid north American grassland. We hypothesized that ponderosa pine long-term growth patterns were positively influenced by an increase in atmospheric CO2 concentrations and a decrease in stand density. To test this hypothesis, comparison of long-term trends in tree-ring width and carbon and oxygen stable isotopic composition of trees growing in dense and sparse forest stands were carried out at two sites located in the Nebraska National Forest. Results indicated that tree-ring growth increased over time, more at the sparse than at the dense stands. In addition, the carbon and oxygen isotopic ratios showed long-term increases in intrinsic water use efficiency (WUEi), with little difference between dense and sparse stands. We found a clear trend over time in ponderosa pine tree growth and WUEi, mechanistically linked to long-term changes in global CO2 concentration. The study also highlighted that global factors tend to outweigh local effects of stand density in determining long-term trends in ponderosa pine growth.
Finally, we discuss the implications of these results for woody encroachment into grasslands of Nebraska and we underlined how the use of long-term time series is crucial for understanding those ecosystems and to guarantee their conservation.
Stand thinning, an important means of forest management, can alleviate soil drying and vegetation degradation caused by excessive afforestation in semi-arid regions. However, how thinning affects leaf-scale and root water use characteristics of artificial forests in different hydrological years remains unclear. In this study, the soil moisture, sap flow, and stable isotopes (δ2H, δ18O, and δ13C) were observed to investigate the effects of thinning (heavy to light) on stand transpiration, soil water sources, and leaf-scale water use efficiency (WUEi) of Robinia pseudoacacia within three years (2020–2022) in the Loess Plateau. The results showed a relatively higher contribution of shallow-middle soil water (0–300 cm) to R. pseudoacacia and a higher soil water content in deep layer (300–500 cm) in thinning plots compared to non-thinning plot. In the normal (2020) and wet (2021) years, an “upward shift” water uptake pattern from deep to shallow-middle soil layers of R. pseudoacacia in thinning plots was observed. In the meantime, thinning led to a significant decrease in transpiration (45.1 % and 40.3 %) and an increase in WUEi (12.0 % and 10.9 %) of R. pseudoacacia in heavy and light thinning plots. However, R. pseudoacacia in turn shifted water uptake depths to deep layer (37.6 %-47.2 %) in the third year with less precipitation (2022). The thinning effects on transpiration and WUEi of R. pseudoacacia also weakened in 2022. There was a linear positive correlation of WUEi with transpiration rate and shallow soil water use, while WUEi was negatively related to the middle and deep soil water contributions to R. pseudoacacia, with a higher slope in thinning plots compared to non-thinning plot, indicating the shifting water absorption strategy of R. pseudoacacia to improve ecological adaptability by thinning. Overall, the temporary effects of thinning on soil moisture and water use characteristics should be fully integrated into forest ecosystem restoration and management efforts.
The Three-North Shelter Forest Program (TNSFP) of China, one of the largest forestry ecological projects, serves as a nature-based solution to addressing ecological, social, and economic challenges and issues. This program, mainly situated in arid and semi-arid regions, critically focuses on improving water use efficiency (WUE)—maximizing carbon sequestration per unit of water consumed—as a key strategy for optimizing water resource utilization and ensuring the long-term success of vegetation restoration efforts. However, the regulatory mechanisms of forest WUE in this region remain unclear. Here, we adopted an interpretative machine-learning method to investigate the influence of main environmental elements, topographical conditions, and stand characteristics on forest WUE in the TNSFP region from 2001 to 2022 based on remote sensing products, ground monitoring data, and forest inventory data. Our study identified soil moisture (SM) as the primary factor influencing forest WUE across the TNSFP region, with higher SM levels generally leading to improved WUE in forests. However, stand characteristics strongly mediated their relationship. Specifically, forest WUE initially increases against forest density before peaking at about 1000 trees hm⁻² for needle-leaved forests (NLF) and 800 trees hm⁻² for broad-leaved forests, respectively, then gradually declining due to water competition. When SM is relatively adequate, moderate thinning could significantly enhance forest WUE. Furthermore, implementing management strategies to improve WUE is crucial as NLFs mature. This study emphasizes the significant impacts of stand characteristics on forest WUE in the TNSFP region, offering essential insights for optimizing water resource management in managed forests across arid and semi-arid regions.
The continuous threat of ongoing climate change and related weather anomalies challenge forest ecosystems. The phytosociological structure of forests plays a crucial role in determining their resilience to various abiotic and biotic stressors. Furthermore, stand density, which partly regulates the allocation of resources within individual trees, is a vital aspect of understanding forest functioning. This study was conducted in Norway spruce (Picea abies [L.] Karst.) forests in the Czech Republic, where we investigated the influence of tree density on sap flow rates within three pre-defined directions corresponding to sun position during the morning (5:00-11:10 hours; East), noon (11:10-15:10 hours; South), and evening (15:10-21:10 hours; West) intervals. Tree density was calculated within a 10 m radius buffer around each sap flow measured tree using high spatial resolution aerial imagery acquired by Unmanned Aerial Vehicle. Sap flow was measured at 10-minute intervals for 25 selected trees during the nine hottest summer days in 2019. Our data reveals an inverse correlation between sap flow and tree density, underscoring the substantial impact of neighboring tree density on transpiration. This relationship was most pronounced during midday, followed by the evening and morning hours, suggesting higher heat loads on the trees and forest grounds during the midday. Our findings emphasize the critical role of stand density in modulating forest functioning and underscore the importance of maintaining specific canopy densities as part of effective silvicultural practices in the face of ongoing climate change.
Key message
Korean pine trees expressed significant crown displacement. Nearest neighbor competition had the largest effect on the crown displacement compared to the slope direction and mean direction of wind.
Abstract
The crown displacement of individual trees exhibits an adaptive response driven by neighbors, but it can also be the result of wind force and slope effects. In our research, we focused on the crown displacement of planted Korean pine trees in northeast China. A total of 51 trees aged 8–56 years were destructively harvested to measure branch attributes. The gravity centers of the upper, lower and entire crown were calculated. The Markov chain Monte Carlo (MCMC) algorithm, generalized mixed effects model, and circular statistics were used to determine the response of crown displacement to biotic and abiotic factors. The results showed that the dominant tree had the largest absolute crown displacement, and the suppressed tree expressed the largest relative crown displacement. The lower crown showed more apparent crown displacement than the upper crown. The Korean pine was displaced in a northeastern direction. Nearest neighbor competition had the largest effect on the crown displacement compared to the slope direction. Slope direction had a slightly larger effect than the mean direction of wind. The crown displacement for the lower crown was more affected by the interaction of the wind, slope and neighbor competition than the upper crown. No relationship between crown displacement and stem eccentricity for the planted Korean pine was detected.
Forest thinning can be used as an adaptive measure to improve the growth and resistance of Norway spruce forests affected by climate change. The impact of different thinning intensities on sap flow, growth, and tree water deficit of 40-year-old Norway spruce was tested. High thinning intensity (–61% of basal area) resulted in increased tree-level sap flow compared to the control (+27%), but it caused a decrease in the stand-level transpiration (–34%) due to reduced leaf area index. Low-intensity thinning (–28% basal area), high-intensity thinning, and control showed similar responses of sap flow to vapour pressure deficit and global radiation, suggesting unchanged isohydric behaviour. Both low- and high-intensity treatments displayed greater radial growth than the control. There were no differences in tree water deficit between the treatments. The low-intensity treatment can be considered the best water utilisation treatment with increased growth and unchanged transpiration at the tree level. The high-intensity treatment had similar radial growth as the low-intensity but lower stand-level transpiration, implying improved soil water availability. The study expands the ecophysiological understanding of thinning as a valuable silvicultural practice for adapting forest management of Norway spruce to the effects of climate change.
The increasing global vegetation aggravated the consumption of soil water and caused soil desiccation, which may result in a threat to the survival and sustainability of vegetation, especially in semi-arid and arid areas. How to solve soil water deficit caused by afforestation is an important practical problem. Here, a field experiment of soil water infiltration and replenishment was conducted before and after forestland-to-farmland conversion. Results showed that the cumulative infiltration of each stage (the initial stage, the transitional stage, and the stable stage) was the highest in farmland, followed by forest interspace, and the lowest in forest understory. The non-capillary porosity at 0-20 cm soil layer in farmland was higher than that in forest understory and interspace, which positively improved the infiltration accumulation in the initial stage. Thus, the cumulative infiltration in initial stage of farmland (28.93 mm) was significantly higher than that of forest understory (19.45 mm). Moreover , soil water at the depth of 0-160 cm soil layer was replenished with short term after forestland-to-farmland conversion. It is concluded that forestland-to-farmland conversion could improve soil water infiltration rate and cumulative infiltration by changing porosity, and effectively replenished soil water storage in the short term. These findings have potential implications for effective mitigation of soil water deficit caused by afforestation, and provide a new idea or method for the solution to dry soil layers caused by artificial forestland in semi-arid areas .
Walnut tree species (Juglans spp.) are commonly used for high-quality wood production in plantation forestry. In this paper, the most relevant walnut plantations in Italy and Spain have been reviewed and analysed under a geographic and techni- cian management point of view. Between 2016 and 2019 a total of 96 plantations (15 - 25 years old) were visited distributed in the North-western part of the Mediterranean basin. A statistical analysis (linear model no interaction and PCA) was then performed to evaluate the relative importance of some environmental and management variables for walnut trees in analysed plantations. Results highlighted a variable situation with many different adopted planting schemes across the regions as well as a not standardised spatial layout and management type (thinning). Lower densities and smaller trees were adopted in Italy with about 200 trees ha-1 versus 330 trees ha-1 in Spain. In addition to the age of the plantation as one of the most influencing parameters also the plantation density and
the average crown diameter were highly statistically significant. Overall, the interesting potentiality of walnut for timber production with active management in suitable areas was detected as the focal point for a successful timber production from walnut trees.
EFECTO DEL SITIO Y DE DIFERENTES ASOCIACIONES ARBÓREAS EN EL CRECIMIENTO Y CALIDAD FUSTAL DEL ROBLE EUROPEO (Quercus robur L.) EN EL SUR DE CHILE Loewe, Verónica 5 ; Siebert, Herbert 6 y Herrera, Rodrigo 7 RESUMEN El proceso de diversificación forestal en Chile ha estimulado el interés por cultivos y modelos productivos no tradicionales, dentro de los cuales las plantaciones mixtas han mostrado utilidad para la realidad forestal al favorecer el crecimiento en altura y diámetro. Debido a la ductilidad de su madera, el roble europeo (Quercus robur L.) es altamente demandado en el mercado internacional. Este estudio determinó el efecto en el crecimiento y la calidad fustal del Q. robur de varias asociaciones establecidas y manejadas mediante silvicultura con apego a la naturaleza en el fundo Miraflores (Lanco, Región de los Ríos, Chile), haciendo un muestreo de 200 árboles futuro por asociación (una pura y nueve mezclas diferentes). Los resultados indican que la proporción de árboles futuro es mayor en las asociaciones mixtas respecto a la pura; y que el crecimiento en altura y diámetro en la situación pura es mayor que en las mezclas analizadas. No obstante lo anterior, no se recomienda la plantación pura, pues este manejo provoca una importante penetración de luz, que favorece el desarrollo de características que descalifican la calidad de madera, como la aparición de brotes epicórmicos. Se concluyó que las asociaciones más favorables para el desarrollo de Quercus robur incluyen arce (Acer pseudoplatanus) y castaño (Castanea sativa), seguida de pino oregón (Pseudotsuga mensiezii) y castaño. Palabras Clave: Diversificación, Plantaciones mixtas, Encino, Silvicultura con apego a la Naturaleza, Producción de madera de alto valor, Monocultivo. SUMMARY The forest diversification process in Chile has stimulated the interest for cultural and productive non-traditional models, among which the mixed plantations have shown usefulness for the forest activity, since in many cases they favor height and diameter (DBH) growth. Due to the ductility of its wood, Quercus robur is highly demanded on international markets. This study determined the effect in the growth and trunk quality of several associations with Q. robur established and managed using silviculture mimicking nature in the property Miraflores (Lanco, Region de Los Ríos, Chile); by sampling 200 future high quality trees per association (1 pure and 9 mixtures). Results showed a higher proportion of future trees in the mixed plantations. Height and diameter growth in the pure situation were higher than in the different mixtures, but the proportion of superior future trees was higher in the later. Consequently, it is not recommended pure plantations given the significant penetration of light that favors the development of characteristics that disqualify wood quality. It is concluded that mixed plantations are more favorable for the development of Q. robur; species that grows better when associated to Maple (Acer pseudoplatanus) and Chestnut tree (Castanea sativa), followed by the association with Douglas Fir (Pseudotsuga menziesii) and Chestnut tree.
The results of peduncolate Oak plantation trials where the Oak is mixed to wild Cherry and narrow-leaf Ash per line and per close mixture with different proportions (25% and 50%) of N-fixing species (Black Locust and Italian Alder) are described in the paper. The plantation, carried out in winter 1988-89, was framed into a reafforestation plan for spoil banks restoration. On a share of the plantation area, free thinnings foreseeing the release of about 70 target trees per hectare, were undertaken in 2001 and 2003; 21% and 27% of basal area were removed, respectively. In the latter trial, the crowns of target trees were completely isolated by felling all the surrounding trees. The performances of valuable timber broadleaves, the effects of intercropping and thinning on the growth of Oak target trees were analysed. Three inventories (2001, 2004 and 2008) and the annual monitoring of target trees growth were performed at the purpose. The two peduncolate Oak and narrow-leaf Ash trees showed the best performances among the set of valuable broadleaves, whilst wild cherry resulted not suited to local site conditions. A higher tree mortality occurred in the mixture with Black Locust. The mixture with both Nfixing species provided a stimulus to the Oak growth both in terms of dbh and tree height. Italian Alder resulted anyway less competitive and easy to manage, considering its progressive self-thinning, while Black Locust was aggressive enough to necessitate the control of its development by pollarding 7 years after the plantation. In the thinned plots, target trees showed significant diameter increments in comparison with control plots; maintaining year by year constant dbh increments of about 1 cm and crown’s diameter increment of about 50 cm. Intercropping with Italian Alder showed to be more effective than thinning on growth of the target trees.
1.Climate change scenarios forecast rising temperatures for the Mediterranean region, which could enhance vulnerability to drought stress in forest ecosystems. The long-term effects of climate forcing on tree performance can be, however, modulated by other environmental factors, such as competition and rising atmospheric CO2 concentrations.
2.We assessed the concomitant effect of competition, climate and CO2 concentrations on the tree-ring δ13C-derived intrinsic water-use efficiency (iWUE) and basal area increments (BAI) of species with different drought tolerance: two Mediterranean deciduous species (Quercus faginea Lam. and Quercus pyrenaica Willd.) and one conifer (Pinus sylvestris L.). Additionally, given that competition may be managed to mitigate the effect of increasing drought stress, we further examined the influence of this variable on iWUE and growth using data compiled from the literature, providing the first review on the response of iWUE to competition.
3.Competition had no significant effect on iWUE in any of the three species studied, whereas, as expected, growth rates were significantly higher under low competition levels. This was consistent with the literature review, which showed that shifts in iWUE with competition changes are rare; supporting the hypothesis that leaf-level gas exchange tends to be a homeostatic trait. In the long term, the three species exhibited a significant increasing trend in iWUE due to the combined effect of increased CO2 concentration, climate and age. Growth, however, was mostly affected by competition and climate and in most cases was not enhanced as a result of the increase in iWUE.
4.Synthesis. Regardless of their functional response to drought, trees respond to reduced competition through structural shifts such as increased radial growth rather than leaf-level gas exchange adjustments. CO2 and climate are, therefore, the main drivers of iWUE variability, rather than competition. Thus, if temperature-induced drought becomes limiting, reducing competition for resources may not offset the detrimental effect of increasing drought stress on tree physiology and growth decline may occur without a CO2 fertilization effect.
http://onlinelibrary.wiley.com/doi/10.1111/1365-2745.12544/full
Context In southern European beech forests coppice is a widespread management system, especially due to the past uses. The existence of large areas either abandoned or under protracted transitory stage raises questions concerning environmental and economic revenues related to the different management options.
Aims We evaluated the effectiveness of anticipating seed cutting in beech coppices to accelerate the coppice transition to high forest, compared with traditional management (periodic thinning) and natural evolution pattern (unthinned control).
Methods
We used an exploratory analysis of ecological variables related to structure, dynamics and productivity of the stands (growth efficiency, leaf area index, litter production, transmittance and canopy heterogeneity), which were monitored during 10 years in beech coppices in Central Italy.
Results
Anticipating seed cutting produced stronger modification in canopy structure, improving growth efficiency as a result of higher resource availability, supporting higher seed production which accelerated the progression of the stand towards more adult stand conditions, compared with traditional management and unthinned control.
Conclusion
The application of different active management options can increase landscape heterogeneity under conditions in which increasing landscape diversity represents a priority management issue, while simultaneously allowing environmental and economic revenues.
The mid-term effects on carbon sequestration of two consecutive pre-commercial thinnings with different intensities were analysed
in a heavily stocked Pinus pinaster Ait. stand in northwestern Spain. Thinning was carried out 5 and 8 years after seedling establishment. Intense thinning reduced
the initial sapling density by 92 per cent after the first treatment and by 87 per cent after the second; moderate thinning
reduced the density by 82 per cent after the first treatment and by 84 per cent after the second. The effect on foliar efficiency
of the first thinning was transient, but was prolonged by the second thinning. Live carbon biomass stock (in saplings and
understorey) decreased after thinning, especially after the most intense thinning. However, when residues were taken into
account, the carbon biomass decreased by only 18 per cent in the intensely thinned plots, and by 2 per cent in the moderately
thinned plots, relative to the untreated plots, by the end of the study period. Very early thinning of these heavily stocked
young stands was found to have a reduced mid-term effect on carbon sequestration per land area, when carbon stock from understorey
and residues were considered.
It is still unclear whether the exponential rise of atmospheric CO2 concentration has produced a fertilization effect on tropical forests, thus incrementing their growth rate, in the last two centuries. As many factors affect tree growth patterns, short -term studies might be influenced by the confounding effect of several interacting environmental variables on plant growth. Long-term analyses of tree growth can elucidate long-term trends of plant growth response to dominant drivers. The study of annual rings, applied to long tree-ring chronologies in tropical forest trees enables such analysis. Long-term tree-ring chronologies of three widespread African species were measured in Central Africa to analyze the growth of trees over the last two centuries. Growth trends were correlated to changes in global atmospheric CO2 concentration and local variations in the main climatic drivers, temperature and rainfall. Our results provided no evidence for a fertilization effect of CO2 on tree growth. On the contrary, an overall growth decline was observed for all three species in the last century, which appears to be significantly correlated to the increase in local temperature. These findings provide additional support to the global observations of a slowing down of C sequestration in the trunks of forest trees in recent decades. Data indicate that the CO2 increase alone has not been sufficient to obtain a tree growth increase in tropical trees. The effect of other changing environmental factors, like temperature, may have overridden the fertilization effect of CO2.
In order to quantify the water use efficiency and water consumption during the early growth of Jatropha curcas L., three genotypes were grown in pots under greenhouse conditions, and subjected to two watering regimes: irrigated (substrate matric potential (Ψm) of −9.8 to −7.4 kPa) and water deficit (Ψm = −98.6 to −33.5 kPa). Independent of watering regime, the genotypes did not differ on the variables analyzed. Despite the reduction of substrate water content in water deficit treatment, no significant decrease (p < 0.05) of leaf water potential (Ψw) was observed, which suggests some water redistribution from the succulent stems of J. curcas. The values of net photosynthetic rate (A), stomatal conductance (gs), and transpiration (E) were reduced to 80, 90 and 85%, respectively, as compared to control plants. Moreover, drought led to 78% reduction in hydraulic conductance (KL). At the end of the experiment, the average water consumption in water deficit plants was 27% lower than in control plants. Drought-induced decrease in biomass production led to reduction of water use efficiency of biomass (WUEBiomass). However, due to the more significant effect on gs and E than A at 66 DAIT, intrinsic (A/gs) and instantaneous efficiency (A/E), water use increased 50% and 27%, respectively. The results showed that there was no intergenotypic variation for the traits evaluated, and that the reduction of water availability in the substrate proved to be an effective technique in the increase of photosynthetic efficiency of water use in plants of J. curcas, reducing water consumption in this species.
Key message With a retrospective growth analysis over
20 years, we showed that silviculture (in particular thin-
ning) of Cedrus atlantica (Manetti) could to some extent
mitigate the effects of drought episodes. Severe reductions
ofdensityresultedinfasterrecoveryofradialgrowthafter
severe drought episodes.
Context Climatechangeisexpectedtoincreasethefrequency
and the intensity of drought in southern Europe. Silviculture
could help in mitigating the effects of water deficit on forests.
Aim The aim of this study is to assess the effect of thinning
intensityontheclimate-growthrelationshipofdifferentcrown
classes in Cedrus atlantica (Manetti).
Material and methods A 20-year annual survey was con-
ductedonplots managed under contrastedthinningregimes in
a site of the southern French Alps. Using a linear mixed
modeling approach, we evaluated the modulation of the
growth response to annual climate by thinning (climate×thin-
ning interaction effect) during the experiment. The effect of
thinning on the growth sensitivity to annual climate and the
effectofthinningonthegrowthresponsetopointeryearswere
also quantified.
Results The highest intensity of thinning significantly
changedtheclimate-growthrelationshipofthetwomostdom-
inant crown classes. Heavy thinning reduced the impact of
negative pointer years during a period of 4–5 years and im-
proved the post-drought recovery for a decade. Heavily
thinned plots and dominant crown classes had significantly
higher relative growth sensitivities to annual climate over the
studied period.
Conclusions Forest management has the potential to reduce
theeffectofwaterdeficitonthegrowthofAtlascedarstands.We
provide keystones for future silvicultural guidelines, in the con-
textofalargerintroductionofC.atlanticaintheFrenchterritory.
Forest management techniques such as intermediate stand-tending practices (e.g., thinning) can promote climatic resiliency in forest stands by moderating tree competition. Residual trees gain increased access to environmental resources (i.e., soil moisture, light), which in turn has the potential to buffer trees from stressful climatic conditions. The influences of climate (temperature and precipitation) and forest management (thinning method and intensity) on the productivity of red pine (Pinus resinosa Ait.) in Michigan were examined to assess whether repeated thinning treatments were able to increase climatic resiliency (i.e., maintaining productivity and reduced sensitivity to climatic stress). The cumulative productivity of each thinning treatment was determined, and it was found that thinning from below to a residual basal area of 14 m²·ha⁻¹ produced the largest average tree size but also the second lowest overall biomass per acre. On the other hand, the uncut control and the thinning from above to a residual basal area of 28 m²·ha⁻¹ produced the smallest average tree size but also the greatest overall biomass per acre. Dendrochronological methods were used to quantify sensitivity of annual radial growth to monthly and seasonal climatic factors for each thinning treatment type. Climatic sensitivity was influenced by thinning method (i.e., thinning from below decreased sensitivity to climatic stress more than thinning from above) and by thinning intensity (i.e., more intense thinning led to a lower climatic sensitivity). Overall, thinning from below to a residual basal area of 21 m²·ha⁻¹ represented a potentially beneficial compromise to maximize tree size, biomass per acre, and reduced sensitivity to climatic stress, and, thus, the highest level of climatic resilience.
The mechanistic understanding of isotope fractionation processes is increasing but we still lack detailed knowledge of the processes that determine the isotopic composition of the tree-ring archive over the long term. Especially with regard to the path from leaf photosynthate production to wood formation, post-assimilation fractionations/processes might cause at least a partial decoupling between the leaf isotope signals that record processes such as stomatal conductance, transpiration and photosynthesis, and the wood or cellulose signals that are stored in the paleophysiological record. In this review, we start from the rather well understood processes at the leaf level such as photosynthetic carbon isotope fractionation, leaf water evaporative isotope enrichment and the issue of the isotopic composition of inorganic sources (CO2 and H2O), though we focus on the less explored 'downstream' processes related to metabolism and transport. We further summarize the roles of cellulose and lignin as important chemical constituents of wood, and the processes that determine the transfer of photosynthate (sucrose) and associated isotopic signals to wood production. We cover the broad topics of post-carboxylation carbon isotope fractionation and of the exchange of organic oxygen with water within the tree. In two case studies, we assess the transfer of carbon and oxygen isotopic signals from leaves to tree rings. Finally we address the issue of different temporal scales and link isotope fractionation at the shorter time scale for processes in the leaf to the isotopic ratio as recorded across longer time scales of the tree-ring archive.
Climate Explorer (www.climexp.knmi.nl) is a web-based application for climatic research that is managed by the Royal Netherlands Meteorological Institute (KNMI) and contains a comprehensive collection of climatic data sets and analysis tools. One of its fields of application is high-resolution paleoclimatology. We show how Climate Explorer can be used to explore and download available instrumental climate data and derived time series, to examine the climatic signal in uploaded high-resolution paleoclimate time series, and to investigate the temporal and spatial characteristics of climate reconstructions. We further demonstrate the value of Climate Explorer for high-resolution paleoclimate research using a dendroclimatic data set from the High Atlas Mountains in Morocco.
The forest canopy is one of the chief determinants of the microhabitat within the forest. It affects plant growth and survival, hence determining the nature of the vegetation, and wildlife habitat. A plethora of different techniques have been devised to measure the canopy. Evaluation of the literature reveals confusion over what is actually being measured. This paper distinguishes two basic types of measurement: canopy cover is the area of the ground covered by a vertical projection of the canopy, while canopy closure is the proportion of the sky hemisphere obscured by vegetation when viewed from a single point. The principal techniques used to measure canopy cover, canopy closure, and a number of related measures are described and discussed. The advantages and limitations are outlined and some sampling guidelines are provided. The authors hope to clarify the nature of the measurements and to provide foresters with sufficient information to select techniques suitable for their needs.
This paper describes the construction of an updated gridded climate dataset (referred to as CRU TS3.10) from monthly observations at meteorological stations across the world's land areas. Station anomalies (from 1961 to 1990 means) were interpolated into 0.5° latitude/longitude grid cells covering the global land surface (excluding Antarctica), and combined with an existing climatology to obtain absolute monthly values. The dataset includes six mostly independent climate variables (mean temperature, diurnal temperature range, precipitation, wet-day frequency, vapour pressure and cloud cover). Maximum and minimum temperatures have been arithmetically derived from these. Secondary variables (frost day frequency and potential evapotranspiration) have been estimated from the six primary variables using well-known formulae. Time series for hemispheric averages and 20 large sub-continental scale regions were calculated (for mean, maximum and minimum temperature and precipitation totals) and compared to a number of similar gridded products. The new dataset compares very favourably, with the major deviations mostly in regions and/or time periods with sparser observational data. CRU TS3.10 includes diagnostics associated with each interpolated value that indicates the number of stations used in the interpolation, allowing determination of the reliability of values in an objective way. This gridded product will be publicly available, including the input station series (http://www.cru.uea.ac.uk/ and http://badc.nerc.ac.uk/data/cru/). © 2013 Royal Meteorological Society
The model of competition for light presented here uses modular autonomy to incorporate plasticity in plant growth under competition. Once plants are characterized as composed of modules, then model structure for competition changes in a fundamental way. Interactions between the plant module and its local resource environment must be modeled rather than the traditionally viewed interactions between whole plants and their neighbors. We assume that a plant module interacts with its local resource environment regardless of whether this environment was altered by a neighbor or by the same plant. Two spatial processes are considered: resource acquisition and growth. The spatial pattern of resource acquisition by a module determines a growth and allocation pattern, e.g., the elongation of branches into a gap. The spatial structure of a module and its connection to the whole tree then determines the pattern of resource distribution and resource acquisition of the next time step. Plasticity of plant growth is incorporated by variation in both the efficiency of resource capture of modules and patterns of resource allocation for individuals of different canopy positions and results in individuals in the community having different spatial structures. The model simulates the three-dimensional development of tree crown structure over time. It is applied to the 30-yr development of a dense, spatially aggregated stand of Abies amabilis beginning with an initial pattern of seedlings. The importance of incorporation of plasticity is apparent when the model output is compared to observed height distribution and crown structure data. Simulations indicate that asymmetrical crown development, one form of plasticity, is advantageous to stand productivity and becomes more advantageous as the degree of spatial aggregation in the initial spacing of trees increases.
The effects of a systematic thinning (alternate row) on water stress and growth in a 19-year-old Douglas-fir plantation (Pseudotsugamenziesii var. menziesii Franco) was studied during 5 years in northeastern France. Thinning has an important effect on water balance. The increase of the soil water reserve led to a lower duration and level of water stress in the thinned plot, especially during the first 3 years after thinning. This study revealed a rapid evolution of the water balance, since the evapotranspiration ratio of the two plots (control and thinned) had increased from 0.83 during the 1st year to 1.03 during the 5th year after thinning. Together with microclimate influences, thinning increased tree growth substantially (more than 100%); this growth increase resulted from a higher growth rate and longer growth periods (from 26 to 49 days).
A key objective for sustainable agriculture and forestry is to breed plants with both high carbon gain and water-use efficiency (WUE). At the level of leaf physiology, this implies increasing net photosynthesis (A N) relative to stomatal conductance (g s). Here, we review evidence for CO2 diffusional constraints on photosynthesis and WUE. Analyzing past observations for an extensive pool of crop and wild plant species that vary widely in mesophyll conductance to CO2 (g m), g s, and foliage A N, it was shown that both g s and g m limit A N, although the relative importance of each of the two conductances depends on species and conditions. Based on Fick's law of diffusion, intrinsic WUE (the ratio A N/g s) should correlate on the ratio g m/g s, and not g m itself. Such a correlation is indeed often observed in the data. However, since besides diffusion A N also depends on photosynthetic capacity (i.e., V c,max), this relationship is not always sustained. It was shown that only in a very few cases, genotype selection has resulted in simultaneous increases of both A N and WUE. In fact, such a response has never been observed in genetically modified plants specifically engineered for either reduced g s or enhanced g m. Although increasing g m alone would result in increasing photosynthesis, and potentially increasing WUE, in practice, higher WUE seems to be only achieved when there are no parallel changes in g s. We conclude that for simultaneous improvement of A N and WUE, genetic manipulation of g m should avoid parallel changes in g s, and we suggest that the appropriate trait for selection for enhanced WUE is increased g m/g s.
The effects of thinning on xylem water potential ('1'wp), transpiration (E) and stornata! conductance (gs) were analysed during the second and third year alter thinning in a holm oak (Quercus i/ex L.) coppice aged 45 in Southern Sardinia. Data have been
,, collected from sample trees in a thinned and in a contrai plot. The thinning applied was intermediate and heavy (60% of basai area removed) and strongly modified stand structure, stocking and canopy cover. Daily courses of '1'wp, E and gs highlighted slight water
stress conditions far the examined stand. Data analysis showed the existence of di/terence between the two years of measurements, due to the different seasonal climatic course, and between contro! and thinned plots. Despite similar daily and seasonal patterns the thinned plot showed higher values than the contro! plot with significant di/terence (P<0.05) in '1'wp, E and gs. The importance of the interactions among site characteristics, thinning and tree physiological status, in arder to define a well ecological-based silvicultura! system far holm oak stands, is discussed.
In this paper we explore how well distance-independent competition measures explain variation in the height and diameter squared growth of individual conifer trees. We investigated a number of stand-level density indices and individual tree competition indices which incorporate tree sizes, but do not include location. We model growth of individual trees as potential growth reduced by competition. The reduction in mean square error relative to no competition index was used to judge performance of each competition index which varies by species and growth component (height or diameter squared growth). Results are summarized by species and type of competition index. The distance-independent measures are also compared to selected distance-dependent measures shown in recent research work to perform well for conifer species. It was found that a new class of distance-independent indices that includes estimated crown parameters performs on par with the best distance-dependent competition indices when used in conjunction with models of individual tree height and diameter squared growth. For. Sci. 41(2):360-377.
We studied physiological responses of mature black walnut (Juglans nigra L.) trees to determine the time necessary for photosynthetic adaptation to plantation thinning. Measurements were taken before treatment (July 25, 2007) and for the first 3 days after thinning (July 29, 30, and 31, 2007). Measurements did not continue in August because trees had developed leaf anthracnose and senescence was occurring, but measurements resumed on May 29, 2008 and July 29, 2008. Repeated measures of net photosynthetic rates (A) showed that thinned trees did not respond immediately to partial release, but nearly doubled in A compared with a 35% increase in control trees 1 year after thinning. Significant increases in light, leaf water status, relative humidity of the air, and nitrogen content per unit leaf area were also found in thinned trees 1 year after treatment. From these variables, light (r2 = 0.79) showed the strongest relationship with A. Results suggest that black walnut requires a full growing season before it responds to treatment when thinned late in the growing season. Thinning earlier, such as in June, may trigger a more rapid adaptation in A of thinned trees that was not detected in our study.
Responses following the application of six precommercial thinning treatments to a 27-year-old Douglas-fir plantation (2.4-m spacing, height at age 100 = 24 m) have been monitored for 25 years. Spacing after thinning ranged from 3.4 m to 8.1 m. Immediately following thinning, trees exhibited thinning shock; that is, substantial height growth reductions. The severity and duration of the shock effect were partially related to the severity of thinning. From 15 to 25 years following thinning, however, height growth was positively related to growing space with the best height growth at the wider spacings. Diameter growth increased following thinning, with the range in diameter growth rates between spacings increasing over time. Basal area and volume growth per hectare were reduced by treatment, but the differences among spacings are decreasing. Forest Sci. 29:33-46.
This study investigated the effects of thinning intensities on tree water use and growth of 50-year-old Korean pine forests for four years. Thinning was conducted with two intensities (light thinning, heavy thinning, and control) in March 2012. Tree water use was estimated from sap flux density using Granier-type thermal dissipation sensors on 84 of total 103 trees. Tree diameter growth was measured in 97 trees with a dendrometer and converted to aboveground biomass increment using an allometric equation. Sap flux density increased initially in both thinning groups, but the effects of light thinning decreased over time. In the heavy thinning plot, sap flux density was stimulated for the entire study period. While light-thinning affected little on tree growth, tree diameter growth significantly increased from second year and this enhancement increased with time in the heavy-thinning plot. The tree diameter and growth rate were positively correlated in the light-thinning plot and negatively correlated in the heavy-thinning plot. The enhancement of sap flux density and diameter growth caused higher tree water use and tree level aboveground net primary productivity in heavy-thinning plot. Due to higher water use in the heavy thinning plot, increase in tree-level water use efficiency was observed in the high growth year only. Our results indicate that physiological responses of trees differed depending on thinning intensity and heavy thinning is an appropriate management practice for mature pine plantations.
Mixed-species plantations containing non-nitrogen (N)-fixing species and N-fixing species have the potential to increase the productivity and the ecophysiological performance of the target tree species in comparison to monoculture. However, there are few and conflicting data on the effects of fixed N transfer on species water use efficiency in the short, medium and long term. In this paper, we evaluate the productivity and intrinsic water use efficiency (WUE i), i.e., the ratio of photosynthesis (A) to stomatal conductance (g s), in Quercus robur L. (pedunculate oak) stands growing in monoculture and in combination with Alnus cordata Loisel. (Italian alder) in a ratio of 25% (stand F25%) and 50% (stand F50%). We analyzed d 13 C in tree rings as a proxy of the inter-annual changes in WUE i , while the influence of the stomatal conductance was explored through d 18 O data. Our results indicate a considerable increase in cumulative basal area (BAI) and in WUE i in the two mixed stands during the period 1990–2002, largely resulting from an increase in N availability, due to the N-fixing species that induced an enhancement of A. After 2002, the differences between the three stands in terms of N% in tree rings, BAI and WUE i leveled off, when natural mortality or management practices decreased the competitive ability of Italian alder. Our study shows the importance of intercropping with a suitable N-fixing species to ensure high levels of productivity and water use efficiency of the target tree species in a Mediterranean-type agroforestry system, but also the need to understand how species interaction changes in time and space with a view to setting the management criteria to maximize tree performance.
http://authors.elsevier.com/a/1TjEU1L~Gw8~wT
Increasing frequency of extremely dry and hot summers in some regions emphasise the need for silvicultural
approaches to increase the drought tolerance of existing forests in the short term, before long-term
adaptation through species changes may be possible. The aim of this meta-analysis was to assess the
potential of thinning for improving tree performance during and after drought. We used results from
23 experiments that employed different thinning intensities including an unthinned control and focused
on the response variables: radial growth, carbon- and oxygen-isotopes in tree-rings and pre-dawn leafwater
potential. We found that thinning effects on the growth response to drought differed between
broadleaves and conifers, although these findings are based on few studies only in broadleaved forests.
Thinning helped to mitigate growth reductions during drought in broadleaves, most likely via increases
of soil water availability. In contrast, in conifers, comparable drought-related growth reductions and
increases of water-use efficiency were observed in all treatments but thinning improved the postdrought
recovery and resilience of radial growth. Results of meta-regression analysis indicate that benefits
of both moderate and heavy thinning for growth performance following drought (recovery and resilience)
decrease with time since the last intervention. Further, growth resistance during drought became
smaller with stand age while the rate of growth recovery following drought increased over time irrespective
of treatment. Heavy but not moderate thinning helped to avoid an age-related decline in mediumterm
growth resilience to drought. For both closed and very open stands, growth performance during
drought improved with increasing site aridity but for the same stands growth recovery and resilience following
drought was reduced with increasing site aridity. This synthesis of experiments from a wide geographical
range has demonstrated that thinning, in particular heavy thinning, is a suitable approach to
improve the growth response of remaining trees to drought in both conifers and broadleaves but the
underlying processes differ and need to be considered.
Prescribed burning (PB) is a widespread management technique for wildfire hazard abatement. Understanding PB effects on tree
ecophysiology is key to defining burn prescriptions aimed at reducing fire hazard in Mediterranean pine plantations, such
as Pinus pinea L. stands. We assessed physiological responses of adult P. pinea trees to PB using a combination of dendroecological, anatomical, hydraulic and isotopic analyses. Tree-ring widths, xylem
cell wall thickness, lumen area, hydraulic diameter and tree-ring δ13C and δ18O were measured in trees on burned and control sites. Vulnerability curves were elaborated to assess tree hydraulic efficiency
or safety. Despite the relatively intense thermal treatment (the residence time of temperatures above 50 °C at the stem surface
ranged between 242 and 2239 s), burned trees did not suffer mechanical damage to stems, nor significant reduction in radial
growth. Moreover, the PB did not affect xylem structure and tree hydraulics. No variations in 13C-derived water use efficiency were recorded. This confirmed the high resistance of P. pinea to surface fire at the stem base. However, burned trees showed consistently lower δ18O values in the PB year, as a likely consequence of reduced competition for water and nutrients due to the understory burning,
which increased both photosynthetic activity and stomatal conductance. Our multi-approach analysis offers new perspectives
on post-fire survival strategies of P. pinea in an environment where fires are predicted to increase in frequency and severity during the 21st century.
The distributional pattern of crowns was analyzed by the coverage of crown covers (regarded as an ellipse) and their center positions and compared with those of stems (standing positions) in several types of natural mixed forests (6 stands) of Hokkaido. The distributions of the crown-cover centers were uniform or random in upper layer trees, and all random in total trees. The crown cover distributions (based on coverage) in a lower layer were more contagious than those in an upper layer, while the distributions of the stems were usually contagious. In the measuring of inter-layer distribution overlapping, the crown covers and their centers showed the same exclusive patterns between 2 of 3 layers, irrespective of the stem overlapping. Trees survive by dividing their crown spaces in a level and escaping from the upper crowns. -from Author
The character of an ecosystem is determined in part by the balance of competition among higher plant species. In most habitats, the physical environment is conducive to the growth and survival of more species than actually persist and compete at a particular site. Competition is, thus, often a sorting proeess that determines which plant species occupy a site. The higher plant species composition in turn has a large bearing on species membership in other trophic levels. Although the importance of competition among higher plants is well appreciated and the subject of much study, relatively little progress has been made toward an understanding of how plants compete with one another for resources, and which traits are of particular advantage in this comptition.
Soil water dynamics under a mixed stand of mature sessile and pedunculate oaks were studied both under natural conditions and during imposed water shortages in a lysimeter. Root densities of each species were described in situ by counting roots in the trench surrounding the dry plot. Soil water contents and potentials, and pre-dawn leaf water potentials (Psi(wp)) were monitored during three successive years. Soil water retention characteristics were obtained from field measurements of water potential and water content. The decreasing rooting density with depth was strongly related to soil physical properties. The root system was separated into two compartments by a layer with a high clay content. The deepest soil compartment was mainly explored by fine roots. Neutron probe measurements allowed the detection of variations in water content down to a depth of 2.00 m. The distribution of water uptake among the different soil layers changed when drought increased. Water was extracted from the deepest reservoir, and capillary rises even occurred after partial water depletion in the upper part of the soil. Seasonal trends of pre-dawn leaf water potential generally matched those of soil water potential in the wettest rooted zone, which was at - 140 cm. In the upper, dry, horizons, the sharp loss of soil hydraulic conductivity reduced water transport to roots leading to impossible equilibrium between roots and soil at pre-dawn. Finally, Psi(wp) presented a low sensitivity to variations of total soil water content between 40% and 100% of extractable water. Below this threshold, Psi(pw) decreased sharply to a minimal value of about -2.0 MPa.
Forest thinning has the potential to be used as a water supply augmentation strategy through the reduction
of sapwood and leaf areas that also decreases stand evapotranspiration. This study investigated the
long term effects of a range of thinning treatments (patch-cutting, uniform thinning, strip-thinning,
understorey removal) on the vegetation structure and water yield of mountain ash (Eucalyptus regnans)
forests in south eastern Australia. The paired catchment method and Light Detection and Ranging (LiDAR)
data were utilised to assess the post-thinning changes in water yield and vegetation structure respectively.
The first post-treatment phase started at the end of the treatments in the late 1970s/early
1980s until the suspension of measurements in 1997, the second post-treatment phase started when
the measurements resumed in 2007/2008 until a wildfire in February 2008. Up to 36% increase in annual
water yield was detected during the first post-treatment phase. Strip-thinning produced the largest
cumulative increase in water yield (up to 1813 mm), followed by uniform thinning and patch-cutting.
The magnitude of the treatment effect appeared to be amplified during a very wet/dry period, which
may be due to post-thinning changes in the runoff generation processes. During the second post-treatment
phase, a trend of decreased water yield was detected at several treated catchments. Canopy height
profiles (CHPs) and mean effective leaf area index (LAI) that were derived from LiDAR data, along with
recent forest inventory data, indicated a recovery of vegetation cover. This may partially explain the
decrease in water yield. Meanwhile, the decade-long drought (1997–2008) that coincided with this period
of decreased water yield might have exacerbated its magnitude. Thinning may not be a net water gain
over the long term if the recent trend of decreasing water yield continues.
For accurate interpretation of oxygen isotopes in tree rings (d18O), it is necessary to disentangle
the mechanisms underlying the variations in the tree’s internal water cycle and to
understand the transfer of source versus leaf water d18O to phloem sugars and stem wood.
� We studied the seasonal transfer of oxygen isotopes from precipitation and soil water
through the xylem, needles and phloem to the tree rings of Larix decidua at two alpine sites
in the L€otschental (Switzerland). Weekly resolved d18O records of precipitation, soil water,
xylem and needle water, phloem organic matter and tree rings were developed.
� Week-to-week variations in needle-water 18O enrichment were strongly controlled by
weather conditions during the growing season. These short-term variations were, however,
not significantly fingerprinted in tree-ring d18O. Instead, seasonal trends in tree-ring d18O predominantly
mirrored trends in the source water, including recent precipitation and soil water
pools. Modelling results support these findings: seasonal tree-ring d18O variations are captured
best when the week-to-week variations of the leaf water signal are suppressed.
� Our results suggest that climate signals in tree-ring d18O variations should be strongest at
temperate sites with humid conditions and precipitation maxima during the growing season.
Biomass accumulation (annual net primary productivity, NPP) in a plantation of Musa sp., Musaceae is linearly correlated with solar irradiance (IR) between 100 and 32% of ambient levels (NPP = 0.82 IR + 20.42, p < 0.01, for the normalized data). The irradiance effects are clearly reflected in the δ13C values of leaf organic matter that are also linearly correlated with irradiance levels (with a slope of 0.23%o for any 10% decrease in IR). We conclude that changes in the organic δ13C values faithfully record the irradiance effects on the plants photosynthetic capacity since they are not accompanied by changes in concentration and δ13C values of air CO2 or by changes in the δ18O values of the leaf cellulose. The results provide a unique, quantitative demonstration of (1) the importance of changes in irradiance such as those associated with cloudiness and aerosols for NPP and (2) the usefulness of the combined 13C, 18O analysis for recording and interpreting these effects.
Long-term (10 years) growth responses of residual trees to prescribed fire and thinning were evaluated using standard dendrochronological protocols to understand the broader effects of the treatments on mixed-oak forest ecosystems in southern Ohio. Analysis of 696 increment cores (348 trees ≥ 25 cm DBH; five species) from 80 0.1 ha permanent plots distributed evenly across four treatments (control, thin, thin + burn, burn) indicated substantial increase in tree basal area increment (BAI) following the treatment. Post-treatment mean BAI of trees from the three active treatments ranged from 20.52 to 23.55 cm2 y−1 compared with pre-treatment values of 16.86–17.07 cm2 y−1. BAI rates (averaging 15.13 and 16.33 cm2 y−1, respectively, for pre- and post-treatments) in the control plots did not change much over time. Mechanical treatments were more effective than prescribed fire at enhancing BAI of trees. However, basal area growth depended to some degree on the severity of prescribed fire. Analysis of percent BAI change revealed an interesting temporal trend with moderate to major growth releases during the first 5-year post-treatment period, and a slight attenuation thereafter, suggesting the need for periodic application of treatments to sustain growth over a longer timescale. Growth responses varied greatly among species, with yellow-poplar and hickories exhibiting the highest and lowest post-treatment BAI rates of 31.11 and 15.71 cm2 y−1, respectively. Given their variable growth responses, integrating residual trees into current monitoring programs may help in elucidating the consequences of prescribed fire and thinning on forest dynamics and development.
Marine (baseline) air from Cape Grim (41°S), collected and archived in high-pressure metal containers, provides a history of delta13C in atmospheric methane from 1978. A similar history is obtained from air pumped from different layers of the firn at Law Dome, Antarctica, after correction for diffusion and gravitational settling effects in the firn. The archive records are linked to measurements since 1992 using 5-L glass flasks filled at Cape Grim, and compared to data since 1989 from a comparable site at Baring Head, New Zealand. Over 18 years the delta13C of atmospheric methane in the extratropical Southern Hemisphere has increased by ~0.60/00 while the methane mixing ratio increased by ~200 ppb. The delta13C growth rate decreases over the 18-year period, but by relatively less than the simultaneous decrease in mixing ratio growth rate. The overall increase in delta13C is significantly smaller than, and the recent slowing is in conflict with, previous estimates [Stevens and Engelkemeir, 1989]. The long-term trend in delta13C, and the different shape to the trend in mixing ratio, are shown to be consistent with constant global methane sources and sinks since 1982. The slower equilibration of observed delta13C, compared to that of the mixing ratio, is an example of an effect pointed out recently by Tans [1997]. The data presented here constrain changes in the relative mix of isotopically heavy and light sources to be small and suggest that there was little change in the ratio of anthropogenic to natural sources in the 1978 to 1995 period.
Interspecific competition is a key process determining the dynamics of mixed forest stands and influencing the yield of multispecies tree plantations. Trees can respond to competitive pressure from neighbors by crown plasticity, thereby avoiding competition. We employed a high-resolution ground-based laser scanner to analyze the 3-dimensional extensions and shape of the tree crowns in a near-natural broad-leaved mixed forest in order to quantify the direction and degree of crown asymmetry of 15 trees (Fagus sylvatica, Fraxinus excelsior, Carpinus betulus) in detail. We also scanned the direct neighbors and analyzed the distance of their crown centres and the crown shape with the aim to predict the crown asymmetry of the focal tree from competition-relevant attributes of its neighbors. It was found that the combination of two parameters, one summarizing the size of the neighbor (DBH) and one describing the distance to the neighbor tree (HD), was most suitable for characterizing the strength of the competitive interaction exerted on a target tree by a given neighbor. By summing up the virtual competitive pressure of all neighbors in a single competitive pressure vector, we were able to predict the direction of crown asymmetry of the focal tree with an accuracy of 96° on the full circle (360°).
Erica arborea (L) is a widespread Mediterranean species, able to cope with water stress and colonize semiarid environments. The eco-physiological plasticity of this species was evaluated by studying plants growing at two sites with different soil moistures on the island of Elba (Italy), through dendrochronological, wood-anatomical analyses and stable isotopes measurements. Intra-annual density fluctuations (IADFs) were abundant in tree rings, and were identified as the key parameter to understand site-specific plant responses to water stress. Our findings showed that the formation of IADFs is mainly related to the high temperature, precipitation patterns and probably to soil water availability, which differs at the selected study sites. The recorded increase in the 13C-derived intrinsic water use efficiency (WUEi) at the IADFs level was linked to reduced water loss rather than to increasing C assimilation. The variation in vessel size and the different absolute values of δ18O among trees growing at the two study sites underlined possible differences in stomatal control of water loss and possible differences in sources of water uptake. This approach not only helped monitor seasonal environmental differences through tree-ring width but also added valuable information on E. arborea responses to drought and their ecological implications for Mediterranean vegetation dynamics.
A procedure is described for estimating the transpiration rate of trees in stands with understory vegetation. The procedure combines soil water balance measurements of stand evapotranspiration rate with a simple vapor diffusion model that requires occasional intensive measurements of stomatal conductance of the trees and understory vegetation. Weekly average transpiration rates of 22-yr-old Douglas fir trees in a thinned stand during sunny weather in July ranged from 23.6 L∙tree⁻¹∙d⁻¹ when θe the fraction of extractable soil water remaining in the root zone, was 0.79 to 4.9 L∙tree⁻¹∙d⁻¹ when θe was 0.20. The transpiration rate of trees in the thinned stand, which contained a salal understory, was very similar to that in a nearby unthinned stand with virtually no understory vegetation. As θe decreased from slightly more than 0.8 to slightly less than 0.2, the fraction of evapotranspiration from the thinned stand due to the salal understory increased from approximately 40 to 65%. Competition for soil water by the understory was considered to be a contributing reason why tree diameter growth in the thinned stand was only slightly greater than in the unthinned stand.
In stands of Salix viminalis growing near Edinburgh accumulated dry matter was linearly related to accumulated intercepted radiation until heavy leaf fall. The slopes of the relationships for above-ground dry matter were 0.99 g MJ-1 in 1984 and 1.38 g MJ-1 in 1985. This difference in light-use efficiency (rather than a difference in amounts of light intercepted) was primarily responsible for a difference between years in above-ground dry matter production (11 t ha-1y-1 in 1984 and 14 t ha-1y-1 in 1985). Greater efficiency in 1985 was attributed to better water and nutrient supplies and lower levels of incoming radiation. Leaf area index reached 2.4 in 1984 and 4.5 in 1985. Stems alone intercepted 60% of total solar radiation after leaf fall in 1984 and 47% in 1985 when the 'stem area index' reached 1.5. Leaf-area development in spring was a function of thermal time, with an earlier starting time for the coppiced stand in 1984, resulting in c20% greater potential light interception (1240 MJ m-2 y-1). -from Authors
The growth and form of a modular organism is determined by the rigid rules of iteration (branching) and the differential response of each growing point to the local conditions around it. The degree of response of each individual module is itself dependent on the degree of physiological integration of the whole organism. Morphological continuity is a requisite but not a guarantee of physiological integration. In general, 'phalanx' growth-forms show more physiological integration than 'guerrilla' growth-forms. Trees, as an example of morphologically integrated modular organisms, show a variety of responses to the presence of modules both of the same and of different species. When two modules interact, three extreme responses are possible: (i) both modules stop growing or change their orientation, or both; (ii) one module is inhibited while the other continues its growth; (iii) neither is affected by the presence of the other. The first case produces a clear separation ('shyness') between neighbouring modules both within and between trees. The second case produces a hierarchy of dominance-suppression. Finally, failure to 'recognize' the presence of a neighbour module may result in physical damage by abrasion of both participants. Under certain circumstances, this can also produce a visual impression of 'shyness'. The importance of this 'recognition' mechanism is discussed for both modular animals and plants.
Process-based models open the way to useful predictions of the future growth rate of forests and provide a means of assessing the probable effects of variations in climate and management on forest productivity. As such they have the potential to overcome the limitations of conventional forest growth and yield models, which are based on mensuration data and assume that climate and atmospheric CO2 concentrations will be the same in the future as they are now. This book discusses the basic physiological processes that determine the growth of plants, the way they are affected by environmental factors and how we can improve processes that are well-understood such as growth from leaf to stand level and productivity. A theme that runs through the book is integration to show a clear relationship between photosynthesis, respiration, plant nutrient requirements, transpiration, water relations and other factors affecting plant growth that are often looked at separately. This integrated approach will provide the most comprehensive source for process-based modelling, which is valuable to ecologists, plant physiologists, forest planners and environmental scientists. * Includes explanations of inherently mathematical models, aided by the use of graphs and diagrams illustrating causal interactions and by examples implemented as Excel spreadsheets* Uses a process-based model as a framework for explaining the mechanisms underlying plant growth* Integrated approach provides a clear and relatively simple treatment* Includes access to electronic and printed spreadsheet examples of the variations of the ecophsyiological model
There was no published abstract for this.
I collaborated with the celebrated expert in plant form Prof Karl Niklas (Cornel), having myself been inspired by anatomical trees such as the pulmonary tree (in our lungs) and its arterial structures. Using a functional analysis and a generic model of rules for branching, we explained how the space of possible designs can be mapped out, noted the biological limits on this space and considered the optimal sets of design (Pareto sets) that are reflected in real plants. The functions are optimal light interception, mechanical resistance (e.g. of winds and gravity) and transportation of materials. The results are illustrative of natural multi-objective optimisation problems in general.
Interception loss represents an important factor of water balance. The reduction of interception loss through silvicultural treatments to the benefit of water yield is very important for countries with large periods of limited rainfall like Greece. In the context of climate change and its possible effects on water availability, oak ecosystems can play a significant role in water production, as they comprise the largest part of the forested area in Greece. The objective of this study is to investigate the relationships between water interception changes, as a result of different forest management treatments, and water yield. For this reason, experimental watersheds have been established for the study of the hydrological impacts of thinning and clearcutting in an oak ecosystem in northern Greece. Two watersheds were used as control while different combinations of thinning (removal 50% of basal area) and clearcutting treatments were used in the other three study watersheds. Canopy annual interception amounted for 9.0%, 6.7% and 1.8% of the total precipitation in the untreated, thinned and clearcut plots respectively. The practiced thinning and clearcutting operations increased the available amount of water by a mean annual average of 13.2 mm and 42.8 mm respectively compared to the control watersheds. The total water surplus represented 29.5%, 30.9% and 33.9% of the average annual precipitation for the control, thinned and clearcut plot respectively. Surface flow was very low even during large rainfall events, possibly due to the soil and bedrock attributes and the topography of the area. Analogous silvicultural treatments can increase water availability but they should incorporate reduced-impact logging and skidding practices and thus cause the least possible soil disturbance, by carefully selecting the best suited wood harvesting systems and methods. © 2010 Elsevier B.V.
Rapid, reliable and meaningful estimates of forest canopy are essential to the characterization of forest ecosystems. In this paper the accuracy of digital hemispherical (DHP) and cover (DCP) photography for the estimation of canopy properties in deciduous forests was evaluated. Leaf area index (LAI) estimated from both these photographic methods and from light transmittance data derived from DHP were compared with direct measurements obtained by litter traps (LAILT) and an AccuPAR ceptometer. Also, comparison with different gap fraction methods used to calculate LAI in DHP and LAI-2000 PCA were performed.