Quercus Forest Research Articles

Holocene palaeoecological changes in a transitional climate zone of western-central Mexico: The pollen and non-pollen palynomorphs record

The Alberca de Tacámbaro (AT) is located at a transitional zone between tropical and temperate climates at the core of the North American Monsoon area. This location features a mosaic vegetation comprising pine-oak forests and tropical dry forests. Currently there is no information regarding the dynamics or evolution during the Holocene of these vegetation types. The palynological record of the last 9400 years BP preserved in the lacustrine sequence of the AT was used to document changes in the composition of terrestrial and aquatic communities, evenness, and rate of change. Pinus and Quercus forests dominated the terrestrial palynological record, but mesophytic forests were also recorded throughout the sequence. Four tropical dry forest taxa assemblage expansions were identified at 9200 to 8420 yr BP; 5900 to 5230 yr BP; 3100 to 2800 yr BP; and 2300 to 2000 yr BP. These phases correlated with times of reduced North American Monsoon intensity, suggesting that these communities thrived during drought periods. Variations in non-pollen palynomorphs were synchronic with the lithostratigraphic, geochemical data as well as with the terrestrial changes. During the Meghalayan, compositional shifts in the vegetation and increases in the herbaceous elements indicated human impact, while aquatic taxa, suggested eutrophic and warmer conditions in the lake. By examining the history of this vegetation mosaic, the data on temporal vegetation dynamics during the Holocene offered clues about the response to ongoing global warming and how climate change will likely shape plant communities in western-central Mexico.

Trends in land cover and in pollen concentration of Quercus genus in Alentejo, Portugal: Effects of climate change and health impacts

Mediterranean forests dominated by Quercus species are of great ecological and economic value. The Quercus pollen season, peaking in April, varies in concentration due to geographical and climatic factors and has a remarkable allergenic potential. This study investigates Quercus trends in the Alentejo region of Portugal and examines the influence of meteorological parameters on DPC, PSD and SPIn, as well as the impact on allergic respiratory disease. The results show a progressive increase in Quercus Forest area from 1995 to 2018. Temperature and Precipitation are a key factor influencing pollen concentration, especially before peak of pollen season and prior to the pollen season. Particularly prior to the season, the precipitation of t-6 before influence, significantly, the pollen production. On the other hand, Global Srad and RH determine the beginning of the season. Using quartile-based categorization and multivariate statistical analysis, we identified years and scenarios within the IPCC projections where meteorological conditions influence may SPIn production. The study found a statistically significant correlation between high Quercus pollen concentrations in April and increased antihistamine sales. These findings are crucial for enhancing pollen forecast models and early warning systems.

Season of burn has minimal effect on groundlayer community structure and composition in an Appalachian mixed‐oak forest

The groundlayer flora has a disproportionate influence on ecosystem function and contributes to the biodiversity in temperate Quercus forests of eastern North America. Historically open understory conditions perpetuated, in part by fire, have become closed and homogenized by long‐term fire exclusion, likely impacting the groundlayer community. We explored the effects of burn season (unburned = CON, dormant season = DSB, growing season = GSB) on groundlayer (<1 m) vegetation attributes pre‐ and post‐burn. The difference (post‐burn – pre‐burn) in tree cover was greater in GSB (+8.22%) than DSB (+1.24%) and CON (+0.15%), while the change in forb cover was greater in GSB (+1.17%) than CON (−0.15%). Minor effects of burning were observed in diversity metrics, with the change in forb richness greater in GSB (+0.11 species/m2) than CON (−0.78 species/m2), while the change in tree richness was greater in GSB (+1.11 species/m2) than DSB (−1.11 species/m2) and CON (−1.67 species/m2). Nonmetric multi‐dimensional scaling provided evidence that between pre‐ and post‐burn, modest composition shifts in DSB and GSB were associated with more open conditions and lower litter depth. Understory composition did not vary among burn treatments pre‐burn, while post‐burn, composition differed significantly between CON and DSB and DSB and GSB. However, overall, a growing season burn had relatively minor effects on the groundlayer community compared to a dormant season burn. A better understanding of multiple factors affecting groundlayer response to burning is critical to the effective use of prescribed burning in attaining restoration goals.

Holocene climate variability and the effect of anthropogenic activities on the vegetation landscape of western-central Mexico

Atmospheric forcings control climate variability and at the same time control vegetation distribution and forest fires during the Holocene. Paleoenvironmental studies are scarce in western Mexico, particularly those documenting vegetation change, landscape dynamics, and fire regimes. This study presents a vegetation and fire occurrence reconstruction in the Etzatlán-Magdalena paleolake, western Mexico, during the Holocene. The reconstruction relies on fossil pollen, macrocharcoal and microcharcoal analyses of a clay sediment core. In the early Holocene (10–5.8 ka), climatic conditions were humid between 10 and 9 ka, represented by cloud forest of Liquidambar, Juglans, and Betulaceae. After 9 ka Quercus forest expanded and a trend towards warm conditions was detected, associated with high fire activity, suggesting the presence of a dry forest. Fire episodes at local and regional scale had a long-term negative effect on temperate and cloud forests. In the middle Holocene (5.8–2.1 ka), temperate forest was replaced by dry forest, indicating a drier climate. In the late Holocene (2.1–0.3 ka), the expansion of disturbance taxa and the low local fires indicated an open landscape and dry conditions. Human activity was documented by an increase of Cheno-Amaranthaceae, Poaceae and microcharcoal concentration after 3.5 ka. This research provides relevant information on the vegetation dynamics in a region with a long history of human settlement.

Investigation the Effect of Dead Trees on the Trend of Changes in Soil Carbon Storage Across an Altitudinal Gradient of Western Quercus Forests (Case study: Qalajeh Forest)

Investigation the Effect of Dead Trees on the Trend of Changes in Soil Carbon Storage Across an Altitudinal Gradient of Western Quercus Forests (Case study: Qalajeh Forest)

Phytosociological characteristics of Betula davurica–Quercus crispula forests in Japan based on a comparison with summergreen broad-leaved forests in Northeast Asia

Betula davurica and deciduous Quercus forests are among the principal forest types in Northeast Asia. They are found throughout continental Northeast Asia and in some mountainous regions of Central Honshu and eastern Hokkaido in the Japanese Archipelago. B. davurica–Quercus crispula forests in Japan are significant for understanding the phytogeography of Japan and Northeast Asia. However, their relationships with B. davurica–Quercus mongolica forests in continental Northeast Asia remain poorly understood. We compared the species composition of B. davurica–Q. crispula forests of Japan, with those of Q. crispula dominant forests and B. davurica–Q. mongolica forests using phytosociological methods. The results suggested that B. davurica–Q. crispula forests of Japan had a significant number of species common to the order Lespedezo bicoloris–Quercetalia mongolicae and the class Querco mongolicae–Betuletea davuricae in continental Northeast Asia than in other associations in Japan. Furthermore, our results showed that associations between B. davurica and Q. crispula forests in Central Honshu and Hokkaido are related to different orders in continental Northeast Asia. The relations of the associations between Japan and the continent are considered to have been caused by the environmental similarities, the histories of taxa, and the changes in vegetation distribution.

Regeneration of Quercus Forest after Fire Under the Influence of Ecological and Environmental Parameters

Fires are one of the major disruptive factors for all forest biomass. The study was carried out at the level of the Algerian Northeast region, where forest sites of Souk-Ahras are remarkably materialized by the species: Quercus suber and Quercus canariensis. The regeneration problem analysed after fire took into account the effects of natural environmental parameters, namely temporality, frequency of individuals and topographical parameters such as exposure, slope and altitude. The results show a very small and relative change. However, the cumulative actions of these latter must be checked by the intensity of the fires, by the energy and the kinetics of combustion in order to be able to pronounce on the possible temporality to the regeneration. Thus, it turns out that the frequency parameter depends closely on the storage and the arrangement of individuals, as this, could give the necessary time for cells to no longer have the ability to function for regeneration. For the topography parameter, regeneration is observed from the altitude 800 m. And, by combining the exposure sub parameter, we concluded that the regenerated parts benefited from better radiation.

Comparison of species composition and community characteristics of Quercus forests on south and north slopes of Taibai Mountain, China.

We examined species composition, community characteristics, diversity, and community similarity of five Quercus communities composed of three Quercus species (Q. variabilis, Q. aliena var. acutiserrata, Q. wutaishanica) on the altitudinal gradient on the south and north slopes of Taibai Mountain. The results showed that there was an altitudinal transition pattern from Q. variabilis pure forest to Q. variabilis-Q. aliena var. acutiserrata mixed forest, Q. aliena var. acutiserrata pure forest, Q. aliena var. acutiserrata-Q. wutaishanica mixed forest and Q. wutaishanica pure forest on the south and north slopes of Taibai Mountain. The main companion species of Quercus community on the north slope were Pinus armandii, Castanea seguinii, and Sorbus alnifolia, and were Pinus tabuliformis, C. seguinii, Carpinus cordata, and Q. spinosa on the south slope. Species richness, woody plant density, and Quercus species dominance on the north slope of Taibai Mountain were higher than those on the south slope. α diversity of tree layer in Quercus community on the south and north slopes of Taibai Mountain increased first, then decreased and then increased with altitude. α diversity of tree layer was higher in mixed forests than pure forests. α diversity of shrub layer was higher than that of tree layer and herb layer in Quercus community on south and north slopes. β diversity fluctuated greatly along the altitudinal gradient on the south and north slopes, indicating that species composition changed greatly with altitude. Results of redundancy analysis showed that mean warmest month temperature, altitude and tree height accounted for 79.0% of the community diversity on the north slope, and that soil water content, tree height, canopy density and mean annual temperature accounted for 79.6% of the community diversity on the south slope. Overall, Quercus dominance was higher on the north slope of Taibai Mountain, and the substitution distribution pattern of Quercus species was clearer than that on the south slope. Environmental factors related to temperature and precipitation jointly affected α diversity of Quercus communities.

Long-term trends and influence of climate and land-use changes on pollen profiles of a Mediterranean oak forest

Climate change is disrupting phenology and interaction patterns of natural ecosystems, but also human activities that modify land-uses have a direct impact, especially on species distribution and loss of biodiversity. The objective of this study is to evaluate the impact of climate and land-use changes on phenology and airborne pollen spectrum in a Mediterranean natural area, dominated by Quercus Forest and ‘dehesa’, in the South of the Iberian Peninsula. 61 different pollen types were identified over a 23-year period (1998–2020), mainly from trees and shrubs, such as Quercus, Olea, Pinus or Pistacia, and from herbaceous plants, such as Poaceae, Plantago, Urticaceae or Rumex. A comparison of pollen data from the first years of the study (1998–2002) up recent years (2016–2020), showed a substantial decrease in the relative abundance of pollen from autochthonous species associated with natural areas, such as Quercus or Plantago. However, the relative abundance of the pollen from cultivated ones such as Olea and Pinus, which is used for reforestation has increased. Regarding flowering phenology trends, our analyses revealed variations between −1.5 and 1.5 days per year. Taxa showing an advance phenology were Olea, Poaceae and Urticaceae, whereas Quercus, Pinus, Plantago, Pistacia or Cyperaceae experienced delayed pollination.Meteorological trends in the area generally resulted in an increase in both minimum and maximum temperatures, along with a decrease in precipitations. Changes in pollen concentration and phenology were correlated with changes in air temperatures and precipitation, although the positive or negative influence varied for each pollen type. The results suggest that climate change together with those motivated by land cover changes lead by human activities are having an impact on the phenology and pollen concentration, with the related consequences on pollination and therefore biodiversity more concerning in threatened areas as the Mediterranean Basin.

Half a century of herb layer changes in Quercus-dominated forests of the Western Carpathians

Species composition of European temperate Quercus forests have undergone dramatic changes in the past century. Observed changes have largely been attributed to anthropogenic environmental changes that drove the processes of thermophilization, eutrophication, or biotic homogenization. However, ecological processes behind these changes can be difficult to explain considering the variability among regions: their history, management, landscape patterns, site properties, and vegetation types. To reveal vegetation change trends and their drivers in the subcontinental Western Carpathians, we analysed vegetation and environmental data from 158 quasi-permanent plots established between 1961 and 1980 in Quercus petraea- dominated forests on the andesite bedrock of the Slovenské stredohorie Mountains in Slovakia (Central Europe), and we resurveyed them again between 2005 and 2020.Among alpha and gamma diversity measures, we found only slight species richness decreases. A significant shift in species composition associated with very high species turnover (64%) and a decrease in herb layer cover (by 24%) resulted in higher spatial heterogeneity of herb understoreys in the resurvey. Winning species were more thermophilous, eutrophic, and mesic/oceanic plants of lower latitudes, replacing original species of open Quercus forests. Increased temperatures was the most significant environmental driver. Climate warming corresponded not only to thermophilization, but, after interaction with management, it was also related to eutrophication of the herb layer. Eutrophication was identified as the main trend of the species composition changes (mean EIV for nutrients of winners was 5.9 compared to 4.1 of losers) even though the effect of anthropic nitrogen depositions was negligible. Successive undergrowing of Quercus canopies by more shade-casting trees (Acer campestre, Carpinus betulus, and Fagus sylvatica) in the period of decreasing management intensity was another major driver. Their increase by 8.6% in the resurveyed plots contributed to decreased species richness and they supported shade-tolerant eutrophic understorey species typical of mesic Carpinus betulus and Fagus sylvatica forests.We concluded that Quercus forests in the Western Carpathians underwent thermophilization and eutrophication, similar to the forests in densely inhabited Western Europe; however, their plant understoreys were not homogenized, and eutrophication was not driven by nitrogen depositions. Eutrophication should be recognised as the next important negative impact of global warming on ecosystems. Dramatic changes in species composition and loss of original characteristic species can only be partly halted by reducing shade-casting trees from lower tree layers in managed stands.

Estimation of Quercus Biomass in Shangri-La Based on GEDI Spaceborne Lidar Data

Accurately estimating forest biomass based on spaceborne lidar on a county scale is challenging due to the incomplete coverage of spaceborne lidar data. Therefore, this research aims to interpolate GEDI spots and explore the feasibility of approaches to improving Quercus forest biomass estimation accuracy in the alpine mountains of Yunnan Province, China. This paper uses GEDI data as the main information source and a typical mountainous area in Shangri-La, northwestern Yunnan Province, China, as the study area. Based on the pre-processing of light spots. A total of 38 parameters were extracted from the canopy and vertical profiles of 1307 light spots in the study area, and the polygon data of the whole study area were obtained from the light spot data through Kriging interpolation. Multiple linear regression, support vector regression, and random forest were used to establish biomass models. The results showed that the optimal model is selected using the semi-variance function for the Kriging interpolation of each parameter of GEDI spot, the optimal model of modis_nonvegetated is a linear model, and the optimal model for rv, sensitivity, and modis_treecover is the exponential model. Analysis of the correlation between 39 parameters extracted from GEDI L2B and three topographic factors with oak biomass showed that sensitivity had a highly significant positive correlation (p < 0.01) with Quercus biomass, followed by a significant negative correlation (p < 0.05) with aspect and modis_nonvegation. After variable selection, the estimation model of Quercus biomass established using random forest had R2 = 0.91, RMSE = 19.76 t/hm2, and the estimation accuracy was better than that of multiple linear regression and support vector regression. The estimated total biomass of Quercus in the study area was mainly distributed between 26.48 and 257.63 t/hm2, with an average value of 114.33 t/hm2 and a total biomass of about 1.26 × 107 t/hm2. This study obtained spatial consecutive information using Kriging interpolation. It provided a new research direction for estimating other forest structural parameters using GEDI data.

Mosaic forest management at landscape scale to enhance fungal diversity and production, in a context of forest fire-prevention in Mediterranean ecosystems

Landscapes of oak (Quercus) forests alternated with extensive fields dominated by rockroses (Cistus) are widespread throughout the Mediterranean Basin. Due to the recurrency of fires and the mycological potential of both Quercus forests and Cistus fields, adequate management of this landscape is a key forest management objective. Although both Quercus and Cistus species are considered super-productive in terms of fungal production and diversity, fungal diversity and productivity vary depending on the stand age and structure. The aim of this study was to assess the complementary mycological potential of these ecosystems by studying sporocarp production, diversity, and community composition to elucidate management practices that would enhance fungal diversity and productivity within a fire management framework. We collected sporocarps over a period of four consecutive years (2012–2015) in young Cistus plots (1-m tall Cistus), old Cistus plots (2-m tall Cistus), and Quercus Forest plots. Our analyses showed that age as well as dominant vegetation influences sporocarp production, diversity, and richness, with young Cistus stands most suited to high levels of sporocarp productivity and diversity. In addition, a progressive restructuring of the fungal community was observed from a large, diverse community in Cistus early-stage stands to a smaller, less diverse but well-defined community in Quercus stands, transiting through an intermediate composition in old Cistus fields. Based on our findings, we suggest that a management process that not only favors stand rejuvenation would achieve greater sporocarp production and richness, including edible commercial species, while reducing the amount of fuel. In addition, the differentiated diversity of the Quercus stands plays an important role in terms of landscape diversity, being necessary the recommendation of a rejuvenation management in order to protect this stands associated diversity. We propose that these goals could be best achieved with a mosaic landscape model to connect the different stages of succession, enabling greater interconnectivity and, hence, allowing the presence of different “fungal stages” at the landscape level.

Short- and long-term responses of nematode communities to predicted rainfall reduction in Mediterranean forests

Climate change is a fundamental process affecting terrestrial ecosystems. However, there is relatively little knowledge about its impacts on soil communities, with a large degree of uncertainty regarding their resistance to predicted alterations in temperature and, particularly, precipitation. Moreover, most studies exploring the response of soil biota to predicted rainfall reduction have focused on mesic environments and soil microbes, which limit our ability to find general patterns across ecosystems and soil organisms. In this study, we analysed the impact of predicted climate change scenarios of rainfall reduction on soil food webs of Mediterranean water-limited forests using nematodes as bioindicators. We took advantage of replicated rainfall exclusion infrastructures (30% exclusion) established in Quercus forests of southern Spain in 2016 (2-year exclusion) and of southern France in 2003 (15-year exclusion) to explore the sensitivity of the soil food web to predicted reductions at short- and long-term scales. Rainfall reduction had large negative short-term effects on nematode abundance, particularly of lower trophic groups (bacterivores and fungivores). Rainfall reduction had also consistent short- and long-term impacts on community composition (decrease of fungivores, marginal increase of omnivores) and nematode-based indicators of soil food web structure (higher maturity and structure index, lower prey:predator ratio). These results can be considered indicative of a low resistance of the soil food web to rainfall reductions predicted by climate change. Overall, our findings demonstrate the sensitivity of water-limited forests to further reductions in soil water availability, which might substantially alter their soil communities and likely affect the many ecosystem processes that they control.

Climate-Adapted Potential Vegetation—A European Multiclass Model Estimating the Future Potential of Natural Vegetation

Climate change will alter the site conditions for European vegetation. This is likely to shift the potential distribution of species and habitats outside its current boundaries. To enable future projections on shifts in vegetation potentials, we fitted a multiclass model to the current potential natural vegetation (PNV) of Europe using climatic predictors. The model was then applied to climate data of the time slice 2061–2080 with the Representative Concentration Pathways (RCPs) 4.5 and RCP 8.5. With an accuracy of 0.78, simulations well represented the site-equivalent vegetation types of the current PNV across Europe. Projections show drastic shifts in vegetation potentials in all parts of Europe. Boreal forests could lose up to 75% of their current potential, while Mediterranean Quercus forests and steppes would double their potential area. Deserts are projected to be on the rice, and the potential of currently widespread vegetation such as Fagus forests would be translocated. These estimated alterations of European vegetation potentials could have great effects on the stability of current forests, affecting nature conservation strategies and forest management.

Vegetation history of a Mexican Neotropical basin from the late MIS 6 to early MIS 3: The pollen record of Lake Chalco

A new detailed pollen record of the penultimate glacial–interglacial–glacial cycle corresponding to the late marine isotopic stages (MISs) 6–3 (146–35 ka ago) has been obtained from Lake Chalco, in the Basin of Mexico. This record provides an insight into vegetation dynamics and climate variability at the northern limit of the American tropics. The pollen record displays a high temporal resolution with a mean sampling interval of ∼230 years. The changes in plant composition were reconstructed by pollen analysis and differences in plant composition between distinct periods were established. The wettest cold stage, indicated by a combination of diverse open vegetation and mesophytic taxa correlates with the penultimate late glacial MIS 6 (146–130 ka), when Lake Chalco was a deep freshwater lake. The penultimate interglacial MIS 5e (126.5–123.6 ka) shows a dominance of Pinus forests, with tropical taxa suggesting warmer than present conditions; environmental proxies indicate drier conditions and that the lake transitioned into a saline water body. Open communities and Pinus and Quercus forests with mesophytic taxa and, during the stadial periods, MIS 5 d, 5c, and 5 b (125–90 ka), with tropical taxa, characterize the record of interstadials. Pinus-dominated forests characterize the landscape during MIS 5a. MIS 5c to MIS 3 showed lower and variable evenness and palynological richness, along with an increase in fire activity. During MIS 4 and 3, a trend towards drier conditions was also recorded with enhanced carbonate precipitation and proxies indicating saline conditions. Tree-line changes in response to climate change and taxa migration were documented. A comparison with long records from the Greenland ice cores, the marine Cariaco Basin and insolation parameters revealed that the pollen data and the Pinus pollen accumulation rates evidence the response of the vegetation to glacial and interglacial changes and to millennial-scale variability. Wetter conditions were inferred to exist during the Greenland interstadials, while drier conditions persisted during Heinrich events.

Susceptibility to Phytophthora cinnamomi of six holm oak (Quercus ilex) provenances: are results under controlled vs. natural conditions consistent?

Aim of study: Quercus forests are being affected by severe decline and mortality. The oak decline is associated with the soilborne pathogen Phytophthora cinnamomi (Pc), among others. This work aims to determine if Quercus ilex growing in Pc-infested soils show mortality differences according to their provenance in the field. It also evaluates whether the most tolerant provenances are those with the greatest constitutive chemical defences.
 Area of study: Acorns from six Spanish National Parks with natural presence of Q. ilex were collected for sowing in the greenhouse and later be planted on soils naturally infested by Pc in the surroundings of Plasencia, western Spain.
 Materials and methods: Seedlings were planted in four field plots located in two areas with oak decline: 153, 156, 157 and 155 plants in plot I, II, III and IV, respectively. The presence and infection of Pc was confirmed before their installation and during the experiment. Symptoms, regrowth, mortality and development was recorded for four years.
 Main results: There was a high mortality (56.0-80.5%) with differences among provenances. The most tolerant provenances in the field coincided with those identified under greenhouse conditions in a previous test. Provenances with higher constitutive condensed tannins better tolerate the pathogen under both conditions. In the southern provenances, some families with higher tolerance and, therefore, candidates for use in reforestation programs in areas infected by Pc, were identified.
 Research highlights: The restoration of Pc-affected areas would be possible through the use of Q. ilex plant material with high constitutive defences, more tolerant to the pathogen.

Functional traits of epiphytic lichen communities in a Temperate-Mediterranean fragmented landscape: Importance of patch size, tree diameter and summer rainfall

Functional traits have become important tools for evaluating the response of epiphytic lichens to environmental changes. In this study, we evaluated which predictors related to fragmentation, habitat quality and climate were driving the richness and cover of lichen growth form, type of photobiont and reproduction traits, at both fragment and plot levels in a Temperate-Mediterranean area dominated by Quercus forests. At fragment level, patch size and summer rainfall positively contributed to richness in most of the traits, while tree diameter and slope were the most important drivers, especially for the type of reproduction and growth form at plot scale. High coverage of growth forms especially sensitive to fragmentation were indicative of high values of total species richness, while early-colonizers indicated the opposite. These results provide important information on how lichen traits respond to environmental conditions in an ecotone area where a shift towards a drier climate is more likely to occur.

Interspecific and intraspecific variability of water use traits in macrolichen species in a fragmented landscape along a climatic ecotone area

Water use traits in lichens are important attributes that determine the duration of hydration and metabolically active periods. In this study, the water holding capacity (WHC) and specific thallus mass (STM) were measured for seven macrolichen species (Parmelia sulcata, Parmelina tiliacea, Evernia prunastri, Ramalina farinacea, Lobaria pulmonaria, Lobarina scrobiculata and Nephroma resupinatum) from a Temperate-Mediterranean fragmented landscape. Twenty Quercus forests with different environmental conditions were selected to gather therein five lichen samples of each species in order to analyse their interspecific and intraspecific variation in WHC and STM. The type of photobiont was mainly responsible for differences in the WHC and the water content per biomass among species. Lichens with cyanobacteria as the main or secondary photobiont showed the highest value for both parameters. However, particular features of species were more important in modulating STM, while growth form had a minor explanatory importance. At the intraspecific level, variation in WHC relied on climatic, microclimatic and forest structure factors, while STM variability was only dependent on the two last predictors. Future research should be focused on other drivers at the microscale to unveil the environmental conditions that shape WHC and STM in lichens.

Stability of soil organic carbon pools affected by land use and land cover changes in forests of eastern Himalayan region, India

Forests are among the largest terrestrial carbon pools that are most vulnerable to land use and land cover change (LULC). Therefore, it is essential to manage forest ecosystems to enhance soil organic carbon (SOC) pools and soil functionality. The present study was carried out to analyze C stability and change in SOC stock under different forest types in the eastern Himalayan region of India. Topsoil (0–15 and 15–30 cm) samples from six dominant forests i. e. tropical wet evergreen, montane subtropical, temperate, Quercus, bamboo, and shifting cultivation (Jhum) lands were collected and analyzed for selected soil properties and SOC stock. Active (very labile + labile), slow (less labile), and passive (non-labile) C fractions were also analyzed to determine the stability of the SOC pool under the LULC scenario. Results show that the percentage contribution of active C to total organic carbon in topsoil was highest in a temperate forest (74.1%) while lowest in a bamboo forest (48.1%). Unlike, slow C (18.4%) and passive C (26.6%) were highest in Quercus forest. Pearson correlation analysis shows significant positive relation of active and slow C pool with SOC and total nitrogen concentration. The estimates of SOC stock (0–30 cm) were significantly higher in temperate forests (132.7 Mg C ha−1). However, the conversion of natural forests to bamboo forest and jhum land reduced SOC stock by 29% and 68%, respectively. C lability index shows higher labile C in jhum land while recalcitrancy index was highest in a bamboo forest. Our study concluded that LULC change significantly altered the stability and stock of SOC in natural forests. Owing to a higher percentage of slow and passive C pools, Quercus forests play a major role in C sink management.

Using machine learning algorithms to estimate stand volume growth of Larix and Quercus forests based on national-scale Forest Inventory data in China

Estimating the volume growth of forest ecosystems accurately is important for understanding carbon sequestration and achieving carbon neutrality goals. However, the key environmental factors affecting volume growth differ across various scales and plant functional types. This study was, therefore, conducted to estimate the volume growth of Larix and Quercus forests based on national-scale forestry inventory data in China and its influencing factors using random forest algorithms. The results showed that the model performances of volume growth in natural forests ( R 2 ​= ​0.65 for Larix and 0.66 for Quercus , respectively) were better than those in planted forests ( R 2 ​= ​0.44 for Larix and 0.40 for Quercus , respectively). In both natural and planted forests, the stand age showed a strong relative importance for volume growth (8.6%–66.2%), while the edaphic and climatic variables had a limited relative importance (<6.0%). The relationship between stand age and volume growth was unimodal in natural forests and linear increase in planted Quercus forests. And the specific locations (i.e., altitude and aspect) of sampling plots exhibited high relative importance for volume growth in planted forests (4.1%–18.2%). Altitude positively affected volume growth in planted Larix forests but controlled volume growth negatively in planted Quercus forests. Similarly, the effects of other environmental factors on volume growth also differed in both stand origins (planted versus natural) and plant functional types ( Larix versus Quercus ). These results highlighted that the stand age was the most important predictor for volume growth and there were diverse effects of environmental factors on volume growth among stand origins and plant functional types. Our findings will provide a good framework for site-specific recommendations regarding the management practices necessary to maintain the volume growth in China's forest ecosystems. (1) The RF model based on large-scale sample data can effectively simulate forest stand growth. (2) Multivariate factors affect Larix and Quercus stand growth across China. (3) Environmental factors play an important role in the stand volume growth of plantations. (4) Planted forests and natural forests have inconsistent responses to site and climate factors.