Dominant Woody Species Research Articles

Response of two dominant woody species to groundwater depth at the transition zone between desert and oasis

Haloxylon species are traditionally considered as dominant desert plants across Central Asia, but recent studies based on stable isotope showed that they are groundwater-dependent, however, their tolerance strategies and limits to groundwater decline remain unknown. Therefore, we adopted the method of spatial-for-temporal, took Haloxylon ammodendron and Haloxylon. persicum in Gurbantunggut Desert as study objects, combined field survey with model estimation exploring their density, growth, age, and biomass characteristics along a natural groundwater gradient, aiming to reveal their responses to groundwater depth changes and predict future development. The results showed that: (1) With the decline of groundwater depth, the population density, and plant height, canopy width, and basal diameter of two species all decreased significantly. （2）When the groundwater depth descended to lower than 12 m, H. persicum replaced H. ammodendron becoming the more dominant species. (3) As the groundwater depth declined, adult individual percentage increased in the population of H. ammodendron, but H. persicum was still dominated by young trees. (4) The above-ground, below-ground and total biomass of two species were all going down with the lowering of groundwater table, H. ammodendron exhibited a greater reduction, while the root-to-shoot ratio of H. persicum increased significantly (p < 0.05). These findings indicated that continuous decline in groundwater depth greatly limited the survival and development of H. ammodendron, the allocation regulation of H. persicum helped to cushion the adverse effects partially. In the long run, decreased accessibility of groundwater would be not conducive to the exertion of their ecological functions. These findings could provide a scientific basis for the protection and management of these valuable species.

Defining large‐scale arid island vegetation recovery targets through evaluating a reference ecosystem within an archipelago extent

Island ecological restoration presents challenges in establishing historical frames and reference ecosystems. Our study takes place in the Galapagos Islands and focuses on North Seymour (NS), recognized as a reference ecosystem for Baltra Island, which has suffered significant degradation. We assessed NS's arid plant community, comparing it with early twentieth‐century records. A first survey identified that dominant woody species on NS include native Bursera graveolens, Cordia lutea, Castela galapageia, Parkinsonia aculeata, and Opuntia echios, while Cleome viscosa is the only exotic species registered. A second survey divided both islands into evenly distributed plots, recording adults and juveniles of the five dominant species from the first survey. NS showed a structured community with higher species richness and density compared to Baltra. Castela galapageia prevailed in disturbed areas on Baltra. Juvenile regeneration was scarce on both islands. NS exhibited high species richness throughout, while Baltra had only two areas with similar high richness. Co‐occurrence analysis revealed significant associations between P. aculeata and B. graveolens on both islands. However, Baltra's network displayed missing links, indicating the need for restoration efforts. In conclusion, the structured plant community of NS can serve as one of the reference ecosystems needed for framing a restoration model for Baltra.

Assessment and Characterization of the Traditional Parkland Agroforestry Practices in Mid and Lowlands of Bale: In the Case of Goro and Ginnir Districts

Agroforestry parklands are playing an important role, through trees and shrubs providing multiple products and important long-term ecological benefits. Purposive sampling methods were applied to select districts, PAs and farmers which mostly used parkland agroforestry practices. Based on information delivered from informal assessment result, formal survey was done with selected 84 HHHs (sample size) for the study purposes. Based on the existences of long lived parkland agroforestry practice and associated challenges four PAs from Ginir and Goro districts of Bale Zones were selected purposively with assistance of district agriculture office expertise and DAs. Survey results showed the presence of 17 woody species of trees and shrubs representing eleven (11) families at the study areas. Of seventeen (17) woody plant species retained/planted and managed on parklands, 82.4% were native. Fabaceae was the most dominant woody species family which accounted about 41.2% of the total number of species recorded. The Croton macrostachyus Hochst., Faidherbia albida, Cordia africana Lam., Acacia abyssinica Hochst., Junperus procera Hochst and Acacia species were the most frequently observed multipurpose woody species in the study area. Almost all of the respondents did practise different types of management activities or practices for the woody species they owned in parkland of the study areas. This finding revealed that pollarding (33.45%), coppicing (21.08%), branch pruning (35.56) and the rest thinning and protection woody species management practices were applied to the scattered trees on croplands of the study areas. On other side, respondents stated that the major challenges for the improvement of parkland agroforestry practices in the study area were instability of rain fail or drought (34.52%) and shortage of farmlands (21.43%). The finding of this study showed that agricultural landscapes (Parkland agroforestery practices) were the home/host of reasonable number of native woody species flora conservation or it’s almost the remnants of the natural vegetation. Therefore, further need for more comprehensive analysis of the multiple benefits and services provided by parkland trees located on farmlands or the interaction effects of the agroforestery components on soil fertility improvement, crop yields and quality in the future.

Diversity and growth patterns of woody species in the Mediterranean Coastal range of Chile: A case study in Altos de Cantillana

Background: The Altos de Cantillana mountain range (ACMR) in central Chile is composed of different vegetation communities, and is currently a priority site for conservation, due to its high endemism, high anthropogenic pressure and vulnerability to climate change. Research on biodiversity and carbon stocks in ACMR is essential to comprehend the resilience of these forests and to define conservation strategies. This study examines the spatial variability of biodiversity and tree biomass patterns along the entire altitudinal gradient of the ACMR. Methods: Six tree species communities were studied in Altos de Cantillana Nature Sanctuary, along an altitudinal gradient ranging from 415 to 2010 m. Woody species regeneration and inventory plots, as well as dendrochronological sampling in ~150 trees were carried out. Diversity patterns were analyzed using the Jaccard index and alpha index. Growth patterns of dominant trees species were analyzed by ring-width and trunk biomass chronologies, focusing on the recent megadrought period since 2010. Results: The forest inventory revealed a notable decline in alfa diversity patterns with increasing elevation. The moist sclerophyllous forest exhibited the highest diversity. However, we did not find a pattern between elevation and diversity (and abundance) at the seed regeneration inventory level. Additionally, we identified three clusters of woody species similarity: (i) sclerophyllous, shrubs and hygrophilous forest (&lt;1,000 m.a.s.l.); (ii) high-elevation sclerophyllous forest (&gt;1,500 m.a.s.l); and (iii) deciduous forests (~ 2,000 m.a.s.l). Furthermore, declining growth rates were observed in all communities studied beginning in the 1980s, with even a stronger reduction in radial growth (35% on average) and biomass accumulation (56% on average) when comparing the megadrought with six decades earlier. Conclusions: We concluded that there is a negative correlation between woody species diversity and elevation. However, there are no altitudinal patterns in seedling regeneration diversity and abundance, which puts the natural succession in ACMR at risk. Additionally, we have determined that the accumulation of trunk biomass in dominant woody species has been significantly impacted by the recent megadrought period. This has affected the sink capacity of forest communities in ACMR. Therefore, our findings can significantly contribute to more efficient and timely decision-making processes regarding the conservation and restoration of this globally unique ecosystem.

Fire effects on the reproductive potential of two dominant woody species along an elevation gradient in central Argentina

Fire and elevation affect reproduction of woody species and, therefore, their distribution in the landscape; however, the effect of both factors are often confounded. In addition, plant size may also influence reproduction. Our objective was to investigate the combined effects of fire, elevation and pre-fire size on woody species reproductive potential in a seasonally dry mountain ecosystem. We tested the predictions that fire and elevation impair reproductive potential and that the negative effects of fire are enhanced at high elevation. Our study was carried out in the mountains of central Argentina, from 800 to 1700 m a.s.l. We selected individuals of two dominant resprouting woody species (Vachellia caven and Lithraea molleoides) in burned and comparable unburned areas. We estimated pre-fire size and fire damage level in each tree. We monitored parameters related to reproductive potential during four post-fire fruiting seasons in 185 V. caven and 78 L. molleoides trees. Our main results for V. caven show negative fire effects on most reproductive parameters, and on the expected number of germinable seeds per tree, which was estimated as an integrated parameter. The negative fire effects decreased over time until the fourth post-fire fruiting season, when we detected almost no fire effects. Moreover, the negative fire effects were greatly enhanced with elevation, while pre-fire size showed consistently positive effects on most reproductive parameters. For large trees located at low elevation, fire reduced the number of germinable seeds per tree by a factor of nearly six in the third post-fire fruiting season (from 2020 to 358 seeds), while at high elevation fire reduced germinable seeds by a factor of 15 (from 106 to 7 seeds) for similarly large trees. Small trees had a lower reproductive potential than large trees and the negative effects of fire were smaller but noticeable, and were enhanced by elevation, as in the case of large trees. For L. molleoides we found similar patterns to those of V. caven; however, since few trees produced seeds during the study, we did not compute formal statistics. We conclude that fire reduction should gradually increase reproductive potential, tree density and forest cover at high elevation, even when, according to previous studies, survival is not affected by fire or elevation in the study species.

Climatic differentiation: Variability in leaf functional and stoichiometry traits among different woody species in semi-arid forests

Structural and nutrient traits of foliage are important for understanding plant ecological strategies. Understanding structural variations of trees in different environmental conditions helps to reveal adaptation mechanisms. We investigated morphological, chemical and stoichiometric traits in the foliage of four dominant woody species in sub-humid vs. semi-arid of the Zagros forests, west of Iran. Dry matter content, specific leaf area (SLA), stomatal length (SL), stomatal width (SW), density (SD) and stomatal pore index (SPI) traits were higher in the trees growing in a sub-humid climate. In Pistacia atlantica (PA) growing in the semi-arid climate, leaf length, SLA, SD and SPI traits were higher than the sub-humid climate. Leaf phosphorus content of Crataegus aronia (CA) was higher in the sub-humid, whereas PA was higher in the semi-arid climate. In PA and CA, the highest leaf C: P and N: P were in the sub-humid and the semi-arid climate. The relationship between SLA and leaf carbon content was significantly negative in PA. Among the different species, carbon content, nitrogen and phosphorus and their stoichiometry had strong positive and negative relationships in two climates. These results show the response of leaf functional traits to climate changes and how trees function under these changes. Furthermore, the leaf traits showing greater variability due to changes in the environmental can be determined. This improved understanding will assist in determining the most important adaptive parameters of trees to climate changes, to provide inputs to global environmental models.

How does Assisted Natural Regeneration (ANR) Improve Soil Fertility and Plant Cover in the Simiri Commune in Niger?

Aims: This study aimed to assess Assisted Natural Regeneration (ANR) impacts on improving soil fertility and plant cover through the physicochemical characterization of soil samples taken from ANR fields and control fields.&#x0D; Study Design: The experimental design is made up of a vegetation observation gradient along an East-West transect and a soil sampling gradient along a North-South transect.&#x0D; Place and Duration of Study: This study was carried out in the Sahelian zone in the rural commune of Simiri in Niger between May and June 2023.&#x0D; Methodology: Data on the diversity of species predominant in the ANR system, the social categories of ANR users and farmers' perceptions of ANR were collected on a sample of 120 farmers chosen at random from three villages in the commune of Simiri.&#x0D; Results: A sandy texture was recorded in all the samples submitted for analysis, with an overall acid of soil pH (5.18 ⁃ 5.62). The proportions of the main nutrients: C(0,16), N(0,015), P(6,88), K(0,066), Mo(0,30) C/N(10,83) were relatively higher in the fields under ANR practices compared with the control fields. With regard to the dominant woody species, the results show that the stands are mainly based on Combretum glutinosum, Combretum micranthum and Guera senegalensis. The ability of woody species to withstand stressful conditions could act as a bulwark against climatic hazards. The strong dominance of these species is due, among other things, to their regenerative capacity, their rapid spread and, above all, their economic interest in the production of firewood and other ecosystem services.&#x0D; Conclusion: The Assisted Natural Regeneration (ANR) adoption in farming practices has often been accompanied by the creation of village committees for the protection and management of trees and other areas of sustainable natural resource management. Despite mutilation and other illegal felling, the new agroforestry parks increase the resilience of agricultural production systems to climatic shocks and biotic stresses.

Responses of plant carbon and nitrogen assimilations to nitrogen addition in a subtropical forest: Canopy addition vs. understory addition

The global atmospheric nitrogen (N) deposition has intensified in recent years, resulting in a complex impact on forest ecosystems. This study investigated the effects of canopy (CAN) and understory additions of N (UAN) on leaf carbon (C) and N assimilations, as well as growth parameters of representative woody plant species in an evergreen broad-leaved forest, i.e. Castanea henryi, Schefflera heptaphylla, Blastus cochinchinensis, and Lasianthus chinensis. The results showed that leaf N assimilation key enzyme nitrate reductase (NR) activities of B. cochinchinensis and S. heptaphylla were significantly decreased by UAN, and were significantly decreased by CAN for C. henryi. CAN significantly decreased the nitrite reductase activity of C. henryi, while significantly increased that of L. chinensis. However, the Amax values of each woody species were not significantly different among control (CK), CAN, and UAN. Community surveys demonstrated that CAN and UAN inhibited the growth (diameter at breast height, height, or crown width) of the representative large tree, C. henryi, while promoting the growths of understory woody species (B. cochinchinensis and L. chinensis). Overall, N addition was found to change the physiological processes of N and C metabolisms of the dominant woody species in an evergreen broad-leaved forest. The community of subtropical evergreen broad-leaved forests may further decline and its C fixation capacity may be detrimentally changed under N deposition in the future.

Accumulation of heavy metals in leaves of tree species on the ash and slag dumps of the Burshtyn Thermal Power Plant

Thermal power plant (TPP) facilities are considered as one of the major reasons for environmental pollution. Ash and slag dumps as a special construction for storage of combustion wastes of TPPs are recognized as sources of heavy metals (HMs) contamination for surrounding ecosystems. The present study is the first report of analyzing HMs contamination of the ash and slag dumps of the Burshtyn TPP.&#x0D; The aim of the study is to estimate the content of HMs in the technogenic substrates of ash and slag dumps and investigate soil-plant interactions through analyzing potential of HMs accumulation in the leaves of native dominant woody species.&#x0D; Materials and methods of research. Soil sampling was carried out in the period of July 2021 at previously determined points. The most common woody species (Populus tremula L., Betula pendula Roth., Salix caprea L.) were selected for testing of HMs accumulation abilities. Samples of plants and soil were subjected to an atomic absorption spectrometer for being analyzed for heavy metals: Cd, Zn, Ni, Cu, Pb, Mn and Fe.&#x0D; Results of research and discussion. The results showed that the substrates of ash and slag dumps of the Burshtyn TPP were mainly contaminated by lead, copper and cadmium. All tested species concentrated high amounts of magnesium, iron, zinc and low concentration of cadmium. Bioaccumulation factor reflected the highest abilities of accumulation of zinc in all tested species and low level of bioaccumulation of cadmium. The highest index of biochemical activity showed Betula pendula. Salix caprea were found as a promising species for remediation due to intensive accumulation of such elements like cadmium, lead, copper, zinc and nickel.&#x0D; Conclusions and prospects for further research. We consider plant organisms particularly useful for analyzing HMs accumulation as they can provide a cost-effective and long-term approach for bioindication and monitoring HMs pollution. Moreover, vegetation covers could be used for remediation of HMs contaminated sites

Contribution of assisted natural regeneration (ANR) to climate change mitigation and diversification of ecosystem services in Dan saga village (Maradi-Niger)

As an agro-ecological intensification technique, assisted natural regeneration (ANR) protects agrosystems and guarantees cereal production in a Sahelian context of high demographic pressure and climate variability. This study aims to assess the local perception of assisted natural regeneration in mitigating the effects of drought and climate change and its impacts on soil fertility and crop production. Surveys, based on a participatory approach of individual and collective consultations, were conducted with stakeholders. The water profile and bulk density of areas under ANR and outside ANR were determined from soil samples taken in the rainy and dry seasons at different depths (0 - 200 cm). Vegetative growth and yield components were monitored on 100 plots of 100 m2 (10x10m) with 50 plots in ANR and 50 in non-ANR areas. The results showed that both zones had the same species composition for the dominant woody species, but their average densities were higher in the areas under assisted natural regeneration than in the areas without. Density is lower in the aureoles close to the village than those far from it in any zone. Soil moisture content is higher in the ANR and non-ANR areas than in the non-ANR area in the shallow horizons. However, in the deep horizons down to 200 cm, the volume moisture is higher in the Non-NAR and Uncovered NAR zones respectively than in the Under-Cover NAR zone. Apart from the seedling density, all agronomic performance parameters are significantly higher in the RNA zone than in the non-RAN zone. In terms of farmers' perception, the practice of ANR attenuates the impacts on natural resources (water, land, vegetation) and on production systems. More than 92.2% of the respondents reported that increased dust winds, increased night time temperature, decreased rainfall events as well as their amounts in height are the impacts experienced before the practice of ANR. The practice of ANR contributes to the mitigation of climate variability, improvement of soil structure and carbon sequestration.

Allometry of bud dynamic pattern and linkage between bud traits and ecological stoichiometry of Nitraria tangutorum under fertilizer addition.

Affected by the pressure and constraints of available resources, plant growth and development, as well as plant life history strategies, usually vary with environmental conditions. Plant buds play a crucial role in the life history of woody plants. Nitraria tangutorum is a common dominant woody species in desertified areas of northern China and its growth is critical to the desert ecosystem. Revealing the allometry of N. tangutorum aboveground bud fates and the linkage between bud traits and plant nutrient contents and stoichiometric ratios can be useful in understanding plant adaptation strategy. We applied seven nitrogen and phosphorus fertilizer addition treatments to natural N. tangutorum ramets in Ulan Buh Desert in three consecutive years. We surveyed three types of aboveground buds (dormant buds, vegetative buds, and reproductive buds) in each N. tangutorum ramet, then measured the plant carbon (C), nitrogen (N), and phosphorus (P) contents and ratios during three consecutive years. We specified that reserve growth potential (RGP), vegetative growth intensity (VGI) and sexual reproduction effort (SRE) are the three indices of bud dynamic pattern. The results showed that the bud dynamic pattern of N. tangutorum ramets differed significantly among different fertilizer addition treatments and sampling years. The allometry of RGP, VGI, and SRE was obvious, showing size dependence. The allometric growth relationship fluctuated among the sampling years. The linkage between bud traits and plant stoichiometric characteristics of N. tangutorum ramets showed close correlation with plant P content, C:P and N:P ratios, no significant correlation with plant C content, N content and C:N ratio. These results contribute to an improved understanding of the adaptive strategies of woody plants growing in desert ecosystems and provide insights for adoption of effective measures to restore and conserve plant communities in arid and semi-arid regions.

Resilience of Mediterranean communities to fire depends on burn severity and type of ecosystem

BackgroundBurn severity plays an important role in shaping vegetation recovery in Mediterranean ecosystems. In the present study, we aimed to evaluate the influence of burn severity on short-term vegetation resilience in different ecosystems. We selected the Cabrera wildfire (northwest Iberian Peninsula), which affected shrubland, heathland, broomland, and oak woodland ecosystems in 2017. Immediately after the fire, we established 249 field plots within the burned area, in which burn severity was quantified by the application of the Composite Burn Index, differentiating three burn severity categories: low, moderate, and high. Moreover, we fixed 136 plots in unburned areas at two different maturity stages: young (unburned for the last 10 years) and old (unburned for the last 20 years) vegetation. Two years after the wildfire, we evaluated the total percentage cover of vegetation in four vertical strata ranging from 0 to > 4 m, as well as the cover of each woody species and total herbaceous vegetation in the lowest stratum (0–0.5 m). Resilience of the 2017 burned areas was interpreted in terms of the difference in vegetation cover and species composition in relation to the two different maturity stages.ResultsThe results showed that the lowest stratum was the most resilient in the short term. In fact, all ecosystems presented high resilience of this stratum in low-severity areas. In shrublands and heathlands, this was mainly the consequence of the regeneration of herbaceous vegetation, as the dominant woody species did not fully recover in any of the burned situations (at least 21% and 11% less cover in shrubland and heathland burned plots compared to areas of young vegetation). Specifically, the resilience of this stratum was higher in broomlands and oak woodlands, mainly under moderate and high severities. In these ecosystems, woody dominant species recovered with respect to young vegetation at the 0–0.5-m level. Despite this, burn severity had a negative impact on the short-term resilience of the uppermost strata in broomlands and oak woodlands (cover values close to 0%).ConclusionsThe effects of burn severity on short-term vegetation resilience differed among type of ecosystems and vertical strata, so these results may constitute a starting point for the evaluation of the influence of burn severity and vegetation composition and structure on ecosystem resilience.

Selective removal of non-woody species released water limitation on vegetation community stagnated at early successional stages in a humid karst region

The use of plantations and natural restoration enhance vegetation coverage and contribute significantly to the hydrologic functions of degraded terrestrial ecosystems. Researchers have investigated the development and use of plantations, however, few studies looked at naturally-restored vegetation, especially for early successional areas. We applied a series of treatments and their impacts on water status and the dominant woody species were monitored. Our goal is to enhance the hydrologic functions of naturally-restored karst vegetation that stagnated as early successional shrubby-grassland. Our results show that vegetation on both the upper and lower slopes intercepted approximately 50 % of the rainfall because of the dense community structure. With more than 60 % of the community-level root biomass concentrated in the upper 20 cm soil depth, shallow soil water content (SSWC) decreased continuously even when there was scattered light rain events. On the lower slopes, competition-reducing oriented removal of non-woody species significantly reduced canopy interception of water, which contributed to the increase of SSWC and water availability for the remaining dominant woody species. Moreover, dominant woody species in the treated plot exhibited more negative leaf carbon isotope values than the same species in the control plot, indicating released water limitation on plant growth because of the treatment. On the contrary, this treatment exhibited negligible effects on SSWC on the upper slope, environmental water status could only be improved by improving soil water storage capacity. Our results highlight strong competition on SSWC for naturally-restored vegetation on karst hillslopes that stagnated during the early successional stages. In lower slope position where soil is relatively deep, competition-reducing oriented treatment alone can release water limitations on plant growth and provide opportunities for the settlement of species with different hydrologic niches, thus providing a path for enhancing hydrologic functions of naturally-restored karst vegetation.

Negative Density Restricts the Coexistence and Spatial Distribution of Dominant Species in Subtropical Evergreen Broad-Leaved Forests in China

Negative densification affects the spatial distribution of species in secondary evergreen broad-leaved forests and is a key mechanism governing species coexistence. We investigated the effects of habitat heterogeneity and density on the spatial distribution of populations of dominant woody species in a secondary evergreen broad-leaved forest in Wuchaoshan using spatial univariate point pattern analyses. This 6 ha forest dynamic monitoring sample area in Hangzhou, China is a typical secondary subtropical evergreen broad-leaved forest. We found (1) a strong effect of habitat heterogeneity that led to the spatial aggregation of dominant species in the plot. Habitat heterogeneity had a strong impact on mature individuals at different life history stages and of different species on a large scale. (2) Negative density dependence (NDD) generally affected spatial distributions of most dominant species and decreased in magnitude with age class. Therefore, different species of subtropical evergreen broad-leaved forests in China have formed unique spatial structures due to their habitat preferences but are generally subjected to density-dependent effects.

Contrasting plant water-use responses to groundwater depth from seedlings to mature trees in the Gurbantunggut Desert

• Stable hydrogen and oxygen isotope method was used to research size-dependent water use pattern of Haloxylon ammodendron woodland. • Both development stage and groundwater depth had significant effect on water use pattern of H. ammodendron . • H. ammodendron used water from increasingly deeper soil layers throughout its development. • Water absorption depth decreased for seedlings but increased for mature trees with increasing groundwater depth. Haloxylon ammodendron is one of the major dominant woody species in Central Asian desert, and the size-dependent water use pattern of this species significantly affects the functioning of the local ecosystem. Here, we investigated the water-use responses of H. ammodendron to groundwater depth from seedling to mature tree in the Gurbantunggut Desert, China. Three sites were selected along a groundwater depth gradient, with 4.6 m, 7.4 m, and 11.0 m, respectively. Based on basal stem diameter, H. ammodendron plants were grouped into three development stages, namely seedling, sapling, and mature tree. Hydrogen isotope ratios ( δ 2 H) and oxygen isotope ratios ( δ 18 O) were measured for xylem water at different basal stem diameter (BSD) values, soil water in different soil layers, and groundwater. The water sources used by the seedlings, saplings, and mature trees were determined by applying the IsoSource model. The relationship between δ 18 O value of xylem for H. ammodendron and basal stem diameter reflected changes in the water source from upper soil water to deeper soil water as H. ammodendron grows. With the decline in groundwater depth, seedlings decreased their water uptake depth, whereas saplings increased at mid depth but decreased at maximum depth. However, mature trees constantly increased their water absorption depth across sites. Tree height, crown width, and BSD presented a decreasing trend as the groundwater depth declined. The above study promotes the evaluation of the impact of groundwater retrogression on H. ammodendron population in its natural habitat.

Woody species dynamics in Sheka Forest Biosphere Reserve, Southwest Ethiopia

Understanding the dynamics of woody species diversity is the foundation for designing sustainable biodiversity management strategies. Despite an extensive history of cross-sectional ecological studies, scientific gen on the dynamics of woody species diversity over time and space is rare and mostly unexplored in the last remaining Eastern Afromontane Forests. This study aimed to examine the spatial and temporal dynamics of woody species composition, structure, and diversity in the Sheka Forest Biosphere Reserve (SFBR). Data were collected from a total of 43 permanent plots with a dimension of 10 m × 50 m that were laid along the altitudinal gradient. In both 2000 and 2021, the same permanent plots were used and the same approach was followed. Diversity indices and Wilcoxon paired-sample test were employed for the comparison of changes. One hundred one woody species that belong to 84 genera and 41 families and 62 woody species that belong to 54 genera and 32 families were recorded in 2000 and 2021, respectively. During the present study, 47 woody species from the 2000 inventory list including three endemics were not encountered, while eight new species were recorded. The aggregated density and total basal area of woody species decreased from 2590 ± 536 ha−1 to 2454 ± 300 ha−1, and 101.3 m2ha−1 to 72m2ha−1, respectively. The dominant woody species was Ficus sur in 2000, while it was shifted to Coffea arabica in 2021. Woody species richness, evenness, and diversity significantly reduced during the study period. In the mid and lower altitudes with lower slope gradients, where settlement and agricultural expansion were prevalent, the greatest decline in woody species richness, diversity, and evenness, and highest turnover were recorded. Unsustainable use for construction, energy production, creation of job opportunities (income generation), as well as the conversion of forestland to farmland resulted in the rapid decline and massive turnover of woody species diversity. It is important to develop and execute comprehensive sustainable forest management strategies, which include diversification of energy sources and use of energy-saving technologies, strengthening tree planting and management practices for household use and income generation, and diversification of eco-friendly livelihood options. The conservation of endemic and priority species is indispensable to maintaining ecosystem integrity and species diversity.

Hurricanes increase tropical forest vulnerability to drought.

Rapid changes in climate and disturbance regimes, including droughts and hurricanes, are likely to influence tropical forests, but our understanding of the compound effects of disturbances on forest ecosystems is extremely limited. Filling this knowledge gap is necessary to elucidate the future of these ecosystems under a changing climate. We examined the relationship between hurricane response (damage, mortality, and resilience) and four hydraulic traits of 13 dominant woody species in a wet tropical forest subject to periodic hurricanes. Species with high resistance to embolisms (low P50 values) and higher safety margins ( ) were more resistant to immediate hurricane mortality and breakage, whereas species with higher hurricane resilience (rapid post-hurricane growth) had high capacitance and P50 values and low . During 26 yr of post-hurricane recovery, we found a decrease in community-weighted mean values for traits associated with greater drought resistance (leaf turgor loss point, P50 , ) and an increase in capacitance, which has been linked with lower drought resistance. Hurricane damage favors slow-growing, drought-tolerant species, whereas post-hurricane high resource conditions favor acquisitive, fast-growing but drought-vulnerable species, increasing forest productivity at the expense of drought tolerance and leading to higher overall forest vulnerability to drought.

Effects of logging on the trade-off between seed and sprout regeneration of dominant woody species in secondary forests of the Natural Forest Protection Project of China

BackgroundPromoting natural regeneration (including seed and sprout regeneration) of dominant woody species is essential for restoring secondary forests. However, such restoration processes have been decelerated by the enclosure under Natural Forest Protection Project of China (NFPP). It remains unclear how to implement appropriate management measures (e.g., whether to apply logging and the suitable intensity) to facilitate natural regeneration according to the responses of two regeneration modes to management measures. We monitored the early stages of seed regeneration (seed rain, soil seed bank, and 1–3-year-old seedlings) and sprout regeneration (stump sprout rate, stump survival rate, probability of sprouting, and number of sprouts per stump) over the first 3 years (2017–2019) after logging under three intensity regimes (control [0%], 25%, and 50% logging intensity) in secondary forests.ResultsThe seed rain density decreased markedly, seedling density increased insignificantly after logging, and logging promoted seedling survival at an increasing conversion rate of 3-year-old seedlings (37.5% under 0%, 100% under 25%, and 80.95% under 50% logging) compared to those of the control. The proportion of 3-year-old seedlings increased with logging intensity and was the highest (16.2%) at 50% logging intensity. Sprout density was not affected by logging intensity, however, under 25% and 50% logging, it decreased by 27% and 6% in 2018, and by 37% and 33% in 2019, respectively. Seedling density was 41.65- and 15.31-fold higher than that of sprouts in the 50% and 25% logging treatments, respectively. Based on the relative contributions of the two regeneration modes after logging, three groups of natural regeneration patterns were classified for dominant woody species in temperate secondary forests, i.e., seed regeneration preference (Betula dahurica, Carpinus cordata and Fraxinus mandshurica), sprout regeneration preference (Acer mono and Acer pseudosieboldianum) and no preference (Quercus mongolica, Fraxinus rhynchophylla, and Juglans mandshurica).ConclusionIn addition to enclosure, appropriate logging can be applied according to the responses of various natural regeneration patterns of dominant woody species to logging in temperate secondary forests under the NFPP.

Water availability, bedrock, disturbance by herbivores, and climate determine plant diversity in South-African savanna

To identify factors that drive plant species richness in South-African savanna and explore their relative importance, we sampled plant communities across habitats differing in water availability, disturbance, and bedrock, using the Kruger National Park as a model system. We made plant inventories in 60 plots of 50 × 50 m, located in three distinct habitats: (i) at perennial rivers, (ii) at seasonal rivers with water available only during the rainy season, and (iii) on crests, at least ~ 5 km away from any water source. We predicted that large herbivores would utilise seasonal rivers’ habitats less intensely than those along perennial rivers where water is available throughout the year, including dry periods. Plots on granite harboured more herbaceous and shrub species than plots on basalt. The dry crests were poorer in herb species than both seasonal and perennial rivers. Seasonal rivers harboured the highest numbers of shrub species, in accordance with the prediction of the highest species richness at relatively low levels of disturbance and low stress from the lack of water. The crests, exposed to relatively low pressure from grazing but stressed by the lack of water, are important from the conservation perspective because they harbour typical, sometimes rare savanna species, and so are seasonal rivers whose shrub richness is stimulated and maintained by the combination of moderate disturbance imposed by herbivores and position in the middle of the water availability gradient. To capture the complexity of determinants of species richness in KNP, we complemented the analysis of the above local factors by exploring large-scale factors related to climate, vegetation productivity, the character of dominant vegetation, and landscape features. The strongest factor was temperature; areas with the highest temperatures reveal lower species richness. Our results also suggest that Colophospermum mopane, a dominant woody species in the north of KNP is not the ultimate cause of the lower plant diversity in this part of the park.

黔中北亚热带喀斯特次生林动态监测样地：物种组成与群落结构

多年来强烈的人为干扰导致我国西南喀斯特原生森林丧失殆尽并呈现植被灌丛化, 甚至石漠化现象。贵州普定县残存的片段化喀斯特次生林是黔中地区北亚热带森林植被的典型代表, 可作为监测该区域植被结构和动态的样本。在普定县天龙山建立2 hm²(200 m×100 m)森林固定样地, 对样地内胸径≥ 1 cm的所有木本植物进行了每木调查, 分析了木本植物的物种组成、区系特征、径级结构和空间分布格局。结果表明, 样地内有木本植物独立个体14, 025株, 隶属于34科55属66种。重要值最大的前3个科依次是壳斗科、胡桃科和樟科。在区系成分上, 温带区系成分占总属数的52.7%, 而热带区系成分占40.0%, 温带成分多于热带成分。稀有种有21种, 占总种数的31.82%。重要值≥ 1的物种共有13种, 贡献了88.81%的重要值, 重要值排名前三的物种分别是窄叶石栎(Lithocarpus confinis)、化香树(Platycarya strobilacea)和云南鼠刺(Itea yunnanensis)。样地内所有个体的平均胸径仅为5.12 cm, 整体径级分布呈倒“J”, 表明群落更新良好。部分优势种的空间分布表现出较明显的聚集性, 这可能与喀斯特生境的高度异质性有关。对北亚热带喀斯特次生林开展长期监测研究, 将有助于掌握亚热带喀斯特植被恢复过程中生物多样性维持和群落构建的机制。;China has the largest and widest karst regions in the world, which is mainly distributed in the subtropical mountainous regions of southwest China where a unique type of karst vegetation grows. However, the karst forests in these regions have been degraded seriously due to strongly anthropogenic disturbance over many years. Therefore, vegetation thicketization and even rocky desertification have occurred in most karst regions in southwest China. The fragmented karst secondary forest in Puding County is a typical representative of the north subtropical forest vegetation in central Guizhou Province, and can be used as a sample for monitoring the vegetation structure and dynamics in this region. In this study, a 2 hm² (200m×100m) permanent forest plot was established in Tianlongshan in Puding County. Within this plot, all woody plants with a diameter at breast height (DBH)≥1 cm were mapped and identified at species level. Based on these data, the community composition and spatial structure of the vegetation community were analyzed. Results indicated that there were 14, 025 woody plant individuals belonging to 66 species, 55 genera and 34 families. The families with high importance values (Ⅳ) are Fagaceae, Juglandaceae, Lauraceae, Saxifragaceae, Rosaceae, Betulaceae, Rhamnaceae, etc. There were more temperate elements (52.7%) than tropical elements (40.0%) found both at genus level, which showed that the flora was mainly the type of transition from tropical to temperate in the study area. Twenty-one rare species (those with individual number fewer than two in the plot) accounted for 31.82% of the species total. The distribution of rare species in Tianlongshan plot might be determined by multi-dimensional factors such as climate, topography, biogeographic processes, as well as anthropogenic disturbance. In the plot, the 13 species with Ⅳ≥1 contributed 88.81% to the Ⅳ of the community. The species with high Ⅳ are Lithocarpus confinis, Platycarya strobilacea Itea yunnanensis, Machilus cavaleriei, Carpinus pubescens, Pittosporum brevicalyx, Lindera communis, etc. The average DBH of all individuals in the plot was only 5.12 cm, and DBH size-class distribution followed a reverse J shape, indicating abundant regeneration. The spatial distribution of some dominant woody species showed obvious aggregation pattern in plot scales possibly related to high habitat heterogeneity in karst landscape. Monitoring and research on secondary forests in the north subtropical karst region will contribute to further understanding the mechanisms of biodiversity maintenance and community assembly in the process of vegetation restoration. Further studies should concentrate on the maintenance mechanisms of diversity and stability of forest community, the coupling relationships between above-ground and underground ecological processes, and the response and adaptation of vegetation to short-term disturbance events and long-term climate change in the north subtropical karst regions in southwest China.