High-elevation Forests Research Articles

A close up of daily temperature and moisture in two Mexican high-elevation forests

The scarcity of meteorological stations and the strong need for climatic information in alpine forests require the use of large-scale climatic algorithms but the lack of in situ information produces high uncertainty on their suitability. In this study, we used linear mixed models to study the topographic effect (elevation and aspect) and time variations (from hourly to monthly) on temperature (T) and relative humidity (RH) with a 5-year instrumental database. Furthermore, we compared climatic information from a geographical algorithm and our in-situ data. Our data covered two mountains (Tláloc-TLA and Jocotitlán-JOC, State of México), four elevation belts (from 3500 m to 3900 m a.s.l.), and two aspects (Northwest and Southwest). We found differences for average temperature (TLA = 7.56 °C ± 0.03 °C and JOC = 6.98 °C ± 0.02 °C), and relative humidity between mountains (TLA = 69.3% ± 0.12% and JOC = 72.5% ± 0.13%,). The most significant variables explaining T were the elevation (Δ= -0.36 °C by 100 m) and aspect, while the aspect was relevant for RH. May was the warmest month (9.50 °C ± 0.10 °C for average temperature) while September the wettest for both mountains (85.1% ± 0.30% and 87.4% ± 0.25 % RH, respectively). Despite the higher correlations between climatic sources (up to r = 0.83), the geographical algorithm overestimates T and underestimates RH. We propose that when climatic information from geographical algorithms is used in alpine forests, calibrations are needed whenever possible with in situ information.

Recent Warming-Induced Tree Growth Enhancement at the Tibetan Treeline and the Link to Improved Water-Use Efficiency

Tree growth in high-elevation forests may increase as a result of increasing temperatures and CO2 concentrations in the atmosphere (Ca). However, the pattern and the physiological mechanism on how these two factors interact to affect tree growth are still poorly understood. Here, we analyzed the temporal changes in radial growth and tree-ring δ13C for Picea and Abies trees growing in both treeline and lower-elevation forests on the Tibetan Plateau. We found that the tree growth at the treeline has significantly accelerated during the past several decades but has remained largely stable or slightly declined at lower elevations. Further results based on tree-ring δ13C suggest that intrinsic water-use efficiency (iWUE) was generally higher at the treeline than in lower-elevation forests, although increasing trends of iWUE existed for all sites. This study demonstrated that the synergetic effects of elevated Ca and increasing temperatures have increased tree growth at the treeline but may not lead to enhanced tree growth in lower-elevation forests due to drought stress. These results demonstrate the elevational dependence of tree growth responses to climatic changes in high-elevation forests from a physiologically meaningful perspective.

Microbial functional genes driving the positive priming effect in forest soils along an elevation gradient

The priming effect is a pivotal mechanism for microbial regulation of soil C cycling; however, the microbial mechanisms underlying priming effects remain elusive. Here, we combined an isotopic approach with metagenomic sequencing to investigate priming effects at five forest sites along an elevational gradient. Positive priming effects were found across the Quercus aliena var. acutiserrata (low elevation), Q. wutaishanica (low-mid elevation), Betula albosinensis (mid elevation), Abies fargesii Franch (mid-high elevation), and Larix chinensis Beissn (high elevation) forest sites. A significant positive correlation was found between the abundance of microbial C decomposition genes and priming effects (p < 0.05). Further analysis revealed that the microbial functional genes for breaking down stable C (lignin, lipids, and chitin) predominately drove the positive priming effects. Moreover, we found strong correlations between the relative abundance of eight near-complete bacterial genome bins and the priming effect. Five out of the eight genomes were associated with the Proteobacteria, indicating their predominant role in priming effects. Our results revealed that SOM quality (soil organic C, total nitrogen, and ratio of alkyl-C to O-alkyl-C), and soil environment (pH and bulk density) were the major drivers of the priming effect in forest soils as they regulated the abundance of microbial decomposition genes. In conclusion, the present study investigated the metagenomic basis of the priming effect, highlighting the importance of bacteria in association with substrate and environmental factors for C decomposition in forest soils.

Long-term occupancy dynamics of the threatened Cheat Mountain salamander and its competitors in relation to linear habitat fragmentation

Amphibians are declining globally and while many factors are contributing to this decline, habitat loss and degradation caused by climate and land use changes are among the most critical. Habitat degradation and increased interspecific competition are both concerns for long-term viability of the federally-threatened Cheat Mountain salamander (Plethodon nettingi) which is endemic to high elevations in West Virginia. In this study, we quantified the impacts of linear habitat fragmentation (i.e., a linear forest clearing for creation of a ski slope) on local colonization and extinction probabilities in adjacent forested habitat for the Cheat Mountain salamander and two co-occurring competitor species, eastern red-backed salamander (Plethodon cinereus) and Wehrle’s salamander (Plethodon wehrlei). We also quantified long-term changes in total occupancy of the species within the high elevation study area. We surveyed the salamander community annually from 1988 to 2021 using diurnal natural cover object searches at 43 plots, with 1988 representing three years following linear habitat fragmentation. For each species, we used dynamic occupancy models to identify and model influential covariates for initial occupancy, colonization, extinction, and detection probability. We found that distance to fragmentation was positively correlated with colonization probability for Cheat Mountain salamanders, indicating negative edge effects of the linear forest clearing. Distance to fragmentation was negatively correlated with colonization probability for eastern red-backed salamanders, potentially indicating this species benefited from increased solar radiation or reduced competition from Cheat Mountain salamanders. Predicted occupancy of eastern red-backed salamanders and Wehrle’s salamanders increased over the 34 year monitoring period, indicating potential for increased competitive interactions. Our study suggests that extensive linear habitat fragmentation could result in degraded habitat for Cheat Mountain salamanders in the adjacent forest, and that potential for interactions with competitor species is increasing in high elevation forest stands.

Optimizing Carbon Cycle Parameters Drastically Improves Terrestrial Biosphere Model Underestimates of Dryland Mean Net CO2 Flux and its Inter‐Annual Variability

AbstractDrylands occupy ∼40% of the land surface and are thought to dominate global carbon (C) cycle inter‐annual variability (IAV). Therefore, it is imperative that global terrestrial biosphere models (TBMs), which form the land component of IPCC earth system models, are able to accurately simulate dryland vegetation and biogeochemical processes. However, compared to more mesic ecosystems, TBMs have not been widely tested or optimized using in situ dryland CO2 fluxes. Here, we address this gap using a Bayesian data assimilation system and 89 site‐years of daily net ecosystem exchange (NEE) data from 12 southwest US Ameriflux sites to optimize the C cycle parameters of the ORCHIDEE TBM. The sites span high elevation forest ecosystems, which are a mean sink of C, and low elevation shrub and grass ecosystems that are either a mean C sink or “pivot” between an annual C sink and source. We find that using the default (prior) model parameters drastically underestimates both the mean annual NEE at the forested mean C sink sites and the NEE IAV across all sites. Our analysis demonstrated that optimizing phenology parameters are particularly useful in improving the model's ability to capture both the magnitude and sign of the NEE IAV. At the forest sites, optimizing C allocation, respiration, and biomass and soil C turnover parameters reduces the underestimate in simulated mean annual NEE. Our study demonstrates that all TBMs need to be calibrated for dryland ecosystems before they are used to determine dryland contributions to global C cycle variability and long‐term carbon‐climate feedbacks.

Comparisons of photosynthesis-related traits among understory lichens, mosses and vascular plant leaves in a high-elevation subalpine forest

AbstractMany mosses and lichens thrive in high-elevation subalpine forests and even become dominant species on the forest floor. Although they play an irreplaceable ecological role in the forest, less is known about their eco-physiological status, and how their photosynthesis-related functional traits differ from those of co-occurring vascular plants. We determined the carbon, nitrogen and phosphorus concentrations and stoichiometric ratios, tissue mass per area, chlorophyll concentrations and photosynthetic light–response curves of three lichens, three mosses and four vascular plants in a subalpine forest in the eastern Tibetan Plateau of China. Trait values were compared among and within each group. The lichens possessed a higher nitrogen concentration than that of mosses. In addition, the two poikilohydric groups exhibited lower concentrations of nitrogen, phosphorus and chlorophyll, light-saturated assimilation rates and photosynthetic nutrient use efficiencies, and higher light compensation points than those of vascular plant leaves. Furthermore, variations in photosynthesis-related traits for lichen species reflect their different adaptation strategies to their corresponding environments. In contrast, the differences were weak among the three forest-floor mosses and the three herb species. These results demonstrate that the high abundance of understory lichens and mosses in the high-elevation subalpine forest cannot be explained by the photosynthesis-related traits.

Bimodal activity of diurnal flower visitation at high elevation.

Successful pollination in animal‐pollinated plants depends on the temporal overlap between flower presentation and pollinator foraging activity. Variation in the temporal dimension of plant–pollinator networks has been investigated intensely across flowering seasons. However, over the course of a day, the dynamics of plant–pollinator interactions may vary strongly due environmental fluctuations. It is usually assumed there is a unimodal, diurnal, activity pattern, while alternative multimodal types of activity patterns are often neglected and deserve greater investigation. Here, we quantified the daily activity pattern of flower visitors in two different habitats contrasting high elevation meadows versus forests in Southwest China to investigate the role of abiotic conditions in the temporal dynamics of plant–pollinator interactions. We examined diurnal activity patterns for the entire pollinator community. Pollinator groups may differ in their ability to adapt to habitats and abiotic conditions, which might be displayed in their patterns of activity. We hypothesized that (a) pollinator communities show multimodal activity patterns, (b) patterns differ between pollinator groups and habitat types, and (c) abiotic conditions explain observed activity patterns. In total, we collected 4,988 flower visitors belonging to six functional groups. There was a bimodal activity pattern when looking at the entire pollinator community and in five out of six flower visitor groups (exempting solitary bees) regardless of habitat types. Bumblebees, honeybees, dipterans, lepidopterans, and other insects showed activity peaks in the morning and afternoon, whereas solitary bees were most active at midday. Activity of all six pollinator groups increased as solar radiation increased and then decreased after reaching a certain threshold. Our findings suggest that in habitats at higher elevations, a bimodal activity pattern of flower visitation is commonly employed across most pollinator groups that are diurnal foragers. This pattern may be caused by insects avoiding overheating due to elevated temperatures when exposed to high solar radiation at midday.

Changes in Root-Shoot Allometric Relations in Alpine Norway Spruce Trees After Strip Cutting.

Silvicultural interventions such as strip cuttings can change the resource availability of the edge trees. This may alter tree allometry, as light regime, water, and nutrient availability can change at the forest edge. Increased root growth may optimize resource uptake and/or enhance tree anchorage to withstand the altered wind regime. However, little is known about the patterns of the root–shoot allometric responses to strip cuttings. In three alpine stands differing in climate, site productivity, and stand characteristics, we selected 71 Norway spruce trees and took increment cores from stems, root collars, and main roots. This enabled us to study changes in the long-term root-stem allometry for 46 years and short-term allometric responses to intervention. The effects of cutting were compared between edge trees and trees from the stand interior in 10 years before and after the intervention. The long-term allocation to roots increased with stem diameter, with the strongest effects on the regularly managed stand with the tallest and largest trees. These results support the allometric biomass partitioning theory, which postulates resource allocation patterns between different plant organs to depend on plant size. Strip cutting on north-facing slopes boosted edge-tree growth in all plant compartments and enhanced allocation to roots. This change in allometry started 2 years after cutting but disappeared 7–8 years later. In the post-cutting period, the highest root–shoot increase was observed in the small trees independent of the site. This indicates the change in growing conditions to have the strongest effects in formerly suppressed trees. Thus, the effect of such acclimation on the wind firmness of subdominant spruce trees is a question with high importance for optimizing cutting layouts in lowering post-cutting vulnerability to disturbance. The results from this case study contribute to a better understanding of the structural acclimation of spruce trees from high-elevation forests to new forest edges. However, for a more mechanistic understanding of environmental drivers, further analyses of tree-ring stable isotopes are recommended.

Characterizing Canopy Openness Across Large Forested Landscapes Using Spherical Densiometer and Smartphone Hemispherical Photography

AbstractCanopy openness is an important forest characteristic related to understory light environment and productivity. Although many methods exist to estimate canopy openness, comparisons of their performance tend to focus on relatively narrow ranges of canopy conditions and forest types. To address this gap, we compared two popular approaches for estimating canopy openness, traditional spherical densiometer and modern smartphone hemispherical photography, across a large range of canopy conditions (from closed canopy to large gaps) and forest types (from low-elevation broadleaf to high-elevation conifer forests) across four states in the northeastern United States. We took 988 field canopy openness measurements (494 per instrument) and compared them across canopy conditions using linear regression and t-tests. The extensive replication allowed us to quantify differences between the methods that may otherwise go unnoticed. Relative to the densiometer, smartphone photography overestimated low canopy openness (&amp;lt;10%) but it underestimated higher canopy openness (&amp;gt;10%), regardless of forest type.

White-headed woodpecker nesting habitat at multiple spatial scales: Are habitat preferences adaptive?

Ecological theory predicts that animals will select habitats for breeding that confer an adaptive advantage through increased reproductive success. We therefore expect to see congruence between habitat preferences and measures of fitness. We studied abundance, nest site selection, and nest survival in white-headed woodpeckers (Picoides albolarvatus) in four forest types along an elevational gradient in the southern Sierra Nevada, California. Our primary objective was to ascertain what habitat features white-headed woodpeckers were selecting for nesting and at what scale, and whether those choices translated into increased reproductive success. We examined sets of models that included abiotic factors and habitat at three spatial scales: nest site (0.04 ha), local (~1 ha), and home range (~125 ha). White-headed woodpeckers were more abundant at higher elevations, with low abundance in low-elevation ponderosa pine forest, moderate abundance in mid-elevation mixed conifer forest, and reached their highest abundance in true fir habitat before becoming rare in high-elevation lodgepole pine forest. They both selected for and nested more successfully at higher elevations in true fir forest. White-headed woodpecker nesting ecology in the Sierra Nevada demonstrated a mixed pattern of congruence between characteristics important to nest habitat selection and nest survival. We found congruence for abiotic and home range scale models (agreement between preferences and nest survival), indicating adaptive selection. At the landscape scale, White-headed woodpeckers selected closed-canopy conifer forests with abundant edges. Habitat preferences at the nest site scale were negatively related to nest survival, suggesting maladaptive habitat selection at this scale. White-headed woodpeckers selected open forest with higher basal area of snags compared to available sites, but nest survival was higher in forest with higher canopy closure and lower basal area of snags. Local scale models were weak and did not help clarify habitat relationships. Our results highlight the importance of considering multiple spatial scales when examining habitat preferences. The primary management considerations for white-headed woodpecker habitat include retention of large, suitable snags and the need to consider forest heterogeneity. The close association with ponderosa pine forests and large-seeded pines found over most of their range did not hold in the Sierra Nevada, where white-headed woodpeckers were most abundant in true fir forests and selected and nested more successfully in true fir forests. Habitat models developed outside the area for which they were developed should be validated before they are applied to other locations.

Drymonia mexicana (Gesneriaceae), a new endemic species from Veracruz (Mexico)

Ongoing research on the systematics of Drymonia (Gesneriaceae) resulted in the discovery of a new species, Drymonia mexicana Clavijo &amp; J.L. Clark of the Gesneriaceae (tribe: Gesnerieae, subtribe: Columneinae). The new species is distinguished by the combination of narrow leaves with large corollas, glabrous leaves adaxially, calyx lobes ovate, and campanulate flowers with the tube slightly recurved ventrally and the limb purple. The new species is endemic to high elevation forests in the the Mexican state of Veracruz. The plant is commonly cultivated, but its introduction from Mexico to the horticultural community is unknown. Here, we describe and illustrate Drymonia mexicana Clavijo &amp; J.L. Clark and present a key to identify the species of Drymonia native to Mexico.

Individual and seasonal variation in the movement behavior of two tropical nectarivorous birds

BackgroundMovement of animals directly affects individual fitness, yet fine spatial and temporal resolution movement behavior has been studied in relatively few small species, particularly in the tropics. Nectarivorous Hawaiian honeycreepers are believed to be highly mobile throughout the year, but their fine-scale movement patterns remain unknown. The movement behavior of these crucial pollinators has important implications for forest ecology, and for mortality from avian malaria (Plasmodium relictum), an introduced disease that does not occur in high-elevation forests where Hawaiian honeycreepers primarily breed.MethodsWe used an automated radio telemetry network to track the movement of two Hawaiian honeycreeper species, the ʻapapane (Himatione sanguinea) and ʻiʻiwi (Drepanis coccinea). We collected high temporal and spatial resolution data across the annual cycle. We identified movement strategies using a multivariate analysis of movement metrics and assessed seasonal changes in movement behavior.ResultsBoth species exhibited multiple movement strategies including sedentary, central place foraging, commuting, and nomadism , and these movement strategies occurred simultaneously across the population. We observed a high degree of intraspecific variability at the individual and population level. The timing of the movement strategies corresponded well with regional bloom patterns of ‘ōhi‘a (Metrosideros polymorpha) the primary nectar source for the focal species. Birds made long-distance flights, including multi-day forays outside the tracking array, but exhibited a high degree of fidelity to a core use area, even in the non-breeding period. Both species visited elevations where avian malaria can occur but exhibited little seasonal change in elevation (< 150 m) and regularly returned to high-elevation roosts at night.ConclusionsThis study demonstrates the power of automated telemetry to study complex and fine-scale movement behaviors in rugged tropical environments. Our work reveals a system in which birds can track shifting resources using a diverse set of movement behaviors and can facultatively respond to environmental change. Importantly, fidelity to high-elevation roosting sites minimizes nocturnal exposure to avian malaria for far-ranging individuals and is thus a beneficial behavior that may be under high selection pressure.

Biotic and abiotic drivers of dispersion dynamics in a large-bodied tropical vertebrate, the Western Bornean orangutan.

Understanding of animal responses to dynamic resource landscapes is based largely on research on temperate species with small body sizes and fast life histories. We studied a large, tropical mammal with an extremely slow life history, the Western Bornean orangutan (Pongo pygmaeus wurmbii), across a heterogeneous natural landscape encompassing seven distinct forest types. Our goals were to characterize fluctuations in abundance, test hypotheses regarding the relationship between dispersion dynamics and resource availability, and evaluate how movement patterns are influenced by abiotic conditions. We surveyed abundance in Gunung Palung National Park, West Kalimantan, Indonesia, for 99 consecutive months and simultaneously recorded weather data and assessed fruit availability. We developed a Bayesian hierarchical distance sampling model to estimate population dispersion and assess the roles of fruit availability, rainfall, and temperature in driving movement patterns across this heterogeneous landscape. Orangutan abundance varied dramatically over space and time. Each forest type was important in sustaining more than 40% of the total orangutans on site during at least one month, as animals moved to track asynchronies in fruiting phenology. We conclude that landscape-level movements buffer orangutans against fruit scarcity, peat swamps are crucial fallback habitats, and orangutans' use of high elevation forests is strongly dependent on abiotic conditions. Our results show that orangutans can periodically occupy putative-sink habitats and be virtually absent for extended periods from habitats that are vitally important in sustaining their population, highlighting the need for long-term studies and potential risks in interpreting occurrence or abundance measures as indicators of habitat importance.

The greening effect characterized by the Normalized Difference Vegetation Index was not coupled with phenological trends and tree growth rates in eight protected mountains of central Mexico

In temperature-limited ecosystems such as high-elevation forests, rising temperatures and increasing carbon dioxide can result in a greening effect and changes in the phenology of the forests. Up to now, phenological metrics of subtropical high-elevation forests remain primarily unquantified, which strongly limits a global comprehension of climate change impacts. We assessed the long-term trend dynamics (greenness and land surface phenology) using the Normalized Difference Vegetation Index (NDVI) and compared them with data from an existing dendrochronological network that came from eight protected mountains in the Trans-Mexican Volcanic Belt in central Mexico during the last 20 yr (2000–2019). We found three main NDVI clusters reflecting a longitudinal geographical pattern (Pacific, Center, and the Gulf of Mexico). A notable greening effect at the canopy level was seen for all mountains (up to 23.8% increase concerning the year 2000). Nevertheless, the NDVI trends were not uniform, and they differed along an elevation gradient with the highest increases at the bottom. Minimum temperature and soil moisture positively impacted the NDVI time series and explained up to 87% of the variance, while maximum temperature negatively affected. Regarding phenological metrics, the start, and end of the growing season were the day of the year 148 ± 20 (late-May) and 9 ± 12 (early-January), respectively, with an average length of 226 ± 33 d, differing from previous studies related to annual tree-ring formation. We did not see a later or earlier start of either the spring or the fall, which partially refutes the hypothesis that the growing season extended despite the increase in temperature. Finally, our investigation revealed that the common greening effect was not parallel with radial growth trends, except for the wettest site from the Gulf of Mexico cluster, and partially related to the forest management strategies. Further modelling of regional phenology coupled with more intensive tree-ring monitoring is needed to explain the factors that mediate the processes of photosynthesis (NDVI) and storage of carbon (tree-ring formation) under a global warming outlook.

Future fire-driven landscape changes along a southwestern US elevation gradient

Over the twenty-first century, the combined effects of increased fire activity and climate change are expected to alter forest composition and structure in many ecosystems by changing postfire successional trajectories and recovery. Southwestern US mountain ecosystems contain a variety of vegetation communities organized along an elevation gradient that will respond uniquely to changes in climate and fire regime. Moreover, the twentieth-century fire exclusion has altered forest structure and fuel loads compared to their natural states (i.e., without fire suppression). Consequently, uncertainties persist about future vegetation shifts along the elevation gradient. In this study, we simulated future vegetation dynamics along an elevation gradient in the southwestern US comprising pinyon-juniper woodlands, ponderosa pine forests, and mixed-conifer forests for the period 2000–2099, to quantify the effects of future climate conditions and projected wildfires on species productivity and distribution. While we expected to find larger changes in aboveground biomass, species diversity and species-specific abundance at low elevation due to warmer and drier conditions, the largest changes occurred at high elevation in mixed-conifer forests and were caused by wildfire. The largest increase in high-severity and large fires were recorded in this vegetation type, leading to high mortality of the dominant species, Picea engelmannii and Abies lasiocarpa, which are not adapted to fire. The decline of these two species reduced biomass productivity at high elevation. In ponderosa pine forests and pinyon-juniper woodlands, fewer vegetation changes occurred due to higher abundance of well-adapted species to fire and the lower fuel loads mitigating projected fire activity, respectively. Thus, future research should prioritize understanding of the processes involved in future vegetation shifts in mixed-conifer forests in order to mitigate both loss of diversity specific to high-elevation forests and the decrease in biomass productivity, and thus carbon storage capacity, of these ecosystems due to wildfires.

Live fast, die young: Climate shifts may favor Great Basin bristlecone pine or limber pine in sub-alpine forest establishment

As a result of climatic warming, tree species ranges are generally expected to move upslope in elevation. Although this upward range migration is likely determined principally by temperature, other factors such as habitat and soil moisture availability contribute to a species’ ability to establish in new areas. Throughout the montane ecosystems of the western US, effective drying is predicted, resulting from increasing temperatures and potentially reduced precipitation. The tree species that can better establish in these future high-elevation forests will likely expand their ranges while potentially excluding other species. Using a greenhouse experiment, we compared the response of limber pine and Great Basin bristlecone pine, the two dominant Great Basin sub-alpine species, to various levels of drought at different stages during their establishment. We found that during the first year of establishment, limber pine had greater diameter growth but lower height growth than bristlecone pine, while during the second year of establishment, limber pine had greater diameter and height growth rates across all treatments. During the post-germination period and in the second year of establishment, bristlecone pine seedlings had a higher survival rate than limber pine. During the first year of establishment there was no determinable difference in survival between the species. Limber pine displayed earlier mortality and lower survival under nearly all treatments across both first-and second-year periods. In general, an increase in drought severity corresponded to an overall earlier mortality onset as well as decreased survival in both species. However, in the first year of establishment under the no water treatment, both species showed later mortality than all other treatments, even having longer survival durations than a treatment with slightly more water. Limber pine seedlings effectively grew at higher rates than bristlecone pine seedlings, while dying younger. The different response of each species to drought stress during the establishment phase suggests an asymmetric competition under two possible climate change scenarios: a warmer, wetter future may favor limber pine, while a warmer, drier future may favor GB bristlecone pine. For the Great Basin’s sub-alpine forest community, this foreshadows a more complex future change in tree demographics than simple upslope migration.

Three new extinct species from the endemic Philippine cloud rat radiation (Rodentia, Muridae, Phloeomyini)

AbstractThe 18 extant members of the Tribe Phloeomyini, the “cloud rats,” constitute an endemic Philippine radiation of arboreal herbivores that range in size from ca. 18 g to 2.7 kg, most occurring in cloud forest above 1,200 m elevation. Although calibrated phylogenies indicate that the Phloeomyini is estimated to have begun diversifying within the Philippines by ca. 10–11 million years ago, no extinct fossil species have been described, severely limiting our understanding of this distinctive radiation. Our studies of fossil and subfossil small mammal assemblages from the lowland Callao Caves complex in NE Luzon, Philippines, have produced specimens of Phloeomyini that date from ca. 67,000 BP to the Late Holocene (ca. 4,000 to 2,000 BP). We identify three extinct species that we name as new members assigned to the genera Batomys, Carpomys, and Crateromys, distinguished from congeners by body size, distinctive dental and other morphological features, and occupancy of a habitat (lowland forest over limestone) that differs from the high-elevation mossy forest over volcanic soils occupied by their congeners. Batomys cagayanensis n. sp. is known only from two specimens from ca. 67,000 BP; Carpomys dakal n. sp. and Crateromys ballik n. sp. were present from ca. 67,000 BP to the Late Holocene. These add to the species richness and morphological diversity of this endemic Philippine radiation of large folivores, and show specifically that the lowland fauna of small mammals on Luzon was more diverse in the recent past than it is currently, and that Luzon recently supported five species of giant rodents (ca. 1 kg or more). All three occurred contemporaneously with Homo luzonensis, and two, the new Carpomys and Crateromys, persisted until the Late Holocene when multiple exotic mammal species, both domestic and invasive, were introduced to Luzon, and new cultural practices (such as making pottery) became evident, suggesting that modern humans played a role in their extinction.

Recovery: Fast and Slow—Vegetation Response During the 2012–2016 California Drought

AbstractThe 2012–2016 California Drought severely impacted natural vegetation across a wide range of environmental gradient. Although several studies have reported an increase in plant water stress and mortality, the spatiotemporal variations of ecosystem productivity responses and the associated environmental and biological drivers remain unclear. Here, using Enhanced Vegetation Index from the Moderate resolution imaging spectrometer, we found that 45% of the natural ecosystems showed an abrupt change (breakpoint [BP]) in productivity during 2012–2016. There were three major contrasting temporal patterns of productivity responses: (i) a steady increase under higher temperature followed by a decline due to accumulated moisture depletion (high elevation forest) or temperature decrease (high elevation nonforest), (ii) gradual decline during the drought followed by a rapid recovery within 1 year after drought stress was partially relieved, and (iii) both a gradual decline and an abrupt decline. The magnitude of abrupt changes was negatively correlated (r = −0.80, p &lt; 0.001) with initial gradual changes. Overall, changes during BP offset, on average, 57% of the preceding gradual responses. The spatial variability in ecosystem response patterns is driven by both environmental and biological factors. Particularly, for forests, positive BP was driven by increasing rainfall and decreasing temperature, while negative BP was mainly driven by the precipitation anomaly. By 2019, 33% of the natural vegetation have recovered to the level of EVI in 2010. Ecosystem responses to multiyear droughts can influence ecosystem dynamics in a complex pattern. Multiple ecohydrological factors should be considered to understand and predict the long‐term drought impacts on ecosystems.

Slow recovery from soil disturbance increases susceptibility of high elevation forests to landslides

Natural hazards such as shallow landslides are common phenomena that disturb soil and damage forests. Quantifying the recovery of forest vegetation after a hazard is important for determining the window of susceptibility to new disturbance events, especially at high elevations, where extreme weather events are frequent and the growing season is short. Plant roots can reduce the size of this window on unstable hillslopes, by adding mechanical reinforcement (cr) to soil and increasing its matric suction, termed here as hydrological reinforcement (ch). These data are used in landslide models to calculate the Factor of Safety (FoS) of a hillslope. We calculated temporal variations in cr and ch in naturally regenerated mixed, montane forests in the French Alps. In these closed-canopy forests, open-canopy gaps were present, with understory vegetation comprising herbs, forbs and shrubs. At three altitudes (1400, 1700 and 2000 m), we dug small trenches as proxies for shallow landslide events and calculated cr before soil disturbance in both open gaps and closed forests. Then, using monthly tree root initiation and mortality data measured in rhizotrons, we calculated monthly cr for four years after the disturbance. To compare results with cr, ch was estimated using matric suction data that were measured in trenches at 1400 m for >1 year. Temporal FoS was then calculated using an infinite slope stability model.Results showed that finer, short-lived roots contributed little to soil reinforcement compared to thicker, long-lived roots. After disturbance, mean cr (over the entire soil profile) never fully recovered to the initial value at any site, although >90% recovery was observed in open gaps at 1400 m. Mean cr was slow to recover in closed forests, especially at 2000 m, where only 19% recovery occurred after 41 months. The ch in closed forests was considerable during the summer months, but marked increases in soil water moisture resulted in lower FoS, especially during December to April, when soil was near saturation. As cr changed little throughout the year, it was a more reliable contributor to slope stability. Our results show therefore, that particular attention should be paid to high elevation forests after a disturbance. Also, during the process of recovery, the highly variable soil water dynamics in closed forest can result in seasonal hotspots of vulnerability. Therefore, when tree transpiration is low, our results highlight a need for careful monitoring on steep or unstable slopes, especially in disturbed closed-canopy forests.

Effects of Surveying for the Federally Endangered Spruce-Fir Moss Spider (Microhexura montivaga Crosby &amp; Bishop) on its Bryophyte Habitat

Microhexura montivaga (Spruce-fir Moss Spider) is a federally endangered arachnid endemic to high-elevation montane conifer forests of the southern Appalachian Mountains. The spider is cryptic and difficult to monitor because this species lives in the interface between the bryophyte mat and the rock surface. Since temporary removal of the bryophyte mat is necessary to monitor the spider, surveyors may negatively impact the spider's habitat during monitoring. To help inform survey protocol for this endangered species, we studied reattachment rates of bryophyte mats to rock surfaces after their removal. In 2017, we surveyed sixty 10 cm × 10 cm plots, assigning a plot to either control or treatment (i.e., application of water post-reattachment). We monitored plots for 1 year post-survey to determine reattachment rates. The majority of plots (70%) reestablished after 1 year, whereas 15% did not reattach or showed substantial prolonged (e.g., ∼1 year) desiccation and 15% completely fell off or had 100% prolonged desiccation and were chlorotic. We found that mat depth and overstory canopy cover had no effect on mat reestablishment, although bryophyte type did. We found no difference between treatment and control plots, suggesting that no treatment is needed for mats to reestablish under the conditions described. Rock slope significantly influenced reestablishment rates, highlighting that surveying bryophyte mats on slopes >80% may diminish or destroy habitat. Further research is needed to determine long-term monitoring effects on the spider and its habitat, especially in relation to disturbance regimes and ecological restoration of Picea rubens (Red Spruce).