Land-use Legacies Research Articles

Looking at the modern landscape of submediterranean Greece through a palaeoecological lens

The importance of understanding the long-lasting legacy of past land use on modern ecosystems has long been acknowledged. However, the magnitude and persistence of such legacies have been assessed only occasionally. Northern Greece has been a gateway of farming into mainland Europe during the Neolithic, thus providing a perfect setting to assess the potential impact of land-use history on present-day ecosystems. Additionally, the marked Holocene climatic variability of the southern Balkans makes it possible to investigate climate-vegetation-land use interactions over long timescales. Here, we have studied a sediment record from Limni Vegoritis (Northern Greece) spanning the past ∼9000 years using palaeoecological proxies (pollen, spores, stomata, microscopic charcoal). We aimed to reconstruct long-term vegetation dynamics in submediterranean Greece, to assess the environmental factors controlling them and to establish the legacies of the long history of land use in the modern landscape. We found that the Early Holocene afforestation, mainly oak woodlands, was delayed because of suboptimal moisture conditions. Later, colder and drier conditions during the rapid climate change centred around the ‘8.2 ka event’ triggered woodland opening and the spread of wooded (Juniperus) steppe vegetation. First indicators of farming activities are recorded during this period, but their abundances are too low to explain the concurrent large deforestation episode. Later, pinewoods (probably dominated by Pinus nigra) with deciduous Quercus spread and dominated the landscape for several millennia. These forests experienced repeated multi-centennial setback-recovery episodes associated with land-use intensification, but pines eventually declined ∼2500–2000 years ago during Classical times under heavy land use comprising intense pastoralism. This was the starting point for the present-day landscape, where the main ‘foundation’ taxon of the ancient forests (Pinus cf. nigra) is missing, therefore attesting to the strong imprint that historical land use has left on the modern landscape.

Forest floor environment overrules global change treatment effects on understorey communities in a mesocosm experiment.

Light availability profoundly influences plant communities, especially below dense tree canopies in forests. Canopy disturbances, altering forest floor light conditions, together with other environmental changes such as climate change, nitrogen deposition and legacy effects from previous land-use will simultaneously impact forest understorey communities. Yet, knowledge on the individual effects of these drivers and their potential interactions remains scarce. Here we performed a forest mesocosm experiment to assess the influence of warming, illumination (simulating canopy opening), nitrogen deposition and soil land-use history (comparing ancient and post-agricultural forest soil) on understorey community composition trajectories over a 7-year period. Strikingly, understorey communities primarily evolved in response to the deeply shaded ambient forest conditions, with experimental treatments exerting only secondary influences. The overruling trajectory steered all mesocosms towards slow-colonizing forest specialist communities dominated by spring geophytes with lower nutrient-demand. The illumination treatment and, to a lesser extent, warming and agricultural land-use legacy slowed down this trend by advancing fast-growing resource-acquisitive generalist species. Warm ambient temperatures induced thermophilization of plant communities in all treatments, including control plots, towards higher dominance of warm-adapted species. Nitrogen addition accelerated this thermophilization process and increased the community light-demand signature. Land-use legacy effects were limited in our study. Our findings underscore the essential role of limited light availability in preserving forest specialists in understorey communities and highlight the importance of maintaining a dense canopy cover to attenuate global change impacts. It is crucial to integrate this knowledge in forest management adaptation to global change, particularly in the face of increasing demands for wood and wood products and intensified natural canopy disturbances.

Cadmium soil contamination alters plant-pollinator interactions

Soil heavy metal contamination is often an unintended byproduct of historic land-use. This contamination can negatively impact resident plants and their interactions with other organisms. Plant fitness in contaminated landscapes depends not only on plant growth, but also on the maintenance of interactions with pollinators. Cadmium (Cd) is a heavy metal that is commonly found in agricultural, urban, and industrial ecosystems as a legacy of historic land-use. It is a prioritized pollutant in soils because of its wide distribution and strong biotoxicity. To understand how Cd influences plant growth and pollinator interactions, we grew sunflowers in media with three different Cd concentrations to represent the range of Cd contamination faced by sunflowers growing on land recovering from past land-use. We measured Cd contamination effects on sunflower morphology and pollinator foraging behavior, specifically the number of visits and visit duration. We then measured seed number and weight to determine if contamination directly or indirectly, as mediated by pollinators, altered plant fitness. Plant height was negatively correlated with Cd concentration, but contamination alone (in the absence of pollinators) did not affect sunflower reproduction. Bumble bees visited sunflowers grown in Exceeding Threshold Cd concentrations less often and for shorter time compared to visits to Below Threshold Cd sunflowers, but honey bees and sweat bees showed similar foraging behavior across Cd contamination treatment levels. Sunflower seed set was positively correlated with the total number of pollinator visits, and sunflowers grown in Exceeding Threshold Cd soil had marginally lower seed set compared to those grown in Below Threshold Cd soil. Our results suggest that at Exceeding Threshold Cd contamination levels plant-pollinator interactions are negatively affected with consequences for plant fitness.

Overstory functional groups indicate the legacy of land use in a secondary tropical forest in southwestern China

Overstory functional groups indicate the legacy of land use in a secondary tropical forest in southwestern China

Land use legacies affect early tropical forest succession in Mexico

AbstractQuestionsAgricultural expansion is one of the dominant drivers of forest and biodiversity loss, and shifting cultivation is the most widely used form of agriculture in many tropical forest regions. Where forests have been cleared, they have the potential to recover once the land is abandoned. However, legacies of land use are often overlooked in successional studies, and a deeper understanding of this legacy effect is needed to define efficient restoration practices using natural or assisted regeneration. Here, we analysed how land‐use history affects soil properties and early succession on abandoned agricultural fields in two contrasting Mexican socio‐ecological systems.LocationMexico, Oaxaca and Chiapas.MethodsWe sampled soil and monitored vegetation for 2 years after agricultural abandonment, and interviewed landowners about their land‐use practices.ResultsLand‐use practices were clearly influenced by landowners’ social context (residence time, rural or urban origin), and topography and soil type also constrained or facilitated land‐use practices. Soil characteristics were strongly affected by three land‐use practices: mechanical tillage decreased soil N and K; frequent herbicide and pesticide use increased N and K; and for pasture systems, stocking density increased soil bulk density and decreased pH and N. High‐intensity land management practices, specifically use of machinery, had the highest impact on early forest succession. When machinery was not used, the frequency of land‐use practices, particularly weeding frequency, is the main factor influencing tree cover and sapling diversity.ConclusionsTo facilitate post‐agricultural forest recovery, we recommend restoration efforts using natural regeneration in areas with low previous land‐use intensity and frequency.

Agricultural land-use legacies affect soil bacterial communities following restoration in a global biodiversity hotspot

Ecosystem restoration in post-agricultural landscapes is a critical response to agricultural land abandonment, climate change, and the escalating biodiversity crisis. However, effective restoration of these landscapes can be hampered by land-use legacies that create biotic and abiotic barriers to ecosystem recovery, particularly in ancient Tertiary landscapes where vegetation is adapted to nutrient deficient soils. While our understanding of how to overcome these barriers when restoring plant communities is improving, there is limited knowledge of how these legacies impact on recovery of soil microbiota – the biodiverse and functionally-important communities of soil microbes. Here, we used amplicon sequencing of the bacterial 16S rRNA gene extracted from soils across a restoration project in southwest Western Australia, a global biodiversity hotspot, to examine recovery of soil microbiota following post-agricultural restoration. We sampled soils at six sites under four land conditions – degraded post-agriculture, actively revegetated post-agriculture, passively regenerated, and remnant bushland – generating 1,609,618 sequences corresponding to 15,009 unique bacterial taxa. We show that soil bacterial communities in revegetated and degraded samples were similar across sites but strongly dissimilar to adjoining remnant samples. We show that limited recovery of bacterial communities was linked to elevated soil phosphorus levels. Together, our results indicate soil microbiota have not recovered despite revegetation taking place up to 17 years ago, and this lack of recovery is likely driven by soil nutrient legacies from past agricultural practices. Our study highlights a key challenge faced by conservation practitioners when integrating soil microbiota into ecosystem restoration in post-agricultural landscapes in ancient, nutrient-poor landscapes.

Land-use legacies affect the composition and distribution of tree species and their belowground functions in a succession from old-field to mature temperate forest

Forests undergoing ecological succession following abandonment from agricultural use (i.e., old fields) are ubiquitous in temperate regions of the U.S. and Europe. Ecological succession in old fields involves changes in vegetation composition influenced by factors such as land-use history, soil conditions, and dispersal limitations. Species’ behavioral, morphological, physiological and life-history attributes influence the outcomes of environmental and biotic filters on distribution and abundance. However, many studies have focused on aboveground attributes, while less attention has been placed on belowground species characteristics that influence community assembly and function. In this study, we used a trait-based approach to examine how aboveground plant composition and distribution vary with plant root functional traits (e.g., mycorrhizal association) that mediate access for nutrients such as nitrogen (N) and phosphorous (P). We inventoried every tree stem (n ​= ​11,551) in a 10-ha forested area containing old-field and historical forests and matched every species with root functional traits (n ​= ​33) from established databases. We found that land-use history influences community composition and distribution in old-field forests, which also varied with belowground root functional traits. Community composition in old-field forests, which were dominated by Acer saccharum and non-native species, were largely associated with arbuscular mycorrhizae (AM) and higher root nutrient concentrations. On the other hand, community composition in historical forests – largely dominated by Tsuga canadensis – were associated with ectomycorrhiza (EcM) and more variation of root length and depth. These results suggest that changes in aboveground communities have implications for belowground ecosystem services (e.g., nutrient cycling) which are important to forest ecosystem development. Trait-based approaches can elucidate mechanisms of community assembly, and understanding how traits influence species coexistence and interactions can inform management decisions related to biodiversity conservation and restoration efforts in disturbed or altered forests.

ArchaeoSRP

AbstractFor much of its history, archaeological research has relied on site-specific projects, regional comparisons, and theory building from case studies. However, recent research themes concerning the emergence of complex social-ecological systems and long-term land-use legacies require a new approach to archaeological data. Large-scale syntheses of archaeological data provide an effective way forward to address these new research themes. In more concise terms, “big questions” require “big data” to help answer them. The archaeological information collected by the USDA Forest Service is one such “big dataset” and represents an incalculable investment in time, resources, and expertise. This article explores this concept and presents an R package (ArchaeoSRP) designed to extract archaeological information from USDA Forest Service site record files. We demonstrate the functionality of this R package through a case study examining the archaeological data for the Cle Elum Ranger District, within Central Washington's Okanogan-Wenatchee National Forest. Our results reveal the efficiency of using automated methods to extract, organize, and synthesize district-level archaeological data, which, in turn, reveal patterns of precontact and historic land use that were otherwise not distinguishable.

Anthropogenic land-use legacies underpin climate change-related risks to forest ecosystems.

Forest ecosystems with long-lasting human imprints can emerge worldwide as outcomes of land-use cessation. However, the interaction of these anthropogenic legacies with climate change impacts on forests is not well understood. Here, we set out how anthropogenic land-use legacies that persist in forest properties, following alterations in forest distribution, structure, and composition, can interact with climate change stressors. We propose a risk-based framework to identify anthropogenic legacies of land uses in forest ecosystems and quantify the impact of their interaction with climate-related stress on forest responses. Considering anthropogenic land-use legacies alongside environmental drivers of forest ecosystem dynamics will improve our predictive capacity of climate-related risks to forests and our ability to promote ecosystem resilience to climate change.

White-tailed deer responses to acoustic predator cues are contingent upon past land use and contemporary fire regime

Abstract Prey can assess the immediate risk of predation by detecting cues of predator presence, and it is expected that prey should invest in costly antipredator behaviors when a cue of predator presence is detected. Features of the habitat in which the cue is detected, such as vegetative concealment, serve as indirect cues of risk and can mediate how prey respond to direct cues of predator presence. Past agricultural land use and contemporary fire regimes are common disturbances that may modify prey perceptions of risk and could, therefore, alter prey responses to direct cues of predator presence. We examined whether the overlap of these two disturbances affected white-tailed deer (Odocoileus virginianus) responses to cues of predator presence by measuring deer vigilance and foraging bout duration in response to coyote (Canis latrans) vocalizations across 20 woodlands that varied in past land use and contemporary fire regime. Frequent fire regimes consistently increased deer visibility to predators across both land-use history contexts. Deer exhibited no behavioral response to the predator cue in habitats containing infrequent fire regimes or agricultural legacies. Deer responded to the cue in frequently burned woodlands without agricultural legacies through increased vigilance and time spent at a foraging location. These findings reveal that land-use legacies and contemporary fire regimes can mediate how prey respond to direct cues of risk. They also suggest that prey may balance the uncertainty associated with cues of predation risk with the urgency of responding to a potential attack by being vigilant and remaining in place.

A bird’s eye view of ecosystem conversion: Examining the resilience of piñon-juniper woodlands and their avian communities in the face of fire regime change

Climate change and land-use legacies have caused a shift in wildfires and post-fire growing conditions. These changes have strong potential to diminish the resilience of many ecosystems, with cascading effects and feedbacks across taxa. Piñon-juniper (PJ) woodlands are a diverse and widespread forest type in the western US and are home to many obligate and semi-obligate bird species. As such, this system is ideal for understanding wildfire resilience, or lack thereof, in terms of both vegetation and wildlife associations. This study evaluated post-fire vegetation structure and associated avian communities following three wildfires; one that burned one year prior to sampling (recent fire), and two that burned approximately 25 years previously (old fires). Vegetation characteristics and the habitat use of PJ-associated bird species were compared across severely burned patches, unburned refugia, and unburned sites outside of the burn perimeter. We expected wildfire to alter vegetation and bird usage for the first few years post-fire, which we observed in our recent burns. However, even 25-years post-fire, little recovery to PJ woodland had occurred and the associated bird communities had not returned, compared to unburned areas. No piñon regeneration was observed in any burned areas and no juniper regeneration in the recent fire. Piñon seedling densities in unburned sites and refugia averaged 80 ha−1 and 151 ha−1, respectively, while juniper seedling densities were 220 ha−1 in both habitat types. Habitat use for thirteen PJ-associated species were modeled, three of which (Woodhouse’s Scrub Jay, Ash-throated Flycatcher, and Virginia’s Warbler) used all habitats. Four species (American Robin, Gray Vireo, Black-throated Gray Warbler, and Gray Flycatcher) were essentially absent from the old burn habitat, reflecting species-specific need for mature piñon or juniper trees and/or greater canopy cover. Conversely, birds that were present in the old burn habitat (including Virginia’s Warbler, Blue-gray Gnatcatcher, Woodhouse’s Scrub-jay, Ash-throated Flycatcher, and Spotted Towhee) are typically associated with habitat edges, high shrub cover, or cavity nests. Altered vegetation structure and bird habitat use in burned areas 25 years post-fire are evidence for enduring conversion to non-forest vegetation types. However, unburned refugia embedded in burned areas maintain forest attributes and support obligate bird communities, supporting ecological function and biological diversity.

Transhumance, shielings and soil fertility – land-use legacies in Menstrie Glen, Scotland

ABSTRACT Whilst transhumance has been researched as a livestock and land management system, its legacy on soil- nutrient levels is unknown. This study addresses changes in soil chemistry associated with historical transhumance grazing management with the aim of establishing if soil-nutrient levels can shed new insights into land-use legacies originating from past transhumance in Scotland. The study is focused on one aspect of transhumance, the shielings associated with milking livestock formerly operating in the uplands of the Scottish Midland Valley. A literature review is presented focusing on the history, functioning and geographic distribution of transhumance systems in Scotland set within a global context. This is followed by a detailed examination of two shieling sites in Menstrie Glen in the Ochil Hills. Their relationship to topography is considered, with vegetation survey and chemical analyses for plant macronutrients of soils collected in the vicinity also carried out. Underpinned by theories integrating biogeochemical fluxes and agropastoral activities it is established that there is moderate enrichment of local nutrient levels still evident at the Menstrie Glen shieling sites today. Review of historical and environmental sources suggests that local nutrient levels reflect temporal dynamics of shieling establishment, functioning and abandonment with limited evidence to suggest this was driven by population pressure and adaptation to Little Ice Age climate change. The analyses lead to insights about wider ecological impacts of different forms of land use in the face of climate change and population pressure, carrying implications for land use in Scotland and the challenges facing extant transhumance systems in countries where both these issues are pressing today.

Drivers of tree colonization, species richness, and structural variation during the initial three decades of natural forest colonization in abandoned agricultural soils

Natural colonization of abandoned agricultural soils has been proposed as a cost-effective strategy for simultaneously mitigating the climate crisis, restoring ecological integrity, and promoting the re-establishment of native biodiversity. The success and speed at which forests develop in the presence of land-use legacies are highly variable, and empirical knowledge on the drivers of the initial phase of temperate forest colonization in a range of site conditions is lacking. We analyzed and compared drivers of the initial three decades of natural forest colonization in 33 afforestation sites laid out between 1990 and 2018, in Denmark. We analyzed how the age of colonization, size of the area, soil type, topography, and abundance of neighboring woody vegetation influenced woody vegetation cover, species richness, and variation in vegetation structure of the colonizing woody species. We found that woody vegetation cover, species richness, and structural variation increased significantly with time since abandonment. Woody vegetation cover was significantly higher in sites with abundant neighboring vegetation and on loamy soils compared to sand or clay. Woody vegetation cover tended to be higher in sites with sloping terrain. Species richness increased significantly in sites with loamy or clay soil and sites with sloping terrain. After accounting for the other drivers, none of the elements were influenced by the size of the area. The results suggest that time since abandonment, neighboring mature woody vegetation, soil and topography are key drivers of the different elements of colonization. This knowledge can be used to prioritize areas for natural colonization and to improve active afforestation methods, especially in new forests where the main focus is on nature quality and biodiversity.

Soil microbiomes in lawns reveal land-use legacy impacts on urban landscapes

Land-use change is highly dynamic globally and there is great uncertainty about the effects of land-use legacies on contemporary environmental performance. We used a chronosequence of urban grasslands (lawns) that were converted from agricultural and forested lands from 10 to over 130 years prior to determine if land-use legacy influences components of soil biodiversity and composition over time. We used historical aerial imagery to identify sites in Baltimore County, MD (USA) with agricultural versus forest land-use history. Soil samples were taken from these sites as well as from existing well-studied agricultural and forest sites used as historical references by the National Science Foundation Long-Term Ecological Research Baltimore Ecosystem Study program. We found that the microbiomes in lawns of agricultural origin were similar to those in agricultural reference sites, which suggests that the ecological parameters on lawns and reference agricultural systems are similar in how they influence soil microbial community dynamics. In contrast, lawns that were previously forest showed distinct shifts in soil bacterial composition upon recent conversion but reverted back in composition similar to forest soils as the lawns aged over decades. Soil fungal communities shifted after forested land was converted to lawns, but unlike bacterial communities, did not revert in composition over time. Our results show that components of bacterial biodiversity and composition are resistant to change in previously forested lawns despite urbanization processes. Therefore land-use legacy, depending on the prior use, is an important factor to consider when examining urban ecological homogenization.

Microbial functioning in Mediterranean forest soils: Does land use legacy matter?

AbstractLand use is known to be one of the major factors driving soil microbial and physico‐chemical properties. Understanding its long‐term effect remains a major challenge in assessing current soil functioning. Here, soil microbial and physico‐chemical properties of recent and very recent forests (forests developed in 1958 vs. after 1958) were compared with those of ancient forests (present in 1860 and 1958) to assess the effect of Land Use Legacy (LUL). LUL effects were further analysed depending on contrasting (i) climate conditions (sub‐humid vs. humid Mediterranean climates) and (ii) seasons (winter and summer), to examine whether LUL modified microbial responses to different spatio‐temporal climate conditions. Microbial indicators (lignocellulolytic activities, basal respiration, and microbial biomass) and physico‐chemical properties (C and N contents, mineralogical analyses, pH and conductivity) were assessed. A strong effect of past agricultural practice (terrace cultivation) was observed in soils from very recent forests: reduced microbial biomass and activities as well as number of Quercus pubescens stems together with increased phosphorous content and pH. Interestingly, LUL effect did not affect microbial and physico‐chemical responses to seasonal contrasts (winter vs. summer). Microbial response to LUL was not influenced by climate while climate modified LUL effects on some physico‐chemical properties (CaCO3, Corg, and K content). Moreover, soil recovered “pristine” physico‐chemical and microbial functional properties after at least 60 years of reforestation.

DETECTION OF PHYTOGEOGRAPHIC INDICATORS WITH REMOTE SENSING AND GEOARCHAEOLOGY FOR DEVELOPMENT OF A LONG-TERM CLIMATE MONITORING STATION IN ISRAEL

Abstract. The Mediterranean basin is a strong candidate for monitoring climate change successfully, a priority of UN SDG 13, because of its long settlement history. Human-environmental contact has typically hindered monitoring efforts because the natural indicators that enable dependable monitoring have been altered anthropogenically. This research describes a two-step process which turns that synanthropism into an advantage through geoarchaeology, remote sensing, GIS, meteorology, and floristic classification. First, archaeological survey data were employed in a semi-arid region of Israel to identify areas of more and less intensive land-use over 2300 years. Trend surfaces were derived in GIS from ancient periods of most intense monoculture agriculture (Hellenistic, Byzantine, and Ottoman). 2020 land-cover was classified using VENμS satellite wet / dry season NDVI imagery and an airborne LiDAR canopy height model. This was reclassed after fieldwork to three broad land-cover classes and cross-tabulated with the 2300-year land-use intensity model in GIS. The results indicate a land-use legacy whereby woody perennial species are more abundant where land-use was cumulatively less intense. Second, unmanned aerial vehicle surveys were conducted in these areas of less-intense land-use. There, on lightly grazed lands where woody encroachment occurs but chamaephytes regenerate due to the grazing, microplots were established. Phanerophyte and chamaephyte shrubs were identified based on Raunkiaer type and the species associated with chorotype (geographic origin). This was compared with aridity index values derived for the study area between 2010-2022. The study provides a prototype, using dependable phytogeographic indicators, that may be developed into a long-term climate monitoring station (LTCMS).

Macroinvertebrate assemblages from a stream-wetland complex: a case study with implications for assessing restored hydrologic functions

Legacies of past land use persist today in the form of incised, single-threaded stream channels with dramatically different hydrologic functions of pre-colonial stream valleys. Restoration practices that aim to return lost hydrologic functions by re-establishing floodplain and groundwater connections should result in stream habitat and biological assemblages that differ from modern, single-threaded channels. The aim of this case study was to identify attributes of macroinvertebrate assemblages that might serve as biological indicators of improved hydrologic functions following the restoration of a stream-wetland complex, similar to a Stage 0 restoration, of a headwater valley in the Western Allegheny region of the USA. We monitored hydrologic functions and macroinvertebrate assemblages from stream reaches of a restored and unrestored site over multiple years during the early years following restoration. Reduced bed mobility and increased flow duration indicated improved hydrologic functions from the restored site. Aggregate metrics that capture functional attributes of macroinvertebrate assemblage (i.e., density and biomass) were consistently greater from the restored site. EPT biomass from restored pools was 3–4 × greater than amounts from the unrestored site as a result of consistently greater mayfly abundance. Restored pools also supported a subassemblage of taxa with life history attributes that are aligned with habitat conditions created from improved hydrologic functions. Results from this case study demonstrate the importance of habitat-specific sampling designs that report the absolute abundance of potential biological indicators. Findings from this case study should help guide the development of rapid biological indicators of improved hydrologic functions.

Effect of land-use legacy on the future carbon sink for the conterminous US

Abstract. Modeling the effects of the terrestrial carbon sink in the future depends upon not just current-day land use and land cover (LULC) but also the legacy of past LULC change (LULCC), which is often not considered. The age distribution of trees in the forest depends upon the history of past disturbances, while the nutrients in the soil depend upon past LULC. Thus, establishing the correct initial state of the vegetation and soil is crucial to model accurately the effect of biogeochemical cycling with environmental change in the future. This study models the effects of LULCC from 1750 to 2014 using the land-use harmonization dataset (LUH2) of land-use transitions with the terrestrial ecosystems model (TEM) for the conterminous US. Modeled LULC include plant functional types (PFTs) of potential vegetation, as well as managed cropland, pastureland, and urban areas. LULCC is treated using a cohort approach, in which a separate cohort occurs every year there is a land-use transition, thereby ensuring proper age structure of forests and regrowth with the correct soil nutrients. From 2000–2014 the modeled net ecosystem productivity (NEP) is 989 TgC yr−1 for the conterminous US but only −15 TgC yr−1 if accounting for carbon lost from land-use transitions and management. The hypothesis is that the initial state of the vegetation and soils significantly affects the future state of the terrestrial carbon sink. In this study, LULC remains constant in the future, with the NCAR CCSM4 RCP8.5 climate used to force the TEM-Hydro model. The following experiments are run from 2015 to 2100, including (a) restarting from existing cohorts in 2014 (RESTART), (b) reinitializing in 2015 based on condensing the cohorts for each PFT into a single cohort (CONDENSED), and (c) restarting from average cohort conditions for each PFT (AVERAGE). The NEP is too low when using condensed cohorts without reinitializing due to a larger increase in heterotrophic respiration (Rh) resulting from the assumption of mature forests. The carbon stocks are larger than using all the cohorts if condensed cohorts are reinitialized due to the assumption of mature, equilibrated forests. Where nitrogen-limited, forest regrowth is enhanced if regrowth starts from more nutrient-rich conditions. Water fluxes are dominated by environmental factors but can be slightly dependent upon the underlying carbon dynamics. It is therefore necessary to account for past disturbances when modeling future changes in carbon dynamics.

Genetic Diversity of Five Broadleaved Tree Species and Its Spatial Distribution in Self-Regenerating Stands

European forest ecosystems are currently subject to various disturbances and shifts in land-use legacies. To be able to forecast the trends and consequences of the changes in genetic diversity following these disturbances, it is of crucial importance to understand the genetic dynamics of natural tree populations. The present study aimed at determining the extent and spatial distribution of genetic diversity in five common broadleaved tree species in Lithuania in both mature (putatively maternal) stands and in natural regeneration (juveniles) of the respective species. The genetic diversity of Quercus robur, Betula pendula, Populus tremula, Alnus glutinosa, and Fraxinus excelsior was assessed using eight nuclear microsatellite loci for each species; 417 samples of regenerating juveniles and 141 samples of putatively maternal trees were analyzed in total. The investigated populations of self-regenerating Q. robur, B. pendula, A. glutinosa, and F. excelsior juveniles showed spatially random genetic structures, while P. tremula regenerated mostly via root suckers and formed clonal groups. The genetic diversity in regenerating juveniles of all species was as high as in putatively maternal stands. The detection of adequate (substantial) genetic diversity in the studied regenerating populations of these five broadleaved tree species suggests that in Lithuania these species have a good potential to adapt to changing environmental conditions.

Measuring the immeasurable: A structural equation modeling approach to assessing soil health

Soil health is recognized as an important ecosystem property sensitive to human impact. As a concept, soil health cannot be directly measured, and so assessment and modeling efforts largely rely upon key biological, chemical, and physical indicators. Efforts to develop an overall soil health index are largely lacking due to significant statistical challenges and the necessity for regional calibration. Taken from the field of educational research, structural equation modeling (SEM) is an attractive approach to enhance the reliability and validity of soil health scoring. Therefore, SEM may be utilized to advance research efforts to understand management practices impacts on soil health. Our objectives were to develop a robust scoring function that (i) captures the concept of soil health and latent variables, (ii) adjusts scores by inherent soil properties and legacy of intensive land use to adequately reflect our regional conditions and contemporary land management, and (iii) meets the diverse practitioner needs. Through this process, we refined our minimum dataset of soil health indicators and reconceptualized soil health indicators into functional properties. Our results support the development of a robust single level or a multilevel SEM model–depending on the practitioner's goals–that accounts for repeated sampling or pseudoreplication. While the SEM scoring functions were highly related to the conventional scoring approach, SEM outperformed the conventional methods in terms of its wider distribution of scores–and thus enhanced discriminatory power on the lower and higher range of scores. We also confirmed that the SEM scoring function that includes adjustments for mineralogy and legacy of intensive land use successfully differentiates among contemporary management practices and land use. Therefore, we have confidence that the tool is reliable and appropriate to further examine more nuanced impacts of land use change and management practices within a given land use across time and space covering a diversity of soils. (300 words).