Scaling up ecosystem productivity from patch to landscape: a case study of Changbai Mountain Nature Reserve,China

Scaling up ecosystem processes from plots to landscapes is essential for understanding landscape structure and functioning as well as for assessing ecological impacts of land use and climate change. This study illustrates an upscaling approach to studying the spatiotemporal pattern of ecosystem processes in the Changbai Mountain Nature Reserve in northeastern China by integrating simulation modeling, GIS, remote sensing data, and field-based observations. The ecosystem model incorporated processes of energy transfer, plant physiology, carbon dynamics, and water cycling. Using a direct extrapolation scheme, the patch-level ecosystem model was scaled up to quantify the landscape-level pattern of primary productivity and the carbon source-sink relationship. The simulated net primary productivity (NPP) for the entire landscape, consisting of several ecosystem types, was 0.680 kg C m⁻² yr⁻¹. The most widely distributed ecosystem type in this region was the mixed broad-leaved and Korean pine (Pinus koraiensis) forest, which had the highest NPP (1.084 kg C m⁻² yr⁻¹). The total annual NPP for all ecosystem types combined was estimated to be 1.332 Mt C yr⁻¹. These results suggest that the Changbai Mountain landscape as a whole was a carbon sink, with a net carbon sequestration rate of about 0.884 Mt C yr⁻¹ for the study period. The simulated NPP agreed reasonably well with available field measurements at a number of locations within the study landscape. Our study provides new insight into the relationship between landscape pattern and ecosystem processes, and useful information for improving management practices in the Changbai Mountain Nature Reserve, which is one of the most important forested landscapes in China. Several research needs are discussed to further refine the modeling approach and reduce prediction uncertainties.     

Nutrient flows and land use change in a rural catchment: a modelling approach

Due largely to unprecedented land-use changes in the Porijõgi River catchment (southern Estonia) losses of nutrients and organic matter have decreased significantly. During the period 1987–1997 abandoned lands increased from 1.7 to 10.5% and arable lands decreased from 41.8 to 23.9%. At the same time, the runoff of total-N, total-P, SO₄ and organic matter (after BOD₅) decreased from 25.9 to 5.1, 0.32 to 0.13, 78 to 48, and 7.4 to 3.5 kg ha^–1 yr^–1, respectively. The most significant decreases occurred in agricultural subcatchments while the changes were insignificant in the forested upper course catchment. A simple empirical model which incorporates land-use pattern, fertilization intensity, soil parameters and water discharge accurately described the variations of total-N and total-P runoff in both the whole catchment and its agricultural subcatchments (R ² varies from 0.95–0.99 for N to 0.49–0.93 for P). In small agricultural subcatchments the rate of fertilization is found the most important factor for nitrogen runoff, whereas in larger mosaic watersheds land use pattern plays the main role. Seven alternative scenarios compiled on the base of the empirical model allow to forecast potential nitrogen and phosphorus losses from the catchment. This information can be used in further landscape and regional planning of the whole region.     

Land use history (1840–2005) and physiography as determinants of southern boreal forests

Land use history has altered natural disturbance dynamics, causing widespread modifications of the earth’s forests. The aim of this study is to reconstruct a regional, spatially-explicit, fire and logging history for a large southern boreal forest landscape (6,050 km²) of eastern Canada. We then examined the long-term influence of land use history, fires, and physiographical gradients on the area’s disturbances regimes, present-day age structure and tree species composition. Spatially-explicit fire (1820–2005) and logging (1900–2005) histories were reconstructed from forestry maps, terrestrial forest inventories and historical records (local newspapers, travel notes, regional historical reviews). Logistic regression was used to model the occurrence of major boreal tree species at the regional scale, in relation to their disturbance history and physiographical variables. The interplay of elevation and fire history was found to explain a large part of the present-day distribution of the four species studied. We conclude that human-induced fires following the colonization activities of the nineteenth and twentieth centuries have increased fire frequency and the dominance of fire-adapted species at lower elevations. At higher elevations, the low historical fire frequency has fostered the dominance of fire-sensitive species. Twentieth-century forestry practices and escaped settlement fires have generated a forest landscape dominated by younger forest habitats than in presettlement times. The expected increase of wildfire activity in North America’s eastern boreal forest, in conjunction with continued forest management, could have significant consequences on the resilience of boreal forests.     

Comparing the carbon sequestration capacity of temperate deciduous forests between urban and rural landscapes in central Japan

Urbanisation is increasing tremendously in some parts of the world. Consequently, many rural forests may become depleted, although many opportunities exist for urban forests to increase. However, few studies have quantified the carbon (C) sequestration capacities of urban and rural forests in specific climatic zones. The present study compared carbon sequestration in two temperate deciduous forests located in Nagoya and Toyota, central Japan. The Nagoya University forest represented an urban forest, and a site in Toyota represented a rural forest. The urban forest at Nagoya University had comparatively smaller areas of green space and larger areas of buildings and roads. Land uses for building and road, which are typical of urban areas, result in smaller diurnal temperature ranges but higher air temperature, vapour pressure deficit, and atmospheric carbon dioxide (CO₂) concentration. The urban forest in this study exhibited higher gross ecosystem exchange (GEE), especially in the active growing season from May to September, suggesting the possible effect of CO₂ fertilisation. However, higher air temperatures caused comparatively smaller net ecosystem exchange (NEE) because of higher ecosystem respiration (RE). Although both forests functioned as CO₂ sinks at annual time scales, the rural Toyota forest site (5.43 t C ha^–1 yr^–1) had 36% higher net ecosystem production (NEP=–NEE; the negative sign indicates uptake by the forest ecosystem from the atmosphere) than that at the urban forest. The higher normalised respiration (i.e., RE/GPP ratio; GPP=–GEE where GPP represents gross primary production) at the Nagoya University forest might be attributable to factors associated with the degree of urbanisation. Thus, in temperate forests, factors associated with urbanisation may reduce the atmospheric carbon sink function by accelerating respiration. This is an issue of global interest, as many countries are experiencing rapid urbanisation.     

Regional land-cover conversion in the U.S. upper Midwest: magnitude of change and limited recovery (1850–1935–1993)

Land-use legacies can persist for hundreds to thousands of years, influencing plant species composition, nutrient cycling, water flows, and climate. To understand how land use has affected regional land-cover composition in Wisconsin (USA), we assessed the magnitude and direction of change in land cover between: (1) c.1850, at the onset of Euro-American settlement; (2) c.1935, the period of maximum clearing for agriculture following widespread forest logging; and (3) 1993, which, especially in northern Wisconsin, follows farm abandonment and forest recovery. We derived land-cover maps using U.S. Public Land Survey records (c.1850), the Wisconsin Land Economic Inventory (c.1935), and Landsat TM satellite data (1993). We stratified Wisconsin (145,000 km²) into two ecological provinces and used spatial error models, multinomial logistic regression, and non-metric multi-dimensional scaling ordination to examine change. Between 1850 and 1935, forest cover in the North declined from 84% to 56%, cropland increased to 24%, and mixed/coniferous forests and savannas were replaced by deciduous forests. In the South, formerly dominant savannas (69%) and prairies (6%) were mostly converted to cropland (51%) and pasture (11%). Remnant deciduous savannas and coniferous forests and savannas were replaced by deciduous forests. Remarkably little recovery to pre-settlement land-cover classes occurred from 1935 to 1993. Less cropland was abandoned than expected, and there was little net gain in coniferous/mixed forest. Based on these general land-cover classes, current cover is significantly different from that in 1850, but not from that in 1935, and thus continues to reflect historical logging and agricultural patterns. These results provide a historical framework for measuring associated changes in ecosystem function and can be used to guide restoration where desirable and feasible.     

Human appropriated net primary productivity as a metric for land use planning: a case study in the US Great Lakes region

Context

Human appropriation of net primary productivity (HANPP) is employed as a measure of human pressures on biodiversity, though largely at global and national scales rather than landscape to regional scales where many conservation decisions take place. Though gaining in familiarity, HANPP is not widely utilized by conservation professionals.

Objectives

This study, encompassing the US side of the Great Lakes basin, examines how regional distributions of HANPP relate to landscape-based biodiversity proxy metrics used by conservation professionals. Our objectives were (1) to quantify the HANPP of managed lands at the county scale; and (2) to assess spatial patterns of HANPP in comparison to landscape diversity and local habitat connectedness to determine if the metric can provide useful information to conservation professionals.

Methods

We aggregated forest and cropland NPP data between 2005 and 2015 and coupled it with previously published potential vegetation maps to quantify the HANPP of each county in the study region. We mapped the outputs at 500 m resolution to analyze spatial relationships between HANPP and landscape metrics of biodiversity potential.

Results

Area-weighted HANPP across our study region averaged 45% of NPP, down to 4.9% in forest-dominated counties. Greater HANPP correlated with reduced landscape diversity (p?<?0.001, r²?=?0.28) and reduced local habitat connectedness (p?<?0.001, r²?=?0.36).

Conclusion

HANPP could be used as an additional tool for conservation professionals during regional-scale land use planning or conservation decision-making, particularly in mixed-use landscapes that both support important biodiversity and have high levels of primary production harvest.

     

Invasions of non-native earthworms related to population declines of ground-nesting songbirds across a regional extent in northern hardwood forests of North America

Non-native invasive earthworms (Lumbricus spp.) substantially change previously earthworm-free hardwood forests of North America by consuming the leaf litter layer, reducing cover and richness of herbaceous plants, and increasing dominance of sedges and grasses. These changes have been associated with reduced density of Ovenbirds (Seiurus aurocapilla) and Hermit Thrushes (Catharus guttatus) in 10–20 ha forest stands, and with reduced Ovenbird nesting success. Whether earthworms reduce songbird populations across a regional extent is unclear. We investigated relationships among Lumbricus, vegetation structure, landscape patterns of forest cover, and density of four ground-nesting songbird species at points scattered across the Chequamegon-Nicolet (Wisconsin) and Chippewa (Minnesota) National Forests, USA. In both national forests, Ovenbird density was significantly lower at invaded points than Lumbricus-free points, but only in sugar maple (Acer saccharum) and sugar maple/basswood (Tilia americana) (hereafter, maple-basswood) woodlands. Density of the Hermit Thrush, Black-and-white Warbler (Mniotilta varia), and Veery (Catharus fuscescens) did not differ in relation to Lumbricus. In maple-basswood forests, Lumbricus biomass was the best predictor of Ovenbird density, with greater biomass associated with reduced density. Vegetation structure and landscape pattern variables received weak support as density predictors. Across all forest types, Ovenbird density was most strongly related to forest cover within 500 and 1,000 m radii. Our results suggest that earthworm invasions may pose a regional threat to Ovenbirds within maple-basswood forests of the U.S. northern Midwest.     

Effects of aspect and altitude on carbon cycling processes in a temperate mountain forest catchment

Context

Varying altitudes and aspects within small distances are typically found in mountainous areas. Such a complex topography complicates the accurate quantification of forest C dynamics at larger scales.

Objectives

We determined the effects of altitude and aspect on forest C cycling in a typical, mountainous catchment in the Northern Limestone Alps.

Methods

Forest C pools and fluxes were measured along two altitudinal gradients (650–900 m a.s.l.) at south-west (SW) and north-east (NE) facing slopes. Net ecosystem production (NEP) was estimated using a biometric approach combining field measurements of aboveground biomass and soil CO₂ efflux (SR) with allometric functions, root:shoot ratios and empirical SR modeling.

Results

NEP was higher at the SW facing slope (6.60?±?3.01 t C ha^?1  year^?1), when compared to the NE facing slope (4.36?±?2.61 t C ha^?1 year^?1). SR was higher at the SW facing slope too, balancing out any difference in NEP between aspects (NE: 1.30?±?3.23 t C ha^?1 year^?1, SW: 1.65?±?3.34 t C ha^?1 year^?1). Soil organic C stocks significantly decreased with altitude. Forest NPP and NEP did not show clear altitudinal trends within the catchment.

Conclusions

Under current climate conditions, altitude and aspect adversely affect C sequestering and releasing processes, resulting in a relatively uniform forest NEP in the catchment. Hence, including detailed climatic and soil conditions, which are driven by altitude and aspect, will unlikely improve forest NEP estimates at the scale of the studied catchment. In a future climate, however, shifts in temperature and precipitation may disproportionally affect forest C cycling at the southward slopes through increased water limitation.

     

Influence of fire regimes on lodgepole pine stand age and density across the Yellowstone National Park (USA) landscape

A probabilistic spatial model was created based on empirical data to examine the influence of different fire regimes on stand structure of lodgepole pine (Pinus contorta var. latifolia) forests across a >500,000-ha landscape in Yellowstone National Park, Wyoming, USA. We asked how variation in the frequency of large fire events affects (1) the mean and annual variability of age and tree density (defined by postfire sapling density and subsequent stand density) of lodgepole pine stands and (2) the spatial pattern of stand age and density across the landscape. The model incorporates spatial and temporal variation in fire and serotiny in predicting postfire sapling densities of lodgepole pine. Empirical self-thinning and in-filling curves alter initital postfire sapling densities over decades to centuries. In response to a six-fold increase in the probability of large fires (0.003 to 0.018 year⁻¹), mean stand age declined from 291 to 121 years. Mean stand density did not increase appreciably at high elevations (1,029 to 1,249 stems ha⁻¹) where serotiny was low and postfire sapling density was relatively low (1,252 to 2,203 stems ha⁻¹). At low elevations, where prefire serotiny and postfire lodgepole pine density are high, mean stand densities increased from 2,807 to 7,664 stems ha⁻¹. Spatially, the patterns of stand age became more simplified across the landscape, yet patterns of stand density became more complex. In response to more frequent stand replacing fires, very high annual variability in postfire sapling density is expected, with higher means and greater variation in stand density across lodgepole pine landscapes, especially in the few decades following large fires.     

The utility of ancient forest indicator species in urban environments: A case study from Poznań, Poland

We aimed to assess the impact of land-use structure on AFIS occurrence and evaluation of these bioindicators in urban conditions. We compiled data about forest continuity based on archival maps and forest management plans; floristic records of 79 AFIS occurrences were collected within a 1 × 1 km grid and land-use form structure in Poznań (W Poland). We tested fidelity of AFIS using χ² tests and effects of land-use structure using random forest models. We also checked spatial autocorrelation and its impact on AFIS distribution patterns within old and recent forests, using spatially explicit generalized linear models. We found a strong relationship between AFIS number per grid square and fraction of forests and waters in land-use structure. Relationships between AFIS distribution and land-use shows that AFIS are a good proxy describing human impact or an urbanity gradient. AFIS number per grid square shows small, but significant positive spatial autocorrelation, which suggests possibilities of migration into new forests. AFIS, treated as a bioindicative group of species, may be a useful indicator of landscape and land-use structure transformation in urban environments. Occurrence of many AFIS that are endangered at the city scale indicates the need for conservation of old forests in urban areas, to preserve biodiversity in urban environments. Thus, AFIS may act as indicators of old forests with high conservation value in cities, which need special protection.     

Restoring the iconic Ulmus americana to urban landscapes: Early tree growth responds to aboveground conditions

Native trees provide a range of benefits, from supporting native wildlife to climate regulation, and many urban natural resource managers prioritize native tree planting and restoration. Ulmus americana (American elm) was once widely planted in American cities but has been decimated by Dutch elm disease (DED; Ophiostoma ulmi). Our study evaluated U. americana establishment and growth across urban landscapes. We planted ramets from three DED-tolerant U. americana genotypes (RV16, RV474, and Sunfield) along an urbanization gradient in Newark, DE and Philadelphia, PA, and assessed physiological and morphological responses. We analyzed how U. americana clone growth, chlorophyll fluorescence, and foliar chemistry relate to impervious surface area, ozone (O₃) concentrations, and soil characteristics. The one-year post planting mortality rate was low (4%) demonstrating these elms can withstand urban environmental conditions when provided ample water supply and protection from deer. As expected, the elms differed in growth rate, chlorophyll fluorescence, and foliar chemistry between the cities. Elms planted in Philadelphia had greater photosynthetic capacity in July (F_v/F_m = 0.76) and September (F_v/F_m = 0.75), while Newark elms had greater photosynthetic capacity in August (F_v/F_m = 0.78). Depleted foliar δ¹³C signatures in Philadelphia suggest elms are experiencing greater fossil-fuel derived atmospheric CO₂ than in Newark, possibly contributing to the greater growth rates observed in Philadelphia compared to Newark. Enriched foliar δ¹⁵N and greater foliar %N in Philadelphia clones suggest they are experiencing greater N deposition from NO_x-derived sources compared to Newark clones. Clones growing in Philadelphia had greater foliar nutrient concentrations despite growing in soils with greater heavy metal concentrations. These foliar-soil chemistry patterns suggest that clones growing in Philadelphia respond positively to urban environmental conditions in a large city, whereas clones growing in Newark may be experiencing N limitation in the first year of growth after planting.     

森林风景区生态系统服务价值评估

基于湖北省利川苏马荡和英山桃花冲2个风景区的森林资源特点与实地调查数据，依据《森林生态系统服务功能评估规范》(GB/T 38582-2020)定量评估2019年湖北省森林风景区生态系统服务价值。结果表明，苏马荡风景区的森林生态服务总价值为3.94亿元/年，以涵养水源价值和固碳释氧价值主(共占79.56%);生态服务贡献最大的是针阔混交林，其次为马尾松林、柳杉林、日本落叶松林和杉木林。桃花冲风景区森林生态服务总价值为5.47亿元/年，涵养水源价值在森林生态系统服务价值所占比例最大，其次为森林游憩价值、固碳释氧价值、生物多样性保育价值、保育土壤价值、林木积累营养物质价值和净化大气环境价值；森林生态服务价值中针叶林贡献最高，其次是针阔混交林、阔叶林。研究结果客观反映这2个典型区域森林生态体系建设取得的成果和对经济社会发展的贡献，同时可为湖北省相关部门“两山”转化和“双碳战略”实施提供依据，对区域森林经营管理水平的进一步提升、实现森林可持续发展具有重要意义。     

Regional ecosystem simulation: A general model for simulating snow accumulation and melt in mountainous terrain

A general snow accumulation and melt model was developed to (1)determine how accurately snow accumulation and ablation can bemodeled over heterogeneous landscapes with routinely available climatologic, topographic, and vegetation data, and (2) improveestimates of annual forest snow hydrology for point and regionalcalculations of annual forest productivity. The snow model wasdesigned to operate within the Regional HydroecologicalSimulation System (RHESSys), a GIS based modeling system tomanage spatial data for distributed computer simulations onwatershed scales. One feature of the RHESSys Snow Model (RSM) isit can use satellite derived forest leaf area index (LAI) torepresent catchment forest cover; difficult to obtain in adequatecover and resolution by any other means. The model was testedover 3 water years (October to September) with data recorded by10 snow telemetry stations (SNOTEL) in 5 states ranging inmeso-climate and elevations from a coastal Oregon site (1067 m)to a continental Colorado site (3261 m).Predictions for the 10 sites were made with identicalparameter values and only site climate varied for all sites. Theaverage difference between observed and predicted snow depletiondates for all sites and water years was 6.2 days and 8 of the 30simulations were within ± 2 days (R² = 0.91). Radiation melt wasthe dominate snow ablation component at the Colorado site wheresublimation was 10% (LAI = 0) to 20% (LAI = 6) ofsnow loss while air temperature was the dominate component at theOregon site with sublimation reduced to 1% (LAI = 0) to6% (LAI = 6) of snow loss. LAI had a greater effectdetermining snow depletion than site aspect. Aspect increased inimportance if the snow depletion occurred during early springwhen solar insolation differences between hillslopes is greaterthan in the late spring.An accurate prediction of daily snowpack water equivalent(SWE) was not a strong determinant for making an accurateprediction of snowpack depletion date. Predicted snowpackdepletion dates were more sensitive to timing when the snowpackreached an isothermal condition. Daily estimates of SWE were mostsensitive to correctly estimating snowfall from SNOTEL data. Thismeans that for purposes of determining the snow depletion dateswhich are useful for forest ecosystem modeling, tracking SWE isless important then triggering snowmelt. Comparisons ofsimulations to published snow depletion dates show that RSMpredicted the relative ranking and magnitude of depletion fordifferent combinations of forest cover, elevation, and aspect.     

Intensive recreational activities in suburban forests: A method to quantify the reduction in timber value

Central European forests are generally multifunctional; the same forest areas are used for timber production and recreation. In frequently visited areas damage to trees can be observed. We developed a method to estimate the actual reduction in timber value due to recreation-induced damage. The method was tested in two suburban (oak–hornbeam and beech) forests sustainably maintained by a selective management system and with free access in northwestern Switzerland. Considering the total forest areas, 9.4% of oak trees and 23.0% of beech trees were damaged by recreational activities. The resulting reduction in timber value averaged 19 and 53 € ha^?1 a^?1 in the two forests. The annual reduction in timber value due to recreation-induced damage can account for up to 16% of the total proceeds. The monetary benefits of forest recreation in these areas, however, by far exceed the damage to trees.     

Quantifying the nitrogen retention capacity of natural wetlands in the large-scale drainage basin of the Baltic Sea

We estimate the nitrogen retention capacity of natural wetlands in the 1.7 million km² Baltic Sea drainage basin, using a wetland GIS data base. There are approximately 138,000 km² of wetlands (bogs and fens) in the Baltic Sea drainage basin, corresponding to 8% of the area. The input of nitrogen to natural wetlands from atmospheric deposition was estimated to 55,000–161,000 ton y¹. A map of the deposition of both wet and dry nitrogen is presented. The input from the human population was estimated to 255,000 ton y¹ in terms of excretory release in processed sewage water. There may also be leakage from forests and agricultural land into the wetlands. Due to lack of data on hydrology and topography, such potential nitrogen sources are not accounted for here. The capacity of the wetlands to retain the atmospheric deposition of nitrogen was estimated to 34,000–99,000 ton y¹. The potential retention by wetlands was estimated to 57,000–145,000 ton y¹ when the nitrogen input from the human population was added. If drained wetlands were to be restored and their area added to the present wetland area, the nitrogen retention capacity was estimated to increase to 196,000–261,000 ton y¹. Our results indicate that existing natural wetlands in the Baltic Sea drainage basin annually can retain an amount of nitrogen which corresponds to about 5–13% of annual total (natural and anthropogenic) nitrogen emissions entering the Baltic Sea. The ecosystem retention service performed by wetlands accounts for a substantial nitrogen removal, thereby reducing the eutrophication of the Baltic Sea.     

Loss of street trees predicted to cause 6000 L/tree increase in leaf-on stormwater runoff for Great Lakes urban sewershed

Urban forests are recognized as a nature-based solution for stormwater management. This study assessed the underlying processes and extent of runoff reduction due to street trees with a paired-catchment experiment conducted in two sewersheds of Fond du Lac, Wisconsin. Computer models are flexible, fast, and low-cost options to generalize and assess the hydrologic processes determined in field studies. A state-of-the-art, public-domain model, which explicitly simulates urban tree hydrology, i-Tree Hydro, was used to simulate the paired-catchment experiment, and results from field observations and simulation predictions were compared to assess model validity and suitability as per conditions in the broader Great Lakes basin. Model parameters were aligned with observed conditions using automatic and manual calibration. Model performance metrics were used to quantify the weekly performance of calibration and to validate predictions. Those calibration metrics differed substantially between the two periods simulated, but most calibration metrics remained positive, indicating the model was not fitting only the period used for calibration. Predicted avoided runoff for a five-month leaf-on period was 64 L/m² of canopy, 4 % lower than the field-estimated avoided runoff of 66 L/m² of canopy. Interception was the most directly comparable process between the model and field observations. Based on 5 storms sampled, field estimation of precipitation intercepted and retained on trees averaged 63 % and ranged from 22 % to 81 %, while model estimation averaged 61 % and ranged from 36 % to 99 %. This model was able to fit predictions to observed catchment discharge but required extensive manual calibration to do so. The i-Tree Hydro model predicted avoided runoff comparable with the field study and earlier assessments. Additional field studies in similar settings are needed to confirm findings and improve transferability to other tree species and environmental settings.     

A multi-scale assessment of human and environmental constraints on forest land cover change on the Oregon (USA) coast range

Human modification of forest habitats is a major component of global environmental change. Even areas that remain predominantly forested may be changed considerably by human alteration of historical disturbance regimes. To better understand human influences on the abundance and pattern of forest habitats, we studied forest land cover change from 1936 to 1996 in a 25000 km² landscape in the Oregon (USA) Coast Range. We integrated historical forest survey data and maps from 1936 with satellite imagery and GIS data from 1996 to quantify changes in major forest cover types. Change in the total area of closed-canopy forests was relatively minor, decreasing from 68% of the landscape in 1936 to 65% in 1996. In contrast, large-conifer forests decreased from 42% in 1936 to 17% in 1996, whereas small-conifer forests increased from 21% of the landscape in 1936 to 39% in 1996. Linear regression models were used to predict changes in the proportion of large conifer forest as a function of socioeconomic and environmental variables at scales of subbasins (mean size = 1964 km², n=13), watersheds (mean size = 302 km², n=83), and subwatersheds (mean size = 18 km², n=1325). The proportion of land in private ownership was the strongest predictor at all three spatial scales (partial R² values 0.57–0.76). The amounts of variation explained by other independent variables were comparatively minor. Results corroborate the hypothesis that differing management regimes on private and public ownerships have led to different pathways of landscape change. Furthermore, these distinctive trajectories are consistent over a broad domain of spatial scales.     

Ecosystem-scale spatial heterogeneity of stable isotopes of soil nitrogen in African savannas

Soil ¹⁵N is a natural tracer of nitrogen (N) cycling. Its spatial distribution is a good indicator of processes that are critical to N cycling and of their controlling factors integrated both in time and space. The spatial distribution of soil δ¹⁵N and its underlying drivers at sub-kilometer scales are rarely investigated. This study utilizes two sites (dry vs. wet) from a megatransect in southern Africa encompassing locations with similar soil substrate but different rainfall and vegetation, to explore the effects of soil moisture and vegetation distribution on ecosystem-scale patterns of soil δ¹⁵N. A 300-m long transect was set up at each site and surface soil samples were randomly collected for analyses of δ¹⁵N, %N and nitrate content. At each soil sampling location the presence of grasses, woody plants, Acacia species (potential N fixer) as well as soil moisture levels were recorded. A spatial pattern of soil δ¹⁵N existed at the dry site, but not at the wet site. Woody cover distribution determined the soil δ¹⁵N spatial pattern at ecosystem-scale; however, the two Acacia species did not contribute to the spatial pattern of soil δ¹⁵N. Grass cover was negatively correlated with soil δ¹⁵N at both sites owing to the lower foliar δ¹⁵N values of grasses. Soil moisture did not play a role in the spatial pattern of soil δ¹⁵N at either site. These results suggest that vegetation distribution, directly, and water availability, indirectly, affect the spatial patterns of soil δ¹⁵N through their effects on woody plant and grass distributions.     

Variation in nitrogen deposition and available soil nitrogen in a forest–grassland ecotone in Canada

Regional variation in nitrogen (N) deposition increases plant productivity and decreases species diversity, but landscape- or local -scale influences on N deposition are less well-known. Using ion-exchange resin, we measured variation of N deposition and soil N availability within Elk Island National Park in the ecotone between grassland and boreal forest in western Canada. The park receives regionally high amounts of atmospheric N deposition (22 kg ha⁻¹ yr⁻¹). N deposition was on average higher ton clay-rich luvisols than on brunisols, and areas burned 1–15 years previously received more atmospheric N than unburned sites. We suggest that the effects of previous fires and soil type on deposition rate act through differences in canopy structure. The magnitude of these effects varied with the presence of ungulate grazers (bison, moose, elk) and vegetation type (forest, shrubland, grassland). Available soil N (ammonium and nitrate) was higher in burned than unburned sites in the absence of grazing, suggesting an effect of deposition. On grazed sites, differences between fire treatments were small, presumably because the removal of biomass by grazers reduced the effect of fire. Aspen invades native grassland in this region, and our results suggest that fire without grazing might reinforce the expansion of forest into grassland facilitated by N deposition.     

Post-disturbance recovery of forest cover and tree height differ with management in Central Europe

Context

Recovery from disturbances is a prominent measure of forest ecosystem resilience, with swift recovery indicating resilient systems. The forest ecosystems of Central Europe have recently been affected by unprecedented levels of natural disturbance, yet our understanding of their ability to recover from disturbances is still limited.

Objectives

We here integrated satellite and airborne Lidar data to (i) quantify multi-decadal post-disturbance recovery of two indicators of forest structure, and (ii) compare the recovery trajectories of forest structure among managed and un-managed forests.

Methods

We developed satellite-based models predicting Lidar-derived estimates of tree cover and stand height at 30 m grain across a 3100 km² landscape in the Bohemian Forest Ecosystem (Central Europe). We summarized the percentage of disturbed area that recovered to >?40% tree cover and >?5 m stand height and quantified the variability in both indicators over a 30-year period. The analyses were stratified by three management regimes (managed, protected, strictly protected) and two forest types (beech-dominated, spruce-dominated).

Results

We found that on average 84% of the disturbed area met our recovery threshold 30 years post-disturbance. The rate of recovery was slower in un-managed compared to managed forests. Variability in tree cover was more persistent over time in un-managed forests, while managed forests strongly converged after a few decades post-disturbance.

Conclusion

We conclude that current management facilitates the recovery of forest structure in Central European forest ecosystems. However, our results underline that forests recovered well from disturbances also in the absence of human intervention. Our analysis highlights the high resilience of Central European forest ecosystems to recent disturbances.