Temperate Forest Regions Research Articles

Quantifying spatially and temporally explicit CO2 fertilization effects on global terrestrial ecosystem carbon dynamics

AbstractCurrent terrestrial ecosystem models are usually driven with global average annual atmospheric carbon dioxide (CO2) concentration data at the global scale. However, high‐precision CO2 measurement from eddy flux towers showed that seasonal, spatial surface atmospheric CO2 concentration differences were as large as 35 ppmv and the site‐level tests indicated that the CO2 variation exhibited different effects on plant photosynthesis. Here we used a process‐based ecosystem model driven with two spatially and temporally explicit CO2 data sets to analyze the atmospheric CO2 fertilization effects on the global carbon dynamics of terrestrial ecosystems from 2003 to 2010. Our results demonstrated that CO2 seasonal variation had a negative effect on plant carbon assimilation, while CO2 spatial variation exhibited a positive impact. When both CO2 seasonal and spatial effects were considered, global gross primary production and net ecosystem production were 1.7 Pg C·yr−1 and 0.08 Pg C·yr−1 higher than the simulation using uniformly distributed CO2 data set and the difference was significant in tropical and temperate evergreen broadleaf forest regions. This study suggests that the CO2 observation network should be expanded so that the realistic CO2 variation can be incorporated into the land surface models to adequately account for CO2 fertilization effects on global terrestrial ecosystem carbon dynamics.

A new seasonal-deciduous spring phenology submodel in the Community Land Model 4.5: impacts on carbon and water cycling under future climate scenarios.

A spring phenology model that combines photoperiod with accumulated heating and chilling to predict spring leaf-out dates is optimized using PhenoCam observations and coupled into the Community Land Model (CLM) 4.5. In head-to-head comparison (using satellite data from 2003 to 2013 for validation) for model grid cells over the Northern Hemisphere deciduous broadleaf forests (5.5millionkm2 ), we found that the revised model substantially outperformed the standard CLM seasonal-deciduous spring phenology submodel at both coarse (0.9×1.25°) and fine (1km) scales. The revised model also does a better job of representing recent (decadal) phenological trends observed globally by MODIS, as well as long-term trends (1950-2014) in the PEP725 European phenology dataset. Moreover, forward model runs suggested a stronger advancement (up to 11days) of spring leaf-out by the end of the 21st century for the revised model. Trends toward earlier advancement are predicted for deciduous forests across the whole Northern Hemisphere boreal and temperate deciduous forest region for the revised model, whereas the standard model predicts earlier leaf-out in colder regions, but later leaf-out in warmer regions, and no trend globally. The earlier spring leaf-out predicted by the revised model resulted in enhanced gross primary production (up to 0.6PgCyr-1 ) and evapotranspiration (up to 24mmyr-1 ) when results were integrated across the study region. These results suggest that the standard seasonal-deciduous submodel in CLM should be reconsidered, otherwise substantial errors in predictions of key land-atmosphere interactions and feedbacks may result.

Effectiveness of national nature reserve network in representing natural vegetation in mainland China

The conservation of natural vegetation directly impacts biodiversity conservation; thus, it is important to evaluate the effectiveness of vegetation protection in nature reserve networks. In this study, ArcGIS 10.0 was used for gap analysis of terrestrial vegetation protection within the national nature reserve network in mainland China. Overall, 9.75 % of the land area was covered by 366 national nature reserves. The bias of the protection ratio was particularly obvious among the different vegetation regions, zones, provinces and districts. The warm temperate deciduous broadleaf forest region was the least protected (1.84 %), and most of the NNRs were located in the Qinghai-Xizang Plateau alpine vegetation region (35.8 %). Moreover, in most vegetation zones (57.14 %), less than 5 % of the area was protected, and in vegetation provinces and vegetation districts, 8.85 and 35.87 %, respectively, were not protected by national nature reserves. However, the number of national nature reserves could be higher in these vegetation zones, provinces and districts than in other areas. The protection bias became more significant as the analysis scale decreased. In addition, nearly 25 % of the natural formations in mainland China were unprotected by national nature reserves. A bias was also observed in the protection of different natural formations, with a lack or lower degree of protection for desert, grass-forb community, steppe, and scrub biomes, which were spread throughout northwest and eastern China. A distinct lack of protected areas was observed in certain parts of the country. Therefore, additional land may require protection in the vegetation provinces and districts in the Tianshan Mountains, Junggar Basin, West Kunlun Mountains, Loess Plateau, and karst districts in southwest Guangxi Province and along the southeast coast of China.

Evolutionary history of a widespread tree species Acer mono in East Asia.

East Asia has the most diverse temperate flora in the world primarily due to the lack of Pleistocene glaciation and the geographic heterogeneity. Although increasing phylogeography studies in this region provided more proofs in this issue, discrepancies and uncertainty still exist, especially in northern temperate deciduous broad-leaved and coniferous mixed forest region (II). And a widespread plant species could reduce the complexity to infer the relationship between diversity and physiographical pattern. Hence, we studied the evolution history of a widespread temperate tree, Acer mono, populations in region II and the influence of physiographic patterns on intraspecific genetic diversity. Analyses of chloroplast sequences and nuclear microsatellites indicated high levels of genetic diversity. The diversity distribution was spatially heterogeneous and a latitudinal cline existed in both markers. The spatial distribution pattern between genetic diversity within A. mono and the diversity at species level was generally consistent. Western subtropical evergreen broad-leaved forest subregion (IVb) had a unique ancient chloroplast clade (CP3) and a nuclear gene pool (GP5) with dominance indicating the critical role of this area in species diversification. Genetic data and ecological niche model results both suggested that populations in region II disappeared during the last glacial maximum (LGM) and recovered from south of Changbai Mt. and the Korean Peninsula. Two distribution centers were likely during the LGM, one in the north edge of warm temperate deciduous broad-leaved forest region (III) and another in the south edge of region III. This was reflected by the genetic pattern with two spatially independent genetic groups. This study highlights the key role of region III in sustaining genetic diversity in the northern range and connecting diversity between southern and northern range. We elucidated the diversity relationship between vegetation regions which could facilitate the understanding of biodiversity origin and maintenance in East Asia.

Increased drought impacts on temperate rainforests from southern South America: results of a process-based, dynamic forest model.

Increased droughts due to regional shifts in temperature and rainfall regimes are likely to affect forests in temperate regions in the coming decades. To assess their consequences for forest dynamics, we need predictive tools that couple hydrologic processes, soil moisture dynamics and plant productivity. Here, we developed and tested a dynamic forest model that predicts the hydrologic balance of North Patagonian rainforests on Chiloé Island, in temperate South America (42°S). The model incorporates the dynamic linkages between changing rainfall regimes, soil moisture and individual tree growth. Declining rainfall, as predicted for the study area, should mean up to 50% less summer rain by year 2100. We analysed forest responses to increased drought using the model proposed focusing on changes in evapotranspiration, soil moisture and forest structure (above-ground biomass and basal area). We compared the responses of a young stand (YS, ca. 60 years-old) and an old-growth forest (OG, >500 years-old) in the same area. Based on detailed field measurements of water fluxes, the model provides a reliable account of the hydrologic balance of these evergreen, broad-leaved rainforests. We found higher evapotranspiration in OG than YS under current climate. Increasing drought predicted for this century can reduce evapotranspiration by 15% in the OG compared to current values. Drier climate will alter forest structure, leading to decreases in above ground biomass by 27% of the current value in OG. The model presented here can be used to assess the potential impacts of climate change on forest hydrology and other threats of global change on future forests such as fragmentation, introduction of exotic tree species, and changes in fire regimes. Our study expands the applicability of forest dynamics models in remote and hitherto overlooked regions of the world, such as southern temperate rainforests.

Restoration of rain forest beneath pine plantations: A relay floristic model with special application to tropical South Asia

In the wet forest regions of southwest Sri Lanka and the Western Ghats, India, Pinus caribaea was a common tree species for reforestation on public lands that were originally cleared of native forest for agriculture but subsequently succeeded to fire tolerant grasses and ferns. Much of this reforestation occurred during the 1970s and 1980s. The ecological literature suggests that in many temperate broadleaf forest regions pine is an important component of early succession on old fields, beneath which second growth hardwood can establish and eventually dominate. More recent studies have demonstrated the establishment of native rain forest regeneration beneath a variety of exotic tree plantations. We review nearly twenty-five years of research on this topic for South Asia through a series of studies done in southwest Sri Lanka. Results demonstrate that native species recruitment of both pioneers and site generalist late-successional trees grow well beneath exotic pine plantations. Diversity and density increase from plantation interior to edge. Protection from groundstory fire is the single most important component of promoting regeneration recruitment beneath pine. Establishing late-successional site and dispersal restricted species requires planting beneath pine rather than reliance on natural establishment. Best establishment and growth occur in openings where rows of canopy pine have been removed. Species considered for planting comprise the major late-successional canopy tree species of the forest in the genera Dipterocarpus, Shorea (Dipterocarpaceae) and Mesua (Clusiaceae). Native species that produce non-timber forest products (NTFP) need to be planted with best results in canopy openings. The most valuable NTFP’s comprise a sugar palm (Caryota urens), rattan (Calamus spp.) and a medicinal liana (Coscinium fenestratum). Financial analyses reveal that pine plantations that are enrichment planted and cultivated with rain forest timber and non-timber species can provide superior economic benefits as compared to land cultivated singly for tea.

Forest Phenology Dynamics and Its Responses to Meteorological Variations in Northeast China

Based on time series of Moderate Resolution Imaging Spectroradiometer (MODIS) Enhanced Vegetation Index (EVI) data (2000–2009), we extracted forest phenological variables in Northeast China using a threshold-based method, which included the start of the growing season (SOS), end of the growing season (EOS), and length of the growing season (LOS). The spatial variation of phenological trends was analyzed using the linear regression method. In Northeast China, SOS was delayed at the rate of <1.5 days per year. The delay trend of EOS was well distributed in the entire region with almost the same rates. LOS increased slightly. The analysis of the relationship between forest phenology and meteorological variations shows that SOS was mainly affected by spring temperature, whereas SOS had a negative relationship with precipitation in the warm-temperate deciduous broadleaf forest region. The EOS in temperate steppe region was affected by temperature and precipitation in August, whereas the others were significantly affected by temperature. Because of the increased temperature in spring, the LOS of the temperate steppe region and temperate mixed forest region increased, and the LOS was positively correlated with the mean temperature of summer in the cool-temperate needleleaf forest region.

不同透光环境下红松光合色素含量的季节变动及应对策略

研究了辽东山区天然次生林内3种不同透光环境（强度透光、中度透光和弱度透光）下红松针叶光合色素（叶绿素a（Chl a）、叶绿素b（Chl b）、类胡萝卜素（Car）和叶绿素总量（Chl T））应对光环境季节变动做出的适应性调整。结果表明，随季节的变动（从春季至秋季），林分透光孔隙度逐渐减小。春季，透光度越大，红松叶绿素含量越高，Chl a/b值升高，Car /Chl T值降低；夏季，不同透光条件对红松光合色素含量无影响；秋季，各类透光条件下红松光合色素含量总体表现为升高的趋势，强度透光与中度透光条件红松针叶Chl a/b显著大于弱度透光，3种透光条件下红松Car/Chl T均降低。在春季红松开始生长前进行适当抚育，能提高光合色素含量，增强光合作用能力，促进生长。;Broad-leaved Korean pine forest (BKPF) is one of several zonal climax vegetation types dominated by Korean pine (<em>Pinus koraiensis</em>) in the temperate forest region of Northeast China. Unfortunately, intense human activities and extreme natural disturbances have continuously affected the succession of the BKPFs for the past century. Most of the historic areas of BKPFs have succeeded into secondary forests that are not dominated by Korean pine. As a result, since the 1960s, <em>P. koraiensis</em> seedlings have been planted under the canopy of secondary forests in an effort to restore the BKPFs. The status of the survival and growth of <em>P. koraiensis</em> saplings under the canopy of secondary forests has been considered to be an important indicator demonstrating the success of these efforts. Many reports suggested that light was one of the most important environmental factors affecting the regeneration and growth of <em>P. koraiensis</em>. Generally, <em>P. koraiensis </em>is considered to be both a tolerant and intolerant species, having a dual response to light conditions in forest communities depending on its habitat and age classes. <em>P. koraiensis</em> seedlings are able to survive under closed canopy conditions; canopy openness ranging from 0.5 to 0.6 is optimal for the survival and growth of <em>P. koraiensis</em> seedlings. However, as the saplings grow, they need more and more light and finally become intolerant to shaded conditions. For example, compared with seedlings, slightly more mature trees will grow under a forest canopy with a canopy openness of 0.7 for the long-term, but they grow poorly and eventually die under those conditions over an extended period of time. Selective thinning is almost always carried out when <em>P. koraiensis</em> saplings reach an age of 8 to 10 years. However, the needles of <em>P. koraiensis </em>may turn yellow after the selective thinning indicating that the type and quantity of photosynthetic pigments in needles changes in response to the selective thinning. This study was conducted to analyze the response of the photosynthetic pigments in <em>P. koraiensis</em> needles to selective thinning in an effort to understand the relationships between the light environment and the regeneration of <em>P. koraiensis</em>. The experiments were conducted at Qingyuan Experimental Station of Forest Ecology, Chinese Academy of Sciences, located in Changsha, Qingyuan County, Fushun City, Liaoning Province, China. We compared the content of chlorophyll a (Chl a), chlorophyll b (Chl b), carotenoids (Car), and total chlorophyll (Chl T) in <em>P. koraiensis</em> needles under three light environments: low-, mid- and high light levels in a secondary forest. The results showed that canopy openness decreased from a high-level light to low-level light environment from spring through summer to autumn. In spring, the chlorophyll content and the ratio of Chl a/b increased, but the ratio of Car/Chl T decreased as the light levels changed from a low-level to high-level light environment. However, the Car content did not change significantly during spring. In summer, no significant differences in pigment content were observed among the three light levels, but the pigment content was higher than that in spring for all pigments analyzed here. In autumn, the ratio of Chl a/b was higher in the high-level and mid-level light environments than that in the low-level light environment. The photosynthetic pigment content increased in all three light levels from spring to summer, but the ratio of Car/Chl T decreased significantly during the same time period. In summary, these results suggest that thinning management designed to increase light-transmittance should be conducted in spring and a mid-level thinning intensity is suitable for improving the photosynthetic capability and for accelerating growth of <em>P. koraiensis</em> under the canopy of secondary forests.

Profile distribution and seasonal dynamics of water-extractable carbohydrate in soils under mixed broad-leaved Korean pine forest on Changbai Mountain

Carbohydrate represents an important part of the soil labile organic carbon pool. Water soluble carbohydrate drives the C cycle in forest soil by affecting microbial activity and hot water extractable carbohydrate is thought related to soil carbon sequestration due to the association with soil aggregation. In a temperate forest region of northeast China, Changbai Mountain, we investigated the abundance, spacial distribution, and seasonal dynamics of cool and hot-water extractable carbohydrate in soils under mixed broad-leaved Korean pine forest. The concentrations of cool-water extractable carbohydrate (CWECH) in three soil layers (0–5, 5–10, 10–20 cm) ranged from 4.1 to 193.3 g·kg−1 dry soil, decreasing rapidly with soil depth. On an annual average, the CWECH concentrations in soils at depths of 5–10 and 10–20 cm were 54.2% and 24.0%, respectively, of that in the 0–5 cm soil layer. CWECH showed distinct seasonal dynamics with the highest concentrations in early spring, lowest in summer, and increasing concentrations in autumn. Hot-water extractable carbohydrate (HWECH) concentrations in three soil layers ranged from 121.4 to 2026.2 g·kg−1 dry soil, which were about one order of magnitude higher than CWECH. The abundance of HWECH was even more profile-dependent than CWECH, and decreased more rapidly with soil depth. On an annual average, the HWECH concentration in soils 10–20 cm deep was about one order of magnitude lower than that in the top 0–5 cm soil. The seasonality of HWECH roughly tracked that of CWECH but with seasonal fluctuations of smaller amplitude. The carbohydrate concentrations in cool/hot water extracts of soil were positively correlated with UV254 and UV280 of the same solution, which has implications for predicting the leaching loss of water soluble organic carbon.

Abies religiosa forests harbor the highest species density and sporocarp productivity of wild edible mushrooms among five different vegetation types in a neotropical temperate forest region

More than 300 wild edible mushrooms are consumed in Mexico. They have been reported mainly from temperate forests in the center and southeast of the country. However, these valuable non-timber forest products are under-utilized because a lack of knowledge on their ecology and productivity. The objectives of this work were to compare the richness and fruit body production of wild edible mushrooms in temperate forests with a distinct vegetation composition in Amanalco, to describe species availability, and to test a new sampling approach in a heterogeneous environmental context. We designed a sampling method with random transects rather than traditional fixed sampling sites. Our method permits the acquisition of data from the highest number of environmental conditions. In 2009 and 2010, we collected and counted mushrooms in 248 transects distributed in five vegetation types (Abies, Abies–Pinus, Pinus, Pinus–Quercus and Quercus). We calculated the ecological importance value of each species as a function of its relative abundance and relative spatial frequency and relative temporal frequency. Abies religiosa pure stands and A. religiosa–Pinus forests had the greatest richness of edible fungi (43.1 and 21.3 species ha−1, respectively) and produced most of the fruit bodies (1,160 and 820 ha−1, respectively). The most abundant species in Amanalco region (combining all the vegetation types), Clavulina cinerea, Clitocybe gibba and Russula brevipes, also had the highest ecological importance value (0.2312, 0.1709 and 0.1516, respectively). These temperate forests maintain a considerable diversity of valuable wild edible mushrooms that are heterogeneously distributed according to the type of vegetation.

Evaluation of factors controlling global secondary organic aerosol production from cloud processes

Abstract. Secondary organic aerosols (SOA) exert a significant influence on ambient air quality and regional climate. Recent field, laboratorial and modeling studies have confirmed that in-cloud processes contribute to a large fraction of SOA production with large space-time heterogeneity. This study evaluates the key factors that govern the production of cloud-process SOA (SOAcld) on a global scale based on the GFDL coupled chemistry-climate model AM3 in which full cloud chemistry is employed. The association between SOAcld production rate and six factors (i.e., liquid water content (LWC), total carbon chemical loss rate (TCloss), temperature, VOC/NOx, OH, and O3) is examined. We find that LWC alone determines the spatial pattern of SOAcld production, particularly over the tropical, subtropical and temperate forest regions, and is strongly correlated with SOAcld production. TCloss ranks the second and mainly represents the seasonal variability of vegetation growth. Other individual factors are essentially uncorrelated spatiotemporally to SOAcld production. We find that the rate of SOAcld production is simultaneously determined by both LWC and TCloss, but responds linearly to LWC and nonlinearly (or concavely) to TCloss. A parameterization based on LWC and TCloss can capture well the spatial and temporal variability of the process-based SOAcld formation (R2 = 0.5) and can be easily applied to global three dimensional models to represent the SOA production from cloud processes.

Continued loss of temperate old-growth forests in the Romanian Carpathians despite an increasing protected area network

SUMMARYOld-growth forests around the world are vanishing rapidly and have been lost almost completely from the European temperate forest region. Poor management practices, often triggered by socioeconomic and institutional change, are the main causes of loss. Recent trends in old-growth forest cover in Romania, where some of the last remaining tracts of these forests within Europe are located, are revealed by satellite image analysis. Forest cover declined by 1.3 % from 2000 to 2010. Romania's protected area network has been expanded substantially since the country's accession to the European Union in 2007, and most of the remaining old-growth forests now are located within protected areas. Surprisingly though, 72% of the old-growth forest disturbances are found within protected areas, highlighting the threats still facing these forests. It appears that logging in old-growth forests is, at least in part, related to institutional reforms, insufficient protection and ownership changes since the collapse of communism in 1989. The majority of harvesting activities in old-growth forest areas are in accordance with the law. Without improvements to their governance, the future of Romania's old-growth forests and the important ecosystem services they provide remains uncertain.

Estimating bark volumes for 16 native tree species on the Sierra Madre Occidental, Mexico

The Sierra Madre Occidental ecoregion accommodates some of the richest biodiversity anywhere in North America and contains about two-thirds of the standing timber biomass in Mexico. Worldwide forest trees provide an industrial output of about 363 million cubic meters, with the volume of bark accounting for an estimated 10% of total tree volume, so that bark is a very important nonwoody product. In this study, the proportion of bark volume (PBV) and its correlation with selected tree characteristics as well as the relationship between total tree volume and wood volume (WV) and total volume and bark volume (BV) were calculated for the first time for the 16 common and commercially most important tree species in the temperate pine-oak forest region of El Salto (Durango) on the Sierra Madre Occidental, Mexico. Measurements were made on 2,027 felled trees. The PBV in the species investigated ranges from 0.129 to 0.260 depending on the species and genus, with a mean value of 0.175. BV and WV can be accurately estimated. The approach used in this study is simple and effective, and very user-friendly. The method is recommended for researchers wishing to develop bark models for other tree species.

Estimating the carbon budget and maximizing future carbon uptake for a temperate forest region in the U.S.

BackgroundForests of the Midwest U.S. provide numerous ecosystem services. Two of these, carbon sequestration and wood production, are often portrayed as conflicting. Currently, carbon management and biofuel policies are being developed to reduce atmospheric CO2 and national dependence on foreign oil, and increase carbon storage in ecosystems. However, the biological and industrial forest carbon cycles are rarely studied in a whole-system structure. The forest system carbon balance is the difference between the biological (net ecosystem production) and industrial (net emissions from forest industry) forest carbon cycles, but to date this critical whole system analysis is lacking. This study presents a model of the forest system, uses it to compute the carbon balance, and outlines a methodology to maximize future carbon uptake in a managed forest region.ResultsWe used a coupled forest ecosystem process and forest products life cycle inventory model for a regional temperate forest in the Midwestern U.S., and found the net system carbon balance for this 615,000 ha forest was positive (2.29 t C ha-1 yr-1). The industrial carbon budget was typically less than 10% of the biological system annually, and averaged averaged 0.082 t C ha-1 yr-1. Net C uptake over the next 100-years increased by 22% or 0.33 t C ha-1 yr-1 relative to the current harvest rate in the study region under the optized harvest regime.ConclusionsThe forest’s biological ecosystem current and future carbon uptake capacity is largely determined by forest harvest practices that occurred over a century ago, but we show an optimized harvesting strategy would increase future carbon sequestration, or wood production, by 20-30%, reduce long transportation chain emissions, and maintain many desirable stand structural attributes that are correlated to biodiversity. Our results for this forest region suggest that increasing harvest over the next 100 years increases the strength of the carbon sink, and that carbon sequestration and wood production are not conflicting for this particular forest ecosystem. The optimal harvest strategy found here may not be the same for all forests, but the methodology is applicable anywhere sufficient forest inventory data exist.

The potential transient dynamics of forests in New England under historical and projected future climate change

Projections of vegetation distribution that incorporate the transient responses of vegetation to climate change are likely to be more efficacious than those that assume an equilibrium between climate and vegetation. We examine the non-equilibrium dynamics of a temperate forest region under historic and projected future climate change using the dynamic ecosystem model LPJ-GUESS. We parameterized LPJ-GUESS for the New England region of the United Sates utilizing eight forest cover types that comprise the regionally dominant species. We developed a set of climate data at a monthly-step and a 30-arc second spatial resolution to run the model. These datasets consist of past climate observations for the period 1901–2006 and three general circulation model projections for the period 2007–2099. Our baseline (1971–2000) simulation reproduces the distribution of forest types in our study region as compared to the National Land Cover Data 2001 (Kappa statistic = 0.54). Under historic and nine future climate change scenarios, maple-beech-basswood, oaks and aspen-birch were modeled to move upslope at an estimated rate of 0.2, 0.3 and 0.5 m yr−1 from 1901 to 2006, and continued this trend at an accelerated rate of around 0.5, 0.9 and 1.7 m yr−1 from 2007 to 2099. Spruce-fir and white pine-cedar were modeled to contract to mountain ranges and cooler regions of our study region under projected future climate change scenarios. By the end of the 21st century, 60% of New England is projected to be dominated by oaks relative to 21% at the beginning of the 21st century, while northern New England is modeled to be dominated by aspen-birch. In mid and central New England, maple-beech-basswood, yellow birch-elm and hickories co-occur and form novel species associations. In addition to warming-induced northward and upslope shifts, climate change causes more complex changes in our simulations, such as reversed conversions between forest types that currently share similar bioclimatic ranges. These results underline the importance of considering community interactions and transient dynamics in modeling studies of climate change impacts on forest ecosystems.

Exotic earthworm distribution in a mixed-use northern temperate forest region: influence of disturbance type, development age, and soils

The impacts of invasive earthworms in northern North American forests include mixing of soil and litter horizons, changes to nutrient availability, and shifts in understory plant communities. Multi...

Nutrient Cycling Studies: A New Approach for Assessing Reclamation Processes of Tropical Degraded Lands and Restoration of Ecosystem Functions

Copyright: © 2012 Leon Pelaez JD. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Nutrient cycling studies have been performed throughout the world for over fifty years. The earliest of these studies were carried out in natural forests of temperate regions, and focused on small number of processes related to litterfall (e.g. nutrient return, nutrient release). Due to increasing interest in tropical forests and an apparent lack of knowledge about their functioning, nutrient cycling studies were later progressively located in tropical and subtropical forests, and began to incorporate other nutrient cycling pathways as well, such as those related to hydrological fluxes and edaphic processes. Pioneer studies that supplied valuable knowledge of nutrient cycling in tropical forests can be attributed to a long list of scientists, among whom could be mentioned H. Jenny, C.F. Jordan, H. Nye, P.J. Edwards, F. Golley, J. Proctor, B. Lundgren, S.N. Rai, J.J. Ewel, and F. Bernhard.

Adaptations to nitrogen form: comparing inorganic nitrogen and amino acid availability and uptake by four temperate forest plants

There are few examinations of the relative availability and plant uptake of inorganic N and amino acid N in temperate forest regions. We determined the availability of amino acid N and inorganic N in soils under two shrub species ( Vaccinium ovalifolium Sm. versus Rubus spectabilis Pursh) on three sites near Jordan River, British Columbia, over a growing season. We compared biomass production of the two shrubs and two conifers ( Picea sitchensis (Bong.) Carr. and Pseudotsuga menziesii (Mirb.) Franco var. menziesii) when given inorganic N (20:80 or 80:20 NH4+–NO3–) or organic N (glycine and glutamic acid) and assessed short-term uptake (24 h) of 15N-labelled NH4+, NO3–, glycine, or glutamic acid by the four species. Water-extracted soil concentrations of NH4+ were up to 1.5 times greater than NO3– averaged across sites. Concentrations of amino acid N and inorganic N were similar on soils under Rubus , but the amino acid N to inorganic N ratio was up to 2.4:1 in soils under Vaccinium . Soils dominated by Rubus had up to twice the NO3–-N and two thirds the amino acid N concentrations of soils dominated by Vaccinium, averaged across sites and Rubus had relatively high short-term 15NO3– uptake. The dry biomass of conifers was approximately four times greater when supplied mainly with NH4+ compared with NO3–, but biomass of the two shrub species was similar in both inorganic N treatments. All plants had comparable rates of short-term 15N uptake from amino acids and inorganic N, suggesting that amino acids could contribute to the N nutrition of these temperate species; however, dry biomass of all four species grown with amino acids was less than one half that of plants grown with inorganic N.

The selection of small forest hollows for pollen analysis in boreal and temperate forest regions

Small forest hollows represent a specialised site type for pollen analysis, since they mainly record the vegetation within an approximate radius of 20–100 m from the hollow. We discuss how to choose the most appropriate small forest hollow for pollen analysis. Hollow size, site topography, location, sediment type, drainage aspects and disturbance characteristics of the specific hollows should be considered during site selection. Guidelines are developed on how to take the core and outline the special characteristics of small hollow palynology that influence data interpretation.

Climatic and topographic controls on patterns of fire in the southern and central Appalachian Mountains, USA

Climate and topography are two important controls on spatial patterns of fire disturbance in forests globally, via their influence on fuel moisture and fuel production. To assess the influences of climate and topography on fire disturbance patterns in a temperate forest region, we analyzed the mapped perimeters of fires that burned during 1930–2003 in two national parks in the eastern United States. These were Great Smoky Mountains National Park (GSMNP) in the southern Appalachian Mountains and Shenandoah National Park (SNP) in the central Appalachian Mountains. We conducted GIS analyses to assess trends in area burned under differing climatic conditions and across topographic gradients (elevation, slope position, and aspect). We developed a Classification and Regression Tree model in order to further explore the interactions between topography, climate, and fire. The results demonstrate that climate is a strong driver of both spatial and temporal patterns of wildfire. Fire was most prevalent in the drier SNP than the wetter GSMNP, and during drought years in both parks. Topography also influenced fire occurrence, with relatively dry south-facing aspects, ridges, and lower elevations burning most frequently. However, the strength of topographic trends varied according to the climatic context. Weaker topographic trends emerged in the drier SNP than GSMNP, and during low-PDSI (dry) years than high-PDSI (wet) years in both parks. The apparent influence of climate on the spatial patterning of fire suggests a more general concept, that disturbance-prone landscapes exhibit weaker fine-scale spatial patterning of disturbance than do less disturbance-prone landscapes.