Soil enzyme activities as potential indicators of soluble organic nitrogen pools in forest ecosystems of Northeast China

Context

Soluble organic nitrogen is considered to reflect the effect of forest types on soil nitrogen status. As a major process affecting the soil-soluble organic nitrogen pool, degradation of insoluble organic nitrogen in the production of soluble organic nitrogen is mediated by a suite of soil enzymes.

Aims

This study aims to examine soil-soluble organic nitrogen pools and their relationships with the activities of soil enzymes in natural secondary forest stands and adjacent larch plantation stands.

Methods

Four pairs of larch plantation stands and secondary forest stands were randomly selected from a mountainous area, and the top 15?cm of the mineral soils were sampled from each field.

Results

The soil-soluble organic nitrogen concentrations were up to 2-fold greater in the secondary forest stands than in the larch plantation stands, whereas the ratio of soluble organic nitrogen/total nitrogen was comparable between the two forest types. The concentrations of soluble organic nitrogen were positively correlated with approximately 2-fold differences in urease and protease activities, a 1.2-fold difference in N-acetyl-??-glucosaminidase and a 1.7-fold difference in l-asparaginase between the two forest types.

Conclusions

Our results suggest that relationships between soil-soluble organic nitrogen and enzyme activities are independent on sampling time, and that the soil enzyme activities can be used as potential indicators of soil soluble organic nitrogen pools in the temperate forest ecosystem.     

Atmospheric deposition and leaching of nitrogen in Chinese forest ecosystems

Data have been compiled from published sources on nitrogen (N) fluxes in precipitation, throughfall, and leaching from 69 forest ecosystems at 50 sites throughout China, to examine at a national level: (1) N input in precipitation and throughfall, (2) how precipitation N changes after the interaction with canopy, and (3) whether N leaching increases with increasing N deposition and, if so, to what extent. The deposition of dissolved inorganic N (DIN) in precipitation ranged from 2.6 to 48.2 kg N ha⁻¹ year⁻¹, with an average of 16.6 kg N ha⁻¹ year⁻¹. Ammonium was the dominant form of N at most sites, accounting for, on average, 63% of total inorganic N deposition. Nitrate accounted for the remaining 37%. On average, DIN fluxes increased through forest canopies, by 40% and 34% in broad-leaved and coniferous forests, respectively. No significant difference in throughfall DIN inputs was found between the two forest types. Overall, 22% of the throughfall DIN input was leached from forest ecosystems in China, which is lower than the 50–59% observed for European forests. Simple calculations indicate that Chinese forests have great potential to absorb carbon dioxide from the atmosphere, because of the large forest area and high N deposition.     

Land cover changes and fragmentation in mountain neotropical ecosystems of Oaxaca,Mexico under community forest management

Changes in land cover have a direct impact on forest ecosystem goods and services. In this study, changes in land cover in Sierra de Juarez–Oaxaca ecosystems were estimated using a consistent processing of Landsat images and OBIA methodology. Additionally, landscape analyses using FRAGSTAT were conducted. In 2014, Sierra de Juarez–Oaxaca was covered by approximately 84% of forests, mainly pine-oak and cloud forests. After extensive deforestation until 2001, this trend was reversed and the forest cover surface area in 2014 was slightly higher than in 1979. The comparison of the landscape structure of the forested and agricultural lands suggests an increase in habitat heterogeneity. However, interspersion and juxtaposition indices, showing the patch shape by patch area and perimeter, were similar throughout the study period(1979–2014). Social and economic drivers can explain this situation: namely, community organization, forest enterprises, payment for ecosystem services programs, and changes of agricultural activity. Communities in the Sierra of Oaxaca have reforested degraded lands, created community forest enterprises, and preserved the forest under conservation schemes like those proposed by the Mexican payment for ecosystem services programs. However, their sustainable management faces internal challenges and has become highly dependent on political and institutional decisions beyond their control.     

Soil nitrogen mineralization under a Eucalyptus plantation and a natural Acacia forest in Senegal

In-vitro and in-situ N mineralization were studied in a natural Acacia seyal stand and in a Eucalyptus camaldulensis plantation in Senegal.Mineralizable N, measured by 20 days in-vitro incubations, averaged 40–50 ppm in Acacia soil and 11–14 ppm in Eucalyptus soil, and reached 3.5 and 2.3%, respectively, of total N. The coarse light fractions (>0.2 mm) of Eucalyptus soil organic matter did not produce any mineral N; about 80% of the mineral N was supplied by the organo-mineral fraction, as against 30–50% in Acacia soil.In-situ mineralization was related to precipitation, and ranged from 18 to 40 ppm over 4 weeks during the rainy season in the Acacia stand where 7–10% of total N was mineralized each year. Under Eucalyptus, N mineralization reached only 10 ppm over 3 weeks in the beginning of the rainy season and then decreased sharply. It was assumed that this decrease was related to a depressive effect of herbaceous root growth, the possible processes of which are discussed.     

SIMULATION OF SOIL NITROGEN MINERALIZATION AND NITRIFICATION IN TWO NORTHERN HARDWOOD FOREST ECOSYSTEMS

INTRODUCTIoNMeasurementsofNmincralizationinun-fertilizedforestsoilsprovideanindexofavail-ableNfortreegrowth(AuchmoodyandFilipl973,Stonel973,AbereIal.l989,BinklcyandHartl989,MclilIoela/.l993).Histori-cally,tWoapproaches(IaboratoryandinsitlIincubations)havebcenuscdtoestimatetheratCofNmineralization,butneitheriswidelyaccepted(Keeney,l98o).Thegenerallackofagrementamongthemethodsisduetodiffer-encesintheirsensitivitytocnvironmentalfac-torswhichinfluencesoilNmineralization(Raisonetal.l987…     

Boron in forest trees and forest ecosystems

This review critically examines the role of boron (B) in forests in view of recent findings on B nutrition and the continuing occurrence of B deficiency. Many perceptions about the role of B in plants and its uptake and mobility have been altered since the last review on B in forest trees in 1990. Now there is evidence for a fundamental role of B in the formation of the pectic structure in primary cell walls in plants, and further roles in membrane function are being explored. In plants, channel-mediated B uptake, active B uptake and B uptake by mycorrhizas have been shown, B transporters have been identified, and B retranslocation has been shown. We explore these findings and their consequences on forest trees and on ecosystems that they dominate. Particular emphasis is placed on B retranslocation and B in mycorrhizal symbiosis, given their importance in trees.     

Seasonal dynamics of water use efficiency of typical forest and grassland ecosystems in China

We selected four sites of ChinaFLUX representing four major ecosystem types in China—Changbaishan temperate broad-leaved Korean pine mixed forest (CBS), Dinghushan subtropical evergreen broadleaved forest (DHS), Inner Mongolia temperate steppe (NM), and Haibei alpine shrub-meadow (HBGC)—to study the seasonal dynamics of ecosystem water use efficiency (WUE = GPP/ET, where GPP is gross primary productivity and ET is evapotranspiration) and factors affecting it. Our seasonal dynamics results indicated single-peak variation of WUE in CBS, NM, and HBGC, which were affected by air temperature (Ta) and leaf area index (LAI), through their effects on the partitioning of evapotranspiration (ET) into transpiration (T) (i.e., T/ET). In DHS, WUE was higher at the beginning and the end of the year, and minimum in summer. Ta and soil water content affected the seasonal dynamics of WUE through their effects on GPP/T. Our results indicate that seasonal dynamics of WUE were different because factors affecting the seasonal dynamics and their mechanism were different among the key ecosystems.     

Effects of environmental changes on the vitality of forest stands

Using the physiological single tree growth model BALANCE, vitality of forest stands was simulated in dependence of the site-related factors, climate and stand structure. At six level II plots in southern Germany with the main tree species beech (Fagus sylvatica L.), oak (Quercus robur L.), spruce (Picea abies [L.] Karst.), and pine (Pinus sylvestris L.), simulated results were compared to measured values (soil water content, bud burst and leaf colouring, diameter at breast height, tree height and crown density) in order to validate the model. Sensitivity tests were done to examine the influence and the interactions of the environmental parameters. The validation results show that BALANCE is capable of realistically simulating the growth and vitality of forest stands for central European regions for medium term time spans (several years). The validation of the water balance module produces mean absolute errors based on field capacity between 2.7 and 6.9% in dependence of sites and forest stands. Senescence of foliage as well as crown density is reproduced with a correlation coefficient of 0.70 compared to measurements. Differences between measured and simulated diameter values were smaller than 1% for spruce and smaller than 6.5% for beech after 7 years of simulation, and smaller than 1% for oak after 8 years of simulation. On the other hand, the simulations for pine trees conform less with the measurements (difference: 22.6% after 8 years). The sensitivity of the model on environmental changes and on combinations of these parameters could be demonstrated. The responses of the forest stands were quite different.     

Carbon and nitrogen dynamics in early stages of forest litter decomposition as affected by nitrogen addition

The effects of nitrogen(N) availability and tree species on the dynamics of carbon and nitrogen at early stage of decomposition of forest litter were studied in a 13-week laboratory incubation experiment.Fresh litter samples including needle litter(Pinus koraiensis) and two types of broadleaf litters(Quercus mongolica and Tilia amurensis) were collected from a broadleaf-korean pine mixed forest in the northern slope of Changbai Mountain(China).Different doses of N(equal to 0, 30 and 50 kg·ha-1yr-1, respecti...     

Fine root production and turnover in forest ecosystems in relation to stand and environmental characteristics

The production and turnover of fine roots (diameter ?2 mm) contributes significantly to carbon cycling in forest ecosystems. We compiled an up-to-date global database covering 186 stands from the literature and estimated fine root production (FRP) and fine root turnover (FRT) for boreal, temperate and tropical forests in order to study the relationships between FRP or FRT and environmental and stand variables. FRP for all plants (trees + understorey) was 311 ± 259 (n = 39), 428 ± 375 (n = 71) and 596 ± 478 g m⁻² a⁻¹ (n = 32) in the boreal, temperate and tropical forests, respectively, and the corresponding annual FRT rates were 0.77 ± 0.70, 1.21 ± 1.04 and 1.44 ± 0.76, respectively. When the FRP and FRT of trees were estimated separately for boreal and temperate forests the differences between the two biomes were insignificant. The mean FRP of trees for the two biomes combined was 306 ± 240 g m⁻² a⁻¹ (n = 86) and the annual FRT was 1.31 ± 1.43. Fine root biomass (FRB) was the most significant factor explaining the variation in FRP, and more so at the tree level than at the stand level, explaining 53% of the variation in FRP for trees at the tree level. The corresponding proportions at the stand level were 21% for all plants and 12% for trees. Latitude, mean annual temperature and annual precipitation each explained <20% of the variation in FRP or FRT. Fine root production and FRT estimates are highly dependent on the species included in the sampling, the sampling depth and the methods used for estimating FRP or calculating FRT. The results indicate that the variation in FRP on a global scale can be explained to a higher degree if we focus on tree roots separately from the roots of the understorey vegetation and on FRP at the tree level instead of FRP at the stand level or on FRT.     

绿竹林碳,氮动态研究

主要讨论了闽南绿竹（Dendrocalamopsisoldhami）林C、N元素的含量、库存量、年动态及C／N。结果表明：（1）绿竹林各组分C、N元素含量有一定差异,含量范围分别为：C38．74％～44．77％、No．557％～1．012％;C／N在38．281～77．792之间。（2）绿竹林C、N元素的现存库存量分别为6760．0369／m2和112．3979／m2,其中地上部分别为5891．5739／m2和94．101g／m2;地下部分别为868．463g／m2和18．296g／m2。（3）1996年7月至1997年6月一年中绿竹叶的C、N元素含量基本上是在生长期的春末夏初含量高,在冬季含量低：C／N在24．707～38．281之间,在生长期的春季比例低,在冬季比例高。（4）绿竹细根的分解过程中C、N元素含量处于释放或累积的相间波动之中,而C／N在细根分解的前几个月下降,而后处于上升和下降的波动之中。     

Soil nitrogen status of larch plantations in comparison with secondary broad-leaved forest

IntroductionSoildegradationofsouthernChinesefir(CunnhaamialanceolaIe)pIantationshavebeenCon-tinuaIlyreiorted(ShenWeitongl992;Che11BingI1aol992;FangQil992).lnthenortI1eastforestregionsofChina,larch(LarirohensisandLa)`ixgInelinii)planta-tionsmade7opercentoftheman-madeforests,andthechangesinsoilpropertiesundertI1econiferouspIanta-tionshavealsodrawnmuchattentionofmanyforesters.OurobjectivewastoexaminethedifferenceinsoilnitrogenstatusbetweenLarchp1antatiol1sandsecon-darybroad-Ieavedforests(…     

Mapping forest dynamics under climate change: A matrix model

Global climate change may be affecting forests around the world. However, the impact of climate change on forest population dynamics, especially at the landscape or regional level, has hardly been addressed before. A new methodology was proposed to enable matrix transition models to account for climate impact on forest population dynamics. The first climate-sensitive matrix (CSMatrix) model was developed for the Alaska boreal forest based on observations from over 15 years of forest inventory. The spatially explicit model was used to map climate-induced forest population dynamics across the region. The model predicted that the basal area increment in the region under natural succession would be hindered by global warming, more so for dry upland areas than for moist wetlands. It was suggested that temperature-induced drought stress could more than offset a predicted increase of future precipitation in the region to lower overall forest productivity. At the same time, stand diversity would increase across the region through transient species redistribution. Accounting for climate conditions made the CSMatrix model more accurate than conventional matrix models.     

Characterisation of and changes in the atmospheric deposition situation in German forest ecosystems using multivariate statistics

Based on the results of the atmospheric deposition classification of the year 1989, a methodical approach should be introduced, which—based on the modelled total deposition rates—enables us to characterise the input situation of forest monitoring plots and to delimit load areas in Germany. In 1989, the deposition situation in nearly 1,800 forest monitoring sites (BZE/extensive Soil Condition Inventory) in Germany could be explained by four factors (or three, excluding sea salt impact) with the help of a factor analysis. The factor values were grouped into six deposition types with typical compounds and regional patterns. The classified input rates of the soil inventory plots adequately represent the stress situation and deposition changes in Germany. The application of the statistical approach on the level of Brandenburg clarifies the special local input situation. Due to the special combination of deposed elements, the sources of emissions can be characterised as well. When the soil inventory is repeated, a project planned for 2006, this approach can be used in order to determine homogenous areas for stratified data evaluation.     

Soil surface properties in Mediterranean mountain ecosystems: Effects of environmental factors and implications of management

Understanding soil processes is fundamental to the success of forest restoration programs. We compared different types of soils in Mediterranean mountain forests with respect to their edaphic environments and influence of vegetation cover and lithology. We then used this information to determine the suitability of current forest restoration programs in these ecosystems.     

Imbalanced forest ecosystems: Assessments and consequences

Few ecosystems can maintain an ideal balance of available resources for primary producers, decomposing organisms, and consumers. When nutrition is optimal for plants, their tissue may be toxic for many consumers and their detritus nutritionally imbalanced for decomposers. Even conditions favoring high rates of primary production soon lead to limitation in light and possibly other resources. Because of the integrated nature of ecosystems, stress induced in one part permeates the entire system. With chronic stress induced by climatic change or air pollution, we might expect reductions in canopy leaf area, decomposition rates, and root mineral uptake, and increases in herbivory, pathological activity, and leaching of material into or through the rooting zone. Each of the six responses can be simply assessed. As a general index of stress to forest ecosystems, we may monitor changes in the ability of folaige to produce wood. Below a particular level of production, trees become susceptible to a variety of insects and diseases. Through an experimental approach, we can identify the relative importance of constraining factors and predict the consequences of management options.     

Water cycle investigations in Hungarian forest ecosystems

From the biological point of view the value of autotrophy plant association is determined by the carbon fixation and the carbon cycle. Among the plant associations of Hungary, forest has the largest biological carbon fixation and carbon cycle.In general, the annual water cycle is the key factor in the organic material production of the Hungarian forests. The most intensive water consumption and organic material production take place from May till July, which period is named main water consumption and respectively main growing period. In Hungary the categories of the forest climate are characterized by main tree species and based on the characteristic meteorological data (Jaro and Tatraaljai, 1985). In Hungary the forest area covered by stand is 1,650,000 hm2. Beech forest climate covers 8% of the forest area, hornbeam-oak forest climate covers 22%, sessile oak-Turkey oak forest climate covers 48% and forest steppe climate covers 22%. Partly in the frame of ICP-Forests, the Department of Ecology in the Forest Research Institute carries out long term, complex ecophysiological investigations on several sample plots (so-called basic plots) throughout the whole country. The organic material production (growth), the nutrient and water cycle, the measurements of air pollutants and meteorological parameters, as well as chemical analyses are all part of the investigations. As a comparison the figure of two basic plots (Sopron-Piispokladany) shows the water cycles of a good growing beech stand in beech climate and a weak pedunculate oak stand in forest steppe climate in the hydrological year of 2001-2002. In the Hungarian forest 60%-70% of the precipitation is used for interception, evaporation, and in the vegetation season, for the transpiration both in beech and forest steppe climate. From other point of view, only 30%-40% of the open air precipitation infiltrates into the soil and can be utilized by the forest.     

Simulation of the biomass dynamics of Masson pine forest under different management

Introduction Masson pine (Pinus massoniana) is important both economically and ecologically in subtropical mountainous areas in China, and it is vital not only as an important source of commercially harvested timber and charcoal fuel, but also as a pionee…