Litterfall production modeling based on climatic variables and nutrient return from stands of Eucalyptus grandis Hill ex Maiden and Pinus taeda L.

Native grasslands in the Pampas of South America are increasingly being replaced by Eucalyptus and Pinus stands.The short rotation regimes used for the stands require high nutrient levels,with litterfall being a major source of nutrient return.To model the litterfall production using climatic variables and assess the nutrient return in 14-year-old Eucalyptus grandis and Pinus taeda stands,we measured litter production over 2 years,using conical litter traps,and monitored climatic variables.Mean temperature,accumulated precipitation,and mean maximum vapor pres-sure deficit at the seasonal level influenced litterfall produc-tion by E.grandis;seasonal accumulated precipitation and mean maximum temperature affected litterfall by P.taeda.The regression tree modeling based on these climatic vari-ables had great accuracy and predictive power for E.grandis(N=33;MAE(mean absolute error)=0.65;RMSE(root mean square error)=0.91;R^(2)=0.71)and P.taeda(N=108;MAE=1.50;RMSE=1.59;R^(2)=0.72).The nutrient return followed a similar pattern to litterfall deposition,as well as the order of importance of macronutrients(E.grandis:Ca>N>K>Mg>P;P.taeda:N>Ca>K>Mg>P)and micronutrients(E.grandis and P.taeda:Mn>Fe>Zn>Cu)in both species.This study constitutes a first approximation of factors that affect litterfall and nutrient return in these systems.

Assessing forest cover changes and fragmentation in the Himalayan temperate region: implications for forest conservation and management

This study comprehensively assessed long-term vegetation changes and forest fragmentation dynamics in the Himalayan temperate region of Pakistan from 1989 to 2019.Four satellite images,including Landsat-5 TM and Landsat-8 Operational Land Imager(OLI),were chosen for subsequent assessments in October 1989,2001,2011 and 2019.The classified maps of 1989,2001,2011 and 2019 were created using the maximum likelihood classifier.Post-classification comparison showed an overall accuracy of 82.5%and a Kappa coefficient of 0.79 for the 2019 map.Results revealed a drastic decrease in closed-canopy and open-canopy forests by 117.4 and 271.6 km^(2),respectively,and an increase in agriculture/farm cultivation by 1512.8 km^(2).The two-way ANOVA test showed statistically significant differences in the area of various cover classes.Forest fragmentation was evaluated using the Landscape Fragmentation Tool(LFT v2.0)between 1989 and 2019.The large forest core(>2.00 km^(2))decreased from 149.4 to 296.7 km^(2),and a similar pattern was observed in medium forest core(1.00-2.00 km^(2))forests.On the contrary,the small core(<1.00 km^(2))forest increased from 124.8 to 145.3 km^(2) in 2019.The perforation area increased by 296.9 km^(2),and the edge effect decreased from 458.9 to 431.7 km^(2).The frequency of patches also increased by 119.1 km^(2).The closed and open canopy classes showed a decreasing trend with an annual rate of 0.58%and 1.35%,respectively.The broad implications of these findings can be seen in the studied region as well as other global ecological areas.They serve as an imperative baseline for afforestation and reforestation operations,highlighting the urgent need for efficient management,conservation,and restoration efforts.Based on these findings,sustainable land-use policies may be put into place that support local livelihoods,protect ecosystem services,and conserve biodiversity.

Afforestation increases microbial diversity in low-carbon soils

Afforestation has an important role in biodiversity conservation and ecosystem function improvement.A meta-analysis was carried out in China,which has the largest plantation area globally,to quantify the effects of plantings on soil microbial diversity.The results showed that the overall effect of afforestation on soil microbial diversity was positive across the country.Random forest algorithm suggested that soil carbon was the most important factor regulating microbial diversity and the positive response was only found with new plantings on low-carbon bare lands but not on high-carbon farmlands and grasslands.In addition,afforestation with broadleaved species increased microbial diversity,whereas planting with conifers had no effect on microbial diversity.This study clarified the effects of plantings on soil microbial diversity,which has an important implication for establishing appropriate policies and practices to improve the multiple functionalities(e.g.,biodiversity conservation and climate change mitigation)during plantation establishment.

Factors affecting poplar wetwood characteristics

Wet wood is an abnormal phenomenon in growing trees,which adversely affects growth,subsequent wood processing and economic values of wood products.In this study,the influences of factors such as clones,afforestation methods,site conditions and climate conditions on the characteristics of poplar wetwood were studied through field investigations in 27 clones from 48 sample plots in 28 counties.Results showed that the incidences of wetwood were almost 100%in all plots.Ratios of wetwood area among the48 plots differed from 15.1 to 90.2%.Wetwood area ratios,moisture contents and pH differed significantly between the 27 clones.Wetwood area ratios of the clones ranged from18.7 to 62.3%.Ratios of wetwood areas were positively correlated with wet wood moisture content and pH,tree age,and negatively correlated with pH of sap wood.The repeatability of wet wood area ratios was 0.52,moderately controlled by genetics.Wetwood moisture content and pH were highly controlled by genetics,indicated by the repeatability of 0.91 and 0.89,respectively.There were significant differences in wetwood area ratios,moisture content and pH between different site conditions,afforestation methods,and geographical regions.Sloping land had the lowest wetwood area ratios and moisture content among four types of sites.Afforestation by direct seeding and rooted cuttings had the lowest wetwood area ratios and moisture content,respectively.In the three geographical regions,the Yellow River Basin had the lowest wetwood values of all three factors.

Vegetation C–N–P accumulation and allocation patterns at the community level in early restored plantations in the loess hilly-gully region

Accumulation of vegetation biomass is a crucial process for carbon fixation in the early stage of afforestation and a primary driving force for subsequent ecological functions.Accurately assessing the storage and allocation of elements in plantations is essential for their management and estimating carbon sink capacity.However,current knowledge of the storage and allocation patterns of elements within plant organs at the community level is limited.To clarify the distribution patterns of elements in plant organs at the community level,we measured the biomass within plant organs of five typical plantations in the early stage of afforestation in the loess hilly-gully region.We assessed the main drivers of element accumulation and distribution by employing redundancy analysis and random forest.Results revealed significant differences in biomass storages among plantations and a significant effect of plantation type on the storages of elements within plant organs.Furthermore,the dominant factors influencing C–N–P storage and allocation at the community level were found to be inconsistent.While the storage of elements was mainly influenced by stand openness,total soil nitrogen,and plant diversity,the allocation of elements in organs was mainly influenced by stand openness and soil water content.Overall,the spatial structure of the community had an important influence on both element storage and allocation,but soil conditions played a more important role in element allocation than in storage.Random forest results showed that at the community level,factors influencing element storage and allocation within plant organs often differed.The regulation of elemental storage could be regulated by the major growth demand resources,while the allocation was regulated by other limiting class factors,which often differed from those that had a significant effect on element storage.The differences in plant organ elemental storage and allocation drivers at the community level reflect community adaptation strategies and the regulation of resources by ecosystems in combination with plants.Our study provides valuable insights for enhancing plantation C sink estimates and serves as a reference for regulating element storage and allocation at the local scale.

Improving Forest Soil Health and Ecosystem Services to Minimize the Impact of Climate Change

The presence of increasing quantities of greenhouse gases is fostering climate change. This review chronicles the emerging research addressing the role of soil to sequester carbon across biomes, understand the soil mechanisms responsible for soil carbon preservation and indicate the need to estimate the intensity for site-specific carbon sequestration. To negate the continuing increase of atmospheric greenhouse gases requires using well-documented soil pathways to sequester carbon. For deciduous forests, emerging concepts center around two approaches: 1) increasing the ecosystem’s net primary productivity coupled with increasing the carbon supply into soil using appropriate land management practices, and 2) supporting soil processes that increase soil carbon retention. New perspectives suggest that soil carbon may be preferentially preserved because organic materials are adsorbed onto phyllosilicates and oxyhydroxides and subsequently protected from microbial degradation because of soil structure improvement. Thus, augmenting soil structure may promote soil organic matter persistence. Each soil has a soil carbon carrying capacity;however, soil survey databases infer that soil organic matter concentrations have a significant variance at the soil series level. The need exists for more precise estimates of the soil’s carbon carrying capacity at the pedon level to support land management practices that encourage land management options designed to preserve soil carbon. However, the complexity of the soil system may limit its usefulness for routine soil management decisions. Our modern understanding of soil carbon preservation processes and emerging soil carbon saturation deficit concepts may potentially improve decision support tools for managing soils for carbon sequestration.

红池坝炼山后生态恢复过程中群落特征研究

This paper studied the species composition and the structure and species diversity of communities in Hongchiba area of Wuxi County after controlled burning and aerial sowing afforestation.The results showed that after burning and afforestation,pure Pinus armandii forest was not developed,but various mixed needle board leaved forests which comprised P.armandii and native board leaved trees grew.Various native species contributed to the communities with great species diversity.Shannon Wiener index was 2 305～3 145,ecological dominance was 0 063～0 151,and evenness was 0 600～0 749 The natural regeneration of P.armandii population was very poor,and there was a trend that P.armandii would be gradually replaced by other native board leaved trees.It was demonstrated that P.armandii should not be taken as a unique afforest tree,and controlled burning was not a favorite ecological measure in subtropical area.Native trees should play more important roles in the process of ecological restoration.

Design Method of Rainwater Harvesting System for Afforestation in Loess Plateau

On the basis of natural conditions of lack of rainfall on the Loess Plateau, this paper presents a method of design and construction in rainwater harvesting system for afforestation, which is suitable to the regions of 300 600?mm rainfall. The system consists of micro catchments of various forms and sizes that include planting areas, where trees are planted and trapped runoff, and contributing areas, where overland flow are produced by rainfall. The design is based on rainfall, runoff coefficients of contributing areas, evapotranspiration of trees and soil surface, water deficiency of soil, and environmental capacity of precipitation in the region, and so on. Runoff coefficient of contributing areas with YJG (organic silicon chemical treatment), compacted surface soil slope and natural slope micro catchments, are 0 8 0 89, 0 23 0 36, and 0 08 0 10 respectively. According to the Penman method, the soil water deficiency varies from 50?mm to 300?mm. In the region of 400?mm precipitation, the contributing area treated with YJG is 3 4?m 2 for timber forests, 8 10?m 2 for cash trees respectively; the contributing area treated with compacted soil surface is 6 8?m\+2 for timber forests, 10 12?m 2 for cash trees respectively; the contributing area of natural slope is 8 10?m 2 for timber forests, 12 15?m 2 for cash trees respectively. Transpiration from trees of micro catchment in YJG, compacted surface soil and natural slope treatment is by 47 65% 53 31%, 24 10% 36 93%, and 18 65% 29 55% of total rainfall (rainfall and harvested rainwater) respectively after the system was applied in the region. This system, which has been widely practising on the Loess Plateau, is now known as runoff forestry.

Problems in Use of Inefficient and Idle Forestland——A Case of Lutian Town

In order to improve fragile eco-environment and develop economy in mountainous regions, problems during use of barren mountains and forestlands were explored with Lutian Town as an example through a survey of 97 farm households in the research. The results showed that barren lands in Lutian Town were exten- sive and the barren rate was as high as 48.6%. It is notable that the rate is in- creasing as farmer ages and education declines. It is proposed that forestry cooper- atives should be established and land management laws and rules can be formulated to promote mountainous area economy and forestland use.

Bioblock Method for Forest Vegetation Recovery in Japan

Bioblock method is a planting method for forest vegetation recovery by just depositing bioblocks without digging planting holes. The process includes collecting objective tree’s seeds or cuttings, nurturing seedlings, preparing and filling ＂ Kaminekkon＂, processing bioblock, and field planting. Seedlings can be planted without damaging root system, can be planted in hard ground or frozen soil and can be planted throughout the year.

The Survey and Assessment on Afforestation Status quo of Danfu Courtyard in Chaozhou City

Danfu Courtyard is a national AAAA-class scenic area integrating relics collection, culture exchange and sightseeing in Chaozhou City. However, there are some problems on afforestation. The research conducted a field survey on status quo of afforestation there to analyze the advantages and disadvantages and proposed suggestions on enriching plant diversity, phytocoenosium and scenic spot characters in order to advance coordinated development of cultural and natural land- scapes in the scenic spot.

Ecotype and Regional Division of Afforestation Plants in China

The selection of afforestation plants,which is based on the ecotype of afforestatioin plant,is the key of plant engineering. There is not final verdict yet on the standard of ecotype of afforestation plant. According to the presentational feature （regional distribution,Climatic indicator）,ecotype （climatoecological type,edaphic ecotype and biota ecotype） and genetic association of afforestation plant,combined with the experience in the greening practice,the afforesting nursery stock （Arbor and Shrub ） is divided into five ecotypes while the herbaceous plant are divided into three ecotypes.

Reforestation Programs in Southwest China:Reported Success,Observed Failure, and the Reasons Why

Ever since the disastrous floods of 1998, the Chinese government has used the Natural Forest Protection and Sloping Land Conversion Programs to promote afforestation and reforestation as means to reduce runoff, control erosion, and stabilize local livelihoods. These two ambitious programs have been reported as large-scale successes, contributing to an overall increase in China’s forest cover and to the stated goals of environmental stabilization. A small-scale field study at the project level of the implementation of these two programs in Baiwu Township, Yanyuan County, Sichuan, casts doubt upon the accuracy and reliability of these claims of success; ground observations revealed utter failure in some sites and only marginal success in others. Reasons for this discrepancy are posited as involving ecological, economic, and bureaucratic factors. Further research is suggested to determine whether these discrepancies are merely local aberrations or represent larger-scale failures in reforestation programs.

Biomass Carbon Storage and Its Sequestration Potential of Afforestation under Natural Forest Protection Program in China

Based on the data from China′s Seventh Forest Inventory for the period of 2004–2008, area and stand volume of different types and age-classes of plantation were used to establish the relationship between biomass density and age of planted forests in different regions of the country. Combined with the plantation area in the first-stage of the Natural Forest Protection(NFP) program(1998–2010), this study calculated the biomass carbon storage of the afforestation in the first-stage of the program. On this basis, the carbon sequestration potential of these forests was estimated for the second stage of the program(2011–2020). Biomass carbon storage of plantation established in the first stage of the program was 33.67 Tg C, which was majority accounted by protection forests(30.26 Tg C). There was a significant difference among carbon storage in different regions, which depended on the relationship of biomass carbon density, forest age and plantation area. Under the natural growth, the carbon storage was forecasted to increase annually from 2011 to 2020, reaching 96.03 Tg C at the end of the second-stage of the program in 2020. The annual growth of the carbon storage was forecasted to be 6.24 Tg C/yr, which suggested that NFP program has a significant potential for enhancing carbon sequestration in plantation forests under its domain.

Effects of climate and forest age on the ecosystem carbon exchange of afforestation

Afforestation is believed to be an effective practice to reduce global warming by sequestering large amounts of carbon in plant biomass and soil.However,the factors that determine the rate of carbon sequestration with afforestation are still poorly understood.We analyzed ecosystem carbon exchange after afforestation based on eddy covariance measurements with the aim to identify factors responsible for the rate of carbon exchange following afforestation.The results indicated that afforestation in the tropical/subtropical and temperate climate zones had greater capacities for carbon sequestration than those in boreal zones.Net ecosystem production(NEP),gross primary production(GPP)and ecosystem respiration(RE)varied greatly with age groups over time.Specifically,NEP was initially less than zero in the\10 year group and then increased to its peak in the 10-20 year group.Afforestation of varied previous land use types and planting of diverse tree species did not result in different carbon fluxes.The general linear model showed that climate zone and age of afforestation were the dominant factors influencing carbon sequestration.These factors jointly controlled 51%,61%and 63%of the variation in NEP,GPP and RE,respectively.Compared to the strong regulation of climate on GPP and RE,NEP showed greater sensitivity to the age of afforestation.These results increase our understanding of the variation in ecosystem carbon exchange of afforestation and suggest that afforestation in subtropical and temperate areas after 20 years would yield greater carbon sink benefits than would afforestation of boreal regions.

Long-term impact of municipal sewage irrigation on treated soil and black locust trees in a semi-arid suburban area of Iran

The effects of municipal sewage irrigation on the soil and black locust （Robinia pseudoacacia L.） tree were studied. For this purpose, two artificial black locust stands under irrigation of municipal sewage and well water were selected in south of Tehran, Iran. Data were collected using technique of systematic random sampling with 4 replicates in each stand. It was found that the growth of black locust tree, as indicated by diameter at breast height, total height, crown length, average crown diameter, basal area and volume, in sewage irrigation stand was much higher than that of well water irrigation stand （P 〈 0.01）. Plant analysis indicated that concentrations of leaf nutrients （N, E K, Ca, Mg, Na, Fe, Mn, Cu and Zn） were greater in sewage-irrigated trees, without toxicity to the minerals of tree leaf, than those of well waterirrigated trees, and positively correlated with their respective value in soil. Ni, Cr and Pb were not detected in leaf samples. Application of sewage resulted in a 1.5-fold increase in the concentrations of soil nutrients, Ni, Cr and Pb. Among these minerals only Pb and Ni in some soil samples exceeded the toxicity limit. The increase in pH, electrical conductivity （EC） and organic carbon of soil was also observed in sewage irrigation. Results confirm that besides the use as irrigation water, municipal sewages are also a potential source of plant nutrients. However, significant accumulation of heavy metals such as Pb and Ni in soil needs to be monitored.

Ecosystem carbon and nitrogen storage following farmland afforestation with black locust(Robinia pseudoacacia) on the Loess Plateau, China

Although afforestation of farmlands has been proposed as an effective method of carbon(C) sequestration, there remain uncertainties that deter us from developing a clear picture of C stocks in plantation ecosystems.This study investigated the dynamics of stand structure and plant diversity, and C and nitrogen(N) pools in trees,herbs, litter, and soil(0–100 cm depth) in black locust plantations aged 9, 17, 30, and 37 years, and in newly abandoned farmlands as pre-afforestation sites, on the Loess Plateau, China. Stand density decreased significantly, while tree diameter at breast height and height increased during stand development. The dominant species of the herb layer differed with age. Afforestation resulted in slight increases in tree C and N storage in plantations from 9 to 30 years of age, and then significantly increased from 30 to 37 years. Compared to pre-afforestation, C and N storage in soil decreased to minimum values in stands aged 17 and 9 years, respectively. The soil re-accumulated C and N during stand development, attaining equilibrium levels similar to those in pre-afforestation when stands reached about 30 years of age. Soil C and N storage in 37-year stands were 29 and 16% higher, respectively, than in pre-afforestation levels. However, C and N concentrations in the subsoil(20–40 cm) were still less than the preafforestation levels for stands of all ages(from 9 to 37 years). The relative contribution to the total ecosystem C and N pools increased in trees and decreased in soil during the observed period. Our results indicate that afforestation reduced soil C and N storage during the early stages of stand development. We conclude that the growing phase of an afforested stand over its initial 30 years is important for C and N sequestration by black locust due to the C and N storage that result from recovered soil quality and an increase in tree biomass.

Sap flow characteristics and physiological adjustments of two dominant tree species in pure and mixed plantations in the semi-arid Loess Plateau of China

It is essential to understand the water consumption characteristics and physiological adjustments of tree species under drought conditions,as well as the effects of pure and mixed plantations on these characteristics in semi-arid regions.In this study,the normalized sap flow(SFn),leaf water potential,stomatal conductance(gs),and photosynthetic rate(Pr)were monitored for two dominant species,i.e.,Pinus tabuliformis and Hippophae rhamnoides,in both pure and mixed plantations in a semi-arid region of Chinese Loess Plateau.A threshold-delay model showed that the lower rainfall thresholds(RL)for P.tabuliformis and H.rhamnoides in pure plantations were 9.6 and 11.0 mm,respectively,and the time lags(τ)after rainfall were 1.15 and 1.76 d for corresponding species,respectively.The results indicated that P.tabuliformis was more sensitive to rainfall pulse than H.rhamnoides.In addition,strong stomatal control allowed P.tabuliformis to experience low gsand Prin response to drought,while maintaining a high midday leaf water potential(Ψm).However,H.rhamnoides maintained high gsand Prat a lowΨmexpense.Therefore,P.tabuliformis and H.rhamnoides can be considered as isohydric and anisohydric species,respectively.In mixed plantation,the values of RLfor P.tabuliformis and H.rhamnoides were 6.5 and 8.9 mm,respectively;and the values ofτwere 0.86 and 1.61 d for corresponding species,respectively,which implied that mixed afforestation enhanced the rainfall pulse sensitivity for both two species,especially for P.tabuliformis.In addition,mixed afforestation significantly reduced SFn,gs,and Prfor P.tabuliformis(P<0.05),while maintaining a high leaf water potential status.However,no significant effect of mixed afforestation of H.rhamnoides was observed at the expense of leaf water potential status in response to drought.Although inconsistent physiological responses were adopted by these species,the altered water consumption characteristics,especially for P.tabuliformis indicated that the mixed afforestation requires further investigation.

Effect of Land Cover Change on Soil Phosphorus Fractions in Southeastern Horqin Sandy Land, Northern China

In the past 50 years, large areas of the Horqin sandy land were afforested to prevent desertification. Although the afforestation policy appears successful, many people now doubt whether it is suitable to plant trees with high density on the poor soils in semiarid regions. Little is known about the impacts of afforestation on the sandy soil properties, although the evaluation of these impacts is fundamental to judge the rationality of afforestation policy. Soil phosphorus （P） fractions, acid phosphomonoesterase activities, and other soil chemical properties were compared among five adjoining typical ecosystems on poor sandy soils in southeastern Horqin sandy land. The ecosystems studied are natural elm savanna, degraded grassland, Mongolian pine （Pinus sylvestris var. mongolica） plantation, Chinese pine （Pinus tabulaeformis） plantation, and mixed plantation of Mongolian pine and poplar （Populus simonii）. The results showed that organic P dominated soil P （47%-65%） was the principal source of available P. The degradation of elm savanna to grassland significantly reduced soil pH and resulted in an overall reduction in soil fertility, although slightly increased labile inorganic P. Grassland afforestation had no significant influence on soil pH, organic carbon, and total N but significantly reduced total P. Impacts of grassland afforestation on soil P fractions depended on tree species. Natural elm savanna had higher soil P conserving ability than artificial plantations. Therefore, with the aim of developing a sustainable ecosystem, we suggested that vegetations with low nutrient demand （particularly P） and efficient nutrient cycling would be more suitable for ecosystem restoration in the semiarid region.

Germination and early seedling growth of Pinus densata Mast.provenances

We studied seed germination and early seedling growth of Pinus densata to explore the range of variability within the species and to inform afforestation practices. Phenotypes were evaluated at a forest tree nursery under conditions that support Pinus yunnanensis, one of the presumed parental species of P. densata. Seeds were col- lected from 20 open-pollinated trees within each of eight autochthonous populations representing the natural distri- bution of P. densata in China to assess variation in ger- mination traits and early seedling growth, and to examine the relationships among these traits. Results showed that seeds from all populations germinated and seedlings established successfully. There were significant differences among populations in 13 of 14 traits evaluated. Seed germination and early seedling growth were strongly related to seed size and seed weight. Bigger seeds germi- nated earlier and faster than small seeds, and seedling size was positively correlated with seed size. Some germination traits were strongly and significantly correlated with cli- matic variables associated with the provenance of the studied populations. Based on these observations, we conclude there were large, significant, and biologically important differences among P. densata populations in seed germination and seedling growth traits. The observed variability probably reflects a high degree of adaptive dif- ferentiation among populations that is likely to be relevant for future afforestation.