Effects Of Afforestation Research Articles

Biogeography and ecological functions of root‐associated and soil fungi of Pinus sylvestris var. mongolica across different afforestation areas in desertified Northern China

AbstractChina has unquestionably led efforts to 'green' drylands, but an evaluation of the large‐scale effects of afforestation in desert ecosystems mediated by soil microorganisms is lacking. The ecological functions of fungi are closely related to soil and plant health. Therefore, there is a lively interest in revealing the biogeographic patterns of root‐associated (RAF) and soil fungal (SF) communities of Pinus sylvestris var. mongolica, a widespread evergreen tree endemic to Northern China. We revealed the community assembly of RAF and SF of natural forest and plantations in the Hulunbuir Desert, Horqin Desert, and Mu Us Desert and investigated fungal responses to geographical location, climate factors, soil properties, and stand age at regional and local scales. The results indicated that (1) SF was more diverse than RAF. For RAF, the diversity indices in the natural forest were significantly lower than those in plantations, and ectomycorrhizal fungi (50.37%) were the predominant functional guild in the natural forest. (2) At the local scale, SF, not RAF, is more sensitive to the impacts of soil properties. More than half of the differential genera were ectomycorrhizal and endophytic fungi, such as Acephala, Cadophora, Pustularia, and Trichoderma. (3) On the regional scale, precipitation and sunshine duration were the main influences on geographical differences in the fungal community composition. Geographical location directly and significantly influences RAF diversity and structure. The effect of climate factors on SF diversity was low, but it had a shaping effect on SF structure. Our results demonstrated that the fungal communities were geographically structured, a stable relationship was established between hosts and RAF, and soil nutrients had a significant impact on SF community composition. The ecological functions of fungi are important in evaluating afforestation efforts and maintaining stability in desert ecosystems.

Agroforestry-Enhancing Typification of Agricultural Territories as a Basic Condition for Increasing the Efficiency of Protective Afforestation

Upgrading the scale of agricultural production and the effectiveness of protective afforestation is based on the strategy of identifying similar crop production conditions. The given research identifies the territories that require different approaches to forest reclamation. The research is based on the use of remote data as well as geoinformation research methods. The area for investigation is the territory of the right bank of the Khoper River in the Volgograd region. This territory is characterized by the distribution of the most fertile soils in the world, southern chernozems and typical chernozems. The study area is a long-standing historical center of agricultural production, and the task of protecting and increasing the fertility of cultivated soils is very urgent for this territory. The investigation of the catchment areas for identifying spatial patterns is an important methodological aspect of the present research. The studies were carried out within the network of catchments in ravines and gullies. The parameters of the areas of each catchment were used to calculate the specific indicators characterizing the territory. Mapping the territory of the research area made it possible to identify the range of parameters which characterize the erosion process as well as the parameters that cause its development. The studies of the interdependence of land structure and relief parameters made it possible to identify the processes for evaluating the agroecological state of the territories and their typification. These parameters include: erosive dissection, km/km2; the density of ravine tops, units/km2; the area of arable land in the catchment located on slopes with a steepness of more than 3°, %; and the nonforested area of slopes with a steepness of more than 8°. The values of indicators estimated on the basis of statistical scoring procedures became the basis for the allocation of four groups of conditional agroecological states of territories: normal, risk, crisis, and disaster. These groups differ in the set of reclamation measures used and their focus and scope.

The effect of afforestation on moist heat stress in Loess Plateau, China

Study regionLoess Plateau (LP), China Study focusThis study aimed to research whether and to what degree afforestation contributes to the variations in moist heat stress in the study area. Here, wet bulb, temperature (Tw) was used to quantify the moist heat stress. Subsequently, The Weather Research and Forecasting model (WRF) is applied to simulate the modulation of climate change related to afforestation during 2001–2015. Based on the analysis of energy fluxes, we identified the biogeophysical mechanism of afforestation impact on moist heat stress. New hydrological insights for the regionSince the operation of the “Grain-to-Green” program, LP has experienced widespread afforestation which perturbs energy and water fluxes, affecting regional climate regimes. The forest expansion increases relative humidity but cools the regional temperature. As a significant combined climate factor, the average moist heat stress decreases with the magnitude of − 0.1∼− 0.3 °C in central LP. While the decrease rate of Tw is slower than near-surface temperature. It is worth noting that, an increased signal occurs in the maximum Tw (almost 0.2 °C in eastern and northeastern LP), which might expose humans to the risk of moist heat stress. By the mechanistic analysis, the research shows that the near-surface temperature and sensible heat flux are dominant driving factors for the change of Tw. Furthermore, the subsidence of the planetary boundary layer enhances moist heat stress. Overall, afforestation’s effects on land surface-atmosphere interaction are non-negligible and the moist heat stress should be accounted for in climate change adaptation strategies.

Effects of Pine Plantation on Native Ecuadorian Páramo Vegetation

Exotic pine plantations, installed mainly for timber production and carbon sequestration purposes, cover an ever-expanding area of equatorial and tropical regions; however, their economic and environmental benefits are under debate due to their potential negative effects on native plant species conservation. The native understory plant species richness and cover under pine (Pinus radiata D. Don) plantations were compared with natural grasslands in the Ecuadorian Páramo. We analyzed the vegetation in four zones: Antisana (8-year-old pines), Cajas (16-year-old pines), Tisaleo (41-year-old pines) and Cotopaxi (53-year-old pines). The total understory plant cover decreased between 29% and 90% under pine plantations in all zones. The mean species richness in the pine plantations decreased by 44% in Antisana, Cajas and Tisaleo but not in Cotopaxi. Pine plantations strongly reduced the abundance of herbaceous light-demanding species (59%), except small herbs whose cover increased under pine (17.6%). Shrub cover was also negatively affected in Tisaleo and Cotopaxi (7.4%). Pine afforestation effects on Páramo vegetation depend mainly on canopy cover which changes with age and growing conditions (altitude) and secondarily on the vegetation state at the time of planting, resulting from land use history and ecological conditions. The pine effect was therefore more pronounced in the young and dense plantations of Antisana and Cajas than in the old and open stand of Cotopaxi, whose understory vegetation was more similar to that of grasslands.

Afforestation may accelerate the depletion of deep soil moisture on the Loess Plateau: Evidence from a meta‐analysis

AbstractAfforestation is an effective way to restore degraded landscapes and protect ecosystems in arid and semiarid regions. However, the responses of soil moisture content (SMC) to afforestation in deep soil layers as well as the related controlling factors on a regional scale are still poorly understood. In this study, a meta‐analysis compiled a total of 3045 individual measurements in 203 sites, was conducted to evaluate the effects of afforestation on SMC to a depth of 300 cm based on a field transect survey covering non‐afforested modes (traditional rain‐fed cropland as the control) and afforested vegetation types (forestland, shrubland, and grassland) from southeast to northwest across the Chinese Loess Plateau and to examine the relationships between the SMC and potential affecting factors. The results showed that afforestation led to a decreasing SMC across the entire profile, especially in forestland and shrubland. Soil moisture changes were significantly affected by restoration types (forests, shrubs, and grasses) and restoration ages. Mean annual precipitation, mean annual temperature, and initial soil moisture jointly affected soil moisture in all land use types along the precipitation gradient. The artificial restoration mode significantly decreased the soil moisture, while the natural restoration mode partially restored the soil moisture. These results indicate that natural restoration may be the better choice from the soil moisture perspective in the context of future climate change in arid and semiarid regions.

Post‐farmland conversion spatio‐temporal dynamics of net soil nitrogen mineralization and availability in a chronosequence of Zanthoxylum bungeanum plantations

AbstractAfforestation on cultivated farmlands causes major shifts in the nitrogen (N) cycle. The consequences of large‐scale Zanthoxylum bungeanum afforestation on spatio‐temporal patterns of soil N mineralization and inorganic N (ION) availability have not been reported. Moreover, the regulatory roles of microbial biomass and soluble organic N (MBN and SON) in the N cycle are poorly characterized in soils below 20 cm. To investigate the long‐term effects of afforestation on the governing mechanism of vertical N dynamics, a 0–100 cm soil profile was collected from a chronosequence of Z. bungeanum plantations aged 8‐year (H8), 15‐year (H15), 20‐year (H20) and 28‐year (H28), as well as adjacent farmland and abandoned‐land (28‐year) as controls in an arid valley in Southwest China. With increasing stand age, conversion of farmland to Z. bungeanum plantations significantly improved soil organic carbon, available nutrients, and all N forms. These impacts were more evident in the topsoil (0–20 cm) than in the subsoil layers. MBN and SON contents improved by 1.42‐fold and 1.34‐fold in H28, respectively, compared to H8. Net N mineralization (1.31‐fold), net nitrification rates (1.30‐fold), and total ION (1.31‐fold) content followed similar trends of increase along with the stand age. Correlation and redundancy analysis also established a positive relationship and demonstrated that increased ION availability is due to improved MBN, SON, and urease activity with the plantations age. Although the nitrate‐N content was highest in abandoned‐land, its content also increased steadily in Z. bungeanum plantations with the stand age. A relatively low ammonium/nitrate ratio (0.331) in H28 advocated improved N supply via nitrification as well as low N leaching risks from plantations. The spatial investigation provided novel insights into controls of N cycle and suggested converting farmland to Z. bungeanum plantations is a suitable approach for restoring soil N.

Biophysical Effects of Afforestation on Land Surface Temperature in Guangdong Province, Southern China

AbstractDeveloping effective climate mitigation strategies under global warming requires a comprehensive understanding of the biophysical mechanism of how afforestation affects the climate and environment. The planted forests in southern China are an essential carbon sink. However, the impacts of radiative and non‐radiative processes on land surface temperature caused by converting open land (i.e., grassland and cropland) and natural forests to planted forests remain unclear. We used satellite observations and intrinsic biophysical mechanism theory‐based energy balance models to estimate the biophysical impacts of potential afforestation of open land and natural forests on surface temperature from 2000 to 2010 in Guangdong Province, southern China. Results showed that afforestation of open land had a consistent net cooling effect. Due to the afforestation of natural forests, the modeled results revealed that afforestation among all conversion types had a net warming effect of 0.15 ± 0.5 K, which caused by the change in energy redistribution factor although uncertainty remains. While the most significant warming caused by converting natural forest to planted forests was also slightly affected by albedo. The afforestation's non‐radiative and radiative processes led to a slight warming of 0.143 ± 0.43 K and a cooling of −0.096 ± 0.19 K, respectively. The non‐radiative process dominates the effect of afforestation on the surface temperature, with the overall non‐radiative forcing index greater than 73% ± 0.59%. Our study highlights the need of protecting natural forests and provides a practical method for assessing the impacts of afforestation on the local climate and the effectiveness of climate mitigation efforts.

Effects of Dodonaea viscosa Afforestation on Soil Nutrients and Aggregate Stability in Karst Graben Basin

Dodonaea viscosa is widely cultivated in the karst graben basin and is crucial for recovering land after rocky desertification. However, the effect of long–time D. viscosa afforestation on changes in the quality of soil remains unclear. Soil nutrients and aggregate composition can be used to evaluate the beneficial effects of afforestation of D. viscosa in improving soil functional stability. In this study, soil nutrients and aggregate stability were investigated using cropland, 10–year, 20–year, and 40–year D. viscosa afforestation and secondary succession shrub. Compared to the cropland, D. viscosa afforestation significantly increased the soil water content (WC), soil organic carbon (SOC), and total nitrogen (TN) contents, with an enhanced effect observed with prolonged afforestation. Soil nutrient contents under D. viscosa afforestation rapidly reached the level of the shrub. Dodonaea viscosa afforestation promoted the formation of >2 mm aggregates and decreased the ratio of 0.053–0.25 mm aggregates, which varied with afforestation years. Compared to the cropland, the content of >0.25 mm water–stable aggregates (R>0.25), mean weight diameter (MWD), and geometric mean weight diameter (GMD) of soil increased exponentially. However, soil erodibility factor (K) and unstable aggregates index (EIt) decreased exponentially with prolonged D. viscosa afforestation, and the latter two indicators did not reach the level of the shrub. These results indicated that soil nutrients, aggregate stability, and erosion resistance increased with prolonged D. viscosa afforestation. However, the aggregate stability and erosion resistance exhibited by D. viscosa could not reach the level of secondary shrub for a long time.

Afforestation can lower microbial diversity and functionality in deep soil layers in a semiarid region.

Afforestation is an effective approach to rehabilitate degraded ecosystems, but often depletes deep soil moisture. Presently, it is not known how an afforestation-induced decrease in moisture affects soil microbial community and functionality, hindering our ability to understand the sustainability of the rehabilitated ecosystems. To address this issue, we examined the impacts of 20 years of afforestation on soil bacterial community, co-occurrence pattern, and functionalities along vertical profile (0-500 cm depth) in a semiarid region of China's Loess Plateau. We showed that the effects of afforestation with a deep-rooted legume tree on cropland were greater in deep than that of in top layers, resulting in decreased bacterial beta diversity, more responsive bacterial taxa and functional groups, increased homogeneous selection, and decreased network robustness in deep soils (120-500 cm). Organic carbon and nitrogen decomposition rates and multifunctionality also significantly decreased by afforestation, and microbial carbon limitation significantly increased in deep soils. Moreover, changes in microbial community and functionality in deep layer was largely related to changes in soil moisture. Such negative impacts on deep soils should be fully considered for assessing afforestation's eco-environment effects and for the sustainability of ecosystems because deep soils have important influence on forest ecosystems in semiarid and arid climates.

Effects of afforestation on soil microbial diversity and enzyme activity: A meta-analysis

Afforestation is thought to be one of the key measures for mitigating climate change by capturing atmospheric carbon. However, despite the importance of afforestation in ecosystem functioning, its effects on soil microbial diversity and enzyme activity remain unclear. In this study, we conducted a meta-analysis of these effects, using a newly compiled dataset of soil microbial diversity and enzyme activity before and after afforestation collected from 80 sites worldwide. Soil fungal diversity and soil enzyme activities increased significantly after afforestation, but soil bacterial diversity did not change significantly. Among these soil enzymes, the activities of β-1,4-glucosidase (BG), urease (UREA), alkaline phosphatase (AP), dehydrogenase (DEH), and catalase (CAT) increased by 104.7%, 84.0%, 101.7%, 199.2%, and 58.3%, respectively. The responses of soil microbial diversity and enzyme activities varied across afforestation durations, climate zones, prior land use types, and species. Specifically, soil bacterial diversity and the activity of BG increased significantly with afforestation duration, and the increase in BG activity was higher in tropical than in temperate zones. In degraded sites, both soil microbial diversity and enzyme activities significantly increased after afforestation. In addition, structural equation models showed that soil carbon content, nitrogen content, and soil pH value were significant driving factors for the soil microbial community diversity and soil enzyme activities. Overall, our results provided a comprehensive understanding of the changes in soil microbial diversity and enzyme activity under different afforestation conditions, as well as scientific bases for locally adapted afforestation in the future.

How to Improve Forest Carbon Sequestration Output Performance: An Evidence from State-Owned Forest Farms in China

China’s state-owned forest farms are the basic sectors of forestry production, and their carbon cycle functions, such as timber processing and forest carbon sequestration, are of great significance to the national emission reduction strategy. By three-stage DEA and Tobit models, this paper measures the carbon sequestration output efficiency of 3706 state-owned forest farms involved in China’s National Forestry and Grassland Administration’s 2008–2018 survey. We figure out how the mechanism on the carbon sequestration impacts output efficiency of these forest farms and analyze the temporal trends and spatial distributions of their outputs in various regions. Our results indicate that the overall output efficiency of state-owned forest farms in China is relatively low compared with the international advanced level and show that distinctive north-south regional differences exist. Specifically, the carbon storage of the state-owned forest farms in Northeast China and Inner Mongolia occupies more than half of the carbon storage of total amounts, but their output efficiency is unsatisfactory. Conversely, the forest farms in Southwest China have a medium amount of carbon storage and the highest output efficiency. After improving the external environments of these farms, the efficiency value in each province appears as a significant increment. Moreover, the effects of afforestation, timber harvests, the under-forest economy, and other operating behaviors exhibit regional heterogeneity to some extent. Therefore, this paper advocates reforming the current forest cultivation strategy that emphasizes afforestation and neglects management, and relevant government departments are supposed to adjust operations according to local conditions to promote sustainable forest management.

Different-aged Pinus afforestation does not support typical Atlantic Forest fruit-feeding butterfly assemblages

The Atlantic Forest of the southern Brazilian highlands is a biocultural mosaic of Araucaria Forest and grasslands. Despite adverse impacts on biodiversity, extensive areas are being afforested with non-native pine (Pinus spp.), triggering forest succession on areas that were previously native grasslands. The long-term effects of afforestation with these non-native trees for biodiversity conservation are still unknown. Here, we assess this issue by comparing the fruit-feeding butterfly assemblages in young (20 year) and old (70 year) pine plots with nearby native Araucaria Forest. Abundance and richness of butterflies were positively correlated with temperature and mean humidity only in the native forest. Abiotic conditions differed between vegetation types: there was more sunlight, and was warmer and drier in the pine afforestation plots than in the Araucaria Forest. Butterfly species composition was similar between young and old pine plots, but distinct from the native Araucaria Forest. Butterfly species abundances in native forests were more evenly distributed than in afforestation sites. In these pine sites, assemblages were dominated by small, grass-feeding satyrines, whereas old pine sites had more liana-feeding biblidines, and the Araucaria Forest had more large-sized bamboo-feeding species. Our results indicate that even after 70 years of succession a non-native pine afforestation cannot support a butterfly assemblage as that found in the neighboring preserved forest. Moreover, threatened grassland specialist species have been locally extinct after only 20 years of pine afforestation. The evidence gathered here points against the use of silviculture with non-native trees in these biocultural mosaic landscapes.

Ecological development of mangrove plantations in the Bangladesh Delta

Afforestation is a process used in recovering the global mangrove cover. Succession or development in mangrove communities during mangrove afforestation has rarely been described yet is important for understanding the potential of afforestation in creating diverse and functional mangroves. Since 1966, the Government of Bangladesh has created nearly 280 km2 of plantation mangroves (7.5% of the extent of the Sundarbans mangrove forest and 0.21% of the global mangroves extent) on the Delta of the Ganges, Brahmaputra and Meghna Rivers, located east of the Sundarbans mangroves. Here, we investigated the development of these plantation mangroves, assessing their community structure and species richness over a 40-year chronosequence in comparison to natural mangroves in the same region. Tree communities in the plantations reached a maximum mean aboveground biomass (AGB) of ∼157 ± 13 Mg dry weight ha−1, achieving equivalence in tree aboveground biomass and tree density (255 ± 2 individuals ha−1) to natural mangroves by 20 and 39 years respectively. Our dataset from plantations aged between 10 and 42 years indicated that structural complexity (Ic) was higher in older plantations than in younger plantations. We found that the tree community structure of older mangrove plantations was more diverse in the eastern region of the delta compared to the central and western regions, and the landward plantations were more diverse than the plantations fringing the oceans. One of the originally planted mangrove species, Sonneratia apetala, was dominant in these plantations. However, we recorded 8 mangrove tree species from 5 genera in the plantations, despite only two species (S. apetala and Avicennia officinalis) being planted. Our data indicated that while the tree structure of the established mangrove plantations was similar to natural mangroves within 42 years, equivalent species richness may not be reached for more than 40 years. Therefore, adoption of management to enhance natural successional or development processes in afforestation programs, for example by planting a diverse mix of species, could improve the effectiveness of afforestation in conserving biodiversity.

The effect of afforestation and green roofs techniques on thermal reduction in Duhok city

Due to Duhok city's suffering from high temperatures compared to the surrounding areas, this case study endeavors to find out solutions based on green technologies so as to restore the thermal balance of the city center and make it more suitable for living. Forestation techniques have been applied to the road sidewalks and the green roofs on the city buildings' roofs, since tree shading is thought to provide better humidity and reduce temperatures compared to the building shades, umbrellas and artificial structure. Additionally, there have been tests conducted on several models of the city main roads taking into account the shaded sidewalks and the buildings green roofs, and compared them to both cultivated and uncultivated land gardens. It has been found out that the technology of forestation and green roofs can bring about thermal reduction of at least 6 Co and increase the relative humidity by at least 10% compared to shaded sidewalks by buildings and umbrellas in the same area. On this basis, this researched technology is expected to reduce the temperature of Duhok city, purify its weather from pollution, and restore the thermal balance of the cities and urban centers.

Potential negative effects of ocean afforestation on offshore ecosystems.

Our scientific understanding of climate change makes clear the necessity for both emission reduction and carbon dioxide removal (CDR). The ocean with its large surface area, great depths and long coastlines is central to developing CDR approaches commensurate with the scale needed to limit warming to below 2 °C. Many proposed marine CDR approaches rely on spatial upscaling along with enhancement and/or acceleration of the rates of naturally occurring processes. One such approach is 'ocean afforestation', which involves offshore transport and concurrent growth of nearshore macroalgae (seaweed), followed by their export into the deep ocean. The purposeful occupation for months of open ocean waters by macroalgae, which do not naturally occur there, will probably affect offshore ecosystems through a range of biological threats, including altered ocean chemistry and changed microbial physiology and ecology. Here, we present model simulations of ocean afforestation and link these to lessons from other examples of offshore dispersal, including rafting plastic debris, and discuss the ramifications for offshore ecosystems. We explore what additional metrics are required to assess the ecological implications of this proposed CDR. In our opinion, these ecological metrics must have equal weight to CDR capacity in the development of initial trials, pilot studies and potential licensing.

Differential responses of ground-active arthropod abundance and diversity to shrub afforestation in heterogeneous textured soils in desertified grassland ecosystems, North China

Shrub afforestation is an effective way for restoration of soil communities and desertification control in desertified regions. However, little is unknown about how heterogeneous textured soils influence the effectiveness of shrub afforestation on the activities and diversity of ground-active arthropods. In the present study, ground-active arthropods were examined by pitfall trapping as well as by herbaceous performances and soil properties investigated in two shrub microhabitats (the shrub canopy and open spaces) in afforested sandy soil and sandy loam soil of northwestern China. The adjacent shifting sandy land, not covered by shrub plantations, served as a control. Total abundance in the open spaces in afforested sandy soil was significantly (p < 0.05) higher than those in the shrub canopy microhabitats in the same soil type and was also higher than those in both shrub microhabitats (open space and shrub canopy) in afforested sandy loam soil. A consistently (p < 0.05) greater taxa richness and the Shannon index as well as taxa richness of trophic groups (phytophages and predators) was found in shrub microhabitats in both soil types compared to the shifting sandy land. However, no significant differences (p > 0.05) were observed in taxa richness, Shannon index, and the Simpson index of ground-active arthropods, and in the abundance and richness of both trophic groups among the four shrub microhabitats in both soil types. In conclusion, soil textural heterogeneity in terms of soil type had a significant effect on the abundance, but not on the biodiversity distribution and trophic relationship, of ground-active arthropods between shrub microhabitats. The facilitative effect of shrubs benefited a stable biodiversity distribution and thus a stable trophic relationship within ground-active arthropod communities through afforestation practices, regardless of soil type.

Impacts of afforestation on land surface temperature in different regions of China

To assess the impacts of afforestation on land surface temperature (LST) in China and provide a basis for future afforestation and warming mitigation policies, adjacent forest and open land are compared using ten years of satellite data. Most regions in China exhibit a diurnal asymmetry in the magnitude and sign of the effects of afforestation, with daytime cooling and nighttime warming. Afforestation has annual daily cooling effects in most regions of China because the magnitude of annual nighttime warming is generally weaker than that of the annual daytime cooling. We attributed the warming and cooling effects of afforestation to the changes of evapotranspiration (ET) and albedo. The annual average albedo of forest is smaller than that of open land, and the albedo differences between forest and open land vary spatially, with larger differences in places with snow cover. In the annual average, ET over forest is greater than that over open land, with the largest values in the southern of Yangtze River. The daytime differences in LST between forest and open land are driven by the cooling effects of ET and warming effects of albedo, and the cooling effects of ET dominate. The nighttime warming effects of afforestation is related with the release of the energy stored in the soil during daytime. Evergreen broadleaf forest and deciduous broadleaf forest are recommended as the choice of afforestation in south and in north of the Yangtze River respectively to decrease the LST if the afforestation program in China is to be expanded.

Effect of afforestation on soil water dynamics and water uptake under different rainfall types on the Loess hillslope

Knowledge on water uptake is crucial for understanding water transport processes of the soil–vegetation-atmosphere continuum and plant survival strategy in the Loess Plateau. Even though vegetation water sources have been widely explored using hydrogen and oxygen isotopes, the quantification of vegetation water sources after returning farmland to forestland/grassland under different rainfall types, especially extreme rainstorm event, still remains challenging due to difficulties in field monitoring. This study collected precipitation, soil water from 0 to 100 cm soil layer and xylem/stem water and measured their hydrogen (δD) and oxygen (δ18O) isotope compositions in Robinia pseudoacacia forestland (PL), natural forestland (NF) and natural grassland (NG) under four typical rainfall events. The results indicated that among three vegetation types, soil water content was lowest in PL during each rainfall event. In addition, the sensitivity of water-use strategies to precipitation was affected by rainfall types, dry/wet periods and vegetation types. When antecedent soil water was deficit, vegetation water use was more sensitive to precipitation, and the primary water sources after rainfall transferred from deep soil to upper soil. However, when the antecedent soil water was sufficient, water uptake after rainfall tended to be more homogeneous in different soil layers. Among three vegetation types, Robinia pseudoacacia was more sensitive to precipitation. During the extreme rainstorm event II, in PL, the primary water source shifted from the 80–100 cm soil water before rainfall (88.7%) to the 0–10 cm soil water at 1 day after rainfall (64.3%) and the 0–20 cm soil water at 7 day after rainfall (82.8%). Thus, Robinia pseudoacacia can adapt to the environment by switching water-use strategy. The finding can provide a guidance for vegetation rehabilitation in the Loess Plateau.

Biophysical feedback of forest canopy height on land surface temperature over contiguous United States

Forests are considered important in the mitigation of climate change. Biophysical effects of afforestation and deforestation on land surface temperature (LST) have been extensively documented. As a fundamental variable of forest structure, however, few studies have investigated the biophysical feedback of forest canopy height (FCH) changes on LST at large scale. This study is designed to investigate the impact of FCH changes on local land LST and clarify the biophysical processes controlling LST change from 2003 to 2005 over the contiguous United States, based on satellite observations. To this end, one satellite-based FCH product is selected, and the space-for-time approach, together with the energy balance equation, is applied. Results show that for different forest types, namely evergreen forest (EF), deciduous forest (DF), and mixed forest (MF), taller forests present a greater net cooling effect (0.056–0.448 K) than shorter forests at annual scale. The increase in net radiation and sensible heat flux was less than the increase in the latent heat flux when FCH classes converted from shorter to taller, resulting in annual net cooling effects. Furthermore, the cooling effect of EF is stronger than that of DF and MF, whether for tall, medium, or short FCH classes. Multiple regression analysis reveals that the changes in biophysical components can effectively explain the LST change during the growing season. Our findings provide a new insight for forest management decision-making with the purpose of mitigating climate warming.

Effects of Afforestation Projects on Tradeoffs between Ecosystem Services: A Case Study of the Guanting Reservoir Basin, China

Evaluating the responses of ecosystem services (ESs) to local land-use changes is critical for understanding the effects of ecological projects related to land planning. Change patterns in the interrelationships between ESs delivered by land-use changes, which are helpful for formulating future strategies, have not been well studied. In this study, we quantified four ESs, namely water yield (WY), water and soil conservation, nonpoint pollution control, and carbon sequestration services, based on the soil and water assessment tool model (SWAT) in the Zhangjiakou section of the Guanting Reservoir watershed, a region with a high concentration of afforestation projects. The impacts of land-use changes on changes in ESs and interrelationships of ESs were investigated by redundancy analysis. The results showed that, along with afforestation, regional water conservation and soil organic carbon content increased by 3.22% and 1.08%, respectively, whereas sediment output, WY, phosphorus output, and nitrogen output decreased by 1.82%, 3.07%, 8.08%, and 12.51%, respectively. Significant tradeoffs of regional ESs were observed between WY and other ESs, while synergies existed between other ESs. Increased areas of evergreen and deciduous forests helped in conserving water, fixing carbon, and regulating runoff. Evergreen forests tended to conserve more water than deciduous forests. With the increase in grassland area, most of the ESs can be improved while introducing fewer tradeoffs compared with those of most of other land-use types. This study provided a better understanding of the effects of afforestation on ESs tradeoffs and benefits to develop better ecological conservation strategies in afforestation regions.